GB2049611A

GB2049611A - Platform bridging member

Info

Publication number: GB2049611A
Application number: GB8011528A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-04-12
Filing date: 1980-04-08
Publication date: 1980-12-31
Also published as: FR2453807A1; DE2914998A1; GB2049611B; FR2453807B1

Abstract

A bridging device for ramps or platforms comprising a bridge plate (1) pivotally mountable at its rear end about a horizontal axis (2) on a load receiving surface (3) the underside of the bridge plate (1) having a cam track (8) formed thereon, a spring-biassed lever arrangement (9, 10, 11,13) co-operating with the cam track so as to support the bridge plate (1), the bridge plate (1) carrying, at its free end a hingeably mounted extension portion (6) supportable on a platform (7) to be loaded or unloaded, wherein the cam track (8) has a first portion defining a first operational pivotal range (a) and (b) in which the weight of the bridge plate (1) and extension portion (6) acting on the spring-biassed lever arrangement (9, 10, 11, 13) causes the bridge plate (1) and extension portion (6) to overcome the spring-biassing force and to pivot downwardly about its pivotal mounting and a second portion defining a second pivotal range (c) in which the spring biassing force tends to be dominant and causes the bridge plate (1) and extension portion (6) to be counter balanced or pivot upwardly about its pivotal mounting. <IMAGE>

Description

SPECIFICATION Bridging member for ramps or platforms The present invention relates to a bridging device for ramps or platforms.

Bridging devices are known which have bridge plates for enabling vehicles to be loaded and unloaded. It will be apparent that the bridge plate tends to render the device unstable, and the plate will tend to follow any lowering movements of the platform to be loaded or unloaded. This is, however, disadvantageous if the device is manually operated because the operator in some circumstances, will be forced to extend an extension portion and to raise it against the natural tendency of the plate to lower itself.

The present invention seeks to provide a bridging device of this general type but in which the operation of the device is facilitated, but the advantages of the instability are maintained.

According to the present invention, there is provided a bridging device for ramps or platforms comprising a bridge plate pivotally mountable at its rear end about a horizontal axis on a load receiving surface, the underside of the bridge plate having a cam track formed thereon, a spring-biassed lever arrangement co-operating with the cam track so as to support the bridge plate, the bridge plate carrying, at its free end a hingeably mounted extension portion supportable on a platform to be loaded or unloaded, wherein the cam track has a first portion defining a first operational pivotal range in which the weight of the bridge plate and extension portion acting on the spring-biassed lever arrangement causes the bridge plate and extension portion to overcome the spring-biassing force and to pivot downwardly about its pivotal mounting and a second portion defining a second pivotal range in which the spring-biassing force tends to be dominant and causes the bridge plate and extension portion to be counterbalanced or pivot upwardly about its pivotal mounting.

Preferably, the extension portion located at the free end of the bridge plate is adapted to be pivoted inwardly or outwardly by means of a linkage that the spring force acting on the lever actuating the pivoting of the extension portion when the bridge plate is in the upper portion of its pivotal path.

Hence, the spring-biassed lever arrangement carries out two functions. In the operating region, the arrangement absorbs a major proportion of the movement set up by the weight of the bridge plate and extension portion, whilst still permitting the bridge plate and extension portion to tend to rotate downwardly about its pivotal axis. Moreover, the arrangement facilitates the movement of the bridging device in the pivotal region located above the operating region.

The bridge may be counterbalanced in this upper pivotal region or may pivot into an end position. In either case, the extension portion can be moved outwardly into its extended state.

The invention will be further described by way of example, with reference to the accompanying drawing, the single Figure of which shows a side view of a bridging device in its operational position.

As shown in the drawing, a bridging device comprises a bridge plate 1, the rear end of which is pivotally mounted about a horizontal axis 2 on a ramp or platform 3. The upper surface of the platform or ramp 3 is denoted by the reference numeral 4. Below the bridge plate 1, a recess which is substantially rectangular in cross-section is formed in the ramp or platform 3 into which the bridge plate 1 may be lowered.

The free end of the bridge plate 1 has an extension portion 6 hingedly mounted thereon, the hinge being denoted by the reference numeral 5. In the operational position, as shown in the drawing, the extension portion 6 is supported on a platform 7 of an automotive vehicle or any other device to be loaded or unloaded. The bridging device is thus supported on the platform 7 almost exclusively by the engagement of the extension portion 6 therewith. In the position as shown, loading and unloading may be easily effected.

In the inoperative position of the device the surface of the bridge plate 1 lies substantially flush with the surface 4 and the extension portion 6 is pivoted downwardly with respect to its operational position.

Moreover, linkages or the like are provided to cause the pivoting of the extension portion 6 about its pivot axis 5.

On the underside of the bridge plate 1, a cam track 8 in the form of a disc is provided, the disc extending vertically downwardly with respect to the bridge plate 1. The cam track 8 is impacted by a roller 9 formed on one end of a lever 10 which extends in the same general direction as the bridge plate 1. The other end of the lever 10is journalled in a bearing 11 located in the base region of the recess. A tension spring 12 is connected to the lever 10. One end of the spring is secured to the rear face of the recess. The action of the spring on the lever 10 tends to pivot the bridge plate 1 and the extension portion 6 upwardly.

The influence of the lever 10 on the plate 1 and extension portion 6 is, however, dependent upon the location of the roller 9 on the cam track 8 and on the form of the track 8. As shown, the track is substantially spherical, that is to say, substantially convex.

However, in its rear portion, nearer the pivot axis 2, the track has a concave indentation 12.

The configuration of the cam track 8 is of vital importance. If the roller 9 is located below the front portion of the track 8, that is to say, forward of the pointx, the weight of the bridge acts on the lever 10 in such a manner that the bridge tends to pivot downwardly about the axis 2. Accordingly, the extension portion abuts against the platform 7 with a downward pressure of, for example, 10 Kp. This is the case in the operational ranges designated a and b. This corresponds to an angle of inclination, with respect to the surface 4, of 10 to 15 on either side of the surface. This allows flexibility of the device to take into account the varying heights of platforms on automotive vehicles.

Above the region b there is a further region c which corresponds to a further 10 to 20 with respect to the surface 4. This operational region is nec essay to permit the extension portion 6 to be swung in or out without hinderance if the platform 7 is located close to the ramp or platform 3.

Movement of the bridge plate in this region c is effected by the action of the spring force on the lever 10, at least to the extent that the manual effort required to swing the plate upwards is minimal. In this region c, the rear section of the cam track, the part thereof extending rearwardly of the pointx to the depression 12, is utilised.

As the plate 1 crosses into the region c by passing of the roller 9 overzenithx of the cam track 8, the plate 1 is biassed upwardly by the tension spring 12 such that it swings upwardly in a controlled manner, without any manual intervention, at or shortly before the maximum permissible swinging movement, the extension portion may be swung out, or in, by employing the linkage. To move the bridge plate downwardly into the region b, a certain amount of force is required. Nevertheless, the lever action in the region c is still favourable, because the lowering ofthe bridge plate 1 is substantially simpler to effect. It is thus possible for the bridge plate to be lowered merely by applying pressure thereto by, for example, the foot of the operator.

Claims

1. A bridging device for ramps or platforms comprising a bridge plate pivotally mountable at its rear end about a horizontal axis on a load receiving surface, the underside of the bridge plate having a cam track formed thereon, a spring-biassed lever arrangement co-operating with the cam track so as to support the bridge plate, the bridge plate carrying, at its free end a hingeably mounted extension portion supportable on a platform to be loaded or unloaded, wherein the cam track has a first portion defining a first operational pivotal range in which the weight of the bridge plate and extension portion acting on the spring-biassed lever arrangement causes the bridge plate and extension portion to overcome the spring-biassing force and to pivot downwardly about its pivotal mounting and a second portion defining a second pivotal range in which the spring-biassing force tends to be dominant and causes the bridge plate and extension portion to be counterbalanced or pivot upwardly about its pivotal mounting.

2. A bridging device as claimed in claim 2, wherein the upward pivoting of the bridge plate and extension portion in said second operational range is limited by an indentation formed in the cam track, the free end of the lever arrangement being located in said indentation in the limit position.

3. A bridging device as claimed in claim 1 or 2, wherein the lever arrangement includes a roller which, in use, co-operates with the cam track.

4. A bridging device as claimed in claim 1,2 or 3, wherein the extension portion located at the free end of the bridge plate is adapted to be pivoted inwardly or outwardly by means of a linkage that the spring force acting on the lever actuating the pivoting of the extension portion when the bridge plate is in the upper portion of its pivotal path.

5. A bridging device constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.