US2863348A - Extractor - Google Patents

Description

EXTRACTOR David L. Conger, Middle Haddam, Conn. Application December 6, 1955, Serial No. 551,378 2 Claims. (Cl. 81-71) This invention relates to an improved twist extractor for use in removing threaded parts such as pipes, screws, and plugs which have been broken off in the aperture in which they are threaded. The removal of the broken part is accomplished by inserting the extractor, which has longitudinally disposed ribs, in an aperture in or provided in the broken part and then turning the extractor in a direction opposite the direction of the thread of the part. As the tool is thus turned, the ribs thereon will engage the broken part and permit its removal.

Twist extractors heretofore available all too often have the tendency to either ream the part desired to be removed or to expand the part during the removal process with the result that the purpose of the tool may be defeated. It is an aim of this invention to provide a twist extractor of novel structure to eliminate any tendency of the extractor to ream or cut and which will, with a high efficiency, transfer to the part being removed the torque applied to the extractor thus precluding any but a negligible expansion of the part during the removal process.

It is another aim of this invention to provide a twist extractor of the type described which may be used to remove threaded parts of a diameter substantially less than the diameter heretofore considered as the minimum diameter of a part to which a twist extractor could be successfully applied.

It is still further an aim of this invention to provide an improved extractor, as described, which will be more economical to manufacture than existing extractors yet which will be equal or superior in strength and service life.

Other objects will in part be obvious, and in part pointed out more in detail hereinafter.

The invention accordingly consists in the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereafter set forth and the scope of the application of which will be indicated in the appended claims.

In the drawings: v

Fig. 1 is a side view of a twist extractor constructed in accordance with this invention;

Fig. 2. is an end view of the extractor of Fig. 1;

Fig. 3 is a side view of the extractor of Fig. l rotated approximately 90 from the position shown in Fig. 1;

Fig. 4 is a side view of a blank from which the ex tractor of Fig. 1 may be fabricated; and

Fig. 5 is an end view of the blank of Fig. 4.

With reference to the drawings, and particularly Figs. 4 and 5, a twist extractor constructed in accordance with the invention is fabricated from a blank having a wrench engageable head or shank 11 and a tapered body or working portion 12. The cross section of the shank 11 may, of course, be of any cross section which is suitable for the application of a wrench during the use of the tool. The tapered blank is preferaby formed by forging in the interests of economy and strength; however, of course, the blank may be formed by milling the body or ite States Patent Working portion 12 from bar stock having the desired cross section of the shank. The working portion 12 is provided with a triangular cross section producing at its juncture with the shank, the largest triangle which can be contained within the cross section of the shank, and thus utilizes to the maximum the strength and stock available in the shank.

As can be seen from Fig. 4, and as will be more fully explained, each of the sides 14 of the blank 10 are, in accordance with the invention, tapered from the shank 11 towards the nose 13 of the blank at an angle of approximately 3 /2 degrees. To complete the extractor, the blank is, preferably, heated to forging temperature either in a furnace or by induction heating and the shank is gripped in the jaws of an air vise or chuck with the nose 13 held stationary. The shank is then rotated slowly through an angle of approximately 240 degrees to form the lands or ribs 16. During the twisting. it is preferable to progressively chill the blank from the nose 13 toward the shank, such as by the local application of compressed air, to prevent the twist from being concentrated at the smallest cross section adjacent the nose. As will be hereinafter more fully explained, the degree of twist given to the piece is also critical. The resulting extractor is then heat treated to produce a finished part.

It has been found that it is not necessary and in fact is preferable not to provide a sharp edge on the ribs 16 as during the use of the tool a sharp cutting edge is not required to bite into the part to be removed in order for the tool to properly grip the part being removed. As

will be apparent hereinafter, the cross section of the tool lends itself to optimum transfer of torque to the part being removed without tending to ream the part and, in fact, even the application of an excess of torque to the tool will not force it through the part being removed.

It is preferred that the twist imparted to the blank results in the lands or ribs 16 describing a spiral, the slope of which increases from the nose 13 to the approximate mid-point of the body or work portion 12. The provision of such an increasing spiral results in an extractor having a rapid initial draw-in with a subsequent increase in the transfer of torque to the part. This, of course, is a distinct improvement over either an extractor having a spiral providing rapiddraw-in but lacking desired torque transferring characteristics or an extractor which has the desired torque transferring characteristics but which has to be forced into the the removal process.

It should be apparent from the description of the method of fabricating the extractor that there are at least two distinct improvements in an extractor of this novel construction over presently available extractors. First, the cross section of the body 12 taken at any point along its length is an equilateral triangle to assure that all three of the lands or ribs 16 of the finished extractor will be in engagement with the part to be removed when the extractor is placed in the aperture in or provided in the part. In the use of conventional extractors having more than three sides, one or more of the lands or ribs thereon will many times not be in engagement with the piece to be removed as the aperture in which the tool is placed is often not a true circle. As this lack of con-centricity of the aperture in the part to be removed will not effect the engagement of the lands or ribs 16 of an extractor constructed in accordance with the invention, the force applied to the extractor will be more evenly transferred to the piece to be removed, thus equalizing the stresses within the extractor as well as providing a more efficient transfer of torque to the threaded part.

Secondly, it should be apparent that it is not necessary to mill or otherwise provide grooves between the lands or ribs of the extractor prior to or subsequent to the twistpart, such as by hammering, to begin ing of the body portion. It is a particular advantage that when an extractor is constructed as described above, the grooves or flutes 17 will be formed during the twisting of the blank 10, to thus eliminate a costly step in the manufacture of the item.

As heretofore mentioned, it has been determined that the taper of the sides 14 and the amount of twist applied to the blank is most critical. Although the reasons therefor are not completely understood, it has been found that if an extractor is constructed from a blank having a triangular cross section and sides 14 tapering at an angle of 3 /2 degrees which blank is then axially twisted 240 degrees, the result will be an extractor having the desired characteristics or producing only a negligible amount of expansion and no reaming of the threaded part during the removal thereof by the extractor. It is possible to deviate slightly from the optimum values of taper and twist cited either by proportionately decreasing the taper and increasing the twist or increasing the taper and decreasing the twist. However, any substantial deviation will not produce the greatly improved results obtained by the use of the critical values cited inasmuch as too great a taper will result in an extractor having a length which is too short to be useful over a reasonable range of aperture diameters; while too little taper will result in an extractor which will bottom in shallow apertures. Also, too great a twist will cause the extractor to tear the piece while too little twist will result in the extractor being unable to properly grip the piece. Thus, it can be seen that if the taper is decreased and the twist increased there is a ten dency for the extractor to bottom in shallow holes and also to tear the part being removed, while if the taper is increased and the twist decreased, the resulting extractor is undesirably short and has a tendency to slip. It has been further found that it is possible to fabricate a twist extractor in accordance with the invention which may be used to remove parts so small that an aperture of of an inch is the largest aperture permissible in the part where heretofore it was not considered possible to fabricate a twist extractor which would remove a part this small.

Thus, it can be seen that there has been provided a twist extractor which has all of the characteristics desired in such a tool while eliminating all of the undesired characteristics. Its structure is simple and by comparison with presently available extractors, exceedingly economical to manufacture. It is, however, of rugged construction so that such an extractor may be fabricated for use with parts provided with an axial aperture of as small as of an inch and will withstand very severe treatment without fracture even after long periods of use.

As many changes could be made in the above construe tion and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the language used in the following claims is intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

i. claim:

1. in a twist extractor, a wrench engageable shank portion, a working portion extending axially of said shank and having a triangular cross section, and a plurality of work engaging ribs on said working portion formed by the juncture of adjacent sides of said working portion, said working portion having a twist whereby said ribs are disposed in a spiral, the slope of said spiral increasing from the end of said ribs opposite said shank to the approximate longitudinal mid-point of said working portion.

2. In a twist extractor, a Wrench engageable shank portion and a working portion extending axially of said shank and having a triangular cross section, one end of said working portion being angularly displaced approximately 240 degrees from the other end thereof whereby three work engaging ribs disposed in a spiral are formed by the juncture of adjacent sides of said working portion, said spiral having a slope which increases from the ends of said ribs opposite said shank to the approximate longitudinal mid-point of said working portion, each of the sides of said Working portion being tapered approximately 3 /2 degrees from the juncture of said shank and said working portion as measured when the ends of said working portion are in untwisted alignment.

References Cited in the file of this patent UNITED STATES PATENTS 1,038,692 Walker Sept. 17, 1912 1,105,535 Roberts July 28, 1914 1,108,059 Zihler Aug. 18, 1914 1,160,706 Fowler Nov. 16, 1915 1,863,045 Randall et al. June 14, 1932

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