An arrangement is already known from DD 260 847 A3 designed to provide smooth, linear elastic support which offers lateral stability and is torsion-proof. The arrangement comprises pre-formed leaf springs which are slit and which are firmly fixed at the ends of the resulting spring tongues into the interlocking spring mechanism of the components. Here, the different pre-formed leaf springs lie parallel to each other, the arrangement having a symmetrical form. The fixing points of the pre-formed leaf springs concerned lie at a level which is parallel to the direction of spring movement, the total width of the spring tongues, which are each fixed within the movable components, being the same for a pre-formed leaf spring and at the same distance from the fixing point. Due to the angle position of the leaf springs concerned during bending, a traverse movement of the actuator is generated which runs at right-angles to the direction of movement.
WO 97/13603 according to the FIG. 1, together with the related description in the penultimate paragraph on page 9, describes a processing machine for manufacturing optical surfaces and formed shells according to individual data specifications in a single processing stage. Here, a tool holder which oscillates in the Z direction is fitted, which is in turn assigned a workpiece holder with a spindle on a slide which can be moved in the Z axis. Here, the slide is brought into a position for preadjustment, and is then clamped firmly in place for the duration of the processing. A dynamic drive according to the invention, which is moved during the processing sequence, is not described in this publication.
An object of the present invention is to form and arrange a lens processing machine and the related linear drive so as to enable simple, low-cost processing of the workpiece.
The present invention provides a highly dynamic lens processing machine that includes a workpiece holder having at least one dynamic linear drive in the direction of a second oscillation axis O2 which is arranged in parallel to the first oscillation axis O1. Furthermore, a runner is guided over a leaf spring bearing arrangement formed from leaf springs in the housing in a coaxial direction to the oscillation axis O1, the leaf spring bearing arrangement being formed in two parts, and comprising a guidance arrangement and a coupling arrangement attached to said guidance arrangement. Here, the linear drive can take the form of a linear motor, or equally a slide-spindle pair. The drive can be regarded as being dynamic when the processing or milling sequence is actively supported or influenced. Here, an incremental, constant or step-by-step trigger is provided.
This enables the oscillation axis 01, 02 required for processing the workpiece or lens to be partially arranged in the tool holder, and in addition to this, partially in the workpiece holder. As a result, in particular the required strokes of the oscillation axis O1, O2 concerned can be used for processing on the one hand, as well as the required processing or oscillation frequencies, the oscillation of an axis or a combination of the oscillations of both axes. In this regard, it is also advantageous that the relationship of the oscillation stroke of the tool holder to the oscillation stroke of the workpiece holder lies between 0.08 and 1, in particular 0.13. When manufacturing a lens, the lens surface, which requires highly dynamic triggering for the cutting chisel, can be guaranteed due to the highly dynamic first oscillation axis O1 of the leaf spring bearing arrangement. The milling processing of the edge is conducted using the dynamic second oscillation axis O2, which comprises a significantly larger stroke than the first oscillation axis O1.
As a result, a simple and, in this respect, maintenance-free linear drive for the tool holder and/or the workpiece holder is guaranteed. Due to the use of a leaf spring bearing arrangement, the use of expensive slide and/or rolling bearings is not required. The stroke of the oscillation axis concerned, which is reduced in this respect due to the use of the leaf spring bearing arrangement can be compensated by overlaying or combining the aforementioned double oscillation arrangement. As well as the oscillation frequency of between 25 and 100 Hz, an oscillation path of between 1 and 20 mm is preferably provided in order to process the optical surface of a lens blank.
For this purpose, it is also advantageous that a second tool holder which is arranged in a stationary position is provided, towards which the workpiece can be moved via the second oscillation axis O2. As well as the overlay or combination of the two oscillation axes, the oscillation axis O2 which is assigned to the workpiece holder can also be used in order to process the workpiece. In this case, an oscillation of the tool holder is not necessary, so that said tool holder is arranged in a stationary position, for example in the form of a milling cutter, and the workpiece conducts the oscillation. When a rotating chisel is used for processing the plastic lens blanks, the first oscillation axis O1, i.e. the dynamic tool drive, is preferably used in order to process the optical surface, the second oscillation axis O2 of the workpiece holder being used to process the edge or to process the phases, and for the basic roughing-down work. Here, the use of a milling cutter is specified as an alternative to the rotating chisel.
Furthermore, it is advantageous that the leaf spring bearing arrangement comprises a coupling arrangement and a guidance arrangement, the coupling arrangement and/or the guidance arrangement being indirectly or directly connected with the runner and/or with the housing. The use of a coupling and guidance arrangement in each case, which in this respect forms a structural unit, guarantees the necessary rigidity of the bearing arrangement on the one hand, and the optimisation of the vibration behaviour of the overall arrangement on the other, in particular taking into account the frequencies of between 25 and 100 Hz to be specified here.
It is also advantageous that the guidance arrangement is formed from a first guide segment and a second guide segment, which is arranged at a distance in the direction of the oscillation axis O1. This guarantees double, front bearing support for the runner.
For this purpose, it is advantageous that the guide segment concerned comprises at least one bar-formed or plate-formed reinforcement element, and that the reinforcement element concerned is preferably carbon fibre-strengthened, or is formed of carbon fibre, the reinforcement element concerned being adhered to an adapter element which is preferably welded to the guide segment. Due to the use of reinforcement elements, the elastic part of the guide element concerned is reduced on its end sections and in the central section, i.e. the section where the runner or housing attachment is located. Here, the elastic length is approximately reduced to between 5 mm and 15 mm. Its structure made of, or using, carbon fibre guarantees the best possible weight ratio. Using the adapter element, the adhesive attachment next to the support surface can also cover the edge areas or front face sides of the adapter element.
Here, it is specified in an advantageous manner that the runner in the direction of the oscillation axis O1 comprises a front face side and a rear face side, the guide segment concerned being affixed to the runner in the area of the face side in order to form a first and a second runner bearing. The use of two guide segments results in the runner being retained on both sides on its two face sides. Due to the face side arrangement of the guide segments on the runner, the interim area which is thus created can be used to attach further runner bearing parts.
Of particular significance to the present invention is the fact that the external end sections of the guide segments in the radial direction to the oscillation axis O2 are connected to the coupling arrangement. The connection between the guide segments to the coupling arrangement guarantees the necessary coupling or restraint, and thus the required discontinuation of the vibration behaviour of the two guide segments. The external ends of each of the guide segments concerned act here as an optimum attachment point in order to attach the coupling arrangement.
In relation to the structure and arrangement according to the invention, it is advantageous that the coupling arrangement is formed from a first coupling segment and a second coupling segment, which are arranged opposite to each other in relation to the oscillation axis O1. This enables the external ends of the guide segments to be connected, which are also aligned in a radial direction to the oscillation axis, and which are also arranged opposite in relation to the oscillation axis.
Furthermore, it is advantageous that at least one end of the first guide segment and at least one end of the second guide segment are connected via at least one coupling segment. This mechanical coupling of the guide segments via the coupling segment concerned guarantees an optimum vibration behaviour on the guide segments, in particular taking into account the different natural frequencies of said guide segments. The natural frequencies are influenced by the coupling and guidance arrangement, and are thus moved into a frequency range outside that of the processing frequency.
Here it is advantageous that the connection between the guide segment and the coupling segment takes the form of a plug connection. The guide segment concerned comprises several recesses at each end, into which the corresponding pins of the coupling segment can be inserted. A weld connection can also be provided in addition to this plug connection.
It is also advantageous that the guide segment has a rhomboidal form or an oval double form, and that it is affixed to the housing via a housing bearing. Due to this basic form, the attachment to the runner or runner bearing is also guaranteed at the height of the runner, as well as the attachment point on the housing, i.e. the housing bearing, whereby starting from this central connection located in the area of the runner, the ends which extend outwards in a radial direction allow the continued attachment of the guide segment to the coupling segment concerned.
Furthermore, it is advantageous that a carrier element, which takes the form of a steering rod, is provided between the housing and the runner in a radial direction to the oscillation axis O1, whereby the steering rod is connected with the housing via a first joint and with the runner via a second joint. The steering rod therefore represents the core part of the leaf spring bearing arrangement, in particular taking into account the vibration behaviour of said bearing arrangement which occurs, and the necessary guidance of the movements which are created as a result. Here, the connection rod is triggered by oscillating movements of the runner, and thus completes a horizontal swing around the first joint on the side of the housing. Here, the joints are preferably formed using elastic spring joints, which do not comprise any slackness, and which have an adequate degree of rigidity alongside their degree of freedom.
Here, it is advantageous that at least one coupling segment is connected with the steering rod via a third joint. The attachment of the coupling segment to the steering rod guarantees an oscillation movement of the coupling segment which depends on the horizontal swing movement of the steering rod, which in turn is transferred to the relevant ends of the guide segments to which it is connected. Here, the third joint is also formed as an elastic flexible joint, so that the coupling segment is subjected to the minimum bending stress when the steering rod is swinging.
Finally, it is advantageous that the joint is formed as a rolling bearing or as an elastic flector. The formation of the joint as an elastic flector or spring joint guarantees the absolute zero flexibility of the attachment or connection of the individual segments, which, taking into account the desired processing frequency of between 25 and 100 Hz, and the masses to be moved, guarantees adequate rigidity on the one hand, and sufficiently low maintenance on the other, together with the ensuing necessary load level.
For this purpose, it is also advantageous that a distance A is provided in a radial direction to the oscillation axis O1 between the first joint and the second joint, and a distance B is provided between the first joint and the third joint, the ratio of A to B of the two distances being 2. An aspect ratio of 2 guarantees that the excursion of the coupling segment in the direction of the oscillation axis is exactly half the amount as the excursion of the runner itself. Any movement of the runner towards the oscillation axis, which brings with it a contradictory alteration in the opening angle concerned, α1, α2, of the rhomboid-formed guide segments, causes the ends of the guide segments to be moved towards the oscillation axis. This movement of the ends corresponds to the movement of the coupling segment which is arranged in the centre of the steering rod. The variation of this distance ratio should be specified here according to the structure of the guide segments.
Finally, it is advantageous that the second joint also guarantees a relative movement between the steering rod and the runner in a right-angled direction to the oscillation axis O1. Due to the tipping motion of the steering rod, the distance between the first and second bearing or bending point is altered, so that the necessary longitudinal compensation at right angles to the oscillation axis, or in the direction of the steering rod, is guaranteed by the second joint.
For this purpose, it is also advantageous that at least one coupling segment is connected with the third joint via a coupling member. The use of the coupling member makes it possible to vary the position of the coupling segment relative to the steering rod independently of the aforementioned attachment, while at the same time, taking into account said attachment.
The coupling element is thus arranged at a distance from the bearing point or swivelling axis of the third joint, whereby using the coupling member, the displacement path which is formed by the steering rod is guaranteed in accordance with the position of the third joint on the steering rod. Here, several coupling segments, in particular those which are arranged adjacent to a steering rod, can also be connected to the steering rod via a coupling member.
Furthermore, it is advantageous that the coupling segment and/or the coupling member has a U-form, L-form or triangular transverse profile. This structure ensures the necessary rigidity, taking into account bending and torsion stresses during operation.
Here, it is advantageous that the coupling segment comprises a connection point with the ends of the guide segments which takes the form of an elastic joint. The elastic joint has a flat structure, so that the relative excursion movement between the coupling segment and the guide segment concerned can be compensated. The aforementioned rigidity is therefore cancelled in the end sections.
It is also advantageous that the distance between the housing and the steering rod and/or the first joint can be adjusted using an adjusting device. Taking into account the required distance ratios between the firs and second bearing on the one hand, and the second and third bearing on the other, the adjustment device guarantees that the required distance ratio will be set, regardless of any given processing tolerances. The distance between the first bearing and the housing, or between the steering rod and the housing, can be created variably, so that the distance between the first and second bearing can be varied, depending on the distance produced between the second and third bearing.
It is also advantageous that the runner runs on bearings on the housing via the steering rod and the guide segment, the guide segment runs on bearings on the coupling segment, and the coupling segment runs on bearings on the housing via the steering rod. The frictional connection circuit thus created between the coupling and guidance arrangement on the one hand, and the housing and runner on the other, guarantees an optimum natural vibration frequency of the runner and an adequate displacement of the natural vibration frequency of the two arrangements in an area outside that of the processing frequency. When a cutting chisel is used as a tool and when plastic lenses are being processed, the cutting force to be applied to the chisel approximately totals between 50 and 200 Newton. Taking into account the processing frequency of between 25 and 100 Hz in relation to the oscillation frequency, and taking into account the masses of this linear drive required here, i.e. the runner, the tool holder and the motor actuator, it becomes clear, that the resulting vibration behaviour of the drive due to the required processing precision must be at an optimum level. Here, it is advantageous that the tool holder comprises a height adjustment feature, so that taking into account the alignment of the tool and the workpiece next to the processing axes, i.e. of the oscillation axis on the one hand, and a processing axis arranged radially to the workpiece on the other, the necessary adjustment to a spatial axis which is arranged at right angles to these two axes is guaranteed.
It is furthermore advantageous that at least one U-formed linear motor is assigned to the runner, which motor consists of the stator, which is formed from two magnetic tracks arranged in parallel, the magnetic tracks retaining the actuator between them. The motor coil of the actuator or the stator is air-core, poured in plastic and therefore very light. The forces of attraction of the opposite magnets are compensated by the U-arrangement of the stator, so that the guidance of the actuator over the runner or leaf spring bearing arrangement is guaranteed. The use of solely non-magnetic material prevents interference fields and disturbances from arising which can be traced back to the use of iron parts positioned at a distance. In addition, the motor, in particular the runner, becomes significantly lighter.
Finally, it is advantageous that the U-formed linear motor is aligned in relation to a level which is fixed by the actuator parallel to a level which is formed by the floor space used by the base plate. The application of force by the actuator on the runner is thus free of moments, since the distance between the point at which the force is applied and the centre of gravity of the runner is almost zero in the vertical direction.