Method for producing gun barrels and apparatus for performing such method

Abstract

A method and apparatus for producing gun barrels having a grooved or ribbed inner surface with straight or helical grooves or ribs, by providing a metallic hollow cylindrical pre-form, placing the pre-form on a core mandrel being part of a flow forming machine having a main machine axis, the core mandrel having a structured outer surface comprising ribs and/or grooves extending straightly parallel to and/or helically around the main axis; and applying forming rollers, in a roller arrangement, to the outside surface of the pre-form so as to apply radial pressure on the pre-form such that its material begins to flow. As the rollers apply force upon the pre-form, a relative motion between the pre-form and the rollers is performed by moving the pre-form in axially parallel to the main axis through the roller arrangement or by moving the roller arrangement alongside the pre-form.

Claims

1. A method for producing gun barrels having a grooved or ribbed inner surface (110) with straight or helical grooves or ribs, the method comprising the steps of: providing a metallic hollow cylindrical pre-form (10); placing the pre-form (10) on a core mandrel (8) being rotatably supported on a free end of a core mandrel extension rod (3) being rotatably supported in a head stock, wherein the core mandrel (8) is a part of a flow forming machine having a main machine axis (A) and a tail stock extension rod (11) being rotatably supported in a tail stock (12) and which is displaceable in a horizontal axial direction (X) parallel to the main machine axis (A) and extending coaxially with the core mandrel extension rod (3) and the core mandrel (8), wherein the core mandrel extension rod (3), the core mandrel (8), and the tailstock extension rod (11) form a unit that is movable in the axial direction (X), the core mandrel (8) being both not driven and freely rotatable about the main axis (A) and having an outer surface comprising ribs (83) or grooves, the ribs (83) or grooves extending parallel to or helically around the main axis (A); applying forming rollers (90) comprised in a roller arrangement (9), to an outside surface of the pre-form (10) so as to apply radial (P1) pressure on the pre-form (10) such that material of which the pre-form (10) is made begins to flow; and as the rollers (90) apply force upon the pre-form (10), performing a relative motion between the pre-form (10) and the rollers (90) by either moving the pre-form (10) in the axial direction (X) parallel to the main axis (A) through the roller arrangement (9) or by moving the roller arrangement (9) alongside the pre-form (10).

2. The method according to claim 1, wherein an axial position of the rollers (90) is fixed such the rollers (90) lie in a predetermined position above the core mandrel (8) between both axial ends of the core mandrel (8).

3. The method according to claim 1, wherein the core mandrel (8) has a tapered shape (82), and the rollers (90) and the core mandrel (8) perform a limited relative motion with respect to one another, the limited relative motion being limited to a relative axial motion of the rollers (90) between both axial ends of the core mandrel (8).

4. The method according to claim 1, wherein the flow forming machine comprises: the head stock (5); the tail stock (12), which is in a position opposing the head stock (5); the core mandrel extension rod (3), which is rotatably supported in the head stock (5); a driving means (1) for driving the core mandrel extension rod (3) in the axial direction (X) along the main machine axis (A); the core mandrel (8), which is freely rotatable with respect to the core mandrel extension rod (3) about the main machine axis (A); and the forming rollers (90), which are provided between the head stock (5) and the tail stock (12), the rollers (90) being radially displaceable toward the core mandrel in order to apply the radial (P1) pressure onto the pre-form (10) placed on the core mandrel (8), wherein the tail stock (12) and the tail stock extension rod (11) extend along the main machine axis (A) and the tail stock extension rod (11) is rotatably supported by the tail stock (12) so as to rotate about the main machine axis (A).

5. The method according to claim 4, wherein the core mandrel extension rod (3) and the rollers (90) are displaceable with respect to each other in the axial direction (X) parallel to the main machine axis (A).

6. The method according to claim 5, wherein the core mandrel (8) is cylindrical with the ribs (83) or grooves formed on or in the outer surface.

7. The method according to claim 5, wherein the core mandrel (8) is conical with the ribs (83) or grooves formed on or in the outer surface and tapering in a direction of the tail stock (12).

8. The method according to claim 4, wherein at least one of the core mandrel extension rod (3) and the rollers (90) is displaceable with respect to the head stock (5) in the axial direction (X) parallel to the main machine axis (A).

9. The method according to claim 8, wherein the core mandrel (8) is cylindrical with the ribs (83) or grooves formed on or in its the outer surface.

10. The method according to claim 8, wherein the core mandrel (8) is conical with the ribs (83) or grooves formed on or in the outer surface and tapering in a direction of the tail stock (12).

11. The method according to claim 1, whereby a gun barrel having a grooved or ribbed inner surface (110) with straight or helical grooves (111) or ribs is produced.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is described hereinafter with reference to the attached drawings depicted in FIGS. 1 through 8c:

(2) FIG. 1 shows a side and sectional view of the apparatus according to the invention in a loading position;

(3) FIG. 2 shows a side and sectional view of the apparatus according to the invention with the pre-form having been set onto the mandrel prior to applying the forming rollers;

(4) FIG. 3 shows a similar view of the apparatus according to the invention at the beginning of applying the forming rollers to the pre-form;

(5) FIG. 4 shows a similar view of the apparatus according to the invention during applying the forming rollers to the pre-form;

(6) FIG. 5 shows a similar view of the apparatus according to the invention at the end of applying the forming rollers to the pre-form;

(7) FIG. 6 shows a similar view of the apparatus according to the invention unloading the finished workpiece;

(8) FIG. 7a shows a perspective sectional view of a first workpiece manufactured by the inventive method;

(9) FIG. 7b shows a perspective sectional view of a second workpiece manufactured by the inventive method;

(10) FIG. 7c shows a perspective sectional view of a third workpiece manufactured by the inventive method;

(11) FIG. 7d shows a perspective sectional view of a fourth workpiece manufactured by the inventive method;

(12) FIG. 8a shows a close up view of the apparatus according to the invention in the vicinity of the core mandrel with a first embodiment of the core mandrel;

(13) FIG. 8b shows a view similar to FIG. 8a with a second embodiment of the core mandrel; and

(14) FIG. 8c shows a view similar to FIG. 8a or 8b with a third embodiment of the core mandrel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(15) FIGS. 1 through 6 show a basic configuration of a flow forming machine which is an apparatus of the present invention. The axis A is the main machine axis.

(16) Drive 1 is designed to drives the core mandrel unit in axial direction X (positive and negative axial direction). The drive 1 may have position and/or force control capabilities. The movement of the drive 1 is independent from the axial movement of headstock 5. In some applications, the drive may be located onto the moveable parts of the headstock 5. In this case, the core mandrel 8 moves in accordance to the motion of headstock 5 to achieve the requested part geometries.

(17) The drive can be isolated from the rotational movements of core mandrel extension rod 3 via a bearing 2. In some cases, the core mandrel axial drive 1 may rotate together or in accordance with the core mandrel extension rod 3. Preferably, the core mandrel extension rod 3 is a solid bar or hollow shaft which is located between the core mandrel 8 and the axial drive 1. The main function of core mandrel extension rod 3 is to keep and/or move the core mandrel 8 in the correct and pre-determined position during or prior to or after the forming process. Such action requires programming which can be made mechanically, e.g. via relay system, PLC or CNC or any other control device. According the requirements of the process, the extension rod 3 may either be guided in axial direction X and/or radial direction Y by the headstock 5using a bearing 4or alternatively by the tailstock 12. Depending on the requirements of the process, the extension rod 3 can be actuated in rotational direction via headstock 5, tailstock 12 and/or any other drive units.

(18) The headstock 5, that comprises a spindle unit, is movable in axial direction X and drives the pre-form 10 through the forming rollers 90 comprised in the roller unit 9, over the core mandrel 8 during the forming process.

(19) The pre-form 10 is driven in rotational direction about axis A via drive ring 6 and/or tapered part and/or any transmission device which is connected to headstock's 5 spindle. The headstock spindle 5 is actuated by common or separate actuation devices (e.g. electrical motor, hydro motor, etc.). Depending on the process requirements, the headstock 5 can be used to pull the pre-form parts 10 through the roller unit 9 (instead of pushing) to form the part in the aforementioned way. The headstock 5 and tailstock 12 units can interchange their functions.

(20) As shown in FIG. 8, the core mandrel 8 can be a mandrel which is tapered or conical in shape (FIG. 8c), it can have single diameter (FIG. 8a) or multi diameters (FIG. 8b) on single and/or multi-part forming mandrel.

(21) The core mandrel 8 forms the free end of the core mandrel extension rod and is freely rotatable via a bearing 7 and/or a guiding device and it will follow the axial position, i.e. the axial movement, of the core mandrel axial drive 1 system. Core mandrel 8 is not actively (e.g. by a controlled rotational drive) actuated in the rotational direction which means that the formed section of the material 10 flows under the radial pressure of the applied rollers 90 and the flow of material accordingly turns the mandrel in rotational direction. The core mandrel 8 is guided on the extension rod 3 via bearing 7 and/or another guiding system. The core mandrel 8 can be centered by using a centering device located on the machine frame, using a lunette, or involving the tailstock 12 and/or headstock 5 as a centering device. The core mandrel 8 may be non-cooled or internally and/or externally cooled using any cooling media.

(22) As stated above, some of the possible geometries of the core mandrel 8 are illustrated in FIG. 8 (FIG. 8a-single diameter flat mandrel, FIG. 8b-multi diameter flat mandrel with a step 81 forming a transition region between two diameters, FIG. 8c-conical mandrel with a conical surface 82). The mandrels 8 preferably have a profiled contour with ribs or/and grooves 83 in the mandrel's 8 outer surface extending parallel to or at angle with the main machine axis A. but the mandrel geometries regarding this method is not limited to these geometries. Reference numeral 80 depicts the free end of the core mandrel 8.

(23) The method according to the invention employs a roller unit 9 with one or more forming rollers 9 to form the barrel. The forming rollers 90 are actuated by axial and/or radial direction using a not shown machine control system. Each roller 90 can be actuated separately or all rollers 90 can be synchronized to move together using the control system. The forming rollers 90 can be free in rotational direction or be actuated by any drive system. The forming rollers 90 can vary in shape and dimensions and/or they can have an offset in axial direction X and/or radial direction Y. The forming position (axial and/or radial) of the rollers 90 can be changed during the forming process via the control system. Each forming roller 90 may have an angle referenced to machine central axis A. This angle can be adjusted automatically via the control system and/or manually. The roller 90 can be used for a stripping function and/or separate stripping devices can be employed.

(24) The tailstock spindle unit 12 is movable in axial direction X and the main function of the tailstock 12 is to guide the pre-form 10 in axial direction X and/or radial direction and/or pull or push the pre-form to assist the process flow. The tailstock spindle 12 can be freely rotatable in rotational direction (about axis A) or can be actuated via separate actuation devices (electrical motor, hydro motor, etc.). The tailstock 12 and headstock 5 may interchange their functions.

(25) The inventive method works as follows: a cylindrical, hollow metallic pre-form 10 is placed over the mandrel 8 and the extension rod 3 to abut against the drive ring 6, FIG. 3. In this situation, the machine is loaded and the tail stock extension rod 11 is moved by the tailstock 12 in axial direction X to abut against the free end of the core mandrel. Now core mandrel extension rod 3, core mandrel 8, and tailstock extension rod 11 form a unit that may be moved as a unit in axial direction. As such, this unit is moved relatively to the rollers 90 in axial direction such that a predetermined axial starting position is reached in which the rollers 90 lie radially above the free end of the pre-form 10 and are axially located at the position of the core mandrel 8. The free end of the pre-form 10 refers to the end of the pre-form 10 not abutting the drive ring 6. The rollers 90 are now moved radially inward (P1) to apply pressure onto the pre-form, FIG. 3.

(26) As the rollers 90 apply pressure they are turned as indicated by the arrows in FIGS. 3 and 4. At the same time, the pre-form 10 is driven radially by the headstock 5 by means of the drive ring 6 and set into relative motion with respect to the rollers in axial direction by means of the axial drive 1. As the rollers 90 apply pressure, the material of the pre-form 10 starts flowing which results in a reduced outer diameter of the part of the pre-form 8 that has passed through the roller unit 90, shown in FIGS. 4 and 5. At the same time, the inner surface of the pre-form is shaped as well, as material flowing into the space between the core mandrel 8 and the pre-form 10. Depending on the particular structure of ribs and/or grooves on the outside surface of the core mandrel 8, the inner surface of the pre-form adapts a negative shape of this structure. This is indicated by the helical profile of the pre-form 10 in FIGS. 5 and 6 and in the examples shown in FIGS. 7a-7d. FIGS. 7a-7d also illustrate finished workpieces (10), namely gun barrels having a grooved or ribbed inner surface (110) with straight or helical grooves (111) or ribs. After the forming process is completed, the rollers 90 are moved radially outward (P2) and the tailstock 12 disengages its extension rod 11 from the free end of the core mandrel. After this, the finished workpiece 10, 10 can be unloaded from the machine