US3865347A

US3865347A - Apparatus for unloading bulk material

Info

Publication number: US3865347A
Application number: US307445A
Authority: US
Inventors: Hugh H Pase
Original assignee: Mimco Inc
Current assignee: Martin Engineering Co
Priority date: 1972-11-17
Filing date: 1972-11-17
Publication date: 1975-02-11
Anticipated expiration: 1992-02-11

Abstract

A device for mechanically connecting hopper car unloading boots to the discharge outlets on the car for unloading bulk material from the car, in which the lift platform for raising the boots is held level with the car and pressure is exerted evenly on the platform in order to maintain full contact with discharge outlets while the material is being unloaded.

Description

United States Patent Pase APPARATUS FOR UNLOADING BULK MATERIAL 1451 Feb. 11,1975

FOREIGN PATENTS OR APPLICATIONS 2| 1,98l ll/l960 Austria 254/l22 [75] Inventor: Hugh H. Pase, Cheshire, Conn. l,9l2.640 9/1970 Germany 254/122 [73] Assignee: Mimco Incorporated, Meriden. D

Conn. Primary Exammer-Al Lawrence SmIth Assistant Examiner-Robert C. Watson Flledi 171 1972 Attorney, Agent, or Firm-Steward & Steward [2]] Appl. No.: 307,445

[57] ABSTRACT [52] U.S. Cl. 254/124 A device for mechanically connecting hopper car un- [Sl] Int. Cl B66! 3/00 loading boots to the discharge outlets on the car for [58] Field of Search 254/l0 C, 124, 122 unloading bulk material from the car, in which the lift platform for raising the boots is held level with the car [56] References Cited and pressure is exerted evenly on the platform in UNITED STATES PATENTS order to maintain full contact with discharge outlets 2 554 494 5/1951 Hodgin 254/122 is bemg 2920373 l/l960 Knabe 254/l0 C 7 Chims' 5 Drawing Figures 3,112,676 l2/I963 Boulsover 254/122 so. I so IE 1a '9' 12 I8 98 96 97 ,1 l I. 1| ll s2 20* 1 e6 e2 PATENTH] FEB] l 1975 SHEET 10F 4 ll/l/l/Vld m .ro

PFJENTED 186E347 SHEET 20$ 4 FIG.3

PATENTEB FEB! 1 I975 SHEET 30F 4 PATENTED 1 3.865.347

sum a nr 4 1 APPARATUS FOR UNLOADING BULK MATERIAL BACKGROUND OF THE INVENTION The present invention relates to apparatus for unloading bulk, material-carrying cars such as railraod hopper cars and the like, and it relates more particularly to improvements in unloading apparatus of the type shown in my prior US. Pat. No. 3,528,570 granted Sept. I5, 1970, wherein a movable platform is supported on the free ends of lifting arms which are pivoted to a fixed frame at the unloading station. One end of a boot or tubular chute for receiving the material as it flows from the outlet of the car is fastened to the platform, so that when the lifting arms are swung upwardly by a power cylinder the movable platform and boot are raised into engagement with the discharge outlet of the car in order to connect the boot thereto and to hold it in sealing engagement therewith. Such unloading apparatus has saved a great deal of drudgery work required where the boot must be connected to the discharge outlet manually.

However, as in the case of most new products, certain problems have been encountered with unloading apparatus of this type. One of them has been difficulty in preventing the lift platform from tilting to one side or the other as it is raised or lowered. While leveling devices have been provided in order to prevent such tilting, they have not always been satisfactory due to the fact that they are exposed to the dust, grit and the caking of the materials being unloaded, such as cement, which has sometimes prevented them from functioning properly.

An object of the present invention is to provide an improved type of leveling device for unloading apparatus of the kind shown in my above-mentioned patent, which is mechanically simple and which will work properly under the most adverse conditions. Another object of the invention is to equalize the force exerted by the lifting arms, in order to maintain sealing engagement between the movable platform and the discharge outlet of the car being unloaded.

SUMMARY OF THE INVENTION Basically the invention resides in providing a leveling device for the movable platform, which includes relatively rigid members pivotally connected together to form a collapsible parallelogram, said members being arranged in such a way that the movable platform and the fixed frame of the unloader in effect form two parallel sides of the parallelogram, thereby tending to prevent the movable lift platform from tilting with respect to the fixed frame. However, since the forces exerted on the lift platform are not always evenly distributed, as for example when a rigid object is disposed between one side of the lift platform and the discharge opening of the car, preventing that side of the lift platform from moving into full engagement with the discharge opening while the other side is free to move, a strain is placed on the entire construction, including the device for holding the lift platform level as well as the lift platform itself. An important aspect of the present invention, therefore, resides in the provision of a safety device which will harmlessly release the leveling device in the event the lift structure is placed under a tilting stress of sufficient magnitude to cause permanent damage to any part of the structure.

More specifically the invention resides in providing a leveling device which includes members that are separate from the lifting arms and the movable lift platform but are connected thereto in such a way that any forces exerted on the platform tending to tilt it out of parallel with the fixed frame of the unloader are transmitted to the leveling device. The platform and lifting arms can, therefore, be retracted when the platform is lowered into substantially co-planar relationship, while the leveling device remians in a somewhat raised position so that the parallelogram does not collapse when the platform is fully retracted and substantially flush with the fixed portion of the frame. As will be more apparent hereinafter, this arrangement ensures that the leveling device remains effective, in preventing the platform from tilting when it is first raised, as well as when it is fully extended and contacting the discharge opening on the car and at all points intermediate its fully retracted and fully extended positions.

Another important aspect of the invention resides in providing a lifting assembly for a bulk unloading apparatus of this kind in which the force exerted by each of the lifting arms is equalized despite the fact that the power means for raising the lifting arms is located at only one side of the lifting assembly.

DESCRIPTION OF SPECIFIC EMBODIMENT The invention is illustrated in the accompanying drawings wherein FIG. I is a side elevation of a bulk unloading apparatus in which the leveling device of the present invention may be employed and showing the boot-connecting assembly elevated into full engagement with the discharge outlets on the underside of a railroad hopper car;

FIG. 2 is a broken side elevational view of only the lifting and leveling linkage for the unloading apparatus of FIG. 1 shown in its fully retracted position with the lift cylinder and crank arm on one side broken away in order to expose the lifting arm and leveling linkage behind,

FIG. 3 is another view of the lifting and leveling linkage by itself with the lift cylinder removed and looking at the opposite side of the apparatus from that shown in FIGS. I and 2;

FIG. 4 is a partial vertical section on the line 4-4 of FIG. 3 of only one side of the apparatus and showing the leveling linkage;

FIG. 5 is a bottom plan view of the unloader apparatus shown in FIG. 1, but on a larger scale, with one end of the unit broken away and the flexible boots removed; and

FIG. 6 is an exploded view of the complete unloader apparatus, looking down on the frame and elevating mechanism with the boot-connecting assembly tilted back and with the boots removed in order to expose the construction.

As in the case of the unloader shown in my prior Pat. No. 3,528,570, the present apparatus is designed for use in unloading railroad hopper cars, but the invention is not limited to such use. The unit consists essentially of a lift platform or boot-connecting assembly 10, which is raised from a retracted position between the rails of a railroad track 12 and substantially flush therewith, to an extended position above the track for connecting the upper ends of a pair of unloading boots I4, l4 with a pair of discharge outlets 16, 16 (FIG. I) at the bottom of the hopper of a railroad car (not shown). The boot-connecting assembly is supported on the free ends of two pairs of oppositely disposed lifting-arms l8, l8 and 18', 18', respectively, which are pivotally mounted on a fixed frame 20 between the rails of track l2. Lifting-arms l8, 18 are pivoted adjacent one of the rails and extend inwardly toward the opposite pair of lifting-arms 18, 18', which are pivoted adjacent the other rail so that they extend inwardly toward arms l8, 18.

A power cylinder 22, having a piston rod 23, is hinged at its opposite ends to a pair of crank-arms 24, 24', one of which is rigidly connected to one pair of lifting-arms l8, l8 and the other to the opposite pair of lifting-arms l8, 18'. Extension of power cylinder 22 causes the lifting-arms to pivot upward lifting bootconnecting assembly 10, while retraction of power cylinder 22 permits the lifting-arms to pivot downward lowering the boot-connecting assembly, in substantially the same manner as the unloader shown and described in my aforementioned patent.

The boot-connecting assembly 10 consists in this instance of a platform or H-frame 26 having two

parallel channel members

28, 28 rigidly connected at their centers, by a cross-piece 30, which is formed of upper and lower plates 31, 31' (FIG. 4) spaced vertically from each other and welded at both ends to the inner sides of

channels

28, 28. A pair of rectangular, hollow coupling frames 32, 32' are slidable supported on H-frame 26 for movement transversely of track 12. The upper surfaces of coupling frame 32, 32' are lined with thick sponge rubber gaskets 34 for sealing the connection between the coupling frames 32, 32' and the flanges surrounding the discharge outlets 16 of the hopper car. The upper end of each boot l4, 14 is fastened to the lower edge of a flange 36, 36' on the underside of each coupling frame 32, 32'. The lower ends of boots l4, 14 are suitably clamped to the openings in the receptacle (not shown) for the material.

As in my prior design, the two coupling frames 32, 32' are provided with means for spreading them apart after the boot-connecting assembly 10 has been raised above the track [2 by lift arms l8, 18'. A simplified system for doing this has been devised in order to save expense and to make it possible to position both frames 32, 32' manually simply by moving one or the other into alignment with the discharge opening on either side of the car to be unloaded. To this end, a spreader bar 38 (FIGS. and 6) is pivoted at its center on a pivot pin 40 within the space between the two center plates 31, 31' of H-frame 26, and a link 42, 42' pivoted at each end of spreader bar 38 connects each of the coupling frames 32, 32' to said spreader bar and therefore to each other, such that movement of one is accompanied by an equal movement of the other in the opposite direction.

Links 42, 42' extend from spreader bar 38 in opposite directions and are provided at their free ends with fixed pins 44, 44', each of which as shown in FIG. 6 extends both above and below its corresponding link. The upper end of each pin 44, 44' is trapped between two tabs or stops 46 and 48 welded to the underside of each coupling frame 32, 32', so that the frames must move with pivotal movement of spreader bar 38 or when either of them is moved manually. The lower ends of

pins

44, 44 are received between a pair of guide rails 50, 50' in slides 52, 52', each welded on the inside of the

adjacent channel

28, 28 and extending outwardly from the cross piece of the H-frame 26.

If desired, an air cylinder 54 may be provided to spread the coupling frames 32, 32' when the lift platform 10 is raised and to draw them together when it is retracted between the tracks 12. Spreader cylinder 54 is bolted to one of the channels 28 with its piston rod 55 connected to the spreader assembly by means of the upper end of pin 44 on link 42, pin 44 extending upward through a hole in a bracket at the end of piston rod 55 so that it is disposed between

stops

46 and 48 on the underside of coupling frame 32. Inverted channels 56 (FIG. 6), 56' are also welded to the underside of the coupling frames 32, 32' adjacent their respective funnel portions 36, 36'. Each of channels 56, 56' is wider than the

channels

28, 28 of H-frame 26 and is disposed on its coupling frame 32 or 32' so that it fits over one of the channels 28 when the coupling frame is in place, thereby limiting the coupling frames to movement perpendicular to the track 12.

The fixed frame 20 of the present unloading apparataus consists of a pair of

parallel stringers

60, 60, formed from heavy angle iron, the adjacent ends which are connected by fixed journal rods 62, 62'.

Stringers

60, 60 are long enough to span the distance between the rails of track 12 so that the ends 64 of the stringers rest on the base flanges of the rails. Since space, or more especially vertical clearance, is a primary consideration in connection with unloader installations, the ends 64 of each of

stringers

60, 60 outward of the rods 62, 62' are sloped upward on their undersides in order to lower the frame 20 as much as possible and at the same time provide surface-to-surface contact with both rails 12 on which they rest. To accomplish this, each end 64 is cut back a short distance. along the apex of its angle, so that the horizontal flange can be bent upward at about a 15 angle. The lower corner of the vertical flange is also cut at the same angle and then welded to the horizontal flange, forming upwardly inclined mounting surfaces 65 on the lower edges of the stringers at both ends. With the ends 64 of

stringers

60, 60 resting on the base flange of the track rails 12, the slope on the mounting surfaces 65 lets the unloader unit as a whole sit somewhat lower between the rails without interfering with the bed of the track or requiring any special support for the unloader other than the track itself. Furthermore, the slope of the mounting surfaces 65 is made to correspond with the outward slope of the track flange, so that the surfaces 65 rest flush on the track flange, thereby facilitating movement of the unloader longitudinally of the track when it is necesary to align it with the outlet of the car.

In the elevating mechanism at one end of the unit, the lifting arms l8, 18' are rigidly mounted, as by welding, at the opposite ends of a torque tube 66' (FIG. 5), through which fits a pivot tube 68' rotatably supported on journal rod 62'. For a reason which will become more apparent hereinafter, torque tube 66 is rigidly fastened, as by welding, to pivot tube 68' only at one point 70' midway between lifting arms l8, l8. Pivot tube 68', which is longer than torque tube 66, extends outward beyond both ends thereof and is held against movement longitudinally of pivot rod 62' by

bushings

72, 72, which are interposed between each of its ends and the vertical flange of the adjacent stringer 60.

Assembly bolts

74, 74 extend through

stringers

60, 60 and are threaded into each end of journal rod 62' for rigidly securing the

stringers

60, 60 thereto.

Referring to FIGS. 1 and 2, the crank-

arms

24, 24 at opposite ends of the unit, by which lift cylinder 22 raises lifting arms l8, 18' in a manner similar to that shown in my prior Pat. No. 3,528,570, are each welded to one end of the corresponding pivot tube 68, 68'. Each crank-arm has a hinge 76, 76' pivotally connecting it to lift cylinder 22 by means of hinge pins 78 and 80. In this instance, hinge 76 consists of a pair of

parallel side plates

82, 82, disposed on opposite sides of crankarm 24. intermediate hinge pins 78 and 80 and between

plates

82, 82 is mounted a cylindrical abutment 84 on a bolt 86 extending through both

side plates

82, 82. Bolt 86 holds the side plates rigidly together against spacers on hinge pins 78 and 80 in order to allow the hinge 76 to pivot freely about both hinge pins.

Crank-arm 24 extends inward from its pivot tube 68 in generally the same direction as lifting

arms

18, 18 and is provided at its inner end with a C-shaped bracket 88, within which the abutment 84 on hinge 76 is disposed for limiting pivotal movement of the hinge about hinge pins 78 and 80. Consequently, when the elevating mechanism is completely retracted, hinge 76 is pivoted to its full-line position shown in FIG. 2 with its abut ment 84 engaging the lower flange of bracket 88. Upon extension of lift cylinder 22, hinge 76 pivots upward about its hinge-pin 80 until abutment 84 engages the underside of the upper flange of bracket 88, as shown in broken lines in FIG. 2. This provides the same action that is achieved in the unloader shown in my prior patent, whereby the lift cylinder elevates itself from a re tracted position between the rails 12 to a raised position where it has the required mechanical advantage to pivot the lifting arms l8, l8 upward in order to elevate the boot-connecting assembly 10 into engagement with the discharge outlets l6, 16 of the hopper car.

It will be noted that the elevating mechanism at the both sides of the track correspond exactly, each having a

torque tube

66, 66 on which the lifting arms l8, 18' are rigidly mounted, and a pivot tube 68, 68' rigidiy connected to its torque tube 66, 66' at the center 70, 70' as well as a hinge 76, 76' by which its crankarm 24, 24' is connected to the power cylinder 22. it will also be noted that upon expansion of lift cylinder 22, both hinges 76, 76 pivot upward until their central abutments 84, 84' engage the upper flange of the

respective brackets

88, 88 on crank-arms 24, 24'. At this point, the force exerted by cylinder 22 is transmitted to crank-arms 24, 24' to pivot lifting

arms

18, 18 and l8, l8 upward.

in order to prevent leakage around the gaskets 34 as the material in the hopper car is being unloaded, it is necessary that the lifting arms each exert substantially equal pressure against the underside of the assembly. A rather expensive way of ensuring that equal pressure is applied on both sides of the assembly is to provide a second power cylinder on the opposite side of the assembly 10 from the cylinder 22 shown in FIG. 5. However, in order to avoid a costly expedient such as this, the present lifting assembly is designed so that even though the single cylinder 22 is mounted on one side of the unit, the force exerted by it is distributed evenly on both sides. Such equal distribution of force is achieved by connecting the pivot tubes 68 and 68' at the centers 70, 70' of torque tubes 66 and 66', respectively, so that the torque transmitted by pivot tube 66 from crank arm 24 is applied to the torque tube 68 at a point equidistant from each of lifting arms l8, 18, while the torque transmitted by pivot tube 66' is applied to torque tube 68' at a point equidistant from each of lifting arms l8, 18'. Therefore, exactly the same force is exerted on each of the arms at each side of the unloader, as if the cylinder itself were mounted midway between the two lifting arms in each pair. On the other hand, the forces on the opposing lifting arms at opposite ends of the lift cylinder are necessarily explained because the cylinder is mounted between them and exerts equal forces of action and re-action on them in opposite directions, as in the unloader of my prior patent.

The free end of each of the four lifting arms l8, 18' is provided with a roller on the inner side of each arm. Rollers 90 ride within the

channels

28, 28 of the H-frame 26 in boot-connecting assembly 10. As best shown in FIG. 4,

channels

28, 28 are C-shaped in crosssection and are disposed so that they open outwardly to receive the rollers 90 of the lifting arms. When lifting arms 18, 18' are pivoted upward upon extension of lift cyiinder 22, their outer ends move lengthwise of

channels

28, 28, and as will be more apparent hereinafter, means similar to that shown in my prior patent are provided for keeping the boot-connecting assembly 10 as a unit centered between the rails of track 12. In addition, it is also necessary to provide means for preventing the boot-connecting assembly 10 from tilting transversely of track 12 when more resistance to lifting the assembly is encountered by the two sets of lifting arms l8, 18 or l8, 18' at one end of the unit that at the other.

One of the most important aspects of the present unloader is the development of a mechanically simpler leveling system for preventing such tilting than the one employed in my prior design. The concept underlying the present leveling system is the use of the well known principle of a parallelogram. in this instance the platform for the boot-connecting assembly and the fixed frame of the unloader in effect form two of the parallel sides of a parallelogram. However, it is essential in unloading apparatus of this kind for the platform or H- frame 26 to lie in its retracted position in the same plane with the fixed frame 20, so that the coupling frames 32 and gaskets 34 do not project above the top of the rails 12. Consequently, if the H-frame 26 itself is used as one of the parallel sides of the figure, there is a considerable distance through which the lift platform must be raised before the parallelogram can effectively prevent it from tilting to one end or the other. Such undesired tilting action results from the fact that the parallelogram thus formed is completely collapsed when the lift platform is retracted with all members of the parallelogram lying in the same plane. In that condition, if the platform 26 were part of the parallelogram, any looseness of the joints of the elevating mechanism would permit the platform to tilt to one end or the other as it starts to rise and then to snap up violently to a horizontal position. Erratic movement of this kind is unacceptable, not only because it is dangerous, but also because it causes excessive wear of the parts and can permanently damage them.

in order to overcome this difficulty, a system of links, indicated generally at 91 (FIGS. 2 and 3), is provided in order to form a parallelogram even when the lift platform is completely retracted. The leveling linkage 91 is separate from the lift platform of the unloader in the sense that the platform itself does not form a part of the parallelogram relied upon for leveling purposes. However, linkage 91 is so closely coordinated with the lift platform that any movement thereof is simultaneously followed by a corresponding movement in the leveling linkage. To this end, leveling linkage 91 consists of a pair of parallel torque links 92, 92' pivotally mounted in spaced relationship to each other along one of the stringers 60 of the fixed frame 20. One of the links 92 is rigidly mounted on the end of pivot tube 68' of the lifting assembly opposite the crank arm 24', and the other torque link 92 is pivotally mounted on a pivot pin 94 located on stringer 60 approximately one-third of the distance from pivot rod 62 to the opposite pivot rod 62.

Torque links 92, 92' are relatively short so that when they are vertical they do not project substantially above the upper rolling surface of the track 12. Link 92 is also disposed at a fixed angle with respect to the two parallel lifting arms 18', 18', such that when all the lifting

arms

18, 18 are pivoted down to their retracted position parallel with

stringers

60, 60 as shown in FIG. 2, torque link 92 extends upward at about a 20 angle to

stringers

60, 60. A tie-bar 96 is pivotally connected to the free ends of links 92 and 92' at 97 and 98, respectively, such that the distance between the pivot points 97 and 98 is equal to the distance between the pivot pin 94 and pivot rod 62', the distance from pivot point 97 to pivot rod 62' being also equal to the distance from pivot point 98 to pivot pin 94.

Mounted integrally with torque link 92, so that it pivots therewith on pivot pin 94, is a leveling arm 100, which is the same length as and parallel to, the adjacent lifting arm 18'. Since leveling arm 100 remains at a fixed angle relative to torque link 92' and lifting arm 18' is fixed with respect to link 92, the upper or free ends of

arms

18 and 100 are held by linkage 91 in a line that is always parallel to the frame 20. Consequently, the H-frame 26 likewise remains parallel to the frame 20. The free end of leveling arm 100 is provided with a roller 900, which rolls within the C-channel 28 of the H-frame 26 similar to the rollers 90 on lifting arms 18, 18'.

lt will be apparent from the foregoing that the bootconnecting assembly is positively held parallel to the fixed frame by the leveling linkage 91, which forms a parallelogram at all times, due to the fact that torque links 92, 92' are disposed at an angle to the arms 18' and 100, respectively, such that tie-rod 96 is held in an elevated position when the lifting arms 18 are completely retracted. Furthermore, when the lifting arms are fully raised upward as far as they will go, links 92, 92' will be nearly perpendicular to tie-bar 96 where the leveling linkage 91 is most effective in maintaining the boot-connecting assembly parallel with the frame 10, thereby providing the greatest resistance to anything tending to prevent the gaskets 34, 34' on the coupling frames 32, 32' from being urged into full engagement with the outlets on the car.

It will also be appreciated that despite the fact that the surface of the leveling linkage 91 is to keep the boot-connecting assembly parallel to the road bed, normal tolerances and resilience of the working parts of the apparatus permits the lift platform to be forced far enough out of parallel to maintain full contact with a car that may be tilting relative to the track, as for example on a banked section of the road bed.

However, in order to prevent permanent damage to any of the parts of the apparatus due to excess pressure which, for example, may be exerted by the lift cylinder 22 when the bootconnecting platform is held at one end against being raised, while being free to move up ward at the other end, it is desirable to provide a safety release against excess bending of the structure. Such a release is readily achieved in the present design simply by providing means for releasing the parallelogram of the leveling linkage 91 at one end of the tie-bar 96. As best seen in FIG. 5, tie-bar 96 is made up of two

parallel bars

102, 102 which straddle the torque links 92, 92'. The pivotal connection 98 between tie-bar 96 and torque link 92' consists of a clevis pin which passes through both

bars

102, 102 as well as link 92' and is held in place by means of a cotter pin. The opposite ends of

bars

102, 102 are resiliently held together by a spring assembly consisting of a bolt 104, which extends freely through both

bars

102, 102 with one end projecting laterally beyond one of the bars 102. A coil spring 106 is placed on the other end of bolt 104 and held in place by a nut, which may be turned down on bolt 104 in order to increase the pressure exerted by spring 106 on the adjacent bar 102.

Tie-bar 96 is pivotally connected to torque link 92 at 97 by means of a pair of inwardly projecting tapered

studs

108, 108, one of studs 108 being mounted on the facing side of each of the

bars

102, 102.

Studs

108, 108 are normally held within outwardly facing sockets in the opposite ends of a bushing 110 in the outer end of torque link 92, the sockets in bushing 110 into which

studs

108, 108 fit being desirably tapered to correspond to the taper of the studs. it will be apparent that upon exertion of a force on tie-bar 96 sufficient to spread

bars

102, 102 apart against the pressure of spring 106, due to the camming action of tapered

studs

108, 108 on bushing 110,

studs

108, 108 will be forced out of their sockets, thereby breaking or releasing the parallelogram and permitting the lift platform of the unloader to drop to one side under the pressure distorting it in that direction. When this occurs, the cause of the difficulty must be determined. This may be, for example, a heavy object resting on one side of the lift platform preventing it from lifting up on that side when the lift cylinder is operated. With the cause of the trouble corrected, the tie-bar 96 may be readily reconnected to the torque link 92 and the unloader again operated normally.

It should be noted that a centering link 112 is pivotally connected atone end to the mid-portion of leveling arm 100 and at its other end to the H-frame 26 of the lift-platform or boot-connecting assembly 10. Centering link 112 simply prevents the lift-platform from moving transversely of the railroad track 12 on the rollers 90 of lifting arms 18, 18' and could, if desired, be mounted on any of the lifting arms, as in the apparatus shown in my prior Pat. No. 3,528,570.

Power cylinder 22 is a doubleacting, hydraulically damped pneumatic cylinder having air supply lines 115 and 116 (FIG. 6) connected to a control valve 118 mounted at a suitable control station adjacent the unloading station. Air under pressure is supplied to control valve 118 from a suitable source (not shown) through a supply line 120. Control valve 118 can be operated to furnish air under pressure to either end of cylinder 22 while exhausting the opposite end, thereby raising and lowering the lift-platform.

I claim:

i. In a lifting assembly having a fixed frame defining a plane, at least one pair of oppositely disposed lifting arms of equal length, each of said arms being pivotally mounted at one end to said fixed frame and having a free end, a movable platform supported on the free ends of said lifting arms and movable thereby from a position substantially within said plane to an elevated position above said plane, and a power cylinder operatively connected at one end to one of said lifting arms and at its other end to the opposite one of said lifting arms for pivoting said lifting arms in opposite directions upon actuation of said power cylinder,

leveling means for equalizing the pivotal movement of each of said lifting arms comprising in combina tion therewith,

at least one leveling arm disposed parallel to one of said lifting arms and pivoted to said fixed frame, said leveling arm being equal in length to said one lifting arm and having a free end in sliding engagement with said movable platform,

a first torque link rigidly connected to said one lifting arm at a fixed angle thereto for pivotal movement therewith. a second torque link rigidly connected to said leveling arm at a fixed angle thereto equal to said firstmentioned angle for pivotal movement with said leveling arm, and

a tie-bar pivotally connected to said torque links parallel to said fixed frame, such that said tie-bar, torque links and fixed frame form a parallelogram,

said angles between said torque links and their respective arms being such that when said lifting and leveling arms are disposed substantially within said plane of said fixed frame, said links extend outward of said plane.

2. The combination defined in claim 1, which further includes means for releasing said parallelogram when a predetermined force is exerted on said movable platform tending to tilt it relative to said plane,

3. The combination defined in claim 2, wherein said means for releasing said parallelogram comprises a spring-loaded pivotal connection between said tie-bar and one of said torque links.

4. The combination defined in claim 3, wherein said pivotal connection comprises a tapered stud on one of said tie-bar member and torque-link member and extending laterally thereof, a socket in the other of said members within which said stud is received and spring means for urging said stud into said socket, whereby an excessive force exerted longitudinally between said members results in a lateral force sufficient to force said stud out of said socket due to the camming action of said tapered stud in said socket.

5. in a lifting device having a pair of parallel lifting arms pivotally mounted on a common axis in spaced relation to each other in order to provide open access between them and having power means for raising both of said lifting arms simultaneously by exerting power at a single point along said axis that is closer to one of said lifting arms than the other,

drive means for transmitting such power from said power means along said axis to said lifting arms comprising in combination therewith,

an elongated pivot member journalled for pivotal movement about said axis and driven by said power means. and

a torque tube co-axially supported on said pivot member for pivotal movement therewith, said lifting arms being fixed to said torque tube for pivotal movement therewith,

said torque tube being rigidly fastened to said pivot member only at the midpoint between said lifting arms in order to distribute the force exerted by said power means equally to said lifting arms.

6. The combination defined in claim 5, wherein said pivot member is disposed within, and supports, said torque tube along its entire length. said pivot member being pivotally supported at both ends and having a crank-arm extending laterally therefrom adjacent one end, said power means comprising a power cylinder operatively connected at one end to said crank-arm.

7. The combination defined in claim 6, in which said lifting device includes a second pair of parallel lifting arms disposed opposite said first pair and pivotally mounted on a second axis in correspondingly spaced relation to each other in order to maintain open access between said lifting arms,

said second pair of lifting arms having drive means corresponding to that for said first-mentioned pair of lifting arms and including a second pivot member rigidly connected to a second torque tube at the mid-point between its lifting arms, said second pivot member having a crank-arm disposed opposite said first-mentioned crank-arm with the opposite end of said power cylinder connected thereto, such that upon extension of said power cylinder pressure is exerted by said cylinder on said crankarms in equal and opposite directions,

the power applied to said pivot-members by said cylinder being transferred to said lifting arms through the mid-points of said torque tubes, thereby ensuring equal lifting effort by each of said lifting arms.

i IF I I I?

Claims

1. In a lifting assembly having a fixed frame defining a plane, at least one pair of oppositely disposed lifting arms of equal length, each of said arms being pivotally mounted at one end to said fixed frame and having a free end, a movable platform supported on the free ends of said lifting arms and movable thereby from a position substantially within said plane to an elevated position above said plane, and a power cylinder operatively connected at one end to one of said lifting arms and at its other end to the opposite one of said lifting arms for pivoting said lifting arms in opposite directions upon actuation of said power cylinder, leveling means for equalizing the pivotal movement of each of said lifting arms comprising in combination therewith, at least one leveling arm disposed parallel to one of said lifting arms and pivoted to said fixed frame, said leveling arm being equal in length to said one lifting arm and having a free end in sliding engagement with said movable platform, a first torque link rigidly connected to said one lifting arm at a fixed angle thereto for pivotal movement therewith, a second torque link rigidly connected to said leveling arm at a fixed angle thereto equal to said firstmentioned angle for pivotal movement with said leveling arm, and a tie-bar pivotally connected to said torque links parallel to said fixed frame, such that said tie-bar, torque links and fixed frame form a parallelogram, said angles between said torque links and their respective arms being such that when said lifting and leveling arms are disposed substantially within said plane of said fixed frame, said links extend outward of said plane.

2. The combination defined in claim 1, which further includes means for releasing said parallelogram when a predetermined force is exerted on said movable platform tending to tilt it relative to said plane.

5. In a lifting device having a pair of parallel lifting arms pivotally mounted on a common axis in spAced relation to each other in order to provide open access between them and having power means for raising both of said lifting arms simultaneously by exerting power at a single point along said axis that is closer to one of said lifting arms than the other, drive means for transmitting such power from said power means along said axis to said lifting arms comprising in combination therewith, an elongated pivot member journalled for pivotal movement about said axis and driven by said power means, and a torque tube co-axially supported on said pivot member for pivotal movement therewith, said lifting arms being fixed to said torque tube for pivotal movement therewith, said torque tube being rigidly fastened to said pivot member only at the mid-point between said lifting arms in order to distribute the force exerted by said power means equally to said lifting arms.

6. The combination defined in claim 5, wherein said pivot member is disposed within, and supports, said torque tube along its entire length, said pivot member being pivotally supported at both ends and having a crank-arm extending laterally therefrom adjacent one end, said power means comprising a power cylinder operatively connected at one end to said crank-arm.

7. The combination defined in claim 6, in which said lifting device includes a second pair of parallel lifting arms disposed opposite said first pair and pivotally mounted on a second axis in correspondingly spaced relation to each other in order to maintain open access between said lifting arms, said second pair of lifting arms having drive means corresponding to that for said first-mentioned pair of lifting arms and including a second pivot member rigidly connected to a second torque tube at the mid-point between its lifting arms, said second pivot member having a crank-arm disposed opposite said first-mentioned crank-arm with the opposite end of said power cylinder connected thereto, such that upon extension of said power cylinder pressure is exerted by said cylinder on said crank-arms in equal and opposite directions, the power applied to said pivot-members by said cylinder being transferred to said lifting arms through the mid-points of said torque tubes, thereby ensuring equal lifting effort by each of said lifting arms.