US2193837A - Air conditioning system for railway cars - Google Patents

Description

March 19, 1940. M. P, wlNTHr-:R ET Al. 2,193,837

AIR CONDITIONING SYSTEM FOR RAILWAY CARS Filed May 23. 1934 Patented Mar. 19, 1940 UNITED; STATES PATENT OFFICE 2,193,837 am coNnrriomNGcsYsTEM Foa nAmwAY Application May 23, 1934, Serial No. 727,150

11 Claims.

In any well designed air conditioning system for passenger cars, it is necessary to provide for air cooling when the car is stopped or is travelling below a predetermined minimum speed. Ordinarily, auxiliary generators and batteries are provided for storing electrical energy while the car is travelling at normal speeds, but the weight of the additional equipment, as well as its bulk and cost are serious objections to this method of providing energy.

The present invention aims to solve the problem by storing up refrigeration rather than electrical energy for this purpose, and some of the resultant advantages of this system, particularly of the embodiment herein disclosed, are: A saving in weight, cost and space required for the auxiliary equipment; the automatic provision of additional refrigeration whenever the reserve supply has been built up to a given maximum, and air cooling is still required, or whenever the primary source of refrigeration is incapable of carrying the load due tolow train speeds; automatically throwing in the reserve supply of refrigeration whenever the car is stopped or is travelling below a. predetermined minimum speed; and making use of a portion of the system for heating the car during cold weather.

Further and other objects and advantages will become apparent as the disclosure proceeds and the description is read in conjunction with the accompanying drawing, in which Fig. l is a diagrammatic lay-out of a preferred embodiment of this invention; and

Fig. 2 shows a slight modification of the means for having the refrigerant compressor operate at different suction pressures.

The particular embodiment of the invention which is shown in the drawing and which will hereinafter be described is used merely for the purpose of disclosure and the appended claims should be construed accordingly.

The body of a standard passenger car, or Pullman, is indicated at III and at one end of the car, adjacent to the roof, is an air conditioning chamber I I in which primary and secondary coils I2 and I3, respectively, are housed. One side of the chamber I I communicates with the car interior H by an overhead duct I5 having outlets IS spaced at intervals along its length. The other side of the chamber II communicates with the exhaust of a centrifugal fan I1 which draws air from the car interior through a grille I8 and fresh air from the car vestibule I9 through a grille 20, the latter air passing through a lter 2| of any suitable form. The wall 22 indicates thc partition between the vestibule and the car interior.

As this invention is more particularly concerned with the means for adding and removing heat units from the current of air which is passed 5 into the car than it is with the particular system of air distribution and its method of control, no attempt will be made to discuss the control of the air movement or the many possible variations from the arrangement shown in the drawing. l0 Sulce it to say that the grilles I8 and 20 may be provided with suitable dampers for controlling the proportion of fresh and recirculated air and these may be controlled in any well known manner. Also, the lter 2l may be of the spray type, 15 if desired, and dehumidifying and humidifying apparatus with their controls may be included in the air eonditioning'apparatus placed within the chamber II or in proximity thereto.

The principal physical equipment of the system 20 includes a compressor 23 driven by a multiple V-belt 24 from a shaft 25 which constitutes a part of the speed control mechanism, generally designated 26, which in turn is driven by a propeller shaft 21 from one of the car axles 28. 25 Bevel gears 29 and 30 effect the drive.

The compressor discharges into a condenser 32 Where the hot volatile refrigerant becomes a liquid and then passes to a liquid receiver 33, and from there through expansion valves 34 and 35 30 into the primary refrigerant coil I2 and evaporator coil 36, respectively, the latter coil being l0- cated Within a fluid tank 31 on the underside of the car body.

The tank 31 contains a liquid having a rela- 35 tively low freezing point and for this purpose, a 10% solution of ethylene glycol in water has been found satisfactory.

The tank is a portion of a fluid circuit which includes the secondary coil I3, so-called because 40 it not only supplements the primary coil I2 in operation but also because it employs a secondary refrigerant.

A steam coil 38 is also located in the tank 31 to heat the liquid in the Winter time. Admission of steam to the coil is controlled by a steam valve 39 which operates in response to a. heating thermostat 40 located directly in the path of the current of air issuing from the air conditioning chamber Il.

In the summertime, a, cooling thermostat Il controls the operation of the refrlgerating equipment.

Circulation of liquid through the secondary coil I3 is effected by a fluid pump which op- 55 crates under predetermined conditions, as will later be described.

A conventional axle generator 43 (Sec. 8 of Car Builders Dictionary, 1931 edition, published by Simmons-Boardman Publishing Co. of New York), is furnished to supply the electrical requirements of the air conditioning system, and car lighting, and a battery 44 is arranged to float on the generator. The generator is driven directly from the car axle by a shaft 45 with a friction clutch 46 interposed in the drive to prevent excessive torques.

For convenience of description, the various circuits will be discussed under the headings of control circuits, cooling circuits, and heating circuits, and to make the drawing more clear, thecontrol circuits are indicated by light lines, the cooling circuits by medium lines, and the heating circuits by heavy lines.

Control circuits There are four shunt circuits which are responsive to the generator voltage, and these four circuits control the operation of an automatic switch- 5|, a compressor control switch 52, a speed control regulator 53, and a generator field control 54.

The switch 5| serves the purpose of connecting the generator 43 with the battery 44 when, and only when, the car speed is suicient to cause the generator voltage to be greater than the battery voltage. The switch includes a solenoid 55 connected across the generator armature 41. l

The compressor control switch 52 is likewise connected across the generator armature, and consequently the switch armature 56 is held against the front contact 51 only when the car speed is suillcient to cut in the compressor, but until that speed has been attained, the armature 56 restsupon a back contact 58 which places the fluid pump 42 in series with the battery 44, provided the cooling thermostat 4| calls for a lower temperature. This circuit will be described under the cooling circuits.

The speed control regulator 53 consists of a carbon pile 53 to which pressure is variably applied by an armature 60 controlled by a coil connected across the generator armature. The speed control regulator serves to prevent the compressor from being driven at a too rapid rate.

'I'he generator field regulator 54 also has a carbon pile, as indicated at 6|, to which pressure is variably applied by an armature 62 operating in response to a coil 63 shunted across the generator armature. The purpose of this control is to cause the generator to operate at a more or less constant voltage.

Cooling circuits The system of air conditioning shown in the drawing is intended to maintain the coil I2 in operation as long as cooling of the air is required, and at the same time, build up a quantity of ice in the fluid tank 31 for use when the" car is 'I'hese various functional characteristics of the system may better be understood by considering the several cooling circuits which are shown i the drawing in medium lines. y

A double throw hand switch 1| initially determines whether the system is set for cooling or for heating, and when the switch connects the contacts 12 and 13, the switch is set for cooling and when it connects the contacts 14 and 15, the system is set for heating.

Let us assume, first of all, that the car is moving at a normal rate of speed, say 40 miles an hour, and that the cooling thermostat 4| is closed, calling for more air cooling. Under these conditions, the compressor control switch armature 56 is in contact with the front contact 51, and 'a circuit may be traced from the positiv'e side of the generator armature through conductors 18 and 11, speed control regulator 53, conductor 18, cooling thermostat 4|, conductor 19, armature 56, front contact 51, conductor a commutator 8| associated with the speed control mechanism 26, thence through a field winding 82, another commutator 83, conductor 84, switch 1|, switch 5| (which is closed because the generator voltage is suiiicient to actuate the solenoid 55) and back to the negative side of the generator armature through conductors and 86. This circuit merely serves to supply a proper voltage to the field coil 82 of the speed control device in order to drive the compressor 23.

The -speed control mechanism 26, which is diagrammatically shown in the drawing, consists essentially of a cup-shaped clutch ring 81 driven by the car axle 28 through the propeller shaft 21 and in turn driving the shaft 45 which connects with the generator 43. The hollow shaft 25, or quill shaft, is supported by suitable bearings in a housing 89, and is telescopically mounted over the shaft 45. One end of the quill shaft 25 carries the eld coils 82 which rotate within the clutch ring 81. The other end of the quill shaft is equipped with a pulley for driving the compressor 23, and intermediate the ends of the shaft is another pulley 9| which drives a compressor fan 92 mounted on a shaft 93 journalled in the bearings 94. The pulleys 90 and 8| are both keyed to the quill shaft.

It is obvious that driving torque is transmitted from the clutch ring 81 to the quill shaft 25 in more or less direct proportion to the current in the eld coil 82, and consequently, when the speed control circuit is open at 51, due to insuiicient generator voltage to hold the armature 56 in raisedV position, the compressor is stopped. When the car speed, however, is suiicient to close the speed control circuit by moving the compressor control switch armature to the position in which it is shown in the drawing, the field coil 82 is energized and driving torque from the car axle is transmitted through the electromagnetic clutch to the compressor 23.

The current in the coil 82 is kept at a more or less uniform value independently of -car speed by the speed control regulator 53 which introduces more resistance in the circuit as the car speed increases. The greater resistance reduces the current passing through the coil 82 and, consequently, more slippage is eiected between the clutch ring 81 and the quill shaft 25. In this way, the compressor is driven at substantially a uniform rate independently of varying car speeds.

Again, let it be assumed'that the car speed is sufficient to close the speed control circuit through the compressor control switch, and that the circuit is also closed at the cooling thermostat. Under these circumstances (which are the same as the conditions previously assumed), a shunt circuit may be traced from the conductor through conductor 95 to a shut-otr valve 96 in the liquid refrigerant line leading to the evaporator coil 36, then through the conduc-tor 91 to the other side of the speed control circuit, in this case the conductor 84. The shut-off valve 96 is open when the shunt circuit is energized, but otherwise closed. Its purpose is to prevent refrigerant from condensing in the evaporator coil 36 when the compressor is shut down. Its use is made necessary by the fact that the evaporator coll 36 in order to be capable of forming ice in the uid tank 31 must operate on a suction pressure in the neighborhood of 15 lbs. whereas the primary-coil |3, which it is desired should be kept at a temperature of around 45 F. must operate on a suction pressure of approximately 50 lbs. Since the feed line 98 to the evaporator coil 36 is connected directly with the feed line 99 leading to the primary coil I2, there would be a tendency, were it not for the valve 86, for the refrigerant to condense in the coil 36 upon stopping the compressor 23 due to the lower suction pressure.

In'order for the compressor to operate the coils I2 and 36 at different suction pressures, three of the four cylinders of the compressor are connected on the intake side through a manifold |00 with the coil I2, While the 4th cylinder is connected by a separate intake to the coil 36.

The discharge from all four cylinders of the compressor may be through a common manifold IOI, as shown in Fig. l, or the discharge from the low pressure cylinder may connect with the suction side of the other three cylinders, as shown in Fig. 2. Either of these methods require little modification of conventional multi-cylindered compressors, and both produce satisfactory results, although the arrangement shown in Fig. 1 is preferred.

Thus far, we have seen that as long as the car is operating above a predetermined minimum speed, i. e. a speed suilcient to energize the speed control mechanism 26, and as long as the cooling thermostat 4I calls for cooling, the refrigerant is being conveyed to the primary coil I2 and to the evaporator coil 36, although the two coils are operated at different suction pressures.

Now, let it be assumed that ice has formed on the coils 36 in suflicient quantity to cover a thermostat |02 placed at a given distance from the coil 36. As soon as the ice completely encases the thermostat |02, there is an immediate drop of temperature in the thermostat, due to the insulating properties of the ice. and this sudden drop of temperature is made to operate a relay |03 which is adapted to place the uid pump 42 in operation. This is accomplished bv a shunt circuit commencing from the conductor 91. thence through conductors |04, |05, relay |03, conductor |06, conductor |01 through the fluid pump 42 and back to the negative side of the generator armature through conductors |08', 85 and 86.

Again, it will be observed that circulation of uid through the coil I3 because of excess formation of ice only occurs when the demand for air cooling is unsatisfied, for the cooling thermostat 4| is in series with this last circuit.

As soon as the ice formation within the tank 31 has been reduced by an amount suihcient to uncover the thermostat |02, the fluid pump circuit is opened and circulation is stopped.

It sometimes happens that the primary coll I2 is incapable of carrying the cooling load due for example to the car ascending a long grade In which case the compressor is not operating at a suiilciently high speed to maintain the required suction pressure in the coil I2. For this situation, a suction pressure relay |08 is provided in the suction line of the coil I2, and whenever the pressure in the line rises above a predetermined value, a circuit is closed which places the iiuid pump 42 in operation and makes the auxiliary refrigeration available. This circuit is in parallel with the relay |03 and may be traced from the junction of conductors |04 and |05, through a conductor |08, the relay |08, conductor I0, thence through conductor |01 to the pump 42 and back again to the negative side of the generator armature through conductors |08', 85 and 86.

The relays 96, |03 and |08 are all in series with the cooling thermostat so that whenever sufricient cooling of the air has been obtained, the primary and secondary coils I2 and I3 are rendered inactive.

The compressor control switch 52 and the suction pressure relay |08 are quite similar in purpose and operation, for both serve to place the fluid pump 42.in operation below predetermined train speeds. For this reason, it is possible to dispense with one or the other without greatly affecting the functioning of the system as a whole, but it is preferred that both switches be used in order to obtain greater eliiciency in the control of the system.

Heating circuits In the wintertime when heating of the air is desired, the main switch 1| is thrown to the left connecting the contacts 14 and 15. This places the heating thermostat 40 in series with the steam Valve 39, which is normally held closed by a spring I|| or equivalent means, but which is adapted to be opened whenever the heating thermostat 40 calls for air heating. 'Ihe steam valve control circuit is readily traced from the contacts 15 and 14, through the conductor I2, solenoid II3, heating thermostat 40. conductor II4, and back to the negative side of the battery and generator.

A shunt circuit is provided for actuating the fluid pump 42 whenever the circuit through the heating thermostat is closed, but a fluid thermostat relay II5 is placed in series with the shunt circuit in order to stop the fluid circulation in case the temperature of the uid should for some reason fall below a predetermined minimum, for example F. The shunt circuit may be traced through conductors IIS, thermostat relay |I5, conductor II1, fluid pump 42, and conductor |08', back to the battery and generator.

The steam employed in the steam coil 38 is taken from the main steam line on the car through a pipe |I8 and after passing through the coil, it discharges into the atmosphere through a trap H8.

The fluid circuit through the secondary coil I3 and the tank 31 includes connecting pipes |25 and |26, the latter communicating with the interior of the tank through small orifices |21.

In place of the speed control mechanism 26, a generator and motor may be used, the generator and motor, of course, being equipped with an automatic switch for rendering the generator inoperative at low train speeds. In this respect, the generator and motor would operate substantially the same as the speed control mechanism. But the speed control mechanism shown in the drawing is preferable, because among other things, it provides for automatically reversing the condenser fan 92 when the direction of car movement is changed. The conventional generator is equipped with automatic pole changers and when the condenser fan is operated by a. generator driven motor, its direction of rotation is constant irrespective of the direction of car movement. When the speed control mechanism, however, is used, the fan 'I2 is automatically reversed when the car changes directions and this is especially desirable as the condenser is located beneath the car and depends in part upon car movement for being cooled.

What we claim, therefore, is:

1. In combination with a passenger car, means for forcing a current of air into the car, cooling apparatus for lowering the temperature of the air current, said apparatus including refrigerating mechanism, and primary and secondary coils in the path of theair current, a fluid circuit including the latter coil, an evaporator coil immersed in said fiuid, said refrigerating apparatus being adapted to simultaneously furnish refrigeration to the primary and evaporator coils in such proportions that any excess capacity of the apparatus over that required for air cooling is utilized for storing refrigeration in the uid circuit for use when the car is stopped, or is operating under a predetermined minimum speed.

2. In combination with a car, means for forcing a current of air into the car, primary and secondary coils in the path of the air, a fluid circuit including the latter coil, means for circulating fluid in said circuit under predetermined conditions, an evaporator coil immersed in the fluid medium, refrigerating mechanism operated by car movement for supplying refrigerant to the primary and evaporator coils, and means responsive to the condition of the primary coil for determining, at least in part, whether or not the fluid circulating means is placed in operation concurrently with the primary coil to supplement the action of the primary coil.

3. In combination with a car, means for forcing a current of air into the car, primary and secondary coils in the path of the air, a fluid circuit including the latter coil, means for circulating fluid in said circuit under predetermined conditions, an evaporator coil immersed in the fluid medium, refrigerating mechanism operated ing a current of air into the car, primary and secondary coils in the path of the air, a fluid circuit including the latter coil, means for circulating fluid in said circuit under predetermined conditions, an evaporator coil immersed in the fluid medium, refrigerating mechanism operated by car movement for supplying refrigerant to the primary and evaporator coils, and means responsive to the speed of the car for determining, at least in part, whether or not the iiuid circulating means is placed in operation concurrently with the primary coil to supplement the action of the primary coil.

5. In an air conditioning system, a conditioning unit including an air passage, a first cooling means in said passage, a second cooling means in said passage, a water freezingtank, means for supplying refrigerant to said first cooling means, and means for supplying water from said freezing tank to said second cooling means whenever the air conditioning load exceeds the capacity of said first cooling means.

6. In combination with a passenger car, means for forcing a current of air into the car, primary and secondary coils in theA path of the air including a fluid medium in the latter coil, apparatus for supplying refrigerant to the primary coil and for abstracting heat from the fluid medium in the secondary coil, and means responsive at least in part to the suction pressure of the refrigerating apparatus forl controlling the circulation of the fluid medium through the secondary coil.

'7. The method of conditioning air for a vehicle by power taken from one of the vehicle wheels which consists in utilizing the power whenever it exceeds a given minimum for operating refrigerating apparatus to cool air delivered by forced draft to the vehicle, concurrently therewith utilizing said power for cooling a holdover, and circulating the holdover in heat ex` change relation to said draft in response to a drop in said power below the predetermined minimum.

8. The method of conditioning air for a vehicle by power taken from one of the vehicle wheels which consists in utilizing the power whenever it exceeds a given minimum for operating refrigerating apparatus to cool air delivered by forced draft to the vehicle, concurrently therewith utilizing said power for cooling a holdover, and circulating the holdover in heat exchange relation to said draft in response to excess refrigerating capacity. stored within the holdover.

9. The method of conditioning air for a vehicle by power taken from one of the vehicle wheels which consists in utilizing the power whenever it exceeds a given minimum for operating refrigerating apparatus to coolair delivered by forced draft to the vehicle interior, utilizing the power thus characterized to provide cooling of a. holdover when the air in the vehicle has been sufficiently cooled, and circulating the holdover in heat exchange relation to said draft in response to a heat load in the vehicle that is in excess of the ability of the refrigerating apparatus to handle without the assistance of said holdover.

l0. In combination with a passenger car, means for forcing a current of air into the car, primary and secondary coils in the path of the air, a fluid circuit including the secondary coil, an evaporator coil in the fluid circuit, means for circulating the fluid in the circuit, and means including the same refrigerating apparatus for supplying refrigerant to the primary and evaporator coils, said refrigerating apparatus including a compressor having two or more cylinders with separate intake manifolds for the two coils whereby the coils may be operated at different suction pressures.

ll. In combination with a passenger car, means for forcing a current of air into the car, primary and secondary coils in the path of the air, a fluid circuit including the secondary coil, an evaporator coil in the fluid circuit, means for circulating the iiuid in the circuit, and means including the same refrigerating apparatus for supplying refrigerant to the primary and evaporator coils, said refrigerating apparatus including a. compressor having two or more cylinders with separate intake manifolds for the two coils whereby the coils may be operated at diiferent suction pressures. the discharge from the cylinder or cylinders operating at the lower suction pressure being connected with the intake manifold of the other cylinder or cylinders.

MARTIN P. WINTHER. ANTHONY WINTHER.

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