Connection Element, And Method For Connecting At Least Two Workplaces

Abstract

The invention relates to a connection element for interconnecting at least two workpieces, having a shaft; a connection-element head, radially protruding beyond the external side of the shaft, at the one end of the shaft; a drive configuration on the connection-element head and a front shaft end, wherein in a holding portion of the shaft that emanates from the lower side of the connection-element head at least one pair of closed annular protrusions are disposed thereon, of which at least one annular protrusion is not completely disposed in a plane that runs perpendicularly to the longitudinal axis of the shaft; and the spacings between the two annular protrusions of the pair along the circumference are of dissimilar size, or the two annular protrusions of the pair of annular protrusions are disposed so as to be mutually parallel; wherein the front end of the shaft is configured as a tapered hole-forming portion, and wherein a maximum external diameter of the hole-forming portion is between 3% and 10% smaller, in particular 5% smaller, than a maximum external diameter of the annular protrusions.

Claims

1. Connection element (10) for interconnecting at least two workpieces, having a shaft (14); a connection-element head (12), radially protruding beyond the external side of the shaft (14), at the one end of the shaft (14); a drive configuration on the connection-element head (12), wherein in a holding portion (24) of the shaft (14) that emanates from the lower side (18) of the connection-element head (12) at least one pair of closed annular protrusions (26, 28) are disposed thereon, of which at least one annular protrusion (28) is not completely disposed in a plane that runs perpendicularly to the longitudinal axis of the shaft (14); and the spacings between the two annular protrusions (26, 28) of the pair along the circumference are of dissimilar size, or the two annular protrusions of the pair of annular protrusions are disposed so as to be mutually parallel; wherein a front end of the shaft is configured as a tapered hole-forming portion (32), characterized in that a maximum external diameter of the hole-forming portion (32) is between 3% and 10% smaller, in particular 5% smaller, than a maximum external diameter of the annular protrusions (26, 28).

2. Connection element according to claim 1, characterized in that the maximum external diameter (A) of the hole-forming portion (32) is larger than a core diameter (D) of the shaft (14) between the annular protrusions (26, 28).

3. Connection element according to claim 1, characterized in that air acceleration region (30) having an at least portion-wise constant external diameter (B) is disposed between the head-side end of the hole-forming portion (32) and the commencement of the holding portion (24), wherein this external diameter (B) of the acceleration region (30) is smaller than the maximum external diameter (A) of the hole-forming portion (32).

4. Connection element according to claim 3, characterized in that the external diameter (B) of the acceleration region (30) is larger than or equal in size to the core diameter (D) of the shaft (14) between the annular protrusions (26, 28).

5. Connection element according to claim 3, characterized in that a length (F) of the acceleration region (30), in particular a length of the portion of the acceleration region (30) having a constant diameter, is between 20% and 50%, in particular 30%, of the length (E) of the hole-forming portion (32).

6. Connection element according to claim 1, characterized in that the hole-forming portion (32) at the free end thereof has a rounded tip (34).

7. Connection element according to claim 1, characterized in that the hole-forming portion (32), at least in the region of the free end thereof, has a polygonal cross section.

8. Connection element according to claim 7, characterized in that the polygonal cross section has rounded corners.

9. Connection element according to claim 7, characterized in that the polygonal cross section is configured so as to be triangular, having rounded corners.

10. Connection element according to claim 1, characterized in that the acceleration region (30) has a circular cross section.

11. Connection element according to claim 1, characterized in that the holding portion (24) has a circular cross section.

12. Method for connecting at least two workpieces (40, 42), wherein the workpieces (40, 42) are placed on top of one another, and a connection element (10) according to claim 1 is set in rotation and is placed on top of an external workpiece of the workpieces (40), wherein an axial pressure (P) is exerted on the connection element (10) until a lower side (18) of the connection-element head (12) bears on that surface of the external component (40) that faces the connection-element head (12).

13. Method according to claim 12, characterized in that the connection element (10), upon the placement of the lower side (18) of the connection-element head (12) on the surface of the external workplace (40), continues to rotate.

14. Method according to claim 13, characterized in that a rotation angle of the rotating movement of the connection element (10), upon the placement of the lower side (18) of the connection-element head (12) on the external workpiece (40), is larger than 360°.

15. Method according to claim 13, characterized in that, upon the placement of the lower side (18) of the connection-element head (12), the connection element (10) is no longer driven to perform a rotating movement until the rotation of the connection element (10) is decelerated to a standstill.

16. Method according to claim 13, characterized in that the connection element (10), upon the placement of the lower side (18) of the connection-element head (12) on the external workpiece (40), continues to be rotated about a predefined angle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Further features and advantages of the invention are derived from the claims and from the following description of preferred embodiments of the invention in conjunction with the drawings. In the drawings:

[0035] FIG. 1 shows a side view of a connection element according to the invention.

[0036] FIG. 2 shows a sectional view of the connection element of FIG. 1, parallel with the longitudinal axis.

[0037] FIG. 3 shows a sectional view of the acceleration region of the connection element of FIG. 1, perpendicular to the longitudinal axis.

[0038] FIG. 4 shows a sectional view of the hole-forming region of the connection element of FIG. 1, perpendicular to the longitudinal axis.

[0039] FIG. 5 shows an illustration of the connection element of FIG. 1, enlarged in portions.

[0040] FIG. 6 shows a further illustration of the connection element of FIG. 1, enlarged in portions.

[0041] FIGS. 7 to 10 show various stages when connecting two workpieces by way of a connection element according to the invention.

[0042] The illustration of FIG. 1 shows a connection element 10 according to the invention, according to a preferred embodiment of the invention. The connection element 10 has a connection-element head 12 and a shaft 14. The connection-element head on the upper s ide thereof is provided with a drive configuration 16. A lower side 18 of the connection-element head 12 is provided with an encircling annular groove 20, see FIG. 2, which is provided for receiving a material excavation of the external workplace when the lower side 18 of the connection element 10 bears on an external workplace. In the radially outward direction, a planar annular face 22 which is disposed perpendicularly to a central longitudinal axis of the connection element 10 adjoins the annular groove 20. The drive configuration 16 allows for the connection element 10 to be driven in only one rotation direction and for axial pressure, acting downwards in FIG. 1, to be applied to the connection-element head 12.

[0043] The salient regions of the shaft 14 are marked by square brackets in FIG. 1. Proceeding from the lower side 18 of the connection-element head 12, a holding portion 24 having a plurality of annular protrusions 26, 28 is disposed first. The holding portion 24 is followed by an acceleration region 30 which has a cylindrical portion and, as is shown by the length of the square bracket, runs from the annular protrusion 26 that is the most remote from the lower side 18 of the connection-element head 12, up to the commencement of a hole-forming portion 32. On account thereof, the acceleration region also has another expanding region in which the external diameter of the acceleration region 30 increases from the constant external diameter in the cylindrical region up to the maximum external diameter of the hole-forming portion 32.

[0044] The hole-forming portion 32 tapers off in the direction towards the free end of the shaft 14, terminating at a rounded tip 34.

[0045] FIG. 4 shows a section through the hole-forming portion 32, said section running perpendicularly to the central longitudinal axis of the connection element 10. It can be seen that the hole-forming portion 32 has a polygonal cross section in the form of a triangle having rounded corners. The rounded corners each are interconnected by means of slightly convexly curved lateral edges. The hole-forming portion 32 has such a polygonal cross section across the entire length thereof up to the tip 34.

[0046] FIG. 3 shows a cross section of the connection element 10, perpendicular to the central longitudinal axis, in the cylindrical portion of the acceleration region 30. The connection element 10 in the cylindrical acceleration region 30 has a circular cross section.

[0047] A cross section of the shaft 14 is also circular in the holding portion 24.

[0048] The enlarged view of FIG. 5 shows only the hole-forming portion 32, the acceleration region 30, and part of the holding portion 24 in an enlarged illustration.

[0049] A maximum external diameter of the hole-forming portion 32 lies at the head-side end of the hole-forming portion 32 and is identified by the reference sign A. A diameter in the cylindrical region of the acceleration region 30 is identified by B. A maximum external diameter of the annular protrusions 26, 28 is identified by C. The external diameters of the annular protrusions 26, 28 are of identical size such that the holding portion 24 has a cylindrical envelope. A core diameter of the holding portion 24 is identified by E.

[0050] It can be seen in the enlarged illustration of FIG. 5 that two annular protrusions 26, 28 always form one pair. The external diameter of the annular protrusion 28 is indeed sized identically to the external diameter of the annular protrusion 26. However, a spacing in the longitudinal direction of the connection element 10, between the two annular protrusions 26, 28 along the circumference, is of variable size, increasing from right to left in the illustration of FIG. 5, and decreasing from left to right. Accordingly, the annular protrusion 28 is disposed so as to be oblique to a longitudinal axis of the connection element 10, whereas the annular protrusion 26 runs perpendicularly to the longitudinal axis.

DETAILED DESCRIPTION

[0051] Alternatively, in a manner not illustrated, the annular protrusions 26, 28 may also be disposed so as to be mutually parallel, wherein the two annular protrusions in this instance are not completely disposed in a plane that runs perpendicularly to the longitudinal axis of the shaft, thus obliquely to the longitudinal axis, for example.

[0052] In terms of a potential design embodiment of the annular protrusions 26, 28, reference is made to the international unexamined and first publication WO 2015/022124 A1 by the same applicant, the disclosed content of which is hereby fully incorporated by reference. In this way, the annular protrusions may run obliquely to the longitudinal axis only in portions.

[0053] Prior to the commencement of the acceleration region 30, three annular protrusions 26 which all run in a mutually parallel manner are sequentially disposed when viewed in the longitudinal direction.

[0054] It can be seen in FIG. 1 that a total of three pairs of annular protrusions 26, 28 are sequentially disposed in the holding portion 24. Thereafter, there follow three annular protrusions 26 that run perpendicularly to the longitudinal axis, prior to the acceleration region 30 then commencing.

[0055] The cylindrical portion of the acceleration region 30 commences after the last annular protrusion 26. The cylindrical portion has the external diameter B. After the end of the cylindrical portion the external diameter of the acceleration region 30 increases until the acceleration region 30 at the maximum diameter A transitions to the hole-forming port ion 32. The hole-forming port ion 32 then continuously tapers off up to the rounded tip 34.

[0056] The maximum diameter A of the hole-forming portion 32 in the case of the illustrated embodiment is 5% smaller than the maximum external diameter C of the annular protrusions 26, 28. In the context of the invention, the maximum external diameter A may be between 3% and 10% smaller than the maximum external diameter C.

[0057] The external diameter B in the cylindrical portion of the acceleration region 30 in the illustrated embodiment corresponds to the core diameter D of the shaft 14 in the holding portion 24. The maximum external diameter A of the hole-forming portion 32 is larger than the diameter B in the cylindrical portion of the acceleration region 30, and also larger than the core diameter D of the holding portion 24. The maximum external diameter of the hole-forming portion 32, and thus also the diameter of the hole that is produced in the workpieces lying on top of one another, thus lies between the external diameter C of the annular protrusions 26, 28 and the core diameter D of the holding portion, or the external diameter B of the cylindrical portion of the acceleration region 30, respectively.

[0058] The illustration of FIG. 6 shows that portion of the connection element 10 of FIG. 1 that has already been illustrated in FIG. 5. FIG. 6 is utilized for illustrating the length ratios between the hole-forming portion 32 and the acceleration region 30. The hole-forming portion 32, from the rounded tip 34 to the maximum diameter A, has a length E. The acceleration region 30, from the maximum diameter A of the hole-forming region 32, the former simultaneously forming the end of the hole-forming region 32, up to the base of the first annular protrusion 26, has a length F. In the case of the connection element according to the invention, the length F of the acceleration region 30 is between 20% and 50% of the length E of the hole-forming portion 32. In the illustrated embodiment the length F of the acceleration region 30 is approximately 30% of the length E of the hole-forming portion 32.

[0059] It has emerged that the length ratios described by means of FIG. 6 and the diameter ratios described by means of FIG. 5 deliver outstanding results when connecting two workpieces by way of the connection element according to the invention. Very short cycle times during the hole formation and also when axially push-fitting the holding portion 24 may be especially achieved. Overall, reduction in cycle times of up to 50% may be achieved in relation to flow drilling screws or other connection elements. The connection elements 10 according to the invention and the method according to the invention are used, for example, for connecting aluminium panels to steel panels, or else for connecting two aluminium panels. The connection elements 10 herein may also serve only for pressing together the workpieces until the adhesive has cured when two workpieces are adhesively bonded.

[0060] The illustrations of FIGS. 7 to 10 show various method steps when carrying out the method according to the invention. The illustration of the connection element 10 is in each case schematic. It is also pointed out that the two workpieces 40, 42 to be interconnected during the connection procedure remain immovable and at the same level, as opposed to what may be assumed based on the arrangement of FIGS. 7 to 10.

[0061] FIG. 7 shows a stage in the method according to the invention, in which the connection element 10, set in rotation, that is additionally impinged with an axial pressure P in the direction of the two workpieces 40, 42, by way of the tip 34 of the hole-forming portion 32 already has penetrated the two workpieces 40, 42. The maximum diameter A of the hole-forming region 32 in FIG. 7 lies approximately so as to be level with the surface of the external workpiece 40.

[0062] The connection element 10 is then further rotated, see FIG. 8, and continues to be impinged with an axial pressure P. The axial pressure P herein does not have to be constant in temporal terms. The hole-forming portion 32 now has formed a hole and a passage 44 in the lower workpiece 42. The acceleration region 30 is now located in the region of the hole, or of the passage 44, respectively. The diameter B in the acceleration region 30, that in relation to the maximum external diameter A at the end of the hole-forming region 32 is reduced, leads to the connection element 10 being able to yield more intensely to the axial pressure P, therefore being accelerated in the direction towards the two workpieces 40, 42.

[0063] This facilitates the axial press-fitting of the connection element 10 into the hole in the workpieces 40, 42 that has been configured by means of the hole-forming portion 32. The axial pressure P that continues to be maintained and the rotation that likewise continues to be maintained lead to the holding portion 24 by way of the annular protrusions thereof penetrating the hole that has been formed in the workpieces 40, 42, see FIG. 9.

[0064] Penetration into the two workpieces 40, 42 is performed until the lower side of the connection-element head 12 bears on that surface of the external workpiece 40 that faces the head, see FIG. 10. In the position of FIG. 10, further rotation of the connection element 10 is performed according to the method according to the invention. This rotation, upon placement of the lower side of the connection-element head 12, may be performed across an angle of more than 360°. It is provided within the context of the invention for a rotating drive (not illustrated in FIGS. 7 to 10) of the connection element 12 to be switched off, or for the connection element 10 to be continued to be driven. While the connection element 10 is the position of FIG. 10 continues to rotate, the material that forms the hole in the workpieces 40, 42 may flow between the annular protrusions 26, 28 of the holding portion 24, or may move into the intermediate spaces between the annular protrusions 26, 28, respectively. This may be performed by an actual flowing movement of the heated material. However, on account of the material that forms the hole in the workpieces 40, 42 cooling alone, the diameter of the hole is also reduced, meshing arising between the wall of the hole and the annular protrusions 26, 28 of the holding portion 24.

[0065] On account thereof, extremely short cycle times may be achieved when connecting the two workpieces 40, 42 using the connection element 10 according to the invention, and using the described method according to the invention. As has been elaborated, the mutually facing surfaces of the workpieces 40, 42 may be coated with an adhesive, the connection elements 10 serving for additionally mutually securing the two workpieces 40, 42 and holding the latter in the mutually compressed state until the adhesive has cured.