United States Patent 3837649

A pocket-sized device for stringing tennis rackets is held against the racket frame by a newly inserted racket string, wound around one end of the operating handle. A torsion spring connects the two ends of the handle. Relative deflection of the ends gives a visible indication of the amount of string tension caused by hand-twisting of the other end of the handle. A wedge is slid against the handle to maintain the string tension, while an awl is inserted into the frame hole. The operation is repeated for each string to be installed.

Application Number:
Publication Date:
Filing Date:
Primary Class:
Other Classes:
International Classes:
A63B51/14; (IPC1-7): A63B49/00
Field of Search:
273/43,73A,73B,73D,73E 73
View Patent Images:
US Patent References:
2352730Tool for stringing tennis rackets1944-07-04Miessner
2043814Racket string tightening machine1936-06-09Saladino
2032217Tensioning device1936-02-25Matthews et al.

Primary Examiner:
Pinkham, Richard C.
Assistant Examiner:
Brown, Theatrice
I claim

1. In a tension adjusting device of the type that winds a flexible strand from a sports racket frame around a rotatable member connected through energy-storing means to a handle, in which the amount of handle deflection is related to the amount of tension in the flexible strand; the improvement comprising:

2. Apparatus according to claim 1, wherein said rotatable member is held against said upper wall of said support member by tension in said flexible strand, and said outer member is adapted to pivot about said lower wall of said support member to lift said rotatable member away from said upper wall of said support member, thereby increasing the tension in said flexible strand.

3. Apparatus according to claim 1 including a wedge adapted to slide between said vertical wall of said support member and said rotatable member in such a way that the tension in said flexible strand is maintained.

4. Apparatus according to claim 3, wherein said wedge is adapted to slide in two directions along said vertical wall of said support member, so that tension in said flexible strand is maintained regardless of the direction in which said strand is wound around said rotatable member.

The present invention relates to devices for pulling flexible strands past an attachment area, and for holding a desired tension on the strand while making the attachment. My copending application, Ser. No. 234,476 filed 3 - 13 - 72, and since abandoned, describes a tension indicator. That device is used to check tension existing in strands already fastened at both ends.

This type of action is used when a tennis racket, or the like, has a broken string replaced. At present, the insertion of a new string at a known tension can only be accomplished with the aid of a heavy and expensive machine found only in professional tennis shops. These are not usually nearby, and the repair can seldom be done while the customer waits.

The presently available stationary machine is used as follows: The racket frame is clamped at two points, and the strings on each side of a broken one are pulled outside the frame and tied off. A new one has a knot tied at one end, and the other end is woven thru the strings that cross its path. The end is then passed thru a hole in the frame and grasped by a movable clamp. The motion of this clamp increases the tension in the string and loads a spring at the same time. When the tension reaches a pre-set value, the spring trips a brake that holds the string in this position while an awl is inserted into the frame hole. The string clamp can then be released, the string end cut and tied, and the awl removed.

An important object of my invention is to provide an inexpensive and pocket-sized device for replacing strings in tennis rackets and the like.

Another object is to provide a tension adjuster for flexible strands that can be operated by one hand.

An additional object is to provide a device for applying tension to racket strings, with the tension indicator always readily visible.

A further object is to provide a strand tensioning device that is held in place by the tension in the strand.

Still another object is to provide simple means for maintaining the tension in a flexible strand at a desired level, while allowing hands to be freed for fastening the end of the strand to an external frame.

A still further object is to provide a strand tensioning device with a variable mechanical advantage for the application of higher forces.

Other objects and advantages of the present invention will become apparent from the following detailed description of specific embodiments thereof, when read in conjunction with the accompanying drawings.

Briefly the preferred embodiment of the present invention comprises a rotatable member around which is wound the end of a tennis racket string after passing thru a hole in the racket frame. An outer member acts as a handle to wind the string tight, with the rotatable member turning in a support member that is then held against the racket frame by the string tension.

The handle is flexibly connected to the rotatable member by a flat spring, so that an increase in tension on the racket string, wound around the end of the rotatable member, causes a torsion deflection of the flat spring. An indicator attached to the rotatable member shows the amount of motion on a scale attached to the handle. When the string tension reaches the amount desired, an awl is inserted into the frame hole with the other hand, and the handle released. The string is then cut and tied off, and the awl removed.

Referring now to the drawings, FIG. 1 is a pictorial view showing the device in position against a racket frame, ready for tensioning of an attached string.

Referring again to FIG. 1, tennis racket frame 1 contains flexible strands 2 and is shown for reference only. Rotatable member 4 is identified at both ends, and is journaled in support member 7 by a hole 16 in the lower wall and a hole 15 in the upper wall, with this wall relieved for half the periphery of member 4. One strand 3 has its end placed in notch 5 and is wrapped around member 4 to cause tension in the strand, to compress resilient member 6 to conform to surfaces of varying radii on frame 1.

Outer member 11 is grasped as a handle and twisted in the direction of arrow A to increase tension in strand 3. Block 12 is attached to outer member 11 by rivet 13. Twisting motion of member 11 causes torsional deflection of energy-storing spring 10, which has one end confined in a slot in block 12 and the other in a slot in member 4. Slot 9 in member 11 moves past pin 18, which is inserted into member 4, when spring 10 deflects. The amount of tension in strand 3 can be read from indicia on scales 8 attached to both sides of member 11. Support member 7 has two notches 14 cut in the vertical wall, to clear strand 3 entering from either side of rotatable member 4. Wedge 17 is slid in the direction of arrow C to hold tension in strand 3 as shown.

Higher tension forces can be created in strand 3 by pushing the lower end of member 11 in the direction of arrow D. This action lifts the upper end of member 4 out of hole 15 in the upper wall of support member 7, and pivots it about hole 16 in the lower wall. The same motion serves as a quick release, when the rotational position of member 4 has been maintained by wedge 17, between member 4 and support member 7. In this case, pushing the end of member 11 in the direction of arrow D reduces the holding force of wedge 17, and allows it to be slid easily in the direction opposite to that of arrow C.

The divisions on scale 8 are most easily worked out empirically. This can be done by clamping member 11 in a horizontal position and suspending various weights from a strand wrapped around member 4, working the position of pin 18 for each condition.

The preferred embodiment of my invention uses a flat spring to store energy as a torsion bar. However, a round wire can also be used, and can have twice the length within the same handle size by doubling back in a "U" shape, with ends attached to members 4 and 11 being adjacent. A helical spring can be used in torsion, or in compression or tension with a cam surface moving member 4 axially as it turns. A flat spring can also be used in bending, with a handle portion similar to member 11 except extending perpendicularly to the axis of member 4.

It is therefore to be understood that the foregoing disclosure is given as an example only, rather than by way of limitation, and that without departing from the invention, the details may be varied within the scope of the appended claims.