US3748674A

US3748674A - Method and apparatus for making hex nuts from sheet metal

Info

Publication number: US3748674A
Application number: US00212130A
Authority: US
Inventors: J Powell; A Treber
Original assignee: All Steel Equipment Inc
Current assignee: All Steel Equipment Inc; Hubbell Inc
Priority date: 1971-12-27
Filing date: 1971-12-27
Publication date: 1973-07-31
Anticipated expiration: 1990-07-31

Abstract

A method and apparatus for making, from sheet metal, hex nuts for electrical fittings in which a twelve sided planar nut blank is stamped from a strip of sheet metal, and is subjected to two successive drawing steps that provide the basic exterior configuration of the nut in the form of a bottom wall with an upstanding hex shaped side wall terminating in a marginal edge portion, after which the end of the marginal edge portion is flattened and simultaneously the inner surfaces of the nut are countersunk for application of threading thereto and trademark indicia and the like are formed in the opposite end of the nut; the nut blank marginal edge portion is then deburred, after which the nut is punched to form the full throat of the nut, and then the margin of the throat inside the nut is press formed to define the nut gland engaging surface. The nut blank is then tapped and barrel plated.

Description

United States Patent 1 Powell et al.

[111 3,748,674 1 July 31, 1973 METHOD AND APPARATUS FOR MAKING HEX NUTS FROM SHEET METAL [75] Inventors: James C. Powell, Elkhart; Andrew S.

Treber, South Bend, both of 1nd. [73] Assignee: All-Steel Equipment Inc., Aurora, 111.

[22] Filed: Dec. 27, 1971 [21] Appl. No.2 212,130

[52] US. Cl. 10/72 R, 10/86 R [51] Int. Cl B2ld 53/24 [58] Field of Search lO/72 R, 72 CN, 72 T, 10/76 R, 76 T, 86 R, 86 F; 85/32.1, 32 V [56] References Cited UNITED STATES PATENTS 680,991 8/1901 Crosby 10/86 F 928,509 7/1909 Dunham.... 10/72 R 1,116,241 11/1914 Carlson 85/321 1,121,369 12/1914 Johnston.... 85/32 V 1,172,427 2/1916 Carlson 85/32 V 1,992,316 2/1935 Kuebrich 10/76 R 2,542,864 2/1951 Friedman.. 10/86 F 3,021,537 2/1962 Hughes 10/72 R Primary Examiner-Charles W. Lanham Assistant Examiner-E. M. Combs Attorney-Robert C. Brown Jr. et al.

[57] ABSTRACT A method and apparatus for making, from sheet metal, hex nuts for electrical fittings in which a twelve sided planar nut blank is stamped from a strip of sheet metal, and is subjected to two successive drawing steps that provide the basic exterior configuration of the nut in the form of a bottom wall with an upstanding hex shaped side wall terminating in a marginal edge portion, after which the end of the marginal edge portion is flattened and simultaneously the inner surfaces of the nut are countersunk for application of threading thereto and trademark indicia and the like are formed in the opposite end of the nut; the nut blank marginal edge portion is then deburred, after which the nut is punched to form the full throat of the nut, and then the margin of the throat inside the nut is press formed to define the nut gland engaging surface. The nut blank is then tapped and barrel plated.

6 Claims, 20 Drawing Figures PATENIEUJUL3 I I975 3 748,674

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PATENTEU JUL 3 1 191a SHEET 5 BF 6 mmm Owm

INVENTORS JAMES C. POWELL ANDREW STRE E ohm mwm m 0mm Q3 .1 mm

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OF N

mm wow Em 3 ATTORN EYS PATENIEDJM" 3. 748.674

JAMES C. POWELL ANDREW STREBER 3 BY 4 a 4 5 W I W AT ORNEYS METHOD AND APPARATUS FOR MAKING HEX NUTS FROM SHEET METAL This invention relates to a method and apparatus for making hex nuts from sheet metal, and more particularly to a method and apparatus for making hex nuts for use in connection with electrical connector and coupling type fittings adapted for such applications as connecting conduit to a box or secure lengths of conduit together.

Hex nuts for use with electrical fittings, such as connectors and couplings, serve a special function of providing a way to clamp the familiar contractible gland between the fitting body and the nut so as to contract the gland against the conduit to secure the conduit to the fitting. Nuts of this general type made by casting and cold impacting have long been available, but cost considerations have recently made it desirable to achieve hex nut manufacture from sheet metal raw material.

A principal object of this invention is to provide a which the nut bottom wall is punched to form the throat of the nut, and then the margin of the nut throat inside the nut is countersunk to define the nut gland engaging cam surface. The nut is then tapped and barrel plated.

The apparatus involved is arranged to provide separate processing stations up to the tapping operation between which the nut blanks are mechanically transferred, with the arrangement being such that during any one processing operation of the machine, a nut blank is at each station being processed by the method method and apparatus for making hex nuts from sheet metal.

Another principal object of this invention is to provide a method and apparatus for making sheet metal hex nuts that requires no secondary machining operations, such as grinding or deburring, after the basic nut structure has been completed.

Another principal object of the invention is to provide a nut manufacturing system that permits one machine to perform substantially'all the basic forming steps in forming nuts from a strip of sheet metal.

Other objects of the invention are to provide a hex nut making method and apparatus that permits formation of the basic nut structure on a step by step mass production basis without requiring manual handling of the nut or special metallic compositions, that provides a basic nut structure that, except for plating, when plating is necessary, requires no further manufacturing processing to be suitable, aesthetically and otherwise, for sale as a commercial product, and to provide a hex nut making machine and apparatus that is economical and convenient in use, and that provides good quality nuts on a mass production basis.

In accordance with this invention, a progressive die structure is provided which permits a strip of sheet metal to be processed into hex nuts of the type indicated in a progressive step by step manner as nut blanks are first formed from the strip and then proceed through the apparatus. Formed from the leading end of the sheet metal strip is a flat nut blank of 12 sided polygonal configuration in which six long sides areseparated by six shorter sides, with the blank then being subjected to two successive drawing operations that provide the basic exterior configuration dimensioning of the nut in the form ofa bottom wall with an upstanding hex shaped side wall terminating in a marginal edge portion, with the corners of the nut wall being aligned with the mid points of the respective six long sides of the blank. Thereafter, the nut blank is simultaneously subjected to a press forming operation in which the end of the nut wall marginal edge portion is flattened, suitable trademarking and the like is formed in the exterior of the nut bottom wall, and the inner surface of the nut side wall are countersunk in an arcuate manner for later application thereto of the nut threading. The nut blank marginal edge portion is then deburred, after step being performed at that station, and after such processing all nuts are simultaneously transferred to the next station in the series, with nut blanks completed except for tapping and plating being consecutively moved to the tapping apparatus employed. In one form of the invention the nuts proceed to a separate but connected tapping apparatus employing a three fluted tapping tool, when in a modified form of the invention, the nuts are tapped at a tapping station employing an expanding forming tool operated as part of the progressive die structure.

Other objects, uses and advantages will be obvious or be come apparent from a consideration of the following detailed description and the application drawings.

In the drawings:

FIG. 1 is an exploded plan view of an electrical conduit coupling of the type employing hex nuts made in accordance with this invention;

FIG. 2 is a perspective view of the nut made in accordance with this invention;

I FIG. 2A is a fragmental cross-sectional view taken substantially along line 2A2A of FIG. 2;

FIG. 3 is a plan view of a sheet metal strip from which the initial nut blanks are formed, showing the configuration of the planar nut blank that is contemplated by this invention;

FIG. 4 is a plan view of a single nut blank prepared for the subsequent nut forming operations, contemplated by this invention;

FIG. 5 is an end view of a three fluted tapping tool that is preferred for forming the nut threads shownat FIG. 2;

FIGS. 6A and 6B are a composite plan view of the lower fixed portion of die structure comprising the apparatus of this invention, with FIG. 6A showing nut blanks proceeding to move through' the die apparatus;

FIG. 7A and 7B are a composite vertical sectional view through the feed path defined by the die structure shown in FIGS. 6A and 6B, showing the nut blanks in their various stages of processing at the respective die stations;

FIG. 7C is a fragmental side elevational view of one of the die forming tools;

FIG. 8 isa fragmentalelevation'al view or onefof the spring arms employed for holding and transferringbetween consecutive die stations the nut blanks that are Code and that the invention may have other embodiments which will be obvious to those skilled in the art, and which are intended to be covered by the appended claims.

GENERAL DESCRIPTION Reference numeral of FIG. 2 generally indicates the hex nut made by the practice of this invention, that is specifically adapted for use in connection with electrical couplings of the general type indicated at 12 in FIG. 1, which comprise a body 14 formed with threaded

end portions

16 and 18 that respectively receive

conduit end portions

20 and 22 together with the respective nuts 10. The respective nuts 10 respectively receive conventional contractible seals or glands 24 which are intended to be contracted against the respective tube ends as the respective nuts are turned on the fitting body portion to fix the tube ends together. The coupling 12 is shown for illustrative purposes only as nuts 10 are widely used in various types of couplings and connectors adapted for use with the various types of electrical conduit in use.

The nut 10 generally comprises a hex shaped body formed to define a planar bottom wall structure 32 at the shoulder or head end of the nut shaped to define an opening 34 that defines the throat of the nut through which the tube end is received. Wall 32 has in circumambient relation thereabout an upstanding flange or side wall 36 of hex configuration comprising a plurality of generally rectilinear segments or sections 37, with adjacent of these merging at nut corners 39. Each segment 37 defines an inner face 40, the latter being formed with threading 42 adapted to cooperate in threaded relation with one of the ends of the fitting body 14 or its equivalent.

The nut bottom wall 32 includes an outer planar surface 44 about its margin, and the flange or side wall defines a substantially planar upper end surface 46 at the flange end of the nut. The surface 46 is formed with tapered inwardly converging screw lead in surfaces 48 in alignment with each threaded portion 42, and the wall 32 includes conically shaped cam surface 50 that is intended to engage the gland or seal 24 as the respective nuts 10 are turned onto the

respective ends

16 and 18 of body 14 (or its equivalent) to-press the respective glands or seals 24 against the respective ends of the body 14 and cam the respective seals or glands inwardly radially to close them against the respective tube ends and thus clamp the tube ends in fixed relation to each other and within the body 14.

The nut 10 thus defines a radial shoulder 52 which is drawn against the respective glands as the nut is turned on the fitting body to press the gland against the terminus 26 of the fitting body, the spherical contour of the gland outer surfaces 28 being engaged by the nut shoulder 52, surface 50 and fitting end portion 26 (which all conventionally has a cam surface 53 formed therein proportioned to engage gland surface 28) to effect the camming action that has been indicated.

In accordance with this invention, nuts 10 are formed from a strip 54 ofa suitable metallic composition (such as conventional 14 gauge sheet metal that has been hot rolled and pickled) which is suitably fed into progressive die apparatus 56 for processing in accordance with this invention. Die apparatus 56 generally comprises a fixed lower or stationary die structure 57 and a movable die head structure 58 that is raised and lowered in any suitable manner to perform the metal forming operations contemplated by this invention.

The die apparatus 56 includes a shearing type blanking mechanism 61 (see FIG. 7A) that initially forms the nut blanks 60 in connected relation in strip 54 (see FIG. 3), a cutter mechanism 63 that severs the individual blanks 60 from the strip 54; a first draw station 65 which operates to change the blank to its generally cup shaped form 60A of FIG. 1 l, and a second draw station 67 which provides the blank form 608 (FIG. l2) that has the final exterior configuration and dimensioning for the nut 10 except at its marginal edge portion 62 which will then have the rough configuration indicated in FIG. 12. Following the draw stations are a press forming station 69 (see FIG. 7B) at which the nut edge portion 62 is flattened to form surface 46, the nut inner side faces 40' are counter sunk in an arcuate cylindrically contoured manner as at 64, the surface 44 is formed to define any trademark indicia or the like that are desired on the nut, and the screw lead in surface 48 are formed in nut edge portion 62, resulting in the nut blank form 60C (FIG. 13). The nut blank next proceeds to a deburring station 71 at which the outer edge of the marginal edge portion 62 is deburred, providing the nut blank form 60D (FIG. 14), after which the nut blank proceeds to punching station 73 at which position the nut throat 34 is formed to provide the nut blank form 60E (FIG. 15), whereupon the nut blank 60E proceeds to counter sinking station 75 at which the cam surface 60 is formed to provide the nut blank form 60F of FIG. 16.

As the individual nut blanks proceed in I series through the apparatus 56, they are engaged, held, and

transferred by a reciprocating transfer member slidably mounted in the die bed 57 and suitably actuated in the timed relationship required to be consistent with the processing operations at the respective die station. The transfer member 70 carries a pair of end spring arms 72 which engage a nut blank 60 prior to its being severed from the metal strip 54 and move the blank 60 to the first draw station 65; at the first draw station 65, on lowering of the die head 56, the nut blank 60 is subjected to its first draw, which separates it from spring arms 72, whereupon transfer member 70 moves back to the position of FIG. 6A after which the now formed blank form 60A is brought into engagement with, by the retracting action of the die) a pair of spring arms 74 carried by transfer member 70 adjacent arms 72.

Spring arms 74 serve the same function as arms 72 in transferring the blank form 60A to draw station 67, where the nut blank form 60A will be released from such spring arms 74 for return of member 70 to the position of FIG. 6A and final draw shaping, whereupon the resulting nut blank 608 will engage a similar pair of arms 74 by the retracting action of the die. Similarly, the succeeding nut blank forms 60C through 60F are transferred, processed at the respective stations indicated, and then engaged by similar pairs of spring arms 74 through the station 75 for further transfer.

The spring arms 74 that engage the nut blank form 60F in the form of FIGS. 6A through 73 move the nut blank 60F into alignment with discharge passage and in vertical alignment with discharge plunger 82 of discharge station 81, whichdischarges the nut blank form 60F to a suitable tapping machine equipped with the three fluted tapping tool 84 of FIG. 5 that operates to form the nut threading 42. In the alternate apparatus 56A illustrated in FIG. 9, a tapping station 83 is included in apparatus 56A between stations 75 and 81 which press forms the threading 42 in the individual nuts. The transfer member 70A of this embodiment is proportioned lengthwise accordingly and includes an additional set of spring arms 74 to provide the nut blank transfer functions that have been indicated.

After tapping, the nut is ready for plating or the like, and then may be barrel plated for application to electrical fittings of the type that have been referred to. No further secondary machining operations are required after tapping is completed to improve aesthetics, eliminate burrs, or the like.

SPECIFIC DESCRIPTION As has been indicated, the basic nut blank 60 that forms the initial work piece (that ultimately becomes the nut is of polygonal configuration comprising six relatively long sides 90 and six relatively short sides 92 (see FIGS. 3 and 4). The blank 60 also is formed with centrally located perforation 94 that serves a locating function at the blank forming and severing

stations

61 and 63 as well as at the initial draw station 65.

As also has been indicated, the shearing type blanking mechanism 96 operating at station 61 forms onehalf of adjacent blanks 60 from the metal strip 54 (see FIG. 6A), leaving the initially formed blank 60 connected together by metal strip sections 98 which are cut away at cut off station 63 (see FIGS. 6A and 7A) to separate a leading blank 60 from the blank 60 that follows it. As indicated in FIGS. 6A and 7A, such blank 60 is held against displacement by arms 72 while being so severed from strip 54.

Die structure 56 is basically only diagrammatically illustrated, with-specific illustration being made only of those parts which vertically affect the shaping of the nut.

At the station 61, a pair of

upper die members

100 and 102 carried by the die head 58 cooperate in shearing relation with a pair of complementing die lower shaping structures 104 and 106 (see FIG. 6A) suitably fixed to the die base structure 57 so that as die members and 102 move past the

die structures

104 and 106, respectively, the shaping of strip 54 that is indicated in FIG. 6A occurs.

At station 61 is also located a punch element 108 suitably fixed to the die head 96 and including a punching end 110 that forms the perforation 94, which perforation 94 receives the reduced end 112 of guide pin 114 when the strip 54 is advanced one position.

In the form shown, the lower die structure 57 is equipped with a hold down plate 116 formed with

window openings

118 and 120 through which the

die members

100 and 102 operate, as well as openings 122 and 124 that respectively receive punch portion 110 of punch element 108 and the reduced portion 112 of guide pin 114. Plate 116 is secured in place by suitable bolts 126 to define a passage 128 of restricted dimension along the basic feed path 130 of apparatus 56. Any suitable intermediate feed type of apparatus may be employed to intermittently feed strip 54 into apparatus 56, such as the Super Falcon feeder Model No. 33HD, made and sold by American Monarch Machine Co., Inc., Peoria Heights, Illinois. The feeder employed should be arranged to maintain the strip 54 properly centered with

stations

61 and 63, and, of course, operate in the necessary timed relation to properly function 7A. The die head 58 also carries at station 63 locating pin 138 having its end portion 140 operating in perfora tion 94 of the blank 60 being severed to maintain alignment of that blank 60 as it is being severed from the strip 54. Associated with pin 138 is pressure block 144 through which pin 138 extends, and which is suitably suspended from head structure 58 for limited vertical movement and is spring biased downwardly by suitable springs 143 to exert spring pressure on blank 60 to hold it in correct position to be engaged by fingers 72, when die head 58 is lowered to its press forming position. When die head 58 is retracted, pressure block 144 is carried with it.

The lower die structure 57 is suitably apertured as indicated at 146, 148, and 152, as well as in alignment with the

die members

100 and 102, to permit the blank shaping tools that have been referred to to complete their forming strokes in a suitable manner, as indicated in the showing of FIG. 7A.

The transfer member 70 is of generally U-shaped or bifurcated configuration comprising a pair of spaced arms and 162 joined together at a base portion 164 which is actuated by suitable reciprocating mechanism operating in the timed sequence required to permit the nut forming steps that have been indicated. In the form illustrated, base portion 164 of member 70 is equipped with a cam follower 165 that rides in a groove of a rotating cam plate (not shown), which groove is shaped to, and the rotation is such, to reciprocate member 70 in the sequence desired. The blank gripping arms 72 in the form shown are secured to the respective transfer member arms by a suitable pivotal connection as at 166 any 168 (see FIG. 6A), respectively, the gripping

portions

170 and 172 being spring biased towards each other by

suitable springs

174 and 176 operating between the respective

transfer member arms

160 and 162 and the respective arms 72.'The respective arms 72 each include a projection 180 serving to engage an adjacent portion of the transfer member to limit movement of the respective blank

engaging portions

170 and 172 towards each other, and the respective blank

engaging portions

170 and 172 are formed with camming surfaces 182 that engage the blank 60 to open the arms 72 as the transfer member 70 is moved in the direction of the blanks 60 to be engaged by the arms 72. As indicated in FIG. 6A, the

blank engagement portions

170 and 172 are socketed as indicated at 184 and 185, respectively, to conform to the marginal configuration of the blank 60.

The blank engaging arms 74 are arranged in spaced

sets

190, 192, 194, 196, 198 and 199 intermediate the arms 72 and the transfer member base 164 in the form of FIGS. 6A 7B. The individual arms 74 are pivotally secured to the respective

transfer member arms

160 and 162 as at 200 and are suitably biased by a suitable spring 202 for engagement with the respective blanks they are to engage. The blank engaging ends 204 of the respective arms 74 are of special configuration to permit them to be cammed open by relative vertical or horizontal movement to receive the blank they are to engage, depending on the portion of the cycle of operation of the apparatus 56. As indicated in FIG. 8, heads 204 are enlarged to define a protubrant portion 206 that is notched as at 208 to receive a corner 39 of the nut blank in question, with the cam surfaces 210 and 213 being provided to permit movement of the transfer member longitudinally of the feed path 130 to cam the arms 74 in question open to receive or pass the nut blank. Also provided are

cam surfaces

212 and 214 provided for the same purpose when arms 74 are stationary at a particular station and the nut blank is moved vertically upwardly from a depressed position within the die structure 57 after the completion of the particular blank forming stroke. While only one of the

surfaces

212 and 214 is required, they are both provided to make arms 74 on either side of member 70 interchangable.

The arms 74 are also each equipped with a stop lug portion 216 cooperating with suitable abutment surfaces of the transfer member 70 to limit the amount that end portions 204 of arms 74 can move towards each other consistent with good functioning of apparatus 56. V

The transfer member 70 is suitably mounted in place and guided for movement longitudinally of the feed path 130 and in the form shown has its

arms

160 and 162 respectively formed with elongate slots 220 and.

222 in which engage suitable guide pins fixed with respect to the fixed guide structure 57, such as pins 223 and 224 (see FIG. 6A), respectively.

At station 65, the die head 58 mounts suitable punch type draw tool 226 formed with a head portion 228 of hex configuration fixedly carrying a centering pin 230 having a tapered tip 232 adapted to cooperate with blank perforation 94 to maintain the blank 60 centered as the initial draw is initiated on the blank 60 once it has been positioned at the station 65. Draw tool 226 operates in alignment with a hex shaped cavity of the die member 236.

The female die member 236, which is suitably anchored to the die structure 57, also receives stripper member 238 that is upwardly biased by spring actuated thrust rod 240 that is subject to the action of a suitable compression spring (not shown). Stripper element 238 is recessed as at 242 to accommocate the end of alignment pin 230.

The arrangement of station 65 is such that when a nut blank 60 is positioned at station 65 by transfer member 70, the blank 60 will be positioned over the female die forming recess 234 so that downward movement of the die head 58 will bring the tool forming end 228 against the blank 60 to press it within the female die 236 against the action of stripper elements 238, substantially to the position indicated in FIG. 7A, whereby the blank form 60A is formed. At this point transfer member 70, from the arms 72 of which the blank 60 has been dislodged by the drawing operation just mentioned, returns to the full line position of FIG. 6A to bring the arms 72 into engagement with the next blank 60 prior toits being severed from strip 54. As die head 58 retracts after completing its working stroke, the action of push rod 240 on stripper element 238 moves the completed blank 60A upwardly into engagement with the set 190 of arms 74, the

surfaces

212 or 214 of the respective arms 74 in question that are facing downwardly serving as cam surfaces to open the arms 74 against the action of the respective springs 202. The

shoulder 239 of the stripper element engages die plate 242 to limit upward movement of the stripper member 238.

At the station 67, draw tool 250 is suitably secured to the die head 58 and has a working end portion 252 of hex shaped configuration for drawing engagement with the nut blank 60A to form the nut blank form 60B in cooperation with female die member 254 that defines hex shaped forming recess 256. Associated with the female die member 254 is stripper member 258 that is similar to stripper member 238 and is upwardly biased by spring actuated thrust rod 260 and has a motion limiting flange 262 thereon to limit upward movement of the stripper element 258.

Stripper plate structure 263 held in place on die structure 57 by suitable bolts 265 and projecting end portions 264 and 266 suitably notched to receive

tools

226 and 250 and disposed in movement guiding relation to transfer member 70, provides desired stripping functions at stations and 67.

As previously indicated, the die elements involved at

station

65 and 67 are arranged so that at the station 65, the blank 60 is given the initial draw to form blank 60A and at the station 67, the blank 60A is given a final draw that gives the nut blank 608 the final exterior contour and dimensioning that nut 60 will have, except at upper edge portion 62. On retraction of the die head 58, the nut 608 will be returned to the set 192 of spring arms 74 in the manner previously described in connection with the set of spring arms 190.

The transfer member 70 then operates to move the blank 603 to station 69, at which location the tubular forming member 270 is suitably fixed to the die head 58 and is provided with a reduced end portion 272 that is circular in cross-sectional configuration and proportioned to form the arcuate countersunk areas 64 in the wall surfaces 40 of nut blank 608. The member 270 is formed with a planar internal shoulder 274 of hex shaped configuration adapted to engage the upper edge portion 62 of the blank 60B to flatten same (thereby forming end surface 56) and spaced arcuate convex surfaces 275 (see FIG. 7C) each aligned with a side of shoulder 274 that form nut surfaces 48. Forming member 270 works opposite a stripper element 277 associated with female die member 276 and upwardly biasing by spring actuated thrust rod 279 that returns the completed blank 60C to the position where it will be gripped by the set of spring arms 174. Stripper member 277 in the illustrated embodiment carries at its upper end a hardened die element 280 secured in place by a suitable bolt 282 and formed about its marginal surface 284 with the usual raised lettering, numbering or the like for indenting into the marginal surface portion 44 of the nut 10 the desired trademarking, nut siae a'nd the like indicia. 4

In the form shown, die head 58 has fixed thereto a pair of depending rods or pins 281 that respectively engage (as at 281A) upstanding rods or pins 283 (see FIG. 7B) suitably fixed to cross head 285 that is suitably fixed to thrust rod 279 (as by employing bolts 285A), so that as die head 58 moved downwardly, thrust rod 279 moves downwardly also, with the result that blank 60B is moved into die member 276 free of any resistance from stripper 277. The press forming of blank 60C is completed with shoulder 277A of stripper seated against shoulder 277B of die structure 57, and as die head retracts, carrying rods 281, thrust rod 279 acts on stripper 277 to bring nut blank 60C to arms 194. In the final forming position at station 69, thrust rod 279 is spaced slightly below stripper 277, as indi cated in FIG. 7B.

Cooperating with the dietool 270 is an upper stripper pin 286 having its lower end 288 proportioned to engage the inside surface 289 of the nut blank 60C; stripper pin 286 is spring biased, as by a suitable compression spring 290, to strip tool 270 from nut blank 60C as die head 58 retracts.

At station 71, a tubular deburring tool 300 is suitably fixed to die head 58 and is formed with a hex shaped recess 302 that substantially complements the exterior surface of the nut wall 38, and a shoulder 304 that is shaped to bend any sharp edging 305 remaining along the outer edge of edge portion 62 flat against the now flattened end surface 48. Tool 300 works against stripper member 306 so as to avoid interference with transfer of the nut blanks between stations. Operably associated with the tool 300 is stripper element 312 proportioned to engage the inner surface of the nut blank 60D to strip same from tool 300 under the action of suitable compression spring 314. Operably associated with the stripper member 312 is a stripper pin 316 that is spring biased by suitable compression spring 318 and has its lower end 320 also engaging the inside surface 289 of the nut blank 60D for stripping purposes.

Tool 300 is of reduced dimension transversely of feed path 130 to avoid interference with the arms 74 adjacent same as the blank deburring at station 71 is performed.

At the station 73, suitable punching tool 322 is fixedly carried by the head 58 and has its working end 324 proportioned to punch out the bottom wall 32 of the nut to the full diameter of throat 34. This is done in cooperation with female die member 326 suitably formed to define operating recess 328 through which the resulting slug 330 is discharged. Tool 322 is enlarged as at 323 for piloting engagement with nut side wall 36, and is tubular in nature to receive stripper pin 325 that is spring biased by suitable spring 327 to shed the slug from tool 322.

At the stations 71 and 73, the nut blanks there being processed do not retract below the level of movement of the spring arms 74. Thus, the

sets

194, 196 and 198 of spring arms 74 are cammed open to receive and pass over the nut blanks in question by being provided with the

surfaces

210 and 213. For instance, the set 196 of arms 74 brings the blank 60D to station 73, and as die head 58 proceeds to lower to perform the metal working functions indicated, transfer member 70 returns to the position of FIG. 6A (after tool 322 engages blank 60D), arms 74 of set 196 moving to the right relative to the blank 60D (being processed at station 73), the shape of their notches 208 readily permitting this action. The set 198 of arms 74 at the same time move toward the nut 60D (being formed into the nut blank 60E at station 73), these arms being cammed open by engagement of surfaces 210 with the corners 39 of the nut blank they engage, and the arms 74 in question snapping shut against the indicated corners of the nut blank.

At the station 75 (to which the nut blank 60 is transferred), countersinking tool 340 is fixedly carried by the die head 58 in any suitable manner and has a working end portion 342 including an extension 344 propor- 6A through 78.

tioned to fit through the nut blank throat 34 and having a rounded side wall 346 which merges into a conical shoulder 348 which press forms cam surface 50 about the inner margin of throat 34.

The tool 340 acts against stripper member 350 formed with a suitable recess 352 to receive the extension 344 of the member 340, and a suitable flange 354 to limit upward movement thereof. Stripper member 350 operates in female die 356 formed with a hex shaped recess 358 which receives the blank 60E being worked on to form the blank 60F. Stripper member 350 is upwardly biased by spring biased thrust rod 360 so that on retraction of die head 58, the completed nut blank 60F is received in the set of arms 199 for transfer to discharge station 81.

The plunger member 82 at station 81 is suitably fixed to head 58 and operates in alignment with discharge opening 80, as previously indicated. As head 58 descends, its working end 362 engages the nut blank 60F to free same from the set 199 of arms 74 for discharge into passage A leading to the tapping machine of the type that is contemplated by the embodiment of FIGS.

Such tapping machine may be of any suitable type equipped with three fluted tapping tool 84 of which each of the flutes 370 are formed with the usual thread forming serrations 372. One suitable machine is the Snow Tapper, made and sold by Snow Manufacturing Company, which is arranged to receive nuts from passage 80, automatically mount them for threading purposes, and then apply the tapping element thereto to form the threading 42 in countersunk surfaces 64.

It has been found that a three fluted tapper is necessary to satisfactorily form threads 42 in this manner in order to avoid catching of the tapping tool in the corners of the nut blank and provide adequate room for discharge of the material excised from the nut blank by the tapping operation being performed.

After the tapping is completed, the nut is barrel plated to complete the nut 10, if plating is desired for the finished product, as it ordinarily is in connection with electrical fittings of the type indicated.

The formation of threading 42 in nut blank surfaces 64, as distinguished from forming in nut surfaces 40 that are wholly planar, increases the amount of threading formed in each nut side wall segment 37 between adjacent nut corners 39, as more material is provided toward the nut corners in which the threading 42 can be formed than would be available if the threading 42 were formed directly in planar surfaces 40.

If the embodiment of FIG. 9 is practiced, the apparatus 56 is modified to form apparatus 56A having an additional station 83 along the feed path and intermediate the stations 75 and 81. The arms and 162 of transfer member 70A are lengthened proportionally and provided with another set of gripper arms 74 (not shown) to transfer the nut blank 60F from the station 75 to the station 83 in a manner similar to that already described.

At the station 83, a tubular collet member 380 that is split longitudinally thereof to define a plurality of spring fingers 382 (one finger to engage each surface 64 of nut blank 60F), with each finger including suitable thread forming ridges 384 at the ends 385 thereof adapted to be pressed into the nut blank surfaces 64 by a thrust pin 386 provided with a conical cam surface 388 adapted to cooperate with complementarily shaped cam surfaces 390 of the respective fingers 382.

In the form shown in FIG. 9, the collet member 380 is telescopingly received in a split retainer 392 disposed about the thrust pin 386. Collet member 380 is spring biased downwardly by a suitable compression spring 394 seated between a shoulder 396 of the collet member and plate 398 of upper die structure 58 in which the thrust pin 386 is suitably fixedly mounted. The fingers 382 of collet member 380 are formed to be spring biased radially inwardly thereof so that when the die head 58 is retracted, and collet member 380 is fully extended from retainer 92, the ends of fingers 382 will freely slip within the side wall 36 of the nut blank until their lower ends engage the bottom wall 32 of the nut, whereupon on further downward movement of the die head 58, the collet member remains stationary and thrust pin 386 moves downwardly relative thereto to cam the finger ends 385 outwardly against the respective nut faces 40 to form the threading 42 therein. On retraction of the die head 58, the collet member 380 initially tends to remain in place while thrust pin 386 moves upwardly relative thereto until the surfaces 390 of the fingers 382 are sufficiently clear from the pin surface 388 so that their inward bias frees them from the blank walls to permit upper withdrawal of the collet member from the now threaded nut.

The lower die structure 57A is formed with a hex shaped recess 400 which receives the nut blank 60F from transfer member 70A. Thrust pin 386 in camming the collet member fingers 382 against the nut walls 40 acts against stripper member 402 that is upwardly spring biased in any suitable manner to aid in stripping the pin 386, and which also elevates the nut for engagement by the additional set of arms 74 for transmittal to station 81. The apparatus 56A is otherwise the same as the female dies at

stations

65, 67, 69, 71, 73 and 75 are preferably formed from carbide or the like and are fixed in position in any suitable manner.

OPERATION The means for feeding the sheet metalstrip 54 into the machine 56, as well as the means for raising and lowering the die head 58 and actuating the transfer member 70 are made such that when the die head 58 is raised, the strip 54 is moved forwardly, to the left of FlGS. 6A through 78, so that the end blank 60 of the strip can be severed from the strip, and so that additional nut blank forming configurations can be formed on the strip itself at station 61. Transfer member 70 at this point will have shifted to the left of FIGS. 6A to 78 to transfer the nut blanks at the

respective stations

63, 65, 67, 69, 71, 73 and 75, respectively to the next

adjacent stations

65, 67, 69, 71, 73, 75 and 81, at which positions these nut blanks are now ready for the next forming action to be performed on them.

The die head 57 then comes down to perform the metal working functions indicated in FIGS. 7A and 78 (described in detail above), transfer member 70 cycling back to the full line position of FIGS. 6A and 6B prior to the severing of the next blank 60 from strip 54 is completed, but after the nut blanks at

position

65, 67 and 69 have moved below the level of the spring arms 74.

As the die head 58 rises, the nut blanks that are below the level of the spring arms 74 at the particular stations involved are raised back up into engagement with those particular sets of spring arms, and at an appropriate point the transfer member then cycles back to the left to again advance the nut blanks to the next working position, with the working cycle repeating continuously to supply nut blanks 60F to the threading arrangement employed.

The timing and part actuation involved can obviously be accomplished in any suitabl manner using existing knowledge in this art.

It will thus be seen that our invention provides a method and apparatus for making nuts from sheet metal that requires no secondary metal working operation, such as grinding or polishing, and after the nut has been completed through threading of same, following the procedures indicated. The two step drawing operation permits accurate exterior dimensioning of the nut leaving only the rough upper edge portion 62 to be flattened for aesthetic purposes. This flattening operation is combined with a trademarking and countersinking of the nut top and inner side walls, the latter resulting in making more of material of the nut side walls towards the nut corners available for threading to increase the amount of threading that can be formed on each side wall in spite of its generally rectilinear configuration.

The deburring step eliminates any rough edge along the nut upper edge portion 62, while the throat forming and throat countersinking steps complete the formation of the throat nut that is essential for nuts of the type described as well as the cam surface at the throat that is required to close the conventional glands 24.

The method and apparatus of this invention permit inexpensive nut manufacture from sheet metal strips made from readily available raw materials in sheet metal form, and of standard metallic composition.

Use of the tapping tool shown in FIG. 5 avoids the application of excess torque to the tapping tool that would tend to distort the blank being worked on due to the frictional drag involved by the use of more than three flutes.

The foregoing description and the drawings are given merely to explain and illustrate the invention and the invention is not to be limited thereto, except insofar as the appended claims are so limited, since those skilled in the art who have the disclosure before them will be able to make modifications and variations therein without departing from the scope of the invention.

We claim:

1. The method of forming sheet metal hex nuts of the type having a shoulder end and a flange end, with the nuts being for use as a clamp nut on electrical conduit connectors and coupling type fittings to secure a conduit end extending through the nut throat at its shoulder end, to the fitting body by having its shoulder end cam a contractible gland, that is received in same through its flange end, against the fitting body to contract the gland against the conduit, said method comprising:

establishing stamping, drawing, press forming, deburring, punching, and countersinking stations arranged in a rectilinear row,

intermittently feeding a sheet metal strip to said stamping station by moving said strip lengthwise figuration defining a bottom wall at the nut shoulder end and a polygonally shaped upstanding side wall having one half the sides of the blank and in the circumambient relation about the bottom wall and terminating at the nut flange end in a marginal edge portion defined by the blank side edge, with the corners of the side wall being centered with the mid points of alternate sides of the blank, and the exterior of the side wall defining the final exterior configuration and dimensioning of the nut,

mechanically transferring the drawn blank to the press forming station and flattening the end of said marginal edge portion while countersinking the inner faces of said side wall from the nut flange end to adjacent the shoulder end thereof,

mechanically transferring the blank to the deburring station and deburring the outer edge of said side wall marginal edge portion,

mechanically transferring the blank to the punching station and punching the bottom wall to form the throat of the nut,

mechanically transferring the blank to the countersinking station and press forming the margin of the nut throat on the side thereof within said side wall to define a substantially conical gland engaging surface at the nut shoulder end,

and tapping the countersunk surfaces of said side wall to threadedly receive a threaded end of a conduit fitting.

2. The method set forth in claim 1 wherein:

subsequent blanks are consecutively processed in like manner to consecutively form the nuts by simultaneously performing said stamping, drawing, flattening, deburring, punching, and press forming steps on consecutively formed blanks.

3. Apparatus for forming sheet metal hex nuts of the type having a shoulder end and a flange end, with the nuts being for use as a clamp nut on electrical conduit connectors and coupling type fittings to secure a conduit end, extending through the nut throat, to the fitting body by having its shoulder cam a contractible gland, that is received in same through its flange end, against the fitting body to contract the gland against the conduit, said apparatus comprising:

a progressive die forming structure including in consecutive order:

a stamping station including means for consecutively stamping from a strip of sheet metal sheet metal blanks of polygonal side edge configuration having twice the number of sides the nut is to have, from a strip of sheet metal,

a drawing station adjacent said stamping station including means for consecutively drawing the individual blanks to a cup shaped configuration defining a bottom wall at the nut shoulder end and a polygonally shaped upstanding side wall in circumambient relation about the bottom wall and terminating at the nut flange end in a marginal edge portion defined by the blank side edges, with the corners of the side wall being centered with the midpoints of alternate sides of the blank, and the exterior of the side wall defining the final external configuration and dimensioning of the nut,

a press forming station adjacent said drawing station and including means for flattening the end of the blank marginal edge portion while countersinking the inner faces of said blank side wall from the nut flange end to adjacent the shoulder end thereof,

a deburring station adjacent said press forming station and including means for deburring the outer edge of said blank side wall marginal edge,

a punching station adjacent said deburring station and including means for punching the blank bottom wall to form the nut throat of predetermined size,

and a countersinking station adjacent said punching station and including means for forming a substantially conical countersink about the inside margin of said blank throat that defines the gland engaging surface,

said stations being arranged along a rectilinear feed path,

and-means for moving successive blanks between adjacent stations including:

an elongate transfer member mounted for reciprocating movement along said feed path,

said transfer member including gripper devices aligned with each of said stations adapted to releasably grip the blanks-being processed at each station, v

means for reciprocating said transfer member longitudinally of said feed path in the timed sequence required to advance each blank held thereby one station prior to operation of the respective means at said stations and return said transfer member to its initial position during operation of the respective means to engage succeeding blanks for advancement to the next station,

and means for intermittently feeding said sheet metal strip to said stamping station.

4. The apparatus set forth in claim 3 including:

means for tapping the countersunk surfaces of the blank side wall of the blank completed at said counter-sinking station.

5. The apparatus set forth in claim 4 wherein:

said tapping means comprises a three fluted tapping tool. p I

6. The apparatus set forth in claim 4 wherein:

said apparatus includes a tapping station aligned with said feed path and adjacent said countersinking stationincluding means for press forming interrupted threads in the blank side wall countersunk surfaces,

said tapping station comprising said tapping means.

Claims

1. The method of forming sheet metal hex nuts of the type having a shoulder end and a flange end, with the nuts being for use as a clamp nut on electrical conduit connectors and coupling type fittings to secure a conduit end extending through the nut throat at its shoulder end, to the fitting body by having its shoulder end cam a contractible gland, that is received in same through its flange end, against the fitting body to contract the gland against the conduit, said method comprising: establishing stamping, drawing, press forming, deburring, punching, and countersinking stations arranged in a rectilinear row, intermittently feeding a sheet metal strip to said stamping station by moving said strip lengthwise thereof and longitudinally of said row, stamping at said stamping station from said strip a planar blank of polygonal side edge configuration having twice the number of sides the nut is to have, mechanically transferring the blank to the drawing station and drawing the blank to a cup shaped configuration defining a bottom wall at the nut shoulder end and a polygonally shaped upstanding side wall having one half the sides of the blank and in the circumambient relation about the bottom wall and terminating at the nut flange end in a marginal edge portion defined by the blank side edge, with the corners of the side wall being centered with the mid points of alternate sides of the blank, and the exterior of the side wall defining the final exterior configuration and dimensioning of the nut, mechanically transferring the drawn blank to the press forming station and flattening the end of said marginal edge portion while countersinking the inner faces of said side wall from the nut flange end to adjacent the shoulder end thereof, mechanically transferring the blank to the deburring station and deburring the outer edge of said side wall marginal edge portion, mechanically transferring the blank to the punching station and punching the bottom wall to form the throat of the nut, mechanically transferring the blank to the counter-sinking station and press forming the margin of the nut throat on the side thereof within said side wall to define a substantially conical gland engaging surface at the nut shoulder end, and tapping the countersunk surfaces of said side wall to threadedly receive a threaded end of a conduit fitting.

2. The method set forth in claim 1 wherein: subsequent blanks are consecutively processed in like manner to consecutively form the nuts by simultaneously performing said stamping, drawing, flattening, deburring, punching, and press forming steps on consecutively formed blanks.

3. Apparatus for forming sheet metal hex nuts of the type having a shoulder end and a flange end, with the nuts being for use as a clamp nut on electrical conduit connectors and coupling type fittings to secure a conduit end, extending through the nut throat, to the fitting body by having its shoulder cam a contractible gland, that is received in same through its flange end, against the fitting body to contract the gland against the conduit, said apparatus comprising: a progressive die forming structure including in consecutive order: a stamping station including means for consecutively stamping from a strip of sheet metal sheet metal blanks of polygonal side edge configuration having twice the number of sides the nut is to have, from a strip of sheet metal, a drawing station adjacent said stamping station including means for consecutively drawing the individual blanks to a cup shaped configuration defining a bottom wall at the nut shoulder end and a polygonally shaped upstanding side wall in circumambient relation about the bottom wall and terminating at the nut flange end in a marginal edge portion defined by the blank side edges, with the corners of the side wall being centered with the midpoints of alternate sides of the blank, and the exterior of the side wall defining the final external configuration and dimensioning of the nut, a press forming station adjacent said drawing station and including means for flattening the end of the blank marginal edge portion while countersinking the inner faces of said blank side wall from the nut flange end to adjacent the shoulder end thereof, a deburring station adjacent said press forming station and including means for deburring the outer edge of said blank side wall marginal edge, a punching station adjacent said deburring station and including means for punching the blank bottom wall to form the nut throat of predetermined size, and a countersinking station adjacent said punching station and including means for forming a substantially conical countersink about the inside margin of said blank throat that defines the gland engaging surface, said stations being arranged along a rectilinear feed path, and means for moving successive blanks between adjacent stations including: an elongate transfer member mounted for reciprocating movement along said feed path, said transfer member including gripper devices aligned with each of said stations adapted to releasably grip the blanks being processed at each station, means for reciprocating said transfer member longitudinally of said feed path in the timed sequence required to advance each blank held thereby one station prior to operation of the respective means at said stations and return said transfer member to its initial position during operation of the respective means to engage succeeding blanks for advancement to the next station, and means for intermittently feeding said sheet metal strip to said stamping station.

4. The apparatus set forth in claim 3 including: means for tapping the countersunk surfaces of the blank side wall of the blank completed at said counter-sinking station.

5. The apparatus set forth in claim 4 wherein: said tapping means comprises a three fluted tapping tool.

6. The apparatus set forth in claim 4 wherein: said apparatus includes a tapping station aligned with said feed path and adjacent said countersinking station including means for press forming interrupted threads in the blank side wall countersunk surfaces, said tapping station comprising said tapping means.