Title:
Racket stringing machine
United States Patent 3918713


Abstract:
A racket stringing machine which includes a turntable for supporting the racket to be strung in a given plane, a capstan for receiving and tensioning the string being strung on the racket and a motor mounted on a rotatable bracket and coupled to the capstan for rotating the capstan to tension the spring, the tension of the string causing the motor bracket to rotate against a resilient bias to operate a switch when the preselected amount of tension is applied to the string thereby deenergizing the motor.



Inventors:
KAMINSTEIN BERNARD
Application Number:
05/451428
Publication Date:
11/11/1975
Filing Date:
03/15/1974
Assignee:
KAMINSTEIN; BERNARD
Primary Class:
Other Classes:
73/862.43, 73/862.44, 254/275
International Classes:
A63B51/14; (IPC1-7): A63B51/14
Field of Search:
273/73A,73B 73
View Patent Images:
US Patent References:
3728502ELECTRIC HOIST OVERLOAD PROTECTION DEVICE1973-04-17Hawkins et al.
3675482AUTOMATIC TENSION SENSING APPARATUS FOR BELT CONVEYOR1972-07-11Hewitt
3635080RACKET-STRINGING MACHINE WITH AUTOMATIC LOCKING1972-01-18Krueger et al.
3538763PNEUMATIC NUT-RUNNER HAVING A TORQUE SENSING DEVICE1970-11-10Amtsberg et al.
3511502MACHINES FOR THE STRINGING OF TENNIS RACKETS1970-05-12Spenle
3441275RACKET STRINGER1969-04-29Held
3302950Racket stringing machine1967-02-07Hartman
3052878Alarm for logging systems1962-09-04Berry
2636953Safety switch1953-04-28Hunt
2309849Racket stringing device1943-02-02Kausal et al.
2292738Safety stop mechanism for hoisting machines1942-08-11Bonney
2262110Racket stringing device1941-11-11Mineck
1962865Apparatus for stringing tennis and other rackets1934-06-12Goodhall et al.
1877171Switch control mechanisms1932-09-13Hallenbeck



Primary Examiner:
Apley, Richard J.
Attorney, Agent or Firm:
Lindenberg, Freilich, Wasserman, Rosen & Fernandez
Claims:
What is claimed is

1. A racket stringing machine comprising:

2. The racket stringing machine of claim 1 wherein said capstan means includes a sleeve of resilient material for preventing slippage of said string during tensioning.

3. The racket stringing machine of claim 1 wherein said means for clamping the segment of the string includes:

4. The racket stringing machine of claim 3 wherein said rod is offset from the center of said turntable.

5. The racket stringing machine of claim 4 wherein said clamp base includes means settable for fixing said clamp base in four orthoginal positions with said rod parallel to the main and cross strings of a racket clamped to said turntable on either side of the center of said turntable.

6. The racket stringing machine of claim 3 wherein said clamping member includes a block member slideably and rotatably mounted on said rod and a pair of coacting jaws pivotally mounted on said block member.

7. The racket stringing machine of claim 6 wherein said jaws include spring means for biasing them towards a closed position.

8. The racket stringing machine of claim 7 further including means for fixing said turntable in selected positions with respect to said clamp base.

9. A racket stringing maching comprising:

10. The racket stringing machine of claim 9 further including means for moving said switch means towards or away from the rest position of said actuating portion of said bracket for varying the distance which said actuation portion must travel against bias to actuate said switch means and thereby vary said preselected tension.

11. The racket stringing machine of claim 10 wherein said means for moving said switch means includes a wheel on which said switch means is mounted the plain of said wheel being substantially parallel to the plain of motion of said actuating portion and means for rotating said switch means.

12. In a racket stringing machine, the combination comprising:

13. The racket stringing machine of claim 12 further including means for moving said switch means towards or away from the rest position of said actuating means for varying the distance which said actuating means must travel against bias to actuate said switch means and thereby vary said preselected tension.

Description:
BACKGROUND OF THE INVENTION

This invention relates generally to machines for stringing sports rackets and more particularly to machines for stringing rackets which apply a settable uniform tension to the string of the racket.

The stringing of sports rackets, such as used for tennis or squash, is quite arduous and time consuming when done by hand. A number of racket stringing machines are available but all of them have serious drawbacks in terms of cost, complexity or mode of use which prevent them from being widely accepted. A typical one of these machines is that taught in U.S. Pat. No. 3,635,080 which describes a very complex racket stringing machine in which the force for tensioning the string is generated by a hydraulic cylinder. Besides the expense and complexity inherent in the use of hydraulic systems with the associated pumps and liquid reservior and supply systems, the machine has the added disadvantage that the hydraulically actuated string tensioning clamp can be moved only a limited distance. Thus, either the throw of the hydraulic cylinder must be quite large, thereby increasing the size and cost of the machine, or the string must be pretensioned, either manually or by some other means in order for the movement of the string tensioning clamp to be enough to draw the string to the proper tension. The clamping mechanism for holding the last tensioned string segment while the racket is repositioned for tensioning the next segment is also quite complex and, more importantly, unless carefully adjusted, the string tensioning and holding clamps may either hold the string too loosely so that it slips, or too tightly, so that it is crushed.

OBJECTS AND SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide an improved racket stringing machine.

It is a further object of the invention to provide an improved racket stringing machine in which the string may be pulled to the proper tension independently of its length.

It is a still further object of the invention to provide an improved racket stringing machine capable of applying a settable uniform tension to the stringing which is much simpler in construction and use than those of the prior art. In accordance with these and other objects of the invention, applicant provides a racket stringing machine which comprises a turntable for supporting and rotating the racket in a given plane, a capstan disposed for receiving and tensioning a string being strung on the racket, means for rotating the capstan until a preselected tension is applied to the string, and means for clamping the segment of the string tensioned by the capstan at a point proximate the interior side of the rim of the racket on the edge of the face toward the capstan for maintaining the tension on the segment of the string within the rim of the racket when the string is removed from said capstan.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of the racket stringing machine according to the invention.

FIG. 2 is a perspective view of the string gripping clamp of the machine of FIG. 1.

FIG. 3 is a top view of the bottom of the racket holding turntable of the machine of FIG. 1.

FIG. 4 is a sectional view of the turntable of FIG. 3.

FIG. 5 is a detail drawing of the racket clamping mechanism.

FIG. 6 is a sectional view of the clamping mechanism of FIG. 5.

FIG. 7 is a sectional view of the capstan drive mechanism of the racket stringing machine according to the illustrated embodiment of the invention.

FIG. 8 is a top view of the capstan drive mechanism of FIG. 7.

FIG. 9 is a sectional view of the capstan drive mechanism of FIG. 8.

FIG. 10 is a schematic diagram of the electrical portion of the machine of FIG. 1.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring now to FIG. 1 of the drawings, the racket holding turntable 11 is rotatably mounted on the rigid base 13 for horizontally supporting the racket 15, in this case a tennis racket, clamped to the top 17 thereof. The pads 18 of a resilient material such as rubber are provided on the top 17 for preventing damage to the racket 15. The string 19 with which the racket 15 is being strung is tensioned by means of the capstan 21 rotatably mounted in the supporting housing 23 which is affixed to the base 13.

An ON-OFF switch 27 for starting and stopping the tensioning action of the capstan 21 and a dial 29 for setting the desired amount of tension are provided on the housing 23. Also provided on the housing 23 is a pilot light 31 which, in the illustrated embodiment, lights only when capstan 21 is rotating to increase the tension on the string 19.

A string clamping assembly 33 is rotatably mounted on the base of the turntable 11 for clamping the last tensioned segment of the string 19 proximate the interior side of the rim of the racket 15 at the edge of the racket face closer to the capstan 21 in order to maintain the tension on the string segment after the capstan tensioning force is released. The structure of the clamping assembly 33 can best be seen in FIGS. 2 through 4 of the drawings. The tensioned segment of the string 19 is clamped between the jaws 35 and 37. Jaw 35 is formed as an extension of the channel member 39 which is pivotally mounted on the block 41 at pin 43. The other jaw 37 is pivotally mounted on the pin 45 and is biased toward the jaw 35 by the compression spring 47 which bears against the channel member 39 and the extension 49 of the jaw 32. The jaws 35 and 37 are notched to allow them to be fit around and crossed string segments on the racket face. The mating surfaces of the jaws 35 and 37 are preferably coated or roughened to increase their coefficient of friction.

The actuating member 51 is pivotally mounted on the channel member 39 and when depressed bears against the extension 49 of the jaw 37 for rotating the jaw 37 against bias to open the jaws.

The block 41 is slidably and pivotally mounted on the rod 53. The hole in the block 41 into which the shaft 53 fits is preferably very close fitting so that a minimum of play exists between the block 41 and the rod 53.

FIGS. 3 and 4 show the bottom plate of the turntable 11 and the mounting of the rod supporting and positioning trough 55. For the sake of clarity of illustration the channel member 39 is not shown in FIG. 3. The trough 55 is rotatably mounted substantially at the center of the bottom plate of the turntable 11. The rod 53 is fixidly mounted in the sides of the trough 55 at a position offset from the center of the bottom plate. The trough 55 may be locked in any one of four orthoginal positions with respect to the turntable 11 by the spring biased clamp 57 which is spring biased downwardly to mate with one of the holes 59 in the bottom plate of the turntable 11. In these four positions the rod 53 is alligned with the main (parallel to the racket handle) or cross strings of the racket 15 clamped to the top 17 of the turntable 11 and is offset on one or the other side of center of the racket 15 by a distance preferably on the order of one fourth of the average of the length and width of the racket face.

Referring to FIGS. 1 and 4, the turntable 11 may be locked to the base 13 in any position by the frictional material 61 which is eccentrically mounted on the shaft 63. The shaft 63 is coupled to and controlled by the knob 64. After positioning the turntable 11 in the desired position the operator turns the knob 64 to bring the frictional material 61 (which may be rubber) into engagement with the bottom of the turntable 11 thereby preventing further rotation. Thus segments of the string 19 strung in all four directions may be tensioned by the capstan 21. The racket 15 is clamped to the top 17 of the turntable 11 by means of the clamps 25, one of which is illustrated in FIGS. 5 and 6 of the drawings. The clamps 25 include an L-shaped racket gripping member 65 positioned in the knotch 67 in the frame 11. The threaded portion 69 of the gripping member passes through the hole 71 in the rod 73 and is in threaded engagement with the thumb screw 75. The shoulder 77 on the L-shaped member 65 limits the distance that the member 65 can drop when no racket is on the turntable 11. The rod 73 is pivotally mounted by the pin 79 the underside of the top 17 of the turntable 11. The tension spring 81 biases the end of the rod 73 in which the gripping member 65 is mounted away from the side of the turntable 11 toward a racket release and insertion position. The rod 73 may be pivoted against bias to bring the gripping member 65 into engagement with the racket 15 by means of the thumb screw 83 which is threaded through the hole in the side of the turntable 11 and bears against the rod 73 proximate the other end thereof. To clamp the racket 15 to the turntable 11, the racket 15 is first positioned with the gripping members 65 within the rim proximate and opposite to the throat of the racket 15. The thumb screws 83 are then rotated to cause the gripping members 65 to engage the rim and to stretch the racket 15 slightly. After this, the thumb screws 75 are tightened to cause the gripping members 65 to clamp the racket 15 firmly against the top 17 of the turntable 11. The mechanism which rotates the capstan 21 until a preset tension is exerted on the string 19 forms an important feature of the machine of the present invention. As can be seen in FIGS. 7, 8 and 9, the capstan 21 is mounted on the shaft 85 which is journaled in the sides of the supporting housing 23 by the bearings 87. The motor support and microswitch actuator member 89 includes a rigid rectangular portion 91 which is rotatably mounted on the shaft 85 and a motor support bracket 93 affixed to the portion 91. The motor 95 is mounted on the motor support bracket 93 for movement with the portion 91 and drives the drive gear 97 which is affixed to its shaft 99. The drive gear 97 engages the capstan gear 101 which is affixed to the shaft 85 for rotating the capstan 21 to exert tension on the string 19.

The member 89 is biased in the clockwise direction as seen in FIG. 7 by the compression spring 103 which bears with one end against the extension 105 of the motor support bracket 93 and with the other end against the bracket 107.

The motor control microswitch 109 is mounted on the microswitch position control gear 111 which is rotatably mounted on the bracket 107. A certain amount of friction is provided in the mounting of the gear 111 so that the actuation of the microswitch 109 by the extension 105 of the motor support bracket 93 does not cause a rotation of the gear 111. The position of the microswitch 109 is controlled by the knob 29 (FIG. 1) through the shaft 113 and the pinion gear 115 which engages the gear 111. The extension 105 of the bracket 93 includes an activating portion 117 extending toward the microswitch 109. To vary the preset tension which is to be exerted on the string 19, the dial 29 is rotated to the desired position as indicated on the associated scale thereby rotating the pinion gear 115 and the gear 111. The rotation of the gear 111 moves the microswitch 109 toward or away from the actuating portion 117 and decreases or increases, respectively, the preset tension to be exerted on the string 19 by the capstan 21. The capstan 21 includes a sleeve 119 of a resilient material such as 20 durometer neoprene rubber.

Referring now to FIG. 10 of the drawing, the ON-OFF switch 27 is connected in a series circuit with the microswitch 109, the motor 95 and the line voltage supply. The indicator lamp 31 is connected across the motor 95 and indicates when power is supplied thereto.

In order to tension the string 19 its end is wrapped around the capstan 21, preferably with a portion of the string 19 on the capstan 21 passing over a portion closer to the end thereof so that the string is self locking on the resilient sleeve 119 of the capstan 21. When the switch 27 is turned on, the motor 95 starts and rotates the capstan 21 in a clockwise direction as viewed in FIG. 1 thereby turning the string 19 wrapped thereabout. As the tension exerted on the string 19 increases, the rotational force of the motor 95 coupled through the gears 97 and 101 to the capstan tends both to rotate the capstan 21 in the clockwise direction and to rotate the motor support and microswitch actuator member 89 against the bias of the compression spring 103 in the clockwise direction as seen in FIG. 7. The rotation of the member 85 swings the actuating portion 117 toward the microswitch until, when the tension on the string is equal to the desired amount set on the dial 29 (FIG. 1), the actuating portion 117 actuates the microswitch 109 thereby removing power from the motor 95 and the indicator lamp 31. The tension on the string 19 (usually between 40 and 60 pounds) is enough to rotate the capstan 21 and the motor drive gear 97 in the opposite direction so that the actuating member 117 swings away from the microswitch 109 thereby causing it to close again and reenergize the motor 95. This again rotates the capstan 21 in the clockwise direction until the actuating portion strikes the microswitch 109. This process of repeated incremental tightening and loosening of the string 19 continues with the indicator lamp 31 flashing on and off thereby indicating to the opertor that the string 19 is tensioned by the preset amount.

The operator then clamps the tensioned portion of the string 19 between the jaws 35 and 37 of the string clamping assembly 33 at the point immediately interior to the rim of the racket 15 on the edge of the face toward the capstan 21. The switch 27 is then turned off and the string 19 is unwound from the capstan 21. The force exerted by the tensioned segment of the string 19 on the jaws 35 and 37 tends to cock the block 41 on the rod 53 thereby locking the block 41 in position so that it cannot slide along the rod 53.

The operator next threads the string 19 along the next segment of its path, rotates the frictional material 61 out of engagement with the turntable 11, rotates the turntable 11 to the proper position for tensioning the next segment and reengages the frictionsl material 61. He then procedes as before, wrapping the string about the capstan 21 and turning on the switch 27. After this next segment is tensioned by the motor 95 acting through the capstan 21, the operator removes the clamping assembly 33 from the previous segment and clamps the new segment in the manner explained above.

The offset of the rod 53 with respect to the center line of the length or width of the face of the racket 15 clamped on top of the turntable 11 decreases the maximum extension of the block 41 and the channel member 39 needed to reach any part of the face of the racket 15 and thereby minimizes the inherent backlash of the clamping system 33.

As is apparent to one skilled in the art the components of the stringing machine according to the illustrated embodiment of the invention upon which forces are exerted during the tensioning of the string 19 must be strong enough to withstand these forces without excessive deformation. The required strength of the various components may be easily determined by experiment or by calculation, working from the knowledge of the tension to be exerted on the string 19.

The above description a preferred embodiment of the invention is given by way of illustration only and, as will be apparent to one skilled in the art, changes in detail can be made without departing from the spirit of the invention whose scope is defined by the appended claims.