GB2157990A

GB2157990A - A grinding machine for the edges of spectacle lenses

Info

Publication number: GB2157990A
Application number: GB08510824A
Authority: GB
Inventors: Otto Helbrecht
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-04-30
Filing date: 1985-04-29
Publication date: 1985-11-06
Also published as: GB8510824D0; SE8502056D0; FR2563456A1; DE3416034C2; ES8607089A1; SE8502056L; DE3416034A1; JPS60249564A; BE902330A; SE454755B; GB2157990B; IT1184512B; IT8520531A0; ES542772A0

Abstract

A grinding machine for grinding the edge of a spectacle lens to a predetermined peripheral shape comprises a rotatable lens mounting and a rotatable grinding wheel (2) which are relatively movable in a linear direction of travel perpendicular to their axes of rotation and in the plane of the grinding wheel (2). The peripheral shape of the lens is produced by a template (6) rotating with the lens mounting. A stop (7) for the template (6) is mounted on an arm (11) which is held laterally of a slide (4) in a linear guide (30) parallel to the direction of travel (5) and is fixed relative to the housing in the direction of travel (5) by a shaft (13) extending parallel to the axis of the lens mounting. The arm (11) is movable on the shaft (13) in a transverse direction so that the stop (7) always remains in the same position relative to the template (6). <IMAGE>

Description

SPECIFICATION A grinding machine for the edges of spectacle lenses The invention relates to a grinding machine for grinding the edge of a specacle lens to a predetermined peripheral shape of the kind comprising a housing, a rotatable lens mounting in which a lens blank to be ground can be retained, a grinding wheel assembly which includes a grinding wheel rotatable about an axis parallel to the axis of rotation of the lens mounting and a linear guide by means of which the lens mounting and grinding wheel assembly are relatively moveable in a direction of travel which is perpendicular to the axes of rotation of the lens mounting and grinding wheel and is in the plane of the grinding wheel. Such a grinding machine will hereinafter be referred to as of the kind set forth.

A grinding machine of the kind set forth is the subject of German Patent Application P34 09 624.8.

In this machine the grinding wheel assembly is mounted at a fixed point in the housing whilst the mounting for the lens is provided, together with its drive, on a slide which is capable of movement along the linear guide inclined in a direction towards the wheel. A spectacle lens blank clamped on the mounting is therefore pressed against the wheel with a uniform pressure automatically by the weight of the slide.

The means for controlling the position of the slide in order to form, by grinding, a lens of predetermined peripheral shape from the initially circular lens blank, includes in the above-mentioned Patent Application an electronic store in which data on the shape of the periphery are stored, and the advance of the slide is controlled in accordance with the data by an appropriate driving means.

However, instead of controlling the relative movement of the lens mounting in the direction of travel electronically it is often preferred, even in grinding machines in which there is relative transverse movement of the lens mounting and the grinding wheel, to control this movement in a known mechanical manner by employing a template mounted on the spindle of the lens mounting and rotating with it, this template engaging an adjustable stop in the direction of travel and, on rotation, displacing the spindle of the lens mounting in accordance with the peripheral shape of the template.

This type of mechanical arrangement is known in grinding machines with swinging arms, such as disclosed in German Gbm 7206781, in which the lens mounting is mounted not in a linear guide but on a swinging arm which is pivoted to swing in the housing up and down around a shaft, the shaft carrying the lens mounting on its free front end. The spectacle lens blank which is clamped to the lens mounting is moved towards the grinding wheel assembly, which is fixed in the housing, from above.

The template which is secured on the spindle of the lens mounting, engages the stop which is secured on another arm pivotally mounted on the shaft. The stop projects from the arm upwards and abuts against the template in the direction of movement, i.e. in the vertical downward direction towards the grinding wheel assembly.

The arm is freely movable in a transverse direction parallel to the axes of rotation of the lens mounting and of the grinding wheel assembly and the spindle so that the template always remains over the stop even on displacement in the said transverse direction.

The above-described manner for supporting the stop on the arm cannot be put into practice in a slide which is movable with respect to the grinding wheel assembly along a linear guide because there is no fixed point, such as is formed by the shaft, about which the swinging arm of the known construction can pivot up and down.

The aim of the invention is therefore to solve the problem of constructing a grinding machine of the kind set forth in such a way that a mechanical movement using a template and a stop is possible.

According to the present invention there is provided a grinding machine for grinding the edge of a spectacle lens to a predetermined peripheral shape comprising a housing, a rotatable lens mounting in which a lens blank to be ground can be retained, a grinding wheel assembly which includes a grinding wheel rotatable about an axis parallel to the axis of rotation of the lens mounting, a linear guide by means of which the lens mounting and grinding wheel assembly are relatively movable in a direction of travel which is perpendicular to the axes of rotation of the lens mounting and grinding wheel and is in the plane of the grinding wheel, a template having a peripheral shape corresponding to the predetermined peripheral shape and which is rotatable about the same axis of rotation as the lens mounting, and a stop engaged by the peripheral edge of the template and mounted on an arm which is fixed relative to the housing in the direction of travel but movable in a transverse direction parallel to the axes of rotation of the lens mounting and grinding wheel, the arm and a movable component of the linear guide being guided for relative sliding movement in the direction of travel.

Preferably the grinding wheel assembly is fixed relative to the housing, and the movable component of the linear guide comprises a slide on which the lens mounting is mounted.

This arrangement achieves the result that the stop mounted on the arm is retained in the direction of travel, i.e. parallel to the linear guide, and accordingly is movable in the transverse direction, i.e. parallel to the axis of rotation of the tens mounting and of grinding wheel. As the movements in the transverse direction are transmitted through the lens blank to the lens mounting and thereby to the slide, the stop necessarily follows the movement of the slide exactly when the arm is connected to the slide. The arm may be connected to the slide in any convenient manner which permits the relative sliding movement between the slide and the arm and which transmits movement in the transverse direction from the slide to the arm. For instance, the arm may be retained on a second linear guide mounted laterally on the slide and extending parallel to the direction of travel.

However this connection does not need to have any adverse effect on the freedom of movement of the slide with respect to the stop in the direction of travel. This is achieved by the second linear guide which permits relative sliding movement between the arm and the slide. The second linear guide may conveniently comprise a cylindrical rod connected to the slide and surrounded by a spherical bush connected to the arm.

Preferably, the arm is mounted for movement in the transverse direction by means of a transverse linear guide fixedly mounted in the housing relative to the direction of travel and which extends parallel to the axes of rotation of the lens mounting and of the grinding wheel. The transverse linear guide may comprise a cylindrical shaft secured to the housing and a plurality of circumferentially spaced rollers arranged on the arm and which roll on the shaft. The rollers support the arm on the shaft and provide a reaction against the weight of the arm and against forces which act on the shaft in the direction of travel.

In particular, where the arm is guided by means of a spherical bush on the rod of the second linear guide, the arm is able to rotate about the axis of that rod. In order to avoid unwanted variations in the angular position of the arm, two of the rollers may be arranged side-by-side in a plane which contains the axis of the shaft of the transverse linear guide and which extends perpendicualrto the direction of travel, the two rollers forming mutually spaced apart support points which fix the angular position of the arm.

In principle the invention can also be put into practice with the lens mounting arrangement in a fixed position in the housing and with a slide arranged movably on the linear guide together with the grinding wheel assembly and its drive. In this case the grinding wheel assembly is moved by the action of the stop and the template.

An embodiment of the invention will now be described by way of example only with reference to the accompanying drawing in which:~ Figure 1 is a diagrammatic partial side elevation of a grinding machine in accordance with the invention; Figure 2 is a partial elevation of the arm taken on the line 11-11 in Figure 1, shown to a larger scale and partly sectioned; and Figure 3 is a partial section on the line Ill-Ill in Figure 1.

The grinding machine which is indicated as a whole at 100 in Figure 1 comprises a housing 1 in which a grinding wheel 2 of a grinding wheel assembly is mounted for rotation at a fixed position.

The axis of rotation of the grinding wheel 2 is perpendicular to the plane of the drawing of Figure 1.

A linear guide 3 which is indicated only in Figure 1 is provided in the housing 1 and extends away from the grinding wheel 2 in an upwardly inclined direction. A slide, indicated as a whole at 4, is movable in a direction of travel 5 relative to the grinding wheel assembly 2. A lens mounting, not shown in Figure 1, is mounted for rotation on the slide 4 and comprises a divided spindle of which the axis is parallel to the axis of the grinding wheel 2 of the assembly. A spectacle lens blank can be clamped between the ends of the spindle by axially urging the two halves of the spindle together.

A disc-like template 6 is rotatable with the lens mounting and its periphery corresponds to the shape of the periphery of the edge of the spectacle lens which is to be produced from the initially circular lens blank.

The template 6 abuts against a stop 7 in the form of a convex shaped metal memberwhich is arranged to be fixed relative to the housing in the direction of the linear guide 3 and parallel to the direction of travel 5. Thus the slide 4, under the action of its own weight and its component resulting from the inclined position of the guide 3, presses against the stop 7 through the template 6.

The stop 7 is mounted on a pin 8 (Figure 2) extending parallel to the direction of travel and is adjustable on it in the direction of the arrow 9, adjustment taking place by means of operation of the hand wheel 10 connected to the pin 8through a suitable drive (not shown).

The stop 7 is mounted on arm 11 which is mounted at two points, namely on a support secured to the housing and indicated as a whole at 20, and on a second linear guide 30 mounted on the side wall 12 of the slide 4.

The support 20 forms a transverse linear guide which comprises a cylindrical shaft 13 secured to the housing 1 and extending parallel to the axis of the grinding wheel 2 and perpendicular to the plane of the drawing of Figure 1. Two ball-bearing mounted rollers 14, 15 are mounted side-by-side in the arm in the same plane, the axes of the rollers 14, 15 extending parallel to the direction of travel 5. The rollers 14, 15 engage the shaft 13 from above as shown in Figure 1 and form the main support for the arm 11 providing a reaction against its own weight.

In addition, because they form support points which are spaced apart from one another, they prevent tilting of the arm 11 about an axis extending parallel to the plane of the drawing of Figure 2. The arm 11 is supported in the direction of travel 5 by a roller 16 which is provided on the side of the shaft 13 remote from the grinding wheel assembly and of which the axis is in a vertical plane and is perpendicular to the axes of the rollers 14, 15. In rder that the arm 11 is held in a fixed position in relation to the housing in both senses of the direction of travel, a further roller 17 is provided on that side of the shaft 13 which is opposite the roller 16 and it has its axis parallel to thatofthe roller 16.

As shown in Figure 1, the support 20 is provided below the stop 7 at that end of the arm 11 which is nearest the grinding wheel assembly 2. The arm 11 extends rearwards from this region substantially parallel to the direction of travel 5 and there it forms a clamping block 18 which is disposed alongside the side wall 12 of the slide 4 and has a cylindrical hole 19 which extends parallel to the direction of travel 5 and in which there is mounted a spherical bush 21 which can be clamped in place in the block 18 by means of securing screws 22.

The spherical bush 21 and a cylindrical rod 23 which is relatively slidable within the bush 23 together constitute the second linear guide 30 which is secured to the slide 4 on supports 24 laterally outside the side wall 12 of the slide. The cover 25 for the second linear guide 30 which is illustrated in Figure 3 has been omitted in Figure 1.

The arm 11 is thus connected to the slide 4 in such a way that it is carried along with the slide 4 on movement in a transverse direction perpendicular to the plane of the drawing of Figure 1. The lower end of the arm 11 moves on the rollers 14, 15, 16, 17 along the shaft 13. The arm 11 is free to move relative to the slide 4 in a direction parallel to the direction of travel 5 but is supported on the shaft 13 fixed to the housing.

Thus on grinding of a spectacle lens the slide 4 and with it the lens blank are displaced in accordance with the peripheral shape of the template 6 as they rotate with respect to the grinding wheel 2, so that the blank has imparted to it the same peripheral shape as the template 6. The edge of the lens generally describes a curve in space and is guided in a peripheral groove of the grinding wheel 2 resulting in the grinding of facets. On rotation of the lens blank there is also a displacement of the slide 4 in a direction perpendicular to the plane of the drawing in Figure 1, which the slide can follow because the support 20 fixed to the housing permits such displacement and the arm 11 is carried along by the linear guide 30.

The stop 7 therefore always remains in the same position with respect to the template 6.

Claims

1. A grinding machine for grinding the edge of a spectacle lens to a predetermined peripheral shape comprising a housing, a rotatable lens mounting in which a lens blank to be ground can be retained, a grinding wheel assembly which includes a grinding wheel rotatable about an axis parallel to the axis of rotation of the lens mounting, a linear guide by means of which the lens mounting and grinding wheel assembly are relatively movable in a direction of travel which is perpendicular to the axes of rotation of the lens mounting and grinding wheel and is in the plane of the grinding wheel, a template having a peripheral shape corresponding to the predetermined peripheral shape and which is rotatable about the same axis of rotation as the lens mounting, and a stop engaged by tie peripheral edge of the template and mounted on an arm which is fixed relative to the housing in the direction of travel but movable in a transverse direction parallel to the axes of rotation of the lens mounting and grinding wheel, the arm and a movable component of the linear guide being guided for relative sliding movement in the direction of travel.

2. A grinding machine according to Claim 1, in which the grinding wheel assembly is fixed relative to the housing, and the movable component of the linear guide comprises a slide on which the lens mounting is mounted.

3. A grinding machine according to Claim 2, in which the arm is retained on a second linear guide mounted laterally on the slide and extending parallel to the direction of travel.

4. A grinding machine according to Claim 3, in which the second linear guide comprises a cylindrical rod connected to the slide and surrounded by a spherical bush connected to the arm.

5. A grinding machine according to any one of claims 1 to 4, in which the arm is mounted for movement in said transverse direction by means of a transverse linear guide fixedly mounted in the housing relative to the direction of travel and which extends parallel to the axes of rotation of the lens mounting and of the grinding wheel.

6. A grinding machine according to Claim 5, in which the transverse linear guide comprises a cylindrical shaft secured to the housing, and a plurality of circumferentially spaced rollers arranged on the arm and which roll on the shaft.

7. A grinding machine according to Claim 6, in which two rollers are arranged side-by-side in a plane which contains the axis of the shaft of the transverse linear guide and which extends perpendicular to the direction of travel.

8. A grinding machine for grinding the edge of a spectacle lens to a predetermined peripheral shape substantially as described herein with reference to the accompanying drawings.