US2113637A

US2113637A - Compressor unloader

Info

Publication number: US2113637A
Application number: US39133A
Authority: US
Inventors: Burton S Aikman
Original assignee: Westinghouse Air Brake Co
Current assignee: Westinghouse Air Brake Co
Priority date: 1935-09-04
Filing date: 1935-09-04
Publication date: 1938-04-12
Anticipated expiration: 1955-04-12

Description

B. S. AIKMAN COMPRESSOR UNLOADER Filed Sept. 4, 1935 April 12, 1938.

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wm b9 Q INVENTOR EURTDN s. AIKMAN NEY I ATTOR Patented Apr. 12,1938

UNITED STATES COMPRESSOR UNLOADER -Burton s. Aikman, Wilkinsburg, Pa assignor to The Westinghouse Air Brake Company, Wilmerding, Pa., a corporation of Pennsylvania Application September 4, 1935, Serial No. 39,133

, 8 Claims.

This invention relates to a control system for a fluid compressor driven by an internal combustion engine.

It is the principal object of this invention to 5 provide a control system for a fluid compressor driven by an internal combustion engine, the control system comprising unloading means associated with the compressor and operated by the vacuum in the inlet passage of the engine.

10 A further object of this invention is to provide a compressor control system of the type referred to and which incorporatesmeans responsive to the pressure of the fluid compressed by the compressor and controlling a communication between 5 the engine intake passage and the unloading means, whereby the unloading means is controlled by the engine intake pressure in response to variations in the pressure of the fluid compressed by the compressor.

Another object of this invention is to provide a compressor control system of the type referred to and which incorporates means subject to the pressure of the fluid compressed by the compressor and subject also to the vacuum in the 25 inlet passage of the engine and controllinga passage between the engine inlet passage and the unloading means.

A further object of this invention is to provide a compressor control system of the type referred 30 to and having means subject to the pressure of the fluid compressed by the compressor, said means being biased to a position to maintain the compressor loaded and being movable on a predetermined increase in the pressure of the fluid com- 35 pressed by the compressor to a position to effect unloading of the compressor, said means being subject also to the vacuum in the engine inlet passage on movement to the unloading position,

whereby said means is maintained invsaid unload- 40 ing position until the pressure of the fluid compressed by the compressor is reduced to a value substantially less than that required to eflect movement of the said means from the loading position to the unloading position.

45 other objects of the invention and features of novelty will be apparent from the following description taken in connection with the accompanying drawing, the-single flgure of which is a diagrammatic-view, partly in section, of a fluid 50 compressor equipped with one embodiment of the control system provided by my invention.

Referring to the drawings compressor is indicated generally by the reference character. I and is driven by an internal combustion engine 3,,

65 which may be of any suitable well-known conloading'device 36 is provided and controls the struction and is provided with a fuel inlet passage or manifold 5 through which fuel is supplied to the cylinders of the engine.

The compressor I comprises a body having a crank case chamber I formed therein, and having a cylinder ll associated therewith and provided with a bore in which is reciprocably mounted a piston It. The upper end of the bore in the cylinder ll is closed by means of a cylinder head l5, which has a chamber it formed therein, and in which is positioned an exhaust valve l8 which is urged by means of a spring 22 into engagement with a seat I 9'surrounding a passage communicating with the chamber above the piston l4 and with the chamber i6 in the cylinder head 15 I 5. The chamber I6 is connected with a reservoir by way of a pipe 26.

The wall of the cylinder I I has an annular passage formed therein surrounding the bore in the cylinder and communicating with this bore by way of a plurality of ports 32 which extend through the wall of the cylinder and which communicate with the bore at a point just above the top of the piston I 4, when the piston is at the lower end of its range of movement. A pas-' sage 35 is provided in the wall of the cylinder ll 25 and communicates with the crank case chamber l0 and with the'passage 30.

A combined air strainer and compressor un- 28w of fluid from the atmosphere to the passage The combined air strainer and unloading'device 36 comprises a body section indicated generally by the reference character 39, and having a sub- 35 stantially cylindrical peripheral portion 39 and a central portion 40 which is connected with the peripheral portion 39 by means of a radially extending portion 4|.

The central portion 40 has a valve chamber 43 40 formed therein in which is mounted a valve 45 having a fluted stem positioned in a bore extending through the central portion 40, and having a head adapted to seat on a seat surrounding the bore in which the fluted stem is positioned.

A pair of annular perforated members 41 and 48 are positioned in the cavity between the central portion-40 and the peripheral portion 39 of the body section 98 and have placed between them a quantity of a suitable air straining mate- 50 rial. such as curled hair, indicated at 49. The member 481s held in position by means of the cover plate 5|, which has a projecting portion 53 formed thereon and extending within-the peripheral portion 39 andengaging the member 48. 55

-an annular flange 56 engaging the inner margin of the cover plate 5|. The exposed end of the casing section 55'is threaded and is adapted to be screwed into a threaded opening in the wall of the cylinder II. so that a passage 58 through the casing section 55 communicates with the passage '39 in the wall of the cylinder I I. I

The combined air strainer and compressor unloading device 36 includes a movable abutment in the form of a diaphragm 69, clamped between the casing section 39 and a casing section. 62, and having on one side thereof a chamber 64 in which is mounted a follower 95 which engages one side of the diaphragm 69 and to which is secured the end of the stem of the valve 45. A spring 91 is also mounted in the chamber 64 and engages the follower 55 so as to normally urge the follower to move to the left and thus move the valve 45 away from its seat. I

The diaphragm 69 has onthe opposite side thereof a chamber, 69 which is constantly con-' nected with a chamber I9 on one side of the air straining means 49 by way of passages I2, and

which communicates with the valve chamber 43 by way of the bore in which the valve 45 is mounted. The chamber 14 on the opposite side of the air straining means 49- is in communication with the atmosphere by way of a passage 16.

The control system provided by this invention includes a control device, indicated generally by the reference character 89, and which as shown comprises amovable abutment in the form of a diaphragm 8| clamped between a casing section 92 and a body section 94, and having on one side thereof a chamber 86 which is constantly con nected to the main reservoir 25 by way of a pipe 81. The diaphragm 8| has on the other side thereof a chamber 99 in which is positioned a plunger 92.

The body section 94 has a wall 9| extending across the chamber 99 and having a passage 94 formed therein which is constantlyconnected with the engine -inlet passage 5 by way of a pipe 95. The end of the passage 94 is surrounded by a seat 96 and a ballvalve 98 is held in engagement with the seat 96 by means of a spring 99 acting through a valve cage I99. The valve cage I99 is moved against the spring. 99 by means of the plunger 92 acting through the push pins I92, which extend through openings in the wall 9I which extends across the chamber 99.

The chamber 99 is constantly connected with the chamber 64 of the combined air strainer and compressor unloading device 36 by way of a pipe I95, and is constantly connected with the atmosphere by way of a passage I96, which has a flow capacity substantially less than that of the passage 94 and pipe 95 by means of which the chamber 99 is connected to the engine inlet passage 5.

In the operation of the system, assuming that the compressor is idle and that the reservoir 25 is at atmospheric pressure, the spring 99 of the control device 99 will maintain the ball valve 98 in engagement with the seat 96, while the chamber 99 will be at atmospheric pressure as it is .in communication with the atmosphere byway of the passage I96. v

Thechamber 64 of the combined air strainer and unloading device 36 will also beat at-mos pheric pressure as it is in communication with the chamber 99 of the control device 89 by way of the pipe I 95, and the spring 61 will maintain the valve 45 in the position in which it is shown in the drawing, in which position communication is permitted betweenthe valve chamber ,43 and the atmosphere through the air straining means 49. This permits fluid to be supplied to the passage 39 from the atmosphere, and effects loading of the compressor.

When the engine 3 is started the crank shaft of the compressor is rotated, and the piston 14 is caused to reciprocate in the bore in the cylinder I I. On upward movement of the piston I4 from the position in which it is shown in the drawing, the piston cuts oil communication through the ports 32, and on further movement of the piston the fluid in the chamber above the piston is compressed and the pressure of the fluid acting upon the exhaust valve I8 causes this valve to be moved upwardly away from the seat I9 against the spring 22 so that air flows from the piston chamber to the exhaust valve chamber I9, and therefrom by way of the pipe 26 to the reservoir 25.

On downward movement of the piston I4 the exhaust valve I9 is moved into engagement with its seat I9 by the spring 22 so as to cut off the flow of fluid from the exhaust valve chamber I9 to the chamber in the bore in the cylinder II above the piston I4, with the result that a partial vacuum is created in the chamber above the piston. When the piston I4 moves to its lower position, in which position the ports 32 are again uncovered, fluid flows from the passage 39 through the ports 32 to the chamber above the piston. This produces a reduction in the pressure of the air or fluid in the passage 39 and causes air or fluid to flow to this passage from the valve chamber'43, and on a reduction in the pressure of the fluid inthe valve chamber-43, fluid will be supplied thereto from the atmosphere by way of the passage I6, the chamber 14, through the air straining means 49 to the chamber I9, and therefrom by way of the passages 12 to the chamber 69, and thence past the fluted stem of the valve 45 to the valve chamber 43.

On the next upward stroke of the piston I4 the air or fluid which is in the chamber above the piston I4 will be compressed, and this process will be repeated with each revolution of the crank shaft of the compressor.

During operation of the engine 3 a partial vacuum will be established in the engine inlet passage or manifold 5,'and this vacuum will be communicated to the pipe 95 and the passage 94, but it will not be communicated to the chamber 99 in the control device 89 at this time as the ball valve 98 is held in engagement with the seat 96 so as to cut oif communication between the passage 94 and the chamber 99.

After a period of operation of the compressor the pressure of the fluid in the reservoir 25 will have increased to a predetermined value such that the pressure of the fluid in the chamber 86 exerts a force on the diaphragm 8| which exceeds that exerted by the spring 99, acting on the other side of the diaphragm 9| through the valve cage I99, the push pinsI92, and the plunger 92. The diaphragm 8I will thereupon be forced downwardly againstthe spring 99, and the ball valve element 99 will be moved by gravity away from theseat 96. i

As soon as the'ball valve 99 moves away from will be drawn through the passage 94 and-the pipe 95 to the inlet passage 5, and a partial vacuum will be established in the chamber 99, as the rate at which fluid is withdrawn from the chamber 99 through the passage 94 and the pipe 95 substantially exceeds that at which fluid is supplied to the chamber 99 from the atmosphere by way of the passage I96.

The resulting reduction in the pressure of the fluid in the chamber 99 increases the force effective to urge the plunger 92 downwardly and the plunger will thereafter be moved very rapidly until it engages the wall 9|, which limits downward movement of the plunger 92.' i

It will be seen, therefore, that as soon as the valve 99 is moved away from the seat 96 as a result of an increase in the pressure of the fluid in the reservoir 25, it will be moved to the full open position very rapidly due to the reduction in the pressure of the fluid in the chamber 99 which occurs when the valve 99 is moved away from its seat. I

On a reduction in the pressure of the fluid in the chamber 99, a similar reduction in the pressure of the fluid in the chamber 69 will be effected, as the chamber 64 is in communication with the chamber 99 by way of the pipe Hi5,

and, on a reduction in the pressure of the fluid in the chamber 69, the diaphragm 69 will be moved to the right against the spring 611 by the pressure of the atmosphere in the chamber 69 on the opposite side of the diaphragm, and the valve 96 will be moved into engagement with the seat surrounding the passage in which the valve is mounted, thus cutting oif the flow of fluid from the atmosphere to the valve chamber 99. This cuts off the supply of fluid to the compressor and causes the compressor to be unloaded, with the result that on continued operation of the compressor no fluid will be compressed by it as long as the valve 45 is in the seated position.

The compressor will continue to run in the unloaded condition until the pressure of the fluid in the reservoir 25 is reduced to a value such that the force exerted by the diaphragm M as a result of thefluid under pressure in the chamber 96 acting upon it, and as a result of the partial vacuum in the chamber 99 acting upon it, is less than the force exerted by the spring 99 acting through the plunger 92 and tending to move the diaphragm upwardly.

When thepressure of the fluid in the reservoir.

95 has been reduced to this value the ball valve 99 will be moved into engagement with the seat 96 so as to cut ofi communication between the passage 99 and the chamber 99. This cuts oil communication between the passage 99 and the chamber 99, and permits the chamber 99 to be restored to atmospheric pressure by the flow of fluid from the atmosphere through the passage l96. When the chamber 99 is restored to atmospheric pressure the force exerted by the diaphragm 9i acting through the plunger 92 and tending to move the valve cage I99 downwardly against the spring 99 will be decreased, with the result that the spring 99 will hold the ball valve 99 firmly in engagement with the seat 96.

When the chamber 99 is restored to atmospheric pressure a similar increase will be efiected in the pressure of the fluid in the chamber 64 of the combined air strainer and unloading device 36, and the diaphragm 69 will thereupon be moved to the left by the spring 61 so that the valve 45 will be moved away from its seat to again permit the flow of fluid from the atmosphere to the" valve chamber 93, thus eifecting loading of the compressor.

The cylinder wall of the compressoris provided with a passage 35, which extends between the passage 39 and the crank case chamber l9, so that on a reduction in the pressure of the fluid in the passage 39 as result of operation of the compressor, fluid will flow from the crank case chamber ill to the passage 39. This produces a partial vacuum in the crank case chamber l9 and causes air to tend to flow into the crank case, chamber from the atmosphere through the joints in the walls of the crank case,

thereby opposing the escape of lubricant from the crank case through the joints in the walls of the crank case chamber.

From the foregoing it will be seen that the compressor control system provided by this invention incorporates means responsive to the pressure of the fluid compressed by the compressor and to the pressure of the fluid in the inlet passage of the engine which drives the compressor; this means controlling the loading and unloading of the compressor.

It will be seen also that the unloading control means is responsive only to the pressure of the fluid compressed by the compressor when this pressure is below a predetermined value, and that upon an increase in this pressure to a value above said predetermined value the control means is rendered subject to the pressure of the fluid in the engine inlet passage and is operated to effect unloading of the compressor, whereby the control means is maintained in the position to effect unloading of the compressor until the pressure of the fluid compressed by the compressor falls to a value substantially lower than that originally required to effect movement of the control means to a position to effect unloading of the compressor. 7

This insures that there will be a pressure differential between the pressure at which the compressor is unloaded and the pressure at which the compressor is loaded. This construction also insures that when the valve means of the unloading control means is moved from the closed position to the open position, it will be moved very rapidly after the initial movement thereof away from the closed position, and that on movement of this valve means to the closed position from the open position it will be held firmly in engagement with its seat.

It will be seen also that the control device provided by this invention opens a passage through which air is supplied to the engine inlet passage when the control device moves to the position in which the compressor is unloaded. The system operates, therefore, to vary the mixture of the fluid supplied to the engine in response to the loading and unloading of the compressor, the supply of air being increased when the compressor is unloaded, at which time the load on the engine is at a minimum. As soon as the compressor is loaded, however, the supply of air to the engine inlet passage through this passage is cut off, and this has theefiect of enriching the mixture of the fuel supplied to the engine when the engine is subjected to load.

While one embodiment of the control system provided by this invention has been illustrated and described in detail, it should be understood that the invention is not limited to these details of construction, and that numerous changes and modifications may be made without departing from the scope of 'the following claims.

claim as new and desire to secure by Letters Patent, is:

1. In a control system for a fluid compressor driven by an internal combustion engine the combination of a fuel inlet passage for the engine, unloading means associated with the compressor, a control device for controlling operation of the unloading means, said control device comprising means subject to the pressure of the fluid compressed by the compressor and biased to a position to efiect loading of the compressor and being moved to a position to effect unloading of the compressor on a predetermined increase in the pressure of the fluid compressed by the compressor, said means being subject to the pressure of the fluid in the engine inlet passage after movement away from the loading position, whereby the pressure required to move said means from the loading position exceeds the pressure required to maintain said means away from the loading position, and whereby the compressor remains unloaded until the pressure of the fluid compressed by the compressor is reduced to a value less than that required to effect unloading of the compressor. V

2. In a control system for a fluid compressor driven by an internal combustion engine, in combination, a fuel inlet passage for the engine, unloading means for the compressor, movable abutment means subject to the opposing pressures of the atmosphere and of the fluid in a chamber for controlling operation of the unloading means, means for supplying fluid to said chamber, and movable abutment means subject to the opposing pressures of the fluid in said chamber and of the fluid compressed by the compressor and controlling communicationbetween said chamber and the engine inlet passage.

3. In a control systemior a fluid compressor driven by an internal combustion engine, in combination, a fuel inlet passage for the engine, unloading means for the compressor, movable abutment'means subject to the opposing pressures of the atmosphere and of the fluid in a chamber for controlling operation of the unloading means, means for supplying fluid from the atmosphere to said chamber at a given rate, and movable abutment means subject to the opposing pressures of the fluid in said chamber and of the fluid compressed by the compressor and controlling a communication between said chamber and the engine inlet passage through which fluid may flow from I the chamber to the engine inlet passage at a rate more rapid than said given rate.

4. In a control system for a fluid compressor driven by an internal combustion engine, in combination, a fuel inlet passage for the engine, unloading means for the compressor, biasing means associated with the unloading means and yieldingly urging said unloading means to a position to effect loading of the compressor, movable abutment means subject to the opposing pressures of the atmosphere and of the fluid in a chamber and operated on a reduction in the pressure of the fluid in said chamber to effect movement of the unloading means to a position to unload the com pressor, means for supplying fluid to said chamber, and movable abutment means subject to the opposing pressures of the fluid in said chamber and of the fluid compressed by the compressor sures of the atmosphere and of the fluid ina chamber and operate on a reduction in the pressure of the fluid in said chamber to effect movement of the unloading means to a position to unload the compressor, means for supplying fluid from the atmosphere to said chamber at a given rate, and movable abutment means subject to the opposing pressures of the fluid in said chamber and of the fluid compressed by the compressor and controlling a communication between said chamber and the engine inlet passage through which fluid may flow from said chamber to the engine inlet passage at a rate more rapid than said given rate.

6. In a control system for a fluid compressor driven by an internal combustion engine, in combination, a fuel inlet passage for the engine, unloading means for the compressor, yielding means urging said unloading means to a position to effect loading of the compressor, movable abutment means subject'to and operated on a reduction in the pressure of the fluid in a chamber to move the unloading means to a position to effect unloading of the compressor, means for supplying fluid to said chamberyand means responsive to the opposing pressures of the fluid compressed by the compressor and of the fluid in said chamber for establishing communication between said chamber and the fuel inlet-passage.

7. In a control system for a fluid compressor driven by an internal combustion engine, in combination, a fuel inlet passage for the engine, unloading means for the compressor, a movable abutment subject to the pressure of the fluid in a chamber for operating the unloading means, means for supplying fluid to said chamber, valve means for controlling communication between said chamber and the fuel inlet passage, means responsive to the pressure of the fluid compressed by the compressor for moving said valve means to a position to establish communication between said chamber and said inlet passage, and means subject to pressure of the fluid in said chamber and opposing movement of the valve means by the means responsive to the pressure of the fluid compressed by the compressor.

8. In a control system for a fluid compressor driven by an internal combustion engine having a fuel inlet passage associated therewith, a movable abutment subject to and operated on a reduction in the pressure of the fluid in a chamber to unload the compressor, means for supplying fluid to said chamber, and a movable abutment subject to the opposing pressures of the fluid compressed by the BURTON S. m