US2422774A - Die set - Google Patents

Description

June 24, 1947. e. o. CONNER DIE SET 3 Sheets-Sheet 1 Filed Jan. 22, 1944 IN VEN TOR. 60) 0' CON/V5}? A TTOENEYS June 24, 1947. G. o. CONNER DIE SET Filed Jan. 22, 1944 3 Sheets-Sheet 2 IN VEN TOR.

A TTOFENEYS June 24, 1947. e. o. CONNER DIE SET Filed Jan. 22, 1944 3 Sheets-Sheet 5 INVENTOR. 60) 0- CO/V/VE/P Patented June 24, 1947 UNITED STATES PATENT OFFICE DIE SET Guy 0. Conner, Redford, Ohio Application January 22, 1944, Serial No. 519,284

22 Claims.

This invention relates to improvements in punch presses and more particularly to improvements in die sets for punch presses or the like.

As is well known to those versed in the art. certain classes of articles are manufactured by the use of presses. These presses usually employ a base which holds a die and a reciprocable plunger which carries another die or punch that mates with that of the base and the sheet metal stock is placed between the two dies, which, when they come together, either stamp out or form the stock to the desired shape. The dies, being the parts where most wear occurs. are the parts that are most often changed; also because of the various types of parts produced, different dies may be substituted to form the desired type of part.

It has been common practice to provide a support for the dies. called a die set which is also removable but which is of a. predetermined form to lit the press and to which the die parts are secured. Since it is desirable to have the dies in proper alignment with each other one of the die set parts is provided with posts that extend toward the other and that are reclprocable in a bearing in the other part thus maintaining alignment between the parts.

It will therefore be seen that the die alignment is almost wholly determined by the fit between the posts or plungers in the bearings. Heretofore one diiiiculty has been to keep the tolerances of these fits between the posts and bearings at a minimum. If the fit was too loose they could become laterally misaligned and destroy the sharp edges of the dies. If the fit was too close, the friction developed during use caused heating and freezing of the parts making the machine inoperative. Still another disadvantage realized due to loose fitting or worn posts was noticed in the parts that were being formed. Instead of the parts having sharp clean edges, flash metal or fins appeared around the edges which made necessary subsequent operations of flattening or trimming for the removal thereof. As a matter of fact, in order to improve the performance of dies particularly where the metal stock is thin and the articles small, it has been customary to employ so-called sub presses where a line of close manufacture and a refined product is desired and a finished product was to be produced without distorting the metal around the edges.

Still further. these disadvantages were greatly aggravated when the punching operations are carried out at a high speed. particularly when the dies are used with an apparatus such as disclosed in my copending application for Forming machines," Serial No. 497,792, filed August 7, 1943.

By my present invention I have made a die set which reduces the tolerance between the pillars or posts and the hearings to a minimum. With a die set employing the improvement of my invention thin as well as thick stock may be stamped or formed with the same die sets; and the same die sets may be employed throughout long periods of time without rebushing.

It is therefore an object of my invention to provide an improved die set for punch presses or the like.

It is another object of my invention to provide a die set where there will be no binding or freezing of the parts in spite of the maintenance of close tolerances.

Another object of my invention is to provide a die set which will prolong the life of the dies.

Another object of my invention is to provide a die set which may be operated at high speed and still maintain truer alignment than was heretofore possible in the prior art.

Another object of my invention is to provide a die set which can be operated at high speed and travel laterally with the stock and still maintain alignment and avoid the extreme wear entailed in this type of operation with die sets of the prior art.

Still another object of my invention is to reduce the friction between the pillars and bearings in die sets.

These and other objects of my invention will become more apparent from the following description of some embodiments of the invention which description is illustrated by the accompanying drawings and which forms a part of this specification.

In the drawings:

Fig. 1 is a vertical section taken through the pillars and bearings of a die set employing my invention;

Fig. 2 is a sectional view taken on the line 2-2 of Fig. 1;

Fig. 3 is an elevatlonal view of a bearing retainer and the bearings in another form of the invention;

Fig. 4 is a fragmentary perspective of a bearing retainer illustrating another form of the invention;

Fig. 5 is a diagrammatic view of another form of the invention;

Fig. 6 is a fragmentary section through a bearing showing a fragment of a pillar in elevation and illustrating another form of my invention;

Fig. '7 is an elevational view of the invention as applied to another type oi press. certain hidden parts being shown by dotted lines: and

Fig. 8 is a horizontal section through a pillar, bearing and sleeve illustrating another form of the invention.

Although the invention about to be described is described as used in connection with punch presses and the formation of sheet metal stock, it is not my intention that the invention shall be limited to the forming of sheet metal only, since it will be clear that it can be used on any type of machine. where dies having a forming matrix are used to operate on raw or semiiinished stock, to give it a predetermined form.

{Referring now to the drawings throughout which like parts have been designated by like reference characters and ilrst particularly to Figs. 1 and 2, in Fig. 1, I have illustrated in section a die set embodying my invention which comprises upper and lower plates l and ii, respectively, which may be adapted for attachment to the traveling cam or slide, and the bed or bolster oi the press.

The base II is provided with a pair of sleeves ii that may be cylindrical in form and each of which is provided with a reduced end portion II having a drive fit in a bore ll in the base. the junction of the reduced portion and the body above the base providing a shoulder I! which abuts the top of the plate and assists in maintaining the sleeves in their proper upright position.

The inner surfaces of the sleeves are provided with cylindrical smooth bores II which may be ground and hardened to provide a bearing surface for bearings later described.

Depending from the top plate II are pillars or posts the upper ends of which may be split and which are disposed in bores II in the plate and held therein in any suitable manner, that shown being by plugs 22 which are driven into the bores of the posts after they are properly positioned within the bores Ii. These posts are the same in number as the sleeves. In this instance two are shown, but it is within the purview of my invention to provide one, three or even more if desired. These posts are arranged to be coaxial with the sleeves and to travel downward from the position shown to thebottom of the sleeve if desired.

Preferably they may travel down into the cups 28, which are secured to the lower side of the plate. These cups may be filled with lubricant and the reciprocation oi the posts into the lubricant forces it up into the bearings. A suitable packing gland I! may be provided at the top of the sleeve which is provided with a packing 29a to prevent loss of the lubricant.

The spaces II and 24, intermediate the posts provide for the reception of the die parts proper which may be secured on the plates Ill and II in any well known manner.

It will be seen that the posts or pillars III are spaced from the sleeve walls. The surface of these posts are ground and hardened and rolllng elements in the form of balls are inserted between the posts and the sleeve wall. the balls being of a size that causes them to be loaded when in position. That is, the balls may be oi a diameter that is at least equal to the width of the space between the post and the sleeve. It is also desirable to utilize balls that are slightly larger than this space. In this event the balls would fit tightly between the walls so that there would be no lateral movement of the post relative to the sleeve. Balls that are slightly larger than the diameter of the space will result in light loading thereof, whereas balls of larger diameter will result in heavier loading thereof. In this manner die sets embodying the invention can be made where the lateral movement is controlled within the desired limit; the loading may be light, medium or heavy, depending upon the character of use for which the die set is intended. It will be understood, however, that it may be desirable to use balls of the same or less diameter in certain instances in which case the balls would not be loaded. As shown in Fig. 1 the balls extend in rows around the post, the rows oi balls being in vertically spaced relation to each other. In the embodiment there are illustrated six such rows although the size and number of rows is only limited by the diameter of the space between the sleeve and post. Although the posts are shown as having a bore therein, it is within the purview of my invention to provide posts 0! solid material where desired.

These balls are held in their proper position by a retainer 2 which also prevents them from dropping out of position when the post is withdrawn from the sleeve to the position illustrated in Fig. 1, since the walls of the openings that receive the balls extend inward slightly to restrict the size of the opening on the side toward the post as can be seen in the figure.

It should be noted that the balls or retainer do not extend for the entire length of the sleeve. This is because the balls and retainer travel vertically about one half the distance of the movement of the sleeve or post or when both upper and lower plates ill and II are moving equally, the sleeve stands still and the balls rotate.

It will thus be seen that a die set can be constructed according to my invention wherein the upper and lower parts may be maintained in perfect alignment and that no lateral movement of the parts during use is realized because oi the loading of the balls between the post and sleeve.

In actual practice for ordinary punch press use the bearing retainer may be made of metal. however, in connection with the high speed press 01 my copending application before mentioned, the bearing retainer is also formed or Bakelite. synthetic resin, or impregnated wood. This is desirable because in a device of this character operating at high speed. tightening the retainer decreases the inertia since the dies in this case not only travel vertically but sldewise, and helps to prevent the retainer from coming into contact with the walls. The soft material also decreases the wear of the parts.

I also dispose the hearings in a single continuous row extending around the post in a spiral or helix form. This is best shown in Fig, 3 which illustrates a retainer 28a removed from the sleeve.

The retainer for holding the balls may also be formed of a spirally wound strip of material 38 as viewed in Fig. 4 which strip is formed with upper and lower concave surfaces 8i and the balls are retained between the adiacent convolutions. In the type or a retainer shown in Figs. 3 and 4 there is a tendency for the balls and the retainer to rotate around the post in a spiral path thus distributing the wear over a greater area of the post and sleeve.

Although I have shown cylindrical posts and sleeves it is within the purview of my invention to provide a square or polygonal post and sleeve with equal efllcacy. In this case roller or needle bearings could be substituted if desired. Also the post and sleeves could be of the form shown in Fig. 5 where the post Illa is elongated in cross section and the ends are provided with V shaped surfaces III. In this case roller bearings 4| could be used on each of the surfaces of the V only and no bearings would be necessary on the sides 2 although they could be used there if desired. The subject matter of this figure is claimed in my co-pending application Ser. No. 597,321, flied June 2, 1945.

In Fig. 6 I have shown another modification of the invention wherein the wear on the parts is reduced. In this case the post and sleeve are provided with greater clearance. Disposed adjacent to the posts 20 are balls 60. Next around the balls 60 is disposed a sleeve BI and finally between this sleeve and the walls of the bore in the sleeve carried by the plate H is an additional set of balls 82. Both sets of balls and the sleeve are assembled in loaded condition. During oper ation the balls in this device only travel about one-half as far as the balls shown in Fig. 1, although the relative travel of the upper and lower plates may be the same. In this manner the life of the balls and other parts is considerably prolonged.

In Fig. 7 I have illustrated my invention as applied to forming heads as described in the aforesaid copending application. In this case upper and lower heads III and H are provided. being supported by the eccentric members 12. The manner oi operation of the head is fully described in said application and will not be described here other than to state that each head travels in a closed circular path in opposite directions the timing being such that upon their closest approach to each other the material disposed between the heads is operated upon. The upper head I0 carries two downwardly extending pillars 13 which are secured by screwing into threaded openings 14 extending through the head, a nut 15 locking the same in position.

The lower head supports sleeves II which may be secured in bores in the head in any suitable manner and the posts 13 extend coaxiall into the sleeves and entirely through the ball retainer 11 with its balls ill. the ends of the posts being provided with collars I9 which may be in the form of a split ring seated in a groove adjacent the end of the post or mounted on a stud screwed into the end of the post. The ends of the sleeves are provided with sumps 8|) the purpose and function of which is the same as that described for Fig. 1.

It should be noted that the posts I! extend entirely through the bearings and that at no time are they withdrawn therefrom. such withdrawal being prevented by the collar 19.

The relative positions and members 01' the posts and sleeves in Figs. 1 and 7 may be varied if desired so that the sleeves are carried by the top head and the posts by the bottom head. Where this is effected the packing gland 29 keeps the lubricant within the bearing.

In Fig. 8 I have shown a cross section of another type of pillar and sleeve. In this case the sleeve 9| is provided with grooves 92 and the pillar 93 has corresponding grooves 94. The balls 95 are seated in the grooves being inserted, as in the other modifications, under loaded conditions. The clearance space 96 between the pillar and the sleeve may be less than in the preceding embodiments. Here the balls always travel in the same path but are provided with a larger bearing surface.

The grooves 92 may extend straight longitudinally in the pillar and sleeve or they may extend spirally. When spiral grooves are provided, for obvious reasons, the grooves on one member should extend spirally to the right and those on the other should extend spirally to the left.

It will thus be seen that I have provided a die set wherein lateral movement of the parts is substantially eliminated. This enables the dies to operate on various thicknesses of stock reducing to a minimum the fins or drawn portions normal ly found on stampings and eliminating subse quent trimming or shearing operations. Thus it is possible to make more accurate parts or stampings at a considerable high speed.

Also a die set of this character is particularly useful where the movement of the upper and lower plates is not only toward each other but laterally where the dies follow the stock as in the case of high speed operation of the aforesaid application.

Because more accurate alignment of the dies is maintained the life of the dies is also materially extended.

Although I have described my invention more particularly as applied to die sets adapted to carry or support dies, it will be obvious to those versed in the art that the invention is applicable to these types of dies where they are not supported on die sets as in the case where the material is cut into plates carried by the pillar and bolster itself.

Having thus described my invention I am aware that numerous and extensive departures may be made therefrom without departing from the spirit or scope of the invention.

Iclalm:

1. An apparatus of the class described comprising members adapted for relative movement toward each other, means to maintain alignment between the members comprising one or more posts carried by the one member and reciprocable in sleeves in the other member and means between the post and sleeves to decrease friction and hold the sleeves and posts against lateral movement relative to each other.

2. A die set comprising plates adapted for relative movement toward and from each other and to support die parts, means for maintaining alignment of the plates with each other comprising posts carried by one plate and extending in spaced relation to the walls of sockets carried by the other and anti-friction means disposed in the space between the walls and posts.

3. An apparatus of the class described comprising members adapted for relative movement toward and from each other and to support die parts, means for maintaining relative alignment between the members comprising posts carried by one member and guides carried by the other, said posts extending into said guides in spaced relation to the walls thereof and anti-friction means comprising rolling elements disposed in the space between the walls and posts, said rolling elements being inserted under loaded conditions.

4. A die set comprising plates adapted for relative movement toward and from each other and to support die parts, means for maintaining alignment of the plates with each other comprising posts carried by one plate and extending in spaced relation to the walls of sockets carried by the other plate and anti-friction means 7 disposed in the space between the walls and posts comprising loaded ball bearings.

5. A die set comprising spaced heads adapted for relative movement toward and from each other and to support die parts, means for maintaining alignment of the heads with each other comprising posts carried by one head and extending in spaced relation to the walls of sockets carried by the other head and anti-friction means disposed in the space between each wall and post, comprising rolling elements inserted under loaded conditions in said space, and retainers for said rolling elements spaced from the walls.

6. A die set comprising spaced plates adapted for relative movement toward and from each other and to support die parts, means for maintaining alignment of the plates with each other comprising posts carried by one plate and extending in spaced relation to the walls of sockets carried by the other, and anti-friction means disposed in the space between each socket wall and post, comprising balls inserted under loaded conditions in said space, and retainers for said balls spaced from the walls, and comprising a, nonmetaliic sleeve of Bake1ite," synthetic resin or like material.

'1. A die set comprising spaced plates adapted for relative movement toward and from each other and to support die parts, means for maintaining alignment of the plates with each other comprising posts carried by one plate and extending in spaced relation to the walls of sockets carried by the other and anti-friction means disposed in the space between each wall and post, comprising balls inserted under loaded conditions in said space, and retainers for said balls spaced from the walls, and comprising a nonmetallic sleeve 01' Bakelite, or synthetic resin, said balls being disposed in spaced rows around said posts.

8. A die set comprising spaced plates adapted for relative movement toward and from each other and to support die parts, means for maintaining alignment of the plates with each other comprising posts carried by one plate and extending in spaced relation to the walls of sockets carried by the other and anti-friction means disposed in the space between the walls and posts, comprising bearings inserted under loaded conditions in said space, said bearings being disposed in spaced rows around said posts.

9. A die set comprising spaced plates adapted for relative movement toward and from each other and to support die parts, means for maintaining alignment of the plates with each other comprising posts carried by one plate and extending in spaced relation to the walls of sockets carried by the other and anti-friction means disposed in the space between the walls and posts, comprising rolling elements inserted under loaded conditions in said space, and retainers for said rolling elements spaced from the walls, and comprising a non-metallic sleeve of "bakelite," or synthetic resin, said rolling elements being disposed in helical relation about said post whereby they rotate around the posts in a helical path during reciprocation oi' the posts. I

10. Means for maintaining alignment between the die carrying heads of a forming machine comprising one or more posts carried by one head and one or more sleeves carried by the other head, said posts extending from the one head coaxially into the sleeves of the other head, and

' 8 loaded bearings interposed between the walls 0 the posts and sleeves.

11. Means for maintaining alignment between the die carrying heads of a forming machine comprising one or more posts carried by one head and one or more sleeves carried by the other head, said posts extending from the one head coaxially into the sleeves oi the other head, loaded bearings interposed between the walls of the posts and sleeves, and a retainer for holding said bearings against displacement formed of relatively light anti-friction material.

12. Means for maintaining alignment between the die carrying heads of a forming machine comprising one or more posts carried by one head and one or more sleeves carried by the other head, said posts extending from the one head coaxially into the sleeves oi the other head, loaded bearings interposed between the walls of the posts and sleeves and lubricant retaining means for said sleeve and engaging said posts.

13. Means for maintaining alignment between the die carrying heads oi a forming machine comprising one or more posts carried by one head and one or more sleeves carried by the other head, said posts extending from the one head coaxially into the sleeves of the other head, loaded bearings interposed between the walls of the posts and sleeves, and lubricant retaining means comprising a sump disposed on the end of the sleeve opposite the entering end of the post, and a packing gland on the other end of the sleeve sealing the sleeve to the post.

14. A die set including spaced plates for supporting parts and adapted for movement toward and away from each other, means for maintaining alignment 01' said plates including one or more posts carried by one plate and one or more sleeves carried by the other plate, said posts adapted to project into said sleeves and means disposed between the posts and sleeves including a ball retainer comprising a helically extending member having the adjacent faces of the convolutions of the helix shaped in concave form to provide a raceway and balls disposed in said raceway.

15. An apparatus 0! the class described including a pair of die carrying members adapted for movement toward and from each other, means for maintaining alignment between said die carrying members and the dies comprising one or more posts carried by one member and sleeves for said posts carried by the other member, said posts extending and reciprocable in said sleeves and spaced from the walls thereof, and means disposed between each post wall and sleeve wall comprising concentric sets of balls and retainers therefor, and a floating sleeve interposed between said ball sets, said balls and sleeve being inserted in said space under loaded conditions.

16. A die set comprising spaced plates adapted for relative movement toward and from each other and to support die parts, means for maintaining alignment of the plates with each other comprising posts carried by one plate and extending in spaced relation to the walls of sockets carried by the other plate, the walls of said posts and sockets being formed with helical grooves, and anti-friction means disposed in the space between the walls and posts in said grooves, comprising rolling elements inserted under loaded conditions in said space, said rolling elements being disposed in helical relation about said post whereby they rotate around the posts in a helical path during reciprocation of the posts.

17. A die set comprising spaced plates adapted for movement toward and from each other with their opposed faces in parallelism, means for maintaining lateral alignment of said plates comprising posts carried by one plate and sleeves carried by the other plate, said posts extending into said sleeves in coaxial alignment therewith and provided with longitudinally extending grooves and balls disposed in said grooves under loaded conditions.

18. A die set comprising spaced dies adapted for movement toward and from each other to stamp, out or press an object to be formed, means for maintaining lateral alignment of said dies in their movement comprising posts carried by one die and sleeves carried by the other die, said posts and sleeves provided with helical grooves of opposite inclination to each othe and balls disposed in said grooves under loaded conditions.

19. An apparatus of the class described comprising members adapted for relative movement toward each other, means to maintain predetermined alignment between said members comprising guide means carried by one member and cooperable with guide means carried by the other member and rollin elements disposed between said guide means to decrease friction resistance and control relative lateral movement therebetween.

20. Means for maintaining in alignment cooperating die means relatively reciprocable toward and away from each other and adapted to operate on work disposed therebetween comprising guide means respectively rigidly connected with said die means, said guide means having opposed spaced apart guiding surfaces extending parallel to the direction of relative reciprocation of said die means, which surfaces reciprocate in parallel paths alongside each other upon relative reciprocation of said dies means, and mean interposed between said surfaces resisting relative movement of said guide means in all directions transversely of the direction of relative reciprocation of said die means.

21. Means for maintaining in alignment cooperating die means relatively reciprocable toward and away from each other and adapted to operate on work disposed therebetween comprising guide means respectively rigidly connected with said die means, said guide means having opposed spaced apart guiding surfaces extending parallel to the direction of relative reciprocation of said die means, which surfaces reciprocate in parallel paths alongsid each other upon relative reciprocation of said die means, means interposed between said surfaces and moving relatively to each of said surfaces resisting relative movement of said guide means in all directions transversely of the direction of relative reciprocation of said die means.

22. Means for maintaining in alignment cooperating die means relatively reciprocable toward and away from each other and adapted to operate on work disposed therebetween comprising guide means respectively rigidly connected with said die means, said guide means having opposed spaced apart guiding surfaces extending parallel to the direction of relative reciprocation of said die means, which surfaces reciprocate in parallel paths alongside each other upon relative reciprocation of said die means, and anti-friction hearing means interposed between said surfaces and movable relatively to each of said surfaces resisting relative movement of said guide means in all directions transversely of the direction of relative reciprocation of said die means.

GUY 0. CONNER REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Certificate of Correction Patent No. 2,422,774.

Number Name Date 1,106,564 Hoffmann Aug. 11, 1914 1,568,017 Danly Dec, 29, 1925 206,648 Tucker July 30, 1878 1,228,312 Gamier May 29, 1917 2,026,721 Broulhiet Dec. 31, 1935 2,032,975 Broulhiet Mar. 3, 1936 2,225,929 Sarozin Dec, 24, 1940 2,316,468 Thomas Apr. 13, 1943 1,603,428 Toilefson Oct. 19, 1926 June 24, 1947.

GUY O. CONNER It is hereby certified that error appears in the (printed specification of the above numbered patent uiring correction as follows:

olumn 10, line 9, claim 21, for

"moving read more la; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Signed and sealed this 0th day of January, A. D. 1948.

THOMAS F. MURPHY,

Am'ctmt Oommn'uioner of Patents.

for movement toward and from each other with their opposed faces in parallelism, means for maintaining lateral alignment of said plates comprising posts carried by one plate and sleeves carried by the other plate, said posts extending into said sleeves in coaxial alignment therewith and provided with longitudinally extending grooves and balls disposed in said grooves under loaded conditions.

18. A die set comprising spaced dies adapted for movement toward and from each other to stamp, out or press an object to be formed, means for maintaining lateral alignment of said dies in their movement comprising posts carried by one die and sleeves carried by the other die, said posts and sleeves provided with helical grooves of opposite inclination to each othe and balls disposed in said grooves under loaded conditions.

19. An apparatus of the class described comprising members adapted for relative movement toward each other, means to maintain predetermined alignment between said members comprising guide means carried by one member and cooperable with guide means carried by the other member and rollin elements disposed between said guide means to decrease friction resistance and control relative lateral movement therebetween.

20. Means for maintaining in alignment cooperating die means relatively reciprocable toward and away from each other and adapted to operate on work disposed therebetween comprising guide means respectively rigidly connected with said die means, said guide means having opposed spaced apart guiding surfaces extending parallel to the direction of relative reciprocation of said die means, which surfaces reciprocate in parallel paths alongside each other upon relative reciprocation of said dies means, and mean interposed between said surfaces resisting relative movement of said guide means in all directions transversely of the direction of relative reciprocation of said die means.

21. Means for maintaining in alignment cooperating die means relatively reciprocable toward and away from each other and adapted to operate on work disposed therebetween comprising guide means respectively rigidly connected with said die means, said guide means having opposed spaced apart guiding surfaces extending parallel to the direction of relative reciprocation of said die means, which surfaces reciprocate in parallel paths alongsid each other upon relative reciprocation of said die means, means interposed between said surfaces and moving relatively to each of said surfaces resisting relative movement of said guide means in all directions transversely of the direction of relative reciprocation of said die means.

22. Means for maintaining in alignment cooperating die means relatively reciprocable toward and away from each other and adapted to operate on work disposed therebetween comprising guide means respectively rigidly connected with said die means, said guide means having opposed spaced apart guiding surfaces extending parallel to the direction of relative reciprocation of said die means, which surfaces reciprocate in parallel paths alongside each other upon relative reciprocation of said die means, and anti-friction hearing means interposed between said surfaces and movable relatively to each of said surfaces resisting relative movement of said guide means in all directions transversely of the direction of relative reciprocation of said die means.

GUY 0. CONNER REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Certificate of Correction Patent No. 2,422,774.

Number Name Date 1,106,564 Hoffmann Aug. 11, 1914 1,568,017 Danly Dec, 29, 1925 206,648 Tucker July 30, 1878 1,228,312 Gamier May 29, 1917 2,026,721 Broulhiet Dec. 31, 1935 2,032,975 Broulhiet Mar. 3, 1936 2,225,929 Sarozin Dec, 24, 1940 2,316,468 Thomas Apr. 13, 1943 1,603,428 Toilefson Oct. 19, 1926 June 24, 1947.

GUY O. CONNER It is hereby certified that error appears in the (printed specification of the above numbered patent uiring correction as follows:

olumn 10, line 9, claim 21, for

"moving read more la; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Signed and sealed this 0th day of January, A. D. 1948.

THOMAS F. MURPHY,

Am'ctmt Oommn'uioner of Patents.

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