WO1993010945A1

WO1993010945A1 - Improved open end wrench

Info

Publication number: WO1993010945A1
Application number: PCT/US1992/010262
Authority: WO
Inventors: Kenneth L. Foster
Original assignee: Stanley-Proto Industrial Tools
Priority date: 1991-11-25
Filing date: 1992-11-25
Publication date: 1993-06-10
Also published as: AU3228193A

Abstract

An open-end wrench (10) is disclosed which can be used with a variety of fastener head shapes and which reduces marring or round-off of the corners of the fastener head (17). The wrench has a wrench cavity (16) for receiving the fastener (17). The wrench cavity (16) includes convex drive surfaces (21) which have a radius of curvature equal to half of the faster head width (A). Clearance surfaces (22, 24) are provided adjacent the drive surfaces (21) to accept the corners of the fastener head (17) when force is applied to turn the fastener (17).

Description

IMPROVED OPEN END WRENCH

Technical Field

The present invention relates generally to wrenches and more particularly to an improved open end wrench which applies force to the flats of a fastener head instead of the comers of the fastener head.

Background of the Invention

Wrenches for turning fasteners such as nuts and bolts are available in a variety of configurations, including fixed jaws, adjustable jaws, or sockets. Open-end wrenches have fixed jaws at one or both ends of a handle which define a U-shaped wrench cavity for accepting the head of a fastener. Th -:e wrenches are primarily designed for use with hexagonal fastener heads but may also be used with any fastener head having an equal number of faces. To turn the fastener, the wrench is placed over the fastener with the flat jaws of the wrench aligned with flat surfaces on the head of the fastener, and force is exerted on the handle.

One problem experienced with conventional open-end wrenches is that the jaws often do not remain aligned with the flat surfaces when force is applied to the handle but rotate relative to the flat surfaces and contact the comers of the fastener head, thereby marring or rounding off the comers of the fastener. This relative rotation results in part from manufacturing tolerances inherent in the manufacture of wrenches and variances in the head sizes of the fasteners among manufacturers. Because of these variations, open-end wrenches are generally ineffective for turning fastener heads which are not hexagonal in shape or which have worn or rounded-off corners, especially if great force is required to turn the fastener.

Many attempts have been made to design an open-end wrench which reduces marring or rounding off of the comers of a fastener head and which can be used with marred fastener heads and non-hexagonal (particularly square) fastener heads. One example of an open-end wrench designed for this purpose is shown in United States Patent No. 2,685,219. The wrench cavity shown in the '219 patent includes two curved bosses for contacting opposite flat surfaces of a fastener head. Each boss includes a thrust zone having a radius of curvature "R" and a pull zone having a radius of curvature "r," wherein "R" is greater than "r." While providing some improvement over conventional open- end wrenches, this design suffers certain disadvantages in that it is not useable with fasteners having square heads.

Furthermore, the shape of the cavity tends to force the fastener away from the wrench when a large amount of torque is applied, and the cavity exerts force primarily at the corners of the fastener head. Another example of an open-end wrench designed to reduce rounding-off of the fastener comers is shown in United States Patent No. 3,242,775. While this design is intended to apply force to the flat faces or surfaces of a nut instead of the comers (Col. 2, lines 15-18), in actuality the disclosed wrench applies force at the comers of the fastener

(see Figs. 8 & 12).

Therefore, despite the various efforts found in the prior art, there remains a need for an improved open-end wrench which can be used to turn a variety of fastener head configurations without marring. Summary of the Invention

The present invention advances the art by providing an improved open-end wrench which can be utilized with a variety of fastener head shapes and which reduces marring of the comers of the fastener head.

Generally described, the present invention provides a wrench cavity for turning a fastener head having a pair of contact surfaces positioned a distance "A" apart. The wrench cavity comprises a first clearance surface positioned at a rear end of the wrench cavity. A pair of drive surfaces are positioned adjacent the first clearance surface. The drive surfaces each have a radius of curvature "R" = A/2.

According to a preferred embodiment, an open- end wrench comprises a handle, a web area positioned adjacent to the handle, and a pair of jaws extending from opposite sides of the web to define a wrench cavity for accepting a fastener head therewithin. The wrench cavity has a first concave clearance surface positioned adjacent the web area opposite the handle and a pair of convex drive surfaces positioned adjacent the first concave clearance surface. For a fastener having contact surfaces positioned a distance "A" apart, e. drive surface of the wrench has a radius of curvature "R" = A/2.

Thus, it is an object of the present invention to provide an improved open-end wrench.

It is a further object to provide an open-end wrench which reduces marring or rounding-off of the comers of a fastener head.

It is yet another object of the present invention to provide an open-end wrench which can be used to turn various fastener head configurations and which can be used to drive worn fastener heads.

A still further object of the present invention is to provide an improved end wrench which exerts force on the flat surfaces of a fastener head instead of the comers. Other objects, features, and advantages of the present invention will become apparent upon reading the following specification, when taken in conjunction with the drawings and the appended claims.

Brief Description of the Drawings

FIG. 1 is a perspective view of a preferred embodiment of the wrench of the present invention.

FIG. 2 is a plan view of a fastener head of a general type for which the wrench of the present invention is intended for use.

FIG. 3 is a plan view of the wrench of FIG. 1 positioned about the fastener of FIG. 2.

FIG. 4 is a plan view of the wrench of FIG. 1 when force is applied to the wrench handle to turn the fastener of FIG. 2.

FIG. 5 is a side view of the wrench of FIG. 1.

Detailed Description of the Preferred Embodiment Referring now to the drawings, in which like numbers indicate like elements throughout the several views, HG. 1 shows an open-end wrench 10 of one-piece forged steel construction. The wrench 10 comprises an elongate handle 11, a web area 12, and a pair of jaws 13 and 14. The handle 11 is shaped for grasping by the hand and is of conventional configuration. The web area 12 is of generally crescent shape and is formed at one end of the handle 11. A hole 15 is provided at the opposite end of the handle for hanging of the wrench 10 when not in use, and this opposite end is rounded for comfort. The jaws 13 and 14 extend from the web area

12 away from the handle 11 and are spaced apart to define a wrench cavity 16 therebetween for receiving a fastener head 17 (FIG. 2) of a nut, bolt, or other fastener. The jaws 13 and 14 are preferably offset at an angle to the handle 11 for more versatility when die fastener head 17 is hard to access. The wrench cavity 16 has three sides 18, 19, and 20. The sides 18 and 19 are formed by mutually facing surfaces of the jaws 13 and 14, respectively. The side 20 is formed by the surface of the web area 12 opposite the handle 11 which is generally perpendicular to each of the sides 18 and 19. The sides 18 and 19 are mirror images of one another and each include a convex drive surface 21, a concave clearance surface 22, and a flat guide surface 23. The side 20 provides a concave clearance surface 24; it being understood that the terms "concave" and "convex" refer to the direction of curvature of the surfaces 21, 22 and 24 relative to the wrench cavity 16.

Referring now to FIG. 2, me fastener head 17 is generally hexagonal in shape. The fastener head 17 comprises a plurality of opposed flat surfaces 25 which intersect at comers 26. The flat surfaces 25 of the fastener head 17 are spaced apart by a distance or width A. The fastener head 17 may comprise the head of a bolt, in which case the fastener head will be located at one end of an elongated threaded shaft. Alternatively, the fastener head 17 may comprise a nut, in which case the fastener head will further comprise a threaded central bore. As used herein, it will be understood that the term "fastener head" will encompass both of these structures.

FIG. 3 shows the jaws 13, 14 of the wrench 10 placed around a fastener head 17, prior to the application of a force on the handle 11 to turn the fastener. The drive surfaces 21 of the wrench jaws 13, 14 are positioned to contact the centers of opposite flat surfaces 25 of the fastener head 17 when the fastener head is received within the wrench cavity 16, thereby to transmit force to the flat surfaces 25 of the fastener head 17 for turning the fastener, as will be explained more fully below. The guide surfaces 23 are used to guide the wrench cavity toward the fastener head 17 and include angled surfaces 27 to further aid in guiding the wrench onto the fastener head. The clearance surfaces 21 and 24 provide clearance space between the fastener head and the wrench cavity, as will also be explained more fully below.

In FIG. 4 there is shown the wrench cavity 16 as it is positioned relative to the fastener head 17 when a rotational force F is applied to the wrench handle 11 to turn the fastener in a counterclockwise direction. As can be seen, each drive surface 21 contacts one of d e flat surfaces 25 at a point of contact 29. Because the wrench cavity rotates slightly relative to the fastener head upon the application of the rotational force F, each point of contact 29 is shifted slighdy relative to the midpoint of the flat surfaces 25 and the drive surfaces 21 from each point of contact 27, but remains located on the flat surface 25 of the fastener head. Thus, it will be appreciated that the drive surfaces 21 do not contact any of the comers 26. In addition, the clearance surfaces 22 and 24 provide sufficient clearance such that contact between the comers 26 and the clearance surfaces of the wrench cavity 16 is minimized when rotational force is applied to turn the fastener. To enable the drive surfaces 21 to contact the flat surfaces 25 instead of the comers 26, the drive surfaces are each configured to have a radius of curvature R of a dimension equal to one-half of the width A of the fastener head, as shown in FIG. 5. Further, the drive surfaces are positioned along the jaws 13 and 14 such that the distance D between the center of each drive surface and the concave clearance surface 24 at the back of the cavity 16 is also about A/2 (FIG. 5). In addition the apex of the drive surfaces 21 are spaced apart a distance M, which distance exceeds the width A of the fastener head just enough to allow the fastener head 17 to be received with the cavity 16. This configuration provides a free-swing (the amount the wrench cavity rotates relative to the fastener head when force is applied to turn the fastener) of no more than about 6 degrees between each drive surface 21 and each contacted flat surface 25 at the point of contact 29. The free-swing is represented by an angle B measured between the contacted flat surface 25 and a tangent 31 taken at each point of contact 29 (shown in FIG. 4). For ease of representation, the plane of each contacted flat surface 5 25 is represented by a plane 30. The low free-swing provided by the novel configuration and placement of the drive surfaces 21 reduces rotation of the wrench cavity 16 relative to the fastener head 17 when rotational force is applied to the handle 11 to turn the fastener. Because of this reduced relative

10 rotation, the drive surfaces 21 of the wrench 10 are not permitted to contact the comers 26 of the fastener head 17 but instead remain in contact with the flat surfaces 25 of the fastener head.

Because the unique configuration of the wrench

15 cavity 16 of the wrench 10 of the present invention transmits torque to the flat surfaces 25 of the fastener head 17 such d at little or no contact between the comers 26 and the wrench cavity occurs, marring of the fastener head and "rounding" of the fastener head comers is reduced. Because the drive

20 surfaces 21 of the wrench 10 contact only the flat surfaces 25 of the fastener head 17, the wrench of the present invention may be used to turn marred or "rounded off fastener heads and to turn fastener heads having configurations other than hexagonal. The novel wrench cavity 16 also allows more

25 torque to be applied to the fastener head 17 with less chance of marring, which is especially beneficial when working with fasteners made of softer materials, plated fasteners, or cosmetical fasteners.

Finally, it will be understood that the preferred

30 embodiment has been disclosed by way of example, and that other modifications may occur to those skilled in the art without departing from the scope and spirit of the appended claims.

Claims

CLAIMSI claim:

1. A wrench for turning a fastener head having a pair of opposed contact surfaces positioned a distance "A" apart, said wrench comprising: a pair of jaws defining a wrench cavity therebetween for receiving said fastener head therewithin; a first clearance surface positioned at a rear end of said wrench cavity; and a drive surface formed on each of said pair of jaws adjacent to said first clearance surface, said drive surfaces each having a radius of curvature R = A/2.

2. The wrench of Claim 1, further comprising a pair of second clearance surfaces, each one of said second clearance surfaces positioned adjacent to one of said drive surfaces opposite one of said first clearance surfaces.

3. The cavity of Claim 2, wherein said second clearance surfaces are concave relative to said cavity.

4. The cavity of Claim 1, wherein said drive surfaces are convex relative to said cavity.

5. The cavity of Claim 1, wherein said first clearance surface is concave relative to said cavity.

6. The cavity of Claim 1, wherein when said fastener head is accepted within said cavity each of said drive surfaces contacts a corresponding one of said contact surfaces of said fastener head at a contact point located approximately at the midpoints of said contact surfaces.

7. The cavity of Claim 6, wherein said contact point comprises a first contact point, and wherein when said wrench cavity is acted upon by an external force to turn said fastener head each of said drive surfaces contacts said corresponding one of said contact surfaces of said fastener head at a second point of contact such that a tangent taken at each second point of contact forms an angle between the drive surfaces and the contact surfaces of no more than about six degrees.

8. An open-end wrench, comprising:

(a) a handle;

(b) a web area positioned adjacent to said handle; and (c) a pair of jaws extending from opposite sides of said web to define a wrench cavity for accepting a fastener head having contact surfaces positioned a distance "A" apart, said wrench cavity comprising: (i) a first concave clearance surface positioned adjacent said web area opposite said handle; and

(ii) a pair of convex drive surfaces positioned adjacent said first concave clearance surface, each drive surface having a radius of curvature "R" = A/2.

9. The wrench of Claim 8, further comprising a pair of second concave clearance surfaces, each one of said second clearance surfaces positioned adjacent to one of said drive surfaces opposite said first clearance surface.

10. The wrench of Claim 8, wherein each of said drive surfaces contacts one of said contact surfaces of said fastener head at a first point of contact when said fastener head is accepted within said cavity, each of said first points of contact being centrally located on one of the contact surfaces and one of the drive surfaces.

11. The wrench of Claim 8, wherein each of said drive surfaces contacts one of said contact surfaces at a second point of contact when said handle is acted upon by a force to turn said fastener head.

12. The cavity of Claim 11, wherein a second tangent taken at each second point of contact forms an angle between the drive surfaces and the contact surfaces of no more than about six degrees.