Abrading – Work feeder – Rotary
Reexamination Certificate
2002-12-23
2004-10-26
Eley, Timothy V. (Department: 3724)
Abrading
Work feeder
Rotary
C451S042000, C451S255000, C451S339000
Reexamination Certificate
active
06808445
ABSTRACT:
TECHNICAL AREA
The present invention relates, according to the preamble of claim
1
, to a device for loading and unloading of optical workpieces, in particular optical lenses, for a lens machine with a loading arms driven swivellable about an axis which in controlled movement processes swivels between a workpiece magazine and the processing station on the lens machine and at its outer end is fitted with a device for picking up and depositing workpieces. Although the description below discusses only the loading or unloading of workpieces, the device is however equally suitable for tool changing.
STATE OF THE ART
Automatic loading systems for lens machines are becoming increasingly important because of rising personnel costs. Such loading systems have to take into account a wide range of workpieces, high accuracy requirements and small batch sizes. According to the state of the art there are three different construction concepts, namely (1) devices with cam-controlled loading arms, (2) devices with pneumatic loading arms driven by cylinders and swivel rotors and (3) devices which for loading or unloading use the CNC axes present on the lens machines.
(1) Cam-controlled loading arms have been in use for decades (e.g. DE-PS 12 38 802). Such cam-controlled loading systems require great expense in set up and adjustment, offer no facility for influencing the speed of the movement—which is very important with different workpiece weights—and can only approach established, unchanging loading and unloading positions.
(2) Pneumatic loading arms driven by cylinders and swivel rotors with automatic stops and dampers are used today in various lens machines. Known automation systems for lens machines (e.g. EP 0 090 752 A1, EP 0 175 431 B1, U.S. Pat. No. 2,933,863) work using pneumatic drive elements with complex devices requiring costly maintenance. Because of the compressibility of compressed air and the stick-slip effect occurring on the pneumatic cylinders, these systems have disadvantages. In these systems the force with which the loading system is set in movement can be restricted relatively simply by restricting the pressure of compressed air, but difficulties occur with an external movement restriction of the loading arm. When this restriction is not present, namely very rapid swivel or linear movements result which lead either to the workpieces being flung off or at least displaced and hence to a change in workpiece position. Furthermore in pneumatically operated loading systems the stops shift due to wear and/or vibration. The movement speed is affected by external influences e.g. the lubrication state of the mechanics and the compressed air, the soiling of the mechanical elements involved or the amount of pressure in the compressed air. This is particularly critical when loading large delicate workpieces. To summarise it can be found that the precision and reliability of the workpiece insertion using such loading systems are relatively low. In addition, such systems can also approach only a few established positions of the loading arm.
(3) Recently more attempts have been made to achieve the supply to lens machines using the existing CNC axes of the lens machine (e.g. DE 198 25 922 A1). The carriages of the horizontal movement axes are moved over long distances, where a piston-cylinder arrangement mounted on one of the carriages collects the workpieces with a suction device from a magazine arranged outside the processing area of the lens machine. This design is indeed flexible and works relatively precisely in position, but large masses must be moved over long distances, leading to relatively long change times. Also the CNC axis can only be used for the feed process when the actual machining processes on the lens machine have previously been completed. A prepositioning of the optical lens to be machined close to the chuck of the workpiece spindle during machining of another lens is not possible. In addition the longer linear axes necessary cause a considerable increase in production costs of such lens machines and also lead to larger and hence heavier machines.
Finally, as the state of the art which does not concern lens machines directly, reference is made to the publications DE 40 37 773 A1 and DE 198 30 365 C1.
DE 198 30 365 C1 discloses a rotary stroke drive with a stroke drive unit coupled to a rotary drive unit. Here the stroke drive unit has a gear motor arranged in a stroke drive housing for stroke drive of a threaded spindle, and the rotary drive unit has a gear motor arranged in a rotary drive housing for rotary drive of an output shaft, which are arranged coaxial to each other and connected together via a coupling unit to transfer the stroke to the output shaft. The output shaft itself can be connected with a robot arm which carries a sucker for collection and deposit of e.g. workpieces.
DE 40 37 773 A1 discloses a swivel arm robot with a rotary stroke unit which has a spindle sleeve and arranged thereon a gripper holder which is rotatable about a rotary axis and longitudinally mobile in the vertical direction. The construction elements which achieve the translatory and rotatory movement of the spindle sleeve are not described in detail in this state of the art.
The present invention is therefore based on the task of producing a device for loading and unloading of optical workpieces, in particular optical lenses, which avoids the said disadvantages of the former systems and allows a compact and simple structure with a high loading and unloading precision.
DESCRIPTION OF THE INVENTION
According to the invention in a device for loading and unloading optical workpieces for a lens machine with a loading arm driven swivellable about an axis, which arm can swivel in controlled movement processes between a workpiece magazine and the machining station on the lens machine and at its outer end has a device for picking up and depositing workpieces, the swivel axis of the loading arm is the centre axis of a spindle rotating in both directions of rotation and drivable mobile in linear strokes in both axial directions by drive elements and guided rotatably and displaceably in guide elements, on which spindle is attached the loading arm, where the spindle is designed both as a splined shaft and as a threaded spindle and is guided by two rotatably mounted, fixed location nut elements forming the guide elements, of which one nut element engages with the splined shaft and the other nut element with the threaded spindle, where the nut elements can be driven individually or simultaneously, in opposite or the same direction of rotation.
Thus an essential feature of the invention is the use of a special spindle equipped with several overlaying degrees of movement freedom, the movement processes of which can be freely programmed, preferably independently of the control of the machining processes being performed on the lens machine. This spindle guides and controls in a compact, simple and stable manner all movements of the loading arm i.e. both its stroke and its rotation movements, without end-of-travel stops being required. In this way the loading arm can approach any intermediate positions at which the device can be fitted with equipment for additional work processes such as precentring, turning or rotating, measuring or washing of the lens. As the loading arm in each direction can be guided over any long or short swivel or stroke movements, all movement processes can be performed with optimum travel and hence time. A spindle which can be used for the purposes of the invention is available commercially under the name “Ball Screw Spline” type BNS from the company THK Co. Limited, Tokyo, Japan. Finally in this connection it should also be stated that the device provided on the loading arm for picking up and depositing workpieces can for example be a vacuum-operated suction element adjustable in height to pick up lenses of different thicknesses against spring force, or a gripper or clamping element driven by compressed air.
In an advantageous embodiment of the invention, the spindle with the
Becker Bernd
Diehl Joachim
Groh Herbert
Eley Timothy V.
LOH Optikmaschinen AG
McAndrews Held & Malloy Ltd.
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