US2513569A

US2513569A - Cupola

Info

Publication number: US2513569A
Application number: US720161A
Authority: US
Inventors: Hugo L Kuehlthau
Original assignee: Whiting Corp
Current assignee: Whiting Corp
Priority date: 1947-01-04
Filing date: 1947-01-04
Publication date: 1950-07-04
Anticipated expiration: 1967-07-04

Description

July 1950 v H. L. KUEHLTHA-U 2,513,569

CUPOLA I Filed Jan. 4. 1947 Y, a Sheets-Sheet 1 July 4, 1950 H. L. KUEHLTHAU CUPOLA Filed Jan. 4, 1947 3 Sheets-Sheet 2 f w m f 0 0 w m v o o o 3 w 7 y k w w 5 Mo" w H 7 H a I w a b m 2. [pl 1,. 1. u I. 2 3

y 1950 H. 1.. KUEHLTHAU 2,513,569

CUPbLA Filed Jan. 4, 1947 s Sheets-Sheet s @atenied .Fuiy 4, 1950 2,513,569 corona Hugo L. Kuehlthau, Chicago, 111., assignor to Whiting Corporation, Harvey, 11]., a corporation of Illinois Application January 4, 1947, Serial No. 720,161

7 Claims.

The present invention relates generally to cupolas. More particularly the invention relates to that type of cupola which serves as an instrumentality or medium for melting metal, is supported in an elevated position by way of a plurality of laterally spaced legs and comprises an upstanding cylindrical shell having at the lower end thereof a drop bottom in the form of a pair of oppositely .disposed, complemental, hinged doors.

In connection with operationof a cupola of the aforementioned type it has heretofore been the practice to utilize a vertically extending prop to maintain the doors constituting the shell bottom in their closed position. At the conclusion of a metal melting operation the prop is jerked from under the doors by the cupola operator. As soon as the prop 'is jerked from its operative position the doors swing downwards and the residual materials within the cupola fall onto the subjacent portion of the fioor over which the cupola is mounted. After opening of the doors the discharged materials are shoveled into a suitable receptacle in order that they may be taken to a dump. The practice of utilizing an upstanding prop for holding the doors in their closed position during operation of the cupola is subject to certain objections. In the first place the cupola operator in connection with jerking of the prop from under the doors is likely to be injured, especially when the doors are heavy and there is a large amount of residual materials within the cupola shell. Secondly, the use of a prop precludes a receptacle from being placed under the cupola so as to receive or catch the residual materials after downward swinging of the doors.

One object of the invention is the provision. in connection with a cupola of the type under consideration, of a novel latch arrangement which, when in its operative orlocked position, serves to hold the bottom forming doors in their closed position and, when released, permits the doors to swing downwards into their open position. By employing such a latch arrangement injury to the cupola operator is avoided and it is possible prior to opening or unlatchingof the doors to insert under the cupola a receptacle for receiving the residual materials within the cupola directly upon opening of the doors.

Another object ofthe invention is to provide in addition to the latch arrangement remotely controlled power means for shifting the latch arrangement into and out of its operative or latched position.

A further object of the invention is the proviwhich like numerals of reference denote corresponding parts throughout the several views:

Figure l is a fragmentary side view of a cupola embodying the invention;

Figure 2 is a horizontal section taken on the line 22 of Figure 1 and illustrating in detail the construction and arrangement of the power means i for shifting the latch arrangement into and out of its operative or latched position;

Figure 3 is a fragmentary vertical section taken on the line 3-3 of Figure 2 and showing the construction, design and arrangement of the power means for swinging the bottom forming doors of the cupola upwards into their closed position;

Figure 4 is an enlarged vertical section taken at right angles to Figure 3 and on the line 44 of Figure 2, and illustrating the design and construction of the latch arrangement for releasably holding the doors in their closed position; and

Figure 5 is an enlarged vertical transverse section taken on the line 55 of Figure 4 and showing one of the latches constituting the latch arrangement.

The cupola which is shown in the drawings constitutes the preferred form or embodiment of the invention. It is designed primarily for use in a foundry to melt metal and as its principal components comprises a shell Ill, a bottom structure ll having a drop bottom [2, legs I3 for supportin the shell in an elevated position with respect to the floor of the foundry or other establishment in which the cupola is disposed, a latch arrangement M for latching or retaining the drop bottom in its operative or closed position, power means l5 for shifting the latch arrangement into and out of its latched position and power means l6 for swinging the drop bottom into its closed position.

The cupola shell I0 is of standard or conventional construction and has the interior or inner periphery thereof lined with refractory material,

. erably two hinges for each of the doors.

It is cylindrical so far as contour o'r configuration is concerned and embodies at a point slight-' ly above the bottom structure M an annular wind box l1 and a circular series of equidistantly spaced tuyeres l8. The wind box is provided with a tangentially arranged nipple I9 whereby it may be connected to receive air under pressure from a compressor or other source (not shown). The tuyeres l8 are located beneath the wind box I! and serve to introduce air under pressure from the wind box into the interior of the shell in, order to promote combustion of the combustible material with which the shell is charged.

The bottom structure ll of the cupola comprises in addition to the drop bottom I2, a square bottom plate 20, a pair of parallel, laterally spaced I-beams 2| and a pair of parallel, laterally

spaced angle bars

22 and 23. The bottom plate 20 underlies and projects outwards from the lower end of the cupola shell l and has a central circular opening 24 which is substantially the same in diameter as the shell interior. The I-beams 2| underlie, and extend lengthwise of. two opposed marginal portions of the bottom plate 20. They ,are arranged so that the webs thereof extend vertically and have the upper flanges thereof suitably fixedly secured to the super] acent marginal portions of the bottom plate 20. The

angle bars

22 and 23 extend at right angles to the I-beams 2|. They correspond in length to the I-beams and embody horizontal, inwardly extending legs and vertical, outwardly disposed legs. The horizontal legs of the angle bars rest on, and are welded or otherwise fixedly secured to, the other two side marginal portions of the bottom plate 20 of the cupola bottom structure The ends of the angle bars are connected to the ends of the I-beams by way of vertically extending gusset plates 25 and vertically extending angle bars 26 in order that the bottom structure It is rigid. The upper marginal portions of the plates 25 are weldedor riveted to the ends of the vertical legs of the

angle bars

22 and 23 and the outer side margins of the gusset plates are connected to the ends of the webs of the I-beams by way of the vertically extending angle bars 26. The drop bottom I2 constituting a part of the cupola bottom structure U consists of a pair of oppositely disposed, com- I plemental,

semi-circular doors

21 and 28 and these are connected to the bottom plate 20 by way of hinges 29 in order that they are capable of swinging downwards from a closed position wherein they are horizontal into an open position wherein they hang down under the supporting structure I I. The doors are so arranged that when they are in their normal or closed position the chordal margins thereof are in aligned and abutting relation. As well understood in the art the drop bottom is covered with sand before the cupola is placed in operation. There are pref- Each hinge comprises a door carried hinge arm 30, a pair of angle brackets 3| and a pivot pin 32. The hinge arms 30 of the hinges are connected to the under sides of the doors and extend outwards as shown in dotted lines in Figure 2. The pairs of angle brackets 3| are connected to, and depend from, the bottom plate 20 and are arranged in straddled relation with the outer ends of the hinge arms 30. The pivot pins 32 extend through aligned holes in the vertical parts of the angle brackets 3| and the outer ends of the hinge arms 30.,

The legs it of the cupola are four in number and extend vertically. The lower ends of the legs have fioor engaging feet 33 and the upper ends of the legs have rigid horizontal plates 34 which underlie, and are welded, riveted or otherwise fixedly secured to, the ends of the bottom flanges of the I-beams 2 I. As shown in Figure l, the legs l3 are spaced laterally apart a suflicient distance to permit a wheel equipped open top receptacle 35 to be moved under the cupola shell I0. It is contemplated that after operation of the cupola the receptacle 35 will be moved into the position shown in Figure 1 wherein it is disposed under the cupola shell. It is also contemplated that after proper positioning of the receptacle the doors 2'! and 28 constituting the drop bottom l2 will be swung downwards into their open position to the end that the residual materials within the cupola shell will fall directly into the receptacle. The top of the receptacle is at least as large as the opening 24 in the bottom plate 20 in order that the receptacle when properlypositioned beneath the drop bottom will catch all of the residual materials upon opening of the bottom.

The latch arrangement I4 serves releasably to hold the doors constituting the drop bottom in their operative or closed position and comprises an I-beam 36 and a pair of latches 31. The I- beam extends at right angles to the I-beams" 2| and consists of a web 38, a top flange-39 and a bottom flange 40. One side portion of the top flange of the I-beam 36 underlies and is bolted to the chordal margin of the door 21 and the other side portion of said top flange is adapted when the drop bottom of the cupola is in its closed position to underlie and support the chordal margin of the door 28, as best shown in Figures 3 and 5. The ends of the I-beam 36 terminate inwards of the I-beams 2| (see Figure 4) and are provided with a pair of studs 4|. The latter extend lengthwise of the I-beam 36 and have the inner end portions thereof disposed within cutouts 42 in the ends of the web 38 of the I-beam 36. The cutout defining portions of the web are welded to the inner ends of the studs in order that the studs are held in fixed or rigid relation with the I-beam 35. The outer ends of the studs are cylindrical and when the two doors are in their closed position are disposed directly inwards of the central portions of the webs of the I-beams 2|. The latches 31 are mounted on the inner ends of a pair of laterally spaced coaxial stub shafts 43. They embody arcuate seats 44 for the outer ends of the studs 4| and are adapted after the doors 2'! and 28 are swung upwards into their closed position, to be swung into a position wherein they underlie said outer ends of the studs and thus hold the doors in their closed position. Reverse swinging or rotation of the latches disengages them from the outer ends of the studs and frees the doors so that they drop downwards into their open position. The arcuate seats are so designed and arranged that when the latches are swung into their latched position while the doors are but partially closed they will cam the doors upwards into fully closed position. The stub shafts 43 are rotatably mounted in bearings 45 which fit within collars 46. As shown in Figure 4 the collars extend through aligned holes in the central portions of the webs of the I-beams 2|. The hole defining portions of said webs are welded to the central portions of the collars 46 in order that the collars are held in fixed or rigid relation with the I- beams 2|. The stub shafts 43 are connected together for conjoint rotation by way of a rock shaft 48, a pair of arms 49, a pair of links 59 and a pair of arms 5|. The rock shaft 48 extends horizontally and is located beneath and outwards of the angle bar 22 of the bottom structure II. It extends in parallel relation with said angle bar and has its ends journalled in a pair of bearings 52. As best shown in Figure 2, such bearings are mounted on certain of the gusset plates 25. The arms 49 are fixedly connected to, and project downwards from, the ends of the rock shaft 48. The arms 5| are connected to, and project downwards from, the outer ends of the stub shafts 43 and are arranged in parallel relation with the arms 49. The links 50 extend horizontally and have certain of the ends thereof pivotally connected to the outer ends of the arms 49. The other ends of the links are pivotally connected to the outer or distal ends of the arms 5 I. When the rock shaft 48 is rocked in a counterclockwise direction as viewed in Figure 1 it operates, through the medium of the arms 49, the links 59, the arms SI and the stub shafts 43, conjointly to swing the latches 31 out of their latched position wherein, as previously pointed out, they underlie the outer ends of the studs 4|. Reverse rocking of the rock shaft operates to swing the latches into their latched position. It is contemplated that after the

bottom forming doors

21 and 28 are swung upwards into their operative or closed position the rock shaft will be rocked so as to cause the latches to swing into latched relation with the studs 4|. At the conclusion of operation of the cupola, the rock shaft is rocked so as to disengage the latches from the studs. As soon as the latches are swung out of engagement with the studs the doors, in response to the action of gravity, swing downwards.

The power means l5 for shifting the latch arrangement l4 into and out of its latched position comprises a cylinder-piston device 53 and this is positioned over one of the I-beams 2| and consists of a cylinder 54 and a piston 55. The cylinder 53 is provided on the central portion thereof with a pair of aligned outwardly extending trunnions 56 and is pivotally supported by way of a U-shaped bracket 51 which, as shown in Figures 1 and 2, is mounted on the bottom plate 20 of the bottom structure 2|. The trunnions 56 fit rotatably within bearing forming holes in the sides of the bracket 51 and permit the cylinder to tilt in a vertical plane. The piston 55 is slidably mounted in the cylinder 54 and is provided with a rod 58 which extends slidably through a packing gland at one end of the cylinder and has its outer end pivotally connected to the upper end of an upwardly extending arm 59. The lower end of such arm is fixedly connected to the rock shaft 48. When the piston is slid in one direction it operates, through the medium of the piston rod 58 and the arm 59, to rock the rock shaft 48 in one direction. Opposite sliding movement of the piston results in rocking of the rock shaft in the opposite direction. As heretofore pointed out rocking of the rock shaft in one direction eflects swinging of the latches 31 into their operative or latched position and reverse rocking of the rock shaft operates to swing the latches into their unlatched position with respect to the studs 4| on the outer ends of the I-beam 36. The cylinderpiston device 53 is controlled by, and forms a part of a fluid pressure system comprising a supply pipe 60 and a 2-way valve 6|. The supply pipe 69 lsconnected to an air compressor or any other suitable source (not shown) of air under pressure. The 2-way valve 6| is located any suitable distance from the cupola and consists of a casing 62 and a rotatable plug 63. The casing has a top port 64, a pair of side ports 65 and 66, and a bottom port 61. The discharge end of the air supply pipe 6ll is connected to the top port 6|. The side port 65 is connected to one end of the cylinder 54 of the cylinder-piston device 53 by a flexible pipe 66 and the side port 66 is connected to the other end of the cylinder by a flexible pipe 69. The bottom port 61 is open to atmosphere and serves as a venting medium. The plug 63 of the 2-way valve 6| embodies a pair of diametrically opposite arcuate ducts 10. Each of these ducts extends through an arc of and is adapted to bridge and establish communication between two adjoining ports in the valve casing 62. When the plug is positioned as shown in Figure 1 one of the ducts 10 effects communication between the

ports

64 and 66 and the other duct effects communication between the ports 65 and 61. This arrangement of the plug results in air under pressure flowing from the air supply pipe 60 into one end of the cylinder 54 via the port 64, the one duct 10 and the pipe 69 and also results in venting of the other end of the cylinder by way of the pipe 68, the port 65, the other duct 19. and the. port 61. The air under pressure entering the one end of the cylinder causes sliding movement of the piston 55 in one direction. When the plug 63 of the valve 6| is turned throughout an arc of 90 from the position shown in Figure 1 one of the ducts 19 bridges and establishes communication between the ports 64 and 65 and the other duct 10 establishes communication between the

ports

66 and 61. In connection with such positioning of the plug air under pressure is delivered from the air supply pipe 60 into the other end of the cylinder via the port 64, the one duct 10, the port 65 and the pipe 68 and the one end of the cylinder is vented by way of the pipe 69, the port 66, the other duct 18 and the port 61. Upon entry of air under pressure into said other end of the cylinder the piston is caused to slide in the opposite direction. As heretofore pointed out sliding movement of the piston in one direction results in swinging of the latches 31 into their latched position and sliding movement of the piston in the opposite direction results in swinging of the latches into their unlatched position wherein they free the

bottom forming doors

21 and 28 so that they swing downwards into their open position.

The power means l6 for swinging the doors constituting the drop bottom |2 upwards into their closed position is in the form of a winch comprising a rotatable drum 1|, a gear unit 12 for turning the drum, and a cable 13. The drum and gear unit are positioned in side by side relation adjacent the central portion of the angle bar 23. The drum extends around and is fixedly secured to a horizontally extending shaft 14, the ends of which are journalled in bearings 15. The latter are connected by way of brackets 16 to a vertically extending plate 11 which is welded or otherwise fixedly secured to the central portion of the vertical flange of the angle bar 23. The gear unit 12 comprises a worm 18 and a worm wheel 19 and these are disposed in a gear box 80. The worm wheel surrounds, and is keyed to one end of, the shaft 14 and is in mesh with, and adapted to be driven by, the worm 18. The latter is mounted on a horizontally extending shaft 8| which is journalled in suitable hearings in the gear box. One end of the shaft projects outwards of the gear box and is provided with a chain wheel 7 22. An endless chain 83 is trained around the chain wheel 82. When the chain is pulled in one direction it operates through the medium of the chain wheel 82, the shaft 8|, the worm 12 and the worm wheel 19 to turn the drum II in one direction. Reverse pulling of the chain results in reverse turning of thedrum. One end of the cable 13 is anchored to, and wound around, the drum and the other end of the cable is provided with a hook 84. When it is desired to use the power means It to swing the

bottom forming doors

21 and 28 upwards into their operative or closed position the hook 84 is hooked onto the central portion of the vertical leg of the angle bar 22. When the hook is so hooked the central portion of the cable underlies the

doors

21 and 2|. bar 22 the drum is turned so as to draw up on the cable. As the cable is drawn up or wound around the drum it operates to swing the doors upwards. Upward thrust resulting from drawing up of the cable is transmitted to the door 21 by a sheave N and is transmitted to the door 21 by way 01' a sheave 86.

The sheave 85 extends vertically, is mounted rotatably on an inverted U- shaped bracket 81, the intermediate part of which fits against, and is connected to, the central portion of the bottom flange 4|! of the I-beam 36. The sheave 86 extends vertically and is mounted rotatably on one end of an elongated bracket 08. The other end of the bracket 88 is connected to the chordal margin of the door 28. The bracket 88 is of such length that when the two

doors

21 and 28 are in their closed position the sheave 86 is disposed at a lower level than the sheave 85. As a result of this the door 28, in connection with a door closing operation, closes slightly ahead of the door 21. As shown in Figure 3, the cehtral portion of the cable 13 is trained around the

sheaves

85 and 86.

After use of the cupola the wheel equipped receptacle 35 is wheeled into place under the drop bottom l2. Thereafter the valve 62 is manipulated so as to cause air under pressure to enter the right hand end of the cylinder 54 as viewed in Figure 1. This results in the piston being shifted to the left and operating through the medium of the piston rod 58, the arm 59, the rock shaft 48. the arms 49, the links 50, the arms BI and the stub shafts 43 to swing the latches 31 into their unlatched position. As soon as the latches are swung into such position the

doors

21 and 28 are released and drop downwards by gravity. In connection with downward swinging of the doors the residual materials in the cupola shell fall into the receptacle 35. When it is desired to close the bottom forming doors the hook 84 on the outer end of the cable 13 is hooked onto the central portion of the angle bar 22 and the central portion of the cable is trained around the

sheaves

85 and 86. After the hook is hooked in place the drum 1| of the winch is turned so as to wind up the cable. In connection with winding up of the cable the doors are caused to swing upwards into their closed position. As soon as the doors reach such position the valve 62 is shifted into its other position in order so to control the cylinder-piston device that the latter operates to swing the latches into their latched position wherein, as previously pointed out, they underlie the studs 4| on the end of the I-beam 36. After the latches are in place the hook 84 is unhooked from the angle bar 22.

The herein described cupola may be manipulated with facility so far as opening and clos- Aiter hooking of the hook onto the angle it includes the latch arrangement I4, the power means it for shifting the latch arrangement into and out of its latched position, and the power means I! for swinging the doors into their closed position.

The invention is not to be understood as restricted to the details set forth since these may be modified within the scope of the appended claims without departing from the spirit and scope of the invention.

Having thus described the invention what I claim as new and desire to secure by Letters Patentis:

1. In a cupola of the type that comprises an elevated shell adapted for use in melting material therein and provided with a horizontal frame-like bottom structure including a bottom hinged to swing upwards'and downwards into and out of a closed position wherein it extends across the lower end of the shell, and a structural element underlying and extending across the bottom and rigidly connected to the latter, the combination of a latch arrangement adapted releasably to hold the bottom in its closed position and embodying a pair of studs connected fixedly to, and projecting outwards from, the ends of the structural element and a pair of latches associated with the studs, respectively, and mounted on the bottom structure so that when the bottom is in its closed position they are capable of being swung about a horizontal axis into and out of a latched position wherein they underlie said studs, and means mounted on the bottom structure and including a horizontal rock shaft for connecting the latches for conjoint swinging movement.-

2. In a cupola of the type that comprises an elevated shell adapted for use in melting material therein and provided with a horizontal frame-like bottom structure including a bottom hinged to swing upwards and downwards into and out of a closed position wherein it extends across the lower end of the shell, and a structural element underlying and extending across the bottom and rigidly connected thereto, a latch arrangement adapted releasably to hold the bottom in its closed position and embodying a pair of studs connected fixedly to and projecting outwards from, the ends of the structural element and a pair of latches associated with the studs, respectively, and mounted on the bottom structure so that when the bottom is in its closed position they are capable of being swung about a horizontal axis into and out of a latched position wherein they underlie said studs, means mounted on the bottom structure and including a horizontal rock shaft for connecting the latches for conjoint swinging movement, and power means mounted on said bottom structure and arranged and adapted to effect rocking of the rock shaft in either direction.

3. In a cupola of the type that comprises an elevated shell adapted for use in melting material therein and provided with a horizontal frame- -like bottom structure including a bottom hinged projecting outwards from, the ends of the structural element and a pair of latches associated with the studs, respectively, and mounted on the bottom structure so that when the bottom is in its closed position they are capable of being swun'g about a horizontal axis into and out of a latched position wherein they underlie said studs, means mounted on the bottom structure and including a horizontal rock shaft for connecting the latches for conjoint swinging movement, and fluid pressure means adapted and arranged to effect rocking of the rock shaft in either direction and including a cylinder-piston device mounted on the bottom structure and operatively connected to said rock shaft.

4. In a cupola of the type that comprises an elevated cylindrical shell adapted for use in melting material and provided with a frame-like bottom structure including a drop bottom in the form of a pair of oppositely disposed, complemental, semi-circular doors hinged to swing upwards and downwards into and out of a closed position wherein they extend across the lower end of the shell, and an elongated structural element underlying and extending across the chordal margin of one of the doors, connected rigidly thereto and adapted to underlie and support the chordal margin of the other door when the two doors are in their closed position, the combination of a latch arrangement adapted releasably to hold the bottom in its closed position and embodying a pair of studs connected fixedly to, and projecting outwards from, the ends of the structural element and a pair of latches associated with the studs, respectively, and mounted on the bottom structure so that when the bottom is in its closed position they are capable of being swung about a horizontal axis into and out of a latched position wherein they underlie said studs, and means on said bottom structure for connecting the latches together for conjoint swinging movement.

5. In a cupola of the type that comprises an elevated cylindrical shell adapted for use in melting material and provided with a frame-like bottom structure including a drop bottom in the form of a pair of oppositely disposed, complemental, semi-circular doors hinged to swing upwards and downwards into and out of a closed position wherein they extend across the lower end of the shell, and an elongated structural element underlying and extending across the chordal margin of one of the doors, connected rigidly thereto and adapted to underlie and support the chordal margin of the other door when the two doors are in their closed position, the combination of a latch arrangement adapted releasably to hold the bottom in its closed position and embodying a pair of studs connected fixedly to, and projecting outwards from, the ends of the structural element and a pair of latches associated with the studs, respectively, and mounted on the bottom structure so that when the bottom is in its closed position they are capable of being swung about a horizontal axis into and out of a latched position wherein they underlie said studs, and means mounted on the bottom structure and including a horizontal rock shaft for connecting the latches for conjoint swinging movement.

6. In a cupola of the type that comprises an elevated cylindrical shell adapted for use in melting material and provided with a frame-like bottom structure including a drop bottom in the form of a pair 01' oppositely disposed, complemental, semi-circular doors hinged to swing upwards and downwards into and out of a closed position wherein they extend across the lower end of the shell, and an elongated structural element underlying and extending across the chordal margin of one of the doors, connected rigidly thereto and adapted to underlie and support the chordal margin of the other door when the two doors are in their closed position, the combination of a latch arrangement adapted releasably to hold the bottom in its closed position and embodying a pair of studs connected fixedly t0, and projecting outwards from, the ends of the structural element and a pair of latches associated with the studs, respectively, and mounted on the bottom structure so that 'when the bottom is in its closed position they are capable of being swung about a horizontal axis into and out of a latched position wherein they underlie said studs, means mounted on the bottom structure and including a horizontal rock shaft for connecting the latches for conjoint swinging movement, and power means mounted on said bottom structure and arranged and adapted to effect rocking of the rock shaft in either direction.

7. In a cupola of the type that comprises an elevated cylindrical shell adapted for use in melting material and provided with a frame-like bottom structure including a drop bottom in the form of a pair of oppositely disposed, complemental, semi-circular doors hinged to swing upwards and downwards into and out of a closed position wherein they extend across the lower end of the shell, and an elongated structural element underlying and extending across the chordal margin of one of the doors, connected rigidly thereto and adapted to underlie and support the chordal margin of the other door when the two doors are in their closed position, the combination of a latch arrangement adapted releasably to hold the bottom in its closed position and embodying a pair of studs connected fixedly to, and projecting outwards from, the ends of the structural element and a pair of latches associated with the studs, respectively, and mounted on the bottom structure so that when the bottom is in its closed position they are capable of being swung about a horizontal axis into and out of a latched position wherein they underlie said studs. means mounted on the bottom structure and including a horizontal rock shaft for connecting the latches for conjoint swinging movement, and fluid pressure means adapted and arranged to effect rocking of the rock shaft in either direction and including a cylinder-piston device mounted on the bottom structure and operatively connected to said rock shalt.

HUGO L. KUEHL'I'HAU.

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

UNITED STATES PATENTS Number Name Date 45,030 Ellis Nov. 15, 1864 1,286,632 Hodge Dec. 3, 1918 1,448,480 Bedell Mar. 13, 1923 1,563,949 -Baker Dec. 1, 1925 1,883,501 Black et a1 Oct. 18, 1932 2,102,823 Walsh Dec. 21, 1! 2,196,789 Dean Apr. 9, 1010 2,429,285 Woolley Oct. 21, 1M!