GB2594080A

GB2594080A - Scissor mechanism

Info

Publication number: GB2594080A
Application number: GB2005555.4A
Authority: GB
Inventors: Toumazis Antonios
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-04-16
Filing date: 2020-04-16
Publication date: 2021-10-20
Also published as: GB202005555D0

Abstract

An apparatus has a scissor mechanism with linked criss-crossing element pairs including a first end pair 120, 122 at a first rigid end 110 of the mechanism and a second end pair 130, 132 at a second rigid end 112 of the mechanism which are pivotally connected by first tips at 310 to the ends. At least one intermediate pair, pivoting at midpoint 430, connects the first and second end pairs at 320. A first rigid element 210, shorter than the elements 120, 122, is pivotally connected to element 120 at a second tip 320 and pivotally mounted to element 122. A second rigid element 220 is connected at the opposite end of the apparatus in a similar manner to the first. The end portions are movable away from each other without a change in orientation of the end portions. A second scissor mechanism may be utilised, and the apparatus can be used as a lifting apparatus or a retractable arm.

Description

SCISSOR MECHANISM

TECHNICAL FIELD

The present invention relates to apparatus comprising a scissor mechanism and the use of said apparatus.

BACKGROUND

The scissor mechanism also known as a shear mechanism has been known for centuries. In this mechanism a plurality of pairs of elements forming a criss-cross "X" pattern are linked together. Relative motion of one element produces motion of a plurality of other elements.

This mechanism is widely used in lifting applications for example aerial work platforms (AWP), elevating work platform (EWP), scissor lifts, shear lifts, cherry pickers, as well as in numerous other applications for example as extensible arms, retractable structures and other applications for example wall mounted mirrors and lamps, fences, lifting tables, car lifts etc. U53246876A (1963) discloses an extensible lift mechanism for elevating a load. More particularly, it relates to such a mechanism including an opposed pair of scissor mechanisms, each of which includes a pair of scissor arms pivotally connected together, where relative pivotal movement of the arms accompanies extension of the lift mechanism.

In the above and numerous other inventions lifting is associated with sliding of at least one tip at each of the two end criss-cross pairs. This results in the tips of the two end pairs becoming closer together as the scissor mechanism extends.

This can lead to reduced stability of the apparatus.

CN102030282A (2011) discloses a scissor mechanism as shown in Figure 5 in which there are no sliding parts. This is achieved by the addition of smaller elements at the two ends. However in this invention the top and bottom frames are not necessarily parallel to each other as the scissor mechanism extends and retracts.

CN102556892B (2014) discloses an electric shear type lifting platform as shown in Figures 6 and 7 in which there are also no sliding parts. As in the previous invention, the two end frames are not necessarily parallel to each other as the scissor mechanism extends and retracts.

A scissor mechanism can also be used as a lifting table as shown in Figure 8. In this mechanism there are two pairs of criss-cross elements linked together and pivoted on relatively immovable hinges on the two end frames. This mechanism has the advantage that there are no sliding parts and the two end frames are parallel to each other but it has the disadvantage that it has limited height.

SUMMARY

Viewed from a first aspect, there is provided apparatus comprising a scissor mechanism, the scissor mechanism comprising a plurality of linked criss-crossing element pairs, including a first end pair at a first end of the mechanism and a second end pair at a second end of the mechanism, and at least one intermediate pair between the first and second end pairs, wherein: (a) the elements of the or each intermediate pair are interconnected at respective mid-points of the elements; (b) the elements of the first and second end pairs have first tips which are pivoted to relatively immovable joints disposed on rigid end portions of the scissor mechanism respectively at the first and second ends thereof; (c) a first rigid element of smaller length than the criss-crossing elements of the first end pair of the criss-crossing element pairs is pivoted at a second tip opposite to a said first tip of an element of said first end pair and is pivotally mounted along the other element of the first end pair; and (d) a second rigid element of smaller length than the criss-crossing elements of the second end pair of criss-crossing elements is pivoted at a second tip opposite to a said first tip of an element of said second end pair and is pivotally mounted along the other element of the second end pair; whereby the rigid end portions are movable towards and away from each other without any change of orientation of the rigid end portions.

The apparatus may further comprise a second scissor mechanism laterally spaced from the first-mentioned scissor mechanism. The second scissor mechanism preferably also comprises features corresponding to those of the first-mentioned scissor mechanism. By providing first and second scissor mechanisms laterally spaced from each other, greater stability of the apparatus can be achieved. 3 -

In use, the first and second scissor mechanisms will extend and retract in parallel to each other.

In an embodiment the smaller length first rigid element is pivotally mounted along the other element of the first end pair at a distance from the pivot at the first tip of that other element which is equal to the length between the pivots of the first rigid element. This assists compact collapsing of the first end pair of criss-crossing element pairs.

In an embodiment the smaller length second rigid element is pivotally mounted along the other element of the second end pair at a distance from the pivot at the first tip of that other element which is equal to the length between the pivots of the second rigid element. This assists compact collapsing of the second end pair of criss-crossing element pairs.

In an embodiment the distance between the pivots of the first smaller length rigid element is shorter than half (and is e.g. one third) of the distance between the pivots at the tips of the elements of the first end pair.

In an embodiment the distance between the pivots of the second smaller length rigid element is shorter than half (and is e.g. one third) of the distance between the pivots at the tips of the elements of the second end pair.

Viewed from a second aspect, there is provided a use of the apparatus according to the first aspect as a lifting apparatus, wherein the rigid end portions are arranged horizontally and are moved towards and away from each other to support a load being moved relative to the ground.

Viewed from a third aspect, there is provided a use of the apparatus according to the first aspect as a retractable arm, wherein the rigid end portions are arranged vertically or inclined and are moved towards and away from each other to vary a horizontal or inclined spacing between the rigid end portions.

The scissor mechanisms of existing inventions and publications have at least one of the following limitations or disadvantages.

1. At least one of the tips at each end of the criss-crossing elements slides or rolls along another element, thus being prone to jamming and requiring regular inspection, maintenance and repair.

2. The distance between the tips of the end criss-crossing elements decreases as the distance between the end frames increases, thus reducing the stability of the supported load. 4 -

3. The end frames are not necessarily parallel if there is no triangulation in all elements.

4. The height of the scissor is limited if the number of allowable criss-crossing elements is limited.

In another aspect, the invention provides apparatus having a scissor mechanism which overcomes these limitations and which comprises: 1. A series of linked criss-crossing elements, whereby there is no restriction on the number of such elements; 2. All the criss-crossing elements, except the end ones are interconnected at mid-point; 3. The end bps of the end criss-crossing elements are pivoted on relatively immovable hinges; and 4. The end criss-crossing elements are constrained in their motion by short elements pivoted at the tip of one of the criss-crossing elements and at the same short distance from the opposite end of the other criss-crossing element.

At least embodiments of the invention have the following advantages: 1 The end frames can move towards and away from each other without any change in orientation; 2 There are no sliding movements; 3 There is no risk of jamming from sliding or rolling components; and 4 The spacing between supports of the platform in scissor lift apparatus remains constant.

Certain embodiments of the invention will now be described, by way of example only, and with reference to the accompanying drawings, in which: Figure 1 shows apparatus comprising an extended scissor mechanism according to an embodiment of the invention; Figure 2 shows the apparatus when the scissor mechanism is fully retracted; Figure 3 shows the apparatus when the scissor mechanism is partially extended; Figure 4 shows apparatus comprising a fully extended scissor mechanism of another embodiment; Figure 5 shows a scissor mechanism of the prior art;

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Figure 6 shows a scissor mechanism of the prior art in an extended state; Figure 7 shows the scissor mechanism of Figure 6 in the retracted state; and Figure 8 shows a lifting table comprising a scissor mechanism of the

prior art.

The drawings, details and descriptions of the embodiments are non-limiting ways in which the concepts of the invention may be applied. Their aim is to illustrate to skilled persons the use of the present invention in any appropriate system, method, apparatus or construction.

Reference in this document to "an embodiment" means that a particular feature, structure, or characteristic is included in at least one embodiment and it does not necessarily refer to the same embodiment. Particular features, structures, or characteristics may be combined in one or more embodiments. Variations may be made within the scope of the invention and parts shown in the drawings or described may be implemented in a more separated or integrated manner, or removed or rendered as inoperable. Numerous alternative and different embodiments may be made using concepts of this invention. Drawings, details and descriptions are interpreted as illustrative and not as limiting the invention.

The figures are illustration examples of embodiments of the invention. The figures are not to scale. Like or similar parts are marked on the figures and referred in the descriptions with the same numbers.

For the sake of clarity some parts in the figures are shown exaggerated, smaller or schematically, some are omitted and some details are not shown.

Figure 1 to 4 illustrate the disclosed scissor mechanism in alternative positions and with alternative number of criss-crossing elements.

In the exemplary embodiment illustrated in figures 1 to 4, end frames or portions 110, 112 are rigid elements which keep their orientation as they move towards and away from each other. The exemplary embodiment comprises a plurality of criss-crossing element pairs including one or more intermediate criss-crossing element pairs and two end pairs connected to the end portions 110 and 112.

A plurality of criss-crossing elements, for example elements 120, 122, 130, 132 are pivoted at the pivots 310 on the end portions 110, 112 and are fixed in the horizontal direction such that the distance between all pivots on the same end 6 -portion 110, 112 is the same as the end portions 110, 112 move towards and away from each other.

The intermediate criss-crossing elements are pivotally interconnected at mid-points 430. The end criss-crossing elements, which are not interconnected at mid-points 430, are constrained in their movement by short elements 210 and 220 disposed at either end of the apparatus. Said short element 210 is pivoted at one end 320 of an end criss-crossing element 120 of the end pair and at a pivot 410 disposed on the other criss-crossing element 122 of the end pair. The distance between pivots 310 and 410 being the same as the distance between pivots 320 and 410. This distance may be of the order of one third of the distance between pivots at the ends of the criss-crossing elements.

All figures illustrate the embodiments of the invented mechanism in a two-dimensional apparatus. However, more than one mechanism may be provided in parallel. The mechanism may for example be applied in an apparatus made of different materials such as steel, aluminium, timber, composite materials etc and for different uses for example lifts, retractable arms, flood barrier supports etc. The relative movement of one element causes the movement of the end frames towards and away from each other. This relative movement may be produced by the application of force for example hydraulic piston, screw motion, human force, gravity or buoyancy force etc. The movement of the scissor mechanism may be achieved through urging at any one element by for example hydraulics action, screw threads, external force etc. At least in the preferred embodiment of the invention the following advantages are obtained.

1 The end frames move towards and away from each other without any change in orientation.

2 There are no sliding movements.

3 There is no risk of jamming from sliding or rolling components.

4 The width of supports of the platform in scissor lift apparatus remains constant. 7 -

Claims

CLAIMS: 1. Apparatus comprising a scissor mechanism, the scissor mechanism comprising a plurality of linked criss-crossing element pairs, including a first end pair at a first end of the mechanism and a second end pair at a second end of the mechanism, and at least one intermediate pair between the first and second end pairs, wherein: (a) the elements of the or each intermediate pair are interconnected at respective mid-points of the elements; (b) the elements of the first and second end pairs have first tips which are pivoted to relatively immovable joints disposed on rigid end portions of the scissor mechanism respectively at the first and second ends thereof; (c) a first rigid element of smaller length than the criss-crossing elements of the first end pair of the criss-crossing element pairs is pivoted at a second tip opposite to a said first tip of an element of said first end pair and is pivotally mounted along the other element of the first end pair; and (d) a second rigid element of smaller length than the criss-crossing elements of the second end pair of criss-crossing elements is pivoted at a second tip opposite to a said first tip of an element of said second end pair and is pivotally mounted along the other element of the second end pair; whereby the rigid end portions are movable towards and away from each other without any change of orientation of the rigid end portions.
2. Apparatus as claimed in claim 1, further comprising a second scissor mechanism laterally spaced from the first-mentioned scissor lift mechanism.
3. Use of an apparatus as claimed in claim 1 or 2 as a lifting apparatus, wherein the rigid end portions are arranged horizontally and are moved towards and away from each other to support a load being moved relative to the ground.
4. Use of an apparatus as claimed in claim 1 or 2 as a retractable arm, wherein the rigid end portions are arranged vertically or inclined and are moved 8 -towards and away from each other to vary a horizontal or inclined spacing between the rigid end portions.