Patent Application
20240399533
This application claims priority to European Patent Application No. 23176169.3 filed on May 30, 2023, the disclosure of which is hereby incorporated by reference.
The invention relates to a device for polishing an optical surface of optical lenses, a connecting element for being fitted on a polishing machine being provided on one end of the device, and a polishing wheel being disposed on another end of the device, said polishing wheel having an axially disposed drive shaft running radially to a longitudinal center axis of a spindle of the polishing machine, and the device having a crown gear or a bevel gear by means of which the polishing wheel is drivable via the drive shaft by means of a rotary part of the spindle of the polishing machine.
For the production of optical lenses, such as aspheres, spheres, plane surfaces and free form surfaces, eyeglass lenses and the like, lens blanks are used which are firstly prefabricated by machining. Due to the resulting relatively high roughness of the optical surfaces, they must then be polished, which reduces the roughness and also creates the fine contour of the optical surface.
EP 2 837 464 B1 describes a polishing method for processing an optical surface of an optical lens and polishing tools suitable for the same. In this polishing method, a polishing surface of a polishing wheel placed on the surface of the lens is moved over the surface of the lens along a helical processing path, said polishing wheel being set in rotation around an axle and a rotation axis perpendicular to the axle, the speed of the polishing wheel being reduced about the axle and/or the rotation axis in the spiral center of the motion path.
It is the object of the invention to propose a device for polishing an optical surface of a lens, to propose a polishing machine having a device of this kind, and to propose a method for polishing by means of which the shape and profile of the polishing imprint on optically effective surfaces of lenses can be set in accordance with the required polishing removal, the dimensional accuracy and the optical quality of the lenses contoured and surface-finished by polishing being further improved and the roughness of the optical surfaces being further reduced.
According to the invention, this object is attained by a polishing machine.
Advantageous embodiments of the invention are characterized in the respective dependent claims.
In the device according to the invention, the crown or bevel gear is formed by a cogwheel disposed on one end of the drive shaft and by a crown or bevel wheel rotatably mounted on a fixed bearing sleeve of the device, said bearing sleeve running coaxially to the spindle of the polishing machine, and additional toothing being provided on an outer circumference of the crown or bevel wheel, the polishing wheel being drivable via the drive shaft by means of said toothing via a toothed wheel driven by a separate drive motor. Because of the additional drive by means of the separate drive motor, which drives the crown or bevel gear or the crown or bevel wheel via the toothed wheel and the drive shaft of the polishing wheel via the cogwheel, the transmission ratio between the crown or bevel wheel and the toothed wheel of the polishing wheel changes, whereby the speed of the polishing wheel changes. Thus, the dimensional accuracy and the optical quality of the lenses when polishing lenses so as to contour and surface-finish them can be further improved, the roughness of the optical surfaces of the lenses also being further reduced.
On an end of the connecting element directed at the polishing machine, the connecting element can have a bearing pin which can be received and mounted by a clamping system of the rotary part of the spindle of the polishing machine, a mounting frame for receiving and supporting the polishing wheel being provided on an end of the connecting element facing away from the polishing machine. By means of the clamping system, a quick adaptation of the device to the polishing machine is ensured, so that an increased workload for mounting the device on the polishing machine is virtually eliminated. The coaxial arrangement of the bearing pin of the connecting element to the clamping system of the rotary part of the spindle ensures a precise concentricity of the connecting element and of the polishing wheel when rotating the spindle and for an optimal power transmission from the spindle to the polishing wheel. In addition to receiving and supporting the polishing wheel, the mounting frame of the connecting element can also provide a certain protection of the polishing wheel against possible external influences.
The clamping system can be a hydraulic expansion chuck which ensures a secure and permanent hold of the connecting element of the device or of the entire device on the spindle of the polishing machine with its high clamping force. Additionally, the hydraulic expansion system provides a very high connecting element concentricity and thus a very high polishing wheel concentricity.
The drive shaft of the polishing wheel can be mounted on lateral legs of the U-shaped mounting frame. The U-shaped mounting frame ensures relatively easy mounting of the drive shaft and of the polishing wheel on or in the same, the polishing wheel can also being replaceable relatively easily and quickly if necessary.
The drive shaft can protrude cover one side of the mounting frame, the cogwheel being mounted on the protruding part of the drive shaft. The cogwheel and thus the polishing wheel can be driven via the spindle when the drive motor is static and the crown or bevel wheel is blocked, the polishing wheel radially rotating around the longitudinal center axis of the spindle, on the one hand, and axially around the longitudinal center axis of the drive shaft and the cogwheel mounted thereon, on the other hand. The cogwheel rolls on the crown or bevel wheel.
The cogwheel and thus the polishing wheel can be driven by means of the operating drive motor via toothed wheel of the drive motor driving the crown or bevel gear, the polishing wheel axially rotating around the longitudinal center axis of the drive shaft and the cogwheel mounted thereon. Simultaneously, the polishing wheel is driven by the spindle, the polishing wheel radially rotating around the longitudinal center axis of the spindle. This changes the transmission ratio and the speed of the polishing wheel. The drive motor can control the rotational speed and the rotating direction irrespectively of the spindle of the polishing machine.
The polishing wheel can be mounted between the two lateral legs of the mounting frame so as to have low backlash. Due to the compact design of the mounting frame of the connecting element and the low backlash between the two lateral legs of the mounting frame, debris and excess polishing agent can hardly settle anywhere.
The polishing wheel can have an elastic rubber coating on its outer circumference, the outer circumference of the elastic rubber coating having a convex surface. Due to the convex shape of the rubber coating and its elasticity, the rubber coating with its polishing surface adapts at least approximately form-fittingly to the surface of the respective lens.
The bearing sleeve can have a retaining element for the drive motor, in or on which the drive motor with its longitudinal center axis can be disposed parallel to the longitudinal center axis of the spindle of the polishing machine. The arrangement of the drive motor on the bearing sleeve makes the device relatively compact and very easy to handle.
The polishing machine according to the invention for polishing an optical surface of optical lenses comprises a device according to the invention. For details on the advantageous effects of the polishing machine according to the invention, reference is made to the description of advantageous effects of the device according to the invention.
In the method according to the invention for polishing an optical surface of optical lenses using a device, which is disposed on a polishing machine, the polishing wheel with its elastic rubber coating is, firstly, positioned on the surface of the lens, the spindle of the polishing machine subsequently being rotated around its longitudinal axis while the crown or bevel wheel is blocked while simultaneously rotating the polishing wheel around the longitudinal center axis of the spindle of the polishing machine and the longitudinal center axis of the drive shaft, the cogwheel rolling on the blocked crown or bevel wheel at a constant transmission ratio. Subsequently, the transmission ratio between the crown or bevel wheel and the cogwheel is changed while simultaneously changing the speed and/or changing the rotating direction of the polishing wheel by operating the drive motor. For details on the advantageous effects of the method according to the invention, reference is made to the description of advantageous effects of the device according to the invention.
The rotating direction of the drive motor can be switched, the speed of the polishing wheel being changeable. The speed of the drive motor can also be changed. By switching the rotating direction and/or changing the speed of the polishing wheel and drive motor, it is possible to make adjustments before and during polishing.
Further advantageous embodiments of the method are apparent from the description of features of the dependent claims referring back to claim 1.
Hereinafter, a preferred embodiment of the device will be described in more detail with reference to the drawings.
Device 1 shown in
For polishing optical surface 2 of optical lenses 3, a polishing wheel 11 provided with an elastic rubber coating 10 is provided on another end of device 1, said polishing wheel 11 having a convex surface on outer circumference 12 of rubber coating 10 and being disposed and mounted on an end of connecting element 5 of a U-shaped mounting frame 13, said end facing away from polishing machine 4. Polishing wheel 11 is disposed on an axially disposed drive shaft 15 running radially to a longitudinal center axis 14 of spindle 9 of polishing machine 4, said drive shaft 15 preferably being mounted on lateral legs 16 of U-shaped mounting frame 13 by means of rolling bearings 17, polishing wheel 11 being disposed between two lateral legs 16 on drive shaft 15 so as to have low backlash.
Furthermore, device 1 has a crown gear or a bevel gear 18 which serves to drive polishing wheel 11 by means of rotary part 8 of spindle 9 of polishing machine 4 via drive shaft 15. Crown or bevel gear 18 is formed by a cogwheel 19 disposed on an end of drive shaft 15, drive shaft 15 protruding over one side of mounting frame 13 or over one of the two legs 16 of mounting frame 13 and cogwheel 19 being mounted on the protruding part 20 of drive shaft 15.
Crown or bevel gear 18 is formed by a crown or bevel wheel 23 rotatably mounted on a fixed bearing sleeve 21 of device 1 via preferably additional rolling bearings 22, said bearing sleeve 21 running coaxially to spindle 9 of polishing machine 4. An additional toothing 25 is disposed on an outer circumference 24 of crown or bevel wheel 23, polishing wheel 11 being drivable via drive shaft 15 by means of said toothing 25 via a toothed wheel 28 driven by a separate drive motor 26, whose longitudinal center axis 27 is disposed at a distance and parallel to longitudinal center axis 14 of spindle 9 of polishing machine 4. For fastening drive motor 26, bearing sleeve 21 has a correspondingly disposed retaining element 29.
Hereinafter, the method for polishing an optical surface 2 of optical lenses 3 using device 1 and polishing machine 4 will be described in more detail.
Firstly, polishing wheel 11 with its elastic rubber coating is positioned on surface 2 of lens 3 disposed in a workpiece clamping system 30 of polishing machine 4, whereupon spindle 9 of polishing machine 4 begins to rotate around its longitudinal center axis 14 while crown or bevel wheel 23 is blocked while polishing wheel 11 simultaneously rotates around longitudinal center axis 14 of spindle 9 of polishing machine 4 and longitudinal center axis 31 of drive shaft 15. Cogwheel 19 rolls on blocked crown or bevel wheel 23 at a constant transmission ratio.
Changing the transmission ratio between crown or bevel wheel 23 and cogwheel 19 while simultaneously changing the speed and/or changing the rotating direction of polishing wheel 11 is effected by operating drive motor 26.
In addition, the rotating direction of drive motor 26 can be switched, the speed of polishing wheel 11 also being changeable. Furthermore, the speed of drive motor 26 can also be changed.
As previously mentioned, the transmission ratio between crown or bevel wheel 23 and cogwheel 19 changes as soon as drive motor 26 is switched on. Accordingly, the speed of polishing wheel 11 changes. Drive motor 26 can control the rotational speed and the rotating direction irrespective of spindle 9 of polishing machine 4.
| Number | Date | Country | Kind |
|---|---|---|---|
| 23176169.3 | May 2023 | EP | regional |
