US 2187647 A
Description (OCR text may contain errors)
Jan. 16, 1940.
P. E. DOUBLE ET AL CLINCH-NUT MACHINE Filed July 28, 1937 6 Sheets-Sheet 1 INVENTORS P/ummer Eflou/e P117174 11 0 cer 1940- v P. E. DOUBLE gr AL 2,187,647
CLINCH-NUT MACHINE Filed July 28, 1937 6 Sheets-Sheet 3 INVENTOR; Plum/new 5 Jo u a F ran/1 h asc e r Jan. 16, 1940. P. E. DOUBLE El AL I 2,137,547
CLINCH-NUT MACHINE Filed July 28, 1937 6 Sheets-Sheet 5 INVENTORS lllillllll ll Fran/f 3 401 c 4 e r hx Patented Jan. 16, 1940 UNITED STATES PATENT OFFICE Flint,
Application July 28, 1937, Serial No. 156,184
- 5 pending application, S. N. 81,887, filed May 26,
An object of the invention is the provision of a machine of the character referred to, which will overcome many of the diiiiculties inherent 10 in devices of this kind heretofore known.
' Another object of the invention is the provision of a device of the character referred to, which is simple in construction, eflicient'in operation, and easily adjustable to take care of a great variety of production problems.
Another object of the invention is the provision of a machine of the character referred to, with which clinch-nuts may be firmly attached to metals of several gauges without the necessity of manual adjustment.
Another object of the invention is the provision of a device of the character referred to, which will permit clinch-nuts to be attached to other elements in positions closer to bends and angles .9 in those elements.
. the machine.
Another object is the provision of a device of the character referred to, which is provided with a resiliently mounted anvil adapted to take up any overload on the anvil during its operation.
A further object is the provision of a device in which a complete riveting operation is accomplished by one revolution of the machine.
The foregoing and other objects and advantages of the invention will appear as the description proceeds, reference being made from time to time to the accompanying drawings, constituting a part of this disclosure, in which drawings like reference characters indicate like parts throughout, in which drawings:
Fig. i is a front elevation of the clinch-nut machine embodying our invention.
Fig. 2 is a side elevation of the machine illustrated in Fig. 1.
Fig. 3 is a perspective view of a clinch-nut such as used in connection with our machine.
Fig. 4 is a perspective view of a fragmentary piece of metal provided with an aperture, and to which the nut illustrated in Fig. 3 is to be attached.
Fig. 5 is a perspective view of the same piece of 5 metal illustrated in Fig. 4, showing how the nut illustrated in Fig. 3, is inserted through the aperture, and before being attached by the machine.
Fig. 6 is an enlarged fragmentary detail, partly in section, illustrating the punch.
Fig. '7 is a section taken on line l--| of Fig. 8. and illustrates the sheet of metal and nut after attaching.
Fig. 8 is a plan view of the piece of metal after the nut has been attached thereto.
Fig. 9 is a side elevation of the machine and illustrates a section taken on line 9-4 of Fig. 1.
Fig. 10 is a horizontal section taken on the line lill|i of Fig. 2.
Fig. 11 is a rear elevation, with parts broken away and partly in section, taken on line ll-H of Fig. 10.
Fig. 12 is a section taken on line [2-42 of Fig. 10.
Fig. 13 is an enlarged fragmentary-' section taken on the line I 3|3 of Fig. 12.
Fig. 14 is a section taken on the line "-44 of Figs. 9 and 16.
Fig. 15 is a section taken on line [5-45 of Fig. 9.
Fig. 16 is an enlarged fragmentary front view with parts broken away and with the anvil, partly in section, taken on line It of Fig. 14.
Fig. 17 is a fragmentary plan view, partly in section,illustrating the tucker bar, raceway, and anvil.
Fig. 18 is a view, partly in section, taken on line i8-l8 of Fig. 1'7, illustrating the raceway from the hopper leading into the nut carrier bar.
Fig. 19 is a fragmentary view, partly in section, taken on the line |8l8 of Fig. 17 and illustrates the position of the tucker bar when ready to place a nut onto the anvil. 45
Fig. 20 is an elevation, partly in section, illus- -trating the anvil and nut carrier bar assembly, and illustrating, by dotted lines, several positions assumed by the tucker arm, tucker, and nut carrier bar. 50
Referring now more particularly to the drawings, it will be seen that in the embodiment herein disclosed, the principal working parts of our invention are housed within a casting 35, the latter being secured to a second casting 36 by 5 is adapted to engage a shoulder 88, formed on the casting 85 to provide a bearing surface. At
the lower extremity the tubular member 88 tele-- scopes a three-footed base member 48, the latter being split ,on one side as at 4|, and provided with flllister head screws 42 adapted to draw the split section together. The pedestal assembly just described enables the operator to adiust the machine to various heights.
Adjustably mounted on the tubular member 88 is a motor supporting bracket 48 which is also split on one side and provided with cap screws 44. to enable it to be secured in any desired position on the tubular. member 88. A cover plate 45 (Fig. 2) is adapted to form a cover for the opening in the side of the casting 85, and its. removal permits ready access to the working parts contained within the casting 85, as is described more particularly hereinafter.
Superimposed on the housing 85 and secured thereto by means of bolts 45, is a bracket 41 which is adapted to support the hopper 48 as hereinafter described.
Tie bolts 48 extend vertically through the casting 85 for purposes of reinforcement. These tie bolts 48 carry nuts 58 at each end, the nuts at the top being arranged to engage ofl'sets 5| formed on the exterior of the casting 85, and the nuts at the bottom being arranged to engage bosses 52 formed inside at the bottom of the casting 85. The front of the casting 85 is provided with a recess 53 which is arranged to provide necessary clearance for stock to be passed over the anvil 54, the latter being supported by the front end of the anvil relief lever 55, as hereafter described. The lever is fulcrumed on a pin 55 which is supported at either end in the sides of the casting 35. The rear end of the anvil relief lever 55 (Fig. 9) terminates in a yoke 51 through which is extended a pin 58, which may be held against displacement by any suitable means such as by cotter pins. An eye bolt 58 is arranged to engage the pin 58 and to extend downwardly through an internally threaded boss 58 formed in the bottom of the casting 85. An externally threaded screw 8| is threaded into the boss 58, and is adapted to put tension on the spring 52, which is carried by the eye bolt 58. The spring 5| is held against downward displacement by means of washer 53, and a casteilated nut 54. By properly adjusting the tension on the spring 52, any overload on the anvil 54 will be automatically compensated for as explained more fully hereinafter.
The anvil 54 (Fig. 20) is provided with a bayonet 55 which is adapted to slide vertically in a bayonet slot 55 formed in the member 51, which is preferably a steel casting secured to the front end of the main casting by means of fillister head screws 58. The anvil 54 rests of its own weight on the front end of the anvil relief lever 55 and is secured against upward displacement by means of a locking pin 88 which is adapted to engage a slot 18 formed in the back of the anvil 54, and a counter bored hole 1| in the steel casting 51. The locking pin 58 has a centrally disposed bore which is arranged to carry a compression spring 12 which normally holds the pin 58 in position of engagement with the anvil 54 as shown in Fig. 20. The anvil is provided with a horizontal passageway 18 immediately in front .of the locking pin 88, into aroma? which a tool may be inserted to force the locking pin 58 out of engagement with the anvil 54. When the locking pin 58 is pushed out of engagement with the anvil 54, the latter may be slid upwardly and removed from the bayonet slot. This is an important feature as it enables the operator to remove the ianvil with great speed and rapidity. The anvil54" (Fig. 20) is provided on one side with a fixed jaw 14 (Fig. 16), which is secured thereto by means of rivets 15, and on the other side with a movable jaw 15 which in turn is provided with a centrally positioned lug 15a, through which passes pivot pin 11, the latter being press-fitted into a bore provided therefor in the anvil.
A compression spring 18 is carried in a recess formed in the anvil below the pivot pin 11, and is adapted to rock the jaw 15 on the pivot 11, and force the upper end of the Jaw 18 toward the fixed Jaw 14 in order that a clinch-nut may be firmly gripped between said Jaws. 4
Supported at each end, by means of bearings 88 (Fig. 9), positioned in suitable recesses at either end of the casting 85, is a main drive shaft 8| which is lubricated in the bearings 88 by suitable oil cups 88. At the front end of the shaft 8|, there is machined an eccentric crank 84 to which is mounted for reciprocal motion, a plunger link 85, which is provided with a suitable bearing 85a and oiling means 85b. To the lower end of the plunger link 85 is movably attached, by means of pin 85, a plunger 81 which is provided with suitable bearings 88 and 88, the latter being part of the cover plate 82. To the lower end of the plunger 81 is threadingly supported the punch 88. The lower portion of the plunger 81 is split, and the split section is provided with a threaded horizontal bore which is adapted to receive a locking screw 8|, the latter being adapted to secure the punch 88 to be advanced or retreated to any desired position, and enables the punch 88 to be easily removed in the event that a replacement 'is necessary. Positioned about the punch 88 is a stripper spring 8| which holds the work in alignment on the anvil 54 during the clinching operation, and automatically releases the work from the punch 88 after the clinching operation.. The eccentric crank 84, the plunger link 85 and the plunger 81 are covered by means of the cover plate 82 which is secured to the casting 85 by screws 88.
Keyed to the shaft 8| is a cam member 84 (Fig. 9) which is arranged to engage a roller 85 carried on the tucker arm 85, the latter being formed at its upper end with. a yoke member 81 (Fig. 15) which is pivoted on the shaft 88, the latter being secured at either end in bosses 88 formed in either side of the main casting 85. The spacer 84b is positioned on the shaft 8| and is arranged to contact a thrust washer 840 also carried on shaft 8|, and in contact with the shoulder formed on the inside of the casting 85. The spacer 84b and the thrust Washer 840 are intended to maintain the cam 84 in predetermined posltion on the shaft 8|.
Mounted on the shaft 88 intermediate the arms of the yoke 81 is a second yoke I88, the arms of which are downwardly disposed and adapted to engage opposite sides of the main shaft 8|, for the purpose of centering the tucker arm 88 immediately below the main shaft 8|. At the lower end of the tucker arm 85 is a roller l8| which is arranged to engage a cam surface I82 formed on the under side of the nut carrier bar I88, the latter being pivoted at its rear end on a pin the housing 35 by means of cap screws I00. Upon loosening the cap screws I00, the bracket may be lowered or elevated by the adjusting screw I01, and locked in position by means of nut I00.
The front end of the nut carrying bar I03 remains free for upward and downward movement under the influence of the cam surface I02 riding on the roller MI.
The arm 36 is moved forward and backward by reason of the engagement of the roller 95 w i igh the camsurface 940. on the member 94. tucker arm 96 is urged forward by means of a tension spring I09, which is secured at one end to the tucker arm 96, and at the other end to a pin IIO extending through the front of the casting 35. The bar I03 is provided in its upper surface with a T-slot III in which is adapted to reciprocate a tucker member I I2, the latter being provided at its rear end with a yoke II3 which is arranged to engage a pin II4 carried by the arm 96. Formed in the upper surface of the bar I03, ahead of the tucker II 2, is a second slot in which is secured, by means of flllister head screws II5, a steel insert II6 (Figs. 18 and 19) in which is formed a T-shaped slot II1, which is of sufficient size to accommodate clinch nuts 0- such as disclosed in Fig. 3. The clinch nuts IIO carried in the insert II6 are arranged to be moved toward the anvil 54 by means of the forward movement of the tucker II2 as will be explained more fully hereinafter.
The insert I6 (Figs. 18 and 19) is provided with an opening -I I9 on one side to permit the introduction of clinch nuts thereto from the raceway I20, which extends from the hopper 40. Secured by means of a rivet I21 to one side of the bar I03 immediately below the opening I I9 in the insert H6, is a cam I2I. This cam extends upwardly along the side of the insert H6 and is intended to push the nuts back in the raceway I20 upon the upward movement of the bar I03, Secured to the steel insert II6 by means of screws I22 is an L-shaped cover member I23. This member I23 is positioned on the insert II6 immediately above the opening II 9 therein. The cover member I23 is provided on its under side with a flat spring I24 which is secured thereto by means of rivets I25. The spring I24 is intended to exert pressure on the nut I26 immediately ahead of the nut I I3 (Fig. 17) so that, when the nut I6 is advanced to the position, of nut I26 and toward the anvil by the tucker bar I I2, there remains an opening in the insert II6 for the reception of another nut from the raceway I20 on the downward movement of the bar I03. An adjustin'g screw I20 (Fig. 20) is mounted in a boss formed in the steel casting 61, and is adapted to limit the downward movement of the free end of the bar I03 so that exact alignment may be had between the opening I I 9 in the insert I I6 and the raceway I20. The set screw I20 is formed with a cone shaped end. The under edge of the bar I03 is provided with a groove I03a which is adapted to contact the cone in such manner that when the screw I20 is moved inwardly the bar I03 is held in a higher position and when the screw is moved outwardly the bar is allowed to assume a lower position. A slight turn of the screw I20 effects the usual required adjustment. A tension spring I29 is secured to the under side of the bar I03 and its other end is connected to the anvil relief bar 55 and is intended to steady.
the bar I03 and prevent vibration thereof on the roller IOI.
The shaft 0i is driven by means of an electric motor I30 through the clutch I3I, the fly wheel I32, the belt I3, the idler pulley I34-and the belt I35. The motor I30 is mounted by any suitable means on the bracket 43. The idler pulley I34 is mounted on the stud I30 which is secured by means of a nut to the casting 35. The idler pulley I34 laprovided with a suitable bearing I31 which s lubricated by means of the oil cup I30. The clutch I3I consists of a plate I39 which is freely mounted on the shaft 3i and is secured by means of illlister head screws I40 to the fly wheel I32, the latter being provided with a bearing I32a and secured on the shaft 3| by means of thrust collar I32b held by suitable set screws. The clutch plate I39 is arranged to engage the clutch collar I which is connected to the shaft 0I as at I42 by means of clutch pin I43, which is slidably mounted in a recess formed in the clutch collar The pin I43 is normally held in extended position by means of compression spring I44 which is carried in an internal bore provided in one end of the clutch pin I43. The spring I44 is arranged to contact the thrust collar I46 which is secured to the clutch collar MI by means of rivets. The clutch pin I43 is held against rotation by means of a key which is arranged to engage a slot formed in the clutch pin I43. The working surface of the clutch pin I43 is adapted to engage corresponding working surfaces I5I formed on the inside of the clutch plate I39. The clutch pin I43 is held in inoperative by means of the clutch release bar I52, the upper end of which is arranged to engage a slot formed in the under side of the clutch pin I43. The clutch release bar is slidably mounted in recesses formed in the main housing 35 and secured against displacement by cover plates I53 and I54 which are secured in position by cap screws I55. The clutch release lever I52 is normally held in upward position by means of a compression spring I56,
which rests at the bottom on the casting 35, and.
at the other end abuts the end of a. bore I51 formed in the lever I52. The clutch releasebar I52 is provided along one side with an under cut bearing surface I58 which is arranged to engage the trip pawl I59 rockingly secured by means of stud I60 to the trip lever I6I, the latter being pivoted bymeans of stud I62 in a boss I63 formed on the inside of the casting 35. The pawl I59 is arranged to rock downwardly and is held against upward displacement by means of an offset, which is arranged to ride on the top surface of the lever I6I. A tension spring I65 is secured between a mounting stud, fastened in the upper side of the pawl I59, and a mounting stud I61 which is carried in the upper surface of the trip lever IN. This spring is arranged to return the pawl I59 to its normal position after it has been rocked downwardly, as will appear more fully hereinafter. I
A cam block I63 is slidably mounted in the casting 35 and secured against displacement by the cover plate I53, and rests of its own weight on the top of the trip lever I6I. The cam block I60 is formed at its upper end with a curved surface I69 which is adapted to ride on cam surface I10, formed on the clutch collar I, for the purpose of holding the pawl I59 out-of engagement with the lever I52, so that the latter may return to its normal position to enable it to engage the slot formed in the clutch pin I43, to
disengage the clutch pin I43 from the clutch plate 15 I30, upon the completion of a single revolution. With this mechanism the clutch can remain in engaged condition only during one revolution of the fly wheel.
The trip lever IGI is connected to a foot pedal III by means of a connecting rod "2 so that the clutch may be engaged for one revolution only by the downward movement of the foot pedal III. In order to re-engage the clutch I3I after one revolution it is always necessary to release the foot pedal I'II.
The hopper 48 is supported by means of a spider I13 which is mounted for rotation on stud Il4, which in turn is secured to the hopper base I", the latter being secured to the bracket 41 by means of cap screws H6. The stud H4 is provided with threads at either end and arranged to engage nuts I". The hopper 48 is rotated on the stud I" by means of a. belt I00, which passes around it, and the pulley I8I the latter being driven by the motor I03. The motor I03 and pulley IOI are supported by a bracket I04 which is secured to the bottom of the hopper base I10. A steel plate IOI is secured to the base I10. The plate IOI covers a groove IOIa. formed in the base I". The groove I9Ia communicates with the raceway I20 and serves as part of the track for nuts fed from the hopper 40.
After the machine is fully assembled as hereinabove described and connected to a proper source of electrical power and a sufficient quantity of clinch nuts is placed in the hopper 40, a typical operative cycle is described as follows:
The nuts travel downwardly in the raceway I20 to a position adjacent the nut carrier bar I03. when this bar is in its lowered position as shown in Fig. 18, the opening H0 in the insert H0 is then in alignment with the raceway I20 so that a nut, designated in this instance 0, may enter the steel insert Hi. When the bar I03 is in the position shown in Figs. 9 and 18, the machine is in neutral position. If the operator then depresses the foot pedal III, the trip lever IOI is actuated, causing the clutch release bar I52 to be lowered, disengaging the same from the clutch pin I43, so that the latter may be moved into engagement with the clutch plate I30, which is secured to the flywheel. Upon engagement of the clutch, the shaft II is caused to rotate, rotating with it the cam 04 and the eccentric crank 84. As the cam 94 rotates it permits \a forward movement of the tucker arm 30 under the influence of the spring I09, and as the tucker arm 08 moves forward, the roller on the end thereof, which is in contact with the cam surface I02, causes the nut carrier-bar I03 to be elevated to the position shown in Fig. 19, and shown by the dotted lines in Fig. 20. After the nut carrier bar I 03 has reached the limit of its upward movement, the tucker arm 00 continues to move forward until the tucker bar II2, which is actuated thereby, strikes the nut which has Just been introduced from the raceway I20 moving it forward a sufficient distance to permit the entrance of another nut from the raceway I20. The pedal III must be depressed a sufficient number of. times to permit a suiilcient number of nuts to enter the nut carrier bar I03 before a nut will be introduced to the anvil. When the nut carrier bar is completely filled with nuts, the next operation of the machine will be effective to introduce a nut to the Jaws of the anvil 04. An element,- such as a sheet of metal with an aperture such as disclosed in Fig. 4, is then positioned on the anvil so that the exposed portion of the nut is extended through the aperture as illustrated in Fig. 5. In this condition the machine is now ready to be actuated for an effectivi clinching operation. when the foot pedal I 'II is depressed this time causing the shaft 0| tc rotate, the punch 00 is moved downwardly to contact the nut then in position on the anvil 54 The spring 0Ia tends to hold the sheet of metal in fixed relation until the punch 90 has clincheC the upper surface of the nut as illustrated in Fig. 6. As the punch 90 is withdrawn from the anvil 54, the spring Ola causes the nut, which is then attached to the metal, to become disengagec from the punch 90.
The operation of the punch 90 is so timed that its working stroke is completed and it has entered its upward movement before the nut carrier bar I03 is elevated. In other words, the upward movement of the nut carrier bar I03 is timed so that it follows the punch 90 in its upward travel. This is an important feature of the invention as three separate and distinct operations are performed with one throw of the bar I03. The operations performed are as follows: First, the bar I03 in moving upwardly contacts the under side of the sheet of metal, or other element to which a nut has been clinched by the punch 90, dislodging the same from the anvil 54; second, when the insert on the bar I03 is in alignment with the anvil jaws, a nut is injected into the anvil leaving a space in the insert opposite the raceway I20; third, the space just referred to is then filled by the introduction of a new nut from the raceway I20.
As hereinbefore described, this machine makes a complete cycle upon one revolution of the shaft and each successive cycle or clinching operation requires the operation of the foot pedal Ill. Should the anvil 54 become overloaded for any reason, because too thick a piece of metal is being used or because the metal is misplaced on the anvil, the overload will automatically be taken up and the shock absorbed by means of the spring 02. This is an important feature of the invention as it obviates much difficulty heretofore encountered in clinching machines. Another important feature of this invention is that because of the construction and arrangement of the hopper, the nuts in the raceway I20 are at all times free to travel up and down in said raceway. Because the nuts are deposited in the raceway I20 in an opposite direction to the rotation of the hopper, there is no opportunity for the nuts to become jammed. The cam I2I positioned on the side of the bar I03 imparts a backward and upward motion to all the nuts in the race way I20 as the bar moves upwardly. This gives the nuts a fresh start downwardly when the bar I 03 is returned to its lower position thereby enabling a new nut to be introduced to the insert I I6 by force of gravity.
Having described our invention, what we claim and desire to secure by Letters Patent is:
1. In a clinch-nut machine, including a housing, the combination of an anvil mounted on said housing. a drive shaft, means for intermittently revolving said shaft, a punch mounted on said drive shaft, a nut carrier bar adapted to guide nuts to said anvil, and means actuated by said shaft for raising and lowering said nut carrier bar and advancing toward said anvil nuts carried by said bar.
2. In a clinch-nut machine, including a housing, the combination of an anvil, a drive shaft, means for intermittently connecting said shaft 1 to a power source, a punch mounted on said shaft, a nut carrier bar adapted to receive nuts and having means for discharging nuts, and means actuated by said drive shaft for raising and lowering said bar and actuating said discharging means.
3. In a clinch-nut machine, including a housing, the combination of an anvil mounted to said housing, a drive shaft intermittently connectible to a power source, a punch adjustably mounted for reciprocation by said shaft, a nut carrier bar, means carried by said bar for receiving and discharging nuts, a cam on the under side of said bar, a tucker reciprocably mounted in said bar, said tucker being in alignment with the nuts received by said bar, means actuated by said shaftadapted to raise and lower said bar, and means connected with said shaft actuated means for punch mounted on said shaft, means for intermittently connecting said shaft to a source of power, a nut carrier bar adjustably pivoted at one end to said housing, a cam actuated by said shaft, an arm actuated by said cam, said arm having a roller at its lower end adapted to ride on a cam surface formed on the under side of said bar, means on said bar for receiving nuts from a source adjacent thereto, and a tucker slidably mounted on said bar in alignment with the nut receiving means, said tucker .being arranged to be actuated by the aforesaid arc.
5. In a device of the character described, including an anvil and a raceway for supplying nuts, the combination of a drive shaft, a nut carrier bar pivoted at one end, the opposite end being adapted to be moved up and down, means between said shaft and said bar, said means being arranged to raise and lower said bar, means carried by said bar for receiving a nut from said raceway, when said bar is in its lowest position, and means actuated by said drive shaft for advancing a nut to said anvil when said bar is in its highest position.
6. A device as defined in claim 5, wherein the nut carrier bar is provided with a cam adjacent said raceway, which said cam is adapted to retain nuts in said raceway during the up and down movement of said carrier bar.
' '1. A combination as defined in claim 5, wherein the free end of said nut carrier bar is arranged to travel adjacent oneside of said anvil, whereby material worked upon is automatically dislodged from said anvil by the up stroke of said bar.
8. In a device of the character described, including an anvil and a nut supplying raceway, the combination of a nut carrier bar, one end of which is arranged to move up and down adjacent said anvil, means carried by said bar for suc cessively receiving nuts from said raceway, a tucker for advancing the nuts on said bar, means for raising said bar, and means for advancing said tucker at the end of the up stroke of said bar.
9. The combination as defined in claim 8, wherein there is a resilient element carried by said bar to hold in predetermined position the nut adjacent said tucker, on the down stroke of said bar.
10. In a clinch-nut machine, including a housing, a punch, and means for driving said punch, the combination of a bearing member secured to said housing, a slot in said bearing member, an anvil having a member adapted to slide in said slot, a rocker arm for movably supporting said anvil, and retractable locking means for limiting the upward displacement of said anvil.
11. In a clinch nut machine. including a housing, and a nut feeding raceway, the combination of an anvil mounted on said housing, said anvil having jaws adapted to grasp a nut, a drive shaft, means for removing said shaft, a punch mounted on said drive shaft, a nut carrier bar, means on said bar for receiving a nut from the raceway, means actuated by said drive shaft for raising and lowering said nut carrier bar, and means actuated by said drive shaft for advancing a nut from said carrier bar to the Jaws of said anvil.
12. The combination defined in claim 11, wherein the punch is arranged to move to and away from said anvil and the nut carrier bar is arranged to follow the punch on the up stroke.
13. A device as defined in claim 5, wherein the nut carrier bar is provided with a cam adjacent said raceway, which said cam is adapted to impart a retreating motion to nuts in said raceway upon the upstroke of said bar.