GB2405858A

GB2405858A - Scissors jack

Info

Publication number: GB2405858A
Application number: GB0321011A
Authority: GB
Inventors: Dan Gavrovski
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2003-09-09
Filing date: 2003-09-09
Publication date: 2005-03-16
Also published as: GB0321011D0

Abstract

A scissor jack 1 for a motor vehicle is disclosed having a moveable platform 8 connected to a pantograph type lifting mechanism 3a, 3b, 4a, 4b and 9. In one position the moveable platform 8 is positioned close to an upper end of the pantograph mechanism 3a, 3b, 4a, 4b and 9 so as to reduce the height of the jack 1. The moveable platform 8 is moveable to a second position in which it is displaced from the upper end of the pantograph mechanism 3a, 3b, 4a, 4b and 9 so as to reduce the clearance between the platform 8 and the part of the motor vehicle to be lifted. Preferably, J-shaped slots 15a,b allow the adjustment.

Description

A Scissor Jack This invention relates to a scissor jack and in particular

to a scissor jack for a motor vehicle having increased ground clearance.

It is well known from, for example, US Patent number 5,449,149 to provide a scissor jack capable of lifting one corner of a motor vehicle in order to facilitate the changing of a wheel. It is a problem when using such a jack with a motor vehicle designed for off-road use that the vehicle normally has increased ground clearance and extra long suspension travel to facilitate use on bumpy or uneven surfaces. In order to enable such a jack to be able to lift such an off-road vehicle the arms forming the pantograph lifting mechanism have to be made very long in order to accommodate the large ground clearance and long suspension travel. Such a scissor jack is relatively large and hence difficult to accommodate in the motor vehicle. It is further known from US Patent number 4,718,519 to provide a scissor jack with a number of pantograph lifting mechanisms joined together in order to provide a high lift capability. It is a problem with this type of jack that the mechanism is relatively expensive to manufacture and, in addition, the jack when collapsed is large and difficult to accommodate within the confines of a motor vehicle.

It is an object of this invention to provide an improved scissor jack for a motor vehicle.

According to a first aspect of the invention there is provided a scissor jack comprising a base member for resting the jack upon the ground, a platform for engagement with a part of a motor vehicle to apply a lifting force thereto and a pantograph mechanism having first and second lower arms, first and second upper arms and a threaded shaft linking the first lower and upper arms to the second lower and upper arms for changing the distance between the base member and the platform when the threaded shaft is rotated wherein means are provided to allow the platform to be moved from a stowed position in which a lifting surface of the platform is positioned near to an upper end of the pantograph - 2 mechanism to a raised position in which the lifting surface of the platform is displaced from the upper end of the pantograph mechanism.

The first lower arm may have a first end pivotally connected to the base member, a second end pivotally connected to a first end of the first upper arm, the second lower arm may have a first end pivotally connected to the base member and a second end pivotally connected to a first end of the second upper arm and the first and second arms may have respective second ends which are pivotally connected together.

The first and second lower and upper arm members may be of an open channel construction so as to allow the first and second upper arms to nest within the first and second lower arms. Alternatively, the first and second lower and upper arm members may be of an open channel construction so as to allow the first and second lower arms to nest within the first and second upper arms.

The first and second upper arms may be connected together by respective first and second upper pivot pins.

The first upper arm may be connected to the platform by the first upper pivot pin and the second upper arm may be pivotally connected to the platform by the second upper pivot pin.

Each of the first and second pivot pins may be engaged with a respective slot formed in the platform so as to provide the means to allow the platform to be moved from the stowed position to the raised position.

Preferably, each of the slots may be 'J' shaped and may have two limbs, a first long limb having an end face near to the lifting surface of the platform and a second short limb having an end face spaced away from the lifting surface of the platform wherein when the first and second upper pivot pins are engaged in the long limbs the platform is located in - 3 the stored position and when the first and second upper pivot pins are engaged in the short limbs the platform is located in the raised position.

Preferably, the support platform may be U-shaped and may have two side members joined together by a common bridging member and slots may be formed in both of the two side members.

Preferably, the width of the support platform between the two side members may be greater than the width of the lower and upper arms and the width of the base member so that, when the jack is in a lowered position and the moveable platform is in the stored position, the two side members overlie the base member.

According to a second aspect of the invention there is provided a method of using a scissor jack comprising a base member for resting the jack upon the ground, a moveable platform for engagement with a part of a motor vehicle to apply a lifting force thereto and a pantograph mechanism having first and second lower arms, first and second upper arms and a threaded shaft linking the first lower and upper arms to the second lower and upper arms for changing the distance between the base member and the moveable platform when the threaded shaft is rotated wherein the method comprises removing the scissor jack from a storage location on the motor vehicle, deciding on whether to move the platform from its stowed position, in which a lifting surface of the platform is positioned near to an upper end of the pantograph mechanism, to a raised position, in which the lifting surface is displaced from the upper end of the pantograph mechanism, based upon the actual clearance between the part of the vehicle to be raised and the ground, taking whatever action is determined to be required based upon the decision, placing the scissor jack on the ground under the part of the vehicle to be raised and rotating the threaded shaft to raise the moveable platform and lift the motor vehicle. - 4

The action determined to be required may comprise, moving the platform to its raised position whenever there is sufficient clearance between the part of the vehicle to be raised and the ground to place the jack under the motor vehicle with the platform in the raised position. Alternatively, the action determined to be required may comprise, leaving the platform in its stowed position whenever there is insufficient clearance between the part of the vehicle to be raised and the ground to place the jack under the motor vehicle with the platform in the raised position.

The invention will now be described by way of example with reference to the accompanying drawing of which: Fig. 1 is a pictorial representation of a scissor jack according to the invention showing the jack in a fully collapsed state ready for storage; Fig.2 is a view similar to that shown in Fig.1 but showing the jack in a ready to lift state; Fig.3 is a side view of the jack shown in Fig.1; Fig.4 is a plan view of the jack shown in Fig.1; and Fig.5 is a partial side view of the jack shown in Fig.2.

With reference to Figs. 1 to 5 there is shown a scissor jack 1 having a base member 2 for supporting the jack on the ground, a platform 8 for engagement with the underside of a motor vehicle to be lifted and a pantograph type mechanism interposed between the base member 2 and the platform 8 for changing the distance between the base member 2 and the platform 8 to raise the platform 8 relative to the base member 2.

The pantograph mechanism comprises of four interlinked arms 3a, 3b, 4a, 4b and a threaded drive shaft 9. In greater detail the pantograph mechanism comprises of first and - 5 second lower arms 3a, 3b each of which is pivotally connected at a first end by a respective lower pivot pin 6a, 6b to two upstanding flanges of the base member 2 and is pivotally connected at a second end by a respective intermediate pivot pin 5a, 5b to a first end of a corresponding upper arm 4a, 4b. The first and second upper arms 4a, 4b have respective second ends which are pivotally connected together by means of respective upper pivot pins 7a, 7b which have outwardly extending portions engaged with corresponding slots 15a, 15b in the platform 8.

The intermediate pivot pins 5a, 5b are adapted for engagement with the thread drive shaft 9. The pivot pin 5a connects the first lower arm 3a to the first upper arm 4a and has a first central portion 19 for threaded engagement with a threaded portion 18 of the drive shaft 9. The pivot pin 5b connects the second lower arm 3b to the second upper arm 4b and has a second central portion 20 in which is formed a bore (not shown) into which a non-threaded portion 17 of the drive shaft 9 is engaged. A thrust washer 21 is interposed between the second central portion 20 and a drive means 10 used to permit a user of the jack 1 to rotate the drive shaft 9.

As is well known in the art, rotation of the drive shaft will cause the first and second central portion 19, 20 to be moved towards each other or moved away from each other depending upon the direction of rotation of the drive shaft 9 and will result in a corresponding change in the distance between the base member 2 and the platform 8. By reducing the distance between the first and second central portions 19 and 20 the distance between the platform 8 and the base member 2 is increased which is used when the jack 1 is used to raise a motor vehicle from the ground to change a wheel and vice-versa.

The first end of the first and second lower arms 3a, 3b have teeth formed in them which are inter-engaged with one another to form a gear drive between the two arms 3a, 3b. Similarly, the second ends of the first and second upper arms 4a, 4b have teeth - 6 formed in them which are inter-engaged with one another to form a gear drive between the two arms 4a, 4b.

The first and second lower and upper arms 3a, 3b, 4a, 4b are of an open channel construction and in this case are of a U-shape in cross-section. The width of the lower arms 3a, 3b is greater than the width of the upper arms 4a, 4b so as to allow the upper arms 4a, 4b to nest within the lower arms 3a, 3b and permit the jack 1 to be lowered into a very low position. It will be appreciated that if required the first and second lower arms 3a, 3b could nest within the first and second upper arms 4a, 4b.

The platform 8 has a lifting surface 12 which as shown in Fig.3 can be positioned a distance h1 from the ground when the platform 8 is in a stowed position. In this case the lifting surface 12 is not a flat surface but is concave and the lowest point of the lifting surface is approximately 10mm lower than the highest points but it will be appreciated that a flat lifting surface could be used.

The platform 8 is U-shaped in cross-section and has two side members 14a, 14b joined together by a common bridging member 13. An upper surface of the common bridging member 13 forms the lifting surface 12.

The width between the two side members 14a, 14b is greater than the width of any of the arms 3a, 3b, 4a, 4b or the width of the upstanding part of the base member 2. This allows the platform 8 to nest over the arms 3a, 3b, 4a, 4b and the base member 2 when it is in the stored position and the jack 1 is in its fully lowered position as shown in Figs 1 and 3.

Each of the side portions 14a, 14b has the two slots 15a, 15b formed in it for engagement with the first and second upper pivot pins 7a, 7b. Each of the slots 15a, 15b is a J-shaped slot having a respective short limb 22a, 22b and a respective long limb 23a, 23b joined together by a curved portion of the respective slot 15a, 15b.

An end face of each of the short limbs 22a, 22b is positioned further away from the lifting surface 12 than an end face of each of the long limbs 23a, 23b so that when the first and second upper pivot pins 7a, 7b are positioned at the end of the short limbs 22a, 22b a central longitudinal axis of the first and second upper pivot pins 7a, 7b is positioned a distance d2 from the lifting surface 12. Whereas, when the first and second upper pivot pins 7a, 7b are positioned at the end of the long limbs 23a, 23b the central longitudinal axis of the first and second upper pivot pins 7a, 7b is positioned a distance d1 from the lifting surface 12.

It will be noted that in this case the difference between d2 and d1 is approximately 45mm and that the distance h1 between the ground and the lifting surface 12 with the jack 1 in a fully lowered position and the platform 8 in the stored position, corresponding to the positioning of the first and second upper pivot pins in the upper ends of the long limbs 23a, 23b, is 94mm. The distance h2 between the ground and the lifting surface 12 when the jack is fully lowered and the platform 8 is in a raised position, corresponding to the positioning of the first and second upper pivot pins 7a, 7b in the upper ends of the short limbs 22a, 22b, is 139mm. However, these dimensions are only given by way of example and other dimensions could be used.

Therefore, in this case, the moveable platform 8 is able to reduce the required jack travel by 45mm by moving the platform from its stored position to its raised position.

Use of the jack is as follows, the first step is to remove the scissor jack from a storage location on the motor vehicle. The jack 1 will be stored fully lowered and with the platform 8 in its stored position in which the lifting surface 12 is positioned near to an upper end of the pantograph mechanism, that is to say near to the second ends of the first and second upper arms 4a, 4b. - 8

The next step is to decide whether to move the platform from its stowed position to the raised position, in which the lifting surface 12 is displaced from the upper end of the pantograph mechanism. This is based upon the actual clearance between the part of the vehicle to be raised and the ground. The next step is to take whatever action is determined to be required based upon the decision. If there is more than 149mm (139+10) of ground clearance then the platform 8 will be moved to its raised position, whereas if there is less than 149mm of ground clearance but more than 104 mm (94+10) the platform will be left in its stored position. If the ground clearance is less than 104mm the jack 1 cannot be used and an alternative method of lifting the vehicle will need to be sought. The next step is to place the scissor jack 1 with the platform 8 in the desired position on the ground under the part of the vehicle to be raised. The final step is to rotate the threaded shaft 9 by engaging a suitably shaped crank with the drive means 10 to raise the moveable platform 8 and lift the motor vehicle.

The platform 8 is moved to its raised position whenever there is sufficient clearance between the part of the vehicle to be raised and the ground to place the jack 1 under the motor vehicle with the platform 8 in the raised position so as to maximise the available lifting height of the jack 1. The platform 8 is left in its stowed position whenever there is insufficient clearance between the part of the vehicle to be raised and the ground to place the jack under the motor vehicle with the platform in the raised position. This allows the jack 1 to be used in situations with lower ground clearance such as when the vehicle has suffered a flat tyre and the tyre has become detached from the wheel or is totally flat so that the ground clearance is less than normal. The height of the jack 1 with the platform in the raised position will be tailored to fit the particular vehicle it is intended to be used on to provide the minimum clearance between the lifting surface and the underside of the vehicle in a typical lifting situation.

It will be appreciated by those skilled in the art that although the invention has been described by way of example to a preferred embodiment of the invention it is not limited to - 9 - such embodiment and that various alternatives or modifications could be made without departing from the scope of the invention. For example, the platform need not be connected to the pantograph mechanism by the same pivots pins used to link the second ends of the upper arms but could be connected in some other way such as, for example, separate pins. Similarly although the invention has been described with reference to the use of J-shaped slots it will be appreciated that other slot shapes could be used. It would also be possible to replace the J-shaped slots with linear slots and provide a spacer to be interposed between the pantograph mechanism and the lifting platform when sufficient ground clearance is present. - 1 0

Claims

1. A scissor jack comprising a base member for resting the jack upon the ground, a platform for engagement with a part of a motor vehicle to apply a lifting force thereto and a pantograph mechanism having first and second lower arms, first and second upper arms and a threaded shaft linking the first lower and upper arms to the second lower and upper arms for changing the distance between the base member and the platform when the threaded shaft is rotated wherein means are provided to allow the platform to be moved from a stowed position in which a lifting surface of the platform is positioned near to an upper end of the pantograph mechanism to a raised position in which the lifting surface of the platform is displaced from the upper end of the pantograph mechanism.

2. A scissor jack as claimed in claim 1 wherein the first lower arm has a first end pivotally connected to the base member, a second end pivotally connected to a first end of the first upper arm, the second lower arm has a first end pivotally connected to the base member and a second end pivotally connected to a first end of the second upper arm and the first and second arms have respective second ends which are pivotally connected together.

3. A scissor jack as claimed in claim 2 wherein the first and second lower and upper arm members are of an open channel construction so as to allow the first and second upper arms to nest within the first and second lower arms.

4. A scissor jack as claimed in claim 2 wherein the first and second lower and upper arm members are of an open channel construction so as to allow the first and second lower arms to nest within the first and second upper arms.

5. A scissor jack as claimed in any of claims 2 to 4 wherein the first and second upper arms are pivotally connected together by respective first and second upper pivot pins. - 1 1

6. A scissor jack as claimed in claim 5 wherein the first upper arm is connected to the platform by the first upper pivot pin and the second upper arm is connected to the platform by the second upper pivot pin.

7. A scissor jack as claimed in claim 6 wherein each of the first and second pivot pins is engaged with a respective slot formed in the platform so as to provide the means to allow the platform to be moved from the stowed position to the raised position. t

8. A scissor jack as claimed in claim 7 wherein each of the slots is 'J' shaped and has two limbs, a first long limb having an end face near to the lifting surface of the platform and a second short limb having an end face spaced away from the lifting surface of the platform wherein when the first and second upper pivot pins are engaged in the long limbs the platform is located in the stored position and when the first and second upper pivot pins are engaged in the short limbs the platform is located in the raised position.

9 A scissor jack as claimed in claim 7 or in claim 8 wherein the support platform is U- shaped and has two side members joined together by a common bridging member and slots are formed in both of the two side members.

10. A scissor jack as claimed in claim 9 wherein the width of the support platform between the two side members is greater than the width of the lower and upper arms and the width of the base member so that, when the jack is in a lowered position and the moveable platform is in the stored position, the two side members overlie the base member.

11. A method of using a scissor jack comprising a base member for resting the jack upon the ground, a moveable platform for engagement with a part of a motor vehicle to apply a lifting force thereto and a pantograph mechanism having first and second lower arms, first and second upper arms and a threaded shaft linking the first lower - 12 and upper arms to the second lower and upper arms for changing the distance between the base member and the moveable platform when the threaded shaft is rotated wherein the method comprises removing the scissor jack from a storage location on the motor vehicle, deciding on whether to move the platform from its stowed position, in which a lifting surface of the platform is positioned near to an upper end of the pantograph mechanism, to a raised position, in which the lifting surface is displaced from the upper end of the pantograph mechanism, based upon the actual clearance between the part of the vehicle to be raised and the ground, taking whatever action is determined to be required based upon the decision, placing the scissor jack on the ground under the part of the vehicle to be raised and rotating the threaded shaft to raise the moveable platform and lift the motor vehicle.

11. A method as claimed in claim 10 wherein the action determined to be required comprises moving the platform to its raised position whenever there is sufficient clearance between the part of the vehicle to be raised and the ground to place the jack under the motor vehicle with the platform in the raised position.

12. A method as claimed in claim 10 wherein the action determined to be required comprises leaving the platform in its stowed position whenever there is insufficient clearance between the part of the vehicle to be raised and the ground to place the jack under the motor vehicle with the platform in the raised position.

13. A scissor jack substantially as described herein with reference to the accompanying drawing.

14. A method substantially as described herein with reference to the accompanying drawing.