Apparatus and method for threading female threads
The apparatus and method for threading female screws with a defined surface contact and eccentric positioning enhance precision and speed in machining, addressing the challenge of complex thread production by reducing tool jamming and supporting diverse thread types.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-05-22
- Publication Date
- 2026-03-13
AI Technical Summary
Existing technologies face challenges in achieving a favorable balance between manufacturing complexity and precision when threading female screws with large length/diameter ratios, particularly in producing multi-start threads and threads with steep angles.
An apparatus and method that utilize a threading mandrel and guide component with a defined surface contact and eccentric positioning, allowing for high-speed machining with precise alignment and support, using a machining tool that can be integral or interchangeable, and enabling threading from both sides of the workpiece.
This approach reduces the risk of tool jamming and ensures high precision and speed in machining female threads, particularly for small diameters and deep bores, supporting various thread types including single and multi-start threads.
Smart Images
Figure 2026508971000001_ABST
Abstract
Description
Technical Field
[0004] , ,
[0001] The present invention relates to an apparatus for threading an internal thread configured according to the preamble of claim 1. Further, the present invention relates to a method for machining and producing an internal thread by threading.
Background Art
[0002] A method for producing an internal thread by threading is known, for example, from European Patent Application Publication No. 1820592. European Patent Application Publication No. 1820592 relates to the production of a multi-start thread profile and proposes synchronizing the rotational speeds and rotational angles of the workpiece and the machining tool so that at least some of the thread flanks of the profile are produced continuously. The threading mandrel used for machining the machine described in European Patent Application Publication No. 1820592 is guided within a so-called support head, which is a tubular part. The support head has, at its end, a cylindrical guiding part as a part with an increasing diameter that is slidably guided on the inner surface of the workpiece. The threading mandrel projects beyond the support head including the guiding part and carries a machining tool in the region that projects beyond the guiding part. In the case of the machine according to European Patent Application Publication No. 1820592, the machining tool comprises a tool body to which a carbide cutting insert is attached.
[0003] Generally, threading is a circular threading process. In this process, the workpiece rotates relatively slowly while the threading tool rotates at high speed. The tool and the workpiece can rotate either in the same direction or in opposite directions. In either case, the relative movement between the tool and the workpiece in the axial direction must be coordinated with the profile to be produced and the rotational movement of the workpiece. Since both the tool and the workpiece are rotationally driven, a machine tool having particularly two opposing spindles is suitable for threading.
[0004] German Patent No. 19922891 discloses a tool holder having a rotatably driven tool spindle for threading female threads, wherein the axis of rotation of the tool extends obliquely with respect to the axis of the threaded bore of the workpiece. The drive spindle is connected to the tool spindle via a two-part connecting shaft. This is intended to provide an adjustment option that allows the tool holder to be used to produce different thread pitches.
[0005] West German Patent Application Publication No. 1280638 relates to an apparatus for threading steeply angled female threads and / or long female threads. According to West German Patent Application Publication No. 1280638, the stroke movement of the threading mandrel is obtained from an obliquely positioned disk on which the threading mandrel is articulated and supported above via a sliding block.
[0006] The threading apparatus described in German Patent No. 102011110131 comprises a tool positioned on a spindle that can be driven to be rotatable and linearly displaceable. It is possible to achieve rotational movement of the spindle only, linear movement only, or simultaneous rotational and linear movement. [Overview of the project] [Problems that the invention aims to solve]
[0007] The present invention aims to achieve an advance over the aforementioned prior art in threading female screws, where a particularly favorable relationship between manufacturing complexity and precision is desired even for screws with large length / diameter ratios. [Means for solving the problem]
[0008] This objective is achieved, according to the present invention, by an apparatus configured to thread a female thread having the features of claim 1. This objective is also achieved by the method for threading a female thread as described in claim 8. The embodiments and advantages of the present invention described below in relation to the manufacturing method, i.e., the machining method of the threading form, also apply to machining apparatus provided for threading female threads, with necessary modifications.
[0009] The machining apparatus according to this application comprises a threading mandrel on which a machining tool for producing an internal thread is positioned, in a basic concept known in itself. Furthermore, the machining apparatus comprises an elongated guide component that supports the threading mandrel. At the end of the guide component, a guide portion is formed which has an increased diameter relative to the adjacent region of the guide component, i.e., the shaft, and is intended to contact the inner circumferential surface of the workpiece.
[0010] The shaft of the guide component, like the guide portion provided by the guide component, does not necessarily have a circular cross-section. By configuring the cross-section of the guide portion such that contact between the inner surface of the workpiece and the surface of the guide portion occurs only on a defined surface portion that is small compared to the entire surface of the guide portion, the risk of tool jamming in the workpiece bore can be effectively countered. In particular, the outer contour of the guide component can be exposed in places where support force is not required. For example, contact with the workpiece bore occurs only on two separate surfaces that face the force applied by the machining process. During machining, i.e., during the machining production of female threads by threading, the threading mandrel is always positioned eccentrically with respect to the guide portion.
[0011] In the apparatus according to this application, the threading mandrel is positioned opposite the guide component, and means for aligning the threading mandrel with respect to the guide component are formed on the opposing end faces of the threading mandrel and the guide component.
[0012] When a workpiece already having a continuous cylindrical inner surface, i.e., a hollow shape with a through bore, is located in the machining apparatus before threading, access to the bore from both sides can be used to provide very effective mechanical support to the threading mandrel during machining and to machine the workpiece with both high machining speed and precision. The machining apparatus can be used for producing single-start threads, multi-start threads, or other structured inner surfaces, and is particularly suitable for diameters small relative to the bore diameter and large bore depths.
[0013] As far as the type of machining tool is concerned, various configuration options exist. For example, the machining tool can be a cutting head that is an integral component of a threading mandrel. Alternatively, instead of a cutting head integrally formed with the threading mandrel, there may be a cutting head that is interchangeably mounted on the shaft of the threading mandrel. Similarly, embodiments can be realized in which the machining tool takes the form of at least one interchangeable cutting plate mounted on the threading mandrel. In all cases, the machining tool can have either a single cutting edge or multiple cutting edges, for example, three cutting edges.
[0014] The means mentioned for aligning the threading mandrel with respect to the guide component allows for relative rotation between the threading mandrel and the guide component, and is formed, for example, by a pin and an associated bore, where the pin is located on one of the two components, the threading mandrel and the guide component, and the bore is located on the end face of the other component. It is also possible to create a contour formed only as segments in order to align the threading mandrel with respect to the guide component during machining.
[0015] In the case of a pin-and-bore combination, the pin is located on the threading mandrel, for example, in a portion that protrudes beyond the machining tool, while the guide portion is provided with a corresponding bore. Conversely, the guide portion may also be provided with a pin-like extension that engages with the end face bore of the threading mandrel. For the same function, the interaction between the threading mandrel and the guide component may also be provided via separate bearings.
[0016] Methods for producing female threads by thread cutting are generally as follows: - To provide a tubular workpiece with an internal thread, i.e., a tubular workpiece having a through bore, - The workpiece is clamped by the central drive spindle of the machine tool so that the through bore is accessible from both sides, - To provide a threaded mandrel and an elongated guide component, wherein an alignment contour is formed on the end faces of the threaded mandrel and the guide component, and the alignment contour enables defined relative positioning of the longitudinal axes of the threaded mandrel and the guide component during simultaneous relative rotation between the threaded mandrel and the guide component. - Feeding a threading mandrel to a workpiece from the first side of a through bore and feeding a guide component from the opposite side, wherein the workpiece, threading mandrel, and guide component are initially positioned at least substantially concentrically with respect to each other. - Moving the threaded mandrel radially and joining the alignment contour of the threaded mandrel to the guide component, wherein the guide portion of the guide component is guided within the through bore, i.e., supported radially, and the joining is performed accordingly. - A method of machining and producing female threads by advancing the position of a threading mandrel and guide components through a through bore, wherein no axial displacement occurs between the threading mandrel and the guide components, the guide components do not rotate, the threading mandrel rotates at a specified high speed, and simultaneously the workpiece rotates at a relatively low speed. Includes.
[0017] During threading, i.e., during machining, the threading mandrel and the workpiece can rotate in the same direction, for example both clockwise, or in opposite directions. The function of the central drive spindle can also be taken over by a finishing machine that moves circularly in such a way that the workpiece is clamped firmly while the rotational axis of the tool and the alignment contour of the guiding parts correspond.
[0018] The method according to the invention can be used, for example, to produce an internal thread in the nut of a screw drive. In the simplest case, the screw drive is a simple motion thread. Otherwise, the screw drive can in particular be configured as a roller screw drive. This means that threading is used to produce a track for the balls in a rotary element, in particular in a ball screw drive.
[0019] In the following, exemplary embodiments of the invention will be described in more detail with reference to the drawings.
Brief Description of the Drawings
[0020] [Figure 1] Shows details of the device for threading an internal thread. [Figure 2] Shows the components of the device according to FIG. 1 in the machining process, i.e., in the position before the start of threading.
Embodiments for Carrying Out the Invention
[0021] The manufacturing machine, designated as a whole by reference numeral 1, is configured as a machine tool with a central drive. This means that it can machine a tubular workpiece 2 from both sides. The manufacturing machine 1 is used as a device for threading an internal thread 3. With regard to the manufacturing technology of threading, generally refer to the prior art cited at the beginning.
[0022] The threading mandrel 4 of device 1 comprises a cutting head 5 and a shaft 6. The cutting head 5 is generally referred to as a machining tool. In this case, the cutting head 5 is integrally connected to the shaft 6. Alternatively, the machining tool 5 may be in the form of a cutting plate attached directly or indirectly to the shaft 6, for example. The central axis of the threading mandrel 4 including the cutting head 5 is denoted as MA4.
[0023] Furthermore, a rod-shaped guiding component 7 is assigned to the device 1, i.e., the manufacturing machine for female thread cutting. At the end of the guiding component 7, there is a cylindrical guiding part 8 having an increased diameter with respect to the rest of the guiding component 7. The diameter of the guiding part 8 approximately corresponds to the inner diameter of the workpiece 2. The shaft of the guiding component 7 is denoted as 9. When the guiding component 7 is inserted into the workpiece 2 as in the case of the structure according to FIG. 1, an annular gap is formed between the outer peripheral surface of the shaft 9 and the inner peripheral surface of the workpiece 2 denoted as 10. The workpiece 2 is supported by the guiding part 8 abutting against the inner peripheral surface 10. In this state, the central axis denoted as MA7 of the guiding component 7 coincides with the central axis of the workpiece 2.
[0024] The machining process carried out using the manufacturing machine 1 to produce the female thread 3 is characterized in that, particularly as can be seen from both FIGS. 1 and 2, the threading mandrel 4 and the guiding component 7 are inserted into the workpiece 2 from opposite sides. In the structure shown in FIG. 2, which shows the preparation step for threading, the threading mandrel 4 is located at the center of the workpiece 2. At this stage, a slightly eccentric arrangement of the threading mandrel 4 is also possible as long as the cutting head 5 does not contact the inner peripheral surface 10. The threading mandrel 4 is displaced from right to left with respect to the arrangement according to FIG. 2. The axial displacement of the threading mandrel 4 is generally denoted as AV4.
[0025] The threading mandrel 4 has a pin 11 that protrudes beyond the cutting head 5, and this pin 11 works in cooperation with a recess 12, which is configured as a blind bore on the end face of the guide portion 8, to form a means for aligning the threading mandrel 4 with respect to the guide component 7. The recess 12 is eccentrically located within the guide portion 8. In order for the pin 11 to be inserted into the recess 12, the radial offset that originally exists between the pin 11 and the recess 12 must be eliminated. This is done by the radial displacement of the threading mandrel 4, which is denoted as RV4.
[0026] The machining of the female thread 3 can be performed either from right to left or left to right, with respect to the arrangements shown in Figures 1 and 2. During the machining process, the axial displacement of the guide part 7, denoted as AV7, corresponds to the axial displacement AV4 of the threading mandrel 4. This means that the axial distance between the guide part 8 and the cutting head 5 does not change during threading. Similarly, the guide part 7, including the guide part 8, remains in a constant angular position during threading. During threading, the threading mandrel 4, including the cutting head 5, undergoes high-speed rotation RS. Simultaneously, the workpiece 2 undergoes relatively slow rotation RW, which is coordinated with the axial displacements AV4 and AV7. [Explanation of symbols]
[0027] 1 Manufacturing machinery 2 Workpiece 3 Female thread 4. Threaded Mandrel 5. Cutting heads, machining tools 6. Shaft of threaded mandrel 7. Induction components 8 Induction part 9. Shaft of induction component 10 Inner surface 11 pins 12 Recessed, blind bore Axial displacement of AV4 threading mandrel AV7 Axial displacement of induction component MA4 threading mandrel central axis MA7 Induction component central axis RS cutting head rotation Radial displacement of RV4 threaded mandrel RW (Rotation of the workpiece)
Claims
1. An apparatus for threading a female screw (3), comprising: a threading mandrel (4) on which a machining tool (5) intended for producing the female screw (3) is positioned; an elongated guide component (7) which supports the threading mandrel (4) and has a guide portion (8) formed at the end of the elongated guide component (7) which is provided as a portion having an increased diameter relative to the adjacent area of the guide component (7) for contacting the inner circumferential surface (10) of a workpiece; and the apparatus wherein the threading mandrel (4) is positioned eccentrically with respect to the guide portion (8), wherein the threading mandrel (4) is positioned on the opposite side of the guide component (7), and means (11, 12) for aligning the threading mandrel (4) with respect to the guide component (7) are formed on the end faces of the threading mandrel (4) and the guide portion (8).
2. The apparatus according to claim 1, characterized in that the machining tool (5) is configured in the form of a cutting head as an integral component of the threading mandrel (4).
3. The apparatus according to claim 1, characterized in that the machining tool (5) is in the form of at least one replaceable cutting plate attached to the threading mandrel (4).
4. The apparatus according to claim 1, characterized in that the machining tool (5) as a cutting head is detachably connected to the shaft (6) of the threading mandrel (4).
5. The apparatus according to any one of claims 1 to 4, characterized in that the means (11, 12) for aligning the threaded mandrel (4) with respect to the guide component (7) exists as a pin (11) of one of the two parts, the threaded mandrel (4) and the guide component (7), and the pin (11) engages with the end face bore (12) of the other component (7, 4).
6. The apparatus according to claim 5, characterized in that the pin (11) is located on the threaded mandrel (4).
7. The apparatus according to claim 5, characterized in that the pin (11) is formed by the induction component (7).
8. A method for threading a female screw (3), - To provide a tubular workpiece (2), that is, a workpiece having a through bore, - The workpiece (2) is clamped by the central drive spindle of the machine tool so that the through bore is accessible from both sides, - To provide a threaded mandrel (4) and an elongated guide component (7), wherein alignment contours (11, 12) are formed on the end faces of the threaded mandrel (4) and the guide component (7), and the alignment contours enable defined relative positioning of the longitudinal axes (MA4, MA7) of the threaded mandrel (4) and the guide component (7) during simultaneous relative rotation between the components (4, 7). - Feeding the threading mandrel (4) to the workpiece (2) from the first side of the through bore, and feeding the guide component (7) from the opposite side, wherein the workpiece (2), the threading mandrel (4), and the guide component (7) are initially concentric with respect to each other during feeding. - Moving the threaded mandrel (4) radially and joining the alignment contours (11, 12) of the threaded mandrel (4) to the guide component (7), wherein the guide portion (8) of the guide component (7) is guided within the through bore, that is, supported radially, and joined. - The process involves machining the female thread (3) by advancing the arrangement of the threading mandrel (4) and the guide component (7) through the through bore, wherein the guide component (7) does not rotate, the threading mandrel (4) rotates at a specified high speed, and the workpiece (2) rotates at a relatively low speed. A method that includes this.
9. The method according to claim 8, characterized in that the threading mandrel (4) and the workpiece (2) rotate in opposite directions.
10. The method according to claim 8 or 9, characterized in that the female thread (3) of the nut of the screw drive device is produced by the method according to claim 8 or 9.