GB2507645A

GB2507645A - Collet and nose jaw assembly for swaging fasteners

Info

Publication number: GB2507645A
Application number: GB1316256.5A
Authority: GB
Inventors: Victor Edward Davey; Carl Hersant
Original assignee: Infastech Intellectual Properties Pte Ltd
Current assignee: Infastech Intellectual Properties Pte Ltd
Priority date: 2012-09-13
Filing date: 2013-09-12
Publication date: 2014-05-07
Anticipated expiration: 2033-09-12
Also published as: JP6147348B2; WO2014041328A1; EP2895753B1; CN104769293A; JP6499677B2; GB201315989D0; EP3150866B1; GB201216367D0; BR112015005575B1; JP2015535909A; GB201316256D0; BR112015005575A2; KR20150052156A; JP2017101830A; US20150252833A1; ZA201501868B; TWI617745B; BR112016003852B1; ES2647120T3; KR20180086530A

Abstract

A single piece collet for fastener installation tools comprises axial slots 116 defining arms120 with internal lips 122 which together define a pulling jaw. The arms are movable between an open position for receiving a pin tail (8, Figure 6a) of a fastener and a closed position in which the lips may locate into a pin tail pull groove (6). Preferably, the collet comprises hardened and tempered high-tensile steel, each slot has a radius on its inner end and the arms are biased open. When the collet is drawn into a minor bore of an anvil a tapered portion forces its arms inwards so that the lips locate into the groove (6) of the pin tail, and further movement of the collet draws the pin tail and the anvil swages a collar (4) of the fastener. On its return stroke an angled surface of the collet lips contacts a complimentary surface of the pin tail groove to force the pin tail and swaged collar out of the anvil, and the collet is biased open to release it from the fastener. The collet may protrude from the anvil mouth but not beyond a lip (13, figure 3b) so that it is protected by the lip.

Description

Nose Jaw Assembly The present invention relates to a nose jaw assembly for a tool, and specifically to a split collet for a tool for installing fasteners in workpieces.

Known tools for installing a fastener such as a lockbolt, into a workpiece, typically comprise two main elements, an anvil, and a pulling jaw assembly. The anvil comprises a mouth portion formed of a tapered bore which, on actuation of the tool to install a lockbolt, swages a collar of the lockbolt onto a pin of the lockbolt.

Pulling jaws of known lockbolt installation tools conventionally comprise several (typically three) pulling jaws, which are mounted within a tapered jaw housing located behind the mouth portion of the anvil (see Figure 1, prior art). Each of the jaws is provided with multiple pulling teeth, which engage multiple pulling grooves provided on the lockbolt pin tail. With no lockbolt pin tail present, the pulling jaws are held forward by a compression spring and the jaw sides are together.

As the pulling jaws are biased into a closed position, the operator must overcome a positive resistance provided by the jaws, when inserting a lockbolt pin tail into the tool. The physical effort required to overcome the resistive force of the sprung loaded jaws and then to insert the lockbolt pin tail into the tool may lead to operator fatigue.

After actuation of a tool to install a lockbolt, the swaged collar of the lockbolt may be positively retained in the mouth portion of the anvil (due to residual radial compression loads and friction). In such cases, it is necessary for the collar to be forcibly removed from the anvil. This is usually achieved by a return stroke of the tool, which is applied to an end face of the collar via a projection at the front of the pulling jaw housing of the tool.

A potential problem with the prior art lockbolt installation tools described above is that the crests of the teeth of the tool may not engage sufficiently with the shallow grooves provided on the pin, e.g. the crests of the teeth may be caused to close directly onto the crests of the pull grooves, which can cause increased loads and slippage, thereby causing damage to the tool and/or fastener.

It is also possible for the tool teeth not to engage all fastener pulling grooves in an axial direction, which can lead to overstressing and stripping of the loaded pulling grooves on the fastener.

The multiple pull grooves and tool teeth of the prior art embodiments are also sensitive to angled entry of the pin tail into the pulling jaw housing, therefore the operator is required to check that the lockbolt pin is correctly aligned within the tool nose before actuating the tool.

A further disadvantage of known lockbolt installation tools is that the narrow, shallow pull grooves, and also the shallow pulling jaws of the tool, can easily become clogged with debris, particularly in dirty working environments. Fine pitch multiple groove jaw teeth are also much more vulnerable to damage by sand and small stones common to the outdoor environments in which these heavy duty lockbolt fasteners are often used (e.g. building of solar power plant structures in desert locations).

Furthermore, manufacturing of multiple pull groove lockbolts requires complex and therefore expensive thread rolling tooling, and the multiple pull groove forms generated on the pin are difficult and time consuming to inspect in production, therefore increasing time and cost of production.

Multiple pull groove teeth on a fastener installation tool require small radii around the tooth roots, which increase stresses and leads to premature cracking.

These teeth are also more complex to manufacture and inspect, and are therefore more costly to produce.

Furthermore, any misalignment of the tool jaw teeth and the pulling grooves on the lockbolt pin tail, or pitch error between the jaw teeth and the pin tail pulling grooves due to normal manufacturing tolerances, may result in an uneven distribution of pulling load and therefore generate higher localised stresses that lead to premature failure.

An aim of the present invention is to at least mitigate the above disadvantages associated with prior art lockbolt fastener installation tools.

Accordingly the present invention comprises, in a first aspect, a collet for a lockbolt installation tool in accordance with claim 1 of the appended claims.

The single piece collet of the present invention minimises the number of tool components, thereby reducing complexity, assembly time, weight and cost, compared to prior art embodiments having multiple-piece jaws, a jaw housing, spring and other component pads.

The single pulling jaw form within the collet of the present invention is larger and more robust to debris accumulation and damage by small stones, etc, than prior art embodiments.

The single pulling jaw form is less sensitive to axial or angular misalignment of the lockbolt prior to tool actuation, and the angled faces actually help to align the pull groove within the collet as it closes down on the pulling stroke.

Preferably, the arms of the collet are biased into an open position. The sprung, fully open jaw arrangement of the present invention, allows unhindered insertion of the lockbolt pin tail into the tool, thereby providing an ergonomic advantage for the operator, compared to prior art embodiments in which the jaws are biased into a closed position and in which a positive resistance must be overcome to insert the lockbolt pin tail into the tool.

The collet is preferably formed of high tensile steel in a hardened and tempered condition.

Preferably, the ends of the slots closest to the first end of the collet are each provided with a large radius. The large radii minimise stress concentrations and fatigue cracking. Thus the collet is capable of undergoing repeated opening and closing of the arms, and carrying significant forces.

Preferably, in the open position, part of the collet protrudes from the front of the anvil mouth. This allows the length of the lockbolt pin tail to be minimised, thereby reducing cost of manufacture of the pin, and decreases the protrusion of the pin tail beyond the installed collar, resulting in improved packaging and operator safety after lockbolts have been installed.

The part of the collet protruding from the anvil mouth may include the pulling jaw form, i.e. the internal lips forming the pulling jaw may be located, prior to actuation of the tool, outside the anvil mouth.

The tool anvil may be provided with a countersink and lip surrounding the countersink, such that, although the collet protrudes from the anvil mouth, it does not protrude beyond the lip of the tool nose jaw assembly. The lip thereby protects the collet, and furthermore increases the robustness of the tool.

The present invention also includes, in a further aspect, a method of installing a lockbolt into a workpiece.

Preferably the method includes a subsquent step comprising a return stroke, wherein after the collar has been fully swaged onto the locking grooves of the lockbolt, the collet in the closed position applies a force to a second angled bearing surface of the lockbolt pull groove located opposite to the first angled bearing surface, wherein the force acts to urge the swaged collar out of the minor bore of the tool anvil, thereby allowing the tool collet to return to the open position, thereby allowing easy removal of the lockbolt pin tail from the tool.

As the collet in the present invention provides the return force required to remove the swaged collar from the tool anvil, it is not necessary to include a further component (such as a protrusion of the jaw housing) to push against the collar end face.

Preferably, when the collet is in the closed position, the pulling jaw has a shape complimentary to at least part of the that of the pull groove of the lockbolt.

This results in minimal clearance between the pulling jaw and the root of the pull groove of the lockbolt. The minimal gaps between the arms of the collet, and a minimal clearance between the pulling jaw and the root of the pull groove of the lockbolt, both result in a maximised contact area between the collet pulling jaw and the lockbolt pull groove, and minimise bearing stresses, deformation and plating damage of the lockbolt pin tail at the first angled bearing surface.

The invention will now be described by way of example only and with reference to the accompanying figures in which: Figure 1 is a cross-sectional view of a prior art lockbolt installation tool nose jaw assembly; Figure 2a is a side view of tool nose jaw assembly in accordance with the present invention at a first stage of installation of a lockbolt fastener (with the tool body and workpiece removed for clarity), wherein the tool collet is in an open position; Figure 2b is a cross-sectional view along the line of Figure 2a and a workpiece into which the lockbolt is being installed; Figure 3a is a side view of a tool nose jaw assembly in accordance with the present invention at a first stage of installation of a lockbolt fastener (with the tool body and workpiece removed for clarity), wherein the tool collet is in an closed position; Figure 3b is a cross-sectional view along the line of Figure 3a and a workpiece into which the lockbolt is being installed; Figure 4a is an isometric view of the collet of the tool nose jaw assembly of Figure 2a, the collet being in an open position; Figure 4b is an end view of the collet of Figure 4a; Figure 5a is an isometric view of the collet of the tool of Figure 2a, the collet being in a closed position; Figure Sb is an end view of the collet of Figure 5a; Figure 6a is a cross-sectional view of a lockbolt for installation by a tool nose jaw assembly according to the present invention; Figure 6b is a simplified cross-sectional view of an alternative tool according to the present invention; Figure 6c is a side view of the tool of Figure 6b with a lockbolt pin tail inserted in the collet; Figure 6d is a simplified cross-sectional view along the line 0-0 of Figure Sc; and Figures 7a and 7b are views correlating to those of Figures 6c to 6d, at a successive stage of installation of a lockbolt wherein the lockbolt collar has been partially swaged onto the lockbolt pin tail; Figures Ba and 8b are views correlating to those of Figures 6c to 6d, at a successive stage of installation of a lockbolt wherein the lockbolt collar has been fully swaged onto the lockbolt pintail; and Figure 7 is a simplified cross-sectional view of the installation tool of Figures 6b being removed from an installed lockbolt.

Referring to Figures 2a to 3b, the present invention comprises an installation tool nose jaw assembly 100 including an anvil 102 having a mouth 104, and a nose-piece jaw assembly comprising a split collet 108. The collet 108 is formed of high tensile steel in a hardened and tempered condition, and is formed as a single piece.

The collet 108 has a first end 110 which is located within the tool nose jaw assembly 100, and a second, lockbolt engagement end 112 remote from the first end 110.

Towards the second end 112 of the collet 108, it is provided with a slotted portion 114 (indicated in Figures 4a and 5a), comprising three axially cut slots 116, thereby defining three integral arms 120 of the collet 108. The slots 116 are tapered in width when the collet 108 is in the open position, such that the widest point of each slot 116 is closest to the second end 112 of the collet 108. The ends 118 of the slots 116 closest to the first end 110 of the collet 108 are radiused.

The slotted portion 114 of the collet 108 is biased during manufacture into a fully open' position, i.e. the arms 120 of the collet 108 are at a maximum separation, such that a lockbolt 2 (for example as shown in Figure 6a), can be inserted into the open, second end 112 of the collet 103 without restriction.

Towards the second end 112 of the collet 108, each arm 120 is provided with an internal lip 122.

Figures 6b, 6c and 6d show an initial position of the tool nose jaw assembly 100, prior to actuation, wherein the collet 108 is located partially within the mouth 104 of the anvil 102. Part of the collet 108 protrudes from the mouth 104 of the anvil 102 (the protrusion is indicated by D' in Figure 6b).

As shown in Figures 6c and 6d, the installation tool nose jaw assembly 100 is initially located over a pin tail 8 of the lockbolt 2 to be installed, such that the internal lip 122 of each of the arms 120 of the collet 108 surrounds a single pull groove 6 provided on the lockbolt 2.

The installation tool anvil includes an internal bore, comprising a tapered portion 126 and a minor bore 124. On actuation of the tool nose jaw assembly 100, as shown in Figures 7a and 6b, the collet 108 is pulled into the minor bore 124 of the tool nose jaw assembly 100. The tapered portion 126 of the anvil 102 causes the collet 108 to be urged into a closed position, i.e. the arms 120 of the collet 108 are urged together until they are almost in contact. The diameter of the anvil minor bore 124 of the tool nose jaw assembly 100 is such that the collet 108 remains in the closed position when it is fully within the tool nose jaw assembly 100.

In the closed position, the three internal lips 122 of the collet 108 together form a singular pulling jaw, the form of which is complimentary to at least part of the form of the pull groove 6 of the lockbolt 2. In the embodiment described herein, the geometry of the pulling jaw closely matches a first angled bearing surface 12 provided on the pull groove 6 of the lockbolt 2. In the closed position, at the second end 112 of the collet 108, the slots 116 are at a minimum width, i.e. minimal gaps are present between the arms 120 of the collet 108 at the second end 112 of the collet 108. The minimal gaps between the arms 120 of the collet 108, and a minimal clearance between the pulling jaw of the collet 108 and a root 16 of the pull groove 6 of the lockbolt 2, both result in a maximised contact area between the collet pulling jaw and the lockbolt pull groove 6, and minimise bearing stresses, deformation and plating damage of the lockbolt pin tail 8 at the first angled bearing surface 12.

Whilst remaining in the closed position, the collet 108 is subsequently pulled back further into the tool nose jaw assembly 100, until a collar 4 of the lockbolt 2 is caused to be fully swaged onto locking grooves 10 provided on the pin tail 8 of the lockbolt 2. The final position of the tool nose jaw assembly 100 on the lockbolt 2, with the collar 4 fully swaged onto the pin tail 8, is shown in Figures 8a and 8b.

During a subsequent return stroke of the installation tool, the closed collet 108 applies a force to a second angled bearing 14 surface of the pull groove 6 of the lockbolt 2, (the second angled bearing surface 14 being located opposite to the first angled bearing surface 12). This force acts to urge the swaged collar 4 out of the bore 124 of the tool anvil 102.

At the end of the return stroke of the installation tool, the biasing of the arms of the collet 108 provides that it resumes a fully open position, allowing unhindered iemoval (indicated by the allow in Figure 9) of the installation tool nose jaw assembly 100 from the installed lockbolt 2.

In alternative embodiments, the collet may protrude further from the anvil mouth, for example the part of the collet which protrudes from the tool mouth may include the internal lips! pulling jaw.

Furthermore, the form of the end of the tool nose jaw assembly may differ to that shown in Figure 6b to 9. For example, the tool nose jaw assembly of Figures 2a to 3b differs from that of Figures 6b to 9 in that the anvil further includes a countersink 128 and a lip 130 surrounding the countersink. Therefore, although the collet 108 protrudes from the anvil mouth 104 as in the latter Figures, it does not protrude beyond an outer face 132 of the lip 130; as the protruding collet is located within the countersink 128, it is protected by the lip 130

Claims

Claims 1. A collet for a fastener installation tool, the collet having a first end and a second, and comprising towards the second end a slotted portion provided with axial slots defining arms; wherein the arms are moveable between an open position wherein a pin tail of a fastener can be inserted into the second end of the collet, and a closed position wherein the axial slots of the collet are at a minimum width at the second end of the collet and the arms of the collet are at a minimum separation from each other, and wherein each of the arms, toward the second end of the collet, is provided with an internal lip, wherein in the closed position, the internal lips together form a pulling jaw; and wherein the collet is formed as a single piece.
2. A collet as claimed in claim 1 wherein the arms of the collet are biased into the open position.
3. A collet as claimed in claim 1 formed of high tensile steel in a hardened and tempered condition.
4. A collet as claimed in claim 1, wherein an end of each slot closest to the first end of the collet are radiused.
5. A tool comprising an anvil comprising a tool nose jaw assembly comprising the collet of claim 1, wherein, prior to actuation of the tool, the collet is located within a mouth of the anvil, and wherein when the collet is in the open position, part of the collet protrudes from the mouth.
6. A tool as claimed in claim 5 wherein the part of the collet protruding from the mouth includes the internal lips of the collet arms.
7. A tool as claimed in claim 5 wherein the nose jaw assembly further includes a countersink in which the part of the collet protruding from the collet mouth prior to actuation of the tool is located within the countersink, and wherein a lip of the tool surround the countersink, and wherein the collet does not protrude beyond an outer face of the lip.
8. A method of installing a lockbolt fastener using the tool of claim 1 comprising; inserting a pin tail of the lockbolt into the second end of the collet, such that the internal lips of the collet are located around a pull groove of the lockbolt; actuating the tool, thereby to pull the collet into an internal bore of an anvil of the tool, wherein a tapered portion of the internal bore causes the collet arms to be urged towards each other, thereby moving the collet from the open position to the closed position wherein the internal lips of the arms of the collet are caused to close around the pull groove; wherein when the collet is subsequently pulled further into the tool anvil, a minor bore of the anvil internal bore causes the collet to remain in the closed position, and wherein the pulling jaw is caused to contact a first angled bearing surface of the lockbolt pulling groove, thereby causing the lockbolt also to be pulled into the tool, and causing a tapered portion of the tool anvil to swage a collar onto pulling grooves provided on the lockbolt.
9. A method as claimed in claim 8 further including a subsequent step comprising a return stroke, wherein the collet in the closed position applies a force to a second angled bearing surface of the lockbolt pull groove located opposite to the first angled bearing surface, wherein the force acts to urge the swaged collar out of the minor bore of the anvil of the tool, and wherein the tool collet is further pushed out of the tool, thereby allowing the tool collet to return to the open position, thereby allowing removal of the tool from the lockbolt pin tail.
10. A method as claimed in claim 8 wherein in the closed position, the pulling jaw formed by the internal lips of the arms of the collet has a shape complimentary to at least part of the that of the pull groove of the lockbolt.
11. A method as claimed in claim 10 wherein of the shape of the pulling jaw closely matches a first angled bearing surface provided on the pin tail of the lockbolt.
12. A collet substantially as hereinbefore described and with reference to the accompanying figures.
13. A tool substantially as hereinbefore described and with reference to the accompanying figures.