Hydraulic Bolt Tensioner and Pressure Indicating Manifold

Abstract

A manifold (20, Figure 1) for connecting a bolt tensioning mechanism 14 to a supply of pressurised hydraulic fluid includes a connector (24, Figure 2) on a manifold body 22 for connection to the fluid

Description

[0001] This invention relates to hydraulic bolt tensioners and to manifolds for use with such devices.

[0002] Hydraulic bolt tensioners are devices that can be temporarily attached to a bolt 5 and activated to apply tension to the bolt when tightening a nut on the bolt. The tension force is applied to the bolt by a hydraulic system that can be energised by connection to a supply of hydraulic fluid. Once the nut has been tightened on the tensioned bolt, pressure can be released to allow the tensioner to be removed and used elsewhere.

[0003] The supply of pressurised fluid is usually a pump with a pressure gauge that 10 can indicate the pressure of fluid supplied to the tensioner. However, it is often not possible to place the pump close to the tensioner, such as when the bolt is located in a confined space. In such cases, the pump can be 2 - 10 m from the tensioner. This means that an operative working on the tensioner may not be able to see the pressure gauge and know when the pressure is being applied to the tensioner. For safety 15 reasons, it is important that an operative knows the pressure state of the tensioner when working on or near to it.

[0004] This invention aims to provide a tensioner that allows an operative to know the pressure state of the tensioner even in confined spaces or where remote from the source of pressurised hydraulic fluid. 20

[0005] One aspect of the invention comprises a manifold for connecting the tensioning mechanism to a supply of pressurised hydraulic fluid, comprising: a manifold body; a connector on the manifold body for connection to the supply of pressurised hydraulic fluid; 25 a pressure conduit extending through the manifold body from the connector to a further connector for connection to a tensioning mechanism; a side branch extending from the pressure conduit to a cylinder housing a primary piston and a secondary piston on the opposite side of the primary piston to the side branch, wherein the secondary piston has an indicator pin projecting into a bore in 24 02 25 the cylinder wall which extends from an end of the cylinder to the outside of the manifold body, and a spring located between the secondary piston and the end of the cylinder to urge the secondary piston towards the primary piston; wherein, when the pressure conduit contains pressurised hydraulic fluid, the 5 primary piston is forced along the cylinder so as to force the second piston along the cylinder against the spring such that the indicator pin projects from the bore outside the manifold body.

[0006] Another aspect of the invention comprises a hydraulic bolt tensioner comprising a tensioning mechanism that can be connected to a bolt and activated by hydraulic 10 pressure to apply tension the bolt, and the manifold connected to the tensioning mechanism by the further connector.

[0007] The pin provides a simple visual indication when the device is under pressure. When pressure is released, the spring will cause the pin to retract into the bore, indicating that the device is no longer under pressure. 15

[0008] A pressure cycle counter can be housed in the manifold body.

[0009] The stiffness of the spring can be selected so that the indictor pin projects from the manifold body only when the pressure of the pressurised fluid in the conduit exceeds a predetermined level. The stiffness of the spring can be selected so that the amount that the indictor pin projects from the manifold body is indicative of the 20 pressure of the pressurised fluid in the conduit.

[0010] The indicator pin can include visual markings along its length to indicate the amount of the pin that projects from the manifold body.

[0011] Other aspects of the invention will be apparent from the following detailed description. 25

[0012] Figure 1 shows a hydraulic bolt tensioner and manifold according to an embodiment of the invention. Figure 2 shows the manifold of Figure 1 in an unpressurised state. Figure 3 shows a cross section through the manifold shown in Figure 2. Figure 4 shows the manifold of Figure 1 in a pressurised state. 30 Figure 5 shows a cross section through the manifold shown in Figure 4. 24 02 25 Figure 6 shows a partial view of a variant of the manifold shown in Figures 1 -5.

[0013] Figure 1 shows an external view of a hydraulic bolt tensioner according to one embodiment of the invention. The hydraulic bolt tensioner comprises a lower bridge 5 section 10 that fits over a nut to be tightened (not shown) that is already engaged on a bolt (also not shown). The bridge section 10 includes a nut drive mechanism 12 that can be activated from the outside of the tensioner and can wind the nut down on the bolt. In use, the bridge section 10 sits on the work piece (not shown) against which the nut is to be tightened. An upper section 14 comprises the tensioning mechanism. The 10 tensioning mechanism comprises a hydraulic cylinder or load cell 16 that houses a piston (not shown). A puller bar 18 sits on top of the piston and can be engaged on the upper end of the bolt in use. Once the puller bar 18 has been engaged on the bolt, pressurised hydraulic fluid can be supplied to the hydraulic cylinder 16 via a manifold 20 mounted on the outside of the hydraulic cylinder 16 to force the piston against the 15 puller bar 18 and apply tension to the bolt. The nut drive mechanism 12 can then be used to wind the nut down into contact with the work piece. Hydraulic pressure can then be released and the puller bar 18 disengaged from the bolts and the bolt tensioner removed from the bolt, leaving it in place with tension maintained by the nut.

[0014] Figures 2 and 3 show external and cross section views of the manifold 20. The 20 manifold 20 comprises a manifold body 22 which is mounted on the outside of the hydraulic cylinder 16 of the tensioning mechanism. The manifold has a connector 24 that can be connected to a supply of pressurised fluid, such as a hose from a compressor (not shown). The connector 24 communicates with an internal conduit 26 which in turn communicated with the hydraulic cylinder of the tensioning mechanism. In 25 this example, the internal conduit has two connections 26a, 26b to the hydraulic cylinder. One connection or more than two connections are also possible.

[0015] The conduit 26 has a side branch 28 that leads into a cylinder 30 formed in the manifold body 22. The cylinder 30 houses two pistons: a primary piston 32 closer to the side branch 28, and a secondary piston 34 on the opposite side of the primary piston 30 32 to the side branch 28. The primary piston 32 forms part of a pressure cycle counter 36 mounted in the manifold body 22. The space 38 between the primary and secondary pistons 32, 34 is filled with hydraulic fluid. 24 02 25

[0016] An indicator pin 40 extends from the side of the secondary piston 34 opposite to the primary piston 32 into a bore 42 through the manifold body 22 that extends from the end 44 of the cylinder 30 opposite to the side branch 28 to open to the outside of the body 22. A compression spring 46 is located in the cylinder 30 around the indicator pin 5 40 between the secondary piston 34 and the end 44 of the cylinder 30. The compression spring 46 acts to urge the secondary piston 34 towards the primary piston 32.

[0017] Figures 2 and 3 show the manifold 20 in an unpressurised state, i.e. before pressurised fluid is supplied through the connector. In this state, the primary piston 32 10 is at the bottom of the cylinder 30 and the spring 44 urges the secondary piston 34 towards the primary piston 32, the fluid in the space 38 maintaining the separation of the pistons 32, 34. In this state, the end of the indictor pin 40 sits within the bore 42 and does not project from the surface of the manifold body 22.

[0018] Figures 4 and 5 show the manifold of Figures 2 and 3 when connected to a 15 supply of pressurised hydraulic fluid. In this case, the primary piston 32 is exposed to hydraulic fluid pressure in the conduit 26 which urges it up in the cylinder 30. This is turn acts through the fluid in the space 38 on the secondary piston 34, forcing it against the spring 44 such that the secondary piston 34 moved up the cylinder 30, compressing the spring 44 and causing the indicator pin 40 to move up the bore 42 so 20 that the end 40a of the indicator pin projects from the bore 42 above the surface of the manifold body 22. The projecting end 40a provides a simple visual indication to an operator that the tensioner is under pressure. To aid visual identification, the pin 40 can be a distinctive colour compared to that of the manifold body 22.

[0019] When pressure is released in the manifold, the primary piston 32 descends in 25 the cylinder 30 and the secondary piston 34 moves back down under the influence of the spring 44, withdrawing the end of the indictor pin 40a back below the surface of the manifold body 22 such that it is no longer visible externally.

[0020] In the embodiment discussed above, the primary piston 32 forms part of a pressure cycle counter 36. Consequently, the primary piston 34 is configured to be 30 either at the top or bottom of its stroke depending on whether or not pressure is present for a clear pressure cycle indication. However, it is not essential that the primary piston forms part of a cycle counter. In such cases, the rate of the spring 44 can be selected such that the amount of the end of the indicator pin 40a that projects above the surface of the manifold body 22 will depend on the pressure of hydraulic fluid supplied to the manifold 20. In such a case, it can be useful to provide visual markings on the indicator pin 40 to provide an estimate of the pressure in the manifold. Figure 6 shows one variant, in which a series of lines 48 are provided on the indicator pin so that the 5 operator can visually estimate the level of pressure in the manifold. Other visual indicators such as coloured stripes, graded colours, or any other such distinctive marks can be used depending on requirements.

[0021] Further changes can be made within the scope of the invention. 24 02 25 24 02 25

Claims

1. A manifold for connecting a bolt tensioning mechanism to a supply of pressurised hydraulic fluid, comprising:a manifold body;5 a connector on the manifold body for connection to the supply ofpressurised hydraulic fluid;a pressure conduit extending through the manifold body from the connector to a further connector for connection to a tensioning mechanism;a side branch extending from the pressure conduit to a cylinder housing10 a primary piston and a secondary piston on the opposite side of the primarypiston to the side branch, wherein the secondary piston has an indicator pin projecting into a bore in the cylinder wall which extends from an end of the cylinder to the outside of the manifold body, and a spring located between the secondary piston and the end of the cylinder to urge the secondary piston15 towards the primary piston;wherein, when the pressure conduit contains pressurised hydraulic fluid, the primary piston is forced along the cylinder so as to force the second piston along the cylinder against the spring such that the indicator pin projects from the bore outside the manifold body.

202. A hydraulic bolt tensioner, comprising:a tensioning mechanism that can be connected to a bolt and activated by hydraulic pressure to apply tension the bolt; anda manifold as claimed in claim 1 connected to the tensioning mechanism25 by the further connector.

3. A hydraulic bolt tensioner or manifold as claimed in claims 1 or 2, wherein the stiffness of the spring is selected so that the indictor pin projects from the manifold body only when the pressure of the pressurised fluid in the conduit30 exceeds a predetermined level.

4. A hydraulic bolt tensioner or manifold as claimed in any preceding claim, wherein the stiffness of the spring is selected so that the amount that the indictor pin projects from the manifold body is indicative of the pressure of the35 pressurised fluid in the conduit.

5. A hydraulic bolt tensioner or manifold as claimed in any preceding claim, wherein the indicator pin includes visual markings along its length to indicate the amount of the pin that projects from the manifold body.24 02 25

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