Abstract:
Device for holding a load on a load support of an industrial truck with the following characteristics:
       a support device on a lifting scaffold of the industrial truck, adjustable in its height by a shifting drive, extending approximately horizontally above the load support,   at least one sack-shaped container, made of flexible, air-impermeable material, which is hanged up on the support device and which is filled with granular material, wherein   the flexible material and the granular material are constituted such that the bottom side of the container adapts itself to the surface contour of the load, when the container is lowered onto the load, and   an aspirating device, connectable with the interior of the container, for generating a negative pressure in the container.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   Not applicable. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
   Not applicable. 
   BACKGROUND OF THE INVENTION 
   The main purpose of industrial trucks is to pick up, transport and set down loads,. These loads are elevated by a load support such as, a load supporting fork. On industrial trucks without a stacking-in function, the load support lifts as much of a load that can be transported. On industrial trucks with stacking-in function, the load support has an adjustable height relative to a lifting scaffold. 
   Transporting objects having a high centre of gravity or a low weight with a small horizontal area when standing-up tend to fall down from the load support, particularly when the industrial truck drives over uneven ground or through curves. For this reason, load holders have already become known which exert a pushing force against the transporting object from above, in order to prevent any falling down of the transported object from the pallet or of the pallet from the load support. From DL 9418354 U1 or EP 467210 B2, a load holding device with a horizontal plate has become known, which can be moved in the vertical direction by a second lifting device, independently of the lifting of the load support, and which is pushed onto the transporting load from above. However this is difficult when transporting objects of different heights because they can not be secured on the load support at the same time. 
   The prior art has proposed attempted solutions to this problem. From DL 412989 C or WO 214206 A2 it is known to mount several load holders side by side on the support device. Through this, it is possible to clamp fast several transporting objects of different height, which are situated side by side on the load support. However, it is not possible to sufficiently clamp fast transported objects of different heights which are situated in the longitudinal direction (fork direction) in front to each other. 
   From GB 2250267 A or from DE 2929621 C2 it is known to dispose several plates side by side or back to back on one load support, which are movable with respect to each other. It is a disadvantage that the height differences between the individual transporting objects have to be in relatively narrow limits. Furthermore, with several load holders or plates, respectively, the construction is limited by weight and complexity of the construction with respect to their number and the extension of the transporting objects. 
   This invention is based on the objective to provide a device for holding a load on a load support of an industrial truck by which transporting objects of significantly differing heights can be fixed on the load support. 
   BRIEF SUMMARY OF THE INVENTION 
   In the device according to the invention, a support device, with an adjustable height, extends in a substantially horizontal direction above the load support. When the industrial truck has a lifting scaffold, the support device is preferably also guided on the lifting scaffold, preferably in an independent fashion with respect to the load support. It is also conceivable, however, to affect the mounting of the load support such that the support device can be guided, adjustable in the height, on the mounting device of the load support. In the case that there is no lifting scaffold, the support device is also guided on the mounting device for the load support, or on a scaffold for its own, along which the support device can be guided, movable in the height, with the aid of a shifting drive. 
   On the support device, at least one sack-shaped container, made from an air-impermeable flexible material, is attached or hanged up, respectively, in a recumbent position. The container is filled with a granular material. The sack-like container can be formed by a sheet, which consists of plastic material, metal, rubber or rubberised fabric and which can have a multilayer structure, the outer side of the outer layer having a corresponding coating for protection against wear and damages at least on the bottom side of the container, whereas an inner layer provides for air-tightness. The sack-shaped container is filled with granular material, e.g. a granulate, the size and shape of the particles being selected such that the sack can adapt itself very well to the contour of the upper side of the load. As the particles, balls or irregularly shaped particles from various materials can be selected, from metal, plastic material, elastomers, rubber, ceramics or wood, for instance. 
   An aspirating device is connected to the interior of the container, which generates a negative pressure in the container. The negative pressure causes the particles to be pressed against each other, and frictional forces prevent easy movement of the particles with respect to each other. particles are quasi frozen, and therefore they maintain the shape of the container they have been positioned against. The container which is fixed in this manner transfers the forces which are necessary for holding the load to the support device by positive fit. The positive fit of the container enables force transmission in the vertical as well as in the horizontal direction. Through this, the load picked up by the industrial truck can be safely transported. 
   It is not necessary to use a closed container mounted on the support device, a sack-like membrane can be used instead. The sack-like membrane is sealingly mounted on the support device, on part of which is a support plate. In at least one embodiment of the invention the container has a fold or bead on its perimeter, which is supportingly received in a horizontal, channel-shaped recess of a frame of the support device. The invention can adapt to the contours of the transported objects in more than one manner. First the bottom side of the wall of the container can be flexible. Second the granular material is inherently able to flow in the lateral or upward direction. In this manner it can maintain the upper side of the container such that it can give way, in an upwards direction with the aid of suitable folds or the like. 
   As the wall of the container must be relatively yielding, there is the danger that the wall buckles out towards the downside. Therefore, one form of realisation of the invention provides that holding means are provided in the container, on which the bottom side of the sack-like container is hanged up. For instance, the holding means can be formed by vertical ribbons, which are connected to a holding element which is horizontally disposed in the container. According to one form of realisation of the invention, the holding element can be held by at least one pipe which is sealingly guided into the container and which is connected with the aspirating device. 
   The end of the aspirating device in the container suitably has a screen, which prevents aspiration of the granular material. 
   The individual functions of an industrial truck are controlled by a suitable control device. The latter can also control the functions of the load holding device according to the invention. Alternatively, a separate control device can also be provided. It can, at least partially, automatically control the operation of the load holding device according to the actuation of the load support. For instance, the load holding device can be lowered onto the transporting object when the load support performs a lift after picking up a load or has performed it. Conventionally, a load is picked up first and then it is brought into a desired height, before the truck drives to a desired place. When the lifting of the load is completed, the activation of the load fixation can take place. The fixing of the load can take place also as a first step, for instance with a double deck high-lift truck, in order to prevent falling off of the load upon lifting. According to a further form of realisation, the control device can stop the lowering of the load when a sensor which measures the push-force on the load generates an output signal which exceeds a predetermined value. 
   The aspirating device can be switched off automatically by the control device, when a pressure sensor detects that the pressure in the container falls below a predetermined value. 
   The invention will be hereinafter explained in more detail by means of a realisation example, which is represented in a drawing. 

   DETAILED DESCRIPTION OF THE INVENTION 
   While this invention may be embodied in many different forms, there are described in detail herein a specific preferred embodiment of the invention. This description is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiment illustrated 
     FIG. 1  schematically shows a load holding device according to the invention in a cross section. 
     FIG. 2  schematically shows an industrial truck and components thereof. 
   A holding plate  1  is mounted on a guiding part  5 . The guiding part  5  is guided movable in its height, in a manner independent from a load support  52 , in a lifting scaffold of an industrial truck  50 , and can be actuated by a not shown lifting drive. The lifting drive contains a hydraulic or pneumatic lifting cylinder, a shaft drive, a thread spindle or the like, for instance. The height shifting is intended to be indicated by the double arrow  20 . Besides to this, rolls  22  are indicated, which are guided in corresponding guiding rails of the lifting scaffold  56 . 
   On the holding plate  1 , a frame  7  is mounted to be horizontally running around. The frame can have a circular or a rectangular contour. The dimension and the contour correspond about to the standing-up area of transporting objects on standardised pallets. Other contours and sizes are also conceivable, however. The wall of the frame  7  has a bead  24 , projecting towards the inside, on the inside of the bottom side. 
   A sack-like container  2  has an upper wall  26 , a bottom wall  28  and a circulatory side wall  30 . The thickness of the walls can be equal or different. Altogether, they are made of a relatively flexible material, which may have elastomeric properties, too. The sheet forming the walls can be a single-layer or a multilayer one. In each case, it must have an air-impermeable layer. The outer side can have a wear-resistant coating. 
   The upper region of the side walls  30  is received inside the frame  7 , the bead  24  forming a corresponding notch  32  in the side wall  30 . The upper part of the side walls  30  can be joined with the inner side of the frame  7  in an appropriate manner, by gluing for instance. The upper wall  26  forms a circulating seam  34  with the side wall  30 , such that the upper wall  26  takes a distance to the holding plate  1 . 
   The bottom wall  28  has upward-directed foldings  36  at distances. 
   A pump  13  is driven by a not shown electric motor and is connected with an aspiration line  8  above the holding plate  1  via a check valve  12 . Via connecting parts  11 , the aspiration line  8  is in connection with two aspiration pipes  10 , which are sealingly guided into the interior of the container  2  across the upper wall  26 . However, the sealing must be such that it does not interfere with any lifting or lowering of the upper wall  26 . Anyway, this would not be the case when a yielding line was guided into the interior of the container  2  instead of a rigid pipe  10 . 
   In the present case, a horizontal element  9  is attached to the pipes  10 , which is supported on a screen  6 , which is mounted on the bottom end of the aspiration pipe  10 . On the horizontal holding element  9 , ribbons  3  are attached at distances, which are connected with the inner side of the bottom wall  28 . Through this, the bottom wall  28  is held and prevented from buckling or sinking through. 
   It is also conceivable to connect the ribbons  3  with the upper wall  26 . Before the check valve  12  with respect to the aspirating direction, a branching  38  is connected to the aspiration line  8 , in which a switching valve  40  is seated. The switching valve  40  connects the aspiration line  8  with the atmosphere, when it is in the opening position. 
   A granulate  4  is filled into the container  2 . The particles of the granulate  4  are selected such in their size and shape that the container  2  can adapt itself as well as possible to the contour of a load, which is disposed below the load holding device  60  on the load support  52 . The particles can be balls or irregularly shaped grains, which may consist of quite various materials. 
   In the following, the principle of operation of the load holding device  60  will be explained. 
   When the operator of the industrial truck  50 , on which there is the load holding device  60  shown in  FIG. 1 , has picked up the load, the operator actuates the lowering of the load holding device  60 . The beginning of the lowering movement can be controlled automatically in that a control device  58  couples the actuation of the load holding device  60  with the actuation of the load support  52 . Preferably, the support device  60  is lowered first, so that the load is securely fixed before it is lifted by the load support  52 . When the load is being lifted, the support device  60  has to be moved synchronously with the load support  52 . This is possible without any problem when the scaffold on which the support device  60  is guided, is fixed on the load support  52 . After a short or even longer lift of the load support  52 , the lowering can be initiated when this lift is ended. 
   The container  2  is lowered onto the load from the upside, in this the bottom side or bottom wall  28  of the container  2  adopts the contour of the load, because the granulate  4  is freely movable inside the container  2 . The end of the lowering movement can also be initiated automatically, in that a pressure sensor  62  detects when the push force of the load holding device  60  upon the load reaches a predetermined value. 
   After the end of the lowering process, the pump  13  is brought into operation and the switching valve  40  is closed. Through this, the air is sucked off from the container  2 , the check valve  12  preventing that any air current in the opposite direction takes place when the pump  13  is switched off. The switching on and off of the pump  13  can be manually controlled or even automatically. For instance, the pump can be brought into operation when the lowering movement of the load holding device  60  is ended. It can be switched off as soon as the air pressure in the container  2  falls below a predetermined value. 
   The aspiration of the air has the effect that the particles of the granulate  4  are pressed against each other and that frictional forces prevent any easy movement of the particles with respect to each other. This results in fixing (quasi a freezing in) of the momentaneous form of the container  2 . The thus fixed container transfers forces, which are necessary for holding the load, in a form-fitting manner. This is valid for the transmission of the forces between the load and the container  2  as well as for the transmission of the forces between the container  2  and the load holding plate  1 . The load holding plate  1  and the frame  7  are formed such that a form fitting is created between the container  2  and the load holding plate  1  or the frame  7 , respectively, which allows for force transmission in the vertical as well as in the horizontal direction. 
   When the industrial truck  50  is to set down the load, its load support  52  is lowered first. Next the lifting device moves up the load holding device  60 . In this manner, the load is released and can be set down. Next, the switching valve  40  is opened. Through this valve, air from the atmosphere can flow into the container  2 . The inflowing air causes the frictional engagement between the particles of the granulate to diminish and the container  2  adopts its original form again. 
   The above disclosure is intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the claims where the term “comprising” means “including, but not limited to”. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims. 
   This completes the description of the preferred and alternate embodiments of the invention. Those skilled in the art may recognize other equivalents to the specific embodiment described herein which equivalents are intended to be encompassed by the claims attached hereto.