Abstract:
A single-wheel driving mechanism for floor transport vehicles is comprised of a gearing housing with at least one gear stage, a flanged-on drive motor, and a driven running wheel. For obtaining the smallest possible installation space or achieving a simplified installation or removal of the single-wheel driving mechanism, in conjunction with high transmission of force at the same time, the running wheel is directly connected with torsional strength with a gear of the transmission, and the gear of the transmission is rotatably supported on a support element.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a single-wheel driving mechanism, in particular for single-wheel floor transport vehicles, which is comprised of a gearing housing with at least one gear stage, a flanged-on drive motor and a driven running wheel. 
     2. The Prior Art 
     single-wheel driving mechanisms of the type specified above are preferably employed for floor conveyor vehicles. It is important in connection with such mechanisms that they have small and narrow dimensions, and that the risk for the vehicle of tilting over is reduced by keeping the center of gravity of the vehicle as low as possible. The installation space has to be kept small, so that the possibilities for maneuvering the vehicle are enhanced. Not to be disregarded in this connection is the fact that the driving forces and loads, which range from 1 to 3 tons, that have to be transmitted to one single running wheel via the single-wheel driving mechanism, are quite high, and that to that extent, the housing and the required gear stage consequently have to be designed for such loads. 
     A single-wheel driving system is known, for example from German Patent No. DE-PS 31 33 027, in connection with which a pinion of a spur gear drive is arranged on the shaft of the electric motor in connection with a two-stage type of gearing. This, however, causes the pitch circle to be relatively large due to the material thickness required between the foot of the tooth and the receiving bore, which means that the reducing gear ratio is consequently limited. Furthermore, such a constructional measure requires high manufacturing expenditure. The downwardly-extending support for the shaft of the spur gear and the bevel-gear pinion is disposed at the level of the rim and tire of the running wheel, which means that it is not possible to keep the spacing of the shaft from the center of the gearing axis as small as desirable for obtaining a particularly small turning radius. 
     Furthermore, known designs of single-wheel drive mechanisms have the disadvantage that their installation and removal require increased labor expenditure in particular for later maintenance and service purposes, and that the construction of the housing has to satisfy increased requirements. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide a single-wheel driving mechanism that has the smallest possible installation space and permits simplified installation and removal while high forces are transmitted at the same time. 
     For solving this problem, the running wheel is directly connected with a gear with torsional strength, and the gear is supported in a rotating manner on a support element that is coaxially disposed on the inside and stationary. Due to the fact that the running wheel is directly connected with a gear with torsional strength and mounted on a support element, the number of structural components used can be substantially reduced. This results in cost savings and permits a substantial simplification of the construction. When the gear is rotatably supported on a pivot of the housing, or on a journal of the shaft that is mounted with torsional strength and received in a passage (or breakthrough) in the housing, it is possible to dispense with a flanged shaft with bearing elements, and to use a single-component housing without any cover and screw connections due to the simplified of construction. Such a design comprises an extremely narrow type of construction. 
     Furthermore, such an embodiment comprises a larger bevel gear combined with the same structural size of the gearing, and therefore leads to a reinforcement of the gearing. Admitting the force directly into the running wheel via the bevel gear is particularly advantageous as well. The shaft journal, which is received in a passage of the housing, may be preferably used when higher loads are involved. Furthermore, the shaft journal, which is not rotating, reinforces the housing in the lower areas in a beneficial manner, whereby the occurring forces are immediately introduced into the housing via the shaft journal. In this connection, the bevel gear located on the driven side may comprise a pot-shaped attachment extending in the direction of the running wheel. Such an attachment is molded on, forming one piece with the bevel gear, so that it is directly connected with the running wheel, and the largest possible support area can be formed versus the pivot of the housing or shaft journal. 
     The transmission system is designed in the form of a two-stage gearing, and a first gear stage, which has the tooth system of a spur wheel, is associated with the drive motor, whereas a second gear stage having the tooth system of a bevel gear, is associated with the running wheel. The two gear stages are connected by a driving shaft that is supported in the housing. The running wheel is connected with torsional strength with the bevel gear on the driven side; and the rim of the running wheel and/or the bevel gear are supported versus the pivot of the housing or the shaft journal via bearing elements. In the embodiment of the single-wheel driving mechanism as defined by the invention, the running wheel, together with the bevel gear on the driven side, is directly supported on a component of the housing, specifically on a housing pivot or shaft journal. Suitable bearing elements such as, for example antifriction bearings are used in this connection. The driving shaft, which is supported in the housing, connects the first gear stage consisting of the spur gear tooth system with the bevel gear stage for driving the running wheel, within the proximity of the driving motor. Due to the housing pivot or shaft journal, no minimum thickness of the wall of the housing is required for the arising forces because such forces can be directly transmitted to the running wheel. Furthermore, due to the special way in which the running wheel is secured, it is possible to design the body of the wheel in a variable manner, and it is in particular possible to continue to use existing wheel bodies in the present novel construction. 
     Viewed overall, it is thus possible to obtain a reinforcement of the transmission system by the novel construction with no change or reduction in the structural size. Such a system, moreover, requires fewer structural components and thus leads to a reduction of the labor expenditure for the installation or removal of the driving system. 
     In such an embodiment of the invention, the support element is arranged axially in relation to the running wheel and is connected with the housing, for example screwed to the latter or designed in a way so as to form one single piece with the housing. Or, in the case of the shaft journal, the support element is pressed into a passage (or breakthrough), whereby the support element is designed for receiving two antifriction bearings, on which the bevel gear and, if necessary, the rim of the running wheel can be supported. Taking into account the dimensions and loads specified for a single-wheel driving mechanism with the smallest possible installation space and an optimal tooth system and support ratio, it is possible to manufacture the driving mechanism at favorable cost by virtue of the novel construction as defined by the invention. 
     A further advantage consists in that the smallest possible radius of pivot around the vertical axis of the single-wheel driving mechanism is achieved especially in connection with running wheels that offer no space for accommodating any other support for the driving shaft because of their relatively small outside diameters between the hub and the rim of the running wheel. Due to the fact that its two bearings each are arranged outside of the tooth system as a result of the relatively large spacing between the two bearings, in particular the support of the driving shaft is realized in this connection in a particularly favorable manner. Adjusting a good support profile and favorable clearance (or play) of the bearing of the bevel gear drive, which has a tooth system in the form of a spiral or circular arc, is simplified because both the spur wheel and the bevel gear pinion can be mounted on the driving shaft in a fixed manner. For the required adjustment of the axial position of the tooth system of the bevel gear pinion and bevel gear, it is necessary to associate shims with the bearing in a simple manner, whereby the spur gear may be connected with the driving shaft by means of a pressed fit. 
     In a special embodiment of the invention, a pump device is integrated in the pivot of the housing or shaft journal, the latter being provided with torsional strength. Such a pump device is comprised of an axially movable tappet and a pressure chamber with an inlet valve and an outlet valve. With the help of the integrated pump device, it is possible to pump transmission oil from the lower interior space of the housing upwards to the lubrication system for the upper bearing elements. The special advantage offered by such a system is that the housing of the gearing does not have to be completely filled with oil, so that, for example no excessive slip can develop, and the degree of efficiency of the transmission is thus enhanced. At the same time, the pump device assures that the upper elements of the gearing and also the bearing elements can be adequately lubricated. The tappet is disposed in this connection with one end in a groove with a wavelike deepening that is formed in the pot-shaped attachment of the bevel gear, whereby the tappet is pressed into the groove in a spring-loaded manner and put into an axial movement that results from the rotational motion. The opposite side of the tappet is sealed off against a pressure chamber and is used as a piston (or plunger) that is capable of pumping the oil present upwards via an inlet valve and an outlet valve. 
     For this purpose, a bore formed to serve as an oil channel is provided in the driving shaft. This bore feeds into the pressure chamber via the outlet valve, whereas the inlet valve is connected with the lower interior of the gearing. The bore ends above the driving shaft at a level assuring adequate lubrication of the upper bearing elements. 
     The stump of the driven shaft of the electric motor may be provided with a pinion tooth system or a pinion and drives the spur wheel of the high-speed shaft of the electric motor with a lower number of teeth. This provides the reduction ratio of the spur wheel drive with an optimal value, so that taking into account the total reduction of this two-stage single-wheel driving mechanism, the reduction ratio of the bevel gear drive needs to be selected only adequately small that a number of teeth greater than the limit number of teeth can be provided for the tooth system of the bevel gear pinion. In this way, a more robust design is obtained in view of the high torque, as compared to driving mechanisms of this type equipped with spur gear pinions with a higher number of teeth. 
     The torque is thus transmitted with a pinion tooth system from the drive motor to the spur wheel. The spur wheel is connected with torsional strength with a driving shaft, whereby the driving shaft drives the bevel gear, the latter being connected with the running wheel, via a tooth system of the bevel pinion. 
     The housing is preferably designed in the form of one single component and comprises a first opening leading to the drive motor, and a second opening leading to the running wheel. These openings of the housing facilitate the installation and removal of the single-wheel driving mechanism. The first opening is closed after the installation by means of a screw connection with the inside ring of the bearing of the rotating ring, and the second opening is closed by the bevel gear and a clipped-in covering flap. Two sealing means are employed in this connection between the non-rotating and rotating elements, which limit the enclosed volume and prevent the transmission oil from leaking out. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings. It is to be understood, however, that the drawings are designed as an illustration only and not as a definition of the limits of the invention. 
       In the drawings, wherein similar reference characters denote similar elements throughout the several views: 
         FIG. 1  is a cut side view of a single-wheel driving mechanism as defined by the invention, comprising a pivot of the housing; 
         FIG. 2  is a cut side view of a single-wheel driving mechanism as defined by the invention, with a pressed-in shaft journal; and 
         FIG. 3  is a cut side view of a single-wheel driving mechanism as defined by the invention, comprising a pivot of the housing and an integrated pump device. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now in detail to the drawings,  FIG. 1  shows a cut side view of a single-wheel driving mechanism  1  comprised of a drive motor  2 , a housing  3  with a two-stage gearing  4 , and a rotating rim bearing  5  for supporting the housing  3  in a pivoting manner. 
     Outer ring  6  of bearing  5  of the rotating rim is provided for the purpose of mounting the single-wheel driving mechanism  1  in a vehicle, whereby a plurality of the threaded bores  7  distributed over the circumference may be used for the screw connections. Inner ring  8  of the bearing of the rotating rim bearing receives a vertically mounted drive motor  2  and housing  3 , which is located underneath drive motor  2 . Thus drive motor  2 , together with housing  3 , can be swiveled vis-à-vis the floor transport vehicle to be driven. For driving the floor transport vehicle, provision is made for a running wheel  9 , which is mounted by pressing it onto a rim  10  of the running wheel. Running wheel  9  may consist of, for example a solid rubber or plastic wheel. According to the invention, rim  10  of the running wheel is screwed to the gear stage with a bevel gear  11  on the driven side by means of a plurality of the screw bolts  12 , which are distributed over the circumference. Rim  10  of the running wheel and bevel gear  11  rest on a pivot  13  of housing  3 , said pivot being shaped by molding on housing  3 , forming one piece with housing  3 . On its outer surface  14 , pivot  13  of housing  3  comprises two antifriction bearings  15  and  16 , which are directed against one another and supported by a contact pressure-exerting disk  17 . Contact pressure-applying disk  17  is screwed to pivot  13  of housing  3  by means of a screw bolt  18 . The antifriction bearings  15  and  16 , as well as screw bolt  18  are protected against soiling by a clamped-in (or clipped-in) cover cap  19 . Cover cap  19  closes opening  20  of housing  3 . 
     With its bevel gear tooth system  21 , bevel gear  11  mates with bevel pinion tooth system  22  of a bevel pinion  29  of driving shaft  24 . Driving shaft  24  is arranged with lateral offset versus drive motor  2  and supported vis-à-vis housing  3  by the upper and the lower antifriction bearings  25 ,  26 . Antifriction bearings  25  and  26  each are mounted at the end side on driving shaft  24  and rest in the recesses  27  and  28 , respectively, of the housing  3 . The lower gear stage is formed by bevel gear  11  and a bevel pinion  29  secured on driving shaft  24 . Alternatively, it is possible to provide driving shaft  24  with a bevel tooth system. 
     The second gear stage is formed by a spur gear  30  with a spur gear tooth system  31  and a pinion tooth system  32  of electric motor shaft  33 . Electric motor shaft  33  protrudes beyond rotating rim bearing  5  into gear housing  3 , so that pinion tooth system  32  leads to engagement with spur gear tooth system  31  of spur gear  30 . Housing  3  is screwed to inner ring  8  of the rotating rim bearing via a plurality of the screw bolts  34 , which are distributed over the circumference. Recess  28  for receiving the upper antifriction bearing  26  of driving shaft  24  is closed by a sealed closing cap  35 . Inner ring  8  of the bearing of the rotating rim thus closes the upper opening of the housing  3  with the drive motor  2 , which is arranged vertically in relation to the transmission  4 . For avoiding soiling, outer ring  6  of the bearing of the rotating rim and inner ring  8  of the bearing of the rotating rim are sealed by seals  36 . Transmission  4  is sealed against dirt or oil loss by sealing elements  37  and  38 . 
     Drive motor  2  is mounted vertically on bearing  5  of the rotating rim and is screwed to inner ring  8  of the rotating rim by a plurality of screw bolts  40 , which are distributed over the circumference. Electric motor shaft  33  with armature winding  41  is supported versus housing  44  via a lower and an upper antifriction bearing  42  and, respectively,  43 , and against inner ring  8  of the bearing of the rotating rim on the other hand. The motor winding  45  is secured in housing  44 . The end of electric motor shaft  33  disposed opposite pinion tooth system  32  is extending from motor housing  44  and connects a steering fork. 
     The single-wheel driving mechanism is driven via drive motor  2 , to which voltage can be admitted, via pinion tooth system  32  of driving shaft  33 . The drive is acting directly on spur gear  30 , which is connected with driving shaft  24  with torsional strength and transmits the torque to bevel pinion  29 , and from the latter via tooth system  21 ,  22  to bevel gear  11 , which is connected with torsional strength with rim  10  of the running wheel, or the running wheel  9 . The pivotal movement of steering drive mechanism  1  is assured by bearing  5  of the rotating rim and may take place via the steering fork (not shown). As compared to the known prior art, the embodiment of the single-wheel driving mechanism as defined by the invention requires no running wheel shaft, which results in a saving of costs, and facilitates the installation or removal of the driving mechanism. Furthermore, the construction is characterized by a relatively simple structure of the housing  3  and, owing to the direct coupling provided between running wheel  9  and bevel gear  11 , leads to a particularly advantageous transmission of the torque to running wheel  9 . In addition, arranging antifriction bearings  25  and  26  for driving shaft  24  outside of spur gear  30  and the bevel pinion  29  provides the possibility for permitting a particularly favorable small amount of play between the wall of the transmission and the driven running wheel. Furthermore, owing to the inventive embodiment, it is possible to have the smallest possible spacing between driving shaft  24  and electric motor shaft  33  in the presence of the same or superior transmission of the torque. 
       FIG. 2  shows a cut side view of another embodiment of a single-wheel driving mechanism  50  comprised of a drive motor  2 , a housing  51  with a two-stage gearing  4 , and a rotating rim bearing  5  for pivotably supporting housing  51 . 
     The structure of single-wheel driving mechanism  50  corresponds almost completely with the embodiment according to FIG.  1 . Only the housing  51  is different from the housing shown in  FIG. 1  on account of its shape. Instead of a pivot of the housing, the lower area of the housing  51  comprises a passage (or breakthrough)  52 , which is provided for receiving a shaft journal  53 . This shaft journal  53  is pressed into passage  52  in such a way that it is received in housing  51  with torsional strength. In the exemplified embodiment shown, shaft journal  53  is provided with a flange-shaped collar  54  that comes to rest in a recess  55  of housing  51 . The shaft journal  53  penetrates the entire lower part of housing  51  and, furthermore, serves for receiving the antifriction bearings  15 ,  16  in the manner shown already from FIG.  1 . Said bearings, furthermore, receive a bevel gear  56  in a supporting manner. As compared to the known design, bevel gear  56  has a pot-shaped attachment  57  pointing in the direction of running wheel  9 . Running wheel  9  with its rim  58 , which deviates in a minor way from the earlier form as well, is secured on said attachment by screw bolts  59 . A contact pressure-exerting disk  60  fixes antifriction bearings  15  and  16 . Disk  60  has a chamfer  61  and is directly screwed to shaft journal  53  by means of screw bolt  18 . Because the contact pressure-exerting disk  60  has a diameter that is dimensioned slightly larger than the one of shaft journal  53 , antifriction bearings  15 ,  16  are fixed in their positions on outer surface  62  of the shaft journal  53 . A covering cap  62  again closes a passage bore extending through to screw bolt  18 ,  50  that no dirt can penetrate antifriction bearing  15 ,  16 . By realizing a housing  51  with a shaft journal  53  pressed into a passage (or breakthrough)  52 , housing  51  is additionally reinforced in the lower area and, furthermore, the manufacture of housing  51  is facilitated in terms of casting technology. In all other respects, the single-wheel driving mechanism  50  offers the same technical advantages as the embodiment shown in FIG.  1 . 
       FIG. 3  shows a further sectional side view of a single-wheel driving mechanism  70  that is also comprised of a drive motor  2 , a housing  71  with a two-stage gearing  4 , and a rotating rim bearing  5  for pivotably supporting housing  71 . The construction of the single-wheel driving mechanism  70  is approximately identical with the one of single-wheel driving mechanisms  1  and  50  according to  FIGS. 1 and 2 , respectively. However, deviations ensue on account of the fact that a pump device  73  is additionally received in a pivot  72  of the housing. Pump device  73  is comprised of a tappet  74 , which is supported in an axially movable manner in a bore  75  of pivot  72  of the housing. Tappet  74  is acting on a pressure chamber  76 , which is connected with an outlet valve  77  and an inlet valve  78 . Inlet valve  78  feeds into a lower interior space  79  of the housing, which, as a rule, is completely filled with oil. Outlet valve  77 , on the other hand, is connected via a connection channel  80  with a bore  81  centrally extending in driving shaft  24 . Bore  81  is extending up to above the antifriction bearing  26  provided for supporting the driving shaft  24 . Due to the action of the pump, the oil is therefore pumped from interior space  79  of the housing and via inlet valve  78  and outlet valve  77  located within the bore  81 , up to antifriction bearing  26 , from where it supplies both the driving shaft  24  and the other components of the gearing with an adequate amount of oil. 
     In the embodiment shown, tappet  74  is pressed by a spring  82  against a pot-shaped attachment  84  of bevel gear  83 , and rests in a groove  85  that is arranged in the form of a ring around screw bolt  18 , and comprises a wavelike deepening, so that when running wheel  9  is rotating, tappet  74  is put into an axial motion against the spring force of the spring  82 . The opposite end of tappet  74  is sealed off against pressure chamber  76  to the extent that it possible to obtain a suction and pressure effect. So that tappet  74  is capable of engaging the groove  85 , the contact pressure-exerting disk  86  has a passage (or breakthrough)  87 . 
     Accordingly, while only a few embodiments of the present invention have been shown and described, it is obvious that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention.