US2352241A - Hoist control mechanism - Google Patents

Description

Filed July 31, 1941 N mm mN o T R L B EZY LL 9 (AAA ATTORNEY I Patented June 27, 1944 ,UNITED STATES PATENT OFFICE HOIST CONTROL MECHANISM Burton S. Aikman, Wilkinsburg, Pa., assignor to Q The Westinghouse Air Brake Company, Wilmerding, Pa.,a corp'orationoi Pennsylvania Application July 31, 1941', Serial No. 404,859

8 Claims, (c1. 60-51) This invention relates to hoist .or elevator control systems and more particularly to the hydropneumatic type in which a liquid such as oil is displaced by compressed air for actuating a pis ton orthe like to elevate a body.-

One object of the invention is the provision of an improved system of this type.

Another object of the invention is the provision of a system ofthis type'in which the liquid pressure actuatedhoisting piston or element can not drop in case of failure of the supply of'compressed air on the hoisting liquid as during or after the completion of a hoisting operation. 7 Another-object of the invention'is the provision of an improved hoist control system of the hydropneumatic typ embodying means for reclaiming the compressed air used toefiect a hoisting operation so as to accelerate the restoration of the compressed air suppl in preparation for a subsequent hoisting operation and to also minimize the amountof power consumed in maintaining the "required amount of compressed air for operating the system: Q I 1 Other objects and advantages will be appar ent from the followin more detailed description of the invention. p I

l v Description In the accompanying drawing the single figure -is a diagrammatic view, mainly'in section, of the improved hoist or elevatorcontrol system.

In the drawing the reference numeral 1 indicates a compressed air storage reservoir which, when the system is-in use, is adapted to'be maintainedcha-rged, with air at apressure between chosen limits such as-from one hundred and fiftyfive to one hundred and seventy-five pounds per square inch,-and'from' which compressed air is adapted 1 to be drawn or used for controlling hoisting or elevating operations, in a manner to be described. 1i The reference numeral '2 indicates an air compressorwhich for the purpose of illustration is preferably of the compound type comprising a low pressure piston 3 and a high pressure piston 4.1 These pistons are connected for operation to a crankshaft 5 whichissuitably supportedin endbearing's 6, only one of 'which isshownr The crankshafti extends through the one endbears ing 6 and on fits outerv endtis provided with-a pulley? which'by means of. abelt 8 is operatively connected to a driveshaft 9 ofzan relectric'xnotor Ill. Outboard of. the crankshaft bearing 6 the compressor casing carries an .oilseal II which contacts theperiphery of the crank shaft extend-- ing therethrough. This seal isoi the pressure. type adapted to prevent leakage of lubricating oilfrom the crank case I2 along the crank shaft 5 when the pressure in the crank caseis above that of the atmosphere. I I

In operation the low pressure piston 3 is adapted to drawair from an intake pipe 13 and to compress same, into one end of an intercooler l4, the opposite end of which is connected to the intake for the high pressure piston 4. I The high pressure piston is then adapted to compress the air. taken from. the intercooler and to discharge same through a discharge pipe l5 into reservoir I. In order to substantially equalize the forces on the two pistons while operating, the displacement of the low pressure piston. 3 is preferably such as to provide a pressure in the intercooler l4 of for instance substantially forty pounds per square inch when the intakepipe I3 is open to the atmosphere providing for the charging of the low pressure cylinder at substantially atmospheric pressure. The high pressure piston is adapted to increase the pressure from that in the intercooler to the degreedesired in the reservoir I, such as from one hundred and'fiftyefive to one hundred and seventy-five pounds per square inch above mentioned. I I l e The electric motorlll is adapted to be controlled by an electric governor 20 of any desired type which will respond to the pressure in the reservoir I. This governor may be adjusted to open the circuit through the motor 10 for stopping'the compressori2 when the pressure in the reservoir I is increased to the desired degree such as one hundred and seventy-five pounds above mentioned, and to close said circuit when the pressure in the reservoir becomes reduced-to a certain lower degree such as one hundred and fifty-five pounds,'so as to cause the motor lll to operate the compressor 2 forrrestoring the pressure in said reservoir.

The. pressure. governor is preferably associated with a cutout device 2| which under a certain condition to be later described is adapted to ren der said governor non-responsive to the pressure of the compressed'air in the reservoir I;

The'cutout device 2| comprises a casing-having'a passage 22 eonnecting the governor to a chamber 23 which normally is "open past a valve 24 to a passage 25 in constant communication with the reservoir I. Withthe valve 24 open as shown, the governor 20 is'therefore'connected to the reservoir I so' as to operatein thenormal manner in response to pressure variations in said reservoir.

The valve 24 is provided on one end of a stem 26 on the opposite end of which is a valve 21 arranged to control communication between chamber 23 and a chamber 28 which is open to the atmosphere through a passage 29. A control spring 39 in chamber 23 acts on an annular collar 3| provided on the stem 26 for urging the valve 21 closed and for opening the valve 24. A pin 32 projects from the valve 21 i'ntc chamber 28 in axial alignment with a plunger 33. The plunger 33 has on its outer end a, follower 34 conis clamped around its edge in the casing. At the opposite side of the diaphragm is a pressure chamber 36 which is connectedto the compressor intake pipe l3 and which under a. condition to be later described is adapted to be charged with fluid under pressure. A chosen relativel -low pressure, in chamber 36, such as two pounds above atmospheric pressure, is adapted to overcome control spring 36 and deflect diaphragm 35 in the direction of the left-hand for thereby unseating the valve 21 and for seating the valve 24. When this condition occurs, control passage 22 for the governor 26 will be opened to the atmosphere through chamber 23 past the valve 21- and thence through chamber 28 and port 29 for thereby reducing the control pressure on the governor to a degree s'uchas to cause said governor to operate to close the electric circuit through the motor [0. 1

The reference numeral 49-indicates an oil reservoir containing a bodyof' oil. Mounted on the top of the reservoir 46 is a manual control valve device 4| which comprises a; vertically extending control handle 42 pivoted at its lower end on a shaft 43. At one side-of the handle 42 is a stand pipe 44 extending through the interior of the reservoir 49 to near the bottom thereof.

46 is a liquid supply pipe 45adaptedto be connected to the elevating piston or plunger (not shown). of the mechanism for conveying liquid under ressure thereto to effect a hoisting oper-. ation. The device 4| contains a check valve 46 so arranged as to provide .for. flow of liquid in the direction from pipe 44 topipe 45 but to.

automatically prevent flowin the i'opposite direction. A spring 41 actingon; check valve 46 is provided for urging same to its closediposition shown.-

Apin 48 projects from the end of checkvalve 4610pposite that engaged .by spring 41.. This pin is aligned with a longitudinally movable plunger 49 :which isdisposed in Ea suitable bore in the device and has an 'oil tight .fit with the side wall thereof. The outer end of plunger 49 is aligned for movement by. an intermediate portion of a lever 59 which. is .fulcrumed at one end on a pin Ihe opposite end of lever 56 is arranged to be engaged by one side of handle 42 upon rocking said handle in a clockwise dimotion from the normal position shown to thereby actuate said lever' and plunger 49 to unseat the check valve 46. With'the handle 42 in its normal position as shown, and also counterclockwise movement of saidhandle fromsaid normal position, the valve 461s adapted to be maintained seated by spring 41. Y

Above the body of "oil in reservoir '46 is a:chamber 55 to'which compressed; air is adapted to be supplied from the reservoir I for displacing oil from said reservoir into .pipe .45 to efiect a hoisting operation and from which compressed air is adapted to be released to permit oil to be Connected to the device- 41 outside of the reservoirtacting one side of a flexible diaphragm which ""air.

released from the pipe for lowering the hoisting element. The supply of compressed air to and its release from chamber is adapted to be controlled by a valve mechanism 56 which forms a part of the manual control valve means 4| but which is located on the side of handle 42 opposite the check valve 46.

I The valve mechanism 56 comprises a casing having a chember 51 which is connected by pipe 58 to the compressed air'reservoir l and thus in use is constantly supplied with compressed In the casing a valve 59 is arranged to control communication between chamber 51 and N a chamber 60 which is open to chamber 55 above the oil in reservoir 46. The valve 59 is connect- "ed' to a' piston 6| which is subject on one face 'to the pressure of compressed air in chamber 51. 1 At the opposite side of piston 6| is a chamber 62 containing a bias spring 63 acting on the piston for urging the valve 59 to its closed position.v Above the piston 6| is a chamber 65 which is in constant communication with chamber 62 through a passage 66. A valve 61 contained in the chamber 65 has a fluted stem extending through ;a suitable bore in the casing in alignment with the left-hand side of handle 42. Projecting from the opposite side of valve 61 is a pin having on its end a tapered valve 69 adapted to cooperate with an aligned seat in the casing. A bias spring 19 in chamber 65 acts on the valve 61 for seating same and for unseating the valve 69. This condition of these valves is adapted to be maintained with the handle 42 in the vertical position shown or upon movementv from this position in a clockwise direction. Movement of the handle 42 from its vertical position in a counterclockwise direction is however adapted to unseat the valve 61 and seat the valve 69.

The valve 59 is provided for supplying compressed air from the reservoir I to chamber 55 in the oil reservoir 49 and for cutting off such sup ply. Coaxially aligned with this valve is an oppositely seating valve 15 which is provided for controlling the release of compressed air from chamber 55. The valve 15 is contained in chamber 16 and has a fluted stem 11 which is slidably mounted in a bore connecting said chamber to the chamber 60. The two valves 59 and 15 are connected together for movement in unlson by a pin 18 connecting the 'stems'of the two valves.

The reference numeral 63 indicates a pressure reducing valve device whichhas a chamber 82 to which the inlet pipe 13 of the compressor is connected. An air cleaner or strainer 66 is connected to the pressure reducing valve device 83 to provide for flow'of air from the atmosphere to the chamber "82 and thenv through the inlet pipe l3,to the air compressor '2 during its normal operation. This flow of air through the strainer device to 'chamber'62 occurs :through a chammr 84 containing a disk type-checkvalve 85 adapted to open under such flow but .to close communication from chamber '82 to the. atmos phere through the "air. strainer '80 atother itimes.

Chamber 16 in the supply and release valve mechanism 56 is connected -.;by .a pipe '81 to a chamber -88 in thelre'duc'ing valve device '83. .A valve 89 is contained in the'chamber. 88 and has a fluted stem "90 extending througha bore connecting'said chamber to the chamber 62. A pin 9-! :slidably'mounted in a suitable bore :15 connected at one end to the lower :end ot'the valve stem 90 and projects into a chamber. 92 wherein -A -plunge r 95; engagesthe oppositeface ot-the diaphragm. 94 and. is acted upon by a spring 96 which urges the diaphragm in the direction for unseating the valve 89.; The chamber 921s connected to c mber, b a a e whi chamber 98 containing spring 96-is inconstantcommunication with the atmosphere through a breather port 99. The pressureotspring 99 on the diaphragm 94 is such; as to require a chosen degree of 'fluid pressure in chamber :92, such for example tas forty pounds per square inch, for deflecting said diaphragm-againstthe spring to thereby permit seating of thevalve 89; When any lesser degree of' fluid pressure is effective in chamber 92 and thereby in chamber. .82- the spring 99is adapted-to unseat'the-valve 89. l

Operation Y v M Letit be assumed thatlthe reservoir 40; contains an-adequate amount of oil for, controlling hoisting or elevating operations and that oil from the-hoist supply pipe 45;has been released tosai'd reservoir, in a manner to-be, hereinafter. de.-- scribed,- to a degree whichprovides for lowering of the hoisting element or piston toits-normal position. Let it also be assumed that the handle 42 is. in the vertical positionshown inwhich it will be normally carried and that the whole. sys-' tem including the air supply reservoir I is void of compressed air. Let it further beassumed that the compressor 2 and motor [,0 are-not-operating, due for instance to a line switchlflflin the circuit of saidmotor being open.

1 To condition the system for operation, switch H .is closedand since the pressure in reservoir l is-belowthe cutting-out point of the pressure governor 20, said. governor will close the circuit to the motor l0 andcause'the compressor 2 to operate to draw air from theinlet pipe l3 and to compress same into the storagereservoir l. Underthis condition the drawing of air from pipe 13 willcreate asufiicient. reduction in pressure in chamber 82 in the pressure'reducing valve device 83 to'provide foratmosphericpres sure acting through the strainer device 80 on the lower face of the check valve 85 to lift said check valvewhereupon thecompressor 2 will draw'air directly from the atmosphere for compressing into the reservoir I. Thecheck valve 85 is preferably a relatively light weight disk so as" to offer substantially no-interference with the-nee flow of air from the atmosphere to the compressor, as just mentioned.-

During'initial charging of the r I phragm chamber 36in the'cut-ofi device 21' will beat substantially"atmospheric pressureso that spring will be efiective to maintain valve 21 seated and valve 24 unseated, thereby subjecting the electric governor 2'0 to control by thecompressed air suppliedto thereservoir I, f The'compressor 2 will thus'operate to pump air into the reservoir l-until the'pressure in said res ervoir is increased to the cuttingi'out point of the governor 20, which may beadjusted to operate to open the circuit through motor I0 when the pressure in the reservoir is increased to the one hundred and seventy-five pounds per square inch above mentioned. When this pressure is attained, the motor 10 and therefore the compressor 2 will be stopped.

' As air is compressed'in'to the reservoir I it flows through pipe 58 to chamber 51 in the manual control device 4| and fromsaid chamber past the line reservoir I 'dia- .stantially at atmospheric pressure.

the unseated valve; 69 to chamber 62 at the oppositefaee of thepiston 6h The pressure of the air acting on opposite races of the piston 6| thus being the same permits the bias spring 63 to hold valve 59-seated. Withvalve 59 seated, the valve 15 is unseatedjso that chamber 55 above the oil in reservoir 40 will be opened past the valves 15 and, 89 to chamber 82 which at this time is sub- The valve 89 will be unseated atthis time by spring 96 due tothe fact that substantially atmospheric pressure will be acting in chamber 92 above the flexible diaphragm 94. The system is now in condition for operation. 7 r .Let it now be assumed that it is desired to effect araising or elevating operation. To accomplish this, the operator moves the handle 42 from the normal vertical position shown in a counter-.- clockwise direction to unseat the valve 61 and seat the valve 69. When the valve i'lv is unseated, the compressed air in chamber 62 is vented to the atmosphere past said valve along the fluted stem .68. The pressure of the air in chamber 51 at the opposite side of piston 6| then moves said piston toward the right-hand against spring 63and such movement unseats the valve 59 and seats the valve 15. Compressed air supplied from the storage reservoir I to chamber 51 then flows past the valve 59 to chamber 60 and thence to chamber 55 above the oil in reservoir 40. I .The compressed air thus supplied to chamber 55; and acting on the top of the body of oil in reservoir 4D is adapted to force said oil out through the stand pipe 44 to the check valve 46 and un-' seat same against the light bias spring 41 so as to then'flow to the pipe leading to the hoisting .means for actuating same to eifect an elevat ing: operation. 5

The amount of oil thus displaced intothe hoist pipe 45. will vary according to the height to which it is desiredto elevate the body being raised,

while thedegree of air pressure required 'in chamber 55. for displacing the liquid will vary in accordance with the amountof oil it is desired to displace as well as the weight of the body being elevated. :The'pressure required in chamber above the oil in reservoir 40 may therefore be equal to the equalization with the pressure in the supply reservoir l orof any lesser degree. If such equalization is desired, the handle 42 will beheld in its left-hand position until such occurs and will then be relieved of manual force. However, if alesser degree of air pressure is desired in chamber 55, then the handle 42 will be held in its left-hand position only until such desired pressure is attained and it will then be relieved of manual pressure; Whenever handle 42 is thus released, spring H1 will act to -seat the valve 61' and unseat the valve 69 and in so doing will return the handle 42 to its normal vertical position whereupon compressed air will flow from chamber 57 to chamber62 and thus equalize on the opposite faces of' the'piston 6|. Spring 63 will then operate the piston 6| to seat the valve 59 for closing communication between the supply reservoir 1 and the oil reservoir 40. It will thus be-apparent that any desired degree of displace ment of oil from the reservoir 40 may be attained and under any desired actuating pressure of compressedair.

I It will be'noted that as long as there is flow of oil into the hoist supply pipe 45 such flow will hold. the check valve 46 op'enbut as soon as the flow'ceases, the check valve will be closed by spring 41 to th'ereby'isolate the hoist supply pipe 45 from any. part of the system in which-there is compressed air. In case of failure of any part of the system in which compressed air is efiectiveor in case ofiailure of the supply-of compressed air for any reason, the check valve 46 will therefore automaticallyoperate to prevent back flow of hoisting. liquid from. the hoist supply pipe 45 to the reservoir 48'. Thus any such failure can not result in an undesiredand possibly disastrous dropping .ofthe elevated load. or body.

When compressedair is drawn from the supply reservoir I for displacing oil from reservoir 40, the pressure of the airin the supply reservoir will become reduced and if this reductionis below the cutting-in adjustment of the electric governor 20, said governor willoperate to close the circuit through the electric motor I and cause the compressor 2 to operate. to recharge said reservoir. The compressor may be thus caused to operate to recharge the reservoir .while the handle 42 is being held in the left-hand or hoisting position and such operation may or may not terminate before it is desired to lower the body which was elevated. Moreover, if the amount of compressed air taken from the reservoir I is not sulficient to reduce the pressure therein to that required for causing the governor to start the compressor, the reservoir I will not be recharged with handle 42 in the left hand hoisting position, as will be apparent. Whenever the handle 42 is returned from its left hand raising. position to its normal vertical position, the valve 59 is seated as above described so as to close communication between the supply reservoir I and chamber 55, and at the same time the valve 15 isvunseated so as to connect .the chamber 55 to chamber 16. The compressed air previously supplied to chamber 55 for efiecting a hoisting operationwill then flow to chamber '16 and thence through-pipe. 8-! to chamber 88 in the reducing valve device 83. Under this-condition the check valve 46 will act to bottle-the liquid in pipe so as to maintain the body previously elevated in its raised position.

When valve 15 is unseated to connect chamber 55 to the. reducing .valve device, the valve 89 therein will be unseated by spring 96, due tothe vfactthat the pressure in chambers 82 and 92' will at this instant be substantially equal to that of the atmosphere. The compressed air supplied from chamber 55 to chamber 88' will therefore flow-past the valve 8 9 into chamber 82 and thence through the compressor. intake pipe I3. to diaphragm. chamber 85in the governor cut-out device 2I. and to the intake of'compressor 2. The pressure of the compressed-air thus-obtainedin chamber 82 of the reducing valvedevice 83 will' seat the check valve 85 to preventloss thereof through the strainer device 80, and will also equalize through-port 91- into chamber 92 on-the upper face of diaphragm 94 and when increased therein to a. degree sufficient to overcome. the pressure of. spring 98 will deflectsaid diaphragm downwardly against, said spring. as to permit movement of the valve 89 inthedirection of its seat and thus prevent the-pressure obtained in chamber 82 irom increasing above that determined-by spring 96.,

When a relatively lightdegree of pressurasuch as for instance two pounds persquare. inch, is attained, as above described,.ln diaphragmphamber. 35.0f 'thegovernor cutoutdevice 2.'I., the diaphragm 3,5 will-be deflected in the dircc-tlonof the leit-hand-ag'ainst the pressure 'of spring'lB'U-L This'movementwill s'hiftthe val-veil 'away'from its seat and seat the valve 24, with the resultthat the governor control passage 22-wi1l-be opened to the atmosphere through chamber '23, past the valve 2-! and thence through chamber 28 and vent port 29.- The control pressure for the electric governor 20 will-thus be reduced to substar'rtially that of the atmosphere and as a result said governor will operate to close, if not already closed, the circuit through the motor I 0 to thereby cause said motor to operate thecompressor 2 to take air out of the intake pipe I3 and to compress same through the discharge pipe I5 into thereservoir-I'.

The compressed air thus taken from the intake pipe I3 and chamber '82 in the reducing valve device 83 will tend to reduce'the' pressure acting in chamber 92 above thediaphragm 84, as a result of which the control sprin 96' will unseat the valve 89' to provide such flow of compressed air from chamber into chamber 82 as to maintain a substantial equilibrium between the pressure of spring 96 acting on one side of the diaphragm 94 and that of the compressed air inchamber 92 acting on the opposite side of the diaphragm. The spring 96 and diaphragm 84 are so related that the maximum pressure obtainable in cha-mber 82 andat the inlet of the compressor under this condition will not exceed a desired degree such as forty pounds regardless of the pressure acting in chamber 55' of the oil reservoir 40, which subsequent toequalization with the pressure of air in the reservoir I during a hoisting operation may be as great as for instance one hundred and fifteen pounds.

-There are several important reasons for employing the reducing. valve device 83 to limit the pressure obtained inthe inletpipe I 3 and thereby at the inlet to theeompressor 2 to a certain relatively low degree as compared to that which may exist in chamber 55 of the oil reservoir 40. Certainof these reasons will now be discussed.

It will be noted that the inlet pipe I3 to the compressor is connected to the. crank case I2 thereof so that whatever pressure is acting in said pipe will also? be actingv on the low pressure faces of the compressor pistons 3 and 4 in opposition to-the pressure of the air being, compressed and actin on theupper' faces of the pistons during operation of the compressor. The object of this is to minimize the loads on the various bearings and other parts of. the compressor particularly when the compressor is recompressi'ng air from chamber 55 abov the oil in oil reservoir 40 back into the supply reservoir I at wh-ich time the pressure in the inlet pip I3 will be considerably above that of the atmosphere; 7

When the crank case I2 ischarged withair at a pressure exceeding that of the atmosphere as above mentioned this pressure will-tend to force oil trom the crank caseout along the crank shaft and through the pressure-seal II. This sealwill efficiently prevent such loss of oil from the crank case only against, a certain degree of pressure therein and another reason for using thereducing valve device 83 is therefore to prevent obtaining. a pressure in the. crank case-above said certain d'eg'ree so a's to' ensure that the seal II will function efiiciently.

The reducing valve'device 83 isof particular importane'c'when the compressor is of. the compoundtype shown, in order to. cause both thehigh and'lcw pressure pistons 4 and 3 to operate as intended and to" avoid excessive loading of the low pressure piston, as will now be described.

Let it be assumed thatQiii eifecting a hoisting operation the pressure 'of. the air in reservoir I becomes eqnalise'd with thatinchamber 55in thec'il'reservo'ir 4'9; at for instance one hundred and fifteen pounds. If the reducing valve device 83 were not employed, then when the handle 42 were returned to its vertical position shown this one hundred and fifteen pound pressure inchamber 55 would become effective at .the intake to the compressor 2 and thus at the pressure 'side of the low pressure piston 3 upon its intake stroke. The low pressure piston 3 on its compression stroke would then increase the pressure of the,

air above the piston to a degree-above that in the supply reservoir I and this air would therefore merely be forced through the inlet and outlet valves for the high pressure piston 4 directly to said reservoir. The low pressure pistonj 3 would therefore operate under extreme load and the high pressure piston 4 would: merely idle. Furthermore, in order to take care of the large quantity of air displaced by the low pressure piston 3 under such a condition excessively large inlet and outlet valves would be required to avoid loading of said piston by a pressure far exceeding that in the reservoir I.

To avoid these difllculties, the reducing valve device 83 therefore functions to reduce the pressure of the air supplied from the chamber 55 to the inlet of the compressor during recompression to a degree such that when theair. is discharged from the low pressure cylinder its pressure will be lower than in the reservoir I so: as to thus It hasbeen found that by using the reducing valve device 83 and obtaining all the benefits thereof, that recompression of the air from chamber 55 back into the storage reservoir l is obtained in substantially the same time as without the reducing valve device. It has also beenfound that by recompressing the air from chamber 55, which may be under a relatively high degree of pressure, back into the storage reservoir I the pressure in said reservoir may be completely restored in only about twenty percent of the time required for a corresponding restoration with the intake of the compressor open to the atmosphere Furthermore, restoration of the pressure in supply reservoir I by recompressing the air from chamber 55 provides asaving in power consumed as great as for instance forty percent, as -com pared to effecting such restoration by drawing air directly from the atmosphere at the inlet of the compressor. a I

The reducing valve device 83 will operate as above described to limit the pressure in chamber 82 and thus at the compressor intake as long as the pressure in chamber-55 ofthe oil reservoir is of a higher degree than in chambers 82 and 92. However, when the pressure in chamber 55-becomes reduced to a degreesubstantially equal to that in chambers 82 and 92, the spring 96 will defleet the diaphragm 94 upwardly and move the valve 89 to its fully open position shown.

With the valve 89 in its fully open position the compressor will continue to operate to recompress'the air from the oil reservoir chamber 55 back into the air supply reservoir I until the pressure in said chamber acting on diaphragm 35 of the governor cutout device 21 is overbalanced by the opposing pressure of spring 39. This overbalancing will be obtained when the pressure of the air in the oil reservoir chamber 55 and intake pipe I3 becomes reduced to some low degree such as two pounds and when such occurs thespring 3,9 will return the diaphragm 35 to its normal position shown 'tothereby close the valve 21 and open'the valve 24 and thus cut the electric governor 20 into control by the pressure of the air in 'the supply reservoir I. I

If at tnjjm the pressure in the reservoir I is at or abovethe cut-out adjustment .of the electric governor 20 said governor will immediately operate to stop thejcompressori! in which case the relatively low degree of air pressure still ex'- isting inchamber 5 5 above the oil in reservoir 40 will be bottled'up. However in case the pressure in the reservoir! isnot yet restored to the cutout adjustment of theelectric governor20 the compressor will continue to operate to compress air into the tank I until such cutout pressure is ob.- tained at which time the governor will operate to stop the compressor. I

If the compressor 2 continues to operate after the cutout'clevice ZIoperatestO connect the electric governor 29 up for control by. the pressure of the'airin the reservoir I, this continuedoperation will" cause a further reduction of pressure in chamber 55 above the oil in reservoir 40, and this further reduction may reduce thepressure in said chamber to substantially atmospheric pressure. Infcase the reservoir I is not completely recharged at "the time the pressure ,in

chamber 55 thus becomes reduced to atmospheric pressure the compressor 2Iwi1l continue to operate and draw air fromf the atmosphere: throughthe air strainer BIJfand past the check valve 85. It will thus beapparentthat at-the time the compressor 2 stops operating the pressure in chamber 55 above the oillin reservoirv 4!] may be ofany degree from substantially atmospheric pressure unto that existing at, the time the cutout device 2I operates to connect the governor 20 up for control from the reservoir I.

,When the hoist is iin its lowered or normal po- I sition it is intended that the reservoir I willjbe substantially filled with-oil as shown in the drawing. Underthis condition a relatively small amount of compressed air from'the tank I'will be required to-displace the required amount of oil from the reservoir, for raising the hoistto its elevated position. 1 I v If a less amount of oil isin-the reservoir I, as may bethe case dueto loss by leakage after long use, a greater amount of compressed air will be required fromthe airsupply reservoir I to displacethe required.amount of oil from'the oil reservoir-to effect adesired hoisting operation.-

Thus the amount of compressed air required from-the reservoir 'I to effect a hoisting operation will varyaccording. tov the amount of oil in the reservoir- I; Where the amount of air required for effecting a hoisting operation is of a minimum and is draw-nfrom the air supply reservoir when charged to the'cutting-out point of the governor 20, reservoir I- may not"become-reduced to the cutting-inpoint' ofthe governor 20. In such a case the compressor 2' will not be caused to operate during the hoisting" operation; but upon movement of the lever 42 back to its normal position will operate to merely recompress theair from'chamber 55 back into the air supply reservoir I andthereby' restore the pressure in said reservoir to substantiallyits originalvalue. v

Where, however, the amount of compressed air needed for effecting a hoisting operation causes a reduction in pressure in reservoir I to below the cutting-in adjustment of the governor or in case the pressure in reservoir 1 is of such a reduced degree as to cause the governor to cut-in, even in case of .a completelyfilled oil reservoir, the compressor 2 .may be caused to .operate as above described to completely recharge the air supply reservoir lduring a hoisting operfifteen pounds above the cutout adjustment of the electric governor 20. However, except under some extreme condition, such as in case of a small supply of .oil in the oil reservoir and the pressure obtained in :the air supply reservoir 1 by recompression from chamber 55 may never attain the value required to operate the safety valve device llll.

When the operator desires to lower the hoist 'heturns the handle 42 in a clockwise direction to a loweringposition at the right hand side of the normal'position in which the handle is shown in the drawing. This operation of the handle to the lowering position actuates the lever and thereby the plunger 49 to unseat the check valve 46 against the opposing pressure of the bias spring 41. With the air pressure in chamber above the oil in reservoir 40 reduced to or near that of the atmosphere the weight of the elevated body will then cause flow of liquid back through the supply pipe 45 and past the unseated check valve 46 into the reservoir 40 and this flow will continue until the body has been returned from its elevated position to its normal lowered position at which time the handle 42 may, if desired, be returned from its lowering position to its normal position shown. The return of handle 42 to its normal position at this time is, however, of no consequence.

In case the handle 42 should be moved directly from its raising position to its lowering position, as might possibly be done under certain conditions, the oil from the hoist will flow back through the supply pipe 45 to the reservoir 40 only as the pressure of the compressed air in chamber '55 is reduced by operation of the compressor to recompress same back into the airsup- .ply reservoir I.. This recompression however occurs rapidly so as to quickly evacuate the chamber 55 of compressed air and thus will not materially retard the lowering of the elevated body.

As above mentioned, a certain low degree of air pressure may be bottled .inchamber 55 above the oil in reservoir 40 at the time the cornpressor stops, this bottled pressure being determined by the pressure oLspring 30 in the governor cutout device 21. The pressure of this spring need only be suflicient to insure that the valve 24 will be open when the pressure in the compressor intake pipe I 3 is substantially that of the atmosphere, and may therefore be such as to require only a relatively low pressure such as two pounds in the intake pipe for seating the valve 24. The bottled pressure in chamber 55 under the condition above mentioned may,

therefore,betwopounds .and this is permissible since normally a greater pressureis required to counteract the weight-of the. parts of hoisting mechanism connected to the oil supply pipe 45. Thus, even with a bottled pressure of two pounds in, chamber .55 above the oil in reservoir 40, a complete lowering of the hoist is normally en- .sured.

Summary It will now be noted that the improved hoist control mechanism provides for positive and selective raising and lowering operations regardless of the load being elevated and ensures that the load or body will not be dropped during a raising operation or while the load is in a raised condition, in case of failure of the compressed air in the system.

The system provides for most economical operation by recom'pressing the once used compressed air from the oil reservoir back into the compressed air supply reservoir. It will be noted that the compressed air which has been once used to effect a hoisting operation is never vented to the atmosphere unlessdue to some rare condition the recompression causes such an increase in pressure in the supply reservoir as to cause opening of the safety valve device IN.

The reducing valve in the recompression connection to the intake of the compressor insures intended compound operation of a compound H compressor, avoids excessive loading of and pos sible damage to any part of the compressor and also prevents loss of oil from the crankcase of the compressor when the crankcase is connected to the compressor inlet and thus charged with compressed air.

The recompression system including the reducing valve device also provides for obtaining a quicker recharge of the air supply reservoir. and a saving of power consumed by motor In to maintain said reservoir in a sufliciently recharged condition for operating the system, as compared to a system not embodying the improved recompression feature.

It should also be noted that recompression of the air from chamber 55 in the oil reservoir is insured regardless of the air pressure which may be acting in the supply reservoir I at the time the operating handle 42 is moved out of its raising position, since the governor cutout device 2| will operate at this time to ensure operation of the compressor 2.

In case the recompression system fails for any reason with a load in an elevated position, the

relief valve I03 provides'for lowering of the load as described.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In combination, a first reservoir adapted to be charged with compressed air, an air compressor having its inlet connected to an inlet pipeand having its discharge opento said-reservoir and adapted to receive air from said inlet pipe and to compress same into saidreservoir, a governor device for controlling said compressor and normally responsive'to the pressure of air in 'said reservoir and operative upon -an increase in'such pressure to a desired degree'to stop said compressor and-upon a reduction in the pressure in said reservoir to a desired lower degree to start said-compressor, saidinlet pipe having a communication with the atmosphere; a check valve in saidborhm'unication arranged toprovid'e for flow of air from the atmosphere to said'inlet pipe-and adapted to' be operated by pressure insaid pipe to close s'aid communication, a second reservoiradapted to be charged with compressed air at a pressure not exceeding that in said first reservoir, valve means operative to open communication-between said second reservoir and said 'inlet pipe to provide for flow of compressed air frorn 'said second reservoir' to the inlet 0f said compressor,-and means controlled bythe pressure in saidinlet pipe and operative when the pressure therein'is increased to a chosen degree above that or the atmosphere to eiiect operation 'of said governor device to cause said compressor to operateregardless of the pressure in said first reservoir.

2. In-combination, a first reservoir adapted to becharged with "compressed air, *an air com-'- pressor adapted to':cha1'ge said reservoir, an air inlet pipe forsaid -compressor a-dapted to be opened "to the atmosphere, a governor device for controlling the operation'of said compressor and normally controlled by the pressure of air in said reservoir and operative upoiran increase in such' pressure 'to a chosen degree to stop said cornpressor and upon a reduction insuch pressure to a 'chosen lower" degree to start said compressor, cutout means controlling cornmunicaw tionbetween'said governor d evice and reservoir and normally establishing'such communication to render said governor device responsive.to1the' pressure of fiuid in said reservoir and operative to close such communication to thereby render said overnor device: operative toefiect operation of sai d compressorregardless-g of fthe pres sure in said reservoir, means 'eontrolled by the pressure of. fluid in said inlet jpipe',oi ;'cont1'ol-;

ling said cutout means and operative when the pressurein said inletpipe oi ad'egree sub stantially no greater than that of the atmosphere to actuate said cutout means to effect opening of said communication and when of a greater degree to actuate said cutout means 'to effect closing of said. communication, a'second reservoir adapted to be charged with fluid at a pressure not exceeding that in said first reservoir, a valve operative to connect said second reservoir to said inlet pipe for supplying compressed air from said second reservoir to the inlet of said compressor, and a check valve operative upon the supply of compressed air from said second reservoir to said inlet pipe to close communication between said inlet pipe and atmosphere.

3. In combination, a first reservoir adapted to be charged with compressed air, an air cornpressor adapted to compress air into said reservoir, an air inlet pipe for said compressor, a compressor governor for controlling said compressor normally responsive to the pressure of air in said reservoir and operative to effect operation of said compressor when the pressure of the air in said reservoir is less than a chosen degree and to stop operation of saidcompressor 'when the" pressure of air in saidmreservoir is increasedto" a chosen'higher degreeya second reservoir adapted to be charged with compressedair'atapressure not exceeding that in said first reservoin valve means operative to connect" said second reservoir to said inlet pi pe to supply-compressed air from said secondreservoir to the inlet of said compressor, and means. operative by the 'pressur'e of airsupplied'from said second reservoir tosaid inlet pipe to effect operation of said governor to cause said compressor to operate reg'ardless of the pressure of fluid insaid first reservoir; said means being operative when 'the pressure in said second reservoi'r'is reduced by operationof i said: compressor to a chosen low'degree to conn'ect said governor to said-first reservoir for control by the air pressure thereini I 1 z 4. A hydropneumatic hoist control mechanism comprisinga liquid reservoir containing a body; of liquid and having-above the "liquid an airchamber to which compressed air is adapted'to be supplied for displacing the liquid to-efiec't' a hoisting operation; a certain" minimum *pres sure of compressed 'air being required :in'sa'idchamber to initiatesaid" hoisting-operation, 'a compressed'air: supply reservoir, an air compres-'- sor adapted to-compress air into-said'supply between said compressed air'supply reservoir andsaid chamber and to connectfsaid chamber'to said inletpipe-for supplying-compressed air from said chamber to the inlet"of -said compressor,

a pressure governor normally responsive 'to the pressurein said air' supply reservoir 'ror imainf taining the pressure ithe'r'ei'n :be'tween' certainchosen limits, and means operative upon supply! of compressed air from: said "chamber to said" inlet pipe .to effect operation of said governor to cause said compressor to operate to recompress the-air from said chamber'into' said reservoir" regardless of the pressure of fluid irr saidreservoir.. r a 1.

5. 'A- hydropneumatic' hoist control mechanism;

comprising" a liquid 're'se'rv'oir containing a body of liquid and having above the liquid anair" chamber toxwhich 'com'pressed' air is' adapted to 'be'suppli'ed .for displacing the liquid to'effect a hoisting operation, a -'certain-ininimum pressure of compressed" air being required in said chamber.to initiate s'aid' hoisting operation, a compressed air supply reservoir, an air' compressor adapted to compress air into said supply reservoir, an air intake pipe for said compressor, manual means operative to open communication between said supply reservoir and said chamber for supplying compressed air to act on said liquid for effecting a hoisting operation, said manual means being operative to close communication between said compressed air supply reservoir and said chamber and to connect said chamber to said inlet pipe for supplying compressed air from said chamber to the inlet of said compressor, a governor for controlling said compressor and normally subject through a passage to the pressure of compressed air in said supply reservoir and operative when such pressure exceeds a chosen degree to stop said compressor and when of a less degree to start said compressor, and means operative upon supply of compressed air communication between said passage and reservoir and to open said passage to the atmosphere so long as the pressure in said chamber is above said minimum degree and to reconnect said passage to said supply reservoir when the pressure in said chamber is less than said minimum degree, to thereby render said compressor operative to compress the compressed air from said chamber into said supply reservoir until the pressure in said chamber is reduced to said minimum pressure regardless of the degree of pressure acting in said supply reservoir.

6. A hoist control system comprising a hydraulic reservoir containing a body of liquid and having above the liquid body a chamber adapted to receive compressed air for displacing said liquid to effect a hoisting operation, an air supply reservoir, an air compressor operative to compress air into said reservoir, a governor controlled by the pressure of air in said reservoir for controlling the operation of said compressorzand providing for the maintenance of the air pressure in ,said reservoir between chosen limits, manually operative valve means movable to a position for supplying air from said supply reservoir to said chamber to displace liquid therefrom and movable out of said position to close communication between said reservoir and chamber and to connect said chamber to the intake of said compressor, and means operative by the pressure of air supplied from said chamber to the intake of said compressor to effect operation of said compressor to recompress the air from said chamber back into said reservoir regardless of the degree of pressure in said reservoir.

,7. A hydropneumatic hoist control system comprising a hydraulic reservoir containing a body of liquid adapted to be displaced by compressed air supplied to a chamber above the liquid to effect a hoisting operation, a compressed air supply reservoir, an air compressor for charging said air reservoir, a pressure governor arranged to be controlled by the pressure of air in said air supply reservoir for controlling the operation of said compressor and operative to regulate said compressor to maintain the pressure in said air reservoir between chosen limits, and manually operable means having one position for venting compressed air from said chamber and movable to another position for connecting said chamber with said air supply reservoir to there-- by provide compressed air on saidliquid to effect displacement thereof, saidv manually operable means comprising two valves, means connecting said valves for movement in unison, one of said valves constituting a supply valve controlling from said chamber to said inlet pipe to close communication between said air supply reservoirian'd said chamber and the other valve constituting an'exhaust valve controlling communication between said chamber and an opening for releasing compressed air from said chamber, the said means-connecting said valves providing for the closing of one valve upon opening of the other,'a movable abutment connected with said valves and constantly subject on one face to the pressure of the compressed air in'said supply reservoir and normally subject on the opposite face to the pressure of air from said supply reservoir, spring means acting on said valves for closing said supply valve and opening said exhaust valve when the opposite sides of said movable abutment are both subject to'the pressure of air from said supply reservoir, pilot valve means controlling communication between said opposite side of said movable abutment and said supply reservoir and operative to close same and to vent the compressed air fromsaid opposite side of said abutment for thereby rendering said abutment operative to open said supply valve and close said exhaust valve, a lever operative by manualpressure to effect operation of said pilot valve means tovent compressed air from said QPDOsite side of said abutment means, and means operative upon release of manual pressure on said lever to actuate said pilot valve means to reconnect said opposite side of said abutment to said compressed air supply reservoir to thereby render said spring means effective to close said supply valve and to open said exhaust valve.

8. A hydropneumatic hoist control system comprising a hydraulic reservoir containinga body. of liquid adapted to be displaced by compressed air supplied to a chamber above the liquid to effect the hoisting operation, an air supply reservoir, an air compressor operative to charge said reservoir with compressed air, manually controlled valve means having one position for supplying compressed air from said air supply reservoir to said chamber to effect displacement of liquid from said hydraulic reservoir, and another position for closing communication between said air supply reservoir and chamber and for connecting said chamber to a pipe-connected said compressor to withdraw the compressed air from said chamber.

BURTON S. AIKMAN.

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