US 2594815 A
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April 29, 1952 c. B. SMITH 2,594,315
UNLOADER FOR SLEEVE VALVE GAS COMPRESSORS Filed May 31, 1946 Y s Sheets-Sheet 1 i g .96 9 3 .;z 5 J7 7 L32"; Q j l 51 g $0 1&4
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Hnnfluwll r W ATTOQ/VEYS April 29, 1952 c. B. SMITH 2,594,315
UNLOADER FOR SLEEVE VALVE GAS CQMPRESSORS Filed May 31, 1946 5 Sheets-Sheet s 4 TTOQNEYS Patented Apr. 29, 1952 UNLOADER FOR SLEEVE VALVE GAS COMPRESSORS Christopher Broom Smith, Naphill, England, as-
signor to Broom and Wade Limited, High Wycombe, England, a British company Application May 31, 1946, Serial No. 673,592
In Great Britain June 4, 1945 This invention relates to reciprocatory compressors for air or gas of the type having a sleeve valve controlling the admission of air to the cylinder from a suction chamber and its delivery to an intermediate delivery chamber from which 8 Claims. (Cl. 23022) the air passes through a non-return valve to the outlet of the compressor. It has been proposed to provide a compressor of this type with a port in its cylinder head which communicates with the atmosphere and is controlled by a valve which normally closes the port but is open to place the cylinder in communication with the atmosphere and unload the compressor.
According to the present invention an air or gas compressor of the above type is provided with a passage extending from the intermediate delivery chamber (delivery to which is controlled by the sleeve valve) to the atmosphere or to the suction chamber and with an unloading valve arranged to open or close that passage.
The invention is particularly applicable to compressors in which one end of the sleeve valve reciprocates in an annular space between the cylinder and an inwardly-projecting part of the cylinder head. The intermediate delivery chamber may be constituted by the portion of this annular space beyond the end of the sleeve valve.
The invention will now be described, by way of example, as applied to a reciprocatory compressor, and with reference to the accompanying drawings in which:
Figure l is a vertical section through a cylininder I l which is surrounded by a suction. chamberl2 communicating "with the cylinder by an annular port or series of ports l3. The'air inlet to the suction chamber is indicated at Hi and.
water-jacket space around the cylinder at I5, 18.
'Within the cylinder there reciprccates a sleeve valve I1 and inside the sleeve valve a piston I8 operated by a connection rod 19, the. crank, crankcase and lower portion of the cylinder being omitted in the drawing as the construction of these parts is well understood. On the top of the cylinder there rests an intermediate head 2 plate '26 and above the inder head 2|, the head plate and the main head 2| together constituting the cylinder head and being secured by studs 22 and nuts 23. To the underside of the intermediate head plate 20 there is secured an inwardly-projecting part 24 of the cylinder head, the part 24 being secured to the intermediate plate 20 by screws 25 and the whole of the three parts of the head, 20, 2|, 24, being secured together by studs 23 and nuts .21. The portion 24 of the cylinder head which pro jects inwardly into the cylinder provides an annular space 28 between itself and the inner wall of the cylinder ll whichfits the upper end of the sleeve valve I! and in which the upper end is able to reciprocate. A suitable internal sealing ring 29 is provided in the top of the sleeve valve I! to afford the tight joint between it and the cylinder head portion 24. This portion 24 is formed with spaced passageways 30, formed by short flutes in its external surface at intervals around its lower edge, which passageways are always open to the cylinder but are covered by the sleeve valve [1, which is raised during the suction stroke, so that throughout this stroke the intermediate delivery chamber 28 is cut oil from communication with the cylinder.
During the delivery stroke the sleeve valve I! is lowered and uncovers the communication of the passageways 30 with the intermediate delivery chamber 28 so'that the piston 18 may, during the delivery stroke, force the air through the passages into the intermediate delivery ber 28. v I
The intermediate head plate 23 is formed with an annular space 3|. in its under surface which constitutes a continuation of the intermediate delivery chamber 28 and this space communicates through a ring of ports 32 with the upper face of the intermediate head plate 23 where it lies within a large outlet port 33 formed within the main head casting 2!. the ring of ports 32 are closed byan'annular plate valve 34 which seats on the'upper surface of the intermediate head plate 23 above the ports 32 and is urged downwardly by springs 35 held in recessesin a ring-shaped casting 36 which overlies'but is spaced from the plate valve 3 t.
The ring-shaped casting 36 is supported from the intermediate head plate 20* by lugs 3'! which project from its underside and rest on the plate 20,
these lugs being pierced by holes through which, pass fixing studs 38.
head plate 20 a main cyl-.
cham- The upper ends of The normal delivery. ofv the compressor thus passes through the plate valve 34 into the outlet 33 and the annular de-- livery chamber 28 does not constitute any dead air space in the compressor because after it has closed the communication of the space above the piston IS with the intermediate delivery chamber through the passages 33 at the end of the delivery stroke, the sleeve valve I? continues to move upwardly and forces air out of the intermediate delivery chamber 28 through the valve 32 until the sleeve valve has reached the top of the space afforded by the intermediate delivery chamber. When the valve H is near the top of its stroke it opens communication between the suction chamber l2 and the interior of the cylinder owing to the ring of ports 39 in the sleeve valve coming into register with the inlet ports l3 in the cylinder wall.
The intermediate head plate 28 is also provided with a passage All which leads out of the intermediate delivery chamber at 3! to one side of the cylinder to a position where it comes beneath an unloading port 4| formed in the main head casting 2|. The unloading port M is closed by an inverted lift-valve 62 which constitutes an unloading valve and is provided with a stem extending upwardly through the cylinder head into a control cylinder 43. In the control cylinder 43 is a control piston 44 which bears upon the stem of the unloading valve 52 and the piston and valve tend to be lifted by a spring d5.
The control cylinder 53 is connected by a pipe 46 to an automatic pilot valve, not shown in the drawing. The pilot valve is connected to the air receiver to which the compressor delivers, or to some part connected therewith, and it admits pressure to the pipe 48 when the desired working pressure is reached. When air is admitted to the pip 46 it causes the control piston to move down to open the valve 42 and places the passage in communication, through the port M, with a further portion 41 of the passage which extends from the intermediate delivery chamber at 3!.
As can be seen from Figure 2 of the drawing, the passage 47 communicates with a port 48 in the lower face of the head 21 and thence by way of a port 48 in the intermediate head plate. 29 and a passage 50 in the cylinder, which constitutes an extension of the passage M, with the suction chamber l2.
In the operation of the unloading device, when the valve 42 is closed compressed air is delivered to the outlet 33 through the plate valve 34. and builds up pressure, in the receiver or other vessel, to'which the compressor delivers. When the air pressure has been built up to the predetermined value, the pilot valve operates and delivers air under pressure to the pipe 43, thus causing the valve 42 to be opened. When the valve is opened theair delivered by the piston to the intermediate delivery chamber 28 passes from the intermediate delivery chamber by way of the passage 40, port 41 and further extensions of the passages 4'! and 56, to the suction chamber I2. Return of air past the valve 42 is prevented because on the suction stroke of the compressor the communication between the intermediate delivery chamber 28 and the cylinder is cut off by the sleeve valve l1 and therefore all the air passing into the cylinder enters it through the ports I3. After the sleeve valve I! has cut off the intermediate delivery chamber from the cylinder it continues to rise and delivers air through the unloading port 4| to the suction chamber 52. In the suction belt l2 the relatively hot air which has been expelled from the cylinder and to the intermediate delivery chamber becomes mixed 4 with atmospheric air from the inlet l4 and cooled before it is drawn again into the cylinder and redelivered through the unloading valve.
Two results follow from this arrangement of the unloading port, namely, first that as hot air is not sucked to and fro past the valve on both suction and delivery strokes of the piston, the valve is not subjected to so much heating as in the case where the valve opens a direct communication between the cylinder and the suction zone. The risk of the valve reaching a high temperature and causing carbonization of the oil is therefore reduced. Secondly, as the intermediate delivery chamber 28 is interposed between the cylinder and the unloading passages and the direction of air flow is alway the same through these parts, and as also after the piston has been shut off from the intermediate delivery .chamber the sleeve valve continues to deliver some air, there is less noise from the operation of the unloader than has previously been the case.
Furthermore, as the valve 42 does not lie over the cylinder or directly communicate with it there is no risk of any damage being done should the head of the valve break or the spring 45 break, while the compressor is in operation. With the prior construction it would have been possible for the valve head in these circumstances to fall into the compressor cylinder, or at least to come in contact with the head of the piston, and cause damage.
Referring to Figures 3 and 4, these, show a twocylinder compressor comprising cylinders 60, 6|, which contain sleeve valves 62, 63 and pistons 64, 65. The cylinders are in a single block surrounded by a waterjacket space 63 and surmounted by an intermediate head plate 67 and a main head casting 63. There is a suction chamber 69 and air inlet it, the general arrangement of all these parts being similar to that already described in connection with Figures 1 and 2. However, the construction difiersin that theunloading port H instead of being located in the head as in the case of the unloading port 4! of Figures 1 and 2 is located in the cylinder block and the lift valve I2 which controls it has a stem which extends downwardly through a guide 13 into a chamber M at the side of the cylinder block. The chamber 74 constitutes a passage which connects the unloading port with the suction chamber 69. The valve 12 is urged in a direction to close the port H by a spring (5.
As can be seen from the plan of Figure 4, there are two valves 72, one, for each cylinder, and the two valves are operated by a single lever 16 having a forked end at 17, 78, the two arm of, the fork engaging the lower ends of the stems of the valves. The forked lever it is pivoted on a bracket i9 secured to the exterior of the'cylinder block and the lever passes. to the outside of the cylinder block through a large aperture in the side thereof. which aperture is covered by a casing 853. The casing 89 embodies in it upper portion an actuating cylinder 3! which contains a piston H2 and is connected to an air-supply pipe 83, corresponding to the pipe 16 of Figure l. Th space 84 in the intermediate head plate 6'1, which cor-" responds to the passage 40 of Figure l, is shaped so as to extend into the intermediate delivery chamber of each cylinder, as indicated by the chain lines 85 of Figure 4. It will be appreciated that the sectioned part of Figure 3 is taken upon an irregular plane which is approxi-.
mately represented by the line 33 of Figure 4.
The operation is the same as in the case of Figures 1 and 2, in this instance both cylinders being unloaded simultaneously by operation of the same lever.
Although a piston and cylinder have been shown in the drawings for operating the valves which control the unloading ports, it will be appreciated that a sore; or cam or other mechanical device could be employed for operatin the valve either in addition to the piston or alternately thereto. The mechanical operation of the unloading device may be of service in cases where it is desired to start up the compressor and connect it by hand to a system of pipe work which is already under pressure, as where there are several compressors connected to supply a single system.
1. A compressor comprising, in combination, a cylinder, a sleeve valve reciprocable therein, a piston reciprocable within the sleeve valve, means for operating the sleeve valve and piston, a suction chamber in the form of an annular zone around the cylinder communicating with the cylinder through ports controlled by the sleeve valve, an intermediate delivery chamber communicating by ports controlled by the sleeve valve with the cylinder, an outlet, a delivery valve between the intermediate delivery chamber and the outlet, a passage extending from the intermediate delivery chamber into communication with atmosphere and an unloading valve arranged to open and close that passage.
2. A compressor as claimed in claim 1 wherein the passage extending from the intermediate delivery chamber, into communication with atmosphere leads into the suction chamber of the compressor which suction chamber is itself open to atmosphere.
3. A compressor as claimed in claim 1 wherein the cylinder has a cylinder head with an inwardly-projecting portion aifording an annular space between the cylinder and said inwardlyprojecting portion of the cylinder head, one end of the sleeve Valve reciprocates in said space, and the intermediate delivery chamber is constituted by a portion of said annular space beyond the end of the sleeve valve.
4. A compressor as claimed in claim 1, wherein the unloading valve is constituted by a lift valve opening against the flow of air from the intermediate delivery chamber to atmosphere and provided with means for lifting it from its seating against the pressure when unloading is to occur.
5. A compressor as claimed in claim 1, wherein the unloading valve is constituted by a lift valve opening against the flow of air from the intermediate delivery chamber to atmosphere, and wherein means are provided for lifting the unloading valve from its seat comprising a cylinder and piston and pipe connections for the supply of operating pressure thereto.
6. A compressor as claimed in claim 1, wherein the cylinder comprises two cast parts, the one a main cylinder-body casting and the other a cast cylinder head, with means to secure the head to the main casting, the unloading valve is a lift valve located in the cylinder head, and the passage which is opened and closed thereby is constituted in part by a passage cast in the cylinder head and in part by a passage in the main cylinder-body casting, the two passage parts communicating by ports formed in the joint between the cylinder head and the main casting.
7. A compressor as claimed in claim 1, wherein the unloading valve is a lift valve mounted on the cylinder of the compressor.
8. A. compressor, comprising, in combination, a cylinder' block and two cylinders side by side in the block; each cylinder having associated therewith a sleeve valve reciprocable therein, a piston reciprocable within the sleeve valve, means for operating the sleeve valve and piston, a suction chamber in the form of an annular zone around the cylinder communicating with the cylinder through ports controlled by the sleeve valve, an intermediate delivery chamber communicating through ports controlled by the sleeve valve with the cylinder, an outlet, a delivery valve between the intermediate delivery chamber and the outlet, a passage extending from the intermediate delivery chamber into communication with atmosphere, and an unloading valve arranged to open and close that passage; and the two unloading valves are located side by side in the cylinder block and an operating lever engages both unloading valves and is operated by a single actuating means.
CHRISTOPHER BROOM SMITH.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 1,668,795 Aikman May 8, 1928 1,805,741 Prestage May 19, 1931 1,878,326 Ricardo Sept. 20, 1932 2,074,911 Hull Mar. 23, 1937 2,160,860 Gustafson June 6, 1939 2,231,904 Gustafson Feb. 18, 1941 FOREIGN PATENTS Number Country Date 234,183 Great Britain 1925