US2387777A - Hoisting mechanism - Google Patents

Description

ct. 30, 1945. A. J. STANTON ETAL I 2,337??? HOISTING MECHANISM Filed March 11, 1942 3 Sheets-Sheet 1 45 INVENTORS 37 O .Afi-hur 11512001213090, wEa-awstfl dampbew.

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A. J. STANTON ETAL HOISTING MECHANISM Filed March 11, 1942 3 Sheets-Sheet 2 ATTORNEY ct. 30, 1 A. J. STANTON EI'AL HOISTING MECHANISM F' iled March 11, 1942 3 meets-Sheet 3 g INVENTORS BY ErfiF I J 1 ATTORNEY Patented Oct. 30, 1945 2,387,777 HoIs'rINo MECHANISM Arthur J. Stanton, Bethesda, Md, and Ernest F. Campbell, Springfield, Va.

Application March 11, 1942, Serial No. 434,248

(Granted under the act of March 3, 1883,as amended April 30, 1928; 3'70 0. G. 757) 11 Claims.

This invention relates to improvements in ammunition'hoist mechanism, and more particularly to mechanisms for hoisting ammunition in naval vessels to the loading deck of a gun turret, or to some intermediate level, from the magazine.

In naval vessels a passageway, or powder trunk, extends from the powder hold, or magazine, to the gun turret or intermediate level. Doors are provided in the walls of this passageway, and in order to reduce the danger from flashback and to prevent fire from spreading from the deck of the vessel to the powder magazine, these doors are arranged so that only one may be opened at a time.

A powder car or hoisting car runs inside the passageway between the several doors, and ammunition can be loaded on or unloaded from this car through the appropriate door. An interlocking mechanism for coordinating the operation of the car and the various doors is provided as hereinafter described.

One of the objects of this invention is to prevent movement of one of the doors when the other door is in a predetermined position.

Another object is to prevent operation of the hoisting mechanism when one of the doors is in a predetermined position.

Another object is to prevent movement of the doors except when the means for operating the hoisting mechanism is in a certain position.

A further object is to prevent the rapid falling of the powder car in the event of a failure of the power which operates the hoisting mechanism.

A still further object is to enable the ammunition carrying mechanism to be restored to a position of rest which is out of the way and will enable the transfer of ammunition through the usual passage by other means, in the event of a failure of the power which operates the hoisting mechanism.

Another object is to provide means for the deceleration of the raising and lowering mechanism which will be automatic in operation.

Another object is to provide a control means for hoisting and lowering ammunition which will be entirely automatic in its operation.

Other objects will be apparent from the following description taken in connection with the accompanying drawings, of which:

Fig. 1 is a diagrammatic outline of the general arrangement according to a preferred embodiment of the invention (not drawn to scale).

Fig. 2 is a view in elevation and partly in section of the latching mechanism for the unloading door taken substantially along the line 22 of Fig. 6.

Fig. 3 is a view in elevation and partly in section of the latching mechanism for the loading door.

Figs. 4 and 5 are detailed elevation and side views respectively of the interlocking mechanism between the door latching mechanism and the power control mechanism shown diagrammatically in Fig. 1.

Fig. 6 is a plan view, partly in section and partly broken away, of the latching mechanism for the unloading door taken substantially along the line B6 of Fig. 2.

Hg. '7 is a view in elevation and partly in sec tion of the hydraulic cylinder and piston shown in Fig. 1.

Fig. 8 is a, view showing a cutaway portion of the valve assembly connected with the hydraulic pump of Fig. 1 showing the relief and replenishing valves together with oil passages to the expansion tank and hydraulic piston.

Fig. 9 is a diagrammatic representation of the positions of the latching mechanisms when the loading door is in other than a closed position.

Fig. 10 is a diagrammatic representation of the position of the latching mechanisms when the unloading door is in other than a closed position.

Referring to Fig. 1, II is an electric motor driven by a suitable source of current which drives a positive displacement multiple cylinder variable discharge hydraulic pump l2 by means of shaft l3. This pump is preferably of the type known in the trade as the Waterbury gear, as disclosed, for example, by U. S. Patents 893,558 924,787; 925,148 and 1,407,047. But it may comprise any positive displacement device which will supply a driving liquid under pressure in either direction while being driven at a substantially constant rate of speed in a single direction by a source of power. The output of this variable discharge pump is connected by pipes I4 and 5 with the upper and lower ends of a suitable hydraulic cylinder l6, which contains a movable piston ll, attached to a piston rod 20. An expansion tank 18 is suitably located so as to be connected to the Waterbury pump by means of pipes l9 and 2|. This expansion tank is provided to take care of variations in the amount of fluid in the system. The amount of liquid necessary to operate the hydraulic cylinder and the rate of outlet from the hydraulic cylinder will vary according to the direction of its motion and its position in the cylinder.

On the lower end of the piston rod 20 there is attached a crosshead 22 which supports a shaft 23 upon which are rotatively mounted the sheaves or pulleys 24. Bracket 25 is preferably mounted below the lower limit of the stroke of piston rod 20, and the shaft 26 is supported by this bracket. A plurality of fixed sheaves or pulleys 21 are rotatively mounted on the shaft. Another bracket 23 is suitably supported, preferably above the cylinder I6, and a shaft 29 is supported by this bracket. A plurality of fixed sheaves or pulleys 3| are also rotatively mounted on this shaft.

A powder trunk, or passageway, is provided on board ship, which passageway extends between the various levels at which powder is handled, such as between the powder magazine and the upper handling room, or between the upper handling room and the turret. A powder car or loading cage 32 runs preferably on rails (not shown) vertically inside this powder trunk or passageway, which is not shown in the drawings. This car or loading cage is supported from above by a flexible wire rope or cable, or any other suitable means 33 which passes through any convenient motion translating system, such as the fixed sheaves or pulleys 34, thence alternately over movable sheaves 24, fixed sheaves or pulleys 3 I, and finally to any convenient anchorage, such as shown at 35 in Fig. 1. Another flexible cable, wire rope, or other suitable means 36, is attached to the bottom of the car 32 to assist in accelerating the car when it is on its downward trip. This cable or rope runs through any convenient motion translating system, such as the fixed sheaves or pulleys 3I, thence alternately over movable sheaves 24 and fixed sheaves or pulleys 21, and finally to some anchorage such as 38.

The motor II is preferably an electric motor driven by a suitable source of electric current, but may be any suitable prime mover which will operate at substantially constant speed in one direction to drive the variable discharge pump I2. The rate of output of oil from this pump, and its direction of flow, can be regulated in the usual type of Waterbury pump by a single tilting plate provided in the interior of the pump, and not shown in the drawings, as such devices are well known in the art. This tilting plate is fixed to the shaft 38, which rotates in suitable bearings provided in the pump casing. Movement of the shaft 38 is controlled by lever 39. An operating handle 4! is rotatively mounted on a pivot 42, which is located at any convenient point at the unloading level. The operating handle 4| is connected to the lever 39 by a linkage 43, or by any other suitable means. Another operating handle 44 is rotatively mounted on the pivot 45, which is suitably located at some convenient point at the loading level. An interlocking plate 45 is fixed on a rotating shaft 99, which is supported in a manner later to be described. The circumference of the interlocking plate is providedwith a plurality of sprocket teeth 40. Rotating on pivot 45 and fixed to the handle 44 is a sprocket wheel 41. The interlocking plate 46 andsprocket wheel 41 just mentioned are operatively connected by means of a flexible cable or rope 48, which connects with the chains 49 and which are in operative engagement with plates 46 and 41, respectively. It will thus be seen that movement of either the interlocking plate or the operating handle 44 will simultaneously operate the other member through the connect ing cable and chains. Fixed upon the shaft 99, and co-acting with plate 45, is a lever 50, which lever is connected to the operating handle M by means of the link 52, or by any other suitable mechanism.

It is apparent, therefore, that any movement of either operating handle 4| or 44 will correspondingly move the other handle, the interlocking plate 46, and the tilting plate of the variable discharge pump fixed to the shaft 38. Any other arrangement than that shown may be used to provide the mechanical connections between these elements, the one shown being merely typical of a satisfactory system.

The powder trunk or passageway, which is not shown in the drawings, is provided with a door 53 at the loading level, and door 54 at the unloading level, as diagrammatically shown in Fig. 1. These doors are arranged to slide vertically in suitable easements in the powder trunk, the opening into the passageway being closed when the doors are in a raised position and open when the doors are lowered. The latching mechanism for the upper door 54 comprises a latch 55 and a resetting lever 56, pivoted at 51. The latching mechanism for the other door 53 comprises the latch 60, a resetting lever 58, pivoted at 59, and a lever 6|, pivoted at 62. These latching mechanisms will be described in detail later. trol wire or cable 63 runs over suitably positioned sheaves or pulleys 64. The levers 56 and 6| are attached to the control cable 63 at 65 and 66, respectively, so that a movement of one of these levers produces a similar movement of the other lever, In addition, this control wire operates two sliding stops 61 and 68,'which will cooperatively engage a pair of slots 69 and I I, cut into a pair of segments I91 and I02 in the interlocking plate 46. A detailed view of this mechanism is shown in Figs. 4 and 5. The engagement of stop 51 with slot 69, or the engagement of stop 68 with the slot I I, provides a positive locking mechanism which will prevent operation of the hoisting mechanism when either one of the doors is in other than a closed position.

Turning to Figs. 2 and 6, the bracket 12 is shown attached to the wall of the powder trunk adjacent to the door 54 by suitable bolts, or by any other means such as riveting or welding. A projection I3 is provided on the bracket, through which a rectangularly shaped guideway I4 is cut, and in which the sliding latch 55 fits. A mortise or opening I5 is also cut in the top of the projection 13. A portion of the upper surface of the latch 55 is provided with teeth 16. The resetting lever 56 rotates about the pivot 51, which is located adjacent to the upper part of bracket I2. Lever 56 is provided with a downwardly projecting arm H, which is provided with teeth I8. This arm extends down through the opening I5 into operative engagement with teeth I6 on latch 55. The door 54 is provided with a stop or abutment I9 near its lower edge. Another projecting arm 8| of the lever 56 extends forwardly into engagement with the stop 19 so that when the door is shut, that is in its extreme uppermost position against the sill 82, the lever 56 and the latch 55 will be in the position shown in Fig. 2. The pivot 65 provides for the connection between lever 56 and the control cable 63 through adjustable turn buckles 83 or any other suitable connection means.

In Fig. 3 is shown a detailed view of the arrangementof the latching mechanism for the door 53. A bracket 84 is attached to the wall of the trunk near the door 53 by any suitable means, such as by bolting, welding or riveting. A projection 85 on the bracket 84 is provided with a A conrectangularly shaped guideway 86, through which the latch 60 slides. A mortise or opening 81 is cut in the top of this projection. A portion of the upper surface of the latch 80 is provided with teeth 88. A resetting lever 58 is pivoted on the bracket at 59, and is provided with downwardly projecting arm 89 and upwardly projecting arm 9|, and a forwardly projecting arm 92. The downwardly projecting arm 89 is provided with teeth 93, which are in operative engagement with teeth 88 on latch 60. A stop or abutment 94 is provided on the door 53, so that when the door 53 is in its closed position (in its extreme uppermost position against the sill 90) it will move the lever 58 into the position shown in Fig. 3. The upwardly projecting arm BI is provided with teeth 95. Lever BI is rotatively supported on bracket 84 by means of the pivot 62. A series of teeth 96, provided on lever BI, serve to engage the teeth 95 of lever 58. The pivot 66 provides a connection between lever El and control cable 63 through the adjustable turnbuckles 9?, or by any other suitable connecting mechanism.

In Figs. 4 and 5 are shown in detail the interlocking mechanism between the control for the tilting plate and the door latching mechanisms, shown diagrammatically in Fig. 1. A bracket 98 is attached to the wall of the powder trunk or passageway by means of bolts, or otherwise by means of welding or riveting. This bracket pref erably is located in line with the pivotal connecticns 65 and 66 of the door latching mechanisms, so as to provide the shortest path for the control wire 63. But it is evident that by the use of suitable motion translating mechanisms, the bracket 98 could be located in other positions. A short shaft 99 is rotatively supported by suitable bearings in the bracket 98, and on one end of this shaft is fixed the interlocking plate 40. On the face of the plate 36, and extending outwardly from it are the arcuate segments WI and I02. Two diametrically opposing slots 59 and II are cut into segments I Ill and I02, respectively. The lever 50 (see Fig. 1) isfixed to the other end of shaft 99, and rotates with it and the interlocking plate 48. Chain 49 and cooperatin sprocket teeth 40, on the plate 65, are shown in this figure in detail. An idler sprocket I03, pivotally mounted on the bracket 93 at I04, may be provided to cause more positive engagement between the chain and the teeth of the interlock ng plate. and also to bring the parallel lengths of chain 49 and cable 48 close to each other in order to conserve space in the powder trunk.

Two extensions I05 and I06 are provided at the upper and lower ends of the bracket 98 to serve as a support for a shaft I01. This shaft projects through the openings I08 and I09, which are cut in the extensions I 05 and I06, respectively. This shaft is cut away on one side so as to leave the sliding stop portions 6! and 68. These stop portions are spaced longitudinally from each other at a distance sufiicient to clear the circumference of the arcuate segments IOI and I 02 when the shaft I0! is in the position shown in Figs. 4 and 5. This is the position obtained when both the loading door and the unloading door are shut. The holes I08 and I09 are drilled insuch a position that the stop 6! will engage the slot- 09 when the interlocking plate 46 is in a neutral position and the shaft I 07 is moved vertically downward by the latch mechanism of the lower door 53, and stop 68 will engage slot II when the interlocking plate is in a neutral position and the shaft I0! is moved vertically upward by the latching mechanism of door 54. One of the extensions I05 may .be provided with a keyway III which engages a feather key II2 attached as by screws H3 in a keyway II=4 out in shaft I01. This feather key prevents rotation of the shaft I01, while allowing vertical movement. Adjustable connections I I5, or any other suitable means, may be used to operatively attach the control cable 63 to the shaft I01.

The interior of the cylinder I5 is shown in Fig. 7. The piston I1 is shown in sliding contact with the wall of the cylinder only along the ridge II'I. Constrictions III] and H9 in the wall of the cylinder form buffer chambers l2l and I22, respectively. The skirts I23 and I24 of the piston head are of a reduced cross-section so that they may pass the constrictions :I I8 and -II-9 when the piston is at either end of the stroke. A suitable gland and packing maintains anoil-tight fit around the piston rod 20 at the lower end of the cylinder.

The pipes I 3 and I5 provide suitable paths for the flow of oil between the variable discharge pump I2 and the hydraulic cylinder I6. When the piston is on the downward stroke the flow of oil is from the pump to pipe Hi to the cylinder and back to the pump through pipe I5. On the upward stroke the direction of flow is reversed. The principal inlet and outlet ports are shown in Fig. 7 at I25 and I29. The ports I21 and I28 are provided in the wall of the buffer chambers HI and I22, respectively. On the downward stroke, oil may be delivered to the upper end of the cylinder I6 through pipe I4 and port I21, through check valve I29, but this check valve prevents the discharge of oil through the port I2l when the piston I! is coming to rest at the end of its upward stroke. Similarly, oil "may be admitted from pipe I5 through check valve .I3I and port I28 to the lower end of cylinder IS, in order to drive the :piston I! in an upward direction. However, the check valve I31 prevents discharge of operating fluid through port I28 when the piston is coming to'rest at the end of its downward stroke. Check valves I29 and I3I are held in place by .anysu-itable compression means.

Fig. 8 illustrates in detail the relief and replenishing valves, together with the interior passages or channels, connecting the pump with the expansion tank and the hydraulic cylinder. Valves I32 and I33 are the replenishing valves, and serve to admit oil from .the expansion .tank I0, coming through pipe 2I and. channel or passage !34, into the circulating system whenever there 'is a deficiency of the operating fluid. The valves I38 and I3! are relief valves, which will admit excess oil from the circulating system into the expansion tank, through the channel 508 and pipe I9. The last mentioned four valves are preferably of the check valve type, held in place by a suitable compression means, and allowing flow of oil in one direction only, as will be seen from the operation of the apparatus. One branch of the channel I 38, specifically noted by reference I39, leads to the interior of the pump casing, and permits any oil which escapes by leakage from the operating mechanism to flew back into the expansion tank. The re plenishing valves I32 and I33 are maintained only under nominal pressure for the purpose of keeping the valves in place. Relief valve I31 passage I4I, pipe I4, and into the upper end of the hydraulic cylinder I6. Inasmuch as gravity tends to pull the car 32 downwardly, this force acting through cable 33 and sheaves 24 and 31 will tend to move the piston I! in an upward direction, thus building up the pressure in the pipe I4 and channel MI. The pressure on valve I31 is also great enough to prevent its opening on power failure when the oil in pipe I4 and passage MI is under pressure created by the action of gravity through car 32 and cable 33 on piston IT. The valve will open, however, when piston II reaches the bottom of its power stroke and can travel no farther.

But for the provision of relief valves I36 and I31, if a power failure should occur during the hoisting or lowering of the powder car, the weight of the car would tend to drive the hydraulic pump as a motor unless the tilting plate is in a neutral position, with disastrous consequences if the car were allowed to drop to the bottom of v the powder trunk unchecked. One way to prevent this would be to provide a signal to notify the operator ,of a power failure so that he would immediately throw the tilting plate into neutral position, in which case, because of the characteristics of a, positive displacement pump, it could not be driven as a motor and the fall of the car would be stopped. The arrangement of the relief valves, as shown, however, provides for an entirely automatic check on the movement of the car in the event of power failure which will function with the tilting plate in any position, entirely without attention from the operator.

This result is achieved by making use of the difference in the effective areas of each face of the piston II. ,When gravity tends to draw the 'car 32 down the piston I! will be driven up, forcing oil from the top of the piston head back to the pump through pipe I4. This oil would pass through the pump l2 driving it as a motor, but for the fact that when it reaches the lower face of the piston I! through pipe I the cylinder I6 cannot accommodate all of the oil because of the presence of piston rod 26 in the cylinderon the lower side of the piston head. The only escape for the excess oil would be through one of the relief valves I36 or I3I. Suitable sprin or compression means are provided to urge these valves toward their closed positions, and these springs are set at a compression sufficient to keep the valves I 36 and I3! closed to prevent such escape of fluid in the event of a power failure. The strength of the spring which holds valve I36 closed will ordinarily be less than that on valve I 37, but this ratio will depend entirely upon the ratio of the effective areas of the faces of the piston head.

A manually-operated by-pass valve I43 is provided so that in the event of a failure of power when the car 32 is in other than its lower-most position, it will be possible to open this valve, allowing oil in the system to return to the expansion tank, whereupon the car will return to the bottom of the passageway.

In the operation of the hoist, if the tilting plate, which is operated by movement of shaft 38, is in a neutral or stop position, the running of the motor II does not force any oil through pipes I4 or I5 in either direction, and the slots 69 and H in the arcuate segments II and I 02 of interlocking plate 46 will be positioned in a vertical direction so that the sliding stops 6'! and 68 are free to move up and down through these slots. Thus, if the loading door 53 is moved downwardly to open it, the bottom edge 53a of the door (see Fig. 3) will contact the inclined face 66a of the latch 66, causing it to move back in the guideway 86. Backward movement of the latch 69 will cause a counter-clockwise rotation of the resetting lever 58 about its pivot 59, which will in turn cause clockwise rotation of lever 6| about its pivot 62. The resetting lever 58, will be free to turn because of the fact that as its arm 92 moves downwardly, the stop or abutment 94 mounted on door 53 will also move downwardlyand out of the way. The clockwise rotation of lever 6| will create a pull through connection 66 on the control wire or cable 63, which will in turn pull shaft I0! downwardly into such a position that its sliding stop 6! will engage with slot 69 in the upper segment of plate 46. At the same time, the downward movement of cable 63 will also cause clockwise movement of lever 56 about its pivot 51. The latching mechanisms will then be in the position diagrammatically shown in Fig. 9.

When the lever 56 has been thus rotated, it will have moved latch ,55 'in a direction forwardly in the guideway I4 and underneath the door 54 (see Fig. 2). At the same time the arm 8| of lever 56 will be moved upwardly and away from the stop or abutment I9 attached to door 54. Because the interlocking plate 46 is locked in position by the engagement of sliding stop 61 with slot 69, it will not be possible to turn either one of operating handles 4| or 44 because of their connection with plate 46 through the link 52 and the cable 48, respectively. In addition, the tilting plate of the variable discharge pump must remain in its neutral or stop position because of its connection through shaft 38, lever 39, and linkage 43 with the operating handle 4|.

The operation of the door latches and interlocks is as follows:

Assuming that the powder car or loading cage 32 was at the loading position at the lower end of the powder trunk or passageway before the door 53 was opened, it is now possible to place powder charge or other ammunition on the car and to close the door 53 by raising it to its upper limit. Just before it reaches this upper limit, the abutment 94 will engage the arm 92 of the resetting lever 58, thus turning the lever in a clockwise direction. This rotation of lever 58 will force the latch 60 forwardly into the position as shown in Fig. 3. Because of the inclined face 66a, the latch will clear the lower edge of the door as it moves into the closed position. As the lever 58 turns in a clockwise direction, it also rotates lever 6| in a counter-clockwise direction, which in turn exerts a force on the control wire 63, thus resulting in a similar counter-clockwise movement of lever 56. Rotation of lever 56 will bring its arm 8| back into contact with the abutment I9, and will also return the latch 55 to the position shown in Fig. 2, in which position it will not prevent downward movement of the door 54. Another effect of the force exerted on cable 63 is that it will raise the shaft 10! so as to disengage stop 61 and slot 69, but will not raise the shaft far enough to engage stop 68 with slot II.

Thus, when both doors are in a closedposition, the interlocking plate 46 is freeto move in either direction. If the operating handle 44, for example, is moved, it will also turn the interlocking plate through the medium of the operating cable or wire 48. The interlocking plate, through its co-acting lever 50 and linkage 52, will turn the handle 4|, and by means of the linkage 43 will operate the lever 39, which is itself operatively connected to the tilting plate of the variable discharge pump I2. By means of the same connecting mechanisms, movement of the operating handle AI would also operate the tilting plate, interlocking plate, and the lower operating handle 44.

Inasmuch as the powder car has been assumed to be at the lower end of the powder trunk, the piston I! will then be at the upper end of the cylinder I5. When the tilting plate is moved by either of the operating handles to the hoist position, oil will be forced from the pump through channel MI, pipe 14, and into the upper end of cylinder IE. At the beginning of the stroke, the oil reaches the upper face of the piston head II6 from pipe Id through check valve I29 and port I21, but when the piston head has moved out of the buffer chamber I2I, the oil will enter principally through port I25. Oil from the lower side of the piston head will flow out from port I26, pipe I5, into channel I42, and then be re-circulated by the pump. Because of the presence of the piston rod 2% in the cylinder IE5, the effective area of the upper face of the head is greater than that of the lower face. Therefore, not enough oil will flow from the lower side of the piston head through pipe I5 to satisfy the requirements of the pump as it forces oil into the cylinder above the head. This deficiency is made up from oil from the expansion tank I8, which flows through pipe 2|, channel I343, check valve 132, thence into channel I42, and to the pump. As the crosshead 22 is moved downwardly by the piston, the sheaves 24 cause a take-up of the wire rope of cable 33, which pulls the powder car 32 upwardly. Because of the presence of a plurality of movable sheaves over which .the cable runs, the consequent. movement of the car is many times greater than the movement of the piston and crosshead.

When the piston is nearing the bottom of its stroke and the car is nearing the top of the powder trunk, the skirt I24 enters the buifer chamber I22 of the cylinder, whereupon the escape of oil through port I26 tends to become choked oft, check valve I3! preventing discharge of oil from chamber I22 through port I28 into pipe I5. The effect of this choking of the discharge is to create a decelerating effect on the piston. At the same time, the amount of oil supplied to the piston through pipe I4 remains the same because the angle of the tilting plate of the pump I2 has not been changed. Therefore, as long as the tilting plate remains in the hoist position, an excess pressure immediately builds up in the pipe I4 and channel MI. When this pressure reaches an amount somewhat above that necessary to opcrate the piston on its downward stroke, the relief valve 13! will open and allow the excess oil to flow back into the expansion tank I8 through channel i38 and pipe 19.

Finally, at the downward end of the piston stroke and until the tilting plate is returned to the neutral or stop position, the flow of oil in the hydraulic system will be from the expansion tank, through pipe 2|, channel I34, past replenishing valve I32, into channel M2, thence through the pump into channel I4I, past relief valve I31, thence back to the expansion tank I8 through channel I38 and pipe I9.

When the tilting plate has been returned to the neutral position, and the powder car is at the unloading position at the top of the passageway, the weight of the car, acting through its supporting cable and the sheaves 24., will produce a pressure on the oil in the hydraulic cylinder. Due to this pressure, the oil will gradually leak out of the cylinder through the pump and the valves in the system. Thus the car will tend to drop very slowly, and, in order to prevent this, a stop mechanism (not shown) may be provided to maintain the car in its upper position.

At this point it will be noted that when the tilting plate and operating handles are in any other than the neutral position, the interlocking plate 46 will be turned one way or the other so that the raised portions of the segments IOI and I 62 will be adjacent to sliding stops 5'! and 68, thereby elfectually preventing vertical movement of the shaft I'll in either direction. Inasmuch as this shaft is connected by cable 63 with the latching mechanisms provided for doors 53 and 54, it will be seen that neither latch can be moved to permit either of the doors to open.

With the tilting plate in neutral position, the interlocking plate will again be in a position "to permit the sliding stops 61 and 68 to slide up and down, into and out of engagement with slots 69 and I I, as previously explained. Therefore, when the unloading door 54 is opened by moving it downwardly, the lower edge 54a of the door will engage in the inclined face 550. of the latch 55 (see Fig. 2). Further downward movement of the door will force the latch backwardly in the guideway 14. This movement of the latch will rotate the upper resetting lever 56 in a counterclockwise direction about the pivot 57. The arm 8| of lever 56 will also be moved downwardly in the direction of the stop or abutment 79 attached to the door. Inasmuch as the door is being moved downwardly, there will be sutficient clearance provided thereby for the movement of the arm 8|. The counter-clockwise rotation of lever 56 will also move the control wire 63 through the pivot connection 65, and this wire will also rotate lever 6| in a counter-clockwise direction about its pivot 62. Movement of this lever 6| will move the latch 66, through the medium of lever 58, in a forward direction, and under the lower edge of door 53, which will prevent it from being opened. At the same time, the arm 92 of lever 58 will be moved upwardly out of contact with the abutment 9d. The latching mechanisms will then be in the position diagrammatically shown in Fig. 10. The movement of the control wire 63 in addition will pull the shaft .IOI in an upward directionso as to engage sliding stop 68 with sl'ot II cut in the arcuate segment I02 on the interlocking plate. Thus, while the unloading door is open, it will not be possible to move the interlocking plate out of its central position, in which the tilting plate and both operating handles are maintained in the neutral position.

To close the unloading door .54, it is raised towards its uppermost position. As it nears the upper limit of movement the abutment 19 engages the arm ill of the lever 56, thus rotating it in a clockwise direct'on. As it does this, the lever also moves the atch 55 forwardly. Because of its inclined face 55a, the latch will clear the under edge of the door as it returns to the position shown in Fig. 2. The lever 56 also exerts a force on a control wire 63, which .will move the shaft Ill! downwardly, and the stop '68 out of engagement with slot -H. However, this downward movement will not be enough to bring the stop 61 into engagement with slot 69. Thus, with both of the doors again in closed positions, the interlocking plate is free to revolve, and the operating handles M and. 44 may be moved to operate the tilting plate.

When the tilting plate has been moved by one of the operating handles to the lower position,

the pump I2 will begin to force oil into channel I42 and pipe I to the lower end of cylinder I6. At first the oil will reach the lower face of the piston head by entering the buffer chamber I22 through check valve I3I and port I28. When the piston head has come up out of the bufier chamber, the oil will be admitted principally through port I26 to the lower face of the head. As the piston moves upwardly, oil in the upper part of the cylinder will be discharged through port I25, into pipe I4 and channel I4I, from which channel the pump will obtain oil for recirculation. Due to the presence of piston rod 20 in the cylinder below the piston head, less oil will be forced intothe cylinder than will be forced out at the upper end. Therefore, the excess oil must escape back into the expansion tank I8, through the relief 'valveI36, channel I38, and pipe I9. The compression of the spring operating on valve I36, while sufiicient to prevent fall of the car by gravity, must not be too strong to'prevent by-passing of the excess oil while the piston I1 is on the lowering stroke. Because the relief valves are maintained under a pressure which will prohibit escape of fluid, and consequent lowering of the car 32 by gravity alone, it will be necessary to exert some work on the under face of the piston head H1 in order to force it up, and the car 32 down. Under suitable operating conditions, the piston will be forced upwardly at such a rate of speed that a pull will be exerted on the bottom of the car 32 through the movable sheaves 24 and the rope or cable 36, which may exceed the accelerating effect of gravity.

When the piston nears the top of the cylinder, the skirt I23 will enter the buffer chamber I2I and begin to choke off the discharge of oil through the port I25, and the check valve I29 prevents discharge of oil through port I21. This causes deceleration of the movement of the piston. At this point, the pump will be supplying more oil than is required to move the piston at its decelerating speed. Consequently, oil will be by-passed by the relief valve I36 into channel I38 and pipe I9, into the expansion tank. Oil is not ordinarily removed from the expansion tank while the piston is actually moving on its upward stroke. But when the piston has reached its upper limit, no more oil can be pumped into or out of the cylinder, so that if the tilting plate of the pump is not returned to the neutral position, the oil pumped will merely go out through channel I42, through valve I36, into channel I38, pipe I9, and into the expansion tank, while oil will enter the intake of the pump from the expansion tank through pipe 2I, channel I34, replenishing valve I33 and channel MI. The car having been returned to the bottom of the powder'trunk, the cycle of operation may be repeated.

While the Waterbury gear is the .type of pump used in this case, any positive displacement type of pump could be used, provided it could be controlled in conjunction with suitable mechanisms so as to provide oil under pressure in either direction, or no oil at all, while being continuously driven at a substantially constant speed in one direction by some primary source of power. For best results, the operating mechanism (the tilting gear in the case of the Waterbury pump) should provide for delivery of oil in proportion to the displacement of the operating mechanism. Under these conditions, the speed of the powder car will be directly proportional to the movement of the operating handles. The system of relief and replenishing valves shown in the preferred embodiment makes it unnecessary to provide for a means, such as a cam, operated by the car, or otherwise, to cut oil the supply of oil at either end of the run. It is obvious that when the powder car has been stopped at any position in the powder trunk, it may thereafter be moved in either direction at any desired speed depending upon the pump discharge, and at rates of acceleration within the limits of the relief valves. Similarly, when the car is in motion, it may be brought to a stop and immediately reversed, within limitations of the relief valves and pump discharge, by moving the tilting plate to change the direction of the flow of oil through the system.

Other means can be substituted, as is well known in the art, for the cables, linking mechanisms, etc., and although the embodiment shown is the preferred form of the invention, it is not intended that the invention should be limited to the disclosure as shown.

The invention herein described 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.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. In an ammunition hoisting apparatus, a powder trunk loading door and a powder trunk unloading door, a latch for each of said doors and cooperating therewith, a pivoted lever cooperating with each of said latches, and connecting means between said levers whereby if one of said doors is in other than a closed position the latch of the other door prevents movement of the other door.

2. In an ammunition hoisting apparatus, a powder trunk loading door and a powder trunk unloading door, a latch for each of said doors and cooperating therewith, a pivoted lever cooperating with each of said latches, an abutment on each of said doors cooperating with the lever which operates the adjacent latch, and connecting means between said levers whereby the closing of one of said doors moves th latch for the other door to an inoperative position.

3. In an ammunition hoisting apparatus, a powder trunk loading door and a powder trunk unloading door, a latch for each of said doors and cooperating therewith, connecting means between said latches, a hoisting car, movement imparting means for said car, control means to operate said movement imparting means, an interlocking means operated by said control means, said connecting means and said interlocking means being operatively engageable with each other so that if one of said doorsis in other than a closed position, said control means will be inoperative.

4. In an ammunition hoisting apparatus, a

powder trunk loading door and a powder trunk unloading door, a latch for each of said doors and cooperating therewith, connecting means between said latches, a hoisting car, movement imparting means for said car, control means to operate said movement imparting means, an interlocking means operated by said control means,

said interlocking means and said connecting means being operatively engageable with each other so that if said control means is in other than a neutral position, said doors cannot be opened.

5. In an ammunition hoisting apparatus, a powder trunk loading door and a powder trunk unloading door, a latch for each of said doors cooperating therewith, pivoted levers cooperating with each of said latches, an abutment on each of said doors cooperating with the lever which operates the adjacent latch, a connecting means between said levers whereby movement of one lever operates the other lever, a hoisting car, movement imparting means for said car, control means to operate said movement imparting means, an interlocking plate operated by said control means, and stops operated by said connecting means which engage with said interlocking plate, whereby said control means is operable only when both of said doors are closed.

6. In an ammunition hoisting apparatus, a powder trunk loading door and a powder trunk unloading door, a latch for each of said doors and cooperating therewith, pivoted levers cooperating with each of said latches, a connecting means between said levers whereby movement of one lever operates the other lever, a hoisting car, movment imparting means for said car, control means to operate said movement imparting means, an interlocking plate operated by said control means, and stops operated by said connecting means which engage with said interlocking plate, so that when said control means is in other than a neutral position, neither of said doors may be opened.

7. In an ammunition hoisting apparatus having a hydraulic cylinder and a piston therein which operates a hoisting car, and having powder trunk loading and unloading doors for,providing access to said car, the combination of cooperating latches for said doors adapted to secure against movement of either of said doors if the other one is in other than a closed position, control means for said pump, an interlocking means operated by said control means, and stops operated by said cooperating door latches and constructed and arranged operatively to engage said interlocking mean so that neither of said doors can be opened unless said control means is in a neutral position.

8. In an ammunition hoisting apparatus having a hoisting car operated by a hydraulic cylinder, a pump for supplying fluid under pressure to said cylinder, control means for said pump, and powder trunk loading and unloading doors for providing access to said car, the combination of an abutment on each of said doors, a movable means for each door operated by said abutment, connecting means for said movable means whereby both movable means are actuated together, stops associated with said connecting means, an interlocking means operated by said control means, said interlocking means being constructed and arranged to engage said stops so that said hoisting car can be operated by said pump only when both of said doors are closed.

9. In an ammunition hoisting apparatus having a hoisting car operable by a piston, hydraulic means for operating said piston, and a powder trunk door for providing access to the car, a control system for said apparatus comprising a control element for said hydraulic means having a neutral position, a latch for retaining said door in closed position, and interlocking means cooperating with said latch for securing said control element against movement from its neutral position while said door is open.

10. In an ammunition hoisting apparatus having a hoisting car operable by a piston, hydraulic means for operating said piston, and a powder trunk door for providing access to the car, a control system for said apparatus comprising a control element for said hydraulic means having a neutral position, a latch for retaining said door in closed position, and interlocking means for retaining said latch in its operative position when said control element is in other than its neutral position.

11. In an ammunition hoisting apparatus having a hoisting car operable by a piston, hydraulic means for operating said piston, and a powder trunk door for providing access to said car, a control system for said apparatus comprising a control element for said hydraulic means having a neutral position, a latch for retaining said door in its closed position, and interlocking means for retaining said latch in its operative position when said control element is in other than its neutral position and for securing said control element against movement from its neutral position when said door is open.

ARTHUR J. STANTON, ERNEST F. CAMPBELL.

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