US2214491A

US2214491A - Attachment for flexible tubing and method of fixing it

Info

Publication number: US2214491A
Application number: US264557A
Authority: US
Inventors: Tondeur Rene
Original assignee: Bowden Engineers Ltd
Current assignee: Bowden Engineers Ltd
Priority date: 1938-04-11
Filing date: 1939-03-28
Publication date: 1940-09-10
Anticipated expiration: 1957-09-10

Description

R. TONDEUR Sept. 10, 1940.

ATTACHMENT FOR FLEXIBLE TUBING AND METHOD OF FIXING IT Filed larch 28, 1939 Fig. 1

Inventor WiM Attorney Patented Sept. 10, 1940 UNITED STATES 2,214,491; ATTACHMENT FOR FLEXIBLE TUBING AND METHOD OF FIXING 1T Rene Tondeur, London, England, assignor to;

Bowden (Engineers) Limited, London, England,-

a British company Application March 28, 1939, Serial No. 264,557

. In Great Britain April 11, 1938 sclaims. (01.29 148) T The present invention relates to methods of swaging attachments or couplings to flexible members having a hollow centre, particularly those o'f'concentric-lay composed of single or multiple shells of helically laid coarse pitched wires surrounding a hollow core. The invention is especially suitable for swaging pieces onto a hollow member used as theinner or extension member of a Bowden mechanism and composed f a single layer or shell of helically laid coarsepitchedwires surrounding a hollow core of opencoiled fine pitched wire. so as to form a hollow structure which is readily transversely deformable when the mechanism is curved and the inner or extension member is underworking tension.

Examples of Bowden mechanisms having inner members according to such last defined'flexible membersare described in the specification of companion applicationNo. 239,476; dated November 8, 1938, patented November 21, 1939, No. 2,180,442.

For the purposes of the present invention more than one s'urrounding'shell can be employed-and the hollow core above referred to' can be replaced by a; close coiled wire if so desired.

My presentiinvention deal's'more particularly with an improvement in that method of anchoring an attachment or coupling to a hollow flexible member, which consists in applying thereto a relatively thick-walled sleeve, socket, collar or the li ke 'attachment, hereinafter termed stock, of;ductile metal, and cont'racting'the attachment ,on' to the flexible member preferably bycold s'waging, so as to gather in or diminish the'diameter "of the stool; substantially evenly therearound. v 3

The process according to" thepresent invention of uniting a surrounding piece of stockontoa hollow flexible member comprising one or more shells of coarse-pitched wires surrounding a sustaining coil of fine pitched wire consists in in- 'serting a'core or plug into one'end of the-member and swaging the stock onto such end to'produce intimate and direct contact between the stock and the coarse-pitched shell or the outer of one of -two or more shells, between such shell or the inner of two or more shells -and the fine-pitched coil and between the fine pitched coil and the core or plug in such'a manner that the wires are 'clamped by an intense frictional grip in' a I Preferablyiat onefend at leastof the tubing the plug is longitudinally holed or grooved in order to permit of the passage of lubricant into the flexible member, and conveniently and advantageously the plug is-provided with a headed end, for example, a cheese-shaped headed end, which may or may not be spaced from the corresponding end of the fiexible member, so that the metalof the surrounding piece'of'stock when contracted on to the flexible member directly grips such head. In this manner any axial load on the fiexible member is partly transmitted through such plug an'd, therefore, the resistance to parting is opposed not only ('1) directly by grip of the surrounding; piece of stock on the flexible member'and (2) by gripof'the'flexible member on the plug, but also directly by'gripof the surrounding piece on the plug, the total hold being thereby considerably increased. The surroundin'g piece of stock-may be of low carbon mild steel having free cutting properties or of alloy steelsuch as nickel steel or chrome steel and I the stock 'is-preferablycontracted on to the hollow member by direct radial pressure. I

The fine-pitchedsustaining coil of the tubing may be of-anysuitable'section. It'may' be of round section wire and of open coil form. The round wire could becoiled, at least where-the joint is to be made, with the end convolutions 1 contacting or they and the rest of the sustaining coil may be coiled with a small separation of the .convolutions as for example is described in my co-pending application No. 239,476. In either case the pressurewill be betterdistributed than if a widely'open coil is used. If however a fine pitched inner coil of square or rectangular sec-. tion isemployed it is possible to obtain a greater surface'area of contactbetweensuch coil and the coarse. pitched wires on the one hand and the plug on the other.

The present invention makes it possible to apply considerable pressureto the stock so as elastically to deform the .wires between the stock and the plug without risk of collapsing of the hollow member but the pressure shouldnot be such as to deform the wires beyond the limit of elastic recovery and is not such as to cause the metal to fill the grooves or to intrude to any substantial extent into the grooves between the coarse-pitched ,wiresh' .A strong union of the stock, wires and the plug can thus'be' obtained.

The inner member of Bowden mechanism is subjected in use tovcry considerable extension forces. In general the inner member consists of 'awire cable composed of a central core and one or more layers of coarsely-pitched helically core or plug. The present invention makes itpossible to apply the necessary pressure to produce a joint of the desired strength. In some cases the core may be in the form of a solid plug but even where one or more passages is formed in the plug or where a hollow core is used, as for example is shown in Fig. 2 of the drawing hereinafter referred to, the plug or core not only permits of the desired swaging pressure being obtained but, by enabling the wires to be sandwiched, in an elastically deformed state between the core and the stock, the hollow member is enabled to withstand the high extension forces without rupture .of the union.

For the stock I have found that annealed steel containing from .1 to .4% of carbon and of tensile strength between 24 to 29 tons with a minimum elongation of 25% is suitable for carrying out the invention. Good results have been obtained by using a steel containing .2 of carbon.

The wires laid with a coarse-pitch to form the shell may for example be of to tons tensile strength having a carbon content between 0.50 and 0.60, manganese 0.50 to 0.70, silicon 0.05 to 0.15, phosphorus under 0.05 andsulphur under 0.05.

The fine pitched coil may conveniently be of plow-steel wire, e. g., of composition about as follows:

Percent Carbon 0.83 Manganese 0.59 Silicon 0.14 Sulphur 0.01 Phosphorus; Nil Gopper 0.03

' The'inner plug maybe of mild steel. The plug affords a supporting inner core against which the surrounding parts are forced by the swaging pressure in order to obtain the desired clamping action and elastic deformation of the wires between the plug and the stock.

' Methods of forcibly closing the stock to the flexible member which work well for the purposes of the present invention are those described in the specification of prior application No. 174,- 075/37, patented Aug. 29, 1939, No. 2,171,280. It is preferred to apply a gradually increasing pressure as in the method described in prior patent specification No. 174,075 using the apparatus therein described to obtain the necessary hydraulic pressure applied to the stock, although a predetermined strength of joint can be produced by delivering a given small number of blows to the piece in a rotary swaging machine. I do not however recommend swaging by delivering' a great number of light blows as it is kliflicult to ensureuniformity of output when mass producing. The stock then is apt to undergo work-hardening and the numerous blows tend often to weaken the joint rather than to strengthen it.

Where the cable is to be used as the inner member of a Bowden mechanism, it is necessary, as explained in my aforesaid concurrent application, for the hollow cable to be of greater external diameter than an ordinary compact cable designed to withstand the same load. Consequently as for a given diameter of hollow member it is not necessary to resist the same load as has to be resisted by 'a. compact cable of such diameter, the formula given in my prior patent application No. 174,075 needs modification when adapted to the presentinvention; e. g., where a hollow inner member according to the invention is used of outside diameter it is not necessary to go above a test load of 2000 lbs. instead of 4:000 lbs. for an ordinary Bowden inner member of diameter. Therefore I do notnow recommend the use of a sleeve of an external diameter of twice the diameter of the bore with a length of five times the latter diameter. Such a sleeve could hold up to 6000 lbs. which would be well above the breaking strain of the hollow inner member, and the diameter of the sleeve for such an inner member could be reduced to RT" therefore saving weight and cost on the metal of the sleeve.

A formula approximately as follows for the total pressure will be found to-produce good reand the formula for ascertaining the pressure per square inch should be modified as follows:

There may be difficulty, particularly when the sustaining coil is of open pitch, in forcing lubricant along the inside of the hollow member to the medial part of the length thereof owing to the tendency for the lubricant to escape somewhat readily through the coiled walling of .the tube at or near the end at which the lubricant is forced into the hollow member.

In such a case the hollow member may be provided with an interior tubing composed of closely interwound coils which are laterally displaceable relatively to one another and are so formed that whether the hollow member be straight or curved, the wall of the tubing does not gape but remains closed. This tubing may extend for example to about nearly half-way along the hollow member and examples of tubing which will serve are described and claimed in prior Patent No. 2,092,898., The outer end portion of the tubing may-form the core between which and the stock the coarse and fine pitched wires are gripped. The tubing should be as resistant as possible to radial compression, the section of the wires being preferably appropriately chosen so as to leave no greater diameter of bore than" is necessary for the passage of lubricant. As the tubing is of small diameter and of comparatively light weight it does not unduly decrease the flexibility of the hollow member.

The wires of the interwound tubing may be made of spring steel of 100 tons tensile strength.

Two forms of swaged hollow members according to the present invention are shown in the accompanying drawing.

In the form shown in Fig. 1, the end of apiece of tubing composed of a single shell I consisting of wires laid alongside each other in the form of coarse pitched helices and an open coil 2 around which the wires are laid is filled by a plug 3 having a head 4 and the sleeve 5 is swaged around such end into intimate contact with thewires .and the head 4. The swaging is preferably effected by steady pressure, the limit "of whichis so predetermined that there is little or no flow of the metal of the stock into the grooves between the wires. Consequently the wires impress only narrow helical bands upon the interior of the stock, or spaced shallow helical grooves of a depth which is equal to only a small part of the radius of the wires, the joint being mainly the result of intense frictional grip. The plug is provided with a passage 9 for lubricant.

The wires of shell I are brought into intimate contact with the open coil 2 .and the coil 2 in turn is brought into intimate contact with the plug 3. Some indentation of the coil 2 into the plug 3 may be produced depending upon the hardness of the plug.

In the alternative form shown in Fig. 2 the plug 3 is replaced by a tubing 6 composed of two (or more)

interwound wires

1, 8 which are of trapezoidal or triangular section so as to be displaceable laterally relatively to one another when the tubing is curved. The tubing extends beyond the swaged end, for example nearly to the middle of the length of the hollow member and since the tubing remains closed whether it is bent or straight, lubricant can be forced-along the tubing to the inner end thereof and thereby the lubrication of the hollow member at or near the centre and towards the other end is facilitated. In this form the coil 2 is brought into intimate contact by the swaging process with the outer end of the tubing. The lubricant can be forced along the inner core and then pass through the coil and the outer shell and thence pass along the space between the inner Bowden member and around the shell of coarse pitched wires at the corresponding end portion of the tubing and swaging the said member on to such end to produce intimate and direct contact between the solid wall of the said member and the wires of the shell without any substantial penetration of the metal of said wall into the grooves formed by the wires of the shell, between such wires and the sustaining coil and between the coil and the core in such a manner that the wires are sandwiched between the core, which forms a permanent part of the joint, and the said wall and are deformed but only within the limits of elastic recovery so that the hollow member is united with the tubing by an intense frictional grip.

2. A flexible tubing adapted to withstand high tractive forces comprising concentric structures at least the out-er one of which is in the form of a shell composed of wires arranged helically in close order with a coarse pitch, said concentric structures including an internal sustaining structure for said shell in the form of a coil of fine pitch, a core fitted into the interior of one end of the tubing and a solid-walled hollow member. said coarse pitched wires defining the external peripheral surface of said concentric structures at the corresponding end of the tubing and said solid-walled hollow member being fitted around said surface, said member being in intimate and direct contact with the coarse pitched wires defining such external surface and strongly frictionally gripping said wires but not substantially penetrating into the grooves formed thereby, the respective structures being sandwiched between the core and said hollow member so that the wires of said structures are deformed but only within the limits of elastic recovery.

3. A flexible tubing adapted to withstand high tractive force's comprising concentric structure at least the outer one of which is in the form of a shell composed of wires arranged helically in close order with a coarse pitch, said concentric structures including an internal sustaining structure for said shell in the form of a coil of fine pitch, a core fitted into the interior of one; end of the tubing and a solid walled hollow member, said coarse pitched wires defining the external peripheral surface of said concentric structures at the corresponding end of the tubing and said solid-walled hollow member being fitted around said surface, said member being in intimate and direct contact with the coarse pitched wires defining such external surface and strongly frictionally gripping said wires but not substantially penetrating into the grooves formed thereby, the respective structures being sandwiched between the core and said hollow member so that the wires of said structure are deformed but only within the limits of elastic recovery, and said core having a portion which protrudes beyond the end of the concentric structures into said hollow member, said protruding portion being frictionally gripped by said hollow member.

4. A flexible tubing adapted to withstand high tractive forces comprising concentric structures, at least the outer one of which is in the form of a shell composed of wires arranged helically in close order with a coarse pitch, said concentric structures including an internal sustaining structure for said shell in the form of an open coil of fine pitch and of rectangular section wire, a core fitted into the interior of one end of the tubing and a solid walled hollow member, said coarse pitched wires defining the external peripheral surface of said concentric structures at the corresponding end of the tubing and said solid-walled hollow member being fitted around said surface, said member being in intimate and direct contact with the coarse pitched wires defining such external surface and strongly frictionally gripping said wires but not substantially penetrating into the grooves formed thereby, the respective structures being sandwiched between the core and said hollow member so that the wires of said structure are deformed but only within the limits of elastic recovery, said core having at least one small bore passage to provide an inlet for lubricant to the interior of the tubing, and said core having a portion protruding beyond the end of the concentric structure into said hollow member, said protruding portion being frictionally gripped by said hollow member.

5. A method of attaching a solid-walled hollow member around a flexible tubing comprising concentric structures formed by at least one shell of coarse-pitched wires and by an inner sustaining coil therefor of fine-pitch, which consists in fitting into the interior of one end of said coil a core and at the corresponding end of the tubing fitting around the coarse pitched wires defining the outer of said structures the said solid-walled hollow member and swaging the said member onto such end to produce intimate and direct contact between the solid wall of the said member and the coarse pitch wires of said outer structure without any substantial penetration of 15 the metal of said wall into the grooves formed by said wires, between the respective structures and between the coil and the core in such a manner that the wires are sandwiched between the core, which forms a permanent part of the joint, and the said wall and are deformed but only within the limits of elastic recovery so that the hollow member is united with the tubing by an intense frictional grip.

6. A flexible tubing comprising concentric structures formed by at least cne'shell of coarsepitched wires and by an inner sustaining coil thereforof fine-pitch, a core fitted into the interior of one end of the coil and a solid-walled hollow member at the corresponding end portion of the tubing fitted around the coarse pitched wires forming the outer one of said structures, said core being in the form of a flexible tube comprising at least two closely interwound coils which are relatively laterally displaceable when the tube is flexed and which forms a closed wall whether the tube be straight or flexed, said tube extending into the tubing considerably beyond the inner end of the solid Walled hollow member, said hollow member being in intimate and direct contact by its solid wall with the coarse pitched wires of the outer structure so as strongly to grip said wires without there being any substantial penetration of the metal of said wall into the grooves formed by said wires, the respective structures being sandwiched between the core and said hollow member; the wires of said structures being deformed but only within the limits of elastic recovery, said tube core forming an inlet to a medial portion of the tubing so that lubricant can be forced along the tube and allowed to escape therefrom into the tubing only at the remote end of the said tube.

RENE TONDEUR.