Device for producing a profiling, and method

Abstract

The invention provides a device (10) for producing a profiling on an inner wall of a projectile-guiding tube (12) by means of electrochemical machining, comprising a holder (20) which is intended for a projectile-guiding tube (12) and has, at two opposite ends, opposing centring elements (22) with a receptacle (24) for the tube (12) to be machined, and comprising a rifling cathode (18), which can be moved through the tube (12) to be machined, wherein at least one centring element (22) is axially adjoined by a guide body (28) which is intended for the cathode (18) and has a central clearance (30) concentric with the receptacle (24), wherein the rifling cathode (18) is driven in such a way that it can be moved into the guide body (28). The invention also provides a method for producing a profiling on an inner wall of a projectile-guiding tube (12) by means of electrochemical machining.

Description

[0001] Device for producing a profile and method

[0002] The invention relates to a device for producing a profile on an inner wall of a projectile-carrying tube by means of electrochemical ablation and a method for producing a profile on an inner wall of a projectile-carrying tube by means of electrochemical ablation.

[0003] To create a profile on the inner wall of a projectile-carrying tube, material is removed from the inner wall of the projectile-carrying tube by means of electrochemical ablation, such that grooves are formed in the bore.

[0004] A profile on the inner wall of a projectile-carrying tube serves to stabilize the projectile's trajectory. Such profiles are also referred to as "grooves." The grooves are typically helical, so that a projectile acquires a spin around its longitudinal axis as it moves through the tube.

[0005] In the known manufacturing process, a rifling cathode is moved through the tube and the tube itself acts as the anode.

[0006] At the entry and exit points of the rifling cathode into the projectile-carrying tube or a corresponding blank, the processing parameters change briefly, particularly the current, voltage, resistance, and / or electrolyte flow. This typically results in an undesirable widening of the internal profile at the tube's entry and exit points due to increased material removal. Therefore, after profiling, the tube ends are shortened by approximately 2 cm, thus removing the area where the unwanted increased material removal occurred.

[0007] A disadvantage of this is that shortening the tubes increases material and machining costs. Furthermore, the tube ends must be deburred after shortening. Therefore, an object of the present invention is to reduce the manufacturing costs of a projectile-carrying tube.

[0008] This problem is solved according to the invention by a device for producing a profile on an inner wall of a projectile-carrying tube by means of electrochemical ablation, with a holder for a projectile-carrying tube, which has centering elements opposite each other at two opposite ends with a receptacle for the tube to be machined, a rifling cathode which can be moved through the tube to be machined, wherein a guide body for the cathode is axially connected to at least one centering element, which has a central, concentric recess for receiving, wherein the rifling cathode is driven in such a way that it can be moved into the guide body.

[0009] The guide body acts as an auxiliary anode and forms a spatial extension of the tube for the cathode. This offers the advantage that no change in process parameters occurs when the rifling cathode exits the tube being processed, in particular no change in current, voltage, resistance, electrolyte flow, or centrality. This effect only occurs when the rifling cathode exits the guide body. Consequently, an expansion effect or undesirable rounding at the tube's inlet or outlet is avoided. In other words, the inner wall of the tube can be processed uniformly without any disruptive effects at the inlet or outlet. The process parameters of the tube being processed can be kept constant until the cathode has completely exited the tube.Subsequent trimming of the pipe is therefore unnecessary, which reduces material usage and eliminates the need for a subsequent deburring step.

[0010] The mounting of the centering elements corresponds in particular to the outer contour of the tube to be machined and thus serves to center the tube.

[0011] The contour of the recess in the guide body can be identical to or slightly larger than the inner contour of the pipe being processed, but only by such an amount that interference effects at the pipe's inlet and / or outlet are reliably avoided. For example, the contour of the recess corresponds to the inner contour of the pipe being processed, or, in other words, the contour of the recess is adapted to the outer diameter of the rifling cathode so that it is guided within the guide body. In this case, the fit for the rifling cathode is preferably the same as in the pipe being processed.

[0012] When a pipe to be processed is arranged in the device, the recess of the guide body is preferably arranged in alignment with the inner wall of the pipe.

[0013] By adapting the contour of the holder to the outer diameter of the rifling cathode, the guide body provides guidance for the rifling cathode, particularly when the inner contour of the pipe being processed is expanded during machining, and thus, as the rifling cathode exits the pipe, guidance is no longer provided by the inner wall of the pipe. This is the case, for example, when the profile to be produced is a polygonal profile.

[0014] However, depending on the type of profiling to be produced, the diameter of the receptacle can also be larger than the inner diameter of the tube, for example up to 4 mm, in particular up to 2 mm, preferably up to 1 mm. In this case, the rifling cathode is guided along the inner wall of the tube until it completely exits the tube. This is generally the case when grooves are created on the inner wall of the tube, so that the tube still has a defined inner diameter. The at least one guide body preferably rests against an axial contact surface of the centering element. This results in a defined axial position of the guide body, such that a tube arranged in the device rests directly against the guide body.

[0015] The centering element is, for example, ring-shaped, but other outer contours are also conceivable.

[0016] A seal may be present on the inner side of the centering element adjacent to at least one guide body to seal it against the pipe, and another seal may be present between the guide body and the contact surface of the centering element. The guide body is thus indirectly sealed against the pipe being processed via the centering element, reliably preventing the leakage of electrolyte solution between the pipe and the guide body. Such a leakage could also cause undesirable malfunctions.

[0017] The outer contour of at least one centering element corresponds, for example, to the outer contour of the guide body in the area adjacent to the contact surface for the guide body. This makes it possible to radially align the guide body on the centering element, thereby indirectly centering the recess of the guide body relative to the pipe being machined.

[0018] According to one embodiment, the device has a projecting pin for axial insertion into the projectile-carrying tube, which can be inserted into the tube by the guide body and an associated centering element. The pin acts as a centering aid to align the guide body with the tube such that the inner contour of the tube is flush with the recess of the guide body. Precise alignment of the guide body with the tube is crucial for preventing interference during the profiling process in the section adjacent to the tube's inlet and outlet. Centering on the tube's inner contour is also more accurate than centering via the guide body's outer contour.

[0019] Precise centering of the guide body is particularly necessary when, due to an expansion of the tube, the guide body assumes sole responsibility for guiding the rifling cathode as it exits the tube.

[0020] The pin is preferably axially displaceable such that it can be moved out of the centering element and at least partially out of the guide body. More precisely, the pin is axially displaceable so that unimpeded machining of the inner wall of the tube by the rifling cathode is possible.

[0021] For example, the pin is spring-loaded towards the tube and can be moved by the rifling cathode. Consequently, no mechanism for actively moving the pin is necessary, making the device particularly cost-effective. In other words, a separate drive for moving the pin can be dispensed with, as the drive for moving the rifling cathode is also used to move the pin.

[0022] The bracket can have a base with an opening at the front, into which one of the guide bodies and its adjacent centering element are inserted. The guide body and its adjacent centering element can be centered in the bracket via their outer contour.

[0023] The holder can simultaneously serve as a supply unit for an electrolyte solution.

[0024] The guide body and / or the centering element can be fastened in the holder by means of a press fit or by means of screws.

[0025] Preferably, a seal is provided between the base and the guide body, thereby preventing leakage of electrolyte solution at the interface between the base and the guide body.

[0026] According to one embodiment, the at least one guide body is made of an electrochemically inert material, in particular platinum or a platinum alloy, or the at least one guide body has a coating of an electrochemically inert material. This results in an extended service life of the guide body, since a guide body made of such a material is not, or only minimally, affected when the rifling cathode moves through the guide body.

[0027] If signs of wear appear after a longer period of inactivity due to frequent movement of the rifling cathode through the guide body, the guide body can be replaced.

[0028] The at least one guide body is preferably up to 5 mm longer than the rifling cathode. For example, the guide body has a length between 15 mm and 30 mm. Such a length is sufficient to reliably prevent interference effects from occurring at the inlet and / or outlet of the tube.

[0029] Preferably, an electrical connection is provided for contacting the projectile-carrying tube and / or an electrical connection for contacting the at least one guide body. In the case of direct contact with the projectile-carrying tube, the guide body constitutes a passive anode, which is electrically contacted via the tube. In the case of direct contact with the guide body, the guide body constitutes an active anode and the tube forms a passive anode. Consequently, only one electrical connection is necessary to electrically contact both the projectile-carrying tube and the guide body.

[0030] According to one embodiment, the at least one guide body is a sacrificial anode, in particular wherein a higher potential can be applied to the at least one guide body than to the projectile-guiding tube. The sacrificial anode provides protection against corrosion and thus contributes to making the removal process efficient and reproducible.

[0031] The problem is further solved according to the invention by a method for producing a profile on the inner wall of a projectile-carrying tube by means of electrochemical ablation, in particular in a device as described above. In a first process step, a tube is provided. A guide body is arranged at the inlet and / or outlet of the tube. This occurs, for example, automatically when the tube is inserted into the device. Subsequently, a rifling cathode is inserted into the tube, and a voltage is applied between the rifling cathode and the tube, with the tube acting as the anode when the voltage is applied. The rifling cathode is moved along the tube and simultaneously rotated, whereby material is electrochemically ablated along the inner wall of the tube such that the desired profile is formed.Immediately before entering the tube and / or immediately after exiting the tube, the rifling cathode is moved by the guide body.

[0032] As already described in connection with the device according to the invention, the method according to the invention achieves the advantage that no change in the process parameters occurs when the rifling cathode exits the pipe to be processed or enters the pipe, thus preventing undesirable rounding at the pipe ends.

[0033] The guide body can also act as an anode and can be connected to a power source directly or via the tube connected to a power source. Thus, the guide body forms a single unit with the tube during processing.

[0034] Further advantages and features of the invention will become apparent from the following description and from the accompanying drawings, to which reference is made. The drawings show:

[0035] Figure 1 shows a device according to the invention for machining a projectile-guiding tube,

[0036] Figure 2 shows the device from Figure 1 in an extended state,

[0037] Figure 3 shows a bracket for the device, and

[0038] Figure 4 shows a holder for the device according to an alternative embodiment.

[0039] Figures 1 and 2 show a device 10 for producing a profile on an inner wall of a projectile-carrying tube 12 (see Figure 2) by means of electrochemical ablation.

[0040] In the exemplary embodiment, the device 10 has several receiving positions 14 for tubes 12 (see also Figures 3 and 4), for example three receiving positions 14.

[0041] In order to accommodate pipes of 12 different lengths, the device 10 has a height-adjustable section 16. For example, the device 10 can accommodate pipes with a length of up to 1.6 meters and more.

[0042] To create a profile on the inner wall of a tube 12, an unprofiled tube is first provided and clamped into the device 10. The tube 12 is then filled with an electrolyte solution.

[0043] A Rifling cathode 18 (see Figure 2) is then inserted into the tube 12.

[0044] A voltage is applied between the Rifling cathode 18 and the tube 12, with the tube 12 acting as the anode.

[0045] While the voltage is applied, the rifling cathode 18 is moved along the tube 12 and simultaneously rotated. Specifically, the rifling cathode 18 is guided along the inner wall of the tube 12. During this process, electrochemical material removal occurs along the inner wall of the tube 12, creating the desired profile.

[0046] The recording positions 14 each have a holder 20, which is illustrated in Figure 3.

[0047] The holder 20 has opposing centering elements 22 at two opposite ends, each with a receptacle 24 for the tube 12 to be machined, in order to clamp the tube 12 at its opposite ends. Figure 3 shows only one side of the holder 20 for illustrative purposes. The opposite side can be designed in the same way.

[0048] An additional stabilizing element 26 (see Figures 1 and 2) is optionally provided in the middle between the centering elements 22 to further stabilize the tubes 12 during machining.

[0049] As can be seen in Figure 3, a guide body 28 for the Rifling cathode 18 is axially connected to the centering element 22. In the exemplary embodiment, the guide body 28 rests directly against an axial contact surface 29 of the centering element 22. However, it is also conceivable that there is a slight gap between the centering element 22 and the guide body 28, as will be explained below.

[0050] During the processing of the tube 12, the rifling cathode 18 is moved by the guide body 28 immediately before entering the tube 12 and immediately after exiting the tube 12. The outer contour of the at least one centering element 22 corresponds to the outer contour of the guide body 28 in the area adjacent to the contact surface 29 for the guide body 28.

[0051] The guide body 28 has a central recess 30 concentric with the receiving 24, the contour of which, in the illustrated embodiment, corresponds to the inner contour of the tube 12 to be machined. In other words, the guide body 28 represents, at least with regard to its inner contour, an extension of the tube 12.

[0052] However, it is also conceivable that the diameter of the recess 30 is somewhat larger than the inner contour of the tube 12 to be machined, for example by up to 4 mm.

[0053] The receptacle 24 of the centering element 22 has a larger diameter than the recess 30 of the guide body 28. As a result, one end face of the guide body 28 is partially exposed, with the exposed surface forming a contact surface for the tube 12.

[0054] If a tube 12 is received in the device 10, a guide body 28 is consequently arranged at the inlet and outlet of the tube 12.

[0055] The Rifling cathode 18 is driven in such a way that it can be moved into the guide body 28, especially from above.

[0056] The guide body 28 is, for example, made of an electrochemically inert material or coated with an electrochemically inert material.

[0057] The length of the guide body 28 is, for example, between 1.5 and 3 cm, in particular 2 cm. In particular, the guide body 28 is up to 5 mm longer than the Rifling cathode 18.

[0058] Both the centering element 22 and the guide body 28 are received in a base 32 of the holder 20. For this purpose, the base 32 has an opening 34 on its end face into which the guide body 28 and its adjacent centering element 22 are inserted.

[0059] The opening 34 is stepped in two stages, forming an axial stop for the guide body 28 and for the centering element 22. Simultaneously, the guide body 28 and the centering element 22 are radially aligned within the opening 34, so that the base 32 already provides centering for both the guide body 28 and the centering element 22.

[0060] In the embodiment shown in Figure 3, the guide body 28 and the centering element 22 are held in the base by means of an interference fit.

[0061] The opening 34 extends beyond the guide body 28 and thus forms a channel in the base 32. This channel serves to supply electrolyte solution into the tube 12.

[0062] Seals 36 and 37 are arranged on opposite end faces of the guide body 28. Specifically, a seal 36 is located between the guide body 28 and the base 32, and another seal 37 is located between the guide body 28 and the centering element to seal the parts against each other in a fluid-tight manner.

[0063] For this purpose, annular grooves 38 are formed on the end faces of the guide body 28, into which the seals 36, 37 are inserted.

[0064] Alternatively, the groove 38 for the seal between the centering element 22 and the guide body 28 can also be present on the centering element 22.

[0065] Another seal 40 is located on the inside of the centering element 22. This seal 40 serves to provide a fluid-tight seal against the pipe 12.

[0066] The guide body 28 is sealed against the tube 12 and the base 32 by the combined seals 36, 37, 40, thus reliably preventing any leakage of electrolyte solution from the device 10. In other words, the guide body forms a hydraulically tight seal against the tube 12.

[0067] The device 10 further optionally includes a projecting pin 42 for axial insertion into the projectile-guiding tube 12. Specifically, the pin 42 can be inserted into the tube 12 by the guide body 28 and an associated centering element 22, at the end opposite the insertion end of the cathode 18.

[0068] The pin 42 can be considered a movable bolt.

[0069] The pin 42 is spring-loaded, for example, in the direction of the tube 12. If no counterforce acts on the pin 42, it projects at least a short distance into the tube 12. This allows the tube 12 to be aligned with the pin 42 when inserted into the device 10. In this way, it is ensured that the inner contour of the tube 12 transitions flush into the recess 30.

[0070] The pin 42 is axially displaceable so that it can be displaced from the centering element 22 and at least partially from the guide body 28, so that the pin 42 does not obstruct the machining of the tube 12.

[0071] In the exemplary embodiment, the pin 42 can be displaced out of the tube 12 by the movement of the cathode 18. Theoretically, it would also be conceivable to provide a separate drive for the pin 42, although this would be rather disadvantageous for cost reasons.

[0072] The device has an electrical connection 44, wherein, in the embodiment shown in Figure 3, the electrical connection 44 is configured for contacting the tube 12. In this case, the guide body 28 represents a passive anode. In other words, the guide body 28 is connected to a power source via the tube.

[0073] Figure 4 shows one end of a holder 20 according to a further embodiment, which can alternatively be used in the device 10.

[0074] For identical structures with identical functions known from the above embodiment, the same reference numerals are used below, and reference is made to the preceding explanations to avoid repetition.

[0075] The embodiment of the holder 20 shown in Figure 4 differs from the embodiment shown in Figure 3 in that the guide body 28 and the centering element 22 are fastened in the base 32 by means of screws 46. The press fit is therefore eliminated. Furthermore, in the embodiment shown in Figure 4, the guide body 28 is not contacted by the electrical connection 44 to the tube 12. In this case, the guide body 28 acts as an active anode, i.e., it is directly connected to a power source.

[0076] For the sake of simplicity, the cone 42 is not illustrated in Figure 4, but it may also be present.

[0077] In another embodiment, which is not separately illustrated in the figures, the guide body 28 can serve as a protective anode. This means that a higher potential is applied to the guide body 28 than to the projectile-guiding tube.

[0078] In this case, an insulator is present between the tube 12 and the guide body 28, which also serves as a seal, so that the seal 37 can be omitted.

[0079] In this case, the insulator results in a slight gap between the tube 12 and the guide body 28, which, however, has no effect on the advantages of the device 10 described above.

[0080] For example, the insulator has a thickness of 0.5 mm to 2 mm, especially 1 mm.

[0081] The potential difference between the tube 12 and the guide body 28 results in particular from the distance between the tube 12 and the guide body 28, i.e. from the thickness of the insulator.

Claims

Patent claims 1. Device (10) for producing a profile on an inner wall of a projectile-carrying tube (12) by means of electrochemical ablation, comprising a holder (20) for a projectile-carrying tube (12) having at two opposite ends opposing centering elements (22) with a receptacle (24) for the tube (12) to be machined, a rifling cathode (18) which can be moved through the tube (12) to be machined, wherein a guide body (28) for the cathode (18) is axially connected to at least one centering element (22), which has a central recess (30) concentric to the receptacle (24), wherein the rifling cathode (18) is driven in such a way that it can be moved into the guide body (28).

2. Device (10) according to claim 1 , characterized in that the at least one guide body (28) rests against an axial contact surface (29) of the centering element (22).

3. Device (10) according to claim 2, characterized in that a seal (40) for sealing against the pipe (12) is provided on an inner side of the centering element (22) adjacent to the at least one guide body (28) and a further seal (37) is provided between the guide body (28) and the contact surface (29) of the centering element (22).

4. Device (10) according to claim 2 or 3, characterized in that the outer contour of the at least one centering element (22) corresponds to the outer contour of the guide body (28) in the area adjacent to the contact surface (29) for the guide body (28).

5. Device (10) according to one of the preceding claims, characterized in that the device (10) has a projecting pin (42) for axial insertion into the projectile-guiding tube (12), which can be inserted into the projectile-guiding tube (12) through the guide body (28) and an associated centering element (22).

6. Device (10) according to claim 5, characterized in that the pin (42) is axially displaceable such that it is displaceable from the centering element (22) and at least partially from the guide body (28).

7. Device (10) according to claim 6, characterized in that the pin (42) is spring-loaded in the direction of the tube (12) and is displaceable through the cathode (18).

8. Device (10) according to one of the preceding claims, characterized in that the holder (20) has a base (32) with an end-face opening (34) into which one of the guide bodies (28) and its adjacent centering element (22) are inserted.

9. Device (10) according to claim 8, characterized in that a seal (36) is provided between the base (32) and the guide body (28).

10. Device (10) according to one of the preceding claims, characterized in that the at least one guide body (28) is made of an electrochemically inert material, in particular platinum or a platinum alloy, or that the at least one guide body (28) has a coating of an electrochemically inert material.

11. Device (10) according to one of the preceding claims, characterized in that the at least one guide body (28) is up to 5 mm longer than the Rifling cathode (18).

12. Device (10) according to one of the preceding claims, characterized in that an electrical connection (44) for contacting the projectile-guiding tube (12) and / or an electrical connection (44) for contacting the at least one guide body (28) is provided.

13. Device (10) according to one of the preceding claims, characterized in that the at least one guide body (28) is a protective anode, in particular wherein a higher potential can be applied to the at least one guide body (28) than to the projectile-guiding tube (12).

14. Method for producing a profile on an inner wall of a projectile-carrying tube (12) by means of electrochemical ablation, in particular in a device (10) according to one of the preceding claims, comprising the following steps: Providing a pipe (12), - Arranging a guide body (28) at the inlet and / or outlet of the tube (12), Inserting a rifling cathode (18) into the tube (12) and applying a voltage between the rifling cathode (18) and the tube (12), which acts as the anode when the voltage is applied, and Moving the rifling cathode (18) along the tube (12) and simultaneously rotating the rifling cathode (18) and thereby electrochemically removing material along the inner wall of the tube (12) such that the desired profiling is formed, wherein the rifling cathode (18) is moved by the guide body (28) immediately before entering the tube (12) and / or immediately after exiting the tube (12).

15. Method according to claim 14, characterized in that the guide body (28) acts as an anode and is connected directly or via the tube (12) connected to a power source.

Images