Patent Application
20090286637
The invention relates to a tensioning device for a traction mechanism, in particular, a belt or a chain, comprising a lever arm over which the traction mechanism is guided and on which a tensioning spring is arranged with its one end and whose other end is arranged on a spring holder by which the tensioning device can be fastened to an external object.
Such a tensioning device is known, for example, from DE 195 01 685 C1. So that the assembly of this tensioning device is simplified, the tensioning device described there has a connection element that can be set in tension in the form of a spring band strip that extends from the spring holder to the lever arm, wherein a tensioning spring is provided in a known way between both the spring holder and the lever arm. With the lower end, the spring band strip is fixed on the spring holder by a pin inserted into a borehole. The spring band strip passes through the tensioning spring in its interior and is guided by a spring support that is provided on the lever arm and on which the tensioning spring is supported with its other end. On the end of the spring band strip, another pin that is engaged transversely is provided whose end is rotated by 90° to the strip longitudinal axis, so that a stop is produced. In the assembled position, the upper pin is inserted and supported on the tensioning lever. Because the length of the spring band strip is shorter than the length of the unloaded tensioning spring, this can thus be fixed conditionally in the pre-tensioned position by the two-sided pin support of the spring band strip.
Now if the tensioning device is installed, then the upper pin is removed, so that the tensioning spring becomes unloaded. Then, in addition to the pre-tensioning function, as a second function, the movement limiting of the tensioning spring path is given to the spring band strip. This is because the tensioning spring can be unloaded only as far as the end of the spring band stop permits. If this runs, namely, against the tensioning lever, then the spring path is limited.
A disadvantage in this construction is, first, that it has a relatively expensive and complicated design with respect to the individual parts that are used, in particular, as concerns the assembly. In addition, the spring band strip remains within the tensioning device or the helical spring after removing the upper pin. If the stop is not contacted, then the spring band strip is not tensioned and consequently is movable, so that it can vibrate, which possibly leads to the generation of noise.
The invention is based on the objective of providing a tensioning device that allows the tensioning spring to be kept pre-tensioned, but that has a simultaneously simple construction.
To meet this objective for a tensioning device of the type noted above, it is provided according to the invention that a holding element that extends from the lever arm to the spring holder and that can be detached from both is provided for holding the tensioning device in a position with the pre-tensioned tensioning spring.
In the tensioning device, the holding element is arranged detachably on the lever arm as well as on the spring holder; thus, it can be removed. In addition, the holding element is a single piece and arranged or fastened on the appropriate part, that is, any external objects, such as connection pins or the like are not required. This results in a tensioning device that has a significantly simpler design and also a more economical production and that also does not tend to generate noise during operation after the holding element is removed.
According to a first construction of the invention, the holding element is constructed as a pin that extends from the lever arm to the spring holder and that has, on both ends, locking sections that are locked on the lever arm and on the spring holder in the assembled position. For releasing the fixed position of the tensioning spring, the holding element that is tensioned by the spring tension is merely unloaded somewhat and then released from its locked position on the lever arm and on the spring holder. This is easily possible during the installation of the tensioning device.
The pin itself preferably engages through the spring holder in a corresponding opening and extends through the tensioning spring and also through or in a spring support provided on the tensioning lever. With its other end, the tensioning spring is supported against this spring support. The pin is then locked on the spring support. A force-optimized locking is also possible due to the orientation of the pin running somewhat axial with respect to the tensioning spring and also the spring direction.
The locking section of the pin provided on the end locked on the spring support is preferably constructed in the form of a bend that can be brought into a position engaging behind an abutment shoulder on the spring support by twisting the pin after it is inserted into or passed through the spring support. For assembly, when the tensioning spring is compressed, the pin is merely to be guided through the spring holder and the tensioning spring and into or through the spring support and then twisted, for example, by ca. 90°, so that the bend on the end side engages behind the abutment shoulder. In this way, the pin is locked on this end. When the tensioning spring is relieved of pressure, the abutment shoulder is pressed against the bend and in this way limits the spring path in connection with the locking of the other pin end. The locking section of the pin that can be locked on the spring holder is preferably realized in an improvement of the invention in the form of a bend transitioning into a handle. This allows, first, the locking section to be constructed in a simple way and, second, the pin can be easily moved and twisted and pulled out from the tensioning device.
In one alternative to the use of a pin, the holding element is constructed as a tensioning band extending between the lever arm and the spring holder. The band itself is flexible, but in each case is mounted detachably on the lever arm and also on the spring holder. For this purpose, according to a first alternative of the invention, the tensioning band can form a ring and can be guided around a guide section on the lever arm and a guide section on the spring holder. For assembly, the lever arm and the spring holder are compressed, according to which the annular tensioning band is placed around the guide sections. Now if force is removed from the tensioning spring, then the spring path is limited by the tensioning band placed on the guide sections. The tensioning band itself can be a metal or plastic band and is preferably formed from a band section that is dimensioned accordingly in its length and whose ends are connected by an adhesive, crimped, or welded connection for the formation of the ring. For this purpose, a crimping sleeve or the like can be used, as well as the two band ends being either welded together metallically or fused thermally for a plastic band.
The guide section provided on the tensioning lever is preferably constructed on a spring support holding the tensioning spring or else as a lateral projection directly on the tensioning section. The guide section provided on the spring holder is preferably formed by the bottom side of the spring holder. In each case, the tensioning band also lies somewhat axial to the tensioning spring or to the spring force direction, so that here, despite fixation in the pre-tensioned state, none or only a negligible tilting moment is exerted on the spring.
In another alternative construction for use of a tensioning band, this does not have an annular construction but instead holders are provided connected on its two ends rigidly to the tensioning band, wherein, in the assembled position, these holders are inserted and locked in holder receptacles provided on the lever arm and on the spring holder. These holders can involve, for example, rigidly connected holding bolts or the like that are inserted into correspondingly shaped receptacles on the lever arm or on the spring holder. The locking is here performed by corresponding shaping of the holders and also their receptacles that can have, for example, a round or triangular or some other shape in cross section. Here, the assembly and disassembly is also extremely simple. All that is necessary is to compress the tensioning spring somewhat, in order to insert or remove the tensioning band with its holders into or out of the receptacles. In this way, force is again removed from the tensioning spring.
Additional advantages and details of the invention will be described below using embodiments with reference to the figures. The figures are schematic diagrams and show:
Now, in order to be able to construct and deliver the tensioning device 1 with a pre-tensioned tensioning spring, it is necessary to lock the tensioning spring 4 in the compressed state. Here, on the spring holder 6 an elongated, essentially central opening 9 is provided. A corresponding opening 10 is provided on the spring support 5. A holding element 11 in the form of a pin 12 is guided through the openings 9 and 10 and also through the helical spring 4. On its end facing the tensioning lever 2, the pin 12 has a bend 13 that forms a locking section. On the opposite end, another bend 14 is provided that transitions into a handle 15. The pin 9 is now guided through the opening 9 with the end having the bend 13, wherein for passing through, the pin 12 is turned by ca. 90° with respect to the position shown in
For releasing the lock, the pin 12 merely has to be unloaded somewhat, so that it can be turned back by 90° using the handle 15 and can then be removed again from the opening 10, the helical spring 4, and also the opening 9.
Here, a holding element 22 is also provided for fixing the tensioning device 18 with a pre-tensioned tensioning spring 20. This holding element 22 is here constructed in the form of an annular tensioning band 23 that can be made from plastic or metal. The tensioning band 23 that is made from an elongated band section, whose band ends are fixed together by a crimping element 24 in the illustrated embodiment, thus closing the tensioning band into an annular shape, that is guided around a guide section 25 on the tensioning lever and also a guide section 26 on the spring holder 21. The guide section 25 on the tensioning lever projects laterally. It forms the spring support 27 by itself or such a part is attached to it. The tensioning spring 20 is supported against this spring support 27. The guide section 25 is formed by the outside of this projection 28. The outside has a curved construction.
The guide section 26 on the spring holder 21 is formed by the outer surface of the bottom side 29 of the spring holder 21 opposite the side on which the tensioning spring 20 is supported. This outer surface 29 also has a round construction.
Now, for assembling the tensioning band 23, the tensioning device 18 is pressed together. Therefore, the tensioning spring 20 is compressed. Then the already closed tensioning band 23 is placed around the guide sections 25 and 26, after which force is removed from the tensioning spring 20 again and the tensioning band 23 is clamped, here, however, limiting the spring path. For detaching the tensioning band 23, the tensioning spring 20 is merely compressed somewhat again, after which the tensioning band 23 can be easily removed by hand. It would also be natural to separate the tensioning band with shears or pincers. Then, however, it cannot be reused.
Finally, it is to be stated that the term “tensioning band” is to be understood generally and comprises not only flat bands, but also, e.g., a cord made from, e.g., plastic or a wire strand, or the like, closed into a ring.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102006026847.4 | Jun 2006 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2007/054683 | 5/15/2007 | WO | 00 | 11/26/2008 |
