US 3398413 A
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Description (OCR text may contain errors)
Aug. 27, 1968 E. J. SKIERSKI 3,393,413
MACHINES FOR PINCH-PC'INTING METAL SCREWS Filed Sept. 20, 1967 2 Sheets-Sheet 1 FIG.!
INVENTOR EDWIN J. SKIERSKI 6 BY )M fi hula/2 ATTYS.
United States Patent 3,398,413 MACHINES FOR PINCH-POINTING METAL SCREWS Edwin J. Skierski, Wayne, N.J., assignor to Parker- Kalon Corporation, Clifton, N.J., a corporation of Delaware Continuation of application Ser. No. 475,533, July 28, 1965. This application Sept. 20, 1967, Ser. No. 675,999 2 Claims. (Cl. 16-9) ABSTRACT OF THE DISCLOSURE A machine for pointing the pilot end of a metal screw blank having means for precisely locating a pair of complementary dies and for guidingly moving the dies into an operative position. The dies are constructed to prevent contact between the work faces thereof during operation of the machine.
The present invention relates to machines for pinchpointing the pilot ends of metal screw blanks prior to threading of the substantially cylindrical shanks thereof; and it is a general object of the invention to provide such a machine of improved and simplified construction and arrangement. The present application is a continuation of my copending application for United States Letters Patent Ser. No. 475,533, filed July 28, 1965, and now abandoned.
Another object of the invention is to provide a pinchpointing machine of the character noted that is characterized by high-speed operation so as to increase significantly the number of blanks that are pointed during each time interval of operation thereof.
A further object of the invention is to provide a pinch pointing machine of the character noted that employs a pair of complementary dies that are mounted for selective relative movements with respect to each other and between a fixed open position and a fixed closed position, wherein the dies respectively carry a pair of mating work faces that are disposed in close proximity to each other with a predetermined clearance therebetween when the dies occupy their fixed closed position, and wherein the dies respectively carry a pair of mating abutments that directly engage each other in the fixed closed position thereof to establish the predetermined clearance mentioned.
A further object of the invention is to provide a machine of the character noted, wherein each of the dies is formed of an extremely hard material, such as a metal carbide.
A still further object of the invention is to provide a machine of the character described, wherein the dies are respectively removably carried by a pair of die holders that are mounted for guided selective relative movements toward and away from each other, so as correspondingly to move the dies into their respective fixed closed and fixed open positions.
Further features of the invention pertain to the particular arrangement of the elements of the pinch-pointing machine, whereby the above outlined and additional operating features thereof are attained.
The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification, taken in connection with the accompanying drawings. It is to be understood that the specific embodiment of the invention shown in the drawings and hereinafter described in the specification is for illustration purposes only and is not to be construed as a limitation of the invention. More particularly, it is to be clearly ice understood that dies having various cavity or recess configurations may be employed without departing from the scope of this invention.
In the drawings:
FIG. 1 is a side elevational view, of a metal screw blank that is to be pointed at the pilot end thereof prior to threading of the shank thereof;
FIG. 2 is a side elevational view of the screw blank following pointing of the pilot end thereof and preceding the threading of the shank thereof;
FIG. 3 is a top perspective view of a pair of dies that are removably carried in a pinch-pointing machine for working the screw blank of FIG. 1 to produce thescrew blank of FIG. 2;
FIG. 4 is a plan view of the pinch-pointing machine incorporating the dies of FIG. 3 and embodying the present invention;
FIG. 5 is an enlarged vertical sectional view of the dies in their partially open position, this view being taken in the direction of the arrows along the line 5-5 in FIG. 4; and
FIG. 6 is another enlarged vertical sectional view, similar to FIG. 5, of the dies in their fixed closed position.
Referring now to FIG. 1 of the drawings, the screw blank 10 there illustrated may be formed of steel, and essentially comprises an enlarged head 11 of any desired form and a substantially cylindrical shank 12. Prior to threading of the shank 12, the pilot end thereof is ordinarily pointed, as indicated at 13, and as illustrated in FIG, 2. This pointing of the pilot end 13 of the shank 12 is effected in the present instance utilizing the dies 21 and 31, as shown in FIG. 3, and employing the pinchpointing machine 59, as shown in FIG. 4. Although FIG. 2 illustrates a screw blank having a conically pointed pilot end, FIG. 3 illustrates dies for forming a conical pilot end and the discussion to follow will be limited to the use of the present invention to manufacture a screw having a conical pilot end, it is to be understood, and is considered obvious, that various other pilot end configurations may be formed utilizing the present invention simply by appropriately altering the die recess or cavity as for example by providing projections within said die recess to form tapping surfaces in the pilot end.
In the operation of the dies 21 and 31, the pilot end 13 is produced in a pinching step with the removal of scrap, as indicated at 14, from the extreme outer end of the shank 12, and without substantial longitudinal elongation of the shank 12. In the blank 10, after the formation of the pilot end 13, the angle between opposed lines along the cone-shaped point or pilot end 13 may be approximately 45, as indicated in FIG. 2. Thereafter, the blank 10 of FIG. 2 is subjected to a threading step, not herein involved; and, specifically, the thread mentioned may be formed in the shank 12 in a thread-rolling step, involving suitable thread-rolling dies, not shown.
Referring now to FIG. 4, the pinch-pointing machine there illustrated, and embodying the features of the present invention, comprises a stationary head 51, a movable head 52, and facility mounting the head 52 for guided movements toward and away from the head 51, this facility including a ram, indicated generally at 53. A block 54 is detachably secured to the stationary head 51, and a block 55 is detachably secured to the movable head 52. The block 54 carries a pair of laterally spaced apart guide bushings 56, and the block 55 carries a pair of laterally spaced-apart guide pins 57; which guide bushings 56 receive the guide pins 57 so as accurately to guide the longitudinal movements of the block 55 toward and away from the block 54. An upstanding recess 54a is formed in the central portion of the block 54 for the purpose of supporting the die 21, and an upstanding re cess 55a is formed in the central portion of the block 55 for the purpose of supporting the die 31. The die 21 is accurately located along the center line of the block 54 and within the recess 54a by substantially U-shapeddie holder 61 including a pair of laterally spaced-apart arms 62 and 63. The die 21 is precisely locatedwithin a die pocket 65 in the die holder 61 in intimate contact with the rear surface of the die pocket, the side of the die pocket formed by a surface of the arm 62 and the lower surface of the die pocket which is formed by the lower surface of the recess 54a. Intimate contact with said surfaces of the die pocket 65 is established by the cooperative action of a conical recess 24x in the die 21 and a clamping screw 64, as hereinafter discussed in detail. This structure facilitates accurate, easy location of .the die 21 along the center line of the block 54. In a similar manner, the die-31 is accurately located along the center line of the block 55 and within the recess 55a by a substantially U-shaped die holder 71 including a pair of laterally spaced-apart arms 72 and 73 which form a die pocket 75 in cooperation with the rear portion of the holder 71 and the lower surface of the recess 55a. Precise location of the die 31 is accomplished in the same manner as the die 21. In the arrangement, the die holder 61 nicely fills the recess 54a in the block 54, and the die holder 71 nicely fills the recess 55a in the block 55.
Before proceeding further with the description of the construction of the machine 50, reference is made to FIG. 3, wherein the dies 21 and 31 are illustrated as being complementary, each being of elongated form and having a substantially rectangular lateral cross-section. Specifically the die 21 comprises a forwardly disposed work face 22, and a top side 23 and a front side 24 illustrated. Similarly, the die 31 comprises a forwardly disposed work face 32, and a top side 33 and a front side 34 illustrated. A substantially cone-shaped recess 24x is formed in the front side 24 of the die 21; and a substantially cone-shaped recess 34x is formed in the front side 34 of the die 31. A pair of mating recesses 22a and 32a are respectively formed in the top central portions of the mating work faces 22 and 32; which recesses 22a and 32a are arranged in registry with each other; and each of these recesses has a substantially semiconical configuration in the illustrated embodiment. The surfaces of the work face 22 are cut-away on opposite sides and below the recess 22a, as respectively indicated at 24a, 24b and 240; and, similarly, the surfaces of the work face 32 are cut-away on opposite sides and below the recess 32a, as respectively indicated at 34a, 34b and 340. A deep clearance recess 25 is formed in the central portion of the work face 22 and positioned below the surface 24c; and, similarly, a deep clearance recess 35 is formed in the central portion of the work face 32 and positioned below the surface 340. Finally, in the illustrated embodiment a generally triangular shaped abutment 26 is formed on the lower portion of the work face 22; and, similarly, a generally triangular-shaped abutment 36 is formed on the lower'porin the dieholder 61. Specifically, the extreme front end of the clamping screw 64 is substantially cone-shaped and is adapted to engage into the recess 24x formed in the front side of the die 21. As illustrated in FIG. 4, the axis of the clamping screw 64 is offset from the. axis of the conical recess 24x when the screw 64 is in an operative position. More specifically, as viewed in FIG. 4, the axis of the clamping screw 64 is offset to the left of and with respect 'to the dieholder -61-an'd quick clamping in precise location of the die '21 when it is disposed in its mounted position in the dieholder 61. In a similar manner, a clamping screw 74 is carried in a nicely fitting opening formed in the front section of the block 55; which clamping screw 74engages a cooperating threaded'opening provided in the front arm 73 of the dieholder 71 and projects therethrough into cooperating clamping'relation with the adjacent die 21- in its supported'position in the dieholder 71. Specifically the extreme front end of the clamping screw 74 is substantially cone-shaped and is adapted to engage intothe recess 34x formed in the front side of the side 31. The axis of the clamping screw 74 is-oflset from the axis of the conical recess 34x when the screw 74 is in operative position. That is, again as viewed inFIG. 4, the axis of the clamping screw 74 is to the right of and below or downwardly from the axis of the conical recess 34x. Thus, when the clamping screw 74 is advanced, the cone-shaped forward end thereof eccentrically engages the conical recess 34x and urges the die 31 rearwardly, downwardly and laterally into intimate contact with the rear, lower and a side surface of the die pocket 75. Thus the screw'74 is selectively operative between clamping and releasing positions with respect to the die 31 so as to ,accommodate ready placement and removal of the die 31 with respect to the dieholder 71 and quick clamping in precise location of the die 31 when it is disposed in its mounted position in the dieholder 71.
Again referring to the dies 21 and 31 of FIGS. 3, 5 and 6, it is noted that they are formed of a material that is extremely hard and .that has a hardness number on the Vickers scale in the general range 1300 to 1400. A suitable such material is a sintered metal carbide alloy, such, for example, as tungsten carbide. This commercial material usually contains a small amount of tantalum carfbide or titanium carbide. Frequently, the commercial alloy contains about 87% to tungsten carbide and about 5% to 13% tantalum carbide or titanium carbide, or a combination of both tantalum carbide and titanium carbide, all by weight. The use of dies formed of material having a hardness of this magnitude requires precise alinement of the dies during operation. It has been found that unless the dies are exactly alined, substantial, immediate damage thereto will result. This is particularly true where dies havingotherthan asemiconical recess such as illustrated are used. That is, if.for example, projections are provided in the die recess to form cutting or tapping surfaces on the pilot end of a screw blank, the projections will be shattered or cracked if the dies are not precisely alined. The cooperation of the guide bushings 56 and guide pins57 and the clamping screws and conical recesses in the dies for exactly locating the dies with repetitive uniformity ensure alinement thereby facilitating the use of such di es. p
In the operation of themachine 50, the ram 53 is operative to reciprocate the block 55, so as to move the block 55 toward and away from the block 54; and which movements are guided by the guide pins 57 sliding in the guide bushings 56. As previously. noted,the pair of guide pins 57 are carried by the block 55,-and the-pair of guide bushings 56 "are carried by the block 54. Thus, the die 31 carried by the 'block 55 is movedinan accuratelysguided path toward and away from the. die 21 carried by the block ,54 Specifically, the die 31 is m o,ved between a fixed closed position, shown in FIG, 6, with'respectto the die 21 and a fixed open position, substantially shown in FIG. 5, with respect to the die 21. More particularly, the die 31 is slightly displaced toward the right with respect to the, die 21 from its position as shown in FIG. 5, when the die 31 occupies its fixed open position. The fixed open position of the dies 21 and 31, is established by the movement of the block 55 into its extreme right-hand position as set by the action of the ram 53. On the other hand the fixed closed position of the dies 21 and 31 is established by the abutments 26 and 36 respectively carried 'by the work faces 22 and 32 of the dies 21 and 31. Specifically, when the dies 21 and 31 are in the closed position thereof, as shown in FIG. 6, the abutments 26 and 36 directly engage each other, so as to prevent striking of the surfaces 24a, 24b and 240 and the corresponding surfaces 34a, 34b and 340 and so as to establish the predetermined narrow clearance, indicated at in FIG. 6, between the dies 21 and 31 in their closed position, as shown in FIG. 6.
Further, the machine 50 comprises in the illustrated embodiment, as shown in FIG. 4, an air blast nozzle 81 carried by the rear section of the block 54 and directed toward the dies 21 and 31 in their closed position, the nozzle 81 serving to direct a stream of air under pressure into the dies 21 and 31 in order to insure the removal of the scrap 14 from the pilot end of the blank 10 in the pinching of the cone-shaped point 13 in the illustrated embodiment on the extreme outer end of the shank 12, as best illustrated in FIG. 6. Also, the machine 50 com prises any conventional facility, not shown, for feeding the blanks 10 successively into the dies 21 and 31 in coordinate relation with the movements thereof between their open and closed positions.
Considering now the operation of the machine 50 to effect pinch-pointing of the blank 10, and referring to FIGS. 5 and 6, it is noted that when the dies 21 and 31 are in their open position, one of the blanks 10 is dropped by the feeding facility into the dies 21 and 31. Specifically, the extreme front end of the shank 12 is dropped into a fixed work position between the recesses 22a and 32a respectively formed in the upper portions of the work faces 25 and of the respective dies 21 and 31, as clearly shown in FIG. 5. The die 31 is then moved from its fixed open position towards its fixed closed position, both with respect to the die 21; whereby the extreme outer end of the shank 12 is first clamped in its work position between the dies 21 and 31 at the apex of each of the semiconical recesses 22a and 32a. Continued closing movement of the die 31, pinches the button-like scrap 14 upon the extreme lower end of the shank 12, while forming the cone-shaped point 13 on the pilot end of the shank 12, and without substantial longitudinal elongation of the shank 12, all as shown in FIG. 6. In the fixed closed position of the dies 21 and 31, as shown in FIG. 6, the abutments 26 and 36 are engaged, with the clearance 20 between the marginal edges of the surfaces 24a, 24b and 240 and the marginal edges of the surfaces 34a, 34b and 340. In the illustrated embodiment, the small shock produced by the impact of the abutments 26 and 36 breaks the scrap 14 from the extreme lower end of the shank 12 and at this time a blast of compressed air is directed from the nozzle 81 into the dies 21 and 31, so as to blow the scrap 14 clear of the dies 21 and 31. The dies 21 and 31 are then moved toward their full open position and the blank 10 is moved forwardly from between the dies 21 and 31 with the result that the blank 10 falls between the die holders 61 and 71 and is caught below the blocks 54 and 55 to be further worked in the thread-rolling step, that follows the present pinch-pointing step. When the die 31 is again moved into its fixed open position, another blank 10 is fed into the dies 21 and 31 in the manner explained above.
In the machine 50, the arrangement, wherein the abutments 26 and 36 respectively carried by the dies 21 and 31 directly engage or strike as the die 31 is moved into its closed position with respect to the die 21, is very advantageous, since it positively establishes the small predetermined clearance 20 between the boundary edges of the recess 22a and 32a in the respective dies 21 and 31 so as to insure breaking off of the scrap 14 from the extreme outer pilot end 13 of the shank of the blank 10 when a conical point is being formed on the blank. Moreover, the abutments 26 and 36 are not deformed or battered during use of the dies 21 and 31 over an extremely long useful life, since the dies 21 and 31 are formed of the exceedingly hard material, and the dies 21, 31 are located in precise alinement in the die pockets 65, 75 and are guidingly moved by the cooperative action of the bushings 56 and pins 57. Furthermore, the abutments 26 and 36 are not shattered in the operation of the dies 21 and 31, notwithstanding the fact that the dies 21 and 31 are formed of the extremely hard material, as noted above.
Also, the arrangement of the clamping screws 64 and 74 and the cooperation thereof with the respective die holders 63 and 73 and with the respective dies 21 and 31 is very advantageous, since the same accommodates ready placement and removal of a plurality of pairs of dies in the recesses 54:: and 55a in the respective blocks 54 and 55, as required in the manufacture of a series of screws of different sizes, as required in the marketing of such screws. As noted above, the clamping screws 64, 74 and conical recesses 24x, 34x ensure uniform alinement.
In a constructional example the dies 21 and 31, in the manufacture of screws of the size numbers 6, 8 and 10, each die may have a length of 1.000", a height of 1.000 and a width of 0.500". The recesses 22a and 32a may have the respective diameters 0.124", 0.144" and 0.160" respectively corresponding to the screw size numbers 6, 8 and 10. The clearance 20 between the dies 21 and 31 may be in the general range 0.003" to 0.004"; and the other dimensions may bear the relations to those noted of the parts set forth in accordance with the scales of FIGS. 3, 4, 5 and 6. Employing the dies 21 and 31 of the character noted, the machine 50 has an operating speed in excess of of that of conventional pointing machines and is operated to work in excess of 600 screw blanks per minute.
In view of the foregoing, it is apparent that there has been provided a machine for pinch-pointing the pilot end of the shank of a screw blank, which machine is of improved and simplified arrangement and incorporating a pair of dies for the pinch-pointing step that are of improved and simplified construction and arrangement.
While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.
Having thus described my invention what I claim as new and desire to secure by Letters Patent of the United States is:
1. A machine for pointing the pilot end of a metal screw blank comprising a stationary mounting member having a plurality of spaced guide bushings extending outwardly therefrom, a movable mounting member movable linearly between a fixed open position and a fixed closed position with respect to said stationary mounting member, said movable mounting member having a plurality of guide pins extending outwardly therefrom and slidingly received Within said bushings whereby accurately to maintain alignment of the movable mounting member relative to the stationary mounting member during movement thereof, die holding and locating means associated with each of said mounting members, complementary dies located in said die holding means associated with said mounting members, said die holding means having die locating surfaces for precisely positioning said dies in a predetermined location whereby to ensure exact alignment of said complementary dies when said mounting members are moved into said fixed closed position, each of said dies having a conical recess formed in a side thereof, means for clamping said dies in precise location in said die holding means in intimate contact with said die locating surfaces comprising clamping screws mounted in said mounting members and having conical forward ends complementary to said conical recesses in said dies, the axes of said clamping screws being oifset from the axes of the conical recesses in said dies when said dies are located in operative position in said die holding means whereby said dies are forced into intimate contact with said die locating surfaces when the conical end of said clamping screw is urged into eccentric engagement with the conical recesses in said dies, a pair of mating work faces respectively carried by said dies and disposed in close proximity to each other with a predetermined clearance therebetween when said dies occupy said fixed closed position, a pair of complementary recesses formed in said work faces and arranged in registry with each other when said dies are clamped in said die holding means, the pilot end of a screw blank being readily insertable into a work position disposed between said work faces and into cooperating relation with said recesses 8., 7 when said dies occupy said fixed open position, movement of said dies into said fixed closed position first clamping therebetween the pilot end of a screw blank in its work position and then pinching a point on the pilot end of the screw having a configuration complementary to the configuration of said die recesses, anda pair, of mating abutments respectivelycarried by said dies and directly engaging each other in said fixed closedposition to establish said predetermined clearance between said work faces in said fixed closed position.
2. A machine according to claim 1 wherein the dies are formed of sintered metal carbide.
References Cited UNITED STATES PATENTS 6/1936 Horton 10 2,4
LEONIDAS VLACHOS, Primary Examiner. 7