Field of technology

The invention relates to a self-drilling blind rivet for the creation of a permanent joint.

State-of-the-art

The currently used blind rivets used to create the permanent joints of flat materials, such as thin sheets, mostly consist of two parts. The rivet itself has the shape of a round tube with a wide flange (head) at its end. In the direction from the tube end towards the flange, a round steel stem is driven. At its lower end, the stem has an upset head with the diameter greater than the inner diameter of the tube but equal to or greater than the outer diameter of the tube. At a distance corresponding to approximately one to two diameters of the stem, a sharp V- shaped groove is formed around the circumference of the stem. On its other side, the stem usually has the shape of a cone or a pyramid, similar to that of a nail. The described set, i.e. a rivet on a stem, is ready for use, to form a joint.

Joints are formed as follows: The materials to be joined are placed on one another and secured against displacement. A hole in which the blind rivet is to form the future joint is drilled or made otherwise. The free end of the blind rivet stem is clamped into riveting pliers resting on the rivet head, which pull the blind rivet stem inside the pliers, thus pushing the blind rivet stem head into the rivet tube and deforming it in both radial and axial directions; this forms the rivet joint closing head and as a result of increasing the tensile stress in the stem, the stem breaks at the recess point, allowing the stem to be removed from the completed rivet joint.

Blind rivets have diameters ranging from 2.4 to 7.8 mm and lengths between 5 and 50 mm. Aluminium, steel, A2 stainless steel, A4 stainless steel, brass and copper are used as rivet materials. The above description demonstrates the disadvantage of the current solution, which requires two steps or two different successive operations in order to create the rivet joint, i.e. hole drilling and the subsequent creation of the rivet joint. The objective of the presented invention is to avoid the drawbacks of the described blind rivet design.

Principle of the invention

The defined objective is achieved by the invention, i.e. the self-drilling blind rivet consisting of a hollow sleeve formed by a tube ended with a flange-shaped head and a tear element formed by a stem with a head, the principle of which is in the fact that the tear element head has the shape of a helical drilling bit with a stem attached to its rear head; the diameter of the cylindrical part of the stem corresponds to the diameter of the through-hole of the tubular part of the sleeve and the outer diameter of the tear element head is equal to or greater than the outer diameter of the tubular part of the sleeve.

With a preferred design, the sleeve head has the shape of a lens or cone or hexagon, and the rear face of the head has a conical chamfer on the outer circumference.

It is also preferred if the cylindrical part of the stem is provided with a circumferential notch groove in its part inserted in the sleeve through hole.

Thanks to the presented design of the blind rivet, it is possible to form a rivet joint in a single operation, and thus substantially increase the riveting work efficiency.

Explanation for drawings

A specific example of the invention design is shown in the accompanying drawings, where:

Figure 1 is a self-drilling blind rivet, as an overall view and a half-section view; and Figures 2(a) - 2(d) show individual phases of the rivet joint formation.

The drawings illustrating the presented invention and the following examples of particular designs do not in any way limit the scope of protection stipulated in the definition, but merely illustrate the principle of the invention.

Detailed description of the invention

The self-drilling blind rivet according to the invention consists of a hollow sleeve N which is formed by a tubular part 6 terminated by a flange-shaped head 7 and a tear element S formed by a stem 1 with a head 2. The head 2 of the tear element S is formed in the form of a helical drilling bit, with a stem 1 attached to its rear face 3. The tear element S and the sleeve N are designed so that the diameter of the cylindrical part 4 of the stem 1 of the tear element S corresponds to the diameter of the hole 5 of the tubular part 6 of the sleeve N and the outer diameter of the head 2 of the tear element S is equal to or greater than the outer diameter of the tubular part 6 of the sleeve N. The head 7 of the hollow sleeve N may have the shape of a lens (lens head), a cone (countersunk head) or a hexagon (hexagonal head). The rear face 3 of the head 2 is provided with a conical chamfer 8 on the outer circumference, for an easier deformation of the tubular part 6 of the sleeve N when forming the closing collar 10 of the sleeve N during the creation of the rivet joint, as shown in figures 2(a) - 2(d). The cylindrical part 4 of the stem 1 is provided with a circumferential notch groove 9 in the area with which it is inserted in the through hole 5 of the sleeve N designed to locate the point where the cylindrical part 4 of the stem 1 breaks at the end of the riveting process, after the creation of the closing ring TO of the sleeve N. The free end of the cylindrical part 4 of the stem 1 is provided with an unmarked cone or pyramid-shaped end, for easier insertion into a riveting drill, similar to a nail, for example. Individual stages of the process of forming a rivet joint using a self-drilling blind rivet are shown in figures 2(a) - 2(d).

The first stage of forming a rivet joint using a self-drilling blind rivet is shown in fig. 2(a) where the cylindrical part 4 of the stem 1_ is clamped into the rotary riveting head JM of a drilling machine (not shown). A sleeve N is placed on the cylindrical part 4 of the stem 1, the tubular part 6 of which comes in contact with the conical chamfer 8 of the rear face 3 of the head 2 of the stem 1 By turning the riveting head H, the stem 1 clamped in it rotates, and its head 2 forms a through hole at the location of the future joint. The second stage shown in fig. 2(b) follows, in that owing to the forward movement of the riveting head H the tubular part 6 of the hollow sleeve N passes through the formed hole. The third stage according to fig. 2(c) starts with the rotary riveting head V\ pushed in the axial direction to the connected component D, which leads to the stopping of the riveting head H and initiating tensile stress in the stem 1, after which the stem 1 is pulled inside the riveting head V\_ and the end of the tubular part 6 of the sleeve Nopens, while forming a closing collar 10 of the hollow sleeve N. In the last fourth stage, according to fig. 2(d), due to the increasing tensile stress in the cylindrical part 4 of the stem 1, the part breaks at the place of the notch groove 9 and subsequently the broken cylindrical part 4 of the stem 1 is removed from the through hole 5 of the sleeve N. The head 2 of the stem 1 remains in the closing collar 10 of the sleeve N or falls off.

Industrial usability

Self-drilling blind rivets are suitable for the creation of non-detachable rivet joints in a single operation, particularly when joining thin materials, such as thin metal sheets.