GB2132147A - Support jack - Google Patents

Abstract

A supporting jack (1) for supporting the chassis of a commercial vehicle, comprising a ram (4) which is guided in a vertically adjustable manner in a guide member, the guide member forming a part of a subframe (2) of the jack (1) the ram (4) being arrestable at a desired level or height, wherein one side of the ram (4) is provided with arresting steps (6) and the guide member comprises guide pieces adapted to the shape of the ram (4); the ram (4) and the guide pieces having a prismatic cross-section, a locking pawl (3) being mounted, at one of its ends, in the subframe (2) and the other end being engageable in one of the steps (6), the locking pawl (3) being displaceable with the raising of the ram (4) and engageable, as desired, in any of the steps. <IMAGE>

Description

SPECIFICATION Support jack The invention relates to a support jack, more especially for supporting the chassis of a commercial vehicle. The jack comprises a ram which is guided, in a vertically adjustable manner, in a guide member formed in a subframe of the jack and which is arrestable at a desired level or height.

Known support jacks of this general type are formed by welding together pipes or tubes and flat iron bars, and the height of the ram is set by the use of an insert bolt. This arrangement is highly unstable, cannot be accurately guided and has insufficient rigidity. In consequence, there is a risk of accidents occurring.

The manufacturing costs and the weight of such arrangements are high. In addition, mechanical treatment is required and such a jack has limited setting positions.

A welded tripod arrangement having a threaded spindle is also known. Such an arrangement is cumbersome to adjust and is not maintenance free.

It is also susceptible to corrosion which can impair its operation. Additional disadvantages of such an arrangement are that it is heavy and high costs are incurred in effecting the necessary mechanical treatment.

The invention seeks to eliminate these disadvantages by providing a support jack which is simple to adjust and has a high degree of stability.

A simple raising movement therefore permits the height of the jack to be set easily and the arresting of the upward movement of the jack occurs automatically with the releasing of the pawl. This ensures that the ram is safely maintained in its desired position.

This maintenance of position does, of course, increase with an increased loading of the jack because the ram 4 is pressed into its prismatic guide more forcibly, and is therefore accurately centred.

Preferably, the locking pawl has a triangular vertical section bounded by an upper, horizontally extending face and an inclined face, and a further inclined face, the adjacent faces being connected by radiused portions, the upper and the inclined faces engaging in recesses formed between the steps, the recesses having a shape corresponding to the faces, the pawl being supported in a cutaway portion of the subframe by the further inclined face and the radiused portion between the two inclined faces, the locking pawl also having a bent or cranked tongue which extends through an aperture formed in the subframe and is guided therein by the boundary edges of such aperture.

This feature appears to be advantageous because the prismatic guide enhances the automatic center ing effect. Accordingly, the ram is automatically fixed and reliably held in a desired position. This results in the apparatus being inherently stable due to its three-point support.

Reliable guidance may be achieved by providing four projecting guide faces, two such guide faces being disposed one above the other and two additional faces being inclined relative thereto, which additional faces are disposed one above the other. A greater number of guide faces on the ram can slide along such guide faces.

Each of the three parts forming the support jack, that is tq say, the subframe, the ram and the locking pawl may each be made by casting as a single part.

By so doing, the safety of the jack is improved and there is also a weight saving. Thus, a jack manufactured in this manner and having a carrying capacity of approximately 6000 kg weights only 6 to 7 kg.

Mechanical treatment is also eliminated, thereby contributing towards further cost savings. In addition, the jack is not susceptible to corrosion and is virtually maintenance-free.

To assemble the apparatus, the locking pawl is initially inserted into the subframe and then, by exerting pressure upon the tongue of pawl, the pawl is pivoted to permit the ram to be inserted into the subframe. By releasing the tongue of the locking pawl, the pawl moves into the path of and stops the descent of the ram. So that the apparatus cannot readily be dismantled again, a stop member may be provided in the lower region of the ram, which stop strikes against one face of the subframe if the ram is raised upwardly by an undesired amount. This prevents the ram from being removed from the subframe and ensures that the jack cannot be dismantled without prior removal of the stop pin.

Even the locking pawl is secured by such an arrangement and cannot be removed.

To balance the individual steps on the ram, stepless adjustability may additionally be achieved, in that the ram has, at its upper end, a threaded portion adapted to receive a threaded bolt, such threaded bolt protruding downwardly from the supporting plate of the jack. The threaded bolt may be provided with stop screws which prevent the support plate from being fully unscrewed.

One embodiment of a jack in accordance with the present invention will be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a vertical section through the jack and shows a subframe and a plunger or ram in both its lowermost and uppermost positions.

Figure 2 is a plan view of a locking pawl forming part of the jack shown in Figure 1; Figure 3 is a horizontal sectional view through the plunger or ram taken along the line Ill-Ill of Figure 1; Figure 4 is a vertical sectional view through the subframe shown in Figure 1, this Figure being on an enlarged scale relative to Figure 1.

Figure 5 is a further vertical sectional view, taken along the line V-V of Figure 4, through a part of the upper portion of the subframe; Figure 6 is a horizontal sectional view taken along the line VI-VI of Figure 4; and Figure 7 is a vertical sectional view through the upper portion of a steplessly adjustable support plate forming part of the jack.

In Figure 1 there is shown a support block or jack 1 which comprises a cast subframe 2. A locking pawl 3 is inserted into the frame 2 and subsequently a ram 4 is introduced into the frame whereupon the locking pawl 3 is screw-connected due to pressure being exerted upon its tongue 5. The. locking pawl 3 and the plunger or ram 4 are each cast in one piece. As best seen in Figure 3, the plunger or ram 4 has a substantially triangular cross-section.

In addition, the ram 4 has arresting steps or projections 6 and a plurality of small guide faces 7 on one side, which faces lie above one another in a common plane. Additional, corresponding guide faces 8 are provided on another side, the faces 8 lying in a plane which is inclined relative to the plane of the faces 7. The guide faces 7 of the ram 4 slide on two support faces 9 of the subframe 2, only one of such faces being visible, in Figure 6. The faces 9 lie above one another in a common plane and projecting from the surrounding region of the subframe 2.

The guide faces 8 of the ram 4 slide on two support faces 10 which also lie one above the other and which project from their surrounding area. The two support faces 9 correspond with the two support faces 10.

As illustrated in Figure 1, in vertical section, the locking pawl 3 is substantially triangular with radiused corners. The locking pawl 3 engages in recesses 13 provided in the arresting steps 6 of the ram 4. The pawl 3 has an upper, substantially horizontally extending, face 11 and an inclined face 12, the recesses 13 being adapted to correspond to the faces 11 and 12. In addition, the locking pawl 3 is supported in a cutaway portion 16 ofthe subframe 2 by means of a further inclined face 14, the radiused portion 15 of which connectes the inclined faces 12 and 14. The cutaway portion 16 corresponds to the shape of the radiused portion 15.

The cranked tongue 5 of the locking pawl 3 is used for guiding and operating the locking pawl 3 and extends through an aperture 17 provided in the sub-frame 2 for this purpose.

When the ram 4 is introduced into the subframe 2, a stop member 18 provided on the lower portion of the ram 4 abuts against the base of the frame 2 and prevents further downward movement of the ram 4.

The stop 18 also prevents the ram 4from being completely removed from the subframe 2 in an upward direction because it strikes against a face of the subframe 2 and prevents further upward movement. To dismantle the apparatus the stop 18 must first be removed fom the ram 4.

If it is necessary for the individual steps to be balanced during vertical adjustment, a threaded member 20 can be inserted atthe upper end 19 of the ram 4. A threaded bolt 22 is then screwed into the threaded member 20 and which protrudes downwardly from the supporting base plate 21 of the jack. The threaded bolt 22 is provided with stop screws 23 which are screwed into corresponding threaded apertures in the threaded bolt 22 through holes 24 in the wall of the ram 4 after the threaded bolt 22 has been screwed into the threaded part 20. If the threaded bolt 22 is unscrewed too far upwardly, the stop screws 23 strike against an annular step 25 provided at the upper end of the ram 4 which prevents the threaded bolt 22 from being fully unscrewed.

Claims (12)

1. A supporting jack for supporting the chassis of a commercial vehicle, comprising a ram which is guided in a vertically adjustable manner in a guide member, the guide member forming a part of a subframe of the jack, the ram being arrestable at a desired level or height, wherein one side of the ram is provided with arresting steps and the guide member comprises guide pieces adapted to the shape of the ram, the ram and the guide pieces having a prismatic cross-section, a locking pawl being mounted at one of its ends in the subframe and the other end being engageable in one of the steps, the locking pawl being displaceable with the raising of the ram and engageable as desired, in any of the steps.

2. A jack as claimed in claim 1, wherein the ram and the guide pieces have a triangular prism crosssection.

3. Ajack as claimed in claim 1 or 2 in which the locking pawl has a triangular vertical section bounded by an upper, horizontally extending face, and an inclined face, and a further inclined face, the adjacent faces being connected by radiused portions, the upper and the inclined faces engaging in recesses formed between the steps, the recesses having a shape corresponding to the faces, the pawl being supported in a cutaway portion of the subframe by the further inclined face and the radiused portion between the two inclined faces, the locking pawl also having a bent or cranked tongue which extends through an aperture formed in the subframe and is guided therein by the boundary edges of such aperture.

4. Ajack as claimed in claim 1,2 or 3 in which the support faces of the guide member provided on the subframe project from the surrounding regions of the guide member, the associated guide faces provided on the ram sliding on said support faces of the guide piece.

5. A jack as claimed in claim 4, in which four support faces are formed on the guide piece, two fo said faces lying above one another and two being inclined relative to one another.

6. Ajack as claimed in any preceding claim in which the two guide faces on the ram which extend in an inclined manner relative to each otherare subdivided into a plurality of guide faces disposed one above the other.

7. A jack as claimed in any preceding claim, in which the subframe, the ram and the locking pawl are each in the form of a one piece casting.

8. A jack as claimed in any preceding claim, in which a stop member is provided on the lower portion of the ram to prevent the ram from being removed completely from the subframe, the stop member striking against one face of the subframe in the upper limit position of the ram.

9. A jack as claimed in claim 8 wherein the stop member is in the form of a countersunk bolt, a tapped screw or a foldable lug or tab.

10. Ajack as claimed in any preceding claim, in which the ram is provided, at its upper end, with a threaded portion for receiving a threaded bolt, the bolt protruding downwardly from the support plate of the jack to permit stepless vertical adjustment.

11. Ajack as claimed in claim 10 wherein the threaded bolt is provided with stop members for preventing the support plate from being unscrewed completely.

12. A jack as claimed in claim 1, constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the acompanying drawings.