GB2513131A

GB2513131A - Torque application tool

Info

Publication number: GB2513131A
Application number: GB201306867A
Authority: GB
Inventors: Christopher John Durling
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 2013-04-16
Filing date: 2013-04-16
Publication date: 2014-10-22
Anticipated expiration: 2033-04-16
Also published as: GB201306867D0; GB2513131B

Abstract

The tool includes two torque application members 106 that are connected at a pivot axis (801, Figure 8) and respective first engagement portions (300, Figure 8) for engagement with angularly spaced castellations 110 on the nut. Two first links 101 are pivotally connected at second and third pivot axes (802, 803, Figure 8). A torque receiving formation 104 is connected to the torque application members at first and second connections thereby allowing the torque receiving formation to receive and transmit a torque to the torque application members via the first and second connections. The torque application members can, via the pivotal connections, vary their relative angular spacing to match the relative angular spacing of engaged castellations. The tool can eliminate uneven distribution of applied torque which may arise when using a conventional tool on a castellated nut due to machining tolerances in the nut. The nut may be a shaft nut for a gas turbine engine.

Description

TORQUE APPLICATION TOOL

Field of the Invention

The present invention relates to a tool for applying torque to a nut, and more particularly to a tool for applying torque to a castellated nut.

Background of the Invention

Nuts of the sort typically used on a main shaft of a gas turbine engine are highly stressed items and are required to resist the high levels of torque which are generated when tooling is applied to tighten or loosen the nut.

The nuts are normally tightened and loosened by means of torque applied to castellations machined on the body of the nut. Typically, the tool which engages with these castellations has its own castellations which are machined to match those on the nut. These are machined using close tolerances in order to engage evenly with the shaft nut castellations which also have to be machined to close tolerances.

Figures 1 and 2 show an example of a conventional castellated shaft nut 412 for use in a gas turbine engine. Castellations 410 are spaced around the circumference of an end of the nut, a thread 413 is formed at the internal surface of the nut, and a clamp face 411 is at the other end of the nut. In gas turbine environments, it is usually the case that torque must be applied through a minimum of four castellations in order not to over-stress the castellations or the body of the nut; but once more than two castellations are employed there arises a problem in that due to machining tolerances employed on both the nut and the torque application tool, it becomes impossible to guarantee an even distribution of torque between the four castellations of the nut.

Figure 3 shows a typical example of a conventional torque application tool 420 for applying torque to the shaft nut 412. Tool castellations 423, corresponding to the castellations 410 of the nut, are spaced around the circumference at an end the tool. The tool 420 further has a hexagonal protrusion 421 for mating with e.g. a torque spanner to allow the application of torque through the tool 420 and to the shaft nut 412.

Typically only about one third of the castellations on a given nut actually transmit torque (because of machining tolerances). It follows that in order to ensure that four castellations are engaged on a shaft nut, many more castellations may have to be machined (ten in the example of Figures ito 3). This is disadvantageous in terms of both the cost and the weight of the shaft nut. Further, the four castellations which are engaged may not be evenly distributed around the circumference of the nut.

Summary of the Invention

It would be desirable to provide a torque application tool which allows the even distribution of applied torque to castellations on a nut, regardless of the tolerance with which the castellations are machined.

Accordingly, a first aspect of the present invention provides a tool for applying torque to angulaily spaced castellations on a nut, the tool including: two torque application members having respective first engagement portions for engagement with respective angularly spaced castellations, the torque application members being pivotally connected to each other at a first pivot axis, two first links, each first link having a first end which is pivotally connected to a respective torque application member at a respective second pivot axis, and a second end which pivotally connects to the second end of the other first link at a third pivot axis, and a torque receiving formation which is operatively connected to the torque application members at first and second connections, thereby allowing the torque receiving formation to receive and transmit a torque to the torque application members via the first and second connections, wherein: the pivotal connections at the first, second and third pivot axes allow the torque application members to vary their relative angular spacing to match the relative angular spacing of the castellations engaged by the torque application members, and the first and second connections are adapted to accommodate changes in distances between the pivot axes produced by a variation in relative angular spacing of the torque application members.

Thus the tool enables evenly distributed application of torque to castellations on a castellated nut. Therefore, instead of having to machine a large number of castellations to ensure that four of them might apply some torque evenly, fewer castellations are required.

For example, the castellated nut can be machined to have just four castellations.

Furthermore, the machining tolerances of these castellations can be relaxed. The nut may therefore be lighter and cheaper than a conventional castellated nut.

In general, the nut has an axis of rotation and the tool can be arranged such that the first pivot axis is at least proximate to that axis. However, the changes in distances between the pivot axes caused by the torque application members varying their relative angular spacing often result in the first pivot axis being non-coaxial with the axis of rotation of the nut.

A second aspect of the present invention provides a use of the tool of the first aspect for applying torque to angularly spaced castellations on a nut.

For example, a method for applying torque to angularly spaced castellations on a nut comprises the steps of: providing a tool according to the first aspect; engaging the first engagement portions of the torque application members with the castellations by varying the relative angular spacing of the torque application members to match the relative angular spacing of the engaged castellations; and applying torque to the torque receiving formation such that torque is transmitted through the torque application members to the engaged castellations.

Optional features of the invention will now be set out. These are applicable singly or in any combination with any aspect of the invention.

The first connection may join the torque receiving formation to the torque application members at the third pivot axis. The third pivot axis may then be slidable relative to the torque receiving formation at the first connection to accommodate the changes in distances between the pivot axes. For example, the first connection may include a pin extending along the third pivot axis, which pin is slidably received in a slot formed in the torque receiving formation.

It is possible to apply torque to the nut at just two castellations. However, preferably torque is applied to the nut at four castellations. Thus the torque application members may further have respective second engagement portions for engagement with respective further angularly spaced castellations, the first pivot axis being located between the first and second engagement portions of each torque application member, the tool further including two second links, each second link having a first end which is pivotally connected to a respective torque application member at a respective fourth pivot axis, and a second end which pivotally connects to the second end of the other second link at a fifth pivot axis, the first pivot axis being located between the second and fourth pivot axes of each torque application member, and the pivotal connections at the first, fourth and fifth pivot axes allow the torque application members to vary their relative angular spacing to match the relative angular spacing of the further castellations engaged by the toique application members. The first and second engagement portions of each torque application member can thus engage with diametrically opposed castellations of the nut.

The second connection may join the torque receiving formation to the torque application membeis at the fifth pivot axis. However, it is possible foi the second connection to join the toique receiving formation to the torque application membeis at the first pivot axis.

The pivot axis of the second connection may be slidable relative to the toique receiving formation to accommodate the changes in distances between the pivot axes. For example, the second connection may include a pin extending along the pivot axis of the second connection, which pin is slidably received in a slot formed in the torque receiving formation.

The torque leceiving formation may be iotatable about an axis (e.g. aligned with the first pivot axis, which in turn may be approximately aligned with the axis of rotation of the nut) to receive and transmit the torque. The torque receiving formation may further have a male or female mating arrangement for mating with a further torque application tool at that axis. The male oi female mating airangement may be a hexagonal protrusion, for mating with, for example, a conventional torque spanner or geared torque multiplier.

The tool may further have a pair of extension members which are relatively rotatable about the first pivot axis, each extension member having a proximal end providing a matching engagement portion for engaging with the first engagement portion of a respective torque application member in place of the coiresponding castellation, and each extension member having a distal end providing a third engagement portion for engagement with that castellation, whereby the extension members allow the tool to apply torque to the castellations when the torque application members are unable to engage directly with the nut. The proximal end of each extension member may further provide a matching engagement portion for engaging with the second engagement portion of the respective torque application member in place of the corresponding castellation, and the distal end of each extension member may further provide a fourth engagement portion for engagement with that castellation. The extension membeis may be in the foim of a pair of coaxial, nested tubes.

A single size of the tool of the first aspect of the invention may be used that may cover a wide range of castellated nut diameters of typical gas turbine engines. The use of extension members with, for example, stepped diameters between their proximal and distal ends can help in this respect. Use of extension members may also allow nuts to be tightened in inaccessible locations such as deep inside an engine.

The nut may be a shaft nut, such as a shaft nut of a gas turbine engine.

Brief Descriøtion of the Drawings Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows an end view of a conventional castellated shaft nut; Figure 2 shows a view of the other end of the castellated shaft nut of Figure 1; Figure 3 shows a conventional torque application tool for the nut of Figures 1 and 2; Figure 4 shows a longitudinal cross-section through a ducted fan gas turbine engine; Figure 5 shows an example of a castellated shaft nut suitable for use with the present invention; Figure 6 shows a front end view of an embodiment of the tool of the present invention engaged with castellations on the shaft nut of Figure 5; Figure 7 repeats the view of Figure 6 with the torque receiving formation 104 made transparent to better show features covered by the formation; Figure 8 shows an isometric view from the rear of the tool of Figure 6; Figure 9 shows an isometric exploded view from the rear of the tool of Figure 6; Figure 10 shows an isometric view of from the rear of the tool of Figure 6 engaged with the shaft nut of Figure 5; Figure 11 shows an isometric view from the front of the tool of Figure 6; Figure 12 shows an isometric exploded view from the front of the tool of Figure 6; Figure 13 shows a detail of the tool of Figure 6; Figure 14 shows a representation of the axes of rotation of a castellated nut and the tool of Figure 6 when the tool is engaged with the castellations on the nut; Figure 15 shows a further representation of the axes of rotation of Figure 14 for a variation in positioning of the castellations; Figure 16 shows an isometric view of the tool of Figure 6 engaged with a special extension device for engagement with the shaft nut of Figure 5; and Figure 17 shows an exploded isometric view of an embodiment of the special extension device of Figure 16.

Detailed Description and Further Optional Features of the Invention With reference to Figure 4, a ducted fan gas turbine engine is generally indicated at 10 and has a principal and rotational axis X-X. The engine comprises, in axial flow series, an air intake 11, a propulsive fan 12, an intermediate pressure compressor 13, a high-pressure compressor 14, combustion equipment 15, a high-pressure turbine 16, an intermediate pressure turbine 17, a low-pressure turbine 18 and a core engine exhaust nozzle 19. A nacelle 21 generally surrounds the engine 10 and defines the intake 11, a bypass duct 22 and a bypass exhaust nozzle 23.

During operation, air entering the intake 11 is accelerated by the fan 12 to produce two air flows: a first airflow A into the intermediate pressure compressor 13 and a second airflow B which passes through the bypass duct 22 to provide propulsive thrust. The intermediate pressure compressor 13 compresses the air flow A directed into it before delivering that air to the high pressure compressor 14 where further compression takes place.

The compressed air exhausted from the high-pressure compressor 14 is directed into the combustion equipment 15 where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive the high, intermediate and low-pressure turbines 16,17,18 before being exhausted through the nozzle 19 to provide additional propulsive thrust. The high, intermediate and low-pressure turbines respectively drive the high and intermediate pressure compressors 14,13 and the fan 12 by suitable interconnecting shafts.

Figure 5 shows a castellated shaft nut 112 suitable for use with the present invention. The nut may be used to connect the fan disk 12 of the propulsive fan of the engine 10 to the respective interconnecting shaft. Other possible uses of such nuts are to connect the high, intermediate and low-pressure turbines 16,17,18 and the intermediate and low-pressure compressors 13,14 to their shafts, and to connect gears to shafts in the engine's internal, intermediate and accessory gearboxes (not shown in Figure 4, but used to start the engine and extract accessory power therefrom). The nut has four equally angularly spaced castellations 110 at one end thereof, a clamp face 111 at the other end thereof, and an internal thread 113.

Figures 6 to 13 show an embodiment of the tool 120 of the present invention. In Figures 6, 7 and 10, the tool is shown engaged with the shaft nut 112 of FigureS. The tool 120 employs two torque application members 106 which are able to rotate relative to each other about a first pivot axis 801, indicated in Figure 8.

As shown in Figure 8, each torque application member 106 has a first engagement portion 300 and second engagement portion 301, separated by thefirst pivot axis 801, which is typically centrally located on each torque application member 106. The torque application members 106 pivot relative to each other at the first pivot axis 801 about a pin 107 extending in the direction of the first pivot axis through holes formed in the torque application members 106. The pin 107 can conveniently be provided by a torque receiving formation 104, as shown in Figure 9. The torque receiving formation 104 has an axis of rotation centred on the pin 107, and further has a hexagonal protrusion 130 at this axis which, in use, mates with, for example, a conventional torque spanner or geared torque multiplier.

The tool 120 has two first links 101, which are connected pivotally at first ends of the first links 101 by pin 108 and hole arrangements to respective ends of the torque application members 106 to form second pivot axes 802. The first links 101 are further connected to each other at their second ends by another pin 118 and hole arrangement to form a third pivot axis 803.

The tool 120 also has two second links 102, which are connected pivotally at first ends of the second links 102 by pin 109 and hole arrangements to respective other ends of the torque application members 106 to form fourth pivot axes 804. The second links 102 are further connected to each other at their second ends by another pin 119 and hole arrangement to form a fifth pivot axis 805.

With such an arrangement of pivot axes, variation in relative angular spacing of the torque application members 106 (produced by pivoting of the torque application members at the first pivot axis 801) in turn causes pivoting at the second 802, third 803, fourth 804 and fifth 805 pivot axes, with a result that the distance between the third and fifth pivot axes changes.

The pins 118,119 at the third 803 and fifth 805 pivot axes respectively are also connected to the torque receiving formation 104. Thus the torque receiving formation 104, which acts as a cross link between the third and fifth pivot axes, is operably connected to the torque application members 106, allowing torque applied to the torque receiving formation 104 at the protrusion 130 to be transmitted to the torque application memberslO6.

More particularly, in a first connection between the torque receiving formation 104 and the torque application members 106, the pin 118 extends into a slot 201 (shown in the detailed view of Figure 13) formed in one end of the torque receiving formation 104. Similarly, in a second connection between the torque receiving formation 104 and the torque application members 106, the pin 119 extends into a slot 201 formed in the other end of the torque receiving formation 104. The pins 118 and 119 are slidably movable in the slots 201, so that the torque receiving formation 104 can accommodate a change in distance between the third and fifth pivot axes 803,805.

As shown in Figures 6, 7 and 10, in operation, the engagement portions 300,301 of the torque application members 106 are offered up against the castellations 110 of the shaft nut 112. Because the torque receiving formation 104 can accommodate a change in distance between the third and fifth pivot axes 803,805, when torque is applied to the torque receiving formation 104, the torque application members 106 are able to automatically adjust their relative angular spacing so that the engagement portions 300,301 of each torque application member 106 engage with a respective castellation 110.

Figure 14 shows a representation of the axis of rotation 810 of a castellated nut 112 and the axis of rotation of the tool 120, the torque application members 106 being illustrated in schematic form, and the axis of rotation of the tool corresponding to the first pivot axis 801.

Typically, thefourengaged castellations 110 will have nominal angularspacings of 90°.

However, Figure 14 shows an extreme example where adjacent castellations have a nominal angular spacing of approximately 60°. The torque application members 106 are engaged with the castellations 110 on the shaft nut 112, and consequently, the angle 34 between the torque application members 106 is 60° to match the angular spacing of the castellations 110. However, the machining tolerances of the castellations 110 result in the engaged flanks of the castellations 110 being removed slightly from their nominal positions, and the torque application members 106 adjust their relative angular position to accommodate this variation. The result is that the first pivot axis 801 is generally not quite coaxial with the axis of rotation 810 of the nut.

As shown in form in Figure 15, the torque application members 106 can adjust their relative angular position quite significantly (e.g. to 55° as drawn) to accommodate different positionings of the castellations 110. When the angle 34 between the torque application members 106 changes, the angle 35 between the links 101,102 and the torque application members 106, and the angle 36 between the links 101,102 and a line drawn through the third and fifth pivot axes, also change. As previously mentioned, this results in a change in the distance between the third and fifth pivot axes 803,805, as indicated in Figure 15 by the double headed arrows 37, which also represent the sliding movement of the pins 118,119 in the slots 201.

As the four engaged castellations 110 typically have nominal angular spacings of 90°, in general! the length of the links 101, 102 can be chosen such that the angle 34 between the torque application members 106 is approximately 90°, and the angles 35 and 36 are approximately equal. Further, because the machining tolerances of the castellations usually only result in the engaged flanks of the castellations 110 being slightly removed from their nominal positions, the slot 201 may only need to be short. The slots 201 and links 101, 102 can be shaped such that pins 118 and 119 do not have bending loads applied to them, only shear loads.

The two torque application members 106 can be identical for manufacturing/cost convenience, but need not necessarily be so. Thus the torque application members 106 may differ in any of e.g. dimension, structure or material. Similarly, the links 101, 102 can be identical, but may be of differing length or may differ in any of e.g. dimension, structure or material. As illustrated, the first to fifth pivot axes are provided by pin and hole arrangements, but the axes can be provided by other arrangements utilising e.g. hinges, bushes, gimbals or toggles. Similarly, as illustrated, the pins 118 and 119 are slidably movable in the slots 201, but slidability of the respective pivot axes relative to the torque receiving formation can be provided by other arrangements, such as e.g. lug and groove mechanisms.

Having first 101 and second 102 links provides a strong and symmetrical tool 120. However, it is possible for the tool 120 to have e.g. only the first links 101 (although the stress applied through the links 101 is then greater). In this case, the tool 120 does not have the fourth and fifth pivot axes, and the second connection between the torque receiving formation 104 and the torque application members 106 can be made at the first pivot axis 801 using pin 107.

As the pin 118 at the third pivot axis 803 is slidably movable in its slot 201, the torque receiving formation 104 can still accommodate a change in distance between the third and first pivot axes 803,801. Nonetheless, in such an arrangement, it may also be helpful for the pin 107 at the first pivot axis 801 to be slidably connected to the torque receiving mechanism 104.

The tool 120, as illustrated in Figures 6 to 15, can be scaled to any diameter of shaft nut, for example nut sizes in the range 0130mm to 0150mm are typical. However, the usefulness of the tool 120 can be enhanced with the use of an extension device which allows the tool 120 to apply torque to the castellations 110 when the torque application members are unable to engage directly with the shaft nut 112.

An example of such an extension device is shown in Figures 16 and 17. The device comprises a pair of extension members in the form of nested coaxial tubes 90,91. In use, the nested coaxial tubes 90,91 are positioned coaxially with the first pivot axis 801. The tubes 90,91 can be of any length to suit the build requirements of the shaft nut 112 (for example, very long tubes 90,91 may be used for shaft nuts 112 which are be buried deep inside an engine).

Each tube 90,91 has stepped engagement castellations 92 at a proximal end for engaging with the first and second engagement portions 300,301 of a respective torque application member 106, instead of the corresponding castellations 110 of the shaft nut 112. Further each tube 90,91 has stepped engagement castellations 93 at its opposing distal end, for engagement with the castellations 110 that would have been engaged by the first and second engagement portions 300,301. The engagement castellations 92,93 do not need to be accurately machined (circumferentially) as the tool 120 automatically compensates for machining inaccuracies. To further enhance the usefulness of the tool 120, the tubes 90,91 can be stepped in or out in diameter at the end which engages with the shaft nut 112, thereby allowing one size of the tool 120 to cover many different shaft nut diameters.

While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. For example, the application of the tool is not limited to shaft nuts of gas turbine engines, and it can be used in any industry where castellated nuts are used. These may include for example the wind turbine industry, power generation industry or machine tool industry. Further, while shaft nuts have been described herein, the nuts may equally be of other type. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the scope of the invention.

Claims

CLAIMS1. A tool (120) for applying torque to angularly spaced castellations (110) on a nut (112), the tool including: two torque application members (106) having respective first engagement portions (300) for engagement with respective angularly spaced castellations, the torque application members being pivotally connected to each other at a first pivot axis (801), two first links (101), each first link having a first end which is pivotally connected to a respective torque application member at a respective second pivot axis (802), and a second end which pivotally connects to the second end of the other first link at a third pivot axis (803), and a torque receiving formation (104) which is operatively connected to the torque application members at first and second connections, thereby allowing the torque receiving formation to receive and transmit a torque to the torque application members via the first and second connections, wherein: the pivotal connections at the first, second and third pivot axes allow the torque application members to vary their relative angular spacing to match the relative angular spacing of the castellations engaged by the torque application members, and the first and second connections are adapted to accommodate changes in distances between the pivot axes produced by a variation in relative angular spacing of the torque application members.
2. The tool as claimed in Claim 1, wherein the first connection joins the torque receiving formation to the torque application members at the third pivot axis.
3. The tool as claimed in Claim 1 or Claim 2, wherein the third pivot axis is slidable relative to the torque receiving formation at the first connection to accommodate the changes in distances between the pivot axes.
4. The tool as claimed in any one of the preceding claims, wherein: the torque application members have respective second engagement portions (301) for engagement with respective further angularly spaced castellations, the first pivot axis being located between the first and second engagement portions of each torque application member, the tool further including two second links (102), each second link having a first end which is pivotally connected to a respective torque application member at a respective fourth pivot axis (804), and a second end which pivotally connects to the second end of the other second link at a fifth pivot axis (805), the first pivot axis being located between the second and fourth pivot axes of each torque application member, and the pivotal connections at the first, fourth and fifth pivot axes allow the torque application members to vary their relative angular spacing to match the relative angular spacing of the further castellations engaged by the torque application members.
5. The tool as claimed in Claim 4, wherein the second connection joins the torque receiving formation to the torque application members at the fifth pivot axis.
6. The tool as claimed in any one of Claims 1 to 4, wherein the second connection joins the torque receiving formation to the torque application members at the first pivot axis.
7. The tool as claimed in Claim 5 or Claim 6, wherein the pivot axis of the second connection is slidable relative to the torque receiving formation to accommodate the changes in distances between the pivot axes.
8. The tool as claimed in any one of the preceding claims wherein the torque receiving formation is rotatable about an axis to receive and transmit the torque, the torque receiving formation further having a male or female mating arrangement (130) for mating with a further torque application tool at that axis.
9. The tool as claimed in any one of the preceding claims further having a pair of extension members (90, 91) which are relatively rotatable about the first pivot axis, each extension member having a proximal end providing a matching engagement portion (92) for engaging with the first engagement portion of a respective torque application member in place of the corresponding castellation, and each extension member further having a distal end providing a third engagement portion (93) for engagement with that castellation, whereby the extension members allow the tool to apply torque to the castellations when the torque application members are unable to engage directly with the nut.
10. The tool as claimed in Claim 9 when dependent on Claim 4, wherein the proximal end of each extension member further provides a matching engagement portion for engaging with the second engagement portion of the respective torque application member in place of the corresponding castellation, and the distal end of each extension member further provides a fourth engagement portion for engagement with that castellation.
11. The tool as claimed in Claim 9 or Claim 10, wherein the extension members are coaxial tubes.
12. Use of the tool as claimed in any one of the preceding claims for applying torque to angularly spaced castellations on a nut.
13. The use of Claim 12 wherein the nut is a shaft nut of a gas turbine engine.
14 A method for applying torque to angularly spaced castellations on a nut, the method comprising the steps of: providing a tool according to any one of Claims ito 13; engaging the first engagement portions of the torque application members with the castellations by varying the relative angular spacing of the torque application members to match the relative angular spacing of the engaged castellations; and applying torque to the torque receiving formation such that torque is transmitted through the torque application members to the engaged castellations.
15. A tool substantially as hereinbefore described with reference to and as shown in Figures5tol7.
16. Use of a tool substantially as hereinbefore described with reference to and as shown in Figures 5 to 17.
17. A method substantially as hereinbefore described with reference to and as shown in Figures 5 to 17.