The present invention relates to a lift truck comprising a rolling frame with at least one lift platform on which to receive a load, the at least one lift platform being connected to lifting means enabling a user to vary a height of the at least one lift platform with respect to a ground surface, the frame comprising at least one driving body underneath the lift platform, which at a first end is connected to a tilting axle of the lifting means and at a facing second end is connected with a swivel axle of a rolling member of the rolling frame. Such a lift truck is known from applicant's International patent application WO2011/129692. In the patent text a pallet truck is described with a lift platform in the shape of a set of pallet forks which extends from a so-called A-frame and is assembled in a movable manner with respect to a mobile undercarriage. Using the pallet forks a load of goods, for example pallet goods, can be lifted from a ground surface so that they can subsequently be moved. In order to be moved manually the pallet truck comprises a number of adjustable swivel castors which are controllable via a set of connecting rods provided underneath the lift platform. The connecting rods engage eccentrically with a wheel arm which carries the swivel castors and is assembled in a swivelable manner around a swivel axle. At their facing end the connecting rods are articulated to a tilting axle in the A-frame. The tilting axle is connected to the A-frame via a set of lift arms of the lifting means. When manipulating the A-frame using the lifting means the tilting axle will show a displacement and result in a drive to full output of the connecting rods. Accordingly the wheel arm will be driven from an initially almost horizontal position to a more upright position until it finally exhibits an almost vertical position. Thus the lift platform, formed by the pallet forks, can be manually adjusted in height at will.

Although this lift truck is already more than capable of lifting a load from a ground surface, further improvements can be made in terms of strength and weight of the device. In the known lift truck a solid steel rod is used as a driving body, the rod being sufficiently thick, in the case of a maximum load of the lift platform when placing a maximum weight of load on it, to prevent deformation, such as a deflection, when making a lifting movement. Accordingly, the driving rod forms a relatively large weight, which is disadvantageous in terms of transport costs and use of the device.

The present invention aims, amongst other things, to address the mentioned disadvantage.

In order to accomplish the intended goal a lift truck of the type described in the opening paragraph according to the invention is characterized in that the frame underneath the lift platform is provided with a rigid tube profile with an axially continuous cavity, in which at least a part of the driving body is confined in an axially moveable manner. Due to a tight-fitting confinement of the driving body in the rigid tube profile a deformation thereof during loading is countered to a large extent. The driving body itself may moreover be relatively light. It is important that the tube profile have a relatively high deflection resistance due to the longitudinal geometry, so that the tube profile enables greater weight saving in the driving body than a weight increase as a result of an own weight of the tube profile. To drive the rolling member the driving body is axially movable through an axially continuous cavity in the tube profile.

Moreover, the tube profile constitutes a construction strengthening the lift platform itself. For instance, in a preferred embodiment the lift truck according to the invention is characterized in that the tube profile lies at least almost touching a bottom of the lift platform. Accordingly the tube profile fulfills a supporting function, wherein a part of a pressure force of a load placed on the lift platform is exercised upon the tube profile. What is special about the lift truck according to the invention is that due to the increased protection of the driving body as a result of using the tube profile the lift platform itself may be realized in a less sturdy and, in particular, a less thick manner. Thus a total thickness of the lift platform can be reduced substantially, which brings about a further reduction in weight. Moreover, the lift truck is thus also suitable for different loads, such as different types of pallets, including European and American pallets, because the lift platform remains lower with respect to a ground surface. In a further preferred embodiment the lift truck according to the invention is characterized in that at least one of a peripheral surface of the driving body and a surface of the tube profile facing the cavity comprises a roughness. Upon placement of a load exceeding the maximum load allowed on the lift platform a deflection of the tube profile occurs which results in the driving body coming up against an inside of the tube profile. A roughness of one or both of the said surfaces further provides for an increased coefficient of friction between the driving body and the tube profile so that in the end the driving body no longer is axially movable in the cavity and thus not capable of forcing the wheel arm into a more vertical position. Accordingly, with the tube profile and the driving body acting in close conjunction a safeguard is created against a lifting of the lift platform when a load exceeding the maximum load allowed is on it.

A further preferred embodiment of the lift truck according to the present invention is characterized in that the driving body comprises two parallel driving rods each confined in an axially movable manner in a continuous cavity of an own tube profile. In stead of centrally underneath the lift platform the two parallel driving rods can be provided on either side of the lift platform underneath the platform in order to spread the forces exercised upon it.

In a special embodiment thereof the lift truck according to the present invention is characterized in that the two parallel driving rods, on at least one side of the tube profiles, extend integrally from a common end part of the driving body. The two parallel driving rods constitute an integral whole benefitting a strength and reliability of the driving body.

Preferably, the two driving rods have a free end at a facing end part of the driving body so that the tube profiles can easily be guided over the driving rods during assembly.

A further preferred embodiment of the lift truck according to the present invention is characterized in that the tube profiles are connected to each other by at least one transversal body. The transversal body, for example a transversal wall or additional tube profile, creates an additional strengthening of the tube profiles and protects them from a possible deflection.

A further preferred embodiment of the lift truck according to the present invention is characterized in that the tube profiles are assembled on a connecting plate. The connecting plate enables a relatively easy assembly of the tube profiles under the lift platform and, furthermore, this results in an especially strong and reliable whole. In addition, the connecting plate constitutes an available surface between the parallel driving rods upon which, if desired, further parts of the lift platform can be provided. Accordingly, in a further preferred embodiment according to the present invention the lift truck is characterized in that, between the tube profiles, electronic weighing means are provided capable of and adapted to register a load of the load platform and to transmit an electronic weighing signal at least at a reference height of the load platform as a weight indication of a current load of the load platform. The lift truck can thus be used as a weighing lift truck not only delivering a transportation of a load provided on the lift platform but also directly delivering a weight indication thereof. In a further special embodiment the lift truck according to the present invention is characterized in that the electronic weighing means comprise a force transducer.

The invention is particularly suitable for a hand lift truck, wherein the load platform comprises a set of pallet forks and will now be explained further based on a relevant example of an embodiment with reference to an accompanying drawing. The drawing shows in:

figure 1 a perspective top view of an example of an embodiment of a lift truck

according to the invention with the lift platform disconnected from the undercarriage.

figure 2 a perspective bottom view of the lift truck of figure 1 with the parts

disconnected; and

figure 3 a perspective view of a cross section of a pallet fork for use in a lift truck according to the invention.

The figures are, moreover, purely schematic and not drawn to scale. In particular some of the parts and dimensions may be exaggerated to a greater or lesser extent in their rendering for the sake of clarity.

The example of an embodiment of the lift truck according to the invention comprises a load platform in the shape of a set of pallet forks and is therefore usually called a pallet truck or hand pallet truck. The pallet forks extend from a so-called A-frame, a left side and a right side thereof meeting in a common head and connected to each other. All these parts are made of sturdy hardened or durable steel united in a coherent whole by welding.

The head is arranged on an extending driving rod of a hydraulic pump operated manually using an operating arm. The operating arm is also designed to manually move and maneuver the pallet truck. At a bottom the A-frame is connected to this part of the frame through the interposition of a set of lifting arms, articulated to a tilting axle in the A-frame. The A-frame can thus be freely varied in height together with the pump, wherein the tilting axle will exhibit a displacement.

Under a lift platform 11 of a lift fork, as shown in the figures, driving rods 31,32 are provided, engaging eccentrically with the tilting axle in the A-frame 10. At their facing ends the driving rods 31,32 engage eccentrically with a wheel arm 51 which is swivelably fitted around a swivel axle 33 and at an end carries a set of freely rotatable support wheels 21. Centrally underneath the pump a third support wheel or set of support wheels (not shown) is located, so that the pallet truck will always be stably supported on a ground surface.

If the A-frame 10 is manipulated with the pump the displacement of the tilting axle will result in a drive to full output of the connecting rods 31,32, so that the wheel arm 51 is driven from its initially almost horizontal position to a more upright position until the wheel arm finally exhibits an almost vertical position. In the operating arm of the pump a handle is present with which a valve of the pump can be opened so that the pump loses its pressure and it all sinks back to the starting position. Thus the load platform 11 can be manually adjusted in height at will.

A tube profile 41,42 is provided around the driving rods 32,32 so that they are axially movable to control the support wheels 21. Within their respective tube profiles 41,42 the driving rods 31,32 have little to no tolerance or leeway in a direction other than the axial direction. The driving rods 31,32 are thus confined in the tube profiles and are protected against deformation such as a deflection. The tube profiles 41,42 are rigidly fabricated as metal tubes. In this embodiment example the tubes are completely integral, the driving rods being arranged through the axial space via an open end of the tubes. The tubes may however also be composed of several loose parts, such as for example two separate halves or even four separate side walls, assembled around the driving rods. The rigid tube profiles 41,42 not only counteract a deformation in the driving rods 31,32, so that the driving rods can be fabricated much more lightly than normal, but they also strengthen the lift platform 11 due to the fact that they are assembled against a bottom thereof. Thus the tube profiles form a part of the supporting construction, so that the lift platform itself can make do with a less heavy construction to be able to lift a certain load reliably. A total thickness of the lift platform is therefore limited so that the lift truck can be use both for European as well as American pallets. The tube profiles 41, 42 are positioned on either side of the lift fork underneath the lift platform to ensure an optimal distribution of power over it. Moreover, this provides a space between the two parallel tube profiles 41, 42, in which, optionally, other parts of the lift truck can be put. In this embodiment example, for instance, a metal connecting plate 61 extends between the two tube profiles 41, 42 on which a set of force transducers 81 is placed as part of electronic weighing means capable of and adapted to register a load of the load platform and to deliver, at least at a reference height of the load platform, an electronic signal as a weight indication of a current load of the load platform. Consequently, the lift truck can be used as a weighing lift truck. To ensure an accurate measurement the force transducers 81 are optimally placed on a central axis underneath the lift platform 11.

The connecting plate 61 not only serves as a base for carrying the force transducers 81, but also supports a carrying function of the tube profiles 41,42 and prevents them from moving apart with heavy loads. For additional reinforcement of the tube profiles one or more additional cross-connections may be arranged between the tube profiles, such as in this embodiment example a metal transversal body 71.

Although the invention was described solely using one single embodiment example it should be clear that the invention is certainly not limited to this. On the contrary, in the context of the invention many variations and embodiments are available to the average person skilled in the art.