US 3656264 A
A method of grinding a drill with arcuate cutting lips comprising supporting the drill relative to a predetermined reference line, pivotally swinging the drill about a pivot point in the horizontal plane of said reference line, rotating the drill as it is being swung about the pivot point to maintain the cutting edge of the drill aligned with the reference line and in engagement with the flat grinding surface that is disposed parallel to and at an angle from the vertical plane of the reference line.
Description (OCR text may contain errors)
i151 3,656,264 [451 Apr. 18, 1972 United States Patent Mackey, Jr. et al.
10/1970 Lhomme...... 549 9/1943 Eich............. 302 12/1958 Amiet 839 2/1961 Erdelyi 244 6/ l 962 Vickerman 114,988 12/1963 Garrison 6,074 ll/l964 Baltz..........
Libertyville; as, Gurnee, both 66,194 8/1966 Winslow....
Appl. No.: 31,642
Primary Examiner-Donald G. KellV Related U.S. Application Data Atmmey 0wen & Owen  Division of Ser. No. 705
[5 7] ABSTRACT A method of grinding a drill with arcuate cuttin ,393, Feb. 14, 1968, Pat. No. 3,521,405.
51/288 g lips comprisl/oo ing supporting the drill relative to a vpredetermined reference 124R line, pivotally swinging the drill about a pivot point in the f said reference line, rotatin g the drill as it is horizontal plane o be' 5l/2l9 R, 219 PC, 131
ing swung about the pivot point to maintain the cutting edge of the drill aligned with the reference line and in engagement with the flat grinding surface that is disposed parallel to and at ertical plane of the reference lin an angle from the v .5 1/288 UX 6 Claims, 15 Drawing Figures PATEMEUAPR 18 ma SHEET 2 UF d 3, 556,264
I N VEN TORS -B/:wcf A. MAC/EY dR. B Y gana/Q0 m'. Manic/m5 METHOD or GRrNDrNG DruLLs RELATED APPLICATION `This is a division of patent application Ser. No. 705,393 filed Feb. 14, 1968, now U.S. Pat. No. 3,521,405.
SUMMARY OF THE INVENTION This invention relates, in general, to a grinding method and, in particular, to a method for grinding and/or sharpening drills. More particularly still, the invention relates to a method for grinding drills in a fashion such as to provide improved cutting lips on them.
. In the U.S. Pat. application Ser. No. 714,393 filed Feb. 14, 1968, now U.S. Pat. No. 3,433,459 granted May 13, 1969, there is disclosed a drill having multiple reliefs and curved cutting lips formed on it, for improving its operation and extending its useful life. Prior to the advent of the grinding apparatus and method of the present invention, these geometries were ground on the drills, by hand. An experienced operator can do a reasonably good job of properly grinding these reliefs on any one drill, however, it is virtually impossible for him to consistently grind identical reliefs on a number of drills of the same diameter. Also, the multiple reliefs provided on drills of different diameters varies, so that the operators difficulties are compounded since he must not only properly grind the multiple reliefs on a drill, but he must first determine the proper multiple reliefs required for a particular diameter drill. It willbe appreciated that, under such conditions, the reject rate is generally quite high.
Accordingly, it is an object of the present invention to provide an improved method of accurately grinding a characterizcd point geometry on a drill. Other objects and advantages of the present invention will be made more apparent hereinafter.
BRIEF DESCRIPTION OF THE DRAWING `For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings in which:
FIG. I is a perspective view of a grinding apparatus capable of carrying out the method of this invention;
FIG. 2 is a top plan view of the grinding apparatus of FIG. 1, generally illustrating its construction;
FIG. 3 is a partial front plan view of the grinding apparatus of FIG. l;
FIG. 4 is a side plan view of the drill chuck of the grinding apparatus;
FIG. `5 is an end plan view of the drill chuck, as illustrated in FIG. 4;
FIG. 6 is a partial side plan view of the grinding apparatus, generally illustrating the slide assemblies for the drill chuck and the manner in which the grinding wheel thereof is angularly positioned;
FIG. 7 is a perspective view, generally illustrating one test position of the drill to be ground;
FIG. 8 is a diagrammatic top view of the grinding apparatus, generally illustrating the manner in which its drill chuck is angularly pivotally positioned to locate the drill for a second test;
FIG. 9 is another perspective view like FIG. 7, generally illustrating the manner in which the drill is located in a second position;
FIG. 10 is a diagrammatic top view of the grinding apparatus, generally illustrating its drill chuck in its initial position prior to grinding a cutting lip on a drill;
FIG. 10A is a partial perspective view, generally illustrating the manner in which the drill initially is engaged with the grinding wheel of the grind apparatus;
FIG. ll is a diagrammatic top view of the grinding apparatus, illustrating the drill chuck just prior to the time that the cam follower of the apparatus is operated to rotate the drill;
FIG. 1l A is a partial perspective view, generally illustrating the position of the drill with respect to the grinding wheel when the drill chuck is positioned as illustrated in FIG. 1l;
FIG. l2 is a diagrammatic top view like FIG. l1, illustrating the position of the drill chuck at the end of a grinding operation; and
FIG. 12A is a partial perspective view, generally illustrating the position of the drill with respect to the grinding wheel when the drill chuck is positioned as .illustrated in FIG. l2.
Similar reference characters refer to similar parts throughout the several views of the drawings.
DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, in FIG. l there is illustrated a drill grinding apparatus 10 exemplary of the invention including, as its principal components, a grinding wheel l1, a diamond dresser l2, and a drill chuck 13, each of which is supported upon the top surface 15 of a cabinet I6. The drill chuck 13 or equivalent drill holder is adapted to be manipulated, in a fashion fully described below, to grind a drill such as the drill 14 so as to provide thereon a cutting point of the type fully described and claimed in said U.S. Pat. No. 3,443,459. The apparatus l0 can be used to provide both conical or cylindrical reliefs on a drill. In most cases, however, a conical relief is preferred since a more uniform relief angle can be provided. Accordingly, the apparatus is shown and described as it is set up to provide a conical relief.
The reference point for the apparatus l0 is a reference line generated by the tip of the diamond 17 of the diamond dresser l2, and all of the components of the apparatus 10 and all rneasurement use this line for three dimensional reference, as explained more fully below. This line is generally indicated by the reference numeral 18 in the drawings.
The grind wheel l1 is affixed to and driven by motor means 19, which can be an electric motor, and the latter is adjustably pivotally supported by a pivot support structure 20, in a fashion such that the longitudinal axis 2l of the grinding wheel l1 and the motor means 19 is disposed perpendicular to the line 18, as illustrated in FIG. 2. The motor means 19 furthermore is pivotally adjustable in a fashion such that the angle a between the face of the grinding wheel ll and the vertical plane of the scribed line 18 can be angularly adjusted, as indicated in FIG. 6. Since the pivot pin 5l, as described below, is vertically disposed, the conical relief :angle ground on a drill is established by the angle a, and the relief angle, in turn, is dependent upon the drill size and the particular material to be drilled. A grinding wheel, as opposed to another type of grinding surface such as a grinding belt, is preferred because of the ease with which it can be rotated, angularly, adjusted and refaced, however, other grinding surfaces can be used so long as they are adapted to function in the described fashion.
The diamond dresser l2 is frxedly supported upon a support pedestal 24, and includes a mounting block 25 supporting its diamond 17. This mounting block 25 is fixedly secured to a guide 27 which is adapted to slidably move the mounting block 25 and hence the diamond 17, along the reference line I8, to re-face the grinding wheel l1, as illustrated in FIG. 3. The grinding wheel ll preferably is re-faced after each of the cutting lips and/or multiple reliefs is ground on a drill so that the exact reference line is established before each grinding operation. If the grinding wheel is permitted to wear, it will be appreciated that the relationship between each of the multiple reliefs will vary since extremely close tolerances are involved. The pivot support structure 20 is slidably mounted for adjustment along axis 27, to position the grinding wheel ll with respect to the diamond dressor 12 so that it can be refaced, as seen in FIG. 6. A threaded adjustment screw 26 which can be threadedly adjusted to adjust the position of the grinding wheel 1l in a micrometer-like fashion preferably is provided for this purpose, so that the grinding wheel can be positioned to remove the least amount of material possible while re-facing it.
The drill chuck 13 or drill holder, which preferably is a Jacobs rubber flex segmented collet, in combination with an Erickson true flexure collet is affixed to a multiple slide assembly 28 including adjustable slides 29-32 which are individually slidably adjustable to fixedly position the drill 14 with respect to the grinding wheel 11 to grind the above-mentioned cutting lips and multiple reliefs on it. Each of these slides 29-32 is generally of like construction and is of the type generally well-known in the art including an inner slide member 33 which is slidably retained within an outer slide member 36, as best seen in FIG. 3. Caged bearing assemblies (not shown) of the type manufactured by The Fafnir Company of New Britain, Connecticut generally are disposed between the matingly beveled side walls 34 and 35 of the slide members 33 and 36, respectively, and generally a wall portion like the wall portion 37 of the slide member 36 is adapted to be adjustably positioned to align the slide member 33 for straight-line movement.
In the illustrated embodiment the inner slide member 33 of the slide 29 is fixedly secured to the top surface 15 of the cabinet 16, with its longitudinal axis perpendicularly disposed to the scribed line 18. As seen in FIG. l, the slide member 36 of the slide 29 has a threaded screw 40 affixed within a correspondingly threaded bore 41 formed in it, which screw is extended through and fixedly rotatably retained within an aperture (not shown) in a wall 42 about the top surface 15 of the cabinet 16. A wheel 43 is affixed to its end, and by turning the wheel 43, the screw 40 can be threaded into or out of the bore 41 to longitudinally position the slide member 36 with respect to the slide member 33. The location of member 36 of slide 29 is used to adjustably position the slide assembly 28, to set the radius which the drill chuck 13 swings about a pivot point 50, with respect to the reference line 18, in a manner and for reasons set forth more fully below.
The slide member 33 of the slide 30 is fixedly secured atop the slide member 36 of the slide 29 so as to be perpendicularly disposed with respect to it, as can be best seen in FIG. 6. Its slide member 36, therefore, moves longitudinally, parallel to the scribed line 18.
A quadrant plate 45 which has a shape generally corresponding to one quadrant of a circle is fixedly secured atop type threaded screw 68 affixed to it, for adjustably positioning it. A gauge 69 also is provided for determining the degree to which it has been longitudinally displaced. This micrometertype adjustment and gauge is provided since the slide 31 is used to adjustably position the centerline of the drill 14 from the pivot point 50, (see FIG. 2), and this adjustment generally is quite small in magnitude but yet critical.
The slide member 33 of the slide 32 is affixed to the top of and is perpendicularly disposed to the slide member 36 of the slide 31, as can be best seen in FIG. 5. A drill chuck support 70 is fixedly secured atop the slide member 36 of the slide 32 k and supports the drill chuck 13 in a fashion such that the latter the slide member 36 of the slide 30, as can be best seen in FIGS. l and 6. This quadrant plate has a number of stop pin apertures 46 for receiving an included angle stop pin 44 formed in it, in two spaced-apart rows adjacent its arcuate peripheral edge. A lever arm 47 is pivotally affixed to a pivot pin 48 secured to the top surface 15 ofthe cabinet 16, and has a linkage arm 49 affixed to it and to the quadrant plate 45. The quadrant plate 45 and hence the slide member 36 of the slide 30 to which it is affixed can be slidably positioned, by pivotally swinging the lever arm 47 about the pivot pin 48. A stop 52 (FIGS. 2 and 3) is positioned to be engaged by the slide member 36 of the slide 30, to limit the travel of the quadrant plate 45. The stop 52 also locates the drill chuck 13 with respect to a gauge 60, so that the latter can be used to angularly align the drill supported by the drill chuck 13.
The quadrant plate 45 also supports a pivot pin 51 forming the pivot point and, as can be best seen in FIGS. l3 and 6, this pivot pin 5l has a swing arm 53 fixedly and pivotally secured to it. The swing arm 53 is held in spaced relation to the quadrant plate 45, by means of a pair of spacers 54 and a cam plate 55 which is disposed between them. This cam plate 55 is fixed with respect to the swing arm 53 and has a cam surface 56 (FIG. 2) of a predetermined configuration which is engaged by a cam follower 57. The cam follower 57 is slidably supported within a pair of guides 6l (FIG. 4) secured beneath the swing arm 53, and is coupled to a back plate 62 for rotating the latter in a manner described below, by means of a linkage assembly including linkage arms 63-65.
The slide members 33 of the slide 31, as can be best seen in FIGS. 1, 4 and 6, is fixedly secured atop the swing arm 53 and is perpendicularly disposed with respect to its longitudinal axis. The slide member 36 of the slide 31 has a micrometercan be adjustably positioned along the longitudinal center line of the slide 32. A lever arm 71 is coupled to a cam assembly 72 and is manually operable by an operator to adjustably position the drill chuck 13.
The drill chuck 13 is affixed to a drill chuck shaft 75 which is rotatably supported by the drill chuck support 70. A lock plate 74 is adapted to be fixedly secured to the end of the drill chuck shaft 75, by means of a set screw 87. This lock plate 74 is in face-to-face sliding contact with the back plate 62, and has a number of locating apertures 76 (see FIG. 6) in it for receiving the end of a positioning lock 77 affixed to the back plate 62. Each of these locating apertures 76 is appropriately marked on the peripheral edge of the lock plate 74, by indexing indicia 88 which may be scribed lines, as illustrated in FIG. l. The back plate 62 has a reference index 89 which may be a scribed arrow as illustrated provided on it in cooperative relationship with the indexing indicia 88, for indexing the lock plate 74, in a manner described below. The lock plate 74 can be rotated by operating the handle 78 of the positioning lock 77 approximately 90, which action retracts and releases the end of the positioning lock from a locating aperture 76. The lock plate 74 then can be rotated and the positioning lock 77 returned to again lockingly engage its end in another one of the locating apertures. The locating apertures 76 are used to angularly position the drill 14 to grind the multiple reliefs on it. In addition, when the back plate 62 is lockingly affixed to the lock plate 74, by the positioning lock 77, the drill chuck 13 is rotated through the movement of the cam plate 55, the cam follower 57, the linkage assembly including linkage arms 63-65, the back plate 62, and the lock plate 74 to rotate the drill 14 to generate the cutting edge on it, in a manner more fully described below.
The drill chuck 13 further is supported atop the cabinet 16 at a height such that its longitudinal axis or centerline is at the exact height of the reference line 18, as can be best seen in FIG. 1. The longitudinal axis or centerline of the drill 14, therefore, also is at the exact height of the reference line 18. As explained more fully below, the drill 14 must be properly angularly positioned about its own axis before grinding it, and
the gauge 60 is provided for this purpose. The gauge 60 is affixed tothe end of a support arm 81 which is pivotally affixed to a support pedestal 82. A stop 83 is aixed to the support pedestal 82 and is engaged by the support arm 81 as the latter is pivotally operated, to locate the tip of the gauges indicator spindle 85 at the intersection point of the drill chucks longitudinal axis and the reference line 18, as can be best seen in FIGS. 1 and 6. The support arm 81 also is arranged to be pivoted rearwardly against a stop 84, to position it out of the way when not in use. l
Now that the construction of the grinding apparatus has been described, the manner in which a drill 14 is located and aligned in the drill chuck 13 and the manner in which the latter is manipulated to grind the cutting lips and the multiple reliefs on the drill can be described. In setting up the grinding apparatus 10, the size of the drill, the particular material to be drilled with it, the settings for the various slides 29-32 and the grinding wheel 11, and the cam plate 55, needed to provide the proper cutting lips and multiple reliefs on the drill, is determined. This information advantageously can be predetermined and prepared in table form so that it can be easily and quickly determined by merely referring to the table. The
lever arm 47 then is operated to slidably position the slide u member 36 of the slide 30 against the stop 52. This positions the drill chuck 13 with respect to the gauge 60, so that the j latter can be used to angularly or rotatably position the drill which is to be ground.
Next, the slides 29 and 31 are positionally adjusted, in accordance with the predetermined settings, to establish the the` cutting lips to join with the drill diameter in an appropriate `predetermined relationship. The slides 29 and 31 are posi- `tionally adjusted by rotating the wheel 43 and the knob 67,
respectively. An indicator 90, shown in FIG. 2, can be affixed to the movable slide member 36 of the slide 29 and adapted to cooperate with an appropriately calibrated scale 91 on the top surface of the cabinet 16, to set the slide 29. The slide 31 is properly positioned, by means of the gauge 69 which is adapted to indicate its setting or location.
A drill such as the drill 14 now is loosely placed within the dr`ill chuck 13, and the support arm 81 is pivotally operated to position the gauge 60 in its test position, as illustrated inFlG. 6. As indicated above, the angular or rotational positioning of the drill in the drill chuck 13 prior to grinding it is critical and, in order to properly grind it, the drill must be located within a 5 tolerance. The angular or rotational positioning of the drill is accomplished by reference to its flute profile shape and its web thickness, since the geometry of a drill, other than a spade drill, is a continuous series of varying curves and normally each drill is slightly different in view of a manufacturers inability to maintain exact dimensions. This is illustrated in FIGS. 7-9. The lock plate 74 is rotated to align the indexing indicia 88 on it which is appropriately marked to indicate the start of a grinding cycle with the reference index 89 on the back plate 62, and then lockingly coupled to the back plate 62. The drill chuck 13 then is adjusted forward against its stops (not shown), and the drill 14 is extended out of the drill chuck so that the tip of the spindle 92 of the gauge 60 engages the drill just rearwardly of its tip, as indicated in FIG. 7. The least amount possible of the drill tip should extend beyond the tip of thespindle 92, since this is the amount of material which will be removed. The drill 14 then is rotated about its own axis, until a reading, preferably as low as possible, such as 12, as illustrated, is indicated on the gauge 60. The drill chuck 13 now is tightened to securely support the drill. The swing arm 53 next is swung about the pivot pin 51, as illustrated in FIG. 8, to a predetermined angular position indicated by a reference mark which is scribed on the quadrant plate 4S and which is keyed to the cam plate 55 being used. In this position, the cam follower 57 is operated to rotate the drill 14, and the tip of the spindle 92 now is positioned on the flute of the drill at a point substantially corresponding to the point at which the cutting lip of the drill will start to revolve away from the grinding wheel l1 during the grinding thereof. The reading on the gauge 60 is observed, and the drill chuck 13 is rotated, by loosening the set screw 87 and rotating the drill chuck shaft 75, to angularly adjust the position of the drill so that the same arbitrary reading such as 12 is again indicated on the gauge. The drill chuck 13 now is again lockingly coupled to the drill chuck shaft 75, by tightening the set screw 87.
The stop pin 44 next is inserted into a predetermined one of the stop pin apertures 46 to establish the predetermined included angle for the drill to be ground, (as further explained and defined in the aforementioned U.S. Pat. No. 3,443,459), and the swing arm 53 is pivoted or swung about the pivot pin 5 l until it engages against the stop pin 44, as illustrated in FIG. l0. Gauge 60 is positioned out of the way, by pivotally swinging the support arm 81 against the stop 84, and the lever arm 47 is operated to slidably adjust the slide member 36 of the slide 30 against a stop (not shown), in which position, the drill chuck 13 is located or aligned in proper working relationship with the grinding wheel l1.
The grinding wheel 11 is adjusted to establish the predetermined angle a required to grind the required relief or reliefs on the drill 14. Motor means 19 is energized to rotate the grinding wheel 11, and a lubricant is splashed onto the surface of the grinding wheel, in an appropriate manner.
The drill chuck 13 is now advanced to engage the drill 14 with the grinding wheel 11, by operating the lever arm 71, as generally illustrated in FIGS. 10 and 10A. The drill chuck 13 can be advanced until the slide member 36 of the slide 32 engages its stops, or several passes can be made and the drill chuck 13 advanced during each pass until the slide member 36 does engage its stops. The swing arm 53 is pivotally operated, about the pivot pin 5l, to grind the cutting lip on one flute of the drill, generally as illustrated in FIGS. ll and 11A. The cam follower 57 affixed beneath the swing arm 53 engages the cam plate 55, and when the swing arm 53 is in the position illustrated in FIG. ll, the cam follower 57 operates the linkage arms 63-65 in a fashion such as to cause the back plate 62 to rotate, as the swing arm 53 is pivoted against its stops, in the position illustrated in FIG. l2. The back plate 62, in turn, being dvingly coupled to the lock plate 74, by means of the positioning lock 77, causes the drill chuck 13 to rotate. By rotating the drill 14 in this described fashion, is cutting edge is maintained in proper engagement with the grinding wheel 11, or the reference line 18, to provide the required relief on it.
The positioning lock 77 now is operated to disengage its end from the locating aperture 76, the locking plate 74 is rotated and the positioning lock is returned so as to again engage its end within another one of the locating apertures 76. As indicated above, these locating apertures 76 are appropriately marked with the indexing indicia 88 so that the proper one can be easily and quickly ascertained. Thereafter, the drill chuck 13 is manipulated in the same fashion to provide the desired cutting lip on the opposite or other flute of the drill 14.
lf the multiple reliefs of the type disclosed in the abovementioned U.S. Pat. No. 3,443,459 are to be provided on the drill 14, the positioning lock 77 is again disengaged and the locking plate 74 is rotatably adjusted until the reference index 89 on the back plate 62 is properly aligned with the appropriately marked one of the indexing indicia 88 on the locking plate 74. The positioning lock 77 is released to lockingly couple the locking plate 74 to the back plate 62, and the drill chuck 13 again is manipulated in the above-described fashion, to provide the additional relief on the one cutting lip. By indexing the locking plate 180, the additional relief is provided on the other one of the cutting lips.
Additional reliefs are provided on the cutting lips, by positionally rotating the locking plate 74 to align its appropriately marked indexing indicia 88 with the index 89 on the back plate 62, and by then manipulating the drill chuck 13 in the described fashion. During each operation, the locking plate 74 is indexed 180 to provide the desired relief on each of its opposite cutting lips. Also, as indicated above, if necessary, the grinding wheel l1 is faced after each ofthe cutting lips and reliefs is ground on the drill 14. Experience, however, has shown that a complete drill generally can be ground without refacing the grinding wheel.
It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are eiciently attained and, since certain changes may be made in the above method without departing from` the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention, which, as a matter of language, might be said to fall therebetween.
Now that the invention has been described, what is claimed as new and desired to be secured by Letters Patent is:
1. A method of grinding a cutting lip on a drill comprising the steps of (a) supporting said drill in a horizontal plane y which passes through a reference line, (b) advancing said drill in said horizontal plane to engage the cutting end thereof with a flat grinding surface, the plane of said grinding surface passing through said reference line and being at an angle from a vertical plane passing through said reference line to provide a relief angle on said drill, (c) pivotally translating said drill within said horizontal plane about a vertical pivot axis spaced from the axis of said drill with said cutting end engaging said flat grinding surface, while (d) simultaneously rotating said drill about its axis to maintain said cutting edge coincident with said reference line and in engagement with said flat grinding surface to grind a cutting lip thereon.
2. The method of claim l wherein said drill is pivotally translated in said horizontal plane between predetermined angular positions relative to said reference line which establish the predetermined included angle for the drill being ground.
3. The method of claim 1 which further includes the step of indexing said drill about its axis by a predetermined angle and again repeating said steps (b) through (d) to grind a second relief angle on said cutting lip.
4. A method of grinding a cutting lip on a drill comprising the steps of (a) lsupporting said drill in a first plane which passes through a reference line, (b) advancing said drill in said first plane to engage the cutting end thereof with a flat grinding surface, the plane of said grinding surface passing through said reference line at an angle other than normal to said first plane to provide a relief angle on said drill, (c) pivotally translating said drill within said first plane about a pivot axis spaced from the axis of said drill with said cutting end passing said flat grinding surface, while (d) simultaneously rotating said drill about its axis to maintain said cutting edge coincident with said reference line and in engagement with said flat grinding surface to grind a cutting lip thereon.
5. The method of claim 4 wherein said drill is pivotally translated within said first plane between predetermined angular positions relative to said reference line which establish the predetermined included angle for the drill being ground.
6. The method of claim 4 which further includes the step of indexing said drill about its axis by a predetermined angle and again repeating said steps (b) through (d) to grind a second relief angle on said cutting lip.
fggo' UNITED STATES PATENT OFFICE CERTIFICATE OF CQRRECTIQN patera; No. 3,656.2@ -Ded @gil 18. 1972 Inventor-(s) BRUCLE. A. IIVIAGPCEY,l Jr; et all It is vcertified tht error appears in the above-identified petent andA that said Letters Patent are lhereby corrected as shown below:
' Signqjfand' eared :wig 8th'V ay' 1 of'zmgl'istr 1972..
(SEA-L) @WS-P Eux/A3D .'M-.LETCHlRJm RoBERc VGQTTSGHALK l All-,testing Officer f Commissioner of Patents'