JP2863006B2 - Fasteners and related improvements - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulically operated fastener device. The present invention relates to hydraulically actuated nuts, bolts and jack tools used for tensioning bolts, including stud bolts.

Such devices are well known. Almost all devices of this type have in common an annular body which can be mounted around the bolt to be tensioned, the body further comprising an annular body adapted to exert an axial force on the bolt. It features a piston and cylinder device.
For example, the cited EP-A-0129440 and GB-A-99178
No. 3 discloses a structure in which a hydraulically operated jack tool is assembled to a nut or bolt surface or assembled as an original tool.

In GB-A-1590131, a piston is provided with a separate threaded puller (pull) which is engaged with a threaded portion of a nut and a separate bolt.
ller) are disclosed.

Such devices have been used for many years, for example for fixing marine propellers, or in general in the field of industrial clamping. A typical example is a screw nut having an annular recess machined on one side to form the cylinder of a piston-cylinder arrangement. The recess has an annular rubber tire and an annular piston. In use, this nut is screwed into a bolt,
The free end of the piston, usually in the form of a flange, known as a load ring, abuts the hardware from which the bolt projects. Next, the working fluid (hydraulic fl
uid) is introduced into the tire via a passage through the nut body, which exerts a thrust on the piston. This thrust is then transmitted directly to the assembly, causing an increase in the axial length of the bolt and compression of the assembly. As a result, the nut body is pressed away from the assembly, and the bolt receives tension. When a suitable gap is formed, a shim is interposed in the space between the lower surface of the nut body and the load ring so that the tension of the bolt is maintained even after the working fluid pressure is released. Similar results can be obtained by assembling the annular piston and cylinder device inside the head of a conventional bolt. For somewhat lighter load applications, it is possible to replace the tire with a regular piston seal which is a rubber ring.

Attempts have been made to use piston and cylinder devices for tensioning such bolts for relatively high temperature applications. For example, it has been applied in land gas and steam turbines and the nuclear industry. However, at the relevant operating temperatures which will exceed 250 ° C., the use of conventional rubber seals and rubber tires is not feasible. Long-term exposure to temperatures above approximately 150 ° C. causes rapid degradation of normal rubber. Therefore, the use of metal tires has been proposed in an attempt to solve this problem. Although this solution can be used at temperatures as high as 500 ° C., metal tires are expensive articles that require special skills in their manufacture.

In accordance with the present invention, a hydraulically actuated nut, bolt or jack tool arrangement includes an annular piston and cylinder arrangement wherein the piston has a pair of tapered annular webs which merely constitute the fluid sealing means of the piston and cylinder arrangement. The innermost web is thinner than the other web to provide maximum flexibility to the radially innermost web, the webs comprising: Together they form an annular recess with an asymmetric cross section between them. Preferably, the web is substantially flush in the axial direction towards the bottom of the recess.

Preferably, the piston slides tightly into the cylinder and no conventional rubber seal is used. Surprisingly, it has been found that the use of the asymmetric shape just described makes it possible to form the web shape without the need for a conventional seal. This means that the piston and cylinder device according to the invention can be used at high temperatures exceeding 500 ° and no conventional seal degrades in such conditions. It has been observed that symmetrical recesses cannot provide the required sealing performance.

To illustrate the effects of the present invention, an example hydraulically actuated nut according to the present invention was pressured to create stress on a bolt. The bolted assembly was then given a holding temperature of about 250 ° C. in the furnace. Removal of the assembly from the furnace demonstrated that the nut could be re-energized, and there was some indication of a slight leak only after a few re-energizations. In view of the lack of conventional seals, this performance is striking.

For a better understanding of the present invention, a preferred embodiment thereof will now be described, by way of example, with reference to the accompanying drawings, which are cross-sectional side views through a nut bolt assembly. In the drawing, a bolt 1 with a head 3 is used to clamp the assemblies, generally designated 2, together. It will be appreciated that the bolt extends through an opening in the assembly 2. The free end of the bolt is provided with a hydraulically actuated nut, which is in the form of a cylindrical body 4 having an internal thread matching the thread of the bolt 1. Nut 4
Are screwed down on the bolts, and a plurality of tommy bar holes 12 are provided for this. The surface of the nut in contact with the body structure 2 in use comprises an annular piston-cylinder device,
The device comprises a piston 15 integral with a cylinder 15 and a load ring 7, the load ring abutting the body structure 2. A port 21 is provided for injecting the working fluid into the cylinder 15, and a screw connection adapter 22 is provided for this. In use, the part of the piston 6 exposed to the working fluid in the cylinder 15 is an annular web 17
And 18 each being directed concentrically to the bottom of the cylinder so as to form an annular recess between each other. The web is tapered to provide a pair of concentric feathered edges, which are referred to as GB-A-15 described above.
Although referred to as a straight edge, such as 90131, it can be configured to constitute this edge. These webs have the same height in the axial direction, but the annular recess formed between them is asymmetric. The effect of this asymmetry is that the web 17 located radially inside the device
Make it relatively thin compared to 18. As a result, web 17 has greater flexibility than web 18. Initially, both webs were machined into a tight but sliding fit within cylinder 15. When the load ring 7 in use coincides with the face of the nut 4 (the piston is completely retracted), the nut is screwed down firmly against the body structure 2. Next, the working fluid flows into the cylinder 15 through the adapter 22 and the port 21.
Thereafter, the pressure increases, causing the nut 4 to move in a direction away from the load ring 7 to form a gap between the members.
When the gap width reaches a position where a desired level of stress is applied to the bolt 1, a shim or spacer is inserted into the gap. The working fluid pressure is then released, thereby completing the mounting procedure.

For example, to remove the nut after a long time at high temperature, the procedure is reversed. Oil flows under pressure into the cylinder 15 and the bolts are further stressed until the shims or spacers can be removed. This working fluid pressure is then released and the nut is unscrewed using the tommy bore 12.

As described above in connection with the nut, such a piston-cylinder structure is used in the head of the bolt, but is a gap for the bolt to be tensioned,
It will be appreciated that the piston can act on a threaded puller that is used incorporated into a separate bolt pulling tool having an opening therethrough and in which the piston is engaged with the threaded portion of the bolt.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F16B 31/04

Claims (6)

(57) [Claims] An annular piston and cylinder device (6, 15)
A hydraulically actuated nut, bolt or jack tool arrangement comprising: a piston having an axially directed side wall portion formed by a pair of tapered annular webs (17, 18), said web comprising said piston. Only constitutes the fluid sealing means of the cylinder device, the radially innermost web (17) being thinner than the other webs (18) to give great flexibility, and these webs together A hydraulically actuated nut, bolt or jack tool arrangement, wherein an annular recess is formed between each other, said recess having an asymmetric cross section. 2. Apparatus according to claim 1, wherein said webs have substantially the same height in the axial direction. 3. Apparatus according to claim 1, wherein the web is configured as a pair of concentric feather edges (17, 18) directed toward a closed bottom of the cylinder (15). An apparatus characterized in that: 4. The device according to claim 1, wherein said piston-cylinder device (6, 15) is incorporated in a nut (4). 5. Apparatus according to claim 1, wherein said piston-cylinder arrangement (6, 15) is integrated into a bolt head. 6. A piston-cylinder device according to claim 1, further comprising a bolt tensioning tool having a gap therethrough for the bolt to be tensioned and a through hole therethrough. A piston-cylinder arrangement, wherein the piston acts on a threaded puller screwed into a threaded portion of the bolt.