Patent Publication Number: US-6705148-B1

Title: End-forming of corrugated metal foil wrap tubing

Description:
The present invention is directed to terminating the ends of lengths of corrugated metal foil wrap tubing, and more particularly to a method and apparatus for end-forming such tubing. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     Metal foil wrap corrugated tubing, also referred to as convoluted multi-ply shielding, has been employed as a protective sheathing in automotive and other applications. For example, metal foil wrap tubing is employed to protect delicate or thermally sensitive items, such as electrical wires, fuel lines and plastic tubes with low heat resistance, from exterior abrasion or heat. Metal foil wrap corrugated tubing is also employed to sheathe high temperature tubes, such as tubes conducting exhaust gas, from adjacent exterior thermally sensitive items such as electrical wires and fuel lines. Such metal foil wrap corrugated tubing may be readily bent and formed around objects and turns, and provides good protection against abrasion of the internal electrical wires. One line of metal foil wrap corrugated tubing is marketed by Clevaflex, Ltd. of Cleveland, Ohio. In general, such tubing comprises an elongated strip of layered material, including metal such as stainless steel, spirally wound into a tube, mechanically locked in place by microcorrugations and bonded with a thermosetting adhesive. When the tubing is cut to desired length, steps must be taken to prevent unwrapping at the end of the spirally wrapped corrugated metal, particularly at high temperatures at which the adhesive may lose adhesion. This is conventionally accomplished by crimping or otherwise securing an end cap or ferrule to the end of the tube. These end caps are expensive relative to the cost of the tubing itself. 
     It is therefore a general object of the present invention to provide a method and apparatus for forming the end of a length of metal foil wrap corrugated tubing that prevent unwrapping at the tubing end, that do not damage the tubing length, and that are adapted for automated implementation. Another object of the invention is to provide a length of metal foil wrap corrugated tubing having a formed end to prevent unwrapping of the tubing material, but without use of additional components such as the conventional end caps. 
     A method of forming an end of corrugated metal foil wrap tubing in accordance with one aspect of the present invention includes providing a length of tubing having a sidewall with spaced corrugations and folding a portion of the end of the tubing into the sidewall to form a sidewall end portion of inner and outer layers. The sidewall end portion is preferably additionally axially compacted by axially compressing the end portion to bring the corrugations into axial abutment. The end portion of the tubing preferably is folded inwardly into itself by bringing the end portion into axial engagement with a folding tool. In the preferred embodiment of the invention, this axial engagement is continued to compact the end portion of the tube in an annular end channel on the compacting tool. By folding the tubing end inwardly upon itself and then axially compacting the corrugations as in the preferred embodiment of the invention, a tight end joint is formed to resist unwrapping or unraveling of the metal foil. 
     In the preferred embodiment of the invention, a length of metal foil wrap corrugated tubing is clamped between jaws for holding the tubing during contact with the compacting tool. These jaws preferably are provided as an opposed set of jaws that have rib segments which, when the jaws are closed around the tubing, form a circumferentially continuous rib to indent a channel around the periphery of the tubing adjacent to the end portion of the tubing. This channel serves both to enhance clamping of the tubing between the jaws against axial forces applied to the tubing by the compacting tool, and to isolate the end portion of the tubing from the remainder of the tubing length during the end-forming operation. In the preferred embodiment of the invention, the compressing operation is preceded by a folding operation, in which the end of the tubing is brought into engagement with a fold-over tool that folds the end of the tubing radially inwardly. This folded portion of the tubing is then engaged by a horn that extends axially from the compacting tool further to fold the end axially into the tubing end portion prior to engagement of the tubing with the channel in the compacting tool. The same set of clamping jaws may be employed to clamp the tubing during both the folding and the compacting operations. In the preferred embodiment of the invention, the folding operation is preceded by a crimping operation, in which the end of the tubing is crimped radially inwardly by a plurality of crimping jaws acting against a conical surface on a mandrel within the tubing. 
     Thus, in its most preferred form, the present invention provides a method for forming a free end of a length of metal foil wrap corrugated tubing in which the free end of the tubing is first crimped against a mandrel, then folded to extend radially inwardly, then folded further to extend axially inwardly within the inside diameter of the tubing end, and then compacted axially to bring the corrugations into facing abutment with each other and tighten the formed end of the tubing against unraveling of the metal foil. The crimping operation involves closure of a plurality of jaws around the free end of the tubing and deforming the tubing end against a tapering surface on an internal mandrel. The tubing is then gripped between jaws that form a radially indented channel in the periphery of the tubing, both to enhance the clamping action of the jaws and to isolate the formed end of the tubing from the remainder of the tubing. The clamped length of tubing is then engaged by a fold-over tool to fold the crimped end of the tubing radially inwardly, and then by a compacting tool further to fold the end axially into the tubing and then to compact the end portion of the tubing to form a tight tubing end joint. 
     Apparatus for forming an end-of corrugated metal foil wrap tubing in accordance with the preferred embodiment of another aspect of the invention includes a set of jaws for closing around a length of foil wrap tubing to clamp the tubing, and for opening to release the tubing. A compacting tool has an axially extending horn and an annular axially facing end channel. The compacting tool is brought into engagement with an end portion of a length of tubing in the jaws so as to fold the end portion into itself and compact the end portion by axially compressing the end portion to bring corrugations in the end portion into axial abutment with each other. In the preferred embodiment of the invention, the apparatus also includes a folding tool having an annular axially facing end channel. The folding tool is brought into axial engagement with the end of the tubing, prior to the compacting tool, so as to fold a portion of the end radially inwardly. Subsequent engagement by the compacting tool deforms this portion of the tubing end axially inwardly by contact with the horn on the compacting tool, and then axially compacts the end portion by engagement with the end channel in the compacting tool. The jaws preferably have arcuate rib segments that, when the jaws are clamped around a length of tubing, form a circumferentially continuous rib that indents a circumferential channel in the tubing to grip the tubing and to isolate the end portion from the remainder of the tubing. 
     A length of corrugated metal foil wrap tubing in accordance with a third aspect of the present invention has a formed end that includes an external end portion in which tubing corrugations are axially compacted together, and an internal end portion integrally folded inward from an axial end of the external end portion and in radially internal abutment with the external end portion. The formed end preferably also has a circumferential channel in the tubing separating the form end from the remainder of the tubing length. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, together with additional objects, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which: 
     FIG. 1 is a partially sectioned side elevational view of a length of corrugated metal foil wrap tubing having a formed end in accordance with a presently preferred embodiment of the invention; 
     FIG. 1A is a partially sectioned elevation view similar to that of FIG. 1 but showing a length of corrugated metal foil wrap tubing having an end cap in accordance with the prior art; 
     FIGS. 2-4 are fragmentary side elevational views of a tubing formed end at successive intermediate stages of manufacture; 
     FIGS. 5A and 5B are schematic diagrams of a tubing end crimping die in accordance with a presently preferred embodiment of the invention; 
     FIG. 6 is a schematic end elevational view of the crimping die arrangement illustrated in FIGS. 5A and 5B; 
     FIG. 7 is a perspective view of an apparatus for folding and compacting the formed end of a length of corrugated metal foil wrap tubing in accordance with a presently preferred embodiment of the invention; 
     FIG. 8 is a fragmentary sectional view of the clamping dies in FIG. 7; 
     FIG. 8A is a fragmentary perspective view of a tubing formed end at the intermediate stage of manufacture after crimping and clamping in the forming die; 
     FIG. 9 is a fragmentary partially sectioned side elevational view of the fold-over tool in engagement with the tubing end as illustrated in FIG. 7; 
     FIG. 9A is a fragmentary perspective view of the tubing end at the intermediate stage of manufacture after folding in FIG. 9; 
     FIG. 10 is a fragmentary sectional view of the tubing end engaged by the compacting tool in FIG. 7; 
     FIG. 10A is a fragmentary perspective view of the formed tubing end after compaction in FIG. 10; 
     FIG. 11 is a fragmentary sectional view of the fold-over tool illustrated in FIGS. 7 and 9; 
     FIG. 12 is a fragmentary sectional view of the compacting tool illustrated in FIGS. 7 and 10; and 
     FIG. 13 is a fragmentary sectional view on an enlarged scale of the portion of FIG. 10 within the circle  13 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a length  20  of metal foil wrap corrugated tubing  22 , also referred to as convoluted multi-ply shielding, having a formed end  24  in accordance with the preferred embodiment of the present invention. Tubing  22  comprises a strip of corrugated metal foil spirally wrapped on itself to form a hollow cylindrical tube, in which the corrugations form axially spaced spiral undulations in the outer and inner surfaces of the tube. An inner ply  28  of fiberglass cloth or the like is captured by spiral wrapping to form the interior wall of the tube as formed. Metal foil wrap corrugated tubing is typically supplied in large rolls, and is cut to desired lengths by the user. Such tubing is employed as a sheathing for electrical wires or fuel lines in automotive applications, for example. The metal foil wrap protects the wires from abrasion, and the foil corrugations add strength to the tubing. The inner fiberglass cloth layer protects the electrical wires from abrasion against the inside edges of the metal foil wrap. This tubing may also be used to cover high heat emitting products, such as exhaust-carrying tubes, to retain their heat and thereby protect surrounding components from this heat. A tube length may be readily bent to desired geometry and will retain this geometry when released. The particular tubing  22  illustrated in the drawings is manufactured by Clevaflex, identified above. However, the present invention is in no way limited to use in conjunction with this particular brand of metal foil wrap corrugated tubing, and can be readily employed in conjunction with tubing provided by other manufacturers. 
     In accordance with the preferred embodiment of the invention, formed end  24  includes an external end portion  30  in which the metal foil wrap corrugations are axially tightly compressed against each other, and an internal end portion  32  integrally folded inwardly from the axial end of external end portion  30 . (There is cloth material  28  sandwiched between portions  30 ,  32 .) Internal end portion  32  is in radially internal abutment with the inside surface of external end portion  30 , and is essentially cylindrical, with the corrugations having been at least partially removed during the end-forming process to be described. Formed end  24  includes a circumferential channel  34  extending around tubing  22  separating formed end  24  from the body of the tubing. Channel  34  is formed to help clamp the tubing body during the end-forming operation, and helps isolate forces applied during the end-forming operation from the remainder of the tube body. The compacted corrugations of outer end portion  30 , coupled with the inwardly folded inner end portion  32 , prevent unwrapping of the foil metal strip, and eliminate the need for the end cap or ferrule  36  typically employed at the ends of corrugated metal tubing, as illustrated in FIG.  1 A. 
     As summarized above, the end-forming operation in accordance with the most preferred embodiment of the invention disclosed in this application involves four steps: (1) The cut end of a length of tubing is crimped over a mandrel (FIGS. 5A-6) so that the crimped end tapers radially inwardly (FIG. 2) and end material is gathered in ridges to facilitate subsequent steps of the forming operation. (2) The crimped end of the tubing is clamped between jaws (FIGS. 7-8A) to hold the tube end during subsequent operations and to form a recessed channel or groove (FIGS. 3 and 8A) that extends around the tubing adjacent to the end. (3) The clamped end of the length of tubing is engaged by a fold-over tool (FIGS. 7,  9  and  11 ) to fold the crimped end portion radially inwardly (FIGS. 4 and 9A) toward the axis of the tubing. (4) The partially folded end portion of the tubing is engaged by a compacting tool (FIGS. 7,  10  and  12 - 13 ) further to fold the partially folded end portion of the tube axially inwardly against the inside diameter of the tubing end (FIGS. 1 and 10A) and to compact the corrugations of the tubing end to form a tight end joint. 
     Referring first to FIGS. 5A-6, the cut end of a length of tubing  22  is placed over a cylindrical support bar or a mandrel  40 . Mandrel  40  has a conical end surface  42  at an angle, such as 30°, to the axis of the mandrel. Tubing end portion  32  radially overlies conical mandrel surface  42  and is radially spaced therefrom owing to the initially cylindrical contour of tubing  22  and tubing end portion  32 . Mandrel  40  and tubing  22  are then placed within a circumferential array of forming dies or jaws  44 . Each jaw  44  has a part-conical forming surface  46  that, together with the forming surfaces  46  of the other jaws  44 , form a cone surrounding mandrel surface  42 . Jaws  44  are then closed, from the positions of FIG. 5A to the positions of FIGS. 5B and 6, so as to crimp or deform tubing end portion  32  against surface  42  of mandrel  40 . During this crimping operation, reduction in diameter of tubing end portion  32  causes material to gather in creases  48  (FIG.  2 ), which generally coincide with the boundaries or edges between surface portions  46  of jaws  44 . The corrugations in end portion  32  are at least partially flattened during the crimping operation. Crimping jaws  44  may be moved radially inwardly and outwardly by any suitable camming means  49  well known in the art. 
     FIG.7 illustrates a presently preferred apparatus  50  for performing the remaining operations of the end-forming process in accordance with the presently preferred embodiment of the invention. A pair of clamping jaws  52 ,  54  are mounted on a die bed  56 . Jaw  52  is mounted in fixed position, while jaw  54  is mounted on a support  58  that is movable on bed  56  into and out of opposed engagement with jaw  52  for clamping a tubing workpiece therebetween. A shuttle  60  is movably mounted on bed  56  under control of an actuator  61 . Shuttle  60  carries a fold-over end-form tool  62  that is movable in the direction of its axis under control of an actuator  64 , and a compacting end-form tool  66  that is movable in the direction of its axis under control of actuator  64  when shuttle  60  is moved to bring tool  66  into alignment with actuator  64 . Actuators  61 ,  64  may be of any suitable hydraulic, pneumatic or electric type. In general, jaw  54  is movable toward jaw  52  to clamp a tubing workpiece for performing the end-forming operation. With shuttle  60  in the position illustrated in FIG. 7, fold-over end-form tool  62  is then brought into axial engagement with the end of the tubing clamped between jaws  52 ,  54  for performing the fold-over operation to be described. Fold-over tool  62  is then retracted, and shuttle  60  is moved laterally (to the right in FIG. 7) to bring compacting end-form tool  66  into axial alignment with the workpiece between jaws  52 ,  54  and with actuator  64 . Actuator  64  is then actuated to bring compacting end-form tool  66  into engagement with the end of the tubing workpiece clamped between the jaws. End-form tool  66  is then retracted and jaw  54  is opened to release the workpiece. 
     As illustrated in FIG. 8, each workpiece clamping jaw  52 ,  54  has a radially inwardly extending rib segment  70  that, when jaws  52 ,  54  are closed, forms a circumferentially continuous rib that extends radially inwardly into engagement with a tubing workpiece clamped between the jaws. This rib  70  forms circumferentially continuous channel  34  (FIGS. 3 and 8A) in the tubing workpiece. Ribs  70  and channel  34  help clamp the tubing workpiece during axial engagement of the tubing end by the forming tools, as will be described. Channel  34  also helps isolate the remainder of the tubing body from the forces applied by the end-forming tools. It will be noted in FIG. 3 that the length  74  of crimped end portion  32  at the tubing end is considerably less than the length  76  of the uncrimped end portion  30  of the tubing end extending between the crimped portion and channel  34 . In a working embodiment of the invention, length  76  is about twice as great as length  74  at this stage of manufacture. In general, as will be described, length  74  is folded inward to form internal end portion  32  (FIG. 1) and length  76  is compacted to form external end portion  30 . It will also be noted in FIG. 8 that the inside diameter of jaws  52 ,  54  is slightly greater at  77  adjacent to tools  62 ,  66  than at  78  at the opposing side of rib  70 . 
     With the tubing workpiece clamped in position between jaws  52 ,  54 , fold-over end-form tool  62  is then brought into engagement with the end of the workpiece, by operation of actuator  64 , as illustrated in FIG.  9 . Fold-over end-form tool  62  comprises a substantially cylindrical body having a circumferentially continuous channel  82  formed in the axially facing end surface of the body. Channel  82  has a first substantially conical radially inner surface  84  extending radially and axially into tool  62  at an angle, such as 80°, to the axis of the tool. A second channel surface  86  extends from the rounded and concave inner end of surface  84  axially outwardly to the end surface of tool  62 , preferably at a slight angle as on the order of 10° to the tool axis. When fold-over end-form tool  62  is brought into engagement with the previously crimped end portion  32  of the tubing body captured between jaws  52 ,  54 , the axial end of crimped portion  32  is folded radially inwardly by sliding contact with surface  84  of channel  82  on tool  62 . At the position in which tool  62  is fully engaged with the tubing, illustrated in FIG. 9, the end of the tubing is folded to a position extending radially inwardly into engagement with the inner end of surface  86 . Tool  62  is then retracted. The slight angle of surface  86  allows tool  62  to be retracted without bending folded end portion  32  axially outwardly during such retraction. At this stage, tubing end portion  32  is folded radially inwardly, as illustrated in FIGS. 4 and 9A. 
     Shuttle  60  (FIG. 7) is then moved to the right under control of actuator  61  until compacting end-form tool  66  aligns with the tubing workpiece, which remains clamped between jaws  52 ,  54 . Compacting end-form tool  66  is then extended by operation of actuator  64  to engage crimped and partially folded end portion  32  of the tubing workpiece. Compacting end  20  form tool  66  (FIGS. 10,  12  and  13 ) has an axially extending horn  90  with a cylindrical outer periphery dimensioned for close sliding fit within the inside diameter of channel  34  formed by rib segments  70  in clamping jaws  52 ,  54 . Surrounding horn  90 , an axially opening circumferential groove  92  is formed on the axial end face of tool  66 . This channel  92  is formed by an annular lip  94  around the outer periphery of tool  66 , and an annular surface or plateau  100  within lip  94 . Plateau  100  is at greater diameter than horn  90 , and blends into the outer surface of horn  90  by means of an angulated ramp surface portion  102 . 
     As tool  66  is extended into engagement with the tubing workpiece clamped between the jaws, the rounded nose of horn  90  engages and folds end portion  32  axially inwardly and then radially outwardly against the inside diameter of end portion  30 . Material creases  48  help accommodate radial compaction and expansion of material during this operation. Further axial engagement of tool  66  with the workpiece brings the now fully folded end of the workpiece into channel  92  on the end of the tool. Inward motion of the tool is continued for axially compressing the formed end by bringing the corrugations of end portion  30  into axial abutment, and radially inward compaction of the formed end due to the tool lip  94  that surrounds channel  92 . The outer periphery of tool lip  94  is on the cylinder of revolution that forms the periphery of tool  66  that is closely slidably received within clamping jaws  52 ,  54 . As best seen in FIGS. 8 and 13, the inner diameter  77  formed by tools  52 ,  54  adjacent to the ends of the tools is greater than the inner diameter  78  on the opposite side of the rib segments  70 . On the other hand, the inside diameter of plateau surface portion  100  on tool  66  is about the same as the inside diameter  78  of jaws  52 ,  54 . In this way, when the end is fully formed, the outside diameter of end portion  24  will be about the same as the outside diameter of tube body  22 . Furthermore, provision of ramp surface portion  102  and plateau  100  helps ensure that the inside diameter of the tube end portion or cuff is equal to or greater than the inside diameter of the remainder of the tube body so that the tube section can be readily slid over components to be located within the tube body. Compacting end-form tool  66  thus completes the folding operation started by fold-over end-form tool  62 , and compacts the formed end of the tubing both axially and radially to complete formed end  24  (FIGS. 1 and 10A) having external end portion  30  and internal end portion  32  coupled to the body  22  of the tubing by circumferential channel  34 . 
     There has thus been disclosed a method and apparatus for end-forming corrugated foil wrap tubing, and a length of corrugated foil wrap tubing having a formed end, that fully satisfy all of the objects and aims previously set forth. The invention has been disclosed in conjunction with a presently preferred embodiment, and a number of modifications and variations have been described. Other modifications and variations will readily suggest themselves to persons of ordinary skill in the art. The invention is intended to embrace all such modifications and variations as fall within the spirit and broad scope of the appended claims.