Abstract:
A pole for a hand pallet truck that includes a pole bar which is linked to a support for a steerable wheel at its lower end and connected to a loop-shaped handle at the other end. An operating device is disposed within the space defined by the handle. The operating device is attached to a holding extension projecting into the handle in prolongation of the bar, and is connectable to a lifting apparatus of the hand pallet truck via a traction and/or pushing element. If applicable, it is connectable via a second traction and/or pushing element to a brake of the hand pallet truck, wherein an operating lever is disposed on either side of the extension. The operating levers are pivotally mounted on the holding extension in a plane essentially defined by the handle.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates to a hand pallet truck.  
         [0003]     2. Technical Background  
         [0004]     In conventional hand pallet trucks, the pole is used to steer and move the vehicle, as well as to pump for lifting a load. To operate the lifting apparatus, especially to lower the load, an operating element is required which should be easily accessible, and allow switching between the functions of lifting and driving as well as sensitive lowering of the load.  
         [0005]     Easy accessibility of the operating element is especially important for effective operation of the hand pallet truck when pulling the vehicle, i.e. when the pole is an inclined position in front of the vehicle. By contrast, actuating the functions with upright pole, i.e. when the vehicle is being pushed, is less important, because in most cases the vehicle is drawn out of the pallet, thereby returning the pole into the inclined position.  
         [0006]     For pumping and moving the vehicle, it is of advantage if the pole handle is centrally grippable in order to avoid unnecessary steering as well as frictional forces. At the same time, the actuating forces at the operating element should be as small as possible in all situations requiring a longer actuating path, which might be realized by providing a longer distance between the circle point and the lever pivot point, for example.  
         [0007]     It is known to use an extension of the pole bar traversing the handle as a mounting component for an operating lever extending to the sides. This known pole handle has the drawback that it cannot be gripped centrally. From DE 297 10 503 U1 it is further known to pivotally mount a control lever at the upper end of the portion of the bar extending into the handle. The lever must be pushed away from the operator to achieve a lowering of the load. Pulling the lever towards the operator will result in a switch to the lifting function. A drawback of this design is that the operator cannot actuate the functions well while pulling the vehicle because the control lever has to be pulled upwards to achieve a lowering action. Further, since the operating element is not familiar from other technical devices, it is less suitable for intuitive operation. The actuating forces are great due to the small distance between the circle point and the lever pivot point.  
         [0008]     Apart from the above described possibility of operating a hand pallet truck, it is also common to provide it with an integrated handbrake. In this context, it is known from EP 1 186 511 A2 to pivotally mount an operating lever on either side of a holding extension traversing the handle of the pole in prolongation of the pole. One operating lever is connected to a traction or pushing element for the lifting apparatus and the other one with a traction or pressure element for a brake. Actuation of the lifting apparatus is effected such that pulling of the operating lever initiates a lowering operation in the lifting apparatus while a push opens up the possibility to effect a lifting operation by pumping on the pole. Pushing the other operating lever leads to braking of the vehicle wherein the extent of the pivotal movement determines the braking power. This known arrangement further provides for a locking/unlocking lever which is also pivotally mounted on the holding extension and has a projection cooperating with a recess of the brake operating lever when the brake operating lever has reached a given hind position. Thus a parking brake is created which is released by pivoting the locking and unlocking lever in the opposite direction. Thereby the brake operating lever may return to its initial position by means of spring bias from the direction of the brake. Finally, the known arrangement also provides that the parking brake is released by actuating the other operating lever. In other words, when actuating the lowering operation, the parking brake is automatically released.  
         [0009]     In the hand pallet trucks described above, the brake is usually optional. Depending on whether a brake is present or not, different handle arrangements have to be provided, thereby complicating the production process.  
         [0010]     An object of the invention is to configure the pole head in a pole for a hand pallet truck such that it may optionally receive a brake operating device. When no brake is present, an especially ergonomic actuation of the lifting apparatus is desired.  
       SUMMARY OF THE INVENTION  
       [0011]     According to the invention, the inside of the housing for the operating device is arranged identically, whether an integrated brake is provided or not. To this end, two identical mounting places are provided in the housing, on each of which an operating lever may be pivotally mounted. If a brake is integrated, one of the operating levers is a brake operating lever while the other lever actuates the lifting apparatus. If the brake is omitted, in general only one operating lever is required for operation. However, a coupling mechanism is provided in the inside of the housing allowing the provision of an identical operating lever on the other side for actuating the lifting apparatus. Hence, it is possible to drive the lifting apparatus either by actuating one or both operating levers at the same time, wherein movement in one direction initiates the lowering operation and a movement in the other direction initiates the lifting operation. As is ergonomically intuitive, pulling at one or the other or both operating levers initiates the lowering operation.  
         [0012]     Therefore the invention allows to manufacture a pole head with operating device which is simple and constructed in an identical fashion, independent of whether a brake has to be actuated or not.  
         [0013]     The invention also provides a particularly simple and effective design for the actuation of the traction or pushing element for the brake. To this end, an interlock portion with a toothing is disposed inside the housing and a catch is movably mounted on the brake lever and engages the toothing, whereby the brake lever can be locked in different pivotal positions. A blocking and unblocking lever also mounted within the housing of the operating device actuates the catch to disengage it from the toothing. The catch and/or the blocking and unblocking lever is biased by a spring. This solution of the invention has the advantage that the brake lever is self-locking over the entire actuating path in several defined positions up to the end position at maximal braking action, i.e. letting go off the brake lever in a certain position leads to the braking force being kept up. Since all actuation components apart from the actuating portions of the operating levers are disposed inside the housing, the design is optically appealing. In addition, the risk of parts being damaged and thereby becoming non-functional is reduced.  
         [0014]     The actuating portion of the three possible operating levers may have the same shape or may be shaped differently. However, it is of advantage if—according to one embodiment of the invention—the material, the colour or the surface quality of the actuating portion for the brake lever differ from the corresponding properties of the other operating levers, so that the operator may recognize at first glance which lever is for braking and which lever is for actuating the lifting apparatus. A corresponding indication may also be achieved by differing shapes of the actuating portions.  
         [0015]     The inner portions of the levers preferably cross each other, so that the pivot point for one operating lever is disposed on the opposite side of the axis extending in prolongation of the pole through the housing. In this way, high lever action may be achieved, i.e. a relatively great actuating force may be achieved with little expenditure of force.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     Further advantages of the invention shall become apparent from the following description in connection with the accompanying drawings, in which  
         [0017]      FIG. 1  shows a top view of a pole head of a hand pallet truck including an operating device according to the invention;  
         [0018]      FIG. 2  shows a cross-sectional view through the device of  FIG. 1  taken along line  2 - 2 ;  
         [0019]      FIG. 3  shows a top view of a part of the pole head of  FIG. 1 . with the upper shell of the housing of the operating device removed;  
         [0020]      FIG. 4  shows a perspective view similar to that of  FIG. 3 , but including a brake operating lever;  
         [0021]      FIG. 5  shows the brake operating lever of  FIG. 4  including an interlock portion; and  
         [0022]      FIG. 6  shows the bottom view of the brake operating lever of  FIG. 5  and the interlock portion. 
     
    
     DETAILED DESCRIPTION  
       [0023]      FIG. 1  shows a bar  10  of a pole generally indicated at  12 . Only the section  10  and a loop-shaped handle  14  of the pole are shown. The other end of the pole bar  10  is connected or linked to the pillow block of a steered wheel of a hand pallet truck (not shown) for the purpose of manipulating the hand pallet truck accordingly. As usual, the hand pallet truck includes a pump for lifting the load carrying means and a valve arrangement for lowering the load carrying means.  
         [0024]     As usual, the handle  14  is formed by a suitably curved tube defining a plane in which is also disposed the axis of the bar  10 . The bar  10  projects into the interior of the handle  14 , thereby forming a holding extension  16 . This holding extension comprises a tube section  18  and a housing  20  which have been mounted and fastened on the tube section  18 . Details about this process will be described below.  
         [0025]     In the housing, two operating levers  22 ,  24  are pivotally mounted for actuation of the lifting and lowering functions of the hand pallet truck (not shown). Details of these levers  22 ,  24  and their mountings are apparent from the further figures.  
         [0026]     As shown by the arrows  26 ,  28 , the levers may be pivoted in both directions in a plane coinciding with or parallel to the plane of the handle  14 . Attention is drawn to the fact that the distance between the housing  20  or the extension  16  and the rear portion  30  of the handle  14  is such that the rear portion of the handle  14  may be gripped by hand in any position.  
         [0027]     As shown in  FIG. 2 , the housing  20  consists of an upper shell  32  and a lower shell  34 , the dividing plane  36  of the two shells being disposed in the central plane of the handle  14 . The left part of the housing  20  is formed by a socket portion receiving the tube section  18  in order to attach the housing  20 .  
         [0028]     As is apparent from  FIG. 3  and the following figures, the two operating levers  22 ,  24  have the same slight S-form. The curved actuating portions  38 ,  40  of the operating levers  22 ,  24  project through side slots  42 ,  44  in the housing  20  towards the outside. The curvature of portions  38 ,  30  is such that the convex sides face the operator and the concave sides face the pole bar, as is readily apparent from the drawings. The inner portions  36 ,  48  of the operating levers  22 ,  24  are curved in opposite directions and are pivotally mounted at pivot points  50 ,  52  in the housing  20 , respectively. Mounting is effected for example by means of a bearing journal extending through a hole in either portion  46 ,  48 . The holes are disposed nearly at the end of portions  46 ,  48 .  
         [0029]     The operating levers  22 ,  24  shown in  FIG. 3  in the neutral position may be pivoted upwards as well as downwards in  FIG. 3 . A stop to the pivotal movement is provided but not shown in detail.  
         [0030]     As is apparent from  FIG. 3  and the further figures, each lever portion  46 ,  48  has a toothed portion having two teeth  54 ,  56 . The toothed portions of the two lever portion  46 ,  48  cooperate with a toothed rack  58  attached to a shifting element  60  which is mounted such that it is linearly movable in the axis of bar  10  in the housing  20 . The toothed rack portion  58  includes two teeth  62 ,  64  on each of its opposing sides, which cooperate with the corresponding teeth  54 ,  56  of lever portions  46 ,  48 , respectively.  
         [0031]     A traction rope  66  is attached to the opposite end of the shifting element  60 , the traction rope being in turn connected to corresponding control devices in the hand pallet truck.  
         [0032]     Referring to  FIG. 3 , the function of the lever mechanism for actuating the traction rope  66  shown in the figures will now be explained.  
         [0033]     If a lever is pivoted in the direction of arrow  26 , i.e. towards the operator or handle portion  30 , as shown in  FIG. 4 , the toothed rack portion  58  will be displaced by tooth  56  in the direction of the operator. This causes rope  66  to perform a traction movement, the displacement being indicated by the distance d between the broken and full lines in  FIG. 4 . The broken line indicates the neutral position as shown in  FIG. 3 . It is apparent that the same operation is achieved when both levers  22 ,  24  are pulled. If one lever is pulled further than the other, the displacement of the lever pulled furthest is decisive. The extent of deflection of the traction element  66  determines the lowering speed of the load carrying means of the hand pallet truck (not shown).  
         [0034]     If the pulled lever is released, it returns to the neutral position according to  FIG. 3  by means of a suitable restoring device. For this purpose, spring means may be provided in suitable positions. It is also conceivable to lock the levers  22 ,  24  lightly in the neutral position in order to prevent a slight touch from triggering a function.  
         [0035]     The lever  22  remains in its neutral position when the lever  24  is being pivoted for the purpose of triggering a lowering function. With respect to the lowering function, the operating levers  22 ,  24  are independent.  
         [0036]     If a lever  22  or  24  is being pushed, i.e. pivoted away from the operating person, the shifting element  60  will be pushed in the same direction. This initiates a lifting function. The displacement of rope  66  relative to the neutral position is indicated at d′. Now lifting of the load carrying means may be effected by “pumping” with the pole bar  10 .  
         [0037]     Teeth  56 ,  56  engage the toothing of toothed rack portion  58  such that a displacement of the toothed rack portion  58  caused by an actuation of one lever leads to pivoting of the other lever as well. Actuating one operating lever  22 ,  24  in the direction away from the operator therefore leads to synchronous displacement of both levers. Hence, it would also be possible to actuate both levers. Due to this synchronous displacement, the operator may recognize the operating position of the actuating device.  
         [0038]     It may happen that one operating lever is being pulled and the other one is being pushed. As is apparent from the drawings, this will activate the function corresponding to the lever on which the greatest force is exerted.  
         [0039]     However, if one lever  24  is being pulled, pushing the other lever  22  is not possible because this lever  22  will be blocked by lever  24  through an interlocking of teeth.  
         [0040]     As far as the same parts as in  FIG. 3  are shown in  FIG. 4 , the same reference signs are used. It is apparent that, with respect to  FIG. 3 , the second operating lever  22  has been removed and in its place an operating lever  70  including an actuating portion  72  and an inner portion  74  has been provided. The inner portion  74  is pivotally mounted at the same mounting place  50  where, in the embodiment of  FIG. 3 , the operating lever  22  was pivotally mounted. The housing is arranged such that the operating lever  22  may easily be replaced by the operating lever  70  and the other way round. The actuating portion  72  may have the same geometry as the actuating portion  38  of  FIG. 3 , alternatively it may be shaped differently or have a different surface or colour so that the operator may distinguish between levers  24  and  70  with respect to their function.  
         [0041]     As is also apparent from  FIG. 4 , a brake rope  76  is attached to a middle portion of the operating lever  70  at  78 . Pulling the operating lever  70  causes actuation of the brake of the hand pallet truck (not shown). The brake rope  76  is preferably accommodated in the tubular pole bar (not shown).  
         [0042]     As further shown in  FIG. 4 , inner portions  48  and  74  of levers  24 ,  70 , respectively, extend through the displacement element  60  in order to cross there. Only the lower part of the displacement element  60  may be seen in  FIG. 3 . This has no bearing on the function, excepting the fact that the levers  24 ,  70  also cross there in order to be able to achieve a great lever force.  
         [0043]     The third lever acting as locking and unlocking lever  80  is pivotally mounted at  82  on lever  70 . For this purpose, lever  70  is reduced in thickness in the mounting area, so that the locking and unlocking lever  80  may also project through the slot  42  of housing  20 . A spring  84  urges or biases the lever  80  in anticlockwise direction. The other end of the spring  84  is fixed at lever  70 .  
         [0044]     Inside the housing is disposed a plate-shaped interlock portion  86  having a saw toothing  88 . It may be removable in case a brake actuation is not desired.  
         [0045]      FIG. 5  merely indicates a bearing bush  90  of the inner portion  84  of lever  70  for mounting at pivot point  50  according to  FIG. 4 .  
         [0046]     On the same shaft as the locking and unlocking lever  80  is mounted a catch  92  on lever  70 . The pivot point is indicated at  94 . Due to the bias of the locking and unlocking lever  80 , the catch  92  is always pivoted against toothing  88 , so when pulling at operating lever  70 , the catch  92  ratchets along the toothing  88  and lockingly engages the tooth space to which the catch  92  is aligned at the moment when the pivotal movement of lever  70  is ended. Thereby the operating lever  70  may be locked in several positions to keep the braking force constant at the set value. The operator may unlock the lock by actuating the locking and unlocking lever  80  and pivoting it in clockwise direction in  FIG. 5 . This causes the catch  92  to pivot in anticlockwise direction and disengage with the toothing  88 . The spring of the brake may return the operating lever  70  to its original position.  
         [0047]     In the housing, appropriate stops to limit the displacement of the operating levers may be provided.