GB2034277A - Scissors-type Lifting Jack - Google Patents

Abstract

A scissors-type jack in which the head part 1 can be fixed to the chassis of a vehicle to be lifted, and the jack can freely follow the movement of the point of articulation because two of the lever arms 3 and 4 are provided with hinge pins 10, 12, which can move along arcuate slots in the base 2 and head 1 respectively, the movement being resisted by a resiliently-loaded spacer member (8), Fig. 3. e.g., (not shown), arranged between the movable pin and a "fixed" hinge pin 9 or 11 respectively. <IMAGE>

Description

SPECIFICATION Scissors-type Lifting Jack This invention relates to a scissors-type jack.

scissors-type jack in which the head part, during and loweririg vehicles, particularly private cars. To an increasing extent, scissors-type jacks are designed for use with specific types of vehicle and have special devices for engagement of the head parts of the jack with the vehicle chassis.

Where known scissors-type jacks are concerned, at the commencement of the lifting process, the point of articulation of the jack and the centre point of the base portion are on a common vertical line. With increasing height of lift, the point of articulation of the jack becomes more and more remote from this common line and moves in the direction of the vehicle centre.

As a result of unintended eccentric loading, the jack is overloaded on one side and in many cases this may cause the destruction of one of the components of the jack. Several solutions have become known which set out to overcome this disadvantageous effect. First of all, it is possible to alter the design of the jack so that it can follow the movement of the point of articulation. To this end, a limited clearance is provided at the base and head of the jack by providing plate-shaped supporting surfaces. Certainly, the friction forces between the plate-shaped supporting surfaces as a result of the load are considerable and lead to an abrupt displacement of the jack.

Another solution to the problem resides in that the two bottom hinge arms of a scissors-type jack are supported on two bolts let into the base portion while the hinge pin is able to move in a vertical slot located between the two bolts.

Eccentrically applied forces are thereby not transmitted to the base without some moment.

The undesired moment positively results in an overloading of one of the bolts. On the other hand, the hinge pin guided in the vertical slot is worn out quickly due to friction. The system of hinge arms and hinge pins thus acquires excessive clearance at the pivot points and the envisaged function and stability are no longer guaranteed.

Another possibility of compensating for the additional forces arising out of the moment is indicated in British Patent No. 1452421.

Reinforcement in the region of the teeth of the hinge arms is intended to make it possible to absorb the additional forces arising without destruction of the teeth.

The present invention aims to provide a scissors-type jack in which the heat part, during the lifting process at the vehicle, can follow the circular path of the point of articulation, without incurring additional forces and their harmful effects on the loading of the components.

According to the present invention there is provided a scissors-type jack, comprising two pairs of lever arms engaged by a spindle for moving the arms of each pair, one lever arm of each pair being connected by a hinged pin to a head member and the other lever arm of each pair being connected by a hinge pin to a base member, one hinge pin at the head member and one hinge pin at the base member being in a fixed position and the other hinge pin at the head member and at the base member being movable in an arcuate slot in the respective head member and base member, and a respective resiliently loaded spacer member engaging the two hinge pins at the head member and at the base member which urges each movable hinge pin to one end portion of its respective slot.

The head and base parts of the scissors-type jack have freedom of movement so that the head part when fixed to the chassis of a vehicle to be lifted can follow the circular path described by the point of articulation. According to the invention, this is achieved in that the head and base parts are arranged for limited pivoting movement on the pairs of lever arms which can be adjusted by means of a screw spindle. The pairs of lever arms are rotatably mounted in the head and base parts and are coupled to one another by tooth systems.

A vehicle when lifted on one side by the scissors type jack assumes an oblique position. So that the head part of the scissors-type jack can easily follow this variation in angle, there are in the head and base parts in each case a hinge pin engaged in an arcuate aperture. For fixing the starting position of the parts of the scissors-type jack in the unladen state, resilient elements are located in the head and base parts. The resilient elements are anchored in the head and base parts and press the hinge pin into the envisaged starting position.

On the new scissors-type jack, the force initiated by the variable asymmetry of the pairs of lever arms does not act directly vertically on the base part. This fact has no disadvantageous effect on the lifting process. Additional loadings on the component parts, the cause of which lay in the immovable anchored head part and the formation of an indefinable moment, are now eliminated.

An embodiment of the invention will now be described, by way of an example with reference to the accompanying drawing, in which: Figure 1 shows the scissors-type jack in its lowered starting position; Figure 2 shows the scissors-type jack in its extended or raised position; Figure 3 shows the base part with spring bolt and space member in section; Figure 4 shows the spacer member in a perspective view; and Figure 5 shows the base part with a spring assembly.

The scissors-type jack shown in Figures 1 and 2 consists of a head part 1, which can be fixed to a vehicle to be lifted, and base part 2, the two parts 1 and 2 being movably interconnected by lever arms 3, 4, 5 and 6. A spindle 7 transmits from a hand crank (not shown) the manual operating force which is applied to the lever arms 3to6.

At the head and base parts 1 and 2, the lever arms 3 and 5 and 4 and 6 are connected to one another by systems of teeth. The lever arms 3-6 are each connected by a respective hinge pin 912 to the respective head and base parts 1 and 2.

Figure 3 shows the base part 2 with a spacer 8 in cross-section. To safeguard the tooth systems against lateral collapse and to fix the position of the respective moveable hinge pin 10, 12, a spacer 8 is in each case provided between the two side bearing plates of the head and base parts 1, 2. The spacer 8 has recesses for supporting the fixed and movable hinge pins 9, 10 or 11, 12. The side bearing plates have arcuate apertures in them for receiving the respective movable hinge pins 10, 12.

Figure 4 shows the shape of the spacer 8. The spacer 8 shown in Figure 3 is retained by a bolt 13 and a thrust spring 14 between the bearing plates at the respective head and base parts 1, 2.

The bolt 1 3 extends through an aperture in the base part 2 and has a head part which is received in a recess in the underside of base part 2. The bolt 13 can rock slightly towards the pin 9. If the position of the movable hinge pins 10, 12 alters, then the spacer 8 rotates about the fixed hinge pins 9, 11. In order to secure the position of the hinge pins 9, 11 and to support the hinge pins 10, 12, the spacer 8 has half-round recesses. A simplified embodiment for supporting the movable hinge pins 10, 12 is shown in Figure 5.

The movable hinge pins 10, 12 contacts a spring member 1 5 which consists of an elastic material and in its size and shape it is adapted to suit the movable hinge pins 10, 12. In the unladen condition of the scissors-type jack, in contrast to the spacer 8, the hinge pins 10, 12 assume an oppositely disposed starting position. Influenced by the angle of inclination of the chassis and of the load which is to be raised, the spring assembly 1 5 becomes more or less compressed.

Claims (5)

Claims

1. A scissors-type jack, comprising two pairs of lever arms engaged by a spindle for moving the arms of each pair, one lever arm of each pair being connected by a hinge pin to a head member and the other lever arm of each pair being connected by a hinge pin to a base member, one hinge pin at the head member and one hinge pin at the base member being in a fixed position and the other hinger pin at the head member and at the base member being movable in an arcuate slot in the respective head member and base member, and a respective resiliently loaded spacer member engaging the two hinge pins at the head member and at the base member which urges each movable hinge pin to one end portion of its respective slot.

2. A scissors-type jack as claimed in claim 1, in which at the head and base parts a substantially circular spacer member fixes the movable hinge pins at their extreme position between the bearing plates.

3. A scissors-type jack as claimed in claim 1 or claim 2, in which the end faces of the spacer bear on the teeth of the lever arms and the periphery of the spacer is provided with half-round recesses which accommodate the hinge pins.

4. A scissors-type jack as claimed in any preceding claim, in which the resilient loading is effected by a member formed of an elastic material located between the movable hinge pins and the respective head and base parts.

5. A scissors-type jack substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.