WO1989009886A1 - Tamper-resistant rotary fasteners and tools for use with them - Google Patents
Tamper-resistant rotary fasteners and tools for use with them Download PDFInfo
- Publication number
- WO1989009886A1 WO1989009886A1 PCT/GB1989/000366 GB8900366W WO8909886A1 WO 1989009886 A1 WO1989009886 A1 WO 1989009886A1 GB 8900366 W GB8900366 W GB 8900366W WO 8909886 A1 WO8909886 A1 WO 8909886A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- recess
- tamper
- fastener
- shank
- head
- Prior art date
Links
- 230000000295 complement effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000010079 rubber tapping Methods 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
- F16B23/00—Specially shaped nuts or heads of bolts or screws for rotations by a tool
- F16B23/0007—Specially shaped nuts or heads of bolts or screws for rotations by a tool characterised by the shape of the recess or the protrusion engaging the tool
- F16B23/0046—Specially shaped nuts or heads of bolts or screws for rotations by a tool characterised by the shape of the recess or the protrusion engaging the tool having one eccentric circular or polygonal recess or protrusion
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25B—TOOLS OR BENCH DEVICES NOT OTHERWISE PROVIDED FOR, FOR FASTENING, CONNECTING, DISENGAGING OR HOLDING
- B25B13/00—Spanners; Wrenches
- B25B13/48—Spanners; Wrenches for special purposes
- B25B13/485—Spanners; Wrenches for special purposes for theft-proof screws, bolts or nuts
-
- 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
- F16B41/00—Measures against loss of bolts, nuts, or pins; Measures against unauthorised operation of bolts, nuts or pins
- F16B41/005—Measures against unauthorised operation of bolts, nuts or pins
Definitions
- This invention relates to tamper-resistant fasteners such as screw, bolts, heads for spindles of door catches and other devices where a rotary fastening movement or unfastening movement is required.
- the object of the invention is to provide an improved tamper-resistant fastener and a corresponding tool.
- the invention is based on the use, in the head of the fastener of a double cylindrical recess of which the parts are eccentric with respect to each other.
- the further recess has a common tangent with the first recess.
- the diameter of the further recess may be less than half that of the first recess and in one embodiment substantially less than half the first recess. However, a preferred embodiment of the invention provides for the further recess a diameter which is substantially more than half that of the -first recess.
- the invention also includes within its scope a tool for use with a fastener according to the invention, the tool being characterised by a cylindrical shank portion having at its end a cylindrical extension which is of lesser diameter than the shank portion and is eccentric relative thereto.
- a further aspect of the invention comprises a combination of a fastener and a tool according to the invention.
- FIG. 1 of the accompanying drawings shows in section one embodiment of a screw according to the invention.
- Figure 2 illustrates in section a screwdriver for use with a screw according to Figure 1.
- Figure 3 illustrates in plan form a preferred configuration of the recesses which are characteristic of a screw according to the invention.
- FIG. 1 of the drawings illustrates one form of a screw according to the invention.
- the application of the invention to a screw is merely by way of example and the invention may be used as rotary fasteners generally.
- the screw 1 has a head 2 which may be in any suitable form and a shank 3 which in this embodiment of the invention has a terminal threaded portion 4.
- the screw may be a self-tapping screw but other forms of screw or bolt may embody the invention.
- a circular recess 5 which is coaxial with the shank and the threaded portion 4.
- a further recess 6 which is likewise circular in section and is eccentric relative to the recess 5.
- the recess 6 has a common tangent with the recess 5 ; in other words the circles defining the cross sections of the recesses 5 and 6 touch at one point.
- the screw head 2 is preferably countersunk. Thus, when it is fully screwed home by means of a tool as described in Figure 2, there is no flat or other angular portion by means of which some other tool can be used to obtain a purchase on the screw.
- the tool shown in Figure 2 is formed in complementary manner to the recess in the head 2 of the screw 1.
- the tool or screwdriver 7 preferably has a handle 8, a shank or shaft 9 which is cylindrical at least in a terminal portion, the terminal part 11 of the shank 9 being formed with a cylindrical extension 10 which is eccentric relative to the shank 9 in a manner similar to the disposition of the recess 6 relative to the recess 5.
- the tool 7 is simply inserted into the recess 5, the extension 10 being located in the recess 6, the eccentricity of the recesses 5 and 6 enabling the tool to obtain purchase on the screw.
- the recess 6 has a very much smaller diameter than the recess 5. However, it is generally preferable to make the diameter of the recess 6 a substantial fraction of the diameter of the recess 5 and it is probably preferable to make the diameter of the recess 6 more than half that of the recess 5.
- Figure 3 shows, not to the same scale as Figures 1 and 2, the recesses 5 and 6 in plan, the recess 6 being slightly more than half the diameter of the recess 5.
- the upper recess is coaxial with the axis defined in the embodiment by the shank " but which is in any case the axis about which the head is to be
- tool 7 would be supplied in restricted quantities to authorised users so as to obtain some control over the use of the combination of fasteners and tools and thereby enhance the security provided by the construction of the fastener.
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Connection Of Plates (AREA)
Abstract
A tamper-resistant threaded fastener (1) comprises a head (2) and shank (3) having a threaded part (4), the head having a circular recess (5) which is coaxial with the screw threading (4) and, at the bottom of the said recess (5) a further circular recess (6) which is of lesser diameter than the first recess and has a common tangent therewith. A tool for use with such a fastener is characterised by a cylindrical shank portion having at its end a cylindrical extension which is of lesser diameter than the shank portion and is eccentric relative thereto.
Description
TAMPER-RESISTANT ROTARY FASTENERS AND TOOLS FOR USE WITH THEM
This invention relates to tamper-resistant fasteners such as screw, bolts, heads for spindles of door catches and other devices where a rotary fastening movement or unfastening movement is required.
It is generally known to provide tamper-resistant screws and other fasteners with specially shaped heads that require special tools for their fastening and unfastening but which are comparatively inaccessible or difficult to operate using ordinary tools. Most of the proposals in the prior art have flats or other angled recesses which can, albeit with difficulty in some cases, be gripped other than by the special tool for which the screw is designed.
The object of the invention is to provide an improved tamper-resistant fastener and a corresponding tool. The invention is based on the use, in the head of the fastener of a double cylindrical recess of which the parts are eccentric with respect to each other.
SUBSTITUTE SHEET
According to the invention, a tamper-resistant fastener which is rotatable about a defined axis comprises a head having a circular recess and, at the bottom of the said recess, a further circular recess which is of lesser diameter than the first recess and is eccentric relative thereto, one of the reces'ses being coaxial with the said axis.
Preferably, the further recess has a common tangent with the first recess.
The diameter of the further recess may be less than half that of the first recess and in one embodiment substantially less than half the first recess. However, a preferred embodiment of the invention provides for the further recess a diameter which is substantially more than half that of the -first recess.
The invention also includes within its scope a tool for use with a fastener according to the invention, the tool being characterised by a cylindrical shank portion having at its end a cylindrical extension which is of lesser diameter than the shank portion and is eccentric relative thereto. A further aspect of the invention comprises a combination of a fastener and a tool according to the invention.
SUBST.TUTE SHEET
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 of the accompanying drawings shows in section one embodiment of a screw according to the invention.
Figure 2 illustrates in section a screwdriver for use with a screw according to Figure 1.
Figure 3 illustrates in plan form a preferred configuration of the recesses which are characteristic of a screw according to the invention.
DETAILED DESCRIPTION
Figure 1 of the drawings illustrates one form of a screw according to the invention. The application of the invention to a screw is merely by way of example and the invention may be used as rotary fasteners generally.
The screw 1 has a head 2 which may be in any suitable form and a shank 3 which in this embodiment of the invention has a terminal threaded portion 4. The screw may be a self-tapping screw but other forms of screw or bolt may embody the invention.
Formed in the head of the screw is a circular recess 5 which is coaxial with the shank and the threaded portion 4. At the bottom of the recess 5 is a further recess 6 which is likewise circular in section and is eccentric relative to the recess 5. Preferably the recess 6 has a common tangent with the recess 5 ; in other words the circles defining the cross sections of the recesses 5 and 6 touch at one point.
SUBSTITUTE SHEET
The screw head 2 is preferably countersunk. Thus, when it is fully screwed home by means of a tool as described in Figure 2, there is no flat or other angular portion by means of which some other tool can be used to obtain a purchase on the screw.
The tool shown in Figure 2 is formed in complementary manner to the recess in the head 2 of the screw 1. The tool or screwdriver 7 preferably has a handle 8, a shank or shaft 9 which is cylindrical at least in a terminal portion, the terminal part 11 of the shank 9 being formed with a cylindrical extension 10 which is eccentric relative to the shank 9 in a manner similar to the disposition of the recess 6 relative to the recess 5.
In use, the tool 7 is simply inserted into the recess 5, the extension 10 being located in the recess 6, the eccentricity of the recesses 5 and 6 enabling the tool to obtain purchase on the screw.
In the embodiment shown in Figure 1 the recess 6 has a very much smaller diameter than the recess 5. However, it is generally preferable to make the diameter of the recess 6 a substantial fraction of the diameter of the recess 5 and it is probably preferable to make the diameter of the recess 6 more than half that of the recess 5. Figure 3 shows, not to the same scale as Figures 1 and 2, the recesses 5 and 6 in plan, the recess 6 being slightly more than half the diameter of the recess 5.
In the foregoing description the upper recess is coaxial with the axis defined in the embodiment by the shank " but which is in any case the axis about which the head is to be
SUBSTITUTE SHEET
turned. However it is feasible to make the second or lower recess coaxial with that defined axis i.e., in this form of the invention, coaxial with the shank. The cooperating tool would then have its extension 10 coaxial with the shank, the part 11 being eccentric relative thereto.
It is envisaged that tool 7 would be supplied in restricted quantities to authorised users so as to obtain some control over the use of the combination of fasteners and tools and thereby enhance the security provided by the construction of the fastener.
SUBSTITUTE SHEET
Claims
1. A tamper-resistant fastener which is rotatable about a defined axis and comprises a head (2) having a circular recess (5) and, at the bottom of the said recess, a further circular recess (6) which is of lesser diameter than the first recess and is eccentric relative thereto, one of the recesses being coaxial with the said axis.
2. A tamper-resistant threaded fastener (1) comprising a head (2) and a shank (3) having a screw threaded part, the head having a circular recess (5) which is coaxial with the screw threading (4) of the shank and, at the bottom of the said recess, a further circular recess (6) which is of lesser diameter than the first recess (5) and is eccentric relative thereto.
3. A fastener according to claim 1 or 2 in which the recesses have a common tangent.
4. A fastener according to claim 3 in which the diameter of the further recess is substantially less than half that of the first recess.
5. A fastener according to claim 3 in which the diameter of the further recess (5) is more than half that of the first recess (6) .
6. A tool for use with the fastener according to any foregoing claim and characterised by a cylindrical shank portion (9) having at its end a cylindrical extension {10)
SUBSTITUTE SHEET which is of lesser diameter than the shank portion and is eccentric relative thereto.
7. The combination of a fastener according to any of claims 1 to 5 and a tool according to claim 6.
SUBSTITUTE SHEET
Applications Claiming Priority (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8808434.8 | 1988-04-11 | ||
GB888808434A GB8808434D0 (en) | 1988-04-11 | 1988-04-11 | Tamper-resistant threaded fasteners & screw-drivers for use with them |
GB888808906A GB8808906D0 (en) | 1988-04-15 | 1988-04-15 | Tamper-resistant threaded fasteners & tools for use with them |
GB8808906.5 | 1988-04-15 | ||
GB8809764.7 | 1988-04-25 | ||
GB888809764A GB8809764D0 (en) | 1988-04-11 | 1988-04-25 | Tamper-resistant fasteners & tools for use with them |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1989009886A1 true WO1989009886A1 (en) | 1989-10-19 |
Family
ID=27263859
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB1989/000366 WO1989009886A1 (en) | 1988-04-11 | 1989-04-10 | Tamper-resistant rotary fasteners and tools for use with them |
Country Status (1)
Country | Link |
---|---|
WO (1) | WO1989009886A1 (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1002962A1 (en) * | 1998-11-19 | 2000-05-24 | France Telecom | Device for securing a fixing element |
GB2361043A (en) * | 2000-04-07 | 2001-10-10 | Uniscrew Ltd | Driving head for a fastener having at least two recesses |
WO2005042985A2 (en) * | 2003-10-24 | 2005-05-12 | Flesher Robert W | Tamper-resistant fastener and method and tool for use with same |
WO2011124823A1 (en) * | 2010-04-06 | 2011-10-13 | Ateliers Lr Etanco | Break-in resistant screw and securing system using such a screw |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4258596A (en) * | 1978-01-18 | 1981-03-31 | Southco, Inc. | Tamper-resistant fastener |
US4473169A (en) * | 1982-02-22 | 1984-09-25 | Fitzgerald Fitz E | Anti-theft plug and fastener |
DE8533887U1 (en) * | 1984-12-14 | 1986-03-27 | Ruote O.Z. S.p.A., Bassano del Grappa, Vicenza | Theft-proof screw for attaching the wheel cover to the wheels of motor vehicles |
-
1989
- 1989-04-10 WO PCT/GB1989/000366 patent/WO1989009886A1/en unknown
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4258596A (en) * | 1978-01-18 | 1981-03-31 | Southco, Inc. | Tamper-resistant fastener |
US4473169A (en) * | 1982-02-22 | 1984-09-25 | Fitzgerald Fitz E | Anti-theft plug and fastener |
DE8533887U1 (en) * | 1984-12-14 | 1986-03-27 | Ruote O.Z. S.p.A., Bassano del Grappa, Vicenza | Theft-proof screw for attaching the wheel cover to the wheels of motor vehicles |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1002962A1 (en) * | 1998-11-19 | 2000-05-24 | France Telecom | Device for securing a fixing element |
GB2361043A (en) * | 2000-04-07 | 2001-10-10 | Uniscrew Ltd | Driving head for a fastener having at least two recesses |
WO2005042985A2 (en) * | 2003-10-24 | 2005-05-12 | Flesher Robert W | Tamper-resistant fastener and method and tool for use with same |
WO2005042985A3 (en) * | 2003-10-24 | 2005-11-24 | Robert W Flesher | Tamper-resistant fastener and method and tool for use with same |
US7441483B2 (en) | 2003-10-24 | 2008-10-28 | Flesher Robert W | Tamper-resistant fastener and method and tool for use with same |
WO2011124823A1 (en) * | 2010-04-06 | 2011-10-13 | Ateliers Lr Etanco | Break-in resistant screw and securing system using such a screw |
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