GB2253802A

GB2253802A - Unscrewing tool for thin wall cylindrical components

Info

Publication number: GB2253802A
Application number: GB9105924A
Authority: GB
Inventors: Stefan Karp
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-03-20
Filing date: 1991-03-20
Publication date: 1992-09-23
Anticipated expiration: 2011-03-20
Also published as: GB9105924D0; GB2253802B

Abstract

An unscrewing tool 6 having hardened slightly tapered circumferential serrations 8 is forced axially into the inside diameter 7 of a thin walled element on member 2 by turning nut 5 clockwise. Serration 8 is embedded onto inside diameter 7 to a sufficient depth that will enable an unscrewing torque applied to unscrewing tool 6 via spanner flats 9 to start the unscrewing process after which nut 5 is removed prior to completely unscrewing member 2. Separation of tool 6 from member 2 is achieved by inserting a spacer and partly screwing back member 2 onto member 1 until separation is realised. <IMAGE>

Description

UNSCREWING TOOL FOR THIN WALL CYLINDRICAL COMPONENTS Unscrewing of thin wall embodyments especially when the mating components are made from metals that corrode, even in normal environment, has been found to be difficult if not almost impossible without damaging the relevant embodyment, often employing costly unscrewing tools.

Although not the only one, a very common example is the freewheeling mechanism of an ordinary bicycle, hereby referred as, freewheel, the inner component which has a fine internal screw thread enabling the freewheel to be attached to another embodyment of the bicycle, known as the wheel hub, that carries the mating external screw thread.

The attachment of the freewheel in this example is achieved by rotating the freewheel in a clockwise direction relative to the wheel hub until the hub geometry prevents further axial movement of the freewheel. This is made possible only because (a) the freewheel and mating hub both have right hand screwing threads and (b) the freewheel is presented to the hub such that freewheel is achieved when turning the bicycle chain anticlockwise.

It is because of the freewheeling ability of such embodyments that once tightened onto the mating hub by a clockwise rotation the unscrewing can only be done by rotating the inner most component of the freewheel, which carries the internal screw thread, anticlockwise.

When this inner most component is relatively thin walled the safe unscrewing becomes difficult if not almost impossible.

This invention satisfies the primary objective in a simple, safe and economical way because it employs the relevant existing components of the mating embodyments to assist the one piece unscrewing tool.

The invention is now described with reference to drawings: Fig.l - Shows, as an example, such an embodyment as normally found on the rear wheel of a simple bicycle with one speed freewheel, 2, with the rear wheel removed from bicycle frame, not shown, and unscrewing tool, 6, almost ready for the unscrewing operation. One view of the unscrewing tool, 6, is drawn only with its upper half in section to show internal and external details (common engineering drawing practice).

For simplicity, only the relevant part of the rear wheel hub, 1 is shown in Fig.1.

The unscrewing tool, 6, is force driven into the internal diameter or bore, 7, of the inner component of the freewheel,2, by turning nut, 5, in direction of arrow, C, (clockwise) on rear wheel spindle, 3, If necessary, employing common engineering practice, the spindle, 3, can be prevented from rotating clockwise by holding the similar nut that is found on the other end of spindle, 3, not shown in Fig.1.

The hardened circumferential slightly tapered serrations, 8, will form corresponding serrations on the bore, 7, to a depth of penetration that the material, from which the inner component is made, will accept.

Holding nut, 5, if necessary, with a suitable spanner, the unscrewing tool,6, is turned in direction of arrow, A, anticlockwise, either by holding the two, four or more flats of the end, 9, of unscrewing tool, 6, in a vice or better still, employing a suitable spanner. The opposing force necessary, in clockwise direction, is applied at the outer rim of the bicycle rear wheel - not shown in Fig. 1.

Unscrewing of the freewheel can also be done simply by securing the special multi-purpose, conventional otherwise, spanner, hereby referred to as special spanner, 10, to the front wheel spindle, 11, and front fork, 12, using front wheel spindle nut, 13, as shown in Fig.2 - Only the necessary part of the front fork, 12, is shown in Fig. 2. The rear wheel complete with the unscrewing tool, 6, is presented to the special spanner, 10, so that the flats of end, 9, of the unscrewing tool, 6, enter the corresponding flats, 14, from the special spanner, 10.

The mechanics of the invention is such that rotating the unscrewing tool, 6, anticlockwise will unscrew the freewheel, 2, from hub, 1, but in doing so will force the hardened serrations, 8, of the unscrewing tool, 6, even deeper into the mating internal circumference, 7, of the inner component of freewheel, 2, ensuring a safe unscrewing operation.

Once the freewheel, 2, as a whole unit has rotated relatively to the hub, 1, a very small amount, the nut, 5, is slackened and the freewheel is completely unscrewed from the hub.

The unscrewing tool is safely separated from the freewheel, once again employing the relevant existing components of the mating embodyments.

The unscrewing tool with the freewheel firmly attached together by the serrations, 8, part of the unscrewing tool, 6, and their indentations on bore, 7, of freewheel, 2, is presented to hub, 1, with spacer ring, 18 (or 18bin between as shown in Fig. 3 (or Fig. 5).

The length of spacer, 18 (or 18b),is such that with the freewheel, 2 (or 2b), only partly screwed on to hub, 1, the unscrewing tool, 6 (or 6b),is forced free from freewheel, 2 (or 2b).

Fig. 4. shows unscrewing tool, 6a unscrewing a derailleur type bicycle freewheel, 2a.

Fig. 5 shows unscrewing tool, 6b, unscrewing another different derailleur type bicycle freewheel, 2b.

Fig. 6 shows unscrewing tool, 6c, unscrewing an industrial freewheel, 2c where the axial force on the unscrewing tool, 6c, is applied by an ordinary bolt, 15, via a washer, 16. This is possible because the freewheel 2c, overhangs the mating component, 17, sufficient for safe operation.

Fig. 7 shows an embodyment where the previously referred internal mating circumference, 7, is no longer existant. Instead the thin walled inner component of freewheel, 2d, offers an external mating circumference, 7d, for unscrewing. In this case the hardened circumferential slightly tapered serrations, 8d of the external type unscrewing tool, 6d, are internal as shown in Fig.7.

Being an aid to manufacturers, repairers and do-it-yourself enthusiasts the internal, Fig 1 to Fig 6, and external, Fig 7, unscrewing tools are made from hardened and tempered suitable steel, especially the serrations 8, 8d, and protected against corrosion thus promoting the user friendly The use of the internal/external unscrewing tools..can be taken beyond examples shown in Fig. 1. to Fig. 7. by small insignificant changes in details to enable "taylor making" them to suit different geometries of embodyments, application of axial and rotating forces and the size range, to name a few.

Claims

CLAItS

1. An unscrewing tool transmitting relatively large torque to thin walled embodiments by embedding its hardened slightly tapered circumferential serrations into the thin walled embodiment by an axial force applied simply, safely and economical ly

2. An unscrewing tool as in claim 1 wherein the embedded serrations imparted by the tool to the thin walled embodiment are permanent and can be simply used again and again

3. An unscrewing tool as in claims 1 and 2 wherein the embedded serrations and relatively large applied unscrewing torques have minimum adverse effect upon geometry and appearance of embodiments

4.An unscrewing tool as in any preceding claim wherein the tool can be employed to screw as well as unscrew the embodiment

5. An unscrewing tool as in any preceding claim wherein the unscrewing torque assists the embedding of the hardened serrations

6. An unscrewing tool as in any preceding claim wherein the axial force is applied employing elements that are part of the thin walled embodiments

7. An unscrewing tool as in any preceding claim wherein the torque can be applied employing elements that are part of or associated with the thin-walled embodiments

8. An unscrewing tool as in any preceding claim wherein the separation of the tool from the thin walled embodiment can be realised employing elements of the embodiment

9. An unscrewing tool as in any preceding claim wherein the unscrewing torque can be applied externally as well as internally

10. An unscrewing tool as in any preceding claim wherein the thin walled embodiments differ widely in size and configuration