CA1054409A - Threaded fastener with plastic head - Google Patents

Threaded fastener with plastic head

Info

Publication number
CA1054409A
CA1054409A CA271573A CA271573A CA1054409A CA 1054409 A CA1054409 A CA 1054409A CA 271573 A CA271573 A CA 271573A CA 271573 A CA271573 A CA 271573A CA 1054409 A CA1054409 A CA 1054409A
Authority
CA
Canada
Prior art keywords
flange
head
plastic
shank
workpiece
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
Application number
CA271573A
Other languages
French (fr)
Inventor
Robert R. Melone
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Elco Industries Inc
Original Assignee
Elco Industries Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Elco Industries Inc filed Critical Elco Industries Inc
Application granted granted Critical
Publication of CA1054409A publication Critical patent/CA1054409A/en
Expired legal-status Critical Current

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Abstract

Abstract of the Disclosure A fastener including a metal portion having a threaded shank adapted to be threaded into a workpiece, a head and an annular flange between the head and the shank. The surface of the head and the upper surface of the flange are irregular so that, when a plastic head is molded around the head and flange of the metal portion, the metal and plastic portions are relatively fixed to each other. The plastic portion includes a section which extends around the periphery of the flange and under the marginal portion of the latter and which mates with an annular deformation extending around the periphery of the underside of the flange to reduce the possibility of failure of the plastic portion as that portion is forced against a workpiece. The section of the plastic portion under the flange is annular and may provide a recess for receiving a resilient sealing ring or, in the alternative, it may be formed with an annular rib which deforms and forms a seal as the fastener is threaded down to bring the annular section into engagement with the workpiece.

Description

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Background of the Invention The present invention relates to a fastener of the type which includes a metal portion having a threaded shank adapted to be threaded into a workpiece, a head above the shank and an annular flange between ::
the head and the shank. A plastic portion is molded around the head and flange of the metal portion so that the two portions are relatively fixed .:. `
to each other and that part of the plastic portion surrounding the head :
is shaped to receive a driving tool. The plastic extends around and under .~
the flange so that the section beneath the flange engages the workpiece ;.:
when the fastener is tightened into the latter. Examples of fasteners .
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of this type are shown in Wagner United States Patent No. 3, 693, 495 and ~ay United ~tates Patent No. 3,618,444. With prior constructions, the plastic portion tends to split or otherwise fail as the plastic beneath the flange is forced against the surface of a workpiece.
Summary of the Invention The general object of the invention is to provide a new and improved plastic headed fastener which reduces the likelihood of '~ -failure of the plastic head as the latter is forced against a surface of a workpiece when the fastener is threaded into place.
Another object is to achieve the foregoing by providing an annular deformation around the periphery of the underside of the flange of the metal portion and providing the plastic portion with an annulus which is comparatively thin and which extends under that periphery and coacts with the deformation to inhibit radial expansion of the plastic .
portion as the annulus is forced against a workpiece surface.
The invention also resides in the provision of novel means for forming a seal between the fastener and the workpiece surface.
In summary, the invention involves a screw comprising a metal portion and a plastic portion, said metal portion being integral and including a head, an elongated and axially extending threaded shank .`
and a circular flange located between and projecting radially from said head and said shank, said flange having an upper surface adjacent said head and a lower surface adjacent said shank, the head and the upper surface of said flange being of irregular contour, a continuous annular rib formed integrally with said flange and depending from the outer peripheral portion of the flange, said rib having a bottom surface and -also having an inner surface defining a circular, radially facing shoulder, said plastic portion being hard and rigid, said plastic portion having a head section molded over the head of said metal portion and across the , : - -- - -. - - - ~ . :, ~Q54~
upper side of said flange and mating with the i.rregularities in said head and said flange to fix said plastic portion rigidly to said metal portion, said plastic portion further including (a) an annular skirt formed integrally ~:
with and depending from the outer peripheral portion of said head section and extending around and downwardly aLongside the outer periphery of said flange and the outer surface of said rib, said skirt being relatively thin and having a thickness in the range of . 020 to . 030 of an inch, (b) a radially extending section integral with the bottom of said skirt and disposed in underlying engagement with the bottom of said rib, said 10 radially extending section having a thickness within said range and having an inner periphery which is spaced outwardly from said shank, (c) an outer sealing ring formed integrally with and depending from said radially extending section and disposed beneath said rib, (d) an inner sealing ring concentric with said outer ring and formed integrally with and depending from the inner peripheral portion of said radially extending section, said rings having lower surfaces adapted to clamp and seal against a workpiece when said screw is tightened, and (e) an annular bead formed integrally with and projecting upwardly from said radially extending section, said bead having an outer radially facing surface 20 located in engagement with said shoulder to restrict outward radial expansion and structural failure of said skirt when said rings are clamped against the workpiec:e.
Brief Description of the Drawings FIGURE 1 is a perspective view cf a fastener incorporating .;
my invention.
FIG. 2 is an enlarged top view of the fastener.
FIG. 3 is a fragmentary sectional view taken along the `
line 3-3 in FIG. 2. `
FIG;. 4 is a top view of the metal portion of the fastener.

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~os~4il)9 FIG. 5 is a fragmentary sectional view similar to FIG.
3 and incorporating a resilient gasket as a sealing means.
FIG. 6 is a fragmentary side view o-f the construction ' shown in FIG. 5 with parts broken away and shown in section and with the elements in position when the fastener is tightened against a workpiece.
FIG. 7 is a fragmentary side view with parts broken away and shown in section and incorporating a modified form of sealing means.
Detailed Description of the Preferred Embodiment `
As shown in the drawings for purposes of illustrationJ
the invention is embodied in a fastener in the form of a self-drilling thread-forming screw 10 which includes a metal shank 11 and a plastic head 12, the head being made of plastic to prevent corrosion and for decorative purposes. The tip 13 of the shank is formed to drill a hole in a workpiece 14 and the lower convolutions of a thread 15 on the shank form threads (not shown) in the workpiece to mate with the upper convolutions. The plastic head 12 includes an annular flange 16 above the shank and a double-square or eight-point portion 17 which is adapted ~ -to be received in the socket of a driving tool. When the screw is fully threaded into the workpieceJ the underside of the flange 16 bears against ;-the opposing surface of the workpiece as shown in FIG. 3.
In order to secure the plastic head 12 to the shank 11 and cause the two to turn together, the shank is a part of a unitary metal piece 18 whichJ in addition to the shank 11J includes an annular flange 19 above the shank and a generally cylindrical portion or head 20 above the flange 19. Radial ribs 21 are formed on the top of the flange 19, -axial ribs 22 are formed on the sides of the cylindrical portion 20 and grooves 23 (FIG. 4) are formed in the top of the cylindrical portion 20.
The plastic head 12 encases the cylindrical portion 20 and the flange 19 .i, :

~ 1~)544Q9 of the metal piece 18 with the plastic of the head filling the grooves 23, the spaces between the ribs 21 and the spaces between the ribs 22 to help insure that the metal piece 18, a~d hence the shar~k 11, rotates with the plastic head.
The plastic for the head 12 may be any suitable engineering t plastic with characteristics suitable for the purpose, and, customarily the head is injection molded. A glass filler may be used ;n the plastic and, if color is desired, an appropriate pigment is added.
The present invention contemplates the provision of a novel arrangement of and coaction between the plastic head 12 and the metal piece 18 to materially reduce the possibility of splitting or other ~-failure of the head as the latter is tightened down against a workpiecc.
This arrangement includes an annular deformation 24 formed arolmd the periphery of the flange 19 of the metal piece and mating with that portion 25 of the plastic head which extends under the flange, the section 25 heing ~i a radially extending portion formed integrally on the lower end of a skirt or longitudinal section 25a (FIGS. 3 and 5) which extends around and alongside the edge or periphery of the metal flange 19. An almular bead `
is formed integrally with and projects upwardly from the radially -2û extending section 25 and includes an outer radially facing surface which engages the annular deformation 24. ~t the same time, the portion or section 25 is a comparatively thin annulus so that the flange 19 is relatively close to the surface of the workpiece 14 and the thickness `
of the section 25a is substantially less than the radial width of the metal flange 19. Desirably, the sections 25 and 25a are made as thin as possible within the limits of good moldi~g practice. It has been found that this arrangement inhibits the tendency of the plastic flange to expand radially and thereby reduces the possi~ility of the flange failing as by splitting when the head is forced against the workpiece.
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In the preferred form, the deformation 24 is a narrow circular rib projecting downwardly from the underside of the flange 19 and extending continuously around the margin of the flange, the inner surface of the rib defining a circular, radially facing shoulder for engaging the outer surface of the bead 25b. The rib 24 projects into a complementally shaped recess 26 in the annulus 25, the recess being formed automatically as an incident to the molding of the plastic head 12. As stated above, the plastic annulus 25 is comparatively thin and ;
suitable dimensions for the annulus are on the order of .040 of an inch from the underside of the flange 19 to the lower surface of the annulus (the dimension a in FIG. 3). The thickness of the section 25 (the dimension b in FIG. 3) should be in the range of .020 to .030 of an inch and preferably .025 of an inch and the thickness of the longitudinal section `
25a (the dimension c in FIG. 3) is of the same range and preferably of the same thickness as the section 25.
In accordance with another aspect of the invention, the fastener 10 is constructed in a novel manner to provide a seal around the shank 11 and between the head 12 and the workpiece 14. In one form (FIGS. 5 and 6), this is achieved by forming the annulus 25 so that it leaves an annular recess 27 under the flange 19 of the metal piece 18 :.
and between the annulus and the shank 11 and a gasket 28 made of a resilient material such as rubber is slipped over the shank 11 and into the recess 27. As shown in FIG. 5, the gasket 28 in its natural state has an outside diameter smaller than the diameter of the recess 27 and a length greater than the depth of the recess. When the fastener is tightened into place with the annulus 25 forced firmly against the surface of the workpiece 14, the gasket 28 expands radially and substantially ;
fills the recess 27 as illustrated in FIG. 6 thereby effectively forming a seal between the head 12 and the workpiece.

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In another form (FIG. 7), the sealing means comprises one or more circular plastic ribs, in this case two concentric ribs 29 and 30, molded integrally with the plastic head 12 and projecting downwardly from the annulus 25. lIerein, the ribs are concentric with the shank 11 and the outer rib 29 is spaced inwardly from the periphery of the annulus 25 while the ir.ner rib 30 is at the inner edge of the annulus.
After the fastener has been threaded into the workpiece to the point where the ribs 29 and 30 engage the workpiece as shown in FIG. 7, tightening of the fastener is continued until the annulus 25 virtually engages the workpiece. This causes the ribs 29 and 30 to flatten and, in their flattened condition, the ribs form a seal around the shank 11 and between the fastener head and the workpiece.
It will be observed that a fastener constructed in $he manner described above provides a plastic head which, as compared to prior fasteners of this type, is substantially less likely to fail when the fastener is tightened into the workpiece to force the annulus 25 of the - -head firmly against the surface of the workpiece. Moreover, the fastener is readily adaptable to form a seal around the shank 11 of the fastener and between head and the workpiece by the addition of either the resilient gasket 28 or the ribs 29 and 30.
:

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. A screw comprising a metal portion and a plastic portion, said metal portion being integral and including a head, an elongated and axially extending threaded shank and a circular flange located between and projecting radially from said head and said shank, said flange having an upper surface adjacent said head and a lower surface adjacent said shank, the head and the upper surface of said flange being of irregular contour, a continuous annular rib formed integrally with said flange and depending from the outer peripheral portion of the flange, said rib having a bottom surface and also having an inner surface defining a circular, radially facing shoulder, said plastic portion being hard and rigid, said plastic portion having a head section molded over the head of said metal portion and across the upper side of said flange and mating with the irregularities in said head and said flange to fix said plastic portion rigidly to said metal portion, said plastic portion further including (a) an annular skirt formed integrally with and depending from the outer peripheral portion of said head section and extending around and downwardly alongside the outer periphery of said flange and the outer surface of said rib, said skirt being relatively thin and having a thickness in the range of .020 to .030 of an inch, (b) a radially extending section integral with the bottom of said skirt and disposed in underlying engagement with the bottom of said rib, said radially extending section having a thickness within said range and having an inner periphery which is spaced outwardly from said shank, (c) an outer sealing ring formed integrally with and depending from said radially extending section and disposed beneath said rib, (d) an inner sealing ring concentric with said outer ring and formed integrally with and depending from the inner peripheral portion of said radially extending section, said rings having lower surfaces adapted to clamp and seal against a workpiece when said screw is tightened, and (e) an annular bead formed integrally with and projecting upwardly from said radially extending section, said bead having an outer radially facing surface located in engagement with said shoulder to restrict outward radial expansion and structural failure of said skirt when said rings are clamped against the workpiece.
CA271573A 1976-11-26 1977-02-11 Threaded fastener with plastic head Expired CA1054409A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US74536476A 1976-11-26 1976-11-26

Publications (1)

Publication Number Publication Date
CA1054409A true CA1054409A (en) 1979-05-15

Family

ID=24996387

Family Applications (1)

Application Number Title Priority Date Filing Date
CA271573A Expired CA1054409A (en) 1976-11-26 1977-02-11 Threaded fastener with plastic head

Country Status (1)

Country Link
CA (1) CA1054409A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2468210A1 (en) * 2010-12-23 2012-06-27 Straumann Holding AG Improved screw head
CN102551902B (en) * 2010-12-23 2016-12-14 斯特劳曼控股公司 Fastening system

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2468210A1 (en) * 2010-12-23 2012-06-27 Straumann Holding AG Improved screw head
CN102551902A (en) * 2010-12-23 2012-07-11 斯特劳曼控股公司 Improved screw head
AU2011253908B2 (en) * 2010-12-23 2013-05-09 Straumann Holding Ag Improved screw head
CN102551902B (en) * 2010-12-23 2016-12-14 斯特劳曼控股公司 Fastening system
US9532856B2 (en) 2010-12-23 2017-01-03 Straumann Holding Ag Screw head

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