US3474921A - Lift tailgate - Google Patents

Description

A. S. ROSSONI LIFT TAILGATE Oct. 28, 1969 4 Sheets-Sheet 1 Filed Nov. 30, 1966 INVENTOR. ANGELO S. ROSSON I Oct. 28, 1969 A. s. Rossom 3,474,921

LIFT TAILGATE Filed Nov. 30, 1966 4 Sheets-Sheet 2 INVENTORQ ANGELO S. ROSSONI Mf/QM ATTORNEY- Oct. 28, 1969 A. s. ossoNl 3,474,921

LIFT TAILGATE Filed NOV. 30, 1966 4 Sheets-Sheet 5 3 ANGELO s w s Nl BY ma W ATToRii Oct. 28, 1969 I A. s. 'ROSSONI f I 3,474,921

LIFT 'IIAILGATE 4 sheets sheet 4 Filed m 30, 1966 INVENTOR. ANGELO S. R OSSONI BY m w United States Patent a corporation of Indiana Filed Nov. 30, 1966, Ser. No. 597,985

Int. Cl. B601) 1/48 U.S. Cl. 214-77 11 Claims ABSTRACT OF THE DISCLOSURE This disclosure relates to lift tailgates for use on self loading vehicles and more particularly to the parallel linkage system for lifting and closing the gate. In this disclosure the tension arms each comprise two segments pivotally connected with a power cylinder connected to the outer tension arm segments to pivot the same and thus move the lift gate to a position closing the end of the vehicle. Each compression arm of the disclosure includes closely spaced arm segments with a lift cylinder disposed therebetween to effect movement of the lift gate from the ground engaging position to a position coplanar with the vehicle bed.

Various load elevating devices have been provided to assist in loading vehicles. Many prior art devices for this purpose include a movable, horizontal platform mounted on the vehicle, which platform is powered to carry the load from the ground or a loading dock to the level of the vehicle bed. Heavy objects are usually hand trucked onto the platform in its lowered position, lifted and then trucked onto the vehicle bed.

It is important that the platform in such a device remain relatively level during its use. Since devices of this type are subjected to repeated loading, prior known devices often sag or the parts thereof become fatigued to the extent that they must be reconstructed to be completely operative.

It is also desirable that the platform in such devices be capable of folding to a position covering the end of the vehicle bed. Not only does this provide a double use for the platform or gate, thus obviating the need for other closures for the vehicle bed, but the projection of the platform from the end of the vehicle creates an unnecessary and unsightly obstruction.

Previous attempts to provide such a gate have usually resulted in complicated and expensive structure which may not be rugged enough to withstand the hard usage required of a device of this type. For instance, most prior art structures now provide one or more cross members extending transversely between and connecting the compression arms of the two parallel linkage systems. A power cylinder is usually mounted to the vehicle and has one end connected to the cross member to effect lifting of the platform. When the compression arms are spaced relatively close together, the cross member need only be small in cross section to withstand the bending stresses imposed by the lifting cylinder; however, the overhang of the platform (that portion extending beyond and to the side of the arm connections) necessarily becomes great. Unequal loading of the platform, particularly on the overhang portion, causes twisting of the linkage mechanism resulting in early failures.

When the compression arms are spaced far apart to reduce the overhang, the bending stresses in the cross member rapidly increase. Accordingly, to be strong enough to withstand heavy loading, the cross member necessarily becomes massive in cross section. Furthermore, when the gate is moved to its closed, traveling position the cross member (when disposed anywhere but outwardly ad- Patented Oct. 28, 1969 jacent the platform where the power cylinder connected thereto then interferes) interferes with desirable outer support for the vehicle bed as well as a trailer hitch or other hardware normally used on vehicles.

To eflect pivoting of the platform to a position closing the end of the vehicle bed, some prior art devices have used power cylinders in the compression arms (it being recognized that the platform is usually too heavy to be closed manually). However, the power cylinder becomes extended when the platform is in its closed position exposing the highly polished piston rods to the road grit and dirt thrown up by the vehicle wheels. This, of course, results in early leaking of the power cylinders.

-It is an object of this invention to provide power cylinders for lifting and closing a lift tailgate which cylinders are substantially closed when the vehicle is traveling and thus not subjecting the piston rods to road dirt, etc.

Another object of this invention is to provide a stable, durable parallel linkage and power lifting and closing structure for a lift tailgate.

A further object of this invention is to eliminate the massive cross member so commonly used for effecting power lifting of a platform.

Still another object of this invention is to provide compression arms incorporating power cylinders for lifting the platform, the structure being such that the power cylinders are protected from damage.

A still further object of this invention is to provide tension arms incorporating power cylinders for closing the gate, the structure being such that the power cylinders are protected from damage.

It is also an object of this invention to provide a powered parallel linkage structure wherein the platform may be closed (or tilted) at any intermediate lift position.

In one preferred embodiment of this invention, a vehicle lift tailgate is provided and comprises a pair of spaced parallel acting linkages pivoted at one end to a mounting means provided on the vehicle and adapted to swing through generally vertical arcs. A horizontal platform extends between and is connected at one edge by pivots to the other end of the pair of parallel acting linkages so that the platform is swung from a grounded position spaced below the bed of the vehicle to a position coplanar with and adjacent the loading end of the vehicle bed. Each of the pair of the parallel linkages comprises a compression arm arrangement and a tension arm arrangement. The tension arm arrangement includes two segments pivotally interconnected with a power cylinder positioned to effect folding of the tension arm segments about their pivotal interconnection to move the platform to a vertical position closing the loading end of the vehicle. In another preferred embodiment the compression arm means includes a power cylinder connected to the arm to effect lifting and lowering of the platform without the need of the common linkage cross member.

Other objects and advantages of this invention will become apparent from the following detailed description when taken in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view of the lift tailgate in its lowered ground engaging position;

FIG. 2 is an enlarged front elevation view of one of the two parallel acting linkage systems and its related hydraulic valve mechanism;

FIG. 3 is an exploded perspective view of the parallel linkage system shown in FIG. 2; and

FIG. 4 is an enlarged perspective view of the lift tailgate in its position closing the end of the vehicle bed.

Referring now more particularly to FIG. 1, a lift tailgate generally designated at 10 is movably secured under the rear of a vehicle bed 12 by a pair of parallel acting linkage systems 14 and 16. While this invention is shown connected to a particular vehicle, it is apparent that this invention may be used with a variety of vehicles and may be mounted thereto in many different ways. However, the vehicle with which this invention is used usually comprises the vehicle bed 12 which is supported on longitudinal extending frame members 18 and 20. The longitudinal frame members are suitably interconnected with cross members (not shown) and the vehicle wheels (not shown) are suitably attached to the vehicle frame through the conventional spring mechanism in a manner well known in the art.

The longitudinal frame members 18 and 20 have downwardly extending brackets 22 and 24 suitably secured thereto as by welds and such brackets have downwardly extending legs apertured to accommodate a large cylindrical torque tube 26 which thus extends transversely of the vehicle under the rear of the bed 12 thereof and is welded to the brackets. The brackets 22 and 24 and torque tube 26 serve as a means for mounting the remainder of the lift tailgate to the vehicle.

The vehicle bed 12 is open at the rear so that a platform (designated generally at 28) when in its lowered position as shown in FIG. 1 may receive the article to be lifted. The platform is then raised to a position coplanar with and adjacent the vehicle bed. From this position the article may then be moved onto the vehicle bed 12 and the lift tailgate 10 pivoted to the position shown in FIG. 4 wherein it forms a closure for the rear of the vehicle bed.

In order to mount the platform 28 for this specialized horizontal and vertical pivotal movement, the pair of parallel linkage systems 14 and 16 are each mounted at one end to the torque tube 26 and at the other end to the platform 28. More particularly, each parallel linkage system, as shown in FIG. 2, consists of a tension arm means 30 and a compression arm means 32.

The tension arm means 30, as most clearly shown in FIG. 3, includes an inner segment 34 and an outer segment 36. The inner segment 34 is elongated and of generally boxlike configuration. A pair of spaced triangular shaped lugs 38 extend outwardly and upwardly from each end of torque tube 26 and are provided with apertures in their outer portions. The inner end of segment 34 is positioned between the spaced lugs 38 and an aperture therein is aligned with the apertures in the lugs 38 and a suitable bolt 40 extends through the apertures in the lugs 38 and the segment 34 to pivotally mount the segment to the torque tube 26. The outer end of segment 34 is bifurcated to form cars 42. The outer segment 36 is a slender member and is positioned between the ears 42 so that an aperture adjacent the upper portion of the segment 36 is aligned with apertures provided in the ears 42. A bolt 44 extends through the aligned apertures in the ears 42 and the segment 36 so as to pivotally secure the segment 36 to the segment 34.

Integral with the segment 34 and extending downwardly therefrom (see FIG. 4) is a rectangular stop member 46. A stop bolt 48 is adjustably positioned in the stop member 46 through its threaded connection there with and is adapted to be engaged by the inner surface of segment 36 to limit counter-clockwise pivotal movement of the segment 36 about its pivotal connection at bolt 44. The outer end of segment 36 is curved upwardly and has an aperture extending therethrough.

A pair of spaced U-shaped constructions 50 (see FIG- URE 4) are provided underneath the inner edge of the platform 28 and each comprises side walls 52, 54 and 56 all formed integral with or welded to a base wall 58 and the under surface of the platfrom. The U-shaped constructions 50 are provided to connect the parallel linkage systems to the platform and to this end, the outer end of segment 36 has its outermost aperture aligned with apertures in the outermost portions of side walls 52 and 54. A bolt 60 extends through the aligned apertures and serves to pivotally mount the segment 36 to the platform 28.

Integrally formed on the upper surfaces of segments 34 and 36 are a pair of upstanding lugs 62 and 64 respectively. The lug 64 is suitably apertured and is received between a pair of spaced ears 66 of a U-shaped member 68. The ears 66 are provided with apertures which are aligned with the aperture in the lug 64 and a bolt 70 extends through the aligned apertures to provide a pivotal connection between the segment 36 and a piston rod 72 which is adjustably secured through a threaded connection to the base of the U-shaped member 68. The piston rod 72 extends within power cylinder 74 and is secured to a piston (not shown) which is adapted for reciprocal movement within the cylinder.

The other end of the cylinder is provided with a pair of projecting ears 76 which receive the lug 62 and are secured thereto for pivotal movement by means of a bolt 78 which extends through apertures in the ears 76 and the lug 62. Power fluid is introduced and withdrawn from opposite sides of the piston by hoses 80 which are connected to each end of the power cylinder 74. The hoses extend to a valve housing 82 which is secured to a valve mounting bracket 84 fixedly positioned on the torque tube 26 approximately midway of the ends thereof. The valve housing 82 is also connected through appropriate hosing to a source of power fluid (not shown).

Accordingly, if it is desired to pivot the platform 28 vertically to the position shown in FIG. 4, after the platform has been moved to a position coplanar with the vehicle bed, the actuating handle or lever 86 provided on the outer end of a control bar 88 is pivoted. The control bar 88 is mounted in spaced brackets 90 secured to the gate mounting brackets 22 and 24 and pivotal movement thereof causes links 92 to operate the valve within housing 82 to effect evacuation of power fluid from the inner end of cylinder 74 to supply power fluid to the opposite side of the piston causing telescoping of the piston rod 72 within cylinder 74. As a result, the segment 36 is forced to pivot clockwise about bolt 44 and the platform is carried with it to the vertical bed closing position. It is apparent that should it be desired to stop closure of the gate at any intermediate position between the horizontal and vertical, it is merely necessary to release the actuating lever 86 and it will return to its original position. To pivot the gate from the vertical-closed to the horizontal position, the actuating lever is merely pivoted in the opposite direction to reverse the foregoing operation.

Each of the compression arm means 32 are spaced inwardly on the torque tube 26 from the tension arm means 30 and to this end a pair of lugs 94 extend forwardly and downwardly from the torque tube 26 at points spaced slightly inwardly of the lugs 38 for the tension arm means.

A pair of elongated members 96 of similar configuration are attached to the set of lugs 94 on each side of the torque tube 26. T accomplish this, the inwardly projecting ends of the elongated members are provided with apertures which are aligned with similar apertures in the outer ends of lugs 94. A bolt 98 extends through the lugs 94 and the elongated members 96 as well as through a cylindrical spacer 100', positioned between the elongated members 96, to pivotally mount the assembly to the torque tube 26. The outer ends of the elongated members are also provided with a cylindrical spacer 102 and the outer end of the assembly is accommodated between side walls 54 and 56 of the U shaped mounting construction 50 underneath the inner edge of the platform 28. A bolt 104 extends through apertures provided in the bottom portions of the side walls 54 and 56 as well as through apertures in the outer ends of elongated members 96 and the cylindrical spacer 102. The platform structure which extends between the U- shaped mounting constructions 50 to which the parallel linkage mechanisms are pivotally secured, serves as a means to connect the outer ends of the parallel linkage systems while it is not essential, it has been found desirable, particularly when heavy loadings are placed on the extreme overhang positions of the platform 28, to provide a cylindrical cross member 107 rigidly welded to the outer end of the inner elongated member 96 of each of the compression arm means 32 to further rigidly connect the same and prevent any swaying of the platform that may exist.

The compression arm assemblies also include power lifting means. More particularly, the elongated members 96 increase in depth toward the outer end thereof and are provided with apertures 105 adjacent the bottom portion. A bolt 106 extends through the apertures in the elongated members 96 and through apertures in ears 108 of a U- shaped member 110. The U-shaped member 110' is threadedly secured to the outer end of a piston rod 112 which extends within a power cylinder 114 similar in construction but larger in size than the power cylinders 74. The piston rod 112 is attached to a piston (not shown) adapted to reciprocate within the cylinder 114 and the inner end of the cylinder is provided with ears 116 which accommodate the outer end of an upwardly and outwardly extending lug 118 secured to the torque tube 26 between the downwardly extending lugs 94. The ears 116 and the outer end of the lug 118 are apertured to receive a bolt 120 which extends therethrough to pivotally mount the cylinder with respect to the torque tube 26.

Accordingly, when it is desired to raise the platform 28 from its ground engaging position as shown in FIG. 1 to vehicle bed height, a control bar 122 which is mounted for rotation in a bracket 124 secured to the rear of the vehicle bed 12 is rotated by manually moving one of the actuating levers 126 extending upwardly from each side of the control bar. Rotation of the control bar causes a link 128 secured thereto to pivot resulting in longitudinal movement of a second link 130. The link 130 actuates a suitable valve encompassed within valve housing 132. The valve housing 132 is positioned on the valve bracket 84 adjacent to the valve 82 which operates the power cylinder 74 of the tension arm means 30.

Suitable hosing 134 connects both sides of the power cylinder 114 to the valve housing 132 and also connects the valve housing to a source of power fluid (not shown). The foregoing movement of the linkages 128 and 130 causes the valve within valve housing 132 to permit evacuation of power fluid from the inner ends of power cylinders 114 and supplies power fluid to the outer ends thereof through the appropriate housing 134. Thus, the piston rods 112 become telescoped within power cylinders I14 and etfect lifting of the platform 28. The platform is therefore raised while maintaining a substantially horizontal position due to the parallel linkage systems 14 and 16, in a manner well known in the art, until the platform 28 reaches vehicle bed height at which time inwardly extending locking members 136 on the internal surface of the inner elongated member 96 of each compression arm means engage spring biased hook-like lock members 138 secured to the mounting brackets 22 and 24. If it is desired to pivot the platform 28 vertically to close the end of the vehicle bed 12, once the platform 28 has reached its horizontal position at vehicle bed height and has been locked in such position, the control bar 88- is pivoted as previously described to operate the tension arm power cylinders 74. I

When it is desired to lower the platform 28 from its vehicle bed height position to the ground, again the actuating levers 126 are pivoted to effect movement of a pair of spaced linkage mechanisms 140 which first release the locking members 136 and 138 while simultaneously causing actuation of the power cylinders 114 through links 128 and 130.

It is apparent from the foregoing description that the power cylinders 114 are positioned between the elongated members 96 of the compression arms and thus shielded from damage. The compression arms 32 may be widely spaced apart along the torque tube 26 and connected to the platform 28 to greatly reduce the side overhang of the platform with respect to the arm connections. Ex-

cessive bending stresses are not created since the power cylinders 114 are connected to the elongated arm members 96 directly and not through a transversely extending cross member (a cross member 107 has been provided for stability but is not subject to bending stresses from the power cylinders 114 during the lifting operation). The power cylinders 114 are in contracted position when the vehicle gate is in its closed traveling position so that the piston rods 112 are contained within the power cylinders 114 and thus not subject to damage which may resuit in early leakage of the power cylinders.

Similarly, the power cylinders 74 of the tension arm means 30 are disposed above the tension arm segments 34 and thus protected from damage thereby. When the gate is in its closed traveling position, the tension arm power cylinders 74 are also in the contracted position with the piston rods 72 accommodated within the power cylinders to further protect the same from damage resulting from stones, dirt, etc., being thrown up by the vehicle wheels. The power cylinders 74 are compactly arranged and uniquely provide a powered vertical pivoting of the platform 28 through an appropriate mechanical advantage due to the tension arm construction for effecting closing of the gate. The platform is provided with two series of slots 142 in the inner edge of the platform adjacent the U-shaped mounting constructions 50 to accommodate the tension and compression arm structures upon pivoting of the platform to the vertical vehicle bed closing position.

The tension and compression arm arrangements 30 and 32 provide a durable and compact powered parallel linkage mechanism for the vehicle gate and as a result, the central portion of the gate linkage does not contain any obstructions. Accordingly, with the construction described, the vehicle may be provided with hardware which is commonly desirable on vehicles of this type. For instance, the drawings disclose a trailer hitch in the form of two vertically spaced plates 144 rigidly secured to the torque tube 26 at the midpoint thereof. The spaced plates 144 are suitably apertured and a pin (not shown) is adapted to be dropped through the apertures and an aperture of the arm of a trailer (not shown) to be attached to the vehicle. Also, due to the novel arm arrangement, a transversely extending mounting plate 146 may be secured to the brackets 22 and serves to accommodate a series of reflectors 148. With the construction provided it is also possible to provide additional support for the end of the vehicle bed without interfering with the parallel linkage system. Thus, without the conventional cross member disposed between the compression arm means at a location inwardly toward the torque tube and the conventional power lift cylinder or cylinders connected between the torque tube and the cross member, many advantages are attained.

While only a single embodiment of this invention has been shown and described, it is apparent that there may be changes in construction and operation without departing from the scope of this invention as defined by the appended claims.

What is claimed is:

1. A lift tailgate for vehicles, the combination comprising:

a pair of spaced parallel-acting linkages adapted to be pivotally carried adjacent one end thereof by the vehicle for swinging through generally vertical arcs;

a platform extending between and pivotally connected adjacent one edge to the other end of said pair of linkages for swinging from the grounded horizontal position below the vehicle to a position coplanar with the loading end of the vehicle and to a position closing such end;

each of said pair of linkages comprising compression arm means and tension arm means, said tension arm means including an inner and outer tension arm segment pivotally connected together intermediate the ends of said tension arm means; and

power means operatively connected to said tension arm means for effecting movement of the platform to a closed position, said power means comprising an extensible and contractable fluid power means with one end anchored relative to the vehicle and the other end pivotally secured to the outer tension arm segment for effecting folding of said tension arm segments about the pivotal connection therebetween to move said platform to the position closing the loading end of the vehicle upon contraction of said fluid power means.

2. The lift tailgate of claim 1 wherein a transversely extending mounting means pivotally secures said pair of spaced parallel-acting linkages to the vehicle and said tension arm fluid power means is disposed above said inner tension arm segment and has one end pivotally secured to said mounting means, the other end of said power means being pivotally connected to the outer tension arm segment, said tension arm power means being extensible to permit said platform to remain in a position horizontal to the ground during lifting and being contractible to cause folding of said tension arm segments about their pivot connection so that said platform closes the end of the vehicle bed.

3. The lift tailgate of claim 2 wherein the pivot connecting said tension arm segments is positioned upwardly on said segments and adjustable stop means is provided adjacent the lower portion of said segments to limit pivotal movement of the outer segment with respect to the inner segment upon extension of said fluid power means.

4. The lift tailgate of claim 2 wherein said compression arm means includes a power means for lifting said platform from said grounded horizontal position to said position coplanar with the loading end of the vehicle.

5. The lift tailgate of claim 2 wherein said compression arm means comprises a pair of compression arm segments each pivotally connected to said mounting means and to said platform and an extensible and contractible compression arm fluid power means disposed substantially between said compression arm segments and being extensible to effect movement of the platform to the grounded horizontal position and being contractible to move said platform to said position coplanar with the vehicle bed.

6. A lift tailgate for a vehicle, the combination comprising:

a pair of spaced parallel-acting linkages adapted to be pivotally carried adjacent one end thereof by the vehicle for swinging through generally vertical arcs;

a platform extending between and pivotally connected to the other end of said pair of linkages for swinging from a first substantially horizontal position below the vehicle bed to a second substantially horizontal position coplanar with the vehicle bed, the platform further being movable to a third substantially vertical position closing the loading end of the vehicle each of said pair of linkages including first and second arm means each pivotally connected substantially adjacent opposite ends thereof to the vehicle and to the platform, respectively, said first arm means being subjected to a tensile force and said second arm means being subjected to a compressive force as said platform is swung between said first and second positions;

said first arm means including first and second arm segments pivotally connected together intermediate the ends of said first arm means;

power means directly connected to one of the segments of said first arm means for effecting relative movement between said first and second segments to move said platform to said third position;

means locating said power means with respect to the other segment of said first arm means for allowing pivoting of said first arm means with respect to said vehicle independently of actuation of said power means; and

additional power means for moving said platform from said first to said second position.

7. A lift tailgate according to claim 6, wherein said power means causes relative movement between said first and second segments for effecting movement of said platform from said second to said third position, said second arm means remaining substantially stationary as the platform is moved from said second to said third positions.

8. A lift tailgate for a vehicle, the combination comprising:

a pair of spaced parallel-acting linkages adapted to be pivotally carried adjacent one end thereof by the vehicle for swinging through generally vertical arcs;

a platform extending between and pivotally connected to the other end of the pair of linkages for movement from a first substantially horizontal position below the vehicle bed to a second substantially horizontal position coplanar with the vehicle bed, the platform being swingable to a third position substantially closing the loading end of the vehicle;

each of said pair of linkages including a compression arm means and a tension arm means with said tension arm means having a pivot intermediate its ends;

first power means directly connected to one of said compression arm means and said tension arm means for effecting movement of said platform from said first to said second position; and

second power means independent of said first power means and directly connected to the other of said compression arm means and said tension arm means for effecting swinging of said platform to said third position.

9. A lift tailgate according to claim 8, wherein said first and second power means are connected to said compression arm means and said tension arm means, respectively.

10. A lift tailgate according to claim 8, further including control means operatively connected to said first and second power means for permitting independent control and operation of said first and second power means.

11. A lift tailgate according to claim 10, wherein said first and second power means include first and second extensible and contractible fluid power means, respectively, said first power means being connected to said compression arm means and being extensible to effect movement of the platform to the first position and contractible to move said platform from the first to the second position, said second power means being connected to said tension arm means.

References Cited UNITED STATES PATENTS 2,624,477 1/ 1953 Messick 214-77 2,696,923 12/1954 Messick 214-77 3,035,721 5/1962 McCarty et a1. 214-77 FOREIGN PATENTS 1,027,999 5 1966 Great Britain.

GERALD M. FORLENZA, Primary Examiner ROBERT J, SPAR, Assistant Examiner

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