US1761578A - Starting device for compressors - Google Patents

Description

June 3, 1930. c, w. METzGA R 1,761,578

STARTING DEVICE FOR COMPRESSORS Filed July 17. 1928 2 Sheets-Sheet l m INVENTOR. heal rllZfMegyae 5p ATTORNEY.

June 3, 1930, c. w. METZGAR STARTING DEVICE FOR COMPRESSORS Filed July 17, 1928 2 Sheets-Sheet 2 6 (/2 1 11 T V 10- 03 l 6' 0r 3 HIS ATTORNEY,

- refer to similar parts,

Patented June 3, 1930 UNITED STATES,

PATENT OFFICE,

CHESTER W. METZGAR, OF, EASTON, PENNSYLVANIA, ASSIGNOR TO INGERSOLL-RAND COMPANY, OF JERSEY CITY, N JERSEY, A CORPORATION OF NEW JERSEY STARTING DEVICE FOR COMPRESSORS Application filed July 17,

This invention relates to compressors, but more particularly to a device adapted to be connected to the unloading control mechanism and the means, such as a switch, whereby the current supply to the driving motor of the compressor is controlled.

One object of the invention is to prevent the starting of the driving motor until the compressor is fully unloaded.

Other objects will be in part obvious and in part pointed out hereinafter.

In the accompanying drawings illustrating a practical application of theinvention and in which similar reference characters Figure 1 is an end elevation of the multicylinder compressor with its intercooler having the invention applied thereto,

Figure 2 is an elevation of a detail partly in section illustrating the position of the throttle valve to prevent closing of the starting switch, v v m Figure 3 is a similar view showing the throttle valve in a position to enable the starting switch to be closed,

Figure 4: is a transverse view taken through Figure 3 on the line 4-4 looking in the direction indicated by the arrows, and Figure 5 is a transverse view taken through Figure 2 on the line 5 5 looking in the direction indicated by the arrows.

Referring more particularly to the drawings, A designates generally a compressor, in this instance a compound compressor having a low pressure cylinder B and a high pressure cylinder C. An intercooler D is disposed on the cylinders 13 and C to convey fluid compressed by the cylinder B to the cylinder C and to extract the heat of compression from such fluid in a well known manner.

Suitable and well known means are provided for reducing the capacity of the compressor cylinders B and C whenever the pressure in a storage receiver (not shown) reaches a maximum value which it is desired to maintain therein. These means in the present instance are illustrated as suitable clearance valves, only the casings E of which are shown to indicate the positions 1928. Serial No. 293,459.

which the clearance valves may occupy on the compressor cylinders.

The unloading devices or clearance valves E may be identical on both cylinders and preferably one clearance valve of each cylinder is in communication through suitable connections with a clearance valve of the othercylinder. This is accomplished in the case of the clearance valves on the adjacent or opposite sides of the cylinders B and C by means of a pipe F having a branchG which leadsto a regulator H of the type disclosed and described in United States Patent No. 1,430,578 grantedto Chester W. Metzgar, October 3, 1922. Reference may be had to the aforesaidpatent fora detail description of the regulator and only so much, of the regulator will be described herein as is necessary to describe the invention and its application.

In the case where additional clearance valves E are provided for the cylinders as for instance, the valve E on the outer or left hand side of the low pressure cylinder B as Figure 1 is viewed, such clearance valves are also preferably connected in pairs or groups by means of a pipe J having a branch K forming a connection between the pipe J and the regulator H.

Suitableunloadin means are also nois l.

vided for the intercooler D. This means comprises a casing L which may be suitably secured to one end of the intercooler and has a passage 0 to afford communication between the interior of the intercooler D and the atmosphere. In the passage 0 is formed a valve seat P for a check valve Q which cooperates with the seat P for controlling communication between the intercooler and the atmosphere.

Inorder to normally maintain the valve Q on its seat a spring R is disposed be tween the valve and a cover plate S on the casing L to constantly exert a slight pressure on the valve for maintaining it in the closed position. Additional means are provided however, for exerting a pressure on the valve to maintain it closed during the normal operation of the compressor and this means consists of a pipe T which com- H whenever pressure fiuid is admitted into the valve chamber U for maintaining the valve closed the pipe T is provided with a branch X which is connected to the regulator H for supplying pressure fluid thereto for the purpose of maintaining the clearance valves E closed.

By referring to the aforesaid patent it will readily be seen that whenever the receiver pressure attains the maximum value at which the regulator H is adapted to operate, one clearance valve E of both cylinders B and C will be simultaneously allowed to open and as the pressure in the storage receiver increases other valves connected in series on both cylinders will also be opened,

' however, the unloading valve on the intercooler D will remain closed.

In accordance with the present invention a valve casing Y is interposed in the pipe T between the branch X and the drain tank V. In this casing Y is disposed a throttle valve Z of the three-way type having ports I) and on diametrically opposite sides of the throttle valve Z to control communica tion between the pipe T and the drain tank V. The throttle valve Z is further provided with a port (I disposed at right angles to the ports I) and c for establishing communication between the pipe T and an exhaust port 6 in the valve casing Y in the open position of the throttle valve Z.

The throttle valve Z is of the type which is adapted to be manually operated and accordingly has a stem 7 which extends beyond the confines of the casing Y to receive '5: a lever 9 whereby the throttle valve Z may be manipulated. The lever g carries a head it through which the stem 7 extends and on the outer end of the head 72 is a cam surface j preferably so formed that its lowermost portion is will lie approximately in the. horizontal plane of the throttle valve Z when the said throttle valve is in a position to exhaust the pressure fluid from the various unloading valves. The high portion .0 of the cam surface preferably lies at right angles to the low portion is so that only a quarter turn of the throttle valve Z will be necessary to carry the high portion 0 into the horizontal plane of the throttle valve Z.

Disposed adjacent to the throttle valve head h is a bracket p which may be secured to. the pipe T by means of a suitable clamp g and bolts 1* which serve to clamp the bracket 9) to the pipe T. The bracket 7) may however be mounted in any other suitable manner and serves as a mounting for a push button switch 8 of a well known type having movable contacts t adapted to be pressed into engagement and held in engagement with stationary contacts a by means of a push button 4;. The push button r in this instance is the starting button, and the function of the contacts 6 and u is to close the circuit between leads an leading from the push button switch 3 to magnetically actuated control switches (not shown) but which may be located at a point remote from the push button switch for opening and closing the circuit of a motor not shown) whereby the compressor is actuated.

Only a brief description of the push button switch 8 is considered necessary since it is a well known device adapted for use such as that described. It may however be stated. that the switch has an additional movable contact a" and a cooperating stationary contact y from which lead leads 2 to the main switches for again opening the main switches. The movable contact as in this instance also carries a push button 2 which may be pressed by the operator to move the contact x against the contact 1 and to hold said contact in engagement until the main switches are again opened.

Both of the movable contacts t and to are provided with springs 3 so disposed beneath the contacts as to exert a pressure to immediately restore the contacts to their open position upon the release of pressure to the push buttons '0 and 2. The push buttons c and 2 are provided with stems 4 and 5 respectively which are guided by suitable apertures 6 in the casing of the push button switch 8. The push button switch 8 is so disposed with respect to the cam surface j that the stem 4 of the switch will lie approximately in the horizontal plane of the throttle valve Z and will therefore be in coaxial alignment with a bore 7 in the bracket p. The bore 7 serves as a guide for a pin, 8 disposed slidably in said bore and said pin is of such length that it may abut with one end the stem 4 of the push button '0 and extends with its other end to a point near the cam surface or, if desired, the end of the pin may come into direct contact with the said cam surface.

The operation of the device is as follows: During the normal operation of the compressor the throttle valve Z occupies the position illustrated in Figure In this position the ports Z) and 0 of the throttle valve will afford communication between the opposite sections of the pipe T. The exhaust port 0 will be closed. Pressure fluid may therefore flow from the drain tank V through the pipe T to the regulator H and thus also to the valve chamber U to maintain the valve Q in its closed position. At the same time pressure fluid will flow through the branch X ofthe pipe T to the regulator H and thence through the pipes i, F, K and J to the clearance valves E for maintaining sai d clearance valves closed.

As will be readily understood, while the clearance valves E and the valve Q are closed the compressor cylinders B and C will operate at their full capacities. The air compressed in the cylinder B will pass through the intercooler D to the cylinder C where it will be compressed to a higher value and from thence will pass to the storage receiver. During such operation of the compressor the step-by-step unloading or the complete unloading of the compressor cylinders will be controlled by the regulator H.

Whenever it is desired, for well known reasons, to quickly unload both the compressor cylinders B and C and the intercooler D the throttle valve Z may be rotated to the open position, in other words to a position in which the port Z) in the throttle valve is in registry with the exhaust port 0 and the port d therefore in registry with the pipe T. The pressure'fiuid previously utilized for maintaining the clearance valves E and the valve Q closed will then be exhausted to the atmosphere and any slight compression which may be created in the low pressure cylinder B will pass into the intercooler D and into the passage 0 where it may unseat the valve Q, and escape to the atmosphere. The pressure of the air compressed in the low pressure cylinder B will however be of low pressure since the spring R acting against the valve Q is preferably capable of exerting a pressure of only a few pounds.

By rotating the throttle valve Z to its open position the low portion 70 will lie in the plane of the pin 8 so that when it is again desired to resume operation of the compressor the contact t may be readily pressed into engagement with the stationary contact a to close the circuit between the a receiver through the various pipes and the regulator H to the clearance valves E into the valve chamber U for loading the compressor cylinders and the intercooler.

As has been previously intimated, when the throttle valve Z is in its open position the low portion In of the cam surface will be in alignment with the pin 8 to enable the contact to be pressed into engagement with the contact a. When the throttle valve Z occupies its other extreme position or in other words, its closed position, the high portion 0 of the cam surface j will be carried to the position previously occupied by the low portion is of the cam surface. WVith the high portion 0 thus disposed the contact 25 will occupy its extreme outermost position and will be held in that position by the high portion 0 of the cam surface which will then bear against the end of the pin 8. With the high portion 0 in this position the throttle valve Z will of course be in a position to admit pressure fluid to the regulator H so that the compressor and the intercooler will be fully loaded. If then it be desired to set the compressor in operation. itwill be impossible to establish contact between the starting contacts t and it until the throttle valve has again been moved to its open position and the compressor motor will therefore be protected against the effects of starting under a full load.

I claim:

1. In a compressor, the combination of a cylinder and a pressure actuated unloading device for the cylinder, means for controlling the supply of pressure fluid to the unloading device, a switch for controlling the current supply to a motor connected to actuate the compressor, and means associated with the first said means and the switch to enable the switch to be closed for starting the compressor only when the first said means occupies a position in which the compressor is entirely unloaded.

V 2. In a compressor, the combination of a cylinderand a pressure actuated unloading device for the cylinder, a valve controlling the supply of pressure fluid to the unloading device, a cam carried by the valve and rotatable therewith, a switch for controlling the current supply to a motor connected to drive the compressor, and means interposed between the cam and the switch to prevent closing of the switch while the compressor is loaded. I

3. In a compressor, the combination of cylinders and an intercooler, pressure actuated unloading devices for the cylinders and the intercooler, means for conveying pressure fluid from a storage receiver to the unloading devices, a valve on said means to control the flow of pressure fluid through said means, a cam carried by the valve and rotatable therewith, a switch adjacent the cam for controlling the current supply to a motor connected to drive the compressor, and a pin interposed between the switch and the cam to prevent closing of the switch when the valve is in a position to admit pressure fluid to. the unloading devices.

4. In a compressor, the combination of cylinders and an intercooler, pressure actuated unloading devices for the cylinders and the intercooler, means for conveying pressure fluid from a storage receiver to the unloading devices, a rotatable valve for controlling the flow of pressure fluid through said means, a cam rotatable with the Valve, :1 switch for controlling the supply of current to a motor connected to drive the compressor, a bracket adjacent the cam and forming a mounting for the switch, and a pin slidable in the bracket and interposed between the switch and the cam to prevent closing 01": the switch while the Valve occupies a position to admit pressure fluid to the unloading means for maintaining the cylinders and the intercooler loaded.

In testimony whereof I have signed this 15 specification.

CHESTER \V. METZGAR.

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