EXTRUSION PRESS MACHINE AND PLATEN FOR EXTRUSION PRESS MACHINE

An extrusion press machine includes: a die configured to extrusion-mold a workpiece; a cylinder configured to apply pressing force to press the workpiece against the die; and a platen configured to receive the pressing force from the die. The platen includes an outside element and an inside element that is disposed coaxially with the outside element, inside the outside element. The inside element includes one or more fluid supply structures each supplying a cooling medium toward an extruded product extruded from the die.

TECHNICAL FIELD

The present invention relates to an extrusion press machine used for extrusion molding of a metal such as an aluminum alloy, and in particular, to a platen.

BACKGROUND ART

To extrusion-mold a metal material by an extrusion press machine, a billet is pressed with extruding force against a die disposed on a platen through a pressure ring. The extruding force is applied by a main cylinder included in the extrusion press machine. When reaction force of the extruding force acts on the platen and a main cylinder housing during an extrusion process, deflection occurs on the platen. With the deflection of the platen, deflection occurs on the pressure ring and the die. The platen may also be referred to as an end platen.

FIG. 9illustrates deflection occurring on a platen220.

As illustrated in an upper diagram ofFIG. 9, reaction force f of extruding force F acts on a substantially center part of the platen220in an extrusion direction through a die260and a pressure ring250. The extrusion direction is the direction same as a direction of a void arrow indicating the extruding force F. In contrast, against the reaction force f, drag f′ in a direction opposite to the direction of the reaction force f is generated in tie rods287. The tie rods287resist the reaction force f by deforming (extending) in a direction parallel to the extrusion direction within an elastic range. As a result, a bending moment M bending the platen220to protrude the substantially center part of the platen220in the extrusion direction is generated in the platen220. However, in the platen220including a discharge path242that penetrates through the platen220in a thickness direction to continuously extrusion-mold (discharge) a product rearward, it is physically difficult to secure sufficient rigidity against the bending moment M near the discharge path242. Therefore, during the extrusion process, deflection and bending deformation occur as illustrated in a lower diagram ofFIG. 9.

AlthoughFIG. 9is a schematic plan view, deflection of the platen220occurs in a view from a side surface as in the plan view because the tie rods287are disposed at four corners of the platen220. In other words, in a three-dimensional view, deflection occurs such that the substantially center part of the platen220protrudes in the extrusion direction.

Further, when the platen220is deflected by the extruding force F during the extrusion process, the pressure ring250and the die260fixed to the platen220also deform with the deflection of the platen220.

The extruding force acting on the platen during the extrusion process is varied, more specifically, is reduced as illustrated inFIG. 10during a period from start to completion of the extrusion. Therefore, the deflection of the platen220is reduced during the extrusion process. With reduction of the deflection, the deformation of the pressure ring and the die may be also reduced. Therefore, a dimension of a product extrusion-molded by the die is varied during the period from start to completion of the extrusion process, and it is difficult to obtain desired dimensional accuracy of the product depending on a degree of deformation variation of the die. A lateral axis of a graph inFIG. 10indicates a length L of the billet during the extrusion process, and a vertical axis indicates the extruding force F necessary for extrusion molding of the billet. The extruding force F is expressed by a sum of necessary extruding force Fa acting on the die through the billet and frictional force fb between an outer peripheral surface of the billet and an inner peripheral surface of a container housing the billet, namely, F=Fa+fb. The above-described reduction of the extruding force during the extrusion process is caused by reduction of the frictional force fb. Further, the necessary extruding force Fa is constant and is not varied during the extrusion process by ignoring thermal influence.

Patent Literature 1 discloses a pressure ring with which deflection during an extrusion process can be suppressed, and an extrusion press machine using the pressure ring. The pressure ring disclosed in Patent Literature 1 has a double structure including an outside member and an inside member, and the outside member is shrink-fitted to the inside member. According to the pressure ring disclosed in Patent Literature 1, since the outside member is shrink-fitted to the inside member, stress from outside to inside in a radial direction is applied to the inside member. Therefore, even when a load is applied in an axial direction of the pressure ring, the stress from outside to inside resists the load, which suppresses deflection.

CITATION LIST

Patent Literature

Patent Literature 1: JP H10-258309 A

SUMMARY OF INVENTION

Technical Problem

According to Patent Literature 1, it is possible to suppress deflection of the pressure ring. However, the deflection of the pressure ring is based on the deflection of the platen. Even when the stress from outside to inside is generated in the pressure ring having the double structure, the deflection of the platen cannot be eliminated. Therefore, it is difficult to suppress deformation variation of the pressure ring and the die during the extrusion process, to a degree sufficient to obtain high dimensional accuracy of the product.

Therefore, an object of the present invention is to provide an extrusion press machine including a platen in which occurrence of deflection can be suppressed.

Solution to Problem

An extrusion press machine according to the present invention includes: a die configured to extrusion-mold a workpiece; a cylinder configured to apply pressing force to press the workpiece against the die; and a platen configured to receive the pressing force from the die.

The platen according to the present invention includes an outside element and an inside element that is disposed coaxially with the outside element, inside the outside element.

The inside element according to the present invention includes one or more fluid supply structures each supplying a cooling medium toward an extruded product extruded from the die.

The inside element according to the present invention is preferably provided to sandwich the outside element from front and rear surfaces of the outside element.

In the platen according to the present invention, the outside element and the inside element are preferably fitted, tensile stress is preferably generated in an axial direction (C) in the inside element, and compression stress corresponding to the tensile stress is preferably generated in the outside element.

The inside element according to the present invention is preferably provided to sandwich the outside element by fastening.

In the platen according to the present invention, the outside element and the inside element fitted to each other preferably have a gap in a portion not concerning fitting.

The inside element according to the present invention preferably includes a large-diameter portion provided on a front side, a small-diameter portion continuous with the large-diameter portion, and a fastening member fastened with the small-diameter portion.

The fastening member is fastened in advance with the small-diameter portion to press the outside element, and a preliminary load greater than or equal to a load acting during the extrusion process is accordingly applied. As a result, tensile stress is generated in the inside element.

In the outside element according to the present invention, compression stress is preferably generated in an area sandwiched by the inside element.

The outside element according to the present invention preferably includes a first outside element adjacently fitted to outside of the inside element, and a second outside element adjacently fitted to outside of the first outside element. The inside element is provided to sandwich the first outside element from front and rear surfaces of the first outside element.

Tensile stress is preferably generated in an axial direction (C) in the inside element, and compression stress corresponding to the tensile stress is preferably generated in the first outside element.

In the outside element according to the present invention, the first outside element and the second outside element are preferably fitted by shrinkage fit.

The inside element according to the present invention preferably includes a plurality of the aforementioned fluid supply structures (160)

The inside element according to the present invention is preferably made of a metal material that has a longitudinal elastic modulus substantially same as or greater than a longitudinal elastic modulus of the outside element.

Advantageous Effects of Invention

According to the present invention, the inside element sandwiches the outside element from the front and rear surfaces of the outside element. The sandwiching generates the tensile stress in the inside element and generates the compression stress in the outside element. Therefore, even when a load acts in the extrusion direction during the extrusion process, the tensile stress generated in the inside element and the compression stress generated in the outside element are maintained while being reduced. Thus, even if deflection occurs on the outside element, a portion where the tensile stress or the compression stress is generated is hardly deflected.

DESCRIPTION OF EMBODIMENTS

An extrusion press machine according to the present invention is described below based on embodiments. The extrusion press machine according to the embodiments includes a platen including a plurality of elements divided in a radial direction. Among the plurality of divided elements, an element disposed on an inside (i.e., inside element) is fixed with a pressure ring. The inside element penetrates an element(s) disposed outside the inside element and sandwich the element(s) disposed on the outside from front and rear surfaces. Since the platen according to the embodiments has such a structure, deflection during the extrusion process can be suppressed.

The embodiments include a first embodiment in which the platen has a structure divided into two elements in the radial direction, and a second embodiment in which the platen has a structure divided into three elements in the radial direction. The first embodiment and the second embodiment are described below in order.

First Embodiment

Based on an extrusion press machine1according to the first embodiment, a platen20according to the present embodiment is described.

As illustrated inFIG. 1, the extrusion press machine1includes an extrusion unit10from which a billet B as a workpiece is extruded, a holding unit70housing and holding the billet B, and a pressure generation unit80generating a load to press the billet B housed in the holding unit70, toward the extrusion unit10. The platen20is a main element configuring the extrusion unit10.

As illustrated inFIG. 1,FIG. 2, andFIG. 3, the extrusion unit10includes the platen20, a pressure ring50supported by the platen20, and a die60supported by the pressure ring50.

The platen20includes an outside element30and an inside element40that is coaxially supported inside the outside element30by fitting, and has a two-layer structure divided in the radial direction.

As illustrated inFIG. 2andFIG. 3, the outside element30is a rectangular parallelepiped member including a thick portion31provided on a rear side and a thin portion33continuous with the thick portion31and is provided on a front side. A “thickness” of each of the thick portion31and the thin portion33indicates a distance from an inner peripheral surface of a holding hole35described below to an outer peripheral surface of the outside element30. The outside element30includes the holding hole35that is provided inside the thick portion31and the thin portion33and penetrates through the outside element30in a front-rear direction. The inside element40is fitted to the holding hole35. The holding hole35includes a small-inner-diameter portion36corresponding to the thick portion31, and a large-inner-diameter portion37corresponding to the thin portion33, and is formed in a step shape in the front-rear direction. The outside element30is normally made of cast iron. The inside element40is similarly fabricated.

In the extrusion press machine1, a side (F) illustrated inFIG. 1is defined as a front side, and a side (B) is defined as a rear side. Further, a dimension in the radial direction is determined based on a center axis C illustrated inFIG. 1andFIG. 2.

As illustrated inFIG. 2andFIG. 3, the inside element40is a cylindrical member including a large- diameter portion41provided with an attachment surface48for the pressure ring50, and a small-diameter portion43continuous with the large-diameter portion41and is provided so as to penetrate through the thick portion31in the front-rear direction. The inside element40has an appearance similar to a bolt. The large-diameter portion41corresponds to a head portion, and the small-diameter portion43corresponds to a shank portion.

An outer diameter of the inside element40is smaller than a length of each of outer surfaces (top and bottom surfaces and both side surfaces) of the outside element30, and is considered to substitute a part on the inner diameter side of the outside element30. When a preliminary load is acted, surface pressure ΔP described below corresponding to the preliminary load is generated on a pressure receiving surface32of the outside element30(thick portion31) inFIG. 2. The diameter of each of the large-diameter portion41and the small-diameter portion43of the inside element40determining an area of the ring-shaped pressure receiving surface32is determined in consideration of a diameter of the used die60and a diameter of the pressure ring50, such that the surface pressure ΔP becomes lower than a yield point of the material strength of the outside element30in anticipation of safety factor.

ΔP: surface pressure of pressure receiving surface32

A: area of pressure receiving surface32

The inside element40includes a discharge path42that penetrates through the inside element40from the large-diameter portion41to the small-diameter portion43in the front-rear direction. An extruded product extruded through the die60passes through the discharge path42and is discharged rearward from the extrusion press machine1. The inside element40further includes a male thread44on an outer peripheral end on the rear side of the small-diameter portion43. The male thread44of the small-diameter portion43is fastened with a female thread47of a fastening member46described below. The inside element40further includes a pressure receiving surface45connecting the large-diameter portion41and the small-diameter portion43. The pressure receiving surface45is a surface receiving pressure from the outside element30in a direction parallel to the center axis C, namely, in an axial direction. As the pressure receiving surface45and the pressure receiving surface32of the outside element30, planes orthogonal to the center axis C are illustrated; however, the pressure receiving surface45and the pressure receiving surface32may have the other shapes as long as the pressure receiving surface45and the pressure receiving surface32can receive pressure from each other. For example, tapered surfaces inclined in an extrusion direction Ed (FIG. 1) or step-shaped surfaces can be adopted.

The inside element40includes the fastening member46to fix the large-diameter portion41and the small-diameter portion43to the outside element30. The fastening member46has a form similar to a nut, and includes, on the inner peripheral surface, the female thread47to be fastened with the male thread44provided in the small-diameter portion43. The first embodiment is characterized in that, in a state where the preliminary load MF is generated during assembly of the extrusion press machine1, tensile stress PF in the direction parallel to the center axis C is constantly generated in the inside element40by fastening the fastening member46in advance with the small-diameter portion43from the rear side of the platen20.

The preliminary load MF is set to a value greater than or equal to a rated load acting on the inside element40through the pressure ring50and the die60during the extrusion process. An example of a procedure to generate the preliminary load MF is described below.

In the first embodiment, at least the male thread44of the small-diameter portion43protrudes rearward from the outside element30, and the female thread47of the fastening member46is fastened with the male thread44. As a result, the thick portion31of the outside element30is sandwiched by the inside element40and the fastening member46that are fastened with each other.

The fastening member46is required to be screwable to the male thread44of the inside element40from the rear side of the platen20and to include the discharge path42to discharge the product extruded from the die60, from the platen20. As long as the fastening member46satisfies the requirements, a female thread44′ processed on the inner peripheral surface of the small-diameter portion43of the inside element40and a male thread47′ processed on the outer peripheral surface of a portion protruding from a fastening member46′ to the inner peripheral surface of the small-diameter portion43may be fastened as illustrated inFIG. 4.

As illustrated inFIG. 1toFIG. 3, the pressure ring50is attached to the attachment surface48of the inside element40with unillustrated bolts or the like, and receives pressing force from the die60and transmits the pressing force to the inside element40. The pressure ring50includes a passage51communicating with the discharge path42of the inside element40. The pressure ring50is made of a material higher in strength than the outside element30and the inside element40, for example, tool steal.

As illustrated inFIG. 1, the holding unit70includes a container71holding the billet B, a container holder73holding the container71, and a container cylinder75pressing the container71against the die60through the container holder73.

The container71includes a holding chamber72penetrating through the container71in the front-rear direction while being supported by the container holder73. The billet B is held by the container71while being housed in the holding chamber72.

The container holder73holds the container71. The container71held by the container holder73can reciprocate in the front-rear direction, integrally with the container holder73.

The container cylinder75includes a cylinder76fixed to the platen20, and a piston rod77provided so as to advance and retreat to/from the cylinder76. The piston rod77has a front end portion fixed to the container holder73. When the container cylinder75is operated, the container71can be pressed against the die60through the container holder73.

Pressure Generation Unit80

As illustrated inFIG. 1, the pressure generation unit80includes a main cylinder housing81disposed to face the platen20, and a main cylinder83supported at substantially center of the main cylinder housing81. The pressure generation unit80further includes a side cylinder85supported by the main cylinder housing81on a periphery of the main cylinder83, and tie rods87supported by the main cylinder housing81on a periphery of the main cylinder83.

The main cylinder83includes a main ram84, a main crosshead86fixed to a front end of the main ram84, and an extrusion stem88attached to the main crosshead86. When the main cylinder83operates the main ram84toward the platen20, the extrusion stem88presses the billet B against the die60.

The tie rods87and tie rod nuts89couple the main cylinder housing81and the platen20. The tie rods87and the tie rod nuts89couple four corners of the platen20and corresponding four corners of the main cylinder housing81. During the extrusion process, reaction force of the extruding force acts on the platen20through the die60and the pressure ring50and acts on the main cylinder housing81through the main cylinder83in a direction in which the platen20and the main cylinder housing81are separated from each other. The tie rod nuts89configuring large-diameter portions of the respective tie rods87restrain movement of the platen20and the main cylinder housing81against the reaction force. Each of the tie rods87is configured to have strength resisting against the reaction force of the extruding force while allowing extension of the tie rod87in the elastic region.

Operation of Extrusion Press Machine1

Operation of the extrusion press machine1including the above-described configuration is described.

To extrusion-mold the billet B as the workpiece by the extrusion press machine1, the container cylinder75presses the container71against the die60disposed on the platen20through the pressure ring50by unillustrated holding means. Further, the extrusion stem88is moved toward the platen20to press the billet B housed in the container71, against the die60. This process is called an upset process. The main ram84is further moved toward the platen20to cause the extrusion stem88to press the billet B against the die60, thereby continuously extrusion-molding a predetermined product rearward from a die hole61of the die60. The process is called the extrusion process. Note that a cylinder rod of the side cylinder85is also fixed to the main crosshead86, and the side cylinder85is driven during the extrusion process, namely, when the main crosshead86is advanced and retreated.

Procedure to Generate Tensile Stress PF

Next, an example of a procedure to generate the tensile stress PF in advance in a direction parallel to the center axis C in the inside element40by the preliminary load MF is briefly described with reference toFIG. 1toFIG. 3.

Temporary Fixing of Outside Element30and Inside Element40

First, the pressure ring50is fixed to the attachment surface48of the inside element40of the platen20with unillustrated bolts or the like. At this point, the fastening member46is detached.

Subsequently, the inside element40to which the pressure ring50has been fixed is inserted into the holding hole35of the outside element30of the platen20by a crane, a dedicated insertion tool, or the like. The outer diameter of the small-diameter portion43of the inside element40and the inner diameter of the small-inner-diameter portion36of the holding hole35have a clearance satisfying positioning criteria of the inside element40to the outside element30. Therefore, it is not particularly necessary to position the inside element40to the outside element30. On the other hand, an opening diameter of a housing chamber39in which the large-diameter portion41is to be housed is greater than the outer diameter of the large-diameter portion41of the inside element40(FIG. 2), and a predetermined clearance S is secured. The opening diameter of the housing chamber39indicates the inner diameter of the large-inner-diameter portion37of the holding hole35. The clearance S is described below. In this state, a part of the male thread44of the small-diameter portion43of the inside element40is exposed rearward from the outside element30. The female thread47of the fastening member46is screwed to the male thread44by using a crane, a dedicated insertion tool, or the like, thereby temporarily fastening the fastening member46with the small-diameter portion43.

Action of Preliminary Load MF

Next, the preliminary load MF greater than or equal to a load (rated load) acting in the extrusion direction Ed during the extrusion process, is applied between the platen20and the main cylinder housing81. More specifically, in place of the die60, for example, a dummy die that has a product shape but has no opening is disposed on the pressure ring50by unillustrated holding means, and the container cylinder75presses the container71in which no billet B is housed, against the dummy die.

Thereafter, the main cylinder83and the side cylinder85are driven, the extrusion stem88including an unillustrated extrusion tool or the like attached to the front end thereof is moved toward the platen20inside the holding chamber72of the container71, thereby directly applying the extruding force to the dummy die by the extrusion tool. At this time, hydraulic oil pressure supplied to the main cylinder83and the side cylinder85is controlled such that the extruding force (preliminary load MF) applied between the platen20and the main cylinder housing81through the dummy die is greater than or equal to the load (rated load) acting in the extrusion direction Ed during the extrusion process. The preliminary load MF is preferably set to 105% to 110% of the rated load.

When the preliminary load MF greater than the rated load is applied, the platen20is largely compressed through the pressure receiving surface45of the inside element40, as compared with during the extrusion process with the rated load.

Further, in this state, the fastening member46temporarily fastened is screwed to the male thread44of the small-diameter portion43of the inside element40from the rear side of the platen20by a dedicated screwing tool or the like, so as to be retightened. Since the preliminary load MF is applied to the inside element40in the extrusion direction Ed, rotation stopper means to restrain relative rotary motion of the inside element40to the outside element30is unnecessary. Further, the outside element30included in a projection area of the pressure receiving surface45in the extrusion direction Ed is further compressed as compared with during the extrusion process with the rated load. Therefore, the tensile stress PF corresponding to the preliminary load MF can be constantly generated in the direction parallel to the center axis C of the inside element40without applying large screwing force, when the preliminary load MF is released after the fastening member46is screwed to the small-diameter portion43of the inside element40.

Effects by First Embodiment

Next, effects by the platen20according to the first embodiment are described. The effects include a first effect by generation of the above-described stress state between the outside element30and the inside element40, and a second effect by provision of the clearance S. The effects are described in order below.

First Effect by Stress State between Outside Element30and Inside Element40

In the first embodiment, the inside element40sandwiches the outside element30from the front and rear surfaces of the outside element30. As a result, the tensile stress PF is generated in the inside element40in the direction parallel to the center axis C, and compression stress CF is generated on a portion of the outside element30sandwiched between the pressure receiving surface45of the inside element40and the fastening member46. The tensile stress PF and the compression stress CF are each corresponding to the preliminary load MF greater than the rated load. Therefore, even when the load acting in the extrusion direction Ed during the extrusion process is the maximum, namely, is substantially equal to the rated load, the tensile stress PF generated in the inside element40and the compression stress CF generated in the outside element30are maintained while being reduced. Therefore, even when the tie rods87are extended and deflection occurs on the outside element30of the platen20, the fastening state of the inside element40and the fastening member46at the substantially center part of the platen20is maintained, and deflection hardly occurs.

As described above, according to the present embodiment, the fastening state of the inside element40and the fastening member46at the substantially center part of the platen20and the compression stress CF in the fastening state are maintained during the extrusion process. Therefore, even when the discharge path42through which the product is extruded and discharged to the rear side of the platen20is provided in the inside element40, rigidity sufficient to resist a bending moment M (FIG. 9) that causes deflection on the platen20, in particular, on the outside element30, can be secured at the portion of the thick portion31of the outside element30held by the inside element40(large-diameter portion41) and the fastening member46, near the discharge path42. Thus, according to the first embodiment, it is possible to exert the first effect to suppress deflection of the platen20.

Second Effect by Provision of Clearance S

In the first embodiment, providing the clearance S makes it possible to suppress, even when deflection occurs on the platen20, influence of the deflection on the pressure ring50. The effect is described below with reference to a partial enlarged view ofFIG. 2.

In the partial enlarged view, a state before deflection occurs on the outside element30is illustrated by a two-dot chain line, and a state after deflection occurs is illustrated by a solid line. The clearance S is provided between the outside element30and the inside element40. The clearance S is a gap provided in a portion not concerning fitting of the outside element30and the inside element40. The clearance S is set such that, even when deflection as illustrated occurs on the platen20, in particular, on the outside element30, an inner peripheral surface38defining the housing chamber39does not come into contact with the large-diameter portion41of the inside element40.

With this configuration, deflection of the outside element30does not directly influence on deformation of the pressure ring50. Therefore, even in the case where deflection occurs on the outside element30and the deflection (deflection amount) is varied due to variation (reduction) of the extruding force F, the die60disposed on the pressure ring50by the unillustrated holding means is not deformed as the second effect. Further, as described above, only the clearance satisfying the positioning criteria of the inside element40to the outside element30is provided between the outer diameter of the small-diameter portion43of the inside element40and the opening diameter of the holding hole35into which the small-diameter portion43is inserted. However, in the state where deflection occurs on the outside element30, most part of an inner peripheral surface (inner peripheral surface of small-inner-diameter portion36) of the opening of the outside element30into which the small-diameter portion43is inserted deforms in the direction separating from the outer peripheral surface of the small-diameter portion43of the inside element40. Therefore, when deflection occurs on the outside element30, smallness of the clearance does not influence on deformation of the pressure ring50. Note that the predetermined clearance S and the deflection of the outside element30inFIG. 2are exaggerated to facilitate understanding of the description.

On the other hand, during the extrusion process, rigidity to resist the bending moment M that causes deflection on the outside element30, secured by maintaining the fastening state of the inside element40and the fastening member46at the substantially center part of the outside element30and maintaining the compression stress CF in the fastening state, can be structurally secured even when the inside element40is made of a metal material having a longitudinal elastic modulus substantially same as a longitudinal elastic modulus of the platen20. Therefore, the inside element40is manufactured by a metal material greater in longitudinal elastic modulus than the platen20, to improve the strength itself of the substantially center part of the platen20in addition to the compression stress CF generated at that center part. This makes it possible to further enhance the rigidity.

As described above, the tensile stress PF is generated in the inside element40and the compression stress CF is generated in the outside element30by the inside element40and the fastening member46. This makes it possible to improve rigidity at the substantially center part of the outside element30and to suppress deflection (deflection amount) of the outside element30during the extrusion process.

Further, even when deflection (deflection amount) occurs on the outside element30and the deflection is varied during the extrusion process by variation (reduction) of the extruding force F, the predetermined clearance S is secured while being reduced by the configuration in which the outer peripheral surface of the large-diameter portion41of the inside element40and the inner peripheral surface of the holding hole35of the outside element30in which the large-diameter portion41is disposed do not come into contact with each other. Therefore, the deflection of the outside element30does not directly influence on deformation of the pressure ring50.

As a result, as compared with the extrusion press machine disclosed in Patent Literature 1, deformation (deformation amount) of the pressure ring50and the die60and variation of the deformation can be considerably suppressed during the extrusion process, and it is possible to obtain the product extrusion-molded by the die60, with desired dimensional accuracy from start to completion of the extrusion process.

Second Embodiment

Next, a platen120according to a second embodiment of the present invention is described with reference toFIG. 5toFIG. 8.

As illustrated inFIG. 5andFIG. 6, the platen120according to the second embodiment has a three-layer structure including a second outside element130, a first outside element140, and an inside element150. The second outside element130is a rectangular parallelepiped member. The first outside element140and the inside element150are cylindrical members and are coaxially disposed on the center axis C. The first outside element140is fitted to an inside of the second outside element130, and the inside element150is fitted to an inside of the first outside element140. The inside element150is provided to sandwich the first outside element140from front and rear surfaces of the first outside element140.

Second Outside Element130

As illustrated inFIG. 5,FIG. 6, andFIG. 7, the second outside element130includes a thick portion131provided on the rear side, and a thin portion133continuous with the thick portion131and is provided on the front side. The second outside element130includes a holding hole135that is provided inside the thick portion131and the thin portion133and penetrates through the second outside element130in the front-rear direction. The first outside element140is fitted to the holding hole135. The holding hole135includes a small-inner-diameter portion136corresponding to the thick portion131, and a large-inner-diameter portion137corresponding to the thin portion133, and is formed in a step shape in the front-rear direction.

First Outside Element140

As illustrated inFIG. 5,FIG. 6, andFIG. 7, the first outside element140includes a small-diameter portion141provided on the rear side, and a large-diameter portion143continuous with the small-diameter portion141and is provided on the front side. The first outside element140includes a holding hole145that penetrates through the small-diameter portion141and the large-diameter portion143. The adjacent inside element150is fitted to the holding hole145. The holding hole145includes a small-inner-diameter portion146and a large-inner-diameter portion147, and is formed in a step shape in the front-rear direction.

The second outside element130and the first outside element140are preferably fitted by shrinkage fit. When the second outside element130and the first outside element140are fitted by the shrinkage fit, compression stress is generated between the second outside element130and the first outside element140in a radial direction. Therefore, a portion including the second outside element130and the first outside element140is greater in rigidity than a case where the portion has an integrated structure. Further, when a longitudinal elastic modulus of a material configuring the first outside element140is greater than a longitudinal elastic modulus of a material configuring the second outside element130, rigidity of the second outside element130can be further improved.

As described above, when the sufficient rigidity of the second outside element130is secured, the clearance S provided in the configuration of the first embodiment can be minimized or eliminated.

As the shrinkage fit, shrink fit and cooling fit are known. In a case where the shrink fit is adopted, the second outside element130and the first outside element140are fitted in a state where the second outside element130is heated to a predetermined temperature and is expanded in the radial direction. In a case where the cool fit is adopted, the second outside element130and the first outside element140are fitted in a state where the first outside element140is cooled to a predetermined temperature and is shrunk in the radial direction.

As illustrated inFIG. 5,FIG. 6, andFIG. 7, the inside element150includes a large-diameter portion151provided with an attachment concave portion for the pressure ring50, and a small-diameter portion153continuous with the large-diameter portion151and penetrates through the housing chamber39in the front-rear direction.

The inside element150includes a discharge path152that penetrates through the inside element150from the large-diameter portion151to the small-diameter portion153in the front-rear direction. An extruded product extruded through the die60passes through the discharge path152and is discharged rearward from the extrusion press machine1. The inside element150further includes a male thread154on an outer peripheral end on the rear side of the small-diameter portion153. The male thread154of the small-diameter portion153is screwed with a female thread157of a fastening member156. The inside element150further includes a pressure receiving surface155connecting the large-diameter portion151and the small-diameter portion153. The pressure receiving surface155is a surface receiving pressure from the second outside element130and the first outside element140in a direction parallel to the center axis C.

The inside element150includes the fastening member156to fix the large-diameter portion151and the small-diameter portion153to the first outside element140. The fastening member156has a form similar to a nut, and includes, on the inner peripheral surface, the female thread157to be fastened with the male thread154provided in the small-diameter portion153. Also in the second embodiment, in a state where the preliminary load MF is generated during assembly of the extrusion press machine1, the inside element150is disposed at the substantially center inner part of the platen120while tensile stress PF in the direction parallel to the center axis C is constantly generated in the inside element150by fastening the fastening member156in advance with the small-diameter portion153from the rear side of the platen120.

The inside element150is fixed to the first outside element140while the tensile stress PF is generated in advance in the extrusion direction, by the preliminary load MF greater than or equal to the load acting in the extrusion direction during the extrusion process. The relationship is the same as the stress relationship between the outside element30and the inside element40in the first embodiment.

The inside element150includes fluid supply structures160. As illustrated inFIG. 5, for example, the fluid supply structures160are provided at four positions with equal intervals in a circumferential direction.

As illustrated inFIG. 6toFIG. 8, each of the fluid supply structures160includes a first structure161that supplies liquid fluid or gas fluid cooling the extruded product, and a second structure165that supplies air to form an air curtain.

The first structure161includes a first flow path162through which a cooling medium supplied from an unillustrated supply source flows, and first nozzles163,163ejecting the cooling medium having flowed through the first flow path162. The first flow path162extends inside the small-diameter portion153of the inside element150from the rear side toward the front side. The first nozzles163,163are connected to front ends of the first flow path162, and each have an ejection port directed to the inside in the radial direction of the small-diameter portion153.

The second structure165includes a second flow path166through which the air supplied from an unillustrated supply source flows, and a second nozzle167provided at a front end of the second flow path166. The second flow path166extends inside the small-diameter portion153of the inside element150from the rear side toward the front side. The second nozzle167is connected to the front end of the second flow path166and has an ejection port directed to the inside in the radial direction of the small-diameter portion153.

The first structure161supplies the cooling medium to the extruded product having just passed through the discharge path152, namely, immediately after being extruded, and cools the extruded product so as to follow a desired temperature history, which achieves effects of strength improvement and the like derived from hardening and other thermal treatment of the extruded product. The supplied cooling medium is selected from gas such as air and inert gas, and liquid such as water. In terms of cooling capacity, liquid, in particular, water is preferably sprayed.

When the liquid is used as the cooling medium, corrosion at a part where the sprayed liquid is adhered is concerned. For example, it is desirable to avoid occurrence of problem that the sprayed liquid adheres to the die60through the discharge path152of the inside element150and the passage51of the pressure ring50, and the die60rusts or generated rust is mixed into the extruded product. Therefore, in the present embodiment, the second structure165is provided as a preferable form. In other words, the second structure165is provided on the front side close to the die60more than the first structure161, and the air is supplied from the second structure165to form the air curtain that prevents the liquid sprayed from the first structure161from reaching the die60.

In this example, the configuration in which the liquid is sprayed from the first structure161to the extruded product is described as the preferable form; however, gas may be sprayed from the first structure161to the extruded product. In this case, possibility of corrosion of the die60is eliminated. Therefore, the second structure165can be omitted.

Further, as illustrated in an upper diagram ofFIG. 8, each of the fluid supply structures160may be provided such that the first nozzles163and the second nozzle167are exposed to the inside of the inside element150through short pipes. Alternatively, as illustrated in a lower diagram ofFIG. 8, the first nozzles163and the second nozzle167may be provided in concave portions processed on the inner peripheral surface of the inside element150. In a former case, a protector164covering the first nozzles163and the second nozzle167is preferably provided.

Effects by Second Embodiment

Next, effects by the second embodiment are described.

The platen120according to the second embodiment has the three-layer structure including the second outside element130, the first outside element140, and the inside element150in the radial direction, and the stress structure by sandwiching similar to that in the first embodiment is provided between the first outside element140and the inside element150. Therefore, as in the first embodiment, deformation of the platen120during the extrusion process is suppressed.

Further, when the second outside element130and the first outside element140are fitted by shrinkage fit, compression stress in the radial direction is generated between the second outside element130and the first outside element140. Therefore, the portion including the second outside element130and the first outside element140is greater in rigidity than the case where the portion has an integrated structure, and it is expected that deformation of the platen120during the extrusion process is further suppressed. As described above, when sufficient rigidity of the second outside element130is secured, the clearance S provided in the configuration of the first embodiment can be minimized or eliminated.

Further, in the second embodiment, since the fluid supply structures160are provided in the inside element150, it is possible to secure rigidity of the second outside element130and the first outside element140of the platen120as described below.

For example, it is assumed that drilling is performed in order to form the first flow path162and the second flow path166of each of the fluid supply structures160around the discharge path242of the platen220that is wholly integrally configured as illustrated inFIG. 9. In this case, if the platen220is deflected, stress concentrates on drilled portions, which may cause breakage of the platen220.

In place of the drilling, pipes configuring the first flow path162and the second flow path166may be disposed on a peripheral edge of the discharge path242. To adopt the alternative, however, it is necessary to increase the opening diameter of the discharge path242in consideration of rising heights of cooling nozzles corresponding to the first nozzles163and the second nozzle167. Therefore, when the alternative is adopted, rigidity of the platen220is deteriorated.

In contrast, in the second embodiment, the first flow path162, the second flow path166, the first nozzles163, and the second nozzle167are disposed inside the inside element150. At this time, as described above in the first embodiment (paragraph 0048), in the state where deflection occurs on the outside element30in the first embodiment, most part of the inner peripheral surface (inner peripheral surface of small-inner-diameter portion36) of the opening of the outside element30into which the small-diameter portion43is inserted deforms in the direction separating from the outer peripheral surface of the small-diameter portion43of the inside element40. Likewise, in a case where deflection occurs on the second outside element130in the second embodiment, most part of the inner peripheral surface (inner peripheral surface of small-inner-diameter portion146) of the opening of the second outside element130into which the small-diameter portion153is inserted deforms in the direction separating from the outer peripheral surface of the small-diameter portion153of the inside element150. Accordingly, in the inside element150, stress concentration caused by deflection of the second outside element130does not occur, and deterioration of rigidity does not occur because of the tensile stress PF corresponding to the preliminary load MF greater than the rated load, constantly generated in the direction parallel to the center axis C of the inside element150.

Further, the stress structure by sandwiching in which the portion including the small-diameter portion141of the first outside element140that is a part of the platen120is held by fastening of the inside element150and the fastening member156, and the compression stress CF at the portion is maintained is provided similar to that in the first embodiment. The stress structure secures sufficient rigidity to resist the bending moment M causing deflection of the platen120, which suppresses deflection itself of the platen120during the extrusion process. As a result, it is possible to avoid stress concentration on the first outside element140and the second outside element130provided outside the inside element150, and to avoid deterioration in rigidity.

Further, the inside element150that is smaller in dimension and weight than the integrated platen220is easily drilled as compared with drilling of the platen220.

Although the preferred embodiments of the present invention have been described above, the configurations described in the above-described embodiments can be selected or replaced with other configurations without departing from the gist of the present invention. For example, the fluid supply structures160can be provided in the inside element40in the first embodiment.

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