WO1999002870A1 - Torque limiting device - Google Patents

Torque limiting device Download PDF

Info

Publication number
WO1999002870A1
WO1999002870A1 PCT/GB1998/001983 GB9801983W WO9902870A1 WO 1999002870 A1 WO1999002870 A1 WO 1999002870A1 GB 9801983 W GB9801983 W GB 9801983W WO 9902870 A1 WO9902870 A1 WO 9902870A1
Authority
WO
WIPO (PCT)
Prior art keywords
torque
arm
tool
fastener
torque limiting
Prior art date
Application number
PCT/GB1998/001983
Other languages
French (fr)
Inventor
Douglas John Gibbons
Original Assignee
Qed Intellectual Property Limited
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 Qed Intellectual Property Limited filed Critical Qed Intellectual Property Limited
Priority to AU82315/98A priority Critical patent/AU8231598A/en
Publication of WO1999002870A1 publication Critical patent/WO1999002870A1/en

Links

Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16BDEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
    • F16B31/00Screwed connections specially modified in view of tensile load; Break-bolts
    • F16B31/02Screwed connections specially modified in view of tensile load; Break-bolts for indicating the attainment of a particular tensile load or limiting tensile load

Definitions

  • the present invention relates to a torque limiting device, such as a torque limiting threaded fastener.
  • Torque limiting wrenches are commonly used to apply a pre- determined torque to such devices.
  • torque wrenches are relatively expensive and consequently torque limiting fasteners, such as nuts, are frequently used.
  • Torque limiting fasteners are generally used in areas where they may become loose and require tightening, such as in the aircraft and automotive industries. Their use in other areas is more restricted due to the relatively high cost of manufacture.
  • a torque limiting device is described in United States Patent No. 3,709,087.
  • the invention resides in the use of a socket element adapted to be torqued by a conventional wrench.
  • the socket element surrounds and is resiliently interconnected with the normal torque applying surfaces of a conventional threaded fastener.
  • the design of the socket element has to be adapted for fasteners of different shapes and sizes.
  • a torque limiting nut assembly is disclosed in United States Patent No. 4,176,582 (Microdot Inc.).
  • the nut assembly has a ratchet construction with a separate wrenching member. Torque is applied to the nut with a conventional wrench acting on the wrenching member.
  • the ratchet construction is set to permit assembly torque of a preselected magnitude, at which point ratcheting begins, preventing the application of additional torque.
  • This device is fairly complex in design, and requires the use of a specially designed wrench.
  • An aim of the present invention is to provide a torque limiting device that is simpler and cheaper to manufacture than existing torque limiting devices.
  • a torque limiting device comprising a body, the body having at least two engagable surfaces which, in use, engage a structure, characterised in that the body has at least one slot therein defining an arm with respect to an adjoining engagable surface, said arm being elastically deformable and deflectable upon application of a force exerted on the arm by the structure, said arms being constructed, dimensioned and arranged relative to the body and the structure so as to permit relative movement therebetween on application of a torque exceeding a predetermined value.
  • a torque limiting threaded fastener the thread of the fastener defining an axis about which the fastener may be rotated relative to a matching thread in order to tighten the fastener, comprising a plurality of adjacent tool engaging surfaces which a tool may engage to tighten the fastener, each surface lying generally in a plane parallel with the fastener axis, characterised in that one or more surfaces has a slot therein, the slot in one tool engaging surface defining a wall with an adjacent tool engaging surface, said wall being elastically deformable in order to limit the maximum torque a tightening tool may apply to the fastener.
  • the structure engaged with the body may be a wrench, a spanner, or other tool.
  • the structure may also be the inside of a shaft into which the torque limiting device has been inserted.
  • the engagable surfaces of the body lie substantially in a plane parallel to the axis of rotation of the device.
  • the engagable surfaces may, however, be inclined at an angle to the axis of rotation.
  • the arms of the device preferably have an outer surface and an inner surface, the outer surface being an engagable surface of the body, and the inner surface being defined by one side of a slot in the body.
  • the outer surface of the arm and the inner surface of the arm may be substantially parallel.
  • the arms are tapered, the free end of the arm being narrower than the fixed end of the arm. This spreads the amount of strain throughout the arm when a force is applied to the arm.
  • at least one edge of the device is formed so as to reduce stress concentrations within the device. Most preferably this takes the form of a rounded edge.
  • the torque limiting device has a polygonal cross-section.
  • the device may have a triangular, square, pentagonal, or, most preferably, a hexagonal cross-section.
  • the device has a cavity formed therein, the cavity being dimensioned so as to receive a member such as a shaft or a shank.
  • the cavity may extend only partially through the body of the device, or it may be in the form of a hole.
  • the surfaces defining the cavity or hole may bear at least one groove or thread.
  • the slots formed in the torque limiting device and/or the threaded fastener may receive a volume of energy absorbing material which acts as a damper. This may reduce component wear, and reduce noise and vibration.
  • the energy absorbing material is an unfilled elastomer such as nitrile rubber, butyl rubber, or polycholorprene, or a copolymer such as nitrile isoprene copolymer.
  • the threaded fastener and/or torque limiting device are composed of a polymer such as Nylon.
  • the fastener and/or device may also be made from a high strength aluminium alloy, titanium alloy, or steel.
  • the fastener and/or device may be injection moulded, cast, or machined, depending on the material used for manufacture.
  • a tool comprising a shank and a head for engaging a recess of a component, the head of the tool comprising the previously described torque limiting device.
  • An example of such a tool is an Allen key, which may be used for tightening and untightening a hex socket fastener.
  • a tool bit comprising a head, a neck, and a body, the head of the tool bit comprising the previously described torque limiting device.
  • the body of the tool bit may have a square or a rectangular cross- section, and it may contain a cavity.
  • the cavity may be dimensioned so as to receive, for example, the drive of a conventional ratchet tool.
  • the torque limiting device may be fitted to an output shaft of an electric motor.
  • a device for limiting torque transmitted to an object by a torque transmitting means the device being adapted to engage said object, and comprising a body dimensioned and arranged to be received by the torque transmitting means, said body including at least one resiliently deformable member which is arranged to deform upon application of a torque which exceeds a predetermined value, thereby decoupling the torque transmitting means from the object.
  • This device may be used for tightening nuts.
  • Figure 1 shows a perspective view of a torque limiting nut, according to the invention
  • Figure 2 shows a perspective view of a torque limiting device having a triangular cross- section, according to the invention
  • Figure 2a shows a plan view of the device of Figure 2, according to the invention
  • Figure 2b shows a plan view of a torque limiting device having a cavity, according to the invention
  • Figure 3 shows a plan view of an arm of a torque limiting device, according to the invention
  • Figure 3a shows a stress contour plot of an arm under load, according to the invention
  • Figure 4 shows a perspective view of a tool having a torque limiting head, according to the invention
  • Figure 5a shows a diagrammatical view of a tool bit having a torque limiting head
  • Figure 5b shows a perspective view of a tool bit having a torque limiting head, according to the invention
  • Figure 6 shows a perspective view of a motor and a motor output shaft having a torque limiting head, according to the invention
  • Figure 7 shows a cross-section and a plan view of a device for limiting torque transmitted to an object, according to the invention.
  • Figure 1 shows a torque limiting nut 10 with an inner threaded surface 16.
  • the nut 10 has a plurality of deformable engaging surfaces 12 in which slots 18 are formed. Slots 18 may be formed by machining a conventional nut, thereby producing a torque limiting device 10. Alternatively, the nut 10 having slots 18 may be cast, or injection moulded, depending on the material used for manufacturing the nut.
  • a torque limiting device 20 having a head 22 with triangular cross-section, and a body 24 is shown in Figure 2.
  • Body 24 may be a threaded body.
  • Slots 18 are formed in the head 22, giving arms 11.
  • the arms 11 are positioned so that the device 20 may be tightened in a clockwise direction.
  • the arms yield inwardly. This ensures that the device 20 may only be tightened a predetermined amount.
  • the value of this predetermined torque depends on certain characteristics of the head 22 of the device.
  • Figure 2a shows the device 20 in plan view.
  • Figure 2b shows, in plan view, the head 22 of device 20 having a cavity 24 formed therein.
  • the cavity, or hole may be of a dimension suitable for a shaft or shank to be received by the cavity. This enables the torque limiting head 22 to be used as one component of another device.
  • Figure 3 shows, in plan view, an arm 11 of a torque limiting device.
  • the torque limiting device may be designed so that it may only be tightened using a predetermined amount of torque.
  • the value of the predetermined amount of torque depends on the dimensions of the arms (or walls) of the device.
  • the amount of applied torque which may be applied to the device before slippage of a surface contacting the device occurs may be increased a) by increasing the thickness of the arms, b) by reducing the length of the arms, or c) by increasing the length of the device itself.
  • Figure 3a shows a stress contour plot of arm 11 when under load. It can be seen from the stress contour plot that corner 28, formed by the meeting of adjoining engagable surfaces, is highly stressed under loading. This may cause wear on the device. Corner 28 should therefore be rounded to increase the area which may be contacted by a torque applying tool in order to reduce wear and stress. It can also be seen from the plot of Figure 3a that the end 26 of the slot 18 is the point of greatest stress. The corners of the slot defining arm 11 are therefore rounded in order to reduce stress under loading at this point.
  • Slot 18 is dimensioned so that the arm 11 may bend freely under full loading. Depending on the flexibility of the material used to manufacture the device, slot 18 may be dimensioned so that, under full loading, the arm does not contact a nearby surface. If the material is fairly flexible, however, slot 18 may be dimensioned so that it comes into contact with a nearby surface under full loading, allowing a greater torque to be applied to the device.
  • the material from which device 22 is manufactured must be flexible enough for the arms 11 to bend without yielding, and strong enough for bearing a load. The material should therefore behave as a spring. In order to select the best materials, the value of e max (the maximum strain of the material before yielding occurs) should be high. & ⁇ a ⁇ is found
  • E the Youngs modulus of the material
  • ⁇ max the maximum stress occurs (either compressive, tensile, or shear) applied before yielding.
  • Suitable materials from which device 22 may be manufactured are engineering polymers such as Nylon, composite materials, or very high strength aluminium alloys, titanium alloys and steel.
  • FIGS 4 to 6 illustrate devices or components incorporating the torque limiting device of the invention.
  • Figure 4 shows an Allen key 40 having a shank 42 and a head 44, the head 44 being a torque limited device.
  • the torque limiting device has a hexagonal cross- section. This tool is suitable for tightening a hex socket fastener.
  • Figures 5a and 5b show a torque limiting attachment 50 for a square-drive ratchet.
  • Attachment 50 has a square drive portion 56, a torque limiting head 52, and a threaded shaft 54 therebetween.
  • the torque limiting head 52 is in contact with a narrow internal surface of a tool 58 into which head 52 has been inserted.
  • An adjusting ring 60 is held transversely at the base of the tool 58.
  • the adjusting ring may be turned, raising and lowering attachment 50 by means of a thread in contact with threaded shaft 54.
  • the arms of flexible head 52 are deflected radially inward when a predetermined torque is applied to the head 52, allowing attachment 50 to slip relative to tool 58.
  • Figure 6 shows an electric motor 62 connected to a motor output shaft 68.
  • Motor output shaft 68 is fitted with a torque limiter 66, and limiter 66 is connected to a drive train 64. If the torque applied to turn output shaft 68 is increased to a level which would normally cause the motor to stall, limiter 66 allows the motor 62 to continue turning, thus preventing burn out of the motor.
  • the limiter 66 can therefore be thought of as a mechanical fuse, preventing damage to drive train 64 in the event of component malfunction.
  • the slots 11 of the torque limiter 66 may be filled with an energy absorbing material acting as a damper. This has the effect of reducing vibration in the drive train 64, reducing noise, and reducing component wear.
  • Figure 7 shows a nut tightening device 70, having deformable arms 11.
  • Device 70 has a cavity 72 formed therein for receiving objects such as nuts.
  • the cavity 72 is hexagonal for receiving hexagonal nuts.
  • arms 11 Upon application of a torque which exceeds a predetermined value to device 70, arms 11 are deformed inwards, thereby decoupling the torque being transmitted to the nut. The nut can therefore only be tightened by a predetermined amount.
  • torque limiting device has been described as having a triangular or hexagonal cross-section. It will be appreciated that torque limiting devices with other polygonal cross-sections such as pentagons may also be used.

Abstract

A device for limiting torque, the device comprising a body, the body having a number of tool engageable surfaces (12). Slots (18) are formed in at least one tool engagable surface, a slot defining an arm (11) with respect to an adjoining tool engagable surface. The arm is elastically deformable and deflectable upon application of a force exerted on the arm. When a torque exceeding a predetermined value is applied to the body of the device during tightening, the arms (11) are deflected radially inward preventing over-tightening of the device. The invention, in a preferred embodiment, offers an advantage over existing torque limiting devices because the device is cheap and simple to manufacture, and is reusable.

Description

TORQUE LIMITING DEVICE
The present invention relates to a torque limiting device, such as a torque limiting threaded fastener.
It is often necessary, for safety or other reasons, to limit the amount of torque applied to a nut, bolt or other device. Torque limiting wrenches are commonly used to apply a pre- determined torque to such devices. However, torque wrenches are relatively expensive and consequently torque limiting fasteners, such as nuts, are frequently used. Torque limiting fasteners are generally used in areas where they may become loose and require tightening, such as in the aircraft and automotive industries. Their use in other areas is more restricted due to the relatively high cost of manufacture.
An example of a torque limiting device is described in United States Patent No. 3,709,087. The invention resides in the use of a socket element adapted to be torqued by a conventional wrench. The socket element surrounds and is resiliently interconnected with the normal torque applying surfaces of a conventional threaded fastener. Of course, the design of the socket element has to be adapted for fasteners of different shapes and sizes.
A torque limiting nut assembly is disclosed in United States Patent No. 4,176,582 (Microdot Inc.). The nut assembly has a ratchet construction with a separate wrenching member. Torque is applied to the nut with a conventional wrench acting on the wrenching member. The ratchet construction is set to permit assembly torque of a preselected magnitude, at which point ratcheting begins, preventing the application of additional torque. This device, however, is fairly complex in design, and requires the use of a specially designed wrench.
An aim of the present invention is to provide a torque limiting device that is simpler and cheaper to manufacture than existing torque limiting devices.
According to a first aspect of the invention there is provided a torque limiting device comprising a body, the body having at least two engagable surfaces which, in use, engage a structure, characterised in that the body has at least one slot therein defining an arm with respect to an adjoining engagable surface, said arm being elastically deformable and deflectable upon application of a force exerted on the arm by the structure, said arms being constructed, dimensioned and arranged relative to the body and the structure so as to permit relative movement therebetween on application of a torque exceeding a predetermined value.
According to a second aspect of the invention there is provided a torque limiting threaded fastener, the thread of the fastener defining an axis about which the fastener may be rotated relative to a matching thread in order to tighten the fastener, comprising a plurality of adjacent tool engaging surfaces which a tool may engage to tighten the fastener, each surface lying generally in a plane parallel with the fastener axis, characterised in that one or more surfaces has a slot therein, the slot in one tool engaging surface defining a wall with an adjacent tool engaging surface, said wall being elastically deformable in order to limit the maximum torque a tightening tool may apply to the fastener.
The structure engaged with the body may be a wrench, a spanner, or other tool. The structure may also be the inside of a shaft into which the torque limiting device has been inserted.
Preferably the engagable surfaces of the body lie substantially in a plane parallel to the axis of rotation of the device. The engagable surfaces may, however, be inclined at an angle to the axis of rotation.
The arms of the device preferably have an outer surface and an inner surface, the outer surface being an engagable surface of the body, and the inner surface being defined by one side of a slot in the body. The outer surface of the arm and the inner surface of the arm may be substantially parallel. Preferably, however, the arms are tapered, the free end of the arm being narrower than the fixed end of the arm. This spreads the amount of strain throughout the arm when a force is applied to the arm. Preferably at least one edge of the device is formed so as to reduce stress concentrations within the device. Most preferably this takes the form of a rounded edge.
Preferably the torque limiting device has a polygonal cross-section. The device may have a triangular, square, pentagonal, or, most preferably, a hexagonal cross-section.
Preferably the device has a cavity formed therein, the cavity being dimensioned so as to receive a member such as a shaft or a shank. The cavity may extend only partially through the body of the device, or it may be in the form of a hole. The surfaces defining the cavity or hole may bear at least one groove or thread.
The slots formed in the torque limiting device and/or the threaded fastener may receive a volume of energy absorbing material which acts as a damper. This may reduce component wear, and reduce noise and vibration. Preferably the energy absorbing material is an unfilled elastomer such as nitrile rubber, butyl rubber, or polycholorprene, or a copolymer such as nitrile isoprene copolymer.
Preferably the threaded fastener and/or torque limiting device are composed of a polymer such as Nylon. The fastener and/or device may also be made from a high strength aluminium alloy, titanium alloy, or steel. The fastener and/or device may be injection moulded, cast, or machined, depending on the material used for manufacture.
According to a further aspect of the invention there is provided a tool comprising a shank and a head for engaging a recess of a component, the head of the tool comprising the previously described torque limiting device. An example of such a tool is an Allen key, which may be used for tightening and untightening a hex socket fastener.
According to another aspect of the invention there is provided a tool bit comprising a head, a neck, and a body, the head of the tool bit comprising the previously described torque limiting device. The body of the tool bit may have a square or a rectangular cross- section, and it may contain a cavity. The cavity may be dimensioned so as to receive, for example, the drive of a conventional ratchet tool.
The torque limiting device may be fitted to an output shaft of an electric motor. According to a further aspect of the invention there is provided a device for limiting torque transmitted to an object by a torque transmitting means, the device being adapted to engage said object, and comprising a body dimensioned and arranged to be received by the torque transmitting means, said body including at least one resiliently deformable member which is arranged to deform upon application of a torque which exceeds a predetermined value, thereby decoupling the torque transmitting means from the object.
This device may be used for tightening nuts.
A number of embodiments of the invention will now be described, by way of example only, with reference to the accompanying Figures, in which:-
Figure 1 shows a perspective view of a torque limiting nut, according to the invention;
Figure 2 shows a perspective view of a torque limiting device having a triangular cross- section, according to the invention;
Figure 2a shows a plan view of the device of Figure 2, according to the invention;
Figure 2b shows a plan view of a torque limiting device having a cavity, according to the invention;
Figure 3 shows a plan view of an arm of a torque limiting device, according to the invention;
Figure 3a shows a stress contour plot of an arm under load, according to the invention;
Figure 4 shows a perspective view of a tool having a torque limiting head, according to the invention;
Figure 5a shows a diagrammatical view of a tool bit having a torque limiting head;
Figure 5b shows a perspective view of a tool bit having a torque limiting head, according to the invention;
Figure 6 shows a perspective view of a motor and a motor output shaft having a torque limiting head, according to the invention; and Figure 7 shows a cross-section and a plan view of a device for limiting torque transmitted to an object, according to the invention.
Figure 1 shows a torque limiting nut 10 with an inner threaded surface 16. The nut 10 has a plurality of deformable engaging surfaces 12 in which slots 18 are formed. Slots 18 may be formed by machining a conventional nut, thereby producing a torque limiting device 10. Alternatively, the nut 10 having slots 18 may be cast, or injection moulded, depending on the material used for manufacturing the nut.
A torque limiting device 20 having a head 22 with triangular cross-section, and a body 24 is shown in Figure 2. Body 24 may be a threaded body. Slots 18 are formed in the head 22, giving arms 11. In this example, the arms 11 are positioned so that the device 20 may be tightened in a clockwise direction. During tightening of the device 20, when a force exceeding a certain value is applied to the arms 11, the arms yield inwardly. This ensures that the device 20 may only be tightened a predetermined amount. The value of this predetermined torque depends on certain characteristics of the head 22 of the device.
Figure 2a shows the device 20 in plan view. Figure 2b shows, in plan view, the head 22 of device 20 having a cavity 24 formed therein. The cavity, or hole, may be of a dimension suitable for a shaft or shank to be received by the cavity. This enables the torque limiting head 22 to be used as one component of another device.
Figure 3 shows, in plan view, an arm 11 of a torque limiting device. The torque limiting device may be designed so that it may only be tightened using a predetermined amount of torque. The value of the predetermined amount of torque depends on the dimensions of the arms (or walls) of the device. The amount of applied torque which may be applied to the device before slippage of a surface contacting the device occurs may be increased a) by increasing the thickness of the arms, b) by reducing the length of the arms, or c) by increasing the length of the device itself.
Figure 3a shows a stress contour plot of arm 11 when under load. It can be seen from the stress contour plot that corner 28, formed by the meeting of adjoining engagable surfaces, is highly stressed under loading. This may cause wear on the device. Corner 28 should therefore be rounded to increase the area which may be contacted by a torque applying tool in order to reduce wear and stress. It can also be seen from the plot of Figure 3a that the end 26 of the slot 18 is the point of greatest stress. The corners of the slot defining arm 11 are therefore rounded in order to reduce stress under loading at this point.
When a force is applied to arm 11, the bending moment at the fixed end of the arm is greater than the bending moment at the free end of the arm. Arm 11 is therefore tapered, so that the width 34 of the free end of the arm is narrower than the width 32 of the fixed end of the arm. This ensures that the area in the vicinity of the fixed end of the arm 11 is increased to cope with the increased bending moment in this region.
Slot 18 is dimensioned so that the arm 11 may bend freely under full loading. Depending on the flexibility of the material used to manufacture the device, slot 18 may be dimensioned so that, under full loading, the arm does not contact a nearby surface. If the material is fairly flexible, however, slot 18 may be dimensioned so that it comes into contact with a nearby surface under full loading, allowing a greater torque to be applied to the device.
The material from which device 22 is manufactured must be flexible enough for the arms 11 to bend without yielding, and strong enough for bearing a load. The material should therefore behave as a spring. In order to select the best materials, the value of emax (the maximum strain of the material before yielding occurs) should be high. &πaκ is found
from emax= max/E where E is the Youngs modulus of the material, and σmax is the maximum stress occurs (either compressive, tensile, or shear) applied before yielding.
Suitable materials from which device 22 may be manufactured are engineering polymers such as Nylon, composite materials, or very high strength aluminium alloys, titanium alloys and steel.
Figures 4 to 6 illustrate devices or components incorporating the torque limiting device of the invention.
Figure 4 shows an Allen key 40 having a shank 42 and a head 44, the head 44 being a torque limited device. In this example, the torque limiting device has a hexagonal cross- section. This tool is suitable for tightening a hex socket fastener. Figures 5a and 5b show a torque limiting attachment 50 for a square-drive ratchet.
Attachment 50 has a square drive portion 56, a torque limiting head 52, and a threaded shaft 54 therebetween. The torque limiting head 52 is in contact with a narrow internal surface of a tool 58 into which head 52 has been inserted. An adjusting ring 60 is held transversely at the base of the tool 58. The adjusting ring may be turned, raising and lowering attachment 50 by means of a thread in contact with threaded shaft 54. The arms of flexible head 52 are deflected radially inward when a predetermined torque is applied to the head 52, allowing attachment 50 to slip relative to tool 58.
Figure 6 shows an electric motor 62 connected to a motor output shaft 68. Motor output shaft 68 is fitted with a torque limiter 66, and limiter 66 is connected to a drive train 64. If the torque applied to turn output shaft 68 is increased to a level which would normally cause the motor to stall, limiter 66 allows the motor 62 to continue turning, thus preventing burn out of the motor. The limiter 66 can therefore be thought of as a mechanical fuse, preventing damage to drive train 64 in the event of component malfunction.
The slots 11 of the torque limiter 66 may be filled with an energy absorbing material acting as a damper. This has the effect of reducing vibration in the drive train 64, reducing noise, and reducing component wear.
Figure 7 shows a nut tightening device 70, having deformable arms 11. Device 70 has a cavity 72 formed therein for receiving objects such as nuts. In this example, it can be seen that the cavity 72 is hexagonal for receiving hexagonal nuts. Upon application of a torque which exceeds a predetermined value to device 70, arms 11 are deformed inwards, thereby decoupling the torque being transmitted to the nut. The nut can therefore only be tightened by a predetermined amount.
Nariation may be made to the aforementioned embodiments without departing from the scope of the invention. For example, the torque limiting device has been described as having a triangular or hexagonal cross-section. It will be appreciated that torque limiting devices with other polygonal cross-sections such as pentagons may also be used.

Claims

Claims
1. A torque limiting device comprising a body, the body having at least two engagable surfaces which, in use, engage a structure, characterised in that the body has at least one slot therein defining an arm with respect to an adjoining engagable surface, said arm being elastically deformable and deflectable upon application of a force exerted on the arm by the structure, said arms being constructed, dimensioned and arranged relative to the body and the structure so as to permit relative movement therebetween on application of a torque exceeding a predetermined value.
2. A threaded fastener, the thread of the fastener defining an axis about which the fastener may be rotated relative to a matching thread in order to tighten the fastener, comprising a plurality of adjacent tool engaging surfaces which a tool may engage to tighten the fastener, each surface lying generally in a plane parallel with the fastener axis, characterised in that one or more surfaces has a slot therein, the slot in one tool engaging surface defining a wall with an adjacent tool engaging surface, said wall being elastically deformable in order to limit the maximum torque a tightening tool may apply to the fastener.
3. A device according to claim 1 wherein the engagable surfaces lie substantially in a plane parallel to an axis of rotation of the device.
4. A device according to claim 1 wherein the at least one arm has an outer surface and an inner surface, the outer surface being an engagable surface of the body, the inner surface being defined by one side of a slot in the body.
5. A device according to claim 4 wherein the outer surface of the arm and the inner surface of the arm are substantially parallel.
6. A device according to claim 4 wherein the at least one arm is tapered, the free end of the arm being narrower than the fixed end of the arm.
7. A device according to any preceding claim wherein at least one corner of the device is formed so as to reduce stress concentrations within the device.
8. A device according to claims 1 or 2 having a substantially polygonal cross-section.
9. A device according to claim 8 wherein the polygon is a hexagon.
10. A device according to any preceding claim having a cavity formed therein, the cavity being dimensioned so as to receive a member.
11. A device according to claim 10 wherein the surfaces defining the cavity bear at least one groove.
12. A device according to claims 1 or 2 wherein the at least one slot receives a volume of energy absorbing material which acts as a damper.
13. A device according to claim 12 wherein the energy absorbing material is an unfilled elastomer.
14. A device according to claim 12 wherein the energy absorbing material is a copolymer.
15. A device according to claims 1 and 2 wherein the device is composed of a polymer.
16. A device according to claim 15 wherein the polymer is Nylon.
17. A device according to claims 1 and 2 wherein the device is composed of steel.
18. A device according to claims 1 and 2 wherein the device is composed of an aluminium alloy.
19. A device according to claims 1 and 2 wherein the device is composed of a titanium alloy.
20. A tool comprising a shank and a head for engaging a recess of a component, the head comprising the torque limiting device as claimed in claims 1 to 19.
21. A tool as claimed in claim 20, wherein the tool is an Allen key.
22. A tool bit comprising a head, a neck and a body, the head comprising the torque limiting device as claimed in claims 1 to 19.
23. A tool bit as claimed in claim 22, wherein the body has formed therein a cavity.
24. A tool bit as claimed in claim 23, wherein the cavity is dimensioned so as to receive the drive of a conventional ratchet tool.
25. A device for limiting torque transmitted to an object by a torque transmitting means, the device being adapted to engage said object, and comprising a body dimensioned and arranged to be received by the torque transmitting means, said body including at least one resiliently deformable member which is arranged to deform upon application of a torque which exceeds a predetermined value, thereby decoupling the torque transmitting means from the object.
26. A torque limiting threaded fastener substantially as described in Figure 1 of the accompanying drawing.
27. A torque limiting device substantially as described in Figures 2, 2a and 2b of the accompanying drawing.
28. A tool substantially as described in Figure 4 of the accompanying drawing.
29. A toolbit substantially as described herein with reference to Figures 5a and 5b of the accompanying drawing.
30. A device for limiting torque transmitted to an object as described herein with reference to Figure 7 of the accompanying drawing.
PCT/GB1998/001983 1997-07-07 1998-07-06 Torque limiting device WO1999002870A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU82315/98A AU8231598A (en) 1997-07-07 1998-07-06 Torque limiting device

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9714136.0 1997-07-07
GB9714136A GB2327107A (en) 1997-07-07 1997-07-07 Torque limiting threaded fastener

Publications (1)

Publication Number Publication Date
WO1999002870A1 true WO1999002870A1 (en) 1999-01-21

Family

ID=10815376

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1998/001983 WO1999002870A1 (en) 1997-07-07 1998-07-06 Torque limiting device

Country Status (3)

Country Link
AU (1) AU8231598A (en)
GB (1) GB2327107A (en)
WO (1) WO1999002870A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021205287A1 (en) * 2020-04-09 2021-10-14 Cochlear Limited Torque limiting drive tools

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FI115665B (en) * 2002-11-08 2005-06-15 Uponor Innovation Ab A connecting piece
DE102014108035B4 (en) * 2014-06-06 2021-05-12 Voss Automotive Gmbh Screw part with integrated limiter for its screw-in torque

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB661643A (en) * 1948-11-19 1951-11-21 Stanley Morton Improvements in and relating to shaft couplings
US3383974A (en) * 1967-07-21 1968-05-21 Norman C. Dahl Load indicating means
GB1287779A (en) * 1969-10-28 1972-09-06 Yorkshire Imp Metals Ltd Screw-threaded nuts
DE2919099A1 (en) * 1979-05-11 1980-11-20 Boellhoff & Co Tightening torque limiting nut - has slots parallel to hexagon faces
US4572041A (en) * 1984-10-05 1986-02-25 Rissmann Horst G Torque limiting wrench
EP0207833A1 (en) * 1985-06-19 1987-01-07 Automobiles Peugeot Threaded stud comprising a torque-limiting means

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE424573B (en) * 1978-11-13 1982-07-26 Atlas Copco Ab BULK FOR AXIAL POWER TRANSFER

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB661643A (en) * 1948-11-19 1951-11-21 Stanley Morton Improvements in and relating to shaft couplings
US3383974A (en) * 1967-07-21 1968-05-21 Norman C. Dahl Load indicating means
GB1287779A (en) * 1969-10-28 1972-09-06 Yorkshire Imp Metals Ltd Screw-threaded nuts
DE2919099A1 (en) * 1979-05-11 1980-11-20 Boellhoff & Co Tightening torque limiting nut - has slots parallel to hexagon faces
US4572041A (en) * 1984-10-05 1986-02-25 Rissmann Horst G Torque limiting wrench
EP0207833A1 (en) * 1985-06-19 1987-01-07 Automobiles Peugeot Threaded stud comprising a torque-limiting means

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021205287A1 (en) * 2020-04-09 2021-10-14 Cochlear Limited Torque limiting drive tools

Also Published As

Publication number Publication date
GB9714136D0 (en) 1997-09-10
GB2327107A (en) 1999-01-13
AU8231598A (en) 1999-02-08

Similar Documents

Publication Publication Date Title
US4267870A (en) Screw fastener with multi-point wrenching head and locking capabilities
US6904833B2 (en) Asymmetric wrench and fastener system
US6758646B1 (en) Structure for preventing loosening of threaded fasteners
US4215600A (en) Torque limiter for use with off-the-shelf fastening elements
US5358367A (en) Screw or nut packing micro-adjustment
US20030147716A1 (en) Structure of loosening-stop tightening means, loosening-stop bolt having the structure, method for producing the same bolt, loosening-stop nut having the structure, and method for producing the same nut
US4076064A (en) Locking thread construction
US5092203A (en) Wrench openings
US5562379A (en) Vibration resistant pin and collar fastener
US6019556A (en) Locking fastener assembly
HU207379B (en) Device for determining the minimum drawing clamping moment of screw connections
WO2003093691A1 (en) Locking fastener
JPH10148205A (en) Fastening tool assembly
HU221044B1 (en) Screw especially for snugly-fitted tightenings and wrench for the same
US5302066A (en) Locking fastener
US5692863A (en) Self-locking preload controlling nut
EP0130304B1 (en) Double locknut assembly and combination of locknut assembly with a bolt
US3329057A (en) Threaded fastener device
JPS58502162A (en) socket drive
EP1371453B1 (en) Asymmetric wrench and fastener system
US5927165A (en) Hex keys and other tools with non-slip feature
WO1999002870A1 (en) Torque limiting device
JP2002066940A (en) Tool socket
CN108730298B (en) Three-point fastener
JP4094818B2 (en) Fasteners, fastener systems, and tools for use in fastener systems

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AL AM AT AU AZ BA BB BG BR BY CA CH CN CU CZ DE DK EE ES FI GB GE GH GM GW HU ID IL IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MD MG MK MN MW MX NO NZ PL PT RO RU SD SE SG SI SK SL TJ TM TR TT UA UG US UZ VN YU ZW

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): GH GM KE LS MW SD SZ UG ZW AM AZ BY KG KZ MD RU TJ TM AT BE CH CY DE DK ES FI FR GB GR IE IT LU MC NL PT SE BF BJ CF CG CI CM GA GN ML MR NE SN TD TG

121 Ep: the epo has been informed by wipo that ep was designated in this application
REG Reference to national code

Ref country code: DE

Ref legal event code: 8642

122 Ep: pct application non-entry in european phase
NENP Non-entry into the national phase

Ref country code: JP

Ref document number: 1999508314

Format of ref document f/p: F

NENP Non-entry into the national phase

Ref country code: CA