EP0004769A2

EP0004769A2 - A games racquet stringing apparatus

Info

Publication number: EP0004769A2
Application number: EP79300545A
Authority: EP
Inventors: Clifford Boyne Gibson; Ronald Jack Langworthy
Original assignee: RECT IT Pty Ltd; U-Rect-It Pty Ltd
Current assignee: U-RECT-IT PTY Ltd; RECT IT Pty Ltd
Priority date: 1978-04-03
Filing date: 1979-04-03
Publication date: 1979-10-17
Also published as: EP0004769A3

Abstract

In order to permit stringing by non-skilled users securing means (2, 3, 4, 7, 8, 9, 10, 11, 12) is provided for holding a racquet frame (34, 37) for permitting adjustment of the racquet head (34) and for positioning a selected stringing hole relative to a pulling means (24, 28) so as to permit tension to be applied by the pulling means (24, 28) to stringing material (39) extending from said hole and means (23) is provided for driving the pulling means (24, 28) to apply a predetermined tensioning force to the stringing material (39).

Description

This invention relates to games racquet stringing and nore particularly to a machine which effectively simulates the conventional manual stringing operation.
In the stringing of such sporting articles as tennis racquets, which have a continuous closed-loop type frame at one extremity of a shaft, it is necessary to be able to thread a filament via oppositely registering holes in the said frame so that the resulting convolutions of one such filament constitute a series of rows and a similarly threaded, second like filament, interwoven with the first, constitutes a further series of rows, usually substantially at right angles to the first series, to thereby form a taut network.
The first series of rows, parallel to the axis of the shaft, are often termed the 'main strings' and the second series, normal to the first series, the 'cross strings'. To achieve the desired tautness it is thus necessary to provide sufficient tension in each separate string of the network as each length of stringing material is threaded backwards and forwards from a starting point to a finishing point after being repeatedly looped and returned across the frame.
Moreover, it is highly desirable to ensure that all the resulting strings have approximately the same tension to thereby produce a uniformly taut network, having due regard to the available stiffness, and also the stability, of the frame itself, to avoid distortion of the latter.
It is, of course, known to carry out the above-noted steps manually, and the entire process may normally require 20 minutes or more of a competent tradesman's time for the stringing of a tennis racquet. However, the probable normal training period for such a tradesman is of the order of six months and it is rare for untrained or partially trained persons, or amateurs, to be able to carry out the operation so as to achieve the desired uniformity of tension with any degree of success.
The invention seeks to provide apparatus which will permit a stringing operation to be undertaken by any reasonably dextrous but not necessarily trained person.
Thus there is provided, according to the present invention, a games racquet stringing apparatus comprising securing means for holding a racquet frame and for permitting adjustment of the racquet head and positioning of a selected stringing hole relative to a pulling means to permit tension to be applied by the pulling means to stringing material extending from said hole and means for driving the pulling means to apply a predetermined tensioning force to the stringing material.
The advantage that is offered by the invention is mainly that it permits a person who is untrained in the craft of racquet stringing to achieve results of craftsmanlike quality in approximately the same period of time.
The securing means may be rotatably mounted and arranged to permit holding horizontally and setting of the angular disposition of a games racquet.head. The pulling means may comprise a pulley and means for driving the pulley via A slipping clutch arrangement adapted to slip at a predetermined load.
Preferably the pulley is driven by a fractional-horsepower electric motor which is reversible; ideally the preset load can be varied according to requirement, and the pulley may be a frusto-conical one for best results.
There also may well be provided a horizontally adjustable string-holding clamp adapted to grip and hold the length of stringing material at a tension predetermined by the slipping clutch arrangement; advantageously, this clamp may be mounted upon a slide which is rotatable about the central spindle of the rotatable means.
In order that the reader may gain a better understanding of the present invention, hereinafter is described a preferred embodiment of it, by way of example only and with reference to the accompanying drawings, in which:-

Figure 1 is a schematic perspective view of a games racquet stringing apparatus constructed in accordance with the present invention, including a discrete, second string-gripping clamp;
Figure 2 is a schematic view similar to Figure 1 but which shows the beginning of a stringing operation; and
Figure 3 is a schematic side elevation of the apparatus shown in Figures 1 and 2, but cut away where necessary to aide understanding of the construction.

Figure 1 shows the games racquet stringing apparatus according to the present invention; on a base plate 1 there is mounted rotatable means for holding horizontally and determining the angular disposition of a games racquet head. This means is comprised of a turntable 2 having first and second support rods 3, 4 oppositely radially directed outwards therefrom, to which, in turn respective lockable but releasable clamps 5, 6 attach a pair of bows 7, 8. These bows 7, 8 are curved and extend upwardly above the level of baseplate 1 and terminate in inwardly directed free ends to which respective pairs of padded jaws 9, 10 and 11, 12 are fastened. These jaws are closable, with selected spacings therebetween, via some suitable adjustment means such as the screw fastenings 13, 14 which allow the respective pairs of the said padded jaws to be brought together to grip the opposite extremities of the head of a games racquet.
Turntable 2 is manually rotatable about a central spindle 15 and is lockable in any desired angular position by means of conventional locking device 16.
Mounted also with respect to spindle 15 and rotatable thereupon there is a second turntable 17 which, in turn, is associated with a slide 18 having a central longitudinal slot 19 upon one end of which a column 20 is mounted. At the upper end of column 20 there is a string-holding clamp 21, the registering jaws of which may be brought lockably together about a filament such as racquet stringing material of gut or plastics by depressing a handle 22 which causes an over centre, camming-surface device to clamp said jaws together. This lever also acts to clamp turntable 17 and slide 18 firmly to spindle 15. Thus column 20 is horizontally adjustable into a wide variety of positions with respect to baseplate 1. Also mounted upon baseplate 1 is a drive unit 23. In the drive unit 23 there is a fractional-horsepower motor (not shown) which is reduction-geared to drive a pulley 24 at about 1C revolutions per minute via a gearbox and slipping clutch adapted to slip at a preset load. The gearbox and clutch are not shown but are of known type. The preset load is capable of being varied according to requirement, in known manner, and a tension selection dial and adjustment knob assembly 24 is, to this end, provided on the drive unit 23. Ideally, assembly 25 permits string tensions of between 5 and 35 kgs to be selected at will according to the kind of racquet desired to be strung. There is also provided an on-off-on reversing switch 26 and an indicator lamp 27.
Pulley 24 is ideally frusto-conical in shape and advantageously may have a suitable, flexible sleeve 28, made of such material as soft plastics, raw latex or the like having a thickness of perhaps 3/16 of an inch. Such materials should possess a natural colour and should not mark the stringing material undesirably. This material is selected by way of a compromise between a good grip on the stringing and a long life for the sleeve, without undue cutting of the latter. In any case, if it is so damaged, the sleeve may be easily cut away from the pulley and replaced. A replacement sleeve may be easily affixed to the pulley by such material as contact cement or the like.
To further assist an unskilled operator or a non-tradesman the pulley 24 is frusto-conical in shape, with a taper of the order to 4 to 5% so that the loop made in the stringing tends to 'climb up' the taper somewhat, just before the slipping clutch action stops the rotation of pulley 24.
As an aid to the firm holding of a length of stringing material, just prior to beginning the threading and tensioning operations, there is also provided a discrete, second string-gripping clamp generally referenced 29. Clamp 29 has spring- biased jaws 30, 31 tightenable about a length of racquet-stringing material by means of wing- nut 32. Extending upwardly from jaw 30 there is a mushroom-headed peg 33; the use of clamp 29 will be later described herein.
Turning now to Figures 2 and 3, the stringing operation will be described with reference thereto, but steps common also to prior art stringing-frame techniques may be disregarded; also, integers already having been referenced in connection with Figure 1 will be given those same numerals.
In use, therefor, bows 7, 8 are moved inwardly or outwardly along the respective supporting rods 3, 4 in order to accommodate, between clamping jaws 9, 10 and 11, 12, a games racquet which it is desired to string. Clamps 5, 6 are clamped on rods 3, 4 by wing-nuts 35, 36, (Figure 3). Turntable 2 is then rotated manually until shaft 37 is lying adjacent drive unit 23, whereupon said turntable is locked onto spindle 15 by the operation of locking device 16. A length of stringing material is taken (usually a standard length) folded evenly in halves and each end threaded through a top end centre hole. The ends of these two halves 38, 39 are then threaded through the two 'throat' holes which are on each side of the frame's shoulder. The left-hand half 38 now must be secured in relation to head 34, and to this end it is passed once or twice about peg 33 of clamp 29 then firmly clamped within its jaws. This is to prevent end 38 from slipping back through the holes when tension is eventually applied to the other end 39 as will be iescribed hereinafter. The mushroomed end of peg 33 prevents damage to the frame of the racquet.
f_he first two strings of the racquet are thus laid in; the free end of the side 39 is then taken and looped once about the sleeve 28 on pulley 24, crossing it upon itself to prevent slipping.
The desired tension is then selected, using tension selection assembly 25, and switch 26 is closed so as to energise the motor which turns the pulley 24 slowly via the high ratio reduction-gear train. The slowly revolving pulley thus imparts a growing tensional force to end 39 until the slipping clutch causes the rotation of pulley 24 to cease when the predetermined tension in free end 39 has been reached. As best seen in Figure 3, the portion of side 39 within head 34 is then caused to be gripped, closely adjacent to its exit position at the throat hole, by the jaws of clamp 21, after horizontally adjusting turntable 17 and associated slide 18 so as to bring column 20 to a suitable angular position as shown, whereupon the assembly is locked rigid, with respect to base 1, by depressing handle 22. Switch 26 is then thrown in the opposite sense whereupon pulley 24 contra- rotates to an extent sufficient to cause slipping of the single turn of side 39 which, however, is kept taut at the desired tension by its being effectively held in the jaws of clamp 21. Free end 39 thus disengages readily from pulley 24, ready for the next step. The end of side 39 is then threaded through the next outer hole at the shaft end of head 34 and the top end registering hole, clamp 21 released and turntable 2, after releasing it through the operation of locking device 16, manually turned through 180° to bring the racquet to a position in which the above operational steps may be repeated.
When the right hand side 39 has been used to string the right-hand side of the racquet head 34, the remaining portion of side 39 is tied off using the standard racquet hitch. Then discrete clamp 29 is removed, and the other side of the racquet is strung as before with side 38. With the 'main strings' now completed, turntable 2 is now rotated through 90° or any other angle at which interweaving of the strings may be recommendable. Starting at the shaft end of the racquet the above- mentioned successive tensioning and clamping steps are repeated so as to permit a similar threading operation, but now interweaving the 'cross strings' with the aforementioned 'mainstrings' in known manner.
Leather or plastics tabs may be employed adjacent the shaft end of the head as is the usual practice, and, as with prior art stringing techniques, strings running together within slots should be laid side-by-side to prevent damage. Again, as with known techniques, a tool such as a blunted awl may be employed to straighten each cross string; and tying-off is effected in accordance with standard practice.
If all the above steps are carried out it will be observed that the 'main strings' and 'cross strings' result in a network of strings withing which each separate string may be given the same preset tension, being that indicated upon a dial - or other calibrated device - of assembly 25 which determines such tension in accordance with the energy imparted to the fractional-horsepower electric motor enclosed within drive unit 23. Ilowever, at all times, the action of handle 22 which temporarily engages clamp 21 about the lengths of stringing material, and subsequently releases it, is similar to that which would be imparted by the hand of a skilled operator and the resulting clamping action, together with the rapid digital engagement and dis-engagement of the lengths of stringing material with respect to pulley 24, ensures a similar result.
As had been previously stated, the lengths of stringing material are easily removable from the flexible sleeve 28; thus, when the motor is de-energised, a slow return motion of pulley 24 occurs with a resultant quick release of the trapped turn of the length of stringing material, which meanwhile is held firmly within the racquet frame by clamp 21, so that the free end is made rapidly ready for the next stringing step. Nevertheless, high speed handling of the lengths is possible owing to the tapered soft surface 28 of pulley 24. The motor is preferably equipped with a suitable micro-switch which shuts off the motor very rapidly when the clutch first slips.
The preset tension means is preferably adjustable to select the tension to suit different kinds of stringing material and/or differing frame materials and designs. An advantage of the invention is the capacity of clamp 21 to grip the lengths firmly at a position close to the inside of the frame to permit accurate manipulations such as tying-off or the like.
As will be readily understood, the purpose of the present invention is generally to string games racquets such as those used for tennis, lawn tennis, squash, badminton, racquetball and similar games. To this end, the universal adjustability of the apparatus adapts it for use in stringing a wide variety of shapes and sizes of frames, for example, any length, width, depth and eccentricity is readily accommodated by reason of the various adjustment means. Moreover, the grip imparted by clamp 21 to the stringing material may be adjusted by varying the degree of effectiveness of an overcentre mechanism in column 20 using a screw adjustment device operable from below the operating region of handle 22, thereby allowing a firm grip upon different grades or gauges of stringing material, which may be of natural gut or of 'synthetics'. This adjustment is desirable since too loose a grip will cause the material to slip, whereas too tight a grip will cause it to be scored or even severed.
It will be appreciated that although the pulling means for applying tension to the stringing material in the described embodiment comprises a pulley any other suitable means for applying a predetermined pulling force to the stringing material could be employed for example the drive unit could be arranged to move a tensioning arm away from the racquet frame which arm may be provided with a clamp for securing the stringing material thereto.
From the above it will be seen that apparatus constructed in accordance with the present invention is readily operated by unskilled or semi-skilled persons to achieve results at least comparable with those achieved by a tradesman but with considerably less effort (even if no actual saving in time is achieved) owing to the close simulation of the well-known hand stringing operation which is possible when using the present apparatus.

Claims

1. A games racquet stringing apparatus comprising securing means (2, 3, 4, 7, 8, 9, 10, 11, 12) for holding a racquet frame (34, 37) and for permitting adjustment of the racquet head (34) and positioning of a selected stringing hole relative to a pulling means (24, 28) to permit tension to be applied by the pulling means (24, 28) to stringing material (39) extending from said hole and means (23) for driving the pulling means (24, 28) to apply a predetermined tensioning force to the stringing material(39).

2. A games racquet stringing apparatus, as claimed in Claim 1, wherein the securing means is rotatably mounted and arranged to permit holding horizontally and setting of the angular disposition of a games racquet head, and the pulling means comprises a pulley (24) and means (23) for driving the pulley (24) via a slipping clutch arrangement adapted to slip at a predetermined load.

3. A games racquet stringing apparatus as claimed in Claim 2 including adjustment means (25) for effecting presetting of said predetermined load.

4. A games racquet stringing apparatus as claimed in Claim 2 or 3, wherein the means (23) for driving the pulley (24) is reversible.

5. A games racquet stringing apparatus as claimed in any one of the Claims 2 to 4, wherein said pulley (24) is frusto-conical in shape.

6. A games racquet stringirg apparatus as claimed in any one of the preceding Claims, wherein there is also provided a string-holding clamp (21) adapted to grip and hold the stringing material (39) under said predetermined tension.

7. A games racquet stringing apparatus as claimed in Claim 6, wherein said adjustable clamp (21) is mounted upon a slide (18) which is rotatable about a spindle (15).

8. A games racquet stringing apparatus as claimed in any one of the preceding claims wherein there is provided, as an adjunct, a discrete string-gripping clamp (29) adapted to prevent a length of said stringing material from slipping back through a hole or holes in the racquet head (34), through which it has been threaded, when tension is applied to the other end thereof.

9. A games racquet stringing apparatus as claimed in any one of the preceding claims, wherein the means (23) for driving the pulling means (24, 28) is a fractional-horsepower electric motor.