US2017795A - Method and apparatus for forming tubular rivets and the like - Google Patents

Description

, Oct. 15, 1935.-

R. J. FRETER 2,017,795

METHOD AND APPARATUS FOR .FORMING TUBULAR RIVETS AND THE LIKE Filed Nov. 10, 1933 5 Sheets-Sheet 1 11 3 5 Q A w f A x 1' n b w z A TTORNEY Oct. 15,1935.

Filed Nov 10, 1933 R.' J. FRETER METHOD AND APPARATUS FOR FORMING TUBULAR RIVET 5 AND THE LIKE 3 Sheets-Sheet 5 ATTORNEY Patented Oct. 15, 1935 METHOD AND APPARATUS FOR FORMING TUBULAR BIVETS AND THE LIKE Roy J. Freter, Toms River, N. J., assignor to Tack Button Company, Toms River, N. J., a corporation of Delaware Application November 10, 1933, Serial No. 697,523

27 Claims. (Cl. 10-27) S I PATENT OFFICE The present invention relates to an improved method and mechanism for manufacturing tubular rivets, buttons, socketed set screws, cartridge shells, and similar hollow or recessed metal forms by displacement or extrusion of the blank stock, without however altering the external di ameter of the blank, as distinguished from prior methods involving the actual removal of a portion of the stock'by drilling or like operations, and

for forming such articles, when desired with an enlarged, generally flattened head, shoulder, or

bo h.

Extrusion methods have been practical in this art, but with various objections and difliculties,

l5 and at the present time the most difficult thing to overcome in the making of tubular rivets and buttons, particularly, when formed of metal, is

the tendency of the metal to adhere to the tool,

used to form the article.

Accordingly, a principal object of this invention is to provide a practicable and efficient method and apparatus generally simplifying and facilitating manufacture of articles of this type and for overcoming difllculties heretofore encountered of sticking, when the material of the stock freezes or sticks to the forming tool, due to the rapidity at which the articles are formed, without however, in any way sacrificing speed of production.

These rivets are usually made on a heading machine travelling at a speed of 85 to 100 blanks per minute, or better, and the impact of the punch with blank is usually effective through only about 7 of the cycle of operation. That is to say, assuming the punch to be crank driven,

although the crank will rotate through a.complate-360 cycle, the eifective action of the punch driven thereby will occupy approximately 7 of that cycle, adjacent an inner dead center of the 40 crank.

The flow of metal over the driven extruding punch or pin is so fast as to cause it to adhere or freeze thereto, and abrasion naturally follows, sothat the tool is broken either in the shank of the formed article, or the punch is pulled apart by the pulling strain necessary to get it out.

Therefore another object of this invention contemplates a method that will increase the time of dwell, or period during-which the extruding punch is actually operating on the metal, from to or more of the cycle, and a slowing or breaking up of the blow or impact of. the heading ram to an extent that will enable the 55 punching pin to be freed or withdrawn frequently, as the forming or upsetting of the metal takes place, in order to keep the punching pin from freezing or adhering to the flowing metal. Such method does not operate to slow down the numerical production of articles, as the mecha- 5 nism for driving the punch will continue through its same cycle, with the same rate of speed as heretofore but rather operates to distribute the working time of the punch over a greater portion of that cycle, thus slowing down the actual opera- 10 tion of the punch on the work, by reduction of waste motion.

By slightly varying the operating mechanism, and utilizing a cam drive instead of a crank, this period of dwell can be increased as high as 15 Naturally, as the eil'ective working period of the punch is increased, it becomes possible to increase the number of individual blows or impacts between the work and punch, so that instead of the rivet being entirely formed by one, two, or 20 at the most three squeezes, as has been conventional, numerous blows or squeezes may be provided and hence the apparatus of the present invention may be regarded as an eight blow header as distinguished from single, double and 25 triple blow headers heretofore known.

The following description relates particularly to the formation of tubular rivets, but such description is not intended as limiting, as the invention is equally applicable to the manufacture 30 of many other articles of a similar nature.

To the attainment of the above and other objects which will appear as the description proceeds, reference may be made to the accompanying drawings, in which:-- 5

Fig. 1 is a side elevation, partly in section, of a cam driven type of machine;

Fig. 2 is a top plan thereof:

Fig. 3 is a side elevation, partly in section of a crank driven type of machine; 40

Fig. 4 is a face view, partly in section, on the line l4 of Fig. 3;

Figs. 5 and 6, are respectively, side and end elevations of a headed and shouldered form of work which may be produced by the present 4,5 invention;

Fig. 7 is an enlarged detail of the right hand portion of Fig. 1; and

Fig. 8 is an enlarged detail of the right hand portionof Fig. 3. I

The general operation of this invention contemplates treatment of slugs or blanks which are severed from a coil of wire that has been fed from a suitable source of supply in any conventional manner, suitable means being utilized to 55 machine.

I measure and cut the slug therefrom, and thereafter feed same into operating position in the One form of wire feeding, measuring and cutting mechanism, together with means for feeding the severed slug is described in my copending applicationSerial No. 670,767 filed May 12th, 1933. The disclosures of the present application relate to formation of the article from the slug after the slug has heen'accurately positioned in the machine with respect to a heading die and a sliding gate or hunter.

When the slug has been positioned in line with a heading die, a punch or hunter advances under the influence of driven, sliding gate, toward the slug and die, and pushes the slug into a i'ecess in the die .and against the tip of an extruding pin which enters the recess from the rear, and is held stationary therein. The hunter or punch continues its advance movement against the slug, with a longitudinal vibrating motion providing a series of impacts, and causing the metal of the slug to flow over the end of the extruding pin and also swelling the metal in the die. 7

The die is arranged to yield slightly, at each impact, while the extruding pin is rigid, and as the hunter retires slightly after each blow the die will be pushed outwardly tending to release the slug from the extruding pin, this action occurring a number of times for each slug. Subsequently the extruding pin is given a forward motion through the die to eject the blank.

Referring specifically to the drawings, in which like reference numerals designate like parts, there is provided a frame or base II) on which is mounted for reciprocable movement, a sliding gate I I in which is detachably mounted a punch or hunter I2. A shaft. I3, conventionally driven from any source of power (not shown) is supported in bearings I4 and has keyed thereto a cam I5. A cam I5 is relieved over approximately 105 of its contour with a series of progressively arranged points I6, the reliefs being spaced by flat portions I'I, which have the effect of depressions, this cam being located'to engage a cam r011 I8 revolubly mounted in the gate on a shaft I9. It will be observed that rotation of the cam I5 will serve to advance the gate (to the right.

in Fig. 1) with a series of vibratory'movements as the roll I8 contacts first a relief I6 and then a flat I1.

Disposed opposite the hunter I2 is a die 20 formed with an opening therethrough, such die being detachably mounted in the frame I10 by means. of a die block 2|, sleeve 2Ia being secured in position by a suitable set screw 22. Behind the die and in position to yieldingly oppose movementof the die inwardly is a spring 23, the die being shouldered as indicated at 24 to engage the spring. A detachably mounted plate 25 serves to act as a hammering anvil for die 20 and to hold the spring in position.

The spring normally holds the die in slightly spaced relation to the plate. The opening of the posite end at 3! to a link 32, which in turn is connected to the end of a second rocker arm 33 as indicated at 34; The connections at 3| and 34 are adjustable to permit variation in the movements of the respective rocker arms relative to each other. The rocker 33 is pivoted in the frame at 35 and carries on its free end a cam 5 roll 36 adapted to engage a cam 31 on the cam shaft I3.

The operation of the device as thus described will be readily apparent. Wire is fed from coils into the machine by means of a suitable roll 10.

. the slug pushing same into the recess or opening of the die and against the pin 26 which is held 20 stationary by the rockers 29 and 33 as the cam 31 at thistime is idling past the roll 36. The

punch I2 continues its advance movement'under the influence of cam I5, pushing the slug further into the die recess and against the stationary pin, 25 the cutting off mechanism having withdrawn to prevent interference. The advancement of the punch is jerky and vibratory due to the reliefs I6 on the cam I5 and thus in effect the slug is advanced under the influence of a series of blows 3 (one for each relief) from the punch or hunter causing the metal of the slug to flow over the reduced tip 26a and into the space between such tip and the side walls of the'cylindrical opening. There will, of course, be some flow of metal out- 35 wardly in the clearance space between the hunter and die and into mating recesses provided therein, as illustrated, this flow serving to form the head of the rivet.

At each advancement of the punch caused by 40 the high spots I6 on the cam I5, the clearance between the die 20 and the plate 25 is taken up and at the same time the spring 23 is compressed, due to swelling of the metal over the pin and adherence of such metal to the die walls, then as 45 the roll I8'passes the high spot, the spring 23 will push the die forward to its original position, releasing or partially stripping the work W from the extruding pin.

Any suitable means may be used to positively 50 hold the gate against the cam I5 and thus insure a return when the low parts of the cam are reached. The high or working portion of the cam, effective to produce the advance movement of the gate, and the series of impacts occupies 55 approximately to of the cam revolution. As the operating portion of the cam I5 passes the roll I8, the cam 31 will have been rotated to bring a high point 38 against the cam roll 36, and the rocker arms 33 and 29 will be actuated to force 60 the pin 20 through the die, pushing the work in advance of it and out of the die.

If found desirable any conventional form of additional stripping mechanism may be utilized.

In Fig. 3 is illustrated a modified form of ma- 65 chine, in which the sliding gate I I is crank driven with a steady advance motion and an oscillatory or vibratory movement imparted to the pin 26. In this form, a crank 40 is utilized instead of the cam I5 for actuating the gate, the crank being 70 connected by means of the pitman 4| to the shaft I9, thus insuring a positive movement forward and backwardof the gate II. In lieu of the cam 31, a cam 62 having a plurality of reliefs 43 separated by flats 43a, is utilized, the distribution of 75 reliefs occupying about 80 of the cam contour, this cam engaging the roll 36 on the rocker 33.

The punch or bunter 44 is detachably carried in the head of a plunger or ram 45, which plunger is mounted for yielding telescoping movement in the gate I l a spring 46 being provided to effect such yielding movement. The die 41 is fixed in the die block He by means of a set screw 48, and is provided with an enlarged recess 49 behind the cylindrical opening in which the extruding pin 26 in mounted. This recess 49 accommodates a spring 50 having one end abutting the interior of the die and the other end abutting a shouldered cap 5| abutting the plunger".

The operation of the machine in Fig. 3 is quite similar to that previously described with the exception that the gate ll moves smoothly while vibrations are imparted to the pin 26. After each vibratory movement the spring 50 retards or returns, the pin to its starting position, releasing same slightly from the work. The cam 42 will of course be formed with a suitably raised portion indicated generally at 52 to eflect an ejection of the work after completion of operations thereon.

Although the head 45 may reach a position where the punch 44 engages the die 41, before the crank 40 has passed dead center, the yielding; telescoping action permitted by spring 46 will insure a holding of the punch and work against the pin 26 until the extrusion is completed. The crank by this time, having passed its dead center, retracts the gate II and related parts.

In both forms of the invention, it will be seen that considering a cycle of operations in terms of 360 rotation of the shaft I3 that the actual pration on the work by relative movement between the'gate I I and the extruding pin occupies from 80 to 105, depending upon the shape of the cams I5 or 42, the distribution of reliefs thereon and the number of blows on the work, of which, there will be, of course, one for each high point or relief on the cam.

The machine and method are, of course, very flexible and many variations in the operation thereof, to the production of varied types of work, can be produced by variations in the cam. While usually a relatively flat headed tubular rivet is desired it will be evident that the extruding pin can be advanced, retarded, or held stationary to suit desired work conditions, by simply changing the contour of the cam 31 or 42 which operates the rocker arms and plunger 28. In Figs. 5 and 6 there is illustrated a shoulder rivet R having the relatively fiat head 55, the shoulder 56 and the tubular stem 51. This shape of work can be produced by holding the pin stationary in the die for the first part of the heading operation. As this operation continues, the pin may be retarded very slightly to relieve internal strain within the die. A tube or hole in the stem 51 will be formed simultaneously with shoulders 55 and 56.

Having thus described my invention, what-I claim as new and desire to secure by Letters Patent of the United States, is:-

1. The method of forming socketed articles which consists in inserting a slug within a die cavity and against an extruding pin having a portion spaced therein from the die walls, and, while holding said pin stationary, driving said slug against the pin with a series of blows, to extrude the material of the slug progressively into the space between said pin and the walls of the die thereby producing a socketed article.

2. The method of forming socketed articles which consists in inserting a slug within a die cavity and against an extruding pin having a portion spaced therein from the die walls, and, while holding said pin stationary, driving said slug against the pin with a series of blows, to ex- 5 trude the material of the slug progressively into the space between said pin and the walls of the die thereby producing a socketed article, and thereafter advancing said pin and article as a unit to eject the article from the die. 10 3. The method of forming socketed articles which consists in inserting a slug within a die cavity and against an extruding pin having a portion spaced therein from the die walls, and, while retaining said pin from advance movement toward the article, driving said article, against the pin with a series of blows, to extrude the material. of the slug progressively into the space between said pin and the walls of the die thereby producing a socketed article.

4. The method of forming socketed articles which consists in inserting a slug within a die cavity and against an extruding pin having a portion spaced therein from the die walls, and, while retaining said pin from advance movement toward the article, driving said article against the pin with a series of blows, to extrude the material of the slug progressively into the space between said pin and the walls of the die thereby producing a socketed article, and thereafter advancing said pin and article as a unit to eject the article from the die.

' 5. The method of forming socketed articles which consists in inserting a slug within a die cavity and against an extruding pin having a por- 85 tion spaced therein from the die walls, and, while retaining said pin from advance movement toward the slug and simultaneously imparting to said pin a series of oscillatory or vibratory movements longitudinally of the slug, advancing the 40 slug against the pin with a substantially constant movement to cause the material of the slug to extrude progressively into the space between said pin and the walls of the die thereby producing a socketed article.

6. The method of forming socketed articles which consists in inserting a slug within a die cavity and against an extruding pin having a portion spaced therein from the die walls, and, While retaining said pin from advance movement toward the slug and simultaneously imparting to said pin a series of oscillatory or vibratory movements longitudinally of the slug, advancing the slug against thepin with a substantially constant movement to cause the material of the slug to extrude progressively into the space between said pin and the walls of the die thereby producing a socketed article, and thereafter advancing said pin and article as a unit to eject the article from the die.

7. The method of forming tubular articles, which comprises inserting a metallic blank in a reciprocating die, and in engagement with an extruding 'tool therein, extruding the metal of said blank over the tool and out of the die by applying a series of progressively advancing blows to the blank thus producing a series of progressively advanced short flows of metal, feeding the blank relative to the die during the extruding operation and freeing the metal of said blank from the extruding tool after each of said blows, and over a period of at least of the cycle of operation.

8. In the manufacture of tubular articles from a solid blank, the method herein described of forming a central chamber or cavity which con- 75 sists in causing a flow of the material of the blank about a substantially stationary extruding pin by driving the blank against said pin under the in-.

fluence of a series of impacts against the blank, and partially stripping said blank from the pin after each impact.

9. In the manufacture of tubular articles from a solid blank, the method herein described of 10. In the manufacture of tubular articles from a solid blank, the method herein described of forming a central chamber or cavity which consists in causing a flow of the material of the blank about a substantially stationary extruding pin by driving the blank against said pin under the influence of a series of impacts against the blank, and while the blank is confined and supported in a.die, preventing enlargement of the diameter of the blank while directing flow of the metal endwise, and partially stripping said blank from the pin after each impact.

11. The method of forming tubular articles, which consists in inserting a slug within a die cavity and against an extruding pin having a portion spaced therein from the die walls, advancing the slug against the pin with a substantially constant movement, and simultaneously therewith imparting to said pin a series of longitudinal vibratory movements while retaining said pin from additional longitudinal movement, whereby to maintain the material of the slug substantially free of adhesion to the pin during the constant advance movement.

12. The method of forming tubular articles,

which consists in inserting a slug within a. die

cavity and against an extruding pin havinga portion spaced therein from the die walls, advancing the slug against the pin with a substantially constant movement, to extrude the material of the slug into the space between the tool and walls of the die, and simultaneously therewith imparting to saidpin a series of longitudinal vibratory movements while retaining said pin from additional longitudinal movement, whereby terial of the slug into the space between thetool and walls of the die, and simultaneously therewith imparting to said pin a series of longitudinal vibratory movements while retaining said pin from additional longitudinal movement,

whereby to maintain the niaterial of the slug substantially free of adhesion to the pin during the constant advance movement, thereby producing a tubular structure, and thereafter advancing said pin and tubular structure asa. unit thereby to eject said structure fromthe die.

* 14. A machine for forming socketed articles, which comprises a die having a substantially cylindrical cavity therethrough, an extruding pin having a portion extending into said cavity in spaced relation to the walls thereof, the remainder of said cavity being effective to receive a work piece, means for holding said pin stationary within said die, and means for driving 5 the work piece in the cavity against the pin with a series of successive blows thereby to extrude the material of the work piece progressively into the space between said pin and the walls of the cavity to produce a socketed article. 15. A machine for forming socketed articles, which comprises a die having a substantially cylindrical cavity therethrough, an extruding pin having a portion extending into said cavity in spaced relation to the walls thereof, the remainder of said cavity being effective to receive a work piece, means for-mounting said die for reciprocating movement along the axis of the cavity, means for holding said pin stationary within said die, means for driving the work piece in the cavity against the pin with a series of suc-v cessive blows, thereby to extrude the material of thework piece progressively into the space between said pin and the walls of the cavity to produce a socketed article, and means for absorbing the shock of blows against the work and die and for moving said die slightly with respect to said pin after each blow thereby to maintain the material of the work piece freeof adhesion to the pin. 16. A machine for forming socketed articles, which comprises a die having a substantially cylindrical cavity therethrough, an extruding pin having a portion extending into said cavity in spaced relation to the walls thereof, the remainder of said cavity being efiective to receive a work piece, means for holding said pin stationary within said die, and means for driving the work piece in the cavity against the pin with a series of successive blows thereby to extrude the material of the work piece progressively into the space between said pin, and the walls of the cavity to produce a socketed article, and means foradvancing said pin and article as a unit relative to the die, to eject the article from the die.

17. A machine for forming socketed articles, which comprises a die having a substantially cylindrical cavity therethrough, an extruding pin having a portion extending into said cavity in spaced relation to the walls thereof, the remainder of said cavity being effective to receive a work piece, means for-imparting to said pin, a series of oscillatory or vibratory movements along the axis of the cavity, and for holding the pin against advance movement toward the work piece, other than that incidental to said vibratory movements, means for advancing the work piece against the pin with a substantially constant movement efiective to cause the material of the work piece to extrude progressively into the space between said pin and the walls of the cavity thereby to produce a socketed article.

18. A machine for forming socketed articles, which comprises a die having a substantially cylindrical cavity therethrough, an extruding pin having a portion extending into said cavity in spaced relation to the walls thereof, the remainder ofsaid cavity being effective to receive a. work piece, meansv for imparting to said pin, a series of oscillatory or vibratory movements-along the axis-of the cavity, and for holding the pin against advance movement toward the work piece, other than that incidental to said vibratory movements, means for advancing the work piece against the pin with a substantially constant movement effective to cause the material 75 of the work piece to extrude progressively into the space between said pin and the walls of the cavity thereby to produce a socketed article, and means for advancing said pin and article as a unit relative to the die, to eject the article from the die.

19. In a machine for forming tubular articles,-

the combination of a frame, a sliding gate reciprocably mounted thereon, a punch carried thereby, a die mounted for yielding movement in opposed relation to said punch, a cavity in said die', aligned with said punch, for the'reception of a work blank at one end thereof, an extruding pin positioned to extend into said die and into engagement with the blank, from the other end thereof, means to drive said punch against the blank in said opening, with a series of progressively advancing movements distributed over at least 75 of the cycle of operation of the machine, thereby to produce a flow of the material of the blank progressively over said extruding pin.

20. In a machine for forming tubular articles, the combination of a frame, a sliding gate reciprocably mounted thereon, a punch carried thereby, a die mounted for yielding movement in opposed relation to said punch, a cavity in said die,

' aligned with said punch, for the reception of a work blank at one end thereof, an extruding pin positioned to extend into said die and into engagement with the blank from the other end thereof, means to drive said punch against the blank in said opening, with a series of progressively advancing movement distributed over at least 75 of the cycle of operation of the machine, thereby to produce a flow of the material of the blank progressively over said extruding pin, and means to move said die slightly with respect to said pin after each advance movement of the work thereby to free the metal from the pin.

21. In a machine for forming tubular articles, the combination of a frame, a sliding gate reciprocably mounted thereon, a punch carried thereby, a die mounted for yielding movement in opposed relation to said punch, a cavity in said die,

, aligned with said punch, for the reception of a work blank at one end thereof, an extruding pin positioned to extend into said die and into engagement with the blank from the other end thereof, cam actuated means to drive said punch against the blank in said opening with a series of progresively advancing movements distributed over at least 75 of the cycle of operation of the machines thereby to produce a flow of the material of the blank progressively over said extruding pin.

22. In a machine for forming tubular articles, the combination of a frame, a sliding gate reciprocably mounted thereon, a punch carried thereby, a die mounted for yielding movement in opposed relation to said punch, a cylindrical opening in said die, aligned with said punch, for the receipt of a Work blank, at one end thereof, an extruding pin positioned to extend into said die and into engagement with the blank from the punch, means providing a yielding relative movement between said die and punch, a cavity in said die aligned with said punch for the reception of a work blank at one end thereof, an extruding pin positioned to extend into said die, and into engagement with the blank from the other end 10 thereof, means to drive said punch against the blank in said opening, thereby to produce a flow of the material of the blank by extrusion in the die cavity, and means to free the material of the blank from adhesion to the extruding pin a plu- 15 rality of times distributed over at least 75 of the cycle of operation of the machine.

24. In a machine for forming tubular articles, the combination of a frame, a sliding gate reciprocably mounted thereon, a punch mounted on said gate for yielding telescoping movement with respect thereto, a die mounted in opposed relation to said punch, a cavity in said die aligned with said punch for the reception of a work blank at one end thereof, an extruding pin positioned to extend into said die and into engagement with the blank from the other end thereof, crank driven means to drive said punch against the blank in said opening with a substantially constant advancing movement, thereby to produce a flow of the material of the blank over said extruding pin, and means to impart a series of oscillatory movements to said pin during said constant movement therebyto form and strip the material of the blank from the pin, said oscillatory movements being distributed over at least 75 of the cycle of operation of the crank driven means.

25. In a machine for forming tubular articles, the combination of a frame, a sliding gate reciprocably mounted thereon, a punch mounted on said gate for yielding telescoping movement with respect thereto, a die mounted in opposed relation to said punch, a cavity in said die aligned with said punch for the reception of a work blank at one end thereof, an extruding pin positioned to extend into said die and into engagement with the blank from the other end thereof, crank driven means to drive said punch against the blank in said opening with a substantially constant advancing movement, thereby to produce a flow of the material of the blank over said extruding pin, and cam means to impart a series of oscillatory movements to said pin during said constant movement thereby to form and strip the material of the blank from the pin, said cam means including a cam having a series of reliefs distributed progressively over at least 75 of its contour.

26. In a machine for forming tubular articles,

the combination of a frame, a sliding gate reciprocably mounted thereon, a punch mounted on said gate for yielding telescoping movement with respect thereto, a die mounted in opposed relation to said punch, a cavity in said die aligned with said punch for the reception of a work blank at one end thereof, an extruding pin positioned to extend into said die and into engagement with the blank from the other end thereof, crank driven means to drive said punch against the blank in said opening with a substantially constant advancing movement, thereby to produce a flow of the material of the blank over said extruding pin, and cam means to impart a series of oscillatory movements to said pin during said constant movement thereby to form and strip the material of the blank from the pin, said cam means including a cam having a contour shaped to slowly advance said pin toward the punch, and a series of reliefs distributed progressively over at least 75 of its contour.

27. In a machine for i'orming tubular articles, the combination of a frame, a sliding gate reciprocably mounted thereon, a punch carried thereby, a die mounted for yielding movement in opposed relation to said punch, a cylindrical opening in said die aligned with said punch, for the -receipt oi a work blank at one end thereof, an

extruding pin positioned to extend into said die and into engagement with the blank from the.

other end thereof, cam actuated means to drive said punch against the blank in said opening, said cam having a series of reliefs progressively distributed over at least 75 of its contour and effective thereby to advance said gate and punch against said blank with a series of progressively advancing movements distributed over at least 75 01' the cycle of operation of the machine to produce a flow of the material of the blank progressively over said extruding pin, and cam means connected to actuate said pin with a slowly advancing movement toward the punch during the progresively advancing movements of the punch.

- ROY J. FRETER.

iifiiifiiior CORRECTION.

Patent No. 2,011,195. October 15, 1935.

' ROY J. FRETER.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, first column, line 13, for "practical" read practiced; and line 33, before "blank" insert the word the; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 19th day of November, A. D. 1935.

h Leslie Frazer (Seal) Acting Commissioner of Patents.

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