Abstract:
A running gear, for example, a single-rail lower-flange running gear for hoisting equipment, includes several wheels running on a rail, at least two of which are arranged one behind the other in the direction of travel of the running gear and adapted to be driven by an electric motor. The driven wheels are joined to at least two shafts, which are oriented coaxially to the axis of rotation of said at least two driven wheels.

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to running gears for hoisting equipment. 
   BACKGROUND OF THE INVENTION 
   From German utility model DE 84 34 418 U1 there is known a running gear of a chain block. The running gear includes a U-shaped frame and four wheels adapted to travel on the lower flange of an I-shaped rail. The wheels each have a wheel flange, with which the wheels are guided at the outer side of the lower flange. In the lengthwise direction of the rail, the four wheels are divided into a right pair and a left pair, in the manner of a four-wheeled vehicle. Within the pairs, the two left and the two right wheels are arranged at a distance from one another and one behind the other. Furthermore, one of the two pairs is driven by means of an electric motor. For this, the driven pair of wheels each has a revolving gear rim, arranged in the region of the outer circumference of the wheel flanges. The wheel flanges of the two driven wheels are joined together by a gear arranged between the driven wheels. Thus, this gear meshes with the two wheel flanges of the driven wheels and is fastened on a take-off shaft of a transmission, which is secured to the side of the frame in the lengthwise direction of the rail and, thus, in the direction of travel of the running gear. The frame is thus located between transmission and gear. At the drive end, the electric motor is flanged to the transmission. Furthermore, the frame with the wheels passes around the rail in the manner of a U and has a bolt-shaped cross arm, from which the chain block is hung at the center. The width of the frame can be altered by the cross arm, so that the running gear can be adjusted to the width of different I-shaped rails. 
   Moreover, from German patent DE 34 18 800 C1 there is known a similar running gear which can travel on the lower flange of an I-shaped rail, especially a suspended rail. This running gear differs essentially from the one previously described in that it has only two wheels with wheel flanges, arranged opposite each other, rather than the four wheels. One of the two wheels is driven by an electric motor with a transmission, which is connected directly to the axle of the driven wheel by its take-off shaft. 
   From German utility model DE 1 902 712 there is already known a single-rail lower-flange running gear for underhung cranes, including a total of four running wheels arranged one behind the other and opposite each other in the direction of travel. The running wheels are mounted on a right and left side shield, at the inner sides of the side shields. The drive for the running wheels comes from a drive shaft positioned through the side shields at their back side, being connected to an electric motor via the gears of a transmission. The gears of the transmission are enclosed by a housing and thus protected against dirt and grime. 
   SUMMARY OF THE INVENTION 
   Based on the problems encountered with the prior art, the present invention provides a running gear, such as a running gear for hoisting equipment, which is low in noise and low in wear, even in dirty surroundings. 
   According to an embodiment of the present invention, a running gear, such as a running gear for hoisting machines, includes several wheels running along a rail, including at least two wheels arranged one behind the other in the direction of travel of the running gear and adapted to be driven by an electric motor. The at least two driven wheels are joined to shafts that are oriented coaxially to the axis of rotation of the driven wheels. The running gear also includes a right side shield and a left side shield, each having projecting hubs on the inner side, on which the wheels are mounted. 
   Optionally, one of the running gears is mounted on each shaft and is adapted to mesh with an intermediate gear. 
   A separation of the wheels from the gears may be achieved in that the shafts are mounted on one side shield of the running gear and the gears and the wheels are arranged at opposite sides of the side shield. This also facilitates a lubrication of the gears, without the lubricant having a negative influence on the transfer of the driving forces of the wheels to the rail. 
   Optionally, one of the shafts extends beyond the gear and is connected to the electric motor via a transmission, such that the intermediate gear is responsible for the transfer of force to the second shaft. 
   Alternatively, the intermediate gear may be mounted on an intermediate shaft, which is connected to the electric motor. A transmission may be provided in the form of a transmission gear, mounted on the intermediate shaft, which meshes with a driving gear connected to the electric motor. 
   Optionally, the running gear may include a housing and a frame. Because of the above described separation of the wheels from the gears, at least the gears or the intermediate gear are enclosed by a part of the housing, which is fastened to the side shield of the frame. The housing or housing part can minimize the running noises of the gears, and more easily enable the gears to be lubricated with oil or grease. 
   In one embodiment, the electric motor is mounted on the housing. Another embodiment calls for the electric motor driving the shafts via a transmission. 
   The shafts and the driven wheels may be configured as a single or unitary piece. 
   In another embodiment, the running gear comprises a U-shaped frame with two driven wheels and two non-driven wheels. The U-shaped frame has a right side shield and an opposite left side shield, which are joined together by a cross arm to make the U-shaped frame and mounted on the respective inner sides of the side shields. The driven and non-driven wheels roll along the lower flange of the rail. 
   Optionally, the hubs for the driven wheels are hollow and the shafts are positioned through the hubs. 
   Further, the running gear may be led by guide rollers running along the rail, such that the wheels are adapted to be designed without wheel flanges and the wheel spacing can be shorter. 
   Thus, the embodiments described above provide a simple bearing of the wheels against the side shields. Because the shafts directly drive the wheels, the wheels can be configured without a revolving gear rim. Furthermore, for wheels with gear rims, the gear rim lies in the rolling contact region of the wheels, which leads to great wear and louder running noise, especially at high speed, due to dirt and grime. Moreover, the diameter of the wheels is smaller than wheels with gear rims, so that the wheel spacing inside the running gear can be chosen to be shorter and, thus, the running gear can negotiate curves more easily. Optionally, a double wheel drive may be implemented. 
   These and other objects, advantages, purposes and features of the present invention will become apparent upon review of the following specification in conjunction with the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a sectional view of a running gear on an I-shaped rail in accordance with the present invention; 
       FIG. 2  is a sectional view from above the running gear per  FIG. 1 , according to a first embodiment; and 
       FIG. 3  is a sectional view of the driven part of the running gear per  FIG. 1 , according to a second embodiment. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to the drawings and the embodiments illustrated therein,  FIG. 1  shows a sectional view of a running gear  1  for a chain block (not shown) or the head piece of a crane. In the illustrated embodiment, running gear  1  includes a frame  2  and four wheels  3 , of which one right wheel  3   r  and one left wheel  3   l  can be seen. 
   Frame  2  is generally U-shaped and encloses from underneath an I-beam rail  4  in the region of its lower flange  4   u  and adjoining web  4   s . Moreover, frame  2  includes a left side shield  5   l  and a right side shield  5   r , on which the wheels  3   r  and  3   l  are mounted, and which are joined together by a cross arm  6 . Side shields  5   l  and  5   r  have a borehole  7  at bottom center, through which the boltlike cross arm  6  is passed or positioned. Cross arm  6  thus connects the two side shields  5   l  and  5   r  to the frame  2 . In the region of the borehole  7 , cross arm  6  is secured in the lengthwise direction by rings  8 , which abut against the respective sides of the side shields  5   l  and  5   r . Thus, side shields  5   l  and  5   r  are adapted to be adjusted to the width of the lower flange  4   u  of the rail  4  by the cross arm  6  with the rings  8 . 
   The wheels  3  run along the top side of the lower flange  4   u  of the I-beam rail  4 . Furthermore, the wheels have no wheel flanges, since the frame  2  is led by guide rollers  9  at the lateral lengthwise sides of the lower flange  4   u . Guide rollers  9  are mounted on the side shields  5   l  and  5   r  and are adapted to turn about vertical axes. The vertical axes are thus vertically oriented when the rail  4  runs horizontally. 
   It can also be seen from  FIG. 1  that only the left wheels  3   l  are driven by an electric motor  10 , flanged onto the left side shield  5   l  via a transmission  23 . 
     FIG. 2  shows a sectional view from above of the running gear  1  per  FIG. 1  in a first embodiment. The left wheels  3   l  and the right wheels  3   r  are secured one behind the other in the lengthwise direction L of the rail  4 , and with a spacing to the respective side shield  5   l  and  5   r . Left wheels  3   l  and right wheels  3   r  are adapted to turn. Left side shield  5   l  and right side shield  5   r  each include two hubs  11 , which extend from the inner side  5   l  facing rail  4  to rail  4 , or the opposite right side shield  5   r . A bearing  12 , such as a ball bearing, is provided on the outer circumference of the hubs  11 . Bearing  12  carries one of the wheels  3 . The hubs  11  on the right side shield  5   r  are fashioned as solid hubs, while the hubs  11  at the left side shield  5   l  are hollow hubs. 
   In order to drive the left wheels  3   l  of the left side shield  5   l , central boreholes  13  are provided in the left wheels  3   l , into which shafts  14   a  and  14   b  are inserted. The shafts  14   a  and  14   b  are adapted to be held in boreholes  13  by positive fit with either multi-tooth connections or press-fit connections. In order to use left and right wheels  3   l  and  3   r  of identical construction, the boreholes  13  can also be provided in the right wheels  3   r , but have no function there. 
   The shafts  14   a  and  14   b  are mounted by another bearing  15  in a housing or housing part  20 . A surface of housing part  20  lies against the left side shield  5   l  and is connected or joined thereto, such as by a screw or the like. Gears  16   a  and  16   b  are arranged on the shafts  14   a  and  14   b  next to the bearing  15 , such as by customary or standard shaft and hub connections. The outer diameter of gears  16   a  and  16   b  may be identical. In order to join together gears  16   a  and  16   b , which may be spur gears, for drive purposes, an intermediate gear  17  is arranged between the gears  16   a  and  16   b , and meshes with gears  16   a  and  16   b . The intermediate gear  17  is mounted on an intermediate shaft  18 , which is arranged parallel and in line with the shafts  14   a  and  14   b . Furthermore, intermediate shaft  18  is mounted at both ends in a bearing  19 , which may be a ball bearing. The bearings  19  are mounted in the walls of housing part  20 . Thus, housing part  20  is adapted to accommodate gears  16   a  and  16   b , shafts  14   a  and  14   b , intermediate gear  17  and intermediate shaft  18 . The transmission formed from the gears  16   a  and  16   b , as well as the intermediate gear  17 , is thus enclosed and is adapted to be provided with an oil or grease filling. 
   In the illustrated embodiment, housing part  20  is configured as enclosed and is thus adapted to be built onto the left side shield  5   l  as a modular component. Housing part  20  may also be configured as a cover, and the left side shield  5   l  as a cup. The reverse could also be done, i.e., housing part  20  may be configured as a cup, while left side shield  5   l  may be configured as a cover. 
   Furthermore, the first shaft  14   a  extends or protrudes from the left wheel  3   l  by gear  16   a  and protrudes or sticks out from housing part  20 . Housing part  20  has a corresponding borehole  24 . The protruding end of shaft  14   a  is joined by transmission  23  to the electric motor  10 , which is fastened to the outer side of the housing part. In this configuration, the first shaft  14   a  is the driven shaft of the transmission  23 . 
   Moreover,  FIG. 2  shows guide rollers  9 , which are mounted on the left side shield  5   l  and the right side shield  5   r  and arranged both in front of and behind the left wheels  3   l  and right wheels  3   r  in the lengthwise direction L of the rail  4 . 
     FIG. 3  shows a sectional view of the left side shield  5   l  per  FIG. 1  in a second embodiment. In the second embodiment, electric motor  10  is not connected directly to the first shaft  14   a , but instead has a drive gear  21  at the power take-off side. Drive gear  21  meshes with a transmission gear  22  fastened onto the intermediate shaft  18 . The first shaft  14   a  has the same length as the second shaft  14   b . Thus, no transmission  23  is required. The shafts  14   a  and  14   b  are mounted by bearings  15  in the left side shield  5   l , which has round recesses on its inner side, by which bearings  15  are at least partially enclosed. 
   As shown in  FIG. 3 , housing part  20  is lid-shaped and left side shield  5   l  is cup-shaped. The reverse could also be the case, i.e., housing part  20  may be cup-shaped, while left side shield  5   l  may be lid-shaped. Housing part  20  may also be enclosed—as shown in FIG.  2 —and is thus adapted to be built onto the left side shield  5   l  as a modular component. 
   Further, shafts  14   a  and  14   b  and the left wheels  3   l  may be configured as a one-piece or unitary item. The second embodiment shown in  FIG. 3  may otherwise be substantially similar to the first embodiment, such that reference is made to the above description of the first embodiment. 
   Changes and modifications to the specifically described embodiments may be carried out without departing from the principles of the present invention, which is intended to be limited only by the scope of the appended claims as interpreted according to the principles of patent law including the doctrine of equivalents.