JPH0323285B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a hemispherical shell having protrusions on its surface into a true sphere, and is particularly suitable for application to large spherical pressure-resistant shells.

In deep-sea submersibles used to investigate the ocean floor, the crew is mounted inside a spherical pressure-resistant shell that serves as a control room. Holes must be formed for cables, etc. to pass through. Generally, a pressure shell is finished by welding together a pair of hemispherical shells that have been machined into true spheres, but before that, a flange for attaching a hatch, a sash for a viewing window, a cable through hole, etc. are machined on the hemispherical shell. It is preferable to keep it in place from the viewpoint of workability and prevention of adverse thermal effects on the pressure shell due to welding. In this case, in order to maintain the strength of the pressure shell, the flanges, sashes, or the area around the cable penetration hole must be made thicker than other parts, so these hatches, observation windows, or A large-diameter hole is drilled to form a cable through hole, and an annular thick-walled metal piece that becomes a flange or sash, or a thick-walled metal piece with a cable through-hole formed therein, is fitted into the hole and welded.

By the way, when machining the inner circumferential surface of such a hemispherical shell into a true sphere, if a part of the above-mentioned thick-walled hardware protrudes from the inner circumferential surface of the hemispherical shell, the existing three-dimensional cutting method will not process it as a hemispherical shell. A part of the joint with the thick-walled hardware becomes a blind spot for the cutting tool, making it impossible to cut this part. As shown in FIG. 4a, the hemispherical shell material 1 is held in a horizontal state, rotated around a vertical axis, and the inner peripheral surface is cut by the cutting tool 3.
This is because the protruding part of the thick-walled hardware 6 interferes with the cutting tool in the conventional method of turning using the method 2. Therefore, in the conventional method, the inner peripheral surface of the hemispherical shell is cut before the thick-walled hardware is fitted into the hemispherical shell and welded. After processing a true sphere, a large-diameter hole was drilled in the hemispherical shell, and thick-walled metal fittings were inserted and welded.

As a result, welding strain remains in the finished hemispherical shell, and in order to ensure a predetermined withstand pressure, it is necessary to increase the wall thickness of the pressure shell in anticipation of a decrease in strength due to welding strain. When driving a deep-sea research vessel in the deep sea, it is important to balance the weight and buoyancy of the deep-sea research vessel to minimize driving energy, but with current technology, it is important to balance the weight and buoyancy of the vessel to minimize drive energy. Deep-sea research vessels are much heavier and need to carry a large amount of buoyancy material.
It was impossible to avoid increasing the size and cost of ships.

The purpose of the present invention is to provide a processing method that eliminates the problems that occur when processing conventional pressure-resistant shells, finishes the inner circumferential surface of a hemispherical shell to a true spherical surface, and minimizes the wall thickness. Therefore, it was intended to reduce the weight of the pressure hull, which in turn would reduce the size and cost of the ship.

The structure of the method for processing the inner circumferential surface of a hemispherical shell of the present invention that achieves this objective is such that a hemispherical shell having a protrusion formed on a part of the inner circumferential surface is arranged such that the central axis of the hemispherical shell is aligned with the center of rotation of the cutter. The cutter is supported so as to be inclined at a certain angle with respect to the hemispherical shell, and the cutter is moved back and forth between the center and the edge of the hemispherical shell along the shape of the inner peripheral surface of the hemispherical shell, and the cutter is moved forward or backward. The hemispherical shell is rotated by a predetermined angle around its central axis each time the hemispherical shell is rotated.

In the method for processing the inner peripheral surface of a hemispherical shell, the cutter reciprocates between the center and the edge of the inner peripheral surface of the hemispherical shell, and the hemispherical shell is rotated by minute angles around its central axis. , the inner peripheral surface of the hemispherical shell is machined radially little by little. Even if there is a protrusion on the inner circumferential surface, the cutter moves to follow the shape of the protrusion, for example, in the vertical direction, and processing continues.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method of processing an inner circumferential surface of a hemispherical shell according to the present invention will be explained in detail based on an embodiment shown in the drawings.

Figs. 1 a to d show the machining steps according to an embodiment of the method of the present invention, Figs. 2 a and b show the state of spherical surface cutting, and Fig. 3 shows the spherical surface machining process according to the present invention. The principle is shown. As shown in FIG. 1a, a large diameter hole 2 as shown in FIG. 1b is bored in a predetermined position of a hemispherical shell material 1 formed into a hemispherical shape.
As shown in FIG. c, a thick-walled metal fitting 4 having a cable through-hole 3 formed therein and a thick-walled metal fitting 6 for a viewing window 5 are respectively fitted and welded. In this embodiment, the thick-walled metal fittings 4 for the cable through-hole 3 and the thick-walled metal fittings 6 for the viewing window 5 are fitted into the large-diameter hole 2 of the hemispherical shell material 1 and welded, but depending on the case, either Only one side may be fitted and welded, or thick metal parts for hatches may be fitted and welded.

Figures 2a and 2b show the equipment used for machining spherical surfaces. This device consists of an inclined rotary indexing table 7 that supports a hemispherical shell material 1 and a large NC horizontal boring machine 8. The tilting rotation indexing table 7 includes a fixed table 11 that can be tilted by a pin joint 9 and a rack 10, a rotary table 13 that is provided on the fixed table 11 and can be rotated in small increments by a gear motor 12, and a rotary table 13 that is arranged on the rotary table 13. It consists of tightening jigs 14 and 15 equipped with. or,
The large NC horizontal boring machine 8 is composed of a column 16, a spindle head 17 that can move up and down along the column 16, etc., like a normal boring machine, but here an angular attachment 18 is attached to the spindle head 17. After installing it, I changed the direction of the cutter attachment part to face down. 19 is a cutter attached to the lower end of the cutter attachment part,
Here, we use a ball end mill that processes the surface of the workpiece in a peeling manner. Katsuta 19
can freely move two-dimensionally in the vertical direction (Z-axis direction) by the spindle head 17 and in the longitudinal direction (X-axis direction) by the attachment 18.
It is controlled by a computer 20. The NC computer 20 is loaded with a program corresponding to the shape of the spherical surface and protrusions (thick-walled metal parts 4 and 6) that make up the shape of the inner peripheral surface. Further, the movement of the tilting rotary indexing table 7 is also controlled by the computer 20.

The hemispherical shell material 1 in the state shown in FIG. Tightening jig 1
4 and 15. During this fixing work, the rotary table 13 is kept horizontal to facilitate the work.

After this, the rotary table 13 is fixed to the fixed table 11.
and tilt it at 45 degrees to the horizontal. In other words, the hemispherical shell material 1 is supported at an angle of 45 degrees with respect to the rotation center 31 of the ball end mill 19, which is a cutter.

In this state, the ball end mill 19 of the NC horizontal boring machine 8 is used to cut the inner circumferential surface. It is moved along the inner circumferential surface from the edge A of the circumferential surface to the center B, and its locus is cut.

When the ball end mill 17 moves to B,
The gear motor 1 is controlled by the action of the NC computer 20.
2 is operated, and the hemispherical shell material 1 is rotated by 0.2 to 0.3 degrees together with the rotary table 13.

After this, the ball end mill 19 is moved from the center B of the hemisphere to the edge A, and from the previously machined part.
Linearly cut the part that is offset by 0.2~0.3°.

When the ball end mill 19 reaches the edge A, the hemispherical shell material 1 is rotated by 0.2 to 0.3 degrees by the rotary table 13.

By repeating the above procedure many times (for example, 1200 to 1800 times) until the hemispherical shell material 1 has made one revolution, the entire inner peripheral surface of the hemispherical shell material 1 is processed.

In this way, the ball end mill 19 is reciprocated two-dimensionally in the radial direction of the inner peripheral surface of the hemispherical shell material 1, and the center axis ( The hemispherical inner surface can be carved into a predetermined three-dimensional shape by rotating it around the axis of symmetry. FIG. 1d shows the cross-sectional shape of the hemispherical shell after machining.

In addition, in the portion where the thick metal parts 4 and 6 protrude, the ball end mill 19 is controlled to move according to the shape thereof. Also, when using the ball end mill 19 as a cutter, the cutting depth of the ball end mill 19 is approximately 0.2 to 2 mm, so
The finished product is made by repeating cutting several times over the entire circumference. Furthermore, since the increment rotation feed angle of the hemispherical shell material 1 is determined by the cutting width by the cutter,
The range is about 0.1 to 1° depending on the size of the katsuta.

The angle at which the hemispherical shell material 1 is tilted is most preferably 45° with respect to the horizontal, but any angle around that is acceptable to some extent. The point is that there should be no blind spots in the katsuta. For example, if the hemispherical shell material 1 is set at an angle of 45 degrees, the cutting length l (X-axis drive length)
should be 1/√2 of the inner diameter D of the hemispherical shell material 1, and the driving length h of the ball end mill 19 in the height direction (Z-axis direction) should be 1/2 (2-√2) of the radius R. Therefore, the angular attachment 18 can be shortened as a whole, the rigidity required for machining can be obtained, and the necessary dimensional accuracy can be sufficiently ensured. Furthermore, even if the hemispherical shell material 1 is set horizontally and processed using the ball end mill 19 as in the conventional method, as shown in Figure 4a, there will be a portion where the angle with the surface to be cut is 0°. 21 and blind areas 22 around the protrusions that cannot be cut, but if the ball end mill 17 is tilted at 45 degrees, the contact angle between the ball end mill 17 and the surface to be cut will change as shown in Figure 4b. The minimum angle is 45° (points A and B in Figure 3), and there are no blind spots in cutting. As described above with reference to the embodiments, according to the method for processing the inner circumferential surface of a hemispherical shell according to the present invention, a thick-walled metal object is welded to the hemispherical shell in advance, and then the inner circumferential surface of the hemispherical shell is cut. In other words, it is possible to cut the inner peripheral surface of a hemispherical shell that has protrusions, and it is possible to finish the inner peripheral surface of the hemispherical shell into a perfect sphere that corresponds to the processing accuracy of the machine tool without being affected by welding distortion. becomes possible. As a result, the wall thickness of the hemispherical shell can be minimized, making it possible to reduce the weight of the pressure-resistant shell and, in turn, to reduce the size and cost of the deep-sea research vessel.

[Brief explanation of the drawing]

Figures 1a, b, c, and d are process explanatory diagrams showing the pretreatment process and cutting process in the method for processing the inner circumferential surface of a hemispherical shell of the present invention, and Figures 2a and b illustrate the implementation state of the method of the present invention together with the equipment. FIG. 3 is an explanatory diagram showing the processing principle of the method of the present invention, and FIGS. 4a and b show the relationship between the cutter and hemispherical shell material in the conventional method and the method of the present invention. FIG. 3 is a cross-sectional view showing the relationship. In the drawing, 1 is hemispherical shell material, 4 and 6 are thick metal parts,
7 is a tilting rotary indexing table, 8 is a large NC horizontal boring machine, 12 is a gear motor, 13 is a rotary table, 1
8 is an anguilla attachment, and 19 is a ball end mill.

Claims (1)

[Claims] 1. A hemispherical shell in which a protrusion is formed on a part of the inner peripheral surface is supported such that the central axis of the hemispherical shell is inclined at a certain angle with respect to the rotation center of the cutter, and the cutter is attached to the inner circumference of the hemispherical shell. The hemispherical shell is reciprocated between the center and edge of the hemispherical shell along the shape of the surface, and the hemispherical shell is rotated by a predetermined angle around its central axis each time the cutter moves forward or backward. A method for processing the inner peripheral surface of a hemispherical shell.