GB2271812A

GB2271812A - Hydraulic jack

Info

Publication number: GB2271812A
Application number: GB9321378A
Authority: GB
Inventors: Hai Liang Chen
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-10-18
Filing date: 1993-10-15
Publication date: 1994-04-27
Also published as: CN2136233Y; GB9321378D0

Abstract

A hydraulic jack having an easily adjustable initial height comprises a cylinder, a piston, an oil-pressure booster, and an oil-pressure unloading device, and a adjustor means for achieving the initial height of the hydraulic jack, which is characterized in that the adjustor means of the hydraulic jack is composed of a spline toothed adjusting rod 5 and a spline toothed piston rod 6 which is hollow and is fitted with the spline toothed adjusting rod. On the inner surface of the spline toothed piston rod, a plurality projecting teeth 11 extend radially to the axis of the piston rod and are spaced uniformly along both circumference and the axial direction. These projection are in alignment axially, and the recess keyways between the projection is aligned axially also. Similarly, on the outer surface of the spline toothed adjusting rod, the projecting teeth extend radially and are spaced uniformly along both circumference and the axial direction. These projecting teeth on the adjusting rod and the recess keyways between the projecting teeth are also in alignment axially. The projecting teeth and the recess keyways between the projecting teeth on the inner surface of the piston rod mentioned above can be slidably fit with the recess keyways (between the projecting teeth) and the projecting teeth respectively on the outer surface of the adjusting rod in the axial direction. To set the initial height of the jack rod 5 is turned so that its teeth are aligned with the keyways on the piston rod, the rod is moved axially and then turned again so that its teeth engage with the teeth on the piston rod. <IMAGE>

Description

TITLE OF THE INVENTION Hydraulic Jack Having An Rapidly Adjustable Height BACKGROUND OF THE INVENTION The present invention relates to a hydraulic jack, and especially to the hydraulic jack used to raise the car.

In a prior hydraulic jack, the height adjustor is composed of a adjusting bolt and a piston rod, and the adjusting bolt is threaded in the piston rod. When the hydraulic jack works, the adjusting bolt must be rotated to reach its initial height, so that the top surface of the hydraulic jack can contact with the object to be lifted.

With such an operation, it is time-consuming and strenuous, and it is inconvenient, especially to the car driver, to attempt to lift his/her car to repair it on the way. Additionally, some impurities may ènter the fitting thread between the bolt and the piston rod, resulting in great difficulty in adjusting the height by rotating the bolt.

The objective of the present invention is to provide a hydraulic jack, the height of which can be adjusted rapidly and conveniently. In this way, the hydraulic jack can be adjusted rapidly to reach its required height, and then the object can be lifted.

SUMMARY OF THE INVENTION To achieve above object, the present invention provides a hydraulic jack which comprising a cylinder, a piston, an oil-pressure booster, an oil-pressure unloading device, and a adjustor for achieving the initial height of the hydraulic jack. Such a hydraulic jack is characterized by that, the adjustor of the hydraulic jack is composed of a spline toothed adjusting rod and a spline toothed piston rod which is hollow and is fit with the spline toothed adjusting rod. On the inner surface of the spline toothed piston rod, the projecting teeth extend radially to the axis of the piston rod and are spaced uniformly along circumference and in the axial direction. These projecting teeth are in alignment axially, and the recess keyways between the projecting teeth are aligned axially, either.

Similarly, on the outer surface of the spline toothed adjusting rod, the projecting teeth extend radially outside and are spaced uniformly both along circumference and in the axial direction. These projecting teeth on the adjusting rod and the recess keyways between the projecting teeth are also in alignment axially. The projecting teeth and the recess keyways between the projecting teeth on the inner surface of the piston rod mentioned above can be slidably fit with the recess keyways (between the projecting teeth) and the projecting teeth respectively on the outer surface of the adjusting rod. The axial height of the said projecting teeth on the inner surface of the piston rod are circumferentially slidably fit with the axial intervals between the projecting teeth on the outer surface of the adjusting rod.Similarly, the axial height of the projecting teeth on the outer surface of the adjusting rod are circumferentially slidably fit with the axial intervals between the projecting teeth on the inner surface of the piston rod the piston of the cylinder is rigidly connected with the lower portion of the said piston rod, the adjusting rod is installed in the piston rod. Inside the piston rod, there is a spring between the adjusting rod and the cylinder piston; there is a blind hole extending radially in a recess keyway between the projecting teeth of the adjusting rod, and inside the blind hole, there is a spring and a steel ball; In a recess keyway between the projecting teeth of the piston rod, there is a longitudinal recess which extends axially and is fit with the steel ball mentioned above.Once the projecting teeth of the adjusting rod are aligned with those of the piston rod, the steel ball will go into the long recess.

Preferably, the projecting teeth of the adjusting rod and those of the piston rod can have a 20 degree ascending helix angle.

When the hydraulic jack works, the adjusting rod is rotated so that the projecting teeth of the adjusting rod can be aligned with the recess keyways between the projecting teeth of the piston rod. With the force action of the coiled spring, the adjusting rod can be pushed from the piston rod automatically to the needed height, then the adjusting rod can be rotated so that the projecting teeth of the adjusting rod can be aligned with those of the piston rod. And the oil-pressure booster can be driven to lift the piston of the cylinder and to lift the adjusting rod too. With tight contact to each other between the projecting teeth of the piston rod and those of the adjusting rod, the weight loaded on the top surface of the adjusting rod can be lifted.Once the oil-pressure is relieved, so long as the reversal action mentioned above is repeated, the adjusting rod will go back into the piston rod again. So, it can save time and effort greatly in using the hydraulic jack of the present invention to adjust the initial height.

Further objectives and advantages of the invention will appear from the following description taken together with the accompanying drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Fig.l is a schematic view of the hydraulic jack having a adjustable height according to the present invention.

Fig.2 is a schematic view showing the fitting between the piston rod and the adjusting rod of the present invention, in which, the piston rod and the adjusting rod are in the unlock state and the adjusting rod can be moved axially and rapidly in the piston rod; Fig.3 is a schematic cross sectional view of the piston rod; Fig.4 is a schematic longitudinal sectional view of the adjusting rod; Fig.5 is a schematic cross sectional view of the adjusting rod.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The first embodiment of the present invention is shown in Fig.1. The hydraulic jack, the height of which can be adjusted rapidly, is composed of an oil-pressure booster 1, an oil-pressure unloading device 2, a cylinder 3, an oilpressure piston 4, and a adjusting rod 5 which is installed in the piston rod 6. The oil-pressure piston 4 is rigidly connected with the lower portion of the piston rod 6.

Inside the piston rod 6, there is a coiled spring 7 between the adjusting rod 5 and the oil-pressure piston 4.

Referring to Fig.4 and Fig.5, the apical plate 8 is installed at the top portion of the adjusting rod 5. The apical plate 8 is used to contact tightly with the object to be lifted in direct manner. The adjusting rod 5 is in rod shape, and on its outer cylindrical surface, the projecting teeth 9 extend radially outside and are spaced uniformly along the circumference and in the longitudinal axial direction. A recess keyways 10 is formed between each projecting teeth 9 along the circumference. These projecting teeth 9 are in alignment in the longitudinal axial direction, and the recess keyways 10 are in alignment too.

The number of the projecting teeth along circumference is three in this embodiment. The piston rod 6 is a hollow rod in shape (as shown in Fig.3), 'and on its inner surface, there are also projecting teeth 11 which extend radially to the axis of the piston rod and are spaced uniformly along both the circumference and the axial direction. A recess keyway 12 are formed between each two projecting teeth 11 along the circumference. These projecting teeth 11 are in alignment respectively in the axial direction, and the recess keyways 12 are also in alignment. The projecting teeth 9 of the adjusting rod 5 can be axially slidably fit with the recess keyways 12 of the projecting teeth 11 of the piston rod respectively. Also, the projecting teeth 11 of the piston rod 6 can be axially slidably fit with the recess keyways 10 of the adjusting rod 5 respectively. The projecting teeth 9 of the adjusting rod 5 can be slidably fit with the axial intervals formed between the projecting teeth 11 of the piston rod 6, and the projecting teeth 11 of the piston rod 6 can be slidably fit with the axial intervals between the projecting teeth in the adjusting rod 5. A blind hole 13 is formed in a recess keyway 10 between two circumferentially projecting teeth of the adjusting rod 5. In the blind hole 13, a spring 14 and a steel ball 15 is provided (as shown in Fig.5). Also, in a recess keyway 12 between the projecting teeth 11 of the piston rod, a longitudinal recess 16 is axially extended (as shown in Fig.3).

Once the projecting teeth 9 in the adjusting rod 5 are aligned with the projecting teeth 11 of the piston rod 6, the steel ball 15 will be received in the longitudinal recess slot 16.

In practice, the initial height of the hydraulic jack is firstrequired, which is achieved only by adjusting the adjusting rod 5. The adjusting rod 5 is rotated, so that the projecting teeth 9 of the adjusting rod 5 can be aligned with the recess keyway 12 between the projecting teeth 11 of the piston rod 6, shown in Fig. 2. Because the adjusting rod and the piston rod are fit slidably, the adjusting rod 5 will be moved upwardly through the piston rod 6 under the force action of the biased spring 7. The adjusting rod 5 moves upwardly until it contacts with the object to be lifted. Then the adjusting rod 5 is rotated again so that the steel ball 15 can go into the longitudinal recess 16.At that time, the projecting teeth 9 of the adjusting rod 5 and the projecting teeth 11 of the piston rod 6 are aligned and the axial movement of the adjusting rod 5 is restricted by the fit between the projecting teeth 9 an 11. The oil-pressure booster is operated to have the piston 4 and the piston rod 6 moving upwardly. As the projecting teeth 9 and 11 are contacted tightly to each other, the adjusting rod 5 isalso lifted, so that the object to be lifted can be lifted.

The second embodiment of the present invention is similar with the first one and the difference between them is only in that the projecting teeth 9 of the adjusting rod 5 and the projecting teeth 11 of the piston rod 6 have a 20 degree ascending helix angle. In this way, it is very convenient to manufacture. At first, the screw machining should be finished on the outer surface of the adjusting rod and the inner surface of the piston rod, then the axial recess keyways between the projecting teeth are formed, and then the axial interval spacings between the projecting teeth are cut.

Claims

1. A hydraulic jack, comprising a cylinder, a piston, an oil-pressure unloading device, and adjustor means for achieving an initial height.

2. A jack as claimed in claim 1 wherein the adjustor means is composed of a spline toothed adjusting rod and a spline toothed piston rod which is hollow and is fit with the spline toothed adjusting rod; on the inner surface of the spline toothed piston rod the projecting teeth extend radially to the axis of the piston rod and are spaced uniformly along both circumference and the axial direction; said teeth are in alignmentlaxially, and recess keyways formed between the projecting teeth are aligned axially, either; on the outer surface of the spline toothed adjusting rod, a pluarlity of teeth extend radially and are spaced uniformly both along circumference and in the axial direction, said projection teeth on the adjusting rod and the recess keyways formed between the projecting teeth are also in alignment axially; said projecting teeth and the recess keyways therebetween on the inner surface of the piston rod can be slidahly fit with the recess keyways (between the projecting teelh) and the projecting teeth respectively on the outer surface of the actjusling rod in the axial direction; the axial height of the said projection toctll oí the piston rod can be circumferentially slidably fit wit c axial intervals between the projecting teeth of the outer surfacc ot lhc adjusting rod; the axial height of the projecting teeth on the outer surface of the adjusting rod can be circumferentially slidably fit with the axial intervals between the projecting teeth on the inner surface of the piston rod.

3. A jack as claimed in claim 1 or 2 wherein the piston of the cylinder is rigidly connected with the lower portion of said piston rod; inside the piston rod, a coiled spring is provided between the adjusting rod and the cylinder piston.

4. A jack as claimed in any preceding claim wherein a blind hole extending radially in a recess keyway is provided between the projecting teeth of the adjusting rod, and inside the blind hole, there is a spring and a steel ball; in recess keyway between the projecting teeth of the piston rod, a longitudinal recess is formed to fit with said steel ball; once the projecting teeth of the adjusting rod are aligned with those of the piston rod, said steel ball is received in said longitudinal recess.

5. Ajack as claimed in any preceding claim wherein the projecting teeth of both the adjusting rod and the piston rod can have a 20 degree ascending helix angle.