CA2267572C - Screw for use as a fastener in fibrous material such as wood - Google Patents
Screw for use as a fastener in fibrous material such as wood Download PDFInfo
- Publication number
- CA2267572C CA2267572C CA 2267572 CA2267572A CA2267572C CA 2267572 C CA2267572 C CA 2267572C CA 2267572 CA2267572 CA 2267572 CA 2267572 A CA2267572 A CA 2267572A CA 2267572 C CA2267572 C CA 2267572C
- Authority
- CA
- Canada
- Prior art keywords
- screw
- thread
- shank
- edge
- shaped
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 239000002023 wood Substances 0.000 title claims abstract description 10
- 239000002657 fibrous material Substances 0.000 title claims description 9
- 230000001154 acute effect Effects 0.000 claims description 5
- 239000011800 void material Substances 0.000 claims description 3
- 230000008901 benefit Effects 0.000 description 4
- 230000007423 decrease Effects 0.000 description 2
- 230000002093 peripheral effect Effects 0.000 description 2
- 241000534944 Thia Species 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000010079 rubber tapping Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
- F16B35/00—Screw-bolts; Stay-bolts; Screw-threaded studs; Screws; Set screws
- F16B35/04—Screw-bolts; Stay-bolts; Screw-threaded studs; Screws; Set screws with specially-shaped head or shaft in order to fix the bolt on or in an object
- F16B35/041—Specially-shaped shafts
- F16B35/048—Specially-shaped necks
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
- F16B25/00—Screws that cut thread in the body into which they are screwed, e.g. wood screws
- F16B25/001—Screws that cut thread in the body into which they are screwed, e.g. wood screws characterised by the material of the body into which the screw is screwed
- F16B25/0015—Screws that cut thread in the body into which they are screwed, e.g. wood screws characterised by the material of the body into which the screw is screwed the material being a soft organic material, e.g. wood or plastic
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
- F16B25/00—Screws that cut thread in the body into which they are screwed, e.g. wood screws
- F16B25/0036—Screws that cut thread in the body into which they are screwed, e.g. wood screws characterised by geometric details of the screw
- F16B25/0042—Screws that cut thread in the body into which they are screwed, e.g. wood screws characterised by geometric details of the screw characterised by the geometry of the thread, the thread being a ridge wrapped around the shaft of the screw
- F16B25/0052—Screws that cut thread in the body into which they are screwed, e.g. wood screws characterised by geometric details of the screw characterised by the geometry of the thread, the thread being a ridge wrapped around the shaft of the screw the ridge having indentations, notches or the like in order to improve the cutting behaviour
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- Geometry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Dispersion Chemistry (AREA)
- Wood Science & Technology (AREA)
- Connection Of Plates (AREA)
Abstract
The thread (15) of a wood or the like screw has pairs of V-shaped recesses (22, 23) in the edge of a selected intermediate length of the thread (17). Each pair defines a W-shaped cutout (19, 20, 11). The cutouts (19-21) extend into only a part of radial width of the thread (15). There are only about three cutouts (19-21) at each convolute (17) of the limited length. The lengths of the thread (16) at the tip and at the head (13) of the screw are smooth.
Each cutout defines a cutting tooth (24) which facilitates the driving of the screw into the workpiece. The recesses 22, 23 provide cavities for fibrous debris generated by the respective tooth (24). When the screw is in place, the teeth (24) are resiliently pressed axially toward the thread produced in the workpiece to reduce the loosening tendency of the installed screw. The disposition and size of the cutouts (19-21), is about three cutouts per one convolute so as not to unduly impede the torque strength of the screw.
Each cutout defines a cutting tooth (24) which facilitates the driving of the screw into the workpiece. The recesses 22, 23 provide cavities for fibrous debris generated by the respective tooth (24). When the screw is in place, the teeth (24) are resiliently pressed axially toward the thread produced in the workpiece to reduce the loosening tendency of the installed screw. The disposition and size of the cutouts (19-21), is about three cutouts per one convolute so as not to unduly impede the torque strength of the screw.
Description
SCREW FOR USE AS A FASTEIVER IN FIBROUS MATERIAL
SUCH AS WOOD.
This invention relates to woodscr~ews or the like type of screws for use in fibrous material such as wood, particularly the self tapping screws. Such screws are typically provided with a smooth, continuous thread. This arrangement is satisfactory where the density of the workpiece of fibrous material is relatively low or where a pilot hole is provided. However, when the wood, fibrous board or the like fibrous material is relatively dense, or a pilot hole is not practical, a high torque may be required to drive the screw fully into the workpiece. It is not uncommon, particularly with the use of a power screwdriver, that the high torque requirement results in breakage of the screw.
The splitting of the workpiece may also occur.
It would therefore be of advantage to have a screw for use with fibrous material which would provide a high pull-out and loosening resistance while avoiding or at least reducing the possibility of breakage of the fastener while it is driven into the workpiece.
UK Patent Specification 1,120,99'1 describes a wood screw wherein the thread on the shank is provided with grooves extending helically for substantially the full length of the threaded portion. Thus the thread is transformed into a number of radially outwardly projecting protuberances.
The drawback of the two references is in that they substantially weaken the overall torque strength of the scrE:w and are thus prone to breakage particularly when used with a power screwdriver. Also, the cutouts do not provide sufficient space for debris formed by the cutting edge of the respective cutout. The cutouts at the tip hamper' the guidance of the screw at the introduction into the workpiece.
It is an object of the invention to facilitate the installation of screws in a fibrous workpiece such as a wood workpiece by reducing the force required to drive the screw into the workpiece while retaining a good torque strength of the screw and avoiding the tendency of self-loosening of the screw once in place.
According to the invention, only a limited portion of the overall length of the thread is provided with radially inwardly narrowing cutouts.
Preferably, in accordance with another feature of the present invention, the cutouts are each comprised of a pair of closely spaced V-shaped cutout section which provide about three W-shaped cutouts about a single convolute of the thread in the limited portion. The limited portion of the thread is an intermediate portion disposed axially between the first end or tip and the second end or head end portion of the thread which are both devoid of the cutouts.
The invention will now be described by way of a preferred and exemplary embodiments, with reference: to the accompanying diagrammatic, not-to-scale drawings.
Figure 1 is a side view of a screw of the present invention;
Figure 2 is a diagrammatic sectional view taken along a section line II-II of Fig. 1 and showing one turn or convolute of the thread in a flattened-out condition to indicate the preferred distribution of the cutouts and their depth;
Figure 3 is a partial, view corresponding to Fig. 2 and showing the geometry of the cutout of another embodiment of the invention;
Figure 4 is a view similar to that of Fig. 3 and showing the geometry of the cutout of yet another embodiment of the present invention;
and Figure 5 is a view similar to that of Fig. 3 and showing the geometry the cutout of a further embodiment of the present invention.
The same reference numbers are used for equivalent parts even though different embodiments of the present invention may be shown and described.
SUCH AS WOOD.
This invention relates to woodscr~ews or the like type of screws for use in fibrous material such as wood, particularly the self tapping screws. Such screws are typically provided with a smooth, continuous thread. This arrangement is satisfactory where the density of the workpiece of fibrous material is relatively low or where a pilot hole is provided. However, when the wood, fibrous board or the like fibrous material is relatively dense, or a pilot hole is not practical, a high torque may be required to drive the screw fully into the workpiece. It is not uncommon, particularly with the use of a power screwdriver, that the high torque requirement results in breakage of the screw.
The splitting of the workpiece may also occur.
It would therefore be of advantage to have a screw for use with fibrous material which would provide a high pull-out and loosening resistance while avoiding or at least reducing the possibility of breakage of the fastener while it is driven into the workpiece.
UK Patent Specification 1,120,99'1 describes a wood screw wherein the thread on the shank is provided with grooves extending helically for substantially the full length of the threaded portion. Thus the thread is transformed into a number of radially outwardly projecting protuberances.
The drawback of the two references is in that they substantially weaken the overall torque strength of the scrE:w and are thus prone to breakage particularly when used with a power screwdriver. Also, the cutouts do not provide sufficient space for debris formed by the cutting edge of the respective cutout. The cutouts at the tip hamper' the guidance of the screw at the introduction into the workpiece.
It is an object of the invention to facilitate the installation of screws in a fibrous workpiece such as a wood workpiece by reducing the force required to drive the screw into the workpiece while retaining a good torque strength of the screw and avoiding the tendency of self-loosening of the screw once in place.
According to the invention, only a limited portion of the overall length of the thread is provided with radially inwardly narrowing cutouts.
Preferably, in accordance with another feature of the present invention, the cutouts are each comprised of a pair of closely spaced V-shaped cutout section which provide about three W-shaped cutouts about a single convolute of the thread in the limited portion. The limited portion of the thread is an intermediate portion disposed axially between the first end or tip and the second end or head end portion of the thread which are both devoid of the cutouts.
The invention will now be described by way of a preferred and exemplary embodiments, with reference: to the accompanying diagrammatic, not-to-scale drawings.
Figure 1 is a side view of a screw of the present invention;
Figure 2 is a diagrammatic sectional view taken along a section line II-II of Fig. 1 and showing one turn or convolute of the thread in a flattened-out condition to indicate the preferred distribution of the cutouts and their depth;
Figure 3 is a partial, view corresponding to Fig. 2 and showing the geometry of the cutout of another embodiment of the invention;
Figure 4 is a view similar to that of Fig. 3 and showing the geometry of the cutout of yet another embodiment of the present invention;
and Figure 5 is a view similar to that of Fig. 3 and showing the geometry the cutout of a further embodiment of the present invention.
The same reference numbers are used for equivalent parts even though different embodiments of the present invention may be shown and described.
Figure 1 represents an exemplary type of a woodscrew to which the present invention has been applied. 'the screw is integrally formed and comprises a cylindric shank portion 10 defining, at a first end, a tapering tip portion 1 1. The opposite, second end of the shank portion 10 merges with a head end portion 12. Preferably, the head end portion has a somewhat increased diameter to provide a smooth transition to a head 13, for instance, by a frustoconical transitional section 14. A helical thread 15 extends from the tapering tip 11 to a point spaced from the head 13. Reference number 25 designates the direction of turning the screw to drive same into a workpiece.
The embodiment shown is a screw having the length of about 250mm.
The shank 10 has a total of ten convolutes or turns, it being understood that the number of the turns is optional. Proceeding from the tip 1 1, there is a first thread portion having about two turns 1 Ei which are continuous and are devoid of the cutouts. The next, intermediate, limited thread portion, includes about five turns 17 and, finally, near the secoind end or head end portion 12, there are about four turns 18 of the third thread portion.
Each turn 17 of the limited portion is provided with radially inwardly directed cutouts (Fig. 2) 19, 20, 21. The cutouts of the first, preferred embodiment of the invention will now be described in greater detail. For simplicity, only one cutout 19 with reference to Fig. 2, it being understood that it is preferred that the remaining cutouts be of the same shape.
The cutouts 19, 20, 21 are spaced from each other at an angle /3 of about 120° which provides three cutouts per each convolute 17. Each cutout, e.g. cutout 19, is comprised of a pair of closely spaced V-shaped or triangular, radially inwardly narrowing cutout sections 22, 23 whereby the cutout 19 has the general configuration of the letter W, defining a central tooth 24. It can be seen from the drawings that the radial depth of each cutout 19, 20, 21 is smaller than the width of the thread at the turn 17.
The embodiment shown is a screw having the length of about 250mm.
The shank 10 has a total of ten convolutes or turns, it being understood that the number of the turns is optional. Proceeding from the tip 1 1, there is a first thread portion having about two turns 1 Ei which are continuous and are devoid of the cutouts. The next, intermediate, limited thread portion, includes about five turns 17 and, finally, near the secoind end or head end portion 12, there are about four turns 18 of the third thread portion.
Each turn 17 of the limited portion is provided with radially inwardly directed cutouts (Fig. 2) 19, 20, 21. The cutouts of the first, preferred embodiment of the invention will now be described in greater detail. For simplicity, only one cutout 19 with reference to Fig. 2, it being understood that it is preferred that the remaining cutouts be of the same shape.
The cutouts 19, 20, 21 are spaced from each other at an angle /3 of about 120° which provides three cutouts per each convolute 17. Each cutout, e.g. cutout 19, is comprised of a pair of closely spaced V-shaped or triangular, radially inwardly narrowing cutout sections 22, 23 whereby the cutout 19 has the general configuration of the letter W, defining a central tooth 24. It can be seen from the drawings that the radial depth of each cutout 19, 20, 21 is smaller than the width of the thread at the turn 17.
The recommended minimum length of the shank of the screw to fully benefit from the present invention is about 30mm. From the standpoint of torsional strength of the screw of the preaent invention, the number of threads 17, of the limited, intermediate portion is. preferably selected in dependence on the overall length of the stem of the screw. For instance, screws with shanks 30mm (1'/4") to 140mm long, should have about 3 turns of threads 17 with the cutouts. Those with shank length of about 150 to about 240mm are preferably provided with four turns of threads 17 and those over 250mm preferably have 5 turns of threads 17. As mentioned above, the threads 17 have each three cutouts 19-21 at an equidistant arcuate spacing.
When viewed from the standpoint of rotation in the direction 25, the cutout section 22 is a front cutout section and the cutout section 23 is a rear cutout section. The cutout sections 22, 23 of the embodiment in Fig. 2 are so arranged and disposed that the tooth 24 has the shape of a trapezoid. The front cutout section 22 has a forward edge 26 and a back edge 27. Similarly, the rear cutout section 23 has a forward edge 28 and a back edge 29.
The back edge 27 defines a cutting edge of the tooth 24 and the forward edge 28 defines a trailing edge of the tooth 24. The cutout sections 22, 23 of each cutout define a void before and after the tooth 24, for debris generated by the tooth of the same cutout 19 or of the preceding cutout 21.
It can be observed from Fig. 2 that the combined width of the three cutouts 19-21 measured peripherally at the crest of the thread 17 is about one-third of the circumference of one convolute of the thread.
In the embodiment of Fig. 2, each cutout section 22, 23 is so disposed that the angle a between the respective forward edge 26, 28 and back edge 27, 29 is about 90°. This relationship is. not present in further embodiments as will now be described with reference to Figs. 3 - 5 where the same reference numbers have been used to designate the corresponding elements of the screw.
When viewed from the standpoint of rotation in the direction 25, the cutout section 22 is a front cutout section and the cutout section 23 is a rear cutout section. The cutout sections 22, 23 of the embodiment in Fig. 2 are so arranged and disposed that the tooth 24 has the shape of a trapezoid. The front cutout section 22 has a forward edge 26 and a back edge 27. Similarly, the rear cutout section 23 has a forward edge 28 and a back edge 29.
The back edge 27 defines a cutting edge of the tooth 24 and the forward edge 28 defines a trailing edge of the tooth 24. The cutout sections 22, 23 of each cutout define a void before and after the tooth 24, for debris generated by the tooth of the same cutout 19 or of the preceding cutout 21.
It can be observed from Fig. 2 that the combined width of the three cutouts 19-21 measured peripherally at the crest of the thread 17 is about one-third of the circumference of one convolute of the thread.
In the embodiment of Fig. 2, each cutout section 22, 23 is so disposed that the angle a between the respective forward edge 26, 28 and back edge 27, 29 is about 90°. This relationship is. not present in further embodiments as will now be described with reference to Figs. 3 - 5 where the same reference numbers have been used to designate the corresponding elements of the screw.
Turning to Fig. 3, the angle betwE;en the forward edge 26 and the back edge 27 (corresponding to angle a in Figi. 2) is an acute angle. The disposition of the edges 26 and 27 is such that thE: back edge 27, i.e., the cutting edge 27 of the tooth 24, is on a line 30 tangent to a first reference circle 31 concentric with the axis of the shank portion 10. The edge 26, however, is on a line 32 tangent to a second reference circle 33. The diameter of the reference circle 31 is smaller than that of the reference circle 33.
Accordingly, the cutting edge 27 in Fig. 3 is radially steeper with respect to the centre of the shank portion 10 than in Fig. 2. The rear cutout section is a mirror image of the front cutout section 22.
The radial steepness of the cutting edge 27 increases with the decrease of the diameter of the reference circle 31 and decreases with the enlargement of such diameter. Thus, the maximum radial steepness is the steepness where the diameter of the first reference circle is zero, i.e. it is the centre of the shank.
The overall peripheral width of thia embodiment is substantially smaller than about one-third of the circumference of one turn 17 of the thread, to provide a good pullout resistance while retaining the advantage of having two voids for the debris made by the tooth 24.
In the embodiment of Fig. 4, the cutout sections 22, 23 are not mirror images of each other as in Figs. 2 and 3. Instead, they have identical contour.
The line 30 of the cutting edge 27 of the tooth 24 displays a maximum degree of radial steepness since the line 30 passes through the centre (31 ) of the shank portion 10. In other words, the reference circle 30 has a zero diameter and is the centre of the shank. Thus, the cutting edge 27 extends exactly radially. On the other hand, the forward edge 26 of the recess 22 is tangent to the second reference circle 33. The forward and the back edges 28, 29 of the rear cutout section 23 are arranged in the same order as the edges 26, 27 _ 7..
of the front cutout section 22. Thus, the: line 34 of the forward edge 28 of the cutout section 23 is a tangent to the reference circle 33, while the back edge is radial. The angle, corresponding to angle a of Fig. 2, of both V-shaped recesses of Fig. 4 is an acute angle, in the embodiment shown, about 45°.
This embodiment presents a further reduction of the peripheral width of the cutout 19.
The embodiment of Fig. 5 is simil<~r to that of Fig. 4 with respect to the angles of the forward and back edges 213, 27, 28, 29 but the overall width of the tooth 24 and if the overall cutout 19~ is smaller. This results in a triangular shape of the tooth 24 and in a smaller overall width of the cutout 19. The width of the cutout of the embodiment of Fig. 5 is the smallest of those shown while sufficient space is provided for fibrous debris.
As already mentioned, the screw of the present invention is intended mainly for woodscrews or the like having the length of about one inch or more.
The screw of the invention has the advantage of a reduced resistance to the driving force when the screw is driven ini:o a workpiece. It has been found that the invention achieves reduction of the torque required by about 30% over known woodscrews. This reduces and in many cases eliminates the occurrence of breakages of the shanks of power driven screws of the present invention.
While the drive-in torque stress is reduced, once the screw is in place, it does not have the tendency to become loose.
While there are certain preferred numbers of the convolutes of the thread at the tip (two) and of the cutout section (about fivel, generally regardless of the overall length of the screw over at least about one inch, those skilled in the art will readily appreciate that it is within the scope of the present invention to modify the numbers of the respective convolutes. Such obvious modification is merely one of a large number of changes of the screw of the present invention, which are readily conceivable: and may result in a structure of a screw differing from the embodiments described, for instance, in the geometry of the cutouts, in the type of screw head used, in the number of cutouts per _$..
a convolute and in many other aspects, without departing from the scope of the invention as recited in the accompanying claims.
Accordingly, the cutting edge 27 in Fig. 3 is radially steeper with respect to the centre of the shank portion 10 than in Fig. 2. The rear cutout section is a mirror image of the front cutout section 22.
The radial steepness of the cutting edge 27 increases with the decrease of the diameter of the reference circle 31 and decreases with the enlargement of such diameter. Thus, the maximum radial steepness is the steepness where the diameter of the first reference circle is zero, i.e. it is the centre of the shank.
The overall peripheral width of thia embodiment is substantially smaller than about one-third of the circumference of one turn 17 of the thread, to provide a good pullout resistance while retaining the advantage of having two voids for the debris made by the tooth 24.
In the embodiment of Fig. 4, the cutout sections 22, 23 are not mirror images of each other as in Figs. 2 and 3. Instead, they have identical contour.
The line 30 of the cutting edge 27 of the tooth 24 displays a maximum degree of radial steepness since the line 30 passes through the centre (31 ) of the shank portion 10. In other words, the reference circle 30 has a zero diameter and is the centre of the shank. Thus, the cutting edge 27 extends exactly radially. On the other hand, the forward edge 26 of the recess 22 is tangent to the second reference circle 33. The forward and the back edges 28, 29 of the rear cutout section 23 are arranged in the same order as the edges 26, 27 _ 7..
of the front cutout section 22. Thus, the: line 34 of the forward edge 28 of the cutout section 23 is a tangent to the reference circle 33, while the back edge is radial. The angle, corresponding to angle a of Fig. 2, of both V-shaped recesses of Fig. 4 is an acute angle, in the embodiment shown, about 45°.
This embodiment presents a further reduction of the peripheral width of the cutout 19.
The embodiment of Fig. 5 is simil<~r to that of Fig. 4 with respect to the angles of the forward and back edges 213, 27, 28, 29 but the overall width of the tooth 24 and if the overall cutout 19~ is smaller. This results in a triangular shape of the tooth 24 and in a smaller overall width of the cutout 19. The width of the cutout of the embodiment of Fig. 5 is the smallest of those shown while sufficient space is provided for fibrous debris.
As already mentioned, the screw of the present invention is intended mainly for woodscrews or the like having the length of about one inch or more.
The screw of the invention has the advantage of a reduced resistance to the driving force when the screw is driven ini:o a workpiece. It has been found that the invention achieves reduction of the torque required by about 30% over known woodscrews. This reduces and in many cases eliminates the occurrence of breakages of the shanks of power driven screws of the present invention.
While the drive-in torque stress is reduced, once the screw is in place, it does not have the tendency to become loose.
While there are certain preferred numbers of the convolutes of the thread at the tip (two) and of the cutout section (about fivel, generally regardless of the overall length of the screw over at least about one inch, those skilled in the art will readily appreciate that it is within the scope of the present invention to modify the numbers of the respective convolutes. Such obvious modification is merely one of a large number of changes of the screw of the present invention, which are readily conceivable: and may result in a structure of a screw differing from the embodiments described, for instance, in the geometry of the cutouts, in the type of screw head used, in the number of cutouts per _$..
a convolute and in many other aspects, without departing from the scope of the invention as recited in the accompanying claims.
Claims (21)
1. A screw fastener comprising:
(a) a shank having a first end defining a pointed tip, an opposed second end and a thread extending over at least a portion of the overall length of the shank;
(b) the thread being provided with a system of radially inwardly narrowing W-shaped cutouts disposed at a predetermined spacing from each other;
(c) said system of W-shaped cutouts being comprised of a plurality of pairs of generally V-shaped cutout sections, the V-shaped cutout sections of each pair being closely spaced from each other, whereby each pair of said V-shaped cutout sections defines a generally W-shaped cutout;
(d) the spacing between adjacent W-shaped cutouts being substantially larger than that between the V-shaped cutout sections of each said pair.
(a) a shank having a first end defining a pointed tip, an opposed second end and a thread extending over at least a portion of the overall length of the shank;
(b) the thread being provided with a system of radially inwardly narrowing W-shaped cutouts disposed at a predetermined spacing from each other;
(c) said system of W-shaped cutouts being comprised of a plurality of pairs of generally V-shaped cutout sections, the V-shaped cutout sections of each pair being closely spaced from each other, whereby each pair of said V-shaped cutout sections defines a generally W-shaped cutout;
(d) the spacing between adjacent W-shaped cutouts being substantially larger than that between the V-shaped cutout sections of each said pair.
2. The fastener of claim 1, wherein only a limited portion of the overall length of the shank is provided with said W-shaped cutouts.
3. The fastener of claim 2, wherein said limited portion of the thread is an intermediate portion axially spaced from the first end of the shaft and from the second end thereof.
4. The screw of claim 3, wherein the length of the shank is at least about 25 mm, and wherein said limited portion of the thread is an intermediate portion axially spaced from the first end of the shank such that a number of convolutes of the thread at said tip are devoid of said W-shaped cutouts.
5. The screw of claim 4 wherein said number of the convolutes at the tip of the screw is about two.
6. The screw of claim 4 wherein said thread includes a number of convolutes devoid of said W-shaped cutouts and disposed between an end of the intermediate portion remote from said tip, and said second end of the shank.
7. The screw of claim 4 wherein the combined width of said W-shaped cutouts of one convolute, measured peripherally at a crest portion of the thread, is about one-third or less of the overall periphery of said one convolute.
8. The screw of claim 4, wherein said W-shaped cutouts are disposed at a density of about three W-shaped cutouts per one convolute of the thread.
9. The screw of claim 8 wherein said intermediate portion includes about five convolutes.
10. The screw of claim 1, wherein the shank is at least about 25 mm long, and wherein each W-shaped cutout includes, from the standpoint of the direction of rotation driving the screw into a workpiece:
(a) a front V-shaped cutout section and a rear V-shaped cutout section, each V-shaped cutout section including a forward edge and a back edge;
(b) the back edge of the front V-shaped cutout section defining a cutting edge of a central tooth of the cutout;
(c) the forward edge of the rear V-shaped cutout section defining a trailing edge of said central tooth;
whereby there is a void ahead of and behind said tooth.
(a) a front V-shaped cutout section and a rear V-shaped cutout section, each V-shaped cutout section including a forward edge and a back edge;
(b) the back edge of the front V-shaped cutout section defining a cutting edge of a central tooth of the cutout;
(c) the forward edge of the rear V-shaped cutout section defining a trailing edge of said central tooth;
whereby there is a void ahead of and behind said tooth.
11. The screw of claim 10, wherein the V-shaped cutout sections are of a triangular contour wherein a radially inner angle of the contour is about 90°.
12. The screw of claim 11, wherein the contour of the tooth is generally trapezoidal.
13. The screw of claim 12 wherein the V-shaped cutout sections are of a triangular contour and wherein a radially inner angle of the contour is an acute angle.
14. The screw of claim 10 wherein the cutting edge is disposed radially to the axis of the shank.
15. The screw of claim 10 wherein the V-shaped cutout sections are of a triangular contour and wherein a radially inner angle of the contour is an acute angle.
16. The screw of claim 10, wherein (a) the cutting edge of the tooth is disposed on a tangent to a first reference circle concentric with the centre of the shank;
(b) the forward edge of the front V-shaped cutout section and the back edge of the rear V-shaped cutout section are each disposed on a respective tangent to a second reference circle concentric with the centre of the shank;
(c) the diameter of said first reference circle is smaller than that of the second reference circle.
(b) the forward edge of the front V-shaped cutout section and the back edge of the rear V-shaped cutout section are each disposed on a respective tangent to a second reference circle concentric with the centre of the shank;
(c) the diameter of said first reference circle is smaller than that of the second reference circle.
17. A screw, for use in fibrous material such as wood, comprising, in combination:
(a) a shank having the length of at least 30 mm, said shank being provided with helical thread and having a head at one end thereof for engagement with a screw driver, and a tip at the other end;
(b) a limited portion of an overall length of the thread being provided with generally W-shaped cutouts disposed at a predetermined spacing from each other;
(c) said limited portion being an intermediate part of the thread axially spaced from tip end of the thread, and from a portion of the thread near said one end of the shank;
(d) the cutouts having a radial depth smaller than the radial width of the thread within said limited portion;
(e) each cutout including, from the standpoint of the direction of driving rotation of the screw into a workpiece, a front V-shaped cutout section and a rear V-shaped cutout section each section having a generally triangular configuration;
(f) said front V-shaped cutout section having a forward edge and a back edge, said rear V-shaped cutout section having a forward edge and a back edge;
(g) the back edge of the front V-shaped cutout section and the forward edge of the rear V-shaped cutout section defining a central tooth corresponding to a central crest portion of the W;
(h) said tooth having a leading cutting edge corresponding to said back edge of said forward V-shaped cutout section, and a trailing edge corresponding to said forward edge of the rear V-shaped cutout section;
(i) the cutting edge of the tooth being disposed on a tangent to a first reference circle concentric with the centre of the shank, the forward edge of the front V-shaped cutout section being disposed on a second reference circle concentric with the centre of the shank, the diameter of said first reference circle being smaller than that of the second reference circle, whereby a radial steepness of said leading edge is smaller than that of the cutting edge.
(a) a shank having the length of at least 30 mm, said shank being provided with helical thread and having a head at one end thereof for engagement with a screw driver, and a tip at the other end;
(b) a limited portion of an overall length of the thread being provided with generally W-shaped cutouts disposed at a predetermined spacing from each other;
(c) said limited portion being an intermediate part of the thread axially spaced from tip end of the thread, and from a portion of the thread near said one end of the shank;
(d) the cutouts having a radial depth smaller than the radial width of the thread within said limited portion;
(e) each cutout including, from the standpoint of the direction of driving rotation of the screw into a workpiece, a front V-shaped cutout section and a rear V-shaped cutout section each section having a generally triangular configuration;
(f) said front V-shaped cutout section having a forward edge and a back edge, said rear V-shaped cutout section having a forward edge and a back edge;
(g) the back edge of the front V-shaped cutout section and the forward edge of the rear V-shaped cutout section defining a central tooth corresponding to a central crest portion of the W;
(h) said tooth having a leading cutting edge corresponding to said back edge of said forward V-shaped cutout section, and a trailing edge corresponding to said forward edge of the rear V-shaped cutout section;
(i) the cutting edge of the tooth being disposed on a tangent to a first reference circle concentric with the centre of the shank, the forward edge of the front V-shaped cutout section being disposed on a second reference circle concentric with the centre of the shank, the diameter of said first reference circle being smaller than that of the second reference circle, whereby a radial steepness of said leading edge is smaller than that of the cutting edge.
18. A screw, for use in fibrous material such as wood, comprising, in combination:
(a) a shank having the length of at least 30 mm, said shank being provided with helical thread and having a head at one end thereof for engagement with a screw driver, and a tip at the other end;
(b) a limited portion of an overall length of the thread being provided with generally W-shaped cutouts disposed at a predetermined spacing from each other;
(c) said limited portion being an intermediate part of the thread axially spaced from a tip end of the thread, and from a portion of the thread near said one end of the shank;
(d) the cutouts having a radial depth smaller than the radial width of the thread within said limited portion;
(e) each cutout including, from the standpoint of the direction of driving rotation of the screw into a workpiece, a front V-shaped cutout section and a rear V-shaped cutout section each section having a generally triangular configuration:
(f) said front V-shaped cutout section having a forward edge and a back edge, said rear V-shaped cutout section having a forward edge and a back edge;
(g) the back edge of the front V-shaped cutout section and the forward edge of the rear V-shaped cutout section defining a central tooth corresponding to a central crest portion of the W;
(h) said tooth having a leading cutting edge corresponding to said back edge of said forward V-shaped cutout section, and a trailing edge corresponding to said forward edge of the rear V-shaped cutout section, wherein the cutting edge of the tooth is disposed on a tangent to a first reference circle concentric with the centre of the shank, the forward edge of the front cutout section being disposed on a second reference circle concentric with the centre of the shank, the diameter of said first reference circle being smaller than that of the second reference circle, whereby a radial steepness of said leading edge is smaller than that of the cutting edge;
(i) said predetermined spacing of the cutouts being selected such that the combined width of the W-shaped cutouts at the crest of the thread of one said convolute is about one-third or less of the overall periphery of the crest of the thread in said one convolute;
(j) the diameter of said first reference circle being zero, whereby the cutting edge is coincident with a radial line.
(a) a shank having the length of at least 30 mm, said shank being provided with helical thread and having a head at one end thereof for engagement with a screw driver, and a tip at the other end;
(b) a limited portion of an overall length of the thread being provided with generally W-shaped cutouts disposed at a predetermined spacing from each other;
(c) said limited portion being an intermediate part of the thread axially spaced from a tip end of the thread, and from a portion of the thread near said one end of the shank;
(d) the cutouts having a radial depth smaller than the radial width of the thread within said limited portion;
(e) each cutout including, from the standpoint of the direction of driving rotation of the screw into a workpiece, a front V-shaped cutout section and a rear V-shaped cutout section each section having a generally triangular configuration:
(f) said front V-shaped cutout section having a forward edge and a back edge, said rear V-shaped cutout section having a forward edge and a back edge;
(g) the back edge of the front V-shaped cutout section and the forward edge of the rear V-shaped cutout section defining a central tooth corresponding to a central crest portion of the W;
(h) said tooth having a leading cutting edge corresponding to said back edge of said forward V-shaped cutout section, and a trailing edge corresponding to said forward edge of the rear V-shaped cutout section, wherein the cutting edge of the tooth is disposed on a tangent to a first reference circle concentric with the centre of the shank, the forward edge of the front cutout section being disposed on a second reference circle concentric with the centre of the shank, the diameter of said first reference circle being smaller than that of the second reference circle, whereby a radial steepness of said leading edge is smaller than that of the cutting edge;
(i) said predetermined spacing of the cutouts being selected such that the combined width of the W-shaped cutouts at the crest of the thread of one said convolute is about one-third or less of the overall periphery of the crest of the thread in said one convolute;
(j) the diameter of said first reference circle being zero, whereby the cutting edge is coincident with a radial line.
19. A screw for use in fibrous material such as wood, comprising (a) a shank having a first end defining a pointed tip, a second end and a thread extending over at least a portion of the overall length of the shank;
(b) a limited portion of an overall length of the thread being provided, at a crest portion thereof, with a system of radially inwardly directed cutouts disposed at a predetermined spacing from each other;
(c) said system of cutouts being comprised of a plurality of generally W-shaped cutout, whereby each cutout comprises two cutout sections and a central tooth between said cutout sections;
(d) the combined width of said cutouts of one convolute, measured peripherally at the crest portion of the thread, being about one-third or less of the overall periphery of the convolute;
(e) the shank being at least about 30 mm long; each cutout including, from the standpoint of the direction of rotation driving the screw into a workpiece:
(i) a front cutout section and a rear cutout section, each cutout section including a forward edge and a back edge;
(ii) the back edge of the front cutout section defining a cutting edge of said central tooth;
(iii) the forward edge of the rear cutout section defining a trailing edge of said central tooth, whereby there is a void ahead of and behind said tooth;
(f) the forward edge of the front cutout section and the back edge of the rear cutout sections are each disposed on a respective tangent to a first reference circle concentric with the centre of the shank;
(g) the cutting edge of the tooth is disposed on a tangent to a second reference circle concentric with the centre of the shank;
(h) the diameter of said first reference circle is larger than that of the second reference circle; and (i) the cutout sections are each of a triangular contour wherein a radially inner angle is an acute angle.
(b) a limited portion of an overall length of the thread being provided, at a crest portion thereof, with a system of radially inwardly directed cutouts disposed at a predetermined spacing from each other;
(c) said system of cutouts being comprised of a plurality of generally W-shaped cutout, whereby each cutout comprises two cutout sections and a central tooth between said cutout sections;
(d) the combined width of said cutouts of one convolute, measured peripherally at the crest portion of the thread, being about one-third or less of the overall periphery of the convolute;
(e) the shank being at least about 30 mm long; each cutout including, from the standpoint of the direction of rotation driving the screw into a workpiece:
(i) a front cutout section and a rear cutout section, each cutout section including a forward edge and a back edge;
(ii) the back edge of the front cutout section defining a cutting edge of said central tooth;
(iii) the forward edge of the rear cutout section defining a trailing edge of said central tooth, whereby there is a void ahead of and behind said tooth;
(f) the forward edge of the front cutout section and the back edge of the rear cutout sections are each disposed on a respective tangent to a first reference circle concentric with the centre of the shank;
(g) the cutting edge of the tooth is disposed on a tangent to a second reference circle concentric with the centre of the shank;
(h) the diameter of said first reference circle is larger than that of the second reference circle; and (i) the cutout sections are each of a triangular contour wherein a radially inner angle is an acute angle.
20. The screw of claim 19, wherein the contour of the tooth is generally trapezoidal.
21. The screw of claim 19 or 20, wherein the diameter of the second reference circle is zero, whereby the cutout edge is disposed radially to the axis of the shank.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2267572 CA2267572C (en) | 1998-04-03 | 1999-03-29 | Screw for use as a fastener in fibrous material such as wood |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002234040A CA2234040A1 (en) | 1998-04-03 | 1998-04-03 | Screw for use as a fastener in fibrous material such as wood |
| CA2,234,040 | 1998-04-03 | ||
| CA 2267572 CA2267572C (en) | 1998-04-03 | 1999-03-29 | Screw for use as a fastener in fibrous material such as wood |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2267572A1 CA2267572A1 (en) | 1999-10-03 |
| CA2267572C true CA2267572C (en) | 2003-05-27 |
Family
ID=25680120
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2267572 Expired - Lifetime CA2267572C (en) | 1998-04-03 | 1999-03-29 | Screw for use as a fastener in fibrous material such as wood |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2267572C (en) |
-
1999
- 1999-03-29 CA CA 2267572 patent/CA2267572C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| CA2267572A1 (en) | 1999-10-03 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US6152666A (en) | Screw for use as a fastener in fibrous material such as wood | |
| EP0579816B1 (en) | Self drilling screw | |
| US6328516B1 (en) | Screw with cutting edge | |
| US5827030A (en) | Thread forming joining elements | |
| CN100482957C (en) | Thread-forming screw | |
| US6296433B1 (en) | Large diameter tapcon with debris reservoir end or tip | |
| US5044853A (en) | Thread-cutting screw | |
| KR101543480B1 (en) | Thread forming fastener | |
| US7785055B2 (en) | Thread forming screw | |
| EP1635077B1 (en) | Fastening arrangement employing thread-forming screw | |
| EP4158208B1 (en) | Separate screw thread helix fixed by means of claws | |
| CA2267572C (en) | Screw for use as a fastener in fibrous material such as wood | |
| EP1850016B1 (en) | Saw Tooth Screw | |
| CN110300858B (en) | Screw nail | |
| US20230175543A1 (en) | Screw with separate thread helix and integral thread start | |
| US11739783B2 (en) | Concrete fastener | |
| EP4074992B1 (en) | Wood screw | |
| US20230392637A1 (en) | Concrete fastener | |
| JP2002039134A (en) | Tapping screw | |
| US20230061383A1 (en) | Fasteners with increased grip strength | |
| TW202336350A (en) | Timber concrete composite screw | |
| WO2023033809A1 (en) | Fasteners with increased grip strength | |
| JP2000065029A (en) | Insert screw | |
| MXPA98002614A (en) | Autotaladrant union element and ro trainer |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKEX | Expiry |
Effective date: 20190329 |