Abstract:
The invention relates to a bending head, for example, for a rotary draw bending technique, of the type including a bend form clamp assembly set in rotation about an axis and at least one roller keeping a tube or a profiled section clamped against the bend form during bending. The single assembly can be positioned in one or other of two bending starting positions that are symmetric with respect to the axis of the tube so as to allow either bending in one direction of bending starting from, or bending in an opposite direction starting from (P 2 ). The rectilinear movement of the clamp in two directions (ox) and (oy) and its optimal orientation relative to the roller are obtained using a system involving an eccentric.

Description:
CROSS-REFERENCE TO RELATED U.S. APPLICATIONS 
       [0001]    Not applicable. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT 
       [0003]    Not applicable. 
       REFERENCE TO AN APPENDIX SUBMITTED ON COMPACT DISC 
       [0004]    Not applicable. 
       BACKGROUND OF THE INVENTION 
       [0005]    1. Field of the Invention 
         [0006]    The present invention relates to a novel device for bending tubes or profiled sections and to a machine comprising this device. 
         [0007]    2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98 
         [0008]    The invention relates specifically, but in anon-limiting way, to the technique known as rotary draw bending, the principle of which is recalled here in conjunction with  FIGS. 1 to 3 . 
         [0009]    A tube (A) is immobilized on a bend form (B) by a clamp (C). 
         [0010]    The assembly (bend form-clamp) is set in rotation, on a work rest (D) or rollers (E) keeping the tube (A) along the axis of the machine. 
         [0011]    This is the most widespread technique used for manufacturing industrial components. 
         [0012]    It can be used for bending thin-walled tubes (E factor 200) at short bend radii (R factor 0.8). 
         [0013]    The quality and the precision of the components produced, using this technique, are dependent on how well the tube is held on the bend form by the clamp. 
         [0014]    Any slippage has two effects:
       wrinkles are created on the intrados (F) (or inside) of the bend; and   the straight parts (G) between bends are affected adversely, hence degrading the geometry of the components.       
 
         [0017]    The clamp has, in order to be effective, to develop a sufficient clamping force and be rigid enough that the clamping force can be transmitted. 
         [0018]    In the existing machines, movement is achieved either by a (hydraulic or pneumatic) ram associated with a mechanical system, generally a toggle lever system, or by an (electric) motor associated with a screw-nut system. 
         [0019]    This assembly is mounted on a bend arm rotating about the bend form. 
         [0020]    The design of thin-walled tubular components is currently “constrained” by the ability of the means available on the market to string together, with greater or lesser ease, sequences of bends in the clockwise direction (see  FIG. 4 ) and in the counterclockwise direction (see  FIG. 5 ). 
         [0021]    This situation therefore dictates that, where there is a need for two directions of bending, the design will need to be modular, made up of a number of components each of which is bent in just one direction, or that more cumbersome and/or more complicated solutions be found. 
         [0022]    There are various solutions put forward in the prior art:
       Achieving the two directions of bending using equipment that has two bending heads, the principle of which is depicted in  FIG. 6 . The tube is bent in a first direction by a first bending head (a) and then afterwards in an opposing direction by passing it through a second bending head (b).   Achieving the two directions of bending with equipment comprising two tools (c, d) mounted one on each side of a bending head and the principle of which is depicted in  FIG. 7 . The two tools (c, d) are mounted on the same axis (e) of bending, the change in direction of bending requiring a complex combination of movements.   Producing the two directions of bending using two tools (f, g) with interchangeable axes of rotation according to the principle of  FIG. 8 . In that case, the changeover of the direction of bending is very quick, but the mechanics of it are complicated. In addition, this solution does not allow the radius of bend to be changed.   Achieving the two directions of bending with two tools (h, i) situated in different planes according to the principle of  FIG. 9 . In this case, the change in the direction of bending entails complex movements.       
 
         [0027]    All these solutions of the prior art entail somewhat complex mechanics and all require two bending tools. 
         [0028]    As a result, in the lead markets, such as the automotive and aeronautic industries, which are always looking for economic solutions well suited to simple and quick production changeovers, designer requirements are not fully met. 
       BRIEF SUMMARY OF THE INVENTION 
       [0029]    It is an objective of the present invention to propose a solution that is more economical than those of the prior art and that meets designer requirements. 
         [0030]    The invention achieves this objective and consists in a bending head, for example for a rotary draw bending technique, of the type comprising an assembly (bend form-clamp) set in rotation about a first axis, one or more rollers keeping a tube or a profiled section clamped against the bend form during bending. The invention comprises a single assembly (bend form-clamp) that can be positioned in one or other of two bending starting positions that are symmetric with respect to the axis of the tube so as to allow either bending in one direction of bending starting from one of two positions, or bending in an opposite direction starting from the other position. The single assembly is a bending head made up of a main platen rotating about the central first axis of a roller mounted concentrically on said first axis, and parallel to the main platen, of a clamp mounted to rotate about a third axis itself mounted eccentrically on a satellite platen mounted to rotate about a second axis borne by the main platen and a predetermined distance away from the first axis. 
         [0031]    The invention also relates to a machine equipped with a bending head of this type, controlled by a numerical control controlling all the movements of the components of the machine. 
         [0032]    More specifically, the numerical control calculates the movements of the components and the bending parameters on the basis of two planar coordinates (x and y) and of the angle of rotation (alpha) defining the movements of the clamp. 
         [0033]    The numerical control also controls, in the conventional way, a guide-work rest means, a tube-positioning means, a mandrel-guide means and another tube-positioning means. 
         [0034]    Finally, the machine has a symmetric structure in which the changes in the direction of bending can be effected simply by rotating the axes. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0035]    The invention will be better understood with the aid of the following description, which is given with reference to the following attached figures. 
           [0036]      FIGS. 1 and 2  are illustrations of functional diagrams of a rotary draw bending assembly. 
           [0037]      FIG. 3  is schematic view of a tube bent by an assembly of  FIG. 1  or  2 . 
           [0038]      FIGS. 4 and 5  are illustrations of operating diagrams for bending in the clockwise or counterclockwise direction. 
           [0039]      FIG. 6  is an illustration of a diagram of equipment with two heads for bending in both directions. 
           [0040]      FIG. 7  is an illustration of a diagram of equipment with two symmetric tools. 
           [0041]      FIG. 8  is an illustration of a diagram of equipment with two interchangeable tools. 
           [0042]      FIG. 9  is an illustration of a diagram of equipment with two tools in different planes. 
           [0043]      FIG. 10  is an illustration of an operating diagram of a symmetric bending head according to the invention. 
           [0044]      FIG. 11  is an illustration of a diagram showing the three main rotational movements. 
           [0045]      FIG. 12  is a detailed schematic view of the positions of the constituent elements of the head in the starting position. 
           [0046]      FIG. 13  is a detailed schematic view of the positions in the tube-clamping phase. 
           [0047]      FIG. 14  is a detail schematic view of the positions in the tube-bending phase. 
           [0048]      FIGS. 15 ,  16 , and  17  are detailed schematic views of the positions for bending in the opposite direction to that of  FIGS. 12 ,  13  and  14 . 
           [0049]      FIGS. 18 and 19  are detailed schematic views of the positions when the clamp is opened and closed. 
           [0050]      FIG. 20  is an illustration of a graphic depiction of the forces involved. 
           [0051]      FIGS. 21 and 22  are illustrations of diagrams of a complete machine and of the movements of its various components. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0052]    The inventive step was to develop a new design to replace the current bend arm and which would allow thin-walled tubes to be bent in both directions (clockwise and counterclockwise) using the same tooling. 
         [0053]    This novel design needs therefore to have a bending means that has a symmetric structure. 
         [0054]    Starting out from this idea of symmetry, the inventive step evolved toward the idea of a circular bending head. The characteristics are depicted in  FIGS. 10 to 17 , which are as follows:
       the bend arm is replaced by a ring, hence giving the rotation the symmetric structure;   the rigidity is substantially improved because the guide diameter is far greater than with a bend arm;   the translational movement (clamping) of the clamp is obtained by three rotations which are controlled by numerical axes; and   the linear movement of the clamp is had by interpolating these three axes.       
 
         [0059]    The clamping system behaves like a link rod hence moving quickly during the travel, in which the forces involved are low, and slower at the end of travel. The forces involved are high because of the triangulation of the axes. 
         [0060]    In addition, the fact that three synchronized rotations are used means that the position of the clamp can be programmed in terms of two perpendicular axes and one rotation. 
         [0061]    Control over the orientation of the clamp through rotation optimizes the clamping. 
         [0062]    The way in which this bending head works will be better understood from the detailed description which follows. 
         [0063]    The circular bending head ( 1 ) (see  FIGS. 10 and 11 ) comprises a circular main platen ( 2 ) rotating about its central axis (A 1 ). The bending tools are made up of a form roller ( 3 ) mounted concentrically on the axis (A 1 ) and above the main platen ( 2 ), of a clamp ( 4 ) that effects a rectilinear movement relative to the axis (A 3 ) in a frame of reference (Ox, Oy). 
         [0064]    This rectilinear movement is the result of the clamp being mounted on an eccentric principle. 
         [0065]    The clamp ( 4 ) is mounted such that it can rotate about an axis (A 3 ) itself mounted at the periphery of a satellite platen ( 5 ) mounted such that it can rotate on an axis (A 2 ) borne by the main platen and a predetermined distance from the axis (A 1 ). 
         [0066]    A work rest ( 6 ) is provided for guiding the tube in the conventional way. 
         [0067]    On the operating diagram of  FIG. 11 , the bending head is made up of a main platen ( 1 ) rotating about the central axis (A 1 ). A second rotation (A 2 ) integral with the first rotation but eccentric relative to the axis (A 1 ) moves a point eccentric from the axis (A 2 ) relative to the axis of the first rotation (A 1 ). This movement in a plane (PL 1 ) perpendicular to the central axis (A 1 ) allows a relative movement of the point (PT 1 ) with respect to the point (PT 2 ). Associating and/or combining the movement of these two axes makes it possible to generate any path in the plane (PL 1 ). This then defines the origin of a vector. The direction of the vector, that is essential for the operation of a bending tool, is given by the third rotation (A 3 ), which orients the vector in the system of coordinates defined along the axis (A 1 ). 
         [0068]    This then gives a system that allows the vector to be moved in any way in the plane (PL 1 ). 
         [0069]    This mechanical principle can be applied to the movement of a vector in a plane. 
         [0070]    This movement is broken down, for tube bending, into a phase of linear movement for clamping the tube against the bend form, another phase of circular movement for bending the tube, and a phase of linear movement for unclamping the tube. 
         [0071]    The phases of bending in one direction are described hereinbelow with reference to  FIGS. 12 to 14 , and the phases of bending in the opposite direction are described with reference to  FIGS. 15 to 17 . 
         [0072]      FIG. 12  corresponds to a phase of loading a tube ( 6 ). With the form roller ( 3 ) and the work rest ( 7 ) aligned, the clamp ( 4 ) is moved away to allow the tube ( 6 ) to be loaded from the front, and lies in a starting position (P 1 ) situated at a distance (S) from the axis (A 1 X) of the machine. 
         [0073]      FIG. 13  corresponds to a tube-clamping phase. The roller ( 3 ) does not move, the work rest comes into contact with the tube ( 6 ), and the combination and synchronization of the rotations of the main platen ( 2 ) in the counterclockwise direction about (A 1 ), of the satellite platen ( 5 ) in the clockwise direction about (A 2 ), and of the clamp ( 4 ) in the counterclockwise direction about (A 3 ) causes the clamp to move in a straight line and clamp the tube ( 6 ) against the form roller. 
         [0074]    Configuring the clamp ( 3 ) like this on an eccentric axis on the satellite platen means that very strong clamping forces can be obtained. 
         [0075]      FIG. 14  corresponds to the tube bending phase. The tube ( 6 ), clamped against the roller ( 3 ) via the clamp ( 4 ), is drawn around the roller ( 3 ) by rotating the roller in the clockwise direction about the axis (A 1 ) and by rotating the satellite platen in the clockwise direction about the same axis (A 1 ). The clamp pivots about (A 3 ) in order always to remain in the optimal clamping position. 
         [0076]    The unclamping phase is not depicted, in this phase, the roller remains stationary, inverse synchronization of the rotations used in the clamping phase allowing the clamp to move away from the form roller. When the clamp has moved away, the work rest ( 7 ) moves away and retreats, the main platen ( 2 ) returns to its position for the next bend. The tube advances and the form roller returns to its position. A further clamping phase may begin. 
         [0077]      FIGS. 15 ,  16 ,  17  depict the same phases of operation using a work rest and a satellite platen positioned symmetrically in  FIG. 15  with respect to their starting positions in  FIG. 12 .  FIG. 15  therefore depicts a loading phase,  FIG. 16  a clamping phase, and  FIG. 17  a phase of bending in the opposite direction to the bending achieved with the phases in  FIGS. 12 to 14 . The point (P 2 ) identifies the starting position of the clamp which is situated a distance (S′) away from the axis (A 1 X) of the machine, and symmetrically with respect to the starting position (P 1 ). 
         [0078]      FIGS. 18 ,  19 ,  20  schematically depict the rotations (AXE 1 ) about the axis (A 1 ), (AXE 2 ) about the axis (A 2 ), and (AXE 3 ) about the axis (A 3 ) for bending in a clockwise direction and respectively show:
       in  FIG. 18 , the position of the axes when the clamp is open, (S) indicating the initial clamping setting;     FIG. 19 , the position of the axes when the clamp is closed, the dimensions (x) and (y) indicating the final clamping setting; and     FIG. 20 , the triangulation of the forces when the clamp is in the closed position, with (Fa) for the clamping component along one axis, and (Fc) for the clamping component on the tube, and (a) the angle through which the clamp is rotated, Tan(component) which shows that for a given force (Fa), when the angle alpha tends toward 0, the clamping force on the tube (Ft) increases very sharply (and tends toward infinity, thus being limited by the rigidity of the whole).         
         [0082]    The fact of using three synchronized rotations means that the rectilinear movement of the clamp can be programmed in two perpendicular directions (Ox) and (Oy) and in terms of its angular rotation (a), which corresponds to the angle through which the clamp has to rotate about its axis (A 3 ) in order always to remain optimally positioned with respect to the roller thus optimizing the clamping of the tube as said roller ( 3 ) rotates. 
         [0083]    In the case of the bending of the tubes or profiled sections which is described hereinafter by way of example, all the functions and movements needed to form a full optimum machine incorporating a bending head according to the invention are detailed hereinafter in conjunction with  FIGS. 21 and 22 . 
         [0084]    The required means are as follows:
       guide-work rest means ( 9 ) for example: for clamping and following the tube or profiled section,   tube-positioning means or carriage ( 8 ): for clamping, feeding and orienting the tube,   guide means ( 10 ): for positioning the mandrel ( 11 ) in the tube prior to bending and removing it therefrom after bending,   tube-positioning means: for positioning to right or to left and turning the clamping head over to position it in a symmetric position.       
 
         [0089]    Numerical control provides the simultaneous and synchronized rotation of the three main axes and also the required additional movements, namely: 
         [0000]    .AXE 1 : rotation for bending the tube,
 
.AXE 2 : rotation for applying the clamp ( 4 ),
 
.AXE 3 : rotation for orienting the clamp ( 4 ),
 
.MVT 4 : rotation of the form roller ( 3 ),
 
.MVT 5 : translational clamping of work rest ( 7 ),
 
.MVT 6 : translational feed of work rest ( 7 ),
 
.MVT 7 : linear movement of tube bearing carriage ( 8 ),
 
.MVT 8 : rotation to orient carriage ( 8 ) for bending in a different plane,
 
.MVT 9 : tube clamping,
 
.MVT 10 : insertion and removal of mandrel ( 11 ),
 
.MVT 11 : bend radius for carriage ( 8 ).
 
         [0090]    It must be emphasized that, in the example depicted, all the rotational movements are planar and horizontal, the axes of rotation being vertical, and that the mandrel is guided conventionally and horizontally along the axis of the tube from an extracted or retreated position of  FIG. 21  in which it is removed from the tube (not visible in  FIG. 21 ) as far as a work position in which it is inserted into the tube to prevent the tube from being crushed while it is being bent. 
         [0091]    Other configurations may be envisioned, without departing from the scope of the invention, for example a configuration in which the bending head is vertical with rotational movements in a vertical plane. 
         [0092]    Provision may also be made for the roller ( 3 ) and the other satellite elements of the eccentric to be positioned under the main platen ( 2 ). 
         [0093]    A machine according to the invention preferably has the ability to bend tubes ranging from 40 to 80 mm in diameter with a maximum wall thickness of 2 mm for a diameter of 80 mm.