US3082703A

US3082703A - Sliding closure outlet frame assembly

Info

Publication number: US3082703A
Application number: US740288A
Authority: US
Inventors: George B Dorey
Original assignee: Enterprise Railway Equipment Co
Current assignee: Enterprise Railway Equipment Co
Priority date: 1958-06-06
Filing date: 1958-06-06
Publication date: 1963-03-26
Anticipated expiration: 1980-03-26

Description

March 26, 1963 G, B. DoREY summe cLosuRE ouTLET FRAME:V ASSEMBLY 5 Sheets-Sheet 1 Filed June 6. 1958 IVENTOR, 660g@ Z3. Daffy, M237? m/ March 26; 1963 G. B. DoRl-:Y

summa cLosURE OUTLET FRAME ASSEMBLY Filed June 6, 1958 3 Sheets-Sheet 2 March 26, 1963 G. B. DoR'EY 3,082,703

SLIDING cLosURE OUTLET FRAME ASSEMBLY Filed June 6, 1958 5 Sheets-Sheet 5 R @y M m /b NN. w. law E E E E E E E E M .EEEEEEEEEH Il id -Jsitlim @Y ,.HHII lli lli: f B mw @M /mm \QN \& IA/ r m f Q I m n MMLW |\hm l m m E. AIE A w h; E El E .Ew El United States Patent O 3,082,703 SLIEHNG CLSURE GUTLET FRAME ASSEMBLY George B. Dorey, Westmount, Quebec, Canada, assigner to Enterprise Railway Equipment Company, Chicago, lil., a corporation of Illinois Filed .lune 6, 1958, Ser. No. 740,238 11 Claims. (Cl. 10S-282) This invention relates to an improved means for operating the sliding gate of a discharge outlet and relates more particularly to that type of outlet structure widely employed for controlling the discharge of lading from railway hopper cars. It constitutes an improvementover the constructions shown in U.S. Patent No. 2,753,815, issued July `lt), 1956, and application Serial No. 534,547, illed September 15, 1955, now abandoned.

The objects of the invention, among others, are: To provide an improved mechanism for operating a sliding gate by rotation of a shaft journaled on the gate and traveling therewith wherein the shaft performs the double function of moving the gate and also acting as a guide element to prevent canting of the gate as force is exerted to rotate the shaft; to provide improved toothed racks for cooperating engagement with geared pinions Vnonrotatably mounted on the shaft; and to provide improved means for simultaneously locking the shaft and gate against opening movement.

The invention further resides in the arrangement of parts and details of construction such as will he described.

The improved structure is shown as applied to the hopper of a railway hopper car wherein the gate is moved from a location adjacent the side of the car by means of a removable bar extending at an angle to the shaft and therefore necessitating the application of operating force at an appreciable distance from the gate. The application of operating force at a location remote from the gate imparts a canting tendency to the gate. To counteract the canting, it is now proposed to dispose the operating shaft immediately beneath the ways supporting the gate and to utilize the operating shaft per se as a guiding element and thereby take advantage of the rolling eifect to minimize frictional resistance.

In the drawings,

FIGURE 1 is a side elevational view of a portion of a hopper car showing the improved structure applied thereto.

FIGURE 2 is an end elevational View of the structure shown in FIGURE 1 as viewed from right to left, said view showing approximately one half of the width of the car and portions of the car frame in section.

FGURE 3 is a plan view of FIGURE l'with the hopper walls and oors eliminated and parts broken away to better illustrate the construction.

FIGURE 4 is a vertical side view similar to FIGURE l except that the gate is shown in opened position and certain parts are broken away.

FIGURE 5 is a fractional vertical sectional view taken on a line 5 5 of FIGURE 2.

FIGURE 6 is a detached perspective view of the outer toothed rack member.

In FIGURE 2 of the drawings 10 indicates the center sill of the car, 11 one of the car side walls, and 11' one of the side sills below the car wall 11. Lying between the side wall and center sill is a hopper 12 which includes inner and outer side walls 13 and 14 that meet with longitudinally sloping floors l15 and y16 to form the four sides of the hopper 12. The walls 1-3 and 14 and floors 15 and 16 have their lower marginal edges spaced from each other to define a rectangular discharge opening 117 to discharge lading between the rails 9.

The discharge opening 17 is closed by va sliding gate ICC 18 which is longitudinally movable in a framing structure 19. The framing structure 19, which is welded to the hopper'lZ, includes an upper section formed of longitudinally extending

members

20 and 21 transversely spaced to accommodate the gate 18 therebetween and transversely extending

members

22 and 23.

The

longitudinal members

20 and 21 are of angular shape of rolled structural steel each with one flange underlying the gate 1S as indicated at 24 for member 20 and at 25 for member 21. The adjacent flanges ofthe angle members 2t) and 21 extend upwardly as indicated at y2t? and 27 to overlie the inner and outer walls 13 and 14. The ilange :27 being bent to present an inclined section 28 conforming to the slope of the outer hopper wall 14. The angle members 2t) and 21 extend longitudinally beyond the discharge opening 17, as indicated at and 21, to provide supporting ways for the gate 1S in open position.

The transversely extending member 22, in like manner to member 2t), includes a horizontally extending flange 29 aligned with

flanges

24 and 25 which are united therewith by welded joints 3i) and 31. The flange that is angularly related to flange 29 extends vertically upwardly, as at 132, and thence upwardly at an incline, as at 33, to conform to the slope of sloping floor 15. The upwardly extending

flange portions

32 and 33 are welded at 34 and 35 to the ends of the members 2.0 and 21. The other transversely extending member 23 is of angular shape with

ilanges

36 and 37 and is inverted to present a transversely extending hood welded at each end to the

longitudinal members

20 and 21 as indicated at 38 and 39. The

members

22 and 23 preferably are rolled structural steel members.

Below the upper framing structure 19 there is disposed a depending chute like enclosure 40; which is located around the discharge opening '17 and in effect constitutes a downward extension of the hopper 12. The enclosure 40 includes three substantially

vertical walls

41, 42 and 43 and a sloping wall 44 all having a common upper marginal wall 45 surrounding the four walls which is welded on three sides to the undersurface of the upper framing structure 19 as indicated at 46.

The lower margin of the chute, like enclosure 40, is provided on two sides with

grooves

47 and 48. On the other two sides it has laterally extending

walls

49 and 50 whereby a removable chute can be received in the grooves and clamped in position to the laterally extending

walls

49 and 50.

The gate 18, in closed position, projects appreciably beyond the chute like enclosure 46. The gate 18 is provided with depending lugs 51-51 which mount sleeve bearings 53 for an operating shaft 54. The shaft 54, which extends transversely of the path of movement of the gate 18 and beyond the longitudinally extending

members

20 and 21, is located immediately adjacent the under surfaces of the

flanges

24 and 25 and constitutes a guide having rolling movement against these surfaces to prevent upward movement of the gate 18.

The outer ends of the sleeve bearings 5.3-53 which are mounted on the lugs 51-,51 are located in close proximity to the

inner edges

24 and 25 of the laterally extending

llanges

24 and 25, as shown in lFIGURE 2, and thus serve las guides to limit undue sidewise movement of the gate 18. On each projecting end ofthe shaft 54 there is fastened a geared pinion 56 which engages with toothed racks 57 and 58 respectively. The racks 57 and 58 are located above the level of the gate 18 and are secured to the upstanding flanges 26` and 27-28 of the

side members

20 and 21 along the extensions 20' and 21' thereof. TheA rack 57, which is located on the inner side of the hopper 12, includes in an integral structure a laterally extending section 59 having a series of downwardly extending teeth 60 and an upwardly extending wall section 61 secured by welding 61 to the upstanding flange portion 26 of the extension 20 of the associated side rail member 2t). The rack 58, which is located on the outer or operating side of the discharge hopper 12, also includes a laterally extending section 62, similar to the section 59, and has depending teeth 63. Above the laterally extending section 62 there is an attaching portion or wall 64 which is inclined and generally conforms to the inclination of the inclined flange section 2S of ange 27 and is welded thereto. Outstanding from the attaching portion 64 is an outwardly spaced wall 65, FIGURE 6, having a trunnion 66 on which is pivotally mounted a locking dog 67 which operates to retain the gate 18 in closed and latched position as will be hereinafter described. The wall 65 is also provided with an integrally formed upward extension 68 having a key shaped opening 69 for accommodating a sealing pin 70 therethrough. At the outer end of the shaft 54 there is an operating head 71 having a series of openings 72 for receiving an operating bar 73 at an angle to the main body of the shaft 54. A pin 74 holds the operating head 71 in place on the shaft 53.

The operating head 71 is provided with a shoulder 75 with which the pivotally mounted locking dog 67 is adapted to engage, as shown in FIGURE 5, in order to prevent reverse rotation of the shaft 53 and opening of the gate "18. The locking dog 67 is formed with a key shaped opening 76 which is adapted to register with the key shaped opening 69 in the toothed rack member 58 to receive a key shaped end 77 of the sealing pin 70. A stop 78, FIGURE 2, is provided to limit axial movement of the sealing pin 70 by engaging handle 79 thereof, it being understood that the sealing pin 7% is axially movable in bearings as provided by extension 68 and an apertured lug 80 which is mounted on the ange 37 of transverse member 36, The stop 78 is welded in place after the sealing pin 70 is inserted in the opening 69 in the extension 68.

-It will be noted that this interengagement between locking dog 67 and shoulder 75 can be effected only when the gate 18 is in closed position. Consequently, the locking dog 67 performs the dual function of directly latching the gate 18 against bodily movement as well as preventing rotation of the operating shaft 54.

The locking dog 67 is swingable to an overbalanced released position, FIGURE 4, to permit opening movement of the gate 18. A stop shoulder 81 projecting laterally from member 58 forms a rest for the locking dog 67 in its released position and, when so positioned, the shoulder 75 on the operating head 71 is below the level of the dog 67 as the lug 75 which moves with the gate 18 is swung downwardly due to rotational movement of the shaft 54. Consequently the gate 18 is freely movable in a non-interfering relation when the dog 67 is in retracted position as shown in FIGURE 4.

The placement of the operating shaft 54 below the level of the gate 18 and adjacent the underside of the ways or

flanges

24 and 25 on which the gate 18 slides in effect provides largely for a rolling action in the direction of movement of the gate `ll8 between the shaft 54 and the under sides of these supporting ways or flanges thus mitigating wear between the parts and making for ease of operation.

The arrangement of the geared pinions 56 in combination With the bearings 53 carried by the lugs 51 on the under side of the gate provides guides on each side of the Ways or

flanges

24 and 25 which maintain them in aligned relation with the gate. This eliminates the necessity for heavy and cumbersome connecting ties between the

extensions

20 and 21 of the

longitudinally extending members

20 and 21.

What is claimed as new is:

1. A hopper discharge opening closure structure for use in a railroad car having an opening providing for the downward discharge of lading and comprising, in combination, a frame having side walls and end walls forming a discharge opening, a support flange parallel to and secured to each of said side walls adjacent the lower portions thereof and extending toward each other along opposite sides of said opening, a gate slidable along the upper surfaces of said support flanges underneath one of said end walls and in closed position having one end projecting beyond said one end wall, a shaft rotatably mounted on the under side of said gate and parallel to the projecting end thereof and extending beyond the sides of said gate in juxtaposition to the under sides of said support anges and cooperating therewith to hold down said gate in slidable position along said upper surfaces of said support flanges and movable with said gate, a pinion non-rotatably mounted on each projecting end of said shaft, a rack engaging each pinion throughout the entire extent of movement of said gate, means stationarily mounting each rack with respect to said frame as a longitudinal extension of each of said side walls and laterally outwardly of and parallel to each side of said gate, and means for rotating said shaft to move said gate between Closed and open positions.

2. A hopper discharge opening closure structure for use in a railroad car having an opening providing for the downward discharge of lading and comprising, in combination, a frame having side walls and end walls forming a discharge opening, a support flange parallel to and secured to each of said side Walls adjacent the lower portions thereof and extending toward each other along opposite sides of said opening, a gate slidabie along the upper surfaces of said support flanges underneath one of said end walls and in closed position having one end projecting beyond said one end wall, bearings stationarily mounted on the under side of the projecting end of said gate between said support flanges, a shaft journaled in said bearings on the under side of said gate and extend ing perpendicularly transversely of said side walls beyond the sides of said gate in juxtaposition to the under sides of said support flanges and cooperating therewith to hold down said gate in slidable position along said upper surfaces of said support anges, a pinion non-rotatably mounted on each projecting end of said shaft, a rack engaging each pinion throughout the entire extent of movement of said gate, means stationarily mounting each rack with respect to said frame as a longitudinal extension of each of said side walls and laterally outwardly of and parallel to each side of said gate, and means for rotating said shaft to move said gate between closed and open positions.

3. A hopper discharge opening closure structure for use 1n a railroad car having an opening providing for the downward discharge of lading and comprising, in combination, a frame having side walls and end Walls formmg a discharge opening, a support flange parallel to and secured to each of said side walls adjacent the lower portions thereof and extending toward each other along opposite sides of said opening, a gate slidable along the upper surfaces of said support anges underneath one of said end walls and in closed position having one end projecting beyond said one end wall, said support flanges having extensions projecting outside of said one end wall for a distance to support Said gate in full open position, bearings stationarily mounted on the under side of the projecting end of said gate between said support anges with one end of each bearing juxtaposed to the adjacent edge of the respective flange extension to guide said gate in its movement between open and closed positions, a shaft journaled in said bearings on the under side of said gate and extending perpendicularly -transversely of said side walls beyond the sides of said gate in juxtaposition to the under sides of said support flanges and cooperating therewith to hold down said gate in slidable position along said upper surfaces of said support flanges, a pinion non-rotatably mounted on each projecting end of said shaft, a rack engaging each pinion throughout the entire extent of movement of said gate, means stationarily mounting each rack with respect to said frame as a longitudinal extension of each of said side walls and laterally outwardly of and parallel to each side of said gate, and means for rotating said shaft to move said gate between closed and open positions.

4. A hopper discharge opening closure structure for use in a railroad car having an opening providing for the downward discharge of lading and comprising, in combination, a frame having side walls and end walls forming a discharge opening, a support flange parallel to and secured to each of said side walls adjacent the lower portions thereof land extending toward each other along opposite sides of said opening, a gate slidable along the upper surfaces of said support anges underneath one of said end Walls and in closed position having one end projecting beyond said one end wall, said support flanges having extensions projecting outside of said one end Wall for a distance to support said gate in full open position, bearings stationarily depending from the under side of the projecting end of said gate between said support iianges, a shaft journaled in said bearings and having cylindrical cross sections underlying and coextensive with the under sides of said extensions of said support flanges and in close proximity thereto, said shaft being parallel to said gate and extending perpendicularly transversely of said side walls and projecting at each end beyond the sides of said gate and movable with said gate, a pinion nonrotatably mounted on each projecting end of said shaft, a rack engaging each pinion throughout the entire extent of movement of said gate, means stationarily mounting each rack with respect to said frame' as a longitudinal extension of each of said side walls and laterally outwardly of and parallel to each side of said gate, and means for rotating said shaft to move said gate between closed and open positions.

5. A hopper discharge opening closure structure for use in a railroad car having an opening providing for the downward discharge of lading and comprising, in combination, a frame having side walls and end Walls forming a discharge opening, a support flange parallel to and secured to each of said side walls adjacent the lower portions thereof and extending toward each other along opposite sides of said opening, a gate slidable along the upper surfaces of said support flanges underneath one of said end Walls and in closed position having one end projecting beyond said one end wall, said support flanges having extensions projecting outside of said one end wall for a distance to support said gate in full open position, bearings stationarily depending from the under side of the projecting end of said gate between said support flanges with one end of each bearing juxtaposed to the adjacent inner edge of the respective flange extension to guide said gate in its movement between open and closed positions, a shaft journaled in said bearings and having cylindrical cross sections underlying and coextensive with the under sides of said extensions of said support flanges and in close proximity thereto, said shaft being parallel to said gate and extending perpendicularly transversely of said side walls and projecting at each end beyond the sides of said gate and movable with said gate, a pinion non-rotatably mounted on each projecting end of said shaft, a rack engaging each pinion throughout the entire extent of movement of said gate, means stationtarily mounting each rack with respect to said frame as a longitudinal extension of each of said side walls and laterally outwardly of and parallel to each side of said gate, and means for rotating said shaft to move said gate between closed and open positions.

l6. A hopper discharge opening closure structure for use in a railroad car having an opening providing for the downward discharge of lading and comprising, in

combination, a frame having side walls and end Walls forming a discharge opening, a support flange parallel to andv secured to each of said side walls adjacent the lower portions thereof and extending toward each other along opposite -sides of said opening, a gate slidable along the upper surfaces of said support anges underneath one of said end walls and in closed position having one end projecting beyond said one end wall, said side Walls and support `flanges having extensions projecting outside of said one end wall for a distance to support said gate in full open position, said extensions having gate supporting surfaces which are coplanar with said upper surfaces of said support flanges, bearings stationarily depending from the under side of the projecting end of said gate between said support flanges and below the plane of said gate supporting surfaces, a shaft journaled in said bearings parallel to said gate below the plane of said gate supporting surfaces and extending perpend-icularly transversely of said side walls and extensions thereof and projecting at each end beyond the -sides of said gate and movable with said gate, a pinion non-rotatably mounted on each projecting end of said shaft, a rack stationarily mounted on the outer side of each of the side wall extensions and engaging each pinion throughout the entire extent of movement of said gate, `and means for rotating said shaft to move said gate between closed and open positions.

7. A hopper discharge opening closure structure for use in a railroad car having an opening providing for the downward discharge of lading and comprising, in combination, a frame having side Walls and end walls forming a discharge opening, a support flange parallel to and secured to each of said side walls adjacent the lower portions thereof and extending toward each other along opposite sides of said opening, a gate slidable along the upper surfaces of said support flanges underneath one of said end walls and in closed position having one end projecting beyond said one end wall, said side walls and support anges having extensions projecting outside of said one end wall for a distance to support said gate in full open position, said extensions having gate supporting surfaces which are coplanar with said upper surfaces of said support flanges, one of the side wall extensions being vertical and the other side wall extension having a vertical lower portion and an upper portion inclined away from the frame, bearings stationarily depending from the under side of the projecting end of said gate between said support anges and below the plane of said gate supporting surfaces, a shaft journaled in said bearings parallel to said gate below the plane of said gate supporting surfaces and extending perpendicularly transversely of said side walls and extensions thereof and projecting at each end beyond the sides of said gate and movable with said gate, a pinion non-rotatably mounted on each projecting end of said shaft, a rack stationarily mounted on the outer side of each of the side wall extensions and engaging each pinion throughout the entire extent of movement of said gate, the rack -mounted on .the one side Wall extension having a vertical wall overlying the outer vertical side wall surface of said one side wall extension, the rack mounted on the other side wall having an upwardly extending wall overlying and conforming to the vertical and inclined outer side wall surface of said other Side wall, and means for rotating said shaft to move said gate between closed and open positions.

8. A hopper discharge opening closure structure for use in a railroad car having an opening providing for the downward discharge of lading and comprising, in combination, a frame having side Walls and end walls forming a discharge opening, a support flange parallel to and secured to each of said side walls adjacent the lower portions thereof and extending toward each other along opposite sides of said opening, a gate slidable along the upper surfaces of said support flanges underneath one of said end walls and in closed position having one end projecting beyond said one end wall, said side walls and support flanges having extensions projecting outside of said one end wall for a distance to support said gate in full open position, bearings stationarily depending from the under side of the projecting end of said gate between said support flanges, a shaft journaled in said bearings and having cylindrical cross setions underlying and coextensive with the under sides of said extensions of said support anges and in close proximity thereto, said shaft being parallel to said gate and extending perpendicularly transversely of said side walls and extensions thereof and projecting at each end beyond the sides of said gate and movable with said gate, a pinion non-rotatably mounted on each projecting end of said shaft, a rack stationarily mounted on the outer side of each of the side wall extensions and engaging each pinion throughout the entire extent of movement of said gate, and means for rotating said shaft to move said gate between closed and open positions.

9. A hopper discharge opening closure structure for use in a railroad car having an opening providing for the downward discharge of lading and comprising, in combination, a frame having side walls and end walls forming a discharge opening, a support ange parallel to and secured to each of said side walls adjacent the lower portions thereof and extending toward each other along opposite sides of said opening, a gate slidable along the upper surfaces of said support iianges underneath one of said end walls and in closed position having one end projecting beyond said one end wall, said side walls and support anges having extensions projecting outside of said one end wall for a distance to support said gate in full open position, said extensions having gate supporting surfaces which are coplanar with said upper surfaces of said support anges, bearings stationarily depending from the under side of the projecting end of said gate between said support flanges and below the plane of said gate supporting surfaces with one end of each bearing juxtaposed to the adjacent inner edge of the respective ange extension to guide said gate in its movement between open and closed positions, a shaft journaled in said bearings parallel to said gate below the plane of said gate supporting surfaces and extending perpendicularly transversely of said side walls and extensions thereof and projecting at each end beyond the sides of said gate and movable with said gate, a pinion non-rotatably mounted on each projecting end of said shaft, a rack stationarily mounted on the outer side of each of the side wall extensions and engaging each pinion throughout the entire extent of movement of said gate, and means for rotating said shaft to move said gate between closed and open positions.

l0. A hopper discharge opening closure structure for use in a railroad car having an opening providing for the downward discharge of lading and comprising, in combination, a frame having side walls and end walls forming a discharge opening, a support flange parallel to and secured to each of said side walls adjacent the lower portions thereof and extending toward each other along opposite sides of said opening, a gate slidable along the upper surfaces of said support anges underneath one of said end walls and in closed position having one end projecting beyond said one end Wall, said side walls and support flanges having extensions projecting outside of said one end wall for a distance to support said gate in full open position, said extensions having gate supporting surfaces which are coplanar with said upper surfaces of said support flanges, bearings stationarily depending from the under side of the projecting end of said gate between said support lianges and below the plane of said gate supporting surfaces with one end of each bearing juxtaposed to the adjacent inner edge of the respective flange extension to guide said gate in its movement between open and closed positions, a shaft journaled in said bearings parallel to said gate below the plane of said gate supporting surfaces and extending perpendicularly transversely of said side walls and extensions thereof and projecting at each end beyond the sides of said gate and movable with said gate, a pinion non-rotatably mounted on each projecting end of said shaft with one end of each pinion juxtaposed to the adjacent outer edge of the respective flange extension to guide said gate in its movement between open and closed positions, a rack stationarily mounted on the outer side of each of the side wall extensions and engaging each pinion throughout the entire extent of movement of said gate, and means for rotating said shaft to move said gate between closed and open positions.

11. A hopper discharge opening closure structure for use in a railroad car having an opening providing for the downward discharge of lading and comprising, in combination, a frame having side walls and end walls forming a discharge opening, support means parallel to and secured to each of said side walls adjacent the lower portions thereof and extending toward each other along opposite sides of said opening, a gate slidable along said support means underneath one of said end walls and in closed position having one end projecting beyond said one end wall, said side walls and support means having extensions extending beyond said one end wall for a distance to support said gate in full open position, bearings depending from the under side of the projecting end of said gate at the projecting end thereof and located between said extensions of said support means, a shaft journaled in said bearings and having cylindrical cross sections underlying and coextensive with the under side of said extensions of said support means and in close proximity thereto, said shaft being parallel to said gate and extending perpendicularly transversely of said side walls and extensions thereof and projecting at each end beyond the sides of said gate and movable with said gate, a pinion non-rotatably mounted on each projecting end of said shaft, a rack stationarily mounted on the outer side of each of the side wall extensions and engaging each pinion throughout the entire extent of movement of said gate, and means for rotating said shaft to move said gate between closed position and open position.

References Cited in the file of this patent UNITED STATES PATENTS 1,122,918 Hart et al. Dec. 29, 1914 2,317,007 Weniger Apr. 20, 1943 2,318,763 Ditchiield May 11, 1943 2,386,702 McBride Oct. 9, 1945 2,690,139 Dorey Sept. 28, 1954 2,753,815 Dorey July 10, 1956 2,791,973 Dorey May 14, 1957 2,993,452 Dorey July 25, 1961

Claims

1. A HOPPER DISCHARGE OPENING CLOSURE STRUCTURE FOR USE IN A RAILROAD CAR HAVING AN OPENING PROVIDING FOR THE DOWNWARD DISCHARGE OF LADING AND COMPRISING, IN COMBINATION, A FRAME HAVING SIDE WALLS AND END WALLS FORMING A DISCHARGE OPENING, A SUPPORT FLANGE PARALLEL TO AND SECURED TO EACH OF SAID SIDE WALLS ADJACENT THE LOWER PORTIONS THEREOF AND EXTENDING TOWARD EACH OTHER ALONG OPPOSITE SIDES OF SAID OPENING, A GATE SLIDABLE ALONG THE UPPER SURFACES OF SAID SUPPORT FLANGES UNDERNEATH ONE OF SAID END WALLS AND IN CLOSED POSITION HAVING ONE END PROJECTING BEYOND SAID ONE END WALL, A SHAFT ROTATABLY MOUNTED ON THE UNDER SIDE OF SAID GATE AND PARALLEL TO THE PROJECTING END THEREOF AND EXTENDING BEYOND THE SIDES OF SAID GATE IN JUXTAPOSITION TO THE UNDER SIDES OF SAID SUPPORT FLANGES AND COOPERATING THEREWITH TO HOLD DOWN SAID GATE IN SLIDABLE POSITION ALONG SAID UPPER SURFACES OF SAID SUPPORT FLANGES AND MOVABLE WITH SAID GATE, A PINION NON-ROTATABLY MOUNTED ON EACH PROJECTING END OF SAID SHAFT, A RACK ENGAGING EACH PINION THROUGHOUT THE ENTIRE EXTENT OF MOVEMENT OF SAID GATE, MEANS STATIONARILY MOUNTING EACH RACK WITH RESPECT TO SAID FRAME AS A LONGITUDINAL EXTENSION OF EACH OF SAID SIDE WALLS AND LATERALLY OUTWARDLY OF AND PARALLEL TO EACH SIDE OF SAID GATE, AND MEANS FOR ROTATING SAID SHAFT TO MOVE SAID GATE BETWEEN CLOSED AND OPEN POSITIONS.