Braking device for an overhead crane traveling on rails
A braking device for limiting the travel of an overhead crane traveling over rails temporarily increases its traveling resistance until it stops. The braking device includes at least one brake shoe which is mounted on the overhead crane and can be pressed against the rails with a force up to a level equivalent to the weight of the overhead crane. The brake shoe can be forcibly caused to move from a resting position a certain distance away from the rail into a braking position, in which the side of the brake shoe or shoes facing the rail can be pressed against the rail.
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 1. Field of the Invention
 The invention pertains to a braking device for limiting the travel of an overhead crane traveling on rails by producing a temporary increase in its traveling resistance until it stops.
 2. Description of the Related Art
 It is known that stops are used in plants with crane systems to limit the travel of an overhead crane traveling on rails and thus to prevent the overhead crane from going beyond the end of the craneway. Bumpers are mounted at the ends of the crane bridge or at the ends of the overhead crane itself, these bumpers being intended to absorb at least some of the kinetic energy of the crane when it collides with the stops. Depending on the type of construction and on the nature of the application, wood pulp and rubber bumpers are used. For high travel velocities, hydraulic bumpers can also be used. Whereas standardized bumpers can be used for travel velocities of up to approximately v=4 m/s, only hydraulic bumpers are used in the higher velocity ranges. Because of their high production and maintenance costs, however, such hydraulic bumpers are not very economical. In addition, the spring characteristics and hysteresis of the bumpers are also subject to change under the effects of weather.
 At travel velocities of v>4 m/s or when two or more cranes travel over the same craneway, the bumper distances increase, and when hydraulic bumpers are used, their lengths increase. Aside from the fact that the maximum possible buckling length imposes a limit on the dimensions of hydraulic bumpers, the length of the bumpers also has a decisive effect on the working range of the overhead rail crane. When all the buffer distances are added together, 10-15% of the working range is usually lost in the direct contact range of the cranes. If the length of the hydraulic bumpers is reduced to increase the working range, the amount of impact energy to be absorbed is so large that the resulting powerful impacts can damage the crane and especially the load suspended from it.
 In many cases, the amount of impact energy to be absorbed is also so large that it becomes necessary to use two bumpers, arranged in parallel. Because the stops at the ends of the craneway must also be designed to handle the bumper forces which are developed, the calculation of the dimensions of the craneway is affected, which means, in the case of an elevated craneway, the dimensions of the columns and foundations.
 As a way of eliminating the bumpers still used in most cases for cranes today, DE-A 22 61 821 discloses a braking device which does not brake the travel of the crane bridge by the collision of bumpers against stops, but which instead makes use of an additional set of wheels, which press into brake rails of rubbery material. The flexing work this produces has the effect of decelerating the crane at a uniform rate. The known brake rails consist preferably of rubber.
 Aside from the fact that brake rails made of rubber undergo considerable wear, especially in the case of cranes which are usually under load when they are braked, the installation of additional brake rails next to the craneway is not always possible because of the lack of space and also calls for a great deal of additional construction work. In addition, there is the cost of the wheels, which must also be obtained and attached to the traveling gear frame of the crane. These wheels work together with the brake rails, and their dimensions must be calculated specifically to be compatible with the rails. Overall, this known braking device suffers from being complicated, but even so it is still not reliable enough to brake the overhead crane repeatedly to a stop.SUMMARY OF THE INVENTION
 The present invention has the task of braking an overhead crane traveling over rails by temporarily increasing its travel resistance until it stops, and also of creating a device suitable for achieving this effect.
 To accomplish this task, a braking device is provided which includes of at least one brake shoe, mounted on the overhead crane, which can be pressed against the rails with a force up to a level equivalent to the weight of the crane. This shoe can thus be moved from a resting position a certain distance away from the rail into a braking position, in which the side of the brake shoe or shoes facing the rails can be pressed against the rails.
 By the use of the new device, a braking action is created by the energy-absorbing buildup of a frictional force, which acts on the rails of the overhead crane. Because the braking device is mounted on the overhead crane itself, and because it can be pressed against the rails, the device can raise the crane far enough to lift the rollers of its traveling gear slightly from the rails. As a result, extremely high braking forces are produced. If several of these braking devices are provided, the entire weight of the overhead crane will rest on the brake shoes and thus on the rails very soon after the brakes have been actuated. It is thus advisable to install several brake shoes; one such brake shoe can be installed, for example, at each of the four corners of the traveling gear frame.
 In one embodiment of the invention, each brake shoe is guided vertically in the traveling gear frame of the overhead crane so that it can move up and down. Providing such vertical guidance means, first, that the brake shoe will be effectively guided in the vertical direction. Second, it also provides the opportunity to provide support within the guide in the transverse direction. It also allows the force of the brake shoe to be introduced vertically into the rails, as a result of which optimum use can be made of the weight of the crane for braking.
 Each brake shoe is preferably attached to the traveling gear frame by a toggle lever or cam. Cams and toggle levers are suitable for transmitting large forces over short distances, which describes the conditions under which the present braking device must operate.
 In a further elaboration of the invention, a pressure medium cylinder is connected to one end to the toggle lever to bend and extend it. The other end of the cylinder is supported on the frame of the overhead crane. According to the invention, this pressure medium cylinder is actuated by a stop or a contact installed somewhere along the route traveled by the overhead crane; that is, as soon as the overhead crane travels over a certain stop or contact, the pressure medium is released into the pressure medium cylinder, so that this cylinder, acting on the toggle lever, causes the brake shoe to extend toward the rail. Then powerful braking forces bring the crane to a standstill within a short distance.
 The distance traveled by each toggle lever is preferably limited by stops to prevent the toggle lever from overextending.
 The novel device is not affected by weather; and, in addition to it originally intended purpose, it can also be used as a wind anchor for holding the overhead crane in position on the rails. The device can also be used as support in the event of wheel breakage and also as an auxiliary device to help with the changing of the track wheels.
 Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.BRIEF DESCRIPTION OF THE DRAWINGS
 FIG. 1 shows a side view of an overhead traveling rail crane with hydraulic bumpers;
 FIG. 2 shows a side view of an overhead traveling rail crane with the braking device according to the invention;
 FIG. 3 show a detailed view of a part of FIG. 2 with a deactivated braking device;
 FIG. 4 shows a cross section through FIG. 3 in the area of the vertical center axis of the traveling gear;
 FIG. 5 shows a detailed view of a part of FIG. 2 with an activated braking device; and
 FIG. 6 shows a cross section through FIG. 5 in the area of the vertical center axis of the traveling gear.DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
 FIG. 1 shows a conventional overhead traveling crane 1, which can move by its traveling gear 2 over the rails 3 of the elevated craneway 4. The overhead crane 1 has conventional, standardized hydraulic bumpers. Y is the length of the overhead crane in the state without actuation of the bumpers. The bumper actuation distance is Z per side, so that, when the bumpers on both sides are actuated, the length of the overhead traveling crane is X=Y−(2×Z).
 FIG. 2 shows the overhead crane 6; it moves by its traveling gears 7 over the rails 3 of the elevated craneway 4 and is braked by the braking device 8 according to the invention. The dimension of the crane up as far as the mechanical stops is the crane length X.
 In FIG. 3, we can see the new braking device 8, consisting of the toggle lever 9, the connecting rod 10, the brake shoe 11, the hydraulic cylinder 12, and the end stop 13, all of this located on the traveling gear 7 above the rail and the elevated craneway 4. The toggle lever 9 of the braking device 8 pivots around the forward support axle 7.1 of the traveling gear 7. The brake shoe 11 is guided vertically in the guide shaft 7.2. The end stop 13 serves to limit the stroke of the hydraulic cylinder 12 and prevents the device from being overextended.
 The braking device 8 is shown in the deactivated state, i.e., the operating state of the overhead crane 6. A sufficient gap 14 is maintained between the brake shoe 11 and the rail 3.
 FIG. 4 shows a cross section through the vertical center axis of the traveling gear 7, in which we can see the gap between the brake shoe 11 and the rail 3, which is maintained during operation of the crane and which is designated 14
 The braking device 8 according to the invention, consisting of the toggle lever 9, the connecting rod 10, the brake shoe 11, the hydraulic cylinder 12, and the end stop 13, can also be seen in FIG. 5, mounted in the traveling gear 7 above the rail 3 and the elevated craneway 4. The toggle lever 9 of the braking device 8 has now been pivoted by means of the hydraulic cylinder 12 around the support axle 7.1 of the traveling gear 7 to the end stop 13. The brake shoe 11 has thus been pushed vertically down through the guide shaft 7.2 toward the rail 3. The braking device 8 here is in the activated state, i.e., the braking state of the overhead crane 6. Between the brake shoe 11 and the rail 3, frictional contact 15 has been produced, by which the crane is decelerated until it stops. This state can also be seen in FIG. 6, which shows a cross section through the vertical center axis of the traveling gear 7. It can be seen how the frictional contact 15 is produced between the brake shoe 11 and the rail 3.
 Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.
1. A braking device for limiting the travel of an overhead crane traveling on rails by temporarily increasing its traveling resistance until it stops, said braking device comprising
- a brake shoe mounted on the overhead crane over one of said rails, and
- moving means for moving said brake shoe from a resting position remote from said rail into a braking position in which said brake shoe is pressed against the rail.
2. A braking device as in
- claim 1 wherein said crane comprises a traveling gear frame over said rail, said brake shoe being guided for vertical movement in said traveling gear frame.
3. A braking device as in
- claim 2 wherein said moving means comprises a toggle lever connected to said traveling gear frame for pivoting movement with respect to said traveling gear frame.
4. A braking device as in
- claim 3 wherein said moving means further comprises a pressure medium cylinder which acts on said toggle lever to move said brake shoe vertically.
5. A braking device as in
- claim 4 further comprising actuating means for actuating said pressure medium cylinder, said actuating means comprising one of a stop and a contact provided along the route traveled by the overhead crane.
6. A braking device as in
- claim 3 further comprising a stop fixed to said traveling gear frame for limiting the travel of said toggle lever.
International Classification: B61H013/00;