US1948572A - Refrigerating apparatus - Google Patents

Description

'Fell 27, 1934. w Q FLOYD 1,948,572

REFRIGERATING APPARATUS Filed Feb. 27. 1931 W @Mwah/#V ATTORNEYS Patented Feb. 27', 1934 UNITED l STATES REFRIGERATING APPARATUS William B. Floyd, Dayton, Ohio, assignor to Frigidaire Corporation, Dayton,y Ohio, a corporation of Delaware Application February 27, 1931. Serial No. 518,701

10 Claims.

This invention relates to refrigerating apparatus and more particularly to a means for collecting lubricant from the refrigerant in the system and for returning the collected lubricant to the compressor.

In the types of refrigerating systems now in general use, the refrigerant to be compressed is drawn from the oil reservoir of the compressor. By so doing, some of the oil is picked up by the refrigerant from the oil reservoir and also from the walls and moving parts of the compressor. This lubricant inthe refrigerant circuit causes many difficulties. It robs the compressor of needed lubricant and collects in the receiver and particularly in the evaporator of the system. This is true in the direct expansion system and is particularly true in the flooded system employing a. flooded type of evaporator where large quantities of lubricant collect and special means must be provided to remove the collected lubricant and return it to the compressor. This is ordinarily done by withdrawing the lubricant from the evaporator along with the gaseous refrigerant and returning it to a crankcase of the compressor. The delivery of the lubricant along vwith the gaseous refrigerant to the crankcase is not entirely satisfactory. With such a system small amounts of liquid refrigerant sometimes enters the crankcase from the suction line and drops to the bottom of the lubricant in the crankcase. When the compressor starts operation there is a comparatively high'vacuum quickly drawn in the crankcase causing rapid vaporization of any refrigerant which may be in the bottom ofthe crankcase. This rapid vaporization causes frothing of the lubricant in the crankcase which robs the compressor of the supply of needed lubricant.

Consequently, one of the objects of the invention is to keep the lubricant and refrigerant separated as far as possible.

Another object of the invention is to pro-- vide an improved means for separating and collecting the lubricant from the refrigerant in any refrigerant circuit and for returning the collected lubricant to the lubricatingvsystem of the compressor.

Another object of the invention is to prevent the frothing of the lubricant Within the systern.

v 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:

The figure represents a diagrammatic illustration of a refrigerating system embodying the invention.

Referring to the drawing, there is shown, for illustrative purposes, a compressor 21 for compressing the refrigerant and for forwarding it through the conduit 49 to a condenser 22 where the refrigerant is liquefied and collected in the receiver 23. A supply conduit 26 supplies liquid refrigerant from the receiver 23 to the evapo- `rator 27 where the liquid refrigerant vaporizes because of the absorption of heat from the refrigerator cabinet 28 and is returned to the compressor through the conduit 31the short conduit 32, through the lubricant separator or chamber 33 and through the conduit 34. The compressor is driven by a motor 24 connected by pulley and belt means 25 to the driving pulley 40 of the compressor 21. A pressure responsive 'switch means 35 is preferably connected to the return conduit 31 for providing alternate operating and idle periods of the compressor according to the pressure and consequently the ternperature of the evaporator 27.

The compressor is preferably of the stationary cylinder reciprocating piston type and has a driving pulley 40 which rotates the eccentric 41 to cause the eccentric rod 42 to reciprocate the piston 43 within the compressing chamber or cylinder 44. Refrigerant is drawn through the conduit 34 and past the inlet valve 45 in the cylinder head into the compressing chamber or cylinder 44. The piston 43 compresses the gaseous refrigerant within the compressing chamber 44 and forces the compressed refrigerant past the outlet valve 46 into the valve chamber 47 in the cylinder head 48 from which chamber the compressed refrigerant is conducted through the conduit 49 into the condenser 22. A lubricant reservoir 50 at the bottom of the compressor contains a lubricant 51 for lubricating the piston, cylinder walls, the eccentric, and parts of the compressor.

It will be seen that in applicants construction the refrigerant is not caused to pass through the lubricant reservoir of the compressor and in this manner the amount of lubricant picked up by the refrigerant is reduced. This prevents also the depositing of liquid refrigerant in the crankcase. But in spite of this precaution some lubricant is picked up by the refrigerant from the top of the piston and from the Walls of the compression chamber and carried through the refrigerant circuit and this stray lubricant collects in the evaporator. This tends to rob the lubricant reservoir 50 of its lubricant 4and therefore it is necessary to provided means for returning the lubricant to the compressor. The lubricant floats as a blanket upon the liquid refrigerant in the evaporator. The liquid refrigerant vaporizes and the bubbles of gaseous refrigerant thus formed break through the lubricant and carry some of the lubricant along with it. A small overflow hole 66 allows excess lubricant to flow into the return conduit 31. A lubricant separator 33 is providedl to remove the lubricant from the refrigerant circuit and return it to the lubricant reservoir.

According to the present invention, the gaseous refrigerant coming from the evaporator 27 through the return conduit 31 is caused to pass through the short conduit 32 into the lubricant separator 33 where, because of its large volume, the velocity of the gaseous refrigerant is reduced to a minimum. With the velocity of the gaseous refrigerant reduced to a very low amount, the lubricant carriedy by this gaseous refrigerant will drop out and collect in the bottom of the lubri- .cant separator 33. The gaseous refrigerant which enters the top of the lubricant separator 33 is removed fom the side of the separator through the conduit 34 so that there is caused a change in direction of the flow of gaseous refrigerant, which aids the separation of the lubricant within the separator 33. Should any liquid refrigerant enter the return conduit from the evaporator, it will collect with the lubricant in the separator. The separator being comparatively warm, will evaporate the liquid refrigerant therein and prevent it from reaching the lubricant reservoir.

Because of the intermittent operation of the compressor, the pressure within the refrigerant circuit varies between comparatively wide limits. When the compressor is idle the pressure within the refrigerant circuit increases because of the evaporation of liquid refrigerant. When the compressor starts, the pressure within the return conduit 34 and a separator 33 is quickly reduced. The pressure within the lubricant reservoir 50` at this time is therefore considerably higher than that in the separator 33. Hence, special means must be provided for conducting lubricant collected in the separator to the oil reservoir. A conduit 55 conducts the lubricant to a check valve 56 shown diagrammatically. The check valve 56 is provided with a needle valve 57 which is directly connected to a piston 58 which operates within the valve chamber 59. The piston is provided with one or more small apertures or bleeders 60 which allow a small amount of lubricant to flow slowly through them. When the pressures within the separator 33 and the oil reservoir 50 are equal, the needle valve 57 will drop by gravity from its closed position and allow lubricant to flow slowly from the bottom of the separator 33 through the conduit 55 to the check valve 56 and through the conduit 61 into the lubricant reservoir 50. When the compressor is started, the pressure within the lubricant separator 33 will be quickly reduced and the greater pressure within thelubricant reservoir 50 will push the piston 58 within the valve chamber 59 upwardly to close the needle Valve 57 and thus stop anyflow between the separator and the oil reservoir 50. The combined` area of the apertures 60 is less than the cross sectional area of either of the connecting conduits 55 and 61 so that there is sufficient throttling therethrough to enable the valve to operate as described above. In order to prevent an excessive differential in pressure between the lubricant reservoir 50 and the separator 33 and to equalize the pressures when the compressor is stopped a conduit 62 is connected to the lubricant reservoir 50 for removing any refrigerant which may collect within the crankcase of the compressor. Refrigerant may enter the crankcase by slipping past the pistons and at times small amounts may condense there. In order to prevent frothing a check valve 63 is connected to the conduit 62 and this check valve 63 is in turn connected by the conduit 64 to the lower return conduit 34. The check valve 63 is similar to check valve 56 but differs in that it is provided with a small fixed orifice or bleeder 65 which allows gaseous refrigerant to be slowly vwithdrawn from the lubricant reservoir of the compressor while the compressor is in operation. By yslowly withdrawing the gaseous refrigerant from the lubricant reservoir, the rapid volatilization of any condensed refrigerant in the lubricant reservoir is prevented and frothing of the lubricant is avoided since the check valve 63 does not open fully until the pressures in the lubricant separator 33 and the lubricant reservoir 50 are substantially balanced. When these pressures are substantially balanced the check valve 63 will open fully and allow refrigerant to be withdrawn from the lubricant reservoir 50 as the lubricant in the lubricant separator 33 is allowed to flow into the lubricant reservoir 50. If no means were provided for preventing the flow through the conduits 62 and 61 when the compressor 'was in operation', refrigerant would be drawn back into the lubricant separator and the return conduit 34, from the lubricant reservoir causing frothing within the separator. Hence it is necessary that the check valves 63 and 56 should 115 close when the compressor starts. If no check valves Were provided, or if the check valves were open while the compressor was in operation, any liquid refrigerant entering the separator would flow directly to the crankcase where it would 120 vaporize and cause frothing of the lubricant because of the vacuum in the crankcase caused by the operation of the compressor with open check valves.

While I have disclosed the operation of the 125 check valves to be such that they remain closed during the entire operating cycle of the compressor, it is to be understood that the undesirable frothing heretofore described is likely to occur only at the beginning of the operating cycle of 130 the compressor. Therefore it is within the purview of my invention that the check valves may open during the operation of the compressor, but after a suicient period of time yhas elapsed so that no deleterious frothing of the compressor 135 is likely to occur. This is particularly true where the operating cyclesof the compressor are abnormally long, and it is to be seen that with the slow bleeding actionthrough the check valves, the pressure in the crankcase is lowered 143 very slowly and at such a slowy rate, that noV frothing occurs and that the 4check valves may fall to the fully open position before the' compressor stops operating under such conditions.

While the form of embodiment of the inven- 145 tion as herein disclosed constitutes a ypreferred form, it is to -be understood that other forms might be adopted, all coming within the scope of the claims whichj follow.

' What is claimed is as follows:

1. Refrigerating apparatus comprising a closed circuit including a compressor, a condenser and a cooling unit, means for supplying lubricant to the compressor, a lubricant separator in said circuit, and automatic means for supplying lubricant from the separator to the lubricant supply means-only when the compressor is idle'.

2. Refrigerating apparatus comprising a closed refrigerant circuit including a compressor having a lubricant reservoir, a condenser, and a cooling unit, means for collecting lubricant from the closed circuit, a conduit connecting said last mentioned automatic means and said lubricant reservoir, meansfor conducting the flow of lubricant through the conduit only when the compressor is idle, and means for preventing the flow of lubricant through the conduit when the compressor is in operation.

3. Refrigerating apparatus comprising a closed refrigerant circuit including a compressor having a compressing chamber and a lubricant reservoir substantially separated from theclosed circuit, a condenser and a cooling unit, a` lubricant separator in said closed circuit for collecting lubricant from the refrigerant, means for conducting lubricant from the separator to the lubricant reservoir when the pressures Within the lubricant reservoir are balanced Within at least one portion of the closed efrigerant circuit, and means for preventing the flow of lubricant from the separator to the lubricant reservoir when the pressures Withinthe lubricant reservoir are unbalanced relative to pressures in said portion of -the closed refrigerant circuit. l v

4. Refrigerating apparatus comprising a closed refrigerant circuit including a compressor having a" compressing chamber and a lubricant reservoir substantially separated from the closed circuit, a condenser and a cooling unit, a lubrimeans for preventing frothing of the lubricant in the lubricant reservoir.

5. Refrigerating apparatus comprising a closed refrigerant circuit including afcompressor having a compressing chamber and a lubricant reservoir substantially separated from the closed circuit, a condenser and a cooling unit, a lubricant separator in said closed circuit for collecting lubricant from the refrigerant, means for conducting lubricant from the separator to the lubricant reservoir when the pressures within the lubricant reservoir are balanced within at least one portion of the closed refrigerant circuit,

=means for preventing the ow of lubricant from a compressing chamber and a lubricant reservoir a condenser and a cooling unit, a lubricant separator in said closed circuit for collecting lubricant from the refrigerant, means for conducting lubricant from the separator to the lubricant reservoir when the pressures within the lubricant reservoir are balanced Within at least one portion of the closed refrigerant circuit, means for preventing the flow of lubricant from the separator to the lubricant reservoir when the pressures Within the lubricant reservoir are unbalanced relative to pressures in said portion of the closed refrigerant circuit, and means for conducting refrigerant from the lubricant reservoir to the closed circuit without frothing the lubricant in the reservoir.'

7. Refrigerating apparatus comprising a closed refrigerant circuit including a compressor having a compressing chamber and a lubricant reservoir substantially separated from the closed circuit, a condenser and a cooling unit, a lubricant separator in said closed circuit for collecting lubricant from the refrigerant, a conduit connecting the lubricant separator and the duit to prevent the flow of lubricant in one direction, and a second conduit for conducting a restricted flow of refrigerant from the lubricant reservoir to the closed circuit.

8. Refrigerating apparatus comprising a closed refrigerant circuit including a compressor having a compressing chamber and a lubricant 'reservoir substantially separated from the closed circuit, a condenser and a cooling unit, a lubricant separator in said closed circuit for collecting lubricant from the refrigerant, a conduit connecting the lubricant separator and the lubricant reservoir, a check valve in said conduit to prevent the flow of lubricant in one direction, and asecond conduit connecting said lubricant reservoir and said closed circuit, and a check Valve having a fixed orifice for controlling the flow of refrigerant through the second conduit.

9. Refrigerating apparatus comprising a closed refrigerant circuit including a compressor having acompressing chamber and a lubricant reservoir substantially separated from the closed circuit, a condenser and a cooling unit, a lubricant separator in said closed circuit for co1- lecting lubricant from the refrigerant, a conduit connecting the lubricant separator and the lubricant reservoir, `a check valve in said'conduit tending to close when the pressure in said 1ubricant' reservoir exceeds the pressure in bricant separator.

10. Refrigerating apparatus comprising a closed refrigerant circuit including a compressor having a compressing chamber and a lubricant reservoir substantially separated from`theclosed circuit, a condenser and a cooling unit, a

llubricant reservoir, a check valve in said con- Said, luf

lubricant separator in' said closed circuit for'- collecting lubricant from' the refrigerant, acon- `duit connecting` the lubricant separator andthe lubricant reservoir, a checkvalve'in said .con.

duit tending to clos`e-when the pressure in said lubricantreservoir exceeds the pressure in said t lubricant separator, anda beedery in said check -valve. f

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