US2204951A - Refrigerant compressor control system - Google Patents

Description

June 18, 1940. B. E. SHAW REFRIGERANT COMPRESSOR CONTROL SYSTEM Filed July 5, 1938 IJVIIIIIII Patented June 18, 1940 REFRIGERAN T COMPRESSOR CONTROL SYSTEM Burton E. Shaw, Bristol, Ind., assignor to Penn Electric Switch 00., Goshen, Ind., a corporation of Iowa Application July 5, 1938, Serial No. 217,434

An object of my invention is to provide a re- 13 Claims.

frigerant compressor control system including a control switch of simple and inexpensive construction adapted to control a refrigerant combe widened in either the cut-in or cut-out direction, a change from one type of operation to the other being readily effected in 15 the field.

Another object is to provide a refrigerant compressor control system including a switch and means associated therewith for compensating for ambient temperature, thus eliminating the necessity of a service man resetting the switch twice a year for summer or winter temperatures to secure satisfactory operation.

Still another object is to provide a switch structure in which the differential of operation can be adjusted from outside the casing of the switch and to provide a switch which necessitates the use of only a very light range adjusting spring v so that the casing of the switch can be made of relatively light sheet metal.

Although the invention is susceptible of a vari- 30 ety of embodiments, it is unnecessary to fully describe and illustrate more than one in order to give a full understanding thereof both from its structural and functional standpoints.

Accordingly, I have illustrated a preferred and desirable embodiment of the invention in the accompanying drawing forming part of this specification and throughout the views of which like reference characters refer to the same parts.

In said drawing:

Figure 1 is a front elevation of a refrigerant compressor control switch used in my system and illustrated as hooked into the system diagrammatically, parts of the structure being broken away and other parts being shown in section.

Figure 2 is a sectional view on the line 2-2 of Figure 1.

Figure 3 is a sectional view on the line Figure 1.

Figure 4 is a perspective view of a range adjusting means for my control system.

Figure 5 is a sectional view on the Figure 3.

line 5-5 of Figure 6 is a similar sectional view showing certain parts of the structure in Figure 3 reversed for affecting the cut-out point rather than the cut-in point of the switch; and

Figure 7 is a perspective view of the upper end of a link used in my structure to accomplish an ad justment thereof which will hereinafter be fully set forth.

On the accompanying drawing I have used the reference numeral 10 to indicate a switch housing. In the housing 10 a bell crank 12 is pivoted at 13. A bellows I4 is operatively connected with one arm of the bell crank 12 by a pin [5 urged to engage the'arm by a spring 16. The spring i6 has one end seated on a stationary sleeve 16a and its other end engaging a flange a on the pin IS. The bellows I4 is enclosed in a housing I1 having a connection 18 with the suction line IQ of a refrigerant compressor 20. The refrigerant compressor 20 is driven by a motor M and is connected in the usual manner of a mechanical refrigerating system with a condenser C and an evaporator E. g

The other arm of the bell crank 12 carries a leaf spring 2|. The leaf spring 21 is connected with a link 22 by a pivot screw 2la. A rod 23 is threaded in the link 22 for adjustment relative thereto. The upper end of the rod 23 as shown in Figure '1 is provided with a reduced portion 24 and an oval shaped head 25. The reduced portion 24 is adapted for travel in a slot 26 of a plate 21. The reduced portion 24 constitutes an actuating traveler in the slot.

An adjusting traveler 28 is mounted in the slot 'for adjusting the effective length of the slot. Adjustment thereof is effected by a threaded screw 29 retainedagainst longitudinal movement and journaled in the plate 21. The screw 29 is threaded through the traveler 28 and the head of the screw may be conveniently engaged by a screw driver exterior of the casing ID by extending the screw driver through an opening 30 therein. An insulating bushing 3| lines the opening 30 to prevent any electrical contact of the screw driver with the casing 10 which is ordinarily grounded, whereas the plate 21 is carried by a switch arm 32 and thereby connected in an electric circuit through the switch.

The plate 21 is formed as a part of the arm 32 which is pivoted at 33. A spring 33a surrounding the pivot pin 33 acts to bias the arm 32 upwardly. The arm 32 is an armature coacting with a permanent magnet 34. The pivot 33 is supported by a bracket 35 on a supporting bar 36 preferably formed of insulating material. The magnet 34 is also supported on the insulating bar as by a screw 31.

Stationary contacts 38 and 39 are carried by a bracket plate 40 which is electrically connected with a terminal screw 4|. A second terminal screw 42 is connected as by flexible pigtail connection 43 to the switch arm 32. The switch arm carries contacts 44 and 45 to coact with the stationary contacts 38 and 39. The terminals 4| and 42 are connected in the supply circuit of the motor M.

Opposing the spring I 6 is a range adjusting spring 44, It is connected with one of the arms of the bell crank it and with a nut 45'. A range adjusting screw 48 is threaded in the nut 45 and has an adjusting knob 41 exterior of the casing ID. The knob 41 may be manually rotated and will be retained in any position to which it is rotated by a radially extending rib 48 adapted to one of a plurality of radially extending grooves 49. The grooves 49 are formed in the casing If) as shown in Figure 4.

I provide a temperature compensating bellows 50. The bellows 59 is operatively connected with the bell crank i2 by a pin The bellows 50 is biased toward expanded position by a spring 52. The bellows 56 is mounted in a housing 53 filled with a vapor 54. This vapor is preferably that of the refrigerant used in the suction line H! of the refrigerant compressor system. Expansion of the vapor caused by ambient temperature warming up the casing 53 results in a tendency to collapse the bellows 5|). By using a vapor of the refrigerant or" the system controlled by the switch, it has been my experience that accurate and most satisfactory compensation for ambient temperature is secured.

Practical operation My refrigerant compressor control system is particularly adapted for such cooler boxes as the walk in type of cooler used in butcher shops and the like. In general, air temperatures vary largely in such boxes where the controller for the refrigerant compressor is operating from the suction pressure and is located remote from the box. The running time becomes greatly shortened in the winter and increased in the summer due to ambient temperature being lower in winter than summer, This results in poor circulation or" the air in the cooler in the winter time because such circulation thereof is dependent on a difference in temperature between the evaporating coil usually mounted high in the box and floor temperatures. if the running time is reduced, the difference in temperatures is reduced and hence poor air circulation results. This causes sliming of meats.

Conversely in the summer, the operating cycle is longer due to higher ambient temperatures surrounding the controller and thereby increasing the pressure in the bellows housing ll". Although this results in good circulation of the air in the box, it also results in excessive icing or frosting oi the evaporator coils. This is detrimental to the proper operation of the system. It means inefficiency, excessive moisture, excessive running time and poor operation generally.

Accordingly it has been standard practice among many control dealers to have a service man make a late fall visit to lower the suction cut-in and cut-out points for proper operation and a late spring call to properly increase the cut-in and cut-out points, thus securing to some degree a manual compensation for the variations in ambient temperatures in winter as compared to summer. By using the compensating bellows 50, the compensating job is done automatically and also compensation is had in proportion to the rise or fall of temperature in any season of the year. The bellows 50 functions to maintain the differential between the low side and high side of the compressor system at some substantially constant limit. If the limit exceeds this amount, the switch opens.

During the opening operation, a reduction in pressure in the line l8 permits the spring 44 to pull upwardly on the horizontal arm of the bell crank l2. This motion is imparted through the leaf spring 2| to the link 22 causing the reduced portion 24 thereof to move upwardly in the slot 26. When the portion 24 reaches the upper end of the slot, it will cause the bracket 21, and the armature 32 to move upwardly after sufiicient tension has been built up in the spring 2| to overcome the pull of the magnet 34 on the armature.

As soon as the armature starts moving, the armature will immediately be in a weaker magnetic field and, aided by the spring 33a, will snap upwardly to its open position and finally be stopped in such position by the end of the arms.- ture striln'ng an insulated lining |||a in the top of the casing H1. The spring 33a is of just sufllcient tension to cause such movement of the armature and retain it in open position yet permit the magnet 34 to close and retain the switch closed whenever it is returned to adjacent closed position. Accordingly after the armature is started on its movement toward either the cutin or cut-out position, the magnet or the spring will cause completion of such movement. Such completion will be permitted due to the lost motion in the connection 24--28 or if the adjusting traveler 28 has been adjusted to take up all lost motion (thereby decreasing the range of the switch to its minimum) the leaf spring 2|, by bending, will permit a degree of such additional movement sufiicient to insure a quick break of the circuit.

Reversely when the switch closes, due to an increase in the pressure against the bellows H, the armature 32 will be pulled downwardly against the tension of the spring 33a after the lost motion has been taken up at the connection 24-26. As soon as the armature is in a strong enough magnetic field, the magnet will overcome the tension of the spring 33a and close the switch as permitted by the lost motion connection. Here again, if the differential of the switch has been adjusted to minimum, the spring 2| will permit quick make of the circuit.

In some installations it is desirable when the differential is widened, to widen it on the cut-in side while in others it is desirable to widen it on the cut-out side. This is accomplished by having the adjusting traveler 28 eilective to lengthen the slot or shorten it as desired and the actuating traveler 24 capable of being positioned either above the traveler 28 as in Figure 3 or below it as in Figure 6. The screw Zia connecting the spring 2| to the link 22 is readily removable whereupon the link 22 can be swung to a position with the elongated head 21 of the actuating traveler 24 in alignment with the slot 28 whereupon the rod 23 can be disassociated from the slot and reassociated therewith on the opposite side of the traveler 28. Thus a change from widening the differential of operation in the cut-in direction to the cut-out direction or vice versa can be easily and readily effected in the field.

My arrangement of parts also enables the use of a relatively light range adjusting spring 44' so that the casing Hi can be fabricated of relatively light sheet metal instead of having to be of sufficient thickness to withstand the strains of a heavy spring particularly one for thrust rather than tension as illustrated.

Some changes may be made in the construction and arrangement of the parts of my device without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims, any modified forms of structure or use of mechanical equivalents, which may be reasonably included within their scope.

I claim as my invention:

1. In a refrigerant compressor control system, means responsive to the suction pressure of a motor operated refrigerant compressor, a switch in circuit with the motor thereof, said switch including an armature, means for limiting the movement thereof, a magnet for attracting said armature, a spring urging said armature away from said magnet and a lost motion connection between said suction pressure responsive means and said armature to widen the differential of operation of said switch, said lost motion connection comprising a slot and an actuating traveler therein, an adjusting traveler in said slot to change the effective length thereof, said actuating traveler being positionable in said slot on either side of said adjusting traveler to widen said differential of operation in either the cutin or cut-out direction of movement of said suction pressure responsive means, the connection between said suction pressure responsive means and said armature including a leaf spring permitting additional movement ofsaid suction pressure responsive means after said actuating traveler has reached the end of its slot, said actuating traveler has actuated said armature and the movement of the armature has been limited by said limiting means.

- 2. In a refrigerant compressor control system, means responsive to the suction pressure of a motor operated refrigerant compressor, a switch in circuit with the motor thereof, said switch including an armature, a magnet for attracting said armature, a spring urging said armature away from said magnet and a lost motion connection between said suction pressure responsive means and said armature to widen the differential of operation of said switch, said lost motion connection comprising a slot and an actuating traveler therein, an adjusting traveler also therein to change the effective length of said slot, said actuating traveler being positionable in said slot on either side of said adjusting traveler to widen said differential of operation in either the cut-in or the cut-out direction of movement of said suction pressure responsive means.

3. In a refrigerant compressor control system, means responsive to the suction pressure of a motor operated refrigerant compressor, a switch in circuit with the motor thereof, and a lost motion connection between said suction pressure responsive means and said switch to widen the differential of operation of said switch, said lost motion connection comprising a slot and an actuating traveler therein, an adjusting traveler also therein to change the effective length of said slot, said actuating traveler being positionable in said slot on either side of said adjusting traveler to widen said differential of operation in either the cut-in or the cut-out direction of movement of said suction pressure responsive means.

4. In a control system, an automatic switch comprising pressure responsive means, a switch arm, an operative connection between said pressure responsive means and said switch arm including a slot and an actuating traveler therein effective to widen the differential of operation of the switch arm, an adjusting traveler in said slot adapted to change the effective length of said slot, said actuating traveler being selectively positionable in said slot on either side of said adjusting traveler to secure widening of said differential of operation in either the cut-in or cutout direction of movement of said pressure responsive means.

5. In an automatic switch, pressure responsive means, a switch arm, an operative connection between said pressure responsive means and said switch arm including a slot and an actuating traveler therein effective to widen the differential of operation of the switch arm, an adjusting traveler in said slot adapted to change the effective length of said slot, said actuating traveler being selectively positionable in said slot on either side of said adjusting traveler to secure widening of said differential of operation in either the cut-in or-cut-out direction of operation of said switch and means to retain said switch arm in either its cut-in or cut-out position when moved thereto until the lost motion of said slot and actuating traveler is taken up by movement of said pressure responsive means in the opposite direction.

6. In a .control system, an automatic switch comprising pressure responsive means, a switch arm, an operative connection between said pressure responsive means and said switch arm including a magnet urging said switch arm toward closed position, a spring urging said switch arm toward open position, said switch arm being retained by said magnet or by said spring in either the closed or open position after movement to such position and a lost motion connection between said pressure responsive means and said switch arm including a slot and an actuating traveler therein effective to widen the differential of operation of the switch arm, an adjusting traveler in said slot adapted to change the effective length of said slot, said actuating traveler being selectively positionable in said slot on either side of said adjusting traveler to secure widening of said differential of operation in either the cutin or cut-out direction.

7. In a control system, an automatic switch comprising pressure responsive means, a switch arm, an operative connection between said pressure responsive means and said switch arm including a magnet urging said switch arm toward one position, a spring urging said switch arm toward the opposite position, said switch arm being retained by said magnet or by said spring in either of said positions after movement thereto by said pressure responsive means and a lost motion connection between said pressure responsive means and said switch arm including a slot and an actuating traveler therein effective to widen the differential of operation of the switch arm, an adjusting traveler in said slot adapted to change the effective length of said slot, said actuating traveler being selectively positionable in said slot on either side of said adjusting traveler to secure widening of said differential of operation in either direction of op eration of said switch arm.

8. In a refrigerant compressor control system, means responsive to the suction pressure of a motor operated refrigerant compressor, a switch in circuit with the motor thereof and having an operative connection with said suction pressure responsive means to control energization of said motor in accordance with the degree of suction pressure and means responsive to the temperature ambient to said control switch to lower the suction pressure to which said responsive means will respond when such ambient temperature is low and to raise the suction pressure to which said responsive means will respond when such ambient temperature is high.

9. In a control system, an automatic control switch comprising suction pressure responsive means, a switch controlled thereby and means responsive to the temperature ambient to said control switch, said last means being mounted in opposition to said first means to lower the suction pressure to which said responsive means will respond when such ambient temperature is low and to raise the suction pressure to which said responsive means will respond when such ambient temperature is high.

10. In a control system, an automatic switch comprising a bellows responsive to the suction pressure of a motor operated refrigerant compressor, a switch controlled by movements of said bellows, a second bellows responsive to ambient temperature, charged with a vapor of the refrigerant in the refrigerant compressor and mounted in opposition to said first bellows whereby an increase in the temperature ambient to said second bellows will compensate for said ambient temperature and cause said first bellows to respond to a higher suction pressure and will cause said first bellows to respond to a lower suction pressure when the ambient temperature is low.

11. In a control system, an automatic switch comprising a bell crank, pressure responsive means acting against one side of one arm thereof to control the position of said bell crank, ambient temperature responsive means modifying the position of said bell crank and opposing said pressure responsive means, a casing having said bell crank mounted therein and pivoted adjacent one corner thereof, a tension spring extending from the other arm of said bell crank at substantially right angles thereto, a threaded rod for varying the tension of said spring and an operating knob for said threaded rod exterior of said casing.

12. In a control system, an automatic switch comprising pressure responsive means, a switch arm, an operative connection between said pressure responsive means and said switch arm including a slot and an actuating traveler therein eilective to widen the differential of operation of the switch arm, an adjusting traveler in said slot adapted to change the effective length of said slot, said actuating traveler being selectively positionable in said slot on either side of said adjusting traveler to secure widening of said difierential of operation in either the cut-in or cut-out direction, said adjusting traveler having an adjusting screw associated therewith, a casing for said automatic switch having an opening therein for gaining access to said adjusting screw for rotating it and a bushing of insulating material mounted in said opening.

13. In a control system, an automatic switch comprising pressure responsive means, a switch arm and operative connection between said pressure responsive means and said switch arm including a slot and an actuating traveler therein effective to widen the differential ofv operation of the switch arm, an adjusting traveler in said slot adapted to change the effective length of said slot, said adjusting traveler having an adjusting screw associated therewith, a casing for said automatic switch having an opening therein for gaining access to said adjusting screw and a bushing of insulating material lining the inner surface of said opening.

BURTON E. SHAW.

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