GB2324329A

GB2324329A - Scaffold jack

Info

Publication number: GB2324329A
Application number: GB9707597A
Authority: GB
Inventors: Demetrios Georgio Papadopoulos
Original assignee: SGB Services PLC
Current assignee: SGB Services PLC
Priority date: 1997-04-15
Filing date: 1997-04-15
Publication date: 1998-10-21
Also published as: GB9707597D0

Abstract

A screw jack for supporting a scaffold tube 5 comprises a support 2 for a vertical threaded stud 3, and a nut 4 threadedly engaged therewith. The nut comprises a body 6 having an outer wall 7 and an axially extending bore 9 defined by a threaded inner wall 10. The upper ends of the inner wall 10 and outer wall 7 are at different heights so that there is an annular rim which can be conically convex (Fig 1) or concave (Fig 3) for centering the scaffold tube 5.

Description

IMPROVENENTS IN OR RELATING TO A JACK THE PRESENT INVENTION relates to a jack and more particularly relates to a jack intended for use in a scaffolding system.

It has been proposed previously to use screw-jacks in the erection of scaffolding. A typical screw-jack comprises a base plate which supporting an upstanding threaded stud. A nut is provided, threadedly engaged on the threaded stud so that rotation of the nut results in it moving upwardly or downwardly along the threaded stud. A scaffold tube, of slightly larger diameter than the threaded stud, has its lower end telescopically engaged over the upper end of the threaded stud so that the lower most end of the scaffold tube rests on top of the nut.

In such a typical screw jack, it is necessary for the scaffold tube to be of greater diameter than the threaded stud to prevent the scaffold tube being jammed by rust, stray bits of cement and concrete or other items found on building sites.

A problem with a typical screw jack is that, as the nut is rotated, the scaffold tube may move eccentrically around the threaded stud. This movement of the scaffold tube is undesirable since it results in instability of the scaffolding.

The present invention seeks to provide an improved jack.

According to this invention there is provided a screw jack for supporting a scaffold tube the screw jack comprising a support which supports an substantially vertical threaded stud, and a nut threadedly engaged with the stud, the nut comprising a body having an outer wall and an axially extending bore, the bore being defined by a threaded inner wall, the upper ends of the inner wall and the outer wall being at substantially different heights, the upper end of the body being provided with an inclined edge extending around the body and connecting the inner wall to the outer wall.

Preferably the upper end of said inner wall is at a substantially greater height than said outer wall so that said inclined edge forms a substantially convex upper region of the collar.

Alternatively the upper end of said outer wall is at substantially greater height than said inner wall so that said inclined edge forms a substantially concave upper region of the collar.

Advantageously said outer wall is substantially cylindrical.

Preferably one or more outwardly extending arms are provided on said outer wall.

Advantageously there are two opposed outwardly extending arms provided on and substantially normal to the outer wall.

In order that the invention maybe more readily understood, and so that further features thereof may be appreciated, the invention will now be described by way of example, with the reference to the accompanying drawings in which: Figure 1, is a perspective view of a screw jack in accordance with the present invention, Figure 2, is an enlarged perspective view of a nut forming part of the jack of Figure 1 and, Figure 3, is an enlarged perspective view of a nut forming part of a jack comprising an alternative embodiment of the present invention.

Referring initially to Figure 1, a screw jack 1 comprises a substantially horizontal base plate 1 in the centre of which is mounted an upstanding tube 2 forming a socket which receives the lower end of a vertically extending threaded rod 3. A nut 4 is provided which is threadedly engaged on the threaded rod 3. A scaffold tube 5, having an internal diameter which is slightly greater than the external diameter of the threaded rod 3, and having an external diameter which is less than the external diameter of the nut 4, is provided telescopically engaged over the upper end of the threaded rod 3, above the nut 4.

The lower end of the scaffold tube 5 rests on the upper surface of the nut 4. As the nut 4 so rotated, and moves axially of the threaded rod 3 the scaffold tube 5 is raised or lowered.

Referring now to Figure 2, the nut 4 comprises a cylindrical body 6 having a substantially outer wall 7 above which is an inwardly extending inclined edge 8. The inclined edge may be curved, but is preferably linear and thus of bevelled from. The bevelled edge 8 is of substantially convex form and is concentric with the cylindrical wall 7, having the appearance of the lower portion of a cone. An axially extending bore 9 is provided in the body 6. The bore 9 is defined by a wall 10 being provided with threads adapted to engage the exterior of the threaded tube 3. Two diametrically opposed outwardly extending arms 11, 12 are provided extending from the cylindrical wall 7. The arms 11, 12 are provided approximately half way between the bottom and the top of the cylindrical wall 7.

In use of the screw jack, the nut 4 is threadedly engaged on the threaded stud 3 and may be moved upwardly or downwardly by rotating the nut in an appropriate direction, utilising the arms 11,12. The cylindrical wall 7, the bevelled edge 8, and the axially extending bore 9 of the nut 4 are all concentric with the threaded rod 3.

The lower end of the scaffold tube 5 engages the upper bevelled edge 8 of the nut 4, and the weight of the scaffold tube 5 causes the scaffold tube 5 to drop to the lowest point possible on the bevelled edge 8. When the scaffold tube 5 reaches the lowest point possible on the bevelled edge the scaffold tube 5 is concentric with the bevelled edge 8. Therefore the scaffold tube 5 is also concentric with the threaded stud 3 and is held in this position by its own weight.

Referring now to Figure 3, a nut 13 which may be used in an alternative embodiment of the present invention is shown. The nut 13 comprises a cylindrical body 6 having a substantially cylindrical outer wall 7 and two diametrically opposed, radially outwardly extending arms 11, 12 as in the previous embodiment. The body 6 has an axially extending bore 9 defined by a threaded inner wall 10 as in the previous embodiment. The outer wall 7 has its upper end of a greater height than the inner wall 10 and a bevelled edge 14 is provided between the 2 walls. The bevelled edge 14 extends concentrically around the body 6 angled upwardly from the inner wall 10, to the outer wall 7. Thus in this embodiment of the invention the upper region of the body 6 is substantially concave in form.

In use of the screw jack according to this alternative embodiment invention, the nut 13 is threaded on the threaded rod 3 and the lower end of the scaffold tube 5 is telescopically engaged about the upper end of the threadedly rod 3 as in the previous embodiment. The lower end of the scaffold tube 5 is directed inwardly by the bevelled edge 14 so that it settles at its lowest point, which is also where it is concentric with the threaded rod 3. The weight of the scaffold tube 5 holds the lower end of the scaffold tube 5 in position within the bevelled edge 14 preventing any eccentric movement of the lower end even when the nut 13 is rotated.

Claims

1. A screw jack for supporting a scaffold tube, the screw jack comprising a support which supports an substantially vertical threaded stud, and a nut threadedly engaged with the stud, the nut comprising a body having an outer wall and an axially extending bore, the bore being defined by a threaded inner wall, the upper ends of the inner wall and the outer wall being at substantially different heights, the upper end of the body being provided with an inclined edge extending around the body and connecting the inner wall to the outer wall.

2. A jack according to Claim 1 wherein the upper end of said inner wall is at substantially greater height than said outer wall so that said inclined edge forms a substantially convex upper region.

3. A jack according to Claim 1 wherein the upper end of said outer wall is at a substantially greater height than said inner wall so that said inclined edge forms a substantially concave upper region.

4. A jack according to any one of the preceding Claims wherein said outer wall is substantially cylindrical.

5. A jack according to any one of the proceeding Claims wherein one or more outwardly extending arms are provided on said outer wall.

6. A jack according to Claim 5 wherein there are two opposed outwardly extending arms provided on and substantially normal to the outer wall.

7. A screw jack substantially as herein described with reference to and as shown in Figures 1 and 2 of the accompanying drawings.

8. A screw jack substantially as herein described with reference to and as shown Figures 1 and 3 of the accompanying drawings.

9. Any novel feature or combination of features disclosed herein.