GB2065600A

GB2065600A - Screw and nut lifting mechanism e.g.forcers

Info

Publication number: GB2065600A
Application number: GB8040141A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-12-18
Filing date: 1980-12-15
Publication date: 1981-07-01
Also published as: IT1134796B; DK538479A; ES497840A0; ZA807874B; ES8202761A1; DE3048319A1; IT8026767A0; FR2471945A1; FR2471945B3

Abstract

In a lifting mechanism for e.g. cars in which the lifting movement is carried out by a threaded lift nut (2) which is positioned inside a housing (1) and is displaced upwards or downwards together with the housing (1) inside a lifting post (16) by means of a threaded lifting spindle, in which a control or safety cord (4) is secured to the housing (1) of the lift nut (2) and a safety nut (3) is positioned inside the housing (1) below the lift nut (2) and engaged with the thread of the spindle and displaceable relatively to the housing (1) along its longitudinal vertical axis, the securing means of the safety cord (4) is constructed so that displacement of the safety nut (3) relative to the housing (1) displace a release means e.g. a pin 9 which in turn releases the securing means and hence the safety cord (4) from the housing (1). The displacement of the safety nut (3) relative to the housing (1) may be longitudinal along and/or angular about the axis of the housing (1). <IMAGE>

Description

SPECIFICATION Lifting mechanism The present invention relates to a lifting mechanism for automobiles and the like in which the lifting movement is carried out by a threaded lift nut which is positioned inside a housing and is displaced upwards or downwards together with the housing inside a lifting post by means of a threaded lifting spindle during its rotation in engagement with the lift nut, a control or safety cord being secured to the housing of the lift nut and safety nut being also positioned in the housing spaced below the lift nut. The safety nut is in engagement with the spindle via its thread and is displaceable along the axis of the housing.In lifting devices by which the lifting movement is carried out by means of a threaded lift nut-and a threaded rotatable lifting spindle extending through the lift nut it is normally requested and often required for acception that the load is not dropped when the internal thread of the lift nut is worn down.

Lifting mechanisms are known having a safety system comprising a safety nut spaced below the lift nut in the housing, the safety nut being inside threaded and being adapted to support the lift nut when the thread of this is gone so that the safety nut takes over the lifting and supporting function of the lift nut.

The lifting mechanism of this known type can then principally continue to be used with the safety nut in function as a support and lift nut, but thereby the security against load dropping is completely eliminated.

To avoid this situation it is known to fasten a monitor or safety release cord to the housing of the lift nut and let this cord control a switch which switches off the driving mechanism or prime mover of the lifting mechanism when the housing is relatively lowered a little as a consequence of the lift nut dropping or gliding downwards, i.e. the safety nut gliding upwards relative to the housing, and the housing will then be resting on the safety nut via the lift nut. In lifting mechanisms where several lift nuts, e.g. via chains, are interacting synchronously, the safety cord can also be adapted to actuate a switch, e.g. when the height difference of the lift nuts gets too big, when one of these meets a hindrance or a stopping impediment or when one of these is passing a maximum or minimum limit for the lifting movement.

The safety cord is positioned with a certain pre-tension and if this pre-tension decreases, e.g. by a rupture in the very cord, the switch in question will be actuated in the same way.

Each adjoining lift nut and safety nut is as mentioned positioned in a lift or support housing, in which both nuts are torsion-proofly positioned and in which at least the safety nut furthermore is positioned displaceably lengthwise of the housing~between a lower stop in the housing and the above positioned lift nut.

Each housing is torsion-proof and height displaceably positioned in their respective lift post.

When the safety cord switches off the power supply to the prime mover of the lifting mechanism or to its operating controls and in the consequences of this one or more worn out lift nuts become replaced then the security system has fulfilled its function. However, some operators of lifting mechanisms when these mechanisms are stopped by the action of the safety cord have shown the ability and willingness to re-adjust the safety cord so that the function of the mechanism could continue without any replacement of the lift nut, but also without any further security against drop of load when the thread of the safety nut is worn down too.

The lifting mechanism according to the invention will avoid the above disadvantages when the securing means of the safety cord is constructed so that a displacement of the safety nut relatively to the housing displaces a release means which in turn releases the securing means and hence the safety cord from the housing, the displacement of the safety nut relatively to the housing being longitudinal along and/or angular about the axis of the housing. Thereby the work of re-adjusting the safety cord is of same size as of replacing the lift nut which makes it more probably that the mechanism is only used with full safety against drop of load.

The invention will now be described, by way of example, with reference to the accompanying drawings, wherein: Figure 1 shows a vertical section of a housing for a lift nut in a lifting mechanism in accordance with the invention, Figure 2 shows a horizontal section of the safety nut in Fig. 1 with a recess having sloped ramps, Figure 3 is a fragmentary vertical section of the recess in the safety nut of Fig. 1, Figure 4 shows a general perspective view of a lifting mechanism in accordance with the invention, and Figure 5 shows a modification of the mechanism of Fig. 1.

Fig.1 shows a housing 1 with a lift nut 2 mounted stiffly against torsion in the upper part of the housing 1 and in the lower part of the housing 1 and a safety nut 3 mounted longitudinally displaceably and at least partly stiff against torsion, i.e. rotatably at least a small angle about the axis of the housing 1.

The threaded lifting spindle of the lifting mechanism has for the sake of clarity been deleted in the interior of the nuts 2, 3 with the interior thread of which the exterior thread of the lifting spindle is in engagement. A control or safety cord 4 is in this embodiment extending from above and downwards along the housing 1 and the securing means for the cord 4 is in the housing 1 adapted so that a displacement of the safety nut 3 inside the housing 1 will activate release means which in turn releases the cord 4 from its engagement with the housing 1.

In the preferred embodiment of the housing 1 shown in Fig. 1 the securing means comprises a dowel or pin 6 fixed perpendicularly to the outer wall of the housing 1 and a cord or cable thimble 5 which is mounted longitudinally displaceably along the dowel 6 and on the outer end of this and so that the thimble 5 will be released from the dowel 6 when displaced beyond the outer end of the dowel 6. The release means of the cord 4 for releasing this comprises a recess 7 performed in the outer side face of the safety nut 3. The recess 7 is as shown extending longitudinally along the safety nut 3 and as shown in Figs.

2 and 3 also extending transversely along the periphery of the safety nut 3. As appears from Fig. 1 the recess 7 downwardly is limited by a sloped plane, cylindrical or otherwise curved ramp 8. The release means further comprises a release pin 9 being mounted longitudinally displaceably in a bore through the wall of the housing 1, the inner end of the pin 9 abutting the surface of the recess 7 and the outer end of the pin 9 being in engagement with a release arm 10, one end of which extends into a space between the cord thimble 5 and the housing 1 and around the dowel 6. In the shown embodiment the release pin 9 is welded to the release arm 10, the other end of which is fixed on the upper outer side face of the housing 1.The release arm 10 is shown in its releasing position by dotted lines after having been displaced outwardly by the release pin 9 in consequence of an upward or angular displacement of the safety nut 3 in the housing 1 by which displacement a sloped ramp 8, 14 or 1 5 of the nut 3 has pushed the release pin 9 outwards and hence the release arm 10 has pushed the cord thimble 5 outwards beyond the free end of the dowel 6 for releasing the cord, the pre-tension of this causes a rapid removal of the thimble 5 from the proximity of the dowel 6.Simultaneously with the outward displacement of the thimble 5 an L-piece, gusset plate or angle bracket 12 of deformable material has been bent outward if secured to the housing 1, but not if secured to the end of the release arm 1 0. This L-piece 1 2 serves the purpose of maintaining the thimble 5 in place on the end of the dowel 6 during normal working conditions of the lifting mechanism. The thimble 5 cannot be remounted on the dowel 6 as long as the safety nut 3 prevents the release pin 9 from being pressed back in place in the recess 7 by the return force of the release arm 1 0.

To prevent that the release arm 10 returns to its normal position shown in full lines in Fig. 1 the safety nut 3 may be provided with a sufficiently long extension below the ramp 8 as shown in Fig. 1 to prevent the return to its normal position in the housing 1 of the release pin 8, or the safety nut 3 may be provided with limited possibilities for its upward displacement, i.e. that the safety nut 3 can only be displaced upwards until the release pin 9 by the ramp 8 just has reached its releasing position, where it remains until the worn out or worn down part, here the lift nut 2, has been replaced. When the release arm cannot return to its initial in Fig. 1 shown position the cord thimble 5 cannot be remounted on the dowel 6, and possibly an alarm signal or a break of an electrical circuit caused by the release of the safety cord 4 is adapted to be reset by qualified personel only.

Thereby the lifting mechanism is secured against being used for continued lifting and simultaneously the release means acts as a wear and tear guard for the lift nut 2.

To be sure that the safety nut 3 is not worn out simultaneously with the lift nut 2 being worn out it is important that the safety nut 3 always substantially frictionlessly follows the lift nut on the lifting spindle. In the prior known devices of this type there have been no monitoring or guard of the safety nut 3 in this respect. The lifting mechanism in accordance with the invention therefore answers this purpose by having the securing means of the safety cord 4 constructed so that the release means can release the securing means and hence release the safety cord 4 from the housing 1 when the frictional force between the safety nut 3 and the lift spindle during its rotation increases beyond predetermined value, i.e. when the safety nut 3 is prevented in a certain degree to follow the lift nut 2 relative to the lift spindle.In a preferred embodiment of the safety nut 3 the recess 7 is therefore provided with the two inclined transversal side ramps 14 and 1 5 which as shown in Fig. 2 may be cylindrical and extending in the circumferential direction of the safety nut 3. Furthermore the safety nut 3 is mounted rotatably in the housing 1 about the center axis of this. The rotation of the nut 3 is limited to an angle of rotation corresponding to the extent of the recess 7 with its two side ramps 14, 1 5 in the circumferential direction of the housing 1 or of the nut 3. In Fig. 2 is opposite to the recess 7 shown a further recess serving this purpose when in engagement with a not shown pin secured to the wall of the nut 3. A rotational displacement of the safety nut 3 relative to the housing 1 will cause the release pin 9 to be displaced radially outwards by means of the ramp 14 or 1 5 and consequently push the release arm 10 outwards to release the cord thimble 5 whether this rotational displacement occurs during lifting or lowering the load carried by the lifting mechanism. This embodiment with two inclined side ramps 14, 1 5 can also include the inclined ramp 8 extending in the longitudinal direction of the housing 1, but may also be without the ramp 8 seeing that the friction between the lift spindle and the safety nut will increase when the load on the lift nut 2 is transferred to the safety nut 3.

This increased frictional force will result in the above mentioned rotation of the safety nut 3 relatively to the housing 1 and hence the activation of the release arm 10. Whether the lift nut 2 is worn out or the safety nut 3 is exposed for frictional forces and consequently exposed to the risk of being worn out, the safety cord 4 will be released. To possibly avoid that the safety nut 3 shall be prevented in its rotational displacement when the housing 3 with its worn out lift nut 2 drops or slides down to rest on the safety nut 3, a low friction trust transferring means, e.g. a ring of polytetrafluoroethylene or self-lubricating material or ball or roller trust bearing, may be mounted in the housing 1 in the space between the lift nut 2 and the safety nut 3. This trust transferring means will only get into function when the lift nut 2 is worn down.In lifting mechanisms without a safety cord or having a safety cord 4 which is not intended to be released from the housing 1, the release means of this invention may be used too, since the displacement of the release pin 9 in the housing 1 then may be utilized for activating a separate switch, e.g. a micro-switch for interrupting the power supply to the prime mover or to the manual control means, for supplying an alarm signal and/or for activating or interrupting other functions.

In Fig. 3 is shown a fraction of a radial section through the recess 7 of the safety nut 3 of another embodiment than the nut 3 shown in Fig. 1. The ramp 8 has a more smooth transition zone to the outermost side face of the safety nut 3.

Fig 4 shows a lifting mechanism according to the invention for lifting automobiles and having two lifting posts 16, inside each of which a lifting spindle is placed with its housing 1 for lift nut 2 and safety nut 3. The housing 1 in each of the posts 1 6 is normally mechanically connected with the housing 1 in the other post 1 6 via the lifting spindles, chain wheels 3 and chains, and with regard to the monitoring or guard or the wear-down of the lift nut 2 and/or the safety nut the housings 1 are connected via the safety cord 4.

Fig. 5 shows the housing 1 of Fig. 1 with a modified end of the release arm 1 0. Here the L-piece 1 2 is mounted on the arm 10 or being an integral part of this. Then the L-piece 1 2 will not be deformed by the release operation of the cord 4 from the housing 1.

Instead of releasing the safety cord 4 the displacement of the safety nut 3 may be utilized for severing or shearing the safety cord 4 in lifting mechanisms equipped with a safety cord. The shearing may be caused by a knife, e.g. on the release pin 9 or, when the safety cord 4 is placed extending through a hole in the wall of the housing 1, by a sharp edge on the safety nut 3, so that this edge cuts the cord 4 during the vertical and/or the angular displacement of the safety nut 3.

Lifting mechanism for automobiles and the like in which the lifting movement is carried out by a threaded lift nut 2 which is positioned inside a housing 1 and is displaced upwards or downwards together with the housing 1 inside a lifting post 1 6 by means of threaded lifting spindle during the rotation of this in engagement with the lift nut 2, a control or safety cord 4 being secured to the housing 1 of the lift nut 2 and a safety nut 3 being also positioned inside the housing 1 spaced below the lift nut 2 and engaged with the thread of the spindle and displacement relatively to the housing 1 along its longitudinal vertical axis, wherein the securing means of the safety cord 4 is constructed so that a displacement of the safety nut 3 relatively to the housing 1 displaces a release means which in turn releases the securing means and hence the safety cord 4 from the housing 1, the displacement of the safety nut 3 relatively to the housing 1 being longitudinal along and/or angular about the axis of the housing 1. The release means 9 is adapted to release a safety release cord 4 normally attached to the housing 1 and/or to activate a detector means, such as a micro-switch, to cut off energy supply or to block manual operation control means for the lifting mechanism. The displacement of the safety nut 3 is a longitudinal or an angular displacement inside the housing 1.

Claims

1. Lifting mechanism for automobiles and the like in which the lifting movement is carried out by a threaded lift nut (2) which is positioned inside a housing (1) and is displaced upwards or downwards together with the housing (1) inside a lifting post (16) by means of a threaded lifting spindle during the rotation of this in engagement with the lift nut (2), a control or safety cord (4) being secured to the housing (1) of the lift nut (2) and a safety nut (3) being also positioned inside the housing (1) spaced below the lift nut (2) and engaged with the thread of the spindle and displaceable relatively to the housing (1) along its longitudinal vertical axis, wherein the securing means of the safety cord (4) is constructed so that a displacement of the safety nut (3) relatively to the housing (1) displaces a release means which in turn releases the securing means and hence the safety cord (4) from the housing (1), the displacement of the safety nut (3) relatively to the housing (1) being longitudinal along and/or angular about the axis of the housing (1).

2. Lifting mechanism according to claim 1, wherein the securing means comprises a dowel or pin (6) fixed perpendicularly to the outer wall of the housing (1), and a cord or cable thimble (5) which is longitudinally displaceably mounted at the outer end of the dowel (6), the release means comprising a release pin (9) being mounted longitudinally displaceably in a bore through the wall of the housing (1), the inner end of the pin (9) abutting the surface of the recess (7) and the outer end of the pin (9) being in engagement with a release arm (10) which extends around the dowel (6) and into a space between the cord thimble (5) and the housing (1).

3. Lifting mechanism according to claim 1 or 2, wherein the release arm (10) is of deformable material, at preference of elastic deformable material, the cord thimble (5) comprising a ring to which an end of the safety cord (4) is secured, and an L-piece or angle bracket (12) is secured to an end of the release arm (1) or to the housing (1) near the dowel (6) in order to maintain the ring or cord thimble (5) on the dowel (6) at least when the release arm (10) is abutting the side of the housing (1), the angle bracket (12) being of plastic deformable material when the bracket (12) is secured to'the housing (1).

4. Lifting mechanism according to claim 1 and 2, wherein the safety cord (4) and the release means and the securing means are replaced by a detector means for detecting the longitudinal and/or angular displacement of the safety nut (3) relatively to the housing (1).

5. Lifting mechanism according to claim 4, wherein the detector means consists of release means for activating a release movement.

6. Lifting mechanism according to any of the claims 1-3 and 5, wherein the release means is constructed to release the safety cord (4) from the housing (1) and/or to activate a control means on the housing (1) when the friction against the displacement of the safety nut (3) relatively to the housing (1) increases to or beyond a prefixed value.

7. Lifting mechanism according to claim 2-6, wherein the recess (7) has two inclined plane or curved side ramps (14, 15) extending in the circumferential direction of the safety nut (3), the safety nut (3) being supported in the housing (1) and mounted easily rotatable an angle substantially corresponding to the angular extent of the recess (7) with the two side ramps (14, 15) in the circumferential direction of the housing (1) or of the safety nut (3).