US2036898A - Air or gas compressor - Google Patents

Description

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.A TTO/QA/EX Patented Apr. 7, 1936 UNITED STATES PATENT OFFICE AIR OR GAS COMPRESSOR Maurice Alberic Twisleton-Wykeham-Fiennes ish company Application December 4, 1934, Serial No. 755,994 In Great Britain May 24, 1933 11 Claims.

This invention relates to air or gas compressors of the reciprocating type, and of the kind in which the adjacent ends of two or more cylinders are interconnected by a valve controlled passage 5. or passages, the said valve or valves being in turn so controlled that on the pressure generated in the receiver attaining a predetermined figure the valve controlling the passage or passages opens and the air or gas surges to and fro between the 10 said cylinders, while when the pressure falls below the said predetermined pressure the valve closes.

To enable a compressor to operate efficiently the clearance volumethat is to say the volume 15 of the space enclosed between the inner ends of the pistons at their inner stroke limits, the inner ends of the cylinders, the inlet and outlet valves and the unloading valve or valvesmust be reduced to a minimum so that the amount of compressed air remaining in a cylinder at the end of the delivery stroke is at a minimum. Hence any unloading means employed must be such that any increase in the clearance volume it may necessitate is as small as possible.

25: The object of the present invention is to provide unloading means which will enable the length of the passages between the cylinders and the unloading means to be a minimum with a view to reducing the clearance volume to a minimum,

30 and, if desired, allow the cylinders tobe arranged as close together as possible where compactness is necessary, without restricting the cross sectional area or volume of the inter-connecting passages between the cylinder working spaces.

35 Another object of the invention is to provide improved unloading means which may be used with a compressor of any desired number of cylinders and give simultaneous unloading between the various cylinders so that the possibility 40 of time lag occurring between different cylinders unloading may be positively eliminated, or alternatively, the unloading between different sets of cylinders effected in stages.

A further object of the invention is to provide 45 an improved control of the unloading means which control shall be positive in its action and entirely free from hunting.

According to the invention the unloading valve comprises a single movable valve member which 50 on the one hand and the cylinders on the other hand are arranged substantially tangential to each other adjacent the clearance space, and having its axis substantially parallel with the axis of the compressor crankshaft.

For unloading in stages, two cylinders having pistons connected to cranks spaced at 180 or three cylinders having pistons connected to cranks spaced at 120 may be interconnected.

With a view to reducing the clearance volume to a minimum, the length of the passage or passages communicating between the cylinder or cylinders and the valve means is a minimum.

The invention will now be described by way of example with reference to the accompanying drawings which show its application to the cylinders of a two-cylinder compressor.

In the said drawings:

Fig. 1 is an elevation partly in section showing the unloading device and its control means in section.

Fig. 2 is a side view of Fig. 1.

Fig. 3 is a sectional plan of Fig. 2 taken on the line III--III of Fig. 2.

Fig. 4 is an enlarged view of a portion of Fig. 1.

Fig. 5 is an enlarged View of the pilot valve and shows its connection with engine throttle.

Fig. 6 is a sectional plan similar to Fig. 3 but showing an axially movable unloading valve.

Fig. '7 is a fragmentary sectional elevation of a suction port controlled by a pilot valve.

Fig. 8 is a view in elevation of a compressor adapted for unloading in stages.

Fig. 9 is a view in elevation of a pilot valve adapted for two stage unloading.

Fig. 10 is a semi-diagrammatic section of the port arrangements of the pilot valve shown in Fig. 9.

Fig. 11 is a detail view of an unloading valve for unloading in stages.

Referring more particularly to the drawings, a compressor is shown having a crank shaft llll and compressor cylinders l and 2, which are connected by separate passages 3, 4 to a transfer passage 5 in an inlet manifold 6. A common hollow unloading valve 1 is located in a bore which intersects the passages 3 and 4, which are thus controlled by the said valve. The valve 1 being hollow itself also provides a connecting passage in addition to the passage 5. The valve 1 has rigid therewith an arm 8 the free end of which engages in a slot formed in the middle of a double ended piston 9 adapted to work in a cylinder Ill secured to the compressor cylinders.

Each end of the cylinder I0 is connected to a casing II in which a weighted pilot valve I2 is adapted to move up and down so as to establish communication with either the upper or lower end of the cylinder Ill according to its position in the casing I I. The connections between the easing and the cylinder [0 comprise pipes l3, I4

fill

' pipe 33 to the engine throttle control.

connected to longitudinally spaced ports l5, IS in the casing l l, the casing l I being connected to the air receiver (not shown) through a port H between the ports l5, l6. Opposite the port l5, which controls the flow of air to move the valve 1 to the unloading position, is a port 48 connected to a cylinder in which is a piston operatively connected to the throttle control of the engine driving the compressor.

With this arrangement when the air pressure in the receiver reaches a predetermined limit, the pilot or control valve i2 is lifted and so allows live air to fiow through the port E6, pipe I4, and enter the lower end of the cylinder i3 and raise the piston 9 so that the valve '3 is turned into the unloading position. Simultaneously pressure air flows through the port 8 to operate a spring piston 48 connected with the prime mover throttle 49 and causes the power of the prime mover driving the compressor to be reduced.

An adjustable needle valve [9 (see Figs. 1 and 4) is provided in the upper end of the cylinder I8 so that the rate of flow from the pipe l3 into the cylinder [9 may be varied at will.

By making the control valve [2 weight controlled instead of spring controlled, the action of the valve is rendered more definite so that hunting such as occurs with a spring controlled valve is avoided.

Fig. 6 shows an alternative form of the invention in which the unloading valve comprises an axially movable valve 2|. The piston 9 is dispensed with and the live air taken through the pipes 22 connected with the pilot valve to each end of the valve casing 23.

Fig. 7 shows a modification wherein the inlet air suction 24 is closed simultaneously with the opening of the unloading valve. This is efifected by connecting the control valve pneumatically to the one side of a piston 26 which at the unloading pressure is moved across the inlet port 24 of the compressor against the action of a spring 27 or weight. This has the advantage of lowering the pressure in the cylinder or cylinders by reason of the fact that air is completely shut off.

Instead of unloading the cylinders simultaneously, it may be desirable to unload by stages, that is to say at a given receiver pressure one group of cylinders only unloads. This may be efiected, for example, by providing an additional pilot valve or valves adapted to operate at a pressure or pressures other than the normal unloading pressure. In the arrangement shown in Fig. 8 a four-cylinder compressor is shown, the cylinders of which are grouped in two pairs A, B. The pair A are controlled by a separate unloading valve 29 and the pair B by a separate unloading valve as. The said unloading valves are identical with that shown in Figs. 1 to 3 so that it is not necessary to show these in detail again. The valve 29 is operated by a pilot valve 3i exactly as in the arrangement shown in Figs. 1 to 4, the pipe 32 being connected to the receiver and the The valve 30 is similarly operated by a second pilot valve 34 which is connected by the pipe 35 to the receiver, and is loaded with less weight that is the pilot valve 3| so that it operates the valve 39 at a lower receiver pressure than that required to operate the valve 29.

Alternatively such stage unloading may be effected by means of a pilot valve which has more than one operative position according to the pressure in the receiver. For this purpose the unloading valve may have an additional port or ports adapted to be placed in communication with the desired group or groups of clearance spaces at the lower receiver pressure or pressures corresponding to the first stage or stages of unloading. Such a pilot valve and unloading valve are shown in Figs. 9, l0, 11, in which 36 is the movable member of the pilot valve and 3'! the pilot valve casing. The first stage of the unloading is controlled by the lower portion of the pilot valve, the pipe 38 being connected to the receiver and the pipes 39, 46 to the two ends of the unloading valve casing or the casing of the piston operating the unloading valve. The second stage of the unloading is controlled by the upper portion of the pilot valve, the pipe 4| being connected to the receiver and the pipes 42, 43 to the unloading valve casing or the casing of the piston operating the said valve. Holes 44, 45, 46 are formed in the casing 3'! for exhaust purposes, the hole 45 being common to both portions of the valve 36. At the first stage of the unloading the weight 50 is raised by the valve 36, the said weight being threaded in an extension 36a of the said valve. The extension 35a passes through a bush 5| flanged at its lower end at Eta and supported in a bracket 52 rigid with the valve casing 31. A second weight 53 is threaded on the bush El and rests on the flange 51a, so that on the first stage of unloading taking place the movement of the valve 36 is arrested when the weight 50 abuts against the weight 52. When the receiver pressure rises to that predetermined upon for the second stage of unloading the weight 52 is raised with the weight 50.

The unloading valve is a single member 4'! controlling the two pairs of cylinders and is shown in Fig. 11. The ports 41a therein are the first stage unloading ports and affect the one pair of cylinders only. Four ports 411) are the second stage unloading ports. The said ports 47?) are spaced circumferentially from the ports 47a and are in alignment with one another so as to eifect simultaneous unloading of all cylinders.

Fig. 9 shows diagrammatically the arrangement of the various pipes, from which it will be seen that after a certain amount of movement of the valve 36 communication is established between the pipes 38 and 39 and the unloading valve 41 is rocked so that first the ports 41a establish communication between the one pair of cylinders and so effect the first stage of unloading. Further movement of the pilot valve 38 establishes communication between the pipes 4! and 42 and so causes further movement of the unloading valve 41 with the result that the ports 4Tb establish communication between all the cylinders and effeet the second stage of unloading.

It will be seen that with the arrangement according to the invention the unloading means is freely accessible, and also allows of the unloading valve being effectively cooled (1) on account of its being situated in a relatively cool position and (2) as its accessible position allows of its being thoroughly water jacketed. Again, it will be seen that in a compressor according to the invention having a number of interconnected cylinders and a common valve, all the transfer ports may be arranged to open simultaneously, so that all possibility of lag between the times of opening of the transfer ports is eliminated, or the said ports may be arranged to open consecutively. Further, on account of the accessibility and arrangement of the unloading valve, means communicating with the said cylinders, a pilot may be provided thereon as at whereby the valve may be manually operated at will.

We claim:

1. A multi-cylinder fluid compressor of the kind described comprising, in combination, a plurality of cylinders, passage means interconnecting the interiors of said cylinders, unloading means adapted to control said passage means, said unloading means comprising valve means adapted to control a plurality of cylinders and said cylinders on the one hand and said valve means on the other hand being arranged substantially tangential to each other adjacent the clearance space, and said valve means having its axis substantially parallel with the axis of the compressor crank shaft.

2. A multi-cylinder fluid compressor of the kind described comprising, in combination, a. plurality of cylinders, passage means interconnecting the interiors of said cylinders, unloading -ders viewed. in the direction of the axes of said cylinders adjacent the clearance space and having its axis substantially parallel with the axis of the compressor crankshaft.

3. A multi-cylinder fluid compressor of the kind described comprising, in combination, a

plurality of cylinders, passage means interconnecting the interiors of said cylinders, unloading means adapted to control said passage means,

said unloading means comprising valve means adapted to control a plurality of cylinders, said cylinders on the one hand and said valve means on the other hand being arranged substantially tangential to each other adjacent the clearance space and said valve means having its axis substantially parallel with the axis of the compressor crankshaft, the said valve being adapted to effect simultaneous unloading of all cylinders.

l. A multi-cylinder fluid compressor of the kind described comprising, in combination, a plurality of cylinders, passage means interconnecting the interiors of said cylinders, unloading means adapted to control said passage means, said unloading means comprising valve means adapted to control a plurality of cylinders, said cylinders on the one hand and said valve means on the other hand being arranged substantially tangential to each other adjacent the clearance space and said valve means having its axis substantially parallel with the axis of the compressor crankshaft, the said valve being adapted to effect unloading of all cylinders in stages.

5. A multi-cylinder fluid compressor of the kind described comprising, in combination, a plurality of cylinders, passage means interconnecting the interiors of said cylinders, unloading means adapted to control said passage means, said unloading means comprising axially movable valve means adapted to control a plurality of cylinders, said cylinders on the one hand and said valve means on the other hand being arranged substantially tangential to each other adjacent the clearance space, and said valve means having its axis substantially parallel with the axis of the compressor crankshaft, a receiver valve adapted to be operated by pressure air from said receiver, and passage means from said pilot valve adapted to take live air to each end of said axially movable valve means to operate said axially movable valve means according to the position of said pilot valve.

6. A multi-cylinder fluid compressor of the kind described comprising, in combination, a plurality of cylinders, passage means interconnecting the interiors of said cylinders, unloading means adapted to control said passage means, said unloading means comprising valve means adapted to control a plurality of cylinders, said cylinders on the one hand and said valve means on the other hand being arranged substantially tangential to each other adjacent the clearance space, and said valve means having its axis substantially parallel with the axis of the compressor crankshaft, a receiver connected to the cylinders, a pilot valve adapted to be operated by pressure air from said receiver, passage means from said pilot valve to said unloading means, such that on, operation of the said pilot valve pressure air is admitted to said unloading means to actuate the movable valve means, means for driving said compressor, control means on said driving means, a pneumatic operating device connected to said control means, a further passage means connecting said pilot valve to the id pneumatic device, so that when a pilot valve 1. in the position to open said unloading means the power of said driving means is reduced.

7. A multi-cylinder fluid compressor of the kind described comprising, in combination, a plurality of cylinders, passage means interconnecting the interiors of said cylinders, unloading m ans adapted to control said passage means, said unloading means comprising valve means adapted to control a plurality of cylinders, said cylinders on the one hand and said valve means I on the other hand being arranged substantially tangential to each other adjacent the clearance space, and said valve means having its axis substantially parallel with the axis of the compressor crankshaft, an inlet air suction port, and means whereby the said suction port may be opened and closed simultaneously with the opening of the unloading means.

8. A multi-cylinder fluid compressor of the kind described comprising, in combination, a p1urality of cylinders, passage means interconnecting the interiors of said cylinders, unloading means adapted to control said passage means, said unloading means comprising valve means adapted to control a plurality of cylinders, said cylinders on the one hand and said valve means on the other hand being arranged substantially tangential to each other adjacent the clearance space, and said valve means having its axis substantially parallel with the axis of the compressor crankshaft, an inlet air suction port, means whereby said suction port may be opened and closed simultaneously with the opening of the unloading means, a receiver, a pilot valve adapted to be operated by pressure air from the said receiver, passage means from said pilot valve to said unloading means, a compressor inlet port, a cyl nder, and in said cylinder a piston adapted for movement across said inlet port, restoring means adapted to act on said piston, and passage means connecting said pilot valve with said cylinder, so that at unloading pressure said piston is moved across said inlet port.

9. A multi-cylinder fluid compressor of the kind described comprising, in combination, a plurality of cylinders, passage means interconnecting the interiors of said cylinders, unloading means adapted to control said passage means, said unloading means comprising valve means adapted to control a plurality of cylinders, said cylinders on the one hand and said valve means on the other hand being arranged substantially tangential to each other adjacent the clearance space, and said valve means having its axis substantially parallel with the axis of the compress r crankshaft, a receiver connected to said cylinders, a plurality of pilot valves adapted to be operated by pressure air from said receiver, passage means from said pilot valves to said unloading means such that on operation of the said pilot valves pressure air is admitted to said unloading means to actuate the movable valve means at different unloading pressures.

10. A multi-cylinder fluid compressor of the kind described comprising, in combination, a plurality of cylinders, passage means interconnecting the interiors of said cylinders, unloading means adapted to control said passage means, said unloading means comprising valve means adapted to control a plurality of cylinders, said cylinders on the one hand and said valve means on the other hand being arranged substantially tangential to each other adjacent the clearance space, and said valve means having its axis substantially parallel with the axis of the compressor crankshaft, a receiver connected to said cylinders, a pilot valve adapted to be operated by pressure air from said receiver, passage means from said pilot valve to said unloading means, such that on operation of said pilot valve pressure air is admitted to said unloading device to actuate the movable valve means, said pilot valve having a plurality of operative positions according to the pressure in said receiver.

11. A multi-cylinder fluid compressor of the ind described comprising, in combination, a plurality of cylinders, passage means interconnecting the interiors of said cylinders, unloading means adapted to control said passage means, said unloading means comprising valve means adapted to control a plurality of cylinders, said cylinders on the one hand and said valve means on the other hand being arranged substantially tangential to each other adjacent the clearance space, and said valve means having its axis substantially parallel with the axis of the compressor crankshaft, a receiver connected to said cylinders, a pilot valve adapted to be operated by pressure air from said receiver, passage means from said pilot valve to said unloading means, such that on operation of said pilot valve pressure air is admitted to said unloading device to actuate the movable valve means, said pilot valve having a plurality of operative positions according to the pressure in said receiver and additional ports in said unloading means adapted to establish communication between groups of cylinders at the various receiver pressures.

MAURICE ALBERIC TWISLETON- WYKEHAM-FIENNES. ERNEST HENRY SWEETSER.

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