Abstract:
A drum is mounted to rotate about its drum axis. A pair of elongated, complementary guides are proximate to and extend along the axial length of the drum. The guides are sized and spaced to allow a workpiece to span the guides and roll upon them. A driver is mounted alongside the guides for rolling the workpiece on them. These guides are positioned between the drive means and the drum. The workpiece is positionable between the driver and the guides to protrude beyond the guides and reach the drum.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to apparatus for preparing an optical workpiece and, in particular, to equipment for finishing, beveling and/or marking such workpieces. 
     Known lenses and mirrors having a generally cylindrical shape are often finished by rubbing their flat surfaces to form either a plane or curved surface. A problem is that the sharp edges of the cylinder can be easily chipped during the finishing operation. Accordingly, it is known to bevel such edges to avoid the possibility of chipping. 
     One technique for beveling an optical device involves pressing the edges of a cylindrical blank against a rotating cup that has been prepared with an abrasive. However the operator often does not hold the blank squarely against the cup or may move the blank during the beveling operation thereby rendering the bevel nonuniform. 
     Another problem with preparing optical devices is distinguishing one side of a cylindrical blank from the other. The flat sides may require different finishes in that one may be slightly convex or concave but to an extent not readily visible. Alternatively one side may be coated. It is known to grind an identifying mark into one of the edges of the optical device before finishing to distinguish its flat sides. In the past this has been done by manually holding the edge against a cutting wheel. 
     A disadvantage with all of the foregoing operations is that they are performed manually and are therefore time consuming and subject to inconsistencies. 
     Accordingly, there is a need for equipment to quickly, reliably and preferably automatically prepare an optical workpiece. 
     SUMMARY OF THE INVENTION 
     In accordance with the illustrative embodiments demonstrating features and advantages of the present invention, there is provided apparatus for preparing an optical workpiece. The apparatus includes a drive means, a power means and a pair of elongated, complementary guides. The guides are proximate to and extend alongside the power means. The guides are sized and spaced to allow the workpiece to span the guides and roll upon them. The drive means is mounted alongside the guides for rolling the workpiece on the guides. These guides are positioned between the drive means and the power means. The workpiece is positionable between the drive means and guides to protrude beyond the guides and reach the power means. 
     In a related method of the same invention an optical workpiece is prepared with a guide adjacent to a rotating drum. The method includes the step of positioning the guide along the length of the drum. Another step is rolling the workpiece on the guide, allowing the workpiece to touch the drum. 
     By employing apparatus and methods of the foregoing type an improved, efficient and reliable technique is provided for preparing the edge of an optical workpiece. In a preferred embodiment, the workpiece is a cylindrical optical device which is rolled along a pair of guides having the shape of beveled bars. Preferably, these beveled surfaces are perpendicular to each other so that a cylindrical optical workpiece can be supported without rocking or shifting. The optical workpieces are allowed to roll along the guides and to protrude between them to touch an abrasive drum. This drum may have a diamond abrasive coating for beveling the edge of the optical workpiece. In this preferred embodiment, the drive for rolling the workpiece is an endless belt that circulates on a pair of wheels rotatably mounted on a hinged beam. Being hinged, the beam can allow the drive belt to descend onto the optical workpiece by the force of gravity. The lower stretch of the drive belt touching the optical workpiece is backed by a channel-like device that provides firmness for driving the workpiece. In a preferred embodiment, the motor for driving the drive belt is mounted on the beam carrying the drive belt and wheels to allow simple mechanical coupling. Such mounting can be advantageous in that the weight of the motor is used to urge the drive belt against the workpiece. 
     Also in one preferred embodiment the optical workpiece can progress from one station to another wherein first one and then the other circular edge is beveled. Furthermore other stations can tilt the optical workpiece so the border of the bevel along the flat surface of the workpiece can be polished at another station. At still another station the other border of the beveled edge contiguous to the curved surface of the workpiece can be notched by a circular saw. All of these stations can be interconnected so that the optics move in procession from one station to the next, automatically grinding, marking and polishing the bevel. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above brief description as well as other objects, features and advantages of the present invention will be more fully appreciated by reference to the following detailed description of presently preferred but nonetheless illustrative embodiments in accordance with the present invention when taken in conjunction with the accompanying drawings wherein: 
     FIG. 1 is a perspective view of apparatus according to the principles of the present invention; 
     FIG. 2 is an end view of the drive means of the apparatus of FIG. 1; 
     FIG. 3 is a side view of the guide of the drive means of FIG. 2; 
     FIG. 4 is an elevational end view, partly in section, of the apparatus of FIG. 1; 
     FIG. 5 is a schematic side view of the work area of the apparatus of FIG. 1; 
     FIG. 6 is a detailed schematic side view showing an arrangement which is an alternate to that of FIG. 5; 
     FIG. 7 is a front view of the apparatus of FIG. 6; and 
     FIG. 8 is a detailed side view of an arrangement which is an alternate to that of FIG. 6. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1-4, the illustrated apparatus for preparing a workpiece includes a pair of bases 10a and 10b which are parallel plates having raised, rectangular portions spanned by a drum 12. Drum 12 is a cylinder having a deposit of diamond abrasives on it, in this embodiment. Drum axis 16 of drum 12 is journalled in end bearings 14a and 14b mounted on the outside surfaces of plates 10a and 10b, respectively. Drum axle 16 extends beyond bearing 14a to a drive pulley 18 which is encircled by drive belt 20. Drive belt 20 is circulated by a drum motor (not shown). Mounted alongside drum 12 to spray a lubricating medium such as a light oil onto drum 12 is wedge shaped nozzle 22 which is fed by inlet pipe 24. Spray nozzle 22 and plates 10a and 10b may be mounted in a basin which acts as a reservoir for the lubricating fluid for nozzle 22, (basin not shown). 
     A pair of guides 26a and 26b are shown herein as a pair of parallel rods having a substantially trapezoidal cross-section. Guides 26a and 26b can be formed from rectangular rods which have had a corner cut into planar, beveled, support surfaces 28a and 28b. Guides 26a and 26b are mounted atop the central raised portion of bases 10a and 10b perpendicular thereto. The guides are secured to the upper edges of plates 10a and 10b by appropriate bolts 30 which fit through elongated holes in guides 26a and 26b to allow adjustment transverse to the axis of drum 12. 
     Mounted atop the rear edges of bases 10a and 10b are upright standards 32a and 32b, respectively. The upper ends of standards 32a and 32b terminate in eyes 34a and 34b, respectively, into which are journalled a support axis 36. Support axis 36 is an axle mounted through a complementary bore in the lower end of rectangular plate 38. Plate 38 is perpendicularly mounted to the underside of beam 40, another rectangular plate. Beam 40 has mounted atop it a pair of spaced, parallel cross-beams 42 and 44, each connected to beam 40 by central, rectangular stubs 47 and 46 by means of bolts 48 and 50. Mounted on each underside of cross-beams 42 and 44 are a pair of dependent bearings all aligned parallel to beam 40: Cross-beam 42 supports on one of its ends right bearing 52a and left bearing 52b on its other end. Cross-beam 44 similarly supports right bearing 54a and left bearing 54b. Bearings 54a and 54b are aligned with bearings 52a and 52 b, respectively. 
     A drive means is shown herein as a pair of drive wheels 56a and 56b, encircled by an endless belt 58. Belt 58 comprises an outer portion above wheels 56a and 56b as well as an inner portion below the wheels. This inner portion is preferably at least as long as drum 12. Wheels 56a and 56b and their respective hubs 70a and 70b  (FIG. 4) are affixed to axles 60a and 60b, respectively, by means of set screws 72a and 72b. Axle 60a is journalled in bearings 52a and 54a, axle 60b being journalled in bearings 52b and 54b. Axles 60a and 60b extend backwardly beyond their respective bearings 52a and 52b and terminate in a drive pulley, only drive pulley 62 of axle 60b being visible herein. These pulleys are encircled by a belt 64 which also encircles drive pulley 66 driven by DC motor 68. Motor 68 is thus connected as the means for driving belt 58. Motor 68 can be controlled by an appropriate controller (not shown) to regulate its DC voltage and thus control its angular speed. The underside of beam 40 has a rectangular channel which receives complementary ridge 76 rising from the upper side of rectangular carrying plate 78. Rectangular plate 78 is mounted flush against the underside of beam 40 by means of bolt 82 and can be longitudinally slid by loosening nut 80 (FIG. 3) which normally holds bolt 82 in place. Sliding is facilitated by elongated slot 84 piercing beam 40. Depending perpendicularly from the forward end of plate 78 is plate 86. Plate 86 has two horizontal parallel edges, a flat upper edge and a lower edge cut by rectangular channel 88. The two other lateral edges of plate 86 are shaped approximately as a quadrant of a circle to match the circumference of adjacent drive wheels 56a and 56b. Plate 86 is positioned and dimensioned so that it holds and backs the inner portion of belt 58 as it travels below drive wheels 56a and 56b. Preferably the bottom of channel 88 is coated with a suitable lubricant or is lined with a Teflon coating. It will be appreciated that drive belt 58 can be shifted by axially readjusting the position of drive wheels 56a and 56b and simultaneously repositioning plate 78 and its channel 88 by loosening and retightening nut 80 to allow bolt 82 to slide through slot 84. 
     The operation of the foregoing apparatus will now be briefly described. The equipment is started by energizing motor 68 and by driving belt 20 to rotate drum 12. Motor 68 has its speed set such that belt 58 can complete its circuit in about one to three seconds. Of course, different speeds can be chosen depending upon the desired feed rates for the workpieces, the fragility of workpieces being handled, etc. A cylindrical optical workpiece 90 can be set down in guides 26a and 26b to span them as illustrated in FIG. 5. The curved surface of workpiece 90 rolls on surface 28a, its flat surface sliding across surface 28b. In the embodiment shown, surfaces 28a and 28b are perpendicular to each other and each bear an angle of 45° with respect to vertical. It is expected that a sequence of workpieces will be set in a row in guides 26a and 26b to roll in procession. The first workpiece reaching drive belt 58 is engaged by that belt at the upper circular edge of the workpiece. Since belt 58 is linearly progressing, it rolls workpiece 90 so that the lower edge is rolled onto drum 12 thereby producing a beveled edge. It will be appreciated that since the spacing between the center of workpiece 90 and the upper surface of drum 12 remains fixed, workpiece 90 cannot be overground. The length of the guides 26a and 26b are chosen such that workpiece 90 turns more than once and preferably one and two-thirds times, over the length of drum 12. This length is chosen to accomodate the largest expected workpiece. Thus, drum 12 acts as a power shaper (or power means). 
     After one of the edges of workpiece 90 is beveled in this fashion, it can roll along guides 26a and 26b to a transfer guide (not shown) which can be in the form of a rectangular conduit having a 90° twist. This twist effectively shifts by 90° the rolling axis of workpiece 90 so the unbeveled edge of workpiece 90 now points downwardly. Thereafter, workpiece 90 can be brought to another station, similar to the one illustrated in FIG. 1, where the other edges of workpiece 90 can be beveled. 
     The resulting workpiece has beveled edges 90a and 90b as illustrated in FIG. 6. These beveled edges have a surface intersecting the flat and cylindrical surfaces of workpiece 90 at 135°. In FIGS. 6 and 7 another operation is illustrated wherein workpiece 90 is rolled to still another station along new guides 92a and 92b, whose supporting surfaces bear an angle at 67.5° and 22.5°, respectively, with respect to horizontal. At these angles bevel 90a is oriented so that its border with the cylindrical side of workpiece 90 points downwardly through guides 92a and 92b. Workpiece 90 rolls along guides 92a and 92b in an apparatus similar to that described in FIG. 1. However, the previously illustrated drum 12 is replaced herein by a pair of circular saws 94a and 94b. Circular saws 94a and 94b are coaxially mounted on drive shaft 96 which drives the saws and allows them to cut a pair of angularly spaced notches at the edges comprising the border between bevel 90a and the cylindrical side of workpiece 90. These notches can be used to identify one side of workpiece 90 from the other. Such differentiation is useful where the sides are prepared differently by having different coatings or different surfaces ground thereon. 
     Next (FIG. 8) workpiece 90 can be rolled onto new guides 98a and 98b to increase the elevation of the rolling axis of workpiece 90. Guides 98a and 98b have reversed angles with respect to horizontal, that is, angles of 22.5° and 67.5°, respectively. This orientation shifts workpiece 90 so that the edge representing the border between bevel 90a and the flat surface of workpiece 90 points downwardly between guides 98a and 98b. Workpiece 90 rolls on guides 98a and 98b through an apparatus similar to that described in FIG. 1 except that previously described drum is replaced with polishing wheel 100. Accordingly, the border between the flat side of workpiece 90 and bevel 90a is polished so that there is a degree of rounding at the border. This avoids chipping at this border. 
     Workpiece 90 may now be rolled along guides to another work station similar to that of FIG. 1. In making this transition, workpiece 90 is shifted from the position shown in FIG. 8 (that is, with its rolling axis at 67.5° to horizontal) by rotating the rolling axis by 180° so that the other edge of the workpiece 90 points downwardly. In particular, the edge representing the border between bevel 90b and the flat surface of workpiece 90 projects downwardly through guides 98a and 98b (FIG. 8) so that border may be polished annd rounded. Alternatively the rolling axis of workpiece 90 may be rotated 135° (clockwise in FIG. 8) so that the above mentioned border is polished. 
     It is to be appreciated that various modifications may be implemented with respect to the above preferred embodiment. For example, various alternate driving means can be employed. For example, each of the workpieces can be straddled by a pair of idler wheels which are moved longitudinally along the guides to drive the workpieces. Furthermore, the illustrated guides can take various shapes and in some embodiments may be a rectangular conduit having a slot cut into its lower corner. Furthermore, in some embodiments the drum may be replaced with an endless belt having abrasives deposited thereon. Furthermore, while the illustrated drive belt is shown bearing against the workpiece by gravity, in other embodiments various springs and other biasing means can be used to apply pressure onto the workpieces. Furthermore, the various dimensions including the length and diameter of the grinding drum can be altered depending upon the size of the workpiece and other factors. It will also be understood that while a three-step process is illustrated (beveling, notching and polishing) in other embodiments, certain of these steps can be deleted, supplemented or substituted, depending upon the application. It is also expected that for some embodiments the grinding drum and the workpiece driving belt can have a common drive and the two systems can be mechanically linked together. Also, instead of a pair of circular saws one or more than two notching devices can be employed. In addition, the various dimensions and materials can be altered depending upon the size of the workpiece, the desired speed of operation, the required accuracy, tolerances etc. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.