Chain or belt drive

Abstract

A chain or belt drive (6), comprising a chain (7) or a belt, which runs around a first chain or belt wheel (14) driven by a drive motor (15) and around a second chain or belt wheel (16) rotatable about an axis, and on which a driver (8) for an object to be moved linearly via the chain or belt drive (6) is arranged, wherein the second chain or belt wheel (16) is rotatably mounted on a carriage (18) which is movable against the restoring force of a spring (20) via which the chain or belt tension is defined, wherein the carriage, in addition to the spring (20), is automatically linearly movable via a tensioning device (19) for maintaining the chain or belt tension, characterized in that the tensioning device (19) has a tensioning element which is movable via a spring (39, 32, 38) and is motion-coupled to the carriage (18),wherein the tensioning device (19) comprises a threaded rod (29) screwed into a threaded bore (28) of the carriage (18) with a cable or chain pulley (30) or a gear wheel (33) arranged thereon, wherein a cable or chain (31) tensioned by the spring (32) runs over the cable or chain pulley (30) or a chain tensioned by the spring (38) runs over the gear wheel (30) or the gear wheel meshes with a rack (36) tensioned by the spring (38).

Description

[0001] The invention relates to a chain or belt drive, comprising a chain or a belt which runs around a first chain or belt wheel driven by a drive motor and around a second chain or belt wheel rotatable about an axis, and on which a driver for an object to be moved linearly is arranged.

[0002] In various fields of technology, it is necessary to move an object linearly, which is possible using various systems. A motion system is a chain or belt drive in which a chain or belt is used as the driven element, to which the object to be moved is connected. For this purpose, a corresponding carrier is attached to the chain or belt side, to which the object is in turn attached. The chain or belt runs around two chain or belt wheels, one of which is driven by a drive motor with a power rating sufficient to move the object, which, depending on the application, can be considerable and weigh several hundred kilograms. The movement can occur horizontally, tilted relative to the horizontal, or even vertically. The second chain or belt wheel is mounted so it can rotate about an axis, allowing chain or belt movement.

[0003] To tension the chain or belt, it is known to guide the chain or belt over a tensioning shoe, for example, which serves to maintain the chain or belt tension. However, such a tensioning shoe cannot be installed everywhere. Furthermore, especially in the case of chain or belt drives that are themselves installed on moving devices or components, the tensioning shoe does not guarantee that the tensioning shoe can perform its tensioning function in every position (for example, when tilted vertically).

[0004] The relevant prior art includes documents EP 0 311 731 A1, US 6 485 207 B1 and US 4 955 046 A.

[0005] The invention is therefore based on the problem of providing a chain or belt drive which enables a defined chain or belt tension to be maintained in every situation.

[0006] To solve this problem, in a chain or belt drive of the type mentioned at the outset, the invention provides that the second chain or belt wheel is rotatably mounted on a carriage which can be automatically moved linearly via a tensioning device to maintain the chain or belt tension.

[0007] In the drive according to the invention, the second chain or belt wheel is not rotatable about a fixed axis, but is mounted on a linearly movable carriage, which in turn can be moved linearly via a tensioning device. This tensioning device enables automatic carriage movement; it is purely mechanical in its function and design, thus requiring no sensors or drives to move the carriage. Consequently, this tensioning device constantly applies a tensioning force to the carriage, enabling continuous chain or belt tension.

[0008] The chain or belt tension itself can generally be adjusted by allowing the carriage to move against the restoring force of a spring. The carriage is therefore coupled via a spring to a fixture frame or similar, on which the drive motor that drives the other chain or belt wheel is also fixed in position. The spring is designed in such a way that it always exerts a tensioning force on the carriage. If the chain or belt elongates due to wear, this is compensated for by the spring acting on the carriage, so the carriage is guided. However, during operation, the movement of the chain or belt or changes in direction, or if the device or drive tilts accordingly when a load is applied, leads to constant load changes in the drive, which lead to tension variations.Since these cannot always be compensated for by this spring, they are now compensated for by the additional tensioning device provided.

[0009] With regard to the design of the tensioning device, various embodiments are conceivable. According to a first alternative invention, the tensioning device has a tensioning element that can be moved or loaded via a spring and is motion-coupled to the carriage. The spring causes the movement of the tensioning element in such a way that the tensioning element immediately adjusts the carriage as soon as a load change occurs that releases the load from the carriage and a necessary carriage movement is required due to decreasing chain or belt tension or the like. According to an embodiment not claimed, the tensioning element is designed as a wedge that is supported on one side by a fixed bearing and on the other side by a bearing connected to the carriage. This wedge, which is pulled or loaded via the spring, is received between these two bearings, which are designed as corresponding inclined or support surfaces.When the chain or belt tension decreases or the load on the carriage is released, the spring pulls the wedge as far as possible between the bearings, which moves the carriage and tensions the chain or belt.

[0010] The wedge is preferably self-locking in its mounting between the bearings, which can be easily achieved by setting an appropriate wedge angle. To achieve self-locking, the wedge angle on one or both sides should be ≥ 80° and ≤ 90°, particularly between 83° and 87°, with a preferred wedge angle of 85°. The wedge angle can be present on only one side of the wedge, but the wedge can also be designed as a double wedge.

[0011] According to the invention, an alternative to designing the tensioning device using the wedge provides for the tensioning device to be implemented by means of a threaded rod screwed into a threaded hole in the carriage, with a rope or chain pulley arranged on it, over which a rope or chain tensioned by a spring runs. A force or torque is continuously exerted by the spring-loaded rope or chain on the rope pulley or chain pulley, which is motion-coupled to the carriage via the threaded rod screwed into the threaded hole on the carriage side. If the carriage is now load-free and a chain or belt elongation or a drop in tension occurs, this can be compensated for by the applied torque, i.e. the threaded rod rotates, albeit by a small angular increment, and is consequently screwed into the threaded hole.After the threaded rod is fixed in position, the carriage runs a short distance on the threaded rod, which depends on the rod rotation angle, taking the chain or belt wheel with it and consequently adjusting the tension again.

[0012] An alternative to the use of a cable or chain pulley according to the invention provides for the tensioning device to be implemented by means of a threaded rod screwed into a threaded bore of the carriage with a gearwheel mounted thereon. A chain runs over this gearwheel and is tensioned by a spring, or the gearwheel meshes with a rack and rack, which is tensioned by a spring. The operating principle is the same as that described for the previously described embodiment with the cable or chain pulley. However, the drive here is a gear drive, which is implemented either via a gearwheel and chain or via a gearwheel and rack.

[0013] In order to also realize self-locking in various designs using the threaded rod which is screwed into the threaded bore on the slide side, the thread pitch is expediently selected to be correspondingly small so that the thread engagement of the rod and bore is self-locking.

[0014] It is evident that all the designs described above are purely mechanical in nature, meaning that no sensors or actuators of an electrical or electromechanical design are required to automatically maintain the chain or belt tension.

[0015] In addition to the chain or belt drive itself, the invention further relates to a medical examination device comprising a carrier on which at least one component of an imaging device, preferably a radiation source and a radiation receiver, is arranged. This device is characterized according to the invention in that the carrier is movable via a chain or belt drive of the type described above, to whose driver it is connected. The carrier itself is movably mounted via suitable linear guides so that it can be moved linearly via the chain or belt drive in order to bring the one or more components of an imaging device arranged on it into a desired position relative to an examination subject.The chain or belt drive is housed in a suitable housing, frame, or similar device, on or in which the support is arranged or guided. This housing, frame, etc., can be moved in space, for example, via a corresponding support structure or movement unit. This spatial mobility means that the chain or belt drive, and thus also the load acting on the drive—namely, the support and its components—can be positioned horizontally, vertically, or at any angle to it. This means that it can experience any load changes, provided they do not already result from the movement of the support via the chain or belt drive itself.

[0016] However, a medical examination device can also be a patient couch, for example, beneath whose support surface an image detector is movable via such a chain or belt drive. Since such patient couches are usually also tiltable, comparable problems arise, which are solved by the chain or belt drive integrated according to the invention.

[0017] Further advantages, features, and details of the invention will become apparent from the exemplary embodiment described below and from the drawings. These show: Fig. 1 a perspective view of a medical examination device according to the invention with a movable image recording unit which is movable via a chain or belt drive according to the invention, Fig. 2 an enlarged detailed view of the examination facility Fig. 1, Fig. 3 a side view relating to the integration of the chain or belt drive according to the invention into the examination device from Fig. 1, Fig. 2, Fig. 4 a perspective partial view of the carriage supporting the second sprocket together with the associated clamping device in the form of a wedge, Fig. 5 supervision of the arrangement Fig. 4, Fig. 6 a perspective view of a further embodiment of a clamping device according to the invention, and Fig. 7 a perspective view of a third embodiment of a clamping device according to the invention.

[0018] Fig. 1 shows an examination device 1 according to the invention, which is used to record radiation images. A C-arm 3 is arranged on a device base 2 so that it can rotate about a horizontal axis. For this purpose, a support frame 4 is provided, via which the C-arm 3 is rotatably mounted on the base 2. The support frame 4 has a frame 5, in or on which a chain or belt drive 6 is arranged, comprising a chain 7 and a driver 8, to which the entire C-arm 3 is fastened. The C-arm 3 basically consists of a first leg 9, which is guided linearly in the frame 5 on the one hand, and is connected to the driver 8 as a support part on the other, and below which the radiation source 10 is fastened. Furthermore, the C-arm has a second vertical support 11, which is connected to the first support 9, and the upper, again horizontally extending third support 12, on which a radiation receiver 13 is arranged.The entire unit comprising the three supports 9, 11, and 12, along with their attachments—i.e., radiation source 10 and radiation detector 13—is movable via the chain or belt drive 6 and ultimately can be moved along the frame 5. Once the frame 5 is mounted on the support 4 and can be pivoted via this, the entire C-arm can also be pivoted. The load is picked up by the driver 8 and transferred to the chain or belt drive 6. The pivot angle is 180°, meaning that the C-arm, starting from a horizontal arrangement with the frame 5 thus positioned vertically, can be rotated by 180° into the opposite position.

[0019] Of course, a patient support table is provided, which is not shown in detail here for reasons of clarity. It can also be pivoted along with the C-arm 3 and is located within the C-arm itself, so that for examination purposes, the radiation source 10 is positioned below the table and the radiation detector 13 is positioned above it. This is therefore an under-table device.

[0020] Fig. Figure 3 shows, in the form of a schematic diagram, a sectional view through the frame 5 to illustrate the course of the chain or belt drive 6. The chain or belt drive 6 comprises, as described, the chain 7 with the driver 8 attached to it. The chain 7 runs over a first chain wheel 14, which is driven directly by a drive motor 15. Furthermore, the chain 7 runs over a second chain wheel 16, which is arranged on a carriage 18 so as to be rotatable about a rotation axis 17. Fig. 3 it can be seen that when the drive motor 15 is operated and the first sprocket 14 consequently rotates, the chain 7 together with the driver 8 is moved and consequently the C-arm coupled thereto is displaced horizontally from this position.

[0021] However, as explained, the arrangement can be made based on the Fig. 3, the C-arm can also be rotated to the left and right by 90° each into the respective vertical position. When rotated 90° to the right, the load rests on the second sprocket 16, which is at the top in this rotated position, while the drive motor 15 and the first sprocket 14 are positioned vertically below it. When rotated 90° in the other direction, the situation is reversed; in this case, the load of the entire C-arm, which can be up to 400 kg, rests on the first sprocket, and the second sprocket 16 and the carriage 18 are therefore unloaded and loose.

[0022] In order to ensure, at least in this situation, when the carriage is at least partially unloaded, an automatic re-tensioning of the chain 7, which can lengthen during operation, for example due to the frequent changes of direction or as a result of tipping processes or start-stop and acceleration processes, a corresponding tensioning device 19 is provided, as is shown in a first embodiment of the invention in Fig. 4 and Fig. 5 is shown.

[0023] Fig. Figure 4 shows a perspective view of the slide 18, to which the clamping device 19 is directly assigned. The slide 18 is minimally movable in order to compensate for the relatively small length variations. In the assembly situation, the slide, see Fig. 5, is pre-tensioned by a spring 20, which is firmly connected to the frame 5. This spring 20 serves to generate a defined chain tension, which is why it is designed accordingly.

[0024] A first bearing 21 in the form of a wedge-shaped support element is arranged on the carriage 20 and thus movable with it. A second bearing 22, also in the form of a wedge-shaped support element, is in turn fixedly connected to the frame 5. Between the two, the actual clamping element 23 is received in the form of a clamping wedge 24, which here has two wedge surfaces 25 that interact with the corresponding abutment surfaces 26, 27 of the two support elements 21, 22. The wedge 24 is loaded by a further spring 39 and is therefore continuously pulled between the two wedge surfaces 26, 27 by the spring.

[0025] If a situation arises during operation in which, on the one hand, the chain has become somewhat elongated and, on the other hand, the carriage 18 is at least partially relieved of load, the wedge 24 can be pulled somewhat further between the two wedge surfaces 26, 27 of the two support elements 21, 22 by means of the spring 39, provided its spring force is sufficiently great. This moves the carriage 18 somewhat further away from the drive motor 15, meaning that the second chain wheel 16 is moved away from the first chain wheel 14 and, inevitably, the chain 7 is also somewhat re-tensioned. This means that a purely mechanical, automatic tensioning system is implemented that has no electrical or electromechanical components whatsoever, but is implemented purely mechanically via the spring-loaded part 24 and the carriage 18.

[0026] The tensioning device 19, i.e., the wedge system, is self-locking, meaning it will not slip back without an external restoring force. This is achieved by the angle of the wedge surfaces 24, 25 and consequently also of the corresponding bearing surfaces 26, 27 being designed to be correspondingly flat. It is approximately 85° at wedge 24 and approximately 5° at the opposite surfaces 26, 27. This means that the wedge 24 can, if the load situation allows, move forward to tension the chain. However, due to the self-locking effect, unloading or releasing the load is not possible.

[0027] Fig. 6 shows an alternative embodiment of a tensioning device 19. Here, again, the carriage 18 is provided, which in the example shown has a threaded bore 28 through which a threaded rod 29 runs or is screwed into it. The threaded rod 29, which is of course mounted accordingly, carries a cable or chain pulley 30 around which a cable or chain 31 is looped. This side, or the chain 31, is in turn connected to a spring 32, which is fixedly arranged on the frame. The function is such that the spring 32 continuously exerts a torque on the cable or chain pulley 30 via the cable or chain 31, thus constantly exerting a torque on the threaded rod 29.As soon as the carriage is sufficiently relieved of load, it is possible, if a corresponding chain elongation is present in the chain or belt drive, that the threaded rod 29 is screwed, albeit minimally, into the threaded hole 28 via the torque, thus the carriage 18 moves on the axially position-fixed threaded spindle 29 in the direction of the cable or chain pulley 30, via which the chain, which runs over the sprocket on the carriage 18 (not shown in detail here), is tensioned.

[0028] Here, too, there is of course a self-locking feature, ie the two interlocking threads of the threaded bore 28 and the threaded spindle 29 have a correspondingly small pitch.

[0029] Fig. 7 finally shows an alternative design of a further clamping device 19, which in principle is similar to that shown in Fig. 6. Again, the carriage 18 is provided with the threaded bore 28, into which a threaded spindle is screwed, which in the illustrated embodiment also carries a gear 33. Its toothing 34 meshes with the toothing 35 of a rack 36, which, as indicated in the schematic diagram, is movable via a linear bearing 37. It is continuously tensioned by a spring 38, which in turn is fastened to the frame 5. If a loose or load-free situation arises on the part of the carriage 18, which of course in turn has the second sprocket around which the chain runs, the rack 36 is moved minimally as a result of the tension continuously acting on the rack 36 via the spring 38, which causes the gear 33 to rotate.A torque is therefore applied to the threaded spindle, which is screwed minimally into the threaded bore 28, so that the carriage 18 in turn moves on the threaded spindle 29 in the direction of the gear 30 under tension of the chain.

[0030] Also the Fig. 6 and Fig. The designs shown in Figure 7 are all purely mechanical clamping systems; no electrical or electromechanical components are required.

[0031] Although a chain or belt drive 6 is described in the figures, the tensioning device according to the invention can of course also be integrated into a belt drive, in which, instead of the two chain wheels, corresponding pulleys are provided, over which a belt then runs instead of a chain.

[0032] Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited to the disclosed examples and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention.

Claims

[1] Chain or belt drive (6), comprising a chain (7) or a belt, which runs around a first chain or belt wheel (14) driven by a drive motor (15) and around a second chain or belt wheel (16) rotatable about an axis, and on which a driver (8) for an object to be moved linearly via the chain or belt drive (6) is arranged, wherein the second chain or belt wheel (16) is rotatably mounted on a carriage (18) which is movable against the restoring force of a spring (20) via which the chain or belt tension is defined, wherein the carriage, in addition to the spring (20), is automatically movable linearly via a tensioning device (19) for maintaining the chain or belt tension characterized byin that the tensioning device (19) has a tensioning element which is movable via a spring (39, 32, 38) and which is movement-coupled to the carriage (18), wherein the tensioning device (19) comprises a threaded rod (29) screwed into a threaded bore (28) of the carriage (18) and with a cable or chain pulley (30) or with a gear wheel (33) arranged thereon, wherein a cable or chain (31) tensioned via the spring (32) runs over the cable or chain pulley (30) or a chain tensioned via the spring (38) runs over the gear wheel (30) or the gear wheel meshes with a rack (36) tensioned via the spring (38). [2] Chain or belt drive according to claim 1, characterized by that the thread pitch is selected such that the threaded rod (29) is self-lockingly received in the threaded bore (28). [3] Medical examination device (1), comprising a carrier on which at least one component of an imaging device is arranged, characterized by that the carrier (3) is movable via a chain or belt drive (6) according to one of the preceding claims, with whose driver (8) it is connected. [4] Medical examination device according to claim 3, characterized by that the carrier is a C-arm (3).

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