Patent Description:
Industrial trucks, such as forklift trucks, are oftentimes battery powered. In some designs, the frame (or chassis) of a counterbalance forklift provides the possibility to exchange the battery from the side, by using for example a further forklift truck or a simple pallet truck. Respective frames can thus be open both laterally (to allow the battery to be removed) and in the plate below (to allow the forks of the pallet truck to enter and lift the battery). Such open structures, despite the provision of relatively thick materials to increase its strength, has areas and points on which very high stress is concentrated. Such points or areas can be suitably reinforced with welded plates.

However, such reinforcement plates and elements may create an unbalance in height with possible disadvantages especially during assembly. To mitigate such problems, it has been proposed to weld other plates on other locations to equalize the height and facilitate handling during assembly and manufacturing. Such frames can be relatively heavy and accordingly expensive, both because of the addition of the welded plates and increased thickness of the structural plates. Disadvantages can be most pronounced at side plates whose thickness can reach, for example, <NUM> and more. In turn, such thicknesses may require dedicated cutting processes (oxy-cutting, plasma cutting), elevated processing times, associated cost, high scrap fraction, and sub-optimal cutting quality with the consequent need for careful cleaning of the contours.

There is therefore a need for an improved frame structure that does not suffer, or at least to a lesser extent, from the above-mentioned drawbacks. Especially, it is desirable to dispense with the complex, costly, and disadvantageous reinforcing measures, whilst obtaining a frame structure providing the necessary strength, rigidity and stability and providing the possibility to easily access and remove the battery.

<CIT> discloses the preamble of claim <NUM> and describes a truck having a power supply unit i.e. battery block, arranged within a frame (<NUM>) in a battery case (<NUM>), where the frame is provided with an opening for exchanging the energy supply unit in a horizontal direction and the opening is formed by a lateral frame opening (5a). A lower frame opening (5b) is connected to the lateral frame opening. A reinforcement element (<NUM>) is provided, which is form-fittingly fastenable at the lateral frame opening and/or transient area from the lateral frame opening to the lower frame opening at the frame.

The mentioned problems are solved by the subject-matter of the main claim. Specifically, the embodiments of the present invention may provide substantial benefits that are described in part herein.

According to an embodiment of the present invention, there is provided a frame for an industrial truck, as defined by claim <NUM>.

Embodiments of the present invention, which are presented for better understanding the inventive concepts but which are not to be seen as limiting the invention, will now be described with reference to the figures in which:.

<FIG> show schematic views of a frame structure according to an embodiment of the present invention, wherein <FIG> shows the frame structure without a battery and <FIG> shows the frame structure with a battery or battery case inserted. More specifically, there is shown a frame <NUM> for an industrial truck. The frame <NUM> forms at least part of a battery compartment <NUM> and comprises a back part <NUM>, a front part <NUM> opposed to the back part <NUM>, and a side part <NUM> connecting the back part <NUM> and the front part <NUM> on one side, thereby forming a space for the battery compartment <NUM>. The frame further comprises a bottom part <NUM> in mechanical connection with said front, back and side parts <NUM>, <NUM>, <NUM>, and comprising an area <NUM> for supporting a battery and an opening <NUM> extending indefinitely away from said side part <NUM>. In this way, a battery can be lifted from the bottom through the opening <NUM> and removed from the compartment <NUM>.

The frame further comprises a bar <NUM> that removably confines in a closed state said opening <NUM> on a side opposing said side part <NUM> and being configured to transfer force between its endpoints on said bottom part <NUM>. In an open state, i.e. with bar <NUM> opened or removed, it is clear that whenever the frame is loaded with the weight of the battery, zones A and B may be subject to displacements and the rest of the structure may be stressed by bending and twisting moments. Embodiments of the present invention consider the removable bar <NUM> positioned between points A and B in order to close the structure of the frame and transfer forces between the zones A and B and accordingly making the whole structure stronger and more rigid. Optionally, the frame may comprise a hinge mechanism <NUM> toward a first end of the bar <NUM> and a lock mechanism <NUM> toward another end of the bar <NUM>, which may facilitate opening and closing of the bar <NUM>.

Preferably, the bar <NUM> may be manufactured from a high-strength material (e.g. S355JR, <NUM> material). Bar <NUM> can thus close the frame in order to create a closed structure which is inherently more resistant to stress. The proposed solutions can make it possible to eliminate any reinforcing plates and elements, reduce the thickness of the plate material and possibly of other structural components by, for example, <NUM>-<NUM>.

As a further advantage, bar <NUM> once closed can also act as a stop for the battery box as can be seen from <FIG>. There, it shown again the frame <NUM> with a battery or battery box <NUM> inserted into the battery compartment <NUM> and accordingly resting on at least areas of the bottom part <NUM>. The bar <NUM> can preferably be positioned to fit to the lower part of the battery <NUM> within a given tolerance to both allow reliable exchange of the battery or batteries (with respective dimension tolerances) as well as holding securely and firmly the battery <NUM> during operation and movement of the industrial truck.

<FIG> show schematic views of a lock mechanism according to an embodiment of the present invention in various views and states. Specifically, there is shown a lock mechanism <NUM> that comprises a pin member for <NUM> blocking a horizontal movement of the bar <NUM> relative to the bottom part <NUM>. The lock mechanism <NUM> may further comprise a handle member <NUM> actuating the member <NUM> by lifting the member out of an opening in the bottom part <NUM>. In the state shown in <FIG>, the locking mechanism <NUM> is closed and the pin member <NUM> engages with the bottom part <NUM> and consequently blocks a movement of the bar <NUM> relative to the bottom part <NUM>. In the state shown in <FIG>, the handle <NUM> is lifted so as to lift accordingly the pin member <NUM> which allows the bar <NUM> to be opened. The locking mechanism <NUM> may further comprise a handle rail <NUM> and a spring <NUM> to guide and facilitate operation and especially shown in <FIG>.

More specifically, the locking member <NUM> can be lifted manually by an operator using the handle <NUM> and by releasing the member <NUM> from its seat in the bottom part <NUM> the bar <NUM> can be unlocked and opened. In addition, a brick <NUM> may be provided which bounds the handle and locking member to move only vertically along the handle rail <NUM>. The mechanism may be provided with the already mentioned spring <NUM> that is adapted to return the blocking member <NUM> to its initial position.

It should be clear that the so far described solutions are in principle independent from any door mechanism, being part of the frame, chassis or casing of the industrial truck. Such door mechanisms may not be essential for holding and/or securing the battery but are generally provided for safety and integrity reasons. In further embodiments of the present invention, the bar is provided with an element configured to interact with a door assembly closing said battery compartment on a side opposed to the side part. Preferably, the element may force the bar into the closed state upon closing the door.

Generally, however, the mentioned door and the bar can be moved and operated separately. For example, the operator may first open the door, bringing it to the end of its stroke, and then move the bar, which can rotate around a respective hinge. Although in such embodiments the operation of the door and the bar remain as such independent they may be still interact in some way or another. In one such embodiment the bar is provided with a locking mechanism as for example described in conjunction with above <FIG>. At the same time, the door may provided with a further hole that may likewise engage with the locking member. The spring <NUM> acts between the handle, with a handle pin <NUM>, and the structure welded on the bar through what may be referred to as a spring pin <NUM>.

As shown in <FIG>, when the door <NUM> is in a suitable open position the bar <NUM> can be fixed to the door <NUM> that is provided with an end-of-stroke locking plate <NUM> into which the locking member can engage just like with the bottom part. Thus, by using the same opening handle and locking mechanism both the bar can be locked and secured as well as the door can be secured during exchange or maintenance operations. This may specifically inhibit the door to move until the operator has finished the battery exchange operation. Further, in this way it may not be possible to close the door <NUM> unless the safety lock of the handle and locking member is activated first. In summary, the door <NUM> can only be closed by first closing the bar <NUM>, lifting the handle again while closing it and releasing the handle once the bar is in the correct closed position. It is to be noted that in <FIG> there is shown the bar in both states, i.e. in a closed state <NUM>-<NUM> and in an open state <NUM>-<NUM>, when the bar is fixed to the door holds the same and grants full access to the opening <NUM>.

According to the invention, the structural improvements obtained by the bar a described so far are combined with a kinematic mechanism that exploits the movement of the door to also move the bar. Consequently, the bar is provided with an element configured to interact with a door assembly closing said battery compartment on a side opposed to the side part, and said element generally force the bar into the closed state upon closing the door.

<FIG> shows a schematic view of an embodiment in which the operation of a door mechanism interacts with the bar. According to the invention an element that is configured to interact with a door assembly is interacts slidably with a rail arranged on an inner side of the door assembly. Specifically, the bar <NUM> is hinged to the frame (e.g. bottom part <NUM> thereof) by a pin <NUM>-<NUM> and can at least to some extent rotate around it. At the other end of the bar <NUM> there is a second pin <NUM>-<NUM>, which may be integrally formed with the bar and which essentially prevents the bar from moving (as e.g. a result of deformation) in a vertical direction.

As the bar <NUM> rotates around hinge or pin <NUM>-<NUM>, the seat for the second pin <NUM>-<NUM> in a rail along the door follows the rotation of the end of the bar itself. For the same reason, also a corresponding opening or furrow in the bottom part may not be straight but may follow an arc of the circumference around the hinge point at pin <NUM>-<NUM>. The two pins <NUM>-<NUM>, <NUM>-<NUM> may be made of a high-strength steel material with different yield strengths (higher for the pins) and may be machined accordingly. A thread can be provided into the lower parts of each pin and the pins may be fixed with e.g. self-locking nuts.

The respective kinematics are shown with greater detail in conjunction with <FIG>. Specifically, the system as disclosed in conjunction with <FIG> may be reduced to rods a, b, c, d as shown in <FIG>, corresponding to the hinge <NUM>, the bar <NUM>, and the door <NUM>, and constituting in all <NUM> DoF (Degrees Of Freedom). In an analysis of the constraint conditions (n is the number of rods connected by the constraint under examination) it follows that at the hinge in (A) with external constraints, 2n, <NUM> DoF can be subtracted, at hinge (B) with external constraints, 2n), <NUM> DoF can be subtracted, at hinge (C) with internal constraint, <NUM>(n-<NUM>), <NUM> DoF can be subtracted, at hinge (D) with internal restriction, <NUM>(n-<NUM>), <NUM> DoF can be subtracted, at the sliding hinge (E) with internal restriction, 2n-<NUM>, <NUM> DoF can be subtracted, and at hinge (F) with external constraint, 2n, again <NUM> DoF can be subtracted. In all, it follows that for a total of <NUM> constraint conditions the degree of freedom is <NUM> - <NUM> = <NUM>.

The bar <NUM> may thus also act as an end stop for the fully open door <NUM>. On the door <NUM>, further modifications can be made to the bar stop with the addition of a piece of elastic material (e.g. neoprene) to prevent metal-to-metal contact. Such a solution may further relieve the hinges (articulated quadrilaterals) from the end-of-travel work of the door, making the system more robust.

Optionally, the door assembly comprises a lock mechanism in turn comprising a member that slidably engages with the bar and the bottom part in a closed state. Preferably, said slidably engaging member comprises a pin arranged to engage vertically in a hole of said bar and a hole in said bottom part. Such solutions are shown for example with the safety latch and lock mechanism as follows: A further pin <NUM> (preferably turned and made of high strength steel) may engage with a hole made on the bar <NUM> and one made on the bottom part <NUM> of the frame. The pin <NUM> may ensure that the bar <NUM>, and indeed the whole system, does not move outwards or open when the door <NUM> is closed. Pin <NUM> may be moved by a knob <NUM> on the outside and guided on an inner side of the door via a rail <NUM> and a spring, which constrains movement of the pin <NUM> to the vertical direction. The return spring, once the operator releases the knob <NUM>, returns the pin <NUM> to its initial position, thus preventing also the operator from closing the door <NUM> (when open) without activating the safety latch. The door can only be closed by lifting the knob again while accompanying it in closing. However, when the door <NUM> is closed and couples with the underlying part of the frame through pins <NUM>-<NUM> and <NUM> a closed and boxed structure is obtained.

According to further embodiments of the present invention there is provided a vertical locking mechanism that prevents or at least inhibits the vertical degree of freedom of the bar at a distal end, assuming a rotatable hinge seat at the opposing proximal end of the bar. In one such embodiment, the vertical locking mechanism comprises a pin, bolt or screw as shown for example in <FIG>: A pin <NUM> locks the bar <NUM> in a vertical direction to the bottom part <NUM> by means of respective holes and a nut <NUM>, preferably embodied by a self-locking nut. Such a pin closed in the lower part by a nut can prevent during nonnegligible deformations of the frame that the bar leaves its seat in the bottom part of the frame and thus not fulfilling the purpose of stability as described throughout the present disclosure. Such a closed pin couples the bar and the bottom part for creating an isostatic system along the z-axis (vertical).

This kind of vertical locking mechanism can be well combined with any embodiment in which the bar <NUM> is accessible even in a closed state through a still open door or some other opening that grants access to it also in a state in which the door <NUM> is closed. For example, the vertical locking mechanism as shown in <FIG> can be well combined with the locking mechanism as disclosed in conjunction with <FIG>, preferably at a distal position relative to the handle lock.

<FIG> shows a schematic view of a vertical locking mechanism according to a further embodiment of the present invention, which can be in principle replace or be combined with the on described in conjunction with <FIG>. Generally, such an embodiment considers lengthening the bar <NUM> along the distal end and up to the portion of the frame where it can engage with an opening thereof. In such an embodiment, the rear part <NUM> provides an opening <NUM> suitably shaped and configured to receive the bar's end portion and constrains therefore the bar in the vertical z-direction. In this way, it is again implemented a safety lock by realizing a hyperstatic system in that direction: the back plate of the frame prevents the bar from moving along z.

As a further explanation, the following calculation can demonstrate the benefits obtained by the embodiments of the present invention, especially in view of a comparison between the strength of a closed and an open structure. These considerations may start with the assumption a circular crown-shaped section in which the ratio between thickness t and external radius Re is equal to <NUM>/<NUM> (<FIG>) : <MAT>.

Let us denote by Ri the internal radius and by R the mean radius of the section. The area A and the circumference <NUM> relative to R are respectively: <MAT> <MAT>.

Applying Bredt's formulae gives τ_zx (mean tangential stress) and θ' (specific torsion angle) respectively: <MAT> <MAT> where M_z is the torque and G is the tangential modulus of elasticity. Consider now the same section from which, however, an infinitesimal piece has been removed (<FIG>). On such a section we obtain τ_(zx max) (maximum tangential tension) and θ_A^' (specific torsion angle for open structures) using the theory of the elongated rectangular cross-section: <MAT> <MAT> from which follows <MAT> <MAT>.

Considering that <MAT> one arrives at the conclusion that <MAT> <MAT>.

That is, the open section is, with the same material and shape, extremely more deformable than the closed section and has tensions that are about <NUM> times greater. Consider that in closed sections the maximum tension is found in correspondence of the smallest thickness, in the case under consideration the thickness is constant and is equal to t, therefore the maximum tension is equal to the average tension.

In summary, one or more embodiments of the present invention may provide at least one of the following benefits, technical effects and advantages: time savings in the design phase: more solid structure, less reinforcements needed; lightening of the frame (elimination of reinforcements and related welds and thinning of thicknesses) with consequent savings on the cost of the product; possibility of using more uniform thicknesses throughout the frame, with consequent improvement in the material purchase and nesting phase (therefore better scrap recovery); elimination of the battery box stop and related welding; possibility of eliminating the safety lock for the battery; savings in terms of logistics for the supplier (warehouse, handling) due to having to manage far fewer codes; possibility of simplifying the articulated door hinges because they no longer have to support the end-of-stroke work; simple and much less expensive solution than reinforcements and thickening distributed throughout the frame: saw-cut commercial bar, laser-cut guide, <NUM> turned pins; strengthening of the frame itself and improving response to torsional and bending loads with resulting possible lightening of the whole structure.

Claim 1:
A frame (<NUM>) for an industrial truck, the frame forming part of a battery compartment and comprising:
a back part (<NUM>), a front part (<NUM>) opposed to the back part, and a side part (<NUM>) connecting the back and the front parts on one side, thereby forming a space for the battery compartment;
a bottom part (<NUM>) in mechanical connection with said front, back and side parts and comprising an area for supporting a battery and an opening extending indefinitely away from said side part; and
a bar (<NUM>) that removably confines in a closed state said opening on a side opposing said side part and being configured to transfer force between its endpoints on said bottom part,
wherein the bar is provided with an element configured to interact with a door assembly closing said battery compartment on a side opposed to the side part, said element forcing the bar into the closed state upon closing the door,
characterized in that said element configured to interact with a door assembly is configured to interact slidably with a rail arranged on an inner side of the door assembly.