GB2067115A - Stud driving or extracting apparatus - Google Patents

Abstract

The apparatus has a housing 1 in which a number of rollers 7 are arranged held in a cage 6. By rotating the apparatus, the rollers engage on one side on ramp surfaces 17 of the housing, which form planes inclined to the axis of rotation, on the other side on a stud, so that the rollers grip the stud through the effect of the ramp surfaces. So that the apparatus can be used for studs of different diameters, the cage is made flexible with fingers extending from a ring- shaped part and retaining the rollers. The finger ends fall within the nominal diameter of the bore which serves to admit the stud, to prevent stud loss. <IMAGE>

Description

SPECIFICATION Driver/extractor apparatus for studs and the like The invention relates to a driver/extractor apparatus for studs or the like having a sub stantially symmetric housing with a number of ramp surfaces spaced on its inner periphery, acting in the radial direction, with rollers roll ing thereon which are carried in a cage coax ial with the housing with freedom to move radially and to rotate, the cage being provided with a coaxial bore with a nominal diameter to accept the stud and comprising a ring-shaped part and a plurality of axially parallel fingers extending therefrom, between which the rol lers are held, and also, flexible in the radial direction, friction surfaces falling within the nominal diameter of the bore for engaging the cage and the stud.

Such a driver/extractor apparatus, in the form of a hand-tool, is for example known from GB-PS 907873. A problem arises in using such tools, in that they are produced in predetermined size steps each suitable for a given nominal diameter. Since the driver/extractor apparatus only works when cage and rollers are set in rotation relative to the ramp surfaces in the housing, so that the rollers are pressed against the stud under the influence of the ramp surfaces, it cannot be guaranteed in all cases where the stud diameter is smaller than nominal that the driver/extractor appa ratus works satisfactorily. In most cases such driver/extractor apparatus is used, however, with threaded bolts which have a helical thread on to which a shaft is joined that has no thread and as a result has a noticeably smaller diameter.Inasmuch as the driver/extractor apparatus must be brought into en gagement with this shaft, the cage and rollers must first be pushed over the threaded part of the stud, that is to say, the driver/extractor apparatus must be spaced apart to correspond with the outer diameter of the threaded part.

But this means that the conditions for-driving by the cage and rollers are unfavourably affected.

To solve this problem it is known from GB PS 907873 to provide radial bores between the rollers in the inflexible metal cage, in each of which a ball and a compression spring are arranged. The balls project into the nominal diameter of the bore and form so-called friction surfaces by which balls, cage and rollers are to be locked into driving engagement.

Quite apart from the fact that with smooth and greasy studs this is not always possible with certainty, the mounting of the balls and springs in the cage is itself difficult, because there is for this purpose only a relatively small wall thickness of the cage in which to do it.

Additionally, practical experience has shown that the balls become fast in the cage after a short period of use through unavoidable contamination, so that the action of locking into driving engagement falls away. It is only possible to clean out the known equipment by dismantling it and this is expensive, so it is mostly not done as a practical matter. The known stud driver apparatus in that event effectively has no friction surfaces.

The invention has for its object to so improve a stud driver apparatus of the abovementioned type, that is adaptable for studs with wide diameter tolerances and also continues to work reliably notwithstanding the usual contamination with long use.

The solution of the problem follows according to the invention in a stud driver as above described, in that the cage is made of flexible material and the ends of the axially parallel fingers remote from the ring-shaped part fall within the nominal diameter of the bore.

By following the teaching of the invention, it is the fingers themselves that, preferably to a small extent, fall within the nominal diameter of the bore and as a result are sprung thereagainst when the driver apparatus is applied to the studs. The rollers in the first instance can deflect into the spaces formed by the ramp surfaces of the housing, that is to say the primary contact, which only effects the driving of the cage and the rollers relative to the housing, is not through the rollers, but through the cage itself or its fingers. The cage is engaged frictionally with the stud, so that already the smallest initial rotation positively drives the cage and with it the rollers, so that they are pressed against the stud by the action of the ramps. By exerting a suitable turning moment the stud can now be tightened or released depending on the direction of the rotation.This action is moreover not precluded by normal contamination, since there are no poorly accessible moving parts inside the fingers. Nor is a complicated machining of the cage necessary as was the case where sprung balls were used. Contaminant particles, which lodge between the other parts of the apparatus, can easily be removed by flushing out with a solvent and/or blowing. In any event, the fingers of the cage have rather the effect of deflectors, which prevent the ingress of contaminants into the inside of the apparatus.

The flexible nature of the cage is preferably brought about in that it is of an elastic, thermoplastic material, preferably a polyamide. The materials available for this nowadays are for the most part highly abrasion resistant and can be accurately shaped by an inexpensive manufacturing process such, for example, as by injection moulding, in quantity. Already, the ring-shaped part of the cage has an inherently elastic form, to which the axially parallel fingers attach as lever arms, and are likewise, however, also inherently elastic. By such a construction of the cage is produced, in re gard to the ends of the fingers that grip the studs, an extremely flat spring characteristic, so that even large diameter tolerances of the studs can be accommodated.The fingers, or at least their wall surfaces directed towards the bore, are made so that when they are in a stress free condition, they have a slight inclination towards the direction of the axis of the whole apparatus, just a few degrees being sufficient.

If an injection mouldable synthetic material is used, and cylindrical rollers, a particularly advantageous construction of the cage has the axially parallel fingers bounded by cylindrical surfaces in the direction of the rollers which partially enclose the rollers. This is indeed also possible with a metallic embodiment, but then costly stress relieving operations are required to give the cage sufficient play with respect to the rollers. Using the solution according to the invention, this play can be kept sufficiently small so that the rollers can also be securely constrained.

For the case in which the driver/extractor apparatus according to the invention is used on studs which according to frequent practice are heated for ease of removal, it is recommended, according to a further inventive measure, to embed, in the wall surfaces of the fingers that bound the bore, metal inserts that project out of the wall surflaces, which come into contact with the studs. It is preferred for this purpose to use roller-shaped inserts which, however, as distinct from the sprung balls of the apparatus according to GB-PS 907873, are rigidly embedded into the fingers. The cross-section of these metal inserts can however be varied as desired; they can be made as T-sections or even as dovetail inserts.

Care must be taken to ensure only that the metal inserts are secured against falling out.

The metal inserts spread out over their surfaces the heat at their point of contact with the stud, which is too high for the material, into a greater volume, so that damage to the cage at the temperatures usually employed is avoided. In the case where metal inserts are used in the fingers, these are naturally not very elastic. The necessary elasticity can then be achieved by providing the ring-shaped pa,-t between the fingers with stiffness-reducing slits extending from abutment surfaces for the rollers.

One embodiment of the subject of the invention will now be explained with reference to Figs. 1 to 3.

Figure 1 a part sectioned side view of a complete driver/extractor apparatus Figure 2: a perspective view of the cage with rollers, and Figure 3: a section through the subject of Fig. 1 along the line Ill-Ill to an enlarged scale.

In Fig. 1 is shown a complete driver/extractor apparatus. This comprises a housing 1 with a generally cylindrical outer surface and a coaxial longitudinal bore 2, a diametral transverse bore 3 for the insertion of an operating lever (not shown) and a hexagonal head 4 to accept a spanner or a ratchet, also not shown.

Within the cylindrical part of the housing is a lengthwise bore 2 in a space 5, the wall surfaces of which together form ramp surfaces to be described later with regard to Fig. 3.

Inside the space 5 is a substantially coaxial cage 6 with three pairs of rollers 7. Cage 6 and rollers 7 are prevented from falling out of the space 5 by a washer 8, which is held in the housing 1 by a circlip 9.

From Fig. 2 it is seen that the cage 6 consists of a ring-shaped part 10 and three axially parallel fingers 11 extending therefrom, between which the cylindrical rollers 7 are held. For this purpose the axially parallel rollers 11 are bounded by cylindrical faces 1 2 in the direction of the rollers 7, which partially enclose the rollers (Fig. 3). The space between the fingers is so dimensioned that the rollers can rotate in the cage and can move to a limited extent in the radial direction.

The ring-shaped part 10 and the fingers 11 form a complete unit, the construction and manner of operation of which is already dealt with in the general description above. The cage 6 has an axial bore 1 3 which, in the region of the ring-shaped part 10, is completely enclosed thereby and in the upper part is bounded by the wall surfaces 1 4 of the fingers 11. The wall surfaces 14 are formed cylindrically to a nominal diameter lying, however, in the unstressed condition on a conical surface of an extremely narrow cone, that is to say the upper ends 1 5 of the fingers 11 are slightly inclined inwardly in the direction towards the axis of 'the cage.

In the wall surfaces 14 of the fingers 11 are embedded metal inserts projecting slightly from the wall surfaces, which have the form of thin cylindric- l pegs. The axial length of the metal inserts corresponds substantially to the axial length of the rollers 7.

The ring-shaped part 10 is bounded between the fingers 11 by abutment surfaces 1 8 for the rollers 7 and is provided at three places with axially and radially extending stiff- ness-reducing slits 19, which give the cage a flat spring characteristic.

From Fig. 3 it is seen that the opening in the housing 1 is bounded by three ramp surfaces 1 7 acting on both sides in the radial direction, as is known in devices of this type.

The ramp surfaces 1 7 are bounded by cylindrical surfaces, the radius of which is smaller than the radius of the surface that encloses all the ramp surfaces, and the axes of which are displaced from the axis of symmetry of the complete apparatus. As shown, the driver/extractor apparatus works in both directions of rotation. On the periphery of the bore 1 3 is shown in dashed lines the greatest circumference of a stud, otherwise not shown, which corresponds to the so-called nominal diameter of the apparatus. When engaging the apparatus on this stud, first the metal inserts 1 6 come into the position in which the fingers 11 of the cage 6 are slightly elastically spread out.The metal inserts 1 6 form with the cage 6 a unit which elastically engages the stud so that the cage is held frictionally against movement in the peripheral direction of the stud. If now the housing 1 is rotated with respect to the cage 6 in either direction, the ramps 1 7 acting in the radial direction press the rollers 7 against the stud (dashed circle). This movement comes to a halt after only slight rotation of the housing 1, whereupon now the whole apparatus according to Fig. 3 is driven in the direction of rotation of the housing 1.

Fig. 2 shows the cage 6 as it appears from a position at the head of Fig. 1. The idea of the elasticity is in regard to the previously known metal cages to be understood in this sense namely that the cage or its fingers 11, in applying the apparatus to a stud by means of the usual manual forces, can be readily sprung open. The necessary flexibility is to be found in most thermoplastic materials, particularly inherently in polyamides, and also by the wall thicknesses shown in the drawings.

When using metallic raw materials for the cage, these can naturally by deliberate reduction of the cross-section, for example at the point where the ring-shaped part 10 joins the fingers 11 be so weak that the requires measure of inherent flexibility is provided.

The inner diameter of the ring-shaped part 10 is made exactly to the nominal diameter.

In axial projection the ends of the fingers 11 fall within this internal diameter in their stressfree state. The elastic cage has thereby the additional advantage that the stud can be carried about in the driver/extractor.

Claims (7)

1. Driver/extractor apparatus for studs or the like, having a substantially rotationally symmetrical housing having a plurality of ramp surfaces acting in the radial direction spaced on its inner periphery, with rollers rolling on the ramp surfaces, which are carried so as to be movable radially and rotationally in a cage coaxial with the housing, which has a coaxial bore with a nominal diameter that accepts the stud and comprises a ringshaped part and a plurality of fingers extending axially parallel therefrom, between which the rollers are carried, and also with friction surfaces in the bore that are flexible in the radial direction and which drivingly engage the cage and the studs, characterised in that the cage is formed elastically and the ends of the axially parallel fingers remote from the ring-shaped part fall within the nominal diameter of the bore.

2. Driver/extractor apparatus according to claim 1, characterised in that the cage is of a flexible thermoplastic material.

3. Driver/extractor apparatus according to claim 2, characterised in that the cage is of a polyamide.

4. Driver/extractor apparatus according to claim 2, characterised in that the rollers are cylindrical rollers and the axially parallel fingers are bounded by cylindrical surfaces in the direction towards the rollers, which partially enclose the rollers.

5. Driver/extractor apparatus according to claim 1, characterised in that in the walls of the fingers bounding the bore are embedded metal inserts that project from the walls.

6. driver/extractor apparatus according to claim 1, characterised in that the ring-shaped part is provided with stiffness-reducing slits between the fingers extending from abutment faces for the rollers.

7. Driver/extractor apparatus according to claim 6, characterised in that the slits run in axial and radial directions.