WO1995002771A1

WO1995002771A1 - A female part that can be locked in selective positions on a round rod

Info

Publication number: WO1995002771A1
Application number: PCT/SE1994/000657
Authority: WO
Inventors: Torgny Jansson
Original assignee: Tormek Ab
Priority date: 1993-07-16
Filing date: 1994-07-01
Publication date: 1995-01-26
Also published as: GB9525846D0; SE9302442L; SE9302442D0; DE4495113T1; GB2294497B; JPH09500196A; SE501268C2; GB2294497A

Abstract

A female part (1) can be locked in selected position on a round rod (5). The female part includes a hollow passageway (2) into which a locking screw (3) can be screwed in a generally radial direction into engagement with the rod (5). When seen in cross section, the passageway (2) includes two flat surfaces (6) which slope towards one another symmetrically in relation to a diametrical plane (7). The angle (α) defined by the surfaces with the plane (7) lies between 2.5° and 15°. The locking screw (3) enters the passageway (2) in the wider part between the surfaces (6).

Description

A female part that can be locked in selective positions on a round rod

The present invention relates to a female part which embraces a round rod and can be locked in selected positions relative thereto. The female part is provided with a locking screw which can be screwed in a generally radial direction in relation to the hollow passageway of the female part and therewith be brought into engagement with the round rod.

There is a need in many instances to lock an object to a round rod or to lock a round rod to a fixed object against movement in an axial direction and against rotational movement. Examples of such machine elements include the grinding supports used in grinding machines, lamps fitted to scenic lighting systems for instance, music stands, bed reading tables, stands for orches¬ tral percussion instruments, walking frames and roller-support¬ ed walking frames, mechanisms for adjusting the height of chairs, stools, workbenches, etc., devices for adjusting the position of rearview mirrors in caravans, camera stands, etc. All of these cases include in common a round hollow passage in one part and a coacting round rod or axle in the other part. Several solutions are known for locking these parts together, of which the most common solution involves the use of a screw threaded hole which extends in towards the centre of the hollow passageway and into which a knob-provided screw can be screwed into abutment with the round rod. The tightening force required to lock said parts together varies widely. The locking effect achieved with this solution, however, is insufficient to with- stand large torsional forces. The screw can be given a sharp point or be made annular, in order to lock the parts more positively relative to one another against twisting and axial movement. This solution, however, damages the rod, while the point or the annular edge at the end of the screw becomes worn and loses its intended locking effect. Other solutions involve providing the axle or rod with holes or recesses in which a screw or cotter engages. This solution, however, results in fixed positions of the parts in relation to each other, and also makes manufacture more expensive. The axle may also be ground flat over a given part thereof, with the screw acting against the flat surfaces thus provided. The other solutions include providing the axle with grooves, which also means in this case that fixed positions are solely obtained in a rota¬ tional or twisting direction. The female part may also be slotted, so as to enable it to be clamped around the round rod with the aid of a screw. A considerable tightening force is required, however, to overcome the resistance of the material from which the female part is made. Other solutions include the use of a chuck, although this solution is not a positive solu- tion and is also relatively expensive. The use of a V-shaped clamp or hasp and other types of simpler clamps and hasps has also been proposed.

In summary, it can be said that there is no solution which fulfills the requirement of a simple device by means of which a strong and durable locking effect can be achieved between a female part and a round rod with the application of a moderate locking force between said parts. The invention as defined in the characterizing clauses of respective following claims provides locking of a female part to a round rod in an effec¬ tive and simple manner.

The invention will now be described in more detail with refer¬ ence to an exemplifying embodiment thereof and also with refer- ence to the accompanying drawings, in which Figure l is a principle schematic illustration of the invention; Figure 2 is a curve which illustrates the increase in locking force in percentage in relation to the angle between the sloping surfac¬ es of the hollow passage, Figure 3 is a schematic perspective section view of a grinding support for grinding machines, in which the inventive concept is applied, Figure 4 is a view from above of the grinding support shown in Figure 3; and Figure 5 illustrates the inventive female part shown in Figure 1 supplemented with a backing-off screw.

Figure 1 illustrates the principle of the present invention and shows a female part 1 in the form of a sleeve having a hollow passageway 2. The female part 1 includes a screw threaded hole which extends generally towards the centre of the passageway 2 and into which a screw 3 can be screwed. The screw 3 is provid¬ ed with a knob 4 for turning the screw. The reference numeral 5 identifies a round rod onto which the female part can be locked against rotational and axial movement.

As will be seen from the figure, the passageway 2 includes two mutually opposing flat surfaces 6 which are inclined symmetri¬ cally relative to one another and therewith to a diametrical symmetry plane 7 through the passageway. The angle of inclina¬ tion between the symmetry plane 7 and respective flat surfaces 6 is referenced .

When the round rod 5 is inserted in the hollow passageway 2 of the female part 1, the rod is accommodated in the passageway 2 in linear abutment with the flat surfaces 6. When the female part 1 is to be locked to the rod 5, the screw 3 is screwed into engagement with the rod 5 therewith urging the rod between the sloping surfaces 6. The screw 3 enters the passageway in the wider part thereof between the surfaces 6, as shown in Figure 1.

Figure 2 shows that the locking force will increase with small¬ er angles α. The increase in locking force is the increase in locking force in relation to conventional locking when using a hollow passageway of circular cross-section and a given tight- ening force. It will be seen from the curve that the locking force increases drastically at an angle a of between 15° and 3°. The angle is chosen in accordance with the tightening force desired in relation to locking force, and is also depen¬ dent on the surface hardness and mechanical strength of the material used. The harder the material the smaller the angle α, in other words a critical smallest angle a is found for each material. In order to avoid this locking, it is therefore necessary for a larger angle to be chosen. When the greatest possible locking force is desired and there is no need to frequently release the locked components, there is chosen an angle which is so small as to lock the components together. To enable these components to be released from one another, there may be provided a backing-off screw 10 which acts in a direc¬ tion opposite to the screw 3 so as to loosen the round rod 5 from its pressed-in position between the sloping surfaces 6, see Figure 5.

Figures 3 and 4 illustrate an advantageous practical applica¬ tion of the invention in the form of a grinding support 8 which includes a grinding support plate 9 and which is used in con¬ junction with grinding machines for tool grinding purposes as shown at 11, for instance. The grinding support 8 is a single- piece extruded aluminium structure having a through-passing hollow passageway 2 which includes the flat, sloping surfaces 6. As in the Figure 1 illustration, the references 3 and 4 identify respectively a screw and a knob. Particularly with this type of machine element, it is necessary to positively lock the position and inclination of the support plate 9 in relation to the grinding stone, indicated at 12, in order to achieve a proper result. As a result of the present invention, the grinding support can be locked in position effectively by applying a very light tightening force through the knob 4. Because of the relatively large surface abutment between the round rod 5 and the surfaces 6, the components are not subject- ed to any noticeable wear and the position of the grinding support 8 can be frequently changed without causing any prob¬ lem.

It will be understood that the support plate 8 in the hollow passageway 2 is supported for axial and rotational movement on a carrier arm in the form of a round rod attached to the grind¬ ing machine stand, not shown.

It will also be understood that the female part must be made of a sufficiently rigid material which will not yield when the screw 3 is tightened. It will also be understood that the screw may be of a kind which is turned with the aid of a tool instead of a knob. The term "round rod" shall also be understood to include a tube or pipe.

Claims

1. A female part (l) which can be locked in selected positions on a round rod (5), wherein a locking screw (3) can be screwed into the hollow passageway (2) of the female part in an essen¬ tially radial direction so as to engage the rod (5), c h a r a c t e r i z e d in that when seen in cross-section the hollow passageway (2) includes two flat surfaces (6) which slope towards one another symmetrically in relation to a dia¬ metrical plane (7), wherein the angle (α) defined by said surfaces with the plane (7) lies between 2.5° and 15°; and in that the locking screw (3) enters the passageway (2) at the wider part between the surfaces (6) .

2. A female part according to Claim 1, c h a r a c ¬ t e r i z e d in that the said female part is formed integral¬ ly with a grinding support plate (8) intended as a support in tool grinding operations.

3. A female part according to Claim 2, c h a r a c ¬ t e r i z e d in that said female part (1) is extruded togeth¬ er with the grinding support plate (8) .

4. A female part according to any one of Claims 1-3, c h a r a c t e r i z e d by a release screw (10) which can be screwed into the female part (1) in a part thereof located generally diagonally opposite the locking screw (3).