Sequence changer

Feb. 25, 1964 _{A D} sullivan 3,122,003

SEQUENCE CHANGER

Filed March 13, 1962

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INVENTOR.

£/?££&gt; D. SULUVAN

BY

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United States Patent Office

Patented Feb. 25, 1964

122 003 . SEQUENCE CHANGER

Alfred D. Sullivan, Dearborn, Mich., assignor to American Radiator &amp; Standard Sanitary Corporation, New York, N.Y., a corporation of Delaware ⁵

Filed Mar. 13,1962, Ser. No. 179,359

Claims. (Cl. 62—157)

This invention relates to control devices, as for example devices which control the operation of refrigerant cir- 10 culating mechanisms in refrigeration machines.

One object of the present invention is to provide an arrangement of control devices which will automatically alternate the operation of the various mechanisms controlled thereby during successive operational cycles. 15

In a particular environmental use of the invention it is an object to provide a control system for a refrigeration f machine wherein the machine is provided with two refrigerant compressors, the control system being operative to alternate the sequence of operation of the compres- 20 f sors during successive refrigerant cycles so that each compressor has approximately the same wear after prolonged service.

A general object of the invention is to provide a sequence altering control which is relatively simple and 25 v/hich requires minimum electrical harness.

Other objects of this invention will appear from the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters desig- 30 nate corresponding parts in the several views.

In the drawings:

The single figure is a schematic showing of a refrigeration machine having one embodiment of the invention incorporated therein. 35

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of ⁴⁰being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring to the drawing there is shown a refrigeration _4gmachine having an evaporator shell 10, a pair of condensers 12 and 14, and a pair of compressors 16 and 18. Each compressor is driven by a power device shown as an electric motor 20 or 22, the arrangement being such that operation of a particular motor causes refrigerant ₅θ to be circulated past an expansion valve 24 or 26, through the evaporator shell 10 and thence into one or the other of the suction lines 28 or 30, depending on which the compressor motors is operating.

In the illustrated machine the evaporator shell is pro- _ggvided with a series of connected water tubes 32 which discharge chilled water into a discharge conduit 34 for use at remote locations (not shown). The general objective is to provide a supply of chilled water in conduit 34 hav, ing a constant temperature, as for example forty-two de- θθ grees. In order to achieve this objective without excessive hunting the mechanism includes two compressor-condensers as shown. When the water temperature in conduit 34 is only one or two degrees above the desired value, one of the compressors is put into operation by low tern- _Ggperature thermostat 40, but in the event that a large demand should raise the temperature of the water in conduit 34 more than one or two degrees above the desired value then the second compressor is put into operation by high temperature thermostat 42. In this way the amount of refrigerant circulated through shell 10 is to a certain extent proportional to the demand for refrigera2 tion such that excessive hunting of the control circuit is avoided.

In order to prevent excessive wear on one or the other of compressors 16 and 18 it is desirable that during successive refrigeration cycles the order in which the compressors begin to operate is reversed, i.e., during one cycle compressor 16 acts as the lead compressor under the control of thermostat 40 and during the next operating cycle compressor 18 acts as the lead compressor. The alternate lead compressor operation is accomplished by the diagrammatically illustrated sequence changing devices designated generally by numerals 36 and 38.

Current is supplied to devices 36 and 38 through the conventional condition responsive thermostats 40 and 42. As shown in the illustrative drawings each thermostat includes a thermostatic bulb 44, a length of capillary tubing 46, a casing 48, and a diaphragm 50 arranged on temperature increase to move switch arm 52 or 54 to the circuit-closed position wherein current from the power line 56 is fed to one or the other of lines 58 and 60. The other power line is denoted by the numeral 62.

Line 60 connects with the terminal 64 and a three-terminal stepping switch having second and third terminals 66 and 68. As shown in the drawing terminal 64 continually contacts the electrically conductive switch element disc 70 which is carried on the rotary non-conductive disc 72. A ratchet 74 is secured to disc 72 so that its teeth are engaged by the operating arm 76. Back and forth movement of arm 76 is accomplished by the armature 78 which may be swingably operably mounted on a pin 77 carried by the base 79. In order to operate the armature 78 there may be provided a solenoid 82, the arrangement being such that energization of the solenoid by current flow in line 60 causes armature 78 to pivot rightwardly about its mounting on pin 77 so as to move ratchet 74 counterclockwise a distance of one ratchet tooth. When solenoid 82 is later de-energized a compression spring 88 moves the armature 78 and arm 76 back to the illustrated positions. A suitable pawl (not shown) may be provided for preventing reverse rotation of ratchet 74.

Sequence changing device 36 is of generally the same construction as device 38, and similar primed numerals are therefore employed for corresponding parts. It will be noted that both solenoids 82 and 82' are energized from line 60 which leads from thermostat 40. Therefore when switch arm 54 is closed both solenoids are energized to move the respective ratchet 74 or 74' counterclockwise one-tooth distance. As soon as permitted by time delay relay 98 current will be fed to one or the other of the compressor motors, depending on the positions of the respective discs 70 and 7Θ'. The respective discs are differently disposed with relation to their associated contacts so that during one operating cycle disc 78' energizes motor 20 while disc 70 energizes motor 22, and during the next operating cycle disc 70 energizes motor 20 while disc 70' energizes motor 22. Each disc constitutes a double throw switch since it is arranged to complete a different circuit in each of its two positions.

Time delay relay 98 as shown in the illustrative drawings comprises a switch arm 180 arranged so that after the low temperature thermostat 40 has supplied current to solenoid S2' the armature 78' operates arm 100 to complete the circuit between lines 97 and 99. The purpose of time delay relay 98 is to delay energization of motors 20 and 22 until after solenoids 82 and 82' have advanced discs 70 and 70' to their new positions at the beginning of each operating cycle.

In one particular environment of the invention thermostat 40 is adjusted so that arm 54 closes when the water temperature in conduit 34 is forty-five degrees and opens when the water temperature drops to forty-two degrees.

3,122,003

High temperature thermostat 42 is arranged so that switch arm 52 thereof closes at forty-six degrees and opens at forty-three degrees. Thus, if there is a moderate demand for chilled water only the thermostatic arm 54 v/ill. be closed, in which event only line 60 will be energized, i.e., line 53 will be a dead line, and no current will flow to cither of the terminals 66' or 68'. Assuming under such conditions that disc 70 is initially in its illustrated position, current from line 60 will energize coils 82 and 82 , whereupon one of tne projections of disc 70 will connect with terminal 68 so that at a suitable lime delay (as.determined by delay means 98) motor 22 will be energized for causing a moderate flow of refrigerant past the expansion valve 26 and into the evaporator shell 10. Motor 22 will continue to operate until thermostat 40 is satisfied, whereupon switch arm 54 will open to interrupt the flow of current to motor 22 and the two solenoids.. Springs 88 and 88' will then reset armatures 78 and 78' to their illustrated positions.

Assume however that, in spite of the flow of refrigerant caused by operation of compressor 18, the temperature of the conduit 34 liquid continued to rise to forty-six degrees or higher. In such event switch arm 52 would close to energize line 58. Current would thereupon be supplied to terminal 65', thence to lines 91 and 92, and thence to motor 29 so that an increased refrigerant flow would take place through shell 10.

On the next call for cooling by thermostat 40 the discs 70 and 70' will be advanced counterclockwise one-tooth distance so that the next projections thereon are engaged with the contacts 6-5 and 68' (as shown). If only thermostat 40 is calling for coolant only motor 20 will be energized, whereas if thermostat 42 should subsequently call for coolant compressor motor 22 would then be energized.

It will be seen that during one cycle compressor 18 acts as the lead compressor to satisfy the low cooling demand, whereas on the next operating cycle compressor 16 acts as the lead compressor to supply the low cooling demand. The lead compressor works for longer periods, and by having the two compressors take turns as the lead compressor the wear on each compressor is made approximately the same. Thus, both compressors last for a relatively long period of time rather than having one compressor wear out prematurely.

The invention may be practiced without using the specific arrangement shown in the drawings. For example, both discs 72 and 72' may be driven from one solenoid-ratchet arrangement, thus dispensing with the extra solenoid-ratchet assembly. If desired a, spring return motor or other power device can be substituted for the illustrated solenoids.

In the illustrated arrangement the sequence changing operation is performed at the beginning of each operating cycle. However the sequence changing operation can if desired be performed at the end of the operating cycle, as by altering the manufactured relationship between arm 76 and ratchet 74.

The drawings show the invention as applied to a refrigeration environment. However it is believed that the invention could have application in certain heating environments. In the appended claims the term “temperature conditioning mechanism” is therefore employed to apply to both cooling and heating mechanisms. The term “condition responsive control device” is used in the claims to denote either the cooling thermostats 40 and 42 or the heating thermostats which would be employed in a heating environment.