US2616576A

US2616576A - Latch operating mechanism

Info

Publication number: US2616576A
Application number: US539497A
Authority: US
Inventors: Hugh W Sanford; Harry W Jones
Original assignee: Sanford Investment Co
Current assignee: Sanford Investment Co
Priority date: 1944-06-09
Filing date: 1944-06-09
Publication date: 1952-11-04
Anticipated expiration: 1969-11-04

Description

Nov. 4, 1952 Filed June 9, 1944 H. W. SANFORD ETAL LATCH OPERATING MECHANISM 5 Sheets-Sheet l Nov. 4, 1952 H. w. SANFORD ETAL LATCH OPERATING MECHANISM 5 Sheets-Sheet 3 Filed June 9, 1944 Nov. 4, 1952 H. w. SANFORD ETAL LATCH OPERATING MECHANISM 5 Sheets-Sheet 4 llllllllllllllll Filed June 9, 1944 Nov. 4, 1952 H. w. SANFORD ET AL LATCH OPERATING MECHANISM 5 Sheets-Sheet 5 Filed June 9, 1944 Patented Nov. 4, 1952 LATCH OPERATING MECHANISM Hugh W. Sanford and Harry W. Jones, Knoxville, Tenn., assignors to The Sanford Investment Company, Wilmington, DeL, a corporation of Delaware Application June 9, 1944, Serial No. 539,497

20 Claims. 1

This invention relates to improvements in latch operating mechanisms, particularly for releasing the latches of drop bottom mine cars or other conveyors. It is related to and in part an improvement on the prior applications of Hugh W. Sanford for Door Latch Mechanisms, Serial No. 132,341, filed February 25, 1942, and now Patent No. 2,399,708, granted May 7, 1946, and for Latch Tripping Mechanism, Serial No. 473,913, and now Patent No. 2,441,978, granted May 25, 1948, filed January 20, 1943.

In these prior applications, the latch tripping mechanisms were located at a point or points between the rails of the car or conveyor in position to engage an actuating portion of the latch means for discharging the lading from the car. In some instances these latch tripping mechanisms were actuated electrically by a circuit closing means that functions in response to a predetermined movement of the car to a particular position relative to the point of dumping. Generally the circuit closing means was actuated by means attached to the body of the conveyor car, which actuating means was located in predetermined position relative to the latch means so as to release the latch means when the car reached the desired position for dumping.

Due to wear between the wheel treads and the track in service, the actuating means on the car or conveyor may be lowered relative to the switch means located adjacent the track so as to change the relative positions of these contacting members. This would influence and vary the actuation of the switch means to an extent that might make uncertain the release of the latch means eilectively and at the proper time.

Moreover, where a single actuating switch is used, mounted adjacent the track, for releasing or actuating the latch means, there would be the danger that the switch means may be actuated by a mine locomotive or some other part of the conveying mechanism when it is not desired to trip the latches, which might result in damage to the tripping mechanism or the conveying equipment.

The object of this invention is to improve the construction of the latch tripping mechanism to insure release of the latch means only when desired and in response to the location of the car or conveyor itself in particular relation for dumping and without this release mechanism being afiected by variations of the conveying mechanism which are the result of wear thereto in service.

In accomplishing'this object, the invention involves preferably the actuation of the latch release means by the wheel or wheels of the car or conveyor reaching a predetermined position on the trackway so as to insure the actuation of the latch tripping mechanism at the proper time and place for dumping the lading and without regard to variations in height of the lading body that may result from wear of the wheel treads or track. It is possible to actuate the latch tripping mechanism by separate wheels of the car or conveyor, as for instance one front wheel and one rear wheel thereof, either on the same side or on different sides, and so coordinated that the latch tripping mechanism will be actuated only by the particular conveyor for which the tripping mechanism is adapted but not by a car or vehicle of a different wheel base, as for instance a mine locomotive, which might result in destruction of or injury to the tripping mechanism.

A further object of this invention is to improve the construction of the latch tripping mechanism to enable it to function in response to an electrical contact, for operation of said tripping mechanism electrically, as by means of a circuit closer actuated by a car wheel.

Still another object of the invention is to provide a circuit closing mechanism capable of being mounted at the trackway for actuation by a car wheel moving thereover, which is capable of being adjusted to any desired position along the trackway and to be secured in proper relation to the trackway, andwhich circuit closing mechanism will function eifectively regardless of variations between the Wheel tread and the trackway due to wear therebetween; is capable of being readily cleaned out to remove cinders and other foreign substances therefrom that might otherwise clog the mechanism; and may be constructed to pro vide electrical contact for the desired length of time sufficient to actuate the tripping mechanism and at the proper point desired.

A preferred embodiment of the invention is set forth in the accompanying drawings in which:

Fig. l is a side elevation of a mine car and track. showing the latch tripping mechanism and switches applied thereto;

Fig. 2 is a diagrammatic view of the wiring diagram of the tripping mechanism;

Fig. 3 is an elevation of a limit switch used in the latch tripping mechanism;

Fig. 4 is a side elevation of the switch assembly Fig. 5 is an end elevation thereof, showing the track in section;

Fig. 6 is a detail top plan view of the retaining bolt and portion of the contact plate;

Fig. 7 is a side elevation of a portion of a mine car and trackway, showing the latch tripping mechanism associated therewith;

Fig. 8 is a longitudinal sectional view therethrough;

Fig. 9 is a top plan view of the track and a portion of the latch tripping mechanism; and

Fig. 10 is a cross-section thereof on the line I-IB of Fig. 9.

The invention is shown as applied to a drop bottom mine car adapted for the conveying of coal or other loose lading from a receiving point to a pit or other point of discharge. The mine car is shown generally of the type set forth, for instance, in prior patent, No. 2,001,471, granted May 14, 1935, to Hugh W. Sanford, representing a four-wheel mine car having three drop bottom doors, adapted to travel on a track formed by a pair of rails designated generally R.

The general structure of the car comprises side and end structures I and 2, respectively, the side wall structures I rising from a pair of oppositely disposed side sills 3 connected together at the ends of the car by means of combined end-sills and bumpers designated generally Q. The side and end-sills 3 and 4 constitute the frame structure of the car for supporting the lading body of the car. The flaring side walls I rise upward at acute angles to the horizontal from the upper edges of the side sills 3.

The car is supported on front and rear wheels 5 and 5' and axles 6 connected with the side sills 3 by axle boxes I (Fig. 8). The flaring sides I of the body are cut away to receive the wheels, which are deeply inserted therein beneath wheel hood coverings 8. Opposite hood coverings 3 are connected together by means of a combined tie plate and shroud 9 which extends over the adjacent axle 6.

The car is shown as of the character provided with three drop bottom doors adapted for discharge in l-2-3 order from front to rear of the car, which doors are designated respectively III, I I and I2. Although any desired door structure may be used, the forward door I!) is shown as pivotally supported on a hinge rod I3, while each of the middle and rear doors II and I2 is slidably and pivotally mounted on a hinge rod I4, extending between opposed boxes II, with the extreme forward edge of said door projecting laterally from the hinge rod and arranged to support the free edge of the next forward door.

Thus upon release of the rear door it may drop sufiiciently to drag and move bodily rearward, thereby releasing the free edge of the middle door which will likewise move downward and rearward releasing the free edge of the forward door. This occurs usually just before the car reaches the bin and permits dropping of the forward door for discharge of the lading as soon as room enough is provided in the bin therebeneath, the other doors dropping in succession during forward movement of the car over the bin, in 1-2-3 order from front to rear of the car.

After dumping in passing over the bin, the doors are adapted to be closed by the usual doorolosing rails located in the track, as set forth more fully in prior United States Patent No. 2,001,471, granted May 14, 1935, to Hugh W. Sanford.

As shown in Figs. 1, 7 and 8, provision is made for latching the free edge of the rearward door I2 for thereby holding the doors I8, II and I2 in their closed positions, retaining the lading in the car until the latching means is released for dumping. For this purpose latches I8 are provided adjacent the rear end of the car, preferably spaced transversely on opposite sides of the center of the car, and pivotally supported by a supporting shaft is, extending transversely thereof on which said latches are fixed for swinging movement.

Each of the latches has a concave seat 28 formed therein in position to engage the latch hook I? attached to the free edge of the rearward door I2 to support said rearward door in closed position.

The shaft I9 is mounted on the end structure of the car, and is so disposed relative to the adjacent end-sill 4 as to locate the latches I8 forwardly of the rear end-sill. The latches I3 are of a size such that their lower end portions do not project below the lower edge of the adjacent end-sill and are disposed within the space between the rear door I2 and the rear end-sill 4 in protected positions. This prevents disarrangement of the latches or accidental injury thereto in the event of wreckage of the car, as occurs frequently in mine operation, thus insuring adequate protection of the latches to maintain them in proper operating positions. The latches I8 and their supporting shaft I9 are protected from the lading in the car by a guard or deflecting plate 22 that extends thereover and is fixed to the car end-wall structure 2.

Provision is made for supporting each latch I8 in its door engaging position, for which purpose I have provided a coiled spring 23 bearing thereagainst. Each of the latches has a lateral pin 26 attached thereto and projecting through a slot 2? in the adjacent portion of the end-sill structure 4. The pin normally seats on the lower end of the slot 27 to limit the forward swinging movement of the latch I8.

The latch tripping mechanism is mounted at the trackway at the proper point adjacent the bin or other lading receiving means, to release the latches IS and thereby allow dropping of the doors to release the lading from the car or other vehicle. This latch tripping mechanism is shown as electrically actuated, and is preferably assembled as a unit so that it may be applied at the desired point in the trackway where the dumping should take place. For this purpose, the tripping mechanism is mounted on a supporting plate 36 (Figs. 7 to 10) that extends transversely between opposite rails R, upon the lower flanges of which this plate is shown as supported and secured, although it may be mounted in any desired relation in the trackway, as by being secured upon ties, sills or other means. The plate 38 has upturned opposite edges 3| seated upon the rail flanges to dispose the body of the plate substantially at the lower faces of the rails. A surrounding frame 32 depends from the plate 30 and partially encloses the latch tripping mechanism, housing the plate 30, both longitudinally and transversely.

A shaft 33 extends transversely beneath the supporting plate 30, and is mounted in journal boxes 34, secured to the under side thereof. The shaft 33 carries one or more latch release arms 35 fixed thereto, one arm 35 being provided for each latch I8 of the car. Where a pair of latches I8 are disposed symmetrically on opposite sides of the longitudinal center of the car, as preferable, tripping arms 35 would be disposed on opposite sides of the longitudinal center of the car in the same longitudinal vertical planes as said latches when thecar is in tripping position thereover. Each of the arms 35 has an upturned free end portion with an engaging end 36 in position to engage an actuating portion 31 on the forward lower end of the latch I8; so that when the end 3% israised to tripping position, as indicated in dotted lines in-F'ig. 7, it is in the path of the actuating portion 3? of the latch and will be engaged thereby to cause movement of the latch rearwardly relative to the car, and thus to disengage the hook trunnions H, releasing the rearward door for dropping. Provision is made in the actuating means for elevating the tripping arm 35 in proper timed relation to the movement of the car along the trackway and for lowering movement again out of the path of the end-sill 4.

The latch release arm 35 is adapted to be supported in its lowered position by means of a hanger bracket 38 suspended from the supporting plate 30, and may also have its downward movement cushioned by a spring 38 telescoped over a bolt til suspended from the supporting plate 39. The spring is shown as interposed between a plate i! sleeved on the bolt Ml and a plate 4?. that is rigidly secured to the inner side of the arm 35, as shown in Figs. 8 and 9. The rising movement of the tripping arm 35 is shown as limited by an adjusting screw 43 screw-threaded through the supporting plate 30, and which is capable of varying the elevated height of said arm to any extent found desirable so as to provide the proper engaging action between the end 36 of the arm and the actuating portion 3'! of the latch.

As shown particularly in Figs. 8 and 9, the supporting plate 3?? has a slot 44 therein through which the upturned end portion of the tripping arm 35 is adapted to project.

For lifting the arm to its elevated position, means is provided, actuated electrically, and connected with the end portion of the arm. This upturned end portion has rigidly fixed thereto, as by welding, an inwardly projecting pin '55. Said pin 35 carries on the inner end thereof a depending link 46 journaled on the pin and extending downwardlyand inwardly therefrom, as shown in Fig. 10. Rigidly secured to the lower end of the link it, as by welding, is a cross bar ill which may extend transversely of the trackway and either mounted therein or connected with the corresponding link for the opposite tripping arm of the mechanism. The cross bar ii is pivotally connected at 58 with a core Gil of a solenoid 56 suitably mounted upon the supporting plate 38. It will be evident that when the solenoid 59 is energized it will attract the core 49, drawing upward the cross bar 41 and link 45, thereby raising the free end of the tripping arm 35 to its elevated position as indicated in dotted lines in Fig. 7, where the engaging end of said arm is in the path of the actuating portion ill of the latch IS. The solenoid will remain energized sufficiently long so that the forward movement of the car relatively to the tripping mechanism will cause movement or" the latch is to release the door trunnion l1 and thereby release the rearward door i2 for dropping. A solenoid 59 may be provided for each tripping arm 35, where more than one is used due to the provision of several latches independently mounted, or one solenoid may be used to actuate the plurality of tripping arms, whichever may be found desirable.

As shown in Fig. 10, the core 49 is surrounded by a coiled spring 5| interposed between a plate 52 loosely surrounding the lower end of the plunger 49, and a plate 53 fixed to the upper edge of the cross-bar 41. The plate 52 is loose on the lower end of the plunger or core 49, and confines the upper end of the coiled spring 5|, so that by the time the plunger 49 has been raised to a point near the top of its stroke, this plate 52 strikes the end of the solenoid, and further movement of the core compresses the spring 5|. The spring is compressed by an amount that equals the difference between the weight of the apparatus lifted and the power exercised by the solenoid. Then when the solenoid becomes deenergized, this spring gives the apparatus a quick impetus downward, more quickly than if gravity alone were relied upon. This facilitates the lowering movement and insures that the arms will drop out of the path of the bumper structure even when the speed of operation of the car or conveyor is quite high.

The coiled spring 39 is compressed when the arm 35 is lowered so as to exert a lifting tendency on the arm. This helps to raise the arm to its latch releasing position whenever the solenoid is energized. Thus by using both springs 39 and 5!, the mechanism functions quickly in the respective directions for engaging and releasing the latches.

For energizing the solenoid 50 at the proper time to release the lading in the trackway, we have provided switch means for controlling an electric circuit thereto, actuated by the car or conveyor when it reaches the proper position in the trackway, as shown more in detail in Figs. 1 to 5. It is preferable that switch devices be provided, connected in series, and arranged for actuation by difierent wheels of the car or conveyor, so as to insure actuation of the tripping mechanism only by the car for which the tripping mechanism is adapted. Accordingly, we have provided switch devices spaced lengthwise along the trackway in position to be engaged and actuated simultaneously by the respective front and rear wheels of the car. These switch devices are indicated in Figs. 1 and 2 by the numerals Kit and 6!, respectively, for the front and rear wheels.

The details of each switching device are shown more particularly in Figs. 4: and 5. A base plate 82 extends transversely under the rail R and is detaohably anchored thereto by rail clamps 83 that overlap the base flanges of the rail, and are secured to the base plate 62 by bolts 54 so as to fasten rigidly the plate 62 to the rail while permitting det chinent therefrom or adjustment relative thereto.

The base plate 52 extends outwardly from the rail R and has an upstanding supporting end portion 55 thereon. The upstanding support 65 has longitudinally spaced brackets t t fixed thereto, between which is received an end of a hinge plate 6?, said hinge plate being secured in place by a hinge pin 88 on which the hinge plate is journaled for swinging movement, said hinge pin 58 extending through the bracket 68 and supported thereby. The hinge plate 5? carries on the inner end thereof a contact plate 89 having an upturned contact end it on the inner edge thereof. The contact edge it normally is disposed immediately beside the head of the rail R, as shown in Fig. 5, with its upper edge at or slightly above the upper surface of the rail in position to be engaged by the tread surface of the wheel 5 or 5. The contact plate 69 is rigidly fixed to the hinge plate 61 as by being welded thereto, as indicated at i I, so as to form substantially a single plate structure that is hinged at one edge while the opposite edge forms a wheel contact.

The contact plate 69 is supported in elevated position upon coiled springs 12, the opposite ends of which springs are confined by cups 73 secured respectively to the base plate 62 and the contact plate 69. The springs 72 are confined by bolts '54 extending therethrough, each of which has a T-head on one end and adjusting nuts 16 on the other end. The T-head l5 normally engages in a depressed seat 11 in the supper surface of the contact plate 69, but said contact plate has a slot 78 transversely of the seat 11, as shown in Fig. 6, so as to allow the passage of the T-head i5 therethrough, for clearing the contact plate 69 to allow outward swinging movement thereof.

Mounted beneath the contact plate 69 is an electric switch, designated generally at 19. While any suitable form of switch may be used as found desirable, we have shown and prefer to use a switch manufactured by General Electric Com pany, and designated Track-Type Limit Switch CR9440-A1A.

The switch 19 is mounted on a switch plate 88 extending transversely inside the upstanding support 55 and spaced therefrom by a filler 8|. The switch is mounted on said support by bolts 82 extending through slots 83 in the switch plate 8'3, to allow vertical adjustment of the switch plate and switch so as to dispose the latter in proper relation to the switching device.

As shown in Fig. 3, the switch it is provided with a shaft 8 2, on which a switch arm 85 within the switch housing is adapted to close contacts at 36 for an electric circuit. Externally of the switch housing (Figs. 4 and '5) the shaft 84 carries a contact arm 8! on which a roller 88 is journaled, normally bearing against the under side of the contact plate 69, as shown in Figs. 4 and 5.

In Fig. 2, the control circuit is shown generally for energizing the solenoid 59. The switch devices 60 and GI are connected in series in a circuit 99, one side of which is connected with a source of electrical supply through a contacter designated generally at 9!. The solenoid 50 is in turn connected with the contactor 91 and will be energized through the circuit 93 when both switch devices 60 and 6! are actuated to close the circuit therethrough simultaneously, as will be evident from Fig. 2. These switch devices are thus actuated by the respective front and rear wheels of the car or conveyor for supplying electricity to the solenoid 50 at the right time to raise the tripping arm 35 to release the latch. The character of the contact edge iii is such that it will provide for actuation of the switch 79 exactly at the right time without regard to the wearing of the wheel tread, so that the operation of the electric contact will be the same on cars with old or worn wheels as on cars with new wheels.

The length of time that the circuit will be closed will depend upon the length and shape of the contact edge T0 which engages the tread of the wheel, and also upon the height of this edge above the top of the rail at the time that the wheel runs over it and presses it down. The time is also controlled by the relation of the switch arm 8'! to the contact plate 69, because the higher that the switch arm is raised above the top of the rail, the lower the wheel tread will depress the contact plate to the point where the circuit is closed. This contact arm 81 may be adjusted around the shaft 84 to vary its relative position.

At the same time, the bolts 14 can be lengthened by loosening the jam nuts 16 which will allow the contact plate 69 to be raised higher so that the contact edge 10 will stay in contact with the tread of the wheel longer to accommodate for this variation in the position of the switch arm 8']. At the same time, the slots 83 provide for vertical adjustment of the switch 19 relative to the base plate 62, which will also control the relation of the contact arm with the contact plate 69.

Furthermore, both of the switch devices 60 and 6| are adapted to be fastened to the rail R at any point desired by the clamps 62-64. Since both of the contact plates 66 for the respective switch devices must be depressed simultaneously so as to close the circuit 90, the timing can be thus controlled so as to raise the latch tripping arm at the proper time when the car is in position for dumping. It is also possible to control the length of time that the current will stay on and the circuit be closed by varying the length of the contact edge iii of the plate 63, one of which, on the switch device 68, is shown longer in Fig. 1 than the other, and this difference also allows for slight variation in the positioning of the respective switch devices.

Since some coal dust and other foreign matter may work into the switch devices, or between the latter and the rail R, which might otherwise clog up the mechanism, each of these switch devices is so constructed that it may be readily opened up for cleaning this out. This is made possible by the T-heads E5 on the bolts "M, which may be shifted to align with the slots 18 at right angles to the seats ll. Then, the bolts M no longer lock the plates in depressed positions, and these plates will then swing on the pin 68 away from the rail. This allows the space in each switch device to be cleaned out and the parts thus maintained in efiicient operating condition. The spring cups '63 will retain the springs in confined relation during this opening of the contact plate. After thus cleaning out the switch device, the plate may be moved back to its normal position, as shown, and the bolt heads 15 turned to engage in the seats TI which will then retain these in locked relation.

As will be evident from Fig. 5 in dot-and-dash lines, the wheel tread will become worn in service which ordinarily forms a circumferential grove in the periphery of the wheel tread. The contact plate 69 and its contact edge l'l] are so formed that this edge will engage the periphery of the wheel substantially on a level with the top surface of the rail R even when such wear occurs. The upturned contact edge 10 will then engage in the groove and the body portion of the plate 69 will then clear the wheel even during such engagement.

It may be desirable also to cut-away a portion of the ball of the rail R at the point opposite the contact edge lil, as indicated in Fig. 5, so as to insure engagement of the edge 18 with the worn portion of the tread of the wheel. This cut-away portion of the rail ball along the length of the contact edge makes it possible to bring this edge closer to the wheel flange where it will be in position to engage the worn tread portion of the wheel.

We claim:

1. In conveying mechanism including a wheeled dumping conveyance mounted on a trackway and having a lading supporting struc ture including a drop bottom door, electrically actuated means for releasing said door for 9 dropping having an energizing circuit, and means actuated by a plurality of spaced wheels of the conveyance, each wheel acting on said means to partly close the circuit and said plurality of wheels acting on said means to close the circuit for causing energizing of said electrical means.

2. In conveying mechanism including a wheeled dumping conveyance mounted on a trackway with lading supporting structure having a drop bottom door, electrically actuated means for controlling the release of the door having an energizing circuit, and circuit closing means connected with said circuit and actuated by a plurality of wheels of the conveyance for causing energizing of said electrical means, said circuit closing means being constructed for partly closing the circuit upon action thereonby one wheel and completing the closing of the circuit upon action thereon by a plurality of the wheels.

3. In conveying mechanism including a dumping conveyance having a plurality of front and rear supporting wheels mounted on a tracliway, said conveyance including a lading supporting structure and a drop bottom door, means for controlling the release of the door to discharge the lading, and means actuated simultaneously by front and rear wheels of the conveyance for actuating said door release means.

4. In conveying mechanism including a dumping conveyance having a plurality of front and rear supporting wheels mounted on a trackway, said conveyance including a lading supporting structure and a drop bottom door and latch means movable to release the door for dropping, power actuated mechanism mounted at the trackway and movable into operative relation with the latch means to release the door for dropping, and means actuated by pressure engagement of a plurality of said conveyance wheels for causing'movement of said power actuated mechanism to latch release position.

5. In conveying mechanism. including a dumping conveyance having a plurality of front and rear supporting wheels mounted on a trackway, said conveyance including a lading supporting structure and a drop bottom door, electrical means for controlling the release of the door to discharge the lading, and means actuated simultaneously by respective front and rear wheels of the conveyance for causing energizing of said electrical means.

6. In conveying mechanism including a dumping conveyance having a plurality of front and rear supporting wheels mounted on a trackway, said conveyance including a lading supporting structure and a drop bottom door, latch means for holding the door closed, electrical means for causing release of the latch. means for opening of the door to discharge the lading, and means actuated simultaneously by a plurality of front and rear wheels of the conveyance for causing energizing of the electrical means.

'7. In conveying mechanism including a. dumping conveyance having a plurality of front and rear supporting wheels mounted on a trackway, said conveyance including a lading supporting structure and a drop bottom door, latch means for holding the door closed, electrical means for causing release of the latch means for opening of the door to discharge the lading, and means actuated simultaneously by a plurality of front and rear wheels of the conveyance for causing energizing of the electrical means, said energizing means including a plurality of switch devices 10 mounted at spaced points in the trackway in position for engagement simultaneously by the respective front and rear wheels of the conveyance.

8. In conveying mechanism including a dumping conveyance having front and rear wheels mounted on the trackway for movement therealong, said dumping conveyance including a lading supporting structure having a drop bottom door, latch means for holding the door closed, electrically actuated means for causing release of the latch means to open the door for discharge of the lading, and switch devices connected with the trackway and with said electrical means, said switch devices being spaced along the trackway in positions for engagement with respective front and rear wheels of the conveyance for simultaneous actuation thereby.

9. In conveying mechanism including a trackway, a dumping conveyance having front and rear wheels mounted on the trackway for movement therealong, said dumping conveyance including a lading supporting structure having a drop bottom door, latch means for holding the door closed and movable to release the same for dropping to discharge the lading, electrically actuated means for moving said latch means to released position, switch devices mounted in the trackway at points spaced therealong in positions for engagement simultaneously by respective front and rear wheels of the conveyance, and means for causing energizing of said electrical means including an electric circuit connecting said switch devices in series and with the electrical means.

10. In conveying mechanism including a track, a drop bottom mine car having front and rear wheels mounted on the track, said mine car including a lading supporting structure and a drop bottom door, latch means for holding the door closed and movable to release said door for dropping, means for moving the latch means to a released position and including an electric solenoid, switch devices mounted in the trackway and spaced therealong in positions for engagement simultaneously by respective front and rear Wheels of the car, and an electric circuit connecting said switch devices in series and with the solenoid for causing energizing of the solenoid upon engagement of the switch devices simultaneously by the respective wheels of the car.

11. In conveying mechanism including a trackway adapted to receive a wheeled dumping conveyance thereon, the combination of a plurality of switch devices mounted in the trackway and spaced lengthwise of the trackway in positions for engagement simultaneously by longitudinally spaced portions of the'conveyance, and an electric circuit connecting said switch devices in series and adapted to control the dumping of the conveyance when switch devices are engaged by the longitudinal-1y spaced portions of the conveyance.

12. In conveying mechanism including a trackway adapted to receive a wheeled dumping conveyance thereon, the combination of a plurality of switch devices mounted in the trackway at points spaced lengthwise thereof in position for engagement by respective front and rear wheels of the conveyance, and an electric circuit connected with said switch devices and adapted to control the dumping of the conveyance upon simultaneous engagement of said switch devices by the wheels of the conveyance.

13. In conveying mechanism, the combination of a latch releasing member, means mounting said member for upward movement thereof to releasing position, power means for causing upward movement of said member on said mounting means, spring means in position to be compressed upon actuation of the power means to move the member to latch releasing position and to facilitate the downward movement of said member from latch releasing position, and spring means arranged to be compressed by said downward movement of the member tending to facilitate the upward movement thereof upon actuation of the power means.

14. In conveying mechanism including a trackway adapted to receive a wheeled dumping conveyance thereon, the combination of a plurality of switch devices mounted in the trackway and spaced relative to the trackway in positions for engagement simultaneously by spaced portions of the conveyance, and an electric circuit connecting said switch devices in series and adapted to control the dumping of the conveyance when said switch devices are engaged by the spaced portions of the conveyance and actuated by the pressure thereof.

15. In conveying mechanism including a trackway adapted to receive a wheeled dumping conveyance thereon, the combination of a plurality of switch devices mounted in the trackway at points spaced relative thereto in position for engagement by respective wheels of the conveyance, and an electric circuit connected with said switch devices and adapted to control the dumping of the conveyance upon simultaneous engagement of said switch devices by the wheels of the conveyance and actuated by the pressure thereof.

16. In conveying mechanism including a trackway adapted to receive a wheeled dumping conveyance thereon, said conveyance including a lading supporting structure and a drop bottom door, means mounted in the trackway for controlling the release of the door to discharge the lading, switch means mounted in the trackway in position for engagement by spaced portions of the conveyance and constructed for controlling the door release means upon engagement of the switch means by said spaced portions.

17. In conveying mechanism including a trackway adapted to receive a wheeled dumping conveyance thereon, said conveyance including a lading supporting structure and a drop bottom door, means for controlling the release of the door to discharge the lading, electrically operated means mounted in the trackway for controlling said door release means, and switch means mounted in the trackway and operatively connected with said electrically operated means and constructed for actuation by spaced wheels of the conveyance to cause actuation of the door release means upon engagement of said switch means by said spaced wheels.

18. In conveying mechanism, the combination with a trackway, of a wheeled dumping conveyance mounted on the trackway and having a lading supporting structure including a drop bottom door, latch means on the conveyance for holding the door closed and movable to release the door for discharge of the lading from the conveyance, electrically actuated means mounted on the trackway for actuating the latch means on the conveyance during movement of the conveyance along the trackway, an actuating circuit for said electrically actuated means, and a plurality of switch means mounted on the trackway constructed for separate respective actuation by the conveyance for controlling said actuating circuit.

19. In conveying mechanism, the combination with a trackway, of a wheeled dumping conveyance mounted on the trackway and having a lading supporting structure including a drop bottom door, latch means on the conveyance for holding the door closed and movable to release the door for discharge of the lading from the conveyance, electrically actuated means mounted on the trackway for actuating the latch means on the conveyance during movement of the conveyance along the trackway, an actuating circuit for said electrically actuated means, and switch devices connected in series in said actuating circuit for controlling the electrical means to release the latch means when the switch devices are engaged by spaced portions of the conveyance and actuated thereby.

20. In conveying mechanism, the combination with a trackway, of a wheeled dumping conveyance mounted on the trackway and having a lading supporting structure including a drop bottom door, latch means on the conveyance for holding the door closed and movable to release the door for discharge of the lading from the conveyance, electrically actuated means mounted on the trackway for actuating the latch means on the conveyance during movement of the conveyance along the trackway, an actuating circuit for said electrically actuated means, and switch devices connected in the electrical circuit for causing energizing of the electrical means upon simultaneous engagement of the switch devices by the wheels of the conveyance and actuated by the pressure thereof.

HUGH W. SANFORD. HARRY W. JONES.

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

UNITED STATES PATENTS Number Name Date 1,020,238 Weer et a1. Mar. 12, 1912 1,082,184 Ward Dec. 23, 1913 1,269,919 Foster June 18, 1918 1,316,129 Williamson Sept. 16, 1919 1,470,149 Davis Oct. 9, 1925 1,771,718 McAvoy July 29, 1930 1,803,384 Dietrichson May 5, 1931 1,813,560 Browne July 7, 1931 2,071,924 Fraser Feb. 23, 1937 2,138,695 Duncan Nov. 29, 1938 2,399,708 Sanford May 7, 1946 2,451,406 Pancake Oct. 12, 1948 2,487,447 Kepner Nov. 8, 1949