US1234602A - Collapsible screw-threading tap. - Google Patents

Description

H. AUSTIN.- COLL APSIBLE SCREW THREADING TAP.

. APPLICATION l'ILED AUG.21, 1916. 1,234,,602w Patented July 24,1917.

' 2 SHEETSSHEET 1.

H. AUSTIN.

COLLAPSIBLE SCREW THREADING TAP.

Patented July 24, 1917.

APPLICATION FILED AUG.2I,1916.

2 SHEETSSHEET 2 HERBERT AUSTIN", OF BROMSGROVE, ENGLAND.

: COLLAPSIBLE SCBEW-THREADING TAP.

Application filed August 21, 1916.

To all whom it may concern:

Be it known that I, HERBERT A s'rIN, a subject of the King of Great Britain, and residing at Bromsgrove, in the county of Worcester, England, engineer, have invented certain new and useful Improvements in Collapsible Screw-Threading Taps, of which the following is a specification.

This invention relates to the type of collapsible tap, for use in the formation of screw-threads, in which dies for cutting the threads are carried by a stock and are moved outward against the force of a spring or springs by means of a central bolt or plug which is moved for the purpose axially of the tap. In this type of collapsible tap, as previously proposed, it has been necessary for the bolt to be moved backward a considerable distance, in relation to the dies, to enable the tap to be withdrawn from the work.

Now, this invention has for its objects to improve the construction of the tap with a view to insuring that quite a small backward movement of the bolt or plug in relation to the dies will enable them to move fully inward, and further to improve the construction of the tap.

Convenient practical forms of the invention are illustrated by the drawings herewith, of which 2- Figure 1 shows, mainly in longitudinal section, a form of the invention especially applicable to a smaller size of tap.

Fig. 2 is a side view of the tap shown by Fig. 1, looking in the direction of the arrow.

Fig. 3 is a section taken in the plane indicated by line 3-3 of Fig. 1.

Fig. 1 shows, in longitudinal section, a form of the invention specially applicable to a larger size of tap.

Fig. 5 is a half section taken in the plane indicated by line 5-5 of Fig. 4.

Fig. 6 is a side view of the tappet and a section of the lever handle used with the tap shown by Figs. 4 and 5; and,

Fig. 7 is a View illustrating a modified arrangement of collars of the bolt or plug.

Referring first to Figs. 1, 2 and 3 :A is the stock of the cap, 13 are radial dies of which the cutting surfaces project through slots at which are formed in from the forward end of the stock. G is a cap which is fixed by screws such as 0 against the outer end of the stock to close the slots a and prevent the dies moving endwise of the tap.

Specification of Letters Patent.

Patented July 24:, 1917.

Serial No. 116,012.

D is a plug which is formed with a number of collars d and passes axially through a chamber a of the stock and is guided at its rear end through an opening a at the inner end of the chamber, and at its outer end, where it is reduced in diameter, is guided through an adjusting nut E. The inner ends or bases of the dies 13 are formed as segments 6 of an annulus, and these bases are situated within the outer portion of the chamber a. Springs F are arranged within holes a of the stock A and abut at their outer ends against plugs f which are screwed into the outer ends of the holes, and abut at their inner ends each partially against one of the bases 7) and partly against the adj acent base, and thedies are constantly pressed in an inward direction by the springs F. The collars cl around the plug D are each formed with a beveled surface cl at the forward end, and the .peripheral surface may be cylindrical, or preferably somewhat tapered, as shown, in either of which cases the thrust of the dies thereagainst will not force back the plug D. The inner surfaces of the bases of the dies are formed with projections b, of which the sides are beveled to correspond with the beveled surfaces d, and of which the faces immediately forward of the beveled surfaces are cylindrical, or somewhat tapered, to correspond with the peripheral surfaces of the collars (Z. In Fig. 1 the peripheral surfaces of the collars (Z are shown as passing across the peripheral surfaces of the projections 6, thus holding out the dies B in their operative positions. When the plug D is drawn back the periph eral surfaces (Z pass clear from the corresponding surfaces of the projections Z) and the springs F move in the dies and allow the tap to be withdrawn from a hole within which it has cut a screw-thread, the projections 7) passing into the spaces between the collars. lVhen the plug is again advanced the beveled surfaces d engage with the beveled surfaces 6 and move out the dies, and by further advancing the plug the peripheral surfaces (Z again engage with the corresponding surfaces of the projections Z) and maintain the dies in their outward positions. G is a lever which may be formed with a handle on its outer end. This lever passes through a. slot a of the stock and engages with a slot (Z which is formed through the rear end of the plug D, and the lever is pivoted to the outer end of an inclined stud H which is secured at its inner end within the stock A. The plug may thus be drawn backward and may, if desired, be moved forward also, by hand, but to render the backward movement of the plug D auto matic, a tappet J is slidably mounted in a lug a of the stock, so that when the forward end of the tappet comes against an outer face of the article which is being operated upon by the tap it will be moved backward in relation to the tap and by pressing against the lever G will move such lever back and consequently the plug. By arranging the tappet to press against the lever near to the fulcrum thereof, a very short movement of the stock, after the tappet has come against an obstruction, causes the plug to move back the necessary distance. A wearing piece j may be let into the forward end of the tappet. The tappet may be arranged to come against any fixed abutment, in lieu of coming against a face of the article which is be ing operated upon. A spiral spring M is shown as surrounding the plug D and abutting at its rear end against a shoulder of the interior of the stock and at its forward end against a collar (Z of the plug, the purpose of this spring being to insure that when the plug has been moved into position in which it holds out the dies in their operative positions it cannot. accidentally move back, the spring, however, being of such strength only that when the plug has been moved back the spring cannot move it forward again sui'ii ciently to move out the dies. As already de scribed, it is preferred to make the peripheral surfaces of the collars (Z and the corresponding surfaces of the projections Z) somewhat taper, as shown, the purpose of this being to enable the degree to which the dies are moved out to be readily adjusted by adjusting the distance to which the plug can be moved in a forward direction. When the plug is in its forward position, a'shoulder thereof comes against the inner face of the nut E, and therefore the point to which the plug can be moved forward may be readily adjusted by screwing up or unscrewing the nut.

For convenience and accuracy of manufacture, it is preferred to form all the peripheral surfaces of the collars (Z and the corresponding surfaces of the projections 12 as surfaces of a common cone; and for the same reason it is preferred to form the dies together in one piece with an annulus and subsequently divide the annulus through to form the separate dies with their bases.

Referring now to Figs. 4, 5 and 6 :The tap illustrated thereby is substantially the same as that shown by Figs. 1, 2 and 3, but varies somewhat in detail. The parts shown in Figs. 4, 5 and 6 which correspond to those shown by Figs. 1, 2 and 3, are similarly lettered. A rod N passes through an axial hole of the plug D. This rod has portions 7?. n of reduced diameter having screwed on their outer ends, respectively, pairs of locknuts n a The portion of larger diameter of this rod enters some distance into the rear end ofthe plug. A lever G, which may be formed with a handle at its outer end, is pivoted within a slot a which is formed through the side of the stock A, and the inner end of this lever passing through a slot d of the plug engages with a slot a which is formed through'the portion of enlarged diameter of the'rod N. The plug D is moved forward by the lever G pressing the forward end of the portion of enlarged diameter of the rod N against a shoulder (i of the interior of the plug, and is moved back again by the lever drawing back the rod N and causing the lock-nuts n to carry back the plug. P is a double-armed tappet which is carried by a stud Q. which is fixed to the stock. then the plug D has been moved forward and is holding out the dies B, the arm 7) of the tappet P is engaged with a shoulder g of the lever G and prevents the lever from being moved in a direction to move back the plug, and the other arm p of the tappet stands outward in a direction approximately at right-angles to the axis of the tap. The arm 7) has an adjusting screw screwed therethrough, and as the tap is completing an operation, the nose [9 of this screw comes in contact with a forward face 7* of an article R- which is being tapped (or it might be arranged to come in contact with a face of a fixed abutment) and moves the arm 7) clear of the shoulder g of the lever G, whereupon a spiral spring S moves back the rod N and plug D. This spring S surrounds the rearward part of the rod N and bears at its forward end against a shoulder a of the interior of the stock and at its rear end against a collar 8 which surrounds the rod and is prevented from moving rearward in relation to the rod by the lock-nuts n and a washer s. The inner face of the inner lock-nut n is, when the plug is in its forward position against the inner face of the adjusting nut E, some little distance back from the outer end of the plug, with the result that when the spring S begins to act it first simply moves back the rod N until the inner lock-nut n comes against the outer end of the plug and then moves back the plug also; otherwise there would be a tendency for the plug to stick and-not yield backward under the pull of the spring, whereas the initial mo-vement of the rod in a backward direction be- The cap C is shown in this case as formed as a flange with a socket-piece 0 formed therewith, and in the forward edge of this socket-piece there are formed a number of turrets 0 with any one of which a key 0 may be engaged and then secured by a screw 6 to the nut E so as to prevent the nut from working loose. Such an arrangement may be also employed in connection with the tap described with reference to- Figs. 1, 2 and 3, as will be obvious.

Referring now to Fig. 7 the collars d of the plug D are cylindrical and enlarge some what in diameter one behind the other, and an extra collar 65* is provided which, when the dies B are worn or have become re-cut, may be brought into action by advancing the plug to such an extent that the leading collar becomes inoperative while the rearmost collar becomes operative, the nut E being screwed forward as required to enable this to be done.

Having fully described my invention, what I claim and desire to secure by Letters Patent is 1. In a collapsible tap for use in the formation of screw threads, the combination of a stock, dies which are slidably fitted within said stock and are constantly pressed in an inward direction by means of a spring or springs, a central bolt or plug which is movable endwise within said stock, collars around said bolt or plug which are spaced apart by a clearance groove or grooves, projections at the inner ends of said dies which are also spaced apart by a groove or grooves, said collars and said projections formed with beveled or corresponding faces, of which those of the collars engage with those of the dies when the bolt or plug is moved endwise in one direction and thereby move out the dies against the force of a spring or springs, and said collars and projections formed, behind the said beveled or corre sponding faces, respectively, with peripheral surfaces which are comparatively sli htly tapered and engage with one another when the bolt has been moved in such direction and insure that the pressure of the dies against the collars will have no substantial tendency to move back the bolt or plug, and means whereby the bolt or plug may be moved in the opposite direction, in relation to the stock, and allow the dies to move in, the projections of the inner ends of the dies then entering within the groove or grooves of the bolt or plug.

2. In a collapsible tap for use in the formation of screw-threads, the combination of a stock, dies which are slidably fitted within said stock and are constantly pressed in an inward direction by means of a spring or springs, a central bolt or plug which is movable endwise within said stock, collars around said bolt or plug which are spaced apart by a clearance groove or grooves, proj ections at the inner ends of said dies which are also spaced apart by a groove or grooves, said collars and said projections formed with beveled or corresponding faces, respectively, of which those of the collars engage with those of the dies when the bolt or plug is moved endwise in one direction and thereby move out the dies against the force of a spring or springs and said collars and projections formed with tapered peripheral surfaces behind the said beveled or corresponding faces, respectively, which are formed as surfaces of a common cone and engage with one another when the bolt has been moved in such direction and insure that the pressure of the dies against the collars will have no substantial tendency to move back the bolt or plug, and means whereby the bolt or plug may be moved in the opposite direction, in relation to the stock, and allow the dies to move in, the projections of the inner ends of the dies then entering within the groove or grooves of said bolt or plug.

3. In a collapsible tap for use in the for mation of screw-threads, the combination of a stock, a cap which is fixed to the forward end of the stock, dies which are slidably fitted within said stock and are constantly pressed in an inward direction by a spring or springs, a central bolt or plug which is movable endwise within said stock, collars around. said bolt or plug which are spaced apart by a clearance groove or grooves, projections at the inner ends of said dies which are also spaced apart by a groove or grooves, said collars and said projections formed with beveled or correspondin surfaces of which those of the collars engage with those of the dies when the bolt or plug is moved endwise in one direction and thereby move out the dies against the force of a spring or springs, a nut which is screwed into the said cap and forms a stop to the movement in said direction of the bolt or plug and may be adjusted in relation to the cap to adjust the distance to which the bolt or plug may be moved in such direction, and means whereby the bolt or plug may be moved in the opposite direction, in relation to the stock, and allow the dies to move in, the projections of the inner ends of the dies then entering within the groove or grooves of the bolt or plu 4. In a collapsible tap for use in the formation of screw-threads, the combination of a stock, dies which are slidably fitted within said stock and are constantly pressed in an inward direction by a spring or springs, a central bolt or plug which is movable endwise within said stock, collars around said bolt or plug which are spaced apart by a clearance groove or grooves, projections at the inner ends of said dies which are also spaced apart by a groove or grooves, said collars and said projections formed with beveled or corresponding surfaces of which those of the collars engage with those of the dies when the bolt or plug is moved endwise in one direction, and thereby move out the dies against the force of a spring or springs, a spring which constantly tends to move such bolt or plug in the direction to move out the dies and insures that the bolt or plug cannot accidentally return afterit has been moved fully in such direction but is not of sufficient strength to cause the bolt or plug after it has been moved back to move forward again sufficiently to move out the dies, and means whereby the bolt or plug may be moved back, in. relation to the stock, and allow the dies to move in, the projections of the inner ends of the dies then entering within the groove or grooves of the bolt or plug.

5. In a collapsible tap for use in the for mation of screw-threads, the combination of a stock, dies which are slidably fitted within said stock and are constantly pressed in an inward direction by a spring or springs, a central bolt or plug which is moved endwise within said stock, collars around said bolt or plug which are spaced apart by a clearance groove or grooves, projections at the inner ends of said dies which are also spaced apart by a groove or grooves, said collars and said projections formed with beveled or corresponding surfaces of which those of the collars engage with those of the dies when the bolt or plug is moved endwise in one direction and thereby move out the dies against the force of the spring or springs, an axial rod which passes through said bolt or plug, a shoulder of such rod which as the rod moves forward comes against a shoulder of said bolt or plug and moves said bolt or plug forward, a shoulder at the forward end of said rod which when the other shoulder is against the shoulder of the bolt or plug is some distance forward of the forward end of the bolt or plug, a spring which surrounds said rod and tends constantly to move it backward, a lever which is carried by said stock and engages with said rod, and a tappet which is carried by said stock and retains said lever in position holding the rod forward but on coming against an abutment releases said lever and allows the spring to move the rod backward until the shoulder at the forward end thereof comes against the forward end of the bolt or plug when the further backward movement of the rod moves back also the bolt or plug andallows the projections of the inner ends of the dies to enter within the groove or grooves of the bolt or plug.

6. In a collapsible tap for use in the formation of screw-threads, the combination of a stock, dies which are s'lidably fitted within said stock and are constantly pressed in an inward direction by the spring or springs, a central bolt or plug which is movable endwise within said stock, collars around said bolt or plug having forward surfaces which are beveled or correspOndinglyshaped, and

peripheral cylindrical surfaces behind the beveled or correspondingly-shaped surfaces, respectively, said collars enlarging in diameter one behind another, and spaced apart by a clearance groove or grooves, corresponding projections at the inner ends of said dieswhich are also spaced apart by a groove or grooves, all the said collars, except the rearmost collar, engaging with the projections of the dies when the bolt or plug is moved endwise in one direction, thereby moving out the dies against the forceof the spring or springs, said rearmost collar being operative only after the dies have become worn or have been re-cut, the foremost collar being then inoperative, and means whereby the bolt or plug may be moved in the opposite direction and allow the dies to move in, the projections of the inner ends of the dies then entering within the groove or grooves of the bolt or plug.

In witness whereof I have hereunto signed my name this 4th day of August 1916, in the presence of two subscribing witnesses.

HERBERT AUSTIN.

WVitnesses:

ERNEST HARKER, STEPHEN WATKINS.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents. Washington, I). G.

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