US1768557A - Refrigerating apparatus - Google Patents

Description

July 1, 1930. I F. w. ANDREWS REFRIGERATING APPARATUS 2 Sheets-Sheet 1 Filed Feb. 28, 1927 July 1, 1930; w ANDREWS 7 1,768,557

REFRIGERATING APPARATUS- F'iled Feb. 28, 1927 2 Sheets-Sheet 2 To Corn resorfrom Eur va n r Ju 46 QWWMW 3% $5 Wz/M atto'cmgl sure in the low-pressure side of I pressor Patented July 1, 1930 FRANK W. ANDREWS; 0F DAYTON, OHIO, FRIGIDAIRE CORPORATION, A

ASSIGNOR, BY *MESNE ASSIGNMENTS, IO CORPORATION' OF DELAWARE REFRIGERATING APIEARATUS Application filed February 28, 1927. Serial No. 171,486.

This invention relates to refrigerating ap- I paratus of the compressor-condenser-expander type controlled automatically in response to a refrigerating demand.

It is among the objects of the invention to improve the apparatus for controlling such a system, to make the system more reliable in operation, and to reduce the power required to operate it. More specifically it is an object to provide a system in which the control is operated in response to the presthe system and which has means for reventing operation of the control when there is no refrigerating demand. 7

Further objects and advantages ofthe present invention will be apparent from the following description, reference being had to the accompanying drawing, wherein a preferred form of the present invention is clearly shown.

In the drawings Fig. 1 is a diagram of a refrigerating system embodying my invention, an

Fig. 2 is a section of a control valve drawn on an enlarged scale.

The system shown in the drawings includes a compressor 10 and a circuit for refrigerant including a high pressure con- .duit 11, condenser 12, receiver 13, expander 14, and low-pressure conduit 15. The comis driven by any suitable sourceof power, such as a motor 16, started and stopped by a switch 17, which is opened and closed by a pressure responsive device 18 connected to the low-pressure conduit at 19.

When refrigeration is required, the expander is warm, and relatively high pressure exists in the expander and low-pressure conduit 15. This moves the pressure responsive switch to start the motor and drive the compressor to circulate refrigerant, which evaporates in the expander to produce refrigeration in' the well-known manner. "When I suflicient refrigeration has been produced, the expander is' cold and the pressure existing in the expander and in the low-pressure conduit is relatively-low. This permits the pressure responsive device to collapse and open the switch, stopping' the motor.

Thecompressor includes a cylinder 20, piston 21 and crankcase 22 having an inlet 23. The cylinder has a discharge check valve '24: and the piston has an intake valve 25.

On the down stroke the piston travels against the pressure of gas in the crankcase, and the piston valve 25 opens, permitting gas to flow into the cylinder, while on the up stroke this valve closes and the gas is compressed and pushed out through check valve 2 1.

In the system thus far described, two difficulties have been encountered. First, due to leaks in the check valve, the system may operate when there is no refrigerating de- 6 mand. In production it is very difficult to make a check valve which will not leak to a small extent. It has been found that even a very slight leak will allow refrigerant to pass from the high-pressure side of the system .back through the compressor into the low-pressureconduit 15 and evaporator 14 when the compressor is idle, thus building up pressure in the low-pressure side when the evaporator is cold and no refrigeration is required. This pressure will, of course, in time operate the switch to start the motor. Secondly, the power required to start the compressor may be excessive. If, forany reason, the power should be disconnected for any-appreciable time, as when shipping or storing the apparatus, the check valve may leak enough to equalize the pressure in conduits 11 and'15. This builds up pressurein the low-pressure side, which mayeven be of the order of fifteen times its normal operating value. Then, when the compressor is started. the piston must travel against an excessive pressure, which puts additional load on the motor. Usually many strokes of the piston against this heavy load are required on starting, because in practice the volume of the low-pressure side, including crankcase, conduit, and evaporator is many times .the piston displacement. Therefore, i

such an apparatus requires a large motor with high starting torque to meet these conditions.

In order to avoid the difliculties above mentioned, I place a shut-off valve 28, shown ing at its edges-in'any suitable manner, such .close at a pressure,v

in the crankcase,

--in the low-pressure side ounces until it has been as being clamped between the housing 29 and another housing 34 by bolts 35. The inlet 32 is provided with a valve seat 36 which co-operates with the valve 37 to close the conduit. The valve 37 is attached to a stem 38 suitably secured to the diaphragm and urged to open position by a spring 39 placed between a collar 40 and a bushing 41 threaded into the upper end of the housing 34. The pressure within the chamber 30 acting on the diaphragm, tends to close the valve against the force of the spring. The spring tension may be adjusted by screwing the bushing 41 in or out. I also provide a thumb nut 42 threaded on the upper end of the stem and adapted to engage the upper end of the bushing for positively closing the valve 37 and holding it closed when desired, as when shipping a refrigerating unit. A spring 43 serves to prevent this nut from rattling, due to vibrations of the compressor, when operating.

Operation The automatic switch 17 may be set to for example, of 2 pounds per square inch and to open at a vacuum of 8 inches of mercury. The upper side of the diaphragm'in the shut-off valve may be exposed to the pressure of the atmosphere, and by suitably proportioning the area of the diaphragm, tension of the spring, and the length of the valve stem, the valve may be set to close at any desired pressure--- between the operating-limits of the pressure switch. For example, it may be set to close at a pressure of 6 ounces per square inch above atmosphere. Consequently if the compressor and check valve should leak, as soon as a pressure of 6 ounces has been established low-pressure conduit and expander, the valve 37 will be closed and be held closed. Further leaking of the check valve may build up the pressure in the crankcase to the pressure existing in the gh-pressure side of the system which may for example, pounds per square inch, but this pressure can not be established in the conduit and expander, and the pressure will remain at 6 increased by the the motor on starting circuit for warming up of the evaporator. It will thus be seen that the pressure existing in the lowpressure conduit is a true indication of the refrigerating demand and the switch can not start the motor unless there is such demand.

While the pressure in the crank-case'under the conditions just supposed may be as high as 70 pounds, the volume of gas at this pressure which must be moved by the piston on starting is limited to the capacity of the crankcase. This is all removed by relativelyfew strokes of the piston, whereas if the pressure had been allowed to build up in the conduit 15 an evaporator 14, a great many more strokes of the piston would be requlred to reduce the pressure. Since the high pressure in the crankcase continues for only a few strokes of the piston, a high starting torque is required only for a very brief space of time. This materially reduces the amount of power required to drive and permits a small motor to be used.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. Refrigerating apparatus comprising a circuit for refrigerant, including a normally open low-pressure conduit, a pump for circulating refrigerant in the circuit, means responsive to the pressure in the conduit for actuating the pump and means positively preventing the operation of, the actuating means in response to pressure existing in the P P- 2. Refrigerating apparatus comprislng a circuit for refrigerant, includin a low; pressure conduit, a pump for circulating refrigerant in'the conduit, means connected to the conduit for actuating the pump in response to pressure within the conduit and means for automatically closing the conduit between the pump and point of connection of the actuating means when the pressure in the conduit exceeds a predetermined amount. 7

3. Refrigerating apparatus comprising a circuit for refrigerant including a normally open low-pressure conduit, a pump for circulating refrigerant inthe circuit, means connected to the conduit for actuating the pump when the pressure in the conduit is above a predetermined amount, and means positively preventing high pressure existing 1n the pumpfrom being communicated to the conduit. Y

4. Refrigerating apparatus comprising a refrigerant including a low-press'ure conduit, a pump-for circulating refrigerant in the circuit, means fordriving the pump, means for actuating the driving and thefpump for closing.

insets means including a pressure-responsive device connected t o the conduit, and a pres sure-responsive value between said devlce the conduit when the pressure exceeds a predetermined amount.

' 5. Refrigerating apparatus circuit for refrigerant including an expander and a low-pressure conduit, one end of which is connected to. the expander, a pump connected to the other end of the conduit for circulating refrigerant in the circuit, means connected tot he conduit intermediate its ends for actuating the pump in response to the pressure in the conduit, the conduit being always open atv the expander end, and

the

means for closing the pump end of conduit when the pressure in the conduit exceeds a predetermined amount.

In testimony whereof I hereto aflix my signature.

FRANK w. ANDREWS.

comprising a

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