fastener

Abstract

The present invention relates to a method for manufacturing a cold formed fastening device having a head and a shaft extending along a main axis. The method comprises cold forming the head by: cold forming a head part connected to the shaft and extending at a radial distance from the shaft with respect to the main axis, the head part having a bottom surface facing towards the shaft, and cold forming a flange connected to and extending radially from the head part; and pressing by cold forming at least a part of the flange towards the bottom surface of the head part, thereby forming an annular groove configured to receive a sealing member, the annular groove being defined by the flange and a radially outer surface of the head part.

Description

[0001] FASTENER

[0002] FIELD OF THE INVENTION

[0003] The present disclosure relates to a method for manufacturing a cold formed fastening device and to said cold formed fastening device.

[0004] BACKGROUND

[0005] Fasteners can be described as devices used to mechanically join or affix two or more surfaces or objects together. Examples of cold formed fasteners are screws, bolts, nuts, or rivets. Screws, bolts, and nuts are particularly effective at joining surfaces or objects, as they are designed with helical threads that grip and secure the surfaces or objects together. Although these fasteners are cheap and easy to use, their application requests formation of holes in the surfaces or objects, before or during their insertion into the surfaces / objects. When a fastener for example becomes loose and / or is used in harsh conditions and gaps between the fastener and the contact surface of a hole or a groove hosting the fastener occur, different fluids may pass through the gaps creating a leakage. This leakage is particularly important to prevent in equipment and machinery that may leak pollutants into the environment, that has internal components which should be protected from exposure to contaminants, and / or should withstand extreme pressure, temperature and / or weather conditions.

[0006] One way to prevent this safety hazard is to use sealing fasteners, such as sealing screws or sealing bolts. The sealing fasteners are configurated with a sealing element such as an O-ring on the underside of the screw or bolt head. When a sealing fastener is tightened, the O-ring compresses and forms a bi-directional seal between the sealing fastener and the contact surface of the object, and thereby prevents potential leakage of fluids. Manufacturing processes for threaded fasteners may be differentiated into two groups, depending on if the fasteners are formed with cutting of materials (machining) or without cutting (hot forming and cold forming). The majority of threaded fasteners are today made using the cold forming process, especially for large quantities. The cold forming (or cold forging) is a technique used to shape metal materials at near room temperature. In this process, the threaded fasteners are typically formed in a multi-step process comprising steps such as upsetting, reduction and / or extrusion, often in combination. Each step of the process is performed by placing the workpiece in-between forming tools, and pounding until the metal assumes its final shape.

[0007] Forming metal at cooler temperatures retains or enhances the tensile strength of the material while still allowing high levels of intricate manipulation. However, sharp-edged transitions and profiles that are thin and with small radiuses are usually unfavorable for the cold forming process as they lead to increased tool wear. In the situation of a cold formed part certain design elements, such as an annular groove for an O-ring, are often machined. The machining process is time consuming, produces waste and reduces durability of fasteners due to coarse machined surfaces.

[0008] There is therefore a need for an improved method for manufacturing a cold formed design element, such as an annular groove for an O-ring, into a cold formed part, such as the head of a cold formed fastening device.

[0009] SUMMARY

[0010] An object of this disclosure is to provide a method for manufacturing a cold formed fastening device, including an annular groove for a sealing element, such as an O-ring, in order to mitigate, alleviate, or eliminate the above-identified deficiencies in the art.

[0011] For this and other objects which will be evident from this disclosure, the present inventive concept provides, according to a first aspect, a method for manufacturing a cold formed fastening device having a head and a shaft extending along a main axis. The method comprises: cold forming the head by:

[0012] - cold forming a head part connected to the shaft and extending at a radial distance from the shaft with respect to the main axis, the head part having a bottom surface facing towards the shaft,

[0013] - cold forming a flange connected to and extending radially from the head part; and

[0014] - pressing by cold forming at least a part of the flange towards the bottom surface of the head part, thereby forming an annular groove configured to receive a sealing member, the annular groove being defined by the flange and a radially outer surface of the head part.

[0015] The inventors have realized that the above-mentioned method comprising cold forming for producing the annular groove in the head of the fastening device in comparison to a corresponding method comprising machining such groove advantageously achieves:

[0016] - reduction or removal of machining of the material during the producing of the groove and therefore decreasing the amount of waste in the manufacturing of the groove and the fastening device;

[0017] - replacing machining of the material to form the groove with cold forming of the groove and therefore producing the final product with less waste , smoother surfaces, and improved durability;

[0018] Cold forming the flange may comprise forming a bottom surface of the flange axially offset from the bottom surface of the head part. The axial offset may be at least 5% of the height of the head part, such as at least 15% of the height of the head part, such as at least 20% of the height of the head part. In some embodiments, the axial offset may be equivalent to or higher than 25% of the height of the head part. The annular groove is defined by the flange and a radially outer surface of the head part. Stated differently, the annular groove may be defined by the bottom surface of the flange and the radially outer surface of the head part.

[0019] The position of the annular groove is dependent on the position of the radially outer surface of the head part in view of the shaft, and it may influence the sealing performance of the sealing member. To this end, cold forming the head part may comprise forming the radially outer surface of the head part radially offset from the shaft. The radially outer surface of the head part being arranged radially offset from the shaft means that the annular groove is spaced-apart from the shaft. It may for example be arranged close to the outer diameter of the head of the cold formed fastening device. The distance between the shaft and the annular groove may be equal or higher than the width of the bottom wall of the annular groove. An advantage of having the radially outer surface of the head part radially offset from the shaft is that the sealing function of the sealing member is activated, as contact with the bottom surface is secured also with mating parts with large hole diameter.

[0020] The flange may have an inner flange part connected to the head part and an outer flange part connected to and extending radially from the inner flange part, and wherein pressing by cold forming at least a part of the flange may comprise:

[0021] - pressing by cold forming the outer flange part in a direction towards the bottom surface of the head part, such that a bottom surface of the inner flange part defines a bottom wall of the annular groove and a bottom surface of the outer flange part defines an outer wall of the annular groove.

[0022] The flange may be pressed to an angle of between 0° and 40°, preferably between 25° and 35° relative to the main axis. In some embodiments, the flange may be pressed to an angle of around 30° relative to the main axis. The pressing by cold forming may also be referred to as bending according to this invention. As a result, the flange may be bent towards the bottom surface of the head part.

[0023] Installation of fasteners comprising sealing members, such as O-rings, may be challenging as the sealing members tend to fall out of the groove prior to assembly, when the fasteners are placed in a substantially vertical or upside down position. Dovetail grooves may be used to hold the sealing members in place; however, such grooves are expensive to manufacture. The dovetail grooves are typically made by machining, which produces waste and may result in reduced durability of such fastening devices. In certain embodiments, the method of the present invention may further comprise: i) cold forming a ledge protruding axially from the bottom surface of the head part; and ii) flattening, by cold forming, the ledge such that the radially outer surface of the head part is forced to flow outwards with respect to the main axis to form a ridge.

[0024] The annular groove featuring an optional ridge keeps the sealing element in place after assembly in the annular groove. The ridge holds the sealing member in the groove and thus prevent the sealing member from falling out of the groove of the cold formed fastening device, which makes the installation of such fastening device easier, especially in a substantially vertical or upside down position.

[0025] The cold formed fastening device may be a screw, a bolt, a nut, or a rivet. The cold formed fastening device may be threaded.

[0026] The sealing member may be a mechanical gasket in the shape of a torus. The sealing member may have different cross-sections, such as a round cross-section in O-rings, a square-shaped cross-section in square rings, a T-shaped cross-section in T- seals, an X-shaped cross-section in X-rings, a delta-shaped cross section in delta seals. To this end, the sealing member may be an O-ring, a T-ring, or an X-ring. Any of the above-mentioned sealing members may be solid or hollow. In a preferred embodiment, the sealing member may be an O-ring, such as a solid O-ring or a hollow O-ring.

[0027] The sealing member may typically be made from elastic materials, such as from one or more of silicone, fluorosilicone, fluorocarbon, neoprene, nitrile , polytetrafluoroethylene , and ethylene-propylene diene monomer (EPDM). In a preferred embodiment, the sealing member is an elastic O-ring, such as an elastic O- ring made from one or more of silicone, fluorosilicone, fluorocarbon , neoprene, nitrile (buna), polytetrafluoroethylene , and ethylene-propylene diene monomer (EPDM).

[0028] According to a second aspect of the inventive concept, there is provided a cold formed fastening device having a head and a shaft extending along a main axis, the cold formed fastening device being manufactured by the method according to the first aspect.

[0029] The head, in particular the head part, may have an inner drive head, which requires a tool (e.g., a screwdriver) that inserts into the head, or an external drive head, which requires a tool (e.g., a wrench) that wraps around the head, like a wrench. The head may be of any type of head styles, including pan heads, external hexagon heads, external hexalobular heads, flat heads, button heads, round heads, truss heads, oval or raised heads, bugle head, cheese head, fillister head, socket head and mirror head.

[0030] The head may have a diameter of between two and six times the diameter of the shaft, such as a diameter of between two and five times the diameter of the shaft, such as a diameter of between two and four times the diameter of the shaft. In an embodiment, the head may have a diameter of around 4.5 times the diameter of the shaft.

[0031] The head part and the flange are connected to each other forming the head of the cold formed fastening device. The flange may be connected to the radially outer surface of the head part. The height of the flange in the axial direction may be equal or higher than the height of the radially outer surface of the head part.

[0032] The flange may be axially offset from the bottom surface of the head part. As previously described in connection with the first aspect of this invention, the axial offset may be at least 5% of the height of the head part. The radially outer surface of the head part may be radially offset from the shaft, such that the annular groove is spaced-apart from the shaft. The annular groove may be placed adjacent to the outer diameter of the head of the cold formed fastening device. As previously described in connection with the first aspect of this invention, an advantage of having the radially outer surface of the head part radially offset from the shaft is that the sealing function of the sealing member is activated, as contact with the bottom surface is secured also with mating parts with large hole diameter.

[0033] The radial distance between the outer wall of the annular groove and the outer diameter of the head may be approximately a sealing member diameter.

[0034] The flange may have an inner flange part connected to the head part and an outer flange part connected to and extending radially from the inner flange part, and wherein a bottom surface of the inner flange part defines a bottom wall of the annular groove and a bottom surface of the outer flange part defines an outer wall of the annular groove. The bottom wall of the annular groove may be substantially parallel to the bottom surface of the head part. The radially outer surface of the head part may define an inner wall of the annular groove, and wherein the inner wall may be substantially parallel with the main axis. The height of the inner wall may thus be defined by the height of the radially outer surface. Stated differently, the depth of the annular groove may be defined by the height of the radially outer surface of head part.

[0035] The outer wall of the annular grove in the cold formed fastening device may be outwardly inclined. The angle between the main axis and the outer wall may be between 0° and 40°, preferably between 25° and 35°. In some embodiments, the angle between the main axis and the outer wall may be around 30°.

[0036] The cold formed fastening device may further comprise a ridge protruding radially outwardly from the radially outer surface of the head part and located adjacent to an opening of the annular groove. The ridge is arranged to hold the sealing member in the groove and thus prevents the sealing member from falling out of the groove of the cold formed fastening device, as described in connection with the first aspect of this invention.

[0037] Preferred embodiments and further aspects are defined in the appended claims and throughout the application text.

[0038] BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The above and other aspects of the present invention will now be described in more detail, with reference to the appended figures. The figures are not necessarily to scale, and generally only show parts that are necessary in order to elucidate the inventive concept, wherein other parts may be omitted or merely suggested. The present disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and to fully convey the scope of the disclosure to the skilled addressee. Like reference characters refer to like elements throughout.

[0040] Fig. 1 illustrates a cross-section of a cold formed fastening device with an inner drive head, according to at least one example embodiment of the inventive concept;

[0041] Fig. 2A illustrates a cross-section of further examples of cold fastening devices with inner drive heads, according to at least one example embodiment of the inventive concept;

[0042] Fig. 2B illustrates a cross-section of a cold formed fastening device with an external drive head, according to at least one example embodiment of the inventive concept;

[0043] Fig. 3 illustrates shape changes during one or more method step of forming an annular groove and optional a ridge in a cold formed fastening device, according to at least one example embodiment of the inventive concept; Fig. 4 illustrates a flow chart for a method for manufacturing a cold formed fastening device, according to at least one example embodiment of the inventive concept.

[0044] DETAILED DESCRIPTION

[0045] Fig. 1 shows a cold formed fastening device 1 with an inner drive head 10 and a shaft 20 extending along a main axis (A). The inner drive head 10 comprises a head part 30 connected to the shaft 20. The head part 30 has a bottom surface 31 facing towards the shaft 20 and a radially outer surface 32 which is radially offset from the shaft 20.

[0046] The inner drive head 10 further comprises a flange 40 which is connected to the radially outer surface of the head part 32 and is bent downward. The flange 40 comprises an inner flange part 41 connected to the head part 30 and an outer flange part 42 connected to the inner flange part 41. The flange 40 also comprises a bottom surface 43 which is axially offset from the bottom surface of the head part 31.

[0047] The inner drive head 10 has an annular groove 50, which is configured to receive a sealing member. The annular groove 50 is defined by the radially outer surface 32 of the head part and the bottom surface 43 of the flange. More specifically, an inner wall 51 of the annular groove is defined by the radially outer surface 32 of the head part, a bottom wall 52 of the annular groove is defined by the inner flange part 41 (i.e., by a bottom surface thereof), and an outer wall 53 of the annular groove is defined by the outer flange part 42 (i.e., by a bottom surface thereof). The annular groove 50 is thus positioned in this embodiment spaced-apart from the shaft 20 and closer to an outer wall 44 of the outer flange part. The inner wall 51 of the annular groove may be substantially parallel with the main axis (A), a bottom wall 52 of the annular groove may be substantially parallel to the bottom surface 31 of the head part, and the outer wall 53 of the annular groove may be outwardly inclined. The inner drive head 10 may further comprise a ridge 60 which may protrude radially outwardly from the radially outer surface 32 of the head part 30. The ridge 60 may prevent the sealing member from falling out of the annular groove 50 before the cold formed fastening device 1 is used.

[0048] Fig. 2A shows further cold formed fastening devices 1 with inner drive heads 10, while Fig. 2B shows a cold formed fastening device 1' with an external drive head 10'. These devices may have the same or similar elements as the cold formed fastening device 1 in Fig. 1.

[0049] Fig. 3 illustrates shape changes during one or more method step of forming an annular groove 50 and optional a ridge 60 in a cold formed fastening device 1. The annular groove 50 is formed by pressing by cold forming the outer flange part 42 towards the bottom surface 31 of the head part 30 to form the annular groove 50. On the other hand, the ridge 60 is potentially formed by flattening, by cold forming, the bottom surface 31 of the head part 30, such that the radially outer surface 32 of the head part 30 is forced to flow outwards with respect to the main axis (A) to form the ridge 60. These two method steps may be performed in parallel or subsequently one after another. In a preferred embodiment, these two steps are performed in parallel to each other.

[0050] In Fig. 3, different shapes of the head part 30 and the flange 40 are shown. In all depicted embodiments, the outer flange part 42 will be pressed by cold forming and thereby bent towards the bottom surface 31 to form the annular groove 50.

[0051] However, Fig. 3 also show different sizes of the ledge 70 before performing the flattening. The size of the ledge 70 will determine the extent of the movement of the radially outer surface of the head part 32 outwards with respect to the main axis (A). The size of the ledge 70, which protrudes axially from the bottom surface 31 of the head part 30, is reduced from the top illustration towards the bottom illustration.

[0052] In the top-left illustration, the size of the ledge 70 is significant, and performing the flattening will thus result in a significant movement of the radially outer surface 32 and formation of a well-defined ridge 60. As the size of the ledge 70 is reduced in the middle-left illustration, the movement of the radially outer surface 32 is smaller and the formed ridge 60 is less defined. Lastly, the bottom picture shows no or very small ledge, and the inner wall 51 of the annular groove 50 comprises no or a very small ridge in the formed product.

[0053] The method for manufacturing a cold formed fastening device according to the present inventive concept will now be described in more detail referring to Figure 4. Although the order of steps is presented for clarity, the invention is not limited to this specific sequence. Furthermore, not all, or more, of the operations need to be performed.

[0054] Fig. 4 illustrates a flow chart for a method for manufacturing a cold formed fastening device having a head and a shaft. The head comprises a head part connected to the shaft and a flange connected to the head part. At SI, cold forming of the head of the cold formed fastening device in performed. This step may be done in two sub-steps: cold forming (Sil) of the head part, and cold forming (S12) of the flange. The sub-steps Sil and S12 are typically performed in parallel, however, these steps may also be performed as consecutive steps, such that S12 is performed after Sil. The sub-step of cold forming (Sil) of the head part may comprise a step of forming (Sil') a radially outer surface of the head part, such that the radially outer surface of the head part is radially offset from the shaft. The sub-step of cold forming (S12) of the flange may comprise a step of forming (S12') a bottom surface of the flange, such that the bottom surface of the flange is axially offset from a bottom surface of the head part.

[0055] At S2, the method comprises formation of an annular grove by pressing by cold forming a part of the flange towards the bottom surface of the head part to form an annular groove. The step S2 is typically performed after the sub-steps Sil and S12.

[0056] The step of pressing by cold forming (S2) the flange may comprise a sub-step of pressing by cold forming (S2') an outer flange part in a direction towards the bottom surface of the head part, such that a bottom surface of an inner flange part defines a bottom wall of the annular groove and a bottom surface of the outer flange part defines an outer wall of the annular groove.

[0057] The method may also comprise cold forming (S3) a ledge protruding axially from the bottom surface of the head part; and flattening by cold forming (S4) the ledge, such that the radially outer surface of the head part is forced to flow outwards with respect to the main axis to form a ridge. The step S3 may be executed substantially concurrently with step SI. The step S4 is typically performed after the step S3. However, the step S4 may be performed in parallel with the step S2.

[0058] In the drawings and specification, there have been disclosed example aspects of the disclosure. However, many variations and modifications can be made to these aspects without substantially departing from the principles of the present disclosure. Thus, the disclosure should be regarded as illustrative rather than restrictive, and not as being limited to the particular aspects discussed above. Accordingly, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation.

[0059] The description of the example embodiments provided herein have been presented for purposes of illustration. The description is not intended to be exhaustive or to limit example embodiments to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of various alternatives to the provided embodiments. The examples discussed herein were chosen and described in order to explain the principles and the nature of various example embodiments and its practical application to enable one skilled in the art to utilize the example embodiments in various manners and with various modifications as are suited to the particular use contemplated. The features of the embodiments described herein may be combined in all possible combinations of processes, products, and systems. It should be appreciated that the example embodiments presented herein may be practiced in any combination with each other.

[0060] It should be noted that the word "comprising" does not necessarily exclude the presence of other elements or steps than those listed and the words "a" or "an" preceding an element do not exclude the presence of a plurality of such elements. It should further be noted that any reference signs do not limit the scope of the claims, and that the example embodiments may be realized in the broadest sense of the claims.

Claims

CLAIMS1. A method for manufacturing a cold formed fastening device (1, 1') having a head (10, 10') and a shaft (20) extending along a main axis (A), the method comprises: cold forming the head by:- cold forming a head part (30) connected to the shaft and extending at a radial distance from the shaft with respect to the main axis, the head part having a bottom surface (31) facing towards the shaft,- cold forming a flange (40) connected to and extending radially from the head part; and- pressing by cold forming at least a part of the flange towards the bottom surface of the head part, thereby forming an annular groove (50) configured to receive a sealing member, the annular groove being defined by the flange and a radially outer surface (32) of the head part.

2. The method according to claim 1, wherein cold forming the flange comprises forming a bottom surface (43) of the flange axially offset from the bottom surface of the head part.

3. The method according to claim 1 or 2, wherein cold forming the head part comprises forming the radially outer surface of the head part radially offset from the shaft.

4. The method according to any one of the preceding claims, wherein the flange has an inner flange part (41), connected to the head part, and an outer flange part (42) connected to and extending radially from the inner flange part, and wherein pressing by cold forming at least a part of the flange comprises: pressing by cold forming the outer flange part in a direction towards the bottom surface of the head part, such that a bottom surface of the inner flange part definesa bottom wall (52) of the annular groove and a bottom surface of the outer flange part defines an outer wall (53) of the annular groove.

5. The method according to any one of the preceding claims, wherein the flange is pressed to an angle of between 0° and 40°, preferably between 25° and 35° relative to the main axis.

6. The method according to any one of the preceding claims, further comprising: i) cold forming a ledge (70) protruding axially from the bottom surface of the head part; and ii) flattening, by cold forming, the ledge such that the radially outer surface of the head part is forced to flow outwards with respect to the main axis to form a ridge (60).

7. The method according to any one of the preceding claims, wherein the cold formed fastening device is a screw, a bolt, a nut, or a rivet.

8. The method according to any one of the preceding claims, wherein the sealing member is an O-ring, a T-ring, or an X-ring.

9. A cold formed fastening device (1, 1') having a head (10, 10') and a shaft (20) extending along a main axis (A), the cold formed fastening device being manufactured by the method according to any one of claims 1 - 8, the method comprising: cold forming the head by:- cold forming a head part (30) connected to the shaft and extending at a radial distance from the shaft with respect to the main axis , the head part having a bottom surface (31) facing towards the shaft, and- cold forming a flange (40) connected to and extending radially from the head part; and- pressing by cold forming at least a part of the flange towards the bottom surface of the head part, thereby forming an annular groove (50) configured to receive a sealing member, the annular groove being defined by the flange and a radially outer surface (32) of the head part.

10. The cold formed fastening (1, 1') device according to claim 9, wherein the flange has an inner flange part (41) connected to the head part and an outer flange part (42) connected to and extending radially from the inner flange part, and wherein a bottom surface of the inner flange part defines a bottom wall (52) of the annular groove and a bottom surface of the outer flange part defines an outer wall (53) of the annular groove.

11. The cold formed fastening device according to claim 10, wherein an angle between the main axis and the outer wall is between 0° and 40°, preferably between 25° and 35°.

12. The cold formed fastening device according to any one of claims 9 to 11, wherein the radially outer surface of the head part defines an inner wall (51) of the annular groove and wherein the inner wall is substantially parallel with the main axis.

13. The cold formed fastening device according to any one of claims 9 to 12, further comprising a ridge (60) protruding radially outwardly from the radially outer surface of the head part and located adjacent to an opening of the annular groove.

14. The cold formed fastening device according to any one of claims 9 to 13, wherein the radially outer surface of the head part is radially offset from the shaft.

15. The cold formed fastening device according to any one of claims 10 to 14, wherein the bottom wall of the annular groove is substantially parallel to the bottom surface of the head part.

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