US2368592A - Expansion valve - Google Patents

Description

Patented Jan. 30, 1945 EXPANSION VALVE Earnest J. Dillman, Detroit, Mich, assignor to Detroit Lubrieator Company, Detroit, Mich, a corporation of Michigan Application February 1, 1943, Serial No. 474,301

1 Claim.

This invention relates to new and useful improvements in valves for controlling the flow of refrigerant medium to an evaporator.

An object of the invention is to provide a valve which will operate efficiently at extremely low ment.

.tinctly claimed.

pressor l.

sageways ll into the chamber l8. Within the, chamber l8 there is a valve member l8 cooperable with a. valve seat member 20 and carried by a supporting member 2| which is urged in valve closing direction by an adjustable spring 22 sup-v The fiuid thermostat temperatures. 6 ported and held under compression by an ad- Another object is to provide a valve in which justable follower member 23. A suitably packed the single temperature and back pressure responadjustment screw 24 is carried by the body [4 sive element has a substantially frictionless conand supports the follower member 23. The valve nection with the valve member. 10 member l9 controls flow of refrigerant medium Another object is to provide in a low temperainto the outlet conduit 25 which is connected ture valve having a single temperature and back to the conduit 8 leading to the evaporator 9. The pressure operating element, means to prevent chamber s closed. y a Partition member 25 contact of the refrigerant medium with the elesealed to the casing I4 and recessed to provide a back pressure chamber 21." Mounted on the Another object is to provide an expansion valve body member I 4 and sealed to the partition memhaving a novel external equalizer connection. ber 26. there is a recessed cap member 28 form- The invention consists in the improved -coning part of the valve operating fluid thermostat struction and combination of parts to be more or p element a nt i an xpansi n fully described hereinafter and the novelty or cha 2 e chamber 29 is p ra from which will be particularly pointed out and disth back p e chamber 21 by a p u sponsive diaphragm member 30, which is hermet- In the accompanying drawing to be taken as ically sealed at it periphery to the partition a part of this specification there is fully and member 25 and p member Within the p clearly illustrated a preferred embodiment of the 25 member 33 there is a helical coil Compression invention, in which drawing: a spring 3| acting on the diaphragm member I! Figure 1 is a diagrammatic view of a refrigera d ur in i toward. the p i i member ating apparatus including the valve of the i The chamber 28 is connected by a capillary tube 32 to the feeler member I I. Fig. 2 is a detail vie partly in section of the s agascharged type Do element vinga limvalve on the line 2-2 of Fig. 1, and ited quantity of volatile liquid, preferably the Fig. 3 is a view of the valve in longitudinal cename as e refrigerant medium used in the tral section on the line 3-4 of Fig. 2. frige tms apparatus, the quant y being su h Referring to, the drawing by characters of refthat all-of the liquid can condense within theerence, l designates generally a compressor driv- 5 chamber y en by a motor or the like, not shown, and 0011- The back Pressure chamber 27 is cted trolled in any suitable manner. The outlet of a a way It to the portion f h u l t the compressor is connected by a conduit 2 to a conduit 25 which is aligned with the valve P condenser 3 from which a conduitl leads to the a formed by the seat member 28. Loosely guided inlet '5 of the expansion valve 6. From the exin the passageway 83, as at 3|, there is a force pension valve outlet 1 a conduit 8 leads to the transmitting thrust member or push rod 35 which refrigerant medium evaporator I which is conextends into the back pressure chamber 21 for nected by a conduit I l to the inlet of the cornoperative abutting engagement with the dia- I'he suction or return line conduit phragm member 30 and which has its other end. II has clamped thereto, adjacent the outlet of extending through the valve port for operative the evaporator, the feeler elementuor bulb of abutting engagement, as at 30, with the valve the thermostatic power element for the valve I. member IS. The passageway 38 is enlarged, as The external equalizer oi the valve 6 is connected at 31, to provide a draw-oi! chamber having an by a pipe I: tothe suction conduit I. at afitting 5 apertured end wall surrounding the thrust ll adjacent the evaporator outlet. member I and separating the chamber Tl irom The valve 6 has a body or casing It with an the outlet conduit II. The aperture through the inlet conduit I for connection to the condensor wall 38 is sufllciently large so that the thrust I by the conduit 4. The conduit l5 leads through member can have free lateral movement. Witha warm liquid refrigerant chamber l6 and pas- II in the'chamber "there is a sleeve member 3! having a close sliding fit on the thrust member 35 and seating on the end wall 38 to close the aperture therethrough, the member 39 being laterally shiftable in the chamber 31 toaccommodate lateral movement of the thrust member 35. Within the chamber 31 there is a helical coil spring 60 which surrounds the thrust member 35 and is held under compression between -the chamber upper end wall and the sleeve member 39 to hold the sleeve member 39 tightly against the end wall 38. Opening into the draw-ofi chamber 31 is the external equalizer connection passageway fil provided with a screw-threaded outlet 52 which opens through the outer wall of the casing hi for connection of the pipe I2 to the suction conduit Ill.

The operation of the valve is as follows. When the compressor I is placed in operation, the refrigerant back pressure is reduced and is transbe admitted to the outlet conduit 25 for flow through the conduit 8 into the evaporator 9. When the evaporator 9 has become floodedor wetted with refrigerant medium to a pointadjacent the evaporator side of the bulb member II, the cooling of the bulb member will permit the spring 22 to move the valve member l9 toward closed position. The expansion valve 6 will now function in the usual manner to throttle the flow of refrigerant medium tothe evaporator 9, maintaining it floodedthroughout its length. Any refrigerant medium which escapes from the outlet conduit 25 into the draw-01f chamber 31 will be withdrawn by the compressor I through the equalizer passageway 4| and not be permitted to flow through the guide portion of the passageway 34 into the back pressure chamber 21. With extremely low evaporator temperatures, say in the, neighborhood of 100 below zero F., the pressure change per degree change of temperature, is so small that frictional resistonce, as by the usual packing, to the thrust member 35 would require a large temperature change in order to move the valve member I9.

Accordingly, it would be impossible to maintain a constant super-heat setting for the expansion valve, and refrigerant medirun would be fed irregularly to the evaporator 9.

What is claimed and is desired to be secured by Letters Patent of the United States is:

A gas charged thermostatic expansion valve comprising a hollow casing having spaced suction pressure and valve chambers and having a straight passageway extending between and opening at its opposite ends through the adjacent end walls of said chambers,-said casing having an annular guideway and closure portion extending into said passageway substantially in the plane of said suction chamber end wall, a diaphragm forming a wall of said suction chamber, a valve member in said valve chamber and controlling flow into said passageway, a thermostatic power element having a pressure chamber with the'expansible wall thereof formed by said diaphragm, said power element having a feeler bulb containing a volatile liquid in limited quantity entirely condensible out of said bulb into said element pressure chamber, said casing having an inletpassageway leading to said valve chamber and having an outlet passageway from said straight passageway, means to warm said power element pressure chamber, a thrust rod extending longitudinally through said straight passageway and reciprocally guided in said "an nular portion and having itsends engaging said diaphragm and said valve member, an annular plug member surrounding said thrust rod. adjacent said annular portion to provide a draw-oft chamber therebetween and separating said outlet passageway from said draw-off chamber, a sleeve member slidably fitting said thrust rod within said draw-off chamber and seating on said plug member to close the clearance space between said plug member and said thrust rod, a helical spring surrounding said rod and held under compression between said sleeve member and said annular portion, said casing having an equalizer passageway opening directly into and through the side wall of said draw-off chamber, said annular portion fitting said thrust rod sufflciently closely so that suction pressure in said equalizer passageway will prevent refrigerant medium which escapes into saiddraw-oif chamber from flowing into said suction pressure chamber. EARNEST J. DILLLMAN.

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