US2407693A - Safety control for hoists and circuit therefor - Google Patents

Description

Sept.' 17; 194e. H, F, VICKERS A 2,407,693"

SAFETY vCONTROL FOR HOISTS AND CIRCUIT THEREFOR Filed Dec. 3, 1936 3 Sheets-Sheet 1 @QQ ,if

E( ATTORNEYS.

Sept. i7, 1946. H. F. vlcKERs SAFETY CONTROL FOR HOISTS AND CIRCUIT THEREFOR Filed Deo. 3, 1936 3 Sheets-sheet 2 @w .www

ATTORNEYS Sept. 17, 1946. H-.F. vlcKERs f' 2,407,693k

SAFETY CONTROL FOR HOISTS AND CIRCUIT THEREFOR ATTORNEYS.

Patented Sept. 17, 1946 "SAFETY CONTROL FOR HOISTS `ANI) CIRCUIT THEREFOR Harry F. Vickers, Detroit, Mich., assignor to Vickers Incorporated, Detroit, Mich., a corporation of -Michigan "Application December 3, 1936, Serial No. 114,008

(Cl. A198--37) 15 Claims. 1

This'device concerns 'a safety control for hoists vand circuit therefor, and has to do particularly with a hoist adapted to convey articles from one station to another and means for controlling the movement of said hoist in either direction between the said stations.

The present device operates by means of a chain type conveyer hydraulically driven and supplemented by a system of controls bothhydraulic and electric, which is believed to be a new idea, when considered together with the safety locking device.

An object of this invention -is to provide an automatic control of starting, stopping and direction of travel, when cert-ain requirements of these functions are to be riuliilled, `said control being practically Tree of 4any parts that are `apt to get out 4of order or lack dependability in operation.

Other objects will be apparent from the `following description and claims when considered together with the accompanying drawings.

In the drawings:

Fig. `1 is a new chart largely diagrammatic. of a chain type hoist and circuit therefor, with the control valves in section, and showing the relative position oi valves at the iirst stage of operation or with both stations loaded.

Fig. la is a diagrammatic illustration of the hoist showing both stations loaded and the relative position of the switches.

Fig, 2 is a view similar to Fig. l., showing the relative position of parts `during the second stage of operation, or with the lower station empty.

. Fig. '2a is a view similar to Fig. la showing the lower station empty 'and the'upper station. loaded.

Fig. 3 is aview similar to Fig. l but illustrating the position of various parts and operation of circuit during the downward motion of the conveyor, both stations being empty and the article in transit,

Fig. 3a is a view similar to Figs. la and 2c showing both stations unloaded and a projectile in transit.

The illustrated embodiment of this invention includes, a delivery station X which may be termed an upper station, a loading or lower station Y, and a chain type conveyor diagrammatically illustrated by the dotted line Z and operatively connected to a hydraulic motor diagrammatically illustrated as at H. The conveyor Z which may be any kind of an endless conveyor unit, is adapted to be actuated simultaneously with the shaftl?, one end of which is operatively connected to a hydraulic motor H and the other cnd to an automatic control unit generally designated U; in other words, the drive is usually from the hydraulic motor H through suitable reduction gearing to the conveyor .Z and to the control shaft T. The unit U also includes a latch and cam mechanism operatively connected with valve mechanisms for controlling the step by step movement ofthe conveyor, including a directional stop control D. The endless conveyor unit above referred to is illustrated and described in detail in my copending application, Serial N o.

` stemmed Aug, 10, 1935.

Fluid under pressure is supplied by a pump I, of the constant displacementtype, supplying fluid from tank reservoir Z Linder pressure to conduit 3. The pressure in conduit 3 is limited by vented relief valve il which operates in the following manner: Through small orince 5 in piston 5a the pressure inconduit 3 is transferred to chamber causing a balance between the said chambers. With spring l set to an initial pressure of approximately 20# per square inch, the resulting pressure 'to the left of piston 5a, las viewed in the drawings, is approximately 2G# per square inch more than the normal operating pressure in chamber 6 and conduit 3. This pressure to the leit of the valve urges it to closed position. The maximum relief pressure is controlled by an emergency relief valve', which by the `adjustment of the spring limits the pressure in chamber 6. If venting line 9 is connected to the tank ror atmosphere, this removes the effect of pressure in chamber E, causing the pressure in conduit 3 to fall to the pressure as limited by spring 'l which is still acting o-n the piston.

On diametrically opposite sides `of the automatic control unit U are located a cam lever a and a latch b and auxiliary control piston valves A and B. The cam operated accelerationdeceleration valve A is on the left hand side of the automatic control unit, as in Fig. l; and the latch operated valve B is 'on the right siede of the automatic control unit. The valve B is connected by conduits to a solenoid operated starting valve C which is connected by conduit 3 to the pressure iiuid through the vented relief valve 4. VThe directional valve D is connected through conduits I3 and i9 to the hydraulic motor H to control the direction of movement of the hoist. The above mentioned valves A, B, C and D Vhave intercommunicating connections. for reception of a pressure fluid, and for actuation of the conveyor when certain conditions exist.

To better understand the operation of the circuit and control of the conveyor motor it is thought best to set forth the primary conditions desirable for obtaining automatic control in a predetermined direction, as follows:

(1) With the upper station iilled, and lthe knob of directional valve D set to lowering position,

Vthe conveyor Z should` move downward only when the lower station Y is empty.

(2) With both upper and lower statioinsX and Y mity. it is important that nio motion of the conveyor should ensue irrespective of the setting do; of the kno-b of directional control valve D.

(3) With both stations lled, as shown in Fig. 1.a, it is important that no motion shall ensue, irrespective of the setting of the directional control valve D.

(4) With the upper station empty and the directional control valve D set to hoist the motion should be upward only when the lower station is filled.

The preferred means for deriving the required results when any of the above listed conditions are met with, is what is commonly called a three point electric control circuit, embodying 'two two-way article sensitive limit switches S1 and S3 interposed by a four-way switch Sz, as will be subsequently described. The switches S1 and S3 are so positioned adjacent the stations X and Y as to be actuated or released by the presence or absence of articles at the respective stations.

Figs. 1 and la illustrate the third condition of operation, the upper station switch S1, being correspondingly set for a filled condition. The

' trol valve A precedes the shift of S1.

intermediate four-way switch S2 is attached to the directional control valve D to eifect a transposition of control wires E1 and E2 whenever the directional control valve D is shifted. With s the lower station two-way switch S3 set to a lled position, the electrical circuit line Ea and E4 is opened causing a solenoid E5 to be ineffective. With the Valves-B and C of Fig. 1 in the inactive position, the venting line 9 through the corresponding ports is opened to the tank through the channels 9, Ill and II allowing the described -fall in pressure, by means of the vented relief valve 4.

Figs. 2 and 2a illustrate the iirst condition of f operation, the switches S1, Sz and S3 being so interconnected as to magnetically actuate the valve C. With the knob of directional control valve D set to lower, the movement of starting valve C vto the left causes the following consecutive functions. Fluid flow through the venting line 9 is cut ofi by closing ports 36 and 31 allowing the pressure in conduit 3 to build up to the required resistance. By this movement of the valve C the pressure conduit 3 is opened through a conduit I2 to port I3 of valve B and with a clear channel to port I4 and conduit I5. With the directional control valve D in the position shown in Fig. 2,

rconduit I5 is connected through ports I6 and I1 with a lower setting of the directional valve D, and finally through the conduit I8 to tend to drive the motor momentarily in a lifting direction. At this described position of the valve D the return uid is directed from channel I9 through the open ports 2U, 2I toI conduit 22 through port 23, and open port 24, which finally connects to the conduit I I, a tank connection.

Pressure in the conduit I5 is maintained to the required value by the spring loaded check valve `25, the function of which will be subsequently def scribed mo-re in detail. By a further movement of starting valve C, pressure conduit 3, through portl 26 and conduit 21, applies pressure to chamber 28, effecting a withdrawal of the motor holding latch b. This withdrawal o-ccurs during the momentary lifting movement of the motor.

With the withdrawal of the latch b and attached valve B, the conduit 22 is diverted from the tank port 24 to the pressure conduit 29, effecting a reversal of the fluid flow to the motor, (see the position of valve B in Fig. 3).

Momentarily after the valve B is moved to the right (as in Fig. 3), the starting valve C still remains to the left as shown in Fig. 2, allowing a clear channel for the return fluid from the llfQlQr through the line I8, ports I1 and I6 to the spring loaded back pressure valve 25, which offers a back pressure to the return flow ofthe motor to prevent over-run when lowering. From the spring loaded valve 25, the return uid has free access to the tank through conduit 33 and ports 3l and II.

Now after motion has started in the downward direction, as shown in Fig. 3a, the upper article, being in transit, allows movement of switch S1 by reason of its spring 32 to divert the electrical ow of current from line E2 to E1, thereby de-energizing solenoid E5 and allowing starting valve C to return to normal as indicated. The member i: U is provided with a cam lobe a; the timing of the cam lobe a', actuating valve A, and the shifting of the electrical switch Si, are so arranged. that a movement to the right of auxiliary con- The purpose of this timing relationship, or lost motion, is to allo-w a continued free flow of the return fluid from the motor before the valve C returns to normal. With the lobe of the cam beyond the roller of valve A, spring 33 forces valve A to the right as limited by the dwell on the cam as shown. With the valve A in this position the return fluid from the motor is directed from the conduit 30 to the ports 34 and 35 to the tank conduit II. By

Vreason of the venting ports 36 and 31 of valve C and ports I and 24 being connected in series,

venting of the relief valve is prevented and pressure maintained by the closure to port 24, regardless of the return of Valve C. With the return of the valve C to normal the port 25 is diverted to conduit II, a tank connection, allowing spring 38 to hold the latch against the periphery of the notch plate, preparatory to its nal mating with the notch at the termination of the cycle to lock the motor M against further movement. With the latch dwelling on the periphery of the said cam plate, the valve B still maintains open channels between the ports 29 and 23 and the necessary closure of conduit I3 to port I4, allowing a continuation of the downward motion of travel. The venting line 9 at the referred position o-f the valve is still obstructed by the closure of ports IIl and 24.

Nearing the completion of the cycle or the termination of the downward movement, the timing of the cam lobe a' with reference to valve A is in advance of the iinal notching'of the latch b for the purpose of maintaining motion to the ultimate destination before conduit 9 is nally vented to the tank.

In movingV to the left by the action of the cam lobe, valve A gradually retards the flow from ports 34 to 35 by the metering action of a tapered valve portion 33. After complete closurel ofthe ports 34 and 35, motion to a lesser degree is still continued by a needle valve 4u, which shunts the aforementioned ports and allows a restricted volurne to iiow from conduit 3i] to II. After slight continued motion the latch. b is allowed to drop into the notch of the cam plate to lock the motor M against further movement, causing the valve B to move further to the left finally opening the venting line 9 through the ports Il) and 24 to the tank conduit II. In addition the conduit 22 is connected by reason of the ports 23 and 24 through the `tank conduit II, preparatory for the next cycle. Coupled with the timing relationship `iust described, the switches Si and S3 again as'- sume the position as indicated by the loading c-ondition at that moment, as in Fig. la.

As previously mentioned the additional purpose ywould. :be -adequate Afor the `desired results. elongated -slot :4l in the `member .forming lobe It is .assumed Yin this circuit that the back pres- .sure setting :of the valve 25 is of sufficient value to .slightly raise or .sufficiently relieve 'the load `'of the conveyor to .facilitate withdrawal `of the latch. ,It will 'be noted that with an .insuicient ipressure setting .of the valve 25 the iiuid 4for Amomentary raising would `lay-pass from conduit I5 to `conduit 3.8. :By `reason of the fact-that the `pressuresetting of valve must be suicient to properly compensate "for the'unbalanced load, it 'fis logical toassume that a slightly higher value `n a is provided to permit adjustment betweenlobe a .and the notchof cam U..

In operation, from the previously mentioned four possible sets of conditionsexisting at .the loading stations, and the corresponding setting of the safety electrical switches Si and Sa, it will be seen that it is impossible to actua-te the hoist 'until -the article at the delivery station has .been

removed. This will :prevent the article at .the

-delivery station from being carried on around the conveyor and possibly damaged, or if it should be `an `explosive such as a can of nitro-glycerine, it will prevent .the movement to .any .other undesired or dangerous position. Any standard mechanism can .be iutilized foreiecting .this automatic stop, and Aone .possible .structure .is shown in all the drawings as `being .a solenoid, operated by two two-point switches .interposed by a four-way switch.

When the motor .is to .be moved in a .hoisting direction, the directional valve TD is .shifted from its position as shown to a position connecting line 22 with line ll. AS .soon as auxiliary control valve B is .shifted .by pressure from valve C to the position shown in Fig. 3, pressure from 4line 3 will .eiect a .hoisting .movement of the motor. This will continue until latch l) drops in cam U to close line 3 from-line 122.

From the present disclosure lit will thus be seen there has not only been produced .a combination of station controls and cooperating valve controls suitable for the safe conveying .of articles, but a mechanism that contains a minimum .number of parts that might be apt to .require attenn tion or replacement.

What I claim is:

l. In a .hydraulic .actuating and control system for controlling the movements of an endless conveyor vextending' between spaced loading and delivery stations, a conveyor, a pressure source, a reversible Aconveyor .motor having two ports interchangeable as pressure-exhaust ports, directional valve means for selectively directing liquid under pressure to said motor parts, a series of hydraulic conduits connecting .said pressure source and said directional valve means, means for limiting the pressure in .said conduits, a starting valve in said .conduits adapted in one position to block flow of pressureliquid from ,said source `and .in another position to passliquid from `said source to said .directional valve means, an `actuating `means for said starting valve, article responsive means `at `each of said stations to be influenced by the presence -of an article at said 'stations and means operatively connecting .said

the station toward which the conveyor will move -is emptyand the station. from which the conveyor will move is loaded, ,a .locking wheel operatively connected to said motor, .a latch for engaging :said 'wheel t'o lock said motor, and .means .con- `.n'ec'ted `to Vsaid .latch .and .operated by pressure `directed from said .starting valve lfor .disengaging l said latch :from said wheel to .permit operation .of'lsaid motor, .said 'starting valve 'being ar- `ranged 'to direct liquid .under pressure to operate said latch mean-s .only when said :starting valve .iss'hifted fromlit's `blocking position.

2. Inzahydraulic actuating and .control-system for controlling the movements :of anendless lcon-- veyor hoist, .extending .between spaced loading @and .delivery stations, a 'pressure source, a 1re versible conveyor :motor having ports intertchangeable .as :pressure-exhaust '.ports. .directional valve means .for selectively `.directing liquid `under ,pressure to'saidmotor Yports to cause hoisting or lowering :act-ion, hydraulic conduits connecting said `pressure source .and said directional lvalve means, Va starting valve inzfsaid conduits adapted, in one position, -tjo `blc-cl: .flow of :pressure liquid from said source and, in another position, topass :liquid from said source to said directional valve means, ya locking wheel operatively connected Ito `said motor, .a latch forengaging said wheel to lock said Amotor against a `downward movement, lmeans connected .to said latch and operable by pressure directed from `the source through said starting valve for -disengag-ing said latch `from said wheel, and `a valve in said `conduits between the starting valve .and the directional valve yopferable with said last named means and .adapted to direct lifting pressure momentarily to said motor .through said directional valve to permit withdrawal of :said latch from said wheel and to direct pressune thereafter to said motor through said `directional valve to eiect lowering action, said starting valvebeing arranged to'direct liquid under pressure to operate said latch means only when .said star-ting valve is shifted from its blocking position.

'.3. In ,a hydraulic actuating and control system 'for controlling 'the movements of .an endless hoist conveyor extending 'between spaced upper .and 'lower loading and delivery stations, a pressure source, `a reversible hydraulic conveyor motor having two `ports interchangeable as pressure and exhaust ports, .a .directional valve means, an .auxiliary .control valve, supply .and return conduits .connecting said directional valve with said motor. and with said auxiliary control Valve, said conduits .to .be used interchangeably as `pressure and Aexhaust conduits, a .tank conduit leading from said directional control, a starting valve, conduits connecting said starting valve with .said pressure source and with said auxiliary control valve, said starting valve being adapted in oneposition to block flow of pressure liquid from vsaid sourceand in another position to pass liquid from said vsource to said auxiliary valve to actuate the same, said auxiliary 'valve being adapted in one position, to pass liquid under pressure Ito one of Vsaid .conduits leading .to the directional `valvel and 1in another :position to pass pressure liquid tothe other :of 4.said conduits leading to said directional valve, locking means operably connected with said motor to prevent lowering, and means for .disengagng said lock-ing means, said valves cooperating to effect .momentary 4lifting action of saildlconveyor motor to permit disengaging of said latch, .and to effect thereafter a lowering action .of .said motor,

4. In ahydraulic actuating and control system for controlling the movements of an endless conveyor hoist extending between spaced upper and Vlower loading and delivery stations, a pressure source, a reversible conveyor motor having one port to be used as a pressure port for hoisting and as an exhaust port for lowering, and a second port to be used as a pressure port for lowering and as an exhaust port for hoisting, a locking means comprising a movable part operatively connected with said motor, and a movable latch for engaging said movable part to lock the same against movement, means for withdrawing said latch, and valve means to be automatically actuated at the start o'f a lowering movement for momentarily directing liquid under pressure to the hoist pressure port of said motor to permit withdrawal of said latch and thereafter directing pressure to said lower pressure port.

5. In a hydraulic actuating and control system for controlling the movements of an endless conveyo1` hoist extending between spaced upper and lower loading and delivery stations, a reversible motor to serve as a power unit for said hoist, a releasable holding means for said motor, means for releasing said holding means, directional and starting means responsive to load conditions, for controlling the movement of said motor, and means responsive to said directional and starting means for causing a momentary hoisting action of said motor before a lowering action to permit release of said holding means.

6. In a hydraulic `actuating and control system for controlling the movements of an endless conveyor hoist extending between spaced upper and lower loading and delivery stations, a pressure source, a hydraulic motor having one port to be used as a pressure port for hoisting and an exhaust port for lowering, and a second port to be used as pressure port for lowering and an exhaust port for hoisting, an auxiliary control valve, hydraulic connections between said valve and said pressure source, two conduit lines connecting said auxiliary valve with said motor ports, a directional valve in said two lines adapted in one position to open each of said motor ports, respectively, to a connecting line leading to the auxiliary control valve, and in another position to open one of said lines to the pressure lowering motor port, a locking means for said conveyor comprising a movable part and a latch for engaging said movable part, said auxiliary control valve being adapted in one position to direct pressure through one of said lines to the pressure hoisting port of said motor to effect momentary lifting movement to permit release of said latch means, and in another position, to effect lowering of said hoist, and means to effect shifting of said auxiliary valve.

'7. In a hydraulic actuating and control system for controlling the movements of an endless conveyor hoist extending between spaced upper and lower loading and delivery stations, a pressure source, a hydraulic motor having one port to be used as a pressure port for hoisting and an exhaust port for lowering, and a second port to be used as a pressure port for lowering and an exhaust port for hoisting, an auxiliary control valve, hydraulic connections between said valve and said pressure source, two conduit lines connecting said auxiliary valve with said motor ports, a directional valve in said two lines adapted in one Y iliary control valve, and in anotherY positionto open one of saidlines to the pressure lowering motor port, a locking means for said conveyor comprising a movable part and a latch for engaging said movable part, said auxiliary control valve being adapted in one position to direct pressure through one of said lines to the pressure hoisting port of said motor to effect momentary lifting movement to permit release of said latch means, and in another posi-tion, to effect lowering of said hoist, and a starting control valve in said system adapted in one position to block flow of pressure liquid from said source, and in a second position to pass pressureliquid from said source to said auxiliary valve to shift the same from the momentary lifting position to a pressure lowering position.

8. In a hydraulic actuating and control system for controlling the movements of an endless conveyor extending between spaced loading stations, a liquid supply tank, a pressure source, a conveyor motor, lines between said motor and said pressuresource, a starting control valve in said lines, an auxiliary line between said valve and said tank, and a relief valve connected to said lines between said starting control valve and said pressure source, said relief valve comprising a housing provided with a cylinder connected at one end by said lines to the pressure source and to the tank and connected at a second end by said lines to said starting control valve, a piston shiftable in said cylinder having a restricted passageway therethrough andV means thereon for normally blocking the tank connection of the cylinder, said starting control valve being adapted in one position to permit flow of pressure liquid from the source to said motor and to close said second end of the relief valve cylinder from the tank, and in a second position to block ow of pressure liquid from the pressure source and to open the second end of the relief valve cylinder to the tank, whereby pressure liquid from the pressure source may actuate said relief valve piston to open the tank connection of the cylinder and bypass the pressure flow, means associated with said motor for controlling the directionof movement thereof, and auxiliary means associated with and responsive to movement of said starting valve for directing liquid under pressure momentarily to drive said motor in one direction immediately prior to prolonged movement in the other direction.

9. In a hydraulic actuating and control system for controlling the movements of an endless conveyor hoist extending between spaced loading stations, a liquid supply tank, a pressure source, a conveyor motor, directional means associated with said motor movable to a lifting or lowering position for controlling the direction of movement thereof, an auxiliary contro1 valve, a starting valve, lines connecting said valves, pressure source and directional means, said valves being arranged to cooperate in one position to block pressure flow from said source to said directional means, and each being movable to a second position to permit flow through said lines to cause a momentary lifting movement and a prolonged lowering movement of said motor when said directionalmeans is set for lowering movement and a prolonged lifting movement when said directional means is set for lifting movement.

l0. In a hydraulic actuating and control system for controlling the movements of an endless conveyor hoist extending between spaced loading stations, a liquid supply tank, a pressure source, a conveyor motor, directional means associated with said motor movable to a lifting or lowering position for controlling the direction of movement thereof, an auxiliary control valve, a starting valve, lines connecting said valves, pressure source and directional means, said valves being arranged to cooperate in one position to block pressure flow from said source to said directional means, and each being movable to a second position to permit ilow through said lines to cause a momentary lifting movement and a prolonged lowering movement of said motor when said directional means is set for lowering movement and a prolonged lifting movement when said directional means is set for lifting movement, a relief valve in said lines normally maintained in closed position by pressure, said starting and auxiliary control valves being adapted to control the pressure closing said relief valve whereby said relief valve will remain open until said starting valve is shifted.

11. In a hydraulic actuating and control systern for controlling the movements of an endless conveyor hoist extending between spaced loading stations, a liquid supply tank, a reversible conveyor motor, a pump, a hydraulic control circuit for directing pressure from said pump to said Inotor, and means for controlling the speed of said motor at predetermined times in the cycle of movement of said conveyor comprising a deceleration valve adapted in one position to pass exhaust liquid from said motor to the tank, and means responsive to the movement of said motor for shifting said valve to cut off gradually the exhaust flow to the tank, and a second valve means located in parallel with said deceleration valve and adapted to further restrict the flow of exhaust liquid upon the shifting of said deceleration Valve.

l2. In a hydraulic actuating and control system for controlling the movements of an endless conveyor extending between spaced loading stations, a pressure source, a conveyor motor, directional means associated with said motor to control the direction of movement thereof, a starting valve, an auxiliary control valve, lines connecting said valves, pressure source, and directional means, said starting valve being adapted to be momentarily shifted in response to certain load conditions at said stations to direct pressure from said source to said auxiliary control valve to shift the same, means for maintaining said control valve in shifted position for a predetermined movement of said motor, said control valve being adapted, when in one position, to direct pressure from said starting valve to said directional means to eect momentary movement of said motor in one direction, and, when shifted, to direct pressure from said source to said directional means to effect prolonged movement of said motor in the other direction.

13. In a hydraulic actuating and control system for controlling the movements of an endless conveyor extending between spaced loading stations, a pressure source, a conveyor motor, directional means associated With said motor, to control the direction of movement thereof, a starting valve, an auxiliary control valve, lines connecting said valves, pressure source, and directional means, a p-ressure controlled relief valve in said lines associated .with said starting valve, said starting valve being adapted to be momentarily shifted in response to certain load conditions at said stations to direct pressure from said source to said auxiliary control valve to shift the same and to effect closing of said relief valve, means for maintaining said control valve in shifted position for a predetermined movement of said motor, said control valve being adapted, when in one position, to direct pressure from said starting valve to said directional means to effect momentary movement of said motor in one direction, and, when shifted, to direct pressure from said source to said directional means to effect prolonged movement of said motor in the other direction.

14. In a hydraulic actuating and control system for controlling the movements of an endless conveyor extending between spaced loading stations, a pressure source, a conveyor motor, directional means associated with said motor to control the direction of movement thereof, a starting valve, an auxiliary control valve, lines connecting said valves, pressure source, and directional means, said starting valve being adapted to be momentarily shifted in response to certain load conditions at said stations to direct pres-V sure from said source to said auxiliary control valve to shift the same, means for maintaining said control valve in shifted position for a predetermined movement of said motor, said control valve being adapted, when in one position, to direct pressure from said starting valve to said directional means to effect momentary movement of said motor in one direction, and, when shifted, to direct pressure from said source to said directional means to effect prolonged movement of said motor in the other direction, and valve means for controlling the pressure utilized for said momentary lifting.

l5. In a hydraulic actuating and control system for controlling the movements of an. endless conveyor extending between spaced loading stations, a supply tank, a pump, a supply line leading from said pump, a relief valve in said supply line comprising a `piston valve for closing said supply line from the tank and a pressure chamber behind said valve for holding it in closed position, a starting valve and an auxiliary valve,

each connected to said supply line, a conveyor motor to be operated by pressure from said pump, receiving lines connecting said auxiliary control valve and said motor, a directional valve in said receiving lines for directing pressure to and from said motor, said starting valve being adapted in one position to connect said relief valve pressure chamber through said auxiliary control valve to the tank and to block flow from the supply line leading thereto and being shiftable to a second position to close said relief valve pressure chamber, and to open said supply line to a receiving line through said auxiliary control valve and to direct pressure to said auxiliary control valve to shift the same, said auxiliary control valve being adapted in one position to block the supply line leading thereto and to pass pressure ow from the starting valve to a receiving line to effect momentary movement of said motor in one direction, and being shiftable by pressure from said starting valve to a seco-nd position in which said supply line is open directly to another of said receiving lines to effect a movement of said motor in the other direction, and in which said relief valve pressure chamber is closed, and means responsive to movement of said motor for maintaining said auxiliary control valve in said second position for a predetermined movement of said motor.

HARRY F. VICKERS,

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