WIRE STRIPPING APPARATUS

Abstract: A tool for stripping insulation from wire has a body (10) defining an aperture in which an end portion of a wire to be stripped may be positionned. A U-shaped clamping member (20) having a pair of clamping jaws (21, 22) is slidable along the length of the aperture, the jaws co-operating with camming surfaces (18, 19). A U-shaped cutter (33) has a pair of cutting edges (34) being controlled jointly by co-operation between the abutments (35) adjacent the edges (34) and the jaws (21, 22), and between the jaws and camming surfaces (18, 19). Movement is imparted to the cutter (33) by pivoting handle (12), and the cutter draws the member (20) until its jaws engage a wire therebetween; continued movement of the cutter (33) causes clasps (31) of the member (20) to ride over the base (36) of cutter (33); simultaneously the cutting edges (34) penetrate a clamped wire, whereby continued movement of the cutter breaks the partially severed layer free and draws the insulation of the end portion of the clamped wire.

Description: WIRE STRIPPING APPARATUS This invention relates to wire stripping apparatus as defined hereinafter, and in particular - but not exclusively - this invention concerns a hand-held tool adapted and arranged to assist the removal of an end portion of a layer of insulating material from one or more elongate electrical conductors which that layer surrounds. The invention may instead concern a bench- mounted production machine for stripping an insulating layer from electrical conductors. The apparatus of this invention may be arranged for use with a wide variety of elongate filamentary members, to assist the removal of at least one layer which surrounds that member. Thus, for example, the apparatus could be arranged to assist the removal of a protective sheath from a fibre-optic filament. More commonly, the apparatus may be arranged to assist the removal of an insulating sleeve from an electrical conductor or a group of conductors which latter may also have a separate insulating layer for each conductor. All such apparatus are referred to herein as 'wire stripping apparatus' and references to 'wire' and 'insulation' should accordingly be construed broadly, as the context may require. There have been very many designs for wire stripping apparatus, many of which are in the form of hand-held and hand-operated tools, adapted to assist the removal of insulation from electric wires such as are encountered in association with electrical equipment and appliances. Many of these tools require specific adjustment or setting-up in order to allow them to be operated with any given size of wire, though there have been proposals for self-adjusting tools, which automatically adjust to perform an effective stripping operation on a range of wire sizes. Many of the designs of wire stripping tools are able to perform adequately when used in conjunction with relatively soft insulation such as is often found on wires intended for connecting electrical appliances to wall outlets, but those tools usually are of only limited benefit when used in conjunction with wires having relatively hard insulation, such as are employed for the fixed wiring of a building. In the United Kingdom, but also in several other countries including the United States of America, such fixed wiring usually is in the form of a pair of separately insulated principal conductors disposed within an outer sheath, an uninsulated earthing conductor extending between and parallel to the two principal conductors. In a domestic dwelling, the power wiring is usually completed with conductors of 2.5mm 2 cross-sectional area, whereas the lighting wiring usually has conductors of either l.Omirr or 1.5mm cross-sectional area. In either case, a relatively hard grade of polyvinylchloride is commonly used for the outer insulating sheath as well as for insulating the individual principal conductors . It is the common practice of electricians when terminating the fixed wiring to employ knives and/or side cutters to remove the insulation, often using the earthing conductor to split the outer sheath, by pulling that conductor sideways. Such an insulation- removing operation requires considerable manual dexterity, and in any event is relatively slow and inconvenient to perform, especially with - for example - power outlets located close to a floor or other position where access is restricted. Also, the earthing conductor may be strained and weakened if mis¬ used in this way. One of the principal aims of the present invention is to provide wire stripping apparatus (as defined above) which is able to assist the removal of insulation from a wire, whilst being able to adjust automatically to a wide range of wire sizes. According to a principal aspect of the present invention, there is provided wire stripping apparatus which comprises a body defining an aperture in which may be received a wire to be stripped, a cutter having a cutting edge arranged to cut into a wire lying in the aperture which cutter is mounted for sliding movement generally along the length of the aperture from a home position where a wire to be stripped may be inserted into the aperture, means controlling the movement of the cutting edge in a direction generally transverse to the length of the aperture which means includes cooperating cam surfaces on the cutter and on a surface over which the cutter slides, and a self-jamming cleat assembly for clamping the wire and cooperating with the cutter whereby sliding movement of the cutter away from its home position brings the cleat assembly into a wire-clamping position. Apparatus of this invention may be configured as a hand-held tool arranged principally for the stripping of the wires used in the fixed wiring of a building, when in-situ for the purpose of so-called second- fixing. Alternatively, the appratus may be arranged for bench-mounting. Most preferably, the self-jamming cleat assembly includes a pair of cleat jaws disposed one on each side of said aperture whereby the wire may be positioned therebetween, the jaws being configured so that on contacting the wire as the cutter moves away from its home position by virtue of the cooperation between the cutter and the cleat assembly, the jaws are urged more firmly to clamp the wire as the wire is pulled by the cutter in the direction of movement thereof. Depending upon the cooperation between the self-jamming cleat assembly and the cutter, the jaws may be spring-urged into or away from a wire-clamping position, with the jaws being moved in the opposite sense against the spring-action by the cutter. It would of course be possible for the cleat assembly to have only one cleat jaw operating in conjunction with an opposed anvil whereby the wire may be positioned between the jaw and anvil. One suitable form of self-jamming cleat assembly may comprise a pair of pivoted jaws spring-urged to positions where the jaws move towards each other to clamp a wire disposed therebetween, the cutter when in its home position engaging those jaws and pushing them to positions where they are clear of a wire disposed therebetween; on the cutter moving away from its home position, the jaws may then move to engage a wire. A more preferred arrangement is however for the self- jamming cleat assembly to comprise two jaws each of which is slidably mounted within the body and cooperates with a cam surface over which the jaw slides, which cam surface serves to deflect the jaw inwardly of the aperture during sliding movement of that jaw. Then, by interconnecting each jaw with the cutter, movement of the cutter away from its home position will also move the jaws along the wire, the jaws simultaneously moving transversely inwardly until they contact the wire therebetween. Thereafter, on the cutter cutting into and pulling on the wire in the direction of movement of the cutter, the jaws will be urged even closer together so more firmly gripping the wire and resisting axial movement of the same, so as to permit the cutter partially to sever an end portion of the insulation, break that end portion free and pull it at least partially off the wire. Advantageously, the cutter has two cutting edges arranged one on each side of the aperture, whereby the cutter will cut into the insulation of a wire from both sides thereof, to assist the severance of the portion of the insulation to be removed. According to a second aspect of this invention, there is provided wire stripping apparatus which comprises a body defining an aperture in which may be received a wire to be stripped, a pair of wire clamping jaws arranged for relative sliding movement with respect to the length of the aperture in the body, each jaw sliding over an associated camming surface arranged to move the jaw inwardly towards the other jaw as the jaws are moved away from a home position, a cutter also mounted for sliding movement along the length of the aperture and having a pair of wire-cutting edges disposed adjacent and between said jaws, releasable means coupling together the cutter and the pair of jaws, and motion means for imparting movement to the cutter with respect to the aperture, whereby the pair of jaws are moved by the cutter upon movement thereof until the jaws grip a wire extending therebetween, whereafter the jaws are released from the cutter upon continued movement of the cutter. It will be appreciated in this second aspect of the invention, the pair of jaws together with its associated camming surface serve as a self-jamming cleat assembly, to grip a wire the insulating layer of which is to be stripped by the apparatus. On using the apparatus, movement is imparted to the jaws by movement of the cutter until such time as the jaws contact a wire disposed therebetween; thereafter, continued movement of the cutter will free the releasable means whereby the cutter will move relative to the jaws which latter will remain substantially stationary with respect to the wire, the cutting edges during this stage penetrating the insulation of the wire. Further continued movement of the cutter will pull on the partially-severed portion of the insulation, in the direction away from the main part of that insulation clamped between the jaws. Most preferably, said releasable means comprises spring means co-acting between the pair of jaws and the cutter, which spring-means requires some force to break the connection between the cutter and the pair of jaws. Once the connection has been broken, there may be little - if any - frictional force connecting the cutter to the pair of jaws. Alternatively, a spring may be used to drive the jaws to a wire-clamping position. In a preferred embodiment, the pair of jaws may be formed from a single strip to have a generally U-shaped profile, the cutter being similarly formed and adapted to fit within the pair of jaws. The body may include a pivoted handle, which handle is connected to the cutter so that pivoting movement of the handle imparts sliding movement to the cutter, the cutter in turn imparting sliding movement to the pair of jaws until such time as said releasable means is released. Control of the movement of the cutting edges in a direction generally transverse to the length of the aperture may be achieved by co-operation between camming surfaces respectively on the cutter and on the pair of jaws. Alternatively, said movement of the cutting edges may be controlled indirectly, solely or primarily by the co-operation between each jaw and its associated cam surface. Advantageously, the apparatus includes a wire cutter which, in a preferred embodiment of hand tool of this invention, comprises a moving blade attached to said pivoted handle and co-operable with a fixed blade mounted on the body. When single-core wires are being terminated for connection to an electrical fitting, frequently it is desirable to strip an end portion of the insulation away from the single core, and then to fold the exposed conductor back on itself, to provide an end portion of increased bulk for reception in a screw connector of the electrical fitting. A preferred form of hand-tool of this invention includes means to effect such folding of an exposed single-core conductor, following the stripping of the insulation therefrom. Such folding conveniently is effected in two stages, the first stage commencing the fold and-the second stage crimping the partly-folded end portion into a completed fold. In a preferred embodiment of tool of this invention, the first stage of the folding action is performed by interaction between a slot having a U- shaped base wall and a blade adapted to pull a wire laid transversely of the slot towards the base of the slot, so that the wire takes up a U-shaped profile. Then, that folded wire may be inserted into a second slot having a planar base wall, a blade crimping the folded wire against the planar base wall to complete a tight fold. By way of example only, one specific embodiment of wire stripping tool arranged in accordance with the present invention will now be described in detail, reference being made to the accompanying drawings, in which:- Figure 1 is a side view of an embodiment of a wire stripping tool; Figure 2 is a vertical sectional view through the tool of Figure 1 taken on line II-II marked on Figure 5, with the parts thereof set in a starting position; Figure 3 is a view similar to that of Figure 2, but with the parts displaced from the starting position; Figure 4 is a plan view of the tool of Figure 1; Figure 5 is a front view of the tool of Figure 1; and Figures 6 and 7 are detailed views on an enlarged scale of the base regions of a clamping member and cutter, in the positions illustrated respectively in Figures 2 and 3. Referring to the Figures, there is shown a hand tool intended for the stripping of insulation from the end portion of a variety of kinds of wires, such as may be encountered in domestic and contracting situations; these may range from relatively light-weight flexes for connecting electrical appliances to fixed wiring outlets, to the fixed wiring itself, including lighting and power cables known as flat twin or three core-and- earth cables of 1, 1.5, 2.5, 4 and 6 mm 2 cross- sectional area conductors. The tool is configured to allow the cutting of wires to length, the separate stripping of the outer sheath from a cable having more than one separately insulated wire, the stripping of insulation from individual wires, and the folding-over of a stripped single-core conductor, ready for termination. The stripper comprises a moulded plastics body 10 including a handle 11 projecting from one end of that body, and a lever 12 pivoted to the main body by pin 13 such that the lever is generally opposed to the handle 11 and may be moved closer thereto by a user grasping both the handle 11 and lever 12, and squeezing those components closer together. The body 10 may be moulded in one piece and includes a pair of side walls 14 joined by an upper edge wall 15A and a lower edge wall 15B, a window- opening 16 being formed in each side wall 14. In this way, the body 10 defines an aperture in which a wire to be stripped may be inserted from the "front" end 17 of the tool and, if necessary, out of one of the window- openings 16 in a side wall 14. The edge walls 15A and 15B define respective camming surfaces 18 and 19. A generally U-shaped clamping member 20 formed from spring steel is disposed in the space enclosed by the side walls 14 and edge walls 15A and 15B, the clamping member being formed to define a pair of clamping jaws 21 and 22 adjacent the front end 17 of the tool. Adjacent each clamping jaw is a respective abutment 23 and 24, co-operable with the adjacent camming surface 18 and 19, respectively. The end of the clamping member 20 remote from the jaws 21 and 22 is restricted from moving towards the upper side wall 15A by part of a sliding bar 25 (to be described below) itself in engagement with a fixed blade 26 fitted into the body 10; and is restricted from moving towards the lower side wall 15B by a moulded insert 27, fitted between the side walls 14. Movement of the clamping member 20 out of the front end of the tool is restricted by a peg 28 on the insert 27, engaged in a slot (not shown) in the clamping member; and movement of the clamping member to the right (in Figures 2 and 3) is limited by leg 29 of the insert 27. Though the position of leg 29 is fixed, it could be made adjustable or replaced by an adjustable stop such as a rotatable cam, to allow fine adjustment of the stripping depth. Part of the material at the base end 30 of the clamping member is cut away, and on the upper side (in the drawings) of the clamping member, the cut-away side walls are turned inwardly to define a pair of clasps 31. The central region of the clamping member 20 is slotted from the base towards the jaws, beyond the clasps 31. F itt ed within t he c l ampi ng member 2 0 i s a generally U-shaped cutter 33 formed from a spring-steel blade , which cutter has a pair of cutting edges 34 f ormed at it s f ree ends , the cutting edges being defined in such a way that an abutment 35 is defined adj acent each cutting edge which abutment is able to co-operate with a cam surface defined by the inner surface of the clamping member forming the respective adjacent abutment 23 or 24. The base 36 of the cutter 33 normally lies adjacent the clasps 31 of the clamping member 20 as shown in Figure 6; on movement of the cutter 33 to the right (in Figure 2), the engagement of the clasps 31 with the cutter base 36 pull the clamping member to the right until the clamping member meets a resistance; the clasps are then forced open over the cutter base 36 (as shown in Figure 7), to allow the cutter to continue its movement as shown in Figure 3. The upper side of the cutter 33 is slotted centrally, adjacent the cutter base 36. The lever 12 includes a profiled plate 37 defining a slot 38 having a leg 39 fitting into the slot adjacent the base 36 of the cutter. Movement of the lever 12 in the direction of arrow A causes leg 39 of the plate to act on the base 36 of the cutter, to move the cutter to the right. A spring 40 acts between the plate 37 and a pin 41 formed on the insert 27, to urge the lever to the position shown in Figure 2, in which part 42 of the plate 37 abuts the cutter base 36 and leg 39 prevents further leftward movement of the cutter. The plate 37 extends beyond pin 13 to form a cutting blade 43, co-operable with the fixed blade 26 to form a wire cutter. The co-operating parts of the blades 43 and 26 are hardened, to allow the cutter to sever copper wires as well as any insulating material thereon. The sliding bar 25 has its "front" end 44 retained adjacent the edge wall 15A by means of lugs (not shown) moulded into the side walls 14. The plate carries an upstanding blade 45 projecting through a slot 46 in the upper edge wall 15A, and the opposite end of the sliding bar 25 defines a slot in which is received the plate 37. Movement of the lever 12 in the direction of arrow A will thus slide the bar 25 to the right. The slot 46 has a "horizontal" component in the plane of the outer surface 47 of the wall 15A, and a "vertical" component 48 extending through the edge wall 15A. A wire laid on surface 47, between the blade 45 and shoulder 49 of the wall 15A will be pulled into this horizontal component and will thus be shaped into a U- profile; that folded-over wire may then be inserted into the vertical component 48 so that the blade 45 will crimp tight the end portion of the wire. In order to use the tool to strip the insulation from a wire, the wire is passed through the opening at the front end 17 of the tool and, if appropriate, out of one of the window apertures 16, when the tool is set in its home position as illustrated in Figure 2. Then, lever 12 is moved in the direction of arrow A, pulling both the cutter 33 and the clamping member 20 to the right. During this movement, the abutments 23 and 24 ride up the camming surfaces 18 and 19 until the clamping jaws 21 and 22 contact the insulation of the wire to be stripped. Further rightward movement of the clamping member 20 cannot occur once the jaws 21 and 22 have firmly engaged the cable, and so continued movement of the lever 12 in the direction of arrow A will pull only the cutter 33, the cutter forcing open the clasps 31 to ride over the base 36 of the cutter as illustrated in Figures 3 and 7. Simultaneously with this, the cutting edges 34 are driven into the insulation of a cable as the abutments 35 ride out of the cam surfaces defined by inner surfaces of the abutments 23 and 24 of the clamping member. The cutting edges thus move closer together and penetrate the insulation; continued movement of the cutter completes the severance of the insulation and pulls the severed material towards the free end of the cable. By keeping the handle 12 in its Figure 3 position and pulling the tool of the cable, the severed insulation will come free, off the cable. Once movement of the lever 12 has been completed it is released so the spring 40 returns the handle, cutter and clamping member to their initial positions illustrated in Figure 2, ready for a further operation. Should it be necessary to clean the clamping jaws, the lower jaw 22 may be lifted clear of the peg 28 on the insert 27 and the clamping jaws may then be moved partially out of the body; conveniently, this is achieved by lifting the clamping jaw 22 when the tool is still in the position illustrated in Figure 3 so that the relative position between the clamping member 20 and the cutter 33 does not change as the lever 12 is returned to its initial position. When stripping good quality fixed wiring twin-and- earth wire having sufficient French chalk or other agents between the outer sheath and inner wires, a single stripping operation may remove, say, 150mm of outer sheath. When poorer quality wire is to be stripped, in which the outer sheath adheres to the inner conductors, a similar length of sheath may still be removed, but by taking a number of 'bites' along the wire end portion, of, say, 25mm each, or even less. Though in the above described embodiment inward movement of the cutting edges with respect to the jaws 21 and 22 is effected by the abutments 35 adjacent the cutting edges riding over cam surfaces formed on the clamping member, the apparatus may function adequately by omitting this camming action. In this case, each cutting edge 34 should project by the required extent inwardly of its associated jaw when the tool is in the position of Figure 2. Then, when the jaws 21 and 22 clamp a cable the edges will already have penetrated the cable and no further inward movement will be required; instead, the cutting edges may simply slide along the adjacent clamping member surfaces.

Claims: CLAIMS 1. Wire stripping apparatus comprising a body (10) defining an aperture in which may be received a wire to be stripped, a cutter (33) having a cutting edge (34) arranged to cut into a wire lying in the aperture which cutter (33) is mounted for sliding movement generally along the length of the aperture from a home position where a wire to be stripped may be inserted into the aperture, means controlling the movement of the cutting edge (34) in a direction generally transverse to the length of the aperture which means includes cooperating cam surfaces (35,23,18) on the cutter and on a surface over which the cutter slides, and a self-jamming cleat assembly (21, 22; 18, 19 ) for clamping the wire and cooperating with the cutter whereby sliding movement of the cutter away from its home position brings the cleat assembly into a wire-clamping position. 2. Apparatus according to Claim 1, wherein the self- jamming cleat assembly includes a pair of cleat jaws (21,22) disposed one on each side of said aperture whereby the wire may be positioned therebetween, the jaws being configured so that on contacting the wire as the cutter moves away from its home position by virtue of the cooperation between the cutter (33) and the cleat assembly, the jaws are urged more firmly to clamp the wire as the wire is pulled by the cutter in the direction of movement thereof. 3. Apparatus according to Claim 2, wherein the self- jamming cleat assembly comprises two jaws (21,22) each of which is slidably mounted within the body and cooperates with a cam surface (18,19) over which the jaw slides, which cam surface serves to deflect the jaw inwardly of the aperture during sliding movement of that jaw. 4. Apparatus according to any of Claims 1 to 3, wherein the cutter (33) has two opposed cutting edges (34) arranged one on each side of the aperture. 5.Wire stripping apparatus which comprises a body (10) defining an aperture in which may be received a wire to be stripped, a pair of wire clamping jaws (21,22) arranged for relative sliding movement with respect to the length of the aperture in the body, each jaw (21,22) sliding over an associated camming surface arranged to move the jaw inwardly towards the other jaw as the jaws are moved away from a home position, a cutter (33) also mounted for sliding movement along the length of the aperture and having a pair of wire- cutting edges (34) disposed adjacent and between said jaws, releasable means (35,23,24; 31) coupling together the cutter and the pair of jaws, and motion means (12,39) for imparting movement to the cutter (33) with respect to the aperture, whereby the pair of jaws are moved by the cutter upon movement thereof until the jaws grip a wire extending therebetween, whereafter the jaws are released from the cutter upon continued movement of the cutter. 6. Apparatus according to Claim 5, wherein said releasable means comprises spring means (31) co-acting between the pair of jaws and the cutter, which spring- means requires some force to break the connection between the cutter and the pair of jaws. 7. Apparatus according to Claim 5 or Claim 6, wherein the pair of jaws (21,22) are formed from a single strip which has a generally U-shaped profile, the cutter being similarly formed and adapted to fit within the pair of jaws. 8. Apparatus according to any of Claims 4 to 7, wherein control means are provided to control movement of the cutting edges (34) in a direction generally transverse to the length of the aperture, which means comprises co-operating camming surfaces (35; 23,24) respectively on the cutter and on the pair of jaws. 9. Apparatus according to any of the preceding Claims and configured as a hand-held tool, there being a handle (12) pivoted to the body (10) and arranged to effect sliding movement of the cutter. 10. Apparatus according to Claim 9, which further comprises a wire cutter including a blade (43) connected to said handle (12) and co-operable with a fixed blade (26) mounted on the body. 11. Apparatus according to Claim 9 or Claim 10, wherein there is provided means (45,48,49) to effect folding-back of an exposed single-core conductor, following the stripping of insulation therefrom.

Inventors: LIVERSIDGE BARRY PETER, LIVERSIDGE, BARRY, PETER
Applicants: LIVERSIDGE BARRY PETER, LIVERSIDGE, BARRY, PETER
Application year: 1991
Main classification: H02G1
IPC codes: H02G1