for, Cutting, Grinding, and Polishing Curved Surfaces.
Year: 1885

page_text: for, Cutting, Grinding, and Polishing Curved Surfaces.
We JOSEF FRIC and JAN FRIC, both of Vinohrady, Prague in the Kingdom of
Bohemia, Austro-Hungary, Engineers, do hereby declare the nature of our.Inven-
tion for IMPROVEMENTS IN THE METHOD OF, AND IN MACHINERY OR APPARATUS
FOR CUTTING, GRINDING AND POLISHING CURVED SURFACES to be as follows:-
"
The object of our invention is to effect improvements in cutting, grinding and
polishing spherical, elliptical, parabolic, hyperbolic, and other curved surfaces,
either concave or convex, and in the machinery or apparatus for effecting the
same.
In carrying out our invention we mount the object to be operated upon in a
suitable chuck, which is rotated in the usual manner. The cutter or cutters,
operating upon the object, is or are also caused to rotate, at the 'same time, but
not necessarily at the same speed as the chuck and the object under operation.
The cutters are preferably made in the form of a disc, the cutting edges being
at or near the outer circumference of the disc..
The cutters revolve on moveable axes, and such axes are so arranged as to cut
the axial line of the mandrel at a certain distance, which distance is controlled by
the necessary curve to be formed upon the object.
The cutters are also mounted so that, while operating, they may be swung upon
their centres, and thereby caused to operate upon every part of the object.
One, two, or more cutters may be mounted and caused to operate upon the
same object, at the same time, 'in cases where several surfaces are required on
the object.
•
:
When both the object operated upon and the cutting tool rotate in circular
paths, the surface produced will be spherical. When the cutting tool describes
elliptical paths, perpendicular to the axis of the cutting tool, an elliptical surface
will be formed; and, by varying the paths of the several rotating chuck's and

page_text: cutters, parabolic, hyperbolic, and other concave and convex surfaces may be
produced.
Our said invention is applicable to the production of exact forms in metal or
glass, and especially to the cutting, grinding and polishing of lenses and reflectors
for optical purposes.
GEO. DOWNING,
Agent for Applicants.
Improvements in the Method of, and in Machinery or Apparatus
for, Cutting, Grinding, and Polishing Curved Surfaces.
We JOSEF FRIC and JAN FRIC, both of Vinohrady, Prague, in the Kingdom of
Bohemia, Austro-Hungary, Engineers, do hereby declare the nature of our said
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :—
The object of our invention is to effect improvements in cutting, grinding and
polishing spherical, elliptical, parabolic, hyperbolic, and other curved surfaces,
either concave or convex, and in the machinery or apparatus for effecting the
same.
In carrying out our invention we mount the object to be operated upon in a
suitable chuck, which is rotated in the usual manner. The cutter or cutters,
operating upon the object, is or are also caused to rotate, at the same time, but
not necessarily at the same speed as the chuck and the object under operation.
The cutters are preferably made in the form of a disc, the cutting edges being at
or near the outer circumference of the disc.
The cutters revolve on moveable axes, and such axes are so arranged as to cut
the axial line of the mandrel at a certain distance, which distance is controlled by
the necessary curve to be formed upon the object.
The cutters are also mounted so that, while operating, they may be swung upon
their centres, and thereby caused to operate upon every part of the object.
One, two, or more cutters may be mounted and caused to operate upon the
same object, at the same time, in cases where several surfaces are required on
the object.
When both the object operated upon and the cutting tool rotate in circular
paths, the surface produced will be spherical. When the cutting tool describes
elliptical paths, perpendicular to the axis of the cutting tool, an elliptical surface
will be formed; and, by varying the paths of the several rotating chucks and

page_text: cutters, parabolic, hyperbolic, and other concave and convex surfaces may be
produced.
Our said invention is applicable to the production of exact forms in metal or
glass, and especially to the cutting, grinding and polishing of lenses and reflectors
for optical purposes.
And in order that our said invention may be more particularly ascertained and
described, reference is hereby made to the accompanying drawings, in which
similar letters of reference indicate corresponding parts.
Fig. 1 is an elevation, partly in section on the line ON of Fig. 2 of a machine
with fixed driving shaft for the cutter.
Fig. 2 is a section of the same on the line A. B. of Fig. 1.
Fig. 3 is a sectional elevation on the line V. W. of Fig. 4, of a machine showing
the cutter mounted on a sliding driving shaft.
Fig. 4 is a horizontal view of the same machine.
Fig. 5 is a side view of the same machine.
Fig. 6 shews the method of grinding or cutting a convex surface,
Fig. 7 that of a concave surface.
Fig. 8 is a machine with a moveable driving pulley.
Fig. 9 is a section of the same on the lines X X X₁ yii y Y.
Fig. 10 is a similar section on the line G. H.
Fig. 11 shews the arrangement for transmitting the driving power.
Fig. 12 is a horizontal view of the same grinding machine.
Fig. 13 is a section of the same on the line C. D.
Fig. 14 is a section through the axis of a double grinding apparatus.
Fig. 15 is the gearing of the horizontal driving shaft, and
Fig. 16 the same in section through K. L.
In most cases we construct our machines so that the object to be operated upon
is placed on a horizontal revolving table a. It is fixed by means of pitch, or other
suitable material, as usual. The cutter or polishing disc b revolves on a separate
axle, which may be inclined towards or in relation to the first. Both axes are
intended to remain constantly in the same geometrical plane, and they must
consequently meet in one point. The surface will be convex, if this meeting point
is below as shewn in Fig. 6 and it will be concave if this point is above the surface,
as shewn in Fig. 7. The meeting point of both the axes is also the centre of the
surface.
The vertical axis meets the surface at its summit, which is common to all the
orbits of the cutting point or the grinding circle. The summit must not lay
exactly on the circumference of a circle which the cutting point describes. It may
be a little inside the circle, but not outside. In the first case a grinding annular
surface must act, and in the latter a central spot would remain on the surface.
In finishing the ground surface, the annular surface is broad and is composed of
soft substances (of leather, lead or pitch), while in the grinding process, the
grinding rim is composed of emery, of metal, or of some other analogous substance.
In many cases a common iron or wooden disc is sufficient, and it is used with a
quantity of sharp quartz-sand.
We prefer the method of driving the axis of the cutter by means of conical or
bevel friction gear, as shewn in the accompanying figures. A horizontal driving
haft nn with one fixed conical wheel 5 and one loose conical friction wheel T
Fig. 9) turns, by means of the conical friction wheel p, the cutter b, at any
nclination. The driving shaft is mounted upon solid standards P and P¹. The
xis of the cutter b is carried by the frame RR which swings on the horizontal
xis n n, and is guided between the standards P and P¹. This frame is provided
with toothed seginents T and T¹, gearing with the pinions and t'. These pinions
re keyed to a shaft which is carried by the standards P and Pl. In turning this
haft every inclination can be given to the grinder or cutter b, and it can be fixed
n any position by well known means, as shewn in figs. 1 and 10.

page_text: Figs. 15 and 16 shew another method of supporting the frame R, R. This frame
is provided with cylindrical bearings or journals q q swivelling in bushes, so that
the driving spindle may not have to carry the bulk of the frame R. R.
Fig. 3 shews a frame which is finished (above) with the bracket H.
In Fig. 14 the horizontal driving shaft nn (see also Fig. 9). is replaced by two
shafts n and n², which turn in opposite directions.-The vertical spindle of the
cutter bis prolonged and carries on the other end another disc b¹. The frame R R
is provided with two complete toothed wheels T and T¹ (instead of the two
segments shewn in the other figures), and it can be rotated upon the axis n¹ n².
In addition to the variation of the inclination of the axis, horizontal and vertical
movements are also required. The vertical motion is provided for by means of
the table a.
The cutter receives the horizontal sliding motion by the means shewn in
Figs. 3, 4 and 5: The upper part of the machine, that is to any, the cutter b and
its frame R, and the gearing S, T, P &c. slides in the guides & §. The horizontal
motion may be produced by means of pinions and racks (y in Fig. 3, 4 and 5).
This arrangement possesses the advantage that several tables b may be worked
with one cutter or grinder.
The table a with its support S slides between S¹ S¹ and the vertical motion is
produced by turning the vertical screws-w and w' by means of the hand wheel d
and the gearing 1, 2, 3, 4, 5, and 6. The whole slides horizontally on the bed
plate M, M, and this sliding motion is produced by turning the hand wheel D and
the horizontal screw h.
In the arrangement shewn in Figs. 9 to 13 the spindle of the disc a carries at its
lower end a second disc a' which is supported by two small india-rubber rings
fitted to pulleys ¹ and s¹ one of which is fast and the other loose. U is the
driving pulley. This may be made to assume different positions by means of
horizontal and vertical sliding motions actuated by the hand wheels d and D.
But all these positions are necessarily confined to one and the same vertical plane.
To meet this requirement the driving belt passes round two tension pulleys and m
which are pivotted to the bolt a, sliding in a vertical slot, by which means they can
be fixed to any height, as shewn in Figs. 9, 11 and 13.
In some cases we prefer to use a vertical driving belt cylinder a, driving the
pulley by means of a belt; this pulley being fixed on the shaft v of the table a,
as shewn in Figs. 1 to 5. The cylinder a is driven by the belt 6, or by any other
suitable means.
If the table a is required to be made to travel horizontally, we fix two guiding
pulleys K, K¹ near the cylinder a on the saddle Q (Figs. 1 and 2).. The driving
belt runs as shewn in the figures, so that its length is not effected either by the
horizontal or by the vertical position of the table a.
It will be understood that concave surfaces are ground or cut by the outside,
and the convex surfaces by the inside rim of the disc, as shewn in Figs. 6 and 7,
and the cutter can therefore be arranged as shewn in Fig. 6, where a metal ring of
angular section is shewn fixed to the grinding disc. Its outside cylindrical face,
with its lower edge, may also be used for cutting the facet of the lens or reflector.
This offers the advantage that the rim or facet is centred accurately without
removing the object.
In case of other curved surfaces besides that of the spherical being required each
cutting point may be caused to describe an ellipse instead of a circle-All the orbits
of the cutting points pass the point where the axis of the spindle of the table a
meets the surface. The perpendicular in the centre of the ellipse on its plane must
meet the axis of the spindle of the table a in the centre line of the rotating
Burface. The machine remains the same, in other respects with the exception
that one or the other axis must be moved so as to obtain ellipses instead of circles
which can be obtained by known mechanical devices.

page_text: The polishing of the reflector or lens is greatly facilitated by preparing the
polishing disc at one operation as described. A negative and a positive object are
readily obtained, both of which are of a nearly analogous form.
Having now particularly described and ascertained the nature of our said
Invention, and in what manner the same is to be performed, we declare that what
we claim is :-
The method and means of cutting, grinding and polishing spherical spheroidal or
other concave or convex surfaces upon objects while rotating on an axis, by a
cutter, rim, disc or other suitable cutting or grinding tool which is caused to rotate
on another axis, and which latter axis can be fixed in any convenient position, or
guided in such a way as to form the desired surface, with or without the inter-
position of sand or emery, substantially as herein before described and shewn on
the drawings.
GEO. DOWNING,
Agent for Applicants.