SCREW HAVING UNDERSIDE CUTTERS AND POCKETS
A screw has a generally flat washer-like head. On an underside of the head are a plurality of cutters or cutting wedges arranged circumferentially around the shank of the screw. The cutters cut or carve off material when the screw is inserted into a fibrous material like wood to thereby facilitate countersinking of the screw head. The cutters may be triangular or quadrilateral wedges. One or more pockets are disposed radially inwardly of the cutters for receiving fibrous material to help lock the screw in place, i.e. to prevent the screw from loosening over time. These pockets may circularly shaped pockets disposed circumferentially around the shank. Alternatively, a single annular pocket may be provided around the shank.
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This is the first application filed for the present invention.
TECHNICAL FIELDThe present invention relates generally to threaded fasteners and, in particular, to screws having generally flat heads.
BACKGROUNDA self-countersinking screw for fibrous material such as wood, wood-like materials and composite materials is disclosed in Applicant's own Canadian Patent 2,198,832 (Walther et al.) which issued Apr. 16, 2002. This self-countersinking screw includes an inverted-conical head portion with a cavity adapted to receive a tip of a screwdriver and having a conical bottom having a plurality of triangular recesses each having a lateral side extending inwardly to form a sharp edge and a space for receiving chips. The sharp edge is designed to create a countersink when the screw penetrates into the workpiece. This self-countersinking screw can be inserted easily and efficiently.
One persistent problem with wood screws (or screws for any other fibrous material) is that they have a propensity to loosen over time. It would thus be highly desirable to provide an improved screw for fibrous material that not only is self-countersinking but is also less prone to loosening.
SUMMARYIn broad terms, the present invention provides a novel screw having cutters and one or more pockets on an underside of the screw head. When the screw is inserted, the cutters scrape or carve off material from the surface of the workpiece against which the head of the screw bears to thereby countersink the head. The one or pockets receive material from the workpiece into which the screw is being inserted to thereby lock the screw in place. The material that enters the pockets prevents the screw from loosening.
Accordingly, one main aspect of the present invention is a screw comprising an elongated shank having a plurality of threads over at least a portion of the shank, the threads terminating in a tip at a first end of the shank. The screw has a head disposed at a second end of the shank, the head having a substantially flat underside. A plurality of cutters are arranged circumferentially on the underside of the head. The cutters are adapted to facilitate countersinking of the head by cutting away material from a surface of a fibrous material into which the screw is being inserted. At least one pocket is spaced radially apart from the cutters for receiving at least some of the fibrous material when the screw is inserted into the fibrous material.
Another main aspect of the present invention is a method of fastening a screw to a piece of fibrous material. The method entails positioning a tip of the screw against a surface of the fibrous material and applying torque to the screw to cause the screw to thread into the fibrous material until cutters on an underside of a head of the screw cut away some of the fibrous material from the surface to thereby facilitate countersinking of the head of the screw into the surface of the fibrous material. The torque is applied until some of the fibrous material enters one or more pockets formed in the underside of the head of the screw.
Yet a further main aspect of the present invention is a threaded fastener including a shank and a head at one end of the shank. The head has an underside in which are disposed a plurality of cutters for countersinking the head into a surface of fibrous material. The head further includes at least one pocket disposed around the shank and disposed radially inwardly from the cutters to receive some of the fibrous material when the fastener is inserted.
Further features and advantages of the present invention will become apparent from the following detailed description, taken in combination with the appended drawings, in which:
It will be noted that throughout the appended drawings, like features are identified by like reference numerals. It should furthermore be noted that the drawings are not necessarily to scale.
DETAILED DESCRIPTIONIn general, and by way of introduction, the present invention provides a novel screw having cutters and one or more pockets on an underside of the head of the screw. When the head bears against a surface, the cutters scrape or carve off material from the surface to help countersink the head. The pockets receive material from the workpiece into which the screw is penetrating to thereby lock the screw in place, i.e. the material extending into the pockets precludes, or at least inhibits, the screws from loosening over time.
As shown in
A plurality of cutters (cutting teeth) 26 are arranged circumferentially on the underside of the head. The cutters have a sharp cutting edge that are oriented and otherwise adapted to cut away (i.e. carve off or scrape off) fibrous material (e.g. wood, composites and like products) when rotated against a surface of this type of fibrous material. The cutters thereby facilitate countersinking of the head. The cutters may incidentally also produce debris or chips when rotated against the surface.
At least one pocket 28 is spaced radially apart from the cutters for receiving some of the fibrous material when the screw penetrates into the material. The pocket may be any suitable recess, hole or cavity for receiving material. In some cases, shards, protrusions or other elements of the fibrous material may extend or enter into the pockets. As the screw is rotated these help lock the screw. In other cases, depending on the nature of the fibrous material in question, it is possible that some of the fibrous material at the surface may partially extrude into the pockets. In addition, it is also believed that possibly some debris (that is generated when the cutters rotate against the surface) will be collected in these pockets. Debris may help pack the fibrous material into the pockets to further secure the screw against unwanted loosening.
The pocket in this first embodiment is an annular recess (annular pocket) that surrounds the shank (stem) and is disposed radially inwardly of the cutters. In the particular embodiment depicted in
In the second embodiment depicted in
In the third embodiment depicted in
The screw described above and depicted in the attached drawings is designed primarily to be used with a fibrous material, e.g. wood, composites and other lignocellulosic materials. The embodiments of this invention may potentially be applied to other types of fasteners and materials where the cutters countersink and the pockets receive material that locks the screw against unwanted loosening. Accordingly, the present invention can be adapted to provide a fastener having a shank (or stem) and a head at one end of the shank, the head having an underside in which are disposed a plurality of cutters for countersinking and at least one pocket disposed around the shank and disposed radially inwardly from the cutters to receive material when the fastener is inserted. While the primary intention is to apply this technology to a screw, it could be applied in theory to other types of threaded fasteners.
The present invention has been described in terms of specific embodiments, examples, implementations and configurations which are intended to be exemplary or illustrative only. Other variants, modifications, refinements and applications of this innovative technology will become readily apparent to those of ordinary skill in the art who have had the benefit of reading this disclosure. Such variants, modifications, refinements and applications fall within the ambit and scope of the present invention. Accordingly, the scope of the exclusive right sought by the Applicant for the present invention is intended to be limited solely by the appended claims and their legal equivalents.
Claims
1. A screw comprising:
- an elongated shank having a plurality of threads over at least a portion of the shank, the threads terminating in a tip at a first end of the shank;
- a head disposed at a second end of the shank, the head having a substantially flat underside;
- a plurality of cutters arranged circumferentially on the underside of the head, the cutters being adapted to facilitate countersinking of the head by cutting away material from a surface of a fibrous material into which the screw is being inserted; and
- at least one pocket spaced radially apart from the cutters for receiving at least some of the fibrous material when the screw is inserted into the fibrous material.
2. The screw as claimed in claim 1 wherein the at least one pocket comprises an annular groove formed radially inwardly of the cutters.
3. The screw as claimed in claim 1 wherein the at least one pocket comprises a plurality of pockets disposed circumferentially around the shank and positioned radially inwardly of the cutters.
4. The screw as claimed in claim 3 wherein a number of cutters exceeds a number of pockets.
5. The screw as claimed in claim 4 wherein a ratio of cutters to pockets is 2:1.
6. The screw as claimed in claim 5 comprising fourteen cutters and 7 pockets.
7. The screw as claimed in claim 1 wherein the cutters are quadrilateral wedges.
8. The screw as claimed in claim 1 wherein the cutters are triangular wedges.
9. A method of fastening a screw to a piece of fibrous material, the method comprising:
- positioning a tip of the screw against a surface of the fibrous material; and
- applying torque to the screw to cause the screw to thread into the fibrous material until cutters on an underside of a head of the screw cut away some of the fibrous material from the surface to thereby facilitate countersinking of the head of the screw into the surface of the fibrous material, the torque being applied until some of the fibrous material enters one or more pockets formed in the underside of the head of the screw.
10. The method as claimed in claim 9 wherein material enters an annular pocket formed in the underside of the head and disposed radially inwardly from the cutters.
11. The method as claimed in claim 9 wherein material enters a plurality of pockets formed in the underside of the head and disposed radially inwardly from the cutters.
12. A threaded fastener comprising:
- a shank; and
- a head at one end of the shank, the head having an underside in which are disposed a plurality of cutters for countersinking the head into a surface of fibrous material, the head further including at least one pocket disposed around the shank and disposed radially inwardly from the cutters to receive some of the fibrous material when the fastener is inserted.
13. The fastener as claimed in claim 12 comprising a plurality of triangular wedge-shaped cutters.
14. The fastener as claimed in claim 12 comprising a plurality of quadrilateral wedge-shaped cutters.
15. The fastener as claimed in claim 12 comprising a single annular pocket disposed circumferentially around the shank.
16. The fastener as claimed in claim 12 comprising a plurality of pockets disposed circumferentially around the shank.
17. The fastener as claimed in claim 16 wherein a ratio of cutters to pockets is 2:1.
18. The fastener as claimed in claim 16 comprising fourteen cutters and seven pockets.
Type: Application
Filed: Sep 17, 2009
Publication Date: Mar 17, 2011
Applicants: (Thunder Bay), (Thunder Bay), (Thunder Bay)
Inventor: Mirco Walther (Thunder Bay)
Application Number: 12/561,931
International Classification: F16B 35/06 (20060101);