WO1996032227A1

WO1996032227A1 - Method and device for connecting machine elements by draw or pin bolts

Info

Publication number: WO1996032227A1
Application number: PCT/SE1996/000480
Authority: WO
Inventors: L.V. Baskakov; G.A. Diduk; V.A. Lihatchov
Original assignee: International Patents & Licenses - Russia Ab
Priority date: 1995-04-12
Filing date: 1996-04-12
Publication date: 1996-10-17
Also published as: SE9501376L; SE9501376D0; SE505839C2

Abstract

The invention relates to mounting of machine parts and can be used for attachment of machine parts by means of draw bolts or pin bolts at mounting of steam turbines, nuclear reactors, high pressure pumps, metallic constructive elements and similar. The invention can be used at profylactic work and repair work. The object of the technical solution is to simplify the construction, increase the reliability of the attachment, increase the accuracy of determining the elongation of the draw bolts or pin bolts, and decrease the weight, size and cost factors. This is achieved by utilizing power members (2), which have thermomechanical shape-memory and at the same time a deformation at transformation, which is direction orientated. The change between the state of shape of the power member (2) is caused by a heating device (3, 8).

Description

Method and device for connecting machine elements by draw or p n bolts.

Trie invention relates to assembling of machine parts and can be used for connecting machine parts by draw bolts or pin bolts at the assembling of steam turbines, nuclear reactors, high pressure pumps, metallic constructive elements and so on. The invention can be utilized for profylactic work and remounting.

It is known in steam turbines to connect with pre-tensioning the flanges of horizontally divided high pressure cylinders by tightening of the pin bolts in heated condition (thermal tightening) (vide Molotchek V.A. , Remounting of steam turbines, Moscow, publisher "Energia", 1974, pages 84-90). At the temperature decrease the pin bolts are shortened, pretensioned and secure sealing of the horizontally divided flanges.

The drawbacks of this known method are:

- Need of special heating elements (corundum heaters) which in practice have a low reliability;

- Necessity of arranging a central channel for the heating element, which results in an increase of the diameter of the pin bolt and nut (in order to secure predetermined pre-tensionings) which increases the metallic volume of the attachment;

- Local heating injuries in the central channel of the pin bolts are in practice often caused by the heating elements, that during operation results in destruction of the pin bolts in the area of these injuries;

- The pre-tensioning is measured in relation to the angular turning of the nut with an accuracy of only +/- 15%.

A method of a pre-tensioned mounting of bolts is known by the withdrawing method (vide Jarkovets, A.I. et al. Making rivet and bolt joints of high resource type at construction of airplanes, Moscow, publisher "Maschinostroenie", 1987, page 1) which presupposes that the bolt is positioned in the hole by a withdrawing tool and an axial tension is applied to the threaded part of the bolt.

The drawback in this case is that the method does not secure an even pre-tensioning in the heigt direction of the connected elements and does not eliminate the deformation wave caused by the pressing together.

It is further known a pre-tensioned mounting of bolts (vide the specification of the Inventor Certificate SU 1751478, Cl. F16B 35/00, publ. 1992) by withdrawing the bolt shank in the opening of the pack of details which are to be connected, in which case before the withdrawing of the bolt in the opening of the pack the bolt is tensioned by applying a static loading in the axial direction of the shank of the bolt and unloads the shank after the withdrawing. When the loading is applied to a detail its deformation is directed in the direction of the load, i.e. the shank of the bolt is elongated and its diameter is decreased. Drawbacks of this method are:

- Impossible to use in practice in existing constructions where one end of the pin bolt is screwed on and not going through a flange, i.e. in a threaded flange (e.g. at flanges of steam turbine cylinders);

- The final pre-tensioning, i.e. the obtaining of a predetermined strongly prescribed pre-tensioning of the pin bolt, is decided only by its pre-deformation (by stretching) and cannot be changed after fixing with the nut.

The method that in technical respect comes closest to the method according to the invention is "Method and means of attachment" (vide the Japanese application No. 2-50329, Cl. F16B 39/01, publ. 1990). This method utilizes bolt and nut made of an alloy having shape-memory characteristics in one direction. Due to the fact that the bolt is pre-heated above the transformation temperature, in austenite phase, a manory impress is achieved of the shape when the bolt has a short axial length and is thicker in radial direction and the nut is stretched in axial direction and has a narrow thread gap.

At mounting of details at a temperature below the transformation temperature in martensite phase the bolt is deformed by stretching it in axial direction and its diameter is reduced at the same time as the nut is deformed by reducing its axial length and increasing its thread gap. After the attachment it is heated to a temperature above the transformation temperature, which gives rise to an increase (clerical error?) of the axial length of the bolt and, inversely, an increase of the axial length of the nut and an decrease of the thread gap. This gives rise to an increase of the pre-tension of the details and, moreover, a constriction in radial direction.

A disadvantage here is, that the nut and the bolt, made of an expensive material with thermcmechanical shape-memory characteristics, form inseparable parts of the structure causing a high total cost of the structure per se.

In technical respect closest to the device according to the invention is an hydraulic device for attaching structural components by draw bolts or pin bolts (vide advertising brochure Wirth, DE, Fig.4, forming a part of the application basis), comprising a drawing device for the bolt or pin bolt, a support device, an hydraulic matiber and a nipple for supply and outlet of liquid.

A disadvantage of this device is a high pressure pump that gives rise to considerable overweight and oversize and high costs.

The object of the technical solution according to the invention is to increase the reliability of the attachment, increase the accuracy of achieved extension of the draw bolts or pin bolts and decrease of weight, volume and cost.

This object is achieved by the method to attach structural components by draw bolts and pin bolts utilizing a material with thermomechanical shape-manory by performing the attachment in that the draw bolts or pin bolts are elongated to a predetermined pre-tension without screwing by means of a power manber made of a material that has simultaneously thermomechanical shape-manory as well as directed deformation transformation, the deformation parameters of the power member being dimensioned in dependence on the required pre-tension and elongation during heating of the power member to a temperature above the return-transformation temperature to martensite in austenite phase, after which chilling is carried out to a temperature lower than the temperature at which direct martensitic transformation in martensitic phase ceases, at which temperature the power member is returned to its initial state.

The object is achieved also in that the attachment device, comprising a driver of the draw bolt or pin bolt, further is provided with a power member and a heating device, the power member being made of a material that simultaneously has thermomechanical shape-manory as well as directed deformation transformation, the driver is formed by a bushing having a threaded bottom opening with a pitch equal to the thread of the draw bolt or pin bolt, the upper part of the bushing is in threaded engagement with an upper support, a support beam is inserted through openings in the wall of the bushing, the power manber together with the mounted heating device are inserted between the upper support and the support beam, in addition to which the ends of the support beam bear on a bottom support and the beam forms a clearance to the inner surface at the bottom of the bushing.

Moreover, the intended object can be achieved in that the attachment device comprising a driver of the draw bolt or pin bolt further is provided with a tubular power matiber with an exterior or interior heating device, the power member is made of a material that has simultaneously thermcmechanical shape-manory as well as directed deformation transformation, and both the power member and the heating device are placed between the driver of the draw bolt or pin bolt and the structural manbers to be attached.

The proposed technical solution has as essential characterizing features the presence of a power manber made of a material possessing thermomechanical shape-memory characteristics in addition to which the material at transformation is deformed directional orientated.

A power manber made of a material that has not only thermcmechanical shape-manory but also directed deformation transformation permits the power member to return to its initial state so that it can be used many times.

Fig.l and 2 disclose in sectional view constructional embodiments of the device for attachment of structural manbers by means of draw bolts and pin bolts.

The attachment device (Fig.l) comprises partly a driver 1 of the bolt or pin bolt designed like a bushing provided with a threaded bottom opening and partly a power member 2 with an interior heating device 3. Both the power member 2 and the heating device 3 are positioned between a beam 4 and an upper support 6, which is in threaded engagement with the upper part of the bushing 1. The beam 4 is inserted through a side opening of the bushing 1, forms a clearance 7 to the interior surface of the bottom of the bushing 1 and bears on a bottom support 5 with its ends.

The attachment device (Fig.2) comprises a driver 1 of the bolt and pin bolt and a power member 2 with an exterior or interior heating device 3. Both the power manber 2 and the heating device 3 are positioned between the driver 1 of the bolt or pin bolt and the structural manber that should be attached.

The method according to the invention to attach structural manbers by means of draw bolts or pin bolts is carried out as follows.

The attachment occurs by elongation of the draw bolt or pin bolt to a predetermined pre-tension without screwing by means of a power member made of a material that has a shape-memory and directed deformation transformation. There is a considerable number of metallic materials which after external deformation are capable to return completely to their initial shape. The characteristics of material with shape-manory are discussed in the monograph V.A.Lihatchov, S.L.Kuzmin, Z.P-Kamenetseva "The shape-memory effect", Lebingrad, Publisher LGU, 1987. These materials can at change of temperature be reversibly deformed many times and with considerable accuracy give rise to a predetermined tension of draw bolts and pin bolts.

The driver 1 is threaded on the bolt. The power manber 2 is heated by the heating device 3 to a temperature above the limit temperature of martensitic transformation in austenite phase, more exactly up to 150 degrees for Ni-Ti alloys. The power member 2 is in advance squeezed together in a press to a predetermined value corresponding to the magnitude of the power load acting on the bolt or pin bolt. When the abovanentioned temperature is reached the power maber 2 reverts to its original shape and acts upon the upper support 6, which transfers the force to the bolt (Fig.l). The force is transferred to the bottom support 5 via the beam 4. When the bolt has been elongated by the power member 2 the nut is tightened by means of a calibrated gauge block with play in relation to the surface of the flange. After that the power member 2 is chilled to a temperature below the limit temperature for the transformation in martensite phase.

After chilling the loaded power member 2 reverts to the original sizes, the draw bolt or pin bolt becomes shorter and the predetermined pre-tension is achieved in them.

The elastic deformation in elongated state should be equal to the magnitude of the reverted deformation of the power manber 2.

The return movement of the power manber 2 to the original shape after tightening of the nut occurs thanks to the directed deformation transformation and the plastic character of the transformation.

The device shown in Fig.2 differs from the device shown in Fig.l by the power member 2, made of a material with shape-manory, acting upon a driver 1, that when displaced directly brings about an elongation of the bolt or pin bolt.

Limitation of the pre-tension applied to the draw bolt or pin bolt occurs by adjusted charging (the member possessing shape-memory cannot cause larger force than the force to which it has been charge ) .

The linear displacement is further limited in the tension device (Fig.l) thanks to the play 7 between the beam 4 and the inner surface of the driver 1.

By the above mentioned devices comprising power members made of a material presenting simultaneously thermomechanical shape-memory and directed deformation transformation the need of further members is eliminated which act as return members.

The heating device 3 shown in the drawings uses electrical heating. As an alternative it is possible to use a device 8 for directing a flow of heated air or steam towards the power member 2. For returning the power member 2 to the opposite state of shape the device 8 can be used for directing a flow of cooler air or steam towards the power member 2.

Claims

C L A I M S

1. Method for connecting structural members by means of draw bolts or pin bolts by using a material with thermcmechanical shape-memory, characterized in that the draw bolts or pin bolts are elongated to a predetermined pre-tension without screwing by means of a power member (2) made of a material that has simultaneously thermcmechanical shape-memory as well as directed deformation transformation, the deformation parameters of the power member (2) being dimensioned in dependence on the required pre-tension and elongation during heating of the power member (2) to a temperature above the revert-transformation temperature to martensite in austenite phase, after which chilling is carried out to a temperature lower than the temperature at which direct martensitic transformation in martensitic phase ceases, at which temperature the power member (2) is returned to its original state.

2. Device for carrying out the method according to claim 1, comprising a driver (1) of the draw bolt or pin bolt, characterized in that the device further comprises a power member (2) and a heating device (3) , the power member (2) being made of a material that simultaneously has thermomechanical shape-memory as well as directed deformation transformation, the driver

(1) is formed by a bushing having a threaded bottom opening with a pitch equal to the thread of the draw bolt or pin bolt, the upper part of the bushing is in threaded engagement with an upper support (6) , a support beam (4) is inserted through openings in the wall of the bushing, the power member (2) together with the mounted heating device (3) are inserted between the upper support (6) and the support beam (4), in addition to which the ends of the support beam (4) bear on a bottom support (5) and the beam forms a clearance (7) to the inner surface at the bottom of the bushing.

3. Device for carrying out the method according to claim 1, comprising a driver of the draw bolt or pin bolt, characterized in that the device further is provided with a tubular power member (2) with an exterior or interior heating device (3) , the power member (2) is made of a material that has simultaneously thermomechanical shape-memory as well as directed deformation transformation, and both the power member and the heating device are placed between the driver (1) of the draw bolt or pin bolt and the structural members to be attached.

4. Device according to any of claims 2 or 3, characterized in that the heating device comprises a device (8) for directing towards the power member (2) cold and/or heated air or steam to bring the power member ( 2) to change state of shape.