Patent Publication Number: US-8539805-B2

Title: Method and forming machine for manufacturing a product having various diameters

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a continuation of and claims priority of U.S. patent application Ser. No. 10/501,758, filed Jul. 16, 2004, which is a Section 371 National Stage Application of International Application No. PCT/NL03/0030, filed Jan. 17, 2003 and published as WO 03/059547 on Jul. 24, 2003, in English, the contents of both of which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     The invention relates to a method and a forming machine suitable for manufacturing a product having various diameters from a workpiece, such as a metal cylinder or plate, in which the workpiece is clamped down in a clamping device, the workpiece and a first tool are rotated about an axis of rotation relative to each other, the workpiece is deformed by means of said first tool by placing the tool into contact with the workpiece and moving the workpiece and/or the tool in a direction along, i.e. parallel to or having a component parallel to, the axis of rotation. 
     Such a method and apparatus are known, e.g. from EP 0 916 426. Said publication describes how one end of a cylindrical workpiece is worked by clamping down said workpiece in a clamping device (indicated by numeral 12 in FIG. 1 of EP 0 916 426) and deforming said ends by means of three forming rollers (28), which are mounted on a rotary member (24). Said forming rollers (28) rotate in the same plane and are pressed against the workpiece at three locations which are evenly distributed over the circumference of the workpiece, after which said rollers move along a number of paths along the workpiece so as to deform the workpiece in steps. 
     For the sake of completeness, attention is drawn to DE 23 27 664 en DE 1964 401, in which methods and apparatuses are described for flow pressing cylindrical tubes, i.e. tubes having a constant diameter. The methods and apparatuses according to these documents are unsuitable for manufacturing a product having various diameters. 
     SUMMARY 
     The object of the invention is to provide an improved method and forming machine. 
     In order to accomplish that objective, the method and the forming machine referred to in the first paragraph are characterized in that at least a second tool is placed into contact with the workpiece at a position behind the first tool, seen in the working direction, and in that the workpiece is also deformed by means of said second tool. Preferably, at least a third tool is placed into contact with the workpiece behind said second tool. 
     Thus, parts of the workpiece that have been deformed by the first tool are deformed by one or more subsequent tools almost immediately. As a result, the material, such as aluminum or steel, will have a relatively very limited opportunity, if any, to harden, so that the next operation will proceed relatively easily and the risk of the material being damaged or adversely affected is considerably reduced. 
     Preferably, the tools each comprise two or more forming rollers, between which the workpiece is retained while being worked and which occupy substantially the same axial position with respect to the workpiece. It is possible to impose relatively large as well as relatively small diameter changes by means of forming rollers. Such rollers are preferably freely rotatable about an axis which extends either horizontally or at an angle with respect to the aforesaid axis of rotation. Furthermore, it is preferred that most or all of the tools form part of one and the same deforming head, or that they are at any rate positioned relatively close together. The question as to the most suitable spacing between successive tools, at least between the positions at which the tools make contact with the workpiece, depends on the properties of the workpiece, of course, and on the nature of the working process to be carried out. In many cases said spacing will vary between 1 and 30 cm. 
     If the material and the dimensions of the workpiece and the intended product (frequently a semifinished product) allow so, the number of working cycles can be reduced to one, if desired. A surface that has been worked once will not be worked anew in that case, so that the load to which the material is subjected will remain limited. In addition to that the programming of any control equipment that may be provided will be significantly simpler, in particular because it will not be necessary to take the shape and the behavior of various intermediate forms into account. 
     For the sake of completeness it is noted that British patent application No. 238,960 describes a roller by means of which the diameter of bars, pipes and the like is reduced to a smaller, uniform diameter in a continuous process, using a number of tools arranged in succession. 
     Further, attention is drawn to U.S. Pat. No. 5,428,980, in which a workpiece is deformed with a first forming roller and glazed with a second roller. A second forming roller is not described. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be explained hereinafter with reference to the figures, which show a number of embodiments of the method and the forming machine according to the present invention. 
         FIGS. 1A and 1B  schematically show the deformation of one end of a cylindrical workpiece by means of five tools. 
         FIGS. 2A and 2B  show the eccentric deformation of one end of a workpiece by means of three tools. 
         FIGS. 3A-3C  show the fixing of an insert member in a cylindrical workpiece, using a method comparable to the method as used in  FIGS. 2A and 2B . 
         FIG. 4  is a cross-sectional view of a forming machine for eccentric deformation of a workpiece, which machine comprises four tools. 
         FIGS. 5A and 5B  are front views of a workpiece which has been subjected to one operation and two operations, respectively, by means of the forming machine of  FIG. 4 . 
         FIG. 6  is a top plan view of a forming machine which is in particular suitable for deforming relatively long workpieces. 
         FIGS. 7 and 8  are a front view and a perspective view, respectively, of a so-called carriage for use in a forming machine as shown in  FIG. 6 . 
         FIGS. 9A and 9B  are schematic sectional views of the carriage of  FIGS. 6-8 . 
         FIG. 10  shows the flow forming process carried out by using the present invention. 
         FIG. 11  shows the so-called bottom-closing process carried out by using the present invention. 
         FIGS. 12A-12D  schematically show the rotary deep drawing of a plate-shaped body carried out by means of seven tools. 
         FIGS. 13A-13D  schematically show the projection of a plate-shaped body by means of six tools. 
         FIGS. 14A-14D  schematically show a variant of the projection process as carried out in  FIGS. 13A-13D . 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Parts which are identical or which have the same or substantially the same function will be indicated by the same numerals as much as possible hereinafter. 
       FIGS. 1A and 1B  schematically show a method and apparatus according to the present invention. A workpiece  1 , in this case a metal cylinder, is rotated about an axis of rotation  2  at a certain number of revolutions. Subsequently a deforming head (not shown) is provided, in which five tools  3 A- 3 E are rotatably mounted. Each tool  3  comprises two forming rollers arranged in minor symmetry with respect to the axis  2 . The radial distance from the tools  3  to the axis  2  decreases stepwise towards the rear, seen in the working direction  4 . 
       FIG. 1A  shows the start of the operation, in which the first forming rollers  3 A just make contact with the edge of an end of the rotating workpiece  1 , whilst  FIG. 1B  shows the situation after one working cycle, in which the forming rollers  3  have made a full pass in the working direction  4 , having deformed the workpiece  1  into a product having five gradually decreasing (in steps) diameters. The part having the smallest diameter has been deformed on a mandrel  5  by the final forming rollers  3 A, so that the inside diameter of said part is precisely calibrated. 
     The magnitude of the steps by which each tool  3  is positioned closer to the axis of rotation  2  than the preceding tool inter alia depends on the design, the material and the dimensions of the unformed workpiece, of course. In the case of a workpiece having a small wall thickness, it will usually be possible to use larger steps. 
       FIGS. 2A and 2B  show a second embodiment of the present invention, in which the tools  3 A- 3 C, likewise comprising two forming rollers each in this embodiment, are freely rotatable in holders  6 A- 6 C. The holders  6  are in turn rotatably mounted, about an axis of rotation  2 , in a deforming head  7  (schematically shown). Also in this embodiment the radial distance from the tools  3  to the axis  2  decreases in steps towards the rear. The holders  6  can be adjusted independently of each other in radial direction. This makes it possible to position said holders  6 , and thus the axis of rotation  2  of each of the tools  3 , eccentrically with respect to the central axis  8  of the (undeformed as yet) workpiece  1 . 
     By rotating the holders  6  and moving the deforming head  7  in the working direction  4 , using driving means  9  (schematically shown) such as a pneumatic or hydraulic cylinder or an electric motor fitted with a spindle, over a workpiece  1  clamped down in a fixed clamping head  10  (schematically shown), said workpiece  1  is deformed in one single operation, in which the worked parts obtained are positioned eccentrically with respect to the axis  2 . 
     For the sake of completeness it is noted that the frictional heat which is generated during the deforming operation can be influenced by disposing the forming rollers at an angle with respect to the axis of rotation  2 . In the case of an inclined position ( FIG. 2A ) less frictional heat will be generated than in the case of a position at right angles ( FIG. 2B ). This position may be varied in dependence on the heat that is required with a particular operation. 
       FIGS. 3A-3C  show how parts can be fixed in a workpiece by means of the forming machine as shown in  FIG. 2B , e.g. in order for the purpose of manufacturing a catalytic converter for a passenger car. 
     First a so-called catalytic brick or substrate  11 A and an insert member  11 B are placed in the workpiece  1  ( FIGS. 3A and 3B ). The insert member  11 B may be supported and placed by means of, for example, an axially adjustable mandrel (not shown) mounted in or through the deforming head  7 . Following that, the workpiece  1  is deformed by a deforming head  7 , in which the end of the workpiece  1  is pressed onto the end of the insert member  11 B and in which a substantially gastight connection between the two ends is obtained. 
       FIG. 4  is a cross-sectional view of a second forming machine for eccentric deformation of a workpiece, which machine comprises four tools  3 A- 3 D. Each tool  3  comprises minimally one forming roller, which is (are) mounted freely rotatable on a separate holder  6 A- 6 D. The holders  6  are arranged in pairs, opposite each other, in four separate rotationally symmetrical housings  12 A- 12 D, which housings in turn form part of a deforming head  7 . The first housing  12 A comprises a substantially annular, static outer part  13 A, in which a, likewise substantially annular, inner part  14 A is rotatably mounted in bearings  15 A. The inner part  14 A may e.g. be driven by means of a motor  16 A (schematically shown), whose drive shaft is fitted with a pinion  17 A, which engages in a set of teeth present on the circumference of the inner part  14 A. In addition, an annular element  18 A of wedge-shaped section, which element  18 A mates with an end  19 A, likewise of wedge-shaped section, of the respective holder  6 A, is present in said inner part  14 A. By moving the annular element  18 A to the left or the right (in the drawing), using driving means  20 A, the holders  6 A, and thus the forming rollers mounted thereon, are moved radially inwardly or outwardly, respectively. Furthermore, driving means  21 A are provided, by means of which the housing  12 A can be adjusted in axial direction, parallel to the axis of rotation  2 , with respect to the other housings  12 . 
     The other three housings  12 B- 12 D correspond to a large extent to the first housing  12 A, but in addition they comprise a circular cylindrical part  22 , whose outside diameter is smaller than the inside diameter of the housing  12  to the left (in the drawing) thereof. As a result, the housings  12  can also be adjusted in radial direction relative to each other, independently of each other, by means of respective driving mechanisms  23 A- 23 D, and the axis of rotation  2  of each of the housings  12  can be positioned eccentrically relative to the central axis of (the part as yet undeformed of) a workpiece. 
     The annular elements  18 B- 18 D in turn each comprise a cylindrical part  24 , whose outside diameter is smaller than the inside diameter of the inner part  14 B- 14 D. Furthermore, the deforming head  7  comprises driving means  9 , by means of which said head  7  can be moved forward and backward in the working direction. Examples of the aforesaid driving means  9 ,  20 ,  21  and  23  include a pneumatic or hydraulic cylinder or an electric motor fitted with a spindle. The driving means are not limited to the above examples, of course. 
       FIGS. 5A and 5B  are front views of a workpiece  1  which has been deformed into an (intermediate) product  25  comprising four reduced portions in one working cycle. By subsequently adjusting the tools  3  in outward direction, the (intermediate) product  3  can be deformed into a product  25  comprising a total of eight reduced portions in a working cycle, in which the stroke is extended by half the axial distance between the first reduced portions. It stands to reason that it is possible to adapt inter alia the number of tools  3 , the number of working cycles and the degree to which the tools are adjusted to the required product. Thus  FIG. 4  shows a working process in which the tools are adjusted during the working cycle(s), so that a product having a continuously decreasing diameter, in this case a product having a conical end, is obtained. 
       FIG. 6  is a top plan view of a forming machine by means of which also relatively long cylindrical workpieces  1  can be deformed. The forming machine comprises a frame  30 , which is provided with guide rails  31 ,  32  on either side, on which a transversely arranged subframe  33  is supported, over which guide rails three so-called carriages can be moved. Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. 
     The subframe  33  comprises a clamping head  34 , in which a first end of a workpiece  1  can be clamped down and which can be rotated, e.g. by a motor which is accommodated in a housing  35 . 
     The first carriage  36  is provided with a carrier plate  37 , on which four tools  3  are mounted. Each tool comprises two forming rollers, which are mounted freely rotatable in holders  38  positioned directly opposite each other. Said holders  38  are in turn tiltably mounted, about respective tilting points  39 , on radially adjustable supports or slides  40  and they can be tilted in a direction towards the axis of rotation  2  and in a direction away therefrom, using driving means such as electric motors  41  or hydraulic cylinders, which are likewise mounted on respective slides  40 . The slides  40 , and thus the holders  38  and the forming rollers, can be adjusted in radial direction, using driving means  9 . In the illustrated embodiment, the slides  40  are moreover detachably connected to the carrier plate  37 , so that the number of slides  40 , the number of tools  3  and the positions thereof can easily be adapted to the product to be manufactured. In the illustrated embodiment, the tilting points  39  are located behind the tools  3 , seen in the working direction, but said tilting points  39  may also be located at other positions, e.g. in front of or between the tools  3 , depending on the operation, or they may even be adjustable. In the latter case the tilting points can be shifted during operation. 
     The second carriage  42  comprises a passage  43 , in which a centering unit, e.g. a bush (not shown), is present, whose central axis coincides with the axis of rotation  2  and which functions to center a workpiece present therein with respect to said axis  2 . The third carriage  44  comprises a so-called tailstock  45 , which supports the other end of the workpiece  1  during the operation and which comprises a mandrel  5  or clamping mandrel. Depending on the operation, the second and/or the third carriage can be coupled to the first carriage, e.g. if it is desirable to maintain a substantially constant distance between the first and the second carriage. 
     A cylindrical workpiece  1  can be loaded into the forming machine, e.g. by moving the third carriage  44  to the front (to the left in the figure) and moving the first and second carriages  36 ,  42  to the rear until the distance between the third carriage  44  and the second carriage  42  is greater than the length of the workpiece  1 . Then the workpiece  1  is guided through the passage  43  and between the tools  3  with its first end and clamped down in the clamping head  34 . The mandrel  5  is placed in the second end of the workpiece  1 , after which the workpiece  1  is centered, the tools  3  are set and the mandrel  5  is placed into contact with the wall of the workpiece  1 . It is also possible to remove the worked workpiece  1  automatically, e.g. by means of a pick and place system, after an operation, when all three carriages are positioned on the left, and load a next workpiece into the machine in the same position of the carriages. 
     The outside diameter of the workpiece  1  can be reduced to a smaller, constant outside diameter, e.g. along the full length of the workpiece, by rotating the workpiece  1  about the axis of rotation  2 , gradually tilting the tools  3  and moving the slides  40  in radial direction towards the workpiece  1  and initiating a translating movement of the carriages. The rear tool  3 D will be the first to make contact with the workpiece  1 , followed by the third, the second and the first tool, respectively. It is also possible to have  3 D and  3 C, or even all the tools  3 , make contact with the workpiece at the same time. The so-called “escaping” of the material can be suppressed more easily in this way. 
     Preferably, the end of the mandrel  5  is only spaced from the front tool  3  by a small distance at all times, at any rate towards the end of a working operation, in order to support the workpiece  1  up to a point just before the working zone and thus further enhance the degree of stability. In addition, the mandrel  5  can be used for generating a tensile force in the workpiece  1 . Such a tensile force can be used for adjusting the reduction of the wall thickness along the entire length, or practically the entire length, of the product or in particular zones thereof. As the force exerted on the workpiece by means of the mandrel  5  increases, the rate at which the material of the workpiece  1  is pulled from the mandrel  5  will decrease, which will in turn result in a smaller wall thickness. It is noted that the tensile force in the workpiece can be varied by means of the aforesaid centering unit in the passage  43  as well. Thus the tensile force can be imposed at the start of the working process, for example, in particular by means of said centering unit, whilst the tensile force can be imposed mainly by the mandrel  5  towards the end, when the workpiece  1  starts to exit from the bush. 
     Incidentally, wall thickness and wall thickness variations can be controlled by varying the radial distance between consecutive tools, for instance by tilting the holders and translating the holders in radial direction, preferably simultaneously. By increasing or decreasing the radial distance between the tools, the wall thickness at that location will be reduced or increased respectively. 
       FIGS. 7 and 8  show variants of the first carriage  36 , in which the carriage is shown to be fitted with, respectively, two and six tools. 
       FIGS. 9A and 9B  show the manner in which the tools  3  can be tilted towards the workpiece in carriages as shown in  FIGS. 7 and 8  and, after the tools have started their working stroke, be moved in radial direction towards the definitive working position. Using the apparatus as shown in  FIGS. 6-9B , a tapered and/or stepped product can be obtained, for example, by adjusting the tools  3  during operation. It is also possible to form two or more products from a workpiece and subsequently separate said products from each other. 
     The number of revolutions, the magnitude of the steps and the rate of translation of the tools depend on factors such as the material being used, the outside diameter and the wall thickness of the workpiece and the dimensions of the intended product. An aluminum tube having a diameter of 25 cm and a length of 4 m, for example, can e.g. be formed into a conical tube having a diameter which decreases from 16 cm to 8 cm and a length of 7 m. Such an operation can usually be carried out at a rotational speed of 200-700 revolutions per minute. 
       FIG. 10  shows an embodiment in which a cylindrical workpiece  1  is placed onto a mandrel  5  until the closed bottom of said workpiece  1  abuts against the end of the mandrel  5 , which workpiece is clamped down by means of a tailstock (not shown) and deformed by means of a flow turning operation. This makes it possible to control the surface quality of the inner wall and, more in particular, prevent porosity of said inner wall. In addition to that it is possible to manufacture a finished product having a variable wall thickness in a single working cycle by adjusting the tools in radial direction during operation. 
       FIG. 11  shows how the invention can be used for a process that is also referred to as “bottom closing”. In this process, the open end of a cylindrical workpiece  1  is closed in one operation, using a number of tools  3  which are each mounted on their own slide, and which can thus be moved relative to each other. Said adjustable slides are in turn mounted on a support (not shown), which can be pivoted about an adjustable pivot point  39 , using driving means as already mentioned before. Since the respective operations of the tools are carried out in quick succession, the risk of adverse effects caused by premature cooling is considerably reduced or even practically eliminated. 
       FIGS. 12A-12D  show an example of the rotary deep-drawing of a plate-shaped workpiece  1 , in this case a metal disc, in which said workpiece  1  is pressed against the central part of a bobbin  46  by means of a tailstock (not shown) and is rotated together with the aforesaid parts. The workpiece is deformed by means of five tools  3 , which each comprise a number of forming rollers. Said forming rollers are each mounted on a separate slide (not shown), so that the rollers can be moved relative to each other during the deforming process. The edge of the workpiece  1  is stabilized by a support or holding-down clamp  47 , at least during the initial part of the operation. In the illustrated example, the final tool  3 E can directly move along a path corresponding to the outside diameter of the intended product, because the other tools  3 A- 3 D have sufficiently pre-formed the workpiece  1 . 
       FIG. 13A-14D  show examples of the so-called projecting of a plate-shaped workpiece  1 , likewise a metal disc in this case, which is pressed against a bobbin  46 , by means of a tailstock (not shown), and rotated. The workpiece is deformed by means of seven tools  3 , viz. six discs  3 A- 3 F and one forming roller  3 G, which are mounted on a common tiltable slide. The discs mainly function to pre-form the edge of the workpiece relative to the block  46 , whilst the forming roller projects the material by means of a flow turning operation.  FIGS. 14A-14D  show how the forming roller on the one hand and the six discs on the other hand are mounted on either side of the block  46 , each on a separate holder  47 ,  48 , which holders can be moved in the X-direction and the Y-direction by means of two respective slides. For more details with regard to the projection process, reference is made to EP 0 774 308. 
     If the workpieces are deformed in only one working cycle in the forming machines as described above, the tools, the centering means and the like will require no readjustment, and in many cases less residual material, e.g. an undeformed end which was fixed in a loose chuck, or even no residual material at all will remain. 
     The forming machines according to the present invention can be operated by a person as well as by a control unit, of course. Such a control unit will be arranged, for example, for controlling the movement of the tools and the workpiece relative to each other, e.g. in axial and radial direction or along X- and Y-coordinates, in accordance with a control programme stored in a memory, in such a manner that the tools will move along one or more desired paths for forming the workpiece into the desired finished product or intermediate product. 
     Although the invention has been explained on the basis of a circular cylindrical metal workpiece in the foregoing, the invention can also be used with workpieces of unround section(s), such as oval, substantially triangular or multilobal sections. The invention can furthermore be used for hot forming as well as for cold forming. 
     The term “tool” as used within the framework of the present invention inter alia comprises a single forming roller and sets of two or more such forming rollers, which take up substantially the same axial position with respect to the workpiece. 
     Consequently, the invention is not restricted to the embodiments as described above, which can be varied in many ways within the scope of the invention as defined in the claims.