Patent Application
20220242704
The present invention relates to lifting gear, in particular a lever hoist, according to the characteristics of the preamble of claim 1.
A piece of lifting gear, in particular a lever hoist, generally comprises a round steel chain as a means of support and pulling and is used to raise, lower and pull loads. The lifting motion can be generated by manual operation, compressed air or an electric motor. The present invention relates in particular to a hand-operated lever hoist.
From DE 41 05 050 C2, a piece of lever-operated lifting gear is known which is also called a traction device or a chain hoist. The lifting gear is characterised by a supporting hook as an upper fastening element and load hook as a lower slinging element. The upper fastening element and the lower slinging element are directly interconnected by a housing. The slinging element is connected to a drive for the means of traction via a load chain as means of traction, which is located in the housing of the lifting gear. By a swivel movement of a manual lever, the drive for the means of traction can be set in rotation within the housing. To do this, the lever arm engages into a transmission device which is in turn connected to the drive for the means of traction. In this way, it is possible to displace or lash an object.
As well as a drive with a shiftable ratchet mechanism, the drive for the means of traction comprises a load pressure brake, a load chain wheel and a transmission, wherein the transmission is frequently design as a planetary gearbox. The hand lever and the ratchet wheel of the ratchet mechanism sit on the end of a drive shaft which presses home the load pressure brake and the load chain wheel. On the other end of the drive shaft is located the transmission, which is then connected to the load chain wheel in such as way as to transfer torque.
The load pressure brake is composed of a ratchet wheel disc with recesses or teeth on its outer circumference, two friction elements located on both sides of the ratchet wheel disc, mostly friction discs or pads, and two pawls articulated on the housing, which are pressed under the effect of ratchet hook springs onto the ratchet wheel disc. Both friction elements are connected frictionally engaged firstly with the ratchet wheel disc and secondly with the pressure disc or ratchet wheel fastened to the shaft. The ratchet wheel can be displaced axially on a movement thread of the drive shaft.
The load pressure brake has the task of stopping the load carried by the lifting gear at any level or position, if the ratchet wheel is stationary. Then the ratchet wheel is pressed over the ratchet wheel disc and the integrated friction elements are pressed onto the compression disc. The pawls are located in the circumferential recesses of the ratchet wheel disc. If the ratchet wheel is rotated in the lifting direction, the pawls slide over the teeth of the ratchet wheel disc until the ratchet wheel comes to a stop. Then the pawls are resting in the recesses of the ratchet wheel disc again. When lowering the load, the ratchet wheel is rotated in the opposite direction, by which it slides axially on the movement thread of the drive shaft and the frictionally engaged contact with the friction elements of the ratchet wheel disc and the compression disc is raised. The load can be lowered until the shaft that continues to rotate compensates for the axial backlash again.
In extremely exceptional situations, particularly when tensioning ropes or when lifting and stopping suspended loads, the acceleration can be so high and the rotational speed of the drive or drive shaft can be so excessive that the standard load pressure brake no longer engages, because the pawls can no longer engage into the recesses or the ratchet wheel disc because of their inertia. Such an exceptional situation, even if extremely rare, may, for example, occur when working at great heights on overhead lines. There is then the risk of the load chain running out. Also, such a situation may occur when lowering against a jammed load chain. Even if the ratchet hooks of the load pressure brake are not free-running due to extraordinary circumstances such as, for example, corrosion or ice formation, such an exceptional situation may occur.
From EP 0 279 144 B1, a safety brake for a driven shaft is part of the prior art. This comprises a brake disc and a curved disc for a roller that can be pressed on by a trigger spring, that causes a pawl to engage into a toothed ring on the shaft if there is excessive rotational speed of the shaft.
EP 3 395 746 A1 also proposes a further safety mechanism in the form of a safety brake in addition to the load pressure brake, which is used as a speed limiter for the centrifugal force of centrifugal elements.
The invention is based, emanating from the prior art, on disclosing a piece of lifting gear that is improved in terms of safety and operation, in particular a lever hoist, in which an unpermitted increase in rotational speed of the drive shaft is suppressed.
The solution of this task consists, according to the invention, of a piece of lifting gear according to the characteristics of claim 1.
Advantageous embodiments and configurations of the lifting gear according to the invention are the object of the dependent claims.
A piece of lifting gear, in particular a lever hoist, comprises a housing in which a load chain wheel and drive shaft driving the load chain wheel via a transmission are supported such that they can rotate. Furthermore, a drive, a load pressure brake and a safety brake are provided. A load chain can be moved via the load chain wheel.
The safety brake exhibits a locking disc with locking teeth and a control disc with control cams as well as a catch hook. According to the invention, the locking disc and the control disc can be rotated in relation to one another, in which the rotation is limited by a rotation limiter. The catch hook is arranged such that it moves in a swivelling manner. The catch hook has two webs and exhibits a latch contour on the front end and a sensing contour on the rear end. The catch hook is arranged on the locking disc and control disc in such a way that the sensing contour rests under the effect of a spring element on the control disc, particularly rests on the external contour of the control disc and slides along this when the control disc rotates. The latch contour can be brought to engage lockingly with a locking tooth of the locking disc. This means that the catch hook is directed via the control disc in normal operation with the sensing contour and the latch contour does not engage in the locking disc. In the triggering case, when a defined rotational speed is exceeded, the sensing contour of the catch hook of the control disc or the control cams of the control disc are raised and the latch contour of the catch hook hooks into a locking tooth of the locking disc. In so doing, the locking disc is held while the control disc arranged coaxially behind the locking disc continues to turn along a specified rotational path of the rotation limiter until the rotational path is exhausted and the locking disc and the control disc interlock.
In so doing, a positive-fit connection between the drive shaft and the lifting gear is produced. Emergency braking occurs. Overrunning of the load chain wheel or running out of the load chain is suppressed. During the interconnection, the control disc actively pushes the catch hook into the recess or the locking tooth of the locking disc. In the locked position, the control disc also prevents the locking hook from turning back, so that the safety brake is locked.
An aspect of the invention provides that the rotation limiter exhibits at least one curved track and one stopper which can be displaced along the curved track. In the end position, therefore after exhausting the rotational path between the locking disc and control disc, the stopper comes lockingly to a stop and the end of the curved track.
The curved track is preferably formed as a slot. In particular the slot is formed in the control disc. A slot is preferably formed as an arc, with radius about the centre of the control disc. Particularly advantageous are several slots displaced mutually offset on a pitch circle provided in the control disc. However, it is also possible that the curved track is formed as a groove. This can be provided in the control disc or also in the locking disc.
The stopper is preferably a pin. The stopper pin or pins are preferably fastened into the locking disc and protrude against this in the direction of the control disc, in which they engage into the slots.
A further configuration is provided that ratchet elements are incorporated between the locking disc and the control disc. These fix the locking disc and the control disc in the starting position or in the end position. Preferably, the ratchet elements are formed as balls. The ratchet elements are held in take-ups and act together with the ratchet surfaces. A further configuration provides that the take-ups are in the control disc and the ratchet surfaces are formed in the locking disc.
Advantageously, several locking teeth are arranged, uniformly distributed on the circumference of the locking disc. Also, several control cams are arranged, uniformly distributed on the circumference of the control disc. The control cams are particularly formed by the contour of the control disc itself. To do this, the control disc is preferably configured as a triangle with a rounded external contour.
The control disc exhibits a central support provided with internal toothing. With the internal toothing, the control disc sits on a longitudinal section of the drive shaft provided with external toothing. On the central support, the control disc is positioned with a central supporting section. The locking disc is secured onto the support by securing elements.
An advantageous, practical embodiment provides that in the starting position of the locking disc and control disc, the rear external contour of the locking teeth is flush with the external contour of the control disc. The control disc covers the adjacent flat side of the locking disc.
The catch hook of the safety brake is supported on a side plate that can move in swivelling manner integrated into the housing, supported on a pin. The spring element is preferably a helical spring.
Optionally, damping elements may be incorporated between the locking disc and control disc, to dampen the braking effect for emergency braking.
After triggering the safety brake, the locking disc is in the locked end position. To release the locking mechanism, the locking disc and the control disc must be aligned flush with each other again. To do this, an unlocking for resetting of the locking disc and control disc in their starting position is provided. The unlocking preferably comprises a stop valve, that is arranged to lock the locking disc, whereas the control disc connected to the drive shaft is rotated in the direction of lifting (clockwise) until both discs are aligned flush with each other, back in the starting position.
In many applications it may be necessary to prevent putting back into operation after triggering or emergency braking. To do this, a return lock is provided which prevents the locking disc from turning back and the control disc to its starting position. In so doing, the safety brake remains in the locked state. An illustrative example of the return lock provides that clamping rollers are positioned in recesses of the locking disc. These are arranged and designed in such a way that resetting of the locking disc and control disc to the starting position is prevented.
So that in this design, there is no undesirable triggering of the safety brake, for example, by pulling out manually, the starting position is secured with a shear pin. Only when exceeding a certain threshold, depending on the rotational speed and torque, does the shear pin shear off and the safety brake performs the emergency braking.
The lifting gear according to the invention may be deployed in the most varied of applications. It may be used in any application with returning loads, for example, in constructing overhead lines or even to secure personnel.
The lifting gear is compact and of light construction. The additional securing function via the safety brake is achieved with few parts. The mechanics require active movement so that falling of the spring, seizing of the locking ratchet of the load pressure brake etc. lead to the safety brake being triggered. The safety brake locks automatically. In so doing, the catch hook always remains engaged, even when the load continues to oscillate.
The invention is explained in more detail in the following using the drawings. They indicate as follows:
On its external circumference, the load pressure brake 16 exhibits a ratchet wheel disc 24 provided with teeth. On both sides, the ratchet wheel disc 24 is provided with friction elements 25 in the form of friction pads. Furthermore, the load pressure brake 16 exhibits two pawls 26 supported in the housing 2 on the side plate 6 such that they can swivel, which are compressed under the effect of locking hook springs 27 onto the ratchet wheel disc 24. Furthermore, a pressure disc 28, on which the ratchet wheel disc 24 is supported, which forms part of the load pressure brake 16. The ratchet wheel 14 can be displaced axially on a movement thread 29 of the drive shaft 20.
The load pressure brake 16 has the task of holding the load supported by the lever hoist 1 when the ratchet wheel 14 is stationary. Then the ratchet wheel 14 is pressed over the ratchet wheel disc 24 and the integrated friction elements 25 are pressed onto the compression disc 28. The pawls 26 are located in the circumferential recesses of the ratchet wheel disc 24. If the ratchet wheel 14 is rotated in the lifting direction, the pawls 26 slide over the teeth of the ratchet wheel disc 24 until the ratchet wheel 14 comes to a stop. Then the pawls 26 are resting in the recess of the ratchet wheel disc 24 again. When lowering the load, the ratchet wheel 14 is rotated in the opposite direction, by which it slides axially on the movement thread 29 of the drive shaft 20 and the frictionally engaged contact with the friction elements 25 of the ratchet wheel disc 24 and the compression disc 28 is raised. The load can then be lowered until the drive shaft 20 that continues to rotate compensates for the axial backlash again.
In addition to the standard load pressure brake 16, the lever hoist 1 exhibits a safety brake 30, 31. The safety brake 30, 31 has the task of undertaking emergency braking in extreme situations in which there is so high a rotational speed of the drive shaft 20 that the load pressure brake 16 no longer engages due to inertia.
A safety brake 30 and its operation are described with reference to
The safety brake 30, 31 exhibits a locking disc 32 with locking teeth 33 and a control disc 34 with control cams 35 as well as a catch hook 36. On the circumference of the locking disc 32 several locking teeth 33, three in the illustrative example, are arranged uniformly distributed. The control disc 34 is configured in a triangular shape with the control cams 35 formed in a rounded shape on their circumference. The control disc 34 exhibits a central support 38 provided with internal toothing 37, on which the locking disc 32 is positioned with a central storage section 39 and is secured in position by securing elements 40, 41. Via the support 38 and the internal toothing 37, the control disc 34 and with the control disc 34 the locking disc 32 is held onto a threaded section 43 of the drive shaft 20 provided with external toothing 42.
The catch hook 36 is arranged such that it can move in a swivelling manner on the side plate 5 of the lever hoist 1. By incorporating a spring element 44 in the form of a helical spring, the catch hook 36 is supported on a pin 45 on the side plate 5 and secured by a securing ring 46. The support of the catch hook 36 on the pin 45 is in the central longitudinal region of the catch hook 36 so that the catch hook 36 is supported like a see-saw.
The locking disc 32 and the control disc 34 can be rotated in relation to each other. The rotation of locking disc 32 and control disc 34 in relation to each other is limited by a rotation limiter 47. The rotation limiter 47 comprises a curved track 48 which is formed in a slot 49 in the shape of a section of a circular arc in the control disc 34. Along the curved track 48, a stopper 50 in the form of a pin can be displaced. It is recognised that three slots 49 are arranged uniformly offset in the control disc 34. Correspondingly, three pins are incorporated as stoppers 50 in the installation holes 51 of the locking disc 32. The stoppers 50 protrude in the direction of the control disc 34 compared with the locking disc 32 and engage into the slots 49. In the illustrative example shown here, the rotation limiter 47 allows a rotation of the locking disc 32 compared with the control disc 34 by 45°.
Between the locking disc 32 and the control disc 34, ratchet elements 52 in the form of steel balls are incorporated. The ratchet elements 52 fix the locking disc 32 and the control disc 34 in the starting position or in the end position after a rotation. The ratchet elements 52 are held in take-ups 53 in the control disc 34 and contact ratchet surfaces 54 that are the shape of spherical sections in the control disc 32 and act together with these as a counter bearing and inhibiting movement.
The catch hook 36 exhibits a latch contour 56 on the front end 55. The latch contour 56 exhibits a catch tooth 57 formed as a point with a catch flank 58 on the abutting side which is configuratively adapted to a front locking flank 59 of a locking tooth 33 of the locking disc 32.
On the rear end 60 a sensing contour 61 is formed on the catch hook 36. To do this, the rear end 60 of the catch hook 36 is formed of a rounded shape. With the sensing contour 61, the catch hook 36 rests under the effect of the helical spring against the outer contour of the control disc 34. The spring element 44 has the effect that in normal operation the latch contour 56 is outside the external circumference of the locking disc 32. In normal operation, the catch hook 36 slides with the rear sensing contour 61 along the control disc 34. The front latch contour is 56 is raised.
When a certain excessive rotational speed is exceeded, the sensing contour 61 of the catch hook 36 lifts as a result of the mass inertia and the acting acceleration forces of the control disc 34 or the control cams 35. The catch hook 36 tips and rotates about the pin 35 in the locking disc 32. The latch contour 56 of the catch hook 36 hooks into a locking tooth 33 of the locking disc 32 and comes to rest there with the catch flank 58 onto the locking flank 59. Consequently, the locking disc 32 is held while the control disc 34 arranged coaxially behind it continues to rotate along the specified rotation path of the rotation limiter 47. The rotation occurs until the stopper 50 comes to a stop at the end 62 of the slots 49 situated in the direction of rotation. The locking disc 32 and the control disc 34 are then locked in relation to each other. In this way, a positive-fit connection between the drive shaft 20 and the lever hoist 1 is produced. Further overrunning of the load chain wheel 17 or running out of the load chain 10 is suppressed.
With increasing acceleration of the drive shaft 20 and with this the safety brake 30, therefore with excessive rotational speed, for example, caused by a falling load, the sensing contour 61 of the catch hook 36 is accelerated outwards and lifts from the control disc 34. The front catch tooth 57 of the latch contour 56 hooks into the locking disc 32 (see
To lift the blocking of the safety brake 30 and to put the control disc 34 and the locking disc 32 back into the flush starting position, a release 63 is provided. This comprises a slider 64 for activation of the release 63 and a blocking body 66 under the effect of a tension spring 65. By operating the slider 64 (arrow P2), this locks the locking disc 32 with the blocking body 66 and holds it firmly so that the locking disc 32 is prevented from rotating, while the control disc 34 is operated in the lifting direction (clockwise) (arrow P3) via the hand wheel 22 or the hand lever 13. In this way, the locking disc 32 and the control disc 34 are displaced in relation to each other and brought into their flush starting position.
A return block 67 is provided for the safety brake 31. A return block 67 prevents a rotation of the locking disc 32 and control disc 34 in its starting position, after the safety brake 31 has triggered, therefore standing in its blocked state. The return block 67 is characterised by recesses 68 in the locking disc 32 arranged offset on a pitch circle. Clamping rollers 69 are accommodated there. The rear wall 70 of a pocket-shaped recess 68 runs inclined so that the recess 68 tapers anticlockwise. Consequently, a wedging effect arises between the locking disc 32 and the control disc 34 via the clamping rollers 69, so that the return block 67 prevents rotation of the locking disc 32 and control disc 34 in relation to each other.
It can furthermore be recognised, particularly in the illustration of
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2019 120 036.9 | Jul 2019 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/DE2020/100101 | 2/13/2020 | WO | 00 |
