US2228996A - Refrigeration control apparatus - Google Patents

Description

Jan. 14, 1941.

w. L. M GRATH REFRIGERATION CONTROL APPARATUS Filed April 14, 1959 Cmorngg Patented Jan. 14, 1941 UNITED STATES PATENT OFFICE I 2,228,996 REFRIGERATION CONTROL APPARATUS Application April 14, 1939, Serial No. 267,807

6 Claims.

This invention relates to refrigeration and more particularly to automatic controls there-' for.

The primary object of this invention is to provide an automatic control arrangement for a refrigeration system having a variable capacity compressor or other type of actuating means, this arrangement acting to vary the capacity in steps, and being readily adjustable so that cutin and cut-out points of the various capacity steps can be independently adjusted.

A further object 0f-this invention is the pro? vision of a control arrangement of this type in which the adjusting means is arranged so that adjustment may be made over a wide control range, but which prevents adjustment which would provide an improper control sequence.

Other objects will appear from the following description and the appended claims.

For a full disclosure of this invention, referonce is made to the following detailed description and to the accompanying drawing in which:

Figure 1 illustrates diagrammatically a refrigeration system having a two-speed compressor 25 controlled in accordance with this invention;

Figure 2 is an elevation, partly in section, of llzllgeedsuction pressure refrigeration controller uti- Flgure 3 is a side sectional elevation taken on 80 line 3-3 of Figure 2, and

Figure 4 is an elevation of the exterior of the instrument.

Referring to Figure 1, reference character I indicates a space to .be refrigerated. Within this 85 space may be located an elaporator coil 2 which is separated from :the space by a baiile 3. A fan 4 may be provided for forcing circulation of air from the space over the evaporator coil 2, and this fan may be controlled by a. thermostat 5.

4.0 This thermostat may either stop or start the fan l or modulate its speed in a manner to maintain the desired space temperature.

The evaporator coil 2 forms a part of a refrigeration system having a compressor 6 which 45 is driven by a two-speed electric motor I. The discharge of the compressor 6 is connected by a pipe 8 to the usual condenser coil 9 which in turn is connected to a receiver III. This reoeiver is connected by a liquid line H to an ex- 50 panslon valve iia at the inlet of evaporator coil 2. The outlet of this evaporator coil 2 is con nected by a suction line l2 to the inlet of the compressor 5. This system functions in the usual manner to condense refrigerant in the condenser 8 and to evaporate it within the evaporator 2 thereby causing the evaporator to become chilled.

The electric motor I is of the two-speed type and is provided with terminals l3, l4, and I5. The terminal [3 is connected to a line wire l3a. If power is supplied to the motor 1 through ter- 5 minal I4, this motor will operate at low speed, while if power is supplied to the motor through terminal I5, this motor will operate at high speed. The terminal I4 is therefore a low speed terminal and the terminal I5 is a high speed term minal.

The Operation of the motor I is controlled by a pair of relays l6 and ii. The relay l6 includes a pull-in coil I8 which actuates through an arm-ature l5 a pair of switch arms 20 and 2| which 15 cooperate with contacts 22 and 23, respectively. When the pull-in coil I8 is energized, the armature .I 9 causes switch arms 20 and 2| to be brought into engagement with their respective contacts. However, when .the coil i8 is deenergized, the 20 switch arms 20 and 2i are disengaged from these contacts -by the action of gravity or springs, not shown. The relay H is similar to relay I5 and includes a pull-in coil 24 which actuates switch arms 25 and 25. The switch arm 25 co- 25 operates with contacts 21 and 28 while the switch arm 2-6 cooperates with contact 29.

The line wire 30 is connected to the switch arm 20 of relay l5 and the contact 22 of this relay is connected by wire 3| to the switch arm 30 25 of relay H. The contact 21 of this relay is connected to the low speed terminal ll of motor I by wire 32, and the contact 28 is connected to the high speed terminal l5 by wire 33. It will be apparent that when relay I6 is deenergized, no power can be transmitted to either terminal I4 or l5 due to the switch arm 20 disengaging contact 22. However, when the relay I5 is energized power will then be transmitted to either terminal II or l5 of motor 1, depending upon the position Of switch arm 25 of relay II. If this relay is deenergized, the switch arm 25 engages cont-act 21 thus completing the power circuit to the low speed terminal H for operating the compressor at low speed. Conversely, if relay I1 is 5 energized, the switch arm 25 engages contact 28 for completing .the power circuit through terminal l5 thereby operating the compressor at high speed. The relay l5 therefore determines whetlrer or not the compressor shall operate, and the relay I! determines at what speed the compressor shall operate.

The relays l6 and H are controlled by means of. a suction pressure controller 35. This controller includes a Bourdon tube 36 which is connect- I ed to the suction line |2 by meansof a pipe 31. Referring now to Figures 2, 3, and 4, the Bourdon tube 86 is suitably secured to a casing 88 and rotates a collar 88 which is secured to a shaft 48. This shaft is rotatably mounted in a hollow boss 4| in the back of the instrument housing and in a pacer. 42 which is secured to the housing 38 by means of a screw 48. It will be apparent that change in suction pressure will cause the Bourdon tube 86 to rotate the shaft 48. Thus an increase in suction pressure will cause rotation of this shaft in a clockwise direction as viewedin Figure 2, while a decrease insuction pressure will cause rotation of this shaft in the opposite direction. Mounted upon the shaft 48 by means of a collar 44 is a pointer 45 which extends upwardly and outwardly to the front face of the casing 88 from which'it may be observed through a slot as (Figure 4).

Rotatably mounted upon the spacer 48 are arms 41, 48, 48, and 58. The arm 48 carries an insulation member 5| which carriw a pair of contacts 52 and 58. Attached to the arm 48 is a. forwardly extending arm or extension 55 which extends through a slot 56 in the instrument cover (Figure 4) and which is provided with a pointer 51. It will be apparent that by shifting the point 51 along the slot 56, the angular position of the arm 48 and hence the position contacts 62 and 58 maybe adjusted. The arm 41 carries an insulation member 58 which in turn carries contacts 58 and 68. The arm 41 is also provided with an extension 6| which also extends through the slot 56 and is provided with a. pointer 62. The arm 48 carries an insulation member 68, supporting contacts 64 and 65 and is connected to an extension or pointer 66 which extends through the slot 61 in the front of the instrument cover. Similarly, the arm 58 supports an insulation member 68 carrying contacts 68 and 18. This arm is also provided with a pointer 1| extending through the slot 61. It will be apparent that by adjusting the positions of the pointers 61, 62, 66, and 1|, the positions of the various sets of contacts may be readily and independently adjusted.

Mounted upon the shaft 48 by means of collars 16, 16, 11, and 18 are contact arms 18, 88, 8|, and 82, respectively. The contact arm-18 carries a contact member 63 which is adapted to bridge contacts 58 and 68. Similarly, the contact arm 88 carries a contact member 84 which is adapted to bridge the contacts 52 and 58. The contact arms 8| and 82 are provided with oii'set portions as indicated at for permitting these arms to clear the arms 41 and 48. These contact arms '88 and 8| also carry contact members 88 and 81. Located within each of the hubs or collars 16, 16, 11, and 18 isa spring 88 which is arranged so as to force the arms 18, 88, 8|, and 82 into contact with a stop member 88 attached to the arm 45. This stop member maintains the various contact arms in alignment. It will be appar ent that upon increase in suction pressure from a minimum value, the shaft 48 will be rotated in a clockwise direction as seen in Figure 2 thereby rotating the contact arms 18, 88, 8|, and 82 in this direction. With the various pointers adiusted as indicated, the contact member 84 will first engage contacts 52 and 68 thereby bridging these contacts. Upon increase in suction pressure, the shaft 48 will be rotated further, this action being permitted by the spring or a strain release connection between the shaft 48 and the hub 16. It will be apparent that as the suction pressure increases the contact member 86 will bridge contacts 68 and 18, the contact member 83 will bridge contacts 58 and 68, and the contact member 81 will bridge the contacts 64 and 65 in the order stated. By adjusting the pointers 51, 62, 66, and 1|, the values of suction pressure at which the various pairs of contacts are bridged and unbridged can be readily and independently adjusted.

Referring again to Figure l, the various contacts and contact members are shown displaced from their normal positions in order to appear in this diagrammatic figure. Assuming that the suction pressure rides to a value causing the contact member 83 to bridge contacts 58 and 68, the coil l6 of relay l6 will be energized as follows: transformer secondary 88 of step-down transformer 84, wire 85, wire 86, contact 58, contact member 88, contact 68, wire 81, pull-in coil I8 and wire 88 to secondary 88. This will cause switch arms 28 and 2| to engage their respective contacts. .Engagement of switch arm 28 with contact 22 will complete a circuit to the switch arm 25 of relay l1, and as this relay is now deenergized the power circuit to the motor |1 will be completed through the low speed terminal l4, thereby causing operation of the compressor at low speed. Engagement of switch arm 2| with contact 23 complete a maintaining circuit for coll |8 which is independent of contacts 68 and 68. This circuit is as follows: secondary 83, wire 86, wire 88, contact 52, member 84, contact 53, wire I88, switch arm 2|, contact 23, coil [8, and wire 88 to secondary 83. Due to this holding circuit, the relay l6 will remain energized even though the contact member 88 disengages contacts 58 and 68 upon falling suction pressure. The compressor will therefore remain in operatlon until the suction pressure falls to a point suilicient to cause the contact member 84 to disengage contacts 52 and 53. The arrangement just described therefore places the compressor into operation when the suction pressure rises to a predetermined high value and maintains the compressor in operation until the suction pressure falls to a predetermined lower value. By adjusting the pointer 62, the cut-in value may be varied to whatever value is desired and by adjusting the pointer 51, the cut-out point for the compressor may be likewise adjusted. Due to the pointers 61 and 62 being located in a common slot, it is impossible to adjust the devic to reverse the relative positions of the various contacts. This prevents the device from being adjusted in a manner which would render it inoperative to obtain proper control sequence.

In the event that the load upon the evaporator 2 is such thatit cannot be carried by operation of the compressor at low speed, the suction pressure will increase toa point wherein the contact member 81 bridges contacts 64 and 66. At this time the contact member 86 will have bridged contacts 68 and 18. Due to bridging of the contacts 64 and 66, the coil 24 of relay |1 will be energized as follows: secondary 83, wire 85, wire 86, contact 65, member 81, contact 64, wire "I, coil 24, and wires I82 and 88 to secondary 83. This will cause the switch arm 26 of this relay to engage contact 28 which will-cause the compressor' motor 1 to operate at high speed. Due to engagement of switch arm 26 with contact 28, a holding circuit for coil 24 will be established through contacts 88 and 18 as follows: transformer secondary 88, wire 86, wire 88, wire I88, contact 88, member 88. contact 18, wire I84,

switch arm 26, contact 29, coil 24, and wires I02 and 98 to secondary 93. This will maintain the compressor in operation until the suction pressure falls to a value at which the contact member 86 disengages contacts 69 and 10. As indicated in Figure 1, the position of contacts 68 and may be adjusted so that the cut-out point for relay i1 is close to the cut-out point of the relay I6. Thus when the compressor is placed into operation at high speed, it will continue to operate at this high speed until the suction pressure is reduced substantially to the cut-out point of the controller. This provides for reducing a cycling of the compressor between low and high speeds to a minimum.

Inasmuch as the pointers 66 and TI are located in the common slot 61, these pointers cannot be adjusted in a manner to mix up the positions of the various contacts. This prevents any possibility of the device being adjusted in an improper manner with reference to the control sequence.

From the foregoing it will be apparent that this invention provides a control arrangement for a refrigeration system which varies the speed or capacity of the compressor or other actuating means for the refrigeration system in accordance with the load on the system. It will also be apparent that this arrangement causes the compressor to cycle between off and low speed for light load conditions while causing the compressor to cycle between low speed and high speed for heavier load conditions. It will be seen that provision is made for readily and independently adjusting the various cut-in and cut-out points thereby rendering the control system readily applicable to different refrigerants and also permitting ready adjustment of a given installation so as to provide the desired results. While for illustrative purposes, the invention has been illustrated as applied to a refrigeration system having a thermostatically controlled fan, it will be understood that this control system is of general application and may be utilized in air conditioning work as well as a refrigeration system. Inasmuch as many modifications which are within the scope of my invention may occur to those skilled in the art. I desire to be limited only by the scope of the appended claims.

I claim as my invention:

1. In a refrigeration system, in combination, variable capacity actuating means for said system, a movable device positioned in accordance with pressure within said refrigeration system which tends to vary upon variations in the load on the system, control means assdciated with.said actuating means for varying thecapacity of said actuating means in steps, a first control device actuated by said movable device, connections between said first control device and said control means for rendering said control device capable of initiating operation of said actuating means, said first control device being incapable of placing said actuating means out of operation, a second control device also actuated by said movable device for placing said actuating means out of operation, a third control device actuated by said movable device and connected to said control means for changing the capacity of said actuating means from a low value to a high value, said third control device being incapable of changing said capacity from a high value to a low value, and a fourth control device actuated by said movable device and connected to said control means for changing the capacity of said actuating means from said high value to a low value.

2. In the refrigeration system, in combination, variable capacity actuating means for said system, a movable device positioned in accordance with pressure within said refrigeration system which tends to vary upon variation in the load on the system, control means associated with said actuating means for varying the capacity of said actuating means in steps, a first control device actuated by said movable device, connections between said first control device and said control means for rendering said control device capable of initiating operation of said actuating means, said first control device being incapable of placing said actuating means out of operation, a second control device also actuated by said movable device for placing said actuating means out of operation, a third control device actuated by said movable device and connected to said control means for changing the capacity of said actuating means from a low value to a high value, said third control device being incapable of changing said capacity from a high value to a low value, a fourth control device actuated by said movable device and connected to said control means for changing the capacity of said actuating means from said high value to a low value, and means for independently adjusting 'the relationship between said first, second, third and fourth control devices and said movable device.

3. In a refrigeration system, in combination, variable capacity actuating means for said system, a movable device positioned in accordance with pressure within said refrigeration system which tends to vary upon variation in the load on the system, control means associated with said actuating means for varying the capacity of said actuating means in steps, a first control device actuated by said movable device, connections between said first control device and said control means for rendering said control device capable of initiating operation of said actuating means, said first control device being incapable of placing said actuating means out of operation, a second control device also actuated by said movable device for placing said actuating means out of operation, a third control device actuated by said movable device and connected to said control means for changing the capacity of said actuating means from a low value to a high value, said third control device being incapable of changing said capacity from a high value to a low value, a fourth control device actuated by said movable device and connected to said control means for changing the capacity-of said actuating means from said high value to a low value, means for independently adjusting at least a pair of said control devices, and means associated with said adjusting means to prevent adjustment of said control devices in a manner causing improper control sequence.

4. In a refrigerating system, in combination, variable capacity actuating means for said system, control means associated with said actuating means for varying the capacity of said actuating means in steps, said control means including a first relay and a second relay, a movable device positioned in accordance with pressure within said refrigeration system which tends to vary upon variaiton in the load on the system, a first contact means actuated by said movable device and connected to said first relay for actuating said relay in one direction, said first contact means being incapable of actuating said first relay in the opposite direction, a second contact means actuated sequentially with respect to said first contact means by said movable device, said second contact means being connected to said first relay for causing movement of said relay in said opposite direction, a third contact means actuated by said movable device and connected to said second relay for causing movement thereof in a predetermined direction, said third contact means being incapable of causing movement of said second relay in said opposite direction, and a fourth contact means actuated sequentially by said movable device and connected to said second relay for causing movement of said second relay in said opposite direction.

5. In a refrigeration system, in combination, variable capacity actuating means for said system, control means associated with said actuating means for varying the capacity of said actuating means in steps, said control means including a first relay and a second relay, a movable device positioned in accordance with pressure within said refrigeration system which tends to vary upon variation in the load on the system, a first contact means actuated by said movable device and connected to said first relay for actuating said relay in one direction, said first contact means being incapable of actuating said first relay in the opposite direction, a second contact means actuated sequentially with respect to said first contact means by said movable device, said second. contact means being connected to said first relay for causing movement of said relay in said opposite direction, a third contact means actuated by said movable device and connected tosai'd second relay for causing movement thereby in a predetermined direction, said third contact means being incapable of causing movement of said second relay in said opposite direction, a fourth contact means actuated sequentially by said movable device and connected to said second relay for causing movement of said second relay in said opposite direction, and means for independently adjusting the relationship between said contact means and said movable member.

6. In a refrigeration system, in combination, variable capacity actuating means for said system, control means associated with said actuatin means for varying the capacity of said actuating means in steps, said control means including a first relay and a second rel y, a movable device positioned in accordance with pressure within said refrigeration system which tends to vary upon variation in the load on the system, a first contact means actuated by said movable device and connected to said first relay for actuating said relay in one direction, said first contact means being incapable of actuating said first relay in the opposite direction, a second contact means actuated sequentially with respect to said first contact means by said movable device, said second contact means being connected to said first relay for causing movement of said relay in said opposite direction, a third contact means actuated by said movable device and connected to said second relay for causing movement thereof in a predetermined direction, said third contact means being incapable of causing movement of said second relay in said opposite direction, a fourth contact means actuated sequentially by said movable device and connected to said second relay for causing movement of said second relay in said opposite direction, means for independently adjusting the relationship between said contact means and said movable member, and means associated with said adjusting means to prevent adjustment in a manner causing improper control sequence.

WILLIAM L. MCGRATH.

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