# US 4,874,170 A · String clamp for racquet stringing machine

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- Number: US 4,874,170 A
- Document ID: US4874170A
- Status: Granted
- Kind: A
- Application number: 07/249,602
- Filed: 1988-09-26
- Granted: 1989-10-17
- Earliest claimed: 1988-09-26
- Assignees: Ektelon
- Inventors: Ronald G. Zech
- Web page: https://patentgrep.com/patent/US4874170A

## CPC

- A63B 51/14: Arrangements for stringing, e.g. for controlling the tension of the strings during stringing
- Y10T 24/44521: Pivoted or rotated element
- A63B: APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT (apparatus for passive exercising, massage A61H)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A toggle action string clamp for a racquet stringing machine comprises two vise members movable along positioning glide bars attached to the stringing machine, which can be locked to the bars and to the strings of a racquet positioned in the machine. An angular link member connects a bottom vise member to a clamp-locking handle, with the top vise member being located therebetween. Locking is achieved by forcing the bottom U-shaped portion of the handle against a locking pin contained in the top vise member, thereyby urging the two vise members together. The clamp is provided with a wedge block mechanism capable of adjusting the effective distance between the bottom of the U-shaped portion and the bottom vise member, thus controlling the clearance between the vise members and, therefore, the clamping force. In the open position, due to the interaction of the clamp handle, clamp gap pings and vise member springs, the vise members open up at both ends simultaneously, facilitating positioning on the glide bars, or their complete removal.

## Claims

### Claim 1

A toggle action string clamp for a racquet stringing machine comprising:
parallel top and bottom vise members having finger-like projections extending along the longitudinal axis of said members from one end thereof, and a semicircular groove located in the other end thereof at right angles to said axis, said grooves facing each other;
a handle member which includes a U-shaped portion and a grip lever portion;
an adjustable U-shaped wedge block;
two spacer nuts, and
two angular link members,
wherein said link members are positioned in slots in said vise members, the end portions of said link members being respectively pivotally connected to said bottom vise member, and to said handle member by means of connecting pins, the connecting pin connecting said handle member passing through elongate holes in the U-shaped portion thereof, and wherein the connecting pin passing through said handle member also passes through said spacer nuts, one of which is positioned on each side of said handle member, and wherein further, said wedge block is connected to said handle member by an adjustment screw and is positioned between shoulders located on said handle member, and said spacer nuts, and wherein still further, said top vise member is located between said bottom vise member and said handle member and has a locking pin extending through the slots located therein, at right angles thereto, whereby the U-shaped portion of said handle member can be formed against said locking pin, urging said vise members together when the clamp is positioned in its closed position.

### Claim 2 (depends on 1)

A toggle action string clamp according to claim 1 wherein said handle portion and the sides of said U-shaped portion are disposed at substantially 90 degrees relative to each other, and the bottom of said sides have a notch located therein to facilitate positioning of said sides against said locking pin.

### Claim 3 (depends on 2)

A toggle action spring clamp according to claim 2 wherein the end portions of said link members form an obtuse angle relative to each other, the vertex of which is positioned adjacent said locking pin when the clamp is in its closed position.

### Claim 4 (depends on 1)

A toggle action string clamp according to claim 1 wherein at least one spring is positioned between said vise members which tends to urge said members apart, and in conjunction with gap pins to separate both ends of said clamp simultaneously when the clamp is opened.

### Claim 5 (depends on 4)

A toggle action string clamp according to claim 4 wherein at least one gap pin passes through both said vise members, at right angles thereto, allowing said vise members to slide therealong during the opening and closing of the clamp, thereby helping to maintain the alignment of said vise members and to control the clamp's opening distance.

### Claim 6 (depends on 1)

A toggle action string clamp according to claim 1 wherein said spacer nuts are rectangular in shape, and wherein the hole therein through which said connecting pin passes is eccentric relative to the sides of said spacer nuts.

### Claim 7 (depends on 2)

A toggle action string clamp according to claim 2 wherein a spring is located between the top of said U-shaped portion and the pin passing through said handle member and said spacer nuts, urging the pin and said U-shaped portion apart.

### Claim 8 (depends on 1)

A racquet stringing machine furnished with toggle action string clamps according to claim 1.