GB2125005A

GB2125005A - Cable breakage safety lock device for a vehicle load lifting apparatus

Info

Publication number: GB2125005A
Application number: GB08222046A
Authority: GB
Inventors: Michael Albert Sidney Marshall
Original assignee: HENDERSON GROUP
Current assignee: HENDERSON GROUP
Priority date: 1982-07-30
Filing date: 1982-07-30
Publication date: 1984-02-29
Also published as: GB2125005B

Abstract

A cable breakage safety lock device for a vehicle load lifting apparatus includes a guide channel (1) in which a cable (4) is located the channel being provided with projecting stop means (6), a saddle member (2) pivotally connected at its upper end to the cable (4) at a point (8) on one side of the vertical centre line through the saddle member, and an elongated bar member (3) supporting a platform (5), member (3) being pivotally connected to the saddle member (2) at a point (10) on the opposite side of the vertical centre line to the cable pivotal connection point and lower than the latter point, the saddle member (2) being spring-biassed away from the member (3) and towards the projecting stop means (6). Thus a reduction or loss of cable tension resulting from cable breakage or disconnection will allow the biassing means (11) to pivot the saddle member (2) away from the bar member (3) and urge the lower end of the saddle member into engagement with the projecting stop means (6) on the platform guide channel (1) and thereby halt downward movement of the platform (5) under gravity. <IMAGE>

Description

SPECIFICATION Cable breakage safety lock device for a vehicle load lifting apparatus This invention relates to a cable breakage safety lock device for a vehicle load lifting apparatus and concerns, particularly but not exclusively, a cable breakage safety lock device for a vehicle tail lift.

Such a vehicle load lifting apparatus usually includes a platform slidably mounted at one end in a pair of spaced apart substantially vertically extending guide channels and movable up and down in the channels by means of electric motor or hydraulic ram operated cables housed in the channels. Such a vehicle load lifting apparatus will hereinafter be referred to as "of the kind hereinbefore defined".

The platform guide channels may be mounted one on either side of a rear opening of the vehicle in the case of a tail lift, and the platform, which can be pivoted between substantially vertical and horizontal positions, may be moved between a vertical raised stowed position in which it closes at least partially the vehicle rear opening at or above the vehicle opening floor level, a horizontal pivoted out raised working position in which it lies at the level of the vehicle opening floor and a horizontal pivoted out lower working position in which it lies substantially at ground level.Thus modes can be put onto the horizontal platform at ground level, the platform raised to vehicle floor level for removal of modes from the platform into the vehicle and vice versa, and the platform can be pivoted back into the vertical stowed position to act as a vehicle opening closure means or tail gate.

Alternatively such a vehicle load lifting apparatus may, of course, be mounted at any other convenient location on the vertical such as on the vehicle side.

However the vehicle load lifting apparatus is located, the cables are a weak link in the apparatus, particularly if overloaded or badly maintained, and can break under load allowing the platform and load thereon to crash rapidly down to the ground with possible disastrous effects to any one or any thing in the downward part of the platform. To avoid such uncontrolled fall of the platform on breakage of a cable or cables attempts have been made to provide a cable breakage safety lock to jam the platform in a raised position on cable breakage. One proposed lock incorporated a pawl on the platform which engaged the inside surface of the guide channel when the cable broke, and thus jammed against the guide channel and prevented the platform from descending any further.Unfortunately this previouly proposed lock has the disadvantage that the pawl, due to its shape, wear or lack of maintenance, may not jam fixedly against the guide channel surface but chatter therealong causing damage to the channel and allow the platform to drop more or less out of control.

There is thus a need for a general improved cable breakage safety lock device to provide more effective engagement with the guide channel.

Accordingly the present invention provides a cable breakage safety lock device for a vehicle load lifting apparatus of the kind hereinbefore defined, including a platform guide channel in which a cable is locatable, which platform guide channel has an innermost face provided with projecting stop means, a saddle member pivotally connectible at its upper end to the cable at a point on one side of the vertical centre line through the saddle member, which saddle member has a passage therethrough in the direction of the vertical centre line, an elongated bar membler, a lower end of which is connectible to the platform and an upper end of which is locatable in the passage and pivotally connectible to the saddle member at a point on the opposite side of the vertical centre line to the cable pivotal connection point lower than the latter point, and a biassing means mountable between the saddle member and the bar member at a point between the saddle member and bar member pivotal connection point and the lower end of the saddle member normally to urge the lower end of the saddle to pivot about the saddle member and bar member pivotal connection point away from the bar member, towards the platform guide channel face provided with the projecting stop means, the arrangement being that such with the saddle member and bar member pivotally interconnected, operatively mounted in the platform guide channel and connected to the cable and platform as aforesaid, operative tension on the cable will pivot the saddle member against the biassing means away from the projecting stop means and maintain the lower end of the saddle member out of contact with the projecting stop means enabling free vertical movement of the saddle member and bar member in the channel, whereas a reduction or loss of cable tension resulting from cable breakage or disconnection will allow the biassing means to pivot the saddle member away from the bar member and urge the lower end of the saddle member into engagement with the projecting stop means on the platform guide channel and thereby halt downward movement of the platform under gravity.

Preferably the pivotal connection points are provided by two pivot pins arranged substantially parallel to one another transverse to the guide channel face provided with the projecting stop means. Conveniently the cable pivotal connection point is located on the platform side of the vertical centre line and the saddle member and bar member pivotal connection point is located on the projecting stop means side of the vertical centre line through the saddle member.

Advantageously the passage is open at one side, such as the platform side of the saddle member to allow the bar member to project therefrom through a longitudinal slot provided in the channel member. Preferably the biassing means is a compression spring located in a blind bore in the bar member and acting against a nose portion of the saddle member lower end.

Conveniently the projecting stop means is in the form of teeth projecting from the plane of the inner surface of the platform guide channel. Preferably the bar member is provided with an extension at its uppermost end located outside the saddle member and provided with screw adjustment means for exerting pressure on the platform side of the saddle member to cause the latter to pivot away from engagement with the projecting stop means, against the action of the biassing means, and thus reset the cable breakage safety lock device of the invention following a cable loss of tension.

For a better understanding of the present invention and to show how the same may be carried into effect reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a schematic perspective view of a saddle member and bar member of one embodiment of a cable breakage safety lock device of the present invention, shown in operative association with a cable and platform, Figure 2 is an exploded view of Fig. 1, Figure 3 is a vertical part sectional view through the mechanism of Fig. 1 shown in operative association with a platform guide channel and in which a position of engagement between the saddle member and guide channel projecting stop means is shown in dotted lines, Figure 4 is a horizontal sectional view from above through Fig. 3 taken along the line A-A, and Figure 5 is a vertical sectional view through part of a platfrom guide channel showing the projecting stop means.

As shown in the accompanying drawings a cable breakage safety lock device of the invention for a vehicle load lifting apparatus of the kind hereinbefore defined, includes a platform guide channel 1, a saddle member 2 and an elongated bar member 3 made in any convenient manner from any suitable material, preferably metal.

Generally vehicle load lifting apparatus such as a vehicle tail lift, include two such platform guide channels 1 which extend substantially vertically in parallel spaced relationship one on either side of an opening on the vehicle.

Although the present invention is described in terms of such a tail lift it can of course be used with other vehicle load lifting apparatus located, for example on the side of the vehicle rather that at the rear. If necessary both such channels 1 can be provided with a cable breakage safety lock device according to the present invention although only one will be described for the sake of convenience. Power driven cables 4 are provided one in each channel 1 for raising and lowering a platform 5 in order to move loads between the ground and an elevated load bearing platform on the vehicle.

As shown in Figs. 3, 4 and 5 the channel 1 has an innermost face provided with projecting stop means 6 conveniently in the form of teeth bent out of the plane of the channel member 1. These teeth may be provided by a simple piercing and pressing operation or may be in the form of projections attached in any convenient manner to the channel 1 such as by bolting, welding or braising thereto.

The saddle member has a passage 7 which extends lengthwise through the member and which conveniently opens out through the rearmost face of the member 2 as shown in Fig. 4 to give the member 2 a generally square U-shaped cross-section. The member 2 is pivotally connected at its upper end to the cable 4 at a point provided by a pivot pin 8, which point is located on one side of the vertical centre line through the saddle member, preferably the platform side of the vertical centre line as shown in the drawings. As illustrated the pivot pin 8 passes through two arms of the generally square U-shaped crosssection of the member 2.

The elongated bar member 3 is connected at a lower end thereof to the platform 5 in any convenient manner to provide a rigid member movable with the platform 5. In order to guide the member 3 and platform 5 for vertical motion in the channel 1 guide wheels 9, such as illustrated in Fig. 3, are provided for engaging opposed inner faces of the channel 1. An upper end of the member 3 is locatable in the passage 7 and pivotally connected to the saddle member 2 at a point provided by a pivot 10 located on the opposite side of the vertical centre line through the member 2 to the pivot pin 8. Advantageously the pins 8 and 10 extend substantially parallel to one another transverse to the face of the channel 1 provided with the stop means 6.

A biassing means such as a coiled compression spring 11 is mounted between the member 2 and the member 3 at a point between the pivot pin 10 and the lower end of the saddle member 2. As illustrated the spring 11 is mounted in a blind bore 1 2 in the member 3 and acts upon the rear surface of a nose portion 13 provided on the lower end of the saddle member 2. The spring 11 normally urges the lower end of the saddle member 2 to pivot about the pin 10 away from the member 3 and towards the face of the channel 1 provided with the stop means 6.

As illustrated the pin 10 projects through the arms of the substantially square U-shaped cross-section of the member 2 and through the member 3 carried in the passage 7. When operatively fitted in the channel 1 the engaged members 2 and 3 interconnect the cable 4 and platform 5 and the pivot pin 8 is located on the platform side of the vertical centre line through the member 2 and the pivot pin 10 is located on the stop means 6 side of the vertical centre line. Of course the pivot pin 10 is located lower than the pivot pin 8 between the pivot pin 8 and the spring 11. When operatively located as aforesaid one side of the member 3 projects from the open mouth of the passage 7 through a slot 14 provided in the channel 1 as shown in Figs. 3 and 4.The portion of the member 3 projecting through the slot 14 outside the channel 1 has an extension 1 5 at its uppermost end provided with an adjustment screw means using a screwed bore 1 6 for exerting pressure on the platform side of the member 2 to pivot the member 2 about the pin 10 against the biassing action of the spring 11 in order to reset the lock as will be hereinafter described.

In operation the weight of the platform 5 causes the cable 4 to exert a tension on the pivot pin 8 sufficient to overcome the biassing action of the spring 11 and cause the member 2 to be pivoted back against the front face of the member 3 as shown in Figs. 1 and 3, such that the nose portion 1 3 cannot contact the projecting stop means 6 during passage of the members 2 and 3, and hence the platform 5 up and down the channel 1. However as soon as there is a loss of tension in the cable 4 due to cable breakage the spring 11 reasserts its biassing effect and causes the member 2 to pivot about the pin 10 with respect to the member 3 so that the nose portion 1 3 takes up the position shown in dotted lines in Fig. 3 where it can engage the top face of the nearest projecting stop means 6 as shown.

When this happens the fixed engagement between the end of the nose portion 1 3 and the stop means 6 effectively locks the members 2 and 3, and hence the platform 5, against further downward movement until the member 2 should be released by means of the screwed adjustment means in the bore 16. Such adjustment means can consist of a bolt which can be screwed in to and out of the bore 1 6 such that when the bolt end engages the rear face 1 7 of the member 2 continuing advancement of the screw forces the member 2 to pivot about the pin 10 against the force of the spring 11 and hence move the nose portion 1 3 out of engagement with the projecting stop means 6 to free the device for continued vertical movement. Of course this should only be done after a fresh cable has been attached to the pin 8 or after the platform 5 has been supported underneath against continuing downward movement. If tension is released in the cable 4 without the cable breaking such as, for example if the platform 5 should hit an obstruction during lowering but before it has reached its lowermost position then the device of the invention will function in the ususal way and the nose portion 1 3 will engage the nearest projecting stop means 6 to prevent further downward movement of the platform 5 if the obstruction should be removed and the cable 4 is not under sufficient tension to overcome the biassing action of the spring 11.

Claims

1. A cable breakage safety lock device for a vehicle load lifting apparatus of the kind herein before defined, including a platform guide channel in which a cable is locatable, which platform guide channel has an innermost face provided with projecting stop means, a saddle member pivotally connectible at its upper end to the cable at a point on one side of the vertical centre line through the saddle member, which saddle member has a passage therethrough in the direction of the vertical centre line, an elongated bar member, a lower end of which is connectible to the platform and an upper end of which is locatable in the passage and pivotally connectible to the saddle member at a point on the opposite side of the vertical centre line to the cable pivotal connection point lower than the latter point, and a biassing means mountable between the saddle member and the bar member at a point between the saddle member and bar member pivotal connection point and the lower end of the saddle member normally to urge the lower end of the saddle to pivot about the saddle member and bar member pivotal connection point away from the bar member, towards the platform guide channel face provided with the projecting stop means, the arrangement being that such with the saddle member and bar member pivotally interconnected, operatively mounted in the platform guide channel and connected to the cable and platform as aforesaid, operative tension on the cable will pivot the saddle member against the biassing means away from the projecting stop means and maintain the lower end of the saddle member out of contact with the projecting stop means enabling free vertical movement of the saddle member and bar member in the channel, whereas a reduction or loss of cable tension resulting from cable breakage or disconnection will allow the biassing means to pivot the saddle member away from the bar member and urge the lower end of the saddle member into engagement with the projecting stop means on the platform guide channel and thereby halt downward movement of the platform under gravity.

2. Device according to claim 1, wherein the pivotal connection points are provided by two pivot pins arranged substantially parallel to one another transverse to the guide channel face provided with the projecting stop means.

3. Device according to claim 1 or claim 2, wherein the cable pivotal connection point is located on the platform side of the vertical centre line and the saddle member and bar member pivotal connection point is located on the projecting stop means side of the vertical centre line through the saddle member.

4. Device according to any one of claims 1 to 3, wherein the passage is open at one side, which is the platform side of the saddle member, to allow the bar member to project therefrom through a longitudinal slot provided in the channel member.

5. Device according to any one of claims 1 to 4, wherein the biassing means is a compression spring located in a blind bore in the bar member and acting against a nose portion of the saddle member lower end.

6. Device according to any one of claims 1 to 5, wherein the projecting stop means is in the form of teeth projecting from the plane of the inner surface of the platform channel guide.

7. Device according to any one of claims 1 to 6, wherein the bar member is provided with an extension at its uppermost end located outside the saddle member and provided with screw adjustment means for exerting pressure on the platform side of the saddle member to cause the latter to pivot away from engagement with the projecting stop means, against the action of the biassing means, and thus reset the cable breakage safety lock device following a cable loss of tension.

8. A cable breakage safety lock device for a vehicle load lifting apparatus, substantially as hereinbefore described with reference to the accompanying drawings.

9. A vehicle load lifting apparatus having a cable breakage safety lock device according to any one of claims 1 to 8.