GB2271334A - Power closure system for vehicle mounted platform lift. - Google Patents

Abstract

The invention relates to a vehicle platform lift of the type for attachment to a vehicle comprising platform support means 3 a platform 1 pivotally attached to said platform support means at a pivot point adjacent one end of said platform and extensible actuation means 5 for opening and closing said platform by, respectively, shortening and lengthening said actuation means, said actuation means being attached at a first end 7 thereof to said platform support means and at a second end 6 to said platform at a point between the pivot point and the said one end of the platform. Preferably the actuation means is a piston and cylinder extended to raise the platform. Preferably a resilient device 13 and a movable link 8 assists opening. <IMAGE>

Description

POWER CLOSURE SYSTEM FOR VEHICLE MOUNTED PLATFORM LIFT It is known to facilitate the loading and/or unloading of a vehicle by the use of a platform attached to the vehicle via a lifting and lowering mechanism. Such a platform may be in a substantially horizontal plane whilst loading or unloading and may be moved to a substantially vertical plane prior to movement of the vehicle. One type of lift mechanism that may be used with such a platform employs one or more spaced-apart slotted columns attached to the vehicle, each column enclosing a runner capable of being raised or lowered within the column, typically by the use of chain or wire rope.

In a lift of the type described, the platform may be pivotally attached to the runner or runners, the pivot axis generally lying parallel to, and near to, the edge of the platform which lies adjacent to the vehicle.

It is also known to provide automatic opening or closure of the platform, by attaching power operated retraction means between the cantilevered part of the platform on the one hand and elevated positions on the appropriate runner on the other hand, such a system being described, for example, in Belgian patent no. 890448.

The retraction means in such a design typically consists of hydraulic rams, and it is a disadvantage of these systems that closure of the platform requires that pressurised fluid be applied to the annular area of the piston in such a cylinder. Thus, closure of the platorm,.despite requiring substantial force, uses the cylinder in its least effective sense. On the other hand, the major area of the cylinder is available for opening the platform, in which mode only slight effort is required to initiate movement of the platform from its vertical stowed position. Thereafter the platform will open under gravity, with no further opening effort being required.

A further disadvantage of the said system is that the retraction means lie, when the platform is deployed, diagonally across the sides of the platform, where they may be vulnerable to impact damage and further, may obstruct side entry to the platform.

It is an objective of the present invention to provide a power closure system for a vehicle mounted platform lift, chraracterised in that extension means are provided for closure of the platform, these extension means being arranged to act substantially vertically on a forward projection of the platform beyond the pivot axis.

Such a closure mechanism is particularly suitable for platforms of lightweight construction, and especlally those manufactured from aluminium alloys.

Where the extension means are hydraulic cylinders, the major area of the piston is used for closure, allowing simpler, smaller and lighter cylinders to be employed than is the case with solutions based on prior art.

It may also be possible to use a counter-balancing means - for example, a resilient member - to further reduce the effort required to close the platform, and so allow further miniaturisation of the extension means. Such a resilient member may be a torsion spring designed to store or release energy as the platform is rotated about its pivot axis, and may be arranged to have its relaxed position intermediate between the stowed and deployed attitudes of the platform, so offering both the ability to urge the platform from its vertical stowed position to initiate opening, and to counter-balance the fully deployed platform to ease closure.

A further advantage of the present invention is that the extension means, lying substantially vertically and close to the runners, do not obstruct side entry to the platform, nor are they vulnerable to accidental damage.

In addition, the very small angle of rotation experienced by the extension means during operation enables a cover to be fitted around each such means to provide additional protection.

During unloading operations of a vehicle a heavy load may be moved along the vehicle floor and on to a co-planar lift platform, its weight being initially applied as a concentrated force on the front edge of the platform adjacent to the vehicle.

In such cases, inadvertent folding of the platform may occur if the pivot axis of the platform is positioned some distance rearwardly from this edge.

It is known to prevent such inadvertent tilting of the platform by using a mechanical locking device to ensure that the deployed platform remains stable in tne horizontal plane. Such locking devices are normally released manually prior to closure of the platform.

A further aspect of the present invention makes use of one or more of the extension means to automatically lock the platform in the horizontal position after deployment, and conversely to automatically unlock the platform prior to closure.

Such an objective may be achieved by interposing between the upper end of the extension means on the one hand and the runner on the other hand, a movable link connected in turn to a mechanical baulk lying between abutment faces on the platform and runner respectively. Such a movable link, together with its associated connection means and baulking device, may be equipped with a resilient element to lightly urge the baulk into its engaged or locked position.

In operation, closure of the platform is achieved by applying power to the extension means, causing it to lengthen. Initial extension wlll drive the movable link, connection means, and baulk, against the action of the resilient means, to cause the baulk to move away from the engaged position.

During this phase of closure, the lower end of the extension means will urge the platform to rotate, but because of the greater effort required to close the platform, no movement occurs.

However, after the movable link reaches the limit of its travel, further lengthening of the extension means causes the platform to rotate to its closed position.

Similarly, when opening the platform, initial movement as the extension means are allowed to shorten, takes the form of rotation of the platform.

When the latter is fully deployed, the resilient means associated with the baulk device urge further shortening of the extension means and urge the baulk device into the locked position.

The invention may be understood with reference to the following figures. The illustrations show one embodiment of the invention and are not intended to limit the scope of the invention to the example shown.

Figure 1 shows a platform (1) pivotally supported at pivots (2) on runners (3) which in turn are slidably located within slotted columns (4).

Chains or wire ropes (not shown) are provided to lift or lower the runners within the columns, and in turn to lift or lower the platform. An abutment face (15) on the platform reacts against the runner, resisting rotation, and so allowing the platform to support a load.

A power operated extension means (5) is pivotally attached to the platform at pivot (6), located forward of the platform pivot centre (2). The opposite end of the extension means (5) is pivotally attached to runner (3) at pivot centre (7).

In operation, power closure is achieved by extending the extension means (5), so applying a substantially vertical downward force to the edge of the platform adjacent to the vehicle, causing the platform to rotate to its stowed position.

Figure 2 shows the extension means elongated, and the platform in its stowed position.

Likewise by allowing the extension means to shorten - under the influence of the platform weight and/or assistance from a resilient device - the platform is allowed to open to its deployed position.

Figure 3 shows a further embodiment of the invention in which, interposed between the pivot (7) and runner (3) is a movable link (8). Link (8) may be slidably movable relative to runner (3) as shown, or may alternatively be a pivotally moving link. Link (8) is connected in turn by a connecting means (9) to a baulk (10), locked when engaged between abutment faces (11) on the platform and (12) on the runner respectively.

A resilient means (13) is provided to gently urge the extension means (5), movable link (8) connecting means (9), and baulk (10), downwardly into the locked position of the baulk device.

To close the platform, power is applied to lengthen the extension means (5), firstly urging the link (8), the connecting means (9) and baulk (10) upwards and in so doing disengaging the latter.

Novement takes place until the link (8) reaches an abutment (14) on runner (3). This position is illustrated in Figure 4.

Further lengthening of the extension means (5) causes the platform to rotate from its deployed to its stowed position as described above.

To open the platform the procedure is reversed, with initial shortening of the extension means (5) allowing the platform to open. When the platform is fully deployed, further shortening of the extension means (5) due to the influence of resilient means (13) urges the baulk (10) back into its locked position, so protecting the platform from inadvertent closure.

Claims (9)

CLAIMS:

1. A platform lift comprising platform support means, a platform pivotally attached to said platform support means at a pivot point adjacent one end of said platform and extensible actuation means for opening and closing said platform by, respectively, shortening and lengthening said actuation means, said actuation means being attached at a first end thereof to said platform support means and at a second end to said platform at a point between the pivot point and the said one end of the platform.

2. A platform lift as claimed in claim 1 in which the actuation means comprise at least one hydraulic cylinder and piston arrangement.

3. A platform lift as claimed in claim 2 in which the piston is attached on one side to a piston rod, which piston rod is also attached to the platform.

4. A platform lift as claimed in any one of the preceding claims further comprising counter-balancing means arranged to counter balance the platform in its open position, to ease closure.

5. A platform lift as claimed in claim 4 in which the counter-balancing means comprised a resilient member which stores or releases energy as the platform is rotated about said pivot point.

6. A platform lift as claimed in claim 4 or claim 5 in which the counter-balancing means comprises a spring which has a relaxed position between an open and closed position of the platform.

7. A platform lift as claimed in any one of the preceding claims further comprising means for locking the platform in an open position, which locking means automatically unlock said platform prior to closure.

8. A platform lift as claimed in claim 7 in which the locking means comprise a movable link and a baulk connected between the actuation means and the platform support means.

9. A platform lift substantially as hereinbefore described with reference to and as shown in the accompanying drawings.