Method of manufacturing barrel shaft
The method simplifies the manufacturing of watch barrel shafts by using a broaching tool for simultaneous processing, addressing the complexity and cost issues in traditional machining.
Patent Information
- Authority / Receiving Office
- RU · RU
- Patent Type
- Patents
- Current Assignee / Owner
- NIVAROX FAR SA
- Filing Date
- 2025-10-20
- Publication Date
- 2026-07-01
AI Technical Summary
Machining of watch barrel shafts is complex and expensive due to the need for precise machining around the hook and spring engagement, especially with challenging angles requiring multiple milling operations.
A method involving profile turning and simultaneous mechanical processing using a broaching tool to form a central part with a hook, support surface, and recess on a cylindrical section, utilizing reciprocating movements and a specialized tool to achieve the required geometry.
Reduces manufacturing steps and costs by enabling efficient production of a drum shaft with a hook and support surface, ensuring secure spring engagement and adequate clearance, using a single tool for multiple features.
Smart Images
Figure 00000001_ABST
Abstract
Description
[0001] Field of technology to which the invention relates
[0002] The present invention relates to a method for manufacturing a drum shaft used in watchmaking, which rotates around an axis of rotation, contains a hook for attaching an inner coil of a drum spring in one winding direction and, on a first part of its periphery, next to the hook and after the hook in the winding direction, contains a curved support surface for a spring to support the inner coil.
[0003] Technology Level
[0004] In a mechanical watch movement, the barrel is the power source that provides the necessary energy to move the various components. The barrel comprises a barrel housing, a lid covering the barrel housing, a barrel shaft around which the barrel housing and lid rotate freely, and a barrel spring housed within the barrel housing. The outer coil of the mainspring is supported by the wall of the barrel housing. The barrel shaft contains a part known as the central section, which contains a hook to which the inner coil of the barrel spring is attached. The barrel shaft is rotatably attached to a ratchet wheel, and this ratchet wheel can be rotated by the winding shaft (manual winding) or oscillating mass (automatic winding) of the watch movement to wind the mainspring and thereby store energy.
[0005] The watch barrel shaft is a small component subject to significant stress, requiring special care when handling it. The shaft's geometry makes machining quite expensive, particularly due to the presence of a hook, which requires machining around the entire perimeter to ensure secure engagement of the hook and spring, and to ensure adequate clearance for the spring's eye.
[0006] Machining drum shafts is typically accomplished through multiple milling operations. However, some angles are difficult to achieve with commonly used milling cutters, as they have very large radii.
[0007] The object of the present invention is to provide a simpler method for manufacturing a drum shaft that requires fewer manufacturing steps.
[0008] Disclosure of the essence of the invention
[0009] For this purpose, the present invention relates to a method for manufacturing a barrel shaft used in watchmaking, which is intended to rotate about an axis of rotation and which comprises a central part having a support surface for an inner coil of a spring, wherein a hook protrudes from this support surface for engaging with the eye of the inner coil, wherein in front of the hook in the direction of winding of the spring, the central part also has a recess for holding the end of the spring.
[0010] According to the invention, the method includes the following steps:
[0011] - ensuring the availability of the rod;
[0012] - profile turning of a rod to form at least one cylindrical section having a vertical surface and a horizontal surface;
[0013] - simultaneous mechanical processing of the said cylindrical section to form a central part that contains a hook, a supporting surface and a recess, using a broaching tool by performing several reciprocating movements in the direction of the axis of rotation of the shaft.
[0014] According to other preferred modifications of the invention:
[0015] - reciprocating movements are performed in steps of 0.2 mm;
[0016] - the spring support surface contains a sector with a snail-shaped section and a sector with a cylindrical section;
[0017] - the recess has a curved surface;
[0018] - the shaft material is selected from metals or metal alloys;
[0019] - the vertical hook forming surface and the curved supporting surface are subjected to simultaneous mechanical processing using the same broaching tool;
[0020] - The broaching tool is a forming tool with a shape for processing a workpiece identical to the required shape of the drum shaft.
[0021] The present invention also relates to a drum shaft obtained by the method according to the present invention.
[0022] Brief description of drawings
[0023] Other characteristics and advantages of the invention will become apparent from the detailed description below with reference to the accompanying drawings.
[0024] Fig. 1 shows a perspective view of the drum shaft according to the invention;
[0025] in Fig. 2 – the shaft from Fig. 1, sectional view along plane P;
[0026] in Fig. 3-5 – steps of the method for manufacturing the drum shaft;
[0027] Fig. 6a and 6b are schematic views of a cutting tool used for machining a drum shaft;
[0028] Fig. 7 is a schematic view of a tool for mechanical processing located on the drum shaft being mechanically processed.
[0029] Implementation of the invention
[0030] The present invention relates to the production of a drum shaft 1 used in watchmaking, which comprises a hook 2 for engaging with an inner coil of a drum spring in one winding direction S.
[0031] As shown in Fig. 1 and 2, the drum shaft 1 according to the invention comprises at least one journal 10 for rotating in the watch mechanism support around the axis D, a section 14 of square cross-section on which a ratchet wheel can be mounted, two cylindrical sections 11, 12 for rotating the drum body and the drum cover, respectively, and a central part 3. The central part 3 comprises a hook 2 for fastening the inner turn of the drum spiral spring (not shown in the figures), placed in the drum body. The winding direction is shown in Fig. 2 by arrow S.
[0032] More specifically, the central part 3 has a supporting surface 30 for the drum spring, on which the hook 2 is located. Said supporting surface 30 continues in the winding direction S of the drum spring from the first edge 31 to the second edge 32. In front of the hook 2, the central part 3 also has a recess 4 for receiving the inner end of the drum spring, which connects the first and second edges 31, 32.
[0033] Hook 2 is configured to engage with an eye or hole in the inner coil of the drum spring so that it can be surrounded by the wall of the eye along the entire perimeter. Hook 2 has two opposite end surfaces 20, 21. In the winding direction S, end surface 20 is located in front of end surface 21 and is at the same level with first edge 31. This end surface 20 acts as a support for the wall of the eye during spring winding. As can be seen in the figures, in the direction of its extension from the axis D of rotation, flat end surface 20 is inclined toward the front end in the winding direction S for better retention of the drum spring on hook 2.
[0034] Regarding notch 4, it has a curved surface profile. However, the notch could have had a different surface shape, such as a flat surface.
[0035] In the example shown in the figures, the supporting surface 30 has a first portion 33 extending from the first edge 31 with a radius that increases in the winding direction S, and a second portion 34 extending from the first portion 33 to the second edge 32 with a constant radius.
[0036] Thus, the support surface 30 has at least one sector with a snail-shaped cross-section, wherein from the hook 2 and in the direction S, the support surface 30 for the spring comprises a sector 33 with a snail-shaped cross-section and then a sector 34 with a cylindrical cross-section. To ensure the deployment of the inner coil of the drum spring, the support surface 30 for the spring accordingly has an increasing radius in the winding direction S.
[0037] It should be clear that the production of the recess 4, the hook 2 and the support surface 30 for the spring using one tool has an advantage in terms of both cost and production time.
[0038] Fig. 5 shows the simultaneous mechanical processing of the recess 4, the hook 2 and the supporting surface 30 for the spring using the same broaching tool, progressively moving along the axis A, coaxial with the axis D.
[0039] As can be seen from Fig. 6a and 6b, the broaching tool 100 is a forming tool with a shape for processing a workpiece identical to the required shape of the drum shaft.
[0040] Tool 100 comprises two parts 101, 102, assembled together to achieve a "radius-free" geometry at the intersection of the two tool parts. The first part 101 of the tool has a tooth shape designed for machining the recess 4 and the flat end surface of the hook 2.
[0041] The second part 102 of the tool has an opening 103 with a profile that has a first sector corresponding to the hook, and a second sector with a first section having a snail-shaped section, and a second section having a cylindrical section, which form a support surface 30 for the spring.
[0042] The method for manufacturing a drum shaft 1 according to the invention includes a first step consisting of providing a rod made of metal or metal alloy.
[0043] The next step, shown in Fig. 3, consists of profile turning the rod to form at least a section with a first diameter, having a vertical surface and a horizontal surface, in order to form at least a first journal 10 for rotation in a support. At this step, other rotation surfaces can also be formed, such as cylindrical sections 11, 12 for rotation of the lid or drum body.
[0044] Next, as can be seen in Fig. 4, the broaching tool is positioned with its front side facing the drum shaft so that the tool and the shaft have a common axis.
[0045] And finally, as shown in Fig. 5, the hook 2, the supporting surface 30 and the recess 4 are produced by drawing with the help of the drawing tool 100, which has a shape for processing the workpiece identical to the required shape of the central part 3 of the drum shaft, by performing several reciprocating movements of the tool along the axis A, which is coaxial with the axis D of rotation of the shaft 1.
[0046] Preferably, the reciprocating movements used for machining shaft 1 are performed in steps of 0.2 mm.
[0047] After machining the first side of shaft 1, it is turned over to perform identical machining on the other side of the shaft.
[0048] The invention also relates to a drum shaft obtained by the method according to the invention.
Claims
1. A method for manufacturing a shaft (1) of a drum used in watchmaking, which is intended to rotate about an axis (D) of rotation and which comprises a central part (3) having a support surface (30) for an inner coil of a spring, wherein a hook (2) projects from this support surface (30) for engaging with an eye of said inner coil, wherein in front of the hook (2) in the direction (S) of winding of the spring, the central part (3) also has a recess (4) for holding the end of the spring, characterized in that it includes the following steps: - ensuring the availability of the rod; - profile turning of a rod to form at least one cylindrical section (13) having a vertical surface and a horizontal surface; - simultaneous mechanical processing of the cylindrical section (13) to form a central part, which contains a hook (2), a supporting surface (30) and a recess (4), using a broaching tool by performing several reciprocating movements in the direction of the axis (D) of rotation of the shaft.
2. The method according to paragraph 1, characterized in that the reciprocating movements are performed in steps of 0.2 mm.
3. The method according to claim 1 or 2, characterized in that the support surface (30) for the spring contains a sector (33) with a snail-shaped section and a sector (34) with a cylindrical section.
4. The method according to any of paragraphs 1-3, characterized in that the recess (4) has a curved surface.
5. The method according to any of paragraphs 1-4, characterized in that the shaft material is selected from metals or metal alloys.
6. The method according to any one of paragraphs 1-5, characterized in that the vertical surface (20) for forming the hook (2) and the curved support surface (6) are subjected to mechanical processing simultaneously using the same broaching tool.
7. The method according to any one of paragraphs 1-6, characterized in that the broaching tool is a forming tool with a shape for processing a workpiece identical to the required shape of the drum shaft.
8. A drum shaft obtained by the method according to any of paragraphs. 1-7.