Automatic air control system for an air bed

<img img-format="tif" img-content="drawing" file="IL115759AD00021.tif" id="idf0001" />

ϊυκ ηυ&gt;» man jvv«win vin tnpa na^»

Automatic air control system for an air beds

SELECT COMFORTCORPORATION C. 99661

IMPROVED AIR CONTROL SYSTEM FOR AN AIR BED

TECHNICAL FIELD

This invention relates to improved methods and apparatus forattaining and regulating the fluid pressure in one or more fluid accommodatingstructures. More particularly, the invention relates to improved air pumps,controllers, information processing and hand controls for measuring and 5 varying the air pressure in an air mattress.

BACKGROUND OF THE INVENTION

Air supported mattresses are used with cots and beds to provide10 yieldable body supports. The air mattresses can be inflated with hand operatedpumps or bag pumps. Motor driven blowers and pumps have also been usedmore effectively to supply air under pressure to air mattresses. U.S. Patents4,908,895 and 4,644,597, assigned to the assignee of the present invention, describe possible constructions of air mattresses. -2-

The air mattresses will typically sit within a border which supportsthe mattress such as that described in U.S. Patent 4,991,244, also assigned to theassignee of the present invention. Double, queen or king size beds can involvetwo air mattresses or two air chambers with individually adjustable air pressures. 5 These air chambers may be further divided internally with free fluid flowbetween these further divisions. The air mattresses can be equipped with a one-way air pressure relief valve operable to limit the air pressure in the air mattressto about 1 psig (pounds per square inch gauge, i.e., relative to ambient pressure)to prevent seam separation and blowout. 10 The biasing or firmness characteristics of an air mattress are determined by the pressure of the air in the air mattress. Control mechanismshave been used to adjust the inflation of air mattresses. Young et al. in U.S.Patent No. 4,224,706, for instance, disclose a mechanism for adjusting the amountof air in an air mattress. The mechanism disclosed in the '706 patent includes 15 one or more receptacles connected to air mattresses for supplying air to andreceiving air from the air mattresses. These receptacles are located in the framebelow the mattress. The internal volumes of the receptacles are changed by therotation of a hand crank. The variation of the volume in the receptacles adjuststhe pressure of the air in the air mattresses. 20 Other control systems for air mattresses have allowed operators to vary the air pressure within the mattress at the touch of a button. The handcontrol units in these systems were either located on the air tube connecting thepump to the mattress or the hand control units made an electrical connection to 2 -3- the pump and solenoid valves. See, for example, U.S. Patents 4,897,890, 4,829,616,4,890,344, also assigned to the assignee of the present invention.

These hand control units typically allowed for the transmittance oftwo instructions to the pump/control unit. These instructions were either to 5 increase or to decrease the pressure. The users had to rely on their tactile sensesin adjusting the air pressure because the units supplied no information to theuser regarding the pressure in the mattress.

One previous design of pressure control for an air mattressinvolved keeping the air pressure constant at all times whether the user was on 10 the mattress or not. See U.S. Patent Nos. 5,142,717 and 4,995,124. A control unitallowed for a preset pressure to be set. One problem with this arrangement wasthe dramatic change in pressure at the time a user applied weight to the mattress.The air mattress had to have an internal structure to support much of the usersweight in order to prevent the escape of large volumes of air while regulating the 15 pressure at the previously set value. The internal structure interfered with thecomfort advantages of having an air supported mattress.

Another design of a pressure control unit provided a digital displayof the internal pressure and push buttons. See U.S. Patent No. 5,020,176. Theuser could either use a constant pressure mode where the pressure could be set by 20 the user. The user also had the option of using a manual mode where thepressure was not kept constant but where the user directly controlled the flow offluid into or out from the mattress.

In these previous designs, if the bed contained two separate 3 -4- mattresses or air bladders, two hand control units were supplied with eachcontrolling its respective air bladder. Therefore, a person lying on one side of thebed could not assist their bed partner on the other side of the bed with anadjustment of the air pressure on the other side of the bed without physicallygoing to that side of the bed. The hand control units were physically attached tothe control unit, thereby restricting the location of a particular unit.

The processing involved in these earlier control systems for air bedswas minimal. The constant pressure systems involved a periodic examination ofthe pressure and a comparison with the desired value. Air was then added orremoved as needed with several steps used if needed to obtain the desiredpressure. In the manual control designs, the operator directly controlled thepump and the release valve to control the flow of fluid into or out of the mattress.

Electric motor driven pumps have been used in the past to inflateair mattresses. The operating noise of such pumps was a common source ofconsumer complaints. The pumps were most frequently utilized when the beduser was preparing to go to sleep. A noisy pump detracted from the restfulatmosphere necessary to induce sleep. The most frequent cause of noisyoperation of such pumps is the rigid mounting of the fan motor to the pumphousing. Such rigid mounting transmits vibrations and noises generated by thepump motor to the pump housing and to the environment around the pump.Further avenues of noise transmission to the environment in air pumps are thesupply air inlet and the cooling air inlet. Sound insulating and dampening 4 -5- materials could be built into the pump motors and housings, but only at the riskof thermal insulation and resultant over heating of the pump motors.

It would be an advantage in the industry to provide a quiet pump inwhich the noise and vibration of the fan motor is dampened with respect to thepump housing and wherein adequate cooling of the pump motor was providedfor. Further, the air inlet and cooling air inlet should be designed to minimizethe amount of fan noise transmitted therethrough. It would be an importantadvance to provide a multi-speed motor to provide for optimal pumping withless noise and with a minimum of overheating problems. With respect to thecontrol of the units, it would be a distinct advantage to have hand control unitswhere the user of the unit was not tethered to the pump unit, and where the user could control both air bladders in the case where each side of the bed had itsown independent bladder. It would also be a decided advance in the art to be ableto accurately and consistently monitor and control the pressure of the airmattress to a desired setting.

SUMMARY OF THE INVENTION

The air control system of an air bed in accordance with the presentinvention in large part solves the problems outlined above. The air controlsystem hereof includes a motorized pump specially designed to reduce noise, andincludes a remotely operated hand held control unit untethered from the airpump. The user of a bed assembly controlled by the air control system hereof canaccurately and consistently adjust the firmness of the air mattress to a desiredsetting. The remote hand control unit in accordance with the air control system 5 -6- of the present invention allows the user to set the firmness of both bladders in adouble bladder air mattress independently of each other.

The hand held control unit communicates with the base unit byway of a radio transceiver. The base unit monitors and transmits to the handheld unit a measure of the air mattress firmness, and responds to commandsfrom the hand held unit to change the firmness of the mattress.

The motorized pump is capable of operating at several speeds tominimize noise while optimizing pumping conditions. The motor speeds can bestepped through a pre-determined manner to obtain optical motor speed while atthe same time monitoring motor temperature to prevent overheating. The baseunit is specially designed to prevent transmission of undue motor noise fromthe base unit into the surrounding environment. Microprocessors in both thehand held control and the base unit allow for the optimization of pumpingconditions without interaction of the user beyond selection of a desired firmness.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a perspective view of an air bed, partly in section, depictedin conjunction with an air control system in accordance with the presentinvention;

Fig. 2A is a plan view of a hand control unit of the air control system;

Fig. 2B is a plan view of a hand control unit of the air control 6 -7- system;

Fig. 3 is an expanded view of one digit and the half digit of thedisplay of the hand control unit;

Fig. 4 is a schematic view of the inside of the hand control unit;

Fig. 5 is an exploded view of the base unit of the air control system;

Fig. 6 is a top plan view of the base unit processor board with aschematic representation of the base processor and the base receiver/transmitter;

Fig. 7 is a side view of a tube and hose fitting that is used to attach anair mattress to the base unit;

Fig. 8 is a perspective view of the hose fitting that connects to areceptacle in the base unit;

Fig. 9 is a cross sectional view of a receptacle in the base unit whichaccepts the hose fitting of Fig. 8;

Fig. 10 is a side elevational view of the fan unit and air distributionunit mounted on the lower housing portion of the air pump housing;

Fig. 11 is a top plan view of the fan unit and air distribution unitmounted on the lower housing portion of the air pump housing;

Fig. 12 is an elevational view, taken from the right side as depictedin Fig. 4, of the fan unit and air distribution unit mounted on the lower housingportion of the air pump housing;

Fig. 13 is a side elevational view of the fan unit;

Fig. 14 is a sectional view taken from the perspective of line 14-14 of

Fig. 13; 7 -8-

Fig. 15 is a side elevational view of the fan of the fan unit;

Fig. 16A is a top plan view with phantom lines depicting the power board beneath the impeller;

Fig. 16B is a schematic partial section view of a re-oriented pumphousing and base;

Fig. 16C is a schematic partial section view of a re-oriented pumphousing and base with improved air routing means;

Fig. 17 is a top plan view of the air distribution unit with the rightsolenoid valve shown in phantom;

Fig. 18A is a side elevational view of the air distribution unit withthe right and left solenoid valves shown in phantom;

Fig. 18B is a perspective view of the inner portion of a snap-fit airdistribution unit;

Fig. 18C is a partial perspective view of the ou;ide of a snap-fit airdistribution unit;

Fig. 18D is a partial top perspective view of the outside of a snap-fitair distribution unit;

Figs. 19a-19c are flow diagrams depicting the processing steps of thehand control processor upon pressing one or two buttons;

Fig. 20 is a flow diagram depicting the transmission sequencefollowed by the hand control processor;

Fig. 21 is a flow diagram depicting the overall operation of the base processor; 8 -9-

Fig. 22 is a flow diagram depicting the receiving and decoding ofmessages by the base processor; and

Figs. 23a-23e are flow diagrams depicting the processing of timedependent actions by the base processor.

DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 contains a view of a resilient support 10 in conjunction withan air control system in accordance with the present invention. Resilientsupport 10 is preferably a fluid filled bed and more preferably an air bed toaccommodate one or more persons. Resilient support 10 has a generallyrectangular base or box spring unit 12 adapted to be supported on a floor or aframe engaging the floor. A mattress unit 14 is located on top of box spring unit 12. Mattress unit 14 has a generally panshaped resilient member 16 havingupright linear side edges 18 and 20 joined to a transverse front edge 22 and acomparable transverse rear edge 24.

Side edges 18, 20, front edge 22 and the rear edge 24 are integral withthe peripheral portions of a generally flat bottom 26 to form therewith a generallyrectangular chamber 28. A pair of side by side longitudinal air bladders 30 and 32are located in rectangular chamber 28. The air bladders 30 and 32 comprise airmattresses or air bags that can include a plurality of transverse and/orlongitudinal chambers adapted to accommodate air under pressure. The airbladders 30 and 32 are of a size to fill rectangular chamber 28. Commerciallyavailable air bladders vary in size from 23 to 34 inches wide and 67 to 84 incheslong. Preferably, the air bladders 30, 32 have an inflated thickness of 5.5 inches. 9 -10-

Other types and sizes of air bladders as well as bladders designed to accept otherfluids, e.g. water, can be used in mattress unit 14 for resilient support 10. A generally rectangular cover 38 fits over edges 18, 20, 22 and therear edge 24 to enclose the top of chamber 28. As shown in Fig. 1, a portion of thecover 38 has been rolled back to illustrate the side-by-side placement of airbladders 30, 32 in rectangular chamber 28.

The air control system 40, in accordance with the present invention,functions to provide air under pressure to air bladders 30, 32 and to control thepressure of the air bladders 30, 32. The air control system 40 includes a handcontrol unit 42 and a base unit 44.

Hand Control Unit Embodiments

Hand control unit 42 shown in Fig. 2A is preferably a remote unitphysically unconnected to the remainder of the air control system 40. Fig. 2Bshows an alternate embodiment hand control unit 742, which comprises ananalog pressure gage indicator 804, and air control buttons 806, 808. Hand controlunit 742 is preferably used with the alternate pump configuration described inrelation to Fig. 16B, although it is useful with various pump configurations.

The hand control unit 42 allows a user to control the air pressurewithin the air bladders 30, 32 while lying on the mattress unit 14 or in any otherposition in the vicinity of the air control system 40. Hand control unit 42 ispreferably used with pump 152 described later below, although it is useful withvarious pump configurations.

The top surface 102 of hand control unit 42 contains a digital display 10 -11- 104, two buttons 106, 108, and a two position switch 110. Digital display 104presents information received from the base unit 44. Preferably, the digitaldisplay 104 is made up of a liquid crystal display (LCD). The LCD is made up oftwo digits 112 ranging from 0-9 and a half digit that can only be a 1 or 5 unilluminated. In this preferred embodiment, each digit 112 is made up of 7segments 113, as shown in Fig. 3, and the half digit 114 is made up of twosegments 115, the top and bottom of the 1. The liquid crystal display is backlit bytwo preferably amber light emitting diodes. Digital display 104 displays for theuser a number related to the pressure within the air bladders 30, 32. Preferably, 10 the button (either 106 or 108) which is designed to increase the pressure in an airbladder has a protruding top portion as felt by the user, while that buttondesigned for deflating or reducing air pressure in an air bladder is designed with a

I depressed top portion as felt by a user. This further optimizes the ergonomics ofthe hand control unit and facilitates use without even viewing the unit. 15 The two buttons 106, 108 and the switch 110 provide for the communication of a command from the user to the air control system 40. Thetwo buttons 106, 108 are adapted to be used by the user to initiate an inflation ordeflation cycle, request the display of the current pressure or to instruct the baseunit 44 to recognize the hand control units 42. 20 The position of two position switch 110 selects the air bladder 30, 32 on which the operations of the hand control unit 42 will function. The topsurface 102 of the hand control unit 42 can include markings indicating left or right near the corresponding side of switch 110. The preferred convention for

I 11 -12- determining the left/right side of mattress unit 14 is from the perspective of aperson laying on their back with their head in the proximity to the front edge 22(hose side) of the mattress unit 14, although other conventions can be used. Fora system having a single air bladder 30, either position of the switch 110 willallow adjustment of the pressure in the air bladder 30 if a Y-hose is used to attachthe base unit 42 to the mattress unit 14, as described below.

Referring to Fig. 4, the interior of the hand control unit 42 containsa portable power supply 116, a hand control processor 118 and a hand controlreceiver/transmitter 120. The portable power supply 116 is made up of adisposable battery or a rechargeable battery. The hand control processor 118receives input from buttons 106, 108 and base unit 44 through hand controlreceiver/ transmitter 120 and sends output to digital display 104 and base unit 44.The hand control processor 118 is a digital processor, for example a MotorolaMC68HC05P4 microcontroller with a little more than 4 Kbytes of ROM (program)memory, 176 bytes of RAM memory, 20 I/O port pins, 1 input-only port pin, 1timer output pin, and a 16-bit capture/compare timer. The software for the handcontrol processor 118 is stored in the ROM memory during fabrication. The handcontrol processor 118 is permanently encoded at manufacture with an eight bitunit ID code and a four bit revision code for the software version by the selectionof appropriate resisters within the hand control unit 42. Hand control receiver/transmitter 120 is adjusted to a proper electromagnetic frequency to receive fromand transmit to base unit 44. The hand control receiver/transmitter 120 canreceive radio signals or transmit radio signals, but it cannot transmit and receive 12 -13- at the same time.

Base Unit Embodiments

The base unit 44 of the present invention is depicted in Fig. 5. Thebase unit 44 contains a motorized pump 152, pressure sensors 156, 158 (Fig. 10),and a base unit processing board 160 (Fig. 11). Referring to Fig. 6, the baseprocessing board 160 contains the base processor 162 and the basereceiver/transmitter 164. The base unit 44 is connected to air bladders 30, 32 byway of flexible tubular lines or tubes 166, 168 through inlet receptacles 170, 172.Tubes 166,168 allow the air control system 40 to place additional air or to removeair from the air bladders 30, 32 to achieve a desired air pressure within the airbladders 30, 32. For a single air bladder 30 mattress unit 14, tubes 166, 168 can bereplaced with a Y-shaped tube (not shown) so either the right or left sidecommands will effect the single air bladder 30 or, alternatively, the unused inletreceptacle 170, 172 can be plugged. An electrical plug 174 is designed to beconnected to a conventional ac power receptacle. An electrical power cord 176connects plug 174 to base unit 44.

The base receiver/transmitter 164 is tuned to an electromagneticfrequency that is preferably selected to be in the radio frequency range. Theelectromagnetic frequency is preferably within the range from 315 MHz (106 Hz)to 350 MHz. The selection of the radio frequency part of the electromagneticspectrum enables the clear transmission of the signal without the need for theuser to point the hand control unit 42 at the base receiver/ transmitter 164. Thesignal is transmitted in digital form at the rate of 833 bits per second. The base 13 -14- receiver/transmitter 164 can receive radio signals or transmit radio signals, but itcannot transmit and receive at the same time.

The pressure sensors 156, 158 are standard piezoelectric pressuresensors such as those available from IC Sensors Inc. The cap on the pressuresensors 156, 158 contain a small hole to allow air under ambient pressure toenter. This allows the measurement of the variation from ambient pressure bythe pressure sensors 156, 158. The circuitry to amplify the signal from thepiezoelectric sensor and .to perform the analog to digital conversion is also standard in the art.

The processor 160 is a digital processor, for example MotorolaMC68HC05P6 microcontroller with a little more than 4 Kbytes of ROM (program)memory, 176 bytes of RAM memory, 20 I/O port pins, 1 input-only port pin, 8-bitanalog to digital converter, and a 16-bit capture/compare timer. The software forthe 162 is stored in the ROM memory during fabrication.

Referring to Figs. 7, 8 and 9, tube 166 is shown in conjunction with atube fitting 180. Tube fitting 180 is selectively, detachably received within an inletreceptacle 170, 172, it being understood that the tube 168 is identical inconstruction with tube 166. Fitting 180 is preferably comprised of a one piece,synthetic resin, generally tubular body 182. The fitting body 182 includes a tubereceiving end 184, a body midportion 186, and male connector head 188.

The male connector head 188 includes an enlarged sealing portion190. The sealing portion 190 carries a sealing o-ring 192. Connector head 188 alsoincludes connecting tip 194. Connecting tip 194 includes a pair of generally semi- 14 -15- circular in cross section prongs 195, 196. The prongs 195, 196 are arranged on thetip 194 in mirror image fashion. Each of the prongs 195, 196 include an axialportion 197 extending outwardly from the enlarged portion 190 of the connectorhead 188, and a half-circumferential portion 198 arranged in generally L-shapedfashion with the axial portion 197. Circumferential portion 198 includes beveledperimeter 199, and a projecting boss portion 200.

Referring to Figure 9, each of the inlet receptacles 170, 172 include agenerally tubular inner wall 201, and a boss receiving aperture 203. A connectorhead 188 of a respective hose fitting 180 is detachably received within a respectivereceptacle 170,172, with the sealing O-ring 192 carried by the enlarged portion 190of the connector head 188 received in sealing contact with the receptacle internalside wall 201. A boss 200 of one of the two connecting head prongs 196, 197 isdetachably received within the aperture 203.

Pump 152 has three major subcomponents: pump outer housing202, fan unit 204, and air distribution unit 206.

Pump outer housing 202 has three subcomponents: lower outerhousing portion 208, upper outer housing portion 210, and flexible mount 212.Generally, the lower outer housing portion 208 provides the mounting base forthe fan unit 204 and the upper outer housing portion 210. The upper outerhousing portion 210 is mated to the lower outer housing portion 208, enclosingthe fan unit 204 without physical contact therewith. Since the upper outerhousing portion 210 of pump outer housing 202 is not in contact with the motorunit 204, mechanical dampening of the fan unit 204 is required only between the 15 -16- fan unit 204 and the lower outer housing portion 208 to which the fan unit 204 is mounted in order to minimize vibration and noise transmission.

Referring to Figs. 5, 10 and 11, the lower outer housing portion 208is comprised of a base 213 and peripheral lip 214. Lower outer housing portion208 is preferably made of a thermoplastic material. The base 213 is designed to begenerally flat in order to facilitate being placed upon the floor proximate to theair bed. The peripheral lip 214 has an upper margin into which interlockingmarginal grooves 215 are formed.

Four upwardly directed support posts 216 for fan unit 204 areformed integral with base 213. The support posts 216 project above the uppermargin of the peripheral lip 214. The support posts 216 have a central bore 218defined therein to facilitate the passage of a connecting screw therethrough.Smaller connecting posts 219 are also formed integral to base 213. Connectingposts 219 are designed to facilitate the connection of the upper outer housingportion 210 to lower outer housing portion 208. A central bore 220 is defined inconnecting posts 219 in order to facilitate passage of a connecting screwtherethrough. A helical wall 221 is formed integral with base 213. Helical wall 221defines a portion of helical air intake passageway 222. Helical air intakepassageway 222 extends from central chamber 223 outward to intake mouth 224.Helical air intake passageway 222 is defined by base 213, helical wall 221, and flexible mount 212.

The intake mouth 224 has two adjacent intake openings 225a and 16 -17- 225b, separated by a central support 226. Support tabs 228 overlie supportingstructure 229 formed in base 213. Screws 230 are threaded through bores formedin support tabs 228 and then threaded into the supporting structure formed inbase 213 to affix intake mouth 224 to lower outer housing portion 208. A nose plate 232 projects from and overlies intake openings 225aand 225b. The nose plate 232 is strengthened by gussets 234. A cooling air mouth 238, depicted in Fig. 12, is also affixed to lowerouter housing portion 208 of pump outer housing 202. The cooling air mouth238 is generally located diametrically opposed to the intake mouth 224.

Cooling air mouth 238 has a cooling air intake 240 defined therein.The cooling air mouth 238 is affixed to base 213 as previously described by meansof support tabs 242 and screws 243. A sealing plate 244 projects from and overliesthe cooling air intake 240.

The flexible mount 212 is placed atop base 213 of lower outerhousing portion 208. The central underside position of flexible mount 212 issupported upon the top portion of helical wall 221.

Flexible mount 212 has a central aperture defined therein. Thecentral aperture 244 is in registry with central chamber 223 of helical air intakepassageway 222. Cutouts 246 are provided in flexible mount 212 to accommodatethe passage of support posts 216 therethrough.

Flexible mount 212 is formed of a relatively thin lower flexiblerubber portion 248 and an upwardly directed relatively thick foam rubbercushion 250. The foam rubber cushion 250 is preferably bonded to flexible rubber 17 -18- portion 248. Flexible mount 212 is formed in a generally circular shape.

The upper outer housing portion 210 of pump outer housing 202 isformed generally in an inverted bowl shape, having a top portion and sideportions defining a considerable depth. Upper outer housing portion 210 has agenerally cylindrical center section 260 with squared corners 262, 263. Theperiphery of the lower portion of squared comer 262 is designed to mate with thenose plate 232 of intake mouth 224. The periphery of the lower portion ofsquared corner 263 is designed to mate with the sealing plate 244 of cooling air mouth 238.

Pressurized air outlets 264 are defined in squared comer 263. Thelower margin of the side portion of upper outer housing 210 has interlockingmarginal lips 268 defined thereon. Interlocking marginal lips 268 are designed tomate with interlocking marginal grooves 215 formed on the margin of lip 214.Downwardly directed mounting posts 270 are designed to be brought into registrywith connecting posts 219 formed in base 213. Upwardly directed screws (notshown) are passed through the central bore 220 of connecting post 219 andthreaded into mounting posts 270 to effect the mating of upper outer housingportion 210 to lower outer housing portion 208.

The fan unit 204 of pump 152 is best viewed in Figs. 13 and 14 andhas two major subcomponents: fan housing 280 and two stage fan 282. The fanunit 204 is preferably fully assembled prior to installation within pump housing202. To facilitate such assembly, the fan housing 280 is formed in two halves 280aand 280b, enclosing the two stage fan 282. The sectional view of Fig. 14 depicts 18 -19- housing half 280a of housing 280 with the fan 282 installed therein. The twohalves of fan housing 280 are held together by screws 276 threaded into supports278.

Fan housing 280 has structure defining a lower impeller chamber284. Lower impeller chamber 284 includes a central air inlet 286 defined therein.

Central air inlet 286 is in fluid flow communication with a central chamber 223of helical air intake passageway 222 when fan unit 204 is mounted to lower outerhousing portion 208.

Upper impeller chamber 288 defines the second chamber for twostage fan 282. Upper impeller chamber 288 has an air outlet 290 designed toexhaust pressurized air from fan unit 204.

Lower impeller chamber 284 and upper impeller chamber 288 arefluidly connected by air passageway 292, designed to convey pressurized air fromlower impeller chamber 284 to the upper impeller chamber 288. A cylindrical core 294 is formed between lower impeller chamber284 and upper impeller chamber 288. Core 294 has cooling air inlets 296 definedtherein. Two O ring grooves 298 are formed around the inner diameter of core 294.

To facilitate the mounting of fan unit 204 to base 213, fourmounting slots 300 are formed integral with the external portion of lowerimpeller chamber 284. Rubber mounting grommets 302 are inserted intomounting slots 300. Mounting grommets 302 have a central bore defined thereinthat is brought into registry with the central bore 218 of support posts 216. 19 -20-

Referring to Figs. 14, 15 and 16A, the two stage fan 282 of fan unit204 is a variable speed unit designed to operate at various selected speeds. Fan282 has a first stage impeller 306 and a second stage impeller 308. First stageimpeller 306 is rotationally mounted within lower impeller chamber 284 andsecond stage impeller 308 is rotationally mounted in upper impeller chamber 288.

The impellers 306, 308 are mirror images in construction and havecurved impeller vanes 310 mounted on an impeller disk 312. Preferably, thereare eight radially directed curbed impeller vanes 310 on each impeller 306, 308.

The fan motor 314 is mounted on an axially shaft 316 extendingbetween first stage impeller 306 and second stage impeller 308. A small coolingfan 317 is mounted on axially shaft 316.

The motor 314 is mounted within housing 318. Two cooling airinlets 320 are formed within housing 318 to admit cooling air to cooling fan 317.Cooling air outlets (not shown) are formed in the bottom portion of housing 318approximate first stage impeller 306. Power leads 324 are brought into the topportion of housing 318 in order to power motor 314, by means of a power board325. Power board 325 is affixed to housing 318 and is stabilized within fanhousing 280 by clips 326.

The two stage fan 282 is mounted within fan housing 280 by two Orings 328. The O rings 328 are compressively held within O ring grooves 298 offan housing 280. No portion of the fan 282 is in physical contact with the fanhousing 280. Accordingly, the two O rings 328 provide dampening of vibrations 20 -21- generated by the two stage fan 282, thereby minimizing the transmission of suchvibrations to fan housing 280.

Various modifications of pump 152 are possible within the scope ofthis invention. For example, it is possible to re-orient the motor 314 andimpellers 306, 308 approximately 90° relative to base 213. Fig. 16B shows a sideschematic view of a re-oriented partial (lower portion) fan housing 280'positioned above a schematic base 213'.

In this embodiment, at least one portion of housing 280 is removedto accommodate a secure contact with base 213'. This configuration results in airintake at inlet 904 after routing through base 213', and then routing of the airthrough the central chamber and impeller chambers substantially as described above.

The vertical rather than horizontal orientation of the fan housing280' allows additional volume of space between housing 280' and an outer pumphousing generally adjacent to air inlet 904. This is quite useful for placement ofcircuitry and electrical components for controlling the pump. However, theelimination of portions of the housing also re-shape the overall configuration ofthe pump outer housing as a smaller, more circular (in plan view) layoutrelative to the pump 152 shape and size described in relation to Fig. 5.

Fig. 16C further illustrates air chamber modifications to improvethe efficiency of air being pressurized within housing 280'. Lip 945, shown inshaded lines, is designed to route air in and out of the impeller chambers.However, this lip has been improved by lengthening to a new shape designated 21 -22- 946. Lip 946 more efficiently routes the air by extending further into the air flow. A further air routing improvement is shown in Fig. 16C. Thisimprovement is schematically similar to the lip extension in its utility witheither the re-oriented pump shown in Fig. 16B or the pump 152 shown invarious prior figures. Line 968 depicts the arc of rotation of an impeller withinan impeller chamber. Line 970 depicts an inner wall of an impeller chamber,with the distance between the lines being less than about 1/4", and morepreferably about 1/8". The remainder of any previous chamber volume ispreferably eliminated (as shown by diagonal lines 985). The overall reduction inchamber volume reduces wasteful vortices and improves the efficiency of pumpsusing this improvement.

Referring to Figs. 10, 17 and 18A, the air distribution unit 206 ofpump 152 is fixedly mounted on pump outer housing 202. The housing 330 ofair distribution unit 206 is preferably made of a thermoplastic material and isconventionally coupled, in one embodiment, to fan housing 280 by screws.Alternate embodiment air distribution units 206', are shown in Figures 18B, 18C,and 18D. Air distribution unit 206' is designed for ease and economy of assemblyby use of snap-in and snap-fit portions. These portions, such as solenoidretaining resilient fingers 331 and snap-fit portions 332, eliminate the need forassembly screws, thereby increasing assembly speed. Precise manufacturing ofembodiments as shown in Figures 18B-18D further enhance the overall qualityand competitiveness of products manufactured according to this invention. Airdistribution unit 206 has a pressurized air inlet 332 that is fluidly coupled to the 22 -23- air outlet 290 of upper impeller chamber 288.

Air distribution system 206 further includes a left pressurized airoutlet 334 and a right pressurized outlet 336. The left pressurized outlet 334 isconnected to a flexible conduit 337a and flexible conduit 337a is connected to apressure sensor 156. The right pressurized air outlet 336 is similarly connected toconduit 337b which is connected to pressure sensor 158. Left pressurized outlet334 is in fluid communication with tube 166 which is in free pressurecommunication with a first air bladder 30 of the mattress unit 14. The rightpressurized outlet 336 is similarly connected to a second air bladder 32 by way oftube 168. The pressurized air flow to the aforementioned two bladders 30, 32 iscontrolled by a left solenoid valve 338 and right solenoid valve 340. Air flowproceeds through the solenoid valves 338, 340 through inlet receptacles 170, 172into tubes 166, 168 to achieve air communication with the air bladders 30, 32.Actuation of valves 338, 340 withdraws the solenoid shaft 341, thereby openingthe inlet receptacles 170,172.

In assembly, flexible mount 212 is first placed upon base 213 of lowerouter housing portion 208. Flexible mount 212 is positioned with respect tointake mouth 224 and cooling air mouth 238 such that air entering intakeopenings 225a, 225d is directed beneath flexible mount 212 and air enteringcooling air intake 240 is directed above flexible mount 212.

Fan unit 204 is then placed on top of the foam rubber cushion 250 offlexible mount 212. Suitable screws 348 are passed through the central bores 218of support posts 216 and are threadedly engaged with rubber mounting grommets 23 -24- 302 that are in the mounting slots 300 of fan housing 280. As these screws aretightened, the fan unit 204 is pulled into compressive engagement with the foamrubber cushion 250 of the flexible mount 212. The rubber mounting grommets302 come into compressive engagement with the support posts 216. By this 5 means, the fan unit 204 is held in fixed engagement with the lower outerhousing portion 208 of pump outer housing 202. At the same time, vibrationsgenerated within fan unit 204 are damped by the foam rubber cushions 250 offlexible mount 212 and the rubber mounting grommets 302. Accordingly, thetransmission of vibrations from fan unit 204 to lower outer housing portion 208 10 of the pump outer housing 202 is minimized. The upper outer housing portion210 of pump outer housing 202 may then be installed over the fan unit 204 andair distribution unit 206 without the physical contact therewith.

The service unit (not shown) performs all of the function of a handcontrol unit 42 in addition to various diagnostic checks of the base unit 44. 15 Operation of the Base Unit Air Pump

In operation of the base unit air pump 152, air is drawn in through intake opening 225a, 225b to helical air intake passageway 222. Fan noise beingtransmitted out through a straight line air intake was a source of noise inconventional air pumps. In contrast, the helical air intake passageway 222 acts to 20 minimize the transmission of fan noise therethrough.

The air is drawn from central chamber 223 of the helical air intakepassageway 222 through air inlet 286 and lower impeller chamber 284. The air ispressurized and accelerated by the rotating of first stage impeller 306. Such 24 -25- pressurized air is then forced through air passageway 292 to the upper impellerchamber 288. The air is then further pressurized by the rotating second stageimpeller 308. The pressurized air is expelled from fan housing 280 via air outlet292 to the air distribution unit 206. The air distribution unit 206 then distributespressurized air to one or both of the air chambers of the air bed as determined bythe left solenoid valve 338 and right solenoid valve 340.

Cooling air is drawn in through the cooling air intake 240. Thecooling air floods the space defined between the upper outer housing portion 210of pump outer housing 202 and the fan unit 204. The cooling air is drawn bycooling fan 317 through the cooling air inlet 296 and into the housing 318 of thetwo stage fan 282. The cooling fan 317 forces the cooling air downward throughmotor 314 of the two stage fan 282 and out through the cooling air outlet. Thecooling air outlets open into the lower impeller chamber 288. The cooling air isthen pressurized by the first stage impeller 306 and mixed with the air receivedfrom central air inlet 286. The cooling air is then provided to the air bed via theair distribution unit 206. The foregoing cooling air path acts to minimize thetransmission of fan vibration and noise therethrough.

Operation of the Air Control System

The function of the air control system 40 relies on the communication link between the base unit 44 and the hand control unit 42.Communications are always initiated by either a hand control unit 42 or a serviceunit. A base unit 44 transmits only in response to messages it receives from theother units. A preamble to the message provides a sequence during which the 25 -26- receiver can synchronize with the transmitter. A preferred preamble consists of14 zero bits followed by 2 one bits.

Every message contains a 8-bit ID field which indicates theoriginator or addressee of the message, a 4 bit revision code which indicates theversion of the software and a four bit instruction. Hand control units 42 placetheir particular ID into messages that they send. All service units put the sameID, all zeros, and revision code, all zeros, into the messages that they send. The 8 bit ID allows for 256 different IDs for the hand control units 42 with the one reserved for service units. The 4 bit revision code allows for 16 different softwareversions, and the 4 bit instructions allow for 16 different messages. It requiresabout 1200 microseconds to transmit each bit. A base unit 44 responds to messages only from service units or fromhand units 42 that it recognizes. A base unit 44 puts the destination unit's ID inthe response message. A base unit 44 maintains a list of hand unit IDs that itrecognizes, up to two. The list can be entered by any hand control unit 42 duringthe first 256 secs, after the base unit 44 is powered on. This facilitates theinitialization of the list of recognized hand control units 42. If there is a poweroutage or the base station is unplugged, previously entered IDs will beremembered by the base unit 44, and reinitialization will not be required. Also,the hand unit introduction procedure, described below, can be used by arecognized hand control unit 40 whenever the base unit 44 is not busy with anadjustment. The hand unit introduction procedure completely rewrites the listof recognized hand control unit IDs. 26 -27-

The hand control processor 118 responds basically to the pressing ofone or both buttons 106, 108. Referring to Fig. 19a, if the hand control processor118 determines that neither button 106, 108 is being pressed at step 400, the handcontrol processor 118 determines whether the unit is currently in the sleep modeor not at step 401. If it was in the sleep mode, the hand control unit 42 continuesin the sleep mode 402. If it was not in the sleep mode at step 401, the handcontrol processor 118 next determines whether 10 seconds have passed withoutactivity at step 408, as depicted in Fig. 19a. The buttons 106, 108 are checked everytenth of a second. If 10 seconds have passed without activity, step 408 proceeds tostep 410 where the digital display 104 is turned off, and the hand control unit 42enters the sleep mode to conserve power. If 10 seconds have not passed withoutactivity, the hand control processor 118 checks at step 403 if buttons had beendisabled and the disabling condition has been removed. If there were disabledbuttons, the buttons are freed from being disabled at step 404, and the processorcontinues with step 400. If at step 403, it is determined that no buttons aredisabled, the hand control processor 118 continues with step 400.

Referring to Fig. 19b, if the hand control processor 118 determinesthat a button 106, 108 is being pressed at step 400, the hand control processor 118initiates the processing of the signal from the buttons 411. First, it is determinedwhether the control is in its active state at step 412. If the hand control unit 42was in sleep mode when the button 106, 108 was pressed, it switches to wake-upmode (step 414). At wakeup 414, the hand control unit 42 zeros its RAMmemory, turns on the power to the display 104 and initializes much of the rest of 27 -28- the system.

After a wake-up mode is initiated at step 414, the hand controlprocessor 118 requests the current pressure 416 from the base unit 44 by way ofthe hand control transmitter/receiver 120 at step 418. to show a pressuremeasurement sampled within the last 30 seconds. A response from base unit 44is received and decoded 419, and the display 104 is updated 420. Then, the handcontrol processor 118 sets a timer counting 422, and returns to determine again ifa button 106, 108 is depressed 400 when the appropriate time to check the buttonsis reached. The value from the timer can be used for the later determination ofhow long the button has been depressed.

If at step 412 the hand control unit 42 was in an awake mode, it isdetermined which buttons are depressed at step 424. To make thisdetermination, the hand control unit 42 reads the buttons 106, 108, every tenth ofa second and updates a byte that shows which buttons are pressed. The relativelyslow sampling rate provides an effective means of debouncing the buttons. Afterdetermining which buttons are depressed at step 424, the hand control processor118 determines if the buttons are disabled 426. If the buttons are disabled at step426, the program continues with step 400. If the buttons are not disabled, theprogram continues with step 428. The hand control processor 118 keeps track ofthe buttons 106, 108 that were pressed on the previous reading. It is thendetermined if the same buttons are depressed which had been depressed at thelast determination 428. If different buttons are depressed, the buttons are disabledat step 430, and they remain disabled until released, see step 403. The program 28 -29- then continues with step 400. Buttons are also disabled when an adjustment isactive (not shown).

After determining that the buttons are not disabled at step 428, it isdetermined how many buttons are depressed 432. If one button is depressed at 5 step 432, it is determined if the button has been depressed for two seconds 434. Ifnot, the program continues with step 400. If yes, the digital display 104 isincremented or decremented appropriately depending on which button 106, 108is depressed 436. Initially, an increment or decrement is processed every 0.5 secs,that the button is held, but after four consecutive actions the rate is accelerated to 10 an increment or decrement every 0.1 secs. Also, the hand control processor 118sends a message 438 that is transmitted 439 to base unit 44 to begin an adjustmentof the pressure. To indicate that an adjustment is in progress, the digital display104 is made to blink 440. Then, the hand control processor 118 resets the timercounting the length of time that the button has been depressed 442, and the 15 program returns to step 400.

If step 432 determines that two buttons 106, 108 are depressed 444,the hand unit processor proceeds as is depicted in Fig. 19c. First, the status ischecked 446, and the hand unit introduction procedure is initiated if it is notalready in progress. This procedure is purposely cumbersome in order to prevent 20 accidental modification of the list of recognized hand control units 40. Uponpressing both buttons, the display starts to count down at step 448 from 10 to 1.Then the display shows two hyphens (—) 450, and the hand control unit 40 sendsa message 452 which is transmitted 453 to the base unit 44. When the base unit 29 -30- 44 receives the message, it rewrites the ID list to contain only the ID of the senderhand control unit 42. Then the base unit 44 sends an acknowledgement to thehand control unit 42. When the hand control unit 42 receives theacknowledgement at step 456, it displays "Cl" or "C2"at step 458 as instructed by the base unit 44.

After the first message is received by the base unit 44, the user hasone minute to complete the hand unit introduction procedure. If the user wantsthe list to contain only one ID, there are two options. First, the user can pressboth buttons again, see step 444. This situation is depicted in the second branchin Fig. 19c for the case where the introduction procedure is already in progress.The hand control process 118 sends a message 460 that is then transmitted 461 tothe base unit 44 that there is only one hand control unit 42. After the message issent, hyphens are again shown on the display 462. The base unit 44 sends anacknowledgement that causes the display of the hand control unit 42 to display(1C) 466. A short time later, the base unit 44 sends an instruction for the handcontrol unit 42 to resume normal operation 468. Then, the hand control process118 continues with step 400.

Alternatively, the user can do nothing for about one minute after"Cl" is displayed at step 458. If the base unit 44 has not received a second messageby the end of the minute, the base unit 44 sends a message that causes the handcontrol unit 42 to stop displaying "Cl" and to return to normal operating mode.(This option is not depicted in the Fig. 19c since the hand control unit does notmake the determination.) 30 -31-

If the user wants the list to contain two ID's, the user can go to thesecond hand control unit 42 and press both buttons step 444 within one minutewhile the first hand control unit 42 displays "Cl". At step 446, the processingwould proceed along the path where the hand control unit had not initiated theintroduction procedure. The display of the second hand control unit 42 starts tocount down 448 from 10 to 1. Then, the display of the second hand control unit42 shows two hyphens (--) 450, and the hand control unit 42 sends a message 452to the base unit 44. When the base unit 44 receives this second message in theprocedure, it adds the second ID to the list. Then, the base unit 44 sends anacknowledgement to the second hand control unit 42. When the second handcontrol unit 42 receives the acknowledgement 456, the display of the second handcontrol unit 42 shows "C2" 458. After a couple of seconds, the base unit 44 sendsmessages to both hand control units 42, causing them to stop displaying "Cl" or"C2" and to return to normal operating mode. The hand unit introductionmessage is the only operation that elicits two responses from a base unit 44, theacknowledgement message and the done message.

With respect to the updating of the display buffers, the hand controlunit software maintains two display buffers of three bytes each in its RAMmemory. The secondary buffer contains information with each bytecorresponding to a display digit 112 or half digit. Information in the primarybuffer is organized according to the segments 113,115 of the display 104.

When a base unit 44 is initialized to accept commands from twocontrol units 42, conflicts can occur in two cases. The first conflict occurs if a 31 -32- hand control unit 42 tries to monitor an air bladder's pressure when the baseunit 44 is already adjusting the pressure in the same air bladder 30, 32. Thesecond opportunity for conflict occurs if a hand control unit 42 tries to adjust anair bladder's firmness when the base unit 44 is already adjusting the pressure ineither air bladder 30, 32 in response to a request by another hand control unit 42.In either of these cases of conflict, the base unit 44 will notify the requesting handcontrol unit 42 that it is busy and cannot currently satisfy the request. This causesthe second hand control unit to display blinking hyphens (--).

When the second hand control unit 42, displays blinking hyphens,it ignores depression of the increment/decrement buttons 106, 108, i.e., thebuttons are effectively disabled as long as a pressure adjustment is occurringunder the instruction of the first hand control unit 42. The hand unit does checkfor changes in the two position switch 110. When the position of the twoposition switch 110 is changed, the hand control unit 42 notifies the base unit 44,and the base unit 44 transmits the pressure of the newly selected air bladder 30, 32to the hand control unit 42 while not terminating the active adjustment of theother air bladder 30, 32 as instructed by the other hand control unit 42.

The digital display 104 will display various error codes in responseto various communication difficulties with base unit 44 and if the motor 152 is too hot to make an adjustment.

Fig. 20 displays the process of receiving and decoding a messagefrom the base unit. A counter is set to one 480, and a message is transmitted 482to base unit 44. After waiting 0.2 to 0.3 seconds 484, hand control processor 118 32 -33- checks 486 if a valid response was received from the base unit 44. If a validresponse was received, the response is processed 488 and the processor returns490 to the programming step awaiting the response. If a valid response was notreceived, the counter is checked to determine if 7 attempts at transmission havebeen made 492. If 7 attempts have been made, an error message is sent to thedigital display 104 and the program returns to step 400. If 7 attempts had not beenmade at step 488, the counter is incremented by one 496, and the hand controlprocess 114 returns to step 482 to continue with the transmission loop.

The software for the base processor 162 has a main loop in whichthe processor spends most of its time. Referring to Fig. 21, the base processor 162updates various timers if a second has elapsed since the last update 602, checks ifa message has been received but not yet processed 604 and checks if a timedependent action needs to be formed 606. The base unit 44 responds only wheninstructed by a hand control unit 42 except for monitoring the pressure whichoccurs every 30 seconds if no other activity is taking place. The base unit 44 sendsa response for every message received from a recognized hand control unit 42.

In order to reduce the chance of a base unit 44 taking an undesirableaction because of an erroneously received message, the base unit 44 only accepts amessage from a hand control unit 42 within 256 secs, of power up of the base unit44 or within 256 secs, of the receipt of a previous acceptable message from thehand control unit 42, unless the message received is just requesting the currentstatus. Similarly, base unit 44 only accepts messages from a service unit withinfive minutes of power up or within five minutes of receipt of a. previous 33 -34- acceptable message from the service unit. As each byte is received, the message is stored in a reception buffer.

At step 604, the processor determines if a message has been received608 and is waiting for processing, see Fig. 22. If there is a message to be processed,the message is decoded 610. If the current pressure was requested 612, thepressure last measured is transmitted 614 to the hand control unit 42. If themessage initiated a inflation/deflation request or the hand unit introductionprocedure, the processor is notified 616 that an activity is requested, and theprogram returns to the main loop 604.

Fig. 23 depicts the various paths the base processor 162 can followwhen a process action is required at step 606. If at step 606, the base processor 162determines that an action is required 618, the processor proceeds to determinewhich action is required (see Fig. 19a): hand unit introduction in progress 620,pressure needs to be read 622, adjustment in progress 624, adjustment request ispending 626. A hand unit introduction procedure can be initiated by arecognized hand control unit 42 whenever the base unit 44 is not busy with anadjustment. The procedure can be initiated by any hand control unit 42 duringthe first 256 secs, after the base unit 44 is powered on.

Referring to Fig. 23b, when the base unit 44 receives the first handunit introduction message, the base processor 162 rewrites the ID list 628 tocontain only the ID of the sender hand control unit 42. Then, the base unit 44sends an acknowledgement 630 that is transmitted 631 to the hand unit 42. Thebase processor 162 sets a timer 632. The base processor 162 monitors the timer for 34 -35- one minute to determine 634 if a second hand unit introduction message isreceived. If no other messages are received within this minute, the baseprocessor 162 concludes that there is only one hand control unit 42, sends amessage 636 to return to normal operation that is transmitted 637 to the handcontrol unit 42, and the base processor 162 ends the hand unit introductionprocedure and returns to the main loop 606.

When the base unit 44 receives a second hand unit introductionmessage within one minute of the first, the base processor 162 determines 638 ifthe ID is the same as the first ID received. If the second ID is different, the baseprocessor 162 adds the second ID to the list of IDs 640. Then, the base unit 44sends a message 642 that is transmitted 643 to the second hand control unit 42. Ifthe second message originated from the same hand control unit 42 as the firstmessage, the base unit sends a message 644 that is transmitted 645 to the handcontrol unit 42 acknowledging that there is only one hand control unit 42. Ineither case, after a couple of seconds, the base unit sends a message 646 that istransmitted 647 to the one or to both units to return to normal operation.

The pressure is read every 30 seconds if no adjustment is takingplace. As described below, the pressure is also read every 3 seconds during anactive adjustment. Note that during an active adjustment, the hand control unit42 sends a request for the pressure every 10 secs, while continuing to display theflashing target pressure. At each request, the base unit 44 transmits to the handcontrol unit 42 the last pressure read as in step 612. Referring to Fig. 23c, to readthe pressure, the base processor 162 first closes 648 the valves 338, 340 if necessary. 35 -36-

Three seconds are allowed to pass 650 to let the pressure in the air bladders 30, 32to stabilize. The base processor 162 then initiates the analog-to-digital (A/D)conversion 652 of the output of the pressure sensors 156, 158. Then, the baseprocessor 162 waits 0.1-0.2 second 654 before calculating the pressure 656 from thedigitized reading. The pressure is obtained from the following formula:

Pressure = Gain * (Reading - Offset) where the Gain and the Offset are determined when the unit is calibrated duringmanufacture or service. The values for Gain and Offset are stored in the baseprocessor's memory. The calculated pressure is stored as a 24 bit number with amaximum resolution of 0.005 psi.

The actual number displayed by the hand control unit 42 can have various relationships to the pressure. It can be an actual expression of the pressure in appropriate units, or it can be a value scaled to some arbitrary and convenient units. This scaling can be linear or non linear. A preferred relationship between the displayed value and the pressure is Hand Controller Value Pressure Value (psig) 00 &lt;0.16 05 0.16 10 0.18 15 0.20 20 0.22 25 0.24 30 0.26 35 0.28 40 0.30 45 0.32 50 0.34 55 0.36 60 0.38 36 -37- 65 0.40 70 0.42 75 0.44 80 0.47 85 0.50 90 0.55 95 0.60 100 0.65

Alternatively, a linear relationship can be used between the displayed value andthe pressure with zero pressure corresponding to a zero display and a maximumpressure of 0.65 psig corresponding to a displayed value of 100.

Referring to Fig. 23d, if an adjustment is in progress, the baseprocessor 162 examines whether the estimated inflation/deflation period hasended 658. If it has not, the program checks to see if 3 secs, have passed since thepressure has been measured. If 3 secs, have passed, the processor measures thepressure 660, as described above. The current pressure is compared with therequested pressure 662. If the calculated pressure is within 0.01 psi of therequested (target) pressure, the base processor 162 returns to the main loop 606since no more adjustment will be undertaken. If the pressure is not within 0.01psi of the requested pressure, the base processor 162 resets a timer to count 3 secs,and returns to the main loop at step 606. As an alternative to checking thepressure every 3 secs, during an active adjustment, the back pressure can bemonitored with the valve 338, 340 open. This back pressure can be correlated bythe manufacturer to correspond to a particular bladder 30, 32 pressure with thevalve 338, 340 closed. Then, the pressure could be checked with the valve 338,340 closed after the termination of the adjustment process to check the final 37 -38- value of the adjustment.

If the estimated inflation/deflation period has ended at step 658, thecurrent pressure is calculated at step 662 by the procedure described above. Next,it is determined if further adjustment is necessary 663. If no further adjustmentis necessary, the base processor 162 returns to the main loop 606. If it isdetermined that further adjustment is necessary at step 663, the base processor162 sets a new adjustment request pending 664, and notes that the previousadjustment overshot 665 before proceeding with the main loop 606.

If the adjustment inflates too much and then deflates too much (orvice versa) three times in a row, the base unit terminates the adjustment, even ifthe current pressure is not within 0.01 psi of the requested pressure. Also, if thebase reads an identical pressure of at least 0.35 psi while inflating a chamber, thebase processor 162 determines that a "stall" condition exists and terminates theadjustment.

To reduce the chance that the motor 152 will overheat, the programfor the base processor 162 implements a thermal model of the motor 152. Themodel assumes the following relationship of the temperature above ambienttemperature with time: T = Tasympt + C e(-kt)

Tasympt is dependent on the motor speed, k has a value of 0.002 when the motoris off and a value of 0.006 when the motor is on. For small steps in time, thisequation leads to the following difference equation: T(n+1) = T(n) + k * At * (Tasympt - T(n)), 38 -39- showing the relationship between the temperature at time n, T(n), and thetemperature at time n+1, T(n+1). When the motor 152 is off, the program uses avalue of At=15 sec. When the motor 152 is on, Δΐ=21 sec.

If the program's thermal model estimates that the temperatureexceeds 170 degrees above ambient temperature, the base processor 162 sets a flagin RAM, turns the motor on at low speed to facilitate cooling and refuses to beginanother adjustment until the estimated (model) temperature drops below 120degrees above ambient temperature. The valve 338, 340 will be closed during thecooling process unless the base processor 162 determines that a useful adjustmentcan be made with the valve 338, 340 open at the motor speed during cooling.When the temperature drops below 120 degrees , the program clears the flag andagain accepts adjustment requests. If the flag is set when the base unit 44 ispowered on, the base unit software initializes the temperature to 170 degreesabove ambient, turns the motor on low speed to facilitate cooling and refuses tobegin an adjustment until the estimated temperature drops below 120 degrees.

Referring to Fig. 23e, when the base processor 162 determines thatan adjustment request is pending, first the current pressure is calculated at step666, as described above. The current pressure is compared with the requestedpressure 668. If the current pressure is within 0.01 psi of the requested pressure,no adjustment is necessary 670, and the program continues in the main loop 606.If the difference is greater than 0.01 psi, it is determined whether inflation ordeflation is necessary at step 672.

If it is determined that inflation is necessary, the base processor 162 39 -40- determines the appropriate motor speed 674. When inflating from pressuresbelow 0.40 psig, the motor is run at medium speed. When inflating from greaterpressures, the motor is run at high speed. The base processor 162 next calculatesan estimate of the required time at step 676 up to a maximum of 256 secs. Also atthis step, the number is stored in an 8-bit counter.

Then, the motorized pump 152 is started at step 678. Whenever theprogram turns on the motor for an adjustment, the motor is started at low speedwith stepwise increases in the speed every two seconds until the required speed isreached. The motor is run at a total of five speeds. Low, medium and high areprimary speeds, i.e. they are used as final target speeds. Low-medium andmedium-high are used only to make the transitions between primary speedsmore gradual and therefore, less audibly annoying. When the motor reaches theappropriate speed, the appropriate solenoid valve 338, 340 corresponding to thecorrect chamber is opened 680. With the adjustment in progress, the programreturns to the main loop 606.

If it is determined that deflation is necessary, the motor speed isdetermined at step 682. When deflating from pressures below 0.40 psig, themotor is off. When deflating from greater pressures, the motor is run at lowspeed. Then, the base processor 162 calculates an estimate of the amount of time684 required for the adjustment up to a maximum of 256 secs. The motor isstarted if necessary at step 686. When the motor reaches the appropriate speed,the appropriate solenoid valve 338, 340 corresponding to the correct chamber isopened at step 688. With the adjustment in progress, the program returns to the 40 -41- main loop 606.

When the base unit 44 is inflating an air chamber 30, 32, it reads thepressure about half a second after the valve is opened to measure the backpressure. Waiting a half second is necessary to obtain a stable back pressure 5 reading. If the base processor 162 calculates a pressure of less than 0.15 psi, itdetermines that the base unit 44 is not connected to an air bladder 30, 32 andterminates the adjustment. 41