Humidifier

Sept. 5, 1967 w. w. martin 3,339,902

HUMIDIFIER

Filed April 29, 1965 4 Sheets-Sheet 1

<img file="US3339902A_D0001.tif" />

<img file="US3339902A_D0002.tif" />

Sept. 5, 1967

W. W. MARTIN

HUMIDIFIER

3,339,902

Filed April 29, 1965

Sheets-Sheet 2

<img file="US3339902A_D0003.tif" />

<img file="US3339902A_D0004.tif" />

ATTORNEYS

Sept. 5, 1967

Filed April 29, 1965

W. W. MARTIN

HUMIDIFIER

3,339,902

Sheets-Sheet 3

FIG-9 a

JTViOdjj

4£

<img file="US3339902A_D0005.tif" />

INVENTOR.

FIG-10

WARNER W. MARTIN

ATTORNEYS

<td> Sept. 5, 1967</td><td> W. W. MARTIN HUMIDIFIER</td><td> 3,339,902</td>

<td> Filed April 29, 1965</td><td></td><td> 4 Sheets-Sheet 4</td>

FIG-11

<img file="US3339902A_D0006.tif" />

118

FIG-12

<img file="US3339902A_D0007.tif" />

<img file="US3339902A_D0008.tif" />

WARNER W. MARTIN

BY

<img file="US3339902A_D0009.tif" />

ATTORNEYS

3,339,902

Patented Sept. 5, 1967

United States Patent Office

3,339,902 HUMIDIFIER Warner W. Martin, Olmstead Falls, Ohio, assignor to The Lau Blower Company, Dayton, Ohio, a corporation of Ohio

Filed Apr. 29,1965, Ser. No. 451,716

Claims. (Cl. 261—142)

This invention relates to the art of adding moisture to air, and particularly to apparatus for increasing the humidity of an inhabited dwelling.

A large percentage of the homes in use today have steam, hot water, or electric heat, rather than the hot air system, and thus do not lend themselves to the installation of a humidifier directly in the furnace. One answer to this problem has been the portable humidifier which can be moved about the home. However, this type of unit requires frequent filling with water by moving the entire unit to a water outlet and then filling the unit manually. Since the unit is designed to be moved about, the amount of the water which can be stored therein is limited thereby requiring frequent filling to maintain effective operation thereof. The water often splashes about when the unit is moved especially when it is being returned to position after filling, and sometimes water is thrown entirely from the unit to cause damage to rugs, furniture and the like.

Moreover, this portable unit consumes space in the living area of the home and must be connected to an electrical outlet thereby interfering with the maximum utilization of the floor area, as well as providing an obstacle on which children can be injured. Since the unit is portable, no drain connection is provided so that all of the dissolved minerals in the water must be accumulated within the unit itself thereby requiring frequent cleaning to maintain efficiency.

Accordingly, it is an important object of this invention to provide a humidifier which is entirely self-contained and adapted for use independently of the heating system and without the disadvantages set forth above.

Another object of this invention is to provide a high capacity humidifier which is adapted to be permanently mounted in place in such a manner that it consumes a minimum of space, and further provide a humidifier with a substantial area of evaporator material having associated air moving devices which force air uniformly through substantially the entire area of the evaporator material for maximum humidification.

A further object of this invention is to provide a high capacity humidifier of the aforesaid type with apparatus for maintaining the concentration of dissolved minerals in the reservoir below a level at which precipitation will occur, and further to provide an automatic control system to regulate the amount of humidification and the temperature of the air passing from the humidifier.

Another object of this invention is to provide a humidifier which is adapted for mounting between the studs of a wall so that a major portion of the components thereof are disposed within the wall, and further to provide a humidifier of this type with an improved evaporation material and supporting structure therefor which can be removed, cleaned, and replaced in the housing by the average person.

Another object of this invention is to provide a wall mounted humidifier capable of handling a relatively large volume of air without excess air currents and which has a minimum portion of the housing projecting into the room, and further to provide such a humidifier which is quiet and dependable in operation due to the particular arrangement of the various components thereof.

Other objects and advantages of the invention will be apparent from the following description, the appended claims and the accompanying drawings.

In the drawings—

FIG. 1 is a front elevation of the humidifier mounted in a wall;

FIG. 2 is an elevation view of the humidifier with the front cover removed;

FIG. 3 is a plan view of the invention shown mounted in a wall;

FIG. 4 is a top view partially broken and the cover removed;

FIG. 5 is a sectional view along the line 5—5 of FIG. 2 with the media assembly removed;

FIG. 6 is an enlarged fragmentary view showing the idler drum and manner in which the evaporator belt passes in the reservoir;

FIG. 7 is an enlarged view showing the guides for the evaporator belt;

FIG. 8 is an elevation view of the media assembly removed from the housing;

FIG. 9 is a view similar to FIG. 8 showing the opposite side of the media assembly with the reservoir pan and blowers in their relative positions;

FIG. 10 is an enlarged fragmentary view showing the drive mechanism for the evaporator belt;

FIG. 11 is an enlarged sectional view showing the float assembly for the reservoir;

FIG. 12 is an enlarged fragmentary view of the evaporator material; and

FIG. 13 is a schematic illustration of the electrical circuitry.

Referring to the drawings wherein a preferred embodiment of the invention is shown, FIGS. 1 and 3 illustrate the humidifier 10 permanently mounted in an interior or exterior wall 11 between the vertical studs 12 and 13 of a house or other structure which is to have the humidity regulated. Normally, when it is used in a home it will be mounted in a central hallway to enable a free movement of the moisture into the various rooms within the house. Basically, the humidifier 10 includes the inner housing. 14 adapted to be mounted in the wall 11, a cover 15 therefor having the inlet 16 and outlet 17 therein, a blower assembly 18 for moving the air, an evaporator media assembly 19 for adding the moisture to the air, and the reservoir assembly 21 for wetting the evaporator media.

Referring now to the inner housing 14, it consists of a sheet metal shell having solid back wall 22 with a width slightly less than the width between the studs 12 and 13, usually about 14 inches. The side walls 24 and 25 on the housing 14 have a depth slightly less than the distance between the outer surface 26 of the wall 11 and the rear edge 27 of the studs 12 and 13 so that the housing 14 fits easily into any existing conventional structures. The side wall 24 and 25 have outwardly extending flanges 30 (FIG. 4) which are secured to the surface 26 to limit the extent that the housing 14 can be inserted into the wall 11, as well as to cooperate with the cover 15 to define the inlet and outlet passages 32 and 33. The bottom and top walls 34 and 35 of the inner housing 14 extend outwardly beyond the side flanges 30, as seen in FIG. 5, to provide the identical outwardly projecting portions 36 on which the media assembly 19 is secured, as will be seen.

The blower assembly 18 is disposed in the righthand corner of the inner housing 14, as seen in FIGS. 2 and 4, and this assembly includes a pair of the volute shaped housings 40 and 41 with end plates 43 at each end thereof. A plurality of brackets 44 are used to secure the housings 40 and 41 against movement in the inner housing 14. Within each of the housings 40 and 41 is mounted a tangential blower wheel 45 each having the opposite ends 46 and 47 suitably journaled for rotation on the end plates 43 of the housings. The dual output electric motor 51 is disposed between the housings 40 and 41 so that

3,339,902 the driving shafts 53 and 54 thereof can be connected to the tangential blower wheels 40 and 41 for rotating the same at high speed.

The tangential blower wheels 45 cooperate with their respective housings 40 or 41 to cause the air to be drawn 5 into the inlet 55 of the housing, through the spaces between the blades 56 (see FIG. 4) into the interior 58 of the blower wheels 45, and be forced outwardly thereof again through the space between the blades 56 and through housing outlets 60. The blowers can be made jq in substantially any length so· that the inlet and outlet 55 and 60 are not restricted in length as in a typical centrifugal blower. In addition, the inlet and outlet, flow of air therefrom is substantially uniform along the entire length thereof and thus a large amount of air can be 15 moved through these blowers in a uniform flow pattern which is particularly important in this humidifier since the air is directed evenly through the evaporation media, as will be further explained. A typical example of a tangential blower assembly which can be used in this 20 invention is shown and described in United States patent application of Donald D. Kinsworthy, Ser. No. 331,140, filed Dec. 17, 1963, now Patent No. 3,251,540, and assigned to the assignee of this invention.

The media assembly 19 is shown in FIGS. 8 and 9 25 and includes a pair of vertical channel members 63 and 64 which are secured by the brackets 65 on the top and bottom thereof to the outwardly extending portions 36 of the top and bottom walls 34 and 35 of the inner housing 22 by the bolts 66, as shown in FIG. 2. Between 30 these channels is welded a flat sheet metal support 68 which is sufficiently rigid to support the various components of the media assembly, as will be described. The evaporator media is in the form of a resilient flexible belt which is supported by the driving and the idler drums 35 and 72, and the movement of the belt 70 between the two drums is restricted by the guides 74.

Each of the drums 71 and 72 consists of a molded plastic back plate 75 which is frustoconical and has a hub 76 adapted to be secured for rotation adjacent the 40 support 68. The drums have a plurality of axially extending fingers 77 formed integrally at the outer periphery of the back plates 75, and each has a length substantially equal to the width of the belt 70, as shown in FIG. 6. The fingers are spaced apart sufficiently so they 45 present a minimum contact with the belt 70.

As shown in FIG. 10, the driving drum 71 is mounted on the drive shaft 80 of the motor-gear reduction unit 81 which is securely mounted by the bolts 82 on the opposite side of the plate 68. The idler drum 72 is 50 mounted on a shaft 84 which has a radial flange 86 thereon so that the nut 87 can be tightened onto the threaded portion to clamp the shaft 85 to the metal plate 68. The opposite end portion 88 of the shaft 85 passes through the hub 76 in the idler drum 72 and the snap 55 ring 89 prevents the drum from moving in an axial direction on the shaft, and this arrangement allows the drum 77 to rotate freely on the shaft 85.

Each of the guides 74 is secured to the plate 68 substantially in the same manner, as shown in FIG. 7, 60 wherein each of these guides has the projections 92 on the end thereof which pass through the plate 68 and receive the speed fasteners 96 to clamp the guides 74 to the plate 68.

Each of the guides 74 has a plurality of rounded shoes 65 or flanges 97 on the intermediate portion therein so that there is minimum contact between the guides and the evaporation belt 70 to minimize the resistance to movement of the belt. The end flanges 98 on the guides are spaced apart a distance slightly greater than the width 70 of the belt 70 so that they prevent the belt 70 from moving transversely in its path and thus it cannot slide axially on the drive and idler drums 71 and 72. The elongated plastic shields 22a and 68a (FIG. 4) are secured on the inner housing 14 and plate 68 on opposite 75 sides of and coextensive with the belt 70 to insure that any water which runs off the belt 70 will be returned to the reservoir.

The evaporator belt 70 consists of a layer of fiberglass netting 101 having relatively large pores therein which is secured to the outside surface of a layer of open-cell polyurethane foam material 102 having relatively large pores, e.g., a porosity of 8 to 13 pores per lineal inch. The fiberglass netting 101 is used primarily for prohibiting change in the length of the belt 70 which tends to stretch when it comes wetted due to the weight of the water thereon. This netting is secured in place by sewing it along the opposite edges 103 of the belt to the material. By using the fiberglass netting 101 on the outside surface of the belt 70, there is no possibility that the length of the belt will change and thus the disadvantage of the potential stretching is not present in this humidifier. It is within the scope of the invention to use other and different materials in place of the fiberglass netting 101.

The foam material 102 of the belt has numerous irregularly spaced pores or passages therethrough, and this characteristic provides relatively large effective surface area to become wetted when the belt is submerged in water. Another advantage of this material is that the total space consumed by the belt is much less than that of other materials capable of providing the amount of surface area, and the particular porosity is dependent upon the thickness, length, and width of the belt, as well as the rate of air flow therethrough. It is important that the belt not be absorbent since it is not desired to completely saturate the material 102 but only to wet the surface area thereof.

As shown in the greatly enlarged view of FIG. 11, this polyurethane foam material 102 is composed of uniformly distributed interconnecting strands 102a which form a three-dimensional structure of openings or pores, without a covering membrane or surface of the type often found in foam rubber materials. The random arrangement of the pores eliminates straight channels through this material so that air flowing therethrough passes around the individual strands thus creating maximum, contact therewith with minimum of air resistance. Also the flow through the material is uniform throughout so. that there is maximum flow therethrough. While the pores are not precisely the same size, they are predominately within a range of similar sizes so that the air flowing through and moisture added thereto is uniform throughout the surface on which water is deposited and evaporated therefrom for maximum efficiency of the unit.

Due to the flexing which occurs as the belt moves past the guides 74 and around the support drums 71 and 72, as well as the washing which occurs as the belt passes through the reservoir 21 and the purging action of the purge pump (to be described), there is substantially no build up of minerals on the belt 70. This is further aided by the fact that the air entering the inlet 17 is at room temperatures rather than at an elevated temperature as would occur in a furnace unit. The netting 101 is of a mesh size that it offers no substantial resistance to air flow nor does it adversely affect the function of the material 102 as set forth above.

For preferred operation, the air flow through the belt 70, the porosity of the material 102, and the rate of movement of the belt 70 are interrelated so that substantially all of the strands 102a remain wet at all times. As a result, only a portion of the water which wets the belt 70 is evaporated therefrom so that the deposits on the sleeve caused by evaporation are reduced to a minimum since evaporation of some of the water merely concentrates with more dissolved minerals. These solutions are subsequently removed when the belt reenters the reservoir assembly 21 wherein the highly concentrated solutions are washed off.

This polyurethane foam material 102 has a minimum

3,339,902 number of very small pores which will be bridged by a film of water so that the streams of air from the blower have minimum tendency to entrain droplets of water. The direction of movement of the belt 70 is such that the upward travel 70a which emerges from the reservoir 21 is adjacent the blower assembly 18 and thus receives the full impact of the air velocity. If any water bridges the space between the strands 70a within the media so that as the water is picked up by the air stream, it will be deposited as it flows through the downward travel 70/? of the belt which is completely free from such bridging action since the relatively high velocity air has already passed through this portion of the belt. Accordingly, the tendency for droplets of water to be carried into the outlet is substantially eliminated thereby prohibiting the creation of lime dust in the outlet air flow. Also of considerable importance to the invention is the ability of this media material to be cleaned by common household detergents and solvents without adverse effect to the person doing the cleaning or to the material itself. Some mineral deposits do occur especially when the belt sits idle after being in use, and periodic cleaning, e.g., once per year, is a requirement in order to maintain efficiency.

.To remove the media belt 70 from the housing, it is merely necessary to remove the cover 15 and media assembly 19 -from the inner housing 1. The removal of the belt 70 from the support drums is relatively simple in view of the flexibility of the belt 70. Moreover, flexibility of the polyurethane and the netting 101 facilitates removal of the mineral deposits in the innermost pores since the belt 70 can be twisted, etc. The polyurethane foam material and the glass fiber netting will withstand temperatures from 250° F. to —40° F., without substantial adverse effects, and thus the material can be washed to remove the usual deposits therefrom and increase the operative efficiency of the unit.

On the side of the evaporator assembly opposite the blower assembly 18, a U-shaped heating coil 110 is mounted on the. vertical member 63 by the brackets 111 for the purpose of heating the air after it passes through the evaporator belt 70. As seen in FIG. 4, the coil 110 is disposed in the outlet passage 32, so that after the temperature of the air is reduced as it evaporates the water from the media, the coil raises the air to the temperature of the inlet air so that there is no draft of cold air produced in this, humidifier.

At the base of the humidifier assembly 10 is the reservoir assembly 21 which includes a rectangular reservoir pan 115 made of plastic and resting on the bottom wall 34 (FIG. 6). The divider wall 116 separates the main chamber 117 of the reservoir pan 115 from the float chamber 118, and opening 120 is provided in this wall so that the water flows readily between the chambers 117 and 118. An overflow opening 119 may be provided and may be connected to a drain to prevent water from spilling over the edge of the pan 115 in case of failure of the float assembly 122. The float assembly 122 is shown in FIG. 11 and is adapted to have a source of water 124 connected to the valve body 125.

The valve body 125 is securely fastened to the vertical wall 126 of the reservoir pan 115 by the nut 128 and has a longitudinal passageway 130 therein terminated at one end by an orifice 132 on the top side of the body 125. The Styrofoam float 133 is secured at the end of the arm 134 which is pivotally secured on the valve body 125 by the pin 136 so that movement of the air 134 forces the valve member 135 into and out of engagement with the orifice 132 to control the flow of water therefrom. The pin 137 extends through the Styrofoam float 133 and secures it to the -arm 134, and a cover member 138 is provided above the orifice 132 and valve member 135 so that any spray of water is confined to the float chamber 117.

When the water level in the float chamber changes, the buoyancy of the float 133 causes it to rise or fall thereby changing the position of the arm 134 which in turn moves the valve member 135 with respect to the orifice 132 to open or close the orifice 132. The level of the water is thereby regulated to the desired depth within the float 5 chamber 118, and consequently within the main chamber 117 of the reservoir pan 115.

As shown in FIG. 2, a small vibrator pump 140 is mounted on the back wall 22 of the inner housing 14, and the inlet tube 142 extends from this pump into the main j₀ chamber 117 of the pan 115. A suitable drain tube 143 and a syphon break 145 therein leads from the pump to a drain exterior of the humidifier 10, and the pump 140 is wired for operation periodically with the operational time, e.g., 3 minutes every 8 hours, for purging a small 15 amount of the water from the main chamber 117 of the reservoir pan 115 to prohibit the concentration of minerals in the solution from reaching the point at which precipitation will occur. The effect of removing a portion of this water is to lower the float 133, and cause fresh 20 water to be supplied to the main chamber 117 of the reservoir to dilute the concentration of dissolved minerals. The concept of purging the reservoir at preset intervals is described and claimed in the copending U.S. application Ser. No. 451,738, filed Apr. 29, 1965, and as25 signed to the assignee of this application.

The outer cover 15 for the humidifier assembly 10 is best shown in FIGS. 1 and 4 and includes a flat central panel having the projections on either side thereto to define the inlet and outlet passages 32 and 33 and open30 ings 16 and 17 which are covered by decorative grill work.

In addition, the cover has a top surface 145 which encloses this portion of the humidifier and allows the electrical control switches to project therethrough for convenience by the home owner. The outside cover 15 is 35 secured to the inner housing 14 by conventional fasteners (not shown).

Referring now to FIG. 13 wherein the electrical diagram is, shown, the source 150 of electrical power supplies current to the lines 151 and 152, and thus current 40 may be supplied to the heating coil 110 in line 155 when the manual switches 156 and 157 are closed. An adjustable humidistat control 160 and another manual switch 161 are provided in the line 151 so that they control the flow of current to the coil 110, the blower, media and 45 pump motors 51, 81, and 140 in lines 155, 163, 164, and 165, respectively. The pump motor 140 has a timer 166 (FIGS. 1 and 13) in series therewith so that the pump is energized for only a portion of the times that the blower and media motors 31 and 51 are energized, e.g., three 50 minutes per eight hours of operation. The adjustable control 168 for the humidistat switch 160 is provided on the top surface of the cover, as shown in FIG. 3, to vary the amount of moisture added to the air.

To mount the humidifier within a wall it is merely 55 necessary to cut an aperture in the wall between two adjacent studs and extending vertically a distance slightly greater than the height of the inner housing 22. Since the studs are usually on 16 inch centers and have a depth which is usually 3% inches, the opening in the wall readi60 ly receives the inner housing 22 which is secured in place by inserting conventional wood screws through the side flanges 30. The media and reservoir assemblies 19 and 21 are then secured in place as indicated above, and the , water supply is connected to the reservoir assembly. After 65 the electrical power has been suitably connected to the various motors, and a drain line connected to the pump 140, the cover 15 is secured in place thereby closing the safety switch 156 (see FIG. 4) so that the humidifier is then ready for operation. The humidity desired is set on 70 the humidistat control 168, and the switch 161 is closed and the humidifier commences operation and continues so long as the humidity of the air in the inlet passage 33 is below that set on the humidistat.

- The media motor 81 rotates the drum 71 which causes 75 the evaporator belt 70 to move therewith around the idler

3,339,902 drum 72 in an endless path. As a belt passes around the idler drum 72, it is submerged below the water level in the main chamber 117 in the reservoir pan 115 and is thoroughly saturated so that as it moves upwardly toward the drive drum 71 and then downwardly again toward the idler drum, it remains wetted. The additional weight of the water on the material 102 increases the weight thereof, but the belt 70 does stretch due to the presence of the flexible fiberglass netting 101 on the outer surface of the belt 70, which prevents a change in the length thereof without obstructing the operation thereof.

Simultaneously with the movement of the belt 70, the blower assembly 18 is also energized to draw a high volume of air through the inlet passage 33 and to force this air first through the upward travel 70a and then the downward travel 70Z> (FIG. 9) of the belt, and then outwardly of the unit through the outlet passage 32. An important part of the invention resides in the use of the tangential blowers 45 which create an elongated flow of air substantially equal to the length of the belt travels 70a and 70h so that the large volume of air is moved through this belt even though the velocity is comparatively low. Air thus flows through both the upward and downward travels of the belt 70 in a uniform manner so that substantially the same amount of air is flowing through each pore in the material 102. As the air passes through the individual pores and around the strands 102a, it evaporates a portion of the water on each of the strands causing the humidity of this air to be increased. The air passes through the belt 70 twice as it moves through the humidifier thereby increasing the rate of humidification.

Since the flow of air over the large area of the belt 70 tends to move or stretch the belt to the right as viewed in FIG. 9, the guides 74 are provided on the right-hand side of both the upward and downward travels 70a and 70b to resist any tendency of the belt to be moved to the right by the flow of air.

As indicated above, the media motor 81 moves the belt 70 at a speed which is correlated with the flow of air and the porosity of the belt 70 so that the individual strands 102a remain wet at all times. As a result, there is a substantial decrease in the minerals which are deposited on the belt 70 since, as water is evaporated from the strands, the concentration of dissolved minerals in the water on the strands is increased. The strands normally do not become completely dry and thus the minerals remain in solution. When the belt again passes into the reservoir pan 115, the concentrated solution is washed from the strands 102a and replaced thereon with water from the pan 115.

After a period of time the concentration of dissolved minerals in solution in the reservoir pan builds up, and if this build-up were allowed to continue precipitation of the minerals would occur. However, the pump 140 periodically, e.g., once every eight hours, purges the water from the reservoir pan 115 so that the float assembly 122 replenishes this level with a fresh supply of water having a concentration of dissolved minerals substantially less than water which was purged. The result is an elimination of a substantial portion of the minerals without having them deposited thereby eliminating a major trouble area in humidifiers of media types.

There is a small build-up of minerals on the belt 70 due to evaporation which occurs when the movement of the belt 70 is terminated, for example, when the humidity in the surrounding area reaches that set on the adjustable humidistat control 168. When this occurs, the water present on the individual strands 102a of the belt 70 dries and leaves the minerals deposited thereon but subsequent flexing action of the belt removes substantially all of these deposits. In normal use, the belt 70 should be removed and cleaned once per year and this can be easily accomplished by removing the outer cover 15 and the media assembly 19 as described above. The belt is then easily removed from the drums 71 and 72 and washed since it ⁸ can be twisted in order to remove the various deposits thereon.

Since there is a decrease in temperature as the air evaporates moisture from the belt 70, this invention provides the heating coil 110 in the outlet passage 32 to restore the temperature to the air as it leaves the humidifier. Thus there is a total absence of any cold draft from the unit as would otherwise occur. Moreover, since the air flow is carefully correlated with the porosity of the belt 70 there is not sufficient air flow through the individual pores to cause droplets of water to be picked up and entrain into the air leaving the humidifier which would create mineral dust in the outlet air flow as these droplets evaporate.

While the invention has been described as a vertical unit, it should be appreciated that the elongated housing could be mounted at an angle or horizontal without departing from the scope of the invention. Moreover, it is also possible to provide other means of wetting the belt, or to use a longer belt and have more than two vertical travels thereof thus increasing the efficiency of the unit. In addition, although the use of polyurethane open cell foam is preferred, it is possible to use other evaporation material without departing from the scope of this invention.

The invention has thus provided an improved humidifier adapted to be mounted between the studs of a wall in a conventional dwelling. The unit consumes a minimum of space, and is entirely self-contained so that there are no cords or water lines to concern the home owner. The blower assembly provides a uniform flow of air over a substantial length of the belt thereby enabling a large volume of air to have the humidity increased without using high velocity air which would tend to pick up droplets of water from the belt and to dry the belt causing the deposit of minerals thereon. The flexible netting restricts the length of the open-cell polyurethane belt, and the purge pump periodically drains the reservoir pan to further contribute to the effective and highly improved operation of the invention.

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.