DE2706301A1 - CONNECTED BOLTS - Google Patents

Description

The invention relates to improvements for self-tightening Bolt.

Self-tightening bolts are for example from the British Patent 1,382,192 known, which shows a bolt with a central bore which is attached to the one end is closed. The bolt is tensioned by a rod in contact along the bore with the terminated end inserted and lifting forces at the opposite end of the bolt between this and the rod are exerted in such a way that the shaft of the bolt is tensioned and stretched and a corresponding compressive force is exerted on the rod. That by stretching the Bolt resulting game is taken up by washers or adjusting a nut, whereupon the Lifting forces are released so that the bolt remains under tension. The rod can then be removed.

The invention is based on the object of developing a self-tightening bolt in which essentially the full cross-section is solid and under tension and which can be clamped by a clamping head, which does not need to be supported against the workpiece in which the bolt is installed. It is further It is desirable that the clamping head not laterally over the outer circumference of the area of the pressure-transmitting Contact between the bolt and the workpiece protrudes.

A composite bolt according to the invention has a hollow one Shank and a core within the shank, the shank and core being adjacent to or adjacent to one another are attached to the first end of the bolt assembly, a releasable transmission device on or adjacent

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bears the second end of the assembly for transmitting tensile forces from the core to the hollow shaft, which Core can withstand the normal tensile force generated in the shaft during use under compressive stress when such a force is transmitted to it through the transmission device and coupling elements at or adjacent to the second end for exerting tensile and compressive forces on the core.

The invention also relates to a method for producing a tensioned bonded bolt connection between two areas which are at a distance from each other, in which method a hollow bolt shank is preloaded by compressively preloading a core in the shank, the shank is brought with the core in the required position for the bolt connection without end play, -the Compressive preload in the core is relieved, thereby preloading the hollow shaft between the two Areas is exerted, the core thereby a tensile stress is communicated that a counter pressure against The shaft is exerted, a backlash-free power transmission path between the two ends of the under tension standing core and the corresponding ends of the hollow shaft is generated and from the outside tensile stress exerted on the core is released, so that the tensile stress in the core is in the compressive direction of the shaft is exercised.

By applying the invention it becomes possible to use a screw connection with high tensile stress establish the use of bolt tighteners that do not protrude beyond the cylinder, the around the head or load transfer flange of the screw

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Connection circumscribed cylinder protrudes. This arrangement is particularly desirable in the case of large, highly loaded Low pitch bolts or studs, such as those used for fastening the Housings of large steam turbines are used, which are described with high temperatures. The present method of tightening such bolts is done by thermal means by which the bolt or pin is rapidly elongated by an electrical Heating element is inserted into a centrally drilled hole in the core of the bolt or pin.

When the bolt has increased its length by the required amount, the nut is tightened and measurements through the center drilled hole show the true tensile stress retained in the bolt or pin and thus the true tensile stress in the bolt or pin. However, this procedure is time consuming and persists there is always the risk that the rapid heating of the core of the bolt or pin will cause plastic cracks to form Deformation of the bolt material caused by the very high thermal stress gradients of such Heating is conditional. To achieve even tightening around an entire turbine housing, it is often necessary to repeat this time consuming process two or three times for each stud or pin .

The invention avoids the need for thermal stresses on the bolts or pins and instead Hydraulic post-tensioning systems are used (which have proven themselves in other areas, such as a great experience shows), while at the same time the need for a device of larger diameter than the head of the bolt or pin that is tightened

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should be avoided.

An embodiment of the invention is as follows For example, described in more detail in connection with the accompanying drawing, the only figure a composite bolt together with a tensioning device for this in axial section and the two adjacent ones Shows bolt in elevation.

In the following description and in the claims, the term "bonded bolt" is used. This designation is used generically hereinafter for convenience and includes similar composite structures.

The composite bolt shown in the drawings has a hollow tubular shank 1, both inside and is provided on the outside at its first or lower end with a thread 2 or 3 and on which a circular flange 4 is formed, which is the base of a head part 5 with an external thread for forms the bolt.

A core in the form of a solid rod 6 is at its lower end at 8 in tight engagement with the thread 2 at the lower end of the hollow shaft. The rod 6 is slightly longer than the shaft 1, so that it protrudes above the top of the head 5, and the upper end part of the rod above the flange is provided with a thread 8 with which a cylindrical nut 9 is engaged, the upper part of which extends up beyond the head 5 and is in the form of a crown, as shown at 10, while the lower part of the nut 9 extends into a recess 11 in the shaft head 5.

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The clamping device for the composite bolt has a substantially cylindrical housing 21, the The lower end is provided with an internal thread for engagement with the external thread on the shaft head 5. The diameter of the housing 21 is equal to the diameter of the shaft head flange 4.

An inner flange 22 extends inwardly from the housing 21 for sliding contact with the cylindrical Surface 23 of a piston and nut combination 24, which has an internal thread, which with the upper part of the thread 8 on the rod 6 is engaged, while its outer cylindrical surface 25 is in sliding contact with the inner wall surface of the housing 21 located above the flange 22. That way will an annular chamber 26 received, which a tire or contains a load cell 27 made of nitrile rubber, which has a connection 28 for receiving an under high Has hydraulic medium under pressure.

The top of the radially inner part of the piston-nut combination 24 is substantially flush with the top of rod 6 and the two form one Seat for a membrane 29, which can be formed by a stack of thin disks made of nitrile rubber. An end cap 30 with an external thread is in threaded engagement with the internal thread of the upper part of the housing 21 and has a central connection 12 for the supply of high pressure hydraulic Fluid to the top of the membrane 29 on.

At the level of the prongs or notches 10, the housing 21 is provided with horizontally curved slots 33 shaped, through which a suitable pivot pin or the like.

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can be used for engagement with the notches 10 for actuating the nut 9.

The installation and fitting of each composite bolt is as follows:

Before being installed in the workpiece W, the composite bolt is preliminarily assembled in the workshop and biased. First, the rod 6 is fixed by means of its thread in the thread 2 in the lower part of the Shank 1 screwed in. The nut 9 is then screwed onto the thread 8 on the upper part of the rod 6.

Then the print head cylinder 21 is screwed down completely with the nitrile rubber load cell 27 and the pressure medium connection 28 until it comes to rest on the surface of the bolt flange 4. Now the nut 24 is screwed on until the top is flush with the end of the rod 6 and a depth micrometer value R _{1 is} read between the upper lip of the printhead cylinder 21 and the top of the rod to obtain a size.

The nitrile rubber membrane 29 is then used and the top plate 30 screwed on tightly. Now a hydraulic pressure of 24 60 kp / cm (35000 psi) supplied via the connection 32, whereby the bolt shank 1 is elongated and its diameter is reduced will. The isolation valve (not shown) closes, relieving the hydraulic pressure within the Head is included. The bolt is then screwed into the workpiece W as shown, with it with a tightening device (hammer and metal drift) is tightened at suitable notches 36 in the flange 4 is set. The isolation valve is opened, where-

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by which hydraulic pressure is released, and the top plate 30 and the nitrile rubber membrane 29 are removed. Repeating this micrometer reading R ₂ gives the actual value of the bolt through R ₂ - R ..

If, as in the case shown in the drawing, a ring of bolts is to be installed, it can It may be desirable that the final tightening of a plurality of bolts take place at the same time. For this Purpose are all connections 32 of the individual clamping heads for each of the bolts for simultaneous tensioning connected to one another, such as the connections 28. The isolating valve which regulates all connections 32 is then activated opened and at the same time released the pressure, with the result that the shaft 1 in length in contact comes, whereby a uniform load is applied to the workpiece W. The depth micrometer values should then for each bolt removed and recorded after verifying that it is within the prescribed limits.

The or each isolation valve connection is now removed from port 32 and made at port 28, and top plate 30 and nitrile rubber membrane 29 are also removed. The high working pressure of about 2460 kgf / cm (about 35,000 psi) is then applied to pressurize the annular load cell or tire 27, thereby stretching the rod 6. The depth micrometer reading R is taken again (R ₃ ) and the tensile stress in the rod 6 is then given by R- - R ₂ . With the hydraulic pressure maintained at the working pressure, each nut 9 on the thread 8 comes into contact with the bottom of the recess 11

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hand screwed down using a suitable pin inserted through the slots 33 in the notches IO is used.

By releasing the pressure in the load cells or The load, which was transmitted by the load cells, is now transferred again via the nuts 9 to the load cells (27) transferred to the heads 5 and the flanges 4 of the bolt shafts. Another micrometer rejection (R.) shows whether there has been any relaxation of the tightening tension when the load is transferred to the nut 9 will. In fact, the loss should not be more than 0.025 mm (0.001 ") when the device is reasonable has been clamped and there are normal machining errors on the threads and on the mating surfaces of the device and the support.

Now the or each clamping head can be removed by pulling the hydraulic line through from the connection Unscrewing is loosened, the piston and nut combination 24 unscrewed and finally the outer housing 21 is unscrewed from the bolt head 5.

The removal of a bolt is done in that the clamping head is again on the head 5 of the respective Bolt is applied, the high loading fluid pressure exerted on the load cell or the tire 27 is, the nut 9 is unscrewed by hand with the aid of a pivot pin which is inserted through the slots 3 3 until nut 9 contacts the underside of piston nut 24, the high fluid pressure through port 32 is exercised and then the isolator valve is closed, using a hammer and driving device, which is attached to the notches 36, the bolt is loosened, the respective bolt fully unscrewed

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and the bolt together with a clamping head for further required work is removed.

As can be clearly seen from the drawing, the housings 21 of the clamping heads do not come into contact with the Workpiece W and are located within the imaginary circumscribing cylinder of the flanges 4. It is therefore only a nominal play between adjacent flanges 4 and the clamping head housings 21 is required.

It should be mentioned here that the structure of the shaft 1 and the rod 6 is regulated to a high value Voltage is fully loaded.

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Claims (14)

PATENTANWÄLTE to Augsburg 22, dn 1 ^ .2.1), ' __,., _ ρ- ι ir — η Ali RilkestraB · 10 DR. ING. E. UEBAU DIPLING G LIFBALJ Our reference P 10 265 2706301 LHf-L. INI ». O. LItDMU (please specify when replying) Your sign from 15.277 new · Address: Birken Jtr. 39 new telephone number 90090 Pilgrim Engineering Developments Limited Beaufort House, St. Botolph Street London EC3A 7DX / England Expectations ; {1 .J connecting bolt, characterized by a hollow Shank (1), a core (6) in this hollow shank, the shank and core on or adjacent to one another attached to the first end of the bolt assembly, releasable transmission means on or adjacent the second end of the bolt assembly for transmitting tensioning forces from the core to the hollow Shaft, which core can withstand the normal tensile force in the shaft when in use is generated when this force is transmitted to him by the transmission device, and a Coupling device at or adjacent to the second end of the core for exerting tensile and compressive forces to the core. Tlton (0B21) 574089) Tel «gr.addr .; ElPATENT - Augiburg Posticheckkonto Münch.n 86510-889 Deutsche Bonk AQ Augibulp toilet no. 08/34 809833/0481 BorkWtMhl ΚΤΛ » Oil 2. A composite bolt according to claim 1, characterized in that the releasable transmission device is a nut (9) threadedly engaged with either the shank or the core, which nut is in abutment a shoulder of the core or shaft is rotatable. 3. A composite bolt according to claim 2, characterized in that the nut (9) is in threaded engagement with the threaded part of the core is engaged and the threaded portion protrudes beyond the nut when the latter is in Abutment on the shoulder is located on the shaft and by a sufficient amount to form a coupling to exert a pulling force on the core. 4. A composite bolt according to claim 2, characterized in that the nut (9) over the end of the hollow shaft (1) protrudes for attaching a setting tool. 5. A composite bolt according to claim 1, characterized in that the shank (1) has an external thread on or adjacent having the second end for engagement with a chuck. 6. A composite bolt according to claim 5, characterized in that the second end of the shank (1) has a flange (4) to rest on a workpiece (W) and the threaded surface of the shaft is outside the flange and is of a smaller diameter than the flange. 809833/0461 7. A composite bolt according to claim 1, characterized in that the shank (1) is pretensioned and the core is under a pressure preload by a force transmitted via the transmission device. 8. A method of producing a tensile bonded bolt connection between two adjacent ones Areas in which a hollow bolt shank is caused by compressive preloading of a core in the shank is preloaded, the shaft with the core in the required position for the bolt connection without Endgame is brought; and the compressive bias in the core is released so that the bias of the hollow shaft is exerted between the two areas, characterized in that a tensile stress is exerted on the core by exerting a counter pressure against the shaft, a backlash-free power transmission path between the two ends of the tensioned core and the corresponding ends of the hollow Shank is created, and the tensile stress exerted externally on the core is released, so that the tensile stress in the core is applied in the direction of the compressive load on the shaft. 9. Clamping head for a self-tightening bolt, with a hollow shaft and a core in this shaft, which The clamping head has a lifting device which can be connected to the shaft and is used to generate lifting forces exert on the end of the core, characterized in that for use with a composite bolt, the Has a nut (9) or the like for the transmission of tensile stresses in the core (6) to the shaft (1), which Head (5) has other lifting organs that are connected to the core 809833/04 * 1 can be connected so that they act between the core and the shaft to thereby create lifting forces to stretch the core with respect to the shaft . 10. Clamping head according to claim (9), characterized in that the core lifting members by a sleeve (21) with a Inner flange (22) and a piston (24) with an outer flange which is slidable in the socket and in the sleeve delimits a closed annular chamber (26), is formed, which piston can be brought into engagement with the coupling device, and a annular hose (27) in the annular chamber, which is connected to a pressure medium source. 11. Clamping head according to claim 9 or 10 for prestressing a composite bolt, characterized in that the shaft (1) has a flange (4) for contact with a workpiece (W), and a threaded surface which is located outside the flange and has a smaller diameter than the flange, the lifting members have an internally threaded sleeve (21) which is connected to the threaded surface of the shaft (1) can be brought into engagement, and the outside diameter the sleeve is not larger than that of the flange (4) on the shaft (1). 12. Clamping head according to claims 9 to 11, characterized in that that the body of the head (5) with 809833/0401 openings (10) is provided in order to allow access to adjust the nut (9) or the like. 13. Clamping head according to claims 9 to 12, characterized in that that the body of the lifting device has an inner stop surface for the attack of the transmission device to maintain the compressive preload on the core when the lifting forces are released will. 14. Clamping head according to claim 10 for a bolt, in which the core is provided with an external thread adjacent to the clamping head, characterized in that the outer surface of the piston can form a radial extension of the end surface of the core (6) and the shaft clamping device can form a membrane (29 ), the outer edge of which is clamped between the outer surface of the piston (24) and an end cap (30) which is releasably fastened in the body of the clamping head in order to delimit a fluid pressure chamber on the side of the membrane opposite the core. 809833/0481