US2663126A

US2663126A - Apparatus for sharpening drills

Info

Publication number: US2663126A
Application number: US183336A
Authority: US
Inventors: Amiet Oscar
Original assignee: Individual
Current assignee: Individual
Priority date: 1950-06-02
Filing date: 1950-09-06
Publication date: 1953-12-22
Anticipated expiration: 1970-12-22

Description

Dec. 22, 1953 .0. AMIET 2,663,126

APPARATUS FOR SHARPENING DRILLS Filed Sept. 6, 1950 3 Sheets-Sheet 1 FIG. 1

INVENTOR 05cm" Am/et ATTORNEY Dec. 22, 1953 Filed Sept. 6, 1950 3 Sheets-Sheet 2 lN-VENTOF? Oscar Ami-6f We ATTORNEY Dec. 22, 1953 I o. AMIET 2,663,126

APPARATUS FOR SHARPENI'NG DRILLS Filed Sept. 6, 1950 3 Sheets-Sheet 3 FIG. 16

INVENTOR 03(0) Amie? ,4 TTGRNE) Patented Dec. 22, 1953 UNITED STATES PATENT OFFICE 2,663,126 APPARATUS FOR SHARPENIN G DRILLS Oscar Amiet, La Chaux de Fonds, Switzerland Application September 6, 1950, Serial No. 183,336

. Claims priority, application Switzerland June 2, 1950 12 Claims. (Cl. 51-219) The present invention relates to apparatus for sharpening drills and is particularly applicable to sharpening twist drills by grinding them on four distinct faces.

It is an object of the present invention to provide drill-sharpening apparatus in which the drill can be positioned quickly and is held firmly and accurately so that the surface will be ground precisely as intended. A further feature of the invention is that, after one face has been ground, the drill can be accurately and quickly re-positioned so as to grind another face in exact predetermined relation to the face first ground. The apparatus in accordance with the invention is characterized by the cooperation of a chuck that holds the drill by its shank and a centering arrangement which grips the drill in the immediate vicinity of the end to be sharpened.

Further objects, features and characteristics of the apparatus in accordance with the invention will be understood from the following description and the accompanying drawings in which:

Fig. 1 is a View, partly in front elevation and partly in section, of apparatus embodying the invention.

Fig. 2 is a plan with certain parts shown in section.

Fig. 3 is a diagrammatic plan of a gauge portion for use in positioning a drill in the chucks.

Fig. 4 is an end view of a drill showing the faces to be ground.

Fig. 5 is a side elevation taken from the right side of Fig. 1.

Fig. 6 is a partial elevation as viewed from the left side of Fig. 1.

Fig. 7 is an elevation of a clamping element which holds the drill in the immediate vicinity of the end to be sharpened.

Fig. 8 is a plan of the part shown in Fig. 7.

Fig. 9 is a plan of a sleeve which receives the part shown in Figs. 7 and 8.

Fig. 10 is an end view from the left of Fig. 9.

Fig. 11 is an elevation showing the parts of Figs. '7 to 10 assembled, together with associated parts.

Fig. 12 is an end view from the left of Fig. 11.

Fig. 13 is an elevation of an element for trueing the grinding wheel.

Fig. 14 is an enlarged side view of the chuck and its support, with portions shown in section.

Fig. 15 is a section approximately on the line XVXV of Fig. 14.

Fig. 16 is a profile view taken from the left side of Fig. 1.

Fig. 17 is a perspective view of a detail of the chuck and its support.

The embodiment of the invention illustrated in the drawings comprises a rotating cup-shaped grindstone l mounted on a frame 2, suitable means being provided for driving the grindstone. The drill 3 that is to be sharpened is held in predetermined position on the grinding wheel i by means of a chuck 4 which grips the drill by its shank and a positioning device 5 which engages the drill in the immediate vicinity of the end to be sharpened. The chuck 4 is pivotally supported by an arm 8 so as to swing about an axis 1a which lies in the plane of the drawing (Fig. 2) and is perpendicular to the longitudinal axis 1 of the chuck and also to swing about an axis 7b which isperpendicular to the longitudinal axis of the chuck and also to the axis la. The two axes are thus perpendicular to each other and perpendicular to the axis 1 of the chuck. The pivotal axis 7a permits the chuck to be swung .up to a position in which it is substantially vertical for the purpose of inserting and positioning a drill in the chuck, as described below. The pivotal axis 1b permits the chuck to be swung in a horizontal plane, as indicated by the arrow 6. The arm 8 that carries the chuck is in turn mounted on a supporting element 9 which is in the form of a circular arc and is calibrated with a scale iii expressed in degrees.

Adjacent the outer end of the arm 8, there is an upwardly projecting column I! which carries a laterally projecting gauge block 12 having an L-shaped portion comprising an edge 12a parallel to the axis la and an edge [2b which is parallel to the axis of the chuck when the latter is in its horizontal position. The gauge block 12 is mounted above the chuck in such position that, when the chuck is swung up to its vertical position, the end portion of the drill 3 is received in the L-shaped portion of the gauge block, as illustrated in Fig. 3. A magnifying glass [3 is mounted on the column 1 l above the gauge block 12 in such position that the gauge block and the end of the drill can be viewed with magnification. A cross-piece at the upper end of the column I I also supports an abutment M which has a downwardly-opening conical recess Ma and is slidably mounted so that it can be raised against the bias of a spring Mb. This abutment is adapted to engage the point of a drill for the purpose of positioning it axially with respect to the chuck :3 when the chuck is swung about'the axis 1a to an approximately vertical position.

The arcuate supporting member 9 (Fig. 2) that carries the chuck i is slidably mounted on a supporting assembly that provides angular movement about a plurality of different axes as well as translational movement. The supporting assembly comprises an L-shaped bracket member is which is supported on a stub shaft It by means of a rotatable screw member H. "The shaft It is supported. by the frame 2 of the apparatus and is normally stationary although it may be moved in an axial direction or angularly about its axis for adjustment. The screw 1'! has an intermediate threaded portion that is received .in .a correspondingly threaded bore extend ng transversely through anenlargedhead portion Hiaon the shaft l8. At the opposite ends of the. threaded portion, the screw I1 is provided with bearing surfaces comprising a conical end portion 18 and a frustoconical shoulder 18a. The

screw can be turned by means of a non-circular shank portion il'a'(Fig.'6). The bracket member l5 (Figs. 1 and 6) has a laterally project ng stirrup portion its having downwardly projecting leg portions tile and Nib which straddle the shaft It and have bearings that receive the bearing portions is, lea of the screw I! so that the bracket is supported by the screw. Thus, the leg portion 55a has a conical hole to receive the conical shoulder portion [8a of the screw while the other leg b has a threadedholefor a screw it which has in its inner end a conical recess "to receive the conical end It of the screw ll. I-ience, rotation of the screw I! in the threaded hole of the shaft it moves the support I5 toward and away from the grinding stone l in a direction parallel to the axis of rotation of the stone. A blocking screw 2i (Figs. 1 and 6) serves to block the screw ll against rotation when the desired adjustment has been made. It will further be seen that the support 15 is swingabl'e about the axis ll of the screw llby means of the bearing portions i8, Ida and the corresponding bearing portions of the bracket stirrup 150. The angular movement of the bracket member H3 in a counterclockwise direction, as viewed in Fig. 1, is adjustably limited by a screw 6'5 which is threaded through the shaft It and is adapted to engage the under side of the stirrup portion IEc of the bracket.

A turret 2&3 (Figs. 1, 2 and 5) is rotatably supported in an opening of the upwardly projecting bracket member 55 by means of a ball-bearing 2'? A friction plate'lil, which is fast to the turret 26 by two screws "ii and an adjustable screw 12, is pressed against the supporting bracket l5 by barrel springs 53 surrounding the screws ll so as to hold the turret frictionally in any position to which it is turned. The adjustable clamping screw it is threaded into the friction plate it! and extends through the turret, its outer end being provided with a handle 12a for rotating the screw.

The arcuate member 9 that carries the chuck :l is slidably mounted on the turret 2-6 (Figs. 1, 2 and 5) so as to slide lengthwise, i. e. arcuately, on the turret. The position of the arcuate slide 9 relative to the turret may be read on the scale it. The slide 9 is held in adjusted position by means of bolts 'M which have end portions Ma (Fig. l) engaging in an undercut groove in the slide.

The support :5 carries three

adjustable abutnients

22, 23 and 24 (Fig. 5) which cooperate with a protuberance 25 on the turret 26 to limit the angular movement of the turret. The n l movement is measured by means of a graduated scale 28 (Fig. 2). The abutment 24 is carried by a block 29 which is pivotally mounted on the supporting bracket It by means of a pin to to which it is secured; said pin rotates in a sleeve 5| (Fig. l) threaded in the support iii. The

pivotal axis of the block 23 intersects the vertical axis 43 shown in Fig. 5 and is perpendicular to this axis and the plane of the paper. By swing- .ing the block: 253 about its pivot, the abutment it is able to occupy the position in which it is shown in Fig.5 or, alternatively, a position symmetrical relative to the vertical axis 553. When the abutment 2 is in the position shown in Fig. 5, the

' turret Etna-n rotate through an arc limited. by

right hand drills or left hand drills. The adjustability of the

abutments

22, 23 and makes it possible to modify the angle of attack of the grindstone on the drill. The two positions of the abutment 2 are determined by a pin '52 (Fig. 1) provided on the under side of the block 29 and adapted to engage in one or another of two holes 62; in the support it under action of a spring as which acts between an inner shoulder of the sleeve iii and the head of a screw Eda threaded into the stem 59 to hold the block 29 resiliently against the outer face of the support iii.

The clamp 5 for holding the drill adjacent the end to be sharpened is also carried by the turret it, as shown in Figs. 1, 2, .5 and 6. The detailed construction of the clamp is shown in Figs. '7 to 12. The clamp comprises two jaws 3i formed inteagrally with a U-shaped piece Sic, the branches am, one being designated id and the other 15.

The plane surfaces as are adapted to engage, and cooperate with, the edges is (Fig. 10) of the projections 36b and the when the member 35a is introduced into the sleeve 3t. An axial displacement of the member 31a in the direction of the arrow 15 (Fig. 11) thus brings about a clamping movement of the two jaws toward one another. Simultaneously, the plane surfaces 35 of the jaws both engage, and cooperate with, the edge i? of the projection 36a to produce a displacement of the jaws laterally in the direction of the arrow 58. In this way, the more the jaws are tightened, the more they are displaced upwardly, as viewed inFig. .11, .i. e. the more closely do they approach the grindstone Thus, by reason of this arrangement, the drill is seized at the base of its conical end portion regardless of its diameter since, when the jaws are clamped more closely together to seize a small diameter drill, they are correspondingly closer to the face of the grindstone. The axial displacement of the piece 3m A saddle 33 (Figs. 11 and 12) pivoted at 34 on the sleeve 36 rests with its free end astraddle the two jaws 3!. The saddle rests on plane surfaces 65 of the jaws which are inclined relative to the axis of the clamp in such manner that the saddle is displaced in the direction of the arrow (Fig. 11) according to whether the jaws are spaced a greater or a lesser distance from one another. A spring 35 (Fig. 6) acts on the saddle 33 to press it against the jaws. The saddle 33 serves as an abutment for the drill 3 and prevents it from being displaced too far to the right, as viewed in Fig. 11. The smaller the cross-section of the drill, the more the jaws of the clamp are moved toward the right in Fig. 11 by the nut 49 and push the pivoted saddle 33 upwardly, as viewed in this figure. Hence, the saddle 33 always bears on the end of the drill in the immediate vicinity of the conical portion.

The details of construction of the chuck d are shown more fully in Figs. 14 and 15. The chuck 4 has an elongated tubular stem portion zla which is slidable and rotatable in a sleeve 5|. At one end, the sleeve 5! is slotted, as indicated at 52 (Figs. 14 and 17) so as to be contractible and terminates in a conical portion 53. At the opposite end, the sleeve 5! has an outwardly projecting flange or shoulder am. A knurled nut 54 screws on to a correspondingly threaded portion of the sleeve 5i and has a tapered portion that cooperates with the conical part 53 of the sleeve to contract the slotted end portion of the sleeve and thereby lock the stem dc of the chuck in the sleeve when the nut 54 is tightened. The sleeve 5| is in turn mounted to slide in a tubular support 55 which, at the right hand end as viewed in Figs. 14 and 17, has two diametrically opp-osite spurs 55a adapted to fit into a diametrical slot 56 in the shoulder 5E0; provided at the end of the sleeve 5| Axial displacement of the chuck d and sleeve Ed in the direction of the arrow El (Fig. 14) against the force or" a return spring 58 acting between an inner shoulder of the nut is and the tubular support 55 disengages the spurs 55a from the slot 56 and permits rotation of the chuck 4 and sleeve 5! relative to the sleeve Upon release of the chuck after a rotation of 180", the spurs 5511 again enter the slot 58. Hence, the chuck can be turned 180 and then again locked in its new position. A knurled nut 59, which screws on the supporting sleeve 55, bears against the shoulder sic of the sleeve 5| to provide a fine adjustment of the axial position of the chuck relative to the sleeve 55. The support 55 is pivotally mounted on the arm 8, as described above, for pivotal movement about the axes la and lb.

The method of operation of the apparatus is as follows: The drill is placed in the chuck t and the latter is then adjusted and swung upwardly about the axis la (Fig. 2) into alignment with the abutment is (Fig. 5). The drill is thereupon adjusted axially until its end engages the recess I ia in the abutment and the nut 54 is tightened slightly. The axial position of the drill is then correct. Since the abutment Is is mounted elastically in its support, it can be displaced axially, thereby liberating the drill. The drill is then swung into engagement with the positioning block l2 and is rotated until it occupies the angular position shown in Fig. 3. The correct position of the drill can be readily ascertained by means of the magnifying glass it. The nut 54 is then looked tightly. As the result of these two operations, the axial and angular positions of the drill are determined.

The chuck 4 is then brought into a substantially horizontal plane and the drill is clamped between the jaws 3!. The end of the drill is then exactly in the plane of the grindstone. Rotation of the nut 59 (Fig. 14) advances the chuck by the amount that it is desired to sharpen the drill. An oscillatory movement of the supporting member i5 about the axis at of the screw ll in the direction of the arrow 3? (Fig. l) to the extent permitted by the adjustable screw til brings the drill into contact with the grindstone in position to grind one of the faces as (Fig. 4) of the point or" the drill. The sleeve 26 is displaced angularly to the extent permitted by the stop 23 to grind the face 39 of the point of the drill. The dihedral angle formed by the

faces

38 and 39 of the drill point corresponds with the angle through which the turret 25 has been rotated and is determined by the position of abutments 23 and 2:3. This angle can be read on the graduations 28.

Upon completion of these operations, the chuck is rotated about its axis l in the manner described above. The two sharpening operations are then repeated to grind the faces 38a and 853a of the point of the drill.

Displacement of the arcuate support 9 in the direction of the arrow 4! (Fig. 2) which is measured on the scale it makes it possible to modify the angle between the axis 1 of the drill and the plane of the grindstone.

The face of the grindstone is maintained plane by means of a diamond point 58 mounted on a support 69 designed to take the place of the jaws in the sleeve 35. The depth to which this diamond point bites into the grindstone is determined by adjustment of the screw i1 which, as described above, moves the supporting bracket 15 toward or away from the grindstone. The disposition of the chisel in the sleeve 35 assures its exact position, i. e. a position in which its point is on the axis 32. This assures that, during the sharpening of the drill, the point of the drill is formed exactly in its center.

The apparatus in accordance with the invention has many advantages. By seeing that the screw 11 is not rotated after the grindstone has been corrected by the diamond point 53, the operator can be sure that the drill will occupy the same position as the diamond point. The centering of the drill is highly accurate and so is the sharpening. Drills of different diameter can be sharpened one after the other Very rapidly without any adjustment being necessary between them. It should be noted that this apparatus is particularly suitable for sharpening drills of small cross-section, for example of a diameter up to 0.30 millimeter. A Wide range of drills, for example from 1 to 6 mm. in diameter, can be sharpened without changing the accessories (chuck, clamp, etc.)

It will be understood that the embodiment of the invention shown in the drawings and speciflcally described is merely by way of example and that modifications may be made within the scope of the appended claims. For example, it would be possible to work on the cylindrical face of a grindstone instead of a flat end face. It would also be possible for the clamp 5 to be mounted on the piece 9 instead of directly on the turret 26. The apparatus can be used for sharpening fiat drills and for sharpening drills otherwise than on four faces, as shown. Still 7 other modifications will be apparent to those skilled in the art.

What I claim and desire to secure by Letters Patent is:

i. In an apparatus for sharpening drills, especially for grinding them on four distinct faces, a positioning means for the rear part of the drill and a centering lll ans for its front extremity, means for supporting said positioning and centerin means, said centering means comprising a fixed member, two jaws movable relative to one another and a movable abutment which operate simultaneously, said jaws being movable relative to said abutment and having inclined faces enga g said member and inclined :faoes engag c said abutment to move the jaws .andthe abutment towards the-point of the drill when said jaws, move toward one another, whereby drills of different sizes are seized in their grinding position, by the two jaws always situated at. the root of the cone constituting their point, on a di meter perpendicular to the plane in which the cutting edges lie, said drills bearing against the movable abutment always by their cylindrical part at the root of one of the cutting edges.

2. In an apparatus for sharpening drills, spe cially for grinding them on four distinct faces, a positioning means for the rear part of the drill comprising a chuclr provided with a tubular extension in which lies a part of the drill and a support pivotally mounted on two axes perpendicular to each other and which extension is introduced and looked after the angular and axial posit-ions of the drill have been determined, a centering means for the front extremity of the drill, and means for supporting said positioning means and centering means, said centering means comprising a fixed member, two jaws movable relative to one another and a movable abutment which operates simultaneously, said jaws being movable relative to said abutment and having inclined faces engaging said fixed member and inclined faces engaging said abutment, to move the jaws and the abutmenttowardsthepoint of the drill when said jaws move towards one another, whereby drills oi different sizes are seized in their grinding position by the two jaws always situated at the root of the cone constituting their point, on a diameter perpendicular to the plane in which the cutting edges lie, said drills bearing against the movable abutment always by their cylindrical part at the root of one of the cutting edges.

3. Apparatus as claimed in claim 2, in which said supporting means comprises on the one hand a split tubular member intended to receive and to lock said extension of the chuck, and on the other hand a sleeve in which is slidably mounted said tubular member, this la ter being provided with a shoulder, a regulating nut screwed on said sleeve and against which abuts said shoulder, a spring bearing on said sleeve and on said tubular member urging to apply said shoulder against said nut, said shoulder being provided with two notches and the extremity of the sleeve showing two lugs entering in said notches when the shoulder abuts against the nut in such a way that the sleeve and the tubular member are then angularly dependent from each other, and that, the lugs being disengaged from the notches after an axial movement of the sleeve and of the tubular member relatively to each other, against the action of the spring, the tubular member can Cir effect a rotation of 180 and the lugs be engaged anew into the notches.

4. In an apparatus for sharpening drills specially for grinding them on four distinct faces, a positioning means for the rear part of the drill comprising a chuck provided with a tubular extension in which lies a part of the drill and a supporting means pivotally mounted on two axes perpendicular to each other and in which said extension is introduced and looked after the angular and axial positions of the drill have been determined, a sliclableabutment situated above said chuck and being provided with a conical seat, a spring holding said abutment in its working position in the axis of which and in the seat of which the drill can be brought, that allows to determine the axial position of .the drill, a square member against which abuts the drill and that allows to determine the angular position of the drill, and a centering means for the front extremity of the drill, this centering means comprising a fixed member, two jaws movable relative to one another and a movable abutment which operate simultaneously, said jaws being movable relative to said abutment and having cam faces cooperating with said fixed member and cam faces cooperating with said abutment, to move the jaws and the abutment toward the point of the drill when the jaws draw near to one another, whereby drills of difierent sizes are seized, in their grinding position, by the two jaws always situated at the root of the cone constituting their point, on a diameter perpendicular to the plane in which lie the cutting edges, said drills bearing against the movable abutment always by their cylindrical part at the root of one of the cutting edges.

5. In an apparatus for sharpening drills specially for grinding them on four faces, a frame, a grinding wheel, a positioning means for the rear part of the drill comprising a chuck provided with a tubular extension in which lies a part or" the drill, and a supporting means pivotally mounted on two axes perpendicular to each other and in which said extension is introduced and looked after the angular and axial positions of the drill have been determined, a centering means for the front extremity of the drill, said centering means comprising a fixed member, two jaws movable relative to one another, and a movable abutment which operate simultaneously, said jaws being movable relative to said abutment and having cam faces cooperating with said member and cam faces cooperating with said abutment, to move the jaws and the abutment towards the point of the drill when the jaws draw near to one another, whereby drills or" different sizes are seized in their grinding position, by the two jaws always situated at the root of the cone constituting their point, on a diameter perpendicular to the plane in which lie the cutting edges, said drills bearing against the movable abutment always by their cylindrical part at the root of one of the cutting edges, and a common support for both said chuck and said centering means, said support being articulated on said frame in such a way that said drill can swing opposite the grinding wheel, the axis of the articulation of said support lying in the plane of the working face of the grinding wheel.

6. In an apparatus as claimed in claim I, a fixed sleeve in which the jaws of the centering means are slidably mounted, the clamping and the .unclamping of said jaws being obtained by means of their axial displacements in said sleeve.

7. In an apparatus as claimed in claim 1, a

fixed sleeve showing edges and in which the jaws of the centering means are slidably mounted, each jaw being provided with two inclined planes cooperating with the edges of said sleeve, one of said inclined planes producing, when the jaws are moved axially in the sleeve, a displacement of the jaw against the other jaw, that is to say the clamping of the jaws, and the other inclined plane, producing a displacement or" the jaw in a direction perpendicular to the first displacement. that is to say towards the point of the drill.

8. In an apparatus as claimed in claim 1, a fixed sleeve in which the jaws of the centering means are slidably mounted, said sleeve showing three right edges situated in a plane perpendicular to its axis, each jaw being provided with two inclined planes, two of these edges cooperating respectively with the first inclined plane of the jaws for producing, when the jaws are moved axially in the sleeve, a displacement of the jaws against one another, that is to say the clamping of the jaws, and the third edge cooperating with the second inclined plane of the jaws for producing a displacement of said jaw in a direction perpendicular to the first displacement, that is to say towards the point of the drill.

9. In an apparatus as claimed in claim 1, a resilient U-shaped member the extremities of the branches of which are provided with said jaws, l

a fixed sleeve in which said U -shaped member is slidably mounted, the clamping and the unclamping of said jaws being obtained by means of their axial displacements in said sleeve.

10. In an apparatus as claimed in claim 1, a resilient U-shaped member the extremities of the branches of which are provided with said jaws, a fixed sleeve in which said U-shaped member is slidably mounted, screw means cooperating with said U-shaped member for allowing it to effect axial displacements in said sleeve, the clamping and the unclamping of said jaws being obtained by means of these axial displacements.

11. In an apparatus as claimed in claim 1, a fixed sleeve in which the jaws of the centering means are slidably mounted, said sleeve showing three right edges situated in a plane 'perpendicular to its axis, each jaw being provided with two inclined planes, two of these edges cooperating respectively with the first inclined plane of the jaws for producing, when the jaws are moved axially in the sleeve, a displacement of the jaws against one another, that is to say the clamping of the jaws, and the third edge cooperating with the second inclined plane of the jaws for producing a displacement of said jaw in a direction perpendicular to the first displacement, that is to r 10 say towards the point of the drill, said movable abutment being articulated on said sleeve, and a spring applying said abutment on the jaws on which it bears.

12. In an apparatus for sharpening drills specially for grinding them on four faces, a frame, a grinding wheel, a positioning means for the rear part of the drill comprising a chuck provided with a tubular extension in which lies a part of the drill, and a supporting means pivotally mounted on two axes perpendicular to each other and in which said extension is introduced and looked after the angular and axial positions of the drill have been determined, a centering means for the front extremityof the drill, said centering means comprising a fixed member, two jaws movable relative to one another, and a movable abutment which operate simultaneously, said jaws being movable relative to said abutment and having cam faces cooperating with said fixed member and cam faces cooperating with said abutment, to move the jaws and the abutment towards the point of the drill when the jaws draw near to one another, whereby drills of different sizes are seized, in their grinding position, by the two jaws always situated at the root of the cone constituting their point, on a diameter perpendicular to the plane in which lie the cutting edges, said drills bearing against the movable abutment "always by their cylindrical part at the root of one of the cutting edges, a common support for both said chuck and said centering means, said support being articulated on said frame in such a way that said drill can swing opposite the grinding wheel, the axis of the articulation of said support lying in the plane of the Working face of the grinding wheel, and three abutments limiting the displacement of said support with respect to said frame, said abutments working by pair, one of them being common to both pairs and being able to occupy two working positions according to the pair to which it belongs.

. OSCAR AMIET.

References Cited in the file of this patent- UNITED STATES PATENTS Raney Nov. 26, 1946