US2467398A - Control for refrigeration apparatus - Google Patents

Description

April19, 149. E. F. MILLER CONTROL FOR REFRIGERATION APPARATUS 2 Shets-Sheet 1 Filed Sept. 9, 1945 Figs! Ap w, 1949. E. F. MILLER 2,467,398

CONTROL FOR REFRIGERATION APPARATUS Filed Sept. 9, 1946 7 2 Sheets-Sheet 2 I Patented Apr. 19, 1949 CONTROL FOR REFRIGEBATIO APPARATUS Eldon F. Miller, Batavia, Ill., assig'nor to Bat:

. Body Company, Incorporated,

corporation of Illinois Application September 9, 1946, serialize. 695,789

This invention relates to the control of refri eration apparatus which is driven from a power source such as the internal combustion engine of an automotive vehicle through the intermediary of a hydraulic or fluid pressure actuated rotary motor.

I The primary object is to provide for operation of the hydraulic drive motor and the refrigeration apparatus at a constant eflicient speed and to control the refrigeration effect produced by the apparatus intermittently in accordance with the changing demands for refrigeration.

A more detailed object is to maintain a constant power source of pressure fluid for the hydraulic drive motor -in spite of wide variations in the speed of the power source, and to stop and start the hydraulic motor by interrupting and resuming the flow of fluid in accordance with the measured demands for refrigeration.

The invention also resides in the novel structural character of the means utilized to carry out the foregoing objects.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which I Figure 1 is a schematic plan view of the chassis of an automotive vehicle equipped with a refrigeration system embodying the novel features of the present invention.

Fig. 2 is a schematic view and hydraulic circuit diagram.

Fig. 3 is a fragmentary sectional view of the main control valve.

Fig. 4 is a hydraulic circuit diagram similar to Fig. 2, but showing aunodiflcation.

' The present invention is especially adapted for use in refrigeration apparatus of the type commonly used on automotive road vehicles for cooling products transported thereby. Such ap- 3 Claims. (cl. 62-4) paratus is preferably driven from the internal combustion engine 5 of the vehicle through a power take-01f such as a V-belt 6 engaging a pulley l on the propeller shaft 8. The refrigeration system comprises the usual compressor 9 which delivers refrigerant through a. condenser 10 into an evaporator or cooling coil I l. The latter is disposed in heat exchange relationship with respect to the compartment of the vehicle to be refrigerated.

The compressor 9 is driven by a rotary fluid pressure operated motor l2 such, for example, as Series ME constant displacement piston type fluid motor manufactured by Vickers, Inc. of Detroit, Michigan. The motor shaft is coupled Bata'vla, 111., a

toone end of the compressor shaft. If desired, the other end of the compressor shaft may be coupled to an electric motor I 3 by which the com-- pressormay be driven when the vehicle is parked and the engine 5 is not'in use.

Pressure fluid for driving the motor i2 is supplied by a pump ll, preferably of the gear type, whose shaft carries a pulley l5 driven by the belt 6. The pump draws fluid such as oil from a sump l6 and delivers the fluid under pressure through a conduit l1 extending to the motor inlet through a valve 18 by which the operation of the motor is controlled. The fluid outlet from the motor i2 is connected by a return pipe is to the sump it.

The size of the pump I4 is such that, when the engine 5 is operating at a normal idling speed, suflicient power will be delivered to the compressor through the hydraulic transmission to supply substantially the maximum refrigeration demand normally encountered in service use. The excess fluid delivered at higher engine speeds is bypassed back to the sump through a relief valve 20 interposed in a pipe connecting the pump discharge pipe I! and the sump.

The loading of the valve 20 by a spring 22 is adjusted for response to the pressure desired to be maintained in thesupply line I! leading to the motor l2. In the form shown in Fig. 2, a restriction formed by an adjustable valve member 23 is interposed in the pipe l1 beyond the relief valve 20.so that the fluid as delivered to the motor l2 will be maintained at a pressure somewhat below that of the pump outlet as determined by the setting of the relief valve 20.

In accordance with the present invention, provision is made for fully opening the valve H3 in response to a rise in the cooling demand above a predetermined value and for fully closing the valve so as to stop the motor I2 when the demand has been satisfied. As shown, the valve I8 is of the balanced. type, having two disks 24 fast on a stem 25 and movable axially toward and away from seats 26 to close and open the fluid passage through the valve casing 21. The valve member thus formed is preferably actuated by a fluid pressure operator 28 comprising a piston 29 fast on the valve stem and slidable in a cylinder 30. A compression spring 3| encircles the valve stem and urges the piston upwardly to open the valve whenever the pressures in opposite ends of the cylinder 30 are equalized. In the form shown in Fig. 2, pressure fluid as delivered by the pump I4 is utilized toenergize the valve operator 28 under the control of a pilot valve 32 comprising a plunger 33 slidable in a cylinder 34 having alincd ports 38 and 88 respectively connected to the head end of the cylinder 30 andthrough a pipe 31 to the higher pressure portion of the supply line I1. When the plunger is positioned as shown in Fig. 2 uncovering theports 35 and 34, pressure fluid will be permitted to flow to the cylinder 30, forcing the piston 28 in a direction to press and hold the valve disks 24 against their seats. The flow of fluid to the motor l2 thus being interrupted, the motor will be stopped. and operation of the refrigeration apparatus will be discontinued immediately. At the same time, a second plunger 38 on the stem 33 of the pilot valve covers other ports 40 and 4| in the cylinder 34, thereby interrupting a passage 42 between the head and rod ends of the actuator cylinder 30.

When the pilot valve stem 38 is shifted to the right to the position shown in Fig. 3, the ports 35 and 36 are covered by the plunger 33, thereby interrupting the connection between the supply line 31 and the valve actuator. At the same time, the ports 40 and 4| are uncovered, thereby opening the passage 42. The resulting pressure equalization between opposite ends of the actuator cylinder 3!! permits the spring 3! to become effective in opening the valve l8. This permits fluid to flow through the pipe IT to the hydraulic motor l2 to start the latter and then continue operation thereof at constant speed.

Deviations of the refrigerant demand from the value required to maintain the desired temperature in the refrigerated compartment may be detected in various ways, and such deviations may be utilized in various ways to actuate the pilot valve 32. Such temperature deviation may be detected by a thermostatic element such as a bulb 45 located in the cooled compartment or, as shown in Fig. 2, adjacent the evaporator ll. Or the detector may be a means responsive to changes in the pressure in the vacuum or refrigerant return line 46 leading back to the compressor 3. To utilize the latter type of detecting means, the line 48 is connected through a capillary tube 41 to a bellows 48, one end of which is anchored, the other end being connected to the stem 34 of the pilot valve so as to move back and forth progressively with changes in the refrigeration demand as evidenced by changes in the compressor return line pressure.

With such an arrangement, the fluid valve l8 remains closed when the demand is below the desired value, the pilot valve plunger 33 then being positioned as shown in Fig. 2 to admit fluid to the valve actuator 28 for holding the valve I 8 closed. As the compressor suction line pressure increases, thebellows 48 expands, moving the plunger 33 to the right until the ports 35 and 36 are eventually closed. This condition indicates a demand for increased refrigeration, whereupon the valve i8 is fully opened by the spring 3| in the manner previously described.

The motor l2 and the refrigeration apparatus are started and eventually satisfy the increased demand. The latter is evidenced by contraction of the bellows 48 sufllciently, to at least partially uncover the ports 35 and 36, whereupon pressure fluid is admitted to the actuator 28 to close the valve [8. Operation of the motor I 2 and the refrigeration apparatus is thus interrupted. In this way, the refrigeration apparatus is started and stopped and operated intermittently for spaced intervals of variable length according to the changing demands of the compartment being cooled by the refrigeration apparatus. The resultis to maintain the temperature of the refrigerated compartment substantially. uniform, subject to the sensitivity of the detecting means employed.

At all times during operation by the motor l2, optimum efficiency of the refrigeration apparatus is maintained because, in spite of variations in the speed of the vehicle'ensine 5, the motor I2 is operated at a fixed speed by the fluid supplied thereto at constant pressure.

when the engine 8 is idle and the apparatus is driven by the electric motor 13, the hydraulic motor I2 is driven alon with the compressor, and this acts as a pump. To facilitate the circulation of fluid by the motor and to avoid the development of an objectionable back pressure, a pressure relief valve is interposed in a pipe Ii connecting the inlet and Outlet of the motor I 2, Fluid may thus be circulated directly between the motor terminals.

In the modified form of the invention shown in Fig. 4, the higher fluid pressure utilized for operating the valve actuator 32 is obtained by a separate small capacity pump 52 driven by the engine 5 and supplying fluid to the conduit 31 which is separated from the conduit H. In this case, a separate relief valve 53 is associated with the auxiliary pump 52 to limit the pressure produced thereby. Preferably, the pump l4 for supplying fluid to the hydraulic motor I2 is a Vickers pump, either of the piston type or of the vane type as shown, having a rotor 54 arranged to be adjusted automatically as by a spring loaded piston 55 for the maintenance of a predetermined pressure in the outlet pipe I! without the necessity of providing a. separate relief valve. Thus, when the valve l 8 is closed to interrupt the operation of the refrigerating apparatus, the resulting pressure build up in the pump outlet causes automatic adjustment of the pump rotor to idling position.

I claim as my invention: 1

1. For actuating refrigeration apparatus on an automotive vehicle, the combination of, a rotary hydraulic fluid motor driving said apparatus, fluid pumping mechanism adapted to be driven by the power plant of an automotive vehicle to supply pressure fluid at two different constant pressures, a conduit for supplying fluid at the lower one of said pressures to said motor to maintain constant speed operation of the latter, a valve interposed in said fluid supply conduit to open and close the latter, a fluid pressure actuator, and means responsive to the refrigeration demands on said apparatus to supply fluid at said higher pressure to said actuator or to interrupt such supply whereby to open or close said valve according to the prevailing demand for refrigeration.

2. For actuating refrigeration apparatus on an automotive vehicle, the combination of, a rotary hydraulic fluid motor for driving said apparatus, a fluid pump adapted to be driven by the power plant of an automotive vehicle, a fluid supply conduit connecting the outlet of said pump and the inlet of said motor, a fluid return conduit connecting the motor outlet and the pump inlet, a by-passage between said supply and return lines including a relief valve spring loaded to by-pass fluid when the pressure of the fluid delivered by the pump exceeds a predetermined value whereby to maintain constant speed operation of said hydraulic motor during the supply of pressure fluid thereto, a valve interposed in said fluid supply conduit to open and close the conduit, and means responsive to the refrigeration demands on said apparatus to eifect rapid actuation of said valve to start and stop said motor while maintaining constant speed operation thereof during the periods that the valve is open. v

3. Foractuating refrigeration apparatus on' an automotive vehicle, the combination of, a rotary hydraulic fluid motor for driving said apparatus, a fluid pump adapted to be driven by the power plant of an automotive vehicle, a fluid supply conduit connecting the outlet of said pump and the inlet of said motor, a fluid return conduit connecting the motor outlet and the pump inlet, means associated with said pump for maintaining the fluid supplied to said motor at a predetermined pressure whereby to maintain constant speed operation of said hydraulic motor during the supply of pressure fluid thereto, a valve interposed in said fluid supply conduit to open and close the conduit, and means responsive to the refrigeration demands on said apparatus to either REFERENCES CITED The following references are of record in the flle'of this patent:

UNITED vSTATES PATENTS Name Date Aspelin Feb. 1, 1944 Number

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