A barrel main body, a sleeve, and a fixing mechanism (a fastening hole and a fastening device) are provided. The barrel main body includes a barrel hole having a cylindrical shape and a slit dividing an inner circumferential surface of the barrel hole. The sleeve having a hollow cylindrical shape is removably incorporated into the barrel hole. The slit includes two cutout surfaces facing each other with a space between. The fixing mechanism brings the inner circumferential surface of the barrel hole into close contact with the sleeve without any gap by narrowing the space between the cutout surfaces and deforming the barrel main body.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liner-type barrel. The liner refers to a hollow sleeve that is removably incorporated into the barrel. The sleeve refers to a cylindrical part that is incorporated into the barrel, thereby allowing a cylinder to be integrally formed in the barrel. The cylinder refers to a hollow duct into which one or more screws are rotatably inserted.

2. Description of the Related Art

In the technical field of liner-type barrels, a technique of forming a cylinder in a barrel by incorporating a sleeve in which a twin-axis hole is formed into the barrel has been known (see, for example, Patent Literature 1). In the technique, the sleeve has such a sectional shape as covers the twin-axis hole (for example, a prolate ellipsoidal shape or an oval [egg] shape). The sleeve is incorporated into a barrel hole formed in the barrel. As a method of incorporation, shrink-fitting or cooling-fitting is applied.

In the method of shrink-fitting, the barrel is heated to expand the barrel hole. The sleeve is inserted into the barrel hole that has expanded. They are left as they are in an environment at a normal temperature. During this process in which they are left, the barrel is restored to an initial shape that the barrel had before it is heated. That is, the barrel hole shrinks. The barrel hole and the sleeve are thereby pressed against each other. As a result, the sleeve is incorporated and fixed in the barrel hole.

In cooling-fitting, the sleeve is cooled to make the sleeve contract smaller than the barrel hole. The sleeve that has contracted is inserted into the barrel hole. They are left as they are in an environment at a normal temperature. During this process in which they are left, the sleeve is restored to an initial shape that the sleeve had before it is cooled. That is, the sleeve expands. The barrel hole and the sleeve are thereby pressed against each other. As a result, the sleeve is incorporated and fixed in the barrel hole.

CITATION LIST

Patent Literature

Patent Literature 1: JP S58-49230 A

BRIEF SUMMARY OF THE INVENTION

Technical Problem

Incidentally, according to the above-described method of incorporation (shrink-fitting or cooling-fitting), large-scale facilities and many workers are needed separately in order to execute the method. Thus, the cost for incorporating the sleeve into the barrel will increase. Especially, the operation of heating the barrel or the operation of cooling the sleeve, and the subsequent operation of leaving them as they are, not only take a lot of time, but also require that spaces for the operations be secured. Thus, the sleeve cannot be efficiently incorporated into the barrel. In addition, the contours of the above sleeve and barrel hole have a prolate ellipsoidal shape or an oval (egg) shape. To process the sleeve and the barrel hole into such a shape is laborious and troublesome. Thus, the processing cost increases.

An object of the present invention is to provide a liner-type barrel into which a sleeve can be easily and efficiently incorporated at low cost without the need to perform shrink-fitting or cooling-fitting.

Solution to Problem

To achieve the object, the liner-type barrel of the present invention comprises a barrel main body, a sleeve, and a fixing mechanism (a fastening hole and a fastening device). The barrel main body comprises a barrel hole having a cylindrical shape and a slit dividing an inner circumferential surface of the barrel hole. The sleeve having a hollow cylindrical shape is removably incorporated into the barrel hole. The slit comprises two cutout surfaces facing each other with a space between. The fixing mechanism brings the inner circumferential surface of the barrel hole into close contact with the sleeve without any gap by narrowing the space between the cutout surfaces and deforming the barrel main body.

Advantageous Effects of Invention

According to the present invention, a liner-type barrel into which a sleeve can be easily and efficiently incorporated at low cost without the need to perform shrink-fitting or cooling-fitting can be achieved.

DETAILED DESCRIPTION OF THE INVENTION

One Embodiment

A liner-type barrel according to a present embodiment is formed to allow a cylinder to be integrated into the barrel by making a liner (that is, a hollow sleeve) removably incorporated into the barrel. The cylinder functions as a hollow duct. One or more screws are rotatably inserted into the hollow duct. In the following, a cylinder into which two screws are rotatably inserted will be assumed as an example of the cylinder.

The liner-type barrel according to the present embodiment is integrated by combining barrel blocks1(refer toFIG. 1toFIG. 4) with each other. In this case, the number of barrel blocks1to be combined is increased or decreased. A cylinder that corresponds to the length of screws to be used thereby can be formed in the one continuous barrel formed of the barrel blocks1. It should be noted that the accompanying drawings show the structure of a part of the barrel, that is, one barrel block1.

[Barrel Main Body2] As shown inFIG. 1toFIG. 4, the barrel blocks1each comprise a barrel main body2.

The barrel main body2is formed to have a contour in the shape of a cube or a rectangular parallelepiped. The barrel main body2comprises end surfaces2aand2bfacing each other, and an outer surface3covering a space between the end surfaces2aand2b. The end surfaces2aand2bare disposed to be parallel to each other. The outer surface3is formed by integrating rectangular four flat surfaces3a,3b,3c, and3dcontinuously.

As the four flat surfaces, for example, the top surface3a, the first side surface3b, the second side surface3c, and the bottom surface3dare defined. The top surface3aand the bottom surface3dare disposed to be parallel to each other. The first side surface3band the second side surface3care disposed to be parallel to each other. The top and bottom surfaces3aand3dand the first and second side surfaces3band3chave the positional relationship in which they are orthogonal to each other.

The barrel main body2comprises two flanges4aand4b. The flanges4aand4bproject outward from the outer surface3of the barrel main body2. The flanges4aand4bare formed to be disposed along the same planes as the two end surfaces2aand2b. The flanges4aand4bhave rectangular contours.

According to the above-described structure, the flanges4aand4bof the adjacent barrel main bodies2are fastened to each other in a state in which the barrel blocks1are arranged in one direction. The one continuous barrel into which the barrel blocks1are integrated thereby can be formed.

Here, as a method of fastening the flanges4aand4bto each other, for example, a technique of fastening them by combining bolts and nuts, which are not particularly shown in the figures, can be applied. In this case, through-holes (not shown in the figures) are provided at intervals in the flanges4aand4b. The through-holes are formed to penetrate the flanges4aand4b.

In this structure, the through-holes of the adjacent flanges4aand4bare positioned to face each other in a state in which the barrel blocks1are arranged in one direction. The bolts are inserted along the through-holes facing each other. The nuts are screwed onto the tips of the inserted bolts. The flanges4aand4bthereby can be fastened to each other. As a result, the barrel blocks1can be integrated.

The barrel blocks1each comprise a barrel hole5. The barrel hole5is provided in the barrel main body2. The barrel hole5is formed to allow a liner (hereinafter, referred to as a sleeve8), which will be described later, to be removably incorporated thereinto. To be specific, the barrel hole5extends straight to penetrate the space between the above-described two end surfaces2aand2b. The barrel hole5comprises an inner circumferential surface5shaving a cylindrical shape.

It is preferable that the inner dimension (that is, the inside diameter) of the barrel hole5(the inner circumferential surface5s) is set to be equal to the outside diameter (that is, the diameter) of the sleeve8or to be slightly greater than the outside diameter (the diameter) of the sleeve8. The sleeve8thereby can be removably inserted (incorporated) into the barrel hole5easily and smoothly.

The barrel blocks1each comprise a slit6. The slit6is provided in the barrel main body2. To be specific, the slit6is formed by cutting out a part of the barrel main body2. In other words, the slit6is formed in a portion remaining when the part of the barrel main body2has been cut out. In the remaining portion, the slit comprises two cutout surfaces6s.

The cutout surfaces6shave an even and flat shape. The cutout surfaces6sface and are parallel to each other with a space between. The cutout surfaces6sare formed straight continuously from the outer surface3of the barrel main body2to the barrel hole5. In the figures, as an example, the cutout surfaces6sare formed straight continuously from the bottom surface3dof the barrel main body2and bottom surfaces4sof the two flanges4aand4bto the barrel hole5.

The slit6is formed to divide the inner circumferential surface5sof the barrel hole5. The inner circumferential surface5sof the barrel hole5is divided by a gap between the two cutout surfaces6s. A direction in which the barrel hole5is divided by the gap extends straight in a direction along the space between the above-described two end surfaces2aand2b. The width of the space between the cutout surfaces6s(that is, the size of the gap or the width of the slit6) is set according to, for example, the size, the shape, and the material of the barrel main body2, and the size of the barrel hole5. Thus its numerical value is not particularly limited herein.

The slit6is provided in a position avoiding a cooling water path7(a duct7p), which will be described later. The slit6is formed in such a way that an introduction port7aand a discharge port7b, which will be described later, are disposed on both sides of the slit6. In the figures, as an example, the slit6(gap) is formed by making the above-described two cutout surfaces6sextend parallel to each other and straight. The introduction port7aand the discharge port7bare disposed on the bottom surfaces4sof the two flanges4aand4b, respectively, on both sides of the straight slit6(gap).

In this manner, the barrel hole5is divided by the slit6(gap), and thus, it becomes easier to elastically deform the barrel main body2. At the same time, it becomes easier to expand and deform the barrel hole5. The barrel hole5is thereby expanded and deformed when the sleeve8is incorporated into the barrel hole5. As a result, the sleeve8can be removably incorporated into the barrel hole5easily and smoothly.

[Other Structures of Barrel Main Body2]

The barrel blocks1each comprise the cooling water path7, a heater and a temperature sensor not shown in the figures, etc. The cooling water path7is capable of cooling the barrel main body2. The heater is capable of heating the barrel main body2. The heater is provided on the outer surface3of the barrel main body2. In this case, the barrel main body2can be heated up to a preset temperature by turning the heater on and off. Here, if the temperature of the barrel main body2exceeds the set temperature, the barrel main body2can be cooled to the preset temperature by making cooling water flow through the cooling water path7.

The cooling water path7is continuously formed to surround the above-described barrel hole5. The cooling water path7is composed of the one continuous duct7p. The cooling water path7(the duct7p) is laid in a circumferential direction along the barrel hole5while shuttling between the above-described two end surfaces2aand2balternately inside the barrel main body2.

The cooling water path7(the duct7p) comprises the introduction port7aand the discharge port7b. The introduction port7aand the discharge port7bare provided at both ends of the cooling water path7(the duct7p). That is, the introduction port7ais provided at one end of the cooling water path7(the duct7p), and the discharge port7bis provided at the other end of the cooling water path7(the duct7p). The introduction port7ais capable of introducing cooling water into the cooling water path7(the duct7p). The discharge port7bis capable of discharging cooling water that has passed through the cooling water path7(the duct7p).

The introduction port7aand the discharge port7bcan be opened at the outer surface3(the top surface3a, the first side surface3b, the second side surface3c, and the bottom surface3d) of the barrel main body2, or at the surfaces of the two flanges4aand4b. In the figures, as an example, the introduction port7aand the discharge port7bare opened at the bottom surfaces4sof the flanges4aand4b, respectively, of the surfaces of both the flanges4aand4b. To be specific, the introduction port7ais opened at the bottom surface4sof the one flange4a. The discharge port7bis opened at the bottom surface4sof the other flange4b. The bottom surfaces4sof both the flanges4aand4bare formed to be parallel to the bottom surface3dof the barrel main body2.

The barrel blocks1each comprise the sleeve8. The sleeve8has such a contour as can be removably incorporated into the barrel main body2(the barrel hole5). To be specific, the sleeve8comprises an outer circumferential surface8shaving a cylindrical shape. The sleeve8is set to a length equal to the distance between the end surfaces2aand2bof the barrel main body2, or a length which makes both sides of the sleeve8slightly project from the end surfaces2aand2b. The length of the sleeve8can be defined as the total length between both the end surfaces8aand8bof the sleeve8. The sleeve8extends straight over its total length.

The sleeve8comprises a hollow cylinder portion9. The cylinder portion9is formed to extend between both the end surfaces8aand8bof the sleeve8. In the cylinder portion9, two cylinder paths9aand9bhaving a hollow cylindrical shape are formed. The cylinder paths9aand9bextend to penetrate both the end surfaces8aand8bof the sleeve8. The cylinder paths9aand9bextend straight while being parallel and adjacent to each other. The cylinder paths9aand9bextend with adjacent portions thereof overlapping each other. Screws (not shown in the figures) can be inserted into the cylinder paths9aand9b, respectively. In a state in which the screws are inserted in the cylinder paths9aand9b, the screws can rotate in the same direction (different directions).

According to the above-described sleeve8, the sleeve8is inserted (incorporated) into the barrel hole5. The sleeve8is fixed in the barrel hole5by a fixing mechanism, which will be described later. The cylinder as a hollow duct, into which the screws are rotatably inserted, thereby can be integrated into the barrel main body2(barrel).

The barrel blocks1each comprise a positioning mechanism. The positioning mechanism is capable of incorporating the sleeve8into the barrel hole5in a fixed orientation. In the figures, a mark10for positioning is applied as an example of the positioning mechanism. The mark10is provided on both the end surfaces8aand8bof the sleeve8. The mark10is provided at a position which is near the periphery of each of the end surfaces8aand8band which faces the adjacent portions of the two cylinder paths9aand9b. The shape of the mark10can be optionally set to a circle, a rectangle, a triangle, etc. In the figures, the circular mark10is shown as an example.

When the sleeve8is incorporated into the barrel hole5, the mark10is brought closer to face the above-described slit6. In the barrel blocks1, the orientations of the sleeves8incorporated in the barrel main bodies2thereby can be aligned with each other in the same direction. As a result, the cylinder in which the cylinder paths9aand9bcontinue straight can be formed in a state in which the barrel blocks1(the barrel main bodies2) are integrated.

As the positioning mechanism, an engagement portion for positioning (not shown in the figures), for example, may be provided between the sleeve8and the barrel hole5instead of the above-described combination of the mark10and the slit6. The engagement portion is formed to extend along a direction in which the sleeve8is inserted into the barrel hole5. For example, an engagement projection is provided on the outer circumferential surface8sof the sleeve8. The engagement projection is formed by making a part of the outer circumferential surface8sof the sleeve8project along the insertion direction. On the other hand, an engagement depression is provided in the barrel hole5. The engagement depression is formed by making a part of the inner circumferential surface5sof the barrel hole5depressed along the insertion direction.

The engagement depression and the engagement projection are capable of engaging with each other. The respective portions where an engagement projection and an engagement depression are provided of the barrel blocks1are set at the same positions. In this case, when the sleeves8are incorporated into the barrel holes5, the engagement projections are made to engage with the engagement depressions. The respective orientations of the sleeves8incorporated in the barrel main bodies2of the barrel blocks1thereby can be positioned in the same direction. As a result, the cylinder in which the cylinder paths9aand9bcontinue straight can be formed in a state in which the barrel blocks1are integrated.

The barrel blocks1each comprise the fixing mechanism. The fixing mechanism is capable of fixing the sleeve8, which is incorporated in the barrel hole5, in the barrel hole5. To be specific, the fixing mechanism comprises one or more fastening holes11and one or more fastening devices12. The figures show four fastening holes11formed at regular intervals and four fastening devices12, which can be inserted into the fastening holes11, respectively, as an example.

The fastening devices12are capable of being removably fastened in the fastening holes11. The fastening devices12comprise head portions12aand axial portions12bextending from the head portions12a. The head portions12aand the axial portions12bhave a cylindrical shape. The head portions12aare greater in diameter than the axial portions12b. Screws (for example, male screws) are cut in the outer circumferences of the axial portions12b.

The fastening holes11are formed at positions avoiding the cooling water path7(the duct7p). The fastening holes11extend from the outer surface3of the barrel main body2to penetrate the slit6(the gap or both the cutout surfaces6s). In the figures, the fastening holes11extend straight from the first side surface3btoward the second side surface3cof the barrel main body2of the outer surface3of the barrel main body2as an example. Extending ends11dof the fastening holes11are set at positions which cross the slit6(the gap or both the cutout surfaces6s) and which do not penetrate the second side surface3c.

The fastening holes11comprise receiving portions11a, insertion portions11bextending from the receiving portions11a, and screw portions11cfacing the insertion portions11b.

The receiving portions11aare capable of supporting the head portions12aof the fastening devices12in a state in which the fastening devices12are inserted in the fastening holes11. The receiving portions11aare formed by making the first side surface3bof the barrel main body2depressed.

The insertion portions11bare formed to allow the axial portions12bof the fastening devices12to be inserted thereinto. The insertion portions11bare provided between the receiving portions11aand the slit6(the gap or both the cutout surfaces6s).

The screw portions11care formed to allow the axial portions12bof the fastening devices12to be screwed thereinto. Screws (for example, female screws) are cut in the inner circumferences of the screw portions11c. The screw portions11care provided at positions facing the insertion portions11b. The screw portions11care provided between the slit6(the gap or both the cutout surfaces6s) and the extending ends11dof the fastening holes11.

For example, the barrel main bodies2and the same number of sleeves8as the barrel main bodies2are prepared. The inside diameter of the barrel holes5is set to be equal to or slightly greater than the outside diameter of the sleeves8. The sleeves8are herein inserted into the barrel holes5. At this time, the marks10on both the end surfaces8aand8bof the sleeves8are brought closer to face the slit6. The sleeves8are positioned in a fixed orientation with respect to the barrel holes5. Both the end surfaces8aand8bof the sleeves8are positioned in the same planes as both the end surfaces2aand2bof the barrel main bodies2. Alternatively, both the end surfaces8aand8bof the sleeves8are made to slightly project from both the end surfaces2aand2bof the barrel main bodies2.

The sleeves8, which are incorporated in the barrel holes5, are fixed in the barrel holes5by the fixing mechanism. That is, the four fastening devices12are inserted into the fastening holes11, respectively. At this time, the head portions12aof the fastening devices12are supported by the receiving portions11aof the fastening holes11. The axial portions12bof the fastening devices12extend from the insertion portions11bof the fastening holes11across the slit6(the gap or both the cutout surfaces6s), and reach the screw portions11c. In this state, the fastening devices12are screwed and fastened. The barrel main bodies2are thereby deformed.

To be specific, when the fastening devices12are screwed, the screw portions11care drawn in the direction of the head portions12aof the fastening devices12with the rotation of the axial portions12bof the fastening devices12. At this time, with the screw portions11c, the peripheral structures of the screw portions11care also drawn in the same direction. The space between the cutout surfaces6sis thereby narrowed. Because of the narrowing of the space, the barrel main bodies2having an initial shape are elastically deformed. The initial shape refers to the shape of the barrel main bodies2before they are deformed, in other words, the shape of the barrel main bodies2before the fixing mechanism is used.

When the barrel main bodies2having the initial shape are elastically deformed, the inner circumferential surfaces5sof the barrel holes5are also deformed with the deformation of the barrel main bodies2. In other words, the narrower the space between the cutout surfaces6sbecomes, the smaller the inside diameter of the barrel holes5(the inner circumferential surfaces5s) becomes. In this case, the cylindrical barrel holes5(the inner circumferential surfaces5s) contract concentrically with the cylindrical sleeves8. The barrel holes5(the inner circumferential surfaces5s) thereby can be brought into close contact with the sleeves8without any gap. At this time, the sleeves8are kept in the state of being held by the whole circumferential surfaces of the barrel holes5(the inner circumferential surfaces5s) without any gap. As a result, the sleeves8can be firmly fixed in the barrel holes5.

On the other hand, the fastening devices12are unfastened from the fastening holes11. That is, when the fastening devices12are screwed in an opposite direction, the screw portions11cmove in a direction away from the head portions12aof the fastening devices12with the rotation of the axial portions12bof the fastening devices12in the opposite direction. At this time, with the screw portions13c, the peripheral structures of the screw portions11calso move away in the same direction. The space between the cutout surfaces6sis thereby widened. Because of the widening of the space, the deformed barrel main bodies2are elastically restored to the initial shape.

When the barrel main bodies2are restored to the initial shape, the inside diameter of the barrel holes5(the inner circumferential surfaces5s) is expanded. This dissolves the state in which the barrel holes5(the inner circumferential surfaces5s) and the sleeves8are in close contact with each other. As a result, the sleeves8become removable from the barrel holes5.

[Advantageous Effects of Present Invention]

According to the present embodiment, the fixing mechanism is provided. The sleeves8thereby can be incorporated and fixed in the barrel holes5(the barrel main bodies2) without the application of a method of incorporation such as shrink-fitting or cooling-fitting.

According to the present embodiment, the hollow sleeves8having a cylindrical shape are removably incorporated into the barrel main bodies2(barrel). This alone enables the cylinder as a hollow duct, into which screws are rotatably inserted, to be integrated into the barrel main bodies2(barrel).

According to the present embodiment, the inside diameter of the barrel holes5of the barrel main bodies2is set to be equal to or slightly greater than the outside diameter of the sleeves8. The sleeves8thereby can be removably inserted (incorporated) into the barrel holes5easily and smoothly. As a result, the cost required to incorporate the sleeves8into the barrel holes5can be greatly reduced.

According to the present embodiment, the slit is formed to divide the inner circumferential surfaces5sof the barrel holes5. In this case, it becomes easier to elastically deform the barrel main bodies2. It becomes easier to expand and deform the barrel holes5. The barrel holes5are thereby expanded and deformed when the sleeves8are incorporated into the barrel holes5. As a result, the sleeves8can be removably incorporated into the barrel holes5easily and smoothly.

According to the present embodiment, in the fixing mechanism, the fastening devices12are screwed and fastened. That is, the space of the slit6(the gap or the space between both the cutout surfaces6s) is narrowed. The barrel main bodies2are thereby deformed from the initial shape. As a result, the barrel holes5(the inner circumferential surfaces5s) can be brought into close contact with the sleeves8without any gap. At this time, the sleeves8are kept in the state of being held by the whole circumferential surfaces of the barrel holes5(the inner circumferential surfaces5s) without any gap. In this manner, the sleeves8can be firmly fixed in the barrel holes5.

According to the present embodiment, in the fixing mechanism, the fastening devices12are unfastened. That is, the space of the slit6(the gap or the space between both the cutout surfaces6s) is widened. The barrel main bodies2are thereby restored to the initial shape. As a result, the state in which the barrel holes5(the inner circumferential surfaces5s) and the sleeves8are in close contact with each other is resolved. Thus, the sleeves8become removable from the barrel holes5. It becomes possible to replace the sleeves8only.

According to the present embodiment, the positioning mechanism is applied. In the barrel blocks (the barrel main bodies2), the orientations of the sleeves8incorporated in the barrel holes5thereby can be aligned with each other in the same direction. The cylinder in which the cylinder paths9aand9bcontinue straight thereby can be formed easily and precisely in a state in which the barrel blocks1(the barrel main bodies2) are integrated.

According to the present embodiment, the contours of the outer circumferential surfaces8sof the sleeves8are cylindrical. In this case, a lathe turning method can be applied to process the outer circumferential surfaces8sof the sleeves8. The lathe turning method is a technique of cutting the outer circumferential surfaces8sof rotated workpieces (that is, the sleeves8) circularly. The efficiency in manufacturing the sleeves8thereby can be dramatically improved.

Modification

In the above-described embodiment, the slit6(the gap or both the cutout surfaces6s) having an even and flat shape is disposed along a center line (not shown in the figures). The center line refers to a segment connecting the center of the bottom surface4sof the one flange4aand the center of the bottom surface4sof the other flange4bin a straight line. The centers refer to positions at which the bottom surfaces4sof the flanges4aand4bare each divided into two along a longitudinal direction. Thus, in the above-described embodiment, the introduction port7aand the discharge port7bare provided at positions avoiding the center line.

In contrast, in the present modification, the case where the introduction port7aand the discharge port7bare disposed along the center line is assumed. In this case, the slit6(the gap or both the cutout surfaces6s) is provided at a position avoiding the center line. The slit6(the gap or both the cutout surfaces6s) is formed into an uneven crank shape. As shown inFIG. 5andFIG. 6, the slit6(the gap or both the cutout surfaces6s), for example, can be formed to comprise a first slit portion6a, a second slit portion6b, and a crank portion6c.

The first slit portion6ais formed from the bottom surface4sof the one flange4ato a middle of the bottom surface3dof the barrel main body2. The first slit portion6ais provided at a position avoiding the center line. The first slit portion6aextends straight continuously parallel to the center line.

The second slit portion6bis formed from the bottom surface4sof the other flange4bto a middle of the bottom surface3dof the barrel main body2. The second slit portion6bis provided at a position avoiding the center line. The second slit portion6bextends straight continuously parallel to the center line.

The first slit portion6aand the second slit portion6bare disposed on both sides of the center line. In this case, the crank portion6cis formed to connect the first slit portion6aand the second slit portion6bto each other at a middle of the bottom surface3dof the barrel main body2. The crank portion6ccontinues across the center line.

According to the present modification, the slit6(the gap or both the cutout surfaces6s) are formed into an uneven crank shape. The introduction port7aand the discharge port7bthereby can remain at positions along the center line, for example, positions adapted to existent facilities. As a result, cooling water can be introduced into and discharged from the cooling water path7(the duct7p) while the existent facilities are used as they are. The other structures and advantageous effects are the same as those of the above-described embodiment, and thus a description thereof is omitted.

REFERENCE SIGNS LIST