US 3609990 A
Description (OCR text may contain errors)
M 3 9 1 i 1 d, 9 .v mM 3 3 w? r W WWW E- W. BOTTUM REFRIGERATION ACCUMULATOR Filed Jan. 22, 1970 Get. 5, 1971 United States Patent Ofice 3,609,990 Patented Oct. 5, 1971 ABSTRACT OF THE DISCLOSURE A suction accumulator is provided for the compressor of a refrigeration system. The accumulator includes inlet means for connection to the output of the compressor for injection of the relatively high temperature, high pressure output gases of the compressor into the accumulator casing when the pressure within the accumulator casing falls below a predetermined level. A valve is provided on the inlet for controlling the injection of compressor gases into the accumulator. The valve is automatically actuated to open when the pressure within the accumulator falls below the predetermined level and is automatically actuated to close when the pressure within the accumulator rises to the preselected value.
BACKGROUND OF THE INVENTION The suction accumulator of the type with which the present invention is concerned is provided between the compressor and the evaporator of a refrigeration system to trap any liquid refrigerant emanating from the evaporator and feed this liquid refrigerant to the compressor at a metered rate. Flow is accomplished by means of the suction created by the compressor. Feeding of the liquid refrigerant back to the compressor at a metered rate prevents large amounts of liquid refrigerant from suddenly entering the compressor and causing damage. 7
The accumulator is useful in any conventional refrigeration system having the basic components comprising a compressor, condenser, evaporator and means of expanding high pressure condenser liquid to a lower pressure liquid and vapor prior to entry into the lower pressure evaporator stage. The suction accumulator may be used in most refrigeration systems such as a system with a hermatic compressor or a system with a thermostatic expansion valve and, in general, on non-automotive systems. However, the accumulator is particularly useful in automotive air conditioning systems because of the particular characteristics of automotive systems such as a need for a wide range of capacity control and the use of a compressor having a shaft seal.
In connection with automotive air conditioning systems, it has been common practice to'utilize an expansion valve, either of the thermostatic or automatic type, to provide expansion means for the liquid refrigerant from the high pressure side of the system to the low pressure side. Such expansion valves have several disadvantages which are well known, reference being made to my copending application Ser. No. 841,032, filed July 11, 1969. It has been suggested that the expansion valve be replaced in said systems with a capillary tube which would provide the desired expansion means. Attempts to use capillary tubes have, however, become generally unsuccessful. However, one suitable system utilizing a capillary tube and suction accumulator is described in my aforesaid copending application. The suction accumulator of the present invention is particularly suitable for use in such a system, but is also useful in an expansion valve or any system where capacity control is desirable to permit the compressor to run continuously.
Basically, the suction accumulator of the present invention incorporates a hot gas bypass system to maintain the pressure within the accumulator at a positive level, thus avoiding a suction or negative pressure condition therewithin, and also to provide a relatively stable pressure within the accumulator. Therefore, although the load may change from zero to maximum the compressor can remain in operation and at a stable suction pressure.
SUMMARY OF THE INVENTION A suction accumulator for the compressor of a refrigeration system is provided. The accumulator comprises a casing having a first inlet and an outlet. A conduit is provided within the casing extending from a point adjacent the bottom of the casing to the casing outlet. This conduit acts as a suction tube to draw liquid from the casing and expel it into the casing outlet at a metered rate. A second inlet is provided for connection to the output of a compressor for selective injection of relatively high pressure compressor output gases into the accumulator. A valve is provided on the second inlet. The valve includes a valve element movable to open and closed positions. A pressure or temperature sensitive valve element actuator is provided within the accumulator to move the valve element to the open position when the pressure in the accumulator falls below a pre-selected value and to move the valve element to the closed position when the pressure in the accumulator rises to a pre-selected value.
IN THE DRAWING FIG. 1 is an elevational view in section of one embodiment of the suction accumulator of the present invention; and
FIG. 2 is a sectional view of a modified valve structure.
DESCRIPTION OF THE PREFERRED EMBODIMENTS As illustrated in FIG. 1, the suction accumulator 10 includes a casing 12 which comprises an open-ended tube 14 having an upper end closure 16 and a lower end closure 18 secured thereto as by brazing.
An outlet tube 20 extends through the upper end closure 16. The outlet tube 20 is U-shaped. One leg 22 of the tube 20 extends downwardly to a point adjacent the lower end closure 18. The tube is then provided with a bend 24 and a second leg 26 extends upwardly and terminates in an open end 28 adjacent the upper end closure 16. A small metering opening 30 is provided in the tube bend 24. Another opening 32 is provided in leg 22 at the upper end to equalize pressure in both of the legs 22, 26.
An inlet tube 34 also extends through the upper end closure 16. The inlet tube 34 extends for a short distance into the casing 12. The lower end 36 is bent sidewardly so that the mouth thereof faces towards the surface of the casing interior approximately tangentially thereto and at a slight downward angle so that gases entering the inlet tube indicated by the arrow 38 exit from the tube as indicated by the arrow 40 in a direction generally tangential and at a downward angle with respect to the casing interior. As a consequence, the gases will follow a spiral path downwardly in the casing. This reduces turbulence Within the casing which may cause frothing and splashing of any liquid which is contained therein.
In operation of the accumulator cold refrigerant gas having a small amount of entrained liquid refrigerant therein is received from the evaporator and enters the accumulator through the inlet tube 34. The incoming gases, which move at a relatively high velocity, are, as above described, directed tangentially against the inner surface of the casing and follow a spiral path downwardly of the casing interior. The gases are free to expand, with resultant reduction of the velocity thereof. As a consequence, incoming gases are not directed as a high speed jet against any liquid which may be retained in the lower portion of the casing 12.
The refrigerant gases which enter the casing are drawn into the open end 28 of the U-tube 20, pass through both legs of the U-tube and exit via the leg 22 as indicated by the arrow 42. The gases are passed from the U-tube 20 to the compressor of the refrigeration system (not shown). The compressor, which creates a suction, draws the gaseous refrigerant through the accumulator at a relatively rapid rate.
Liquid refrigerant which enters the accumulator through the inlet tube 34 drops to the bottom of the accumulator and is subsequently drawn through the opening 30 and thence through the leg 22 and out of the accumulator. It will be appreciated that the liquid which is metered into the leg 22. is entrained in the stream of gaseous refrigerant. It remains entrained in the gas as it passes from the accumulator and is drawn to the compressor of the system. The opening 30 acts as a restriction and causes liquid refrigerant to be metered into the compressor at a controlled rate. The acumulator thus acts to prevent large amounts of liquid refrigerant from suddenly entering the compressor. Such sudden surges of liquid may result in seriously damaging the compressor.
During operation of the refrigeration system in which the accumulator is installed, there are times when an unusual amount of refrigerant will collect in the accumulator. For example, when the system is shut off, such as is the case with an intermittently-operated air conditioning system, for example, an automotive air conditioning sys tem, the refrigerant tends to condense in the entire system and collect in the accumulator. A similar situation may occur when the system is operated under low load conditions. The metering of the liquid refrigerant via the opening 30 results in liquid refrigerant being delivered to the compressor at a non-harmful rate.
The gaseous refrigerant which passes through the accumulator 10 is preferably subjected to the action of a drier to remove moisture therefrom. Illustratively, a drier 44 is mounted on the upper closure 16. The drier 44 is of the type described in my copending application Ser. No. 795,827, filed Feb. 3, 1969. This drier comprises a casing 46 which encloses a desiccant material. A tube 48 extends from the casing 46 into connection with the closure 16. The tube 48 provides fluid communication between the interior of the casing 12 and the casing 46. Gases may flow into and out of the casing 46 via the tube 48. When pressure is increased, gases tend to flow into the casing 46 and are subjected to the drying action of the desiccant. Upon a reduction of pressure in the casing 12, gases will flow out of the casing 46 and pass to the compressor via the U-tube 20. Other types of driers may be used in place of the drier 44. For example, a porous bag containing desiccant material may be directly mounted in the casing 12.
The accumulator 10 is illustratively utilized for heat exchange in addition to its function as a suction accumulator. As will be noted, a jacket 50 defining a compartment 52 is secured to the lower end of the casing 12 in heat exchange relationship with the lower closure member 18. An inlet 54 and outlet 56 are provided on the jacket 50. A relatively warm fluid may be passed through the jacket 50. For example, hot water from the vehicle heater may be passed therethrough. Alternately, the heat exchanger may be connected between the condenser and evaporator of a refrigeration system. Warm liquid refrigerant will then circulate through the jacket 50 in heat exchange relationship with the suction accumulator 10. This heat exchange relationship will assist in preventing flooding of liquid refrigerant to the compressor in that it will aid in vaporizing the refrigerant therewithin so that less will pass through the metering opening 30. Additionally, this heat exchange relationship will permit the evaporator to be run in a variable load superheat condition. Because of the fact that the low side of the evaporator coil may be run in a completely flooded condition, the capacity of the evaporator will be increased to provide superior performance. Additionally, the liquid exiting from the condenser is sub-cooled which is advantageous.
Referring now to the structure intermediate the ends of the casing 12, it will be noted that an inlet tube 58 extends in to one side of the casing. A portion 60 of the inlet tube 58 extends interiorly of the casing 12. A closure 62 is provided on the inner end of the tube 58. A perforated strainer or screen 64 is provided in the tube 58 to capture any foreign matter which may be entrained in gases entering the casing 12 via the tube 58. The use of a strainer 64 is optional. The tube 58 is connected to the high pressure hot gas outlet of the compressor of the system and bleeds off, at selected times, some of the high pressure hot gas emanating from the compressor.
A tubular valve element 66 is slidably received on the portion 60 of the tube 58. One end 65 of the valve element 66 is open while the other end 68 is closed. A vent 93 is provided to equalize pressure in the valve element. A plurality of spaced apart openings 70 are provided around the periphery of the inlet tube portion 60 and spaced from the end closure 62. Similar openings 72 are provided in the valve element 66 spaced from the end 68. The openings 70, 72 may be placed in alignment with each other as illustrated in FIG. 1. Upon movement of the valve element 66 to the right as viewed in FIG. 1, and shown in dotted lines, the openings are moved out of registry. As a consequence, it will be appreciated that high pressure gases may flow into the casing 12 when the openings 70, 72 are in alignment and that flow of such high pressure gas is terminated upon movement of the valve element 66 to the dotted line position.
An actuator 74 is provided to move the valve element 66 to place the openings 70, 72 into and out of registry depending upon the pressure conditions prevailing within the casing 12. The actuator 74 comprises a tubular member 76 which is mounted in an opening 78 in the side wall of the casing 12. This mounting may be effected as, for example, by brazing. The tubular member 76 is openended. The inner end projects into the casing 12. A resilient bellows 80 is mounted on the inner end of the tubular member 76. The bellows 80 may be fabricated of a material such as rubber or plastic. The bellows is cup-shaped, the mouth being in registry with the tubular member 76 and secured thereto. The inner end 82 is closed. A plunger 84 extends from the inner end 82 into connection with the closed end 68 of the valve element 66.
The exterior portion of the tubular member 76 is both internally threaded at 86 and externally threaded at 88. An externally threaded support disc 90 is threaded into the tubular member 76. A plurality of ports 92 are provided in the disc 90. These ports provide fluid communication between the interior of the bellows 80 and the ambient atmosphere so that interior pressure in the bellows will be substantially atmospheric. The disc 90 has a central threaded opening which receives a screw 94. A disc 96 is provided on the inner end of the screw 94. A coil spring 98 is mounted within the bellows and extends between the inner surface of the end wall 82 and the disc 96. The degree of compression of the spring 98 may be varied by threading the screw 94 into or out of the disc 90. An internally threaded cap 100 is received on the external threads 88 of the tubular member 76. A sealing element 102 is provided in the cap 100 to engage the tubular member 76 to substantially seal the inlet thereto. The main function of the cap 100 is to protect against ingress of foreign matter into the bellows construction.
The above-described high pressure hot gas inlet and associated val've structure may be termed a hot gas bypass system. The function of the hot gas bypass system is basically to maintain the pressure within the casing 12 at a positive level and thereby prevent a negative pressure or vacuum from developing therewithin. Such a negative pressure is undesirable because of the connection of the outlet 20 with the inlet of the system compressor. By use of this system, the suction accumulator may be connected in, for example, an automotive air conditioning system and the usual cycling clutch in such systems may be eliminated because the hot gas bypass system provides for capacity control and the compressor may therefore be run continuously. In other systems, which pump down it is possible for the compressor, crankcase seal and other parts of the system to be under a vacuum at times or a reduction in pressure due to decreased load may cause dangerous slugging of the compressor. This is undesirable. By use of the hot gas bypass system, suction pressure at the compressor is kept quite constant and at a positive level, not at a vacuum. Therefore the compressor can run constantly at reduced load or no load without risking the dangers caused by intermittent starting and stopping of the compressor.
Operation of the hot gas bypass system will now be described. As will be appreciated, the pressure within the interior compartment defined by the bellows 80 is relatively constant for any geographical area. Adjustments for different geographical areas and for different temperature conditions may be effected by manipulation of the adjusting screw 94.
Consequently, assuming the bellows to be at equilibrium, the gas within the bellows will be compressed when the pressure within the casing 12 rises and will expand when the pressure within the casing 12 falls. Assuming a condition where a very low pressure approaching a vacuum develops within the casing 12, the relatively higher pressure within the bellows and the spring 98 will cause the bellows to expand. Expansion of the bellows causes the valve element 66 to be shifted to the left as viewed in the figure. This brings the openings 70, 72 in registry allowing high pressure hot gas from the compressor outlet to enter the casing 12. This gas will cause the pressure within the casing 12 to rise. The rise of pressure will be accompanied by compression of spring 98 and contraction of the bellows with resultant movement of the valve element 66 to the right as viewed in FIG. 1 to the dotted line position. This will cause termination of incoming high pressure hot gases. As will be appreciated, the valve element 66 will be moved back and forth depending upon the pressure conditions prevailing within the casing 12 with the result that the pressure within the casing 12 will always be maintained at a relatively fixed value regardless of operating conditions of the overall refrigeration system. This fixed value is pre-selected to be a positive pressure. The pressure level is determined by the physical characteristics of the bellows 80 and spring 98 and by the position of the adjusting screw 94.
Alternate to the use of a bellows 80 wherein the interior of the bellows is at atmospheric pressure, a completely sealed bellows 104- charged with a gas, such as Freon, as shown in FIG. 2, may be used. Such a bellows may be either pressure sensitive or temperature sensitive, a temperature sensitive structure being illustrated. The temperature within the casing 12 is directly related to pressure conditions and therefore a charged temperature sensitive bellows is effective to control pressure within the casing 12.
As will be noted, the bellows 104 is connected to a tubular member 106 mounted in an opening in the casing 12. The outer end of the tubular member 106 is sealed by a disc 108.
The bellows 104 is connected to valve element 66 by the plunger 84. Upon an increase in temperature, which means an increase in pressure in casing 12, the bellows will expand as a result of expansion of the gas charge therein. This will cause the valve element 66 to move to the left, as shown in dotted lines, as viewed in FIG. 2, moving the inlet ports out of registry and preventing compressor gases from being injected into the casing 12. Upon a decrease in temperature in casing 12, the reverse will occur.
In similar fashion a bimetal element or other temperature sensitive device may be used to actuate the bypass valve.
What I claim as my invention is:
1. In a suction accumulator for the compressor of a refrigeration system, said accumulator comprising a casing having a first inlet and an outlet, a conduit within the casing extending from a point adjacent the bottom of the casing to the casing outlet, said conduit acting as a suction tube to draw liquid from the casing and expel it into the casing outlet at a metered rate, a second inlet for connection to the output of a compressor for selective injection of relatively high pressure gases into the accumulator, a valve on said second inlet, said valve including a valve element movable to open and closed positions, and a valve element actuator sensitive to one of pressure and temperature within the accumulator to move the valve element to the open position when the pressure in the accumulator falls below a pre-selected value and to move the valve element to the closed position when the pressure in the accumulator rises to a pre-selected value.
2. An accumulator as defined in claim 1, and further characterized in that said valve element actuator comprises a resilient bellows secured in the casing, the interior space of said bellows being sealed from the interior of the casing, said bellows being connected to the valve element whereupon expansion of the bellows will move the valve element to one position and contraction of the bellows will move the valve element to the other position.
3. An accumulator as defined in claim 2, and further characterized in the provision of a spring interiorly of the bellows, said spring biasing the bellows to move the valve element to the open position, interior pressure in said accumulator tending to cause collapse of the bellows and move the valve element to the closed position whereupon the valve element will be moved to the open or closed position depending upon pressure conditions within the accumulator casing.
4. An accumulator as defined in claim 3, and further characterized in the provision of a manually adjustable compression element in engagement with said spring, said compression element being adjustable to vary the force exerted by the spring against the bellows.
5. An accumulator as defined in claim 1, and further characterized in that said second inlet comprises a tubular member, a portion of said tubular member extending into the accumulator casing, the interior end of said tubular member being closed, the portion of said tubular member extending into the casing having opening means in the side wall thereof, said valve element comprising a tubular member slidably received on the portion of the second inlet tubular member extending into the accumulator casing, said valve element tubular member having opening means in the side wall thereof, said opening means of the valve element tubular member being in registry with the opening means in the inlet tubular member when the valve element is moved to the open position and being out of registry thereof when the valve element is moved to the closed position.
6. A suction accumulator as defined in claim 2, and further characterized in that said bellows defines a sealed space, said space being filled with a charge of a temperature sensitive gas which expands upon an increase of temperature thereby tending to close the valve and contracts upon a decrease in temperature thereby tending to open the valve.
7. An accumulator as defined in claim 1, and further characterized in the provision of a perforated strainer element in said second inlet to prevent ingress of solid foreign matter into the accumulator casing.
8. An accumulator as defined in claim 1, and further characterized in the provision of heat exchange means on 8 said suction accumulator, said heat exchange means com- References Cited prising a jacket around the suction accumulator and spaced UNITED STATES PATENTS therefrom to provide for flow of Warm fluid thereby in heat exchange relationship therewith. 3,012,414 12/1961 La Porte 62503 9. An accumulator as defined in claim 1, and further 5 3,021,693 2/1962 Anne characterized in the provision of a drier for the accumulator casing, said drier including a desiccant charge MEYER PERLIN Primary Exammer for removing moisture entrained in refrigerant which Us Cl XR passes through the accumulator. 62 278 503