US2200657A

US2200657A - Refrigerant compressor control

Info

Publication number: US2200657A
Application number: US238613A
Authority: US
Inventors: Burton E Shaw
Original assignee: Penn Electric Switch Co
Current assignee: Penn Electric Switch Co
Priority date: 1938-11-03
Filing date: 1938-11-03
Publication date: 1940-05-14
Anticipated expiration: 1957-05-14

Description

B. E. SHAW REFRIGERANT COMPRESSOR CONTROL May 14, 1940.

Filed Nov. 5, 195a 3 INVENTOR.

ATTORNEY .5

Patented May 14, 1940 UNITED STATES PATENT OFFICE.

Burton E. Shaw, Bristol, Ind., assignor to Penn Electric Switch 00., Goshen, Ind., a corporation of Iowa Application November 3, 1938, Serial No. 238,613

6 Claims.

An object of my present invention is to provide a control structure particularly adapted for the control of refrigerant systems wherein it is desirable to compensate the control for ambient temperature.

A further object is to provide means to compensate the control for ambient temperature in such fashion that the compensation is effective below a predetermined degree of ambient temperature and ineffective when the ambient temperature is above such predetermined degree.

A further object is to provide a compensator which is responsive to ambient temperature and which is so designed and associated with control 5 operating mechanism that it is ineffective for the purpose of compensation when the ambient temperature is above a predetermined degree; is effective only on the cut-out operation of the control when the ambient temperature is adjacent said predetermined degree, and is effective on both the cut-in and cut-out limits of the control when the ambient temperature recedes to below the predetermined degree, the cut-in and cut-out points thereafter being compensated in proportion to the degree of drop in temperature.

With these and other objects in view, the features of my present invention which I believe to be novel and patentable will be pointed out in the claims appended hereto. For a better understanding of the invention in detail, reference is made to the following description and to the accompanying drawing, in which Figure l is a front elevation of a refrigerant compressor control embodying my invention with the cover removed from the casing, portions of the structure shown in section and the refrigerant system and circuit of the motor thereof being shown diagrammatically;

Figure 2 is a diagrammatic view showing normaloperation of the control structure when the ambient temperature is above a predetermined degree;

Figure 3 is a similar diagrammatic view showing the position the parts assume when ambient temperature is adjacent the vpredetermined degree';

Figure 4' is a similar diagrammatic view showing the position of the parts when ambient temperature is below the predetermined degree, and

Figure 5 is a graphical view showing the operation of the control.

On the accompanying drawing I have used the reference numeral ID to indicate a control housing. A pivot pin I2 is supported therein by a bracket I3. A bell crank lever having arms l4 and I5 is pivoted on the pin l2.

A supporting bar "5 has mounted thereon a bracket ll. The bracket l'l carries stationary contacts l8 and I9. Another bracket mounted on the bar IS supports a pivot pin 2|. A switch arm 22 is pivoted thereon and-has an armature portion 23. Movable contacts 24 and 25 are carried by the switch arm 22 for coaction with the contacts l8 and l9 respectively.

A permanent magnet 25 is mounted on the bar it by the bracket ll. Terminals 26 and 21 are electrically connected to the bracket I1 and the switch arm 22. These are included in the circuit of a motor M.

The motor M is provided for driving a refrigerant compressor RC. The refrigerant system further includes a condenser C, an evaporator E and high and low sides of the refrigerant line at 28 and 29 respectively. A bulb ll controls the expansion valve V in the usual manner. The bell crank lever l4l5 is connected to the switch arm 22 by an extension 30 connected with arm l5 and links 3! and 32. The upper end of the link 32 is pivoted to the switch arm 22.

For automatically controlling the bell crank lever I provide a bellows housing 33 and a bellows 34 mounted therein. A stem 35 is connected with the head of the bellows 34 and engageable with arm M of the bell crank lever to rotate the lever clockwise upon an increase in pressure against the bias of a range-adjusting spring 35**. The tension of the spring 35 is adjustable bya threaded rod 36 entering a nut 3'! mounted in the upper end of the spring 35 secured to the rod 36 for rotating it. The bellows housing 33 is connected by a line 39 with the low pressure side 29 of the refrigerant system.

In connection with the foregoing described con trol structure, I provide a novel compensating means which will now be described. A bracket 40 is mounted in the housing It and carries a pivot pin 4|. A lever 42 is pivoted thereon and is retained in a counterbalanced position by opposing forces. The opposing forces are supplied by a spring 43 ten-ding to rotate the lever 42 counterclockwise and a bellows 44 tending to rotate it clockwise. The bellows 44 is contained in a housing 45 which is responsive to ambient temperature and may contain a charge of ether or the like, whereby an increase in ambient temperature surrounding the housing 45 tends to collapse the bellows 44. A stem 46 extends upwardly from the head of the bellows and coacts with the lever A knob 38 is tin 42. The tension of the spring 43 may be adjusted by a screw 41. Engagement between the lever 42 and the arm it of the bell crank lever occurs at certain times. The engagement is with a set screw 48 carried by the lever 42 so that the position of engagement can be varied as desired. A look nut 49 isprovided to retain the adjustment after once made.

Practical operation Referring to Figure 5, a winter cycle of operation is shown by lines a and b. This may be the normal operation disregarding the compensating bellows 44. Likewise, a normal summer operation is indicated by the lines 0 and d. It will be noted that the winter cycle is shorter than the summer cycle. In certain installations this long summer cycle is satisfactory, but it is desirable to lengthen the winter cycles and also lower the cut-in and cut-out points. The normal cut-in and cut-out points are indicated by the lines CI and CO.

It is very desirable, from the standpoint of efilcient operation, to eliminate sliming of the evaporator coils in the winter time and also to prevent dehydration of the contents of the refrigerated space in the summer time. This is particularly desirable in connection with meat which might be purchased with an eighty per cent water content and the content can reduce to sixty per cent if the air in the refrigerated space is comparatively dry.

Sliming in the winter time is caused by an absence of adequate air circulation in a refrigerated space. This results in sliming because there is practically no dehydration taking place, whereas it is desirable to have some dehydration to avoid sliming. Also high temperature moisture from the outside, when the door opens, increases the tendency to sllming. By lowering the cut-in and cut-out points in proportion to the lowering of outside temperature below eighty degrees or thereabouts, the temperature of the refrigerated space is pulled somewhat lower and I have found that this accomplishes the desirable result of eliminating slime.

On the other hand, long periods of operation in the summer time result in a lower temperature of the evaporator coil and consequently result in dehydration and low humidity but a good air circulation. This air circulation causes excessive hydration and consequently undesirable shrinkage of the products in the refrigerated space. Accordingly, by setting the control so that the desired operation is secured in the summer time, or above eighty-five degrees or thereabouts, the compensator 44, 45 and 46 can take care of what would be an otherwise undesirable operation when the ambient temperature goes below eighty degrees.

In Figures 2, 3 and i, I have shown the bellows 34 and 44 as P and '1 respectively indicating a'pressure-responsive device and a temperature-responsive device. In the summer time when the ambient temperature exceeds a pre determined degree (such, for example, as 85), ambient temperature causes the bellows 4d to be compressed to such a point that the set screw it! is retained spaced from the arm it of the bell crank lever during its entire range of movement between cut-in and cut-out positions, as shown in Figures 1 and 2 respectively. This arrangement accordingly secures the desirable results of normal operation of the pressure-responsive controller during the summer time. When ambient temperature is adjacent the predetermined degree such, for instance, as between and the bellows 44 is so expanded that the set screw 43 will contact with the arm l5 while the arm moves between an intermediate position and cut-out position, as shown by solid lines in Figure 3. As it moves from intermediate position to cut-in position, however, the arm l5 will leave the set screw. This is shown by the lines e and f in Figure 5 and a new cut-out point CO This obviously will lengthen the cycle of operation somewhat, whereas the normal cycle would be according to the lines e and Q.

As the ambient temperature further decreases as, for instance, to a point below 80, the set screw 43 will contact with the arm l5 continuously as shown in Figure 4. This will effect lowering of both the cut-out and cut-in points as indicated at C0 and C1 in Figure 5. A further reduction in ambient temperature will cause still more lowering of the cut-in and cut-out points as indicated at C]? and CO whereby compensation after the ambient temperature has reduced to below 80 will be in proportion to the ambient temperature.

From the foregoing it is obvious that the desirable results of no compensation above a predetermined ambient temperature; compensation for the cut-out point only at adjacent the predetermined ambient temperature, and compensation for both cut-in and cut-out points when ambient temperature is below the predetermined degree, is bad. Compensation of this character is made possible by a very simple arrangement of the counterbalanced bellows 44 and spring 43,

selected, of course, as to size and tension respectively so that the desired type of compensation is secured for any desired ambient temperature at which the cut-out point only of the control is to be modified and there is to be no modification of both the cut-inand cut-out points when ambient temperature is below the predetermined degree.

Any desired amount of compensation can be secured by relative changes in the parts of the compensating mechanism. The charge of gas or liquid in the bellows chamber 45 can be changed in character or volume to secure the desired results, or the change in tension per unit of expansion of the spring 43 may be varied by difierent sized springs. Another way of accomplishing a different degree of compensation is by changing any one of the leverage points at 4!, 46, 43 and 48, or by diiferent combinations of changes of the points with relation to each other.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention together with one embodiment thereof which may be considered as representative, but I desire to have it understood that the embodiment shown is only illustrative and that the invention may be carried out by other means coming under the scope of my claims.

I claim:

1. A refrigerant compressor control comprising switch mechanism in circuit with a refrigerant compressor motor, means responsive to pressure in the low side of a refrigerant system for normally actuating said control between predetermined cut-in and cut-out positions and means to modify the action of said first means comprising means responding to ambient temperature and coacting with said first means to permit normal operation thereof upon ambient temperature above a predetermined degree affecting said means responsive to temperature; to lower the cut-out pressure thereof upon ambient temperature appro'. ching said predetermineddegree and to lower the cut-in and cut-out pressures thereof upon ambient temperature dropping below said predetermined degree.

2. A refrigerant compressor control comprising switch mechanism for a refrigerant compressor motor, means responding to the condition of the refrigerantsystem for normally actuating said switch mechanism between cut-4n and cut-out positions and means responding to ambient temperature and coacting with said first means to permit normal operation thereof upon the ambient temperature rising above a predetermined degree; to lower the cut-out point only thereof upon the ambient temperature decreasing to a point adjacent said predetermined degree and to lower both the cut-in and cut-out points upon the ambient temperature decreasing below said predetermined degree.

3. A control for refrigerant compressors com prising control mechanism, a lever operable through a given range to move said control mechanism between cut-in and cut-out positions, condition-responsive means responding to pressure in the low side of the refrigerant system for moving said lever through said range, a second lever engageable with said first lever, ambient temperature-responsive means and a spring opposing each other and connected with said second lever, to position said second lever spaced from said first lever throughout the range of movement of the first lever upon the temperature-responsive means responding to ambient temperature above a predetermined degree; to engage the secondlever with the first lever upon movement of the first lever from an intermediate to a cut-out position when the ambient temperature is adjacent said predetermined degree and to engage the second lever with the first lever continuously throughout the range of movement of the first lever when the ambient temperature is below said predetermined degree.

4. A control for refrigerant compressors comprising control mechanism, a lever operable through a given range to move said control mechanism between opposite cut-in and cut-out positions, condition-responsive means responding to the refrigerant system for moving said lever through said range, a second lever engageable with said first lever, ambient temperature-responsive means and a spring opposing each other and connected with said second lever, to position said second lever to engage the first lever upon movement of the first lever from an intermediate to one of its opposite positions upon said ambient temperature-responsive means responding to ambient temperature adjacent a predetermined degree, and to respectively space said second lever from said first lever throughout the range of movement of the first lever and engage the second lever with the first lever continuously throughout the range of movement of the first lever when the ambient temperature departs in opposite directions from said predetermined de gree.

5. A refrigerant compressor control comprising control mechanism for a refrigerant compressor, means responding to the condition of the refrigerant system for normally actuating said control mechanism between cut-in and cut-out positions and means responding to ambient temperature and coacting with said first means to permit normal operation thereof while the ambient temperature remains in one predetermined range and to modify the operation to cause it to depart from normal operation in proportion to a change in the ambient temperature upon departure of the ambient temperature from said pre= determined range.

6. In a refrigerant compressor control, means responsive to pressure in a refrigerant system for normally actuating said control between predetermined cut-in and cut-out positions and means to modify the action of said first means comprising means responding to ambient temperature and coacting with said first means to permit normal operation thereof upon one ambient temperature affecting said means responsive to temperature; to alter the cut-cut position thereof upon another ambient temperature aifecting said means responsive to temperature and to alter both the cut-in and cut-out positions thereof upon still another ambient temperature affecting said means responsive to temperature.

BURTON E. SHAW.