Abstract:
The welding machine comprises within a frame ( 1 ), a horizontal heating plate ( 21 ), a first lower piece-holder ( 22 ), a second upper piece-holder ( 23 ), means ( 41 ) for displacing horizontally the heating plate ( 21 ), means ( 42 ) for displacing vertically ( 29 ) the heating plate ( 21 ), and means ( 26 ) for displacing vertically the second piece-holder ( 23 ). The heating plate ( 21 ) and its vertically actuating cylinder ( 42 ) constitute an assembly connected to a heating plate carrier ( 33 ) by indexing means ( 27 ) for adjusting the vertical position of the vertical displacement ( 29 ) of the heating plate ( 21 ). The first piece-holder ( 22 ) is a telescoping table with adjustable height and capable of being locked mounted on the frame ( 1 ). Thus the possibilities of adjusting and adapting the welding machine to the different sizes of pieces to be welded are increased.

Description:
SUMMARY OF THE INVENTION 
     The present invention concerns heating plate welding machines, which are generally used to weld together two heat-weldable material parts along respective plane or non-plane connecting surfaces. 
     In the heating plate welding machines usually employed, such as that described in document FR 2 320 839 A, for example, a frame carries the various functional units of the machine including a heating plate, a first workpiece support device, and a second workpiece support device facing the first workpiece support device. First means move the heating plate along a transverse insertion travel parallel to its plane between a welding position engaged between the first and second workpiece support devices and a loading position withdrawn from the first and second workpiece support devices. Second means move the heating plate along a welding travel perpendicular to its plane between two extreme positions. The first workpiece support device is fixed to the frame. The second workpiece support device is mobile, and can be moved by third means along a contact travel perpendicular to the plane of the heating plate between the extreme positions and toward or away from the first workpiece support device. The machine also includes cylinders for moving the first workpiece support device toward or away from the second workpiece support device. 
     The movements of the heating plate, along the insertion travel and along the welding travel, are generally linear and driven by cylinders which provide amplitudes of movement limited by the allowed overall size of the cylinders of the machine. Similarly, the second workpiece support device is moved along the contact travel by a cylinder providing a limited amplitude of movement. 
     In operation, at least one first workpiece to be welded is placed on the first workpiece support, while at least one second workpiece to be welded is fixed to the second workpiece support, dedicated tooling providing the connection between each workpiece support and the corresponding workpiece to be welded. The machine is set up so that during a heating step the first face of the heating plate can be pressed onto the first workpiece to be welded on the first workpiece support, while the second workpiece to be welded is pressed against the opposite face of the heating plate by the second workpiece support. The second workpiece support is then moved away, after which the heating plate is moved away from the first workpiece to be welded carried by the first workpiece support and then withdrawn from the two workpiece supports. The second workpiece support is operated again to press the connecting surfaces of the two workpieces to be welded against each other, the plastics material being sufficiently softened or melted to assure a weld. 
     Clearly, for each given machine, the various movements that are necessary limit the maximal dimensions of workpieces that can be welded. 
     Workpieces of different shapes can be welded on the same machine by fitting appropriate dedicated tooling, but setting up the machine is complex because the travels of the cylinders moving the heating plate and the second workpiece support device are affected by the differences in the dimensions of the tooling and the workpieces to be welded. 
     Accordingly, in document FR 2 320 839 A, the adjustment can be effected by the cylinders moving the first workpiece support. This kind of adjustment is not reliable, however, and no adjustment means are explicitly described, and also this document concerns the welding of storage battery housings, the dimensions of which would appear to be constant. 
     Document FR 2 688 736 A describes a similar machine, but in which the first workpiece support is fixed, without any adjustment means. 
     Document GB 2 085 354 A (FIG. 5) describes a similar machine in which the heating plate is suspended vertically from a carriage that is movable to adjust it, and so is not positively held so that it can be moved along a particular welding travel. This means that the weld is not reproducible. 
     Accordingly, in prior art machines, there are no means for reliably and quickly adjusting the machine to track variations in the size of the workpieces to be welded, and to maintain the pressures exerted during operation of the machine effectively. 
     SUMMARY OF THE INVENTION 
     The problem addressed by the present invention is that of designing improvements to machines for welding workpieces using heating plates which, without modifying the overall size of the machine, and using conventional tooling available until now, significantly increase the possible variation in the dimensions of the workpieces that the machine can weld, retaining good reproducibility of the weld. 
     The improved possibilities of modifying the dimensions of workpieces to be welded must preferably be obtained without complicating the operations of control of the cylinders actuating the mobile parts of the machine, and without increasing the travel itself of the cylinders, so preserving a good speed of the welding cycle. 
     Accordingly, an improved machine in accordance with the invention must be able to replace a plurality of existing machines each suited to a range of dimensions of the workpieces to be welded. 
     To achieve the above and other objects, a welding machine in accordance with the invention having a heating plate comprises a frame, a heating plate, a first workpiece support device, a second workpiece support device facing the first workpiece support device, first means for moving the heating plate along an insertion travel parallel to its plane between a welding position engaged between the first and second workpiece support devices and a loading position withdrawn from the first and second workpiece support devices, second means for moving the heating plate along a welding travel perpendicular to its plane between two extreme positions, and third means for moving the second workpiece support device along a contact travel perpendicular to the plane of the heating plate toward and away from the first workpiece support device and between respective bearing and withdrawn positions, together with means for moving the first workpiece support device perpendicular to the heating plate toward or away from the second workpiece support device. 
     The first workpiece support device further comprises: 
     an adjustable position table, mounted on the frame, being movable it toward or away from the second workpiece support device, and 
     means for locking the table in a particular position chosen from a set of predefined positions and to withstand thus pressure forces exerted on the table during operation of the machine. 
     This means that the workpiece supports and the heating plate are mechanically strong, to guarantee good reproducibility of the weld. 
     For example, the means for locking the table comprise transverse screws selectively engaged in corresponding holes in respective fixed lateral guide plates of the frame and in guide brackets carried by the table. 
     Improved possibilities of adjusting the machine can be obtained by further providing indexing means for indexing the welding travel of the heating plate by moving its two extreme positions of welding travel perpendicularly to the plane of the heating plate toward or away from the first workpiece support device. 
     In one advantageous embodiment, the table comprises a top plate joined to a bottom support by expandable connecting members each including a first arm, one end of which is articulated to the bottom support and the other end of which slides under the top plate, and a second arm, one end of which is articulated under the top plate and the other end of which slides on the bottom support, the two arms being articulated to each other in their central areas, the sliding end of the second arm being slid horizontally on the bottom support by a cylinder to adjust the height of the table. 
     The design of a machine of the above kind can be adapted to heating plates oriented vertically or horizontally. In a preferred embodiment, the heating plate is oriented in a substantially horizontal position, its insertion travel is substantially horizontal and its welding travel is substantially vertical, the first workpiece support device is in a lower position on the frame, and the second workpiece support device is in an upper position on the frame and its contact travel is substantially vertical. 
     The means for indexing the welding travel of the heating plate can advantageously be such that: 
     the heating plate support carriage comprises at least two vertical lateral flanges each having an indexing opening with a vertical linear main part, one end of which is joined to a plurality of oblique secondary parts diverging from each other in the downward direction and offset from each other in the vertical direction, 
     the heating plate support frame comprises transverse horizontal lugs or rods engaging in the indexing openings of the heating plate support carriage, and able to slide in said indexing openings to penetrate selectively into one of the oblique secondary parts and to abut against its bottom. 
     An advantageous arrangement for reducing the overall size of the welding machine is for the heating plate support carriage to be moved, along its insertion travel, by two horizontal cylinders in the upper part of the frame on respective opposite sides of the interior part of the frame. 
     With a machine of the above kind with improved adjustment possibilities, it is advantageous for the door providing access to the interior space of the frame to open quickly and wide. To this end, the door may comprise two telescopic lateral flaps. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects, features and advantages of the present invention will emerge from the following description of specific embodiments, given with reference to the accompanying drawings, in which: 
     FIG. 1 is a side view of a heating plate welding machine constituting one embodiment of the invention, showing the heating plate in the loading position and the lateral wall of the frame removed; 
     FIG. 2 is a plan view of the welding machine from FIG. 1 showing the door open, the heating plate in the loading position and the top wall removed; 
     FIG. 3 is a front view of the welding machine from FIG. 1 showing the door open; 
     FIG. 4 is a partial side view in section, showing the means for indexing the heating plate support in one embodiment of the present invention; 
     FIG. 5 is a side view showing in detail the construction of a variable height table in one embodiment of the present invention; and 
     FIG. 6 shows the possibilities of adjusting the welding machine from FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the embodiment shown in the figures, in particular in FIGS. 1 to  3 , a welding machine in accordance with the invention comprises a substantially parallelepiped-shape frame  1  defining an interior space  2  containing all of the functional units of the welding machine. The frame  1  comprises a supporting structure defined overall by four vertical uprights  3 ,  4 ,  5  and  6  disposed at the four corners of the interior space  2 , two bottom longitudinal members  7  and  8 , two end bottom crossmembers  9  and  10 , and two opposed top longitudinal members  11  and  12  and two end top crossmembers  13  and  14 . 
     In the embodiment shown, there are also two opposed intermediate longitudinal members  15  and  16 , substantially three-quarters the height up the frame  1 , together with intermediate uprights  17  and  18  near the uprights  4  and  5 , respectively. 
     An electrical equipment cabinet  19 , containing switching and control devices, is provided against the rear face of the frame defined by the rear uprights  3  and  6  and the rear crossmembers  9  and  13 . A door system  20  is provided against the front face of the frame defined by the front uprights  4  and  5  and the front crossmembers  10  and  14 . 
     The interior space  2  of the frame  1  contains the functional units of the welding machine, including particularly a heating plate  21 , a first workpiece support device  22 , a second workpiece support device  23  facing the first workpiece support device  22 , first means  24  for moving the heating plate  21  along an insertion travel  39  parallel to its plane, second means  25  for moving the heating plate  21  along a welding travel  29  perpendicular to its plane, and third means  26  for moving the second workpiece support device  23  along a contact travel  129  perpendicular to the plane of the heating plate  21 . In accordance with the invention, indexing means  27  are further provided for indexing the welding travel  29  of the heating plate  21 , by movement of its two extreme positions perpendicularly to the plane of the heating plate  21  toward or away from the first workpiece support device  22 . 
     In the embodiment shown in the figures, the heating plate  21  is substantially horizontally oriented, its insertion travel  39  is substantially horizontal and its welding travel  29  is substantially vertical. The first workpiece support device  22  is in the bottom part of the interior space  2  on the frame  1  and the second workpiece support device  23  is in the top part of the interior space  2  of the frame  1 , its contact travel  129  being substantially vertical. 
     The heating plate  21  is mounted on a mobile heating plate support bracket  28  in turn movable in vertical translation along said welding travel shown by the arrow  29  in FIGS. 1 and 4, perpendicularly to the plane of the heating plate  21 , sliding on vertical guides  30  and  31  of a frame  32  in turn carried by a heating plate support carriage  33 . 
     The heating plate support carriage  33  has a carriage top main crossmember  34  the ends of which have skids  35  and  36  which slide on longitudinal guides carried by the intermediate longitudinal members  15  and  16 . The heating plate support carriage  33  also has two vertical side flanges  37  and  38  shaped to retain the frame  32  and joined at their top ends by a horizontal connecting plate  133  retained by the top main crossmember  34 . The horizontal connecting plate  133  is preferably mounted to slide longitudinally in the direction of the welding travel  29 , its two lateral edges being engaged in lateral slides  134  and  135  fastened to the top main crossmember  34 . A rear adjuster screw  136  adjusts the longitudinal position of the flanges  37  and  38  and of the connecting plate  133  relative to the top main crossmember  34 , so allowing fine adjustment of the position of the heating plate for the welding step, as shown by the arrow  139 . 
     In executing its insertion longitudinal travel  39  shown in FIG. 1, the heating plate support carriage  33  slides on the longitudinal guides when acted on two horizontal cylinders  40  and  41  in the top part of the frame  1  on respective opposite sides of the interior welding space  2  and coupled to the ends of the top main crossmember  34 . 
     The particular position of the cylinders  40  and  41  actuating the heating plate  21  along the insertion travel  39  produces a compact welding machine that is short in length. 
     In executing its welding travel  29 , the mobile heating plate support bracket  28  slides on the vertical guides  30  and  31  of the frame  32  and is operated on by a vertical cylinder  42  carried by the frame  32  and the travel of which is adjustable. 
     In accordance with the invention, the position of the first workpiece support device  22  can be adjusted by movement perpendicular to the heating plate  21 , in the vertical direction, toward or away from the second workpiece support device  23 . 
     To this end, in the embodiment shown in FIGS. 1 and 5, the first workpiece support device  22  can include an adjustable height table  50  mounted on the frame  1 , for example. 
     In the embodiment shown, the table  50  has a top plate  51  connected to a fixed bottom support  52  by expandable connecting members each including: a first arm  53 , one end  54  of which is articulated to the bottom support  52  and the other end  55  of which slides under the top plate  51 , and a second arm  56 , one end  57  of which is articulated under the top plate  51  and the other end  58  of which slides on the bottom support  52 . The two arms  53  and  56  are articulated to each other in their central areas  59 , and the sliding end  58  of the second arm  56  is slid horizontally on the bottom support  52  by a cylinder  60  to adjust the height of the table  50 . 
     As shown in FIG. 3, the table  50  can be immobilized or locked in a particular position chosen from a set of predefined vertical positions by transverse screws such as the screws  150  and  151  selectively engaged in corresponding holes respectively formed in fixed lateral guide plates  152  and  153  of the frame  1  and in guide brackets  154  and  155  carried by the table  50 . 
     The operation of the welding machine is described hereinafter. In the loading position, shown in FIGS. 1 to  3 , the heating plate  21 , carrying heating blocks with the same profiles as the respective connecting surfaces of the workpieces to be welded, is in a loading position, withdrawn from the first and second support devices  22  and  23 , the second workpiece support device  23  being withdrawn from the first workpiece support device  22 . A first workpiece to be welded, held on the first workpiece support device  22  by a first dedicated tooling adapted to the shape of the first workpiece to be welded and shaped to be fixed to the first workpiece support device  22 , can then be moved into place. The second workpiece to be welded, fixed to the second workpiece support device  23  by second dedicated tooling adapted to the shape of the second workpiece to be welded and shaped to be fixed to the second workpiece support device  23 , can equally be moved into place. The respective connecting surfaces of the two workpieces to be welded are then face-to-face and separated from each other. 
     The cylinders  40  and  41  move the heating plate  21  along the insertion travel  39  between the two workpieces to be welded, that is to say between the first and second workpiece support devices  22  and  23 , in the sufficient gap that must exist between the two connecting faces of the workpieces to be welded. The cylinder  42  lowers the heating plate  21  along the welding travel  29  until the bottom face of its lower heating block is pressed against the connecting face of the first workpiece to be welded fixed to the first workpiece support device  22 , the heating plate  21  then bearing against abutments carried by the tooling of the first workpiece support device  22 . The cylinder  26  lowers the second workpiece support device  23  along the contact travel  129  so that the connecting face of the second workpiece to be welded that it carries is pressed against the top face of the top heating block of the heating plate  21 , abutments carried by the tooling of the second workpiece support device  23  bearing against the heating plate  21 . The heating plate  21 , which is maintained at an appropriate temperature by electrical heating elements connected to an external electrical power supply, heats the two connecting faces of the workpieces to be welded and partially melts their surfaces. 
     The cylinder  26  then raises the second workpiece support  23  after which the successive operation of the cylinder  42  and of the pair of cylinders  40  and  41  raises the heating plate  21  and then moves it to the loading position withdrawn from the first and second workpiece support devices  22  and  23 , after which the cylinder  26  lowers back the second workpiece support device  23  until the two connecting faces of the workpieces to be welded are pressed together. The two workpieces to be welded are pressed together for long enough to effect the weld, and finally the second workpiece support device  23  is raised and the two workpieces that have been welded together are removed. 
     The invention enables the position of the first workpiece support device  22  to be adapted to the respective size of the two workpieces to be welded reliably, quickly and at low cost. To this end, depending on the workpieces to be welded, the first workpiece support device  22  is positioned at an appropriate vertical position, by actuating the cylinder  60 . Movement of the first workpiece support device  22  is thereafter prevented by inserting the transverse screws  150  and  151  in the corresponding holes in the plates  152  and  153  and the brackets  154  and  155 . 
     Accordingly, without increasing the welding travel  29  of the heating plate  21 , the total relative vertical area that the heating plate  21  can reach is increased in size, which increases the range of different sizes of workpieces that can be welded. 
     FIG. 6 shows this first possibility of adaptation in accordance with the invention. The righthand part of the figure shows several possible positions of the first workpiece support device  22 , to which it is moved by the cylinder  60 . Clearly the bottom position is suitable when the first workpiece to be welded is high and the second workpiece to be welded is relatively low. Conversely, the upper position is suitable when the first workpiece to be welded has a lower height and the second workpiece to be welded has a greater relative height. 
     The combination of the frame  32 , the heating plate support bracket  28  and the cylinder  42  can additionally or instead be moved vertically in its entirety by the indexing means  27  to execute an indexing movement between a plurality of distinct positions on the heating plate support carriage  33 . This indexing movement simultaneously moves both extreme positions of the welding travel  29  of the heating plate  21 . In this way the position of the extreme positions of the welding travel  29  can be chosen in the interior space  2 , allowing adaptation to the size of the workpieces to be welded. 
     In the embodiment shown in the figures, and in particular in FIG. 4, the indexing means  27  for indexing the welding travel  29  of the heating plate  21  comprise means for selectively fixing the frame  32  to the heating plate support carriage  33  in a plurality of positions offset from each other in the vertical direction perpendicular to the heating plate  21 . 
     In practice, the heating plate support carriage  33  comprises at least two vertical side flanges  37  and  38  each of which has an indexing opening such as the opening  42 . The opening  42  has a vertical linear main part  43 , a vertical edge  44  of which is joined to a plurality of oblique secondary parts  45 ,  46 ,  47  and  48  diverging in the downward direction, offset from each other in the vertical direction, as shown, and having bottoms aligned with a common vertical axis. 
     The frame  32  has horizontal lugs or rods  49 , oriented transversely and shaped to engage in the indexing openings such as the opening  42  of the heating plate support carriage  33  and to slide in said indexing openings  42  to penetrate selectively into one of the oblique secondary parts  45  through  48  and to abut against the bottom of said chosen oblique secondary part  45  to  48 . Corresponding faces of the heating plate support carriage  33  and of the frame  32  form bearing surfaces opposing tilting of the armature, for holding the heating plate  21  in a fixed horizontal position relative to the heating plate support carriage  33 . 
     The lefthand part of FIG. 6 shows the additional possibilities of vertical adjustment provided by the indexing means  27 . Clearly the welding travel  29  can be moved vertically and the possibilities of adapting the position of the heating plate  21  relative to the first workpiece support device  22  according to the sizes of the workpieces to be welded can be increased. 
     The additional possibilities for adjusting the relative heightwise positions of the functional units of the welding machine lead to the provision of a door system  20  that is well adapted to such possibilities. A door with two telescopic lateral flaps that retract laterally is preferably employed, as shown in FIG.  2 : the door, which is shown in the open position in the figure, has a first telescopic lateral flap formed of a first panel  61  and a second panel  62  sliding laterally relative to each other and relative to the frame  1 . Similarly, a telescopic second lateral flap comprises a first panel  63  and a second panel  64  sliding laterally relative to each other and relative to the frame  1 . This provides a door that is of compact overall size in the open position, and that can be closed and opened very quickly during the operating cycle. 
     The present invention is not limited to the embodiments explicitly described, but includes variants and generalizations thereof within the scope of the following claims.