US2185022A - Refrigerating apparatus - Google Patents

Description

Original Filed July 31, 1935 3 Sheets-Sheet 1 INVENTOR.

Dec.26, 1939. R, AN R 2,185,022

REFRIGERATING APPARATUS Original Filed July 31, 1935 3 Sheets-Sheet 2 K INVENTOR.

. CA VVPOIE I Le. BY

Dec. 26, 1939. CANDQR 2,185,022

REFRIGERATING APPARATUS Original Filed July 31, 1935 3 Sheets-Sheet 3 70 I ,4 I B 43a.

INVENTOR.

fQ/Y OQ BY E 7 Q ATTORNEY$ Patented Dec. 26, 1939 PATENT OFFICE REFRIGERATING APPARATUS Robert R. Candor, Dayton, Ohio, assignor to General Motors Corporation, Dayton,-hio, a corporation of Delaware Application July 31, 1935, Serial No. 34,035 Renewed April 5, 1939 7 Claims.

This invention relates to refrigeration and more particularly to the refrigeration of a vehicle such as a railway car or the like.

An object of this invention is to provide a re- I '5 frigerating system for a vehicle in which the compartment to be cooled can be refrigerated by thermal contact with an evaporator while the car travels above a predetermined speed and can be refrigerated through the same evaporator by liquid refrigerant pumped from a second evaporator which is in a lower position.

Another object of this invention is to provide a refrigerated car with a novel variable ratio drive in which a plurality of fixed ratio drives are automatically interposed between the live axle and the refrigerant liquefying unit, compressor or the like. 7 Further objects and advantages of the present invention .will be apparent from the following deao scription, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings: Fig. 1 is adiagrammatic cross-sectional-elevag5 tional view of an apparatus embodying features of this invention;

Fig. 1a indicates a different type of liquid refrigerant pump to be used in lieu of the liquid refrigerant pump shown in Fig. l.

Fig. 2 is a diagrammatic cross-sectlonal-elevational view showing more details of the liquefying unit drive;

Fig. 3 is across-sectional view of. a gear box which may be used;

5 Fig. 3a shows a modification applicable to the mechanism shown in Fig. 3.

Fig. 4 is a wiring diagram showing the electricalcontrol of a system in which a single ratio change is accomplished;

, Fig. 5 is a diagram, somewhat similar to- Fig. 4,- but showing how a plurality of gear ratio changes may be controlled;

Fig. 6 is a diagrammatic-showing of a portion of the apparatus shown in Fig. 2 modified to 45 indicate how a plurality of ratio changes is incorporated;

Fig. 7 shows a modified form of gear box;

Fig. 8 is an enlarged detail of Fig. 7;

Fig.8a shows the drive between clutch faces;

no and ll to be refrigerated. This vehicle is provided with one or more live axles ll, l2 on which the wheels of the vehicle are mounted. The functions i to be performed by one or more of the live axles are in this figure show to be performed by two live axles, although it is evident that all of the 5 drives may be taken off of one axle as indicated in Fig. -2.

A first evaporator I3 is positioned so thatit is in heat exchange relationship with air to be cooled for the compartment l0. Air may be 10 blown over the evaporator l3 by the fan ll driven by the motor IS. The air blown by the fan i5 may be derived either from the compartment III, or from the outside, or from both. A second evaporator I6 is positioned below the evaporator I 3, 15 and preferably below the floor ll of the compartment III. This latter evaporator I6 is in thermal contact with a liquid holdover l9 placed in an insulated compfirtment 20. This holdover may be water, brine or a holdover which freezes above :0

A refrigerant liquefying unit 2| is placed in refrigerant flow relationship with the evaporators l3 and I6 and is driven from the live axle II. The liquefying unit 2! may include a compressor :5 22 and a condenser 23 with or without receiver 24.. Ifdesired, a fan, not shown, may. also be driven 'from the live axle II to blow air over the condenser 23.

The drive between the axle l I and the com- 80 pressor 22 may be a direct drive such that the 7 speed of the compressor varies in accordance with the speed of the car throughout the entire speed range of the car. However, I prefer to use a variable ratio drive in which the ratio between the axle and the compressor is varied in accordance with conditions of the vehicle, preferably by steps at different increases of speed of the vehicle as will be hereafter more fully described.

The capacity of the refrigerant liquefying unit 40 is such that at all substantial speeds of the vehicle the capacity of the unit is sufficient to provide the necessary refrigeration demanded of the evaporator l3. On certain occasions, or on all occasions, the capacity is also suflicient to prowide refrigeration in the evaporator l6 and to cool or freeze the holdover l9 so that it is in readiness to provide refrigeration when the speed of the car falls below a predetermined limit or stops entirely. It is to be understood that the naming of a speed below a predetermined limit 4 includes complete stopping of the car The evaporator I3 is provided with liquid refrigerant through the line 25 and the evaporated refrigerant returns to the compressor through the u line 26. An automatic expansion valve 21 is provided at the inlet of the evaporator and is under the control of a thermostatic bulb 28 placed near the outlet of the evaporator. The construction of the valve 21 is such that it is substantially closed when the pressure in the evaporator is above a predetermined limit and opens when the pressure therein is reduced by the suction of the compressor below a predetermined limit. However, when the refrigerating effect reaches the bulb 28, the valve-21 is automatically throttled or entirely closed. This construction maintains the evaporator l3 in .a substantially flooded condition, but prevents flooding of the refrigerant ting. of the valve 30, however,'is such that a lower temperature tends to be maintained in the evaporator l6 than in the evaporator I3. That is, the valve3ll is calibrated to open at a lower refrigerant pressure than valve 21. For. example, if holdover I3 is water, the valve 30 opens at a pressure corresponding to a temperature suitably below 32 F.

In addition, an automatic valve 32 is placed in the suction line and this valve is responsive to pressures in the evaporator 13 as diagrammatically indicated at 33. When the compressor tends to reduce the pressure of the evaporator l3 below a predetermined limit (corresponding to a temperature slightly above,1 32 F. and yet below the setting of valve 21), the valve 32 is. throttled. At this time, if the compressor continues to operate, the suction effect of the compressor is then transmitted through the suction line 34 to the evaporator 13 and refrigeration is produced in the evaporator l6 thus cooling or freezing the holdover l9. Because of the action of the valve 32 it is possible for refrigeration to be produced at the same time in both the evaporators l3 and I6, but the temperature in evaporator 13 is preferably maintained higher than that in evaporator It. It is to be understood, however, that, under certain conditions, many of the advantages of my invention may be derived when both the evaporators are maintainedat the same temperature. This is particularly true, where the holdover I 9 ischosen to have a freezing point substantially the same as ohhigher than the temperature desired to be maintained in the evaporator 13.

' 'Automatic controls are provided for controlling .the refrigerating effect of the evaporators in accordance with refrigeration demands. To this end a thermostat 40 is provided in compartment III which contacts at 4| when the temperature in the compartment 10 rises to a predeterpressor can continue to operate until such a time as the temperature of the holdover I9 is reduced to a predetermined limit. At this point, if desired, the thermostatic switch 43, in response to the .bulb 44, automatically stops the compressor 22 through the action of the pneu matic valve whichactuates the pneumatic clutch 46. If desired, a valve 26a may be placed in line 26, which is automatically throttled, as indicated diagrammatically by 261) when the pressure in line 26 between the valve 26a and the evaporators is reduced below a desired limit. This pressure limit is below the pressure at which the valve 30 opens. This valve 26a may be used in lieu of or in addition to control 4344. That is, with the valve 26a in operation, the compres'sor may be allowed to run all the time the car runs and if there is no refrigeration demand at either I3 or IS the power required to drive the compressor is very little. The valve 26a. may be closed completely but preferably always has an oil bleeding action. w

Means are provided for causing liquid volatile refrigerant to be pumped from the evaporator Hi to the evaporator 13 when the'speed of thecarfallsbelowapredeterminedslow speed limit orcompletelystops. providing a pump 41, driven by a motor 48, which withdraws liquid refrigerant through the pipe 49 and forces the same through pipe 50 to the lower This maybe accomplished by portion of ,the evaporator I3. At the same time i that the motor 48 is energized a solenoid valve 5| is opened, thus openingthe by-pass 52 between the outlet of the evaporator 13 and the pipe 34. Under these conditions, while the pump 41 operates, liquid volatile refrigerant is pumped from the lower portion of the evaporator Hi to the lower portion of the evaporator l3 and gaseous refrigerant, or liquid refrigerant, or both, return from the evaporator l3 to the evaporator l6,'through the by-pass 52 and pipe 34. Thus the cooling effect oi. holdover I9 is transferred by this circulation to evaporator l3.

Under these conditions the pressures in the evaporators l6 and 13 are such that the valves 21 and 38 are closed, and'thus receiver .24 is effectively isolated from the evaporators. The

compressor 22 is provided with a checkvalve (its usual discharge check-valve) opening in the direction of the condenser 23. Therefore. any tendency of refrigerant to force its way backwards from the condenser through the compressor to the evaporators is effectively stopped.

Solenoid valve 55 and check valve 56 are provided, which prevent the flow of refrigerant backwards in the line 49-50 during the time that the pump 41 is not operating. These valves, however, permit the flow of refrigerant from the evaporator J3 to the evaporator 13 while the pump 41 is operating as will be hereinafter apparent.

A different type of pump maybe used in lieu of pump 41. Thus, as shown in Fig. la the pipe '49 may discharge into a casing 4111.. The pipe 53 extends to a point near the bottom of easing 41-a.' A check valve is provided at 41b. An overflow compartment 410, iscorinected by large pipe 41c and small pipe 41 withtheupper part of casing 41a. Compartment 410 is heated, as by electric heater 41g. The heater 419 is placed in the wiring diagrams at the same place as motor 48. As will be apparent, when compressor 22 cannot furnish enough refrigeration, valve 55 is opened and heater 41g is heated. Liquid refrigeration flows from evaporator l6 into casing 41a until a small amount overflows at Hi. This small amount flashes into gas and fills the upper part of casing 41a through pipe 41c with gas under pressure. This forces liquid up pipe 58 past check valve 56 into evaporator I3. This intermittent pumping action continues as long as the automatic controls require.

In Fig. 1, some of the mechanisms are shown as driven from shaft I I and others from shaft I2, it being obvious that all can be driven from one shaft, as shown in Fig. 2.

To provide precooling for the car after it has remained idle and the holdover I8 has lost its refrigerating power, a trap door 28a is provided to insert frozen cooling medium into the tank 20 around the spaces not filled by the evaporator I6. When water is used as the holdover I9, then ice may be introduced through the trap door 20a. The water displaced by the ice overflows through overflow pipe 200. When holdovers other than water are used, the corresponding frozen holdover may be inserted, or small tanks containing ice may be inserted. In this case the overflow at 200 may be preserved and reintroduced through the trap door after the small tanks of ice are removed when the car is about-to start. trap door 28a is indicated to be at the top of tank 28; but it is to be understood that it may be located in the side above the level of the hold-' drives, and means are provided for automatically, changing from one fixed ratio drive to another fixed ratio drive in accordance with conditions of the car, such as at certain predetermined speeds of the car. While this change is going on, the drive is automatically declutched. The fixed ratio drives are shown to be of the gear type, but may be of other types, such as a plurality of belts or pulleys of different diameters.

As shown in Fig. 2, the live axle Ila is connected to a drive shaft 66 by universal joints 5'! and 58 and a bayonet coupling 59 so that the axle Ila is free' to turn while rounding curves. A centrifugal switch box 68 is provided in which two or more centrifugal switches, diagrammatically indicated as 6| and 62, are provided. In addition, a pneumatic or electrical clutch 63 is provided in which energization of the solenoid 64 automatically declutches the drive either by direct magnetic pull of the solenoid or by causing the solenoid to vary air-flow to a diaphragm actuator in the clutch. Pneumatic clutches, of themselves, are well-known'and details thereof are therefore not illustrated. A gear-box 65 is also interposed between the shaft Ila and compressor 22. This gear box is provided with one 8 or more pairs of gear drives, so that a change can be made from one fixed ratio drive to another fixed ratio drive. Thereafter the shaft section 660 is connected to the compressor 22, identical with the compressor shown in Fig. 1, from whence refrigerant is delivered to the condenser 23 and receiver 24 which comprises the liquefying unit- 2I and which is connected to evaporators I3 and I6 exactly as in Fig. la

Fig. 4 shows the electrical controls for changwhichcontrol the drive.

ing the fixed ratio drives and for controlling the operation of the refrigerant pump, and other parts, where only two gear pairs are provided. In this figure, the lines 18 and II are placed across the battery I2, which battery is charged by the H generator 13 of the character usually provided on current flows through the motor 48 and solenoid valves SI and 55. This permits liquid refrigerant to be pumped from the evaporator I6 to the evaporator I3 by means of the pump 41, the gaseous or l'quid refrigerant returning to the evaporator I6 through the open valve 5| and by-pass 52 and line 34. In this manner cooled refrigerant is transferred from evaporator I6 to I3 and provides cooling power from the holdover I9 for cooling the air. This continues as long as the thermostat contacts at 4|. If this contact should be opened, when the temperature in I 0 is low enough, then the action of motor 48 and valve 5| is stopped.

When the car starts, or, if desired, after the car has attained a speed above a low limit, the centrifugal switch 6| opens thus stopping the action of pump 41. The axle IIa, at slow speeds, drives the compressor 22 with a relatively high gear ratio through the gears I9 and 88. At some higher predetermined car speed, the centrifugal switch 62 closes and caures the drive to go through gears BI and 82 at lower ratio as will be hereinafter apparent. Fig. 4 shows the control for gears I9, 80, 8| and 82, while Fig-5 indicates the control for additional gears 19a, 88a, 8Ia and 82a.

With the wiring diagram of Fig. 4, gear box 65 contains only gears I8 to 82 inclusive. The portion 66a of the shaft line 66 is connected to shaft 65a upon which gears 19 and 8| are fixed, the shaft 16 is connected to the portion 66b of the drive in a manner indicated by dotted lines in Fig. 3. Gears 80 and 82 are rotationally fixed on the shaft 16; but are axially slidable by lever 11. The top of the lever I1 is moved to the left by the tension spring I8, gears I9 and 88 are meshed together and the drive is eifective through the fixed ratio determined by the gears I9 and 88.

The compressor then turns relatively fast with respect to the axle Ila, or at a relatively high gear ratio.

When the car speed increases to another pre determined speed where it would not be safe to drive the compressor at a high speed through the gears 19 and 80, the centrifugal switch 62 closes and this initiates a change from the fixed ratio drive through the gears 19 and 80 to the fixed ratio drive through the gears 8| and 82. When the switch 62 closes, itenergizes the solenoid valve'83. This admits air to the slow motion dash-pot 84 which is provided with a bleeder 85 .of. less fiow capacity than the air-flow through the valve 83. This causes the piston 86 to move slowly upwardly against thev spring 81 and thereby move the rod 88 slowly to cause a sequence of operations including declutching at 63, changing from gear drive 19-80 to reclutching at 63.

The slow movement of the rod 88 accomplishes this sequence by operating a series of switches Thus the first switch gear drive 8I-82 and is closed by the action. of the spring 89'forcing the lever 98 of the snap switch 9| upwardly so that the contacts 92 are closed. Any suitable type of known snap switch, such as diagrammatically indicated may be used. Under such conditions, as switch 99 is closed, current flows through the solenoid 64. This opens an air valve 93 and causes air to flow to the pneumatic actuating member of the clutch 63, it being understood, however, that the solenoid 64 can, if desired, be used to actuate the clutch directly by magnetic pull. Ableeder I88 is provided which is of less flow capacity than air valve 93 so that when valve '93 is open air pressure is produced on the clutch to declutch it, and when valve 93 is closed, slow air bleeding at I88 releases the air pressure and reclutches the clutch. After the clutch 63 is thus declutched by air pressure the continued upward movement of the rod 88 next actuates the lever 94 by the action of spring 942. which in turn closes the snap switch 95. This. causes current to flow through the solenoid 96 and moves the top of the lever H to the right against the tension of the spring 18. This causes the gears 8| and 82 to mesh and the gears 19 and 88 to unmesh by sliding the pair 88', 82 to the left. Thereafter the continued upward movement of the rod 88 next moves the lever 91 upwardly'and opens the contacts 98 of the snap switch 99. The opening of these contacts, which are in series with contacts 92, deenergizes the solenoid 64 and again clutches the clutch 63 by closing the valve 93 and permitting air to bleed slowly through the bleeder I88. Thus when the rod 88 has reached its upper position the clutch 63 is again clutched and the live axle Ila drives the compressor 22 through fixed ratio drive gears 8|, 82 with which the compressor does not turn relatively as fast with respect to the shaft Ila. This permits the car to travel at a higher speed without driving the compressor excessively fast.

When the car starts to slow down a reverse sequence takes place. When the car slows down to the point where the compressor'would not be driven at a sufllciently high speed with the low ratio drive, then the centrifugal switch 62 opens and this closes the solenoid valve 83. The slow leakage of air through the bleeder 85 causes the spring 81 to move the rod 88 slowly downward. The first action thus produced is the closing of contacts 98 which, with the closed contacts 92,

causes a declutching at 63 by admitting air through the valve 93. Next the contacts of switch 95 are opened and this deenergizes the solenoid 96 so that spring 18 moves the top of the lever 11 to the left thus meshing the gears 19 and 88. Thereafter the contacts 92 are opened thus closing the valve 93 and again clutching at 63 so that the compressor is now driven through the gears 19 and 80 through a relatively high gear ratio at a sufiicient speed notwithstanding the relatively low speed of the car.

If the car should continue to slow down to the point where the live axle I la can no longer drive the compressor at a refrigerating speed even through high ratio gears 19, 88, or if the car should stop entirely, then the centrifugal switch 6| closes and causes the pump 41 to operate and the valves and 55 to open to provide refrigeration from the holdover l9 as heretofore described.

If at any time the compartment l8 should be pneumatic clutch 46 and disconnected the drive between the shaft and the compressor. The pneumatic clutch 46 preferably is a different one from the clutch 63 and is interposed anywhere between the compressor and the live axle.

If the car is operating, and the holdover I9 is completely frozen and has disconnected the drive of the compressor at 46 and the compartment l8 should then require refrigeration, the solenoid 48 contacts at 4|. Current then flows through the lines I84 and I82 to actuate the pneumatic valve 45 and the clutch 46 causing the compressor to be driven to provide refrigeration for the compartment it! through the evaporator 19.

Figs. 5 and 6 indicate of fixed ratio drives can be used so that the car can be driven through a greater speed change range than can be taken care of with two fixed how more than one pair.

ratio drives. Under such conditions, the cen- 62a which is calibrated to close at a still higher speed than the switch 62. These are diagrammatically illustrated in Fig. 6.

Under the conditionsshown in Figs. 5 and 6 the gear box 65 contains additional gears 19a, 880., Ma and 82a. Instead of connecting shaft 16 to 66b (Fig. 2), the additional shaft 65b is connected to the section 660 (Fig. 6). When the car runs at speeds between the closing of switch 62 and the closing of switch 62a, the gear drive is through 8|, 82 and through 19a and 88a. When the speed increases to a point where switch 62a closes, then the drive changes to pass throughgears 8|, 82, Ma and 82a as will be hereinafter apparent.

The closing of the switch 62a causes a declutching at 63, an unmeshing of the gears 19a and 88a, meshing of the gears Ma and 82a and a reclutching at 63 as will be apparent from a further description of Fig.. 5. With respect to Fig. 5, the circuitscontrolled by the switch 62 are exactly the same as in Fig. 4 and they are therefore numbered similarly and the description heretofore given of the action is not here repeated. After the car has attained a speed such that the switch 62 is closed then the drive from the live axle Ila is through the gears 8| and 82 as heretofore pointed out. Thereafter if the speed increases to the point where the switch 62a closes, then the clutch 63 is again declutched, the gears 19a and 88a. are unmeshed, the gears 8 la and 820. are meshed and thereafter the clutch 63 is again clutched. This is accomplished by an action substantially identical with that heretofore described with respect to Fig. 4. Thus when the switch 62a closes the valve 83a. is. opened. This causes a slow movement upward of the rod 88a exactly as heretofore described with respect to rod 88 by the-flow of air to dash-pot 84a. The first action of the rod 88a is to close the contacts 92a similarly to the closing of contacts 92. This causes air to flow through the air line H8 and declutch the clutch 63 it being understood that the flow of air throughthe line I I is faster than through the bleeder I00. The next action of the rod 861: is to close the contacts of the snap switch 950.. This energizes solenoid 96a and moves'the top of the rod IIa. to the right. The movement of this rod 'IIa meshes the gears 8Ia and 82a while unmeshing the gears 19a and 60a by sliding the pair 80a and 82a to the left. The next action of the upward movement of the rod 86a is to open the contacts 9811., which causes the valve 63a to close and thus stop the flow of air to the pneumatic member of the clutch 63. The slow bleeding at I00 again reclutches clutch 63. Under the foregoing conditions the drive between the axle Ila and the compressor is at a still lower ratio and the car can travel at a high speed without driving the compressor too fast.

As the car slows down from this high speed the action is reversed. Thus the switch 620. opens; this reverses the train of events so that the clutch 63 is declutched, the gears 8Ia and 62a are unmeshed while 190. and 80a are meshed and the clutch 63 again clutched. If thecar continues to slow down, the switch 62 is opened, and this (as was described with respect to Fig. 4) opens the clutch 63, unmeshes gears 8| and 82 and meshes the gears I9 and 80' and again clutches at 63. Thereafter if the car continues to slow down further the switch 6| closes and this causes the opening of solenoid valve 6| and the operation of the pump 41 to provide refrigeration from the holdover ,I 9. It is to be understood that the portion of the diagram below the dotted line A in Fig. 4 is to be attached to the bottom of the diagram shown in Fig. at the line A.

With the modification shown in Figs. 7, 8 and 9, the gear box I 20 replaces clutch 63 and gear box 65 of Figs. 6 and 2. The shaft section 66a. of Figs. 6 and 2 are connected to shaft I2I of Fig. 7. The shaft section 660 of Fig. 6 is connected to shaft I22 of Fig. 7. If but a single gear ratio change is sufiicient then shaft section 661) of Fig. 2 may be connected to shaft I23 as indicated in dotted lines in Fig. '7. V

The gear box I20 has a combined clutching, declutching and gear ratio changing action. Gears I24 and I25 are fixed on shaft I2I. Gears I26 and I 21 rotate freely on shaft I23 but are axially'fixed by fixed abutments I26a and I2'la. Gears I28 and I29 are fixed on shaft I23. Gears I30 and I3I rotate freely on shaft I 22 but are axially fixed by fixed abutments I 30a and I3Ia. A collar I32 is rotatably fixed on shaft I23 but axially movable by the keyed action shown in Fig. 8 at I32a. The collar I32 is provided with clutch faces I33 and I34, and is moved axially by the yoke I 35 on the lever I36. Whenthe yoke I35 moves the collar face I34 against gear I26, this gear is rotatably fixed to shaft I23 by being clutched through face I34 and collar I 32. When the yoke I35 moves the collar face I33 against gear I21, this gear is similarly rotatably fixed to shaft I23 and gear I26 is released. A corresponding action takes place with respect to gears I30 and I3I where collar I62 is axially free but rotatably fixed on shaft I22 and is provided with clutch faces I31 and I38 and is axially moved by yoke I39 of lever I40. Thus the drive is effective through whatever gears are contacted by the collars I32 and I36 and an unclutching action takes place while the collars are being shifted.

Automatic controls are provided for progressively moving the collar I32 from left to right and then collar I 36 from left to right. This automatically changes gear ratios and automatically unclutches the drive during the change. These automatic controls, including the control of the pump motor 48 and its refrigerant, controls, are indicated in Fig. 9.

In Fig. 9 battery leads I0, II are placed across the battery I2 and generator I3. The fan motor I5 is under the control of manual switch I6I. The centrifugal switch 6I controls relay I4, motor 48 and solenoid valves 5I and 55 as in Fig. 4. The thermostat 40, switches 43 and 43a and valve 45 correspond in function and operation to that described with respect to Fig. 4. Centrifugal switch 62 controls solenoid MI and centrifugal switch I62a. controls solenoid I42. When solenoid I4! is energized the top of lever I36 moves to the left against the tension spring I43. When solenoid I42 is energized the top of lever I40 is moved to the left against tension spring I44.

The sequence of actions of the drive shown in Figs. 7 and 8 as combined with the refrigerating system shown in Figs. 1, 2 and 6 is indicated in Fig. 9. As the car stands and gradually starts and runs to a high speed switch 6| remains closed until the start or until a relatively low first speed limit is reached. During this time pump 41 pumps liquid refrigerant from I6 to I3 as heretofore described. ,This action stops when the speed reaches the first low limit. As the car starts and before the speed reaches a second limit, higher than the first speed limit, the live axle IIa (Fig. 2) drives the compressor through gears I24, I26, I28 and I30, as the tops of the levers I 36 and I40 are pulled to the right by springs I43 and I44. When the car speed reaches the second speed limit switch 62 (Fig. 9) closes and pulls the top or lever I 36 to the left and moves the collar I32 to the right. The compressor drive is then through gears I25, I21, I26 and I30. When the car reaches a third and higher speed limit the centrifugal-switch I62a closes and this pulls the top of lever I40 to the left and moves collar I62 to the right. The drive is now through gears I25, I21, I29 and I3I. Thus the gear ratio is progressively decreased as the speed of the car increases. from its high speed to a stop the actions are reversed.

The showing in the gear boxes 65 and I 20 is intended to be diagrammatic. It is to be understood that details may be varied in accordance with transmission practice. Thus, as shown in Fig. 3a the gears in box 65 may be provided with synchronizing discs to prevent clashing. Thus gear'19 may be provided with a disc I50 fixed thereto rotationally but slidable axially on pins I5I against the springs I5Ia. The disc I52 is secured axially and rotationally to gear 60. The discs I50 and I52 contact on relatively smooth frictional faces'before contact of the gears I9 and 80, thus synchronizing them. The other gears tion as herein disclosed, constitutes a preferred form, it is to be understood that other forms When the car slows down might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A vehicle having a compartment tobe rewith said unit, pumping means, separate from said liquefying unit, for elevating liquid volatile refrigerant from said second evaporator to said first evaporator, a live axle, a variable ratio drive between said live axle and said liquefying unit, means changing the drive ratio of said drive in accordance with changing conditions of said vehicle and means for controlling said pumping means in accordance with vehicle speed conditions.

2. A vehicle having a compartment to be refrigerated, a refrigerant liquefying unit, an evaporator positioned in.heat exchange relationship with air for said compartment and in refrigerant flow relationship with said unit, a second evaporator below said first evaporator and in refrigerant flow relationship with said unit, pumping means, separate from said liquefying unit, for elevating liquid volatile refrigerant from said second evaporator to said first evaporator, a live axle, a variable ratio drive between said live axle and said liquefying unit and including a plurality of positively meshable gears, means for changing the drive through said gears to change said ratio in response to changing conditions of said vehicle, means automatically declutching the drive between said axle and unit while said ratio is being changed and when the vehicle speed falls below a predetermined limit, and means controlling said pumping means in accordance with vehicle speed.

3. A vehicle having a compartment to be refrigerated, a refrigerant liquefying unit, an evaporator positioned in heat exchange relationship with air for said compartment and in refrigerant flow relationship with said unit, a second evaporator below said first evaporator and in refrigerant fiow relationship with said unit, pumpin means, separate from said liquefying unit for elevating liquid volatile refrigerant from said second evaporator to said first evaporator, said refrigerant liquefying unit including a compressor and condenser, a live axle, a variableratio drive between said live axle and said compres-- sor and including a clutch, a plurality of fixed ratio drives, means for changing the effective drive between said axle and compressor from one I to another of said fixed ratio drives and means automatically declutching said axle from said compressor during said change and when said compartment is sufficiently cooled.

4. A vehicle having a compartment to be refrigerated, a refrigerant liquefying unit, an ev'ap-. orator positioned in heat exchange relationship with air for said compartment and in refrigerant fiow relationship with said unit, a second evaporator below said first evaporator and in refrigerant flow relationship with said unit, pumping means for elevating liquid volatile refrigerant from said second evaporator to said first evaporator, means automatically causing operation .of said pumping means when the speed of the vehicle is below a predetermined speed, said refrigerant liquefying unit including a compressor and condenser, a live axle, a variable ratio drive between said live axle and said compressor and including a clutch, a plurality of fixed ratio drives, means for changing the effective drive between said. axle and compressor from one to another of said fixed ratio drives and means automatically declutching said axle from said compressor during said change and when said compartment is sufficiently cooled.

5. A vehicle having a compartment to be refrigerated, a refrigerant liquefying unit, an evaporator positioned in heat exchange relationship with air for said compartment and in refrigerant flow relationship with said unit, a'fan forcing air in heat exchange relationship with said evaporator, a live axle, a variable ratio drive between said live axle and said liquefying unit and including a plurality of positively meshable gears, means for changing the drive through said gears to change said ratio in response to changing conditions of said vehicle, means declutching the drive between said axle and unit while said ratio is being changed, and means responsive to a psychrometric function of air controlling said last mentioned means.

6. A vehicle having a compartment to be conditioned, a live axle, a unit connectable with said live axle, an air modifier positioned in air modifying relationship with air for said compartment and in fluid flow relationship with said unit, a variable ratio drive between said live axle and said unit and including a clutch, a plurality of fixed ratio drives, means for changing the effective drive between said axle and said unit from one to another of said fixed ratio drives, and means automatically declutching saidaxle from said unit during said change and in response to air conditions in said compartment.

'7. A vehicle having a compartment to be conditioned, a live axle, a unit connectable with said live axle, an air modifier positioned in air modifying relationship with air for said compartment and in fluid fiow relationship with said unit, a variable ratio drive between said live axle and said unit and including a clutch, a plurality of fixed ratio drives, means for changing the ef-

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