Preassembly unit for the drive of an industrial truck

A preassembly unit for the drive of an industrial truck, with a fifth wheel on which the driving wheel is rotatably mounted around a horizontal axis and which on its part is rotatably mounted in a bearing member around a vertical axis, a drive motor arranged on the fifth wheel, which is coupled with a driving shaft of the driving wheel via a gearbox, optionally a steering motor on the bearing member in order to turn the fifth wheel in the bearing member around the vertical axis, a parallel rod assembly between the bearing member and a frame of the industrial truck, which permits an essentially vertical movement of the preassembly unit in relation to the frame, and a spring arrangement between the bearing member and a frame-fixed section, wherein at least one upper drag rod of the parallel rod assembly is articulated on the lower end of a separate attachment section, which forms an interface with a counter-attachment position on the frame by attachment positions, and that at least one spring acts between a shoulder of the bearing member and an abutment of the attachment portion below the attachment positions.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not applicable.

BACKGROUND OF THE INVENTION

Irrespective whether industrial trucks have a three wheel chassis, four wheel chassis or five wheel chassis, only one single driving wheel is provided at most, which is also a steered wheel at the same time in most cases. For this purpose, the driving wheel is rotatably mounted around a horizontal shaft in a so-called fifth wheel, which is rotatably mounted around a vertical shaft in a second bearing member. With the aid of a steering drive, the fifth wheel is pivoted in relation to the frame-fixed or not turnable bearing member. On the fifth wheel sits a drive motor, which is pivoted together with it and which drives the driving wheel, via a conical wheel- or spur wheel gearbox, for instance.

The driving wheel is often not cushioned, a certain cushioning effect taking place via the tires. It is also known to suspend the driving wheel in a spring-cushioned way and optionally to load or relieve it depending on the load.

In industrial trucks with driver seat, the spring-cushioned suspension of the driving wheel is desired, so that the driver is not subjected to strong shocks. From U.S. Pat. No. 6,488,297 B2, the entire contents of which is incorporated herein by reference, a suspension for an industrial truck has become known, in which that bearing member, in which the bearing member for the driving wheel is rotatably mounted around a vertical axis, is suspended vertically movable by means of a parallel rod assembly. A spring acts on the first bearing member and thus it counter-acts the upward movement of the first bearing member.

The present invention is based on the objective to provide a preassembly unit for the drive of an industrial truck which permits a selectionable connection with the frame of an industrial truck, irrespective of its actual construction. The construction is to be compact, at spring-cushioned suspension of the driving wheel in particular.

BRIEF SUMMARY OF THE INVENTION

In the preassembly unit of the present invention, at least one upper drag rod of the parallel rod assembly is articulated on the lower end of a separate attachment section, which forms an interface with a counter-attachment position on the frame by attachment positions. At least one spring is arranged between a shoulder of the bearing member and an abutment of the attachment section below the attachment positions. Preferably, the attachment section has two flanges located in one plane, with attachment holes (57).

Neglecting fixed specifications for the preassembly unit, the same can be realised in any way. The steering may be servo assisted or it may be directly actuated by a drawbar. The preassembly unit can be connected to a low lift truck, a high lift truck or any other industrial truck, and it may replace a non-cushioned drive unit, for instance. The frame of the industrial truck is shaped completely similar with regard to the installation of the drive unit. Correspondingly, different preassembly units (a set) have the same attachment section, irrespective of their actual realisation. Therefore, one embodiment of the present invention provides to provide a set of different preassembly units which each have the same attachment section for the installation on the frame of the industrial truck.

According to one embodiment of the present invention, the attachment section is formed in one piece with a cylinder shell of a lifting cylinder, the piston rod of which acts on the load portion of an industrial truck above the attachment section, For instance, such a preassembly unit serves as a drive for a low-lift industrial truck with spring cushioned driving wheel suspension.

According to a further embodiment of the present invention, the bearing member is provided with two parallel spaced bearing lugs, between which a longitudinal member with an axial through-bore is arranged, a pipe for instance. The lower drag rods are fixedly connected to that member, Through its bore, a bearing shaft is lead through. One of the lower drag rods is pivotally mounted on the inner side of the bearing lug and the other one on the outer side of the other bearing lug. In such a mounting, the lower drag rods and the member attached between them form a structural unit which permits a stable vertical guiding of the driving wheel at vibrations. The structural unit may be a welded structural unit or even a cast piece. In addition, it may be pre-fabricated in a simple manner and subsequently be joined with the bearing member. This is because the first one of the two lower drag rods is on the other side of the assigned bearing lug than is the other drag rod, so that by simply moving it laterally on the bearing shaft, the whole unit of fifth wheel, bearing member and driving wheel is released from the lower articulation. Thus, installation and removal of the preassembly unit can be performed extremely simply, even at narrow spatial conditions.

According to one embodiment of the present invention, it is provided that the bearing member has a bearing lug standing upward approximately in the centre between the lower bearing lugs, on which one single upper drag rod is articulated, which is laterally articulated to a flange of the attachment section which is detachably connectable to the counter-attachment section of the frame. This construction limits the number of levers for the parallel guiding to three. Thus, sufficient space is also created in order to arrange a spring on each side of the upper bearing lug, which according to one embodiment is supported on the lower end on an approximately horizontal plate-shaped section of the first bearing member. The articulation of the single upper lever is preferably such that it also permits the sideways movement of the complete drive unit in the frame for detaching it.

For low-lift industrial trucks it is known to actuate the load wheels which are mounted on the front end of load arms via a drawer- or presser rod assembly. The rod assembly is articulated on a lever with plural arms, which on its part is rotatably mounted on the load portion. An additional aim of the lever is articulated on the frame of the drive portion. When the load portion is lifted with the aid of the lifting cylinder, this results in a swivelling of the lever at the same time, which acts on the rod assembly towards the load wheels and pivots the same downward with respect to the load arms, so that the load arms can be lifted parallel to each other and being also supported on the front end. In this context, one embodiment of the present invention provides that the axles of the lower drag rods of the parallel rod assembly and the articulation of the levers on the frame are coaxial. Preferably, the levers are pivotally mounted on the bearing shaft. Thus, a simple and compact construction for the suspension of the driving wheel is achieved.

DETAILED DESCRIPTION OF THE INVENTION

InFIG. 1, a low-lift industrial truck is partially depicted. It has a drive portion and a load portion. The drive portion is only represented with a frame100and a drive unit10. The drive unit10will be described in more detail below by means of theFIGS. 2 to 6.

A load portion102has two parallel wheel arms104,106. Further, a battery accommodation can be recognised, which is fixedly connected to the wheel arms104,106. It will not be further dealt with the same. The part of the battery accommodation drawn upward, which is designated with108, is connected with the lifting cylinder of the drive portion10, as will be shown later.

A three-arm lever110is pivotally mounted on the load portion102around a horizontal axis at112. On the opposing side, a corresponding lever is provided. One arm of the lever110is pivotally articulated on the flame100at114. A third arm of the lever is articulated at116on a presser rod, which is lead inside the wheel arm106. The same applies for the wheel arm104. At the end of the wheel arms104,106, there are load wheels (not shown), which are mounted in a rocker which is connected with the respective presser rod. When the load portion102is lifted, the lever110pivots in the clock direction and by this it exerts a pressure on the presser rod. This kinematics is commonly known in low-lift industrial trucks.

InFIGS. 2 to 6, the drive unit10is depicted in more detail. InFIG. 1, the industrial truck is a three-wheel vehicle. It may be an usual handlebar- or drawbar-steered industrial truck, also with a four-wheel or five-wheel chassis.

A driving wheel12is rotatably mounted in a fifth wheel14around a horizontal axis. The fifth wheel14has an angle gearbox16and an upper horizontal toothed ring18, on which a drive motor20is attached. The drive motor20may be a three-phase current motor or even a direct current motor, which brings the driving wheel12into rotation via the gearbox16. The toothed ring18is rotatably mounted around a vertical axis in a bearing member22. On the top side of the bearing member22sits upright a steering motor24, which turns the fifth wheel14around the vertical axis when it is correspondingly triggered via a steering transmitter. The described components are conventional and therefore they have not to be discussed further in detail.

As results from the figures, the bearing member22has an upper horizontal section and a skirt26extending downward from the same in various degrees, which is partly formed in the shape of an arc of a circle. However, it is partly open on the rear side and there it forms a horizontal shoulder28below the disc18. From the same, bearing lugs30,32stand downward. They are approximately parallel and in a distance to each other. As becomes clear from the figures, relatively short drag rods are articulated on the beatings lugs30,32. On the bearing lug30a drag rod34is articulated, and on the bearing lug32a drag rod36. The drag rod36is articulated on the outer side of the bearing lug32, and the drag rod34on the inner side of the bearing lug30. The articulation takes place via rotational necks in corresponding bores of the bearing lugs30,32, which are not shown in more detail. Only inFIGS. 2 and 6, a bearing neck can be recognised at38.

The drag rods34,36are welded together with a pipe40. They form an entity with the pipe. Through the pipe, a bearing rod or -shaft42is guided through, which is attached on the frame100of the industrial truck (FIG. 1).

On the top side of the bearing member22, an upper bearing lug44is attached on the rear side of the drive motor20, which is arranged approximately in the centre between the lower bearing lugs30,32. On the bearing lug44, one single upper drag rod46is articulated, which is articulated on a lower lug48of an attachment section50at its other end. Thus, the drag rods34,36and46, the bearing lugs30,32and the attachment section50form a parallel rod assembly, which permits an approximately vertical movement of the drive unit10.

The attachment section50has attachments flanges54,56located in one plane on opposing sides of a shell of a lifting cylinder52, formed in one piece therewith, each with two attachment bores for attachment on a wall section of the vehicle frame100. On the piston rod of the lifting cylinder52, a flange plate58is attached for connection with the load portion102of the industrial truck.

Below the flanges54,56, disc-shaped abutments60,62for springs64,66are arranged. The springs64,66are supported at the lower end on a plate section of the shoulder28.

In order to dismount the drive unit10, it is only necessary to bring the bearing necks out of engagement with the bearing lugs30,32through a small sideways movement of the drive unit10. When the bearing rod42is pulled out of the pipe40, the drive unit is free and it can be removed. Naturally, this functions only when the fastening of the flanges54,56on the frame has been released before.

As results fromFIG. 1in particular, the lower drag rods34,36on the frame100of the drive portion are mounted on the same axle as the one arm of the lever110for the lifting rod assembly. Thus, the construction expenditure is kept very low and the drive unit is realised compactly.