US2267448A

US2267448A - Controlling apparatus

Info

Publication number: US2267448A
Application number: US368430A
Authority: US
Inventors: James L Dooley
Original assignee: Ingersoll Rand Co
Current assignee: Ingersoll Rand Co
Priority date: 1940-12-04
Filing date: 1940-12-04
Publication date: 1941-12-23
Anticipated expiration: 1958-12-23

Description

Dec. 23 1941. L b L'E' 2,267,448 CONTROLLING APPARATUS Filed Dec. 4, 1940 H IS ATTORNEY.

Patented Dec. 23, 1941 CONTROLLING APPARATUS James L. Dooley, Berkeley, Calif assignor to Ingersoll-Rand Company, New corporation of New Jersey York, N. Y., a

Application December 4, 1940, Serial No. 368,430

9 Claims.

. The present invention relates to a controlling apparatus, and more particularly it relates to an apparatus for controlling the operationof a constant speed motor driven compressor.

For satisfactory and economical results the operation of a fluid compressor should be related in some manner to the load demand. In the ordinary compressor unit, consisting of a fluid-compressor driven by 'a variable speed motor, it is customary to regulate the operation of the unit to permit the compressor to deliver compressed fluid to the compressor receiver tank until a predetermined receiver tank (herein termed compressor discharge) pressure is reached. Upon reaching such a pressure a device provided on the-compressor and actuated by the compressor discharge pressure, stops the discharge offluidv to the receiver tank, commonly termed unloading and, at the. same time, the speed of .the driving motor is decreasedto idling speed. Thereafter, the compressor operates in this manner. until the receiver pressure (the compressor dis? chargepressure) reaches a predetermined low pressure at which time the device operates to permit the compressor to resume the delivery of, fluid under pressure to the receiver, commonly termed reloading and, at approximately the same time, the speed of the driving motor is accelerated to its maximum speed. Where the driving motor is a constant speed motor, such as an electric motor, the speed cannot be changed for varying load conditions.

I With such an arrangement, instead of operating the motor at idling speed when the compres sor is unloaded, the motor is stopped so that upon reloading of the compressor itis necessaryto first restart the motor. Frequent starting and stopping of the motor, as occurs when the flow of fluid under pressure from the compressor is not suflicient to prevent unloading of the compressor but is sufficient to require reloading.

shortly after the compressor has been unloaded,

is obviously undesirable and un'economical.

' Accordingly, it is an object of the present invention .to provide a compressor unit controlling apparatus wherein the compressor may be unloaded while the compressor driving motor continues to operate.

Another object. is to provide a compressor. unit controlling apparatus wherein the compressor may unload and the driving motor may continue to operate when there is a predetermined fluid flow from the compressor to the load.

' Still another object is to provide a compressor unit controlling apparatus wherein the compressor may be unloaded and the driving motor stopped when the load on the compressor is light.

A further object is to provide a compressor unit controlling apparatus wherein the compressor may be operated continuously.-

' An additional object is to provide a compressor unit controlling apparatus wherein the unit may be operated continuously or the compressor may be unloaded and, reloaded in accordance with variations in the compressor discharge pressure and the-motorstopped, or the compressor may unload and reload while the motor continues to operate if there is a predetermined flow of fluid from the compressor to the load at the time that the compressor is unloaded.

These andother objects will be apparent from thefollowing description and the drawing which forms a part thereof.. e p I'I'he drawingillustrates a diagrammatical view showing the electric circuits and the controlling apparatus of the present invention as applied to a constant speed motor driven compressor.

In the drawing is shown a fluid compressor I having two cylinders 3 and which receive fluid to be compressed through the conduits 1 and 9. The compressed fluid is discharged from the compressor through the discharge conduit H to a receiver tank l3 and a'pipe l5 conveys the compressor discharge pressure fluid from the receiver tank to the load, or point oi. use.

The compressor is driven by a motor H by means of a belt l9, and the motor is energized by electric current supplied from'the main lines 2|, 23 and 25 by an appropriate electric circuit. The

wires

21, 29 and 3|, respectively connected to the main lines 2|, 23 and 25, form a part of this circuit. Also, in the motor operating circuit is a switch 33 which is magnetically operated and on the main line side of the switch 33 is a manually operable switch 35.

The switch 33, which is commonly designated as a magnetic starter switch, has three terminals 31. 39 and 4|, respectively connected to wires 21', 29' and 3|. leading directly to the motor.

Overload relays

43 and 45 are respectively connected to the terminals 31 and 4| and to the switch blades 41 and 5|, while a wire 53 connects switch blade 49 to the terminal 39. Each blade 41, 49 and 5| is provided with a coacting contactor 55, 51 and 59 respectively connected with the blades 36. 36 and 36" of switch 35 by wires 6|, GI and 6|" through the

fuses

63, 63' and 63".

In order to move the blades 41, 49 and 5| against their respective contactors 55, 51 and 59, each blade is pivotally connected at 65 to a movable rod 61. The rod 61 is in turn rotatably connected by pin 69 to the bell crank 1| pivoted at 13. Upward or downward movement of the arm 15 of the bell crank 1I will move the rod 61 to the right or left in order to open or close the switch 33. This movement is governed by the solenoid 11 which, when energized, will raise arm 15, close switch 33 and start the motor. As long as the solenoid remains energized, the motor will continue to. operate but, when the solenoid becomes deenergized, the switch will open. and the motor will be deenergized.

One control circuit for energizing the solenoid 11 consists of a wire 19 connected to the solenoid and the terminal 8| of the switch 83. One blade 85 of this switch is designed to contact the terminal 81, which. is con-nectediby wire. 89 to the terminal 90 in wire 6|". The solenoid 11 is also connected by wire 9| to an overload interlock 93, provided to prevent overloading of the solenoid and designed to open upon a predetermined high current, and the interlock 93 is connected by wire 95 to the terminal 91 in the wire 6 I". Y I

Assuming that the switch 35 is closed and that the switch 83 is in the" position where the blade 85 is in electrical contact with the terminal 81, electric current may then flow through the main line 25, wire 3|, blade 36", fuse 63", wire GI", terminal 90, wire 99, terminal 81, switch blade 85, terminal 8|, wire 19, solenoid 11, wire SI, overload interlock 93, wire 95, terminal 91', wire 6I',.fuse 63', blade 36', wire 29- and main line 23 to energize the solenoid;

Energization of the solenoid closes the starter switch 33 and current may then fl'ow through the

mainlines

2I,23 and 25,. the switch 35, starter switch 33' and wires 21'', 29', and3I" to the motor to start it. As long asthe switch 83 remains in this position: and,. assuming that there is no overload, etc.,. the. motorwill operate the compressor at constant speedand. the. compressor will deliver fluidunder pressure to the receiverwhilethe receiver delivers. fluid to the load. This method of operation will be satisfactory 'solong as the'load-r on: the compressor is heavy enough torequire continuous operation of the compressor. When, however, the load is light, or fluctuating, a differentformof controlis desirable and, for this reason; a second control circuit having'two branches'is employed.

One-of the branch circuits includes. a fluid pressure flow actuated1switch-andthe other a fluid pressure actuated switch. In the-first mentioned branch the other blade 99 of the switch- 83"is adapted to contact a terminal IIlI. From this: terminal extends a wire IIJ-Sleading to the pressure fluid flow actuated. switch I95.

The flow switch I95is secured inthe pipe I5 which conveys pressure fluid from the receiver andconsists of a body I01 having a seat ms for the flapper 'I'I'I. When there is a flow of fluid" from the receiver'- through" the valve, the flapper I'I'I' israi's'ed'from its seat I89 and a cam II 3 'on the flapper'ismovedas'the fl'apper leaves its seat. The arm II'5,'resting on the cam surface, will move when the" cam surface is to be moved to a position permitting" movement of the arm. In the upper part of the'body' I91 is an electric switch enclosed in an'insulating casing HT. A plunger I I9 extending through the lower wall of the insulated casingrests on the arm H5 and is normally urged downwardly by the electric spring contact I2I'.

Two terminals I23, and I25 areflocated' on the top of the valve body I91 andare electrically connected by wires I21 and I 29 with'the" con tacts I2I and I3I. When there is no flow of fluid through the valve body, the arm I I5 and plunger II9 prevent the spring contact I2I from touching the contact I3I to close the circuit between terminals I23 and I25 and, consequently, preventing flow of current from wire I03 to the terminal I23. As fluid flows through the pipe I5, however, the flapper is moved from its seat and at a predetermined flow, determined by the movement of cam I I3 necessary to permit the spring contact I29 to move into a position where it would bear against contact I3I, the switch will close. A wire I33 from terminal I23 leads to the starter interlock I35 and wire I31 connects the starter interlock to terminal thus completing this branch circuit.

The other branch of this controlling circuit consists of a wire I39 leading from terminal I25 to the pressure switch, generally indicated at MI, and is secured to the contact I43. A second contact I45 is connected by wire I41 to the terminal 81 of the switch 83. A plate switch I49 normal-- 1y connects the contacts I43 and I45. Under certain conditions, as will be described hereinafter, the plate switch may break this contact and prevent the flow of current between contacts I43 and I45. With this arrangement, if the blade 99 of switch 83 is closed, that is, in contact with the terminal IOI, which means that blade 85 is not in contact with switch contact 81, current may flow along main line 23, wire 29, blade 36', fuse 63', wire 6|, terminal 91, wire 95, overload relay 93, wire 9|, solenoid 11, wire 19, terminal 8|, blade 99, terminal IIlI, wire I93, terminal I25, wire I39, contact I43, plate I49, contact I45, wire I41, terminal 81, wire 89, terminal 90, wire 6|, fuse 63-", blade 38", wire 3I and main line 25.

The closing of this circuit will also energize solenoid 11 and close starting switch 33 to initiate operation of the motor and compressor. As long as the pressure switch plate I49 closes the circuit between I43 and. I45, the motor will continue to operate, but, if this circuit is broken, the solenoid will be deenergized and the motor will stop, provided that there is no flow of fluid through the pressure switch I05. If there is a flow of fluid through. the. pipe I5 sufficient to close the circuit in the flow switch between terminals I23 and I25 the-motor will continue to operate. Thus, if the switch is closed, current may flow along the main line- 25, the wire- 3|, blade 36", fuse 63 wirefi'l", contact 90, wire I31, starter interlock I35, wire I33, terminal I23, wire I21; contact I31, spring contact I2I, wire I29; terminal I25, wire I03, terminal IIl'I, blade 9'9, terminal 8 I, wire 19, solenoicl'11, wire 9I,'overload" interlock 93; wire 95, terminal 91, wire GI". fuse 63'', blade 36, wire 29 and main line 23, thus completing the circuit between the

main lines

23 and 25 and maintaining the motor in operation.

If, under such circumstances, the flow of fluid ceases, the circuit will, of course, open and the starter interlockI35 will also open. When this occurs, the motor cannot be started by a re.- sumption offluid flow through the-flow switch and. in. order. for the. motor to be started again, the pressure. switchv I4I must act to complete. the circuit between'contacts' I43 and I45. In other words, the only time that the solenoid can be. reenergized andthe motor-restarted is when the pressure switch recloses. The pressure switch MI in itself forms no part of the present-invention and the form shown is merely by way of illustration.

. As shown, the switch consists of a casing II in which is a valve" body I53 having two valve seatsI55 and I51. A valve I59 having enlarged heads I6I and I63 each provided with a tapered face to coact respectively with the valve seats I55 and I51 is slidably arranged in the valve body. A spring I65 bearing against the head I6I normallyholds this head against its seat I55 and maintains head I63 off its seat I51. Above valve head IB'I is a passage I61 in which the conduit I69 is threadedly secured. There is also a second passage I1I between valve seats I55and I51 in the valve body communicating with a second conduit I13. Below the casing I5I is a diaphragm housing I having a passage I11 through which fluid under pressure may be introduced into the housing for actuating the diaphragm I19. The passage is connected to the receiver by the T I8I and the conduit I83. Fluid from the receiver may alsobe conveyed through the conduit I69 to the valve body I53 since that conduit is connected tothe T I8I.

When the pressure in the receiver increases, the diaphragm, being constantly subjected to the receiver pressure, tends to move upwardly and, upon a predetermined maximum compressor discharge, or receiver, pressure, the diaphragm moves sufliciently to pivot the plate I49 by means of the system of levers and springs, generally indicated at I85. The springs and levers I85 in themselves form no part of the present invention and,-accordingly, are not described. At the same time, the movement of the diaphragm causes the valve I59 to rise which permits fluid under pressure to enter the valve body I53 from conduit I69 and flow past valve seat I 6| to the conduit I13.

The other end of the conduit I13 is connected to the compressor unloading mechanism which is of standard construction and consists of a valve housing I81 mounted on the compressor intake. A portion of the valve housing I81 extends within the outer walls thereof and forms valve guides I89 for the cylindrical valve I9I. A spring I93 normally maintains valve I9I in its open position as indicated in the drawing. In this position, fluid may enter from the atmosphere and pass around ribs I95 into the inlet pipes 1 and!) of the compressor.

The casing I91 having a piston chamber I99 communicates with the housing I81 and contains a piston I adapted to transmit its motion to the projection 203 on the cylinder valve I9I.

Another casing 295 is secured to casing I91 and also to conduit I13. This casing has one chamber 201 opening into the piston chamber I99 and a second chamber 209 with which the conduit I13 communicates. There are two means of communication between the

chambers

201 and 209, namely the orifice 2 I I and the port 2 I3, both located in the wall separating the'chambers. In chamber 209, between the orifice 2H and the port 2I3, is a ball check 2I5 held on the seat 2 I1 by the spring 2I9. Accessto the spring and ball check may be had by removing the plug 22I from the casing 205.

With this arrangement, when the receiver pressure reaches a predetermined value, the pressure valve allows fluid under pressure to flow into the conduit I1I as has been explained. Fluid then enters chamber 209 and forces the ball check 2l5 away from its seat 2I1. Raising a ball check 2I5 from its seat allows fluid from chamber 209 to, not only enter chamber 201 through the orifice 2I I, but also'through the port 2I3 and receiver pressure will, therefore, be present in chamber 201 to force the piston 20I and the valve I9I to the left which unloads the compressor.

Upon a decrease in the compressor discharge or receiver pressure to a predetermined minimum pressure, the diaphragm I19 moves downwardly and thus permits head I6I on valve I59 to seat and prevent the further flow of fluid under pressure through conduit I13 to the unloading mechanism. Any fluid in the conduit I13 may escape between valve head I63 and the seat I51 to atmosphere, since the head I63 is no longer resting on its seat. Meanwhile the decrease of pressure in the conduit I13 permits the higher fluid pressure present in the piston chamber I99 and. chamber 201 to urge the ball check 2I5, with the aid of spring 2I9, to its seat 2I1 thus preventing the escape of fluid from chamber 201 through the port 2I3. The spring I93 then moves the valve I9I and piston 20! toward the right, but since the fluid cannot escape very fast from chamber 201, due to the restriction of the orifice 2I I, the valve is delayed in reloading the compressor to a certain extent so that there is a certain time delay between the time that the pressure valve acts to move the valve I50 and the time when the compressor is reloaded, depending on the size of the orifice. In this way the pressure valve may cause restarting of the motor but the compressor is not reloaded until the motor has reached its normal operating speed.

Under the practice of the present invention, therefore, it is possible to operate the compressor at constant speed continually without unloading or reloading of the compressor by closing switch 83 on terminal 81 as has been explained. Furthermore, under light fluctuating loads, the switch 83 is closed on terminal IOI and, in that event, the compressor will operate at constant speed so long as the receiver pressure does not reach a predetermined high value. When the pressure does reach the predetermined high value, the pressure switch opens the circuit between contacts I43 and I45, thus tending to stop operation of the motor unless there is a predetermined flow of fluid through the flow actuating switch I05. pipe I5, the flow switch I05 maintains a circuit through the solenoid and the compressor motor continues to operate despite the fact that the compressor has been unloaded. If, for any reason, under these circumstances the flow through pipe I5 ceases, the motor will shut down and the motor cannot again be started until the presssure switch is actuated to close the circuit between contacts I43 and I45, since the starter interlock I35, which is in circuit with the flow switch I05, prevents the flow switch from starting the motor again if the flow of fluid through pipe I5 should recommence.

V I claim:

1. In a controlling apparatus for an electric motor driven fluid compressor, the combination of an electric circuit for the motor, a normally open switch in the circuit, a solenoid to close the switch in the circuit, a first and a second electric control circuit connected to the first said electric circuit, a two position manual switch in the circuit for selecting either control circuit for energizing the solenoid, a second switch in one branch of the second control circuit, a pres- If there is a flow of fluid through v sure responsive device adapted to. open the second; switch in response to apred'etermined compressor discharge, pressure, and-a'flow switch in a second branch of said second control circuit normally openadapted to close said second-branch of. said: second control circuit upon a predetermined flow of fluid from the compressor and maintain the solenoid energized when the second switch is opened.

2. In a controlling apparatus for an electric motor driven fluid compressor, the combination of an electric circuit for the motor, a magnetically energized means in the circuit for closing the circuit to the motor, a control circuit for said means, pressure responsive means in the control circuit to deenergize the magnetic means and open said circuit upon a predetermined, compressor discharge pressure, and flow actuated means in the control circuit to close the circuit upon a predetermined flow of fluid from the compressor to maintain the magnetic means energized when the pressure responsive means opens said circuit.

3. In a controlling apparatus for an electric motor driven fluid compressor, the combination of an electric circuit for the motor, a switch in the circuit, a solenoid to close the switch in the circuit, a control circuit for energizing the solenoid, a pressure responsive switch in the control circuit to open the control circuit upon a predetermined compressor discharge pressure to deenergize'the solenoid, and a fluid flow actuated switch in 'the control circuit to maintain the control circuit closed upon a predetermined compressor discharge fluid flow to maintain the solenoid energized when the pressure control switch opens the control circuit.

4. In a controlling apparatus for an electric motor driven fluid compressor, the combination of an electric circuit for the electric motor, means in the electric circuit normally open to close the circuit to the motor, magnetic means to close the last means, a control circuit to energize the magnetic means connected to the electric circuit, pressure responsive means in the control circuit to open the circuit and deenergize the magnetic means upon a predetermined compressor discharge pressure, and a fluid flow actuated means in the control circuit to maintain the magnetic means energized upon a predetermined rate of fluid flow from the compressor when the pressure responsive means opens said control circuit.

5. In a controlling apparatus for an electric motor driven fluid compressor, the combination of an electric circuit for the electric motor, means in the electric circuit to close and open the circuit to the electric motor, magnetic means to close the last means upon energization, a control circuit connected to the electric circuit having two branches to energize the magnetic means, a two position switch in the control circuit for selecting a branch of the control circuit to energize the magnetic means, a pressure responsive means in one branch of the control circuit to open said branch circuit to deenergize the magnetic means upon a predetermined compressor discharge pressure, and a fluid flow actuated means in the other branch to maintain the magnetic means energized upon a predetermined flow of fluid from the compressor when the pressure responsive means opens said branch circuit.

6. In a controlling apparatus for an electric motor driven fluid compressor, the combination of an electric circuit for the motor, a switch norape /gees mallyn maintaining the circuit open,.a;solenoid.toclose the switch upon energization, a first-and a. second control circuit for energizing the solenoid, a manual switch to selectively close either control circuit to energize the solenoid, a pressure responsive switch in the second control circuit to open said second circuit upon a predetermined compressor discharge pressure, and a flow actuated switch in said second control circuit to maintain said circuit closed to energize the solenoid upon a predetermined flow of fluid from the compressor when the pressure responsiveswitch opens said second control circuit.

'7. In a control apparatus for an electric motor driven fluid compressor, the combination, of. an electric circuit for the motor, a switch normally maintaining the circuit open, a solenoid to close the switch upon energization, a first and asecond' control circuit for energizing the solenoid, av mane ually operated two contact switch having a contact in each control circuit for selectively connectingeither control circuit to the electric motor circuit, a second switch in the second control: circuitnormally closing said circuit, a fluid pressure operated unloader for the compressor, a compressor discharge fluid pressure responsive device to open the second switch and direct compressor discharge fluid to the unloader for unloading the compressor upon a predetermined. compressor discharge pressure when the second control circuit is energized, and a fluid flow actuated switch in said second control circuit' to' maintain the solenoid energized upon a predetermined flow of fluid from the compressor when. said second switch is opened by the pressureresponsive device.

8. In a control apparatus for an electric motor driven fluid compressor, the combination of an electric circuit for the motor, a switch normally maintaining the circuit open and adapted to start the motor upon closing, a solenoid to close the switch upon energization, a control circuit for energizing the solenoid, a second control circuit for energizing the solenoid, a second switch in. the second control circuit normally closing the second control circuit, a fluid pressure operated unloader for the compressor, a compressor discharge fluid pressure responsive device to open, the second switch and direct compressor dis-' charge fluid to the unloader for unloading the compressor upon a predetermined compressor discharge pressure, a branch circuit in the second control circuit for energizing the solenoid, a fluid flow actuated switch in the branch circuit to maintain the solenoid energized upon a predetermined flow of fluid from the compressor when said second switch is opened, and a manually operated switch to selectively connect either control circuit to the electric motor circuit.

9. In a controlling apparatus for a motor driven fluid compressor, the combination of means to operate the motor continuously, means to operate the motor intermittently comprisingmeans to start operation of the motor when the compressor discharge fluid pressure is less than a predetermined minimum and to stop operation of the motor upon a predetermined maximum compressor discharge fluid pressure, means to maintain operation of the motor upon a predetermined maximum discharge pressure when there is a predetermined rate of fluid flow from the compressor, and selecting means for the first and second said means.

JAMES L. DOOLEY.