Screw for Composite/Plastic Materials

Abstract

A fastener for composite or plastic material having a dense composition employs a head which has a socket and a recessed underside and a lower rim. In one embodiment, the shank has an upper portion with an enlarged diameter and a left hand thread while the lower portion has a tri-lobed configuration and is traversed by a right hand thread. The right hand thread may have a plurality of notches which, in one embodiment, are arranged in a spiral array.

Description

BACKGROUND OF THE TECHNOLOGY

This technology relates to fasteners which are employed for fastening composite and plastic materials to a support structure. More particularly, the fasteners relate to deck screws employed for securing dense composite and plastic materials.

Numerous fasteners have been advanced for fastening deck members which are composed of composite material. Several of these such deck fasteners are directed to eliminating the volcanoing or mushrooming effect. As the technology of composite materials has advanced, the denseness of the composite members has increased. The increased denseness has had a significant impact on the effectiveness of conventional deck screws. Accordingly, many deck screws which were adapted to perform in earlier composite environments are significantly less effective in the more dense material. A significant issue resides in the difficulties of driving fasteners into very dense composite materials.

SUMMARY OF THE DISCLOSURE

In one embodiment, a fastener for composite or plastic lumber comprises a head having a socket rotatably couplable for application of a torque and having a recessed underside with a lower rim. An elongated shank extends from the head and terminates at a distal tip. The shank has an upper portion with an enlarged diameter and a lower portion with a reduced diameter. The upper portion is traversed by a left hand thread. The lower portion has a tri-lobed configuration and is traversed by a right hand thread with the right hand thread having a plurality of notches.

The right hand thread may extend substantially to the tip. At least one notch may be formed in the tip thread. In one embodiment, at least two notches are formed in the tip thread with at least two notches being out of phase. The notches form a spiral array. A land extends between the threads. The socket is preferably a square socket. The number of threads per inch of the left hand thread is less than the number of threads per inch of the right hand thread. The thread angle of the left hand thread is greater than the thread angle of the right hand thread. The left hand thread preferably has a minor diameter greater than the minor diameter of the right hand thread.

A screw which is especially adapted for securing trim board material comprises an elongated shank which extends from the head and terminates at a distal tip. A portion of the shank adjacent the head has an enlarged diameter which is traversed by a left hand thread. The lower shank portion has a reduced diameter which does not have a trilobial form but includes a right hand thread with a plurality of notches which extends substantially to the tip. The number of threads per inch of the left hand thread is less than the number of threads per inch of the right hand thread. The thread angle of the left hand thread is greater than the thread angle of the right hand thread. In one embodiment the screw has a length of approximately 2.75 inches and the left hand thread extends approximately 0.3 inches.

A screw which is especially adapted for securing extremely dense composite or plastic material comprises an elongated shank which extends from the head and terminates at a distal tip with an upper portion having an enlarged diameter and a lower portion of the shank having a reduced diameter. The upper portion is traversed by a plurality of rings having a uniform major diameter. The lower portion is traversed by a second thread with a plurality of notches. In one embodiment, there are three longitudinally spaced rings which are equidistantly spaced. The rings have an effective minor diameter greater than that of the second thread.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal view, partly in phantom and partly in diagrammatic form, of a deck screw;

FIG. 2 is an end view of a head portion of the deck screw of FIG. 1;

FIG. 2A is an end view of an alternative embodiment of a head portion of the deck screw of FIG. 1;

FIG. 3 is an enlarged sectional view, partly in diagrammatic form, of a head and end portion of the deck screw of FIG. 1 taken along the lines of A-A of FIG. 2;

FIG. 4 is a diagrammatic view illustrating a representative thread profile for a top portion of the deck screw of FIG. 1;

FIG. 5 is a diagrammatic view illustrating a representative thread profile for a bottom portion of the deck screw of FIG. 1;

FIG. 6 is a sectional view illustrating the deck screw of FIG. 1 as employed for securing a composite material to a support structure;

FIG. 7 is an enlarged longitudinal view of a medial portion of the deck screw of FIG. 1;

FIG. 8 is an enlarged cross-sectional view, partly in diagrammatic form, taken along the lines of B-B of FIG. 7 and rotated 90°;

FIG. 9 is an enlarged fragmentary view, partly in diagrammatic form, of a tip portion of the deck screw of FIG. 1;

FIG. 9A is an enlarged fragmentary view, partly in diagrammatic form, of an alternative tip portion of the deck screw of FIG. 1;

FIG. 10 is a sectional view, partly in diagrammatic form, taken along the lines of C-C of FIG. 9;

FIG. 11 is a longitudinal side view, partly in diagrammatic form, illustrating a first stage workpiece for the deck screw of FIG. 1;

FIG. 12 is a longitudinal sectional view, partly in diagrammatic form, of a second stage workpiece for the deck screw of FIG. 1;

FIG. 13 is an end view of the workpiece of FIG. 12;

FIG. 14 is a longitudinal view, partly in diagrammatic form, and partly in phantom, of a third stage workpiece for the deck screw of FIG. 1;

FIG. 15 is an enlarged sectional view, partly in phantom and partly in diagrammatic form, taken along the lines D-D of FIG. 14;

FIG. 16 is a longitudinal view, partly in phantom and partly in diagrammatic form, of another embodiment of a screw suitable for securing trim board; and

FIG. 17 is a longitudinal view, partly in phantom and partly in diagrammatic form, of yet another embodiment of a deck screw.

DETAILED DESCRIPTION

With reference to the drawings wherein like numerals represent like parts throughout the several views, a deck screw is generally designated by the numeral 10. Deck screw 10 is especially adapted for securing elongated deck members 20 to a support member 22 wherein the composite material is a highly dense material such as, for example, Trex™ deck material, Timber Tech™ deck planks, etc. As illustrated in FIG. 6, the deck screw 10 functions to be driven through the composite member 20 into the support structure 22 to a depth wherein the head is below the upper surface of the material and forms a cylindrical counterbore above the head. The deck screw 10 can be driven without volcanoing or mushrooming of the material around the head and can be relatively easily driven without intense resistance to the application of torque during the driving process.

With reference to FIG. 1 the deck screw 10 includes a head 30 and an elongated shank 40 which extends from the head and has a generally bifurcated form. In one embodiment, the screw length l1 is 2.75 ins with a head diameter dl of 0.285 ins. The shank 40 has an upper portion 42 of length l2 of enlarged nominal diameter and a lower portion 44 of length l3 of reduced nominal diameter which has a distal tip 46. The tip terminates in a well-defined vertex point 48 which in the preferred form has a vertex angle of 25 degrees. The tip 46 functions as a drill point.

With additional reference to FIGS. 2 and 3, the head 30 includes a recess 32 which at an upper portion is defined by a #1 square socket 34 and is adapted for coupling with a torque driver bit (not illustrated). Socket 34 preferably has a minimum depth of 0.075 ins and preferably a depth from .075 ins to .095 ins. If the socket depth is too shallow, the head will disengage during driving. If the head is too deep, the structural integrity of the head is jeopardized. The corners of the socket 34 may be rounded (not illustrated).

With reference to FIG. 2A, an alternative socket 34A is defined by 8 radial slots and is adapted for coupling with a torque driver (not illustrated). The coupling socket 34A may be similar in form and function to that described co-pending U.S. patent application Ser. No. 11/185,377 filed Jul. 20, 2005 which is assigned to the applicant of the present invention and the disclosure of which is incorporated by reference. The eight point torque driving engagement provides an efficient coupling engagement to facilitate torqueing of the deck screw and mitigate against disengagement of the tool during the driving process.

The head 30 includes a tapered skirt-like periphery 36 which includes a recessed underside 38 and a lower cutting rim 39. In one form, the angle of the underside flaring is on the order of 39 degrees as illustrated in FIG. 3. The head socket 34 is adapted to efficiently couple with the driver. The underside 38 of the head is configured to prevent composite material from being displaced past the head during the driving process and for capturing the composite material and trapping same at its underside. The cutting rim 39 is adapted to provide a clean, circular opening in the composite material and to present a pleased, finished setting of the deck screw in the drive bore so that the top surface of the head is below the surface of the dense composite material (FIG. 6).

The shank 40 has an upper portion 42 proximate the head which has a larger diameter than that of the lower portion 44. In one embodiment, the upper portion 42 includes a left hand thread 52 which extends a length l7 or approximately 0.750 inches and is 9 threads per inch. Thread 52 has a thread angle of 48 degrees as illustrated in FIG. 4. In a preferred embodiment of thread 52, the minor thread diameter is 0.133 inches and the major thread diameter is 0.210 inches.

Various approximate dimensions for one embodiment are summarized in Table I.

TABLE I
d1 0.285 ins
l1 2.75 ins
l2 0.80 ins
l3 1.75 ins
l4 0.02 ins
l5 0.10 ins
l6 0.12 ins
l7 0.75 ins

In another embodiment l7 is approximately 0.45 ins. and l3 is approximately 1.675 ins.

As will be further described, the lower shank portion 44 also has a tri-lobe configuration as best illustrated in FIG. 15. The lower shank portion 44 is traversed by a right hand thread 54 which is 12 threads per inch and has an included thread angle of 30 degrees as illustrated by the profile of FIG. 5. A preferred embodiment of thread 54 has a minor diameter and of 0.123 inches and a major diameter Md of 0.190 to 0.196 inches.

With reference to FIGS. 1 and 7, the thread 54 for a length l8 of approximately 0.5 to 0.9 inches is traversed by a spiral array of notches 60. As best illustrated in FIG. 8, the spiral array 60 subtends an angle of approximately 90 degrees about the shank axis with the depth of each notch being approximately the minor diameter. The notch width nw1 is approximately 0.10 inches. The spiral array 60 extends approximately 1 revolution per 1.5 inches in length.

With reference to FIG. 9, the shank terminates in the tip 46 which continues the spiral thread 54. A notch 62 is shown in section. The width nw2 may be longer for notch 62. In some embodiments, only one notch may be employed for the tip. If two notches are employed, the second notch 64 is slightly out of phase to create a split point. The notches 62, 64 may extend to a depth slightly into the minor diameter at the tip as illustrated in FIG. 10. The depth wd2 of the notch is 0.12 inches. Another tip 46A having a blunt point with notches 62A and 64A is illustrated in FIG. 9A.

Representative dimensions for lower portion 44 for a preferred embodiment are set forth in Table II.

	TABLE II
	l8	0.5 to 0.9	ins
	nw1	0.10	ins
	nd2	0.12	ins
	md	0.123	ins
	Md	0.190 to 0.196	ins

The manufacturing process for the deck screw 10 is best illustrated in the FIGS. 11-15. The initial work piece cut off shown as 10A in FIG. 11 has a workpiece diameter wd1 of 0.15 ins and a workpiece length wl1 of 2.70 ins. The first blow shown in FIG. 12 produces workpiece 10B which forms the bifurcated shank portions 425, 44B and the head 30B with workpiece lengths wl2 of 2.68 ins and wl3 of 0.125 ins and workpiece head diameter wd2 of 0.250 ins. The coupling recess 32 is then punched into the head portion to form the final head detail as shown in FIG. 3.

FIG. 14 shows the tri-lobe formed shank portion 44A for the workpiece 10C. The dimensions for workpieces 10A, 10B and 10C are given in Table III for a screw 10 having a final length l1 of 2.75 ins.

TABLE III
l1  2.75 ins
Wd3 0.137 ins
wl1 2.70 ins
wd1 0.15 ins
wl2 2.68 ins
wd2 0.250 ins
wl3 0.125 ins
wl4 2.69 ins
wl5 1.715 ins
wl6 0.875 ins
wl7 0.115 ins

The threads 52, 54 are then rolled onto the workpiece 10C. The notches 60 and 62 are then punched into the workpiece. Alternately, the notches may be formed during the thread forming process.

With reference to FIG. 16, a screw which is especially adapted for securing trim board for composite or plastic materials is designated by the numeral 110. The trim board typically has a plastic composition. Screw 110 does not have a trilobial form as previously described with respect to deck screw 10. The screw 110 is efficiently configured to be driven through trim board of composite material into a composite member or a support structure. The screw 110 is preferably driven a depth in the trim board (not illustrated) wherein the head 130 is sunk below the upper surface of the material (not illustrated) and forms a cylindrical counter bore above the head. The screw can be driven without volcanoing or mushrooming of the material around the head and can be relatively easily driven without intense resistance to the application of torque during the driving process.

The head 130 is substantially identical in form and function to head 30. A representative embodiment of screw 110 is hereinafter described. The length of I₁ of one embodiment of the screw 110 is 2.750 ins. with the head diameter of 0.26 ins. The shank 140 has an enlarged diameter neck 141 and an extended portion 142. A lower portion 144 of length I₃ of 1.900 ins. with a distal tip 146 is substantially similar in form and function to tip 46. Portion 142 has a larger diameter than portion 144.

The portion 142 includes a left hand thread 152 which extends a length I₂ of approximately 0.300 ins. The thread 152 has 9 threads per inch with a 48 degree included angle, such as illustrated by the FIG. 4 profile. The thread 152 in one embodiment has a minor diameter of 0.133 ins. and a major thread diameter 0.250 ins.

The lower shank portion 144 is traversed by a right hand thread of 12 threads per inch and has an included thread angle of 30 degrees, as illustrated by the FIG. 5 profile. A preferred embodiment of thread 154 has a minor diameter of 0.123 ins. and a major diameter of 0.185 to 0.191 ins. The remaining portions are substantially similar to that described for deck screw 10 and include a spiral array of notches 160 with notches in the tip being substantially the same as described with respect to deck screw 10.

Various approximate dimensions for one embodiment of trim screw 110 are summarized in Table IV.

TABLE IV
l1 2.750 ins
l2 0.300 ins
l3 1.900 ins
l4 0.060 ins
l5 0.105 ins
l6 0.850 ins
l7 0.375 ins

With reference to FIG. 17, deck screw 210 is especially adaptable for use with very dense material, such as, for example, Trex Escapes™ and EverGrain™ composite or plastic materials. A representative embodiment of deck screw 210 is hereinafter described. Deck screw 210, in one embodiment, has a length L₁ of 2.75 ins. and a head diameter of 0.26 ins. The upper portion 242 of the shaft includes an enlarged neck 241 which extends for a length of 0.20 inches and an adjacent shank portion 242 which extends a length L₂ for 0.900 ins.

Three rings 251, 252, 253 are formed on an intermediate shank portion 243. In one embodiment, the rings have an included angle of 30 degrees with an effective minor diameter of 0.133 ins. (the nominal diameter of portion 242) and a major diameter between 0.205 and 0.210 ins. The rings 251, 252, 253 are substantially identical and are spaced apart a pitch distance of approximately 0.121 ins.

The rings 252, 252, 253 have an included thread angle of 30°, such as illustrated in FIG. 5. The lower shank portion 244 is substantially identical to that of lower shank portion 154.

Various approximate dimensions for one embodiment of deck screw 210 are summarized in Table V.

TABLE V
L1 2.75 ins
L2 0.900 ins
L3 1.675 ins
L4 0.200 ins
L5 0.105 ins
L6 0.900 ins
L7 0.700 ins
L8 0.121 ins

While preferred embodiments have been set forth for purposes of illustration, the foregoing description should be deemed a limitation of the invention herein. Accordingly, various modifications, adaptations and alternatives may occur to one skilled in the art without departing from the spirit and the scope of the present invention.

Claims

1. A fastener for composite or plastic material comprising: a head having a socket rotatably couplable for application of a torque and having a recessed underside and a lower rim;an elongated shank extending from said head and terminating at a distal tip and comprising an upper portion having an enlarged diameter and a lower portion having a reduced diameter;said upper portion being traversed by a left-hand thread; andsaid lower portion traversed by a right-hand thread, said right-hand thread having a plurality of notches.

2. The fastener of claim 1 wherein said right-hand thread extends substantially to said tip.

3. The fastener of claim 2 comprising at least one notch in said tip thread.

4. The fastener of claim 3 wherein there are at least two notches in said tip thread, two of said notches being out of phase.

5. The fastener of claim 1 wherein said notches form a spiral array.

6. The fastener of claim 1 wherein a land extends between said threads.

7. The fastener of claim 1 wherein the fastener has a length of approximately 2.750 ins. and the left hand thread extends approximately 0.300 ins.

8. The fastener of claim 1 wherein the number of threads per inch of the left-hand thread is less than the number of threads per inch of the right-hand thread.

9. The fastener of claim 1 wherein the thread angle of the left-hand thread is greater than the thread angle of the right-hand thread.