GB2117348A

GB2117348A - Screw-driven jack

Info

Publication number: GB2117348A
Application number: GB08209566A
Authority: GB
Inventors: Chuan Wu An; Long Jiang Ah; Nan Jiang Sheno
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-03-31
Filing date: 1982-03-31
Publication date: 1983-10-12

Abstract

A screw-driven pantograph jack 10 has its screw shaft 31 driven via reduction gearing 37, 36. Gear wheel 37 is fixed to operating member 28, and is rotatably mounted on a support 22 fixed to nut 14. <IMAGE>

Description

SPECIFICATION Screw-driven jack The present invention relates to screw-driven jacks for use, for example, in lifting vehicle loads.

A consideration of the prevailing type of screwdriven jacks will remind one of the fact that operation thereof is generally done by having an operation jacket rod engaged directly with the screw before exerting torque to turn the screw to lift up or lower down vehicle loads. This mode of operation requires excessive labour and time out of proportion with the work done, and in addition, the rather long working arm of the jacket rod will easily result in quivering conditions owing to lack of balance of the forces exerted. Furthermore, rotation of the screw together with the jacket rod accounts for frequent failure of force concentration and slip-off and fall-outs, as experience of operation will justify.This not only adds inconvenience, one way or another, to operation, but also greatly drags down working efficiency and working morale, and this has to be corrected, the sooner the better.

The invention provides a screw driven jack having a screw shaft and a transmission mechanism drivingly connected to the screw shaft, the transmission mechanism comprising a drive inlet and a reduction gear transmission so as to provide a reduction ratio between the drive inlet and the screw shaft.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a front view of a jack according to the subject invention; Figure 2 is a right-hand view of the jack of Figure 1; and Figure 3 is a sectional view of the operation mechanism in conjunction with the transmission mechanism as parts of the same jack.

Referring to Figure 1 it is seen that the embodiment is a jack 10 with a transmission mechanism 30 to activate a long transmission screw shaft 31 and an operation unit 20 positioned above the mechanism 30 including a fixture support 22.

The jack 10 comprises a footing 11, a stand 12 annexed thereunto to give support to two twin movable lower arms 1 5a the other ends of which are each engaged with nut crowns 14 and 1 4a which also serve concurrently as the joint crowns respectively for two movable upper arms 1 5 the other ends of which are both terminated in a loader mount 1 6 to stand altogether generally like a rhomboidal structure. Annexed atop the mount 16 is a loader 17 shaped roughly like the letter U, whose function is to engage a vehicle body.

The transmission mechanism 20 drives a transmission screw shaft 31 that passes through both nut crowns 14 and 14a to protrude at one end, whereas the other end is journalled in a nut bearing 32 and is secured in a huge gear 36 that meshes with a small gear 37.

The operation unit 20 comprises a fixture support 22 complete with a round cavity 22a provided above the nut crown 14, to accommodate intromission of a sleeve 26 finished with inner threads (nto shown in the drawing) to be engaged with a centre screw 21. The screw 21 pierces through the small gear 37 and extends exposed on the other side of the fixture support 22 for locking with a nut 24. This arrangement serves to secure the engagement of the small gear 37 with the huge gear 36 by means of the fastening effects due to the sleeve 26 and the centre screw 21, and moreover, the other end of the small gear 37 is adjoined with a grooved operation member 28 shaped like a flattened letter C by rivets 27, meant to facilitate fixing of an operation jacket rod (not shown) therein to achieve rotation operations.

To operate the jack 10 just set an operation jacket rod straight into the operation member 28 and exert thereto some torque to achieve rotation, whereupon the linked-up gear couple 37, 36 will be driven to rotate, which in turn will serve to turn the transmission screw 31 installed within the huge gear 36 to run in step according to the reduction ratio principle. Rotation of the screw 31 will be executed in the arrowed direction as the external threads 31 a provided along most of the length thereof match with the internal threads (not shown) provided in the nut crown 14a.Thus the rhomboid arm structure 15, 15a will lift upwards in the arrowed direction to lift up vehicle loads engaged by the U-shaped loader 1 7 on top of the operation unit 16, and whenever it is intended to lower down loads carried by the jack, such operation will be done just by having the jacket rod rotated in the reverse direction.

An advantage of the above embodiment is that it provides a simple-to-use jack characterised in that the speed reduction principle governing the transmission of smaller gears to bigge? gears serves to increase the torsion for the jack screw in rotation so as to help achieve reduction of labour and time for a given job.

Another advantage is that the precision engagement of the gears and the screws will serve to yield a much smoother, evenly distributed and stable transmission that will reduce quivering conditions due to unbalanced transmissions thereby helping to reduce mechanical wear and to lengthen the life of service of the jack.

Equally as important a feature as even distribution and stability of the forces exerted in operating the described jack according to the present invention is that working therewith will save up to or even more than 70% of the labour required in working with conventional jacks by virtue of the gear transmission arrangement, that is to say, 30% of the labour normally required for a job with conventional jacks will suffice to work with the above described jack on the same job. This reduced labour requirement will enable even the aged, the handicapped, and womenfolk to use it in jobs like replacing automobile tyres and so forth with ease.

On account of all of the unique structure and operational benefits described, the above jack is believed to be a truly worthwhile invention.

Claims

1. A screw driven jack having a screw shaft and a transmission mechanism drivingly connected to the screw shaft, the transmission mechanism comprising a drive inlet and a reduction gear transmission so-as to provide a reduction ratio between the drive inlet and the screw shaft.

2. A jack as claimed in claim 1, wherein the reduction transmission comprises a large gear drivingly mounted on the screw shaft, and a small gear connected to the drive inlet and meshing with the large gear.

3. A jack as claimed in either claim 1 or claim 2 of the type having a pair of lower arms pivoted to a base and a pair of upper arms each pivoted to a corresponding lower arm and pivoted to a member for engaging a load to be lifted, the screw shaft being arranged to move the pivot points of the arms towards and away from each other.

4. A jack as claimed in claim 3 comprising a support fixed relative to one of the pivot points of the arms and to which the drive inlet is rotatably mounted.

5. A screw-driven jack substantially as hereinbefore described with reference to and as shown in the accompanying drawings.