Background Art In the related art, to form a plurality of grooves 5 on a pipe material 1 that constitutes, for example, a support leg of an adjustable headrest attached to a vehicle seatback as shown in FIG. 9, a forming block 50 may be compressed onto the outer circumferential surface of the pipe material in a direction perpendicular to an axis of the pipe material as shown in FIG. 10.

Alternatively, the grooves may be formed through a preliminary forming process in which a rotary forming block is moved downward in a direction perpendicular to the outer circumferential surface of a pipe material, prior to executing a main forming process that is a pressing process to finish the forming of the grooves (referred to the following cited patent document 1).

[Cited patent document 1]

Japanese Patent Laid-open Publication No. 2002-215019 However, the former of the above-mentioned conventional methods is problematic in that, in the case of forming grooves on a pipe material having a thin sidewall, the pipe material may be easily broken due to the compression force of the forming block.

In the meantime, the latter (the cited patent document 1) is problematic in that it requires an execution of two processes, which are the preliminary forming process and the main forming process, thus reducing the productivity of products.

Disclosure of the Invention Accordingly, an object of the present invention is to provide a method of forming grooves on a pipe material which forms desired grooves on a pipe material having a thin sidewall, without breaking the pipe material, and which improves productivity of products.

In order to accomplish the above object, a method of forming a groove on a pipe material as claimed in the accompanying claim 1 is characterized in that the method comprises: inserting a core, which is provided on an outer circumferential surface thereof with one or more depressions functioning as female forming blocks for the groove, into a hollow space of the pipe material to support the core

therein; and moving one or more rotatably installed rotary male forming blocks relative to the pipe material in a vertical direction, so that rotating outer circumferential surfaces of the male forming blocks are in contact with a part of an outer circumferential surface of the pipe material, which is spaced apart from an axis of the pipe material, in a direction perpendicular to another direction opposite to the depressions of the core and compress the part of the outer circumferential surface of the pipe material into the depressions to form the groove.

Furthermore, the method of forming the groove on the pipe material as claimed in the accompanying claim 2 is characterized in that a cutout part is provided along the outer circumferential surface of the core to define a space of which a height is higher than a height of the groove, so that the core after the forming of the groove is rotated to place the cutout part around the groove and, thereafter, is removed from the pipe material.

Furthermore, the method of forming the groove on the pipe material as claimed in the accompanying claim 3 is characterized in that a cutout part is provided along the outer circumferential surface of the core to define a space of which a height is higher than a height of the groove, so that the pipe material after the forming of the groove is rotated relative to the core to place the cutout part of the core around the groove and, thereafter, the core is

removed from the pipe material.

Furthermore, the method of forming the groove on the pipe material as claimed in the accompanying claim 4 is characterized in that the rotary male forming blocks include a short cylindrical male forming block or a conical male forming block.

Furthermore, the method of forming the groove on the pipe material as claimed in the accompanying claim 5 is characterized in that a longitudinal plate-shaped male forming block, which is not rotated and has a part with a cross-section similar to that of the depressions of the core, is used in place of the rotary male forming blocks, such that the plate-shaped male forming block is in contact with the part of the outer circumferential surface of the pipe material, which is spaced apart from the axis of the pipe material, in the direction perpendicular to the direction opposite to the depressions of the core and compress the part of the outer circumferential surface of the pipe material into the depressions to form the groove.

Furthermore, the method of forming the groove on the pipe material as claimed in the accompanying claim 6 is characterized in that the plate-shaped male forming block is provided with a straight inclined surface or a rounded inclined surface on a part of an end thereof at which the male forming block comes into contact with the pipe material.

Brief Description of the Drawings FIG. 1 is a front view showing a method of forming grooves on a pipe material according to a first embodiment of the present invention ; FIG. 2 is a side view showing important parts used in the method of forming the grooves on the pipe material of FIG. 1; FIG. 3 shows a core used in the method of forming the grooves on the pipe material of FIG. 1, in which: (a) is a front view, and (b) is a side view; FIG. 4 is a front view showing a method of forming grooves on a pipe material according to a second embodiment of the present invention ; FIG. 5 shows a plate-shaped male forming block used in the method of forming the grooves on the pipe material of FIG. 4, in which : (a) is a front view, and (b) is a side view; FIG. 6 shows plate-shaped male forming blocks according to further embodiments of the present invention, in which : (a) is a front view of a plate-shaped male forming block with a straight inclined surface, and (b) is a front view of a plate-shaped male forming block with a rounded inclined surface; FIG. 7 is a front sectional view showing a groove formed on a pipe material;

FIG. 8 shows a plate-shaped male forming block according to a still another embodiment of the present invention, in which: (a) is a front view, and (b) is a sectional view taken along the line A-A of (a); FIG. 9 is a perspective view of a conventional adjustable headrest for vehicle seatbacks; and FIG. 10 is a front sectional view showing a conventional method of forming grooves on a pipe material.

<Description of the important elements in the drawings> 1: pipe material la, 3: outer surface 2: hollow space 4: cutout part 5: groove 6: partially thickened part 10: core 11: depression 12: flange 20: rotary male forming block 21: cylindrical male forming block 22 : conical male forming block 23: plate-shaped male forming block 30a: inclined surface 40: fixing jig 41: upper mold 42: lower mold 43,45 : spiral spring 44: compression-forming block 50: forming block Best Mode for Carrying Out the Invention

The preferred embodiments of the present invention will be described in detail herein below in conjunction with the accompanying drawings. A method of forming grooves on a pipe material according to a first embodiment of the present invention will be described herein below with reference to FIGS. 1 to 3. FIG. 1 is a front view showing the method of forming the grooves on the pipe material.

FIG. 2 is a side view showing an important section of the method. FIG. 3 shows a core used in the method, in which: (a) is a front view, and (b) is a side view.

The groove forming method according to the embodiment of the present invention forms a plurality of grooves 5 on a pipe material 1, which constitutes a support leg of an adjustable headrest attached to a vehicle seatback, along the length of the pipe material 1.

In the above-mentioned groove forming method, the pipe material 1 is first placed on a lower mold 42 of a fixing jig 40 that comprises an upper mold 41, the lower mold 42 and a spiral spring 43. Thereafter, a core 10, which is provided on an outer circumferential surface 3 thereof with a plurality of depressions 11 functioning as female forming blocks for forming the grooves 5 on the pipe material, is inserted into a hollow space 2 of the pipe material 1 to be fixed therein. The above-mentioned fixing process is accomplished by assembling a flange 12, which is provided on an end of the core 10, with a fixing unit (not

shown).

Thereafter, a compression-forming block 44, which is installed just above the fixing jig 40 with the spiral spring 45 interposed between them, is moved downward. In the above state, a plurality of rotary male forming blocks 20 which are rotatably mounted to the compression-forming block 44 are moved downward in a vertical direction. At the same time, the upper mold 41 of the fixing jig 40 is moved downward to support the pipe material 1 in cooperation with the lower mold 42. Thus, the rotary male forming blocks 20 rotate around their axes and move vertically while the outer circumferential surfaces of the male forming blocks 20 are in sliding contact with a part la of the outer circumferential surface of the pipe material 1. Therefore, the male forming blocks 20 forcibly compress the part la of the outer circumferential surface of the pipe material 1 into the depressions 11 of the core, respectively, thus forming the plurality of grooves 5.

In a detailed description, the outer circumferential surfaces of the male forming blocks 20 rotate and slide while being in contact with the part la of the outer circumferential surface of the pipe material 1, which is spaced apart from the axis of the pipe material 1 (in FIG.

1, the part la is spaced apart from the axis of the pipe material 1 to the right), in a direction (in FIG. 1, a vertical direction between upper and lower sections)

perpendicular to another direction (in FIG. 1, a horizontal direction between left and right sections) and being forced toward the depressions 11 of the core 10. Thus, the male forming blocks 20 forcibly compress the part la of the outer circumferential surface of the pipe material 1 into the depressions 11 to form the grooves 5.

In the preferred embodiment, the rotary male forming blocks 20 include a short cylindrical male forming block 21 and a conical male forming block 22, while the depressions 11 of the core 10 include a vertical depression and an inclined depression respectively corresponding to the above-mentioned male forming blocks.

Furthermore, the core 10 used in the preferred embodiment has a cutout part 4 which is longitudinally formed along one of upper and lower parts of the outer circumferential surface of the core 10 (in FIG. 1, the cutout part is formed along the lower part), so that the cutout part 4 defines a space of which the height is higher than the height of each of the grooves 5. Thus, after the forming of the grooves 5, the core 10 is rotated in a direction (in FIG. 1, a counterclockwise direction) toward the grooves 5 at an angle of 90°, so that the core 10 is easily removed from the pipe material without interfering with the grooves 5.

In the above-mentioned preferred embodiment, the core 10 is removed from the pipe material 1 after the core 10 is

rotated as described above. However, the removal of the core 10 from the pipe material 1 may be accomplished after the pipe material 1 is rotated relative to the core 10 that is in an immobile state.

A method of forming grooves on a pipe material according to a second embodiment of the present invention will be described herein below with reference to FIGS. 4 and 5. FIG. 4 is a front view showing the method of forming the grooves on the pipe material. FIG. 5 shows a plate- shaped male forming block used in the groove forming method, in which: (a) is a front view, and (b) is a side view.

The groove forming method is characterized in that a plurality of longitudinal plate-shaped male forming blocks 30 which are not rotated are used in place of the rotary male forming blocks 20 according to the first embodiment.

The plate-shaped male forming blocks 30 are moved downward while forcibly compressing a part la of the outer circumferential surface of a pipe material 1 into the depressions 11 of the core 10, respectively, thus forming a plurality of grooves 5 on the pipe material through a single forming process without breaking the pipe material 1.

As shown in FIG. 6, each of the plate-shaped male forming blocks 30 may be provided with an inclined surface 30a, such as a straight inclined surface (see (a) of the figure) or a rounded inclined surface (see (b) of the

figure), on a part of an end thereof (a lower end) at which the male forming block 30 comes into contact with the pipe material 1.

In the above state, the part la of the outer circumferential surface of the pipe material 1 may be gradually and slowly deformed by the inclined surface 30a, so that the grooves 5 may be formed without leaving any partially thickened part 6 on the pipe material 1 (see FIG.

7).

In the preferred embodiments, the longitudinal plate- shaped male forming blocks 30, which are not rotated, are used with the core 10 having the vertical depressions 11, thus forming the vertical grooves 5 on the pipe material 1.

However, the longitudinal plate-shaped male forming blocks 30 may be used with another core 10 having inclined depressions 11 as shown in FIG. 8, thus forming inclined grooves 5 on the pipe material 1. That is, longitudinal plate-shaped male forming blocks 30 having a part of which the cross-section is similar to that of the depressions 11 of the core 10 may be preferably used to form the grooves.

Industrial Applicability According to a method of forming grooves on a pipe material as claimed in the accompanying claim 1, rotary male forming blocks are moved in a vertical direction so

that the rotating outer circumferential surfaces of the male forming blocks form the grooves on the outer circumferential surface of the pipe material. Thus, the groove forming method does not break the pipe material even when the pipe material has a thin sidewall. That is, because the rotary male forming blocks compress the outer circumferential surface of the pipe material in a vertical direction, the male forming blocks cannot tear the sidewall of the pipe material.

Furthermore, a core, which has a plurality of depressions functioning as female forming blocks, is inserted into a hollow space of the pipe material, and thereafter, the rotary male forming blocks and the depressions of the core cooperate to form the grooves on the pipe material. Thus, it is possible to form the grooves on the pipe material through a single forming process.

Therefore, the groove forming method improves productivity of products.

According to the method of forming the grooves on the pipe material as claimed in the accompanying claim 2, a cutout part is formed along the outer circumferential surface of the core to define a space of which the height is higher than the height of each of the grooves. Thus, in addition to the operational effect disclosed in the accompanying claim 1, the groove forming method is advantageous in that the core is easily removed from the

pipe material when pulling the core after rotating the core.

Thus, the groove forming process is more easily executed to further improve the productivity of the products.

According to the method of forming the grooves on the pipe material as claimed in the accompanying claim 3, a cutout part is formed along the outer circumferential surface of the core to define a space of which the height is higher than the height of each of the grooves. Thus, in addition to the operational effect disclosed in the accompanying claim 1, the groove forming method is advantageous in that the core is easily removed from the pipe material when pulling the core after rotating the pipe material relative to the core.

Thus, the groove forming process is more easily executed to further improve the productivity of the products.

According to the method of forming the grooves on the pipe material as claimed in the accompanying claim 4, the rotary male forming blocks include short cylindrical male forming blocks or conical male forming blocks. Thus, in addition to the operational effect disclosed in any one of the accompanying claims 1 through 3, the groove forming method easily forms rectangular grooves or inclined grooves.

Furthermore, according to the method of forming the grooves on the pipe material as claimed in the accompanying claim 5, a plurality of longitudinal plate-shaped male forming blocks which are not rotated are used in place of the rotary male forming blocks. Thus, the groove forming method can form the grooves on a pipe material having a thin sidewall. Furthermore, the grooves are formed on the pipe material through a single forming process.

Furthermore, according to the method of forming the grooves on the pipe material as claimed in the accompanying claim 6, each of the plate-shaped male forming blocks is provided with a straight inclined surface or a rounded inclined surface on a part of an end thereof at which the male forming block comes into contact with the pipe material. Thus, in addition to the operational effect disclosed in the accompanying claim 5, the groove forming method gradually and slowly deforms the pipe material, so that the grooves can be formed without leaving any partially thickened part on the pipe material.