Patent Application
20160256909
The present invention relates to a mandrel which is inserted into a pipe material when the pipe material is bent.
As a bending machine for bending a pipe (pipe material) to a predetermined curvature, for example, a bending machine is known which includes a first supporting portion configured to support a part of a pipe on one end side thereof and a second supporting portion configured to support a part of the pipe on the other end side thereof, and which is configured to bend the pipe along an arc-shaped guide face provided on the first supporting portion by rotating the first supporting portion about a predetermined rotation axis and also causing the second supporting portion to linearly move.
Such a bending machine is equipped with a mandrel for preventing the deformation (flattening) of a pipe at bending, and a pipe is bent with the mandrel inserted in the pipe.
In the bending of a pipe using a mandrel, lubricant oil is used in some cases to reduce the sliding friction between the inner surface of the pipe and the mandrel and to prevent the formation of scratches on the inner surface of the pipe. However, since the lubricant oil is attached to the inner surface of the pipe, the bending using lubricant oil requires a washing operation for removing the lubricant oil by washing the inside of the pipe after the bending.
Here, to avoid the use of lubricant oil at the bending of a pipe and to eliminate the need for the washing operation for removing the lubricant oil, a technique has been developed in which a synthetic resin such as MC nylon is provided to a front end portion of a mandrel. The technique in which a synthetic resin such as MC nylon is provided is described in, for example, Patent Literature 1.
Patent Literature 1 discloses a mandrel including: a cylindrical main body made of a tool steel and provided with a male-screw portion; and a semi-sphere shaped spherical portion made of a synthetic resin (MC nylon) and provided with a female-screw portion, the main body and the spherical portion being assembled together by screw fastening.
However, in the case of the mandrel described in Patent Literature 1, the spherical portion of the mandrel may be deformed because of the formation of a space at a screw-fastened portion between the main body and the spherical portion.
In addition, in the case of the mandrel described in Patent Literature 1, the process for forming the male-screw portion in the main body and the process for forming the female-screw portion in the spherical portion are conducted separately from each other. Hence, the central axes of the main body and the spherical portion may be misaligned, when the male-screwportion and the female-screwportion are screw fastened. The misalignment of the central axes of the main body and the spherical portion not only exerts an influence on the precision of the bending, but also influences the strength of the mandrel. Note that, for the alignment of the central axes, it is necessary to conduct the process for forming the male-screw portion in the main body and the process for forming the female-screw portion in the spherical portion with high precision.
The present invention has been made in view of the above-described problems, and an object of the present invention is to keep a shape of a mandrel including two members.
A first aspect of the invention, with which the problems are solved, provides a mandrel which is inserted into a pipe material when the pipe material is bent, the mandrel comprising: a core member having a rod-shaped main body portion and a small-diameter portion which is provided on one end side of the main body portion and which is thinner than the main body portion; and a front end member which is provided on one end side of the core member and which is formed integrally with the core member so as to cover the small-diameter portion.
A second aspect of the invention, with which the problems are solved, provides the mandrel according to the first aspect of the invention, wherein the front end member is a resin member formed by injection molding.
A third aspect of the invention, with which the problems are solved, provides the mandrel according to the first aspect of the invention, wherein the front end member is a ceramic member formed by sintering.
A fourth aspect of the invention, with which the problems are solved, provides the mandrel according to the first aspect of the invention, wherein the small-diameter portion has a groove portion, and the front end member is formed on the core member so as to fill the groove portion.
According to the mandrel according to the first aspect of the invention, the mandrel including the core member and the front end member is configured such that the front end member is not mounted on the core member by press fitting, screw fastening, or the like, but the front end member is formed integrally with the core member so as to cover the small-diameter portion of the core member. This improves the degree of closeness of contact between the core member and the front end member, and makes it possible to keep the shape of the mandrel. In addition, since the front end member is not mounted on the core member by press fitting, screw fastening, or the like, but the front end member is formed integrally with the core member, it is possible to reduce the misalignment of the central axes of the core member and the front end member, and this makes it possible to keep the shape of the mandrel.
According to the mandrel according to the second aspect of the invention, a front end member made of a resin is formed by injection molding. This makes it possible to surely form the front end member on the core member in a close contact state. In addition, the resin member improves the slidability between the mandrel and a pipe material to be bent. Hence, no lubricant oil is used at the bending of a pipe material, which makes it possible to eliminate the need for the washing operation for removing lubricant oil.
According to the mandrel according to the third aspect of the invention, a front end member made of a ceramic is formed by sintering. This makes it possible to surely form the front end member on the core member in a close contact state. In addition, the ceramic member improves the slidability between the mandrel and a pipe material to be bent. Hence, no lubricant oil is used at the bending of a pipe material, which makes it possible to eliminate the need for the washing operation for removing lubricant oil.
According to the mandrel according to the fourth aspect of the invention, the groove portion is provided in the small-diameter portion of the core member, and hence the front end member is formed, while entering the groove portion. Hence, the groove portion acts as a retainer. In other words, when a force acts on the core member in the mandrel in a direction to release the front end member, the front end member is caught by the groove portion in the core member, and does not come off from the core member.
Hereinafter, embodiments of mandrels according to the present invention will be described in detail with reference to the attached drawings. As a matter of course, the present invention is not limited to the embodiments described below, and, needless to say, various modifications can be made within a range not departing from the gist of the present invention.
A structure of a bending machine equipped with a mandrel according to a first embodiment of the present invention is described with reference to
As shown in
The first supporting portion 10 has a guide face 11 having an arc shape with a predetermined curvature. The first supporting portion 10 is rotatable about a rotation axis 12 positioned at a center of the arc of the guide face 11. On the other hand, the second supporting portion 20 is configured to linearly move with the rotation of the first supporting portion 10 to push the pipe P toward the front end (in a direction of a tangent to the guide face 11). Accordingly, the pipe P is bent along the guide face 11 of the first supporting portion 10 by the rotation of the first supporting portion 10 and by the linear movement of the second supporting portion 20.
The bending machine 1 is provided with a mandrel 30 for preventing the pipe P from collapsing under pressure during the bending. The mandrel 30 is configured to be inserted into the pipe P supported by the first supporting portion 10 and the second supporting portion 20.
Accordingly, when the straight pipe P is bent to a predetermined curvature, the part of the pipe P on the front end side (the one end side) is supported by the first supporting portion 10, and the part of the pipe P on the rear end side (the other end side) is supported by the second supporting portion 20, as shown in
The mandrel 30 includes a core bar (core member) 40 having a substantially cylindrical shape (rod-like shape), and a front end member 50 which is provided on one end side of the core bar 40 (on the right side in
The core bar 40 includes a main body portion 41 which has a cylindrical shape (rod-like shape) with an outer diameter D1 insertable into the pipe P, and a small-diameter portion 42 which is provided on one end side of the main body portion 41 (on the right side in
The front end member 50 is formed integrally with the core bar 40 so as to cover the small-diameter portion 42 of the core bar 40. The front end member 50 includes a tubular portion 51 which has an outer diameter substantially the same as the outer diameter D1 of the main body portion 41 of the core bar 40 and which covers a circumferential surface 42a of the small-diameter portion 42 of the core bar 40, and a semi-sphere portion 52 which is provided on a front end side of the tubular portion 51 and which covers an end surface 42b of the small-diameter portion 42 of the core bar 40. Note that the front end member 50 is made of a material having a good slidability to reduce the sliding friction of the pipe P on the inner surface Pf at the bending. The material of the front end member 50 may be, for example, a resin having a good slidability, such as a phenolic resin.
The front end member 50 is formed integrally with the core bar 40 by injection molding. In the mandrel 30, the core bar 40 and the front end member 50 are in close contact with each other, with no space therebetween. An example of a method for manufacturing the mandrel 30, i.e., a method for forming the front end member 50 integrally with the core bar 40 is described below.
First, as shown in
In the mold 60, a resin injection port 63 opened to a front end side (the right side in
In addition, a groove portion 43 extending in a circumferential direction is formed on the circumferential surface 42a of the small-diameter portion 42 of the core bar 40. The front end member 50 is provided so as to fill the groove portion 43. Accordingly, the resin solidified in the groove portion 43 acts as a retainer of the front end member 50. In other words, when a force acts on the core bar 40 in the mandrel 30 in a direction to release the front end member 50, the front end member 50 is caught by the groove portion 43 of the core bar 40, and hence is prevented from coming off from the core bar 40.
As described above, the front end member 50 made of the resin is formed integrally with the core bar 40 by injection molding. This makes it possible to surely bring the front end member 50 into close contact with the core bar 40, and also makes it possible to easily align shaft centers of the core bar 40 and the front end member 50.
Note that, when a front end member is mounted on a core member by press fitting, screw fastening, or the like as in the conventional case, the front end member may be deformed, because a space is created between the core member and the front end member, and also because the central axis of the core member and the central axis of the front end member are misaligned. In addition, to align the central axis of the core member and the central axis of the front end member in the mounting of the front end member on the core member by press fitting, screw fastening, or the like, it is necessary to process the core member and the front end member with high precision.
Operations of the bending machine equipped with the mandrel 30 according to the first embodiment of the present invention are described with reference to
First, a pipe P is set to the bending machine 1 as shown in
Next, the first supporting portion 10 is rotated about the rotation axis 12 (counterclockwise in
Then, as shown in
In the mandrel 30, the front end member 50 is formed integrally with the core bar 40 by injection molding. Hence, the core bar 40 and the front end member 50 are surely brought into close contact with each other, with no space therebetween. In addition, the central axes of the core bar 40 and the front end member 50 are aligned. Accordingly, a sufficient strength is provided to the front end member 50, so that the front end member 50 is not broken by the pressure, friction, or the like applied by the pipe P at the bending.
In addition, the groove portion 43 is provided on the circumferential surface 42a of the small-diameter portion 42 of the core bar 40, and the front end member 50 is provided so as to fill the groove portion 43. Hence, even when a force acts on the core bar 40 in a direction to release the front end member 50, the front end member 50 is caught by the groove portion 43 of the core bar 40, and hence does not come off from the core bar 40.
In the mandrel 30 according to this embodiment, the groove portion 43 extending in the circumferential direction is formed on the circumferential surface 42a of the small-diameter portion 42 of the core bar 40. However, the groove portion in the present invention is not limited thereto, but may be any, as long as the groove portion can act as a retainer of the front end member 50 formed integrally with the core bar 40. As the groove portion of the present invention, for example, multiple groove portions 43 arranged in an axial direction and each extending in the circumferential direction may be provided on the circumferential surface 42a of the small-diameter portion 42 in the mandrel 30, or a notched portion may be provided by cutting a part of the circumferential surface 42a of the small-diameter portion 42 in the mandrel 30.
Note that, to keep the strength of the resin solidified in the groove portion 43, i.e., to sufficiently exhibit the effect of preventing the front end member 50 from coming off, the groove portion 43 preferably has an obtuse angle or a curved surface, and the depth (the length in the radial direction) d of the groove portion 43 is preferably about 50 to 100% of a thickness t to which the front end member 50 is formed.
In addition, to provide a sufficient strength to the small-diameter portion 42 of the core bar 40, and a sufficient strength to the front end member 50 provided on the small-diameter portion 42, the diameter D1 of the main body portion 41 and the diameter D2 of the small-diameter portion 42 in the core bar 40 are preferably such that D2≈D1/2, and it is preferable that t≈D2/2≈D1/4, where t represents the thickness to which the front end member 50 is formed.
A structure of a bending machine equipped with a mandrel according to a second embodiment of the present invention is described with reference to
A mandrel 130 according to this embodiment is provided instead of the mandrel 30 in the bending machine 1 in the first embodiment of the present invention (see
The mandrel 130 includes a core bar 140 having a substantially cylindrical shape (rod-like shape) and the front end member 150 provided on one end side of the core bar 140 (on the right side in
The front end member 150 is formed integrally with the core bar 140 so as to cover a small-diameter portion 142 in the core bar 140. The front end member 150 includes a tubular portion 151 which has an outer diameter substantially the same as an outer diameter D1 of a main body portion 141 of the core bar 140 and which covers a circumferential surface 142a of the small-diameter portion 142 of the core bar 140, and a semi-sphere portion 152 which is provided on a front end side of the tubular portion 151 and which covers an end surface 142b of the small-diameter portion 142 of the core bar 140. Note that the front end member 150 is made of a material having a good slidability to reduce the sliding friction of the pipe P on the inner surface Pf at the bending. The material of the front end member 150 may be, for example, a ceramic.
The front end member 150 is formed integrally with the core bar 140 by sintering. In the mandrel 130, the core bar 140 and the front end member 150 are in close contact with each other, with no space therebetween. An example of a method for manufacturing the mandrel 130, i.e., a method for forming the front end member 150 integrally with the core bar 140 is described below.
On the core bar 140 made of a metal by rolling or the like, a ceramic powder 150a is molded under pressure by using an unillustrated mold, and sintered by heating at high temperature. In this manner, the front end member 150 is formed integrally with the core bar 140, as shown in
In addition, a groove portion 143 extending in a circumferential direction is formed on the circumferential surface 142a of the small-diameter portion 142 of the core bar 140, and the ceramic powder 150a is molded under pressure so as to fill this groove portion 143. For this reason, the ceramic sintered in the groove portion 143 acts as a retainer of the front end member 150. In other words, when a force acts on the core bar 140 in the mandrel 130 in a direction to release the front end member 150, the front end member 150 is caught by the groove portion 143 of the core bar 140, and does not come off from the core bar 140.
As described above, the front end member 150 made of a ceramic by the molding under pressure and by the sintering is formed integrally with the core bar 140. This makes it possible to surely bring the core bar 140 and the front end member 150 into close contact with each other, and also makes it possible to easily align shaft centers of the core bar 140 and the front end member 150.
In the mandrel 130 according to this embodiment, the groove portion 143 extending in the circumferential direction is formed on the circumferential surface 142a of the small-diameter portion 142 of the core bar 140. However, the groove portion in the present invention is not limited thereto, but may be any, as long as the groove portion can act as a retainer of the front end member 150 formed integrally with the core bar 140. As the groove portion of the present invention, for example, multiple groove portions 143 arranged in an axial direction and each extending in the circumferential direction may be provided on the circumferential surface 142a of the small-diameter portion 142 in the mandrel 130, or a notched portion may be provided by cutting a part of the circumferential surface 142a of the small-diameter portion 142 in the mandrel 130.
Note that, to keep the strength of the ceramic sintered in the groove portion 143, i.e., to sufficiently exhibit the effect of preventing the front end member 150 from coming off, the groove portion 143 preferably has an obtuse angle or a curved surface, and the depth (length in the radial direction) d of the groove portion 143 is preferably about 50 to 100% of a thickness t to which the front end member 150 is formed.
In addition, to provide a sufficient strength to the small-diameter portion 142 of the core bar 140 and a sufficient strength to the front end member 150 provided to the small-diameter portion 142, the diameter D1 of the main body portion 141 and the diameter D2 of the small-diameter portion 142 in the core bar 140 are preferably such that D2≈D1/2, and it is preferable that t≈D2/2≈D1/4, where t represents the thickness of the front end member 150 formed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-041920 | Mar 2015 | JP | national |
