WO2007073326A1

WO2007073326A1 - Screw

Info

Publication number: WO2007073326A1
Application number: PCT/SE2006/050557
Authority: WO
Inventors: Chao-Wei Lin
Original assignee: Essve Produkter Ab
Priority date: 2005-12-22
Filing date: 2006-12-06
Publication date: 2007-06-28
Also published as: SE0502886L; SE529577C2

Abstract

A screw comprising a head part (50), a pointed insert part (52) and a shank part disposed between said head part and said pointed insert part and having a shank axis (A). The shank part comprising a first shank segment (53) adjacent to said head part and having a first radius (r0) relative to the shank axis, and a second shank segment (54) adjacent to said pointed insert part and having a surface that is formed with a helical screw thread (55) including interconnected thread sections that have a second radius (ii) relative to the shank axis and larger than the first radius. The second shank segment is provided with one lengthwise groove (56) having a curvature so that the depth of said groove is larger than zero but smaller than the outer diameter of said threads, and the length of said groove is larger than zero but smaller than the whole length of said shank part, said lengthwise groove extends upward from the pointed end. The surface of the second shank segment being further formed with at least one projecting element (57) between two neighbouring interconnected ones of said thread sections, said projecting element having a greatest radial dimension (r2) with respect to the shank axis that is greater than the first radius (r0) and less than or equal the second radius (r1),

Description

Title

Screw

Field of the invention The present invention relates to a screw according to the preamble of the independent claim.

Background of the invention

Various kinds of conventional screws are widely known, such as shown in figs. 1-4. Those shown in figs, ϊ and 2 have their ends formed with a multi-angled cone A or a cutting edge B so as to cut wood in their rotation. The figs. 3 and 4 show screws having their ends formed with a lengthwise groove C or a lengthwise cutting groove D. However, those four kinds of conventional screws do not have good function in being driven in rather hard wood, still having drawbacks of breaking of screws and rippings in an object wood during driving action.

A known conventional screw disclosed in US-3,492,908 has scrap grooves that are shaped curved and the same depth at a front and at the rear end, and there are three of them evenly provided from the bottom end. Each scrap groove has two fifths of the length of the rod so when the screw runs in longer than the length of the scrap grooves some wood scrap may not be able to be removed out, and possible to let the wood split, lowering the strength of the wood structure.

Next, US-1,465,148 has scrap grooves of triangle of a right angle. In addition, the scrap grooves of the triangular right angled shape has a cutting function larger than the scrap removing function. Then the threads for engaging wood are formed intermittently due to the scrap grooves extending from the bottom end to the head, decreased in its engaging force.

US-4,673,323 has a scrap groove of a triangular shape, a triangle with a right angle, and the difference between the last two mentioned patents is the scrap grooves having different length only,

US-6,106,208 discloses a kind of screw having little resistance in being driven, and quick in moving in a wood, without possibility of breaking of itself and ripping of an object wood during its driving action. This screw is illustrated in figure 5. A feature of the screw disclosed in US-6,106,208 is two lengthwise grooves 5, 6 formed in the shank 2 of a screw. Also disclosed in the figure is a flat head 1, helical threads 3 and a pointed end 4. Each groove has any shape, but preferably of a curved lengthwise and extend from the end. Another feature is that the grooves overlap or do not overlap when viewed projectively from the horizontal surface of the axis of the screw and one more feature is that the grooves overlap or do not overlap when viewed protectively from the vertical surface of the axis of the screw.

Thus, the object of screw according to US-6,106,208 is to achieve a screw having little resistance in being driven, and quick in moving in a wood, without possibility of breaking of itself and ripping of an object wood during its driving action.

In particular the two grooves can hold therein wood scrapes out off by the helical threads, and consequently the portion of the wood around the helical threads may not be pressed so hard that the object is ripped.

US-6,672,812 relates to a wood screw, more particularly to a wood screw with a low driving torque requirement. The object of the screw according to US-6,672,812 is to provide a wood screw with a low driving torque requirement, which can be produced at a relatively low cost, having reduced risk of over-boring and which can maintain a sufficient holding effect with wood material. That is primarily achieved by arranging two projecting elements neighbouring interconnected thread sections wherein the projecting elements press away the wooden fibres during screwing such that wooden chips and scrapes are assembled around the shank of the screw in order to achieve low driving torque requirement and to avoid ripping or ciacking of the object wood. According to US-6,672,812, and which is illustrated in figures 6 and 7, a wood screw 3 includes a head part 30, a tapered insert part 32, and a shank part 31 disposed between the head part and the tapered insert part and having a shank axis (A). The shank part has a first shank segment 311 adjacent to the head part 30, and a second shank segment ,312 adjacent to the tapered insert part 32, The first shank segment has a first radius (rθ) relative to the shank axis (A). The second shank segment 312 has a surface that is formed with a screw thread 33, The screw thread 33 includes interconnected thread sections 34 that have a second radius (rl) relative to the shank axis (A) and larger than the first radius. The surface of the second shank segment 312 is further formed with at least one projecting element 38 between two neighbouring interconnected ones of the thread sections 34 that are proximate to the tapered insert part 32. The projecting element has a greatest radial dimension with respect to the shank axis that is greater than the first radius and less than the second radius. In one embodiment of the prior art screw, all of the thread sections on the surface of the second shank segment have the second radius relative to the shank axis

In another embodiment of the prior art screw, illustrated in figure 7, the two neighbouring interconnected ones of the thread sections 341 on the surface of the second shank segment have a third radius (r3) relative to the shank axis that is greater than the first radius and less than the second radius, and remaining ones of the thread sections on the surface of the second shank segment have the second radius relative to the shank axis. The third radius is not less than the greatest radial dimension of the projecting element. Preferably, each projecting element 38 is formed as a plate that projects radially relative to the shank axis (A) and that has a convex shaving edge 380.

Referring to figure 8, a third preferred embodiment of the wood screw 4 according to the prior art screw in US-6,672,812 is disclosed where each projecting element 48 is formed as a rib that extends parallel to the shank axis (A), In this embodiment, each projecting element 48 has a rounded cross-section along a plane transverse to the shank axis (A). Referring to figure 9, a fourth preferred embodiment of the wood screw 5 according to the prior art screw in US-6,672,812 is disclosed where each projecting element 58 has a triangular or tapering cross-section along a plane transverse to the shank axis.

Referring to figure 10, a fifth preferred embodiment of the wood screw 6 according to the prior art screw in US-6,672,812 is disclosed where each projecting element 68 has a generally trapezium cross-section along a plane transverse to the shank axis.

There are different objects of the screws disclosed in US-6,106,208 and in US-6,672,812: in '208 it is not desired that the wood scrapes are assembled around the screw shank, i.e. that grooves collect the wood scrapes, whereas in '812 the purpose of the projecting elements is to press away the wooden fibres during screwing such that wooden chips and scrapes are assembled around the shank.

In spite of the advantages obtained by the above screws still deficiencies remain with regard to high driving torque requirement and also having drawbacks of breaking of screws and rippings in an object wood during driving action.

Thus, the object of the present invention is to achieve an improved screw having low driving torque requirement and low risk of breaking during driving action.

Summary of the invention

The above-mentioned object is achieved by the present invention according to the independent claim.

Preferred embodiments are set forth in the dependent claims.

During extensive testing the inventor has found that by replacing one of the grooves in the prior art screw according to US-6,106,208 by at least one projecting element essentially in accordance with those described in US-6,672,812 surprisingly low values with regard to driving torque may be obtained. Furthermore and preferably, by arranging the projecting elements proximal the groove, even more advantageous performance is obtained,

Short description of the appended drawings Figures 1-4 show various screws according to prior art.

Figure 5 show a prior art wood screw provided with grooves. Figure 6 and 7 show side views of a prior art wood screw provided with projecting elements.

Figures 8-10 show cross-sectional views of preferred embodiments of a prior art screw, Figure 11 and 12 show a top view and a side view, respectively, of a wood screw according to the present invention. Figure 13 shows a perspective view of the wood screw according to the present invention.

Detailed description of preferred embodiments of the invention With reference to figures 1 1-13, and in particular figure 13, a preferred embodiment of the present invention is illustrated.

The screw comprising a head part 50, a pointed insert part 52 and a shank part disposed between said head part and the pointed insert part has a shank axis (A),

The shank part comprising a first shank segment 53 adjacent to said head part and having a first radius rO relative to the shank axis, and a second shank segment 54 adjacent to said pointed insert part and having a surface that is formed with a helical screw thread 55 including interconnected thread sections that have a second radius rl relative to the shank axis and larger than the first radius.

The distance from the shank axis to the surface of the second shank segment is designated r4.

The second shank segment 54 is provided with one lengthwise groove 56 having a curvature so that the depth of said groove is larger than zero but smaller than the outer diameter of said threads, and the length of said groove is larger than zero but smaller than the whole length of said shank part, the lengthwise groove extends upward from the pointed insert part 52.

The surface of the second shank segment being further formed with at least one projecting element 57 between two neighbouring interconnected ones of said thread sections. The projecting element having a greatest radial dimension r2 with respect to the shank axis that is greater than the first radius and less than the second radius.

According to a preferred embodiment of the present invention all of said thread sections on said surface of said second shank segment have the second radius rl relative to the shank axis.

Thus, preferably, the preferred relation between the distances is then rl>r2>rθ>r4.

The at least one projecting element is preferably positioned essentially proximal the one groove with regard to the pointed insert part.

Preferably said surface of said second shank segment between said two neighbouring interconnected ones of said thread sections is provided with a pair of projecting elements 57 that are diametrically opposite relative to the shank axis.

Preferably the projecting element is formed as a plate that projects radially relative to the shank axis and that has a convex shaving edge.

Figures 8-10 show alternative embodiments of the projecting element.

With references to figure 8 the projecting element 48 is formed as a rib that extends parallel to the shank axis having an essentially round cross-section along a plane transverse to the shank axis.

With references to figure 9 the projecting element 58 has a triangular or tapering cross- section along a plane transverse to the shank axis. And finally, with references to figure 10 the projecting element 68 has a generally trapezium cross-section along a plane transverse to the shank axis.

The present invention is not limited to the above-described preferred embodiments, Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the invention, which is defined by the appending claims.

Claims

1 , A screw comprising a head part (50), a pointed insert part (52) and a shank part disposed between said head part and said pointed insert part and having a shank axis (A), said shank part comprising a first shank segment (53) adjacent to said head part and having a first radius rO relative to the shank axis, and a second shank segment (54) adjacent to said pointed insert part and having a surface that is formed with a helical screw thread (55) including interconnected thread sections that have a second radius rl relative to the shank axis and larger than the first radius, said second shank segment is provided with one lengthwise groove (56) having a curvature so that the depth of said groove is larger than zero but smaller than the outer diameter of said threads, and the length of said groove is larger than zero but smaller than the whole length of said shank part, said lengthwise groove extends upward from the pointed end, c h a r a c t e r i z e d i n that said surface of said second shank segment being further formed with at least one projecting element (57) between two neighbouring interconnected ones of said thread sections, said projecting element having a greatest radial dimension (r2) with respect to the shank axis that is greater than the first radius (rO) and less than or equal the second radius

(rl).

2. Screw according to claim 1 , wherein rl>r2>rθ>r4, where r4 designates the distance from the shank axis to the surface of the second shank segment.

3, Screw according to claim 1, wherein all of said thread sections on said surface of said second shank segment have the second radius (rl) relative to the shank axis.

4. Screw according to claim 1 , wherein said at least one projecting element is positioned essentially proximal the one groove with regard to the pointed insert part.

5. Screw according to claim 1, wherein said surface of said second shank segment between said two neighbouring interconnected ones of said thread sections is provided with a pair of said projecting elements that are diametrically opposite relative to the shank axis.

6. Screw according to claim 1 , wherein said projecting element is formed as a plate that projects radially relative to the shank axis and that has a convex shaving edge.

7. Screw according to claim 1, wherein said projecting element is formed as a rib that extends parallel to the shank axis and having a round cross-section along a plane transverse to the shank axis.

8, Screw according to claim 1 , wherein said projecting element has a tapering cross-section along a plane transverse to the shank axis.

9. Screw according to claim 1, wherein said projecting element has a generally trapezium cross-section along a plane transverse to the shank axis.