DE2440353A1 - FASTENING BOLTS - Google Patents

Description

703 o / wa

THE BOEING COMPANY, SOUTH SEATLE, WASHINGTON

United States

Fastening bolts

The invention relates to a fastening bolt for fastening a plurality of workpieces with one another with through openings essentially aligned with one another
a head section which is conical in the axial direction and a cylindrical one hanging axially downwards from the head section

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Shanky the head and the shank essentially in use match with the openings of the workpieces.

Nowadays, fastening bolts have a wide range of applications, however, are used extensively in the aerospace industry, where usually quite high resistance to Stresses is required. Because aircraft design is becoming more and more complicated, it is beyond that clear that fastening devices are required which several Perform functions. For example, fasteners are used to secure both fuel-tight sockets for To ensure the fuel tank of aircraft, as well as a tensile or shear-proof connection between two parts create that need to be connected to each other in a certain way.

Currently, high strength flat headed fasteners with a single 100 ° countersunk head in conjunction with a Rubber based sealant is used to provide the required fuel tightness and corrosion protection. The sealant is used for fuel tightness and for corrosion protection of the fasteners arranged in countersunk holes. However, this fastening combination has different ones Disadvantages, including increased labor costs and added weight.

Although the fastening bolt with a simple 100 ° tapered countersunk head can in some cases be designed as sd, that it creates an inherent fuel tightness, corrosion below the head remains a notable problem, because there is no corresponding interference fit between the head of the fastening bolt and the walls of the opening in the material of the

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Workpiece is present. In addition, fatigue defects occur topically in the vicinity of the counterbore, which seriously shortens the useful life of the aircraft or the assembly fastened by the fastening bolt.

With respect to the fastening portion of the known fastening bolts It should be noted that in general circumferential rings are provided at wide distances from one another, the walls of which have an angle of about 4 5 ° to each other, as well as large radii of curvature both in the valley of the thread and at the head of the Rings. In order to allow enough space for an adequate number of circumferential rings that are attached to a fastening bolt for Tensile stress must be applied while the overall length of the mounting bolt is kept to a minimum the length of the shank of the fastening bolt is reduced, so that the shear strength of the fastening bolt and sleeve existing combination is seriously reduced. So you are forced to use a bolt training in the known technology to be used for shear stress and another training for tensile stress.

The invention is therefore based on the object of creating a fastening bolt that is fuel-tight in the simplest possible way Connection enables and moreover with the same, as easy as possible training, both for the inclusion of Shear as well as tensile loads is suitable.

This object is achieved according to the invention with a fastening bolt of the type mentioned at the outset in that the conical head has two sections which are conical in the axial direction, from where a first conical section is a much larger one

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Cone angle than the second conical section has that the difference of the angle is such that when detecting the one Workpiece through the head an interference fit between the head and the one workpiece can be present and the head one Pulling the fastening bolt through which a workpiece can resist.

According to a preferred exemplary embodiment, the invention comprises a fastening bolt, which generally consists of a Number of sections including a head with a first and second circumferential conical section in the axial Expansion of the head. A shaft adjoins the head and a fastening section with circumferential grooves adjoins the shaft. When the fastening bolt is tightened in use, the head engages one of the workpieces, the shank fits snugly into the aligned openings of the workpieces into it and a sleeve is pressed onto the rings or into the grooves of the fastening section around the workpieces to fasten and hold together tightly. A predetermined breaking point and an end for gripping with a tool are also included provided axially adjacent to the fastening section, so that the fastening bolt under the sleeve when pressing on Tension can be maintained. The predetermined breaking point makes it possible to easily remove the bolt end intended for holding remove remaining fastening bolts after pressing is finished. In more detail, according to another aspect of the invention, the fastening section comprises a design that is circumferential Rings with a relatively small radius of curvature for the valley and the apex and an angle between the walls of the Rings in the range of 60 °.

So the difficulties mentioned at the beginning by the

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Invention significantly reduced because of the inventive Fastening bolt has a double-tapered head, which has the ability to both provide adequate fuel density as well as creating corrosion-free fastening without the use of sealants and also has the ability to with with a minimum weight to withstand both high shear and tensile forces.

The invention is explained in more detail below using an exemplary embodiment with reference to the drawing. It shows:

Fig. 1 is a side view of a fastening bolt according to the prior art,

2 shows a side view of a fastening bolt according to the invention ,

Fig. 3 is a section showing the arrangement of an inventive Fastening bolt illustrated in workpieces, and

4 shows a section showing a completed fastening of two workpieces using the inventive Mounting bolt illustrated.

Referring to Fig. 2, there is shown a mounting bolt embodying the principles of the present invention. A fastening bolt is generally divided into four sections and can vary depending on the size of each other

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fastening parts have different lengths and diameters. Although prevalent in the aviation industry, For example, fastening bolts of this type can be used for many other technologies as well. In addition, the shown Fastening bolts, although commonly made from either steel or aluminum, are numbered Other materials are made, the particular material being influenced by factors such as cost, manufacturing time and depend on the particular environment in which the fastening bolt is to be used, as well as on the functions, which he has to fulfill.

The general structure of a fastening bolt used in the aerospace industry comprises five principal sections, which are designated by the reference numerals 11 to 15 in FIG. The first section of the fastening bolt is the head 11, which is typically conical, and in the present invention has a double cone, so that it is in a with A countersunk surface in the upper workpiece fits into it. The section 12, adjacent to the head 11, is the Shank of the pin and is typically cylindrical. The shank gives the fastening bolt the shear strength. A third section 13, adjacent to the shaft is the fastening section of the fastening bolt, which passes through the opening in the workpieces protrudes and around which a sleeve is pressed. The technique of attaching a sleeve to a fastener bolt is one of skill in the art known. After the sleeve has been pressed precisely and well around the fastening section, a remarkable one results Structural strength from the fastening bolt, the workpieces and the existing combination of the sleeve. The number of rings in the fastening section depends on the tensile strength

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the fastening bolt as well as the one to pull out of the fastening bolt from the workpieces necessary force, which is known as the pull-out force. The greater the number the rings, the greater the tensile resistance of the fastening bolt. For one. Tensile mounting bolts are usually provided while five such rings a shear force-absorbing bolt usually has only two rings, which are only used for fastening.

The last section of the fastening bolt is the bolt end 15, which when used by a special pressing tool is detected so that the fastening bolt and the workpieces can be pulled together tightly during the pressing the sleeve is carried out. After the sleeve is in place, the bolt end 15 is at the predetermined breaking point 14 canceled and the fastening process is complete. One completed combination is shown in FIG. The workpieces 30 and 31 are now fixed by means of the countersunk head Head 11 and the pressed sleeve 18 held together.

In known fastening bolts, as shown in Fig. 1, there is only one conical section on the head, the cone angle a of which is typically between 70 and 100 °. This conical one Section mates with the surface of the counterbore of the upper workpiece and creates a resistance against that Pulling the head through the opening when the combination is pulled tight. This only cone of the known fastening bolts is similar to the first cone 20, which axially adjoins the shaft 12 of the fastening bolt according to the invention, as shown in FIG. The first cone 20 has at the

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present invention an angle b of 82 + 0.5 °, can however, it can be changed practically essentially depending on its application. A second cone 21 with a Angle c of 10 + 0.5 is provided axially adjacent to the first cone 20 and extends to the top of the 11. The meaning of the double-conical head is explained in the explained in more detail in the following paragraphs.

It has been found that a single 82 to 100 ° taper does not provide a good interference fit between the head and the counterbore provided workpiece results. An interference fit is available if the original outside diameter of the fastening bolt larger than the original diameter of the opening in the workpiece is in which the fastening bolt is to be inserted. When the head of the fastening bolt is in place is driven into the opening, the opening becomes so vigorous wedged on the outside, which leads to an extremely tight "press" fit between the head of the fastening bolt and the workpiece.

Such a press fit is not possible with a large taper angle, e.g. 80 °, because this angle does not allow a wedge effect. It has been found that this effect occurs only when the taper angle is 30 or less. It has also been found that cone angles between 20 and 30 ° have certain disadvantages in that there is a change in the press fit in the axial direction of the Cone results. This disadvantage of precise control of the interference fit decreases as the taper angle decreases. It was found that a cone angle in the order of magnitude of 10 ° creates a high-quality interference fit between the head of the fastening bolt and the workpiece. This interference fit creates an inherent seal between the workpieces and the mounting bolt

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as well as corrosion resistance under the head of the fastening bolt .

However, this small taper angle, which is desirable for press fit purposes, does not provide any significant resistance against pulling through the fastening bolt the opening in the workpieces. So a second cone is provided, to bring about a high pulling resistance. The first cone 20 is adjacent to the shank 12 of the fastening bolt arranged to create the necessary high resistance to pulling out the fastening bolt.

Thus, by using the double cone design, one cone forms the resistance to pulling out and the other The cone forms a press fit, a head for a fastening bolt is created, which provides protection against corrosion for both the Head as well as the countersunk bore improves, causing fuel tightness without the need for additional sealants are necessary, and brings about an increased service life against fatigue of the combination of fastening bolts and workpieces.

The interference fit for the head of the fastening bolt according to the invention is between 0.203 mm and 0.127 mm, i.e. the diameter of the head of the mounting bolt is 0.127 mm to 0.203 mm (0.005 and 0.008 ") larger than the original Inside diameter of the opening in the workpiece. A 0.051 mm (0.002 ") interference fit was found to provide fuel tightness sufficient. It was found, however, that the additional excess reduced the fatigue strength of the combination

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Fastening bolts and workpiece increased.

As noted above, for a predetermined given thickness of the workpieces, the shank length of the known fastening bolt becomes determined by the type of stress to which it is primarily exposed. When the combination of the fastening bolt is primarily intended to withstand shear forces, a long shaft with a minimal length is required of the fastening section, i.e. the length of the fastening section is sufficient for two circumferential rings. If the combination with the fastening bolt is primarily subjected to tensile stress, the shaft portion becomes shortened and the fastening section is lengthened a little to make room for a sufficient number of circumferential rings in the fastening section to give, which can withstand the large tensile loads.

The formation of the individual circumferential rings 26 on the fastening section of the known fastening bolt is shown in FIG. Because weight is often a critical parameter is, and must be reduced to a minimum, allows the use of such a general ring configuration only two such circumferential rings at the fastening end of a fastening bolt exposed to high shear stress This number gives the fastening bolt only a minimal ability to withstand tensile stress and so can Such a fastening bolt can only be used where shear forces occur.

If a tension-sustaining fastener is desired, more circumferential rings are required, and so will

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the shaft, as mentioned above, shortened a little and the fastening section lengthened to make room for the rings to accomplish. Five circumferential rings are typically provided for fastening bolts that can withstand tensile stress, so that when attaching the sleeve over the fastening section of the fastening bolt and pressing it is sufficient Contact between the sleeve and the circumferential rings is achieved by means of a fastening bolt and sleeve To create combination with high resistance to tensile stress. Because the length of the shaft section necessarily is reduced for weight reasons, as noted above, the ability of this type of fastener bolt is shear stress to endure, significantly reduced. So this fastening bolt is used when the stress on the fastening bolt and the workpieces are primarily tensile. This is how it becomes with the well-known ring training required to make two types of fastening bolts, one for use with shear forces and one for use with tensile forces.

A particular embodiment of the present invention however, uses a new design of the circumferential rings in the fastening section of the fastening bolt, so that a fastening bolt can withstand both tensile and shear forces. By changing the tip angle d in the range of 55 to 65 °, e.g. about 60 °, and reducing it significantly the radii of curvature of the valley and the tip of the circumferential rings (see. Fig. 2 with Fig. 1) can be considerably larger Number of circumferential rings can be formed in the fastening portion of a given axial length. Furthermore This change in the formation of the rings becomes one

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greater inherent resistance of each ring to Tensile stress reached. The shaft can thus be left at a length which is equal to that of the known fastening bolt for absorbing shear forces, while sufficient circumferential rings can be provided in a fastening section of minimal length in order to provide a large resistance to create against tensile stress. So the total length of the fastening bolt according to this embodiment is the Invention not greater than the length of known fastening bolts for absorbing shear forces. But because of the new Ring formation, a sufficient number of rings arranged in the fastening portion can be provided to the Resistance to tensile stress of longer known fastening bolts to absorb tensile stress obtain. So a fastening bolt is created by using the training of the circumferential rings, of which a single embodiment has high resistance to both shear and tensile forces and a minimal overall length and therefore has a minimal weight. The circumferential rings are preferably in the middle between the circumferential ones Grooves arranged and the circumferential rings are arranged in such proximity to each other and have such a design, that essentially at least five of these rings within an axial distance on the mounting pin of 6.4 mm (1/4 ") can be arranged.

In Fig. 3 is the physical relationship between the fastening bolt and the counterbore and opening of the workpiece in the application. The workpiece is made actually consists of two workpieces 30 and 31, which are firmly together by the combination of the fastening bolt and the sleeve.

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being held. The head is double-conical, as explained above. The first cone 33, adjacent to the stem 35, has an angle of approximately 82 ° and the second cone 34, adjacent to the surface 36 of the head, has an angle e of about 10 °. Applicants have found that an angle of the counterbore in workpiece 30 is equal to the taper angle of the head of the fastening bolt often leads to fatigue defects on the side of the counterbore. It has been found that these errors are due to fatigue Tensile stress occur that are generated on the counterbore of the workpiece.

With regard to fatigue failure in general, it is a goal the design that such defects eventually occur at the interface between the two workpieces 30 and 31. By a design that eliminates all other fatigue defects, If a fault occurs in the fastening bolt and therefore in the combination finally on the parting surface and the structural effect of the opening in the workpiece is essentially eliminated. This achieves the highest fatigue strength of the combination with respect to a given fastening bolt.

Such a result is achieved by dividing the portion of workpiece 30 that is to mate with the 10 ° taper head, is countersunk by a few degrees less than 10 °. In which preferred embodiment, the angle f of this countersunk hole is usually 8 °. The reduction in the counterbore angle relative to the cone angle e des to be pressed in Head, largely eliminates the problems of fatigue failure due to stress at the top of the counterbore and increases the fatigue strength of the finished combination considerably.

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In Fig. 3, the dashed lines 37 show the dimensions of the fastening bolt before it is inserted into the workpiece, while the solid lines 38 represent the original interior surface of the finished counterbore and opening in the workpieces 3O and 31 represent. When the fastening bolt is pushed through the workpieces 30 and 31, the surrounding Metal in the workpieces is driven outwards through the fastening bolt so that the interference fit is created. The use of the smaller counterbore angle f, relative to the cone angle e of the head, leads to a fuel-tight Press fit and also shifts the effect of any stress present in the counterbore down into the shank of the fastening bolt in the vicinity of the interface between the two workpieces 30 and 31. This leads to a longer service life the combination of workpieces and fastening bolts, because the stresses are now in the part of the fastening bolt that they can best resist.

For example, a new fastening bolt for securely fastening different designs of materials to one another has been described. In one respect, it includes a double-tapered head portion, with the taper angle being adjacent to the top of the head of the fastening bolt is a few degrees larger than the counterbore angle of the workpiece. This leads to both to a fuel tight fit with no sealant, as also a reduction in corrosion under the head of the fastening bolt and a significant reduction in Fatigue defects in the vicinity of the counterbore. Another aspect includes a new design of the circumferential rings Fastening portion of the fastening bolt, which makes it possible to use a fastening bolt in both shear than

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also to use tensile stresses and thus considerable advantages and cost savings compared to the known technology to accomplish.

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Claims (16)

Claims Fastening bolts for fastening several workpieces with through openings substantially aligned with one another, with one in the axial direction tapered head section and one axially from the head section downwardly depending cylindrical shaft, the head and the shaft in use being substantially fit together with the openings of the workpieces, thereby characterized in that the conical head (11) has two sections which are conical in the axial direction, of which a first conical section (20) has a substantially larger cone angle than the second conical section (21) has that the difference in angle is such that when grasping the one workpiece by the head a press fit between the head and the workpiece can be present and the head a pulling through of the fastening bolt through which a workpiece can withstand. 2. Fastening bolt according to claim 1, characterized in that g e k e η η draws that the second tapered section has a taper angle in the range between 5 ° and 35 °, e.g. about 10 °. 3. Fastening bolt according to claim 1 or 2, characterized g e indicates that the first cone section has a cone angle in the range of 70 ° to 100 °, e.g. approximately 82 °. a - 17 509813/076 4 4. Fastening bolt according to one of the preceding claims, characterized in that a fastening section (13) provided with circumferential grooves is arranged axially adjacent to the shaft is, and that the fastening portion is substantially free of the workpieces when the head is with one of the Workpieces is engaged. 5. Fastening bolt according to claim 4, characterized in that the fastening section (13) has a plurality of circumferential rings between the circumferential grooves that the circumferential rings are in such proximity to one another are arranged and designed so that essentially at least five of the rings within an axial Distance of the mounting bolt of 6.4 mm (1/4 ") can be arranged. 6. Fastening bolt according to claim 5, characterized in that the adjacent sides of adjacent circumferential rings form an angle in the range of 55 to 65 °. 7. Fastening bolt according to one of the preceding claims, characterized in that the first conical section (20) axially adjoins the shaft (12) and the second conical section (21) axially adjoins the first conical section adjoins. 8. Fastening bolt according to one of the preceding claims, characterized in that a the bolt end (15) provided for engaging the application - 18 - ■ 509813/0764 allows an axial tensile force on the mounting bolt so that the head is in close engagement with a Workpiece can be brought and that a predetermined breaking point (14) axially on the fastening bolt between the Fastening section (13) and the bolt end (15) is arranged, and that the predetermined breaking point breaks off allows the bolt end from the rest of the fastening bolt. 9. Fastening bolt according to one of the preceding claims, which is arranged for fastening the plurality of workpieces to one another, the opening of the one the plurality of workpieces includes a counterbore and means which can be brought into engagement with the fastening bolt is present, which for clamping the between the head of the fastening bolt and the clamping device arranged workpieces can be actuated, characterized in that the second conical Section (21) has a larger cone angle than the counterbore that the difference in the cone angle so is that when the head engages the one workpiece, there is an interference fit between the head and the one workpiece may be present, and that the head pulling the fastening bolt through the one workpiece • can withstand. 10. Combination according to claim 9, characterized in that the counterbore has two counterbore angles has that the cone angle of the first conical portion (20) is substantially equal to that first counterbore angle is that the taper angle - 19 509813/0764 (e) of the second conical section (21) greater than the second counterbore angle (f) is that the difference in taper angles is such that an interference fit between the head and the one workpiece is present when the first and second tapered portions of the head die Detect counterbore of a workpiece, and that the head portion against the head of the fastening bolt pulling through which a workpiece can withstand. 11. Combination according to claim 10, characterized in that the second counterbore angle (f) is on the order of 8 °. 12. Combination according to one of claims 9 to 11, characterized characterized in that an interference fit between the second tapered section and part of the counterbore with the second counterbore angle is present when the fastening bolt · is arranged under tensile stress is, and the workpieces are clamped together by the action of the clamping device. 13. Combination according to one of claims 9 to 12, characterized characterized in that the clamping device is a sleeve (18) which is connected to the circumferential Fastening portion provided with grooves can be brought into engagement. 14. Fastening bolts for fastening several individual parts to one another, each one arranged therein - 20 - 50981 3 / 076A Have opening, the boundaries of the opening of the part substantially coinciding with the boundaries of the openings the other parts are aligned, the fastening bolt has a head, a shaft essentially axially protrudes downward from the head, the shaft essentially with the boundaries of the openings of the parts fits together and a fastening portion provided with circumferential grooves axially adjacent to the shaft is arranged, the fastening portion is substantially free of the parts when the head portion which detects one of the parts and has a plurality of circumferential rings between the circumferential grooves, characterized in that the circumferential rings are arranged in such proximity to each other and are formed so that at least five of the rings within a axial distance of the mounting bolt of 6.4 mm (1/4 ") can be arranged. 15. Fastening bolt according to claim 14, characterized in that the adjacent sides adjacent circumferential rings form an angle in the range of 55 to 65 °. 16. Fastening bolt according to claim 14 or 15, characterized in that a gripping section formed bolt end enables an axial tensile force to be exerted on the fastening bolt so that the head can be brought into close engagement with one part and that a predetermined breaking point is provided is. 509813/0764