GB2309020A

GB2309020A - Safety device for a four-wheeled jack

Info

Publication number: GB2309020A
Application number: GB9600597A
Authority: GB
Inventors: Michael Hung
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-01-04
Filing date: 1996-01-11
Publication date: 1997-07-16
Also published as: NL1002020C1; FR2743794A3; FR2743794B3; GB9600597D0

Abstract

A safety device for a four-wheeled jack includes two side frames 2 respectively provided with a through hole 21 for insertion of a stop shaft 8 to form a stop between the side frames 2 and a rocker arm 3. A through hole 21 may also be formed in a lower portion of the rocker arm 3 to accommodate the stop shaft 8. Alternatively (Fig 5 not shown) a sleeve 81 may be welded to a bottom side of the rocker arm (3) for passage of the stop shaft 8 therethrough to abut the side frames 2 to prevent sudden dropping of the rocker arm 3 due to mechanical failure so as to ensure work safety.

Description

SAFETY DEVICE FOR A FOUR-WHEELED JACK The present invention relates generally to a safety device for a four-wheeled jack, and more particularly to a safety device in which a stop shaft is provided at a suitable position between two side frames and a rocker arm to prevent sudden falling of the rocker arm due to mechanical failure.

Conventional four-wheeled jacks basically comprise a hydraulic cylinder, two side frames, a rocker arm, two side pull bars, a lift board and a lever. When the lever is operated, a pump will cause the rocker arm to rise gradually as a result of the hydraulic action so that the lift board may lift up a load. However, the rocker arm may fall suddenly as a result of mechanical failure, which may jeopardize the safety of the workers.

Improvements on the prior art to prevent accidental dropping of the rocker arm are therefore necessary.

According to a first aspect of the invention, the safety device for a four-wheeled jack according to the invention comprises a stop shaft securely disposed between a rocker arm and two side frames, without affecting the structural strength of the side frames.

The stop shaft is provided to prevent accidental dropping of the rocker arm as a result of mechanical failure. The stop shaft is inserted through a couple of through holes respectively formed in two side frames of the jack so that it may not easily slip out of the through holes upon pressure.

According to a second aspect of the invention, the safety device for a four-wheeled jack according to the present invention comprises a stop shaft inserted through a through hole formed in a lower portion of a rocker arm for preventing accidental dropping of the rocker arm during mechanical failure.

According to a third aspect of the invention, the safety device for a four-wheeled jack according to the present invention comprises a rocker arm having a sleeve welded to a bottom side thereof and a stop shaft passing through the sleeve so as to prevent accidental dropping of the rocker arm.

The structure and opertional characteristics of the present invention and its advantages as compared to the known state of the priorart will be better understood from the following description, in conjunction with the attached drawings which show illustratively but nnot restrictively an example of a dart board assembly.

In the drawings: Fig. 1 is an elevational view of a preferred embodiment of the invention; Fig. 2 is a partly exploded view of the preferred embodiment of the invention; Fig. 3 is a side view of the preferred embodiment of the invention; Fig. 4 is an elevational view of another preferred embodiment of the invention; and Fig. 5 is an elevational view of still another preferred embodiment of the invention.

With reference to Fig. 1 to 3, a common fourwheeled jack mainly comprises a hydraulic cylinder (not shown in the figures as it is concealed by a cover 11, only a piston 12 at one end thereof being shown to project on the outside), two side frames 2, a rocker arm 3, two side pull bars 4, a lift board 5 and a lever 6.

By means of a pump 7 and a hydraulic reflux arrangement, the lever 6, when operated, may cause the rocker arm 3 to be pushed by the piston 12 to rise gradually so that the lift board 5 may lift up a load. The side pull bars 4 are provided to support an inverted-U shaped seat 41 to ensure that the lift board 5 is positioned to orient upwardly. All of the above construction is, however, known in the art and will not, therefore, be discussed in detail herein.

The safety device for a four-wheeled jack according to the present invention is directed to provide a stop shaft 8 at a suitable position between the side frames 2 and the rocker arm 3 such that the stop shaft 8 will stop the movement of the rocker arm 3 after the rocker arm 3 is lifted, providing safety effects. The feature of the invention resides in that the side frames 2 are respectively provided with a through hole 21 for insertion of the stop shaft 8 therethrough. By means of such an arrangement, after the rocker arm 3 is lifted, the stop shaft 8 may serve as a bar between the side frames 2 and the rocker arm 3 to prevent abrupt falling of the load or the rocker arm 3. Furthermore, it should be pointed out that the upper portion of the side frames 2 may be punched to form outwardly bent, extended flaps 22 to enhance the strength of the side frames 2. With reference to Fig. 4, the rocker arm 3 may be provided with a through hole at a determined position of a lower end portion thereof so that the stop shaft 8 may be passed therethrough to serve as a stop between the rocker arm 3 and the side frames 2, achieving similar safety effects.

In addition, as shown in Fig. 5, a sleeve 81 may be welded to a bottom side of the rocker arm 3 at a predetermined position. After the rocker arm 3 is lifted, the stop shaft 8 may be inserted into the sleeve 81 to form a stop between the side frames 2 and the rocker arm 3 to prevent abrupt dropping of the rocker arm 3. All of the above-described preferred embodiments are simple to construct and may achieve desired effects.

Furthermore, since the stop shaft 8 is provided to be inserted through a through hole or sleeve, the connection is strong so that, even though the rocker arm 3 and the load may fall suddenly during mechanical failure, the stop shaft 8 will not be forced out of the through hole or sleeve and will baffle against the rocker arm 3, providing excellent safety.

In summary, the safety device according to the invention is not only simple in construction but also effective and reliable. In particular, the arrangement of the stop shaft will not have any adverse effect on the structural strength of the side frames or the rocker arm; besides, as the stop shaft is inserted into a through hole or sleeve, it will not easily slip out, rendering the safety device very reliable.

Claims

1. A safety device for a four-wheeled jack of the type including two opposed side frames and a rocker arm located between said side frames and pivotal upwardly on actuation of an associated hydraulic cylinder, the safety device comprising a stop shaft reacting between the rocker arm and the opposed side frames when the rocker arm is in a raised position to prevent return downward movement of said rocker arm.

2. A safety device as claimed in claim 1 and comprising two through holes one formed in each of said two side frames at pre-determined positions adjacent the upper regions thereof, the stop shaft being inserted through said two holes to form a stop between said rocker arm and said side frames with the rocker arm in its raised position.

3. A safety device as claimed in claim 1 in which each side frame has an upper rim bent outwardly therefrom to form an extended flap.

4. A safety device as claimed in claim 1 in which a hole is formed transversely through a lower region of said rocker arm, the stop shaft passing through said hole in the rocker arm to react between said rocker arm and said side frames.

5. A safety device as claimed in claim 1 in which a transverse sleeve is rigidly secured to the bottom side of said rocker arm, and said stop shaft is inserted through said sleeve of said rocker arm after said rocker arm is raised to react between said rocker arm and said side frames.

6. A safety device for a four-wheeled jack substantially as described with reference to and as illustrated by the accompanying drawings.