US3128799A

US3128799A - Strand forming device

Info

Publication number: US3128799A
Application number: US113385A
Authority: US
Inventors: Robert A Kerr
Original assignee: Northern Electric Co Ltd
Current assignee: Nortel Networks Ltd
Priority date: 1961-05-29
Filing date: 1961-05-29
Publication date: 1964-04-14
Anticipated expiration: 1981-04-14

Description

April 14, 1964 R. A. KERR 3,128,799

STRAND FORMING DEVICE Filed May 29, 1961 4 Sheets-Sheet 1 April 14, 1964 R. A. KERR STRAND FORMING DEVICE Filed May 29, 1961 4 Sheets-Sheet 2 RAKE/91? April 14, 1964 R. A. KERR 3,128,799

STRAND FORMING DEVICE Filed May 29, 1961 4 Sheets-Sheet 3 April 14, 1964 R. A. KERR 3,128,799

STRAND FORMING DEVICE Filed ma 29. 1961 4'Sheecs-Sheet 4 m-- H MH WMH @H FW .MHE? a United States Patent Ofiice Patented Apr. 14, 1964 3,128,799 STRAND FORMWG DEVICE Robert A. Kerr, Lachine, Quebec, Canada, assignor to Northern Electric Company, Limited, Montreal, Quebee, Canada, a corporation of Canada Filed May 29, 1961, er. No. 113,385 8 Claims. (til. 140-149) The present invention relates generally to the art of manufacturing stranded wire structures, and more particularly to the apparatus for preforming the individual component strands into the helices they will assume in the finished cable.

Stranded wire structures, hereinafter referred to as cables, are composed of a plurality of elongated elements twisted or stranded together into helices of equal and constant pitch about a longitudinal axis or a central core member. The individual elongated elements, or strands, are either solid filaments or wires, or a plurality of solid wires stranded together similarly to the strands in the finished cable. The central core element, if used, may be solid or stranded wire, or a fibrous rope. In electrical cables the strands may be individually insulated by coverings of paper or other suitable material.

The cross-sectional shape of the individual component strands will vary in different cables. Concentric lay cables are usually composed of strands that are solid Wires or a plurality of stranded solid wires of circular cross-section. A cable that is constructed of circular wires will, therefore, be referred to in this specification as a concentric lay cable, and its component strands as concentric strands.

Compact cables, which, because of their construction, contain the same amount of material in a smaller crosssection than concentric lay cables, are manufactured by Winding sector-shaped component strands into longitudinal helices in an assembled radial relationship such that their flat sides are disposed radially to the central longitudinal axis of the finished cable. The individual component strands are usually concentric strands drawn through shaping dies or between pairs of shaping rolls to compress the wires into the sector shape. These cables may or may not have a central core member. One construction employs component strands of a keystone shape that provide a hollow core for admission of pressurized oil.

In order that the finished cable will not exhibit tendencies to coil or twist, or that the individual strands will not unravel should the cable be severed, it is common practice to preform the strands separately into the required helices prior to their being laid into the finished cable. Prior art methods show this preforming to be done either before or after the individual strands have been placed in the cable forming machine. The preferred method is to preform the strands after they have been placed in the cable forming machine and as they are being laid into the cable because preforming them beforehand creates diiliculties in winding the twisted strands onto the supply reels.

A common apparatus used for preforming circular strands and the sector strands of mechanical cables, consists of a cylindrical bar or quill individual to each strand with a groove in the form of the desired helix machined into its surface. Each quill is mounted in a close-fitting sleeve attached to the cable forming machine and the strands are drawn through their respective preforming passages defined by the helical grooves. Because the grooves are in the form of helices of constant pitch corresponding to the required helices of the strands in the finished cable, these quills impose sudden twisting loads on the strands as they enter the grooves and cause undue abrasion of the surfaces of the strands and the entrance surfaces of the grooves. Also, the power required to pull the strands through these preforming passages is higher because of the sudden twisting loads than if the passages were designed to apply the twisting loads gradually.

In the manufacture of electrical cables from paper insulated sector strands a preferred form of the preforming apparatus consists of a split die individual to each of the strands with the preforming passage formed longitudinally between the die halves. These passages also are in the form of helices of constant pitch and have the same effect on the strands as those of the quills men.- tioned above, except that in this case the layers of insulating paper are subjected to the frictional damage. Lubrication of the strands may be employed to reduce the eifects of the frictional forces, but on the paper insulated strands, even if the oil is that with which cables of this type are subsequently impregnated, it provides a sticky surface to which undesirable foreign particles may adhere. Other forms of insulation may be adversely affected directly by the application of a lubricant.

It is, therefore, the object of the invention to provide on the cable forming machine forming dies for each of the individual strands which will preform them into the desired longitudinal helices without imposing undue twisting loads or sudden changes in loads.

Another object of the invention is to provide forming dies that will reduce the amount of power heretofore re quired to preform the strands.

A further object is to provide forming dies that will not make lubrication necessary for smooth passage of the strands therethrough.

These and other objects are accomplished by providing for each strand a passageway formed either between two halves of a die or in the surface of a quill such that the passageway is a helix of infinite pitch, that is, a straight line, tangential to the strand at the entrance end, and decreasing pitch toward the exit end such that a strand passing therethrough will emerge from the exit end in the form of the helix required for proper laying-in of the strand into the finished cable.

A complete understanding of the invention may be obtained from the following detailed description and 'explanation which refer to the accompanying drawings, illustrating preferred embodiment in which like reference numbers refer to like parts, and in which:

FIG. 1 is a diagrammatic side elevation of a cable forming machine having this invention embodied therein;

FIG. 2 is a sectional view of a compact cable formed of sector strands;

FIG. 3 is a side elevation of one embodiment of a forming die mounted on the cable forming machine of FIG. 1;

FIG. 4 is an end elevation of the forming die of FIG. 3;

FIG. 5 is a perspective view of a forming die insert;

FIGS. 6, 7 and 8 are sections taken along lines 6-6 7-7 and 88 respectively in FIG. 5;

FIG. 9 is a perspective view of a forming die cap inverted from its position in the forming die of FIG. 4;

FIG. 10 is a sectional View of a concentric lay cable formed of concentric strands;

FIG. 11 is a partial side elevation of another embodiment of a forming die;

FIG. 12 is an end elevation of the forming die of FIG. 11;

FIG. 13 is a perspective view of a quill .for the forming die of FIG. 1'1; and

FIGS. 14, 15 and 16 are sections taken along lines 1414, 15-15 and 1'616 respectively in FIG. 13.

In FIG. 1 is illustrated a cable forming machine which comprises a central tubular shaft 1 supported at one end by a bearing 2 mounted on a pedestal 3, and at the other end by freely rotatable rollers 4 adapted to contact the cylindrical surface of a strand guide plate 5. Attached to shaft 1 is a reel support plate 6 to which are mounted reel cradles 7. In this embodiment four cradles are equally spaced around and at the same distance from the shaft 1, two of which have been deleted in the illustration for clarity. One supply reel 8 is rotatably mounted in each cradle 7 by means of the arbor 9. Also mounted on shaft 1 is a forming die plate 10 additionally supported by rollers 11 rotatably mounted in a housing 12. Rotation of the forming machine about its axis is achieved by a driving means (not shown) through gear 13 rigidly attached to the rearmost end of shaft 1.

In the manufacture of a compact cable the sector strands 14 are coiled on the supply reels 8. As shown in FIG. 2 the cross-section of the sector strand 14 is bounded by two intersecting fiat surfaces 15 and an arcuate surface 16. When the machine is in operation the individual sector strands 14 are drawn from the reels 8 through apertures in the guide plate 5 and through separate forming dies '17, to which this invention is directed, attached to the forming die plate 10, equally spaced around and at the same distance from the shaft 1. The forming dies 17 impart a twist to each sector strand 14 to assist in the laying-in of these strands as they converge at a closing die 18 to form a compact cable 19 of crosssectional shape as shown in FIG. 2. The cable is drawn from the forming machine and coiled by a suitable capstan and take-up indicated generally as the haul-01f mechanism 21' supported on stand 22'. The rate at which the capstan draws the sector strands 14 from the reels 8, coupled with the rotary speed of the forming machine determines the helical pitch or lay of the strands in the assembled compact cable 19. If desired a central core wire may be supplied through the tubular bore of the central shaft 1 from a reel 21 mounted on a stand 22.

FIGS. 3 and 4 show in detail one embodiment of a forming die 17 adapted especially for the sector strand 14. Attached to the forming die plate 10 by means of a backing plate 23 and screws 24 is an adaptor plate 25 suitably constructed to provide a mounting surface 26 substantially normal to the sector strand 14. To the surface 26 is mounted a die holder 27 by means of cap screws 28 passing through arcuate slots 20 in the mounting flange 30. When the cap screws 28 are loosened the slots 29 permit rotation of the die holder 27 about its longitudinal axis by means of a prying bar inserted in a hole 31 passing through a tab 32. The backing plate 23, forming die plate 10, adaptor plate 25, and the mounting flange of the die holder 27 have an aperture 33 extending through them to permit passage of the sector strand 14 therethrough to the forming portion of the die.

The portion of the forming die 17 in which the sector strand 14 is twisted into the desired helix consists of a die insert 34 and a die cap 35 held in co-operating relationship within a seat in the saddle portion 36 of the die holder 27. The elongated die insert 34 is adapted for a sliding fit within the seat which is formed by the parallel side walls 37 and a lower surface 38 extending at right angles between them. The die insert 34 is secured against movement within the seat by means of cap screws 39. The (to-operating die cap 35 has an extended portion between the parallel edges adapted for a sliding fit within the side walls 37 of the saddle portion 36, and is held in position by wing screws 31 extending through longitudinal horizontally extending tabs 42.

A passage within which the sector strand 14 is twisted lies between and longitudinally of the die insert 34 and die cap 35. Thatportionof the passage which is formed in the die insert 34 is more clearly shown in FIGS. 5 to 8 inclusive. At any cross-section of the die insert 34 such as at line '66 in FIG. 5, the groove is V-shaped as defined by the side walls 43 inclined with respect to each other at an angle at which corresponds to the angle between the fiat surfaces 15 of the sector strand 14. The intersection of the side walls 43 forms a straight line AA that extends normal to the cross-section of the die insert 34 in a plane the edge view of which, as represented by line BB in FIG. 6, bisects the cross-section. The widths of the side walls 43 are equal to each other and to the width of a flat surface 15 of the sector strand 14. As shown the upper edges of the side walls 43 are formed by intersections with the

surfaces

44 and 45 respectively which surfaces in the cross-sectional plane extend parallel to the lower surface 46 of the die insert 34.

The twist is imparted to the sector strand 14 by changes in the angular position of the groove cross-section in one rotational direction about the line AA between the entrance end 47 and the exit end 48 of the die insert 34. This change in angular position is shown in FIGS. 6 to 8 by the rotation of the bisector CC of the angle at of the V-shaped groove through an angle 0 which determines the total amount of twist applied to the sector strand 14. Because it is impractical to rotate the groove beyond the point where either of the side walls 43 becomes parallel to the lower surface 46, a maximum twist angle 0 is obtained by constructing the groove with the bisector CC at the entrance end 47 an angle to one side of the line BB and at the same angle to the other side at the exit end 48. The direction of rotation of the bisector CC determines the lay direction of the sector strand 14 in the finished compact cable 19.

At any intermediate cross-section of the die insert the bisector CC is at some angle 0 less than the final angle 0, to its original position at the entrance end 47 as now represented by line D-D in FIG. 7. This angle 0 determines the twisting force or torque applied to the sector strand 14 at that point a distance x from the entrance end 47. In this invention the angles fi at the cross-sections throughout the length of the die insert are such that the torque T on the sector strand 14 increases from zero, or a very low value, at the entrance end 47 to a maximum value T at the exit end 48 proportionally to the distance x from the entrance end 47. In a die insert of length D, therefore,

The relation between the torque T and the angle 0 is obtained from the equation for a cylindrical bar of length I under a constant torque T about its longitudinal axis:

Tl e? where 0 is the angle through which the sector strand is twisted and G and I represent physical constants for the particular sector strand. This equation may be rewritten as T=GJ Equation I from which it is apparent that the torque is proportional to the rate of change of the angle of twist of the sector strand. For the groove of this invention in which the torque on the sector strand '14 is increased evenly, a simplified form of the above expression for any point along the die insert a distance x from the entrance end 47 is d0, T or'czg lAt the exit end 48 the rate of change of the angle 0 is determined from the helical pitch or lay of the com- Equation II pact cable 19 in which the sector strand 14 twists through 360 in a distance L. This rate of change is nan! dw L From Equations I, II and III the rate of change of the angle 0,, is

Equation III E5 D X L for the torque T to increase evenly over the die insert of length D. Integration of Equation IV gives Equation IV Example A plurality of sector strands 14 are to be assembled into a compact cable with a 60 inch right-hand lay, that is, each strand will form a helix with a clockwise twist and a pitch of 60 inches. The forming die inserts 34 are inches long. The equation for the angular position of the groove at any distance x from the entrance end 47 of the die insert 34 is, from Equation V above,

The total twist 0 of the groove is determined at the exit end 48 where the distance x equals the length D of the die insert 34. Its value in example is The groove, therefore, will begin 15 degrees to the left of the line BB at the entrance end 47 and rotate through degrees clockwise to 15 degrees to the right of line BB at the outlet end 48. The distance from the entrance end 47 to the point where line B-B and bisector CC coincide, or, in other words, to where bisector CC has rotated through 15 degrees, is, again from Equa- The portion of the passage between the die insert 34 and die cap 35 that is formed within the die cap 35 and co-operates with the V-shaped groove in the die insert 34 to impart the desired twist to the sector strand 14 is shown in FIG. 9. The groove is arcuate in cross-section as shown at 49, the radius of curvature corresponding to that of the arcuate surface 1 6 of the sector strand 14. When the die cap 35 is in co-operating relationship with the die insert 34 the surface 49 at any cross-section has its center of curvature on the line A-A of the die insert 34 and is disposed angularly about the line A-A such that the lines of intersection between the surface 49 and the

surfaces

50 and 51 are adjacent the aforementioned lines of intersection of the side walls 43 and the

surfaces

44 and 45 respectively of the V-shaped groove in the die insert 34. These

surfaces

50 and 51 are disposed at right angles to the side walls of the die cap 35 and contact throughout their surface are as the surfaces 44 and respectively of the die insert 34.

In this embodiment of the forming die 17 a die insert 34 and a die cap 35 are necessary for each size and lay of the sector strand 14. When the proper die insert 34 and die cap 35 are assembled about a sector strand 14 in a cable forming machine, the die holder 27 is rotated Equation V 6 about the longitudinal axis of the sector strand 14 by means of a prying bar inserted in the hold 31 in the tab 32, as hereinbefore described, to position the sector strand 14 so that its flat surfaces 15 are disposed radially to the longitudinal axis of the compact cable I1 9 at the closing die 18.

Another embodiment of a forming die 17 is shown in FIGS. 11 and 12 and is particularly adaptable to the manufacture of concentric lay cables, a typical form of which is shown in FIG. 10. This cable 52 is composed of concentric strands 53 substantially circular in crosssection, stranded in close relationship about a central core strand 54. The forming die 17 for preforming these concentric strands 53 is substantially the same as hereinbefore described for the sector strands 14 except that the forming portion consists of a cylindrical quill 55 having a groove 57 in its cylindrical surface 58 of U-shaped cross-section adapted to accept the concentric strand 53 in a close-fitting but slidable relationship.

The quill 55 is secured against movement within a close fitting concentric sleeve 56 by cap screws 59. The combination of the quill 55 and sleeve 56 is fixed rigidly by cap screws 60 within a concentric seat 61 formed in a saddle portion 62 of a die holder 63 and lies coaxially with respect to the longitudinal axis of the concentric strand 53. The die holder 63 is the same as the die holder 2.7 of FIGS. 3 and 4 except for the saddle portion 62. The quill 55, sleeve 56 and saddle portion 62. constitute the forming portion of the second embodiment of the forming die 17.

The quill 55 as shown in FIG. 13 is constructed of such diameter and the groove 57 of such depth that the concentric strand 53 will lie just completely within the groove 57 and that in this position the longitudinal axis of the concentric strand 53 is the same radial distance from the longitudinal axis of the quill 55 as it would be from the longitudinal axis in the finished concentric lay cable 52. Also the angular position of the groove 57 about the longitudinal axis of the quill 55 and between the entrance end '64 and the exit end 65 thereof is determined by the previously developed Equation V. A typical position of the groove 57 at the entrance end 63 is shown in FIG. 14, and at the exit end 65 in FIG. 16 after rotating counterclockwise through a total twist angle 0. FIG. 15 shows the groove 57 at a point a distance x from the entrance end 64 after having rotated through angle 0 In these figures the line BE represents the position of the groove 57 at the entrance end 64 and line F-F, the position at any other point in the length of the quill 55. In this embodiment there is no restriction on the total twist angle 0 for the groove 57. A separate combination of quill 55 and sleeve 56 is required for each particular diameter and lay of the concentric strand 53, and for different radial distances of these strands from the longitudinal axes in various concentric lay cables 52.

Although this embodiment is particularly suited for concentric strands 53 it is also adaptable for other strand shapes such as the sector strand 14. For these applications in which the sector strands 114 must be properly aligned at the closing die 18, the die holder 63 may be rotated about its longitudinal axis similarly to the die holder 27 of FIG. 3 by means of a prying bar inserted in a hole 66 formed in the tab 67.

Either form of the twisting passage described in the two embodiments of the invention may be modified to over-twist the component strand so that if there is any relaxation of the twist in the strand as it leaves the passage the added twist will compensate and the strand will assume the required form. The amount of added twist will be specific for each size and material of the strand, and for each lay of the strand in the finished cable. It may be determined experimentally and decreases the helical pitch L in Equation V to less than the actual value for the cable, resulting in an increase in the twist angle 0.

Although only two embodiments of the invention have been described, it will be apparent that other adaptions and modifications will be possible within the scope of the following claims.

What is claimed is:

1. In an apparatus for making a stranded wire structure from a plurality of component strands which comprises a rotary cable forming machine, a 'closing die adjacent the outlet end thereof, a haul-off mechanism adjacent said closing die 'for pulling the stranded Wire structure through said machine and said closing die; a forming die plate included in said machine and rigidly attached to the output end thereof, havingaflixed thereto a forming die individual to each of said strands, a longitudinal passage formed in said forming die adapted to engage and impart a twist to said strand, said passage at the entrance end thereof being a helix of infinite pitch, tangential to said strand, and having the form of a helix at the exit end thereof corresponding to the helix of said strandin said stranded wire structure,'said passage being smoothly transitional between said entrance and said exit ends thereof in the form of a helix of progressively decreasing pitch.

2. In an apparatus'in accordance with claim 1 wherein said forming dieincludes a' die holding means, a die insert, and a co-operating'die cap.

3. In an apparatus in accordance with claim 2 said die insert with a longitudinal groove formed within one surface thereof, said groove defined by two side walls disposed with respect to each other at anangle equal to the angle'betwee'n the flat surfaces ofsaid sector-shaped strand, said side walls intersecting along a straight line parallel to the longitudinal axis of said die insert, the position of said groove along the length of said die insert defined by rotation of said side walls about said line of intersection according to the expression where 9,, 'is the angle through which said side walls rotate in a distance x measured from one end of said die insert, D is the lengthof said die insert, L is the helical pitch of said strand in said stranded wire structure; and said die cap with a longitudinal groove therein having an arcuate cross-section with a radius of curvature equal to that of the arcuate surface of said strand, said die cap co-operating with said die insert to form said longitudinal passage therebetween.

4. In an apparatus in accordance with claim 2 saiddie holding means comprising a flange, a saddle portion having a rectangular groove therein and having means for rigidly positioning said die insert and said die cap in co-operating relationship with said longitudinal passage extending perpendicularly to said flange, said flange having a central aperture to permit passage of said strand therethrough to said longitudinal passage, arcuate slots positioned adjacent to and lying inside the outer periphcry of said flange for passage therethrough of mounting screws into said forming die plate, said slots'permitting rotation of said forming die with respect to said forming die plate about the longitudinal axis of said strand.

5. In an apparatus in accordance with claim 1 said forming die including a die holding means, a cylindrical 8 quill anda concentric sleeve positioned coaxially within a cylindrical seat in said die holding means, said longitudinal passages formed within the surface of said quill adapted to engage and impart a twist to said strand, said passage at the entrance end thereof being a helix of infinite pitch, tangential to said strand, and having the form of a helix at the exit end thereof corresponding to the helix of said strand in said stranded wire structure, said passage being smoothly transitional between said entrance and said exit ends in the form of a helix of progressively decreasing pitch.

6. In an apparatus in accordance with claim 5 said quill with a longitudinal groove in the cylindrical surface thereof, said groove adapted to receive said strand therein in a close slidable relationship, the position of said groove along the length of said quill defined by the rotation of the cross-section of said groove about the longitudinal axis of said quill according to the expression where 0 is the angle through which said cross-section rotates in a distance 2: measured from one end of said quill, D is the length of said quill, L is the helical pitch of said strand in said stranded wire structure; and said sleeve co-operating coaxially with said quill to form said longitudinal passage therebetween.

7. In an apparatus in accordance with claim 6 said die holding means comprising a flange, a saddle portion having a cylindrical seat therein and having means for rigidly positioning said quill and said sleeve in coaxial co-operating relationship with the longitudinal axis of said quill extending perpendicularly to saidflange, said flange having a central aperture to permit passage of said strand therethrough to said longitudinal passage, arcuate slots positioned adjacent to and lying inside the outer periphery of said flange for passage therethrough of mounting screws into said forming die plate, said slots permitting rotation of said forming die with respect to said forming die plate about the longitudinal axis of said strand.

8. A forming die for imparting a uniform twist to a wire strand comprising; a die body, a longitudinal passage formed in said die body and adapted to engage and impart a twist to said strand, said passage at the entrance end thereof being a helix of infinite pitch, tangential to said strand, and having the form of a helix at the exit end thereof with apitchdesired in the finished strand, the portion of said passage between said entrance and said exit ends having the form of a helix of progressively decreasing pitch from the infinite pitch of said entrance end to the pitch of said exit end, whereby a strand passing through said die body will be subjected to an evenly increasing amount of torque for imparting a twist to said strand.

References Cited in the file of this patent ,UNITED STATES PATENTS 152,557 Haskell et al June 30, 1874 1,243,353 Snedeker Oct. 16, 1917 1,761,482 Laubenthal June 3, 1930 2,218,104 Brignall Oct. 15, 1940

Claims

1. IN AN APPARATUS FOR MAKING A STRANDED WIRE STRUCTURE FROM A PLURALITY OF COMPONENT STRANDS WHICH COMPRISES A ROTARY CABLE FORMING MACHINE, A CLOSING DIE ADJACENT THE OUTLET END THEREOF, A HAUL-OFF MECHANISM ADJACENT SAID CLOSING DIE FOR PULLING THE STRANDED WIRE STRUCTURE THROUGH SAID MACHINE AND SAID CLOSING DIE; A FORMING DIE PLATE INCLUDED IN SAID MACHINE AND RIGIDLY ATTACHED TO THE OUTPUT END THEREOF, HAVING AFFIXED THERETO A FORMING DIE INDIVIDUAL TO EACH OF SAID STRANDS, A LONGITUDINAL PASSAGE FORMED IN SAID FORMING DIE ADAPTED TO ENGAGE AND IMPART A TWIST TO SAID STRAND, SAID PASSAGE AT THE ENTRANCE END THEREOF BEING A HELIX OF INFINITE PITCH,