CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 61/400,899 filed August 4, 2010, the disclosure of which is hereby incorporated by reference in its entirety.

STATEMENT CONCERNING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.

FIELD OF THE INVENTION

[0003] This invention generally relates to devices for tensioning fasteners and more particularly to devices for tensioning fasteners connecting adjacent sections of a turbine shaft.

BACKGROUND OF THE INVENTION

[0004] Gas turbine shafts are typically formed in multiple sections that are coupled at flanges by sets of fasteners. These fasteners are specially designed to carry the relatively high loads transmitted by the shaft, which in some cases can exceed 250 MW. In particular, each fastener typically includes a stud that extends through the flange and nuts that connect to the ends of the stud. The heads of the fasteners are recessed in the flanges so as not to protrude when the shaft is rotated at high speed. During installation, the studs are elongated, and thereby subjected to a pre-stress on the order of 20 ksi, and the nuts are then tightened down against the flange to maintain the pre- stress.

[0005] Unfortunately, such fasteners are relatively cumbersome to install. In particular, fastener tensioners capable of applying such large pre-stresses are heavy, in some cases exceeding 75 pounds in weight. Furthermore, these tensioners are typically hoisted into position using ropes, belts and chains and are maneuvered around the flange by multiple technicians. Such a task is physically demanding, but to further exacerbate these issues, a tapered threaded shaft of the tensioner must then be connected with a high degree of precision to a tapered threaded hole of each stud which has a limited length of thread engagement and is easy to cross-thread or strip. [0006] Considering the drawbacks of previous fastener tensioners, improved tensioning devices and methods that involve a reduced amount of physical labor and facilitate ease of use are needed.

SUMMARY OF THE INVENTION

[0007] In one aspect, the present invention provides a device for tensioning a fastener connecting ^' adjacent components. The fastener has a tapered threaded surface, and the device comprises an adapter including a tapered threaded surface configured to engage the tapered threaded surface of the fastener. The adapter further includes a cylindrical threaded surface opposite the tapered threaded surface of the adapter. The device further comprises a tensioner including a housing and a puller member supported within the housing. The puller member has a cylindrical threaded surface configured to engage the cylindrical threaded surface of the adapter, and the puller member is translatable within the housing to translate the adapter and thereby apply tension to the fastener.

[0008] In another aspect, the present invention provides a device for tensioning a fastener that connects adjacent components. The device comprises a clamshell including a stationary member configured to be fixedly connected about the perimeter of one of the adjacent components. The clamshell further includes a rotatable member rotatably supported by the stationary member. The device further comprises a tensioner supported by the rotatable member. The tensioner includes a housing and a puller member supported by the housing. The puller member is translatable relative to the housing to thereby apply tension to the fastener.

[0009] In yet another aspect, the present invention provides a method of tensioning a fastener using a tensioning device. The method includes the step of positioning the fastener in an opening of a joint formed at an interface of two separate components such that a proximal end of the fastener is disposed on a proximal side of the joint and a distal end of the fastener is disposed on a distal side opposite the proximal side. The method further includes the step of connecting a clamshell about a perimeter of one of the two separate components. The clamshell includes a stationary member fixedly connected about the perimeter of the one of the two separate components and a rotatable member rotatably supported by the stationary member. The method further includes the steps of connecting a tensioner to the rotatable member, engaging the proximal end of the fastener with the tensioner, and applying a tensile force to the fastener using the tensioner.

[0010] The foregoing and other objects and advantages of the invention will appear in the detailed description which follows. In the description, reference is made to the accompanying drawings which illustrate a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and:

[0012] FIG. 1 is a perspective view of a fastener tensioning device according to the present invention connected to a turbine shaft;

[0013] FIG. 2 is a perspective view of an adapter of the tensioning device of FIG. 1 and a fastener to be tensioned by the tensioning device;

[0014] FIG. 3 is an exploded perspective view of the adapter and the fastener of FIG. 2;

[0015] FIG. 4 is a perspective view of the tensioning device of FIG. 1 separated from the turbine shaft;

[0016] FIG. 5 is a cross sectional view of the tensioning device and the turbine shaft along line 5-5 of FIG. 1;

[0017] FIG. 6 is a perspective view of a tensioner of the tensioning device of FIG. 1 in a disengaged position;

[0018] FIG. 7 is a section view of the tensioner along line 7-7 of FIG. 6;

[0019] FIG. 8 is a perspective view of a tensioner of the tensioning device of FIG. 1 in a tensioning position;

[0020] FIG. 9 is a section view of the tensioner along line 9-9 of FIG. 8;

[0021] FIG. 10 is a perspective view of a second embodiment of a tensioning device according to the present invention connected to a turbine shaft;

[0022] FIG. 11 is another perspective view of the tensioning device of FIG. 10;

[0023] FIG. 12 is a side view of the tensioning device of FIG. 10 in a tensioning position; [0024] FIG. 13 is an end view of the tensioning device and the turbine shaft of FIG. 10;

[0025] FIG. 14 is a perspective view of a tensioner of the tensioning device of FIG. 10 in a disengaged position;

[0026] FIG. 15 is a side view of the tensioner of FIG. 14 in a tensioning position and illustrating schematically a locking mechanism of the tensioning device in a locked position;

[0027] FIG. 16 is a section view of the locking mechanism along line 16-16 of FIG. 15; and

[0028] FIG. 17 is a section view like FIG. 16 but with the locking mechanism in an unlocked position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0029] Referring now to FIGS. 1-9, a tensioning device 50 according to the present invention generally includes a clamshell 52 that is mounted about the perimeter of one section of a turbine shaft 10. The clamshell 52 rotates a support frame 54 and one or more tensioners 56 about the perimeter of the turbine shaft 10 to permit the tensioners 56 to pre-stress a set of fasteners 12. Each of the fasteners 12 supports an adapter 58 that is easily connected to the tensioners 56. In the following paragraphs, the clamshell 52 and the support frame 54 are first described in detail followed by the tensioners 56 and the adapters 58.

[0030] Referring particularly to FIGS. 1 and 4, the clamshell 52 generally includes a stationary member 60 that is configured to fixedly connect to the turbine shaft 10. The stationary member 60 includes semicircular segments that allow the component to be positioned circumferentially around the shaft 10. These segments house internal bearings (not shown) that support a rotatable member 62. As such, the rotatable member 62 can be made to spin about a central axis of the stationary member 60 when driven by a motor (not shown). Other features of the clamshell 52 may be as described in U.S. Patent Nos. 4,739,685, 4,939,964, 5,549,024 and/or 6,619,164, for example, and incorporated herein by reference. The clamshell 52 is not limited to the structure disclosed in these references, but can also include other components and features of similar devices. [0031] Using a clamshell to rotate and reposition one or more tensioners 56 about the perimeter of a turbine shaft 10 is relatively easy compared to the previous methods of hoisting tensioners 56 into position using belts and chains.

[0032] Referring now to FIGS. 4-6, in the embodiments shown in the figures the support frame 54 includes two generally identical halves that each support one of the tensioners 56. In particular, each half of the support frame 54 includes a first

connection bracket 64 that fixedly connects to the rotatable member 62 of the clamshell 52. The first connection bracket 64 engages a second connection bracket 66 through, e.g., a dovetail connection. The second connection bracket 66 mounts two axially extending support rods 68 that support several components.

[0033] For example, the support rods 68 translatably mount tensioner brackets 70 that secure one of the tensioners 56. As such, both the tensioner brackets 70 and the tensioners 56 may be translated from a disengaged position in which the tensioner 56 is spaced apart from the adapter 58 (FIG. 6) to a tensioning position in which the tensioner 56 engages the adapter 58 (FIG. 8).

[0034] The support rods 68 also mount resilient bumpers 72 proximate the

connection brackets 64, 66. The resilient bumpers 72 are configured to stop the tensioner 56 if the adapter 58 unintentionally disconnects from a fastener 12 while tensioning the fastener 12 and begins to move away from the fastener 12. As such, the resilient bumpers 72 may comprise rubber or other materials that are capable of undergoing significant reversible deformation when impacted by another object.

[0035] The opposite ends of the support rods 68 mount a roller bracket 74. As the name implies, the roller bracket 74 includes one or more rollers 76 that engage the surface of the turbine shaft 10 and support the support frame 54 and the tensioners 56 there about. These ends of the support rods 68 also mount arcuate connectors 78 that extend about the perimeter of the turbine shaft 10 and connect to one of the support rods 68 on the opposite side of support frame 54. As such, the arcuate connectors 78 provide further rigidity for the support frame 54 and ensure the tensioners 56 remain in diametrically opposed positions relative to one another.

[0036] Referring now to FIGS. 6-9, each tensioner 56 generally includes a housing 112 that accommodates a translatable internal puller member 1 14. The housing 112 also supports a hydraulic port 116 in communication with one or more internal hydraulic chambers 118. These chambers 118 receive hydraulic fluid to displace the puller member 114 and thereby elongate and apply a pre-stress to the fastener 12.

[0037] As shown most clearly in FIGS. 7 and 9, the puller member 114 includes an internal cylindrical threaded surface 120 at a first end that engages an external cylindrical threaded surface 122 of the adapter 58. The opposite end of the puller member 114 extends through the housing 112 and includes a square drive hole 124. These features permit a technician to connect a tool (e.g., a ratchet) to the square drive hole 124 and turn the puller member 114 to thereby engage the puller member 114 and the adapter 58. In addition, such a process of connecting the puller member 114 and the adapter 58 is relatively easy compared to those required to connect the tapered threaded surfaces of previous puller member designs to a fastener.

[0038] In addition to the components described above, the tensioner 56 further includes a gearbox 126 that is driven (e.g., by rotating a tool connected to another square drive hole 128) to rotate a collar 130 supported by the housing 112. The collar 130 includes one or more pins 132 that are engageable with a nut 14 connected to the end of the fastener stud 16. As such, the collar 130 is rotatable to tighten down the nut 14 and maintain the pre-stress on the fastener stud 16 after the tensioner 56 elongates the fastener stud 16.

[0039] Referring now to FIGS. 2 and 3, the adapter 58 includes the external cylindrical threaded surface 122 described above to connect to the puller member 114. The end of the adapter 58 proximate the cylindrical threaded surface 122 defines a square drive hole 134. This feature permits a technician to connect a tool (e.g., a ratchet) to the square drive hole 134 and turn the adapter 58 to thereby engage an external tapered threaded surface 136 of the adapter 58 with an internal tapered threaded surface 18 of the stud 16. Due to the relatively small size of the adapter 58, the process of connecting the adapter 58 to the stud 16 is relatively easy compared to those required to connect the tapered threaded surfaces of previous puller member designs directly to a fastener (provided, of course, that the adapter 58 is connected to the stud 16 before the puller member 114 is connected to the adapter 58).

Furthermore, if the tapered threaded surface 136 of the adapter 58 is damaged, only the adapter 58 would need to be repaired or replaced. With previous tensioner designs, the entire tensioner would typically be sent for repairs in such a case.

[0040] Referring now to FIGS. 10-17, a second embodiment of a tensioning device 50 according to the present invention is generally as described above; that is, the tensioning device 50 includes a clamshell 52 that rotatably mounts a support frame 54. The support frame 54 translatably mounts one or more tensioners 56, and each tensioner 56 applies a pre-stress to fasteners 12 through adapters 58. In addition, the second embodiment of the tensioning device 50 also includes a locking mechanism 140 for each tensioner 56 that prevents the tensioner 56 from moving if the adapter 58 unintentionally disconnects from a fastener 12 while tensioning the fastener 12.

[0041] As shown most clearly in FIGS. 14-17, the locking mechanism 140 includes a rod 142 translatably supported by one of the tensioner brackets 70. The rod 142 includes first diameter sections 144 and second reduced diameter sections 146. In the tensioning position (FIGS. 15-17), the rod 142 may be moved to a locked position in which the first diameter sections 144 of the rod 142 are disposed within reduced diameter sections 148 of the support rods 68 (see FIG. 14). As such, in the locked position the first diameter sections 144 of the rod 142 may contact ends 150 of the reduced diameter sections 148 to prevent the tensioner 56 from moving relative to the support rods 68.

[0042] Conversely, the rod 142 may be translated to a unlocked position in which the reduced diameter sections 146 of the rod 142 are disposed adjacent the reduced diameter sections 148 of the support rods 68. In this position, the surface of the rod 142 does not contact the support rods 68 and, as such, the tensioner 56 may be translated to the disengaged position (FIG. 14). The locking mechanism 140 also preferably includes a compression spring 152 that biases the rod 142 toward the locked position.

[0043] The tensioning device 50 described above may be modified in various manners. For example, instead of supporting two tensioners 56, the tensioning device 50 could include a single tensioner 56 and a diametrically opposed counterweight (not shown). Similarly, the tensioning device 50 could include more than two tensioners 56.

[0044] From the above description, it should be apparent that tensioning devices and methods according to the present invention reduce the amount of physical labor required by technicians to install turbine fasteners. It should also be apparent that these tensioning devices and methods may be used with current tapered flange fastener designs; that is, no redesign is needed to provide fasteners that may be used with the fastening device.

[0045] A preferred embodiment of the invention has been described in considerable detail. Many modifications and variations to the preferred embodiment described will be apparent to a person of ordinary skill in the art. Therefore, the invention should not be limited to the embodiment described, but should be defined by the claims that follow.