Abstract:
A marking machine including a frame, an arm articulated on the frame about an axis of articulation, and a marking tool movably mounted on the arm, The marking tool is movable in translation with respect to the arm.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a marking machine, and more particularly to a marking machine comprising a frame on which a marking assembly is articulated. It is applicable to producing a pattern on the surface of a piece, whether by printing on this surface, deformation thereof, or removal of matter therefrom. 
     2. Brief Description of the Related Art 
     EP-A-0 586 328 discloses a marking machine comprising a frame and a first arm, free to pivot with respect to this frame. A second arm, whose end opposite the first arm receives a marking tool, is articulated on the end of this first arm opposite the frame. 
     However, this machine, of which the marking assembly is formed by two mutually articulated arms, presents certain drawbacks. For example, the first arm is heavy, insofar as it bears drive elements for displacing the second arm. In addition, as these drive elements are placed near the end of this first arm opposite the frame, this induces a high moment of the marking assembly on the frame, which is detrimental to the correct functioning of the machine. 
     In addition, the programming of such a marking machine proves to be complex, since it is necessary to take into account the angular divergences existing, on the one hand, between the frame and the first arm, and, on the other hand, between the first and second arms. Moreover, a determined point may be attained via two different positions of the first and second arms. 
     It is an object of the present invention to overcome the drawbacks set forth hereinabove. 
     SUMMARY OF THE INVENTION 
     To that end, it relates to a marking machine comprising a frame, an arm articulated on said frame about an axis of articulation, and a marking tool mounted mobile on said arm, characterized in that a single arm is provided and in that said machine further comprises means for displacing said marking tool in translation with respect to said single arm. 
     Other characteristics of the invention from the subject matter of the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be more readily understood on reading the following description given by way of non-limiting example with reference to the accompanying drawings, in which: 
     FIG. 1 is a view in perspective of a marking machine according to the invention, 
     FIG. 2 is a longitudinal section in perspective of a mobile marking assembly belonging to the machine shown in FIG. 1, 
     FIGS. 3 and 4 are sections on a larger scale along lines III—III and IV—IV of FIG. 2, and 
     FIG. 5 is a schematic plan view illustrating, in two different positions, a tab forming marker element with which the mobile marking assembly of FIGS. 2 to  4  is equipped. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     Referring now to the drawings and firstly to FIG. 1, the marking machine according to the invention, generally designated by reference  2 , comprises a base  4  for receiving a piece to be marked (not shown), from which a vertical support  6  extends. This support  6  receives a bracket or frame  8 , and a wheel  10  conventionally allows the height of this bracket  8  to be adjusted with respect to the support  6 . 
     The bracket  8  presents a lower area  12  projecting with respect to the front of the support  6 . A substantially cylindrical, vertical box  14 , of axis A, projects from the periphery of the area  12 . As will be described in greater detail hereinbelow, this box  14  provides pivotal housing about axis A for a mobile marking assembly, designated by reference  16  and equipped with a marking tool  18 . The area  12  supports a housing  20  interposed between the support  6  and the box  14 , which receives a motor (not shown), intended to ensure pivoting of the marking assembly  16  with respect to the box  14 . 
     As shown in FIGS. 2 to  4 , the marking assembly  16  comprises a single elongated arm  22 . This arm, which is open in the direction of the base  4 , is provided with an upper web  24  extended by a peripheral lateral wall  26 . 
     The marking assembly  16  also comprises a substantially cylindrical, hollow chamber  28  mounted to pivot in the box  14  and fast with the arm  22 . To that end, a worm wheel  30  is arranged on a shoulder  32  with which the outer wall of the chamber  28  is provided. This worm wheel  30  cooperates with an endless screw  34 , received in the housing  20  and actuated by a motor (not shown). This endless screw comes into contact with the worm wheel  30  through a cut  36  made in the box  14 . The marking assembly  16  is therefore free to pivot about the principal axis A of the chamber  28 . 
     The chamber  28  is maintained axially with respect to the box  14  via an upper flange  38  provided around the chamber  28 , cooperating with an inner shoulder  40  of the box  14 . Ball bearings or the like (not shown), are interposed between this flange  38  and this shoulder  40 , in order to ensure easy pivoting of the box with respect to the chamber. 
     The chamber  28  is obturated in its upper part by a cover  42  disposed below a securing ring  44 . A disc  46  is placed beneath the cover  42  and abuts, by its lower face, against a lower ring  48 . Springs  50 , interposed between the disc  46  and the cover  42 , tend to push the latter against the upper ring  44 . In this first position, the cover  42  is prevented from rotating, by friction on the ring  44 , relative to the marking assembly. 
     The cover  42  is secured to a rod  51  extending along axis (A) and terminating in a handle  52 . The end of this rod opposite the handle has a threading cooperating with a central tapping made in the disc  46 . The cover is also secured to a tab or marker element  54  extending radially beyond the periphery of the chamber  28 . This marker element is adapted to come plumb with a detector  56 , for example incorporating a photo-electric cell, fixed to the box  14 . 
     It should be noted that there is a certain axial clearance between the opposite walls of the cover  42  and of the disc  46 , with the result that they may be disconnected from the respective rings  44  and  48 , by screwing the rod  51  downwardly against the springs  50 . In this second position, the cover  42 , as well as the marker element  54 , are free to pivot with respect to the chamber  28 . 
     The chamber  28  is provided with a bottom  58  receiving a motor  60  whose downwardly projecting driven shaft is connected to a pinion  62  for actuating a synchronous belt  64 , forming a loop. This belt, which extends axially over a major part of the length of the arm  22 , passes, at its end opposite the pinion  62 , around a roller  66 . The latter penetrates, by an axial finger  68 , in a cut  70  made in the upper web  24  of the arm  22 . This finger  68  is fixed in this cut by a screw  72  passing through the peripheral wall  26 . 
     The belt  64  drives a carriage  74  bearing the marking tool  18 . The belt and the carriage are for example joined by adhesion. This carriage has a bore  76  made therein, which is traversed by a longitudinal guiding bar  78  extending between the two ends of the peripheral web  24 . This bore  76  is disposed in the direction of the tool  18  with respect to the belt  64 . The carriage is in addition provided with an end stirrup element  80 , opposite the tool, which overlaps a blade  82  intended to avoid pivoting of the carriage and fixed on the upper wall of the web  24 . The marking tool  18  is supplied, in known manner, by pneumatic or electric means (not shown). 
     The marking tool  18  may therefore be displaced, with respect to a piece to be marked, both under the effect of the pivoting of the arm  22  with respect to the bracket  8  and under the effect of the translation of the carriage  74  with respect to this arm  22 . 
     The position of the marking tool may be determined by using so-called polar coordinates, namely on the one hand, the radial distance separating it from its point of origin in translation, which corresponds to its abutment against an origin (not shown) fast with the arm and, on the other hand, the angle of the arm with respect to the position of origin in rotation, in which the marker element  54  is plumb with the detector  56 . 
     Once the marking has been effected, the marking assembly  16  should be pivoted about axis A of the box  14 , so as to clear the region occupied by the marked piece  86 , shown in broken lines in FIG. 5, and to return the marking assembly  16  into its position of origin. In the position shown in FIG. 5, it is therefore theoretically necessary to pivot the marking assembly  16  through an angle α corresponding to the angular divergence between the marker element  54  and the detector  56 . However, this angle α is clearly greater than the angle β representing the pivoting sufficient to disengage the arm from the region of the marked piece  86 . 
     In order to reduce the duration of pivoting of the arm, it is possible to pivot the marker element  54  with respect to the arm  22  through an angle γ corresponding to the difference between the theoretical angle α and the angle β sufficient to disengage the arm from the marked piece. Such pivoting of the marker element  54  is represented in broken lines. To that end, the rod  51  is screwed downwardly so as to axially move the cover  42  and the disc  46  apart with respect to the rings  44  and  48 . The cover  42  and the disc  46  are then disconnected in rotation with respect to the chamber  28 , and the marker element  54  is rotated through angle γ. 
     With a view to driving the marking tool, it may be provided to replace the synchronous belt by a screw extending along the principal axis of the arm and cooperating with a nut secured to the carriage. 
     The invention enables the objectives set forth hereinabove to be achieved. The use of a single pivoting arm, with respect to which the marking tool is mobile in translation, guarantees an easier programming compared to the prior art. In effect, the position of a point may be determined in polar coordinates, which is notably easier than by taking into account two different angles, as in the prior art. Moreover, a determined point presents one sole couple of polar coordinates, which may be achieved by means of a single position of the arm and of the carriage, contrary to the prior art. 
     As the marking tool is mobile in translation, it presents a low inertia, which guarantees it a satisfactory mobility. The marking produced by the machine of the invention may therefore be effected more rapidly than in the prior art. 
     As the marking tool is mobile in translation with respect to the single arm, the weight of the latter is notably less than in the prior art, insofar as it does not bear any drive element at its end opposite the frame, contrary to what exists in the prior art. 
     It is also advantageous to arrange, near the pivot axis of the arm, drive means for displacing the marking tool. In effect, this characteristic reduces the moment of the arm on the frame of the machine, very substantially with respect to the prior art. 
     It is advantageous to use of a marker element capable of being disconnected in rotation with respect to the mobile marking assembly. In effect, it makes it possible to limit the movement of pivoting of this mobile assembly when it returns into the position of origin. A substantial amount of time is therefore saved by such an arrangement.