TECHNICAL FIELD

The invention relates to a strength-improved fastener which is widely used for the connecting of mechanical elements in many industrial sectors, especially in the automotive and its production method. The invention particularly relates to a hexagon socket conical head fastener with flange whose strength has been improved by means of a customized head form to ensure its use in areas requiring higher strength, and its production method.

PRIOR ART

Fasteners are mechanical components with a wide range of applications, widely used in the production of commercial products in different sectors. Fasteners are expected to show sufficient mechanical performance due to their design and material properties in order to ensure a safe connection depending on the intended use and the area in which they are used.

The main task of the fasteners is to connect the assembled parts in a detachable manner and to carry the loads on them. The fastener on which externally loads are applied must have a certain strength to provide the desired performance during the carry and transmission of the applied load. Therefore, metals with sufficient strength, especially steel alloys, are mostly used in the production of fasteners. Aluminum and titanium alloys are used as an alternative to steel alloy in applications where weight reduction is desired. Flowever, it is known that the fasteners produced using aluminum alloy are insufficient to provide the desired strength values. The products produced from titanium and similar alloys are often preferred to be used in specific areas such as aviation due to both their production processes and very high production costs.

Metal materials with high elasticity (stretching or elongating when the load is applied and returning to their original state when the load is removed), for example steel alloys, are used in the production of fasteners. The fastener stretches beyond the yield point and enters the plastic zone and is permanently deformed when a load above a certain level is applied to the fasteners. The fastener extends to the final tensile strength and breaks after this point when the load on it is further increased. Accordingly, the tensile strength of the fastener is defined as the tensile load that the fastener can carry at the maximum flexural capacity reached before breaking under the tensile load. Tensile strength is a term used to describe the strength and load carrying properties of the fastener and is one of the most important mechanical properties in determining the load to be carried by the fastener. Fasteners with lower tensile strength with mechanical properties that will provide sufficient performance can be used in applications requiring low operating loads. However, the tensile strength of the fasteners is lower due to their design characteristics (these designs are made for weight reduction purposes and therefore the fastener tensile strength is reduced) even though the tensile strength of the materials used in the production of the fasteners here is at the standard specified tensile strength values. Bolts complying with DIN EN ISO 7380-1 , DIN EN ISO 7380-2, DIN 7991 , DIN EN ISO 10642, DIN 7984, DIN 34805-1 , DIN 34805-2, ISO 14581 , MBN 10228 can be used to perform connections subject to lower operating loads as mentioned. For instance, DIN EN ISO 7380-2 flanged hex socket button head bolts, which are widely used in many sectors, especially in automotive, cannot be used in applications under high loads because they cannot meet the minimum final tensile loads, even though they meet the reduced minimum final tensile loads corresponding to the relevant metric value specified in ISO 898-1. Accordingly, the use of fasteners with lower tensile strength as described above only in applications subjected to low operating loads and their insufficient mechanical performance for applications subjected to higher operating loads considerably limits the area of use of the said fastener. This situation may become an obstacle specific to fasteners in weight reduction studies, which is one of the main goals of automotive. The use of bolts with higher strength instead of these bolts due to their low strength causes an increase in bolt weight due to design differences and this causes an increase in the total product weight in complex products such as automobiles where thousands of bolts are used.

However, the bolts used to provide connections between the parts are subjected to variable stresses and vibration as well as constant stresses during their working life. Even if their static strength is high, the bolts may be damaged at a load below their static strength due to these dynamic loads they are exposed to. The breakage of the fasteners with a load below their static strength due to variable loads in this way is called "fatigue". Fatigue fractures are sudden fractures. The rate of fatigue damages in the damages is fairly high since the damages in the bolts used in the automotive industry are examined. The fatigue strength of the bolts is critical for the safety of the connections considering that thousands of bolts are used in an automobile. Therefore, it is necessary to improve the fatigue strength as well as the tensile strength in order to increase the strength of the bolt under both static and repetitive and time-varying loads. It is possible to fasten the bolt by applying higher torque and to increase the clamping force if higher torque is applied by increasing the tensile strength of a bolt used to connect two or more parts. Thus, the relaxation strength of the connection element under vibration increases in response to the increased torque value.

Considering the above, there is a need to develop bolts conforming to the said standard, which have a reduced minimum final tensile load, for safe use in applications requiring higher strength in order to overcome the aforementioned disadvantages.

Additionally, it is necessary to improve their mechanical properties with the changes made in their design without causing an increase in weight in order to prevent the disadvantages arising from the weight increase in the applications where the said bolts are used (especially considering the amount of use in a car).

All the problems mentioned above have made it necessary to make an innovation in the relevant technical field as a result.

BRIEF DESCRIPTION OF THE INVENTION

The main object of the invention is to improve the mechanical properties of a fasteners conforming to the standard with the abovementioned properties by improving the head shape to be used in applications subjected to higher static, variable, and repetitive loads.

Another object of the invention is to provide a fastener that can withstand the minimum final tensile loads met by conventional fasteners without breaking, by improving the tensile strength of the fastener conforming to the standard, which meets the reduced minimum final tensile loads specified in the standard.

Another object of the invention is to ensure that its weight is the same as the weight of the fastener conforming to the standard (the fastener conforming to the standard with lower tensile strength) while improving its mechanical properties thanks to the head-shaped improvements made to the fastener conforming to the invention.

Another object of the invention is to improve the fatigue strength by ensuring the safe use of the fastener, whose mechanical properties are improved in a way that its weight is the same as the fastener conforming to the standard, under static, variable and repetitive loads, and to ensure its use in a wider area than the connection element conforming to the standard. Another object of the invention is to mount the fastener by applying higher torque, by improving the tensile strength of the fastener conforming to the standard, and thus to ensure a safe connection by increasing the loosening strength of the connection element under vibration.

Another object of the invention is to extend the life of the fastener and its fracture resistance by increasing the tensile strength of the fastener conforming to the standard as well as the loosening and fatigue resistance.

The fastener according to the invention developed to achieve the above-mentioned purposes, comprising the following;

- a head part having lower and upper surfaces, a lateral surface extending flat between the lower surface and the upper surface,

- a space part inside the head part, which extends from the upper surface to the lower surface and transfers the torque from the tool to the threaded part,

- a flange part adjacent to the lower surface of the head part, radially extending from the longitudinal axis of the fastener, having a diameter greater than the diameter of the lower surface of the head,

- a body extending from the lower surface of the flange part to the end of the fastener, characterized in that the head part has a decreasing diameter from the lower surface to the upper surface of the head and that the distance between the lower boundary of the space part extending from upper surface to the lower surface in the head and the lower surface of the flange is greater than the thickness of the flange.

The fastener according to the invention is a bolt. The lower and upper surfaces of the head part are planar and parallel to each other in the fastener according to the invention whose head shape has been developed to improve its mechanical properties. The fact that the lateral part extending from the lower surface to the upper surface of the head part is flat and the diameter of the head decreases while advancing from the lower surface to the upper surface ensures that the head part is in a frusto-conical shape.

In the context of present invention, the term “planar” refers to geometric shapes formed by points on the same plane. The term “plane” refers to the region that is supposed to extend to infinity, with a width and a length but no thickness and width. Accordingly, the fact that the upper surface and the lower surface of the head part of the fastener according to the invention are planar means that each surface is the surface formed by the points on the same plane.

The space part inside the frusto-conical head part is designed in a way and dimensions that a tool for mounting and removing the fastener, for example sockets or a standard wrench, can fit easily. In the fastener according to the invention, the said space part is the socket space and is of any structure such as groove, cross, star, triangle, square, pentagon, hexagon, 12-point, hexagonal lobular, three-point or any special structure and is such as to allow the fastener to be advanced with an existing socket wrench conforming to the standard. In the fastener according to the invention, the socket space inside the head part is preferably hexagonal and extends from the upper surface of the head part to the lower surface of the head part and ends when it reaches the lower boundary of the space. The socket, which is preferably used to advance the fastener according to the invention having a preferably hexagonal socket space during tightening or loosening thereof, is a standard socket, preferably a hexagonal socket wrench. The socket space in the fastener allows the fastener to be advanced by transmitting the torque applied with the socket wrench to the thread part of the fastener during the fastening or removing of the fastener according to the invention.

The flange part adjacent to the head part of the fastener according to the invention is positioned perpendicular to the body of the fastener and extends radially from the longitudinal axis of the fastener. The flange part of the fastener has lower and upper surfaces, as in the head part, and both of these surfaces are planar. The lower and upper surfaces of the flange part of the fastener according to the invention can be in any suitable geometric shape, but are preferably circular. Diameters of the lower and upper surfaces of the flange part of the fastener according to the invention may be different or are preferably the same. Therefore, the diameter of the flange part of the fastener according to the invention is the same as the diameter of the lower surface and the upper surface of the flange part. There is a lateral surface extending flat between the lower surface and the upper surface of the flange part and connecting these two surfaces. The fact that the diameters of the planar and circular lower and upper surfaces of the flange are the same and the lateral surface is flat ensures that the flange part is in a cylindrical structure. Accordingly, the length of the lateral surface between the lower and upper surface of the flange part also refers to the thickness of the flange within the scope of the present invention.

The head part of the fastener according to the invention is positioned on the flange part and the lower surface of the head part and the upper surface of the flange part are adjacent to each other. Therefore, the head part and the flange part of the fastener are integrated. The diameter of the upper surface of the flange part is also larger than the diameter of the lower surface of the head part.

The distance between the lower boundary of the socket space inside the head part of the fastener and the lower surface of the flange part is expressed by “w” in the context of present invention. It has been determined that the w value is highly effective on these mechanical properties of the fastener in the development studies carried out in the form of a head in order to improve the tensile strength of the fastener, which meets the reduced minimum final tensile strength in accordance with the standard, as well as the loosening resistance to vibration and fatigue strength, and thus its mechanical properties. However, it has been observed in the studies carried out that when the w value (millimeters) is changed in size according to the flange thickness (millimeters), it causes changes in the strength of the fastener. Accordingly, it has been observed in cases where the w value in the fastener is greater than the flange thickness that the mechanical properties of the fastener have improved, the fastener in accordance with the standard meeting the reduced minimum tensile strength before these head-shaped improvements now provides the minimum final tensile strength specified in ISO 898-1 , and thus the fastener can be advanced and tightened by applying higher torque with the help of a tool, for example a socket wrench. Tightening of the fastener used to connect two or more parts applying higher torque with the help of a tool has also increased the vibration resistance and fatigue strength of the fastener. It has been observed that the life of the fastener is extended and its fracture strength increases with the improvement of the said mechanical properties of the fastener. Thus, it has been made possible to use the fastener according to the invention safely in applications requiring the use of the fastener with better mechanical performance.

The w value of the fastener according to the invention is greater than the flange thickness. The ratio of the w value (mm) to the flange thickness (mm) is from 1.1 to 4, preferably from 1.2 to 3, more preferably from 1.3 to 2.5 according to a preferred embodiment of the invention.

The ratio of the w value to the flange thickness of the fastener according to the invention also affects the conical angle of the head part. Accordingly, the value of the conical angle of the head part of the fastener changes as the ratio of the w value to the flange thickness of the connection element changes. However, the value of the conical angle of the head part of the fastener also directly affects the weight of the connection element. Thus, the mechanical properties of the fastener according to the invention are improved without causing an increase in the weight of the fastener with the changes made in the head shape by optimizing the w value, flange thickness, and conical angle.

It has a frusto-conical shape due to the lower and upper surfaces of the head part of the fastener according to the invention being planar, the decrease in the head diameter while advancing from the lower surface to the upper surface and lateral surface joining the lower surface and the upper surface being flat. The angle at the top of the cone is expressed as a conical angle within the scope of the invention if the lateral surface proceeds to form a cone due to the frusto-conical shape of the head part. In other words, the angle formed by the intersection of the extension of these two sides is the conical angle of the head part, when two opposing edges are determined on the lateral surface of the head part, proceeding flat from the lower surface to the upper surface of the head part in the shortest way. The value of this described conical angle in the head part of the fastener according to the invention is between 25° and 85°, preferably between 35° and 80°, more preferably between 40° and 75°.

Improvements have been made in the mechanical properties of the fasteners as mentioned above by changing the ratio of the w value to the flange thickness and the head shape by keeping the mechanical properties of the fastener material constant, in other words, without any other change that will affect the strength and thus the mechanical properties of the fastener.

The part extending from the lower surface of the flange part of the fastener according to the present invention to the end of the fastener is the body part of the fastener. The body part of the fastener allows two or more parts to be held together. The body part of the fastener can have a threaded structure formed by threads with the same or different pitch values. The pitch value of the threads in the body can be the same or different. The number of threads in the body part, the pitch values between the threads, and the structure of the threads are determined according to the application in which the fastener will be used.

The fastener according to the invention can be produced completely by the cold forging process without the need for an additional cutting process or any machining process. There was no significant increase in unit costs of the fastener thanks to the improvement of the head shape of the fastener in accordance with the standard and the improvement of its mechanical properties thereof without causing weight increase. The fastener developed within the scope of the invention is a hexagon socket conical head fastener with flange and the head part of the fastener is designed to allow the fastener to be advanced with an existing standard socket wrench, for example a hexagonal socket wrench according to a preferred embodiment of the invention.

The fastener according to the present invention can be produced from aluminum, titanium and steel alloys as raw material, or preferably produced from steel alloys. The said steel alloys may include, in addition to carbon, silicon, manganese, phosphate, sulfur, chromium, copper, boron, or any combination thereof.

It is possible to produce and use the fastener according to the present invention coated or uncoated. The use of zinc, lamellar or Cr alloy coating as a coating may be preferred if said fastener is produced by coating.

References to the following figures and detailed descriptions are intended to provide a better understanding of the invention and have no purpose limiting the scope of the invention. The components in the figures were not scaled, only the description of the principles of the invention was emphasized. Different modifications of the parts of the figures represented by references are also possible within the scope of the invention.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows a perspective view of the fastener of the invention.

Figure 2 shows a vertical cross-sectional view of the fastener of the invention at the level of an A-A axis.

Figure 3 shows a vertical cross-sectional view of the fastener of the invention.

Figure 4 shows a top view of the fastener of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The subject of the invention is explained with examples that do not have any limiting effect, only for a better understanding of the subject in this detailed description.

S Figure 1 illustrates the head part (2), the flange part (10) adjacent to the head part (2), and a body part (14) extending from the flange part (10) to the end (16) of the fastener, which are the basic parts of the fastener (1) according to the invention. The head part (2) of the fastener (1) is bounded by the planar upper surface (3) and the lower surface (4). It has a lateral surface (5) extending flat between the upper surface (3) and the lower surface (4). Inside the head part (2) is a space part (6) for transferring torque transmitted by a tool, for example a socket wrench, from said tool to the threaded part (15) in order to tighten or loosen the fastener (1), which extends from the upper surface (3) to the lower surface (4).

It is seen in Figure 2 that the head part (2) of the fastener (1) according to the invention is in a frusto-conical shape, representing the vertical view of the fastener (1) at the level of the A- A central axis due to the fact that the upper surface (3), lower surface (4) and lateral surface (5) of the head part (2) are flat and the diameter of the head part (2) has a decreasing diameter from the lower surface (4) to the upper surface (3). In addition, it is seen that the head part (2) and the flange part (10), which form the head shape of the fastener (1) according to the invention, are positioned in a way that head part (2) is above the flange part (10) adjacently in Figure 2. These parts are integrated with each other according to a preferred embodiment of the invention. In other words, the lower surface of the head part (4) and the upper surface of the flange part (11) are in direct contact. The diameter of the upper surface of the flange part (11) is also larger than the diameter of the lower surface of the head part (4).

According to a preferred embodiment of the invention, the upper surface (11) and the lower surface (12) of the flange part of the fastener (1) are circular and have the same diameters as seen in Figures 1 , 2, and 3. The surface being flat and extending between the upper surface (11 ) and the lower surface (12) of the flange part (10) is the lateral surface (13) of the flange part and the length of the lateral surface (13) expresses the flange thickness (d') due to the fact that the diameters of the upper surface (11) and the lower surface (12) of the flange part (10) are the same. There is a body part (14) extending from the lower surface of the flange part (12) to the end (16) of the fastener and connecting two or more parts, and a threaded part (15) on the body part (14), which allows the fastener to be fastened at the connection point.

The socket space part (6) inside the head part (2) and extending from the upper surface (3) to the lower surface (4) of the head part is hexagonal, where a preferred embodiment of the fastener (1) according to the invention is shown in Figure 3. The hexagonal socket space part (6) is located between the upper boundary (7) and the lower boundary (8) of the space part (6). The upper boundary of the socketspace (7) is in the same plane as the upper surface of the head part (3), i.e., they are of the same alignment. The hexagonal socket space part (6) terminates at the lower boundary of the space (8) and there is an additional groove (17) in a tapered frusto-conical shape starting from the lower boundary of the socket space (8) to ensure that the socket wrench that allows the fastener (1) to advance is firmly inserted into the space (6) during tightening or loosening of the fastener (1) and the fastener

(1) is tightened or loosened reliably and effectively. The socket wrench for advancing the fastener (1) during tightening and loosening of the fastener (1) according to the invention is preferably a standard hexagonal socket wrench.

In the context of present invention, the distance between the lower boundary of the socket space (8) of the fastener (1) according to the invention and the lower surface of the flange part (12) is expressed by “w” and is shown in Figure 3. It has been determined in the development studies carried out in the form of the head of the fastener (1) that the mechanical properties of the fastener (1) in accordance with the invention have improved thanks to the improvement of its tensile strength as well as the loosening resistance to vibration and fatigue strength in case the w value is greater than the flange thickness (d'). In the fastener (1) according to the invention, if the w value is greater than the flange thickness (d'), it has been ensured that it is used safely in connection applications that require the use of fasteners with better mechanical properties both by improving the mechanical properties of the fastener (1 ) and by increasing the life and fracture strength of the fastener (1 ).

The w value of the fastener (1) according to the invention is greater than the flange thickness (d'). The ratio of the w value (mm) to the flange thickness (d') (mm) is from 1.1 to 4, preferably from 1.2 to 3, more preferably from 1.3 to 2.5 according to a preferred embodiment of the invention.

The head part (2) of the connection element (1) is in a frusto-conical shape due to the fact that the upper (3) and lower surfaces (4) of the head part according to the invention and the lateral surface (5) connecting these two surfaces are flat and the diameter of the head part

(2) decreases from the lower surface (4) to the upper surface (3) as seen in Figure 3. The upper (3) and lower surface (4) of the head part are planar and parallel to each other, as clearly seen in Figure 2, where the vertical view of the fastener (1) according to the invention at the level of the central axis of A-A is given. Accordingly, the angle at the top of the cone is the conical angle of the head part (9) of the fastener (1) according to the invention when it is considered that the lateral surface of the head part (5) in the form of a frusto-conical in Figure 3 proceeds to form a cone. The ratio of the w value to the flange thickness (d') of the fastener (1) according to the invention also affects the conical angle of the head part (9) of the fastener (1). However, the w value, the flange thickness (d') and the conical angle (9) are optimized to ensure the improvement of the mechanical properties of the fastener (1) without causing an increase in the weight of the fastener (1) according to the invention with the changes made in the head shape since the conical angle of the head part (9) of the fastener (1) according to the invention also affects the weight of the fastener (1). The value of this conical angle (9) described in the head part (2) of the fastener according to the invention is between 25° and 85°, preferably between 35° and 80°, more preferably between 40° and 75°.

The part extending from the lower surface of the flange part (12) to the end part (16) of the fastener according to the present invention along the central axis of the fastener (1) is the body part (14) of the fastener (1). The body part of the fastener (14) has a threaded structure (15) formed by threads with the same or different pitch values according to a preferred embodiment of the invention.

The fastener (1) according to the invention described in detail above is a hexagon socket conical head fastener (1) with a flange because it has a hexagonal socket space part (6) in the head part (2) and a flange part (10) adjacent to the head part (2) and the head part (2) is in a frusto-conical shape. The fastener (1) is advanced by transferring the torque force applied by the tool to the socket space part (6) to the body part (14) and hence to the thread part (15) during the loosening and tightening operations using a standard tool adapted to the socket space part (6), for example a hexagonal socket wrench, taking into account the distance shown in Figure 4 which is the top view of the fastener (1) according to the invention, and expressed by “d” between each of the two mutually parallel edges in the hexagonal structure of the socket space part (6).

The scope of protection of the invention is specified in the attached claims and cannot be limited to those explained for illustration purposes in this detailed description. It is evident that a person skilled in the art may make similar embodiments in light of above-mentioned facts without departing from the main theme of the invention. REFERENCE NUMBERS GIVEN IN THE FIGURES

1 Fastener

2 Head Part of Fastener

3 Upper Surface of Head Part

4 Lower Surface of Head Part

5 Lateral Surface of Head Part

6 Space Part

7 Upper Boundary of Space Part

8 Lower Boundary of Space Part

9 Conical Angle of Head Part

10 Flange Part

11 Upper Surface of Flange Part

12 Lower Surface of Flange Part

13 Lateral Surface of Flange Part

14 Body Part

15 Threaded Part

16 End Part

17 Groove w Distance Between Lower Boundary of Space Part and Lower Surface of Flange Part d Distance Between Two Mutually Parallel Edges in the Socket Space d' Flange Thickness