Technical field

The present invention relates to assembly of pieces of wood using a nail or a screw. Specifically, the present invention relates to such assembly where the nail or screw is used through an end portion of a piece of wood, which is prone to formation of cracks.

Background

Pieces of wood are commonly mounted using fasteners such as nails or screws. When attaching an end portion of a piece of wood to another piece of wood, the end portion tends to crack upon loading of the structure formed or upon driving the nail or screw into the end portion. The problem is usually solved by moving the nail or screw further away from the end to avoid cracks but that affects the ability to freely design the structure to be formed. Another common option is to use some sort of bracket, such as a 90 degree angular bracket, thereby moving the points of entry of the nails or screws further away from the end portion and also allowing use of a higher number of nails or screws which can thus be chosen to have a smaller diameter. However, brackets are expensive, may not be aesthetically acceptable and may not even fit where they have to be positioned. Also, the tools needed to mount the bracket may not be able to operate in the region around where the bracket is to be attached due to space restrictions.

Accordingly, it would be advantageous to find an alternative solution for how to attach an end portion of a piece of wood to another piece of wood.

Summary

According to a first aspect of the present disclosure, the above-mentioned drawbacks of the prior art are mitigated or alleviated by a washer for use with a fastener in the form of a nail or a screw. The washer comprises a base portion provided with a central through hole for insertion of the fastener, and the washer is provided with a plurality of legs extending from the base portion in a first direction normal to the base portion. The legs jointly define a central through passage extending between the plurality of legs normal to the first direction.

In use, the legs of the washer are driven into a piece of wood with the fibers of the wood extending through the passage such that the legs do not break the length of the fibers when driving the legs into the wood. The fastener is driven through the central hole of the washer and through the passage wherein the fibers in the passage are further compressed towards the legs of the washer as the fastener is driven between those fibers. Effectively, the fibers in the passage are compressed both at driving of the washer into the wood and at driving of the fastener into the wood, which altogether strengthens the friction between fibers and fastener. Since the fibers extending through the passage are not broken along their length by the washer, the fastener is well connected to a bunch of fibers extending further into the piece of wood. The head of the fastener abuts the base portion of the washer such that any forces normally acting on the head of the fastener to force it outwards are now spread over the surface of the base portion instead of only the surface of the head and also spread along the extent of the legs and their engagement to surrounding wood. Altogether, the present washer enables a very strong and robust connection between the fastener and the piece of wood, suitable for attachment close to an end portion of the piece of wood without the fastener cracking the wood along the direction of the fibers.

The passage may have a width extending at least 50% of the width of the base portion, such as at least 80% or 90% of the width of the base portion. Such a width of the passage allows for a large amount of fibers to be fitted in the passage for a given size (width) of the washer.

The plurality of legs may comprise a first substantially planar leg extending in a first plane on a first side of the passage, wherein the plurality of legs comprise a second substantially planar leg extending in a second plane on a second side of the passage opposite the first side, and wherein the first plane and the second plane are substantially parallel, such as parallel within 10 degrees, or within 5 degrees of each other, or entirely parallel

The planar and parallel configuration of the legs allows the legs to have a large surface area facing fibers whilst breaking a minimum of fibers upon driven into the wood with the legs aligned with the fiber direction. This promotes a strong connection between washer and wood.

The legs may be provided with sharpened front portions.

The sharpened front portions promote easier separation of fibers upon driving the legs of the washer into a piece of wood.

The sharpened front portions may be formed by a one-sided bevel of each respective leg. The one-sided bevel is easy to produce.

The one-sided bevel may face the passage. By configuring the legs with a respective beveled portion facing the passage, more wood fibers are led into the passage upon driving the legs of the washer into a piece of wood, thereby increasing compression of the wood fibers in the passage, which in turn promotes a stronger grip between washer and wood.

The legs may be provided with sharpened side portions.

The sharpened side portions promote easier separation of fibers upon driving the legs of the washer into a piece of wood.

According to a second aspect of the present disclosure, the washer is provided as part of a kit/assembly together with said fastener in the form of a nail or screw.

The central through hole of the washer may be countersunk and a head of the fastener also countersunk. A shaft of the fastener may be press-fitted in the central through hole of the washer with the tip of the fastener extending a predetermined distance from the base portion in the first direction.

The predetermined distance may be chosen shorter than the length of the legs. Such configuration of the extent of the tip of the fastener enables the legs of the washer to engage a piece of wood before the fastener engages the piece of wood, and thus improves control of the entry of the washer into the piece of wood.

A plurality of washers or fastener assemblies/kits may be interconnected inline, forming a band. The band of washers or fastener assemblies/kits enables improved handling of a plurality of washers/fastener assemblies/kits and further enables them to be easily loaded into a driving tool.

The washers may be formed from a single metal band folded along its length for forming the legs, wherein said metal band is provided with transverse weakened portions separating each washer. Alternatively, the end portion of the band is deformed and machined as needed and then punched/cut off the band to form individual washers.

According to a third aspect of the present disclosure, a driving tool is provided for use with said fastener assembly described above. A front end of the driving tool is provided with a drive surface for impacting the base portion of the washer for driving the legs of the washer into a piece of wood. Also, the driving tool is provided with an elongate central channel emanating in the front end of the shaft for receiving the shaft of the fastener.

According to a fourth aspect of the present disclosure, a method for producing the above-described washer is provided. The method comprises the steps of cutting a washer precursor from a piece of sheet metal, wherein said precursor comprises a square region defining the base portion and wherein the legs are formed by folding the precursor about a first fold line at one side of the square region for forming a first set of legs extending substantially perpendicularly to the base portion, and by folding the precursor about a second fold line at an opposite side of the base portion for forming a second set of legs extending substantially perpendicularly to the base portion.

The method may comprise the further step of removing material from outer portions of the legs for forming the sharpened front portions defined in claim 4 or any one of its dependent claims.

Also, the removal of material may be performed prior to the folding of the precursor.

The removal of material may be made subsequent to the folding of the precursor.

For example, the removal of material may be made by grinding using one or more grinding wheels.

Instead of removing material to form the sharpened front edges (or side edges), the method may comprise a step of plastically deforming the front edges (or side edges) in order to form the sharpened front portions. The use of plastic deformation rather than removal of material saves material since no material has to be removed. Material separated by punching/cutting is easier to handle for recycling than metal dust formed by grinding.

A fifth aspect of the present disclosure relates to a method of using the fastener assembly described above for joining an end portion of first piece of wood to a second piece of wood, wherein the method comprises the steps of: driving the legs of the washer into the end portion of the first piece of wood, and driving a fastener in the form of a nail or a screw through the central through hole and further into the second piece of wood until the head of the fastener abuts the base portion of the washer.

The driving of the legs of the washer into the piece of wood may be effected using the head of the fastener, such as by rotating the screw or by driving the nail with the head of the fastener pressing the washer.

Brief description of drawings

Figs. 1 -6 and fig. 11 all relate to a first embodiment of the washer.

Fig. 7 show a second embodiment of the washer provided with serrated side edges and a sharpened front edge.

Fig. 8 shows a third embodiment of the washer provided with sharpened side edges and a sharpened front edge.

Fig. 9 shows a fourth embodiment of the washer provided with a circular base portion, serrated side edges and a sharpened front edge. This washer looks like an ordinary circular washer after being mounted.

Fig. 10 shows a fifth embodiment of the washer provided with two legs, wherein each leg comprises three pins or teeth.

Fig. 11 shows a destructive strength test of the washer for joining an end portion of a first piece of wood (top) to a second piece of wood (bottom).

Fig. 12 shows a fastener assembly comprising both washer and fastener as a kit.

Fig. 13 shows a cross-sectional view of a driving tool and a fastener assembly.

Specifically, fig. 1 is a top perspective view of the washer according to the first embodiment.

Fig. 2 is a top perspective view of the washer together with a fastener in the form of a screw.

Fig. 3 is a top perspective view of the washer and the fastener holding together an end portion of a first piece of wood to a second piece of wood. Detailed description

A first embodiment of a washer 1 for use with a fastener 2 in the form of a nail or a screw will hereinafter be described with reference mainly to the appended figures 1-6. The washer 1 comprises a base portion 3 provided with a central through hole 4 for insertion of the fastener 2. Also, the washer is provided with two legs 5 extending from the base portion 3 in a first direction D1 normal to the base portion 3. The legs 5 jointly define a central through passage 6 extending between the legs 5 normal to the first direction.

The general sizing of the washer, such as length and thickness of the legs and sizing of the base portion is chosen based on the intended use of the washer, such as the hardness of the wood into which the washer is to be driven. For example, the washers shown in figs. 7 and 8 have base portions being 11 mm x 11mm and 6 mm long legs. In other embodiments this may be varied without departing from the scope of the invention. For example, the legs may be made shorter or longer and the size and the shape of the base portion varied as appropriate.

The passage 6 has a width W1 extending across a majority of the width W2 of the base portion 3 as shown in figs. 1 and 6. However, the width W1 of the passage 6 could alternatively in other embodiments extend across a smaller amount of the width of the base portion 3, such as at least 50%, 80% or 90% of the width W2 of the base portion 3, largely depending on the positioning of the legs 5 on the base portion 3 and the number of legs 5.

The plurality of legs 5 in this embodiment comprise a first substantially planar leg extending in a first plane P1 on a first side of the passage 6, and a second substantially planar leg extending in a second plane P2 on a second side of the passage 6 opposite the first side, wherein the first plane P1 and the second plane P2 are entirely parallel but could alternatively in other embodiments be angled up to 5 degrees to each other or up to 10 degrees to each other. The planar and parallel configuration of the legs 5 allows the legs 5 to have a large surface area facing fibers whilst breaking a minimum of fibers upon driven into the wood with the legs 5 aligned with the fiber direction, i.e. with the first plane P1 and the second plane P2 aligned with the fiber direction. This promotes a strong connection between washer 1 and the wood.

The legs 5 are provided with sharpened front portions 7 but may in other embodiments alternatively have any other suitable rounded or dull front edge shape, largely depending on the length and thickness of the legs 5 and the hardness of wood into which the legs 5 are to be driven, i.e. related to the stability of the legs 5 and expected driving resistance at installation. For example, longer legs 5 are more prone to deformation in the initial stage of driving the legs 5 into the wood and as such benefit more from the sharpened front portions 7 which reduce the driving resistance when driving the legs into the piece of wood. The sharpened front portions 7 are in this embodiment formed by a one-sided bevel of each respective leg 5. The one-sided bevel faces the passage 6 but may in other embodiments alternatively face outwards, away from the passage 6. By configuring the legs 5 with a respective beveled portion facing the passage 6, more wood fibers are led into the passage 6 upon driving the legs 5 of the washer 1 into a piece of wood WD1 , thereby increasing compression of the wood fibers in the passage 6, which in turn promotes a stronger grip between washer and wood WD1.

The central through hole 4 of the washer 1 is countersunk to accommodate a countersunk fastener head/screw head but may in other embodiments alternatively have any other suitable shape such as a straight cylindrical hole.

In other embodiments, such as the one shown in fig. 7, the legs 5 of the washer 1 may be provided with serrated side portions 8. The serrated side portions 8 cut some fibers in order to ease driving in of the washer 1 legs 5 into the piece of wood WD1 . The serrations may be manufactured by punching rather than by removal of material by grinding. In other embodiments, such as the one shown in fig. 8, the legs 5 may be provided with sharpened side portions 8. The sharpened side portions 8 promote easier separation of fibers upon driving the legs 5 of the washer into a piece of wood WD1 .

The washer 1 may be provided as part of a fastener assembly/a kit 9 together with the fastener 2 in the form of a nail or screw, as shown in fig. 12. Please note that the washer in fig. 12 has a slightly different embodiment than the washer 1 of the first embodiment and that the washer 1 according to the first embodiment or any other embodiment of the present disclosure could alternatively be provided as part of the fastener assembly/kit 9. The fastener 2 depicted in fig. 2 is a nail but any other suitable fastener could be used instead, such as a screw.

When the washer 1 is provided as part of a fastener assembly 9 with a fastener 2, the shaft of the fastener 2 may be press-fitted in the central through hole 4 of the washer 1 with the tip of the fastener 2 extending a predetermined distance PD from the base portion in the first direction D1 as shown in fig. 12.

As shown in fig. 12, the predetermined distance PD may be chosen shorter than the length of the legs 5. Such configuration of the extent of the tip of the fastener 2 enables the legs 5 of the washer to engage a piece of wood WD1 before the fastener 2 engages the piece of wood WD1 , and thus improves control of the entry of the washer 1 into the piece of wood WD1 .

A plurality of washers 1 /fastener assemblies/kits 9 may be interconnected inline, forming a band (not shown in the figures).

The interconnected washers 1 may be formed from a single metal band folded along its length for forming the legs 5. The metal band is provided with transverse weakened portions allowing for easy separation/detachment of each washer 1. Alternatively, the end portion of the band is deformed and machined as needed and then punched/cut off the band to form individual washers 1 . Also, the washers 1 may be interconnected by provision of a plastic band or metal wires which are separated from the washer 1 upon installation of the washer 1 .

Although the washer 1 may be installed by driving it into a piece of wood WD1 using a hammer, a suitable driving tool 10 may be provided to ease guiding and driving of the washer 1 /fastener assembly 9. Also, the driving tool 10 may be configured to assist in separating a washer 1 from other interconnected washers upon installation by cutting the washer 1 off from the interconnected washers/fastener assemblies.

Fig. 13 shows an embodiment of a driving tool 10 for installing a single washer 1 with a fastener 2 in the form of a screw. The driving tool 10 comprises a front part and a rear part. A front end of the front part is provided with a drive surface for impacting the base portion 3 of the washer 1 for driving the legs 5 of the washer 1 into a piece of wood WD1 .

In an alternative embodiment (not shown in figures) of the driving tool 10, one or more guide means in the form of shoulders/heels/protrusions are provided around the circumference of the drive surface for aligning the drive surface with the washer by extending in front of the drive surface and aside the washer. Alternatively, or additionally, the guide means may comprise a magnet configured to attract the washer towards the drive surface. The guide means is especially advantageous when driving the washer diagonally into a first piece of wood WD1 for use with a fastener entering the first piece of wood diagonally, since such diagonal entry of the legs of the washer tends to create forces acting unevenly on the washer thereby trying to rotate the washer. The guide means mitigates such rotation of the washer and aids in correct driving of the washer.

The front part is provided with an elongate central channel emanating in the front end of the front part for receiving the shaft of the fastener 2. The front part is provided with a rear opening into the central channel such that a rear portion of the fastener 2 is able to protrude out through the opening. The rear part is provided with a central recess shaped to mate with the front part such that the rear part can be used to drive the front part and then be subsequently removed by sliding the rear part off along the length of the fastener 2 whilst allowing the front part to remain around the fastener 2. The front part is provided with outer shoulders for the rear part to engage/hit upon mating with the front part. Accordingly, the rear part is provided with a central recess for accommodating a rear portion of the fastener 2, thereby allowing the rear part to impact the front part without impacting the fastener 2. In alternative embodiments of the driving tool 10, the length of the central recess of the rear part is adapted to a specific length of fastener 2, i.e. to the fastener 2 of a fastener assembly 9, such that the rear part is able to drive the fastener 2 a predetermined distance forward through the washer 1 before the rear part hits the front part and thereby also causes the front part to drive the legs 5 of the washer 1 into the piece of wood WD1 . Once the washer 1 has been driven into the piece of wood WD1 , the rear part can be removed, and the fastener 2 further screwed or driven into the piece of wood WD1 - optionally with the front part still positioned around the fastener 2 for additional guiding. The front part and rear part may be provided with means for releasably holding them together such that they do not accidently separate upon handling.

In another embodiment, the driving tool 10 is alternatively an automatic electrically or pneumatically driven tool, such as a screwgun or nailgun for magazines.

According to an aspect of the present disclosure, a method for producing the above-described washer 1 according to the first embodiment is provided. The method comprises the steps of cutting a washer precursor from a piece of sheet metal, wherein said precursor comprises a square region defining the base portion 3 and wherein the legs 5 pare formed by folding the precursor about a first fold line at one side of the square region for forming a first leg/set of legs extending substantially perpendicularly to the base portion 3, and by folding the precursor about a second fold line at an opposite side of the base portion 3 for forming a second leg/set of legs extending substantially perpendicularly to the base portion 3.

The method comprises the further step of removing material from outer portions of the legs 3 for forming the sharpened front portions 7. Alternatively, the removal of material may be performed prior to the folding of the precursor, or even prior to forming the precursor, by machining the piece of sheet metal/the sheet metal band. The removal of material is made by grinding using one or more grinding wheels, but any other suitable process may be used instead to form the sharpened portions. For example, the sharpened portions may be formed by deformation by applying local pressure to achieve plastic deformation of the outer portions or by cutting at an angle to the sheet metal. Although the transformation of a metal band to a precursor and further to a washer 1 is reliable and inexpensive, any other suitable manufacturing method may be used to manufacture the washer, such as casting or molding of a suitable material such as steel or fiber-reinforced thermoplastic.

Instead of forming sharpened front or side portions by removing material, the front portions and/or side portions may be plastically deformed by use of a suitable pressing tool or die cutting tool. The plastic formation can, depending on the design of the pressing or cutting tool create either a one-sided bevel or a two-sided bevel.

An aspect of the present disclosure relates to a method of using the fastener assembly 9 for joining an end portion of first piece of wood WD1 to a second piece of wood WD2. First, the legs 5 of the washer 1 are driven into the end portion of the first piece of wood WD1 and then a fastener 2 in the form of a nail or a screw is driven through the central through hole 4 and further into the second piece of wood WD2 until the head of the fastener 2 abuts the base portion 3 of the washer 1. The driving of the legs 5 of the washer into the first piece of wood WD1 may be made using a hammer directly on the washer 1 or by using the head of the fastener 2, such as by rotating the screw or by driving the nail with the head of the fastener pressing the washer 1 .

Preferably, the above described driving tool 10 is used to drive the washer 1 into the first piece of wood WD1 . Once installed, a bunch of wooden fibers extend through the central passage of the washer 1 . The legs 5 hold the bunch of wooden fibers together and the fastener 2 tensions the fibers towards the legs such that grip between washer and wooden fibers is increased. The front-end portion of the fastener engages the second piece of wood by friction or by threaded connection.

Fig. 11 shows a destructive strength test of the connection between the upper first piece of wood WD1 and the lower second piece of wood WD2. Here, it is clear that the wooden fiber bunch of the first piece of wood WD1 is intact and still held to the second piece of wood WD2 by means of the fastener extending through the washer 1. If the washer 1 would not have been used, the head of the fastener 2 would have moved straight through the first piece of wood WD1 in a crack of the first piece of wood WD1 and the joint between the first piece of wood WD1 and the second piece of wood WD2 would thus be much weaker than when using the present washer 1 . With the user of the washer 1 , cracks have formed along much larger vertical and diagonal fiber surfaces, the formation of those cracks requiring a much higher force than the force required to cause the crack along the fastener 2 if the washer 1 would not have been used. Since the present washer 1 design provides a passage 6 for the wooden fibers, fibers are not cut by the washer 1 , thereby allowing stress to spread further throughout the first piece of wood WD1 before the first piece of wood WD1 finally breaks/separates as cracks form as depicted in fig. 11.