US2065596A - Refrigerating apparatus - Google Patents

Description

Dec. 29, 1936. D. E. MACCABEE I 3 5 REFRIGERATING' APPARATUS a Filed March so, 1929 III III 5 0m 2? 4 ya 5M 5!!!! U G Q 37 37 30 27 "L": I II I.- Q Q 7////./ ///////,1. 1% 7////////. AW/////A 3mm Patented Dec. 29, 1936 PATENT OFFICE rmrmenm'rme APPARATUS David E. Maccabee, Dayton, Ohio, assignor, by

mesne assignments, to General Motors Corporation, a corporation of Delaware Application March 30, 1929, Serial No. 351,362 '4 Claims. (01. 62-8) This invention relates to refrigerating apparatus and particularly to arrangements for controlling the circulation of refrigerant in such apparatus.

One of the objects of the invention is to provide an improved control system particularly adapted to multiple installations which automatically prevents the circulation of refrigerant in such unit or units of the system as do not need refrigeration.

Another object of the invention is to provide an improved refrigerating system in which one condensing element supplies a number of evaporating elements with refrigerant and automatically maintains each of them within predetermined temperature limits independent of the remaining elements.

More specifically it is an object to provide such a system in which the outlet of one or more. of the evaporators is positively closed when there is no refrigerating demand upon such evaporator,

Further objects and advantages of the 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 drawing:

Fig. 1 is a diagrammatic representation of one form of refrigerating system embodying my invention, and

Fig. 2 is a sectional view showing the construction of a control valve of the system.

It has previously been proposed to provide a number of evaporators which are supplied with refrigerant from a common condensing element and to operate the-system so as to maintain the different evaporators at different temperatures. In the previously known systems of this character the different evaporators are not entirely independent of each other and the condensing element does not circulate refrigerant through the various evaporators in accordance with the refrigerating demand upon each. The difliculties experienced have been the more pronounced in cases in which it is sought to maintain widely different temperatures. My invention is concerned with'providing a simple, economical and reliable system which will satisfactorily maintain widely different temperatures and in which the various refrigerating elements are operated independently of one another.

Referring to the drawing, l0 designates in general a condensing element for withdrawing gaseous refrigerant from a vapor conduit ll,

liquefying the refrigerant and delivering it to a liquid supply conduit l2. The condensing element may be of any desired type, for example it may include the usual motor I4, compressor l5 and condenser IS, the motor beingactuated in response to the pressure within the conduit II by means of an automatic switch l8 which connects the motor to power mains l9. Evaporators 20 and 2| are connected in parallel between the liquid supply conduit and the vapor exhaust conduit II for cooling compartments 20a and 2la. The evaporators are connected to the conduit H by means of independent outlet conduits 23 and 24. Preferably each of the evaporators is of the flooded type and includes a reservoir for liquid refrigerant which is kept at a constant level therein by means of a float valve, not shown herein but fully disclosed in the patent to Osborn 1,556,708, October 13, 1925. Since the evaporators are of the flooded type, the pressure of the refrigerant in each will correspond to -its temperature. Assuming that the evaporator 2| is to be kept at the higher temperature and pressure, I place in the outlet of this evaporator a shut-off valve 26, the construction of which is illustrated in Fig. 2 and which automatically closes when the evaporator 2! has reached a predetermined low pressure.

A valve casing 30 having an inlet 3| and an outlet 32 is connected in the conduit 24. Within the casing is a valve seat 2'! and a valve proper 25 which is either moved to the left to permit unrestricted communication between the inlet and outlet, or else is moved to the right against the seatto positively close the outlet, by means about to be described. The casing 30 is provided with a boss 34 to which is sealed the open end of a flexible metal bellows 35, the other. end of which .is closed. in any suitable manner. Preferably the bellows is closed at its upper end by a cap 36 soldered to the bellows and its other end is soldered to an end cap 31 secured to the boss 34 in any suitable manner, the cap 37 having an opening 38 to provide communication between the bellows and the casin 30. I

The end cap 36 0f the bellows is connected to the valve by a link 39, the bellows forming a motor for operating the valve in response to the pressure within the casing 30. When the pressure is high the bellows. expands to open the valve and when the pressure is low the bellows contracts to close the valve.

In order that the valve may be suddenly opened at. a predetermined high pressure and remain open until suddenly closed by a predetermined low pressure I provide a snap acting mechanism for controlling the movement of the valve under the influence of the pressure in a casing. This is exemplified in Fig. 2 as a rod 40 secured to the end cap 36 of the bellows and reciprocable in a guideway formed by openings 4| and 42 in stationary posts 43 and 44 suitably secured to a base 45 upon which the valve casing may also be supported by being attached to a bracket 46. The portion of each post 43 and 44 below the openings 4| and 42 is hollow and contains a spring-loaded plunger or detent including a piston 41, a ball 48, a spring 49 and a spring abutment 50. The hollow. portion of the post is slotted as indicated at 5|, the spring abutment projecting through the slots to the outside of the post and resting upon a nut 52 by which the tension of the spring can ,be adjusted. The rod 40 is provided with detent receiving means in the form of a pair of notches 54 and 55 which are adapted to receive the detents in posts 43 and 44 respectively. The notches 54 and 55 are so spaced that when the notch 55 receives the detent in the post 44 the valve is held in a fully opened position and when the notch 54 receives the detent in the post 43 the valve is held closed. The posts may be suitably braced or held together at their upper ends by means of a bar 60 secured to each post by screw 6|.

The operation of the valve is as follows.

With the parts in the position shown in Fig. 2, assume that the pressure in the casing 30 is diminishing. The bellows attempts to contract and close the valve, but is prevented from moving the valve by the force of the spring detent in the notch 55. Eventually the pressure reaches such a low value that the force of the bellows overcomes the force of the detent, and the rod 40 slides suddenly to the right, suddenly and positively closing the valve. As this occurs the notch 54 registers with the detent in the post 43 and retains the rod in the position in which the valve is closed. Upon a subsequent increase in pressure, the bellows tends to expand, but the notch 54 prevents movement of the rod and of the valve until a definite high pressure is reached which overcomes the force of the spring detent in tube 43. When this occurs the rod is suddenly moved to the left and the valve suddenly opened.

The springs in posts 43 and 44 may be independently adjusted to determine the pressures at which the valve opens or closes respectively. Thus any desired closing pressure can be selected which is independent of the opening pressure and vice versa.

I have found that at certain pressure settings difficulty may be experienced in getting the rod to suddenly jump from the position in which the notch 55 is engaged to the position in which the notch 54 is engaged or vice versa. This may result in leaving the rod unlocked and render the valve subject to movement in response to gradual or small changes of pressure. To overcome this the rod is given a large inertia, as by attaching a weight 10 so that when the rod has been placed in motion a suflicient amount to release the detent in either notch, the momentum will snap it to the other position, positively flexing the bellows to insure locking the rod in the other notch. In order to facilitate the attainment of this momentum, particularly on opening the valve, the link 39 is secured to the cap 36 thru a lost motion connection II. It has also been found desirable to provide a light spring 12 for positively holding the valve tight on its seat to prevent leakage due to wear in the lost motion connection or play between the detents and notches.

In operating with closing pressures in the neighborhood of atmospheric, the pressure of the atmosphere on the bellows may not be sufficient to close the valve. In such cases the spring 13, under compression between the post 43 and a pin in the rod 40, assists in the closing of the valve, the tension of the spring detent in post 44 being regulated accordingly.

The automatic switch i8 is set to operate at low pressures corresponding to the temperatures to be maintained in the evaporator 20. Whenever the temperature of 20 is above the maximum permissible value, the pressure of the refrigerant will actuate the switch l8 to operate the condensing element. Under these conditions refrigerant will not be evaporated in the evaporator 2| unless the valve 26 is open. Whenever the valve is open, the condensing element will reduce the pressure and temperature of the evaporator 2| to its lowest permissible value (which is above the setting of the switch l8) at which point the valve will close to prevent further refrigeration in 2|. If the evaporator 20 should at any time be within its normal temperature limits, and the condensing element consequently be idle, and the evaporator 2| should become too warm, the pressure in 2| will open the valve and allow the high pressure to be communicated to the conduit II and switch l8. Since this high pressure is above the value which closes the switch, the switch will be operated immediately to start the condensing element. Refrigerant will then be withdrawn from both evaporators until both have reached their minimum permissible temperature. If the evaporator 2i reaches its minimum temperature first, the valve 26 will close to prevent further refrigeration, and the condensing element will continue to refrigerate the evaporator 20. Ii, however, the evaporator 20 should reach its minimum temperature first, the valve will remain open, and the pressure of the refrigerant evaporated in 2! will keep the switch open. However, since each evaporator contains a relatively large quantity of liquid refrigerant, whose pressure corresponds to its temperature, the rates of evaporation of the liquid will correspond with the pressures. Hence refrigerant will be evaporated rapidly in 2! and quickly reduce its temperature, whereas refrigerant will be evaporated but slowly in 20, and thus its temperature will not be reduced to a value appreciably below its normal minimum value.

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. A refrigerating apparatus including a pinrality of evaporators, means for supplying liquid refrigerant to and for withdrawing gaseous refrigerant from the evaporators, and a mechanically operated two-temperature snap acting valve responsive to a. predetermined high pressure within one of said evaporators for abruptly opening the withdrawing means for said one evaporator and responsive to a predetermined low pressure within said one evaporator for abruptly closing the withdrawing means for said one evaporator, said valve having a relatively heavy weight for providing ample inertia to carry the valve abruptly from one position to the other, said valve including adjusting means for independently varying said predetermined high pressure and said predetermined low pressure at which said valve opens and closes.

2. A mechanically operated two-temperature snap acting valve including a valve case having an inlet portion and an outletportion, a valve for'controlling the flow of fluid from said inlet portion to said outlet portion, a flexible wall in communication with said inlet portion for opening and closing said valve, means for controlling the valve to cause it to open abruptly when a. predetermined high pressure is reached and to cause it to close abruptly when a predetermined low pressure is reached, said last mentioned means including a weight for providing inertia to carry the valve from one extreme position to the other extreme position, and adjusting means for independently varying said predetermined high pressure and said predetermined low pressure at which said valve opens and closes.

3. A mechanically operated two-temperature snap acting valve including a T-shaped valve casing having an inlet portion in one leg and an outlet portion in another leg, a flapper type valve located at the entrance of the outlet leg for controlling'the flow of fluid from the inlet leg to the outlet leg, a flexible bellows located at the end of the leg opposite the outlet leg, a connecting member connecting said valve and the movable portion of the bellows, a horizontal rod connecting to the movable portion of the bellows, said horizontal rod having a plurality of notches therein, a plurality of ball detent meansvadapted to yieldingly engage the notches in the horizontal rod for causing said rod to move with a snap action from one extreme position to another, said ball detent means being independently adjustable and the weight mounted upon said horizontal rod for providing inertia to aid in the abrupt movement from one position to the other, said horizontal rod providing a snap acting opening and closing the flapper valve.

4. A mechanically operated two-temperature snap acting valve including a valve case having an inlet portion and an outlet portion, a valve for controlling the flow of fluid from saidinlet portion to said outlet portion, pressure operated means for opening and closing said valve, means for controlling the valve to cause it -to open abruptly when a predetermined high pressure is reached and to cause it to close abruptly when a predetermined low pressure is reached, said last mentioned means including a weight for

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