WO2005123568A1

WO2005123568A1 - Collapsible scissor construction

Info

Publication number: WO2005123568A1
Application number: PCT/NL2005/000392
Authority: WO
Inventors: Michiel Brokkaar
Original assignee: B.J. Kroese Holding B.V.
Priority date: 2004-06-18
Filing date: 2005-05-27
Publication date: 2005-12-29
Also published as: NL1026457C2; EP1756000A1

Abstract

Disclosed is a scissor construction comprising pivotable arms (2) and arm adjusting means (3) that are pivotally connected to the scissor construction on one side and to a fulcrum (A) on the other side. The fulcrum is positioned such that it will lie in the plane between the ends (4-3,4-4) of the pivotable arms in any adjusted position of said arms. The arm adjusting means take up a flat position between said ends in the collapsed condition of the scissor construction, so that the height of the construction will be minimal in that condition. Moreover, the force to be applied by the arm adjusting means is significantly smaller, especially in the case of a small scissoring angle. An additional pivotable connecting member (7) is connected between the fulcrum and an arm in order to generate a lifting force when the scissor construction is collapsed.

Description

COLLAPSIBLE SCISSOR CONSTRUCTION

The present invention relates to a scissor construction comprising pivotable arms and arm adjusting means that are pivotally connected to the scissor construction on one side and to a fulcrum on the other side.

The invention furthermore relates to a lifting mechanism and to a finished product or a device provided with a lifting mechanism.

Such a scissor construction, in an embodiment in which it is used as a lifting mechanism, is known from European patent application No. EP-A-0 613 852. The known scissor construction comprises arms provided with arm adjusting means, which pivot about a cross joint. The pivotable arms can be unfolded from a collapsed position of the scissor construction and be folded again by the arm adjusting means. The arm adjusting means comprise one or more hydraulic cylinder units, which cylinder unit (s) is (are) pivotally connected to one end of an arm on one side and to a plate member on the other side. The plate member is mounted on the cross joint, whilst a fulcrum is present on the plate member itself, to which fulcrum the cylinder unit, which is capable of generating large forces, is attached. In the collapsed condition of the scissor construction, both the plate member and a respective elongated cylinder unit extend at an albeit small but not negligible angle. Said angle is important because the cylinder unit can derive a reaction force from the fact that the magnitude of said angle is not negligible, which reaction force is needed for adjusting and unfolding the arms of the scissor construction from the collapsed condition by means of a moment that has been generated therewith.

A drawback of the known scissor construction is the fact that the arm adjusting means, which extend at a certain angle, add to a minimal but nevertheless considerable height of the scissor construction in the collapsed condition thereof, as a result of which said scissor construction is not suitable for all kinds of possible applications.

Another drawback is the fact that, in particular in the case of small scissoring angles, substantial forces occur in the construction, so that higher demands are made of the construction, leading to a heavy and costly scissor construction.

The object of the present invention is to provide a constructionally improved scissor construction having a minimal height .

In order to accomplish that object, the scissor construction according to the invention is characterized in that the fulcrum is positioned such that it lies in the plane between the ends of the pivotable arms in any adjusted position of said pivotable arms.

The advantage of the scissor construction according to the invention is that the arm adjusting means push off on a fulcrum that is located between the ends of the arms over the entire adjusting range. As a result, the arm adjusting means will take up a flat position between said ends in the collapsed condition of the scissor construction, so that a device provided with the scissor construction according to the invention will exhibit a minimal overall height or depth. In addition to that it has become apparent that when the scissor construction according to the invention is used, the force to be applied by the arm adjusting means can be significantly reduced, especially in the case of a small scissoring angle. As a result, the finished product can be made lighter, and generally it can be produced at a lower cost price in practice, therefore, whilst retaining the level of reliability.

One embodiment of the scissor construction according to the invention is characterized in that the scissor construction comprises one or more horizontal members arranged between the arm ends, on which the fulcrum is slidably supported. The advantage of this embodiment is that the fulcrum that is slidably supported between the ends of the arms leads to an angle between the arm adjusting means and the horizontal that slidably adjusts itself by sliding in an advantageous manner upon unfolding of the scissor construction. This leads to a more uniform exertion of forces during adjustment, as a result of which a light construction can be used whilst improving the stability, also during said adjustment.

One embodiment of the scissor construction according to the invention is characterized in that the arm adjusting means are coupled to a pivot point of the pivotable arms on one side, whilst another embodiment of the scissor construction is characterized in that the arm adjusting means are coupled to a point on one of the pivotable arms on one side, in which case longer arm adjusting means may be used, if desired, which may even comprise one or more gas springs, possibly provided on either side thereof. Further variants and advantageous embodiments are defined in the dependent claims.

The scissor construction according to the present invention will now be explained in more detail with reference to the figures below, in which like parts are indicated by the same numerals. In the drawing: Figures 1 and 2 show a possible embodiment of the scissor construction according to the invention in two positions thereof; Figures 3 and 4 show the scissor construction according to the invention as shown in the preceding figures in partially collapsed and fully collapsed condition, respectively.

Figures 1 and 2 show a scissor construction 1, in this case comprising a pair of pivotable arms 2-1, 2-2 (hereinafter jointly indicated by numeral 2) . In principle, several pairs of arms 2 can be stacked together so as to realise a larger range of the scissor construction 1. The scissor construction 1 is provided with arm adjusting means 3. The arm adjusting means 3 may comprise one or more pneumatically, hydraulically or electrically operated, possibly remotely controlled adjusting means, if required. For specific applications, such as a footstool, lightweight gas springs are preferred. Further possible applications can be found in various other products that include a lifting mechanism that comprises a scissor construction 1, such as a lifting table, a hydraulic arm, a car lift, a motorcycle lift, a jack or, for example, vertically adjustable furniture such as a (treatment) table or chair or a bed (usually on wheels) . The arm adjusting means 3 are pivotally coupled to a fulcrum A (yet to be explained) . In the embodiment of figures 1 and 2, the arm adjusting means 3 are furthermore pivotally connected to an end 4-1 of the pivotable arm 2-1. In one embodiment (not shown) , the arm adjusting means 3 might be coupled between the fulcrum A and, for example, the scissor point S or another point generally located on one of the arms 2-1, 2-2. In all these cases the fulcrum A is positioned such that it lies in the plane between the lower arm ends (in this embodiment) 4-3 and 4-4 in any adjusted position of the pivotable arms 2. The fulcrum A is supported in a rail on the base, for example, in which one or more horizontal members 5 are present in this embodiment. When the opening angle of the scissor construction 1 changes, the angle between the arm adjusting means 3 and the horizontal will change as well, as a result of which the force that is generated by the adjusting means 3 upon unfolding of the scissor construction 1 is increasingly utilised to assist in the lifting of the load on the platform 6. Moreover, calculations have shown that in that case the differences between the forces that occur with different opening angles will be limited to factors rather than orders of magnitude as has been the case so far. This makes it possible to make the scissor construction 1 lighter in weight and thus produce it at a lower cost price. Moreover, the range of possible applications is thus increased. Figure 3 shows the embodiment of the scissor construction 1 in nearly collapsed condition, whilst figure and 4 shows the scissor construction in fully collapsed condition. As figure 4 shows, the arm adjusting means 3 lie completely in the plane between the ends 4-1 and 4-2 that is defined by the folded arms 2. The overall depth of the scissor construction 1 is minimal, therefore. In the illustrated embodiments of the scissor construction 1, the fulcrum A is slidably mounted in the horizontal member (s) 5, whilst the arm adjusting means 3 form part of a triangular construction of which the fulcrum A forms a corner point. From said fulcrum A, a pivotable connecting member 7 extends towards a connecting point 8 on the arm 2-1 as a side of the triangle. Said connecting point 8 is located slightly above the aforesaid plane (see figures 3 and 4) or the central axis H of the horizontal member 5, so that the arm adjusting means 3, in spite of their horizontal position in the collapsed condition of the scissor construction 1 (in this embodiment) , are nevertheless capable of generating a sufficiently large moment for folding and unfolding the scissor construction 1. In the case of a small, increasing scissoring angle of the scissor construction 1, the fulcrum A will start to move already, as a result of which the force that needs to be generated by the arm adjusting means 3 for opening the scissor construction further will quickly decrease. The connecting point 8 can engage the arm 2-1 at several positions, making it possible to influence the interplay of forces, especially in the aforesaid triangle, in dependence on the intended use of the scissor construction, if required.

Claims

1. A scissor construction comprising pivotable arms with arm adjusting means that are pivotally coupled to the scissor construction on one side and to a fulcrum on the other side, characterized in that the fulcrum is positioned such that it lies in the plane between arm ends of the pivotable arms in any adjusted position of said pivotable arms .

2. A scissor construction according to claim 1, characterized in that the scissor construction comprises one or more horizontal members arranged between the arm ends, on which the fulcrum is slidably supported.

3. A scissor construction according to claim 1 or 2 , characterized in that the arm adjusting means are coupled to a pivot point of the pivotable arms on one side.

4. A scissor construction according to any one of the preceding claims, characterized in that the arm adjusting means are coupled to a point on one of the pivotable arms on one side.

5. A scissor construction according to any one of the claims 1-4, characterized in that the arm adjusting means form part of a triangular construction of which the fulcrum forms a corner point, and in that the arm adjusting means lie in that side of the triangle which, in the collapsed condition of the scissor construction, extends parallel to the plane defined by the collapsed arms.

6. A scissor construction according to claim 5, characterized in that the scissor construction comprises a pivotable connecting part that is arranged between the fulcrum and the arm in question.

7. A scissor construction according to claim 6, characterized in that the position at which the connecting member is connected to the arm is question is adjustable.

8. A scissor construction according to any one of the preceding claims, characterized in that the arm adjusting means comprise one or more gas springs.

9. A lifting mechanism provided with a scissor construction according to any one of the preceding claims.

10. A device such as a footstool, a lifting table, a hydraulic arm, a car lift, a motorcycle lift, a jack or vertically adjustable furniture, for example a treatment table or chair or bed, provided with a lifting mechanism according to claim 9.