US3897812A

US3897812A - Screw driver

Info

Publication number: US3897812A
Application number: US473840A
Authority: US
Inventors: Edward T Arnn
Original assignee: Individual
Current assignee: Individual
Priority date: 1974-05-28
Filing date: 1974-05-28
Publication date: 1975-08-05
Anticipated expiration: 1992-08-05
Also published as: SE423341B; BE829614A; DE2522729A1; FR2272795B3; DE2522729C2; CA1025253A; GB1498684A; AU8151575A; JPS5743387B2; SE7505508L; FR2272795A1; JPS513098A

Abstract

A screw driver having a foot portion on the lower extremity of the blade for increasing the effectiveness of the blade in gripping the sidewalls of a screw slot.

Description

United States Patent Arnn Aug. 5, 1975 SCREW DRIVER 1.782.981 11/1930 Anderson H 145/50 A 3.026.920 3 [962 Y k 145 50 A [76] Inventor; Edward T. Arnn, 505 Country Ln., 3.120251 2x964 ygtknwnn N 145150 A Lfluisvlllei y- 40207 3.405.748 l0/l968 Sorteberg v. 145/50 R [221 Filed: May FOREIGN PATENTS OR APPLICATIONS [2i] Appl. No.1 473,840 26,6[9 6/l93l Australia [45/50 A 18:102 8/19l3 United Kingdom .1 145 50 A US. Cl. 145/50 A; [45/50 D Int. Cl. Bb 15/00 Field of Search. [/50 A, D, 50 R, 50 B,

[45/50 C, 50 DA, 50 E, 50 F [56] References Cited UNITED STATES PATENTS 697,836 4/[902 Gorham [45/50 A [.476.653 [2/[923 Stanton... [45/50 A l.74l,349 [2/1929 Sullivan 1. /50 A Primary Examiner-Al Lawrence Smith Assistant ExaminerJ. T. Zatarga [57] ABSTRACT A screw driver having a foot portion on the lower extremity of the blade for increasing the effectiveness of the blade in gripping the sidewalls of a screw slot.

4 Claims, 4 Drawing Figures PATENTEU RUB 51975 24 III/M1111, 2O

SCREW DRIVER BACKGROUND OF THE INVENTION It has been long recognized that present clay screw drivers fall far short of being adequate to insert or remove screws which have substantial resistance to turning. Most typically, if a screw has a substantial resistance to being turned, upon applying a torque thereto, the screw driver blade slips upwardly out of the slot in the screw head. This slippage is an undesirable result arising from the current screw driver blade geometry.

Many attemps have been made to modify screw driver blades to make them perform better when in use on difficult-to-turn" screws. Representative of these attempts are US. Pat. Nos. 3,236,275; 2,684,094 and 370,255. Generally, these attempts have included modifying the screw head as well as the screw driver blade. However, modification of the screw head is impractical, since screws currently in use do not have modified heads and industry acceptance of any modification is a major obstacle. Another approach is to modify the screw driver blade by providing ribs which project downwardly on each side of the screw head as shown in U.S. Pat. No. 697,836. However, such a screw driver is generally unacceptable since the screw head must be protruding above any adjacent surfaces in order for the screw driver to be used.

The invention of this application is a rugged, inexpensive. readily constructed and easily employed screw driver which overcomes all of the defects of prior art screw drivers.

SUMMARY OF THE INVENTION The present invention relates to a screw driver including a blade which terminates in a lower foot portion which in turn protrudes outwardly from the blade faces to provide a gripping means. The gripping means imbeds itself into the sidewalls of the slot in a screw head to prevent the blade from slipping out of the slot as the screw driver is turned.

More specifically, the invention includes a screw driver comprising a shank portion and a blade portion integral therewith, the blade portion having generally converging sides and generally converging edges terminating integral with a foot portion, said blade including torque transmitting ribs integral with said sides along the opposed edges of said blade, said foot portion delining the lower most portion of said blade and being generally isosceles trapezoidal in crosssection with its widest base portion lying in a plane perpendicular to the axis of said shank and being engageable with the bottom of a slot in a screw head and its inwardly tapered sidewalls extending across the entire width of the blade and being engageable with the parallel sidewalls of a screw head slot. The junction of said base and respective inwardly tapered sidewalls define wedge like bites which cut a groove in the parallel sidewalls of said screw slot upon application of a torque to the shank.

The screw driver of this invention has been found to be capable of transmitting a torque to a screw head which is many times the torque that can be transmitted by a conventional screw driver. Also, the screw driver of this invention has been found to be resistant to being dislodged once inserted into a screw head slot and subjected to a torque. In addition, the screw driver of this invention can engage a screw head from an angle other than straight on and still provide its superior torque transmitting qualities, and, lastly, the screw driver of this invention allows the user to position a screw thereon by first engaging one bite of the blade foot means in a screw head slot and then with a rocking motion engaging the other bite in the slot, whereupon the screw is removably held by the foot portion and easily positioned in a hole not otherwise accessible to a screw.

DESCRIPTION OF THE DRAWING FIG. I is an isometric view of the screw driver of this invention.

FIG. 2 is a front view of the blade and shank of the screw driver of this invention.

FIG. 3 is a sectional view taken along lines 3-3 of FIG. 2.

FIG. 4 is a sectional view taken along lines 4-4 of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a screw driver 10 having a handle 12, a shank l4 and a blade 16. The blade 16 includes a generally outwardly or diverging portion 18 and generally converging edges 20. It also includes faces 22 which are located in opposed relationship to each other on opposite sides of the blade. Included in faces 22 are cutaway portions 24 of increasing depth near the blade end and running substantially the entire length of the blade. Cutaway portions 24 define strengthening ribs 26 on either side of blade 16. Ribs 26 run generally parallel to the longitudinal axis of blade 16. Ribs 26 also gener ally converge from the shank of the screw driver to the blade end, both in thickness and in width, being of greatest cross section at the point of intersection of diverging portions 18 and converging edges 20, to the blade end. Blade 16 terminates in foot portion 28 which includes wedge like bites 30 on either side thereof. Foot portion 28 is generally isosceles trapezoidal in cross-section diverging outwardly away from the longitudinal axis of the shank and finally terminating at a flat base 32. It should be noted that blade 16 is of a configuration such that the strengthening ribs 26 define, in cooperation with cutaway portions 24, a blade having an I-beam cross-section when viewed in a plane perpendicular to the longitudinal axis of the shaft.

In using the screw driver of this invention, one simply inserts the blade into the slot of a screw head with the base of the foot portion extending downwardly thereinto. The screw driver shank is then twisted either manually with the aid ofa handle, or by mechanical means such as an electric motor arrangement, for example, a power drill and chuck.

It should be noted that the screw driver of this invention need not be inserted in the screw head so that the longitudinal axis of the shank is in line with the longitudinal axis of the screw: but rather, the axis of the shank may be slightly angled with respect to the axis of the screw since the bites 30 run the entire length of the foot portion 28 and may thus cut into the screw slot side walls at any angle. This feature is particularly advantageous when one considers the number of times screw heads are encountered where the head is not accessible from a straight on position, yet considerable torque is needed.

The material of construction of the screw driver can vary widely; however, a high quality steel is preferred. One such steel is designated as A.I.S.l. No. A3150 and is a high carbon steel having about 0.48 0.53 percent carbon 0.70 0.90 percent MN, l.l l.40 percent nickel and 0.70 0.90 percent chromium contained there among its principal additives.

It should be recognized that although the drawing depicts a square shank and a round handle for the screw driver shown therein, any suitable configuration can be employed in the practice of this invention.

Having thus described the invention, What is claimed l. A screw driver comprising a shank and a blade integral therewith, the blade having generally converging sides and generally converging edges terminating integral with a foot portion, which protrudes outwardly from the incline of the blade faces to provide a gripping means, said blade including torque transmitting ribs, integral with said sides, and extending along the opposed edges of said blade terminating at said foot portion, said foot portion defining the lower most portion of said blade and being generally isosceles trapezoidal in cross-section with its base lying furthest from the shank in a substantially flat plane perpendicular to the axis of said shank at the lowest extremity of the blade thereby being engageable with the bottom of the slot in a screw head, said foot portion further having its inwardly tapered sidewalls extending across the entire width of the blade and being engageable with the parallel sidewalls of a screw head slot, said base of said foot portion and said respective inwardly tapered sidewalls defining wedge-like bits comprising said gripping means engageable with opposed sides of a screw slot to removably hold a screw thereon and cut a groove in the parallel sidewalls of a screw head slot upon application of a torque to said shank.

2. The screw driver of claim 1 wherein the upper portion of said isosceles trapezoidal foot portion merges with said torque transmitting ribs at their respective ends while a central portion thereof merges substantially abruptly with a central cutaway portion of said blade, the cross-section of the blade viewed in a plane parallel to the base of said foot portion passing above said points of merger being generally ofl configuration.

3. A screw driver comprising a shank and a blade portion, said blade portion being of generally I cross sectional configuration in a plane perpendicular to the longitudinal axis of said shank and terminating in a blade foot portion having a generally isosceles trapezoidal cross-sectional configuration in a plane parallel with the longitudinal axis of said shank with its base lying furthest from the shank in a substantially flat plane perpendicular to the axis of said shank at the lowest extremity of the blade thereby being engageable with the bottom of a slot in a screw head, said blade foot portion further having its inwardly tapered sidewalls extending across the entire width of the blade, said base of said blade foot portion and said respective inwardly tapered sidewalls defining wedge-like bites extending outwardly beyond the incline of the blade faces and engageable with opposed sides of a screw slot to removably hold a screw thereon and cut a groove in the parallel sidewalls of a screw head slot upon application of a torque to said shank.

4. A screw driver comprising: a shank having a handle attached to one end; and, a blade integral with the other, the blade having generally convergingly tapered sides and edges and including ribs formed by central cutaway portions in said sides running generally parallel to the longitudinal axis of said shank to define an I cross-section viewed in a plane perpendicular to the longitudinal axis of said shank. said cutaway portions terminating at a point longitudinally spaced from the lower end of said blade; a lower terminal foot integral with said blade, said foot extending downwardly and outwardly from the sides of said blade to form wedge portions at the lower terminal of said blade engageable with opposed sides of a screw slot to removably hold a screw thereon and cut a groove in the parallel sidewalls of a screw head slot upon application of a torque to said shank.

Claims

1. A screw driver comprising a shank and a blaDe integral therewith, the blade having generally converging sides and generally converging edges terminating integral with a foot portion, which protrudes outwardly from the incline of the blade faces to provide a gripping means, said blade including torque transmitting ribs, integral with said sides, and extending along the opposed edges of said blade terminating at said foot portion, said foot portion defining the lower most portion of said blade and being generally isosceles trapezoidal in cross-section with its base lying furthest from the shank in a substantially flat plane perpendicular to the axis of said shank at the lowest extremity of the blade thereby being engageable with the bottom of the slot in a screw head, said foot portion further having its inwardly tapered sidewalls extending across the entire width of the blade and being engageable with the parallel sidewalls of a screw head slot, said base of said foot portion and said respective inwardly tapered sidewalls defining wedge-like bits comprising said gripping means engageable with opposed sides of a screw slot to removably hold a screw thereon and cut a groove in the parallel sidewalls of a screw head slot upon application of a torque to said shank.

2. The screw driver of claim 1 wherein the upper portion of said isosceles trapezoidal foot portion merges with said torque transmitting ribs at their respective ends while a central portion thereof merges substantially abruptly with a central cutaway portion of said blade, the cross-section of the blade viewed in a plane parallel to the base of said foot portion passing above said points of merger being generally of I configuration.

4. A screw driver comprising: a shank having a handle attached to one end; and, a blade integral with the other, the blade having generally convergingly tapered sides and edges and including ribs formed by central cutaway portions in said sides running generally parallel to the longitudinal axis of said shank to define an I cross-section viewed in a plane perpendicular to the longitudinal axis of said shank, said cutaway portions terminating at a point longitudinally spaced from the lower end of said blade; a lower terminal foot integral with said blade, said foot extending downwardly and outwardly from the sides of said blade to form wedge portions at the lower terminal of said blade engageable with opposed sides of a screw slot to removably hold a screw thereon and cut a groove in the parallel sidewalls of a screw head slot upon application of a torque to said shank.