US879387A

US879387A - Ammunition-hoist control.

Info

Publication number: US879387A
Application number: US39084507A
Authority: US
Inventors: John D Ihlder
Original assignee: Otis Elevator Co
Current assignee: Otis Elevator Co
Priority date: 1907-08-30
Filing date: 1907-08-30
Publication date: 1908-02-18
Anticipated expiration: 1925-02-18

Description

J. D. IHLDER. AMMUNITION HOIST CONTROL.

APPLIOAfION FILED AUG. 30. 1907.

PATENTED FEB. 18, 1908.

2 SHEETSSHEET 1.

2 SHEETS-SHEET 2.

v PATENTED FEB. 18, 1908.

J. D. IHLDER.

APPLIUATION FILED AUG. 30. 1907.

AMMUNITION HOIST CONTROL.

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UNITE snares JOHN D. 1HLDER,

PATENT oErroEi. p

or Ew YORK, N. Y1, :ASSIGNOR TO orIs ELEVATOR COMPANY, OF- JERSEY CITY, NEW JERSEY, A CORPORATION or NEW JERSEY.

unrrron-nolsr coN'rRoL.

Specification of Letters Patent.

Application filed August 30.1907. serial No. 390.845.

hoist and means for controlling the starting and stopping thereof.

@ne of the objects ofthe invention is the provision of means for stopping the hoist at different positions corresponding to the different elevations of the gun.

Another object of the invention is to provide means to vary the position of the upper limit stop against which the hoist is held, to correspond with the gun elevation.

Other objects are to provide simple and effective means for automatically effecting the changes in the positions of the hoist at which the motor controller or stop motion switch operate, and automatic means for varying the position of the upper limit stop to correspond with the elevation of the gun when such limit stop is used.

Other objects of the inventionwill appear hereinafter, the novel combinations of elements being set forth in the claims.

' Referring to the accompanying drawings in which is illustrated more or less diagrammatically a-construction embodying my invention, Figure 1 is an elevationof the ammunition hoist and appurtenances; Fig. 2 is a sectional elevation of the automatic stop motion switch; and Fig. 3 is a diagrammatic view of the motor and the controlling system therefor.

In practice it is comm-on. to have the am munition in a compartment located some distance below the gun, and to elevate the ammunition by means of some form of hoist. In the present invention I have shown a hoist which isoperated by an electric motor and automatically brou ht to rest at a point site the breach of the gun. As this point varies with the diflerent'elevations of the un, it is desirable that the position in Whic the hoist is brought to rest should be varied automatically as the position of the gun is changed. The present invention com rises means for accomplishing this resu t by automatically varying the position of the hoist at which the motor control" operates, whether such operation consists in cutting ofi thecurrent from the motor and applying the brake, or iii some other method of controlling the motor. It is the general practice now, however, to stop the hoist, not by applying the motor brake, but by running the hoist up against an up er limit sto under reduced current and holding it in such position by means of the reduced current. In such case it is desirable to automatically Patented Feb. 18, 1908.

vary the position of the upper limit stop as p the elevation of the gun is varied, and also to correspondingly vary the time at which the motor controller is operated to reduce the current. The present invention comprehends means for accomplishing these results.

The hoisting mechanism comprises a loadcarrying device or carrier C which is raised and lowered in the well or shaft B by means of a motor M. Any suitable form of driving connections between the carrier and the motor may be employed, and in the construction here shown the motor shaft 1 is geared to a hoisting drum D which is connected to the carrier C by a rope or cable E. The cable E passes over direction sheaves 2 on the. overhead beam 3. A counterbalance Weight W is connected to thecarrier C by a rope or cable 4 passing over the sheaves 5. A compartment 6 from which ammunition may be supplied to carrier 0 is located near the bottom of the shaft B and communicates therewith through a door or o ening 7 The ammunition may be conveye from the compartment 6 .to the carrier C- by means of a small car or truck 8 Which is adapted to travel on rails 9 and 10 on the floors of the compartment 6 and carrier C, respectively, these rails being in alinement when the carrier is at its lower limit of travel. The carrier when in this position "rests on the stops 11 and a coil sprin buffer 12, or the ammunition may be trans erred manually to a holder fixed to the carrier C in the usual way.

The gun carriage 13 is sup orted by a latform 14 near the upper end of the sha t B, and the-gun 15 is mounted on its carriage 13 in the usual way by means of horizontal trunnions which permit the inclination or ele-' I which operates to bring the carrier C to rest with the shell or cartridge 17 opposite the breach of the gun. This limit stop comprises a horizontal bar or bars 18 carried by a vertical supporting member 19, and having a pin and slot connection 20 therewith which permits a vertical movement of the bar 18 These arms each carry a pawl 22 pivoted to its outer end and also resting on the bar 18. Fastened to the under side of the bar 18 are sockets 23 in which are secured depending coil spring buffers 24in the path of move ment of the stops 25 on the carrier C. Secured to the inner walls of the shaft B are stationary ratchet bars 26 formed with ratchet teeth 27 which coliperate with the pawls 22. The limit stop or cable 28 connected at one end to the member 19, passing over a direction sheave 29,

and connected at its opposite end to a sheave secured to one of the trunnions of the gun. The sheave 29 is journaled in a bracket secured to the beam 3 in such position that the limit stop will be held 'midwa'y between the ratchet bars.

The operation of the limit stop L is as follows: As the carrier C approaches the upper limit, the current in the motor is weakened and the speed reduced in a manner explained later. The stops 25 on the carrier C now engage the spring buffers 21 and raise the bar 18, swingin the arms 21 downwardly toward a horizonta direction and moving the pawls 22 into engagement with the ratchet teeth 27. The pawls 22 now form fixed stops to limit the upward movement of the bar 18. The buffer springs 24 are compressed by anv further upward movementof the carrier, and bring it graduallyand smoothly to rest with the shell 17 in position for loading the gun. When the elevation of the gun is changedthc position of thelimit stop 1s correspondingly changed. if, for example, the elevation of the 11 1s increased, the breach of the gun will e lowered, but the sheave 30 carried by the gun will at the same time be rotated in 'a direction to len then the cable 28, and the hmit st o L'wi move downwardly by its own weig t to a lower position, and so 0 we ate to stop the car at a lower lane wit 1 a shell 17 again opposite the breac 1 of the gun. Obviously the size of the sheave 30 may be ad usted to vary the range of movement of the limit stop for any given movement of the gun, so that the roper relative movement of'the arts may be obtained. Also, a system of evers or other means for obtaining a movement of the limit stop in unison with that of the gun could be employed if desired.

The system of control for the motor which is shown diagrammatically in Fig. 3 forms the subject matter of my 'copending application,

is suspended by a rope- Serial No. 271,777, filed July- 29, 1905, in which is a full disclosure of the system and its operation. 1

32 connects the apparatus to the source of current supply designated by the characters and A manually operable switch 33 is adapted to be placed in any convenient position, and as shown Fig. 1 is located near, the gun 15. The motor M has its armature' connected in series with the main lines 34 and 35 through the brushes 36 and; 37. The field 38 of the motor is connected in shunt to the constant potential mains by means of the wire 39. The armature circuit is normally open at the contacts 10, but may be closed by means of the magnet 11 through the starting resistances $2. 43, 44. 46, -17. The accelerating magnet 18 is arranged to operate the contacts 49. 50, 51, 5:2 to successively short-circuit the.

resistances

43, 44, 45, 46. The slow speed magnet 53 operates the contacts 54 to control the resistance -12, while the fast speed magnet 55 with the contacts 56 contro the resistance 47.

A load magnet 58 operates the contacts 59, 60 and 61 toshort-circuit the

load resistances

62, 63, 64. The contacts 59, 60. 61 are connected by wire with the resistances -12 and 43, and the

resistances

62, 63 and 64 are connected to the contact 66 of the manual switch 33 by wire 67, and by wire 68 to the lower one of the contacts 40.

An automatic stop motion switch or con-- troller 69 comprises a number of circularlyshaped contact strips such as 74, 75, 76, 77, 78, with insulating sections 79, 80, S1, S2, S3, 84, 85. The circular strips or conductors may be arranged concentrically as shown in Fig. 3 and mounted on a ilate or disk of insulating material, the whole being connected for rotation in conjunction with other moving parts of the hoisting mechanism. But I refer to mount these conductors on the peripheral surface of a drum 86 as shown in Fig. 2, the. operation in this case being the same, the arrangement shown in Fig. 3 being chosen to simplify the illustration and enable the operation to c more readily understood.

The, automatic controller 69 as shown in Fig. 2 embodies the drum 86, having its sur face covered with insulating "material 87 on which are mounted'the contact strips 74, 75, 76, 77, 78, these strips being arranged spirally, as indicated. The controller is mounted in a bracket or frame 89 which is secured to the frame of the motor. This bracketcarries a worm shaft 88 on which the drum 86 is mounted for rotation. The drum is rotated by means of a cross-head 90 secured to a sl1aft-91 which is journaled in the bracket 89. Keyed t0 the shaft. 91 is a sprocket wheel 92 wlnch is driven by a sprocket chain 93 from a sprocket wheel 9-4 secured to the shaft of the hoisting drum D. An extension of the Referring to Fig. 3, the main line switch shaft 88 is; fixed to the left-hand arm of the] magnet 41 maybe traced from the positive main through the wire 34, magnet coil 41,

bracket 89 and the shaft 88 itself. extends loosely into the cross-head 90. The drum 86 is connected for adjustment in unison with the adjustment of the gun by means of a.

. sprocket chain 96. uniting the

sprocket Wheels

95 and 97, the latter being secured to one of the trunnions of the gun. Mounted loosely on the extension of the shaft 88 is a disk 98 which carries an arm 99 provided with

insulated brushes

100, 101 102 and 103 bearing against the contact-

strips

74, 75, 76 and 77 respectively. A similar arm 104 is secured to a disk 105 and is provided with a brush 150 engaging the strip 74. Other arms are also fixed to the disk 105 to carry the

brushes

125, 126, 127, 128, 129 and brushes 153-and 154 shown in Fig. 3 diagrammatically. Also mounted loosely on the extension of the shaft 88 is a sprocket wheel 95 which is geared by 'means of the chain 96 to the sprocket wheel 97 moving with the gun.

An electro-magnetic brake K of any approved form is used in connection with the motor. As here shown a brake pulley 107 iskeyed to the motor shaft, and the brake arms 108 are normally held a'gainst the brake pulley by a coil spring 109. The brake arms 108 are released by means of an electromagnet 110 Whose armature is connected to the toggle-links 111. p

The function and operation of the various parts of the motor-controlling devices shown in Fig. 3 will now be described.

Assuming the main switch 32 to be closed, as'shown, let the lever 112 of the manual switch 33 be moved to the left to cause the carrier C to. move upwardly. The contact strip 113 is connected to the negative main and is always in contact with the segment i 114 of the switch. The segment 1 14 is rigidly connected to the lever 112 which is pivoted at 115 to the insulating base and provided with a handle 116. In addition to the contact strip 113 on the base are-fixed contacts I 117, 118, 119,120 at the right and the contacts 66, 121 and 122 at the left.

The contacts 117, -118'are connected by means of the Wires 123, 124 to the contact brushes 100, 101, which engage the pircular conductors 74 and 75, respectii'rely. The

brushes

100, 101 are respectively ine ect connection with the brushes 125, 126, which in turn are connected by the wires 130, 131 to the brake magnet 110 and the main line magnet 41. Therefore when the lever 112 is moved toward the left to elevate the carrier C as indicated, the segment 114 will first electrically connect the contacts 1 17 and 1 18, whereupon the magnet 41 and brake magnet will be operated, the one to close the motor armature circuit through the contacts 40 and resistances 42, 43, etc. and the other to release the brake against the action ofthe spring 109. The circuit for the main line rical from the wire 34, through the wire 134, .magnet coil 110, brush 125, strip 74, brush 100, Wire 123,.,contaot 117 and segment 114. The circuit through the motor armature is from the wire 34 to and through the contacts 40, wire 135, starting

resistances

42, 43, 44, 45,46, 47, wire 136, motor armature brush 36, motor armature, brush 37, wire 35, to the negative main; The shunt field circuit is also completed when the main line switch 32 is closed, so that now the motor can start and attain a predetermined slow speed.

On .moving the handle 116 of a switch 33 farther toward the left the contact 119 is engaged by the segment 114. This completes a circuit from the positive main through Wire 34, to and throu h the contacts 40, wire 135,

coil of slow spee magnet 53, wire 138, brush 127, strip 76, brush 102, wire 139, contact 119, segment 114, contact 113 and ire 133 to the negative main. The magnet 53 is therefore connected across the constant potential mains, as is magnet 41, and operates to close the contacts 54 and short-circuit the resistance 42 The motor will thereupon re ceive more current and run at full slow speed.

The nextoperation is-the moving of the handle 116' to its extreme left-hand so that the segment 114 will engage t e fixed contact 120 in addition to the contacts 117, 118, 119. A circuit will now be completed from the positive main to and through the wire 34, contacts 40, wire 135, contacts 54,

osition;

wire 55,

resistances

43, 44, 45, 46, 47, wire 140, coil of accelerating magnet 48, wire 141, brush 128, strip -77, segment 114, stri 113, wire 133 to the negative main. Thus t h celerating magnet 48 is connected directly across the motor armature and will operate automatically to cut out or short-circuit the startin resistances 43 44, 45, 46 successively in a we 1 known manner, depending upon the load on the motor. The contacts 49, 50, 51

and 52 are closed successively, but when the last is'rlosed the wire 137 is connected through contact 144 to and through the fast speed magnet'55 to the wire 141. energization of this magnet 55 the contacts 56 are connected and the resistance 47 shortcircuited. 'The current can now flow direct-1y from wire 137 through wire 136 to the motor armature. The motor armature is therefore connected directly across the mains and will run up to fast speed.

The stop motion switch 69 being positlvely connected to rotate in harmony with the motor, will'move in a clockwise direction as.

soon as the carrier C starts upwardly. As

Upon the the carrier approaches its upper limit of travel, the first operation of the switch 69 will be to break the circuits of the fast speed magnet 55 and the accelerating magnet 48. This is caused by the insulating section 84 running under tlie brush 103. This will opcrate to place the

resistances

43, 44, 45, 46, 47 in'the motor armature circuit and therefore slow down the motor. Very shortly after this operation, the insulating section 83 runs under the brush 102 to break the circuit including the magnet 53. The contacts 54 therefore become separated and the resistance 42 reinserted to still further reduce the speed of the motor.

All the starting resistances having been replaced in the armature circuit, the motor will run at a very slow speed. carrier C has almost reached its upper limit of travel and operates the upper limit stop L in ,the manner before explained. The carrier is held at its extreme upper limit of travel by the actionof the motor, and when in such position the stopmotion switch 29 is at restwith the

brushes

102, 103 on the insulation sections 83, 84, respectively, and the

brushes

100, 101 in contact with the'strips 74, 75, respectively. The brake magnet 110 and the main line magnet 41 are therefore kept energized, but since the current must traverse the starting resistances it will be insuilicient to injure the armature by heating but will produce sufiicient torque to hold the carrier at its upper limit of travel. If desired, however, the automatic stop motion switch may be adjusted to rotate a little farther so that the insulating sections 81 and 82 will run under the

brushes

100 and 101, respectively, to automatically deenergize the brake magnet 110 and the main line magnet 41. The current will then be entirely out ofl' from the motor armature and the brake applied to hold it against rotation, in which case the upper limit stop L may be dispensed with.

\Yhen it is desired to lower the carrier C the switch handle 116 is brought back to its central position as shown in .the drawing. This will cause the brake to be applied as the circuit to the magnet 110 is broken at the contact 117. Furthermore, the circuit of magnet 41 is broken at the contact 118 and therefore the contacts 40 are separated. The current to the motor is thus cut off, but the car is kept from descending by means of the brake which is now applied, since the magnetv 110 is deenergized. I

I will now describe my automatic means for slowing down the movement of the carrier and stopping it at its lower limit of travel. ()n moving the handle 116 to the right the contact segment 114 will engage the fixed contacts 66, .121, 122. Then the segment 114 is brought into connection with the contact 66, a local circuit including the motor By'this time the armature, the starting resistances and the

additional resistances

62, 63, 64 is closed. This local circuit will be established before the segment 114 engages the contacts 121 and 122. When the segment 114 engages contact 122 the brake magnet 110 is energized and the brake released. The circuit,

to the brushes 154 and 153 which are in contact with the strips 156 and 155 insulated by the insulation sections 80, ,83 and 79, 85, res ectively..

he brake having been released, the carrier can descend by reason of its own weight, and in so doing drives the motor armature backwards. Since the field is connected across the main lines by wire'39, it will be fully excited, and the armature being driven by the carrier will generate a current through the various resistances forming a closed circuit with it. This arrangement constitutes an electro-dynamic brake and prevents excessive speed of the carrier as it descends.

As thecar descends the automatic stop motion switch 69 will beslowlly turned in an anti-clockwise direction through nearlj; 180. As the carrier approaches its lower limit of travel the slow down operation is automatically controlled by means of said s'to. motion switch. The first change will ta e place when the insulation section ,83 runs under and past the brush 154 so that the brushes 154 and 127 are electrically connected by the strip 76. The slow speed magnet 53 will then be connected in shunt to the

load resistances

62, 63, 64, the circuit being as follows: from wires 68 and 135 toand through magnet 53, wire 138, brush 127, strip 76,

brush 154, brush 153, wire 160, contact 121, segment 114*, contact 66, and wire 67 to the other side of the

load resistances

62, 63, 64.

The energization of the magnet 53 depends on the potential across the load ma et

resistances

62, 63, 64. This potentia varies directly as the s eed of the motor armature and consequent y of thecarrier C. If the speed rises above a predetermined point the magnet 53 will operate to short-clrcuit the resistance 42 by the closure of the contacts 54. The resistance in the armature circuit being thus decreased, more current can flow strip 78. This occurs when the carrier is a short distance from'its lower limit of travel. v

The load magnet 58 is now connected difrom the spirit or scope of my invention. I

rectly across the motor armature from the brush 36 and wires 136, 140 and 161 to the coil of magnet 58, through wire 162, brush 129, strip 78, brush 153, wire 160, contact 121, segment 114, strip 113,

wires

133 and 35 to the other motor armature brush 37; The load magnet 58 will be energized to a degree depending upon the speed of the motor, to close one or more of the contacts 59, 60, 61 which will operate to cut out one or more of the

load resistances

62, 63, 64.

The next operation is the application of the brake to stop the carrier. This occurs whenthe insulation section 81 runs under the brush 150 to interrupt the circuit of the brake magnet, and therefore allowing the brake to be applied. It should be noted that the brake magnet can again be energized as another brush 100 is still in electrical connection with the brake magnet so that the latter may be energized by moving the hand'le 116 to theleft to bring the segment 114 and contact 117 into engagement.

The

brushes

100, 101, 102, 103 which control the circuits afi'ected in the operation of the stop motion switch 69 as the carrier moves upwardly, are carried by the arm 99 (Fig. 2) secured to the disk 98. As the disk 98 is connected for rotation about its axis in unison with any adjustment of the gun to different elevations, the positions of the brushes will be correspondingly changed, resulting in a change in the time at Which the stop motion switch operates in the upward movement of the carrier. For example, if the gun is inclined to a higher elevation the disk 98, as viewed in Fig. 1, will be rotated backwardly or in a counter-clockwise direction. This will shift the position of the brushes on the drum 86, being equivalent to a forward movement of the drum. The distance through which the drum rotates before it operates to stop the motor will therefore be reduced and the carrier brought to rest in alower position corresponding to the low ered position of the breech of the gun.

As the position in which the carrier stops at its lower limit of travel is always the same,

the brushes 150, 153, etc., are mounted onthe stationary disk 105, only the brush 150 being shown in Fig. 2 for the sake of clearness.

Although the upper limit stop and the stop motion switch are both adjusted entirely automatically in unison with adjustment of the gun, either or both of them may be adjusted manually if desired. Also, either one is adapted to be used alone as varying conditions may require. It is obvious also that various forms of connections between the gun and the part adjusted thereby might be adopted, and that various other changes in details of construction and arrangement of parts might bemade without departing Wish, therefore, not to be limited to the precise construction disclosed.

What I claim as new and desire .to secure by Letters Patent of the United States is 1. In an ammunition hoist, the combination with a carrier, a motor and driving connections therebetween, of a gun, and means for stopping the carrier automatically at different positions varying with the gun elevation.

2. In an ammunition hoist, the combination with a carrier, and driving mechanism therefor, of a gun, and means for stopping the carrier automatically at difierent positions varying in proportion to variations in the gun elevation.

In an ammunition hoist, the combination with a carrier, and means forv raising and lowering the carrier, of a gun, and means for stopping the. carrier automatically at different elevations corresponding to difierent gun elevations.

4. In an ammunition hoist, the combination with a carrier, means for, elevating the carrier, and means for stopping the carrier in an elevated position, of a gun adjustable to different elevations, and connections be tween the gun and said stopping means operable to change the position in which the carrier is stopped to correspond with changes in the gun elevation.

5. In an ammunition hoist, the combination with a carrier, means for elevating the carrier, and an upper limit stop, of a gun adjustable to dilferent elevations, and means for adjusting the limit stop to positions corresponding with the gun elevation.

6. In an ammunition hoist, the combination with a carrier, means for elevating-the carrier, and an upper limit stop,'of a gun adjustable to different elevations, and connections between the gun and limit stop for automatically varying the position of the limit stop when the gun is adjusted.-

7,. In an ammunition hoist, the combination with a carrier, and means for elevating the carrier, of .a gun located near the path of travel of the carrier and adjustable to different elevations, an upper'limit stop for the carrier, and automatic means to adjust the position of the limit stop when the gun is adjusted.

8. In an ammunition hoist, the combination of a gun adjustable to iliflerent elevav moving the stop up or down, and means for nections between the carrier and motor, of a gun, means for stopping the carrier opposite the gun, andconnections between said means and the gun for varying the position at which the carrier stops as the gun elevation is varied.

10. In a hoisting device, the combination with a carrier and means for elevating the carrier, of an upper limit stop, means for looking to stop against such movement when it is engaged by the carrier,

11. In a hoisting devicefthe combination with a carrier, means for raising and lowering the carrier, an upper limit stop movable to different heights, a stationary ratchet bar, and a pawl carried by the limit stop and movable into engagement-with the ratchet bar when the carrier engages the limit stop.

12. In an ammunition hoist, the combina- 5 tion with a carrier and means for raising and lowering the carrier, of an upper limit stop, a gun adjustable to different elevations, connections between the gun and limit stop for moving the limit stop when the gun is adjusted, arid means for locking the limit stop against movement when it is engaged by the carrier.

13. In an ammunition hoist, the combination with a carrier, 3. motor, and driving connections between the carrier and motor, of a gun adjustable to different elevations, and means for stopping the carrier at different elevations governed by the position of the D 14. In an ammunition hoist, the combination with a carrier. a motor, and driving con, nections between the carrier and motor, of a ad'ustable to diflerent elevations, and means or automatically stop ing the motor with the carrier in a position epending upon the gunelevation. g, 15. In an ammunition hoist, the combination with a carrier, a motor, and driving connections between the carrier and motor, of a gun adjustable to different elevations, means or sto ping the motor when the carrier has reache a predetermined position, and means for automatically varying such position as the gun is adjusted.

16. In an ammunition hoist, the combina- 1 tion with a carrier, a motor, and driving connections between the carrierand motor, of a adjustable to different elevations, means orstopping the motor with the carrier in different positions depending upon the adjustment of said means, and connections between the gun and said stopping means for automaticallyadjusting said means as the gun is adjusted.

17 In an ammunition hoist, the combination with a carrier, an electric motor, and driving connections between the carrier and motor, of a gun adjustable to different eleval l; l l

.for automatically fnember as the gun is adjusted.

mined position, and means for automatically varying such position as the gun is adjusted.

18. In an ammunition hoist, the combination with a carrier, an electric motor, and driving connections between the carrier and motor, of a gun adjustable to different elevations, an adjustable stop motion switch operable to stop the carrier at predetermined positions dependingon the adjustment of the stop motion switch, and connections between the gun and switch for automatically ad'usting the switchwhen the gun is adjuste 19. In an ammunition hoist, the combination with a carrier, an electric motor, and driving connections between the motor and carrier, of a gunadjustable to different elevations, a brake for the motor, a stop motion switch automatically operable to cut off the current and apply the brake when the carrier reaches a position opposite the gun, and

means to automatically vary the operation of the stop motion when the gun is adjusted to corres 0nd with such adjustment.

20. an ammunition hoist, the combinationjwith a carrier, an electric motor and driving [connections therebetween, of a gun adjustable to different elevations, a stop motion switch comprising a rotatable member and a stationary member, electrical connectionsbetween said members and amotor controllingthe current supply to the motor, driving connections between the motor and said rotatable member, and connections between said stationary member and a gun adjusting said stationary 21. In an elevating device, the combination with aload'carrying member, a motor, and driving connections betweefi said arts, of a limit sto adjustable to different heights, means for re( ucing the s eed of the motor as the load carrying mem er approaches the limit stop, and means to vary the time at which the motor speed is reduced to correspond to the position of the limit stop.

22. In an elevating mechanism, the combinationwith a load carrying device, an elec tric motor and driving connections between the motor and said device, of a limit stop adjustable to different heights, means for auto matically reducing the current supply to the 'motor as the load carrying device approaches the limit stop, and means for automatically varying the time at which the current is reduced to correspond with the position of the limit stop. I

23. In an ammunition hoist, the combination with a carrier, an electric motor, and driving connections between the carrier and motor, of a gun adjustable to different elevations, an upper limit stop for the carrier, connections between the gum and limit stop for varying the position of the stop when the gun In testimony whereof I have signed my is adjusted, means for reducing the supply of name to this specification in the presence of current to the motor as the carrier approaches two subscribing witnesses.

the limit stop, and means to automatically JOHN D. IHLDER. vary the time at which the current supply is Witnesses:

reduced to correspond with the position of ,T. W, ALGAN GoLDY, the limit stop. W. H. BRADY.