CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefits of prior U.S. Provisional Patent

Application Serial No. 60/593,482 filed on January 18, 2005.

BACKGROUND OF THE INVENTION

[0002] This invention relates to a tool for extracting screws with damaged screw heads. More specifically, this invention relates to a single-piece tool adapted to be installed in the chuck of a counter-clockwise rotating drill to extract screws with damaged screw heads of the type with symmetrical recesses, such as Phillips or Robinson type screw heads.

[0003] A number of extractor patents have issued to Eli Polonsky in which a left-hand drill bit is provided with a gripping fixture on its stem, and adapted to bite into the hole made by the drill so that the remnant may be removed in a single operation as the device is turned counter-clockwise. The Polonsky patents are 4,604,917, which issued August 22, 1986; 4,777,850, which issued October 28, 1928; and 5,032,487, which issued July 16. 1991.

[0004] U.S. Pat. No. 5,251,516 and U.S. Design Pat. D 340,184, both issued Oct.

12, 1993 in the name of Donald Desaulniers and assigned to Alden Corporation, disclose tools for extracting broken bolts and the like. One end of the tool drills a cylindrical hole in the remnant, and the other end has a gently tapered extraction section with a left-hand thread for biting into the side of the hole thus drilled to enable removing the remnant.

[0005] Most of the previous extractor techniques involve first drilling a hole into a remnant in which the screw head is broken off or missing, and then inserting some form of extractor which engages the drilled hole thereby allowing the remnant to be rotated out of its bore. However in many cases, the screw head remains attached to the screw proper, but the screw head is damaged when attempting to remove the screw. This problem is particularly acute when a screw head has a symmetrical recess adapted to mate with a special tool, which damages the screw head while attempting to remove the screw, so that it can no longer obtain a purchase on the screw head. In such a case the tool will merely turn in the recess

and slip from one position to the next without generating enough torque to remove the screw. Typical of this problem are Phillips head and Robinson head screws, which become damaged and are difficult or impossible to remove with the regular tools designed for this purpose.

[0006] U. S. Patent 6,761,089 issued July 13, 2004 to Peter J. Bergamo and now assigned to Alden Corporation discloses a tool for extracting screws with damaged screw heads of the type with a symmetrical center recess defining circumferentially spaced recess extensions having a major diameter, alternating with resistive sections having a minor diameter. The most common example of this type of screw head is known as a Phillips head screw, although there are other less well-known types as well. U. S. Patent 6,761,089 is incorporated herein by reference in its entirety. [0007] The tool described in the aforementioned patent has a central section with flat longitudinal surfaces adapted to be engaged by a drill chuck, a left-hand recess-forming section at one end of the central section, and a screw-removing section on the other end.

[0008] The recess-forming section has a forming distal end with a first portion arranged to make a cylindrical drilled hole with a diameter intermediate the major and minor diameters into the resistive sections and a second flared portion curving away from the axis of rotation so as to form the resistive sections into a flared shape, which is designed to limit the depth of the cylindrical hole so that it does not extend from the screw head into the screw proper.

[0009] A screw-removing section is provided at the other end of the central section, the screw-removing section having a tapered portion extending toward its distal end and being formed with left hand threads on the exterior of the tapered portion, the tapered portion being at an angle such that the tapered portion threads will engage the flared walls of the resistive sections as the rotating tool is inserted into the recess. The tapered portion further includes at least one longitudinal gash extending along the tapered portion and interrupting the threads, so as to facilitate engagement of the threads to enhance the screw-removing process. [0010] The tapered portion is frusto-conical with two diametrically opposed gashes skewed slightly with the axis of rotation, from the proximal end to the distal end, the direction of skew being such that, as the tool rotates in a counter-clockwise (left hand) direction, the distal end of the gash engages the flared walls of the resistive sections before the proximal end of the gash. The threads are adapted to engage the flared walls of the resistive sections of the screw as the tool is inserted

into the recess and rotated counterclockwise about the axis of rotation within the recess to fill said gash with metal removed by the threads and thereby firmly to engage the screw.

[0011] While the foregoing described tool of U. S. Patent 6,761,089 is very effective in removing screws with damaged heads, the effectiveness of the gashes in engaging the flared walls of the resistive sections and transmitting torque to the screw head to remove it can be greatly improved by altering the orientation and shape of the gash without substantially changing any of the other features of the tool.

[0012] Accordingly, one object of the present invention is to provide an improved tool for removing screws or bolts with damaged screw heads.

[0013] Another object of the invention is to provide an improved single-piece tool adapted to be installed in the chuck of a counter-clockwise rotating drill to extract screws with damaged screw heads of the type with symmetrical recesses, such as Phillips or Robinson type screw heads.

[0014] Another object of the invention is to provide an improvement to the tool described in U.S. Patent 6,761,089.

SUMMARY OF THE INVENTION

[0015] Briefly stated, the invention comprises an improvement in a tool for extracting screws with damaged screw heads, the tool having at least a chuck section with flat longitudinal surfaces adapted to be engaged by a drill chuck and a screw- removing section provided at the end of the chuck section. The screw-removing section has a tapered portion extending toward its distal end and is formed with left- hand threads extending outward from thread roots on the tapered portion, the tapered portion being at a pre-selected angle such that the tapered portion threads will engage previously prepared flared walls of the screw head as the rotating tool is inserted into the recess. The tapered portion further includes at least one longitudinal gash extending along the tapered portion and interrupting the threads, so as to facilitate engagement of the threads to enhance the screw-removing process. [0016] The improvement of the present invention is characterized by a shaped and contoured gash, wherein the depth of the gash commencing at the top of the gash gradually increases in a circumferential direction opposite to the direction of rotation of the tool to terminate in an engagement wall at the bottom of the gash. The engagement wall extends abruptly from the bottom of the gash to the top of the

gash to form a biting edge with a positive rake angle that assists the left-hand threads to engage the walls of the damaged screw. In its preferred form, the tapered portion is frusto-conical with two diametrically opposed gashes, wherein the bottom of the gash coincides with the thread roots of the left-hand threads at both the distal and proximal ends of the gash. The bottom of the gash is preferably also contoured radially inwardly below the root depth of the threads between the distal end and the proximal ends of the gash.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Other features and objects of the invention will be apparent to those skilled in the art after a study of the following specification, including reference to the appended drawings, all of which show a non-limiting embodiment of the invention. In the drawings:

[0018] Fig. 1 is a front elevational view of the improved screw-extracting tool,

[0019] Figs. 2 and 3 are enlarged left end and front elevational views, respectively of the screw-removing section, on the left hand end of the tool of Fig. 1; [0020] Figs 4 and 5 are enlarged left end and front elevational cross-section views, respectively of the screw-removing section, on the left hand end of the tool of Fig. 1, taken along lines V-V and TV-IV, respectively of Figs. 2 and 3, respectively; [0021] Fig. 4a is a further enlarged cross-sectional view of a part of Fig.4 showing the shape of the gash; and

[0022] Fig. 6 is an enlarged fragmentary cross-section showing engagement of a damaged Phillips head screw by the screw removing section of the tool.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0023] A tool embodying the invention is shown in Fig. 1 and generally designated 10. It comprises a chuck section 12 having a plurality of flat longitudinal surfaces 14 adapted to be engaged by a drill chuck. The section 12 of the Fig. 1 embodiment is hexagonal in cross section.

[0024] On the right hand end of the chuck section 12 shown in Fig. 1 there may be provided a left-hand recess-forming section 16 being necked in as at 18 intermediate the chuck section 12 and the recess-forming section 16 in order to help locate the tool in certain types of standard chucks. The recess forming section 16 is made up of a cylindrical hole-drilling portion 20 and a flared portion 22 terminating in a short hexagonal portion 24 and is used to prepare the damaged screw or bolt by

providing correspondingly flared walls arranged to receive screw-removing section. Optionally, the recess forming section may be on a separate tool with its own chuck section (not shown).

[0025] On the left-hand end of the chuck section 12 in Fig. 1 is screw- removing section 26 with a tapered portion 28, narrowing toward its distal end; that is, the end not connected to the chuck section 12. The tapered extraction section is formed with left-hand threads 30 on the exterior of the taper as shown. [0026] The distal end of the threaded tapered portion terminates in a flat surface 32. The proximal end of the tapered portion is indicated at 33 and flares out to a short hexagonal section 34. The area between the chuck section 12 and the hexagonal section 34 is necked down at 36 to help locate the tool in the chuck. [0027] Referring now to FIGS. 2 and 3 of the drawings, further details are shown for the screw removing section 26. The end elevation view of FIG. 2 is again shown looking toward the chuck (not shown) of a rotary drill rotating in a left-hand or screw removing direction, as indicated by the arrows. The tapered portion 28, shown in FIG. 3 is preferably frusto-conical as shown. The taper is at an angle A to the axis of rotation of the tool in a range of from 7° to 24° and is preferably about 12°. The threads 30 are left-hand threads of single or multiple starts, i.e., helically oriented on the tapered portion so as to screw into the workpiece when the drill is operated in a reverse or left hand direction. The preferred pitch of the threads is in a range of 20 to 50 threads per inch depending on the size screw. For example, I prefer to use 30 threads per inch for standard No. 8 or No. 10 Phillips head screws. In accordance with one aspect of the invention, two longitudinal gashes 38, 40 are disposed diametrically opposite one another and interrupt the threads 30. There should be at least one such gash and as many as four are useful to enhance the ability of the threads to obtain purchase on the flared walls of the resistive sections of the screw head, as will be explained in further detail.

[0028] Fig 4 is a cross-section taken along lines IV-IV of Fig. 3 showing the location of gashes 38 and 40. Thus far, the tool is as described in U.S. Patent 6,761,089 incorporated herein by reference.

[0029] In accordance with the present invention, the shape, contour and orientation of the gashes are altered for improving the performance of the tool. Reference to the further enlarged view in Fig.4a, the top of gash 38 is seen to commence at the surface of the threads 32, and to gradually increase in depth in a circumferential direction opposite the direction of rotation until reaching the bottom

of the gash at 44, and thereafter abruptly extending to the top of the gash at the thread surface to form an engagement wall 46. The intersection of the engagement wall 46 with the surface of the threads 30 comprises a biting edge 48 with a positive rake angle that assists in bringing about the engagement of the threads 30 with the previously prepared flared walls 72 of the damaged screw head. [0030] Fig 5 is a cross-section taken along lines V-V of Fig. 2 through the gashes 38 and 40. The radius from an axis of rotation designated "X" of the bottom 44 of the gash at a point "R ₁ " on the distal end is preferably at the same radius as the root of the threads 30 at the same point. Similarly, the radius from the axis of rotation of the bottom 44 of the gash at a point "R ₂ " on the proximal end 33 is preferably at the same radius as the root of the threads 30 at the same point. Even though the depth between the distal and proximal ends may follow a straight line, it is preferred that the bottom 44 of the gash is contoured radially inwardly as shown by reference number 50.

[0031] Fig. 6 shows a standard Phillips head screw portion with a damaged screw head 52, a gently tapered neck 54 and part of a threaded portion 56 imbedded in a substrate 58. As set forth in the incorporated description of Patent 6,761,089, the damaged screw head 52 has been prepared by the recess forming section 16 of tool 10, or with a separate tool having a recess-forming section, summarized as follows. The recess forming section 16 of the tool has been inserted into the damaged screw head recess and rotated counter-clockwise. A cylindrical hole 70 has been drilled, which is of greater diameter than the minor diameter, and a flared portion 72 has been formed to prepare the screw for removal.

[0032] The cylindrical hole 70 and the flared section 72 that are created by the recess forming section 16 of the tool are precisely formed to cooperate with the screw removing section 26 of the tool. The tool is removed from the chuck, turned end for end and rotated in a counter-clockwise direction at slow speed. FIG. 6 illustrates the section 26 of the tool, with the tapered portion 28 of the inserted into the screw head recess. The left-hand threads 30 engage the flared walls 72 and bite into the walls lodging the tool firmly into the screw head 52. The engagement action is facilitated by the gashes 38, 40 that provide surfaces on the interrupted threads 30 to enhance the engagement. Since the depth of the gash increases gradually from the surface of the threads to an engagement wall 46, this enhances the ability of the tapered portion 28 to lodge in the flared section 72. Engagement of all of the threads increases the torquing action tending to remove the screw head. The fact that the

depth of the gash flares inwardly between the distal and proximal ends enables the engagement wall of the gash to more effectively engage the similarly contoured wall 72 of the screw head 52.

[0033] Continued slow rotation exerts counterclockwise torque to withdraw the screw. It should be understood that the tool of the invention is designed to work with a portable or a stationary drill, the condition being that the drill must be run in a counter-clockwise or left-hand direction.

[0034] One of the reasons for the chuck section being hexagonal is that when the screw is removed and still attached to the screw-removing section, the screw may be clamped in a vice and a wrench or socket applied onto the axial chuck section. Turning the wrench section clockwise, the tool is removed from the damaged screw and ready for reuse. Also, in the removal process, if the drill stalls, the chuck can be opened and the drill disengaged and taken out of the way and a wrench may be used on the hexagonal shape of the chuck section to manually proceed with the extraction.

[0035] The above description relates only to the preferred form of the invention. The invention is not limited to the embodiment described but is subject to reasonable variations. It is desired to cover all such variations and modifications as fall within the scope of the above-described invention.