US3881378A

US3881378A - Machine for producing aspherical surfaces

Info

Publication number: US3881378A
Application number: US427447A
Authority: US
Inventors: Bruno P Bettiol
Original assignee: Essilor International Compagnie Generale dOptique SA
Current assignee: EssilorLuxottica SA
Priority date: 1972-12-29
Filing date: 1973-12-26
Publication date: 1975-05-06
Anticipated expiration: 1992-05-06
Also published as: JPS557700U; JPS5850823B2; DE2365084A1; AU6459374A; CS181736B2; DE2365084C3; IT1002331B; GB1450710A; AU468886B2; DE2365084B2; CA1014381A; JPS54161181A; JPS49124679A; FR2212772A5

Abstract

A machine for producing concave or convex aspherical surfaces, comprises a blank carrier spindle mounted for rotation about a first axis, a cutting tool mounted for travelling movement in the direction of the second axis and pivotable about a third axis perpendicular to the first two axes, a control cam, and drive means controlled by the said cam and adapted to displace the said cutting tool, in response to the cam, along its travelling axis between two positions, one of which is an advance position and the other a withdrawn position and either of which is a cutting position and the other a position of rest, the axis of rotation of the spindle and the axis of movement of the tool passing through the centre of the aspherical surface to be cut, and wherein the blank carrier spindle is adjustable in a stable axial position in a spindle support, the control cam is fixed, and the cutting tool is carried by a shoe displaceable on a rotating turret, a drive means being disposed between the said shoe and the said fixed control cam.

Description

United States Patent 1 [111 3,881,378 Bettiol May 6, 1975 [54] MACHINE FOR PRODUCING ASPHERICAL 3,744,357 7/1973 Anderson 82/12 SURFACES [75] Inventor: Bruno P. Bettiol, Quincy-Voisins,

France [73] Assignee: Essilor International S.A.,

Joinville-le-Pont, France [22] Filed: Dec. 26, 1973 [21] Appl. No.: 427,447

[30] Foreign Application Priority Data Dec. 29, 1972 France 72.46934 [52] US. Cl 82/19; 82/12 [51] 1823b 3/28 [58] Field of Search 82/12, 19

[56] References Cited UNITED STATES PATENTS 1,513,883 11/1924 Bausch 82/12 2,423,941 7/1947 Laisne 82/12 2,539,941 1/1951 Allen 82/12 X 2,725,776 12/1955 Hopkins 82/12 X 3,079,732 3/1963 Rawstron et al. 82/12 X 3,106,857 10/1963. Langenberg et a1... 82/12 X 3,139,083 6/1964 Seidel et a1. 82/12 X 3,212,371 10/1965 Banke 82/19 Primary Examiner-Harrison L. I-linson Attorney, Agent, or Firm-Young & Thompson 5 7] ABSTRACT A machine for producing concave or convex aspherical surfaces, comprises a blank carrier spindle mounted for rotation about a first axis, a cutting tool mounted for travelling movement in the direction of the second axis and pivotable about a third axis perpendicular to the first two axes, a control cam, and drive means controlled by the said cam and adapted to displace the said cutting tool, in response to the cam, along its travelling axis between two positions, one of which is an advance position and the other a withdrawn position and either of which is a cutting position and the other a position of rest, the axis of rotation of the spindle and the axis of movement of the tool passing through the centre of the aspherical surface to be cut, and wherein the blank carrier spindle is adjustable in a stable axial position in a spindle support, the control cam is fixed, and the cutting tool is carried by a shoe displaceable on a rotating turret, a drive means being disposed between the said shoe and the said fixed control cam.

21 Claims, 14 Drawing Figures PATENTEUMAY 61975 3,881,378

SHEET 10F 5 FIG] PATEMED HAY 6 ms SHEET 3 BF 5 MACHINE FOR PRODUCING ASPHERICAL SURFACES BACKGROUND OF THE INVENTION The present invention relates to a machine for producing concave or convex aspherical surfaces.

Machines of the kind in question are undoubtedly already known in which a blank is driven rotationally by means of a rotating chuck, and in which a cutting tool carried by a tool carrier is driven in a travelling movement with the aid of mechanical means, such as a control cam.

When in particular it is required to cut concave or convex aspherical surfaces on blanks intended to form two parts ofa mould, for example a mould intended for producing corneal lenses. it will be understood that great precision ofthe moulds is indispensable if suitable products are to be obtained.

ln addition to the precision required. the surface quality obtained must be such that no defect occurs which would be transmitted to the resulting product.

It should be made clear that the precision required is of the order of a micron in order to obtain suitable products subsequently requiring only the usual machining correction. In order to obtain such precision of mould parts it will be understood that this will be governed by the different mechanical parts of the machine effecting this work, and particularly by the accuracy of assembly of these parts.

lt is in fact necessary that the different movements of the operative parts. that is to say the tool carrier. the chuck carrying the blank, and the cam. should have only the necessary operating play.

The problem posed is made still more complex by the diversity of lens profiles and consequently of the mould parts. which may vary considerably.

Machines known at the present time for producing such surfaces do not give complete satisfaction. particularly in respect of precision. ease of modification of the profile to be machined. and rate of production.

This consequently results in a high cost price due not only to the number of rejects caused by defects, but also by the lengthy and delicate machining operations required to produce a faultless product.

The present invention relates to a machine intended to overcome the various disadvantages briefly recalled above.

SUMMARY OF THE INVENTION According to the invention the machine for producing concave or convex aspherical surfaces comprises a blank carrier spindle mounted for rotation about a first axis, a cutting tool mounted for travelling movement along a second axis and pivotable about a third axis perpendicular to the first two axes. a control cam, and drive means controlled by the said cam and adapted, through the action of the latter, to displace the said cutting tool along its travelling axis between an advanced cutting position and a withdrawn position of rest. the axis of rotation of the spindle and the axis of displacement of the tool passing through the centre of the aspherical surface to be cut, and wherein the blank carrier spindle is adjustable in a stable axial position in a spindle support, the control cam is fixed, and the cutting tool is carried by a shoe which is displaceable on a rotating turret. the drive means being disposed between the said shoe and the said fixed control cam.

According to another characteristic of the inventior the blank carrier spindle is provided at one end with z chuck intended to carry the blank, while at its other end it cooperates with damping means, the said chuck being provided internally with at least two pairs 0: contact points for a blank carrier and a means of apply ing the latter against these points.

According to another characteristic of the invention the spindle support is adjustable at will horizontally anc vertically, the said support being disposed on the to; surface of a base comprising two superimposed parts joined together, the top part carrying means for adjust ing the position of the said spindle carrier, while the bottom part has an extension adapted to receive the rotary turret which has a central pivot fastened to a base on which the aforesaid movable shoe can be displaced According to another characteristic of the invention the spindle support rests naturally on a support plate provided on the top portion of the two-part base, by three support points constituting the apices of a triangle, the said top portion of the base having a box-like structure ballasted with concrete.

According to a particular feature of the invention. the spindle support is positioned horizontally by three lateral contact points. one of these points being disposed in the middle of a lateral support face with the interposition of an elastic means, while the other two points are disposed towards the terminal portions of the other lateral face, a second point being formed by a first pillar with the interposition of a pivoting element. while the third. so-called thrust point constitutes the actual adjustment means, while with regard to vertical adjustment this is effected by three screws having a vertical axis, which are associated with the bottom portion of the base and cooperate with a support frame. these screws being so disposed as to form the apices of a triangle.

According to another feature of the invention the thrust point is fastened to a lever adapted to oscillate on a vertical axis with the aid of an orientation screw acting on the said lever, which in turn is subjected to the action of an elastic means placed between the said lever and the lateral face of the spindle support, the pivoting point being close to the orientation screw while the thrust point and the orientation screw are close to one another.

According to another feature of the invention the drive means of the movable shoe, which are disposed between the latter and the fixed control cam. comprise in particular a lever arm extending substantially in a vertical direction and mounted for rocking; a lever arm of this kind is adapted to cooperate by its bottom portion with the fixed cam, which advantageously has a variable profile, and it is so equipped as to permit, in conjunction with the cam, the production of concave or convex profiles simply by changing the position of a micrometer mechanism which is associated with it, this mechanism being adapted to cooperate by one end with one or the other of two elements which are de tachably fixed to the movable shoe carrying the too! carrier, the said elements being offset in height one or each side of the axis of rotation of the lever arm and also being spaced longitudinally.

According to yet another feature the lever arm cooperates with the aforesaid cam with the aid of a follower which is adjustable at will, in such a manner that depending on the position of this follower it is possible tc vary the desired profile. and this can be done on each side of a common trunk, thus avoiding the dismantling of the cam.

With regard to the cam, according to another important feature of the invention the cam of variable profile is fixed and is automatically positioned on the machine when it is placed in position, thus making it possible, after suitable adjustment, to obtain parts having convex or concave aspherical surfaces.

According to yet another important feature the adjustment of the desired cam profile is advantageously effected outside the machine by means of an arrangement which comprises, on a support, a frame pivoting about an axis and carrying on the one hand a follower adapted to cooperate with the cam and, on the other hand, a pointer adapted to move past a graduated sector on the support.

With the aid of a machine of this kind the machining operations are simplified substantially and consequently lead to high production rates compared with the prior art, while the precision obtained is quite remarkable.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a partial view in perspective of the machine according to the invention;

FIG. 2 is a view in side elevation;

FIG. 3 is a corresponding plan view;

FIG. 4 shows in elevation a support point of the base on the frame;

FIG. 5 shows on a larger scale, in a plan view, the assembly comprising the blank carrier with its adjustment and damping means;

FIG. 6 is a view in section on the line VIVI in FIG. 4;

FIG. 7 is a view partly in section of an alternative form of the aforesaid damping device;

FIG. 8 is a view on a larger scale, in side elevation, of the tool carrier, the tool carrier turret being shown only diagrammatically in dot-and-dash lines;

FIG. 9 is a corresponding front view in the direction of the arrow IX in FIG. 8;

FIG. 10 is a plan view in the direction of the arrow X in FIG. 8;

FIG. 11 shows in perspective the support of the work carrier spindle;

FIG. 12 is a plan view showing a cam of variable profile and also the means of adjusting its profile;

FIG. 13 is a section on the line XIIXII in FIG. 12, and

FIG. 14 shows in elevation, partly broken away, one form of the workpieces obtained.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the embodiment selected and illustrated, which is given solely by way of example, the machine according to the invention for producing aspherical surfaces comprises essentially, on a rigid frame 10, a base 11 which on the one hand carries a spindle support 12 extending horizontally along an axis XX, and on the other hand a tool carrier turret 14 mounted for pivoting about an axis Y-Y with the aid of a central pivot 15.

The aforesaid axes X-X and Y-Y respectively are perpendicular to one another and concurrent. and the displacements of the actual tool are controlled by means of a fixed cam 16.

All these elements, which have been indicated generally. will now be described in greater detail.

The frame 10 is made of sections welded with lacing (not visible in the drawings) in order to increase its rigidity. It rests on the ground with the aid of four rigid supporting feet.

The frame 10 is entirely closed and is intended to support the base 11 and to accommodate accessory devices, such as hydraulic pumps, liquid and lubricant tanks, compressed air and oil mist production circuit, etc.

The various aforesaid accessory devices are indicated generally at 19 in FIG. 2.

The base 11 rests on the frame 10 by means of three support points (FIG. 3), each of which is given the

general designation

20, 21 and 22 which form the apices of a triangle.

Referring to FIG. 4, it is seen that at each of the aforesaid support points the top surface of the frame 10 has a covering of material 23, such as suitable rubber, on which rests a ground washer 24 whose free surface is intended to cooperate with the end of a threaded rod 25 screwing into a bracket 26 rigidly fastened to the central body.

For the purpose of its operation the screw 25 has a head 27 provided with radial holes 28, while a lock-nut 29 effects the locking of the screw 25.

This arrangement therefore permits adjustment of the seating of the base 11; this base will now be described.

The base 11 is composed of a welded sheet steel structure which comprises a first lower portion Ila to which is attached a second upper portion 11b intended to support the spindle carrier 12 and also the damping device 13. The bottom portion (see in particular FIG. 3) has an extension Il'a intended to support the tool carrier turret l4 and its central pivot 15.

The base 11 rests naturally on the frame 10 and the damping of vibrations which may occur in the course of the machining of the blank is effected (FIG. 2) by concrete 30 poured into compartments of the structure of the base 11; apertures 31 are naturally provided in the base 11 for the passage of the drive elements which will be described later on. On its top surface the portion 11b of the base is provided with a ground plate 32.

Reference will now more particularly be made to FIGS. 5 to 8, which show in greater detail the support 12 of the spindle, together with its fastening means.

The aforesaid spindle support (see also FIG. 11) comprises essentially two casing

halves

40 and 41 each of which has a semi-circular

axial cutout

42, 43 respectively. The lower casing half 40 is intended to rest on the ground plate 32 and to be held there by a means which will be described in greater detail later on.

The semi-circular bores 42, 43 are adapted to receive without play a spindle carrier 45, which is advantageously of the hydrodynamic type and in which is axially movable a spindle 46 whose so-called front end 46A receives a chuck, which is indicated generally by 47, and a so-called rear end 468 carries a drive pulley 50.

By means of a transmission 51 of the usual type the aforesaid drive pulley is coupled to an electric motor, which is for example fastened on the lower face of the frame 11.

The chuck 47, which is fastened to the front part of the spindle 46, is provided with means for holding the blank which is to be machined. this blank being indicated at E in FIGS. 2 and 3.

As can be clearly seen particularly in FIGS. 5 and 6, the chuck 47 is provided internally with two pairs of support points 55, 56 and 57, 58, which are offset longitudinally, and a radial orientation pressure screw 59 intended to apply the tail of the blank E against the aforesaid points.

The support points of each pair have a radial orientation (FIG. 6); they are advantageously offset in a transversal plane at 120 to one another. while the radial pressure screw 59 is disposed in the middle of the remaining portion of the circumference.

Particularly effective and accurate five-point centring is thus obtained.

It should be observed that the support of the spindle carrier 12 rests naturally on the ground plate 32 and that its lower portion cooperates with positioning means which are disposed laterally and which, as can be clearly seen particularly in FIG. 5, comprise a first fixed pillar disposed in the middle of one side of the spindle support. and a second pillar 61 disposed on the other side and one towards an apex.

In its lower portion situated opposite the lower portion of the support of the spindle 40 the pillar 60 has a recess for a compression spring 64, whose free end is intended to cooperate with the said part 40.

On its opposite side (FIG. 11), that is to say on the side of the pillar 61, the lower portion 40 of the spindle support has two recesses and 71 respectively; one of them (70) is intended to receive a pivot 72 having a substantially semicylindrical sector 73, while the other (71) is intended to receive a ground support element 74.

The pillar 61 is equipped with a depression 75 in which a portion of the semicylindrical sector 73 is at least partly supported.

Two lateral contact points holding the support 12 of the spindle are thus formed. while a third contact point is formed on the same side as the pillar 61 by a sector associated with a lever 81 substantially parallel to the side of the support 12; the lever 81 is mounted for rocking in a horizontal plane by means of a pin 82 disposed beyond the aforesaid sector 80 and by means of an operating screw situated at the other end of the lever 81, near the pillar 61; the screw 83 is screwed into a tapping in a fixed part 85 and bears against the lever 81, while a spring 87 interposed between the lower portion 40 of the support 12 and the aforesaid lever urges the latter towards the outside in the direction of the arrow F, that is to say into contact with the end of the screw 83.

Adjustability of the orientation of the axis XX, and consequently of the support of the spindle and of the blank, is thus obtained. and this adjustment can be extremely accurate, particularly because of the reduction ratio obtained by means of the lever 81 and the sector 80.

The spindle 46 is free to slide in the spindle carrier 45 and its axial position is determined by means adapted to effect micrometer adjustment of the advance of the blank and, furthermore, permits the retraction of the latter if the tool support force exceeds a predetermined threshold.

Damping means, which will now be described with reference to FIG. 5, are in addition provided in order to avoid return shocks.

As can be seen in this Figure, the rear end face of the spindle 46 has a notch 90 intended to receive a ball 91 while the front face 92 of the damping device 13 is likewise adapted to cooperate with the ball 91.

In order to return the spindle 46 towards the front stop face 92, magnets 48 are fixed on the mutually opposite faces of these elements (FIG. 5).

This damping device comprises a central body 93 situated in alignment with the spindle 46 and adapted to slide in the direction of the arrow F2 on the ground plate 32 by means of a slide arrangement, which is not shown in the drawings because it is known per se.

The front portion 92 can be displaced longitudinally by means of a graduated disc 94 and it acts directly on the end of the spindle 46. A first axial adjustment of the spindle is therefore obtained in this manner.

The central damper body 93 is disposed between two pillars and 101 fixed on the plate 32, and towards the rear it has

lateral extensions

103 and 104.

Between the pillar 100 and the aforesaid lateral extension 103 is placed, on the one hand, a damping jack designated generally 105 whose barrel is for example fastened to the pillar 100, while the piston head is attached to the extension 103; in parallel, a spring 107 is attached by each of its ends to the pillar 100 and to the extension 103. On the other side the pillar 101 carries a micrometer mechanism 110 having an end 11] adapted to cooperate with a ball 112 interposed between a support plate 113 fixed on the extension 104, and another operating end 114.

Through the operation of the mechanism 110 it is possible to displace the central damper body in the direction of the arrow F2, thus providing a second. additional adjustment of the spindle which is slidable in the spindle carrier 45.

Due to a damping device of this kind, if the force imparted by the tool to the blank E exceeds a certain threshold, the central body 93 is pushed towards the rear by the ball 91, that is to say towards the right in the drawing, while the spring 107 is subjected to a tractive force. When the force applied by the tool to the blank has become normal again, the central body 93 returns gently to its original position because of the intervention of the jack 13.

In the example illustrated in FIG. 7 the damping device comprises a hollow body in which a piston 121 forms two

chambers

122 and 123.

In the hollow body 120 a threaded piston rod 124 passes through the chamber 122 and receives a ring 128 which is adapted to slide axially and is locked in respect of rotation by means of a slot 129 and a radial screw 130 cooperating with the said slot. A ball thrust bearing 131 is provided between one face of a graduated disc 132 associated with the aforesaid screw 124 and the corresponding face of the spindle 46.

On its other face the piston 121 is subjected in the chamber 123 to the action of a spring 135 effecting adjustment from outside by means of a screw 136.

Laterally the central body has an extension 138 which is in communication through a conventional non-leakproof ball valve 139 and a calibrated passage 140 with the chamber 123 in which the piston 121 moves.

1n substantially similar manner to the preceding arrangement. the rotation of the disc 132 permits longitudinal adjustment, while excessively rapid return of the spindle 46 after a retraction is delayed by the ball valve 139 and the calibrated passage 140.

The tool carrier turret 14 will now be described in greater detail and for this purpose particular reference will be made to FIGS. 8 to 10.

The tool carrier turret 14 (FIGS. 1 and 2 in particular) is mounted on the central pivot 15 resting by means of a roller bearing (not shown in the drawings) on the extension 11'A; this central pivot 15 is rotated by means of a motor 151 and transmissions 152. 153 which are carried by the lower face of the frame and drive a shaft 154 fastened on the central pivot 15.

The motor 151 is of the variable speed type rotating in two directions. The central pivot carries a base 160 on which by means of a slide known per se a shoe 161 is adapted to slide, this shoe being equipped with splined coupling means 162 intended to receive a corresponding portion 163 of a tool carrier 164.

On its front side the base 160 carries bearings 170, 171 (see in particular FIGS. 8 to 10); these bearings carry

shafts

172 and 173 whose free terminal portions are engaged in

lugs

175 and 176 fastened to a lever arm I77 extending vertically.

The lever arm is therefore adapted to rock about

horizontal axes

172, 173.

These rocking movements are controlled by means of the cam 16 which will be described in greater detail later on, and by means of a follower 181 disposed at the bottom part of the arm 177; in order to keep the follower 181 applied against the outer face 222 of the cam 16 there is provided a spring 190 which is attached by one end to the lever 177 and by the other end to a fixed point 191 of the base 160.

The transmission of the movement imparted by the fixed cam to the lever arm 177, and consequently to the base 161, is effected by means of a micrometer mechanism 200 having one end 201 (FIG. 10 in particular) adapted to cooperate with either of two rod-shaped

elements

202 and 203 which are carried by the said base and are offset longitudinally along the pivoting axis of the lever arm 177; in addition, these rods are also offset in respect of height (see in particular FIG. 9).

Each of the free ends of the rods has a tip 204 which is eccentric in relation to the axis of the said rod. and punctiform contact is thus obtained between the end of the mechanism 200 and a corresponding end of the

rods

202 and 203, which in addition are adjustable longitudinally; this adjustment is obtained by rotating the

rods

202, 203 and through the resulting displacement of the point of contact of the tip 204 with the mechanism 200. Extremely accurate adjustment of the reduction ratio can thus be achieved.

The mechanism 200 can therefore be disposed in such a manner as to cooperate either with the rod 202 or with the rod 203; for this purpose the lever arm 177 has judiciously disposed bores 205 and 206, either of which can be used depending on circumstances. while these screws 207. 208 are intended to effect the locking of this mechanism.

With a view to holding the tips 204 in contact with the end 201 of the mechanism 200, a spring 183 is provided which is attached to the base 160 at one end and to the shoe 161 at the other end.

With the aid of an arrangement of this kind, depending on the situation of the mechanism 200 it is possible to obtain all the desired aspherical shapes either by concave cutting or by convex cutting.

The follower 181 (FIG. 8) is fastened to a plate 210 having a horizontal orientation aperture 211, while a screw 212 engaged in the aperture is fixed to the lever arm 177 and permits the possible horizontal displacement of the plate 210 and its associated follower.

An arrangement of this kind has essentially the aim of permitting the production of different profiles from a common central trunk.

Reference will now be made particularly to FIGS. 12 and. 13, which show the variable profile cam given the general reference 16.

The cam in question comprises a plate 216 having the general shape of an arc of a circle; this plate is notched at 217 so as to receive the cam comprising a blade or strip 218 of steel or other deformable material, the notch forming a heel 219 for a plurality of adjustment means. which in the example illustrated comprise screws 220. These screws have one end intended to cooperate with a rear face 221 of the blade, while the front face 222 of the latter cooperates with the follower 181 of the lever arm 177.

The back face of the blade is advantageously provided with a layer 223 of suitable material, such as metallic, elastic, or plastics material, which may have either a continuous or a discontinuous structure. A layer of this kind is in particular intended to eliminate discontinuities due both to the tension of the tape which is necessary to obtain good rigidity of the cam, and to the distance between the screws 222.

In order to adjust the profile of a cam of this kind there is available a plate 225 on which is adapted to pivot, about an axis 226, a frame 227 carrying a pointer 228 controlling a comparator 229, this index being adapted to cooperate with the front face 222 of the blade 218.

The plate 225 also carries stops 240 permitting the fastening of the cam support, the relative arrangement of these stops corresponding to that of similar stops on the frame of the machine, as will be seen later on.

The plate 225 also has graduations 232 opposite which a pointer 233 fastened on the shaft 226 can move.

Thus, if the distance between the pivoting point and the end of the pointer 228 is known for a given angle, it is possible to determine the profile of the cam by acting on the adjustment screws 219.

With a device of this kind it is thus possible to adjust the profile of the cam in a particularly accurate and rapid manner, since such adjustments are advantageously effected outside the machine without lengthy and delicate mounting and dismantling operations being required.

When the cam is adjusted in accordance with the selected profile, it is placed on the top part of the frame, which for this purpose (see in particular FIG. 3) has a centring system comprising four

points

250, 251, 252, 253 corresponding to the previously mentioned stops 240, so that its positioning automatically corresponds to the position of symmetry of the axis of rotation YY of the central pivot and the axis of rotation X-X of the spindle.

It should be observed that in this machine the fixed cam 16 controls the cutting tool directly. and not a tool for trueing a grinding tool.

The advantage is thus gained that it is thus possible to cut the blank directly with a diamond wheel 254 and obtain a far finer and more regular finish. Furthermore,

even concave surfaces having small radii of curvature can easily be worked.

in addition, the variable profile cam of the kind described provides the not negligible advantage of offering numerous adjustabilities, for example in order to eliminate any deformation of the product which may be caused by certain phases of the production cycle.

The variable profile cams can be used in any reproduction machines. such as optical machines for producing aspherical surfaces. or else in any machines for mechanical engineering or any other applications.

The operation of a machine of this kind, for example for producing a mould intended for moulding contact lenses, may be analysed as follows:

a. a sphere is produced and, after verification (with i the aid of usual means), the axis of the cutting tool is made to coincide with the axis of rotation f the spindle 46;

b. the machine being thus geometrically ready, the fixed cam 16 is then adjusted in accordance with the desired profile of the workpiece, with the aid of the cam adjustment apparatus;

c. the fixed cam 16 is placed on the machine and by means of a few trials the central radius of curvature is then adjusted with the aid of the micrometer mechanism carried by the lever arm 177;

d. the blank is cut with a suitable wheel;

e. the tool carrier turret is removed and another turret carrying a finishing tool is placed in position;

f. various passes are made by advancing the work carrier with the aid of the micrometer mechanism 110 associated with the damping unit, until a two-part mould MMl (FIG. 14) is obtained which provides a moulding cavity free from any defects, each part having a concave and convex aspherical surface respectively.

The invention is obviously not limited to the embodiments selected and illustrated, which on the contrary are capable of modifications without thereby departing from the scope of the present invention.

1 claim:

1. A machine for producing concave or convex aspherical surfaces comprising a frame, a spindle, support means carried on the frame for mounting said spindle for rotation about its axis, a blank carrier. means for supporting said blank carrier on said spindle, a cutting tool, first mounting means for mounting the cutting tool for travelling movement along a second axis, second mounting means for mounting the cutting tool for rotation about a third axis substantially perpendicular to said axis of the spindle and said second axis, a fixed control cam fastened to said frame, drive means controlled by said control cam and coacting with said first mounting means to effect the displacement of the cutting tool along a path of movement for cutting the aspherical surface, and first adjustment means for adjusting the orientation of said axis of the spindle in a plane substantially perpendicular to said third axis so that said axis of rotation of the spindle may be brought into precise coincidence with said path of movement of the cutting tool at the center of the aspherical surface to be cut.

2. A machine for producing aspherical surfaces according to claim 1, wherein said third axis is substantially vertical and said plane in which the orientation of said axis of the spindle is adjustable is substantially horizontal.

3. A machine for producing aspherical surfaces according to claim 2, wherein said frame includes a base at the top thereof, and further comprising second adjustment means for adjusting the orientation of the base relative to the rest of the frame so that the base and therefore the said plane may be adjusted to a precisely horizontal position.

4. A machine for producing aspherical surfaces according to claim 2, wherein force damping means are provided at one end of said spindle opposite said blank carrier.

5. A machine for producing aspherical surfaces according to claim 4, wherein the means for supporting the blank carrier on said spindle is a chuck including at least two pairs of contact members extending radially into engagement with the blank carrier, and securing means for maintaining the contact members in engagement with the blank carrier disposed axially between the two pairs of contact members and opposite thereto.

6. A machine for producing aspherical surfaces according to claim 3, wherein said second mounting means includes a base plate secured for rotation on a turret, and wherein said first mounting means includes a slide mounted for reciprocating displacement on said base plate in response to said control cam.

7. A machine for producing aspherical surfaces according to claim 6, wherein said base comprises two superimposed portions joined together, the upper portion carrying said first adjustment means, and wherein the lower portion has an extension adapted to receive the turret.

8. A machine for producing aspherical surfaces according to claim 7, wherein said lower portion is boxshaped and is at least partially filled with a dense material for weighting the frame.

9. A machine for producing aspherical surfaces according to claim 2, wherein said first adjustment means includes three support points in contact with the support means for said spindle, one said point being defined by resilient means in contact in the middle of one side of said support means substantially parallel to the axis of the said spindle, the two other points being defined by a pivot and by a thrust point that contact said support means near the ends of a side of said support means opposite said one side.

10. A machine for producing aspherical surfaces according to claim 9, wherein said thrust point is disposed on a lever mounted for rocking movement about a substantially vertical axis, an orientation screw engaging the lever remote from said thrust point and adjacent to said pivot and resilient means disposed axially between said thrust point and said orientation screw and operating between the support means and said lever.

ll. A machine for producing aspherical surfaces according to claim 4, wherein said force damping means comprise a central body having a longitudinally displaceable front face and a ball thrust bearing coacting with said spindle and the displaceable front face. said central body having, on each side of its longitudinal axis, means for adjusting the axial position of the central body and means for maintaining the central body in a desired stable position, said last mentioned means being constituted by a traction spring operatively attached between a fixed pillar and said central body and a damping pot in parallel with said traction spring compensating for additional traction forces during machinmg.

12. A machine for producing aspherical surfaces according to claim 4, wherein the force damping means is disposed in a fixed, hollow central body also housing said axial adjustment means.

13. A machine for producing aspherical surfaces according to claim 11, wherein the central body is hollow and has two internal chambers situated one on each side of a piston. a first chamber accommodating a threaded rod connected to the piston having a free ter minal portion located outside the body and a graduated disc, said threaded rod turning in a sleeve, said sleeve being fixed against rotation but axially displaceable. and a second chamber in which the free face of the piston is urged by a spring, and wherein an adjoining chamber leads into the said second chamber through a passage controlled by a valve having a calibrated aperture.

14. A machine for producing aspherical surfaces according to claim 6, wherein said drive means includes a lever arm substantially vertically oriented and pivotally mounted about a substantially horizontal axis and in point contact at its upper end with said slide and in contact at its lower end with said control cam.

15. A machine for producing aspherical surfaces according to claim 14, wherein said point contact between the lever arm and the slide is effected by a micrometric mechanism carried by said lever arm and having an axially displaceable end in contact with a tip of an element associated with said base.

16. A machine for producing aspherical surfaces according to claim 14, wherein said base carries a pair of elements having tips spaced along the pivot axis of said lever arm at different distances therefrom and offset, said micrometric mechanism being detachably mounted on said lever arm.

17. A machine for producing aspherical surfaces according to claim 16, wherein each of said pair of elements comprises a rod rotatable about its axis and terminating in a tip eccentric to its axis.

18. A machine for producing aspherical surfaces according to claim 14, wherein the lower portion of said lever arm has a follower that coacts with said control cam, the follower being displaceably mounted on the arm.

19. A machine for producing aspherical surfaces according to claim 18, wherein said follower is displaceable in an aperture parallel to the cam, thereby permitting variations of machining profile.

20. A machine for producing aspherical surfaces according to claim 14, wherein the control cam comprises a deformable strip fixed at its ends to a removable plate, and a plurality of adjusting elements displaceable parallel to the plane of the said plate and therefore perpendicular to the strip for obtaining the desired shape of the strip.

21. A machine for producing aspherical surfaces according to claim 5, wherein the securing means for maintaining the contact members in engagement with the blank carrier includes a pressure screw.

Claims

1. A machine for producing concave or convex aspherical surfaces comprising a frame, a spindle, support means carried on the frame for mounting said spindle for rotation about its axis, a blank carrier, means for supporting said blank carrier on said spindle, a cutting tool, first mounting means for mounting the cutting tool for travelling movement along a second axis, second mounting means for mounting the cutting tool for rotation about a third axis substantially perpendicular to said axis of the spindle and said second axis, a fixed control cam fastened to said frame, drive means controlled by said control cam and coacting with said first mounting means to effect the displacement of the cutting tool along a path of movement for cutting the aspherical surface, and first adjustment means for adjusting the orientation of said axis of the spindle in a plane substantially perpendicular to said third axis so that said axis of rotation of the spindle may be brought into precise coincidence with said path of movement of the cutting tool at the center of the aspherical surface to be cut.

8. A machine for producing aspherical surfaces according to claim 7, wherein said lower portion is box-shaped and is at least partially filled with a dense material for weighting the frame.

11. A machine for producing aspherical surfaces according to claim 4, wherein said force damping means comprise a central body having a longitudinally displaceable front face and a ball thrust bearing coacting with said spindle and the displaceable front face, said central body having, on each side of its longitudinal axis, means for adjusting the axial position of the central body and means for maintaining the central body in a desired stable position, said last mentioned means being constituted by a traction spring operatively attached between a fixed pillar and said central body and a damping pot in parallel with said traction spring compensating for additional traction forces during machining.

13. A machine for producing aspherical surfaces according to claim 11, wherein the central body is hollow and has two internal chambers situated one on each side of a piston, a first chamber accommodating a threaded rod connected to the piston having a free terminal portion located outside the body and a graduated disc, said threaded rod turning in a sleeve, said sleeve being fixed against rotation but axially displaceable, and a second chamber in which the free face of the piston is urged by a spring, and wherein an adjoining chamber leads into the said second chamber through a passage controlled by a valve having a calibrated aperture.