GB2063207A

GB2063207A - Loading dock ramp

Info

Publication number: GB2063207A
Application number: GB8035664A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-11-20
Filing date: 1980-11-06
Publication date: 1981-06-03
Also published as: FR2470075A1; GB2063207B; DE2946743A1

Abstract

A bridging ramp comprising a bridge plate (1) pivotally mounted on the face defining the rear end of a recess (2) to be bridged about a horizontal axis (4), the bridge plate (1) having an extension portion (5) pivotally mounted thereon, the extension portion being locatable on a platform to be loaded or unloaded, the front end of the bridge plate (1) being connected to a resilient tension member (9), one end of said tension member (9) being fixedly anchored and the other end of the arrangement being capable of being wound on and unwound from a rotatable drum (7), the drum (7) being capable of being locked against rotation, a torsion spring (8) being provided on the drum such that unwinding of the member (9) is effected by overcoming the force of the spring (8) such that the tension member prevents upward pivotal movement of the bridge plate (1) when the drum (7) is in a state of tension and is locked against rotation so long as the spring exceeds the tensional forces wherein the drum (7) is provided with at least one pawl and ratchet mechanism (14, 15) for locking the drum against rotation. <IMAGE>

Description

SPECIFICATION Bridging ramp The present invention relates to a bridging ramp. More particularly, the present invention relates to a ramp comprising a bridge plate pivotally mounted on the rear end of a recess to be bridged about a horizontal transverse axis. The plate is provided, at its free or front end with a pivotal extension portion which can be pivoted into a position in which it rests on a plafform to be loaded or unloaded.The bridge plate is connected to a resilient tension arrangement, one end of which arrangement is fixedly anchored and the other end of which can be wound up on a drum which is rotatable but also lockable against rotation and which can be unwound by overcoming the force of a torsion spring, whereby the tension arrangement, in the locked state of the drum, in a tension state, eliminates a (further) pivot movement of the bridge plate upwardly. The tension arrangement is intended to prevent unwanted upward pivotal movement of the bridge plate. This can occur, for example, if in practice, the counterbalanced bridge plate and extension are relieved from their load after being laid on the platform to be loaded or unloaded.Indeed, a strong spring or the like, may be additionally attached to the tension arrangement which, with excessive forces, still permits certain upward pivotal movement of the bridge plate. This may occur, for example, with vehicles, if the unloaded platform is resting on a vehicle whereby the springs of the vehicle try to lift the platform.

The present invention seeks to make possible effective stopping of the rotation of the drum in contrast to known brake units which prevent rotation solely by friction contact. The invention further seeks to provide an arrangement in which the rotation of the drum can be prevented on the surface of the bridge plate.

In accordance with the present invention there is provided a bridging ramp comprising a bridge plate pivotally mounted on the face defining the rear end of a recess to be bridged about a horizontal axis, the bridge plate having an extension portion pivotally mounted thereon, the extension portion being locatable on a platform to be loaded or unloaded, the front end of the bridge plate being connected to a resilient tension member, one end of said tension member being fixedly anchored and the other end of the arrangement being capable of being wound on and unwound from a rotatable drum, the drum being capable of being locked against rotation, a torsion spring being provided on the drum such that unwinding of the member is effected by overcoming the force of the spring such that the tension member prevents upward pivotal movement of the bridge plate when the drum is in a state of tension and is locked against rotation so long as the spring force exceeds the tensional forces wherein the drum is provided with at least one pawl and ratchet mechanism for locking the drum against rotation. The pawl and ratchet unit or units may be operated by lever, which lever may lie, in its rest position, coplanar with the surface of the bridge plate and which is movable into its operative position therefrom. Such a ratchet arrangement which, advantageously, engages with an external catch may be in the form of a toothed wheel, which is arranged on the side of the drum, or even forms the lateral flanges of the drum.Desirably, two ratchets are used having mutually offset or staggered pitches (displaced by about one-half of the pitch of the ratchet teeth), in order to reduce the back-lash from the drum. If such a ratchet is employed, then stopping of the pivotal movement of the bridge plate is ensured. It is, therefore, ensured that the bridge plate does not effect any unwanted upward movement.

The invention will be further described, by way of example, with reference to the accompanying drawings, the single Figure of which shows a side elevational view, partially in section, through a bridging ramp in accordance with the present invention. The ramp comprises a bridge plate 1 which is pivotally mounted on a surface 3 defining a recess 2 to be bridged. The bridge plate 1 is pivotal about a transversely extending horizontal axis 4. Means, not shown, are provided on the bridge plate 1 which permit pivoting of the bridge plate 1 about its axis 4 by hand. The bridge plate 1 is provided, at its free end remote from the axis 4, with an extension portion 5 which can be swung out to form an extension of the bridge plate 1 and supported on the loading or unloading platform of a vehicle.When not in use, the extension portion can be pivoted about a horizontal axis so as to be located in the recess 2. At the rear end of the bridge plate 1, there is provided a box-type bearing 6 for a drum 7, the drum being rotatable about a horizontal axis 8. One end of a cable 9 is mounted on or affixed to the drum 7. The cable 9 is wound on this drum 7 and then extends towards the free end of the bridge plate along a generally horizontal path. Adjacent the free end of the bridge plate, the cable 9 passes over a guide roller 12 supported from above by the bridge plate 1.

The cable 9 then passes downwardly and the other end of the tensioned cable 9 is firmly anchored to the base of the recess 2. A strong tension spring 10 can, however, also be passed over the cable 9 and be connected with the anchorage point.

On the side of the drum 7 a torsion spring 13 is mounted which firmly retains the cable but permits to be unwound by overcoming the resistance thereof.

On the one end of the drum, two juxtaposed ratchets are provided, only the outer teeth 14 of one of the ratchets being shown. A pawl 1 5 engages in these teeth 14, the pawl being located below the bridge and being pivotal about a horizontal axis 1 6. The pawl has a lever portion 1 7 extending forwardly which is acted upon by an operating lever 18. The lever 18, in the engagement position of the pawl 1 5 with ratchet 14, lies in the plane of the surface of the bridge plate 1.

The operating lever 18 forms part of the bridge plate surface in the operating position of the ratchet and the free end of the lever rests on a block 19. The lever 18 is pivotal about an axis 18 and, in the region of such axis 20, has a cam member 21 extending downwardly therefrom which is capable of co-operating with the lever 17 in the manner of an eccentric.

To raise the bridge plate 1, the operating lever 18 is pivoted upwardly in the direction of the arrow 22. The cam 21 strikes against the lever 17 which is pivoted downwardly and causes the pawl 1 5 to move upwardly out of contact with the ratchet 14. Thereby, the plate 1 can be pivoted through a desired amount with corresponding unwinding of the cable 9 from the drum. When the desired position of the plate is reached, the operating lever 18 is re-pivoted into the plane of the bridge plate so that the pawl 15 once again engages with the ratchet 14. By so doing, further unrequired raising of the bridge plate can be avoided. However, with greater forces, a certain yielding can arise due to the provision of the spring 10.

It is particularly favourable to locate the ratchet 14 beneath the bridge plate 1, so that the locking pawl 15 can be operated directly by an operating lever 18 forming a part of the bridge plate.

It will be appreciated that the pawl 1 5 can thus be regulated by weight and, if necessary, can remain under the force of the spring so that the engagement thereof with the ratchet 14 is ensured as long as the operating lever 18 lies in the plane of the bridge plate surface.

Claims

1. A bridging ramp comprising a bridge plate pivotally mounted on the face defining the rear end of a recess to be bridged about a horizontal axis, the bridge plate having an extension portion pivotally mounted thereon, the extension portion being locatable on a platform to be loaded or unloaded, the front end of the bridge plate being connected to a resilient tension member, one end of said tension member being fixedly anchored and the other end of the arrangement being capable of being wound on and unwound from a rotatable drum, the drum being capable of being locked against rotation, a torsion spring being provided on the drum such that unwinding of the member is effected by overcoming the force of the spring such that the tension member prevents upward pivotal movement of the bridge plate when the drum is in a state of tension and is locked against rotation so long as the spring force exceeds the tensional forces wherein the drum is provided with at least one pawl and ratchet mechanism for locking the drum against rotation.

2. A ramp as claimed in Claim 1, wherein two or more ratchets are provided, the pitches of which are off-set or staggered from one another.

3. A ramp as claimed in Claim 1 or 2 wherein the at least one ratchet is coaxial with the drum and is fixedly connected to an end face of the drum.

4. A ramp as claimed in any preceding claim wherein the ratchet is fixedly mounted below the bridge plate.

5. A ramp as claimed in any preceding claim, the pawl engaging with the at least one ratchet is actuated by an operating lever which, in its position of engagement with the ratchet lies in the plane of the surface of the bridge plate.

6. A ramp as claimed in Claim 5, wherein the pawl is pivotally mounted and the operating lever has an eccentric or cam which acts on the end of the locking pawl on the opposed side of the pivot axis to the ratchet.

7. A ramp as claimed in Claim 4, wherein the ratchet unit is located in the region of the pivot axis for the bridge plate.

8. A ramp as claimed in Claim 5 or 6, wherein the operating lever forms a window-type portion of the bridge plate and is supported by support means in its position of engagement with the at least one ratchet.

9. A ramp as claimed in Claim 8, wherein the operating lever is pivoted at an angle to the bridge plate to cause said pawl to be disengaged from the at least one ratchet.

10. A ramp as claimed in any preceding claim wherein a guide roller is supported below the front, free end portion of the bridge plate, the guide roller guiding the tension unit to an anchoring point in the base of the recess.

11. A bridging ramp constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the 'accompanying drawing.