GB1584029A

GB1584029A - Fibre cutting tool

Info

Publication number: GB1584029A
Application number: GB1843578A
Authority: GB
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC
Priority date: 1978-05-09
Filing date: 1978-05-09
Publication date: 1981-02-04
Also published as: AU4637779A

Description

(54) FIBRE CUTTING TOOL (71) We, STANDARD TELEPHONES AND CABLES LIMITED, a British Company of 190 Strand, London W.C.2. England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to cutting tools, and in particular to a tool for cutting glass or silica optical fibres.

A major problem with the field installation of fibre obtic communication systems is that of cutting, and preparing the cut ends of, individual optical fibres prior to termination in a connector or a splice. At present such fibres are in general terminated at the factory prior to shipment and installation, but this practice does not lend itself to unforeseen changes in, nor repairs or addition to, an installed system. Tools and jigs for cutting optical fibres have been constructed, but these are usually somewhat delicate and are quite unsuited for use by installation engineers in the field.

The object of the invention is to minimise or to overcome this disadvantage.

Our published specification No. 1,524,808 describes and claims a device for scoring a glass fibre perpendicular to the fibre axis, the device including a housing, a spring loaded arm pivoted at one end in the housing, the other end of the arm extending from the housing and provided with a knife edge, and means for moving the pivot of the arm so as, when in use, to draw the knife edge across a glass fibre supported adjacent the housing.

The function of the device of specification No. 1,524,808 is to move or scribe a fibre so as to facilitate subsequent cleaving perpendicular to the fibre axis by the application of axial tension.

According to the present invention there is provided a tool for cutting a glass or silica optical fibre, including a lever whereby the tool is operated and provided with a return spring, first and second anvil members arranged adjacent one another so as to provide a contiguous convex anvil surface, two clamps, one against each said anvil and adapted to secure a fibre across the anvil surface, spring means - for urging the anvils apart so as to provide axial tension to the fibre, and means including a knife edge for scoring the fibre so as to initiate fracture, the arrangement being such that the application of pressure to the lever causes, in sequence, the clamps to secure a fibre against the anvil surface, the knife edge means to score the fibre, the application of axial breaking tension to the scored fibre via said spring means and disengagement of the clamps from the anvil surface so as to release the severed fibre portion.

An embodiment of the invention will now be described with reference to the accompanying drawings in which: Fig. 1 shows one view of the fibre cutting tool; Fig. 2 shows another view of the tool of Fig. 1; Fig. 3 shows the fibre tensioning mechanism of the tool; Fig. 4 shows the fibre clamp mechanism of the tool; and Figs. 5a to Fig. 5e show the sequence of operations of the tool drive mechanism in the performance of the fibre cutting process.

Referring to Figs. 1 and 2, the tool includes a lever handle portion 10 whereby the tool is operated via bell cranks 11, and a housing 12 in which the fibre cutting mechanism is mounted. Extending from the housing 12 are a pair of anvils 13 and 14, one of which (14) is pivoted on a pivot 15 secured to a housing cover plate 16. The anvils 13 and 14 are provided with curved surfaces 17 and 18 respectively against which a glass or silica fibre (not shown) to be cut is secured by movable clamps 19 and 20. As shown in Fig. 4 the clamps 19 and 20 are mounted each on a slotted bar 21 slidably mounted in the housing. Scribing of a glass or silica fibre (not shown) urged against the anvil surfaces 17 and 18 by clamps 19 and 20 is effected by a knife blade 22 which is advantageously operated via a mechanism of the type described in our specification No.

1,524,808.

Referring now to Figs. 3 and 4, the movable anvil 14 and the clamps 19 and 20, each carried on their respective slide bars 21, are each operated via a respective cam slide bar 23, surface 24 of which is profiled to form a cam. Cam followers 25 are pivoted one adjacent the cam surface of each cam bar 23. The clamps 19 and 20 are operated each against the action of a return spring 26 located in a slot 27 in the respective slide bar 21, whilst the movable anvil 14 is operated against the action of a return spring 28 located between the anvils in sockets 29. In some applications the spring 28 may be provided with spring locating pegs 30. Each cam bar 23 is reduced in thickness for part of its length so as to define a channel 31 (Fig. 4) in which a cam block 32 is slidably located.

Figs. 5a to 5e show the sequence of operation of the cam bars 23 with their respective cam followers 25 and cam blocks 32 during a completed cutting operation provided by the application of hand pressure to the lever 10. The mechanism advantageously provides a 'non reversing action' so that the lever 10 can return to its rest position without the repetition of the cutting sequence in reverse order.

Fig. 5a shows the location of the parts prior to the fibre cutting sequence. In Fig.

Sb the cam bar 23 is drawn in the direction of the arrow A by operation against a return spring (not shown) of the lever 10 and bell cranks 11, the cam block 32 being moved with the cam bar by shoulder 33 defining one end of the channel 31. The cam follower 25, which is prelocated by the respective spring 26 or 28 slides down ramp 34 of the cam surface of the bar 23 and rotates about its pivot 35 in the direction of the arrow B thus allowing backward movement of its slide bar 21. Further movement of the cam bar 23 (Fig. 5c) causes the cam follower 25 to engage ramp 36 of the cam block, which is so designed as to protrude slightly above the raised surface portion of the cam bar, rotating the cam follower back to its original position and returning the slide bar 21 against the respective spring 26 or 28. At this point the cutting sequence is completed.

The three cam bars 23 are so designed as to provide the following cutting sequence during depression of the lever 10.

1. The clamp 19 is urged by its spring 26 against the fixed anvil 13 so as to secure a glass or silica fibre placed between that clamp and the anvil.

2. The clamp 20 is urged by its spring against the movable anvil 14 thus bending the fibre across the anvil surfaces 17 and 18.

3. Tension is applied to the fibre by the spring 28 between the anvils.

4. The knife blade is drawn across the fibre so as to score the fibre and permit rupture caused by the spring pressure between the anvils.

5. The clamp 19 is pushed away from the anvil 13 so as to release one portion of the severed fibre. This reduces the risk of damage to the cut ends of the fibre during the remainder of the cutting sequence.

6. The clamp 20 is pushed away from the anvil 14 releasing the other portion of the severed fibre and completing the cutting sequence.

When the lever 10 is released each cam bar 23 is pushed back (Fig. 5d) leaving the cam block 32 in engagement with the cam follower 25 thus preventing movement of the slide bar 21. Further return movement of the cam bar 23 causes the cam block 32, retained in position by the cam follower 25, to engage the shoulder 36 defining the other end of the channel 31 in the cam bar thus disengaging the cam follower from the cam block and on to the top of the ramp 34 as shown in Fig. 5e. At the point of transfer of the cam follower load from the cam block to the cam bar the spring loading of the follower causes a sharp impulse to be applied to the cam block throwing the block back along the channel 31 towards the shoulder 36. The operating sequence is thus completed and the mechanism is ready for the next cutting operation.

WHAT WE CLAIM IS:- 1. A tool for cutting a glass or silica optical fibre, including a lever whereby the tool is operated and provided with a return spring, first and second anvil members arranged adjacent one another so as to provide a contiguous convex anvil surface, two clamps, one against each said anvil and adapted to secure a fibre across the anvil surface, spring means for urging the anvils apart so as to provide axial tension to the fibre, and means including a knife edge for scoring the fibre so as to initiate fracture, the arrangement being such that the application of pressure to the lever causes, in sequence, the clamps to secure a fibre against the anvil surface, the knife edge means to score the fibre, the application of axial breaking tension to the scored fibre via said spring means and disengagement of the clamps from the anvil surface so as to release the severed fibre portion.

2. A tool as claimed in claim 1, and in which the arrangement is such that return

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Fig. 4 the clamps 19 and 20 are mounted each on a slotted bar 21 slidably mounted in the housing. Scribing of a glass or silica fibre (not shown) urged against the anvil surfaces 17 and 18 by clamps 19 and 20 is effected by a knife blade 22 which is advantageously operated via a mechanism of the type described in our specification No. 1,524,808. Referring now to Figs. 3 and 4, the movable anvil 14 and the clamps 19 and 20, each carried on their respective slide bars 21, are each operated via a respective cam slide bar 23, surface 24 of which is profiled to form a cam. Cam followers 25 are pivoted one adjacent the cam surface of each cam bar 23. The clamps 19 and 20 are operated each against the action of a return spring 26 located in a slot 27 in the respective slide bar 21, whilst the movable anvil 14 is operated against the action of a return spring 28 located between the anvils in sockets 29. In some applications the spring 28 may be provided with spring locating pegs 30. Each cam bar 23 is reduced in thickness for part of its length so as to define a channel 31 (Fig. 4) in which a cam block 32 is slidably located. Figs. 5a to 5e show the sequence of operation of the cam bars 23 with their respective cam followers 25 and cam blocks 32 during a completed cutting operation provided by the application of hand pressure to the lever 10. The mechanism advantageously provides a 'non reversing action' so that the lever 10 can return to its rest position without the repetition of the cutting sequence in reverse order. Fig. 5a shows the location of the parts prior to the fibre cutting sequence. In Fig. Sb the cam bar 23 is drawn in the direction of the arrow A by operation against a return spring (not shown) of the lever 10 and bell cranks 11, the cam block 32 being moved with the cam bar by shoulder 33 defining one end of the channel 31. The cam follower 25, which is prelocated by the respective spring 26 or 28 slides down ramp 34 of the cam surface of the bar 23 and rotates about its pivot 35 in the direction of the arrow B thus allowing backward movement of its slide bar 21. Further movement of the cam bar 23 (Fig. 5c) causes the cam follower 25 to engage ramp 36 of the cam block, which is so designed as to protrude slightly above the raised surface portion of the cam bar, rotating the cam follower back to its original position and returning the slide bar 21 against the respective spring 26 or 28. At this point the cutting sequence is completed. The three cam bars 23 are so designed as to provide the following cutting sequence during depression of the lever 10.

3. Tension is applied to the fibre by the spring 28 between the anvils.

5. A hand operated tool substantially as described herein with reference to the accompanying drawings.

WHAT WE CLAIM IS:-

1. A tool for cutting a glass or silica optical fibre, including a lever whereby the tool is operated and provided with a return spring, first and second anvil members arranged adjacent one another so as to provide a contiguous convex anvil surface, two clamps, one against each said anvil and adapted to secure a fibre across the anvil surface, spring means for urging the anvils apart so as to provide axial tension to the fibre, and means including a knife edge for scoring the fibre so as to initiate fracture, the arrangement being such that the application of pressure to the lever causes, in sequence, the clamps to secure a fibre against the anvil surface, the knife edge means to score the fibre, the application of axial breaking tension to the scored fibre via said spring means and disengagement of the clamps from the anvil surface so as to release the severed fibre portion.

of the lever upon release causes substantially no movement of the clamps and knife edge means.

3. A tool as claimed in claim 1 or 2, and in which said knife edge means includes a scoring device as claimed in U.K. Specification No. 1,524,808.

4. A tool as claimed in claim 1, 2 or 3, and in which said lever is coupled to the clamps and to the knife edge means end via a slidable cam bar provided with a spring loaded cam follower.