WO1997013982A1

WO1997013982A1 - Setting device for a threaded fastener

Info

Publication number: WO1997013982A1
Application number: PCT/AU1996/000633
Authority: WO
Inventors: Philip Charles Clark; Michael John Finlay
Original assignee: Ramset Fasteners (Aust.) Pty. Limited
Priority date: 1995-10-10
Filing date: 1996-10-09
Publication date: 1997-04-17
Also published as: ZA968508B; GB9807466D0; AUPN589695A0; GB2320306A

Abstract

A setting device for setting a threaded fastener to a predetermined torque, for example for setting a bolt of a masonry anchor, comprises a torque-transmitting body (2) interposed between the tool and the threaded fastener, the body (2) shearing in a thin-walled annular zone (10) at application of the predetermined torque. A separate pin (12) within the body (2) maintains a secondary torque-transmitting connection but is subject to substantial plastic deformation after shearing of the thin-walled zone to provide a cushioning effect which prevents sudden release of the setting device. The pin (12) is designed to shear at a lower torque across the reduced diameter defined by an annular groove (26), or disengage by progressively deforming and stripping the engagement between the distal end (18) and the central aperture (16) of the engaging portion (4). The pin (12) can be used to transmit a vertical impact force applied to the head (22) to the nut (6) and bolt. Also provided is an indicator ring (30) showing the correct torque setting, and any subsequent disturbance or tampering of the torque setting, if removed.

Description

"SETTING DEVICE FOR A THREADED FASTENER"

The present invention relates to a device for setting a threaded fastener to a prescribed torque and more particularly, but not exclusively, to a device for setting to a prescribed torque an expansion bolt or nut of a masonry anchor.

One well known form of masonry anchor comprises a sleeve which is expanded into engagement with the wall of a hole drilled into masonry by drawing an expansion element into the sleeve upon tightening of a bolt or nut of the anchor. When an anchor of this type is used in certain high stress fixing applications it is necessary that the bolt or nut is tightened to a specified torque. Although this can be achieved by using a torque wrench, these are not always readily available on a building site and, furthermore, even if a torque wrench has been used, it cannot be ascertained on subsequent inspection that the fastener has been tightened to the required torque.

There has been proposed in U.S. patent 4,144,796 a masonry anchor of the type described above, in which the bolt head carries a hexagonal tightening cap which is connected to the head by shear pins which shear at a predetermined torque applied between the cap and the head. The assembly of the cap to the bolt head by means of the shear pins significantly increases the cost of the masonry anchor and also a different bolt and shear pin combination (and hence a different anchor) needs to be provided for each different required torque setting.

We have determined that with a torque setting arrangement such as may be provided by a shear pin connection as described above and in certain other torque limiting devices which operate by shearing of a driving connection between a driving wrench and a bolt head or nut, shearing may take place relatively suddenly, without any significant advance warning being given to the operator. In the environment of a building site where certain masonry anchors may require setting to a high torque, the relatively sudden shearing of a driving connection between the wrench and anchor might cause injury to the hands or body from an uncontrolled follow- through of movement as the resistance to effort is suddenly removed and 4 -

torque application has taken place. Such indication may consist of the absence of indicating means which is removed by the application of torque to the portion by a suitable tool and/or the presence of visible markings which may appear on the portion if torque is applied. As an example of the latter, the engaging poπion of the body may be coated with a paint incorporating micro-capsules of another colour which are shattered upon application of torque directed to that portion of the body

According to a further aspect of the mvention, there is provided a setting device for setting a threaded fastener to a predetermined torque, comprising a torque-transmitting body interposed between a tool and the threaded fastener, said body shearing in a predetermined zone at application of the predetermined torque, and coupling means within the body to maintain a secondary torque-transmitting connection after shearing of said zone, said coupling means being subject to substantial plastic deformation after shearing of said zone to provide a cushioning effect which prevents sudden release of the setting device.

An embodiment of the invention will now be described, by way of example only, with reference to d e accompanying drawings, in which: -

Figure 1 is an axial section of a setting device in accordance with a preferred embodiment of the invention; and Figure 2 is an exploded view of the device shown in Figure 1.

In accordance with the preferred embodiment of the invention, there is provided a torque limiting setting device comprising a main body 2 of one-piece construction and comprising a socket portion 4 for engaging, by fitting over, a bolt head 6 of a masonry anchor of expansion type as described earlier. Outwardly of the socket portion 4, the body 2 has a driving portion 8 configured for engagement by a torque applying tool. As shown, the outer surface of the driving portion 8 is configured with a so-called double hexagon (12- point) configuration for driving connection with a ring spanner, socket wrench, or electric driving tool; however the configuration of the driving portion 8 can be different from that shown and other configurations compatible for use with suitable spanners, wrenches, or other driving connection provided thereby breaks after a progressive deformation which wiJl be sensed by an operator.

Advantageously, the further torque-transmitting means is composed of a non-brittle plastics or alloy which is capable of substantial plastic deformation before breakage of me further drive transmitting connection.

Advantageously, the body of the device is of integral cast or moulded construction, preferably from a suitable alloy, with the first torque-transmitting means being defmed by a thin-walled zone of the body, preferably a thin-walled annular zone. The engaging portion of the body preferably defmes a socket for receiving a bolt head or nut.

Advantageously, the further torque-transmitting means comprises a pin or other coupling mounted on the axis of the body and in driving relationship with the driving portion and engaging portion of the body.

In one advantageous form, the setting device in accordance with the invention is particularly applicable to the setting of a masonry anchor into a hole drilled into the masonry with the head of an anchor bolt being engaged to the engaging portion of the body of the setting device. In this form, the pin which constitutes the further torque-transmitting means advantageously also acts as means for transmitting hammer blows directly to the head of the anchor to drive the anchor into the masonry prior to setting. In this configuration the torque transmitting means of the body itself will not be degraded by transmitted hammer blows during installation of the anchor.

Advantageously, the driving portion is completely removable from the engaging portion after setting has taken place, and indicator means are preferably provided to provide a clear visual indication of setting at the required torque upon removal of the driving portion. Advantageously, the engaging portion is of a configuration to permit application of further torque directly to the portion after setting, with indication being provided that such further masonry anchor engaged within the socket portion 4.

Although a significant function of the pin 12 is to improve the operation of the setting device when die required torque is attained and as will be described subsequently, another important function of the pin 12 is to transmit hammer blows applied to the head 22 of the pin 12 direcdy to the masonry anchor as may occur when a masonry anchor with the setting device pre-installed thereon is being initially driven into a hole drilled in masonry prior to setting of the anchor within the hole. The use of the pin 12 as the means for transmitting hammer blows within the setting device avoids the hammer blows being transmitted through the relatively thin-walled shear zone 10 of the body 2 and which could, in some circumstances, result in damage to me thin- walled zone whereby subsequent shearing could occur at a torque setting lower man the design setting. Although for many applications it is particularly advantageous for the pin 12 to perform both of the described functions, in applications where the anchor is not likely to be hammered into the hole prior to setting it would, in principle, be feasible for the pin 12 to perform only the single function of improving the torque setting characteristics of the device, although as a matter of practical reality a pin which performs both functions will usually be provided.

As described, the pin 12, and in particular me shank of the pin 12, provides a secondary torque-transmitting connection between the driving portion 8 and socket portion

4 of the body 2 of the setting device. The pin 12 is designed to shear at a torque less dian that required to shear the min- walled zone 10 of the body 2, the shank of the pin having a shearing zone of reduced diameter defmed by an annular groove 26 located immediately outwardly of its distal end portion 18 and also in substantial axial alignment with the thin- walled zone 10. The diameter of the shearing zone of the pin shank will determine the torque at which the shank shears and that can be controlled by varying the depdi of the groove 26 during manufacture of the pin. Although the shearing zone of the pin 12 is designed to shear at a torque less than that of the thin-walled zone 10 of the body, it will be appreciated that until the thin- walled zone 10 of the body has actually sheared and rotational movement takes place between the driving portion 8 and socket portion 4 of die setting device, the shank of tools may alternatively be adopted. The driving portion 8 is connected to the socket portion 4 via a part of the body which forms a relatively thin- walled annular zone 10 which shears on application of a predetermined torque in order to break me driving connection when the required torque setting has been reached. The body 2 is produced as a one-piece casting in a suitable alloy which exhibits the strength characteristics necessary for transmission of the required torque and which also has predictable shearing characteristics in its thin-walled annular zone 10 upon application of a predetermined torque. The torque at which shearing occurs is determined by me mickness of the thin- walled annular zone 10 and this can be varied during manufacture by altering the thickness of the annular zone by incorporation of different inserts into the mould so as to permit a range of setting devices to be produced with different torque characteristics at which shearing takes place.

In addition to the torque-transmitting connection provided by me thin-walled annular zone 10 between the driving portion 8 and socket portion 4, the driving portion 8 and socket portion 4 are also interconnected by means of a central pin 12 composed of a non-brittle plastics material with a degree of inherent resilience or, alternatively, an alloy having similar characteristics. However, plastics is the preferred material for the pin 12 and a suitable grade of nylon can be used for this purpose. The driving portion 8 of die body is shaped widi an internal socket 14 and the base 4a of die socket portion 4 of the body is formed with a shaped central aperture 16. The shank ofthe pin 12 is so shaped mat the distal end portion 18 of the shank mates with the correspondingly-shaped central aperture 16 in the base 4a of d e socket portion 4 and the proximate end portion 20 of the shank is shaped to mate with the socket 14 within the driving portion 8. The cross-sections of me distal and proximate end portions of the shank of the pin 12 and the mating cross-sections of the socket 14 and aperture 16 in me base of the socket portion 4 are such that a torque-transmitting driving connection is established. Although u e particular cross-sectional configurations as illustrated will achieve an effective driving connection, it will be apparent that other cross-sectional configurations can achieve the same purpose. The pin 12 terminates at its end in a head 22 which overlies d e outer end face 8a of the driving portion 8 and the distal end of the shank projects urough the aperture 16 in the base 4a of the socket portion 4 so as to engage die head 6 of die example by means of a suitable adhesive or by swaging me end of me socket portion over the end of the anchor head.

In practice, in situations where the setting device is intended to remain permanently 5 attached to die head cf die anchor to provide an indication of correct setting for inspection purposes, it is also necessary for there to be provision for the anchor to be released and/or reset at a later date aldiough in this event it is necessary that the setting device should exhibit evidence diat resetting has taken place. In the present embodiment mis is achieved by providing die outer surface of the socket portion 4 with a double hexagonal configuration (a

10 12-point configuraάon) whereby subsequent tightening or loosening of the anchor requires the use of a ring spanner or socket placed over me socket portion 4. The body of die socket portion 4 carries at its outer end a ring 30 of a relatively brittle plastics material. The ring 30 is fixed relative to die socket portion 4, for example in the manner described below, and is likewise provided around its outer periphery with a double-hexagonal configuration.

15 Aldiough uie ring 30 does not inhibit me application of a ring spanner or socket to the socket portion, when torque is applied to die socket portion by me ring spanner or socket, the applied torque will cause breakage of me brittle ring; this effect can be achieved either by slighdy angularly offsetting the double-hexagonal formation on die ring relative to that on the socket portion, or by making the double-hexagonal configuration on e ring to a closer 0 tolerance than diat on the socket portion. The ring 30 in effect provides an indicator of whether or not the socket portion has been tampered with after setting by application of a ring spanner or socket. For this purpose, the indicator ring 30 is in a prominent colour which contrasts widi uiat of the socket portion 4 of the setting device so d at its presence will readily be observable; and, conversely, its absence will also be apparent.

25

The ring 30 also is used to facilitate remote observation of the correct setting of e anchor after removal of the driving portion when d e correct torque has been attained. For d is purpose, the ring 30 is located within the annular groove of the body 2 which defmes the thin-walled shear zone 10 so diat in the original state of the setting device prior to application

30 of me torque, the indicator ring 30 will be partially concealed by die driving portion 8 and me pin 12 will not actually be loaded widi a torque which is able to engender its shearing.

In operation, when the prescribed torque limit for the body 2 is reached, die annular torque-transmitting zone 10 will shear; due to the nature of the material from which the body 2 is formed, although shearing will take place at an accurately determinable torque, it will occur relatively suddenly. Upon shearing me driving portion 8 will start to rotate relative to the socket portion 4 and to me head 6 of die masonry anchor therein, but that movement will immediately be resisted by me torque loading which is tiien applied to the shank of the pin 12. The characteristics of the material of the pin 12 are such that it will not suddenly shear under die applied torque, but rather it will firstly undergo some elastic deformation and then plastic deformation and, eventually the plastic deformation will occur over a sufficient angular extent that the shank of the pin 12 will shear in the zone defined by d e groove 26. However unlike d e action which occurs when the tJiin- walled annular zone 10 of the body 2 shears, die pin 12 will not suddenly shear. Instead, die operator will experience a distinct "feel" when d e pin is under torque and is being deformed prior to shearing so d at the operator is able to prepare himself for complete shearing of d e pin at which point the driving portion 8 and the part of the pin attached thereto will be fully released from any constraint by the remainder of titte device. In omer words, after shearing of d e main torque-transmitting zone 10 ofthe body has occurred at die prescribed torque for setting the anchor, the operator will experience a relatively gende and progressive let-down prior to final detachment of the driving portion. As will be apparent, as die torque at which the pin shears is less dian d e design torque setting of the body of die device, d e presence of d e pin and its subsequent action will not increase the setting torque which is applied to die anchor.

Advantageously, d e setting device is so constructed diat it remains permanently attached to die anchor head 6 after setting so as to permit visual inspection, for example by building inspectors, for verification that setting to die required torque has taken place; d e absence of d e driving portion 8 will demonstrate diat correct setting has taken place, aldiough, preferably a prominent visual indicator is also provided as will be described below. The socket portion of d e device may be peπnanendy attached to the anchor head 6 for - 10 -

pin progressively deforms under die applied torque after shearing of the primary driving connection between die driving portion 8 and socket portion 4 of die main body 2 so diat, in effect, the driving teeth provided by die configuration of die distal end portion 18 are deformed or "stripped" whereby die driving connection widi die central aperture 16 in the 5 base 4a of the socket portion 4 is broken and d e distal end portion 18 of d e pin 12 will men simply rotate within die central aperture 16 widiout transmitting torque. It will be appreciated diat during diis action, die driving portion 8 will be constrained by die pin for rotation about the central axis of the device and will not be liable to eccentric rotation as may occur with the preceding embodiment. As die driving teetii provided by die distal end poπion 18 of the pin

10 12 have stripped, die driving portion 8 togetiier widi the complete pin 12 can tiien be removed simply by withdrawing die distal end portion 18 of the pin from the central aperture 16. When breakage of the secondary torque transmitting connection is to be achieved in this manner, the distal end portion 18 of d e pin may be shaped differently from that illustrated in Figure 2, for example with a reduced number of driving teeth to that illustrated or in any

15 other way which leads to a reduction in die effective surface area through which torque is transmitted between die distal end portion 18 and central aperture 16 of d e socket portion 4 so as to cause greater localised loading which will result in breakage of d e driving connection under e effect of the applied torque. In general, die drive-transmitting connection between the distal end poition 18 of die pin and the central aperture 16 of die socket portion 4a can 0 be of any non-circular shape which will deform under d e applied torque such as to break die secondary driving connection.

Aldiough the embodiments described are designed in particular for application to a bolt head of an anchor bolt, wid appropriate modifications it could be used widi an exposed 25 nut of an anchor bolt. It may also be used widi odier forms of anchor or tiireaded fastener which require setting to a required torque.

The embodiment has been described by way of example only and modifications are possible in the scope of the invention. 30 not readily be visible. Preferably, die ring 30 is assembled from two identical parts snap- fitted together and having projections 32 engaged in corresponding recesses 34 in the socket portion 4 to retain die ring 30 to the socket portion 4. When die required torque has been attained and me driving portion 8 has been removed from die socket portion, die ring 30 will be easily visible for me purposes of inspection from a remote position. Likewise, if the ring 30 is subsequendy broken and removed as a result of torque application by a ring spanner or socket to the socket portion of die setting device retained on tie head of die anchor, die absence of die indicator ring 30 will also be readily apparent to an observer even on inspection from a remote position. Although die indicator ring 30 provides a ready means of providing an indication of the correct setting and also an indication of subsequent disturbance of die setting, diere are other ways in which this could be achieved as discussed previously.

In die embodiment described above, die pin 12 provides a secondary driving connection between the driving portion 8 and socket portion 4 and diis secondary driving connection is broken by shearing of the pin at the weakened zone provided by die annular groove 26. When die pin 12 shears, the driving portion 8 togedier with die part of die pin outwardly of the shear zone can be removed. Shearing of the pin 12 occurs as a result of continuing rotation of d e driving portion 8, and shearing of d e pin 12 does not take place as a sudden action but, ratiier, as a progressive action which occurs with the continuing rotation. It has been determined d at while d e driving portion 8 is being rotated during d e shearing of the pin, the progressive shearing of d e pin can cause the effective axis of rotation of the driving portion 8 and part of d e pin coupled tiiereto to shift laterally, in odier words eccentrically, wid respect to d e axis of the socket portion 4 and bolt head 6 and in some circumstances this might result in some damage occurring during d is phase to d e indicator ring 30.

To avoid d e effect just described, in a modified embodiment of die invention instead of shearing the pin 12 in order to break the secondary driving connection between the driving portion 8 and socket portion 4 as established by die pin 12, the distal end portion 18 of the 12

3. A device according to claim 1 or claim 2, wherein the body of me device is of integral construction, widi die first torque-transmitting means being defined by a tiiin-walled zone of the body.

4. A device accordmg to claim 3, wherein the ώin-walled zone is an annular zone.

5. A device according to any one of claims 1 to 4, wherein the further torque- transmitting means is composed of a non-brittle plastics or alloy which is capable of substantial plastic deformation.

6. A device according to any one of claims 1 to 5, wherein the further torque- transmitting means comprises a coupling mounted on the axis of the body in driving relationship wid d e driving portion and engaging portion of the body.

7. A device according to claim 6, wherein the coupling is adapted to break d e driving connection between the driving portion and engaging portion by shearing of the coupling in a predetermined zone of die coupling.

8. A device according to claim 6, wherein the driving connection between the coupling and die driving portion and engaging portion of die body is provided by zones of non-circular shape on d e coupling engaging widi correspondingly shaped zones of die driving portion and engaging portion of me body, and wherein breakage of the driving connection occurs as a result of distortion of d e shape of one of said non-circular zones of d e coupling under die effect of d e applied torque whereby continued application of torque to e driving portion will result in rotation of die driving portion about die axis of die device but witiiout fuπher torque transmission via the coupling to the engaging poπion.

9. A device according to claim 8, wherem me said one zone of die coupling is shaped to provide driving teeth which strip or odierwise deform under d e application of d e applied torque.

Claims

CLAIMS:-

1. A setting device for setting a threaded fastener to a predetermined torque, comprising a body having a portion for engagement with die direaded fastener, and a driving poπion for engagement with a torque-applying tool, means defining a first torque-transmitting connection between the poπions so as to transmit torque from the driving poπion to die fastener, said first torque-transmitting connection being adapted to break when a predetermined torque is attained, and means defining a fuπher torque-transmitting connection between the portions, said further torque-transmitting connection being adapted to break die driving connection provided diereby at a torque less dian said prescribed torque after the first torque-transmitting connection has broken, said fuπher torque- transmitting connection being such that breakage of die driving connection takes place after substantial deformation of die fuπher torque- transmitting connection which will be detectable by an operator.

2. A setting device for setting a threaded fastener to a predetermined torque, comprising a body having a poπion for engagement wid d e direaded fastener, a driving poπion for engagement with a torque-applying tool, and first torque-transmitting means between d e portions so as to transmit torque from the driving poπion to die fastener, said first torque- transmitting means being adapted to shear when a predetermined torque is attained, and further torque-transmitting means between the pσπions, said fuπher torque-transmitting means being adapted to break die driving connection provided diereby at a torque less than d e prescribed torque after die first torque-transmitting means has sheared, wherein die first torque-transmitting means shears relatively rapidly upon application of d e required torque widiout substantial movement occurring of d e driving portion relative to die engaging portion and die fuπher torque-transmitting means men acts to transmit torque between the poπions, die further torque- transmitting means permitting the driving poπion to rotate relative to die engaging portion against resistance provided by deformation of d e fuπher torque-transmitting means until the driving connection provided diereby breaks after a progressive deformation which will be sensed by an operator. 10. A device according to any one of claims 6 to 9, wherein the said coupling forming the further torque-transmitting means comprises a pin.

11. A device according to claim 10 for use in setting a masonry anchor into a hole drilled 5 into masonry, with die head of an anchor bolt being engageable to the engaging poπion of the body of die setting device, wherem said pin has an exposed end to which hammer blows can be applied and an opposite end engageable with die head of die anchor bolt to transmit die hammer blows directiy to the head of die anchor bolt without affecting the integrity of the first torque-transmitting means. 10

12. A device according to any one of claims 1 to 11 , wherein the driving poπion is completely removable from the engaging portion after settmg to the predetermined torque has taken place.

15 13. A device according to claim 12, fuπher comprising indicator means visible from a remote location to facilitate remote visual verification of removal of the driving poπion after setting to the predetermined torque.

14. A device according to claim 13, wherein the indicator means is such diat it is at least 0 partially obscured from view by die driving poπion when still attached to die engaging poπion of the device.

15. A device according to claim 13, wherein die body of die device comprises an annular groove having opposed walls defined by the engaging poπion and driving poπion and die 5 indicator means comprises a ring mounted within the groove wid d e ring being partially obscured from view by the driving portion when still attached to die engaging poπion.

16. A device according to any one of claims 1 to 14, wherein the engaging poπion has a configuration to permit application of further torque directiy to the engaging portion after 0 setting, said device fuπher comprising means for providing an indication of die application