Rapid Discharging Hopper Car Door Actuating Mechanism

Abstract

A mechanism for opening and closing a horizontally hinged door, such as on railroad hopper cars and trucks, having a tie-rod actuating means adapted to be rotatably mounted to a container, a tie-rod pivotally and slidably joined at a first end to the tie-rod actuating means and joinable at the second end to the door on the container, the first end of the tie-rod being slidable in and between ends of an arcuate sector guide path in the tie-rod actuating means, means at one end of the guide path being capable of limiting downward displacement of the tie-rod when the door is open and said same means at the guide path end upon rotation of the tie-rod actuating means in one direction lifts the tie-rod to maximum position thereby rotating the door to which it is attached into closing and locking position, and means at the other end of the guide path which, upon rotation of the tie-rod actuating means in the opposite direction through an angle defined by the length of the arcuate sector guide path and with the tie-rod stationary, forces and frees the first end of the tie-rod from maximum lifted and locked position to fall unrestrainedly downwardly through the arcuate guide path thereby permitting the door to which it is attached to rotate open rapidly by gravity.

Description

This invention relates to apparatus for quickly opening doors, and especially doors which function as barricades to prevent flow or movement of a free flowing solid particulate or granular material from a hopper or storage tank. More particularly, this invention is concerned with improvements in apparatus or mechanisms for quickly opening doors over discharge openings on vehicles used to transport granular or particulate material, such as doors on railroad hopper and gondola cars.

Particulate materials which readily flow are often stored in a hopper or tank. The hopper or tank is often fitted with one or more doors which close suitable discharge openings in the hopper or tank through which the particulate material can be readily emptied by gravity flow upon opening of the door. Although one or more doors may be used to close an opening, each door is generally rotatably mounted by means of a horizontal hinge arrangement. Not only are such doors used on stationary tanks and hoppers but they are also widely used on vehicles for transporting particulate material, such as trucks and railroad hopper and gondola cars.

The prior art discloses various types of apparatus and mechanisms for opening and closing doors which when closed bar flow of a particulate material through an opening in a hopper, tank or other storage container. Prior art pertaining to apparatus and mechanisms for opening and closing doors on railroad hopper and gondola cars is as follows: U.S. Pat. Nos. 3,675,590; 3,675,591; 3,654,873 and 3,187,684.

Although the door opening mechanisms of the prior art can be employed for the intended purpose, it is believed that alternative mechanisms characterized by unique quick opening features could be advantageously employed, not only on a railroad hopper or gondola car, but also on other vehicles which transport or store particulate material such as stone, coal, sand, corn cobs, grain, wood chips, ores, plastic pellets and the like as well as on stationary storage tanks and hoppers for such material.

According to one aspect of the invention there is provided a novel mechanism for quickly opening a horizontally hinged or pivoted door used to close or seal off a discharge opening in a tank or hopper for particulate material. The mechanism is suitable for use on stationary storage containers as well as on containers or hoppers located on transport vehicles, such as trucks or railroad cars.

The mechanism of the invention, apart from its installation on a container for particulate material, comprises a tie-rod actuating means adapted to be rotatably mounted on a hopper or other storage container, whether stationary or mounted on a vehicle, a tie-rod pivotally and slidably joined at a first end to the tie-rod actuating means and adapted to be joined at the second end to a door which is horizontally hinged, the first end of the tie-rod being slidable in an arcuate sector guide path in the tie-rod actuating means, means at one end of the guide path being capable of limiting downward displacement of the tie-rod when a door to which it can be attached is opened and the said same means at the guide path end upon rotation of the tie-rod actuating means in one direction lifts the tie-rod to maximum position to thereby rotate a door to which it can be attached into closed and locked position over an opening in the storage container, tank or hopper. The mechanism also includes a means at the other end of the guide path which upon rotation of the tie-rod actuating means in the opposite direction through an angle defined by the length of the arcuate sector guide path and with the tie-rod stationary, forces and frees the first end of the tie-rod from maximum lifted and locked position to fall unrestrainedly downwardly through the arcuate guide path thereby releasing the tie-rod and permitting any door to which it is attached to rotate open rapidly by gravity and the force of a particulate load against it. The tie-rod actuating means can comprise specifically a horizontal shaft, an arcuate sector having an arcuate guide path therein mounted on the horizontal shaft, a circular drive gear on the horizontal shaft, said arcuate sector and drive gear rotating in unison on the horizontal shaft, and means cooperating with the drive gear to rotate it in two directions.

The door opening mechanism provided by this invention is particularly suitable in use in trucks and railroad vehicles which employ hoppers or other containers for transporting particulate material. The mechanism is readily installed in such vehicles for opening one or more doors horizontally hinged at the bottom of a hopper or other container for closing a gravity discharge opening therein.

The door opening and closing mechanism of this invention can be used to open and close a single door or a pair of doors which rotate in opposite directions so that they can be opened simultaneously or closed simultaneously. In addition, the mechanism can be used in a plurality of installations on a vehicle or other stationary apparatus having a multitude of doors to open all of the doors singly or in pairs simultaneously, and with each door of each pair rotating opposite to the other door in the pair during the opening and closing operation sequences.

The invention will be described further in conjunction with the attached drawings, in which:

FIG. 1 is a side elevational diagrammatic view of a railroad hopper car equipped with a plurality of the door opening and closing mechanisms of this invention;

FIG. 2 is a side elevational view, partially broken away and partially in section, of a door opening mechanism of the invention mounted in the center sill of the railroad hopper car of FIG. 1;

FIG. 3 is a side elevational view like FIG. 2 but with the door opening mechanism rotated to the position where the doors are ready to drop open instantly by gravity action;

FIG. 4 is a side elevational view like FIGS. 2 and 3 but with the doors partially open and free to fall to fully open position;

FIG. 5 is a side elevational view much like FIGS. 2-4 but with the doors fully open and the mechanism positioned to coincide with the doors in fully open position;

FIG. 6 is a side elevational view in section taken along the line 6--6 of FIG. 8, of a door opening and closing mechanism like that of FIGS. 2 to 5 but with the elements in somewhat different proportional relationship and with greater detail shown for such embodiment;

FIG. 7 is a sectional view of FIG. 1 taken along the line 7--7 but with the embodiment of FIGS. 6 to 10 positioned in the center sill;

FIG. 8 is a view from the bottom upwardly towards to door opening and closing mechanism shown in FIGS. 6 and 7;

FIG. 9 is a sectional view taken along the line 9--9 of FIG. 6;

FIG. 10 is a sectional view taken along the line 10--10 of FIG. 9; and

FIG. 11 is a side elevational view of a mechanism quite similar to that shown in FIGS. 2 to 5 except that the mechanism of FIG. 11 does not use an intermediate pinion gear between the rack gear and one of the circular drive gears.

So far as is practical the same parts or elements which appear in the various views of the drawings will be identified by the same numbers.

With reference to FIG. 1 of the drawings, there is illustrated a railroad hopper car comprising a body 10 mounted on conventional wheel trucks 11. The railroad hopper car body 10 has conventional vertically disposed side walls terminating at their ends in inclined end walls having slope sheets 12 which terminate in a more or less horizontal bottom rectangular area defined by the sidewalls of the car and the bottom of slope end sheets 12. The rectangular bottom area is divided into four car emptying areas A, B, C and D. Each of the emptying areas A, B, C and D is divided in a direction longitudinal to the railroad car by a center sill 13 which extends the length of the railroad car. Each of the emptying spaces A, B, C and D has a pair of horizontally hinged doors 14 and 15 of similar construction. Each door when in closed position is downwardly sloped to further aid in gravity unloading of particulate material transported by the railroad car.

As shown in FIG. 7, door 14 is made in two sections 14a and 14b. Each of the door sections is rotatably secured by hinges 141 along its top horizontal edge to the bottom part of the railroad hopper car. Each door section 14a and 14b is joined together by a bar 16 to form a door which moves as a unit. The door 15 is in all essential respects identical to the door 14. Door 15 is also rotatably mounted by hinges 151 to the bottom of the railroad car body shown by FIG. 2. Each of the doors 14 and 15 opens and closes one-half of the open spaces A, B, C and D (FIG. 1). The construction of such doors is considered conventional and not part of this invention. The invention, however, is not to be considered limited to such specific door structures as described since it is applicable to many other horizontally hinged door arrangements used to close discharge openings to prevent flow of particulate material from a storage hopper or container.

FIGS. 2 to 5 illustrate one embodiment of a door opening and closing mechanism provided by this invention. Mounted on horizontal shaft 20 below center sill 13 is circular gear 21. Mounted on the same shaft 20 is arcuate sector 22 having a guide path 23. The circular gear 21 and arcuate sector 22 together comprise a tie-rod actuating means which is rotatably mounted on the vehicle. Tie-rod 24 has its upper end 25 pivotally and slidably positioned in guide path 23. The lower end 26 of tie-rod 24 is pivotally mounted on arm 27 which extends outwardly and downwardly from a bar, like bar 16 on door 14, but on door 15. The tie-rod 24 has a bent portion 28 where it comes into close relationship with hub 29 of arcuate sector 22. The described mechanism when activated serves to open and close door 15.

The mechanism used to open and close door 14 is much like that used to open and close door 15. Thus, circular gear 30 is mounted on horizontal shaft 31. The gear teeth of gear 30 are positioned to mesh with the gear teeth in circular gear 21 so that each gear rotates in a direction opposite to the other gear. Arcuate sector 39 having guide path 32 therein is also mounted on shaft 31. Circular gear 30 and arcuate sector 39 are positioned and fixed with respect to shaft 31 to rotate in unison. The upper end 33 of tie-rod 34 is pivotally and slidably positioned in guide path 32. The lower end 35 of tie-rod 34 is pivotally joined to arm 36 which is joined to bar 16 (FIG. 7) which unites the two sections of door 14. Tie-rod 34 has a bent portion 37 which projects around hub 38 of arcuate sector 39.

Gear rack 40 is mounted on the bottom side of beam 41. Between gear rack 40 and circular gear 30 is positioned pinion gear 42. Mounted on the top of center sill 13, at one end of the railroad car, is cylinder 42' which can be hydraulically or air operated to move rod 43 in or out and thereby, by means of arm 44 joined to the end of rod 43, slide beam 41 back and forth as desired to achieve longitudinal movement of gear rack 40. Sliding movement of rack gear 40 causes pinion gear 42 to rotate which in turn causes the rotation of circular gear 30 which in turn causes circular gear 21 to rotate although in a direction opposite to circular gear 30.

FIG. 2 shows the position of the mechanism when doors 14 and 15 are both closed and the mechanism is in locked position. A locking action is achieved by having the ends of each tie-rod positioned such that a line drawn through the ends will be on a side of shaft 20 or 31 to form an overcenter toggle lock, as the case may be, opposite the side on which the bent or curved portions 28 or 37 of the respective tie-rod is located. Movement of the upper end 25 of tie-rod 24 in guide path 23 is barred by the end of the guide path and by the bent portion 28 contacting hub 29 or by some other suitable stopper arrangement. Movement of tie-rod 34 is similarly barred when the mechanism is in locked position.

The door opening and closing mechanism of FIG. 2 effects opening of doors 14 and 15 simultaneously by moving the gear rack 40 to the right. This causes pinion gear 42 to rotate clockwise and for circular gear 30 to rotate counterclockwise which in turn causes circular gear 21 to rotate clockwise. The counterclockwise movement of circular gear 30 results in arcuate sector 39 moving from the position shown in FIG. 2 to the position shown in FIG. 3. During such movement the upper end 33 (FIG. 4) of tie-rod 34 remains essentially in the same position as it was in FIG. 2. The arcuate sector 39 however moves through the entire angle defined by the ends of the guide path 32 and shaft 31. Simultaneously, but in an opposite direction there is effected rotation of arcuate sector 22 to the position shown in FIG. 3. This results in angular movement of guide path 23 for about its maximum displacement but with the upper end 25 of tie-rod 24 remaining in essentially fixed position during such movement.

After the mechanism has reached the position shown in FIG. 3, only a slight additional rotation of circular gears 30 and 21 is required to place the upper ends of tie-rods 34 and 24 in a free sliding state in guide paths 32 and 23, respectively. The tie-rods then slide freely as shown in FIG. 4 with the weight of the doors 14 and 15, and the cargo pressing against the doors, forcing them open rapidly. The doors continue their downward rotational opening movement until door 14 hits a spring bumper 45 mounted on a base 44. Similarly, door 15 hits the spring bumper 46 mounted on base 47. The spring bumpers 45 and 46 prevent undue force from being applied to the tie-rods 34 and 24 as the doors swing open rapidly.

The mechanism described with reference to FIGS. 2 to 5 closes the doors tightly by reversing the movement of gear rack 40. By pulling gear rack 40 to the left, pinion gear 42 is caused to rotate counterclockwise. This causes circular gear 30 to rotate clockwise and to drive circular gear 21 counterclockwise. Arcuate section 39 thus rotates on shaft 31 in a clockwise direction and lifts tie-rod 34 while simultaneously arcuate sector 22 rotates counterclockwise at the same speed and lifts tie-rod 24 thereby causing door 15 to be rotated upwardly at the same rate of rotation as door 14 is rotated upwardly. The same rate of rotation is guaranteed by gears 21 and 30 which are of the same size. Upward rotation of the doors continues until they are in closed locked position as illustrated by FIG. 2.

FIGS. 6 to 10 illustrate a door lifting mechanism similar to the mechanism described in FIGS. 2 to 5. However, the mechanism illustrated by FIGS. 6 to 10 is presented in substantially more detail, and with a slightly different proportional relationship between the parts, than the mechanism illustrated by FIGS. 2 to 5.

With reference to FIGS. 6 to 10, gear housing 50 is made of two sections 51 and 52. The two halves 51 and 52 of the gear housing 50 are held together by bolts 53. The vertical ends of gear housing 50 terminate in flanges 54 and 55 which are bolted respectively to vertically positioned angles 56 and 57 welded to the inside walls of vertical webs 58 and 59 of center sill 113 (identical to center sill 13).

Mounted inside of gear housing 50 is a pair of circular gears 60 and 62 of equal size (FIG. 10). Circular gear 60 is mounted on shaft 61 and gear 62 is mounted on shaft 63 (FIG. 9). Shaft 61 rotates in bearing 64 mounted in a nose 65 which extends outwardly from gear housing section 52. The other end 67 of shaft 61 rotates in bearing 68 in bearing block 69 mounted on the bottom surface of flange 70 on the bottom side edge of center sill 113. In a similar manner, bearing block 75, mounted on the bottom surface of flange 76, extending outwardly from wall 59 of center sill 113, supports one end of shaft 63 while the other end of the shaft is supported by a bearing mounted in protruding nose 77 extending outwardly from gear housing section 51.

Pinion gear 80 is mounted to rotate on shaft 81 in bearings provided in gear housing sections 51 and 52. Pinion gear 80 has its teeth engaged with the teeth of circular gear 60 and also with the teeth of gear rack 82. Gear rack 82 is mounted on the bottom of beam 83. Beam 83 slides between rollers 84 and 85 held in place by bracket 86. Beam 83 is slidably connected at the end of a power supply means which can slide the beam back and forth as desired to operate the door opening and closing mechanism. Cylinder 42' shown in FIGS. 1 and 2 could be used for this purpose.

Mounted on shaft 63 is arcuate sector 90 which has a guide path 91. Pin 96 extends through guide path 91 and into the ends 93 and 95 of tie-rods 92 and 94. The tie-rods 92 and 94 are operatively identical to the tie-rod 24 in the mechanism of FIGS. 2 to 5. The lower ends of tie-rods 92 and 94 are joined to bar 16 joining the two sections 14a and 14b of door 14 together.

Arcuate sector 100 is mounted to rotate on shaft 61. The upper ends 101 and 103 of tie-rods 102 and 104 are connected by a pin 105 to the arcuate guide path (not shown) in arcuate sector 100. The lower ends of tie-rods 102 and 104 are joined to door 15. The tie-rods 102 and 104 are the equivalent of tie-rod 24 in the mechanism of FIGS. 2 to 5. Also, arcuate sector 100 is the equivalent of arcuate sector 22 in the embodiment shown in FIGS. 2 to 5.

The door opening and closing mechanism described with reference to FIGS. 6 to 10 operates in the same manner as does the embodiment of FIGS. 2 to 5 and therefore it will not be described further with respect to its operation.

The mechanism of FIG. 11 shows an alternative arrangement which can be used for opening doors quickly and subsequently closing them. The elements or parts of the mechanism shown in FIG. 11 are essentially identical to those shown in the mechanism of FIG. 2. However, the pinion gear 42 in the mechanism of FIG. 2 is not employed in the mechanism of FIG. 11. Instead the circular gear 21 is raised and positioned so that its teeth will directly engage gear rack 40. Of course, the teeth of circular gear 21 are positioned to mesh with the teeth of circular gear 30. By positioning the parts as described, the mechanism of FIG. 11 will operate in the same way as the mechanism of FIG. 2.

Regardless of which of the described door opening and closing mechanisms is employed, by using one of the mechanisms for each of the pair of doors 14 and 15 in the railroad hopper car of FIG. 1, each of the pair of doors 14 and 15 can be opened simultaneously to empty the car quickly. Opening and closing of the doors can be effected automatically as the railroad car is in motion rolling on the rails. A suitable trip mechanism can be employed in order for cylinder 42 to activate the beam which contains the gear rack used to drive the door opening and closing mechanism. In this way an entire train of railroad hopper or gondola cars can be automatically emptied while the train is in motion and the doors subsequently closed automatically without stopping the train.

While the specific embodiments of the invention illustrated by the drawings show how the mechanism can be used to open two adjacent doors simultaneously, it is within the scope of the invention to employ a single tie-rod actuating unit comprising for example a single circular gear 30 and arcuate sector 39 to open and close only door 14. Such a mechanism would find a number of uses where a single door is to be opened quickly and subsequently closed.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom as modifications will be obvious to those skilled in the art.

Claims

What is claimed is:

1. In a vehicle for transporting particulate solid material having at least one opening in the bottom, closeable by a horizontally hinged door, for gravity discharge of the material therethrough, the improvement comprising:

a tie-rod actuating means rotatably mounted on the vehicle,

a tie-rod pivotally and slidably joined at a first end to the tie-rod actuating means and joined at the second end to the door,

the first end of the tie-rod being slidable in an arcuate sector guide path in the tie-rod actuating means,

means at one end of the guide path being capable of limiting downward displacement of the tie-rod when the door is open and said same means at the guide path end upon rotation of the tie-rod actuating means in one direction lifts the tie-rod to maximum overcenter locked position whereby rotating the door into closing and locked position, and

means at the other end of the guide path which, upon rotation of the tie-rod actuating means in the opposite direction through an angle defined by the length of the arcuate sector guide path and with the tie-rod stationary, forces and frees the first end of the tie-rod from maximum lifted and maximum overcenter locked position to fall unrestrainedly downwardly through the arcuate guide path thereby releasing the tie-rod and permitting the door to rotate open rapidly by gravity.

2. A vehicle according to claim 1 including gear means for driving the tie-rod actuating means.

3. A vehicle according to claim 2 in which the gear means includes a circular gear and a gear rack means for driving the circular gear.

4. A vehicle according to claim 1 in which the tie-rod actuating means comprises:

a horizontal shaft,

an arcuate sector, having the arcuate sector guide path therein, on the horizontal shaft,

a circular drive gear on the horizontal shaft,

said arcuate sector and drive gear rotating in unison on the horizontal shaft, and

means cooperating with the drive gear to rotate it in two directions.

5. A vehicle according to claim 4 in which the vehicle is a railroad car having a center sill and the tie-rod actuating means is located substantially beneath the center sill.

6. A vehicle according to claim 4 in which the tie-rod is bent and when in maximum overcenter locked position the ends of the tie-rod are in a line which runs on one side of the center of the horizontal shaft and the adjacent part of the tie-rod is on the other side of the center of the horizontal shaft.

7. A vehicle according to claim 4 in which the means cooperating with the drive gear to rotate it in two directions includes a gear rack slidably mounted on the vehicle.

8. A vehicle according to claim 7 in which a pinion gear is operably located between the gear rack and the circular drive gear.

9. In a vehicle for transporting particulate solid material having at least a pair of openings in the bottom, each opening being closeable by a horizontally hinged door which rotates in a direction opposite to the other door, for gravity discharge of the material therethrough, the improvement comprising:

a pair of tie-rod actuating means rotatably mounted on the vehicle,

means for simultaneously rotating each tie-rod actuating means in opposite directions and for simultaneously reversing the direction of rotation thereof,

each tie-rod actuating means having a tie-rod pivotally and slidably joined at a first end to the tie-rod actuating means and joined at the second end to one of the doors, with the first end of the tie-rod being slidable in an arcuate sector guide path in the tie-rod actuating means,

means at one end of the guide path being capable of limiting downward displacement of the tie-rod when the door to which it is attached is open and said same means at the guide path end upon rotation of the tie-rod actuating means in one direction lifts the tie-rod to maximum overcenter locked position thereby rotating the door into closing and locked position, and

means at the other end of the guide path which, upon rotation of the tie-rod actuating means in the opposite direction through an angle defined by the length of the arcuate sector guide path and with the tie-rod stationary, forces and frees the first end of the tie-rod from maximum lifted and locked position to fall unrestrainedly downwardly through the arcuate guide path thereby permitting the door to rotate open rapidly by gravity,

said tie-rods being lifted and locked in overcenter position, and subsequently released, simultaneously.

10. A vehicle according to claim 9 having a plurality of pairs of bottom openings, with each pair of openings being closeable by separate horizontally hinged doors operated by a pair of said tie-rod actuating means and tie-rods.

11. A vehicle according to claim 9 including gear means for driving the pair of tie-rod actuating means.

12. A vehicle according to claim 11 in which the gear means includes a circular gear and a gear rack means for driving the circular gear.

13. A vehicle according to claim 9 in which each tie-rod actuating means comprises:

a horizontal shaft,

an arcuate sector, having the arcuate sector guide path therein, on the horizontal shaft,

a circular gear on the horizontal shaft,

said arcuate sector and drive gear rotating in unison on the horizontal shaft, and

means cooperating with the drive gear to rotate it in two directions.

14. A vehicle according to claim 13 in which the vehicle is a railroad car having a center sill, and the tie-rod actuating means are located substantially beneath the center sill.

15. A vehicle according to claim 13 in which each tie-rod is bent and when in locked position the ends of the tie-rod are in a line which runs on one side of the center of the horizontal shaft and the adjacent part of the tie-rod is on the other side of the center of the horizontal shaft.

16. A vehicle according to claim 13 in which the means cooperating with the drive gear to rotate it in two directions includes a gear rack slidably mounted on the vehicle.

17. A vehicle according to claim 16 in which a pinion gear is operably located between the gear rack and the circular drive gear.

18. In a vehicle for transporting particulate solid material having a plurality of pairs of adjacent openings in the bottom, each pair of openings being closeable by horizontally hinged doors which rotate in directions opposite to each other, for gravity discharge of the material therethrough, the improvement comprising:

a pair of tie-rod actuating means for each pair of doors, rotatably mounted on the vehicle,

each tie-rod actuating means having a tie-rod pivotally and slidably joined at a first end to the tie-rod actuating means and joined at the second end to one of the doors of the pair of doors, with the first end of the tie-rod being slidable in an arcuate sector guide path in the tie-rod actuating means,

means for simultaneously rotating each tie-rod actuating means of each pair thereof in opposite directions and for simultaneously reversing the direction of rotation thereof,

means at one end of each guide path being capable of limiting downward displacement of the tie-rod slidable therein when the door to which it is attached is open and said same means at the guide path end upon rotation of the tie-rod actuating means in one direction lifts the tie-rod to maximum overcenter locked position thereby rotating the door into closing and locked position,

means at the other end of the guide path which, upon rotation of the tie-rod actuating means in the opposite direction through an angle defined by the length of the arcuate sector guide path and with the tie-rod stationary, forces and frees the first end of the tie-rod from maximum lifted and overcenter locked position to fall unrestrainedly downwardly through the arcuate guide path thereby permitting the door to which it is attached to rotate open rapidly by gravity.

said tie-rods being lifted and locked in overcenter position, and subsequently released, simultaneously, and

means for simultaneously rotating all tie-rod actuating means.

19. A mechanism for opening and closing a horizontally hinged door comprising:

a tie-rod actuating means adapted to be rotatably mounted to a container,

a tie-rod pivotally and slidably joined at a first end to the tie-rod actuating means and joinable at the second end to a door on the container,

the first end of the tie-rod being slidable in and between ends of an arcuate sector guide path in the tie-rod actuating means,

means at one end of the guide path being capable of limiting downward displacement of the tie-rod when the door is open and said same means at the guide path end upon rotation of the tie-rod actuating means in one direction lifts the tie-rod to maximum overcenter locked position thereby rotating a door to which it may be attached into closing and locking position, and

means at the other end of the guide path which, upon rotation of the tie-rod actuating means in the opposite direction through an angle defined by the length of the arcuate sector guide path and with the tie-rod stationary, forces and frees the first end of the tie-rod from maximum lifted and overcenter locked position to fall unrestrainedly downwardly through the arcuate guide path thereby permitting a door to which it may be attached to rotate open rapidly by gravity.

20. A mechanism according to claim 19 in which the tie-rod actuating means comprises:

a horizontal shaft,

an arcuate sector, having the arcuate sector guide path therein, on the horizontal shaft,

a circular drive gear on the horizontal shaft,

said arcuate sector and drive gear rotating in unison on the horizontal shaft, and

means cooperating with the drive gear to rotate it in two directions.

21. A mechanism for opening and closing a pair of horizontally hinged doors which rotate in opposite directions comprising:

a pair of tie-rod actuating means adapted to be rotatably mounted on a vehicle,

means for simultaneously rotating each tie-rod actuating means in opposite directions and for simultaneously reversing the direction of rotation thereof,

each tie-rod actuating means having a tie-rod pivotally and slidably joined at a first end to the tie-rod actuating means and joinable at the second end to one of the doors, with the first end of the tie-rod being slidable in an arcuate sector guide path in the tie-rod actuating means,

means at one end of the guide path being capable of limiting downward displacement of the tie-rod when the door to which it may be attached is open and said same means at the guide path end upon rotation of the tie-rod actuating means in one direction lifts the tie-rod to maximum overcenter locked position thereby being capable of rotating the door into closing and locked position, and

means at the other end of the guide path which, upon rotation of the tie-rod actuating means in the opposite direction through an angle defined by the length of the arcuate sector guide path and with the tie-rod stationary, forces and frees the first end of the tie-rod from maximum lifted and locked position to fall unrestrainedly downwardly through the arcuate guide path thereby permitting a door to which it may be attached to rotate open rapidly by gravity,

said tie-rods being lifted and locked in overcenter position, and subsequently released, simultaneously.

22. A mechanism according to claim 21 in which each tie-rod actuating means comprises:

a horizontal shaft,

an arcuate sector, having the arcuate sector guide path therein, on the horizontal shaft,

a circular gear on the horizontal shaft,

said arcuate sector and drive gear rotating in unison on the horizontal shaft, and

means cooperating with the drive gear to rotate it in two directions.