GB2156934A - Screw fasteners - Google Patents

Screw fasteners Download PDF

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Publication number
GB2156934A
GB2156934A GB08404970A GB8404970A GB2156934A GB 2156934 A GB2156934 A GB 2156934A GB 08404970 A GB08404970 A GB 08404970A GB 8404970 A GB8404970 A GB 8404970A GB 2156934 A GB2156934 A GB 2156934A
Authority
GB
United Kingdom
Prior art keywords
screw
dome
fastener
shaped portion
tool
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.)
Withdrawn
Application number
GB08404970A
Other versions
GB8404970D0 (en
Inventor
John Edward Pearce
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.)
HYBLOCK SALES Ltd
Original Assignee
HYBLOCK SALES Ltd
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 HYBLOCK SALES Ltd filed Critical HYBLOCK SALES Ltd
Priority to GB08404970A priority Critical patent/GB2156934A/en
Publication of GB8404970D0 publication Critical patent/GB8404970D0/en
Publication of GB2156934A publication Critical patent/GB2156934A/en
Withdrawn legal-status Critical Current

Links

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
    • 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
    • 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
    • F16B31/00—Screwed connections specially modified in view of tensile load; Break-bolts
    • F16B31/02—Screwed connections specially modified in view of tensile load; Break-bolts for indicating the attainment of a particular tensile load or limiting tensile load
    • F16B31/021—Screwed connections specially modified in view of tensile load; Break-bolts for indicating the attainment of a particular tensile load or limiting tensile load by means of a frangible part
    • 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

Abstract

A screw fastener comprising a member having a part spherical dome-shaped portion 10 and a tool engageable polygonal portion 11 connected to the dome shaped portion by a breakable connection portion (12) of reduced thickness, the dome-shaped portion having an internally threaded bore 13. The portion 11 is detached by turning it relative to the dome-shaped portion after tightening. The dome-shaped portion cannot be conveniently gripped by a tool for subsequent removal. Flat-sided portion 17 prevents rotation of the fastener. <IMAGE>

Description

SPECIFICATION Screw Fasteners This invention relates to screw fasteners primarily intended for fastening objects together in a tamperproof manner.
A screw fastener in accordance with the invention comprises a member having a dome-shaped portion of substantially circular external crosssection and a tool engageable portion of noncircular section connected to said dome-shaped portion by a connecting portion of reduced thickness, the dome-shaped portion having an internally threaded bore and the arrangement being such that the fastener can be engaged with a co-acting screw and tightened utilizing a tool engaged with said tool engageable portion, and the connecting portion can then be broken by turning of the tool engageable portion relative to the dome portion so as to leave the dome-shaped portion on the screw.
An example of the invention is shown in the accompanying drawings in which Figure 1, is a part-sectional view of an embodiment of a screw fastener in accordance with the invention and Figure 2 is a view of the fastener of Figure 1 aftertightening on to a co-acting screw.
As shown in Figure 1 the screw fastener includes a dome-shaped portion 10, which preferably has a part-spherical outer surface, and a tool engageable portion 11 which is hexagonal in section so as to be engageable by a spanner or wrench. The two portions 10, 11 are connected together by a connecting portion 12. A threaded bore 13 is formed in the portion 10 and a co-axial counter bore 14 is formed in the portion 11 and extends into the connecting portion 12 so that portion 12 has a relatively thin wall.
The fastener of Figure 1 is intended to be used with a screw as shown in Figure 2. The screw has a threaded shank 15 complementary with the threaded bore 13. The head 16 of the screw is of flattish domed configuration with a central conical recess 16a. The head 16 is joined to the shank 15 by an intermediate portion 17 of diameter larger than the shank. Portion 18 is formed with two flats 17a on opposite sides.
The screw is inserted through two parts to be joined together and pressed into place like a coach bolt so that it is held in position by the flats 17a. The fastener of Figure 1 is then engaged with the shank 15 and tightened using a suitable spanner or wrench. Once the fastener is tight, increasing torque is applied to the portion 11 using the spanner or wrench until the connecting portion 12 shears.
This operation leaves just the dome-shaped portion 10 on the screw. Removal of this remaining portion 12 is extremely difficult since it is very difficult to grip the part spherical surface thereof with a tool, which will tend to slip axially rather than providing a good grip. Should it become necessary for the fastener to be removed, a drill bit can be located in the recess 16a and the shank removed by drilling. In its preferred mode of use, however, the fastener would be used in a situation in which the screw head 16 is inaccessible to an unauthorised person.
It will be appreciated that the portion 10 need not be part-spherical so long as it has a circular cross-section. Furthermore the portion 11 can be of some non-circuiar sectional shape other than hexagonal.
1. A screw fastener comprising a member having a dome-shaped portion of substantially circular external cross-section and a tool engageable portion of non-circuiar section connected to said dome-shaped portion by a connecting portion of reduced thickness, the dome-shaped portion having an internally threaded bore and the arrangement being such that the fastener can be engaged with a co-acting screw and tightened utilizing a tool engaged with said tool engageable portion, and the connecting portion can then be broken by turning of the tool engageable portion relative to the dome portion so as to leave the dome-shaped portion on the screw.
2. A screw fastener as claimed in claim 1 in which said dome-shaped portion is of part-spherical configuration.
3. A screw fastener as claimed in claim 1 or claim 2 in which said tool engageable portion is of non-circular cross-section externally.
4. A screw fastener as claimed in claim 3 in which said non-circular cross-section is hexagonal.
5. A screw fastener as claimed in any preceding claim in combination with a coacting screw.
6. The combination claimed in claim 5 in which the screw has a dome-shaped head.
7. The combination claimed in claim 6 in which the head is formed with a central conical recess.
8. The combination claimed in claim 6 or claim 7 in which the screw has an intermediate portion beween the shank and said head, said intermediate portion being of larger diameter than the shank and formed with flats to prevent it turning when in use.
9. The combination claimed in claim 8 in which there is a single pair of flats on opposite sides of said intermediate portion.
10. A screw fastener substantially as hereinbefore described with reference to and as shown in the accompanying drawings.
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Screw Fasteners This invention relates to screw fasteners primarily intended for fastening objects together in a tamperproof manner. A screw fastener in accordance with the invention comprises a member having a dome-shaped portion of substantially circular external crosssection and a tool engageable portion of noncircular section connected to said dome-shaped portion by a connecting portion of reduced thickness, the dome-shaped portion having an internally threaded bore and the arrangement being such that the fastener can be engaged with a co-acting screw and tightened utilizing a tool engaged with said tool engageable portion, and the connecting portion can then be broken by turning of the tool engageable portion relative to the dome portion so as to leave the dome-shaped portion on the screw. An example of the invention is shown in the accompanying drawings in which Figure 1, is a part-sectional view of an embodiment of a screw fastener in accordance with the invention and Figure 2 is a view of the fastener of Figure 1 aftertightening on to a co-acting screw. As shown in Figure 1 the screw fastener includes a dome-shaped portion 10, which preferably has a part-spherical outer surface, and a tool engageable portion 11 which is hexagonal in section so as to be engageable by a spanner or wrench. The two portions 10, 11 are connected together by a connecting portion 12. A threaded bore 13 is formed in the portion 10 and a co-axial counter bore 14 is formed in the portion 11 and extends into the connecting portion 12 so that portion 12 has a relatively thin wall. The fastener of Figure 1 is intended to be used with a screw as shown in Figure 2. The screw has a threaded shank 15 complementary with the threaded bore 13. The head 16 of the screw is of flattish domed configuration with a central conical recess 16a. The head 16 is joined to the shank 15 by an intermediate portion 17 of diameter larger than the shank. Portion 18 is formed with two flats 17a on opposite sides. The screw is inserted through two parts to be joined together and pressed into place like a coach bolt so that it is held in position by the flats 17a. The fastener of Figure 1 is then engaged with the shank 15 and tightened using a suitable spanner or wrench. Once the fastener is tight, increasing torque is applied to the portion 11 using the spanner or wrench until the connecting portion 12 shears. This operation leaves just the dome-shaped portion 10 on the screw. Removal of this remaining portion 12 is extremely difficult since it is very difficult to grip the part spherical surface thereof with a tool, which will tend to slip axially rather than providing a good grip. Should it become necessary for the fastener to be removed, a drill bit can be located in the recess 16a and the shank removed by drilling. In its preferred mode of use, however, the fastener would be used in a situation in which the screw head 16 is inaccessible to an unauthorised person. It will be appreciated that the portion 10 need not be part-spherical so long as it has a circular cross-section. Furthermore the portion 11 can be of some non-circuiar sectional shape other than hexagonal. CLAIMS
1. A screw fastener comprising a member having a dome-shaped portion of substantially circular external cross-section and a tool engageable portion of non-circuiar section connected to said dome-shaped portion by a connecting portion of reduced thickness, the dome-shaped portion having an internally threaded bore and the arrangement being such that the fastener can be engaged with a co-acting screw and tightened utilizing a tool engaged with said tool engageable portion, and the connecting portion can then be broken by turning of the tool engageable portion relative to the dome portion so as to leave the dome-shaped portion on the screw.
2. A screw fastener as claimed in claim 1 in which said dome-shaped portion is of part-spherical configuration.
3. A screw fastener as claimed in claim 1 or claim 2 in which said tool engageable portion is of non-circular cross-section externally.
4. A screw fastener as claimed in claim 3 in which said non-circular cross-section is hexagonal.
5. A screw fastener as claimed in any preceding claim in combination with a coacting screw.
6. The combination claimed in claim 5 in which the screw has a dome-shaped head.
7. The combination claimed in claim 6 in which the head is formed with a central conical recess.
8. The combination claimed in claim 6 or claim 7 in which the screw has an intermediate portion beween the shank and said head, said intermediate portion being of larger diameter than the shank and formed with flats to prevent it turning when in use.
9. The combination claimed in claim 8 in which there is a single pair of flats on opposite sides of said intermediate portion.
10. A screw fastener substantially as hereinbefore described with reference to and as shown in the accompanying drawings.
GB08404970A 1984-02-25 1984-02-25 Screw fasteners Withdrawn GB2156934A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB08404970A GB2156934A (en) 1984-02-25 1984-02-25 Screw fasteners

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB08404970A GB2156934A (en) 1984-02-25 1984-02-25 Screw fasteners

Publications (2)

Publication Number Publication Date
GB8404970D0 GB8404970D0 (en) 1984-03-28
GB2156934A true GB2156934A (en) 1985-10-16

Family

ID=10557181

Family Applications (1)

Application Number Title Priority Date Filing Date
GB08404970A Withdrawn GB2156934A (en) 1984-02-25 1984-02-25 Screw fasteners

Country Status (1)

Country Link
GB (1) GB2156934A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2218170A (en) * 1988-03-31 1989-11-08 Mark John Charles Stevens Tension control stud bolt
GB2259554A (en) * 1991-09-13 1993-03-17 Security Fasteners And Fixings Anti-tamper cover for nut or bolthead

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB867012A (en) * 1957-02-28 1961-05-03 Hi Shear Rivet Tool Company Improvements relating to nut and bolt fasteners
GB1098864A (en) * 1964-04-28 1968-01-10 Standard Pressed Steel Co Lock nut
GB1144080A (en) * 1968-01-19 1969-03-05 Gkn Screws Fasteners Ltd Improvements in or relating to nuts
GB1204294A (en) * 1968-02-16 1970-09-03 Lockheed Aircraft Corp Nut formed with multiple torque-off collars
GB1208171A (en) * 1968-01-31 1970-10-07 Hi Shear Corp Inherently torque-limited fastener
GB1238374A (en) * 1967-07-31 1971-07-07
GB1252834A (en) * 1968-09-09 1971-11-10

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB867012A (en) * 1957-02-28 1961-05-03 Hi Shear Rivet Tool Company Improvements relating to nut and bolt fasteners
GB1098864A (en) * 1964-04-28 1968-01-10 Standard Pressed Steel Co Lock nut
GB1238374A (en) * 1967-07-31 1971-07-07
GB1144080A (en) * 1968-01-19 1969-03-05 Gkn Screws Fasteners Ltd Improvements in or relating to nuts
GB1208171A (en) * 1968-01-31 1970-10-07 Hi Shear Corp Inherently torque-limited fastener
GB1204294A (en) * 1968-02-16 1970-09-03 Lockheed Aircraft Corp Nut formed with multiple torque-off collars
GB1252834A (en) * 1968-09-09 1971-11-10

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2218170A (en) * 1988-03-31 1989-11-08 Mark John Charles Stevens Tension control stud bolt
GB2259554A (en) * 1991-09-13 1993-03-17 Security Fasteners And Fixings Anti-tamper cover for nut or bolthead
GB2259554B (en) * 1991-09-13 1995-04-05 Security Fasteners And Fixings Fastener and cover and method of covering a part of a fastener

Also Published As

Publication number Publication date
GB8404970D0 (en) 1984-03-28

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)