US2490797A - Hoisting apparatus - Google Patents

Description

1949 P. H. GIRIOUARD ETAL 2,490,797

HOISTING APPARATUS Filed on. 29, 1942 4 Shets-Sheet 1 FIGZI INVENTORS Pl-l/L MS H. GIROUAR DAV/D WERTMAQ kg Dec. 13, 1949 P. H. GIROUARD El'AL 2,490,797

HOI ST ING APPARATUS 4 Sheets-Sheet 2 Filed Oct. 29, 1942 W \lll INVENTORS PHIL/AS H. GIROUARD DAVID WERTMAN 7ZJTOR5EY 2 HOI STING APPARATUS 4 Sheets-Sheet 5 Filed OG'b. 29, 1942 Patented Dec. 13., 1949 UNITED STATES HOISTING APPARATUS Philias H. Girouard and David Wertman, Washington, D. C.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 13 Claims.

Our invention relates generally to hoist apparatus and in particular to a hoist for use in the ordinance art in raising powder bags from a handling room to a gun chamber where it is then removed from the hoist car and loaded into the gun.

In the hoist apparatus incorporating our invention, the hoist car operates in an enclosed passageway (commonly referred to as a powder trunk) which rises from the handling room and terminates in a control room at the same level with, and next to the gun chamber.

The powder bags are loaded on the car at the handling room through a door having locking means therefor and opening into the powder trunk and an operator stationed in the handling room opens and closes the door.

In the control room at the top of the powder trunk, a second operator is stationed. This operator manipulates the control for operating the powder oar between the loading and unloading levels.

A door opens from the powder trunk and control room into the gun chamber, this door including locking means and being under the control of a third operator positioned in the gun chamber.

Suitable signal means are utilized to advise the operator in the control room when the powder bags have been loaded onto the car at the handling room and the door from the handling room to the trunk has been closed and locked. Likewise suitable signal means are utilized to indicate to the operator in the gun chamber when the loaded car has reached the top of the trunk and is ready for unloading.

To prevent fire from traveling from the gun chamber to and into the handling room in the event of a flashback in the gun chamber caused by fragments of powder bags burning in the gun after it has been fired and the breech opened, it is necessary to arrange the operation of the upper and lower doors so that only one, either the upper or lower, may be opened at any one time and then only when the car is at the door to be opened.

In our apparatus we attain this objective by interlocking the locking means for the lower door with the control for operating the car so that the car cannot be moved upwardly when such locking means are released and similarly interlocking the locking means for the upper door with the car operating controlso that the car cannot be moved downwardly when the upper door locking means are released.

The lockingmeans for each of the doors are automatically released by the car as it reaches the door. Thus since the car cannot be moved upwardly while the lower door is unlocked or downwardly while the upper door is unlocked, and also since neither door can be unlocked except when the car is opposite the door, it follows that only one of the doors may be opened at any one time and that neither of the doors may be opened while the car is operating between the loading and unloading levels.

The powder car is provided with top and bottom trays upon which powder bags are placed for hoisting from the powder room to the gun chamber. In order that the time element for hoisting the car and unloading the powder bags may be made as short as possible, it is necessary to provide means for first automatically stopping the loaded car at the unloading level with the top tray of the car at the correct level for discharging the powder bags onto the loading trays in the gun chamber when the upper door is opened, after which the car can be raised and stopped with the bottom tray at the correct, unloading position. We attain this objective by use of a two-position car stopping cylinder including a piston and piston rod adapted when fully extended to abut and stop the car with the top tray of the car at the unloading position and when fully retracted to stop the car with the bottom tray at the unloading position. Movement of the piston rod of the stop cylinder from its extended to retracted position is under the control of the operator in the control room but the piston rod is automatically extended and thus set to initially stop the car with the top tray of the car at the unloading level.

In the drawings, in which like parts are indicated by like reference characters in the several views, Fig. 1 is a diagrammatic perspective of our apparatus with the car at the bottom of the powder trunk, the door at the loading level being unlocked and open, and the door at the unloading level closed and locked;

Fig. 2 is a view similar to Fig. 1 but with the car at the top of the powder trunk, the upper door open and the lower door closed;

Fig. 3 is a view of the hydraulic system and controls therefor utilized in the invention;

Figs. 4 and 5 are enlarged detail views of the means operated by the car for unlocking the door at the unloading level as the car ascends in the trunk;

Fig. 6 is an enlarged detail view of the means for locking the door at the unlocking level; and,

Fig. 7 is an enlarged detail view of a portion 3 of the apparatus associated with the door at the loading level.

Referring now to the drawings, a powder trunk I illustrated in Figs. 1 and 2 by broken lines, extends upwardly from a powder handling room and terminates in a control room which is adjacent to the gun chamber. A door ll opens from the handling room into the trunk I0 and a door I2 opens into the gun chamber from the control room adjacent the top of the trunk ID.

A powder car l3 operates in the trunk between the powder handling room and the control room. This powder car is divided into upper and lower compartments M and [5 respectively, and powder bags it are carried in each of the compartments.

A hydraulic system is provided for operating car l3 within the trunk i0. This system includes a hydraulic cylinder ll, a hydraulic pump I8, amotor [9 for driving the pump l8, an expansion tank 20, a control valve 2 I, and a second hydraulic cylinder 22.

Hydraulic cylinder H, which is single acting, i. e., the car l3 being lowered by gravity, contains a piston 23, and a piston rod 24, connected to the bottom of car l3. The upper end of cylinder ll terminates in a buffing region formed by an internal collar 25. Piston 23 is provided with an enlarged tapered portion 21. Thus on the upward stroke of the piston 23, as the car 3 approaches its initial unloading position, at which position the upper compartment [4 in car [3 will be directly opposite the door l2, the tapered portion 21 on the piston 23 will enter the buffing region 25 and thereby provide for automatic deceleration of the car l3 due to the throttling action of oil between tapered surface 27 and collar 23. A check valve 28 permits unrestricted flow of oil into the buffing region 25 at the beginning of the upward stroke of the piston 23, but traps the oil in the buffing region 25 as the tapered portion 2'! begins to enter this region.

Likewise an internal tapered recess 29 provided at the bottom of cylinder ll cooperates with a complementary external tapered protuberance 38 provided at the bottom of piston 23 to provide for automatic deceleration of piston 23, and hence car 13, as the latter is lowered.

A check valve 3! is provided at the bottom of cylinder H to trap oil in the recess 29, as the tapered portion 39 of piston 23 enters the recess.

The hydraulic pump [8 is provided for operating piston 23 within the cylinder I1. This hydraulic pump is preferably of the positivedisplacement, multiple piston, variable discharge type, such as, for example, as described in U. 53. Patent No. 1,794,946, and is controlled by a tilting plate operated by means of a handle 32 located inv the control room and connected to the tilting plate in the pump l8 by linkage means comprising shaft 33, crank 3G, rod 35, and crank 36. The pump I8 is also provided with a replenishing valve 31 to permit flow of oil from the expansion tank 26 to the pump and a relief valve 38 connected between the high and low pressure sides of the pump.

The cylinder 22 containing a piston 39 and piston rod 43 connected thereto is provided at the top of powder trunk H] and serves to bring car l3 to a positive stop at the correct positions for unloading the powder bags H5.

When piston 39 occupies its downmost position in cylinder 22, piston rod 40 will abut and stop car l3 at its lower unloading position with the upper compartment [4 therein opposite the door 52 so that when the door i2 is opened, the operator in the control room can push the powder bags in the compartment l4 onto a loading tray located in the gun chamber. When piston 39 and rod 40 move to their uppermost position, car l3 will be stopped at its upper unloading position with the lower compartment therein opposite the door I2 so that the powder bags IS in the lower compartment [5 may likewise be pushed onto the loading tray by the operator in the control room. Piston 39 is provided with a tapered recess 4| which cooperates with a tapered protuberance 42 at the top of the cylinder 22 to provide automatic deceleration for car l3 as it approaches its upper unloading position. Cylinder 22 also includes anorifice 43 which connects with the expansion tank 20 by means of conduit 44 for expelling any air which may be entrapped in the 1 upper end of cylinder 22.

,; car I 3 at both its lower and upper unloading positions. This valve includes pistons 45 and 45, a push rod 4'! for operating thepistons, a rod 48 protruding from the lower end of the valve casing and connected to piston 46, a check valve 49, and orifices 56 and 5!.

The control handle 32 is movable to three positions which are labeled respectively Hoist, Stop, and Lower. When handle 32 is moved to Hoist, the tilting plate in pump i8 is moved so that oil is ported under pressure from pump I8 through conduit 52 to all parts of the cylinder l'l causing piston 23 therein and hence car It to move upwardly. At the same time, cylinder 22 is connected to high pressure conduit 52 by conduit 53, orifice 55 in valve 2|, check valve 49 and conduit 54. As car 13 rises in the trunk I0 and approaches its initial unloading position, the tapered portion 2! of piston 23 will begin to enter the bufiing region 25, causing car l3 to decelerate and finally be brought to restas the top of the car l3 strikes against the bottom of the extended piston rod 43. When oil can no longer flow into the cylinder l1, relief valve 38 will open and permit the oil to pass therethrough into the low pressure sideof the pump it.

When handle 32 is moved to th Stop position, the tiltin plate in pump ['8 moves to a neutral position and does not pump oil.

When handle 32 is moved to the Lower p0- sition, the tilting plate in pump I 8 is moved to permit oil to flow outwardly through conduit 5'5 into the expansion tank 20. Thus as car l3, piston rod 2 8 and piston 23 are lowered under gravitational forces, oil will be ported under pressure from cylinder I! through conduit 52 into pump it and out of pump l8 through conduit 55 and into expansion tank 26. Oil also flows under pressure through conduit 53, valve 2| and conduit 54 into cylinder 22, moving piston 39 to its initial downmost position.

As piston 23 nears the end of its travel, the tapered portion 33 will begin to enter recess 29 causing car I 3 to decelerate and finally be brought to rest at the loading position with car l3 opposite door H.

A two-position indicator 55 is located also. in the control room. At one position this indicator reads Hoist and in the other position it reads Car down. This indicator, which signals the operator in the control room to raise car 13 or to move the handle 32 to Stop, is operated by means of a shaft 51 which extends between the control room and the lower powder handling room.

It is desirable to provide interlocking mechanism between the lower door II and the handle 32 so that under no conditions can car I3 be raised while the lower door II is unlocked. Door II, manually opened and closed, and which is arranged for sliding movement in guideways 58, is provided with a transverse slot '59 near the top which is adapted to receive a latchin lever 99 which is operated by means of a pivoted handle 6| located in the handling room, the end of which rides upon a crank arm 62 which is rigidly secured to a shaft 63, the latter being connected to a midpoint of the latching lever 69. One end of the latching lever 99 is pivotally connected to the shaft 51. The lower end of shaft 51, shown in detail in Fig. 7, terminates in a lost motion coupling consisting of a cylinder 94, a spring 65, and a rod member 66. A bifurcated connecting member 61 is afilxed to rod 68 and also connected to one end of a pivot lever 68. The other end of the lever 68 is acted upon by car I3 and serves a function to be described hereinafter in detail.

When in abutting engagement with the lower end of operating handle 32 for pump I8, a pivoted dog 69 serves to prevent handle 32 from being moved to the Hoist position. Dog 69 is connected to shaft 51 by suitable linkage means comprising link I9, pivoted lever II, rod I2, pivoted lever I3, rod I4, pivoted lever 15, rod I9, and pivoted lever 11.

Thus, when car [3 is in the position shown in Fig. l, with the bottom of the car riding upon the free end of lever 58, which causes shaft 5! to be raised to its uppermost position and thereby draw latching lever 99 out of slot 59, dog member 69 will effectively prevent handle 32 from being moved to the Hoist position. However, when the lower door II is closed, movement of handle SI from the Car down position inscribed on a plate I9 in Fig. 1 to the Ready to hoist position shown in Fig. 2, will cause latching lever 69 to enter slot 59 of door II and the shaft 51 to move downwardly through th aforesaid lost motion mechanism, turning pivoted lever 11 and the remaining linkage mechanism In to 79 to move the dog 69 out of engagement with the lower end of handle 32. This downward movement of shaft '51 also causes the indicia Hoist to show on the indicator 56. Thus the operator in the control room knows that the lower door II has been closed and locked and is the signal for him to operate handle 32 to the Hoist position.

A hydraulic system is provided for opening and closing the upper door I2. This system includes a hydraulic pump 19 which may be of any suitable type, an electric motor 89 for driving the pump I9, a control valve 8| and operating lever 82 therefor located in the gun chamber, a hydraulic cylinder 83 for operating locking latches 85 on the door I2, another hydraulic cylinder 85 for moving door I2 to its open and closed positions, a valve 86 operated by the door I2, a relief valve 81 and an expansion tank 88.

Cylinder 85 is supported pivotally at 89 and is provided with a double acting piston 99 and a piston rod 9| connected pivotally at 92 to door I2. To open door I2, oil is ported under pressure into the top of cylinder 85, driving piston -99 and piston rod 9| downwardly to the position shown in Fig. 2. To close the door, oil is ported under pressure into the bottom of cylinder 95 driving the piston 99 and rod 9| upwardly to the top, as shown in Fig. 1.

Cylinder 99 is pivotally supported at 93 and is also provided with a double acting piston 94 and piston rod 95 connected pivotally to lever 99. Lever 96 is connected to latches 84 by pivoted lever Sland links 98 and 99. For unlocking the door I2, oil is ported under pressure into the bottom of cylinder 83, driving piston 94 and piston rod 95 upwardly to the position shown in Fig. 2. For locking door I2, oil is ported under pressure to the top of cylinder 83, driving piston 94 and piston rod 95 downwardly to the position shown in Fig. 1.

It will be evident that when door I2 is to be opened, piston 99 in cylinder 83 must operate to rotate latches 84 out of locking position in advance of the operation of the piston 99 in cylinder 85. To obtain this sequence of operation, we have arranged for the cylinder 83 con-' trolling the latches 94 and the cylinder controlling the opening and closing of door I2 to be connected hydraulically in series.

Thus, when lever 82 on valve 9| is moved to the position shown in full lines in Fig. 3, oil will be ported from pump '59, through conduit I99, through valve 9i, and through conduit I9I to the bottom of cylinder 83, causing piston 94 therein to move upwardly. When piston 94 reaches its topmost position, entrance to conduit B92 is uncovered and oil is then ported through this conduit into the top of cylinder 85, driving piston 99 to the position shown in Fig. 3 to open the door I2. When piston 99 reaches the bottom of cylinder 95, the flow of oil will cease, causing its pressure to be built up in conduit I99 leading from pump 59. 'When the pressure of the oil is equal to the predetermined operating pressure ofthe relief valve 8'8, oil will be ported from the pump i9 through conduit I93 and relief valve 91 into expansion tank 88.

When the lever 82 on valve 8! is moved to the position shown in broken lines in Fig. 3, oil will be ported from pump I9 through conduit I99, through the valve 8! and through conduit I94 to the bottom of cylinder 85, causing piston 99 therein to move upwardly and close door I2. As door I2 closes, arm I will move to the position shown in broken lines in Fig. 3, in which position the piston Q99 in valve 86 is then moved to the upper part of the valve I91 against the opposing force of spring I99, which is operative to connect conduit I99 with conduit H9 leading to the top of cylinder 89. Thus, after the piston 99 in cylinder 85 has moved to its topmost position and closed door I2, oil in conduit I 94 will be ported through conduit I99, valve 99, and conduit l I9 to the top of cylinder.83, causing piston 94 therein to move downwardly and rotate the latches 84 to their locking position on the door I2.

We provide an interlock to prevent the upper door 12 from beingopened while car I3 is below the'proper level for unloading. A shaft I II is provided with a rounded stub portion II2. This stub portion is flattened on opposite sides at H3 and provided with a slot II4.

A support memberl I5 is provided for mounting a bell crank lever H9 having arms II! and I9. Arm 5 i9 is provided with a roller I I9 which is adapted to move over the top and bottom faces of a diamond shaped cam member I29 which is carried by car I3. The other arm I" terminates in afo'rked portion I2I and the latter is connected to the flattened portion of stub I12 by means of a pin !22 which extends between the forks I2I through the slot H4.-

A helical spring I23 is carried in compression between a fixed collar I24 on the stub H2 and a movable collar I25 which is slidable transversely upon stub II2. Since the spring 123 is under compression, movable collar I25 will always be urged to the right andagainst the forked portion I2I of lever Ill, and thereby tends to keep pin I22 at the righthand side of slot II4.

As car I3 ascends in the trunk I0, the top face of cam I rides against roller II9, causing bell crank I I6 to rotate clockwise from its rest position (the middle position shown in Fig. 4) to the position shown in full lines, thereby moving shaft member H I to the right.

When car I3 descends, the bottom face of cam I20 will ride against roller H9 causing the bell crank II I5 to rotate counterclockwise from its rest position to the position shown in broken lines in Fig. 4. However, at this time, the shaft I II cannot move to the left but movement of the lever I I? is taken care of by movement of pin I22 to the left in slot I I 4, which causes-the spring I23 to be further compressed.

Shaft II I is coupled through linkage means to a pivoted lever I26 and rod I21 to a pivoted latching lever I 23 shown in detail in'Fig. 6, which is carried by a support member I29. The support I29 includes a cylinder I30, a piston I3I operable within cylinder I 30, and a helical spring I32 carried in compression between the end of piston I3! and the bottom wall of the cylinder I38. Piston I3! includes an extension I33 which abuts a latch portion I34 on lever 96 and a recess I35 which coacts with the end of the latching lever I28.

Rod member I2! is biased downwardly by means of a spring I35 carried in compression between a stop I31 and a collar I38 affixed to rod I21.

When car I3 reaches the unloading position shaft III will be moved to the right, causing rod member I21 to move upwardly, and turn latching lever I23 clockwise to the position shown by the broken lines in Fig. 6. This disengages the latching portion I32. on lever 96. As lever I rotates, the lower end thereof moves in alignment with recess I which permits piston I3I and its extension I33 to move upwardly to the position shown by the broken lines under the restoring force embodied in the spring I32. Upward motion of the'extension I33 gives lever 96 and lever I 39 connected thereto a positive thrust in an upward direction.

As latching lever I23 rotates, a pointer I40 connected with latching lever I28 by means of a shaft I4I will'be moved to a position opposite indicia reading Car up inscribed on a suitable plate I42 located in the gun chamber. The oper ator in the gun chamber then knows that car I3 is up to the proper level to be unloaded and can then open door I 2 at will, since, as previously explained, release of the levers 96 and I39 from the latching lever I28 frees piston rod 95 for upward movement in cylinder 83.

It is not desirable to have the door I2 open automatically as car I3 reaches the unloading position because the loading tray for the gun (not shown) on which the powder bags I6 are discharged through the doorway closed by the door I2, must occupy a certain position relative to the door I2 as the latter is opened. Since operation of car I3 is independent of operation of the load- 8 ingtray, it necessarily follows that control over the door must be under the operator positioned in the gun chamber.

To insure that car I3 as it rises in the trunk ID will always first come to a stop with the upper compartment I4 at the unloading position, we prefer to provide a mechanical interlock. This interlock comprises a pivotally mounted rocker plate I43 which is operable while the car I3 is below the level of the upper door I2 to prevent the operator in the control room from manipulating push rod 47 on control valve 2I.' As clearly shown in the drawings, rocker plate I43 is connected for operation with the shaft III by means of a link I44 and a pivoted lever I45.

When the car I3 is below the level of the upper door I2, shaft IiI will occupy an extreme left position since rod I2? is biased downwardly under the restoring force of sprin I36 acting against stop member I3'I.- This places rocker plate I43 in the position shown in Fig. 1, with the end thereof abutting rod member 43 which is secured to piston 45. This holds valve 2i in the position shown in Fig. 3, in which position, piston red 46 occupies its downmost position, stopping car I3 with compartment I4 at the proper unloading position.

After car I3 has thus been stopped, which is effective to move shaft I H to the right, plate I43 is moved to the position shown in Fig. 2, which then allows the operator in the control room to operate pistons 45 and 46 within valve 2| by downward movement of push rod 41.

When push rod il is moved downwardly, cylinder 22 is connected to expansion tank 20 through conduit 54, orifice 5!] in valve 2| and conduit I46. Also the bufimg region 25 in cylinder I'I is connected to the high pressure conduit 53 through conduit I 47 and orifice 5i in control valve 2 I.

To prevent car I3 from being lowered while door I2 is unlockedand therefore free to open at will of the operator in the gun chamber, we have provided further interlocking mechanism for the operatin handle .32 controlling pump I8 consisting of a rocker arm I48 fixedly secured to shaft 33 to which handle 32 is also fixedly secured. As previously explained, when car I3 reaches its initial unloading position shaft III is caused to move to the right, rotating latching lever I28 and rocker plate I43 to the positions shown in Fig. 2. With rocker plate I43 in this position, operating handle 32 cannot be moved to the Lower position, due to the fact that as'handle 32 is moved back from the Hoist position to the Stop position, rocker arm I46 will abut the end of rocker plate I43 and prevent further movement of handle 32 in this direction. This interlock is not released until latching lever I28 is reset to the position shown in Fig. 1 by the operator in the gun chamber as door I2 is closed.

Rocker arm I48 performs the additional function of preventin car I3 from creeping downwardly due to loss of oil in cylinder N. This is accomplished by arranging the position of rocker arm I48 on the shaft. 33 so that when the latter abuts the end of rocker plate I43, handle 32 and hence the tilting plate in pump I8 will be held slightly towards the Hoist position. This is effective to port oil to cylinder I! in an amount sufiicient to offset the leakage.

Operation lower door I I is closed manuallyand the operator in the powder room moves handle BI downwardly from the Car down position shown in Fig. 1 to the Ready to hoist position shown in Fig. 2. As previously explained, downward movement of handle 6| moves shaft 51 downwardly which causes latching lever 60 to rotate and lock door II in its closed position. Downward movement of shaft 51 also operates the indicator 56 to read Hoist and, through the linkage means described, causes dog 69 to rotate away from the control handle 32 to permit movement of the latter to the Hoist position by the operator in the control room at the top of the trunk I0. Oil is now ported from pump I8 to cylinder I1, causing car I3 to rise in the trunk I8. As car I3 nears its initial stop position, it will be decelerated by the bufiing arrangement located at the top of cylinder I1 and finally brought to rest as the car abuts the extended piston rod All in cylinder 22 with the upper compartment M in the correct position for unloading. The operator in the control room now moves control handle 32 back towards the Stop position until rocker arm I43 abuts the end of rocker plate I43.

As car I3 reaches this first stop position, shaft II I will move to the right and effect rotation of latching lever I28 to the position shown in Fig 2, which unlatches lever 96 therefrom and turns indicator arm I40 in the gun chamber to a position opposite the Car up indicia carried on plate I42.

When the operator in the gun chamber is ready to open the upper door, he presses downwardly on operating handle 82 of control valve BI, whereupon oil under pressure will be ported from the pump 19 into cylinder 83 to move piston rod 95 upwardly and thereby rotate the pivoted latches 84 away from door I2. Oil will now be ported from cylinder 83 to cylinder 85 causing piston rod ill to move downwardly and thus open the door I2. As soon as door I2 opens, the operator in the control room will push the two powder bags I6 in the upper compartment I4 through door I2 onto the loading tray in the gun chamber.

The operator in the control room now pushes downwardly on push rod 41 of the control valve 2| which connects cylinder 22 with expansion tank 20 through valve 2I and once again moves control handle 32 to the Hoist position whereupon more oil will be ported from the pump IB into cylinder I1, causing car I3 to rise further in the trunk ID. As the lower tray I5 in car I3 nears its unloading position. car I3 will be decelerated by the bufling arrangement in the top of cylinder 22 and finally brought to rest. The operator in the control room can now push the two powder bags I6 from compartment I5 onto the loading tray in the gun chamber.

As car I3 moves between its first and second unloading positions, the buffing region 25 in cylinder I1 is connected through valve 2! with the high pressure conduit 53. This arrangement permits the enlarged tapered portion 21 of the piston 23 to move upwardly in the buffing region 25 at a rapid rate since with such connection there no billing or decelerating action.

As soon as the iast two powder bags have been transferred from car I3 to the loading tray, the operator in the gun chamber pulls back on handle B2 whereupon oil will be ported under pressure from pump 13 to the bottom of cylinder 35, moving piston rod 3! upwardly to close door 22. When door I2 is almost completely closed piston I06 in valve 86 will move upwardly to permit oil 10 under pressure to flow into the top of cylinder 83, moving piston rod downwardly and rotating the pivoted latches 84 into locking position across the face of the door I2.

At this time, the latching portion I34 on lever 96 pushes downwardly upon the projection I33 and drives piston I3I downwardly. As soon as the recess I35 clears the lower end of latching lever I28, the spring I36 acting against its stop member I31 causes rod I21 to move downwardly and rotates latching lever I28 to the position shown in Fig. 1.

Downward movement of rod I21 also causes 'shaft II I tomove to the left and rotate rocker plate I43 clockwise. This motion pushes rod 48 in control valve 2i upwardly restoring the pistons 45 and 46 thereof to the position shown in Fig. 3 and releasing the interlock on control lever 32.

The operator in the control room can now move lever 32 to the Lower position. As previously described, as the car I3 descends oil will now be ported from cylinder I1 through conduits 52 and 53, valve 2|, and conduit 54 to cylinder 22, thereby pushing piston 39 and piston rod 40 to their lowermost positions. 011 will also be ported through conduit 52 into one side of the pump I8, out the other side of this pump and through conduit 55 to the expansion tank 20.

When car I3 nears the bottom of trunk I0, the former will be decelerated by the bufiing action provided between recess 29 and tapered portion 30. As car I3 reaches the bottom of trunk II), lever 68 will be rotated to cause upward movement of rod 51. This unlatches lever 60 from slot 59, thus unlocking the lower door I I and rotating the handle 6| to the position shown in Fig. 2 opposite the Car down indicia. Door II can now be opened and the loading operation repeated.

In conclusion, we wish it understood that while the embodiment of our invention which has been described herein is to be preferred, many changes and modifications may occur to those skilled in the art without departing from the spirit and scope of the invention, as defined by the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

We claim:

1. In hoist apparatus including a trunk extending between upper and lower levels, a door at each of said levels openable to said trunk, a car operable within said trunk, and movement imparting means for said car, the combination comprising control means for operating said movement imparting'means, locking means for each of said doors, means positively retaining said locking means for said upper door in operative position, means operable by said car for rendering said retaining means inoperative and for locking said control means against operation to efiect downward movement of said car as said car reaches said upper level, and means operable by said car for releasing said locking means for said lower level door and for locking said control means against operation to effect upward movement of said car as said car reaches said lower level door.

2. In hoist apparatus including a trunk extending between upper and lower levels, a door at each of said levels openable to said trunk, a car operable within said trunk, and movement im- 11 parting means for said car, the combination comprising control means for operating said movement imparting means, first and second stop means for said control means, locking means for each of said doors, means positively retaining said locking means for said upper door in operative condition, means connecting said first stop means with said retaining means for operation therewith, said first stop means being operable upon a release of its associated retaining means to prevent operation of said control means to effect downward movement of said car, and

means connecting said second stop means with said locking means for said lower level door for operation therewith, said second stop means being operable to prevent operation of said control means to effect upward movement of said car upon its associated locking means being rendered inactive.

3. The combination in claim 2 wherein said retaining means for said upper level door locking means is automatically rendered inactive by said car as the latter reaches said upper level and wherein said locking means for said lower level door is also automatically released as said car reaches said lower level.

4. In hoist apparatus including a trunk extending between upper and lower levels, a door at each of said levels openable to said trunk, looking means for each of said doors, said locking means being operable to secure said doors against opening when in a closed position, means associated with said upper door locking means for positively retaining said locking means in operative condition, a car operable within said trunk, a hydraulic cylinder including a piston therein operatively connected to said car for hoisting and lowering said car, a pump for operating said piston, and a control lever for said pump, the combination comprising first stop means for said control lever, means connecting said stop means with said retaining means for said upper level door locking means for operation therewith, said first stop means being operable to prevent said control lever from being moved so as to effect 1 lowering movement of said car when said retaining means for said upper level door locking means is unfastened, second stop means for said control lever, and means connecting said second stop means with said lower level door locking means for operation therewith, said second stop means being operable to prevent said control lever from being moved so as to effect hoisting movement of said car when said lower level door locking means is unfastened.

5. A hydraulic system'for operating a car within a trunk from a lower loading level to first and second upper unloading levels comprising a main cylinder including a piston and piston rod operatively connected to said car, a stopping cylinder including a piston and piston rod adapted when fully extended to abut and stop said car at said first unloading level and when fully retracted to "stop said car at said second unloading level,

means for operating said main cylinder to raise said car, means for porting fluid to said stopping cylinder to cause the piston rod thereof to become fully extended and therefore operable to stop said car at said first unloading position, said last mentioned means also being operable to permit fluid to be ported outwardly from said stopping cylinder as said car moves upwardly from its first to its second unloading position, and means controlled by said car for preventing porting of fluid from said stopping cylinder until said car has reached its first unloading level.

6. A hydraulic system for operating a car within a trunk from a lower loading level to first and second upper unloading levels comprising a main cylinder including a piston and piston rod operatively connected to said car, a stopping cylinder including a piston and piston rod adapted when fully extended to abut and stop said car at said first unloading level and when fully retracted to stop said car at said second unloading level, a hydraulic pump, conduit means connecting said pump to said main cylinder, means for connecting said main cylinder with said car stopping cylinder whereby fluid may be ported from said main cylinder to said car stopping cylinder during downward movement of said car to cause the piston rod of the stopping cylinder to become fully extended and therefore operable to stop said car at its first unloading position upon the return upward movement of said main cylinder piston and car, and means for porting said fluid outwardly from said stopping cylinder as said main cylinder piston and car move upwardly from said first to said second unloading position.

7. The combination in claim 6 and including means controlled by said car for preventing porting of fluid outwardly from said stopping cylinder until said car reaches said first unloading level.

8. A hydraulic system for operating a car within a trunk from a lower loading level to up per first and second unloading levels comprising a main cylinder-including a piston and piston rod operatively connected to said car, a buffing cylin-- der including a piston, bufiing means and a piston rod adapted when fully extended to abut and stop said car at said first unloading level and when fully retracted to stop said car at said second unloading level, a hydraulic pump, means connecting the high pressure side of said pump to said main cylinder, means including a control valve for connecting said main cylinder with said buifing cylinder whereby fluid may be ported from said main cylinder to said buffing cylinder during downward movement of said car to cause said piston rod in said buffing cylinder to become fully extended and therefore operable to stop said car at its first unloading position upon the return upward movement of said main cylinder piston and car, and means including said control valve for connecting said bufiing cylinder with the low pressure side of said pump whereby fluid may be ported from said bufling cylinder to the low pressure side of said pump as said main cylinder piston and car move upwardly from the first to the second unloading position.

9. The combination in claim 8 and including means controlled by said car for preventing operation of said control valve to connect the buffing cylinder with the low pressure side of the pump until said car has reached said first unloading position.

10. A hydraulic system for operating a car within a trunk from a lower loading level to first and second upper unloading levels comprising a single-acting main cylinder including a piston and piston rod operatively connected to said car, a bufiing cylinder including a piston, bufiing means therefor and a piston rod adapted when fully extended to abut and stop said car at said first unloading level and when fully retracted to stop said car at said second unloading level, a hydraulic pump, an expansion tank, a multiple position control valve including check valve means and a by-pass therefor, first conduit means leading from the high pressure side of said pump to said main cylinder to supply fluid for hoisting the piston in said main cylinder, second. conduit means leading from said first conduit to said control valve, third conduit means leading from said control valve through said check valve means to said buffing cylinder, fourth conduit means leading from said control valve to said expansion tank, and fifth conduit means leading from said expansion tank to the low pressure side of said pump, said control valve being operable when in one position to connect said second and third conduit means through said check valve means whereby fluid will be ported from said main cylinder to said bufiing cylinder upon a downward movement of said main cylinder piston and car to cause said piston rod in said bufiing cylinder to become fully extended and therefore operable to stop said car at its first unloading position upon the return upward movement of said main cylinder piston and car, said control valve being operable when in the other position to connect said third and fourth conduit means through said bypass whereby fluid will be ported from said bufiing cylinder to said expansion tank as said main cylinder piston and car moves upwardly from its first to its second unloading position and bringing said car to a stop when said buffing cylinder piston rod is fully retracted.

11. In a hoist apparatus, the combination with a car, a hydraulic cylinder the piston of which is connected to said car for raising said car to a predetermined position, a hydraulic pump, and control means for said pump including an operating handle movable between Hoist, Stop" and Lower positions, of stop means associated with said handle and operable when said car is raised to its predetermined position for preventing said control means from being returned completely to its Stop position thereby porting a relatively small quantity of fluid to said cylinder from said pump to ofiset any leakage of fluid in said cylinder which would otherwise permit said cylinder piston to creep downwardly.

12; In a hydraulic system for operating a car within a trunk between a lower loading level and first and second upper unloading levels, the comb'ination comprising means for moving said car, hydraulic car position defining means including a piston adapted when fully extended to stop said car at said first unloading level and when fully retracted to stop said car at said second unloading level, control means for said piston normally maintaining said piston in said extended position and operable to release said piston for movement to said retracted position to permit said car to move to said second unloading level, and means operable by said car for assuring that said control means maintains said piston in said extended position until said car reaches said first unloading level.

13. In a hydraulic system for operating a car within a trunk between a lower loading level and first and second upper unloading levels, the combination comprising means for operating said car, a piston adapted when fully extended to stop said car at said first unloading level and when fully retracted to stop said car at said second unloading level, control means for said piston, said piston control means being operable to maintain said piston in said extended position and to release said piston for movement to said retracted position to permit said car to move to said second unloading level, means operably connecting said car operating means with said piston control means and operable to move the piston to its extended position upon downward movement of said car, and means operable by said car during upward movement for assuring that said piston control means maintains said piston in said extended position until said car reaches said first unloading level.

PHILIAS H. GIROUARD. DAVID WERTMAN.

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

UNITED STATES PATENTS Number Name Date 540,169 Kidder May 28, 1895 1,959,786 Hodgkinson May 22, 1934

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