CA1171701A - Self-sealing threaded fastener - Google Patents
Self-sealing threaded fastenerInfo
- Publication number
- CA1171701A CA1171701A CA000396482A CA396482A CA1171701A CA 1171701 A CA1171701 A CA 1171701A CA 000396482 A CA000396482 A CA 000396482A CA 396482 A CA396482 A CA 396482A CA 1171701 A CA1171701 A CA 1171701A
- Authority
- CA
- Canada
- Prior art keywords
- washer
- shoulder portion
- undersurface
- assembly
- head
- 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
Links
- 238000007789 sealing Methods 0.000 title claims abstract description 17
- 230000003467 diminishing effect Effects 0.000 claims description 3
- 238000010079 rubber tapping Methods 0.000 claims description 3
- 230000001154 acute effect Effects 0.000 claims description 2
- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical compound [Cu+2].C1=CC(C(=C2C=CC([N-]2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3[N-]2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 RKTYLMNFRDHKIL-UHFFFAOYSA-N 0.000 claims description 2
- 239000012858 resilient material Substances 0.000 claims description 2
- 239000000463 material Substances 0.000 description 7
- 239000002184 metal Substances 0.000 description 6
- 229910000831 Steel Inorganic materials 0.000 description 3
- 230000000712 assembly Effects 0.000 description 3
- 238000000429 assembly Methods 0.000 description 3
- 229920001971 elastomer Polymers 0.000 description 3
- 239000010959 steel Substances 0.000 description 3
- JJLJMEJHUUYSSY-UHFFFAOYSA-L Copper hydroxide Chemical compound [OH-].[OH-].[Cu+2] JJLJMEJHUUYSSY-UHFFFAOYSA-L 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- 230000006835 compression Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 229920001084 poly(chloroprene) Polymers 0.000 description 2
- -1 polyethylene Polymers 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 238000004513 sizing Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 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
- F16B43/00—Washers or equivalent devices; Other devices for supporting bolt-heads or nuts
- F16B43/001—Washers or equivalent devices; Other devices for supporting bolt-heads or nuts for sealing or insulation
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Bolts, Nuts, And Washers (AREA)
Abstract
ABSTRACT
There is provided a self-sealing threaded assembly which includes a threaded fastener and a resilient washer. The threaded fastener has a head with hexagonal faces or other means by which torque can be applied to the head. An undersurface is provided by the head, and a shoulder portion extends downwardly beneath this under-surface, the shoulder portion having a smaller diameter than the undersurface. A threaded shank extends downwardly from the shoulder portion, the shank being sized diametrally such that an opening engageable by the threaded shank is too small to accept the shoulder portion. The resilient washer has a maximum thickness greater than the axial dimension of the shoulder portion, so that when the threaded shank is screwed into an opening in a wall, the shoulder portion will abut the wall and cause the resilient washer to be squeezed between the wall and the undersurface.
There is provided a self-sealing threaded assembly which includes a threaded fastener and a resilient washer. The threaded fastener has a head with hexagonal faces or other means by which torque can be applied to the head. An undersurface is provided by the head, and a shoulder portion extends downwardly beneath this under-surface, the shoulder portion having a smaller diameter than the undersurface. A threaded shank extends downwardly from the shoulder portion, the shank being sized diametrally such that an opening engageable by the threaded shank is too small to accept the shoulder portion. The resilient washer has a maximum thickness greater than the axial dimension of the shoulder portion, so that when the threaded shank is screwed into an opening in a wall, the shoulder portion will abut the wall and cause the resilient washer to be squeezed between the wall and the undersurface.
Description
11'~ l'~C~l SELF-SEALING THREADED FASTENER
This invention relates generally to self-sealing fastener assemblies which includes a fastener member and a washer member. More particularly, this invention has to do with a fastener/washer assembly which exhibits improved characteristics over those conventionally known.
BACKGROUND OF THIS INVENTION
In general, self-sealing washers used in conjunc-tion with fastening members consist of a metal backing in conjunction with a soft sealing component such as rubber, neoprene or plastic. The sealing component may be either bonded directly to the metal backing, or may itself be a separate washer. When the fastener is driven, the soft sealing component is compressed between the metal backing and the surface through which the fastener is inserted, creating a watertight seal. In some self-sealing assemblies, the metal backing is designed so that metal-to-metal contact is achieved between the backing and the wall. This pro-vides a more reliable seal by preventing excessive compression of the soft sealing component, and also increases the pull-over and shear resistance of the system.
It is an aspect of this invention to provide afastener and washer assembly with improved characteristics, capable of self-sealing while attaining metal-to-metal con-tact. A further aspect of this invention is to provide a fastener/washer assembly which is economical to manufacture.
Acc~rdingly, this invention provides a self-sealing threaded assembly comprising a threaded fastener and a resilient washer.
1 1 ';~ ~'7~1 The threaded fastener has a head with means by which tor~ue can be applied to the head. The head has a sub-stantially flat undersurface and there is provided a shoulder portion beneath the undersurface of smaller diameter than the undersurface. An inward step is provided at the bottom of the shoulder portion, and the fastener includes a threaded shank sized diametrally such that an opening engageable by the threaded shank is too small to accept the shoulder portion, and would abut the inward stop.
The resilient washer is of integral, resilient material throughout and has a maximum thickness greater than the axial dimension of the shoulder portion. The cross-section of the washer, taken in a plane extending radially from and including the axis of the washer, has a thicker portion closer to the axis and has a tapering portion ex-tending with diminishing thickness away from the thicker portion and remote from the axis. The tapering portion is defined by two outwardly convergent surfaces, one of which slopes away from the undersurface of the head, the other of which slopes ~oward the undersurface. In this manner, when the threaded shank is screwed into an opening in a wall, the shoulder portion will abut the wall so that the resilient washer is squeezed between the wall and the undersurface.
Two embodiments of this invention are illustrated in the accompanying drawings, in which like numerals denote like parts throughout the several view, and in which:
Figure 1 is an elevational view of a screw together with a sectional view of the first embodiment of the resilient washer when the latter is in unstressed con-dition;
Figure 2 is a sectional view through a panel through which the screw has been inserted, showing the screw again in elevation, and showing the panel and the first embodiment of the washer in section; and Figure 3 is a sectional view of the second embodi-ment of the washer.
In Figure 1 the~e is shown a self-sealing screw assembly lO which includes a screw 12 and a resilient 2a washer 1~. The screw includes a head 16 with means by which torque can be applied to the head. More specifically, the head shown in Figure 1 has a hexagonal portion 17 of conventional construction surmounting an integral annular portion 18 of circular outer circl~ference.
The integral annular portion 18 has a larger diameter than the maximum diameter of the hexagonal portion 17 and has a flat under-1.~';'17Ul surface 20. The upper surface of the integral annularportion 18 slopes inwardly and upwardly to join the hexagonal portion 17, as shown at 21 in Figure 1.
The screw 12 has in addition an integral shoulder portion 23 located coaxially beneath the integral annular portion 18, the shoulder portion being of cylindrical configuration but of smaller diameter than the integral annular portion 18. Below the shoulder portion 23 is a standard threaded shank 25.
In the figures, the threaded shank is of self-tapping construction, although any other form of thread could also be utilized, as will be obvious to those skilled in the art.
More particularly, the threaded shank 25 is sized diametrally in such a way that an opening which is engageable by the threaded shank is too small to accept the shoulder portion 23. In the specific embodiment shown, the shoulder portion 23 has a diameter larger than the outside thread diameter of the threaded shank 25.
The resilient washer 14 may have various sections, and could include the standard resilient washer section, in which an annulus is simply stamped from resilient sheet material. ~owever, the section preferred for use with the screw of this invention is that shown in Figures 1 and
This invention relates generally to self-sealing fastener assemblies which includes a fastener member and a washer member. More particularly, this invention has to do with a fastener/washer assembly which exhibits improved characteristics over those conventionally known.
BACKGROUND OF THIS INVENTION
In general, self-sealing washers used in conjunc-tion with fastening members consist of a metal backing in conjunction with a soft sealing component such as rubber, neoprene or plastic. The sealing component may be either bonded directly to the metal backing, or may itself be a separate washer. When the fastener is driven, the soft sealing component is compressed between the metal backing and the surface through which the fastener is inserted, creating a watertight seal. In some self-sealing assemblies, the metal backing is designed so that metal-to-metal contact is achieved between the backing and the wall. This pro-vides a more reliable seal by preventing excessive compression of the soft sealing component, and also increases the pull-over and shear resistance of the system.
It is an aspect of this invention to provide afastener and washer assembly with improved characteristics, capable of self-sealing while attaining metal-to-metal con-tact. A further aspect of this invention is to provide a fastener/washer assembly which is economical to manufacture.
Acc~rdingly, this invention provides a self-sealing threaded assembly comprising a threaded fastener and a resilient washer.
1 1 ';~ ~'7~1 The threaded fastener has a head with means by which tor~ue can be applied to the head. The head has a sub-stantially flat undersurface and there is provided a shoulder portion beneath the undersurface of smaller diameter than the undersurface. An inward step is provided at the bottom of the shoulder portion, and the fastener includes a threaded shank sized diametrally such that an opening engageable by the threaded shank is too small to accept the shoulder portion, and would abut the inward stop.
The resilient washer is of integral, resilient material throughout and has a maximum thickness greater than the axial dimension of the shoulder portion. The cross-section of the washer, taken in a plane extending radially from and including the axis of the washer, has a thicker portion closer to the axis and has a tapering portion ex-tending with diminishing thickness away from the thicker portion and remote from the axis. The tapering portion is defined by two outwardly convergent surfaces, one of which slopes away from the undersurface of the head, the other of which slopes ~oward the undersurface. In this manner, when the threaded shank is screwed into an opening in a wall, the shoulder portion will abut the wall so that the resilient washer is squeezed between the wall and the undersurface.
Two embodiments of this invention are illustrated in the accompanying drawings, in which like numerals denote like parts throughout the several view, and in which:
Figure 1 is an elevational view of a screw together with a sectional view of the first embodiment of the resilient washer when the latter is in unstressed con-dition;
Figure 2 is a sectional view through a panel through which the screw has been inserted, showing the screw again in elevation, and showing the panel and the first embodiment of the washer in section; and Figure 3 is a sectional view of the second embodi-ment of the washer.
In Figure 1 the~e is shown a self-sealing screw assembly lO which includes a screw 12 and a resilient 2a washer 1~. The screw includes a head 16 with means by which torque can be applied to the head. More specifically, the head shown in Figure 1 has a hexagonal portion 17 of conventional construction surmounting an integral annular portion 18 of circular outer circl~ference.
The integral annular portion 18 has a larger diameter than the maximum diameter of the hexagonal portion 17 and has a flat under-1.~';'17Ul surface 20. The upper surface of the integral annularportion 18 slopes inwardly and upwardly to join the hexagonal portion 17, as shown at 21 in Figure 1.
The screw 12 has in addition an integral shoulder portion 23 located coaxially beneath the integral annular portion 18, the shoulder portion being of cylindrical configuration but of smaller diameter than the integral annular portion 18. Below the shoulder portion 23 is a standard threaded shank 25.
In the figures, the threaded shank is of self-tapping construction, although any other form of thread could also be utilized, as will be obvious to those skilled in the art.
More particularly, the threaded shank 25 is sized diametrally in such a way that an opening which is engageable by the threaded shank is too small to accept the shoulder portion 23. In the specific embodiment shown, the shoulder portion 23 has a diameter larger than the outside thread diameter of the threaded shank 25.
The resilient washer 14 may have various sections, and could include the standard resilient washer section, in which an annulus is simply stamped from resilient sheet material. ~owever, the section preferred for use with the screw of this invention is that shown in Figures 1 and
2. The main characteristic of the section of the resilient washer is that it must have a maximum thickness, i.e. a dimension measured parallel to the ax~s of the washer, which is greater than the axial dimension of the cylindrical shoulder portion 23. This is clearly illustrated in Figure 1. By providing this configuration, one ensures that the resilient washer, after it rides up around the shoulder portion 23, will be resiliently squeezed between the undersurface 20 and the surface 28 of a wall 30 through which the screw is threaded (see Figure 2).
In Figure 1, this enlarged or thicker portion 1.1 ~17~1 is seen to be located at the inward region of the washer, and it is essential, of course, that this thicker portion be located within the outer diameter of the integral annular portion 18, so that the undersurface 20 can act in conjunc-S tion with the surface 28 to squeeze the washer.
As further seen in Figure 1, the section of a preferred form of washer, taken in a plane extending radially from and including the axis of the washer (i.e. the axis of the screw as seen in Figure 1), has a tapering portion 32 extending with diminishing thickness away from the thicker portion 33, and extending remote from the axis of the washer.
Expressed in even more specific language, the preferred washer shown in Figures 1 and 2 is of tetragonal cross-section, having two walls 34 forming an o~tuse angle with the apex toward the washer axis, and two walls 36 forming an acute angle with the apex away from the washer axis.
It is preferred that the inner diameter of the washer 14 be small enough to interfere with and hence locate itself on the threads of the shank 25.
When the assembly is put into use, as shown in Figure 2, the screw is threaded into the wall, with the washer 14 in place on the threaded shank 25, until the shoulder portion 23 abuts firmly-against the wall surface 28, thus preventing further rotation of the screw. Because of the comparative sizing of the washer 14 and the shoulder portion 23, the washer 14 will be resiliently squeezed to a controlled degree (determined by the axial extent of the shoulder portion 23), and it is understood that the resilient washer 14 will be sized in such a way that the degree of compression applied to it in the Figure 2 configuration will be sufficient to seal the opening 38 of the panel 30 against the ingress of water or other liguids.
It will now be appreciated that, by providing the shoulder portion 23, angular misalignment can be corrected as the shoulder portion 23 comes in contact with the surface 28 of the panel 30. Moreover, even when the l a~ 7~l screw is initially threaded at an angle from the normal, the taper ~walls 36) of the washer is such as to minimize or eliminate spin-out of the washer during the turning.
Actual tests have shown that, whereas flat washers tend to spin-out at about 15 angle from the normal, resulting in poor appearance, the tapered washer shown in Figures 1 and 2 remains completely functional at a misalignment angle of up to 20 from normal. Also, the shoulder portion ensures that the screw remains tight in the event that the resilient sealing member is subject to the long term creep or relaxation which might otherwise lead to a degree of loosening of the clamped members.
The provision of the shoulder portion 23 provides excellent clamping and pull-over resistance, on the basis S of tests which have been conducted.
The following general size ratios characterize typical fasteners to which this invention may be applied, although these ratios are not considered limiting in terms of the scope of the invention. In what follows, the term "nominal diameter" refers to the threaded shank of the fastener.
(a) The ratio of the undersurface 20 (bearing surface to the nominal diamete~ may be in the range of about 1.7 to about 2.7.
(b) The ratio of the height of the shoulder portion 23 to the nominal diameter would be in the range of about 0.15 to 0.45.
tc) The ratio of the diameter of the shoulder portion 23 to the diameter of the hole into which the fastener would be driven is in the range from about 1.1 to about 1.5. Normally, members drilled in situ will have the same size hole in all components to be clamped.
(d) The ratio of the washer thickness to the thickness of the shoulder portion 23 would be about l.Q6 to about 2.5, with a more typical range being from about 1.2 to about 1.5.
7()1 As a further illustrative example, which is not offered in any limiting sense, the following may be considered t~pical dimensions for a ~" type AB self-sealing tapping screw to which this invention would apply:
5 Undersurface 20 diameter (flange diameter of head) .550"
Diameter of cylindrical shoulder .275"
Height (axial dimension) of shoulder portion .075"
Washer thickness (maximum axial dimension) .110"
Outside diameter of washer .500"
10 Inside diameter of washer .225"
In regard to the material from which the washer may be constructed, there are the following fundamental requirements which should be met in order to achieve proper function.
(a) There must be sufficient resilience to seal the space between the fastener bearing surface (undersurface 20) and a clamped member (wall surface 28).
(b) There must be an appropriate relationship between strength and coefficient of friction between the fastener bearing surface (undersurface 20) and the washer, or between the clamped member (wall surface 28) and the washer, such that as the fastener head is rotated, generat-ing frictional forces and compressive strain on the washer, the washer material will be able to resist failure under these resultant stresses and strains. The lower the coefficient of friction between the washer and the member against which it is sliding, the lower will be the resultant stresses (shear stresses) in the material of the washer. Hence, for a given material strength, a reduced coefficient ~f friction will reduce the likelihood of failure. Conversely, for a given coefficient of friction, the material strength properties can be made sufficiently high that failure will not occur.
For example, a neoprene rubber washer used in the present application would have a high friction, in that it would grip 11'~'J '7~1 the members well and resist sliding, resulting in very high stresses and strains in the rubber, usually high enough to fracture the rubber. On the other hand, polyethylene is not significantly better in mechanical properties, but has low friction and permits the members to slide easily, generat-ing low shear stresses and strains in the polyethylene, and hence usually avoiding failure. By contrast, a steel washer has a high friction and resists sliding, frequently galling the two surfaces, but at the same time it has sufficient material strength that it can resist the stresses and hence not fail. The problem with a steel washer is the lack of a sufficiently high resiliency. Hence, a steel washer would not provide the requisite seal.
Attention is now directed to Figure 3, which shows the second embodiment of the washer of this invention.
The washer shown in Figure 3 at the numeral 40 is essentially flat annular washer having a flat annular upper surface 42, a flat annular lower surface 44, a cylindrical outside surface 45 and a cylindrical inside surface 46. The diameter of the inside surface 46 is slightly less than the outside thread diameter of the threaded shank 25, which will cause the washer 42 to undergo a slight mechanical interference with the threads of the threaded shank 25, thus holding the washer 40 in place on the threaded shank 25 prior to the time of driving or turning of the screw 12. It is pointed out that the inner diameter of the flat washer 40 does not need to be angled in order to allow it to mount the shoulder portion 23 during driving. It is found that, due ~o the resiliency of the flat washer 40, it readily expands to accommodate the shoulder portion 23. While an annular washer such as shown at 40 is not as preferred as the tetragonal-section washer 14 seen in Figures-~ and 2, it is nonetheless a functionally workable embodiment, and considered to have definite advantages over conventional sealing assemblies.
In Figure 1, this enlarged or thicker portion 1.1 ~17~1 is seen to be located at the inward region of the washer, and it is essential, of course, that this thicker portion be located within the outer diameter of the integral annular portion 18, so that the undersurface 20 can act in conjunc-S tion with the surface 28 to squeeze the washer.
As further seen in Figure 1, the section of a preferred form of washer, taken in a plane extending radially from and including the axis of the washer (i.e. the axis of the screw as seen in Figure 1), has a tapering portion 32 extending with diminishing thickness away from the thicker portion 33, and extending remote from the axis of the washer.
Expressed in even more specific language, the preferred washer shown in Figures 1 and 2 is of tetragonal cross-section, having two walls 34 forming an o~tuse angle with the apex toward the washer axis, and two walls 36 forming an acute angle with the apex away from the washer axis.
It is preferred that the inner diameter of the washer 14 be small enough to interfere with and hence locate itself on the threads of the shank 25.
When the assembly is put into use, as shown in Figure 2, the screw is threaded into the wall, with the washer 14 in place on the threaded shank 25, until the shoulder portion 23 abuts firmly-against the wall surface 28, thus preventing further rotation of the screw. Because of the comparative sizing of the washer 14 and the shoulder portion 23, the washer 14 will be resiliently squeezed to a controlled degree (determined by the axial extent of the shoulder portion 23), and it is understood that the resilient washer 14 will be sized in such a way that the degree of compression applied to it in the Figure 2 configuration will be sufficient to seal the opening 38 of the panel 30 against the ingress of water or other liguids.
It will now be appreciated that, by providing the shoulder portion 23, angular misalignment can be corrected as the shoulder portion 23 comes in contact with the surface 28 of the panel 30. Moreover, even when the l a~ 7~l screw is initially threaded at an angle from the normal, the taper ~walls 36) of the washer is such as to minimize or eliminate spin-out of the washer during the turning.
Actual tests have shown that, whereas flat washers tend to spin-out at about 15 angle from the normal, resulting in poor appearance, the tapered washer shown in Figures 1 and 2 remains completely functional at a misalignment angle of up to 20 from normal. Also, the shoulder portion ensures that the screw remains tight in the event that the resilient sealing member is subject to the long term creep or relaxation which might otherwise lead to a degree of loosening of the clamped members.
The provision of the shoulder portion 23 provides excellent clamping and pull-over resistance, on the basis S of tests which have been conducted.
The following general size ratios characterize typical fasteners to which this invention may be applied, although these ratios are not considered limiting in terms of the scope of the invention. In what follows, the term "nominal diameter" refers to the threaded shank of the fastener.
(a) The ratio of the undersurface 20 (bearing surface to the nominal diamete~ may be in the range of about 1.7 to about 2.7.
(b) The ratio of the height of the shoulder portion 23 to the nominal diameter would be in the range of about 0.15 to 0.45.
tc) The ratio of the diameter of the shoulder portion 23 to the diameter of the hole into which the fastener would be driven is in the range from about 1.1 to about 1.5. Normally, members drilled in situ will have the same size hole in all components to be clamped.
(d) The ratio of the washer thickness to the thickness of the shoulder portion 23 would be about l.Q6 to about 2.5, with a more typical range being from about 1.2 to about 1.5.
7()1 As a further illustrative example, which is not offered in any limiting sense, the following may be considered t~pical dimensions for a ~" type AB self-sealing tapping screw to which this invention would apply:
5 Undersurface 20 diameter (flange diameter of head) .550"
Diameter of cylindrical shoulder .275"
Height (axial dimension) of shoulder portion .075"
Washer thickness (maximum axial dimension) .110"
Outside diameter of washer .500"
10 Inside diameter of washer .225"
In regard to the material from which the washer may be constructed, there are the following fundamental requirements which should be met in order to achieve proper function.
(a) There must be sufficient resilience to seal the space between the fastener bearing surface (undersurface 20) and a clamped member (wall surface 28).
(b) There must be an appropriate relationship between strength and coefficient of friction between the fastener bearing surface (undersurface 20) and the washer, or between the clamped member (wall surface 28) and the washer, such that as the fastener head is rotated, generat-ing frictional forces and compressive strain on the washer, the washer material will be able to resist failure under these resultant stresses and strains. The lower the coefficient of friction between the washer and the member against which it is sliding, the lower will be the resultant stresses (shear stresses) in the material of the washer. Hence, for a given material strength, a reduced coefficient ~f friction will reduce the likelihood of failure. Conversely, for a given coefficient of friction, the material strength properties can be made sufficiently high that failure will not occur.
For example, a neoprene rubber washer used in the present application would have a high friction, in that it would grip 11'~'J '7~1 the members well and resist sliding, resulting in very high stresses and strains in the rubber, usually high enough to fracture the rubber. On the other hand, polyethylene is not significantly better in mechanical properties, but has low friction and permits the members to slide easily, generat-ing low shear stresses and strains in the polyethylene, and hence usually avoiding failure. By contrast, a steel washer has a high friction and resists sliding, frequently galling the two surfaces, but at the same time it has sufficient material strength that it can resist the stresses and hence not fail. The problem with a steel washer is the lack of a sufficiently high resiliency. Hence, a steel washer would not provide the requisite seal.
Attention is now directed to Figure 3, which shows the second embodiment of the washer of this invention.
The washer shown in Figure 3 at the numeral 40 is essentially flat annular washer having a flat annular upper surface 42, a flat annular lower surface 44, a cylindrical outside surface 45 and a cylindrical inside surface 46. The diameter of the inside surface 46 is slightly less than the outside thread diameter of the threaded shank 25, which will cause the washer 42 to undergo a slight mechanical interference with the threads of the threaded shank 25, thus holding the washer 40 in place on the threaded shank 25 prior to the time of driving or turning of the screw 12. It is pointed out that the inner diameter of the flat washer 40 does not need to be angled in order to allow it to mount the shoulder portion 23 during driving. It is found that, due ~o the resiliency of the flat washer 40, it readily expands to accommodate the shoulder portion 23. While an annular washer such as shown at 40 is not as preferred as the tetragonal-section washer 14 seen in Figures-~ and 2, it is nonetheless a functionally workable embodiment, and considered to have definite advantages over conventional sealing assemblies.
Claims (8)
1. A self-sealing threaded assembly comprising a threaded fastener and a resilient washer, the threaded fastener having a head with means by which torque can be applied to the head, the head having a substantially flat undersurface, a shoulder portion beneath said undersurface of smaller diameter than said undersurface, an inward step at the bottom of the shoulder portion, and a threaded shank sized diametrally such that an opening engageable by the threaded shank is too small to accept the shoulder portion, and would abut said inward stop, the resilient washer being of integral, resilient material throughout and having a maximum thickness greater than the axial dimension of said shoulder portion, the cross-section of the washer, taken in a plane extending radially from and including the axis of the washer, having a thicker portion closer to the axis and having a tapering portion extending with diminishing thickness away from the thicker portion and remote from the axis, said tapering portion being defined by two outwardly convergent surfaces one of which slopes away from the said undersurface of the head, the other of which slopes toward said undersurface, whereby when the threaded shank is screwed into an opening in a wall, the shoulder portion will abut the wall so that the resilient washer is squeezed between the wall and said undersurface.
2. The assembly claimed in claim 1, in which the said washer cross-section is tetragonal and has two walls forming an obtuse angle with the apex toward the washer axis, and two walls forming an acute angle with the apex away from the washer axis.
3. The assembly claimed in claim 1 or. claim 2, in which the fastener head is hexagonal.
4. The assembly claimed in claim 1 or claim 2, in which the fastener head has a hexagonal portion surmounting an integral annular portion of circular outer circumference, said undersurface being the underside of said annular portion.
5. The assembly claimed in claim 1 or claim 2, in which the shoulder portion is cylindrical.
6. The assembly claimed in claim 1 or claim 2, in which the fastener is a self-tapping screw.
7. The assembly claimed in claim 1 or claim 2, in which the inside diameter of the washer is smaller than the outside diameter of said shoulder portion.
8. The assembly claimed in claim 1 or claim 2, in which the shoulder portion is cylindrical, and in which the inside diameter of said washer is sized smaller than the diameter of said shoulder portion and such that the washer interferes with the threads on said threaded shank.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000396482A CA1171701A (en) | 1982-02-17 | 1982-02-17 | Self-sealing threaded fastener |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000396482A CA1171701A (en) | 1982-02-17 | 1982-02-17 | Self-sealing threaded fastener |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1171701A true CA1171701A (en) | 1984-07-31 |
Family
ID=4122086
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000396482A Expired CA1171701A (en) | 1982-02-17 | 1982-02-17 | Self-sealing threaded fastener |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1171701A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015002598A1 (en) * | 2013-07-01 | 2015-01-08 | Nord-Lock Ab | Fastening element and fastening assembly |
| EP2157324A3 (en) * | 2008-08-21 | 2016-03-02 | HILTI Aktiengesellschaft | Screw with sealing disc assembly |
| EP4102086A1 (en) * | 2021-06-11 | 2022-12-14 | Company Domido Limited (CY) | Self-centering sealing insert |
-
1982
- 1982-02-17 CA CA000396482A patent/CA1171701A/en not_active Expired
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2157324A3 (en) * | 2008-08-21 | 2016-03-02 | HILTI Aktiengesellschaft | Screw with sealing disc assembly |
| WO2015002598A1 (en) * | 2013-07-01 | 2015-01-08 | Nord-Lock Ab | Fastening element and fastening assembly |
| CN105358846A (en) * | 2013-07-01 | 2016-02-24 | 螺得牢有限公司 | Fastening element and fastening assembly |
| US9845821B2 (en) | 2013-07-01 | 2017-12-19 | Nord-Lock Ab | Fastening element and fastening assembly |
| CN105358846B (en) * | 2013-07-01 | 2019-03-08 | 螺得牢有限公司 | Tightening member and fastening assembly |
| EP4102086A1 (en) * | 2021-06-11 | 2022-12-14 | Company Domido Limited (CY) | Self-centering sealing insert |
| US20220397197A1 (en) * | 2021-06-11 | 2022-12-15 | Domido Limited | Self-centering sealing insert |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEC | Expiry (correction) | ||
| MKEX | Expiry |