US2461076A - Oil pressure safety control - Google Patents

Description

Feb. 8, 1949. c. R. NEESON OIL PRESSURE SAFETY CONTROL Filed March 20, 1946 NEWEMQR "v m/ 0R. CHARL ES R NEESO/V M zq WGR Q2 kemwwkktow Patented Feb. 8, 1.949

. 2,461,076" oinPREssURs SAFETY CONTROL Charles R. Neeson, Oakwood, Ohio; assignor to Chrysler Corporation, Highland Park, Mich.-, a 1 corporation of Delaware UNITED" STATES PATENT OFFICE Application March 20, 194-6, SerialNo. 655,874

8 Claims. 1

My present invention relates to an improvement in control systems for apressure lubricated mechanism suchv as refrigerant compressors, air compressors,stationary engines andthe like. The invention is. of particular utility in connection with a refrigerating or air conditioning" system but in its" broaderaspects. is applicable to any pressure lubricated mechanism.

The object of the presentinvention" is to provide-acontrol system: for operatinga motor starting switch or similar devicetori applying current to? an electric motor d'r'ivingja refrigerant com pressor or like: machine; The. control system comprises meansfordisconnecting the source of current upon failure of: the-lubrication system.

' Specifically, my invention comprise's means" in cluding a pressure responsive device for closing an: open" switch in the? control: circuit, said switch being in parallel with a: second switch normally in closed-position to" provide" a starting circuit. The pressure responsive switch is normally in open position when the compressor is at rest and is closed when the compressor is operating and the oil press'ures'yst'em is" functioning satisfactorily. 'Ihfirs't switch is associated with'nieans" for opening the switch a time iriterval after the second switch has closed; and" further means for latchi'ngit in open position' if the first switch is opened during operationoi the'compressor, which would be: anindication oi oil pressure failure; More specifically, the: pressure responsive device comprises a diaphragm having: means toapply the pressure of the lubrication system against one side and means for applying the pressure of the'compressor crankcaseagainst the opposite side, the crankcasepressurebeing operative to open the witcnwheni the lubrication system is not functioning and: having insufficient effect to open the switch if the lubrication system i's functioning normally.

Theobjects andtnature oithe? present invention will be more fully understood from the fol lowing specification taken in connection with the accompanying drawings wherein like numerals refer to like pa'rts throughout.

In the? drawings; Fig; 1' disclosesia"schematically illustrated refrigerating system having a": simplifled: control circuitin which is incorporated: the present invention; and Fig. Zis apartia-l' view of a modified form-of controlcircuit;

The-invention: is shown as applied: to a refrigerantcompressor: Hl having a piston III which compressesgas entering the cylinder space from a suction inlet l2 anddischarges the compressed gas into a discharge head l3. Details of asuit- 2. ableform of refrigerant compressor may be ascertained from my prior Patent No. 2,185,473 dated J anuaryZ, 1940, but any form of compressingl device or other refrigerating mechanism may have the present invention applied thereto. A refrigerating system is showncomprising a condenser l5 in which the compressed refrigerant is cooled and an expander l5 receiving refrigerant through an expansion valve ll under control ofa superheat bulb 18 in accordance with known practices. A feature of the preferred type of compressor is that the expanded gasentering the suction inlet l2 may also enter the crankcase space'20' of the compressor through a hole 21, for reasons'more fully set forth in my prior Patents'No. 2,185,743 dated January 2, 1940 and No. 2,204,510dated January 11', 1940'. The pressure existing. in the crankcase 2'8 therefore fluctuates from a high pressure when the system is at rest to a low pressure when'the'sys'tem is func tioning, but'in either case the pressure is a substantially steady pressure and varies from high to low when the system commences or from low to high when the system comesrto rest at a fairly smooth rate depending upon the size of the hole 211 The compressor is controlled by a control system of which the basi'celements are herein disclosed; Details'of a control system not essential to the present invention may beascerta'ined from any prior Patent No; 2,247,449 of July 1,1941. As herein disclosed thecompressor driving motor 25 is supplied With current through a manual switch 25' and an automatic, motor starting switch-21 operated by a'solenoid 28. The solenoid 28 is iplaced'in a control circuit deriving-a reduced voltage from a transformer 2-9 having its primary winding in a single phase branch of the'main current and in parallel with a blower motor 30 controlled" by a manualswitch' 3|, the blower motor beingprovided in a forced draft air conditioning systemor the like. The solenoid 28 is alsoinseries with the usual controls such as compressor motor overload switches 32 and 33, a high pressure cut-out 34, a suction pressure cut-out 35,;a manual switch 36' and a thermostatic switch 31. As illustrated the switch-34 is controlled by adiaphragm motor 40' subject" to the pressure of the discharge head l3,-the switch 351s control-led'by a-diaphragmmot'or 41 subject to the pressure inthe suction inlet l2 and: the switch 31 is controlled by a'diaphragm motor 42 operated by the pressure of gas or liquidenclosed Within a sensing device 43 positioned within the ref 'igerated space or in the air conditioning duct system. As will be readily apparent to those skilled in the art the switches 32, 33, 34 and 35 will normally be closed and will only open if an abnormal condition occurs requiring attention of the operator or at least requiring that the compressor cease operating, thus, the switch 2? will be closed if pushbutton 36 is closed when thermostatic switch 3'! is closed, indicating that cooling is required. The subject of the present invention comprises further switches which must be satisfied before the switch 27 can be closed. I

As seen in Fig. 1 the present invention comprises a first switch so in series with the others and including a bimetallic bar 5|. In parallel with the switch 56 is a switch 52 which is normally open when the system is at rest. Switch 52 is operated by a rod 53 attached to a diaphragm54 in a diaphragm motor 55. The space above the diaphragm 54 is supplied with oil from the pressure lubricating system through an inlet 56. As illustratedthe pressure lubricatin system may comprise a compressor driven oil pump 69 operated by the compressor, details of such a device being disclosed in my above-mentioned prior patents. The space below the diaphragm 54'is connected by means of a tube 5| and inlet 62 to the crankcase space 29. The pressure lubrication system is of the normal type operating at a pressure such as 40 pounds per square inch. When the compressor is idle the pressure of the crankcase may be in the nature of 100 pounds per square inch, thus, when the compressor is idle a positive force is applied to the diaphragm to open switch 52 even though there may be residual pressure in the space above the diaphragm. When the compressor is in operation and the pressure lubrication system is functioning normally there is a greater operative force above the diaphragm tending to close switch 52. Normally'this greater pressure may occur within a very few number of reciprocations of the piston H, but due to absorption of the refrigerant in the lubricant the pump may be slightly gasbound and the greater pressure may not be applied above the diaphragm until several seconds have elapsed after the compressor commences operation. In any event a starting circuit is supplied by the bimetallicbar 5| and soon thereafter a holding circuit is completed by the closing of switch 52.

In accordance with the present invention it is desired that the compressor cease operating if the oil pressure is below a predetermined minimum sufficient for lubrication purposes. To this end the upward thrust of the crankcase pressure which, when'the compressor is operating may be in the nature of 5 pounds per square inch, or even negative pressure, is aided by a spring 63 of sufiicient strengthto overcome a predetermined minimum low oil pressure above the diaphragm even when the downward thrust of insufficient oil pressure is aided by a slight vacuum below the diaphragm. The spring 63 is so designed as to hold switch 52 in open position unless the oil pressure is satisfactory. In order to make certain that the diaphragm device 55 will take over control after the compressor starts operating with satisfactory oil pressure there is provided means to open the normally closed switch 56 a time interval after the compressor commences operation. This means comprises a resistance heater 54 placed in series with the other controls and located adjacent the bimetallic bar 5 i. The heater will cause warping of the element 5| a predetermined time after current commences to flow 4 through the control circuit. If the refrigeration system is in proper order the warping of element 5! will not disrupt the control circuit since switch 52 is in parallel therewith. However, if any of the switches 32, 33, 34, 35, 36 or 31 are opened current will cease flowing through the control circuit, switch 21 will open, the compressor will stop, the oil pressure willdrop, and switch 52 will open. Soon thereafter element 5! will have cooled and closed switch 50 to set the system in readiness for the next operation.

The foregoing is satisfactory and sufiicient for compressor control under the conditions stated. If, however, all of the switches 32, 33, 34, 35, and 3! remain closed while switch 55 is open.

and under such circumstances insuihcient oil pressure causes switch 52 to open, I provide means to lock switch open thereby preventing reoperation of the compressor until a service man corrects the faulty lubrication system. This means comprises a solenoid in parallel with switches 55 and 52. The solenoid'comprises an operating rod attached to a bell crank having a free end adapted to contact the element 55 and warp it out of normal position, or if the element 5| has been previously warped by the heat of resistance 54 to lock it in the open position. Since switches 50 and 52 are open all of the current flowing through the control circuit will flow through the solenoid 55 and maintain the locking device'in the lookout position. The electrical characteristics of solenoid 65 may be designated as being of the high resistance type, or in other words the solenoid B5 is so designed with respect to the solenoid 28 that solenoid 28 will have insufiicient flux to hold the motor starting switch 27 in closed position when current flows through solenoid 55. Therefore, the compressor will stop when current flows through solenoid 55 even though a closed circuit is thus provided. Since this circumstance will arise when the manual switch 36 is closeclno further action is possible until an operator arrives to correct the faulty lubrication system; in other words, since no currentis flowing to motor 25 switches 32 and 33 will remain closed, since the compressor is at rest the refrigeration system will tend to balance and there will beno excessive reduction of head pressure to open switch 34 or excessive reduction of suction pressure to open switch 35, and switch 31 will remain closed since the temperature will rise due tofailure of refrigeration. When an operator arrives and opens switch 35 the crank 55, either by automatic means such as a spring (not shown) or manually, will be caused to assume inoperative position and switch 50 will close but no harm will be done since a serviceman will be present to correct the cause of insuiiicient oil pressure. 7

In Fig. 2 I have illustrated a modified form of theinvention in which switch 5!! is operated by a delayedaction solenoid l0 placed in the same position in the circuit as the resistance 64. Switch 50 is urged'to closed position by a'spring 'II and is caused toopen after a short time interval by the magnetic buildup of will"). Switch 52 is operated by the rod 53 extending from the diaphragm device as previously described, but in this instance solenoid 65 operates a block or cam 72 cooperating with a block or cam 73 mounted on a rod 14 extending to switch 50. If switch 52 opens after switch 50 has been opened in this modification the block 12 is urged into contact with block 13 and switch 50 is held in open position. I

aces-gore Other formsv of time delay devices and switch lockout devices will'be readily apparent to'others skilled in the arts pertaining'thereto'and' I do not intend to be limited to'the types herein: disclosed. All such modifications as perform the functions herein disclosed. are deemed'to be. a part of my invention.

It will be readily apparent'to those skilled in the art of refrigeration that the pressure insubtion inlet l2 might be applied to'th'e diaphragm device, but I prefer the crankcase pressure since suction pressure is usually. fluctuating. Itwill also be apparent that the present invention may be applied to an air compressor, or to an internal combustion engine or the like. In such cases the pipe 6i may be omitted since crankcase pressure will be normalair pressure or close to it. In the case of an internal combustion engine or the like the control circuit may include a starting motor and an ignition cut-off in case of oil pressure failure.

Having illustrated and described preferred embodiments of the invention I now claim as my invention the following:

I 1. In a refrigerant compressor mechanism'having a pressure lubrication system; a' control system for said mechanism comprising a normally closed switch, a normally open switch in parallel therewith, a high resistance induction coil in parallel with said switches, a time-delay device for opening said normally closed switch a short time after current flows through the control system, a pressure-responsive device for closing said normally open switch as long as suificient pressure exists in said lubrication system, and means controlled by said high resistance coil to lock said normally closed switch in open position if the pressure falls below a predetermined minimum.

2. In a pressure-lubricated mechanism; a control circuit comprising a normally closed switch, a normally open switch in parallel therewith, means responsive to the pressure of the lubricant for closing said normally open switch, means in series with said switches and responsive to the flow of current through said circuit to open said normally closed switch a time interval after current commences flowing, and electrically controlled means operative upon both switches being simultaneously in open position to lock said normally closed switch in open position.

3. In a pressure-lubricated compressor mechanism having a motor starter switch; a control circuit comprising a normally open switch, 2. normally closed switch in parallel therewith, a first induction coil in parallel with said switches, a second induction coil in series with said switches and said first coil, means in series with said switches and said induction coils and responsive to the flow of current through said circuit to open said normally closed switch an interval of time after current commences to fiow, means responsive to pressure of the lubricant to close said normally open switch, and means associated with said first induction coil and operative upon simultaneous opening of both said switches and resulting flow of current through said first induction coil to hold said normally closed switch in open position, said second induction coil being adapted to operate said motor starter switch or similar device when either of said switches is closed but having such characteristics, electrically, with respect to said first induction coil, as to be inoperative when both said switches are open and current flows through said first induction coil.

4. In an oil-pressure safety control for a' pres sure-lubricated refrigerant compressor; a control circuit including a pair of switches in parallel, one normally open-arid'the other normally closed, time-delay means in series with said switches and adapted to open said normally closed switch short interval of time after current commences to flow through said circuit, lubricant pressure responsive means to close said normally open switch,- means to' oppose said lubricant pressure responsive means by the compressor crankcase pressure to reopen said normally open switch it the pressure of the lubricant falls below a predetermined minimum, a locking device, and a shunt around said switches including electrically controlled means operative upon said locking device to lock'said normally closed switch in. open position if said normally open switch is reopened while said normally closed-switch is open.

5: In a refrigerant compressor having a compressor-drivenv oil pump and connected pressure lubrication system; a control circuit includin a switch, a diaphragm device for operating said switch, means connecting said diaphragm device to: said pressure lubrication system for closingsaid switch after the compressor starts operation, means connecting said diaphragm device to the crankcase of said compressor for operation in the opposite direction if the oil pressure falls below a predetermined minimum, a second switch in parallel with said first switch having a bimetal contact and adapted to be in closed position when said control circuit is deenergized, and time-delay electrical heatin means in series with said switches and adapted to warp said bimetal contact to open said second switch a short interval of time after said first switch is closed by the action of said diaphragm device.

6. In a refrigerant compressor having a compressor-driven oil pump and connected pressure lubrication system; a control circuit including a first switch, a diaphragm device for operating said switch, means connecting said diaphragm device to said pressure lubrication system for closing said switch after the compressor starts operation, means connecting said diaphragm device to the crankcase of said compressor for operation in the opposite direction if the oil pressure falls below a predetermined minimum, a second switch is parallel with said first switch having a bimetal contact and adapted to be in closed position when said control circuit is de energized under normal circumstances to thus complete a closed circuit for starting said compressor when energized, time-delay electrical heating means in series with said switches and adapted to warp said bimetal contact to open said second switch a short interval of time after said first switch is closed by the action of said diaphragm device, a shunt around both of said switches including a high resistance induction coil, and latching means energized thereby to lock said second switch in open position if said first switch thereafter opens.

'7. In a refrigerant compressor having a compressor-driven oil pump and connected pressure lubrication system; a control circuit includin a first switch, a diaphragm device for operating said switch, means connecting said diaphragm device to said pressure lubrication system for closing said switch after the compressor starts operation, means connecting said diaphragm device to the crankcase of said compressor for operation in the opposite direction if the oil pressure falls below a predetermined minimum, a

second switch in parallel with said first switch and adapted to be in closed position when said control circuit is deenergized under normal circumstances to thus complete a closed circuit for starting said compressor when energized, time-delay means in series with said switches to open said second switch a short interval of time after said first switch is closed by the action of said diaphragm device, a shunt around both of said switches including a high resistance induction coil, latching means energized by said high resistance induction coil thereby to lock said second switch in open opsition if said first switch thereafter opens, and resilient means urging said first switch toward open position at all times.

8. A control system for a refrigerant compressor having a compressor-driven oil pump and connected pressure lubrication system, comprising a control circuit including a first switch, a diaphragm device for operating said switch, means connecting said diaphragm device to said pressure lubrication system for closing said switch after the compressor starts operation, means connecting said diaphragm device to the crankcase of said compressor for operation in the opposite direction if the oil pressure falls below a predetermined minimum, a second switch in parallel with said first switch and adapted to be in closed position when said control circuit is deenergized under normal circumstances to thus complete a closed circuit for starting said compressor when energized, time-delay means to open said second switch a short interval of time after said first switch is closed by the action of said diaphragm device, a shunt around both of said switches including a high resistance induction coil, latching means energized thereby to lock said second switch in open position if said first switch thereafter opens, and resilient means urging said second switch toward closed position, said latching means comprising a movable part rendering said resilient means ineffective.

CHARLES R. NEESON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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