GB2199014A

GB2199014A - Compact jack for vehicles

Info

Publication number: GB2199014A
Application number: GB08729829A
Authority: GB
Inventors: Jean Jacques Felix Rousseau
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-12-23
Filing date: 1987-12-22
Publication date: 1988-06-29
Anticipated expiration: 2007-12-22
Also published as: GB2199014B; DE3743886A1; FR2608579A1; FR2608579B1; GB8729829D0

Description

COMPACT JACK FOR VEHICLES 2199014 The invention relates to a compact jack

for vehicles, the jack being derived from the scissor or lozenge-type and formed of four struts hinged at their ends, a displacement member being fixed along one diagonal between two apices to vary their distance apart, the other two apices forming the base and the head capable of being disposed between the support point and the load-to be lifted.

Lozenge-jacks and their derivatives generally comprise as displacement member a screw-threaded rod operable by a crank, acting on two diagonally opposed hinges of the struts. The hinges carry sockets of which one is screw-threaded and co-operates with the screw-threading of one end of the screw-threaded rod and the other of which, maintained by a ballrace abutment, co-operating with the other end of the screw-threaded rod on which is mounted the crank.

On rotation of the crank in one direction or the other, the two apices of the lozenge connected to the screw-threaded rod move towards or away from each other while producing respectively an increase or decrease in the distance between the other two apices which carry the base and the head of the jack when the latter is disposed between the support point and the load to be lifted.

Lozenge/jacks or derivates of the lozenge have a maximum lift travel slightly less than twice the length of a strut when the struts forming it are equal or slightly less than the sum of the lengths of the struts when the latter are unequal.

51 t- In its lowered position, when the jack is completely folded, its greatest dimension corresponds to the length of the screw rod which is approximately equal to twice the length of a strut.

q Generally, the lift height required of a current jack is of the order of 39Omm. Consequently, the length of the screw rod is of the same order of magnitude. If this dimension is not too excessive when it is sufficient to place the jack in the boot of a car, it will no longer be the same when it is decided to increase the usable volume of the latter, and to house the jack in the spare wheel. The usable internal diameter of a wheel of a particular car being of the order of 30Omm, the actual known lozenge-jacks cannot be placed there.

In conventional lozenge-jacks, the ends of the struts which carry the head and/or the base are not generally hinged at the same point on a unique pin but on two spaced pins provided on the members forming the base and the head. The lozenge thus formed presents therefore at least one truncated end. Moreover, it is generally arranged that the struts are displaced symmetrically in such a manner that the two diagonals of the lozenge remain perpendicular to each other.

The invention envisages the realisation of a jack of a type derived from the lozenge type presenting an overall dimension less than the diameter of the wheel in which it is to be housed and of which the lift travel is equal to that of conventional jacks.

In the jack, in accordance with the invention, use is made of the spacing between the axes in order to diminish the length of the diagonal carrying the screw-rod while maintaining the same length for the struts.

The jack, according to the invention, is remarkable in that the struts hinged on the spaced pins of the head and/or base are crossed in such a manner as to form a quadrilateral of which at least the sides of one of the apices formed by the free crossing of the struts, other than one of those connected to the displacement member, are extended to form, with the head and/or base, a triangle.

The explanations and figures given hereby by way of example, will t k 1 permit how the invention may be realised to be understood.

Figure I shows schematically a lozenge-Jack according to the prior art.

Figure 2 is a schematic view of a jack according to a first embodiment.

Figure 3 is a view of the jack according to Figure 2 in its maximum lift position., Figure 4 is a schematic representation of a second embodiment of a jack according to the invention.

Figure 5 is a schematic representation of a third embodiment of a jack according to the invention.

Figure 6 and 7 show scheme in elevation and plan an example of rotation control device.

Figure 8 is an example of an embodiment of a jack according to the scheme of Figure 5.

Figure 1 shows in a schematic manner a jack of the lozenge type known from the prior art. Such a jack comprises four struts 1 to 4. One of the ends of the struts_ 1 and 4 is hinged to a part forming the head 5 by two spaced pins 6,7. One of the ends of the other two struts 2,3 is similarly hinged to two spaced pins 8,9 carried by a part forming the base 10. The struts 1,2 and 3,4 are hinged to each other in pairs at their ends 11,12 and carry along one diagonal a displacement member 13 formed by a screw rod.

It will be observed that the jack, shown in its folded position, has an overall length, that is to say from the apex 11 to the apex 12, approximately equal to twice the length of a strut. As the maximum height development of the jack should be of the order of 40Omm, and this development corresponds to the position in which the struts 1,2 and 3,4 form extensions of each other, the latter should have a length of about 20Omm. The overall length of the jack between the apices 11 and 12 would be of the order of 40Omm. This length is substantially that of the screw rod of the displacement member.

Figure 2 shows schematically a Jack according to a first embodiment of the invention. The struts which are hinged on the spaced pins of the head 5 and of the base 10 are crossed, that is to say that the strut 4A which in the jack according to Figure 1 corresponds to the strut 4 and is directly hinged on the pin 6 of the head 5 situated on a same side in relation to the vertical axis of symmetry YY' of the jack, is hinged on the pin 7 of the head 5 situated on the other side in relation to the same vertical axis of symmetry YV. The strut 1A, which corresponds to the strut 1 of Figure 1, is hinged on the pin 6 of the head 5 situated on the other side in relation to the axis of symmetry YV. The struts 2A and 3A are similarly crossed. As is readily appreciated in comparing Figures 1 and 2, which are drawn on the same scale maintaining the same distances between the pins 6 and 7 and 8 and 9, as well as the same length of strut, the jack, in accordance with the invention, presents an overall length plainly less than that of the conventional lozenge-jack.

If d is the distance separating the pins 6,7 or 8,9 and 1 the length of a strut, the length 11-12 in Figure 1 is approximately 21+d and Figure 2 is 21-d. For a distance d approximately equal to the length of the strut, the length 11-12 is little different from the latter.

The jack, according to the invention, thus enables a lift travel near to that of a conventional lozenge-jack to be obtained while having a clearly smaller bulk. This reduction in the bulk brings with it an equivalent reduction in the length of the screw rod.

Figure 3 shows schematically the appearance of the Jack according to Figure 2 in its position of maximum lift.

1 In the embodiment described above, the quadrilateral formed by apices 11 and 12 and points of intersection of the struts is not necessarily a lozenge but may take any shape in accordance with the relative positions of the head and the base.

In a general manner, the struts form a deformable quadrilateral of which at least the sides of one of the apices, formed by the intersection of two struts, other than those connected to the displacement member, are extended.to form, with the head and/or the base a triangle.

In two other embodiments schematically shown in Figures 4 and 5, only two struts are crossed, for example 12 and 13 and 16 and 17. The other two struts 14 and 15 in Figure 4 are hinged together on the same pin or joint provided for example on the base.

In Figure 5, the struts 18,19 are hinged to the same pin carried by the longer strut 18 the free end of which is hinged by a pin or a joint to the base.

Of course, in the examples of Figures 4 and 5, the relative positions of the hinges to the head or the base maybe interchanged without modifying the operation of the jack according to invention.

The examples described above, in which the rotation of the struts around the pins carried by the head and/or the base is free, are only suitable when the load to be lifted has only one degree of freedom in relation to the support point.

In the case of lifting an automobile, the load which it respresents has two supplementary degrees of freedom which result in displacements which, although limited, must be taken into consideration to avoid risk of shifting of the Jack.

I- il- With a view to avoiding such a disadvantage, the two ends cooperating with the head or the base of at least two struts are provided with a rotation control device 26.

These devices have the function of controlling the rotation of one of the struts in relation to the other in such a manner that the direction of rotation is inverted and that the angles of rotation are equal or have predetermined values as a function of the trajectory which the head of the Jack is to follow during lifting.

An example of an embodiment of such a device is given in Figure 6 an 7. Preferebly, in a Jack which is to be equipped with such a device, the hinge pins are fixed to the ends of the struts and turn in housings acting as bearings formed in the head and/or base parts.

The pins 20 and 21 are fixed to the ends of the struts which are hinged to the head andlor base part. They are connected by straps 22, 23. The strap ends 22 or 23 are fixed to generatrices of each pin, (Figure 6), the ends of each strap on the same pin being themselves fixed symmetrically in relation to the axis of symmetry XX' passing through the centres of the pins.

The operation of this device is readily understandable. When the pin 21 turns through an angle in trigonometric sense, the pin 20 is driven by the strap 23 through an angle in the opposite direction. The rotations of the pins are equal and with opposite direction and any force tending to turn one strut reacts through the intermediary of the rotation control device on the other strut.

Other examples of such devices make use of lever arms, gearing, cams or others are equally usable.

In the embodiment illustrated in Figure 8, corresponding to the scheme of Figure 5, only two struts 16 and 17 are crossed, the other two struts 18 and 19 are hinged together at a common point 24 provided at a certain distance from the M25 of the strut 18 hinged to the base 10.

As is known, in the technique of jack manufacture, some of the k struts are formed with a U-shaped cross-section, for example, strut 16 and 19, the others being formed by two parallel flat irons, for example the struts 17 and 18, between which pass the U-section struts. One end of the struts 16 and 17 of U-cross section serves as a bearing for the pins on which are fixed the ends two flat iron strips forming the co-operating struts 17 and 18.

According to a detail of the embodiment shown, the ends of the struts cooperating with the head comprise on their inner edges, facing and in the. same planes, perpendicular extension 27,28 in which are fixed the moveable pins 29,30 in the bearings provided in the head 5. The pins are provided with a rotation control device 26 formed by two co-operating toothed sectors 31,32 fixed to pins 29 and 30.

1

Claims

1. Compact Jack for vehicles, of the lozenge-type with four struts hinged at their ends, a displacement member being fixed along one diagonal between two apices to vary their distance apart, the other apices carrying the base and the head capable of being disposed between a support surface and the load to be lifted, the ends of the struts carrying the head and/or the base crossing before their hinging on spaced pins provided on the base and/or the head, in such a manner as to form a quadrilateral of at which the sides at one of the apices, other than one of those connected to the displacement member, are extended to form, with the head and/or the base, a triangle, the hinge pins being fixed to the ends of the struts carrying the head and/or the base and turning in bearings formed in the head and/or the base, characterised in that the hinge pins (20,21) are provided with a device for controlling the rotation of one of the struts (16,17) relative to the other, in such a manner that direction of rotation is opposite and that the angles of rotation (Oe-) are equal or have predetermined values as a function of the trajectory which the head (5) of the jack used to follow during lifting.

2. Jack according to claim 1, characterised in that the hinge pins (20, 21) are fixed to the ends of the struts (16,17) hinged to the head part (5) and/or base part (10) and are connected by straps (22,23) the ends of which are fixed on_generatrices of each pin (20,21).

3. Jack according to claim 2, characterised in that the ends of each strap (22,23) on the same hinge pin (20,21) are themselves fixed symmetrically in relation to the axis of symmetry (XX') passing through the centres of the pins (20,21).

4. Jack according to claim 1, characterised in that the ends of the struts (16,17) co-operating with the head (5) andlor the base (10) comprise on their inner facing edges, and in the same planes, perpendicular extensions which carry pins (29,30) co-operating with Z1 bearings provided in the head (5) and/or the base (10), the said pins being provided with a rotation control device for the arms (26).

J.,v

5. Jack according to claim 1, characterised in that the rotation control device is formed of two co-operating toothed sectors (31,32), fixed on the pins (29,30).

Published 1988 at The PELtent Office. State House. 66 71 Iligh Holborn, London WC1R 4TP. Firther copies maybe obtained from The Patent OEice. hv Vultjniex technioues ltd. St Mary Cray, Kent. Con, 1187.