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Publication numberUS2784267 A
Publication typeGrant
Publication dateMar 5, 1957
Filing dateAug 16, 1954
Priority dateAug 16, 1954
Publication numberUS 2784267 A, US 2784267A, US-A-2784267, US2784267 A, US2784267A
InventorsFred P H Nackenhorst
Original AssigneeOklahoma Steel Castings Co Inc
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Lead screw tapper
US 2784267 A
Abstract  available in
Previous page
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Claims  available in
Description  (OCR text may contain errors)

March 5, 1957 F. P. H. NACKENHORST LEAD SCREW TAPPER Filed Aug. 16, 1954 INVENTOR.

fi ll E my my 8 l on s I I I 5 1 HQ 0 l I lllll I E I. I N I! ll [I .hfll h wi v N F h il 2 IQH=IQHQ W I. l .d m M uh x H ll. 1 I I 8 I 5 mm y l o w mm 2 1 L United States Patent i LEAD SCREW TAPPER Fred P. Nackenhorst, Drums, Pa., assignor to Oklahoma Steel Castings Co., Inc, New York, N. Y., a corporation of Delaware Application August 16, 1954, Serial No. 450,055

4 Claims. (Cl. 200-47) This invention relates generally to a lead screw tapper and in particular to an automatic reversing lead screw tapper wherein the depth of tap may be accurately and easily adjusted.

The tapper consists of a motor-operated lead screw which rotates in a fixed lead screw nut so causing the screw to advance a tap which is mounted in a chuck attached to one end of the screw a predetermined amount for each rotation of the screw. The screw has a fixed shoulder and a movable collar mounted thereon for axial movement which are adapted to engage a pivotally mounted lever when the tap reaches the limit of its axial movement either towards or away from a work piece. Upon engagement of the lever by the shoulder or collar, the lever is caused to rotate about its pivot and to contact one of two micro limit switches, depending on whether the collar or the shoulder contacts the lever. Actuation of the micro limit switches causes the motor to reverse its direction of rotation and to withdraw or to advance the tap.

The tapper will be more easily understood by referring to the drawing in which is shown a side partial sectional view of a lead screw tapper constructed according to my invention.

1 is a housing for the tapper unit and serves as a base for mounting the unit to a work table. 2 is a lead screw spindle mounted for rotation in a lead screw nut 3. Mounted on the end of lead screw 2 is a chuck 4 which carries the tap 5. This chuck may be of the type known as a Jacobs Rubber Flex Chuck.

The lead screw 2 is rotated by a reversible electric motor 6 whose shaft 7 is connected to a drive sleeve 8 by means of socket set screws 9 and 19. This drive sleeve is connected to the lead screw 2 by means of a driving pin 11. The set screws 9 and 10 bear down on a key 12 which fits in a keyway of the shaft 7 so that there can be no relative rotation between the shaft and the driving sleeve. The driving sleeve 8 is slotted as at 13 so that the driving pin 11 may slide axially of the motor shaft as the screw 2 is rotated in nut 3. The complete coupling assembly is surrounded by a drive sleeve cover 14 so that the assembly is kept comparatively dust-free. This cover can be made of a material such as neoprene so that it may be easily inserted over the driving sleeve.

Mounted on the lead screw 2 is a collar 15 which can be moved axially of the screw in order to adjust for the depth of tap. This collar can be held in place by a set screw 16 after it has been positioned. Also on lead screw 2 is a fixed shoulder 17 which is of the same radial width as the collar 15. Both collar 15 and shoulder 17 are adapted to contact bearing 18 which is on one end of lever 19.

Lever 19 is made to pivot about a point 20 when it contacts either collar 15 or shoulder 17. Moving the lever about its pivot point 20 causes it to contact either micro limit switch 21 or micro limit switch 22, depending on which way the lever is rotated. Springs 23 and 24 are 4 2,784,267 C Pate'ntedMar. s, 1957 attached at the end of the lever away from bearing 18 in order that the lever may be held in a neutral position (one in which it does not contact a limit switch) whenever the bearing 18 is not in engagement with either shoulder 17 or collar 15. The micro-lirnit switches are of the common variety and are such that the slightest engagement of the lever with points 25 and 26 actuates the switches. The switches in this form of the invention are so wired that they will cause complete reversal of rotation of the motor 6 when they are actuated by the lever 19.

The lead screw nut 3 is retained at its inner end by bearing 27 which serves as a bearing for the lead screw. This bearing is held in place by a retaining ring 28. Lead screw nut 3 is held in place on its outer end by from hear ing 29 which is held in place by a retaining nut 30. A felt seal 31 is fitted in a groove of retaining nut 30 so that the system will be oil-tight. The housing 1, bearings 27 and 29, and the lead screw nut are all keyed so as to receive a key 32 which prevents relative rotation among the parts. Oil cups 33 and 34 are provided so that the system may be readily lubricated.

The electric motor 6 has attached at the end opposite from the lead screw tapper a Stearns magnetic brake 35. This brake stops rotation of the electric motor when actuated by the switches 21 and 22 and so allows for substantially instantaneous reversal of direction of rotation of the lead screw.

In operation the collar 15 is positioned so that the distance between it and the shoulder 17 is equal to the exact amount of depth of tap desired in the work piece. The machine is then turned on which causes the lead screw to rotate in one direction. Assuming that the lead screw begins to rotate in a direction so that it advances towards the work piece, it is seen that the screw will continue to advance until the collar 15 contacts bearing 18 of the lever 19. At this point the lever 19 will rotate about point 20 until the lever contacts point 25 of switch 22. At that instant switch 22 will then reverse the rotation of motor 6, causing the lead screw to advance towards the left as seen in the drawings until shoulder 17 contacts bearing 18. This will then actuate switch 21 which will reverse rotation of the lead screw and so repeat the cycle. It is to be understood that switches 22 and 23 could be set up so that insead of causing the motor 6 to reverse its rotation, they could merely cause the motor to stop. This arrrangement would then necessitate another switch for starting the motor.

It is obvious that taps of different pitch could be used by merely using a different pitch on the lead screw and on the lead screw nut. It is seen from the drawings that by removing retaining nut 30 and raising the unit carrying the limit switches, that the complete lead screw and nut assembly can be easily removed and a new assembly inserted in place of the old.

It is a further advantage of my lead screw tapper that it is adapted for mass production methods of manufacturing wherein extreme tolerances must be maintained. A series of such units could be set up in many different positions surrounding work pieces in order to tap as many holes in as many positions as was desired.

1 claim:

1. A lead screw tapper having a housing, a motor, a tap-carrying lead screw adapted to be rotated by said motor, a fixed lead screw nut engaging said lead screw, a fixed shoulder on said lead screw, an axially adjustable collar slidably mounted on said lead screw, and a pivoted lever adapted to be engaged by said shoulder and said collar upon the extreme limits of axial travel of said lead screw; said lever upon engagement with said shoulder and collar being made to rotate about its pivot point to actuate a pair of micro-limit switches.

2. A lead screw tapper according to claim 1, having in said screw nut and collar are adapted to fit into a bore in addition spring means for centering-said lever in a neutral said housing as a unitary member." position when not in engagement with said collar and aid hould r, References Cited in the file of this patent ead screw tapper accor ing t la m' wherein 5 UNITED STATES PATENTS said spring means comprises two springs connected'to the I q end of the lever opposite the end of said lever adapted to 496372 Ward "."T May 1893 engage said shoulder and said collar. EQBEIGN PATENTS lead screw m: fcp d ps t dai 1 rg y seo,oso Great Britain Apr. 12, 194p

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US498372 *May 28, 1890May 30, 1893 Barton b
GB520050A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4820087 *Oct 8, 1987Apr 11, 1989Shigeru IkemotoTap drive unit for machine tools
US5639191 *Sep 4, 1996Jun 17, 1997Womack; Robert C.Short coupled hydraulic lead screw tapping apparatus
US20080171605 *Feb 15, 2005Jul 17, 2008Jeung-Kyun LeeMaster Spindle for Tapping Machine
U.S. Classification200/47, 408/129, 408/9, 470/181
International ClassificationB23G1/16
Cooperative ClassificationB23G1/16
European ClassificationB23G1/16