Protected prong file fastener and method of making
A prong style file fastener, and method of manufacturer, is disclosed which has a protective element to prevent damage to paper documents and personal injury. In one embodiment, the prongs of the fastener is covers with a heat shrinkable sheath. In another, the prongs are overcoated with a powder coating which is melted thereon. A method of applying the sheath to the prongs uses a pair of jaws to drive the sheath onto the prongs. In the case of the powdercoat covering, the production line uses a cam drive sprocket retractor to release the line onto a takeup.
1. A method of making a protected file fastener having a pair of prongs having proximal and distal ends, comprising the steps of:
a. cutting a length of heat shrinkable tubing from a supply of continuous tubing, said length having distal and proximal ends;
b. providing a flow of air into an opening of the length of tubing to expand its distal open end;
c. driving said length of tubing between a pair of rollers onto the proximal end of a prong;
d. with the length of tubing covering at least part of said prong, further gripping the proximal end of the tubing between a pair of jaws and further driving the tubing on to the prong until the distal end of the tubing reaches the distal end of the prong;
e. shrinking the length of tubing by applying heat to thereto.
2. The method of claim 1 , wherein the step of gripping includes, providing a reciprocating pair of upper and lower jaw members each having teeth, and bringing said teeth close together and without releasing the jaws, driving the jaws toward the distal end of the prong, thereby driving the tubing further onto the prong.
3. The method of claim 1 , wherein the cutting step includes cutting at least one end of the tubing to have a concave end cut.
4. The method of claim 1 , wherein the cutting step includes cutting away a portion of one end of the tubing to create a concave end.
5. The method of claim 1 , wherein said step of providing an air flow includes providing a jet of air to alter the cross sectional shape of the end of the tubing to create an oblong shaped opening sized to be better slid onto said prong without snagging, during insertion.
6. The method of claim 1 , wherein the step of driving the tubing includes placing a pair of rollers adjacent each other with their circumferential edges touching, said rollers having a recess sized to receive said tubing, and rotating said rollers to drive said tubing onto a prong.
7. The method of claim 6 , further including the step of separating said rollers after said tubing has been applied to said prong, so that no further driving force is applied to the tubing.
8. The method of claim 2 , wherein the step of bringing said teeth close together includes connecting at least one jaw member to a pivotal link and reciprocatingly driving said link forward and backward, thereby causing said jaws to open and close.
9. The method of claim 2 , wherein the step of bringing the teeth close together stops before the teeth can compress the tubing to the point where the opening in the tubing is too small to receive the prong.
10. The method of claim 1 , wherein the step of gripping includes providing a reciprocating driver arm and driving said jaws, thereby driving the tubing further onto the prong and thereafter withdrawing the driver arm.
11. The method of claim 1 , further including the step of providing a tapered prong with a wider portion at the distal end and narrower portion and tip at the proximal end.
12. A method of minimizing kinking of a bendable prong of a pronged fastener when said prong is bent, comprising the steps of:
a. increasing the bending radius of the prong by:
b. applying a length of heat shrinkable tubing, shorter than the prong length over the prong covering at least the portion of the prong to be bent;
c. heating the prong and tubing simultaneously to bond the tubing to the prong thereby increasing the bending radius of the prong and minimizing kinking.