Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
2000-04-13
2001-11-13
Banks, Derris H. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C451S384000
Reexamination Certificate
active
06315642
ABSTRACT:
The present invention relates to a method for the tracing of a bezel of a spectacle frame ring for the purpose of supplying data representing the contour of the bezel to a spectacle glass grinding machine which comprises a bevelling wheel having a bevelling groove of standard profile, the said method being of the type in which the frame ring is positioned, a fine tracer is introduced into the bezel in a predetermined radial orientation relative to a predetermined axis of rotation, until the tracer is in contact with the bottom of the bezel, and the tracer is caused to execute a revolution about this axis, at the same time ensuring the contact of the tracer with the bottom of the bezel at least for a predetermined series of radial orientations.
The invention also relates to a tracing apparatus intended for carrying out such a method and to a spectacle glass grinding machine equipped with such an apparatus.
The context and the basic problem of the invention will first be explained with reference to
FIGS. 1
to
3
of the accompanying-drawings.
FIG. 1
illustrates the section of a metal or plastic ring
1
of a spectacle frame, and
FIG. 2
illustrates a front view of the same ring
1
.
As seen in
FIG. 1
, the ring
1
comprises, on its inner periphery, a groove or bezel
2
in the form of a V open at 120° and with a flat bottom
3
.
FIG. 3
illustrates diagrammatically, in perspective, the parts, relevant to the invention, of a conventional spectacle glass grinding machine:
A wheel train
4
, the horizontal axis X—X of which is integral with the stand (not illustrated) of the machine. This wheel train comprises at least one roughing wheel
5
having a substantially cylindrical outer surface, and a bevelling wheel
6
provided with a standard groove
7
in the form of a V open at 120°. The drive motor of the wheel train is indicated at
8
.
A glass-carrying carriage indicated diagrammatically by its horizontal axis Y—Y parallel to the axis X—X. O indicates the centre of a glass to be ground
9
, held on the carriage by a two-part mandrel (not illustrated) which extends along the axis Y—Y and which forms part of the carriage. In this example, the centre O is located on the axis Y—Y.
Electronic carriage control means
10
. During the bevelling operation, these means control the displacement of the pointed tip
0
along the axis Y—Y and perpendicularly to the latter, as indicated by arrows, as a function of the angular position of the glass which is driven in relatively slow rotation about the axis Y—Y by a suitable motor (not illustrated).
A tracing apparatus
11
which may be integrated into the machine or carried by a separate stand. Such an apparatus is conventional and is sold under the trademark SCANFORM by the company BRIOT International.
The apparatus
11
comprises: a horizontal circular plate
12
rotatable about its vertical axis Z—Z; a substructure
13
fastened to this plate and provided with parallel and horizontal rods
14
located on either side of a diameter of the plate
12
; a slide
15
mounted moveably on the rods
14
; a vertical sleeve
16
fastened to the slide
15
; a tracer-carrying rod
17
mounted slideably in the sleeve
16
; and a tracer
18
fastened to the upper end of the rod
17
.
The tracer
18
is a so-called “fine” tracer, that is to say, at least in its active part, it is in the form of a pointed tip, the vertical thickness of which is smaller than that of the bottom
3
of the bezel
2
, as may be seen from the broken lines in FIG.
1
.
The apparatus
11
also comprises displacement means, the function of which will become apparent below, a sensor
19
of the angle of rotation of the plate
12
, a sensor
20
of the position of the slide
15
along the corresponding diameter of the plate and a sensor
21
of the vertical position of the tracer
18
. These sensors send corresponding signals to an electronic unit
22
which operates the control means
10
. Suitable interfaces are, of course, provided between the electronic elements of the assembly as a whole.
The conventional procedure takes place as follows.
The frame ring
1
is positioned above the apparatus
11
by means of suitable grippers indicated diagrammatically at
23
in
FIGS. 10
to
12
. Such grippers are described, for example, in the Applicant's FR-A-2 754 356.
The plate
12
is then brought into a predetermined initial angular position indicated at
24
in FIG.
2
. The rod
17
is brought along the axis Z—Z by the displacement of the slide
15
, and the tracer is brought substantially level with the bezel. The slide
15
is then pushed away from the axis Z—Z with a predetermined constant force, typically of 60 gf, until the pointed tip of the tracer
18
is in contact with the bottom of the bezel at the pointed tip
25
(FIG.
2
), as illustrated in FIG.
1
.
The means for the vertical displacement of the rod
17
comprises a friction disc which co-operates with this rod when the latter coincides with the axis Z—Z. As soon as the rod
17
leaves this position, it can be displaced vertically by sliding under the effect of a vertical force, whilst remaining immobile in the absence of such a force by virtue of a counterweight (not illustrated) with which it is equipped.
For this angular position &thgr;=0 of the plate, the sensors
20
and
21
measure the radial displacement &rgr;
0
of the slide
15
and the level z
0
of the plate.
The plate
12
is then rotated over one complete revolution, the tracer being permanently applied with the abovementioned constant force in the bezel
2
. The sensors
19
to
21
thus supply the unit
22
with a set of triplets (&thgr;, &rgr;, z) which represent the spatial form of the bezel.
On the basis of this information transmitted to the control means
10
, the glass
9
intended for equipping the frame ring
1
will be roughed by the wheel
5
and then bevelled by the wheel
6
. The control of the glass-carrying carriage will be such that the edge
26
of the bevel is at each moment located at the distance &rgr; from the axis Y—Y which corresponds to the angular position &thgr; of the glass in relation to its original position.
If the bezel
2
has, in fact, an opening of 120° or a greater opening, the glass will fit perfectly into the ring
1
(FIG.
4
). If, by contrast, this opening is smaller than 120°, the glass will interfere with the frame (
FIG. 5
) and cannot be fitted. It will then be necessary to recover the glass and carry out a reworking operation.
In order to avoid this additional manipulation, it has been proposed (FR-A-2,637,830) to use a thick tracer having a profile in the form of a V at 120° of the bevelling groove
7
. The glass then undoubtedly fits into the bezel, but at the expense of the two following disadvantages:
on the one hand, the thick tracer tends to escape from the bezel during tracing, unless increased force is exerted on it, which then risks deforming the frame ring;
on the other hand, the rapid wear of the tracer alters its profile, so that the angle of 120° is no longer guaranteed, thus impairing the tracing accuracy.
The object of the invention is to make it possible to carry out tracing reliably and economically, avoiding the need to recover the glass after bevelling, whatever the opening of the V of the bezel or even the form of its section.
To achieve this, the subject of the invention is a tracing method of the type mentioned at the beginning, characterized in that, furthermore, a second tracer, the profile of which substantially matches that of the said groove, is introduced at a predetermined point on the periphery of the bezel, and information representing the difference in penetration of the pointed tips of the two tracers into the bezel at the said predetermined point is supplied to the grinding machine.
This method may comprise both or either one of the following characteristics:
the relative position of the pointed tips of the two tracers is measured beforehand by bringing them successively into contact with the same reference surface parallel to the said axis, and information rep
Bonbony Stephane Pascal Bertrand
Videcoq Jean-Jacques
Banks Derris H.
Briot International
Wenderoth , Lind & Ponack, L.L.P.
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