Method and device for joining a screw body of a concrete screw

Abstract

The invention relates to a method and a device for joining a screw body (1) of a concrete screw, said screw body consisting of a plurality of components, according to the following production steps: providing (A) a cylindrical shaft blank (2) which consists of a steel material; molding (B) a helical groove (4) into the lateral surface of the cylindrical shaft blank (2); installing (C) a helical component (6), which produces the thread turns, by screwing the component into the molded helical groove (4) of the shaft blank (2); and fixing (D) the helical component (6) in the helical groove (4) by means of at least one deformation step in which material of the shaft blank (2) is displaced in the direction of the helical component (6) in the region of the helical groove (4) such that the material partly surrounds the helical component (6) in the groove region in order to produce a combined form-fitting and force-fitting component connection.

Description

[0001] Method and device for joining a screw body of a concrete screw

[0002] The invention relates to a method for joining a screw body of a concrete screw consisting of several components. This method begins with providing (A) a cylindrical shaft blank made of steel material, subsequently forming (B) a helical groove into the outer surface of the cylindrical shaft blank, and then assembling (C) a helical component creating the threads by screwing it into the previously formed helical groove of the shaft blank. The helical component is then fixed in its desired position. Furthermore, the invention also relates to a device for carrying out a manufacturing method comprising these assembly steps.

[0003] Technical area

[0004] A concrete screw of the type in question here is considered to be a screw fastener which has a shank whose length is tailored to the desired screw-in depth or the geometric dimensions of the components to be detachably connected to one another. On the cylindrical outer surface of the shank there is an external thread with which an internal thread can be cut into a mineral anchor base, in particular concrete. For this purpose, the special external thread has, at least in some sections, a hardness and strength that allows it to cut into the usually hard mineral anchor base. The concrete screw can then be used to directly fasten an attachment, for example a steel bracket, to the anchor base. In order to achieve the direct cutting of the internal thread into preferably concrete, which is characteristic of the component, such concrete screws are usually made of hardened carbon steel.However, if a concrete screw is used outdoors, there is a risk that a fastener made of conventional carbon steel will corrode to an unacceptably high extent over its service life.

[0005] State of the art

[0006] For the aforementioned specific application, the generally known state of the art therefore identifies concrete screws in which the shaft and part of the external thread are made of a corrosion-resistant material. However, for the application in question here, the concrete screw must also be able to cut into the reinforcing iron of reinforced concrete. However, due to the lack of the necessary strength of the external thread, this is problematic for corrosion-resistant concrete screws. Therefore, design concepts are currently being used in which part of the external thread is made of hardened carbon steel or even carbide, which, however, entails correspondingly high manufacturing costs.

[0007] WO 2009 / 033637 A1 describes a concrete screw body assembled from multiple components. This screw has a shaft made of a corrosion-resistant material. The external thread, however, consists of a separate helical component, referred to here as a helix, which is positively connected to the shaft. The positive connection is achieved by providing the helical component or the shaft with regularly spaced recesses, and the shaft or the helical component with matching projections that can be snapped into the recesses. When assembled, the front turns of the helical component serve as a pre-thread area for cutting the internal thread into a prefabricated borehole wall.This pre-thread section, which acts as the cutting section, is made of a non-corrosive, hardened carbon steel with sufficient hardness and strength to cut into the borehole wall. The subsequent section of the helical component, in contrast, is made of a corrosion-resistant spring steel, which, unlike the pre-thread section, primarily serves as a load-bearing section. The material combination of this technical solution also requires a considerable manufacturing effort, especially given the different material selection and heat treatment of the helical component in certain areas.

[0008] It is therefore the object of the present invention to create a screw body of a corrosion-resistant concrete screw consisting of several components, which can be mass-produced in a simple manufacturing manner and within a short cycle time.

[0009] Disclosure of the invention

[0010] The problem is solved in terms of process technology by claim 1. The subordinate claim 13 specifies a special device for carrying out the manufacturing method according to the invention. The subsequent dependent claims specify advantageous developments of the inventive solution.

[0011] The invention includes the process engineering teaching that after a conventional screwing of a helical component of sufficient hardness and strength into a previously formed helical groove of a shaft blank, a special fixing D of the helical component in the helical groove is carried out by means of at least one forming step, in which material of the shaft blank in the area of ​​the helical groove is displaced in the direction of the helical component in such a way that it partially encompasses the helical component in the groove area in order to create a combined positive and non-positive component connection.

[0012] In contrast to the prior art discussed above, the solution according to the invention deviates from a purely positive locking connection and, with the additional material-displacing forming step, creates a force-locking connection component. This achieves a much more stable component connection that does not rely solely on the shear stability of individual material tabs in associated recesses.

[0013] On the other hand, since the solution according to the invention also departs from an otherwise usual material connection of the individual parts, which requires welding or at least soldering, the manufacturing effort can be reduced considerably, since only one forming tool, preferably a progressive tool with the process steps implemented therein, can be used for implementation.

[0014] Preferably, the at least one forming step for fixing D the helical component in the helical groove comprises a transverse extrusion step. This causes, in particular, the inventive displacement of material from the shaft blank in the region of the helical groove toward the helical component. This then also ensures force transmission between the two metallic components during the setting process of the concrete screw. In addition, the closing movement of the tool cavity of a transverse extrusion tool or tool part required for this purpose is used to position one end of the helical component into the depth of the tip imprint. The actual joining of the helical component to the shaft then takes place in the next moment. The volume of the shaft material that is displaced during transverse extrusion is ensured by the cylindrical shape and length of the screw tip.In other words, transverse extrusion is primarily responsible for joining the screw helix to the shaft in the tip area of ​​the screw body. In this process, shaft material is displaced axially from the tip to the helix groove.

[0015] Optionally, a pre-threaded area can also be formed at the distal end of the shaft blank. This can include a helix groove recess adjacent to the helix groove for accommodating the distal end portion of the helix component, into which the component is pressed. The helix groove recess can be created, for example, by stamping, which is performed before transverse extrusion. Alternatively, the pre-threaded area can also be provided with a molded lead-in thread as a transition to the thread of the helix component. The lead-in thread can be created from the shaft material during the transverse extrusion process.

[0016] According to a measure further improving the invention, the at least one forming step for fixing D the helical component in the helical groove can also include a stamping step in which the material in the region of the helical groove is displaced in the direction of the helical component. This combined stamping preferably achieves a material displacement with respect to the helical groove in which material in the region of the helical groove is forced onto the flank region of the helical component and also into optional lateral recesses in the flank region of the helical body, which further increases the stability of the component connection. In other words, this additional stamping step, or one superimposed on the transverse extrusion step, is responsible for joining the helical component to the shaft over the entire length of the helical component.

[0017] Therefore, it is proposed to perform an additional stamping step after the transverse extrusion process or, if possible, simultaneously with it. When performed simultaneously, both the transverse extrusion process and the additional stamping process as described above are performed in a single tool stroke.

[0018] Alternatively, it is also possible to form the pre-thread area as a lead-in thread for fixing D during a single forming step performed as a transverse extrusion step—if desired—and to displace the material in the area of ​​the helical groove toward the helical component. During bulk forming by transverse extrusion, an actively acting clamping force is applied to the tool cavity throughout the entire process. Subsequently, the workpiece material is displaced radially outward by an axially acting punch force. As a result, the material flows perpendicular to the punch direction.

[0019] In the inventive solution described here, one end of the helical component is joined to the distal end of the shaft by transverse extrusion in a form-fitting and friction-locking manner. This ensures force transmission between the two metallic bodies, even during the concrete screw setting process. In addition, the closing movement of the tool cavity can also be used to position the end of the helical component into the depth of the tip imprint (if implemented). The joining of the helical component to the shaft, as described above, then takes place in the next moment.

[0020] According to a further measure improving the invention, it is proposed that the provided shaft blank be prefabricated from a round steel as a semi-finished product by extrusion. A suitable screw head for tool engagement can be formed on the shaft. However, it is also possible to form a screw head with a known geometry such as an external hexagon, internal hexagon, TORX, or the like, either during a later process step or separately.

[0021] Additionally, it should be noted that the process step B of forming the helical groove into the cylindrical shaft blank can be carried out by a forming process selected from a preferred group of cold forming processes, comprising extrusion, cold rolling, and radial stamping. Cold forming, in principle, results in advantageous material hardening in the groove area, which benefits the stability of the subsequent positive and non-positive component connection. The helical groove can have a trapezoidal, rectangular, or U-shaped groove cross-section within the positive connection component. The cross-sectional shape also depends on the fact that the stamping tool used for this purpose must be demoldable with respect to the groove. For example, flat-die or roller rolling can be used during cold rolling.In an alternative radial stamping process, the contour of a stamping tool is stamped radially into the shaft blank's outer surface several times along its circumference. This generally eliminates the need for the otherwise common and more complex machining process.

[0022] In this context, it should be noted that the step of forming the helix groove can also include stamping an optional pre-thread area at the distal end of the shaft blank. The goal is to create a starting point for the helical component using a suitable stamping contour. The pre-thread area has a defined depth and length across a defined thread pitch angle. The transition to the rolled or stamped groove diameter of the helix groove is created tangentially by stamping.

[0023] Detailed description based on drawing

[0024] Further measures improving the invention are described in more detail below, together with the description of a preferred embodiment of the invention, with reference to the figures. It shows:

[0025] Fig. 1 is a schematic flow diagram of the sequence of steps of the manufacturing process according to the invention,

[0026] Fig. 2 a side view of a cylindrical shaft blank with a screw head already formed on it,

[0027] Fig. 3 is a side view of a helix groove formed in the shaft blank according to Fig. 1, Fig. 4 is a side view of the shaft blank with additional embossed

[0028] Pre-threaded area,

[0029] Fig. 4a a detail Y of the pre-thread area from Fig. 4,

[0030] Fig. 5 a side view of the screw body with pre-assembled helix component,

[0031] Fig. 6 a side view of the screw body with the helix component fixed by transverse extrusion,

[0032] Fig. 6a a detail W of the transversely extruded component connection according to Fig. 6,

[0033] Fig. 7 a side view of the screw body with additional stamping step in the context of fixing the helical component,

[0034] Fig. 7a a detail V of the additionally stamped component connection according to Fig. 7,

[0035] Fig. 8 is a schematic representation of a tool concept for transverse extrusion for fixing the helical component to the screw body,

[0036] Fig. 9 is a schematic representation of a tool concept for additional stamping of the shaft in the context of fixing the helix component to the

[0037] Very strong body,

[0038] Fig. 10 is a schematic representation of a tool concept for the optional additional stamping of the pre-thread area. According to Fig. 1, the manufacturing method according to the invention initially starts with the provision A of a cylindrical shaft blank made of a steel material (Fig. 2), in which a helix groove is formed B into the lateral surface (Fig. 3). In this context, an intermediate step B1 is also carried out in this exemplary embodiment, in which a helix groove recess is created by stamping on the side of the distal end of the shaft blank (Fig. 4). Subsequently, a helix component creating the threads is mounted C by screwing it into the formed helix groove of the shaft blank (Fig. 5).During the final positive and force-locking fixation D of the helical component in the helical groove, material from the shaft blank in the area of ​​the helical groove is displaced toward the helical component by transverse extrusion (Fig. 6). Fixation D also includes a stamping step, during which material in the area of ​​the helical groove is also displaced toward the helical component (Fig. 7).

[0039] According to Fig. 2, the screw body 1 of a concrete screw to be manufactured consists, in its initial state, of a shaft blank 2, which is made from a round steel as a semi-finished product by extrusion. A screw head 3 is formed at the proximal end of the shaft blank 2, which in this embodiment ensures a hexagonal screw drive.

[0040] It should also be noted that the cylindrical shaft blank 2 has several regions of different diameters, of which the largest shaft diameter located adjacent to the screw head 3 serves as the underhead diameter, and the smallest diameter located at the distal end of the shaft blank 2 is dimensioned such that the subsequent assembly of the helical component can be ensured by screwing it on. Furthermore, the material volume of this smallest diameter region of the shaft blank 2 is required in the later manufacturing step of transverse extrusion to form the screw tip. According to Fig. 3, the next manufacturing step involves forming B a helical groove 4 into the lateral surface of the cylindrical shaft blank 2, for example by cold rolling in the region of the central shaft diameter. The rolled helical groove 4 has a trapezoidal groove cross-section.

[0041] According to Fig. 4, in connection with this, a pre-thread region 5 is created at the distal end of the shaft blank 2. The shape of the pre-thread region 5 is evident from detail Y in Fig. 4a, which is provided with a helical groove recess 5a adjoining the helical groove for receiving the distal end region of a helical component described in more detail below. The helical groove recess 5a is a local depression of the helical groove formed by embossing. The aim is to create a starting point for the helical component to be subsequently assembled through the embossed contour. The embossed point has a defined depth and length over a defined thread lead angle, as shown. The transition to the cold-rolled groove diameter in this exemplary embodiment is created tangentially by embossing.

[0042] According to Fig. 5, in the subsequent manufacturing step, the previously mentioned helical component 6 is inserted by screwing it into the formed helical groove 4 to complete the screw body 1. The helical component 6, made of a corrosion-resistant steel material, forms the threads of the concrete screw.

[0043] According to Fig. 6, the helical component 6, which has been pre-assembled by screwing in, is then fixed in its desired position on the screw body 1 by forming, in that material from the shaft blank 2 in the area of ​​the helical groove 4 - here hidden by the helical component 6 - is displaced in the direction of the helical component 6 by transverse extrusion. Detail W in Fig. 6a illustrates the distal end of the screw body 1 after transverse extrusion. During the transverse extrusion, a lead-in thread 5b is formed from the shaft material in the pre-thread area 5 as a transition to the thread of the helical component 6. With regard to Fig. 7, an additional stamping step is carried out in this exemplary embodiment, in which a stamped impression 7 is created on the edge of the helical groove 4 - here hidden by the helical component 6 - which can be seen more clearly in detail V of Fig. 7a.The embossed impression 7 runs adjacent to the helix groove 4 on both sides and is realized by the individual, spaced-apart, adjacent embossed impressions 7 by means of a suitable embossing tool, which presses the material of the shaft blank 2 into lateral recesses - not visible here - of the helical component 6 to increase the connection stability.

[0044] It should also be noted that the embossed contour is created by the forming process along the entire length of the helical component in several embossing zones, each of which has a special characteristic. Between each of the embossing zones, a material accumulation forms, forming a kind of bridge.

[0045] The manufacturing steps described above can be carried out in individual tools or - preferably - in a progressive tool in which the tool cavities described individually below are contained.

[0046] Fig. 8 schematically illustrates a first tool cavity for a shaft blank 2 inserted therein for transverse extrusion during the fixing process D. For this purpose, a transverse extrusion die 10, 10' has a helical groove 11, matching the profile of the helical component 6 inserted into the shaft blank 2. The transverse extrusion die 10, 10' is actuated with a transverse closing force FQ. A stationary punch axially fixing the shaft blank 2 at the distal end prevents axial relative movement. After the transverse extrusion die 10, 10', which completely encloses the shaft blank 2, is closed, a closing force is applied to the die by the tool kinematics. In the next sub-step, an axial relative movement takes place between the closed die or the closed die package (in a multi-part design) as well as the enclosed shaft blank 2 and the axially fixed punch 12.This initiates a forming process on the distal end of the screw blank 2 and ensures the forming joining between the helical component 6 by means of force closure and form closure.

[0047] In the optional additional stamping step shown in Fig. 9, additional material of the shaft blank 2 in the adjacent edge area to the helical component 6 is displaced in the direction of the latter. Stamping dies 13, 13' are used for this purpose, which are provided with a stamping contour 14 adapted to the shape of the helical component 6. The stamping dies 13, 13' penetrate the material of the shaft blank 2 with a radial force FQ. The pitch of the stamping dies 13, 13' is selected such that the stamping step creates all necessary stamping points with a maximum of two forming steps. The design of the stamping dies 13, 13' is such that deformation of the screw center axis is prevented at any time during the process.

[0048] Fig. 10 schematically illustrates a further cavity of the device for carrying out the manufacturing step, preferably preceding the two manufacturing steps described above, for optionally stamping the distal pre-thread region 5 as a helical groove recess 5a on the shaft blank 2. For this purpose, a tip stamping die 15 has a corresponding tip stamping contour 16, so that a radial movement of the tip stamping die 15 is carried out for the separate stamping of an optional helical groove recess 5a.

[0049] The invention is not limited to the exemplary embodiment described above. Rather, modifications thereof are also conceivable, which are also encompassed by the scope of the following claims. For example, it is also possible to dispense with the shaping of a pre-threaded region 5 or, if desired, to realize it in a single forming step executed as a transverse extrusion step.

[0050] List of reference symbols

[0051] Screw body Shaft blank Screw head Helix groove

[0052] Pre-thread area a Helix groove recess b Inlet thread Helix component Embossing impression 0 Cross extrusion die 1 Helical groove 2 Punch 3 Embossing die 4 Embossing contour 5 Embossing die 6 Tip embossing contour

Claims

Claims 1. Method for joining a screw body consisting of several components (1) a concrete screw, according to the following manufacturing steps: Providing (A) a cylindrical shaft blank (2) made of a steel material; Forming (B) a helix groove (4) into the lateral surface of the cylindrical shaft blank (2); Mounting (C) a helical component (6) creating the threads by screwing it into the formed helical groove (4) of the shaft blank (2); characterized by: Fixing (D) the helical component (6) in the helical groove (4) by means of at least one forming step, in which material of the shaft blank (2) in the region of the helical groove (4) is displaced in the direction of the helical component (6) in such a way that it partially encompasses the helical component (6) in the groove region in order to create a combined positive and non-positive component connection.

2. Method according to claim 1, characterized in that the at least one forming step for fixing (D) the helical component (6) in the helical groove (4) includes a transverse extrusion step.

3. Method according to claim 1 or 2, characterized in that a pre-threaded region (5) with a helix groove recess (5a) adjoining the helix groove (4) for receiving the distal end region of the helix component (6) is formed at the distal end of the shaft blank (2).

4. Method according to claim 1, characterized in that the at least one forming step for fixing (D) the helical component (6) in the helical groove (4) includes a stamping step in which the material in the region of the helical groove (4) is displaced in the direction of the helical component (6).

5. Method according to claim 4, characterized in that by embossing such a material displacement takes place which on the one hand displaces material in the region of the helix groove (4) onto the flank region of the helix component (6) and on the other hand displaces the material into lateral recesses on the flank region.

6. Method according to claim 4, characterized in that the embossing step is carried out after the transverse extrusion step or simultaneously therewith.

7. Method according to claim 3, characterized in that during fixing (D) in the course of a single forming step carried out as a transverse extrusion step in the pre-thread region (5) a run-in thread (5b) is formed as a transition to the thread of the helical component (6) and also the material in the region of the helical groove (4) is displaced in the direction of the helical component (6).

8. Method according to claim 1, characterized in that before the step of providing (A) the shaft blank (2) is manufactured from a round steel as a semi-finished product by extrusion.

9. Method according to claim 1, characterized in that the forming (B) of the helix groove (4) into the cylindrical shaft blank (2) is carried out by a forming process which is selected from a group of cold forming processes, comprising extrusion, cold rolling, radial stamping.

10. Method according to claim 9, characterized in that the helical groove (4) is provided with a trapezoidal, rectangular or U-shaped groove cross-section.

11. Method according to claim 1, characterized in that after the step of forming (B) the helix groove (4), as an intermediate step (B1) a helix groove recess 5a is produced by embossing at the distal end of the shaft blank (2).

12. Method according to one of the preceding claims, characterized in that a screw head (3) for tool engagement is formed on the end of the screw body (1) opposite the pre-thread region (5).

13. Device for carrying out the method according to claim 5, comprising a first closable tool cavity for transverse extrusion of the shaft blank (2) and at least one further tool cavity for additional embossing of the shaft blank (2) for the combined positive and non-positive component connection with the helical component (6).

14. Device according to claim 13, characterized in that it is designed as a progressive tool.

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