Marking device

This invention relates to a marking device for making two-dimensional identification signs on the surface of any object, of the type in which the micro-percussion tool is borne axially by a slewable rod which is retained angularly along its axis and which penetrates in a fixed housing through a Universal joint allowing free orientation thereof in all directions along an axis of symmetry, characterized in that orientation of the rod is controlled with the aid of two independent motors which act on one and the other, respectively, of the two orthogonal pivot pins of the joint.

FIELD OF THE INVENTION 
The present invention relates to marking devices used for making figures, 
letters or other two-dimensional identification signs on the surface of 
any object maintained immobile. 
BACKGROUND OF THE INVENTION 
The invention concerns devices of the type described in Patent EP-A-0 519 
850 (TECHNIFOR). It will be recalled that, in these devices, the marking 
tool, of the micro-percussion type, is mounted axially at the end of a 
slewable rod of which the opposite end penetrates inside a fixed housing 
through an articulated link constituted equally well by a Universal joint 
and by a simple ball-joint. 
In order to control orientation of the tool-holder rod, the housing 
contains an actuation mechanism which comprises two telescopic jacks 
oriented parallel to each other to act on two arms fixed radially on the 
rod and disposed perpendicularly to each other. One of the two elements of 
each jack is coupled by a ball-joint to the housing, while the other 
element is connected, itself by a ball-joint, to the end of the radial arm 
which corresponds thereto. 
In one of the embodiments described in the prior art document mentioned 
hereinabove, the two actuation jacks are oriented parallel to the axis of 
symmetry of the slewable rod, being coupled to that wall of the housing 
opposite the one which bears the articulated link. It will be appreciated 
that, if this rod is retained angularly against any rotation along its 
axis, such an actuation mechanism ensurers control of the displacement of 
the tool under excellent conditions. 
However, it should be noted that such an arrangement also presents a 
substantial drawback, in that, due to the geometry of the assembly, any 
control exerted by one of the two jacks necesarily involves a correcting 
action applied to the other jack, even in the case of the device being 
used for marking rectilinear lines. This permanent correction complicates 
the electronic apparatus used for controlling the actuation mechanism. 
In order to overcome this drawback, Applicants have proposed, in their 
European Patent Application No. 94 420 041.9 filed on Feb. 9, 1994, 
disposing the ball-joints which ensure coupling of the telescopic jacks to 
the fixed housing, in the plane transverse to the slewable rod which 
passes through the centre of the articulated link interposed between this 
rod and said housing. 
Such structure has proved to be of high performance, but it requires the 
use of jacks which are always very delicate to control very precisely. It 
is in this spirit that the present invention has for its object another 
embodiment which, by employing electric motors of the step-by-step type, 
makes it possible, at least in the case of the articulated link being 
constituted by a Universal joint, to simplify actuation of the device 
while maintaining the same performances. 
SUMMARY OF THE INVENTION 
The invention relates to a marking device for making two-dimensional 
identification signs on the surface of any object, of the type in which 
the micro-percussion tool is borne axially by a slewable rod which is 
retained angularly along its axis and which penetrates in a fixed housing 
through a Universal joint allowing free orientation thereof in all 
directions along an axis of symmetry, characterized in that orientation of 
the rod is controlled with the aid of two independent motors which act on 
one and the other, respectively, of the two orthogonal pivot pins of the 
joint. 
In fact, in the case of adopting a Universal joint for the articulated 
assembly of the tool-holder rod in the fixed housing, the invention 
consists in associating with each of the two orthogonal pivot pins of this 
joint an independent motor to ensure angular control of each pin. 
This basic arrangement is clearly distinguished from the structure in 
accordance with document EP-A-0 504 691 (MAUSER). In fact, although this 
document discloses a machining device equipped with two independent motors 
(referenced 11 and 13) associated with a tool-holder (referenced 15), it 
is not a question of a Universal joint, in that, if one (13) of these 
motors ensures pivoting of said tool-holder about an axis oriented 
transversely thereto, the other motor (11) effects rotation of the 
tool-holder assembly about its own axis. 
The framework is consequently totally different from that of the Universal 
joint envisaged in the present invention, to such a point that, even if 
document EP-A-0 504 691 (MAUSER) were combined with document EP-A-0 519 
850 (TECHNIFOR) mentioned hereinbefore, the structure claimed in the 
present Application would not be reconstituted. 
In particular, such a combination would not make it possible to obtain the 
result sought herein, namely allow the marking of rectilinear lines with 
the aid of one and the same control.

DESCRIPTION OF PREFERRED EMBODIMENT 
Referring now to the drawings, reference 1 designates the slewable rod 
which bears along its axis the micro-percussion tool 2 which is supplied 
pneumatically via a pipe 2a so that its mobile tip 2b marks the surface 3 
of the object to be identified. Rod 1 penetrates inside a fixed housing 4 
through an opening 4a in which is mounted the Universal joint 5 which 
supports said rod 1 while allowing it to slew freely in all directions 
with respect to its axis of symmetry X--X'. 
Joint 5 comprises an inner disc 6 provided with two diametrally opposite 
pivots to form a first pivot axis; pivot 6a is borne by an outer piece 7 
of stirrup shape, while the opposite pivot 6b is supported by a vertical 
plate 7a. Between the disc 6 and the plate 7a there is provided a pulley 8 
fitted on the pivot 6b and connected by a synchronous belt 9 to an upper 
pulley 10 of smaller diameter; this pulley 10 is fixed to the end of the 
shaft of an electric motor 11 of the step-by-step type. 
Like the inner disc 6, the outer stirrup 7 of joint 5 is fast with two 
opposite pivots 7b and 7c which define a second pivot axis oriented 
perpendicularly to the first and which are supported in the edges of the 
opening 4a. Pivot 7c bears a drive pulley 12 which is connected by a 
synchronous belt 13 to a small pulley 14 fitted on the shaft of a motor 
15, identical to motor 11 and borne by a vertical plate 4b fast with 
housing 4. 
It will be readily appreciated that the motors 11 and 15 in no way disturb 
the articulated coupling of the slewable rod 1 and the fixed housing 4. 
The structure described above makes it possible to obtain, with the aid of 
two motors, identically the same mode of control as that produced with the 
two jacks of European Patent Application No. 94 420 041.9 mentioned above: 
the production of a rectilinear marking line on the marking surface 3 
requires the actuation of one motor, without any correcting action to be 
made on the other motor. The electronic programmation which ensures 
automatic actuation of the two motors 11 and 15 is thus simplified.