Screen changer

Abstract

Reduces the possibility of the slide bar becoming stuck. [Solution] The screen changer comprises a body 11 provided with a resin flow passage 18 and an insertion hole 20, a slide bar 12 having a screen 24 and a bar body portion 22, and a hydraulic cylinder 13. The resin flow passage 18 has an upstream hole portion 18a located upstream of the insertion hole 20 in the direction of molten resin flow, and a downstream hole portion 18b located downstream of the insertion hole 20. The bar body portion 22 has a body step surface 31 that is recessed from the outer circumferential surface of the bar body portion 22 in a region located inside the insertion hole 20 and on the return direction side of the opening of the upstream hole portion 18a in the insertion hole 20 when the screen 24 is in the replacement position.

Description

Technical Field

[0001] The present invention relates to a screen changer.

Background Art

[0002] In a resin kneader, a resin extruder, etc., a filtering device for removing foreign substances from the kneaded molten resin is used. This filtering device has a screen (filter body), and a screen changer is provided such that a screen with a reduced filtering capacity can be replaced with a new screen. As this type of screen changer, for example, Patent Document 1 below discloses a screen changer having a housing 102, a slide bar 103 provided slidably with respect to the housing 102, a screen 104 provided on the slide bar, and a slider drive unit 105 for moving the slide bar 103 forward and backward, as shown in FIG. 13.

[0003] The slide bar 103 is fitted into a slider insertion hole 111 provided in the housing 102 and is movable between a screen operating position in which the screen 104 is positioned within the resin flow hole 110 formed in the housing 102 to filter the molten resin, and a replacement position in which the screen 104 is positioned outside the housing 102 to allow for screen replacement. When the slide bar 103 is in the screen operating position, the portion of the slide bar 103 located inside the housing 102 (base end portion) becomes hot, close to the temperature of the molten resin, while the portion of the slide bar 103 located outside the housing 102 (tip portion) is maintained at a temperature close to room temperature. Therefore, when the screen changer is in operation, the base end portion of the slide bar 103 has a larger diameter than the tip portion at room temperature. Taking this into consideration, the fitting state between the slide bar 103 and the slider insertion hole 111 is designed so that when the slide bar 103 and the slider insertion hole 111 are at a high temperature close to the temperature of the molten resin, they can maintain a sealed state (a state in which the molten resin does not penetrate into the gap between the slide bar 103 and the inner surface of the slider insertion hole 111, nor does the molten resin flow out from the gap).

[0004] Therefore, when the slide bar 103 is slid from the screen operating position to the replacement position, the tip portion, which is at room temperature, enters the slider insertion hole 111, creating a gap 125 between the slide bar 103 and the slider insertion hole 111. Pressurized molten resin may flow into this gap 125 from the resin flow hole 110. If the slide bar 103 slides while molten resin is present in this gap 125, contact scratches may occur on the inner circumferential surface of the slide bar 103 or the slider insertion hole 111. For this reason, in the screen changer disclosed in Patent Document 1, a recess 120 is provided near the opening of the slider insertion hole 111 in the housing 102. By providing the recess 120, the contact pressure between the slide bar 103 and the housing 102 is reduced, preventing the occurrence of contact scratches and the sticking of the slide bar 103. Patent Document 1 also discloses an example in which a recess is provided on the end face of the slide bar 103. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2007-112068 [Overview of the project] [Problems that the invention aims to solve]

[0006] In the screen changer disclosed in Patent Document 1, contact scratches and sticking of the slide bar 103 are prevented by reducing the contact pressure between the slide bar 103 and the housing 102. However, since molten resin remains between the slide bar 103 and the inner surface of the slider insertion hole 111, it is not guaranteed that the slide bar 103 will not stick.

[0007] Therefore, the present invention has been made in view of the above-mentioned prior art, and its purpose is to reduce the possibility of the slide bar becoming stuck. [Means for solving the problem]

[0008] To achieve the above objective, the screen changer according to the present invention is a screen changer which is a filtration device for molten resin, comprising: a body provided such that a resin flow passage and an insertion hole intersect with each other; a slide bar having a screen and a bar body portion and slidably provided in the insertion hole; and a hydraulic cylinder which is a power source for sliding the slide bar. The hydraulic cylinder is configured to slide the slide bar between a screen operating position in which the screen is located within the resin flow passage and a replacement position in which the screen is exposed to the outside of the body. The resin flow passage has an upstream hole portion located upstream of the insertion hole in the flow direction of the molten resin and a downstream hole portion located downstream of the insertion hole. When the direction of movement of the slide bar from the screen operating position to the replacement position is defined as the removal direction, and the opposite direction is defined as the return direction, the bar body has a stepped surface formed so as to be recessed from the outer circumferential surface of the bar body in a region located within the insertion hole and on the return direction side of the opening of the upstream hole in the insertion hole when the slide bar is in the replacement position, and the stepped surface of the bar body scrapes out at least a portion of the molten resin that has flowed out from the upstream hole to the outside of the body when the slide bar slides from the replacement position to the screen operating position.

[0009] In the screen changer according to the present invention, when the slide bar is in the replacement position, molten resin may flow from the upstream hole in the resin flow passage between the inner circumferential surface of the insertion hole and the outer circumferential surface of the bar body portion of the slide bar. However, when the slide bar slides from the replacement position to the screen operating position, this molten resin is scraped out of the body by the stepped surface of the bar body portion. Therefore, it is possible to prevent molten resin from remaining between the inner circumferential surface of the insertion hole and the slide bar, or to reduce the amount of molten resin remaining between the inner circumferential surface of the insertion hole and the slide bar. Consequently, the possibility of the slide bar becoming stuck can be reduced.

[0010] The stepped surface of the main body may be formed on a part of the circumferential direction of the outer surface of the bar body, excluding the side facing the downstream hole.

[0011] In this embodiment, since no step is formed on the outer circumferential surface of the bar body on the side facing the downstream hole of the resin flow passage, the contact area between the bar body and the body is wider on the downstream hole side compared to the case where the stepped surface of the bar body is formed over the entire circumference in the circumferential direction of the outer circumferential surface of the bar body. As a result, the contact pressure is reduced. Furthermore, the molten resin that flows from the upstream hole of the resin flow passage between the inner circumferential surface of the insertion hole and the outer circumferential surface of the bar body is mainly located on the upstream hole side. Therefore, even if the bar body is pressed by the presence of the molten resin, since there is no step on the side of the outer circumferential surface of the bar body facing the downstream hole, stress concentration at the step can be prevented.

[0012] The slide bar may further have an auxiliary stepped surface located on the return direction side of the main body stepped surface. In this case, the auxiliary stepped surface may be formed over the entire circumferential surface of the outer circumferential surface of the bar body.

[0013] In this embodiment, since the stepped surface of the main body is formed only on a portion of the circumferential direction of the outer surface of the bar body, the increase in contact pressure on the side facing the downstream hole can be suppressed. However, in this case, the amount of molten resin scraped out is limited, so to suppress this, an auxiliary stepped surface is added that extends over the entire circumferential direction of the outer surface of the bar body. As a result, the molten resin present on the downstream hole side of the gap between the inner surface of the insertion hole and the outer surface of the bar body can also be scraped out by the auxiliary stepped surface. This makes it possible to increase the amount of molten resin scraped out.

[0014] The auxiliary stepped surface may form a gap between the outer surface of the bar body and the inner surface of the insertion hole that is larger than the gap width between the outer surface of the bar body formed by the main stepped surface and the inner surface of the insertion hole.

[0015] In this embodiment, the stepped surface of the main body facilitates the flow of a portion of the molten resin that has entered the stepped recess formed between the outer circumferential surface of the bar body and the inner circumferential surface of the insertion hole into the recess formed between the outer circumferential surface of the bar body and the inner circumferential surface of the insertion hole, which is facilitated by the auxiliary stepped surface. Therefore, the amount of molten resin scraped out can be further increased.

[0016] The screen changer according to the present invention is a screen changer that is a filtration device for molten resin, comprising: a body provided such that a resin flow passage and an insertion hole intersect with each other; a slide bar having a screen and a bar body portion and slidably provided in the insertion hole; a hydraulic cylinder which is a power source for sliding the slide bar; and a joint which has a region smaller in diameter than the bar body portion and connects the bar body portion and the hydraulic cylinder. The hydraulic cylinder is configured to slide the slide bar between a screen operating position in which the screen is located within the resin flow passage and a replacement position in which the screen is exposed to the outside of the body. The resin flow passage has an upstream hole portion located upstream of the insertion hole in the direction of molten resin flow and a downstream hole portion located downstream of the insertion hole. When the direction of movement of the slide bar from the screen operating position to the replacement position is defined as the removal direction, and the opposite direction is defined as the return direction, the bar body has a stepped surface that is recessed from the outer surface of the bar body in a region located within the insertion hole and on the return direction side of the opening of the upstream hole in the insertion hole when the slide bar is in the replacement position.

[0017] In the screen changer according to the present invention, when the slide bar is in the replacement position, molten resin may flow from the upstream hole in the resin flow passage between the inner circumferential surface of the insertion hole and the outer circumferential surface of the bar body of the slide bar. However, the bar body has a stepped surface that is recessed from the outer circumferential surface of the bar body in a region located on the return direction side of the opening of the upstream hole when the slide bar is in the replacement position and located within the insertion hole. Therefore, the molten resin present between the inner circumferential surface of the insertion hole and the outer circumferential surface of the bar body can be scraped out of the body by the stepped surface of the bar body as it slides from the replacement position to the screen operating position. As a result, it is possible to prevent molten resin from remaining between the inner circumferential surface of the insertion hole and the slide bar, or to reduce the amount of molten resin remaining between the inner circumferential surface of the insertion hole and the slide bar. Consequently, the possibility of the slide bar becoming stuck can be reduced.

[0018] The stepped surface of the main body may be formed on a part of the circumferential direction of the outer surface of the bar body, excluding the side facing the downstream hole.

[0019] In this embodiment, since no step is formed on the outer circumferential surface of the bar body on the side facing the downstream hole of the resin flow passage, the contact area between the bar body and the body is wider on the downstream hole side compared to the case where the stepped surface of the bar body is formed over the entire circumference in the circumferential direction of the outer circumferential surface of the bar body. As a result, the contact pressure is reduced. Furthermore, the molten resin that flows from the upstream hole of the resin flow passage between the inner circumferential surface of the insertion hole and the outer circumferential surface of the bar body is mainly located on the upstream hole side. Therefore, even if the bar body is pressed by the presence of the molten resin, since there is no step on the side of the outer circumferential surface of the bar body facing the downstream hole, stress concentration at the step can be prevented.

[0020] The end face of the bar body to which the hydraulic cylinder is coupled functions as an auxiliary stepped surface located on the return direction side of the main body stepped surface, and the auxiliary stepped surface may be formed over the entire circumferential surface of the outer circumferential surface of the bar body.

[0021] In this aspect, since the main body step surface is formed only on a part of the circumferential direction on the outer peripheral surface of the bar main body part, it is possible to suppress an increase in the contact surface pressure on the side facing the downstream hole part. However, in this case, the scraping amount of the molten resin is limited. Since the end surface of the bar main body part to which the hydraulic cylinder is coupled functions as an auxiliary step surface, even for the molten resin existing on the downstream hole part side in the gap between the inner peripheral surface of the insertion hole and the outer peripheral surface of the joint, it can be scraped by the auxiliary step surface. Thereby, the scraping amount of the molten resin can be increased.

[0022] The auxiliary step surface may form a gap having a gap width larger than the gap width between the outer peripheral surface of the bar main body part formed by the main body step surface and the inner peripheral surface of the insertion hole between the outer peripheral surface of the joint and the inner peripheral surface of the insertion hole.

[0023] In this aspect, it is possible to easily make a part of the molten resin flowing into the stepped recess formed between the outer peripheral surface of the bar main body part and the inner peripheral surface of the insertion hole by the main body step surface flow into the recess formed between the outer peripheral surface of the bar main body part and the inner peripheral surface of the insertion hole by the auxiliary step surface. Therefore, the scraping amount of the molten resin can be further increased.

[0024] The corner portion formed by the outer peripheral surface of the bar main body part and the main body step surface may be an acute angle.

[0025] In this aspect, since the corner portion formed by the outer peripheral surface of the bar main body part and the main body step surface is formed as an acute angle, when this corner portion contacts the inner peripheral surface of the insertion hole in the body, the contact surface pressure can be relaxed. Thereby, the possibility of occurrence of contact scratches and slide bar sticking can be further reduced.

[0026] The corner portion formed by the outer peripheral surface of the bar main body part and the auxiliary step surface may be an acute angle.

[0027] In this aspect, since the corner portion formed by the outer peripheral surface of the bar main body portion and the auxiliary step surface is formed as an acute angle, when this corner portion contacts the inner peripheral surface of the insertion hole in the body, the contact surface pressure can be relieved. As a result, the possibility of contact damage and slide bar fixation can be further reduced.

Advantages of the Invention

[0028] As described above, according to the present invention, the possibility of the occurrence of slide bar fixation can be reduced.

Brief Description of the Drawings

[0029] [Figure 1] It is a perspective view of a screen changer according to the first embodiment. [Figure 2] It is a view showing the screen changer in a state seen from the side. [Figure 3] It is a schematic cross-sectional view of the screen changer. [Figure 4] It is a view for explaining the state when the slide bar is in the replacement position. [Figure 5] It is a view for explaining the state when the slide bar is in the screen operation position. [Figure 6] It is a view for explaining the case where the main body step surface is formed by eccentric machining. [Figure 7] It is a view for explaining the case where the recess forming the main body step surface has a constant depth over the entire circumferential direction. [Figure 8] It is a view for explaining the bar main body portion in the second embodiment. [Figure 9] It is a view for explaining the auxiliary step surface in the second embodiment. [Figure 10] It is a view for explaining the relationship between the bar main body portion, the joint, and the hydraulic cylinder in the third embodiment. [Figure 11] It is a view for explaining a modification example when the main body step surface forms an acute-angled corner portion. [Figure 12]This diagram illustrates a modified example where the auxiliary stepped surface forms an acute-angled corner. [Figure 13] This is a schematic cross-sectional view of a conventional screen changer. [Modes for carrying out the invention]

[0030] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

[0031] (First Embodiment) The screen changer according to this embodiment is installed in a filtration device located at the outlet side of a resin kneader or extruder and at the inlet side of a molding machine such as a pelletizer, and is used to remove foreign matter contained in the molten resin sent out from the resin kneader or extruder. As shown in Figures 1 to 3, the screen changer 10 comprises a body 11, a slide bar 12, and a hydraulic cylinder 13.

[0032] The body 11 is provided with a resin flow passage 18 through which molten resin R (see Figure 4) flows, and an insertion hole 20 through which the slide bar 12 is inserted. The insertion hole 20 intersects with the middle portion of the resin flow passage 18. In the resin flow passage 18, the portion located on one side of the insertion hole 20 communicates with the outlet of upstream equipment such as a kneader and an extruder (not shown), and the portion located on the other side of the insertion hole 20 communicates with the inlet of downstream equipment such as a pelletizer and a molding machine (not shown). Therefore, molten resin R flows through the resin flow passage 18 from one side to the other. Hereinafter, the portion of the resin flow passage 18 located on one side (upstream) of the insertion hole 20 will be referred to as the upstream hole 18a, and the portion located on the other side (downstream) of the insertion hole 20 will be referred to as the downstream hole 18b. The molten resin R flows through the resin flow passage 18 from the upstream hole 18a to the downstream hole 18b under pressure from the upstream equipment.

[0033] The body 11 is provided with two through holes 20, one above and one below, and the resin flow passage 18 has two upstream holes 18a and two downstream holes 18b that intersect these upper and lower through holes 20.

[0034] The slide bar 12 is fitted into the insertion hole 20 so as to be slidable while maintaining a sealed state (a state in which the molten resin R does not penetrate into the gap between the slide bar 12 and the inner surface of the insertion hole 20, nor does the molten resin R flow out from the gap) so that the molten resin R does not leak out of the body 11 during filtration. Since there are two insertion holes 20, one slide bar 12 is fitted into each insertion hole 20.

[0035] The slide bar 12 has a round bar body portion 22 with a constant outer diameter along its longitudinal direction. A communication hole 22a is provided at one end (tip) of the bar body portion 22, penetrating in a direction perpendicular to the longitudinal direction of the bar body portion 22, and the screen 24 is held in this communication hole 22a. In other words, the slide bar 12 has a bar body portion 22 and a screen 24. Although only the screen 24 of the upper slide bar 12 is shown in Figure 2, a screen 24 is also provided on the lower slide bar 12.

[0036] The screen 24 is made of a metal member with multiple small holes or a mesh-like structure to filter impurities from the molten resin R, and is detachably installed in the communication hole 22a. Therefore, when the filtration capacity of the screen 24 decreases, it can be replaced with a new screen 24.

[0037] The hydraulic cylinder 13 is a power source for sliding the slide bar 12 along the insertion hole 20. As shown in Figure 3, the hydraulic cylinder 13 has a cylinder body 13a and a rod 13b that moves back and forth relative to the cylinder body 13a and is connected to the other end (base end 12a) of the slide bar 12. The cylinder body 13a is attached to a bracket plate 27 positioned at a predetermined distance from the body 11 via a tie rod 26. The rod 13b is positioned to extend from the cylinder body 13a toward the slide bar 12.

[0038] The body 11 is provided with two slide bars 12 corresponding to the two through holes 20, and therefore two hydraulic cylinders 13 are provided to correspond to each slide bar 12. However, the body 11 is not limited to having two through holes 20; it may also have one through hole 20, or three or more through holes 20. In that case, the number of slide bars 12 and hydraulic cylinders 13 will also be changed according to the number of through holes 20.

[0039] The hydraulic cylinder 13 is configured to slide the slide bar 12 between a screen operating position and a replacement position. The screen operating position is the position where the screen 24 is aligned with the resin flow passage 18, and the replacement position is the position shown in Figure 3 where the screen 24 is exposed to the outside of the body 11. When filtering the molten resin R with the screen 24, the hydraulic cylinder 13 moves the slide bar 12 to the screen operating position, and when replacing the screen 24, it moves the slide bar 12 to the replacement position. Here, the direction in which the slide bar 12 moves from the screen operating position to the replacement position is called the extraction direction, and the opposite direction is called the return direction (see Figure 4).

[0040] In this embodiment, since two slide bars 12 are provided, even when one screen 24 is replaced, the other slide bar 12 is positioned in the screen operating position and filtration is performed. Therefore, the screen 24 can be replaced without stopping the flow of molten resin R.

[0041] When the slide bar 12 is in the screen operating position, one side of the slide bar 12 located inside the body 11 (for example, the part around the screen 24) is at approximately the same temperature as the molten resin R (for example, 100°C to 300°C). On the other hand, the other side of the slide bar 12 that is exposed to the outside of the body 11 (the part closer to the base end 12a) is at approximately room temperature. Therefore, when the slide bar 12 is filtering the molten resin R, thermal expansion occurs at one side, resulting in a difference in outer diameter between the one side and the other side. Furthermore, since the outer diameter of the bar body 22 and the inner diameter of the insertion hole 20 are designed to maintain a sealed state at the temperature of the molten resin R flowing through the resin passage 18, the outer diameter of the other side, which is at room temperature, is slightly smaller than the inner diameter of the insertion hole 20. Therefore, as shown in Figure 4, when the slide bar 12 is switched from the screen operating position to the replacement position, the other side of the slide bar 12 enters the insertion hole 20, resulting in a gap 29 between the other side and the inner surface of the insertion hole 20.

[0042] Even when one slide bar 12 is in the replacement position, the other slide bar 12 is in the screen operation position, and molten resin R is supplied from the upstream equipment, so pressure from the molten resin R acts on the upstream hole 18a of the resin flow passage 18. At this time, on the side of the slide bar 12 that is in the replacement position, a gap 29 is created between the inner circumferential surface of the insertion hole 20 and the outer circumferential surface of the slide bar 12 that has been exposed to room temperature, so molten resin R may flow into the gap 29. If the slide bar 12 is slid while molten resin R is present in the gap 29, contact scratches may occur on the inner circumferential surface of the insertion hole 20 or the outer circumferential surface of the bar body 22, or the slide bar 12 may become stuck. It is thought that such problems occur due to the interaction between the resin, which has cooled and hardened in a wedge-like shape due to the outer circumferential surface that has been exposed to room temperature, and the sliding motion of the slide bar 12.

[0043] In order to reduce the amount of molten resin R present in the gap 29, the screen changer 10 of this embodiment is provided with a stepped surface 31 on the outer circumferential surface of the bar body 22. That is, when the slide bar 12 slides in the return direction from the replacement position to the screen operating position, the stepped surface 31 acts to scrape out at least a portion of the molten resin R present in the gap 29 to the outside of the body 11.

[0044] The stepped surface 31 of the main body is located on the return side of the opening 32 of the upstream hole 18a leading to the insertion hole 20, and is also located inside the insertion hole 20, when the bar body 22 is in the replacement position shown in Figure 4. In other words, the stepped surface 31 of the main body is located between the opening 32 of the upstream hole 18a and the end 11a of the body 11 on the return side.

[0045] The inner circumferential end of the stepped surface 31 of the main body is connected to a bottom surface 33 that extends in the axial direction of the bar body 22 at a position on the inner circumferential side of the outer circumferential surface of the bar body 22. The stepped surface 31 and the bottom surface 33 together form a recess 34 that is stepped inward from the outer circumferential surface of the bar body 22. This increases the gap width between the inner circumferential surface of the insertion hole 20 and the outer circumferential surface of the bar body 22.

[0046] In order to facilitate the flow of molten resin R from the upstream hole 18a into this recess 34, it is preferable that the distance from the edge 18c of the opening 32 of the upstream hole 18a on the return direction side to the main body stepped surface 31 when in the replacement position be set to half or less (or 1 / 3 or less or 1 / 4 or less) of the distance from the edge 18c of the opening 32 of the upstream hole 18a on the return direction side to the end 11a of the body 11 on the return direction side. Alternatively, the distance from the edge 18c of the opening 32 of the upstream hole 18a on the return direction side to the main body stepped surface 31 when in the replacement position may be set to a range of 5% to 30% of the outer diameter of the bar body 22.

[0047] As shown in Figure 5, when the slide bar 12 slides from the replacement position to the screen operation position, the stepped surface 31 of the main body scrapes out the molten resin R present in the recess 34 to the outside of the body 11. That is, when the molten resin R hardens at the stepped portion between the outer peripheral surface and the bottom surface 33 of the bar body portion 22, this hardened resin is held at the stepped portion and carried out to the outside of the body 11 along with the slide bar 12. The resin carried out to the outside of the body 11 is removed from the slide bar 12 by the worker's cleaning work. Therefore, the amount of molten resin R remaining in the gap 29 between the inner peripheral surface of the insertion hole 20 and the outer peripheral surface of the bar body portion 22 can be reduced.

[0048] As shown in Figure 6, the main body stepped surface 31 is formed by machining only a portion of the outer circumferential surface of the bar body portion 22. Specifically, when viewed in the axial direction, the main body stepped surface 31 is provided on the side of the outer circumferential surface of the bar body portion 22 facing the upstream hole portion 18a, while it is not provided on the side facing the downstream hole portion 18b. That is, the molten resin R flowing from the upstream hole portion 18a into the gap 29 is mainly located on the upstream hole portion 18a side in the circumferential direction of the outer circumferential surface. For this reason, the main body stepped surface 31 is provided on the side of the outer circumferential surface of the bar body portion 22 facing the upstream hole portion 18a. Note that the main body stepped surface 31 may be formed over the entire circumferential surface of the outer circumferential surface of the bar body portion 22. However, it is preferable that the slide bar 12 is not provided on the side facing the downstream hole 18b, in order to alleviate the contact pressure when the slide bar 12 is pressed against the inner circumferential surface of the insertion hole 20 on the downstream hole 18b side by the molten resin R mainly present on the upstream hole 18a side.

[0049] In the example shown in Figure 6, the main body stepped surface 31 is formed by eccentric machining, so the depth of the recess 34 formed by the main body stepped surface 31 is deepest in the circumferential center of the main body stepped surface 31 and shallowest at both ends in the circumferential direction. However, the main body stepped surface 31 is not limited to this shape, and as shown in Figure 7, it may be formed by machining so that the depth of the recess 34 is constant over the entire circumferential surface of the main body stepped surface 31.

[0050] As described above, in the screen changer 10 according to this embodiment, when the slide bar 12 is in the replacement position, molten resin R may flow from the upstream hole 18a of the resin flow passage 18 between the inner circumferential surface of the insertion hole 20 and the outer circumferential surface of the bar body portion 22 of the slide bar 12. However, when the slide bar 12 slides from the replacement position to the screen operating position, this molten resin R is scraped out of the body 11 by the stepped surface 31 of the bar body portion 22. Therefore, it is possible to prevent molten resin R from remaining between the inner circumferential surface of the insertion hole 20 and the slide bar 12, or to reduce the amount of molten resin R remaining between the inner circumferential surface of the insertion hole 20 and the slide bar 12. Consequently, the possibility of the slide bar 12 becoming stuck can be reduced.

[0051] Furthermore, in this embodiment, the main body stepped surface 31 is formed on a portion of the outer circumferential surface of the bar body 22, excluding the side facing the downstream hole 18b. Therefore, compared to the case where the main body stepped surface 31 is formed over the entire circumference of the outer circumferential surface of the bar body 22, the contact area between the bar body 22 and the body 11 is increased on the downstream hole 18b side. As a result, the contact pressure on the downstream hole 18b side is reduced. In addition, even if the bar body 22 is pressed due to the presence of molten resin R mainly on the upstream hole 18a side, there is no step on the side of the outer circumferential surface of the bar body 22 facing the downstream hole 18b, thus preventing stress concentration at the step.

[0052] (Second Embodiment) As shown in Figures 8 and 9, in the second embodiment, an auxiliary stepped surface 40 is further provided. Note that the same reference numerals are used for the same components as in the first embodiment, and their detailed descriptions are omitted.

[0053] In the first embodiment, the recess 34, formed by the main body stepped surface 31 and the bottom surface 33, extends to the end (base end 12a) on the return direction side of the bar body 22. In contrast, in the second embodiment, the recess 34 extends to the axial middle part of the bar body 22. That is, the bar body 22 includes a main body 42 on which the recess 34 is provided, and an extension 43 extending axially from the end of the main body 42 on the return direction side. The extension 43 has a smaller diameter than the main body 42, and an auxiliary stepped surface 40 is formed by the stepped surface that forms the boundary between the main body 42 and the extension 43. A second recess 44, which is recessed more than the recess 34, is formed by the auxiliary stepped surface 40 and the outer circumferential surface of the extension 43. Therefore, a gap with a width larger than the gap width between the outer circumferential surface of the bar body portion 22 formed by the main body stepped surface 31 and bottom surface 33 and the inner circumferential surface of the insertion hole 20 is formed between the outer circumferential surface of the extension portion 43 (outer circumferential surface of the bar body portion 22) and the inner circumferential surface of the insertion hole 20.

[0054] The auxiliary stepped surface 40 is located between the opening 32 of the upstream hole 18a and the end 11a of the body 11 on the return direction side when the slide bar 12 is in the replacement position. The auxiliary stepped surface 40 and the second recess 44 are formed over the entire circumferential surface of the outer circumferential direction of the bar body portion 22.

[0055] Therefore, in this embodiment, the stepped surface 31 of the main body is formed by machining only on a part of the circumferential direction of the outer surface of the bar body portion 22, thereby suppressing an increase in the contact pressure between the body 11 and the slide bar 12 on the side facing the downstream hole portion 18b. However, this limits the amount of molten resin R that can be scraped out, so in order to suppress this, an auxiliary stepped surface 40 is added that extends over the entire circumferential direction of the outer surface of the bar body portion 22. As a result, the molten resin R present on the downstream hole portion 18b side of the gap 29 between the inner surface of the insertion hole 20 and the outer surface of the bar body portion 22 can also be scraped out by the auxiliary stepped surface 40. This increases the amount of molten resin R that can be scraped out.

[0056] Furthermore, the auxiliary stepped surface 40 forms a gap between the outer surface of the extension portion 43 and the inner surface of the insertion hole 20 that is larger than the gap width between the outer surface of the bar body portion 22 formed by the main stepped surface 31 and the bottom surface 33 and the inner surface of the insertion hole 20. This makes it easier for a portion of the molten resin R that has flowed into the recess 34 formed by the main stepped surface 31 and the bottom surface 33 to flow into the second recess 44 formed by the auxiliary stepped surface 40 and the extension portion 43. Therefore, the amount of molten resin R that can be scraped out can be further increased.

[0057] The other configurations, functions, and effects will not be described here, but the description of the first embodiment can be applied to the second embodiment.

[0058] (Third embodiment) In the first embodiment, the rod 13b of the hydraulic cylinder 13 is directly connected to the base end 12a of the slide bar 12. In contrast, in the third embodiment, as shown in Figure 10, a joint 47 is provided to connect the bar body 22 and the hydraulic cylinder 13. Here, the same reference numerals are used for components that are the same as those in the first and second embodiments, and their detailed descriptions are omitted.

[0059] The joint 47 is connected to the end face 22b of the return-direction end (base end 12a) of the bar body 22 using a fastener 49. The rod 13b of the hydraulic cylinder 13 is connected to the joint 47.

[0060] The joint 47 has an outer circumferential surface that is spaced further apart from the inner circumferential surface of the through hole 20 than the bottom surface 33 that constitutes the recess 34 in the bar body 22. As a result, a space with a gap width larger than the gap width between the bottom surface 33 of the recess 34 and the inner circumferential surface of the through hole 20 is formed between the inner circumferential surface of the through hole 20 and the outer circumferential surface of the joint 47. In this way, the end face 22b on the return direction side of the bar body 22 functions as an auxiliary stepped surface 40. That is, the second recess 44 is formed by the end face 22b on the return direction side of the bar body 22 and the outer circumferential surface of the joint 47. The second recess 44 is formed over the entire circumferential direction of the bar body 22.

[0061] Therefore, in the third embodiment, as in the second embodiment, the molten resin R present on the downstream hole 18b side of the gap 29 between the inner circumferential surface of the insertion hole 20 and the outer circumferential surface of the bar body portion 22 can also be scraped out by the auxiliary stepped surface 40. This makes it possible to increase the amount of molten resin R that can be scraped out.

[0062] Furthermore, the joint 47 forms a space between itself and the inner surface of the insertion hole 20 that has a larger gap width than the gap width between the outer surface of the bar body portion 22 formed by the main body stepped surface 31 and bottom surface 33 and the inner surface of the insertion hole 20. This makes it easier for a portion of the molten resin R that has flowed into the recess 34 formed by the main body stepped surface 31 and bottom surface 33 to flow into the second recess 44 formed by the auxiliary stepped surface 40 and the joint 47. Therefore, the amount of molten resin R that can be scraped out can be further increased.

[0063] In addition, a second recess 44 is formed in the joint 47, which is recessed one step from the bottom surface 33 of the recess 34, so that the end face 22b on the return direction side of the bar body portion 22 functions as an auxiliary stepped surface 40. However, the dimensions of the joint 47 are not limited to this. For example, the main body stepped surface 31 may be formed in the shape shown in Figure 7, and the depth of the recess 34 may be set so that the outer peripheral surface of the joint 47 is flush with the bottom surface 33 of the recess 34. Alternatively, the main body stepped surface 31 may be formed in the shape shown in Figure 6, and the depth of the recess 34 may be set so that the outer peripheral surface of the joint 47 coincides with the inner end of the circumferential center of the main body stepped surface 31. The other configurations, functions, and effects will not be described here, but the description of the first embodiment can be applied to the second embodiment.

[0064] (Other embodiments) It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The present invention is not limited to the embodiments described above, and various modifications and improvements are possible without departing from its spirit.

[0065] In the first to third embodiments, the main body stepped surface 31 is perpendicular to the outer circumferential surface of the bar body portion 22, but is not limited to this. As shown by the dashed line in Figure 11, the main body stepped surface 31 may be connected to the outer circumferential surface of the bar body portion 22 at an acute angle with respect to the outer circumferential surface of the bar body portion 22. That is, the corner portion 51 formed by the outer circumferential surface of the bar body portion 22 and the main body stepped surface 31 may be acute. In this case, the main body stepped surface 31 is inclined such that the outer circumferential edge connected to the outer circumferential surface of the bar body portion 22 is located on the return direction side than the inner circumferential edge connected to the bottom surface 33 of the recess 34.

[0066] In this configuration, when the corner portion 51 formed by the outer circumferential surface of the bar body portion 22 and the stepped surface 31 of the main body comes into contact with the inner circumferential surface of the insertion hole 20 in the body 11, the contact pressure between the body 11 and the corner portion 51 can be reduced. Therefore, the possibility of contact scratches or sticking of the slide bar 12 can be further reduced. If the corner portion 51 formed by the outer circumferential surface of the bar body portion 22 and the stepped surface 31 of the main body is obtuse, it becomes difficult to scrape out the molten resin R, so it is preferable that the corner portion 51 be right-angled or acute-angled.

[0067] Furthermore, as shown in Figure 12, the auxiliary stepped surface 40 may also be connected to the outer circumferential surface of the bar body portion 22 (or the outer circumferential surface of the main body portion 42) at an acute angle with respect to the outer circumferential surface of the bar body portion 22. That is, the corner portion 53 formed by the outer circumferential surface of the bar body portion 22 (or the outer circumferential surface of the main body portion 42) and the auxiliary stepped surface 40 may be at an acute angle. In this case, the auxiliary stepped surface 40 is inclined such that the outer circumferential edge of the bar body portion 22 connected to the outer circumferential surface of the main body portion 42 is located on the side in the return direction than the inner circumferential edge connected to the outer circumferential surface of the extension portion 43. Alternatively, the auxiliary stepped surface 40 is inclined such that the outer circumferential edge of the bar body portion 22 connected to the outer circumferential surface is located on the side in the return direction than the inner circumferential edge connected to the outer circumferential surface of the joint 47. [Explanation of symbols]

[0068] 10: Screen changer 11: Body 12: Slide bar 13: Hydraulic cylinder 18:Resin flow path 18a:Upstream hole 18b: Downstream hole 20: Through hole 22: Bar body 22b: End face 24: Screen 29: Gap 31: Stepped surface of the main body 32 :Aperture 40: Auxiliary step surface 42: Main body 47: Joint 51: Corner part 53: Corner part R: Molten resin

Claims

1. A screen changer, which is a filtration device for molten resin, A body provided with resin flow passages and insertion holes that intersect with each other, A slide bar having a screen and a bar body, and slidably mounted in the insertion hole, The system includes a hydraulic cylinder which is a power source for sliding the slide bar, The hydraulic cylinder is configured to slide the slide bar between a screen operating position in which the screen is located within the resin flow passage and a replacement position in which the screen is exposed to the outside of the body. The resin flow passage has an upstream hole located upstream of the insertion hole in the direction of molten resin flow, and a downstream hole located downstream of the insertion hole. When the direction of movement of the slide bar from the screen operating position to the replacement position is defined as the removal direction, and the opposite direction is defined as the return direction, The bar body portion has a stepped body surface formed to be recessed from the outer circumferential surface of the bar body portion in a region located within the insertion hole and on the return direction side of the opening of the upstream hole portion in the insertion hole when the slide bar is in the replacement position, and the stepped body surface scrapes out at least a portion of the molten resin that has flowed out from the upstream hole portion to the outside of the body when the slide bar slides from the replacement position to the screen operating position.

2. The screen changer according to claim 1, wherein the stepped surface of the main body is formed on a part of the circumferential direction of the outer surface of the bar body, excluding the side facing the downstream hole.

3. The slide bar further has an auxiliary stepped surface located on the return direction side of the main body stepped surface, The screen changer according to claim 2, wherein the auxiliary stepped surface is formed over the entire circumferential surface of the outer circumferential direction of the bar body portion.

4. The screen changer according to claim 3, wherein the auxiliary stepped surface forms a gap between the outer surface of the bar body and the inner surface of the insertion hole that is larger than the gap width between the outer surface of the bar body formed by the main stepped surface and the inner surface of the insertion hole.

5. A screen changer, which is a filtration device for molten resin, A body provided with resin flow passages and insertion holes that intersect with each other, A slide bar having a screen and a bar body, and slidably mounted in the insertion hole, A hydraulic cylinder which is a power source for sliding the slide bar, A joint having a smaller diameter region than the main body of the bar and connecting the main body of the bar and the hydraulic cylinder, Equipped with, The hydraulic cylinder is configured to slide the slide bar between a screen operating position in which the screen is located within the resin flow passage and a replacement position in which the screen is exposed to the outside of the body. The resin flow passage has an upstream hole located upstream of the insertion hole in the direction of molten resin flow, and a downstream hole located downstream of the insertion hole. When the direction of movement of the slide bar from the screen operating position to the replacement position is defined as the removal direction, and the opposite direction is defined as the return direction, The bar body portion of the screen changer has a stepped surface that is recessed from the outer surface of the bar body portion in a region located within the insertion hole and on the return direction side of the opening of the upstream hole portion of the insertion hole when the slide bar is in the replacement position.

6. The screen changer according to claim 5, wherein the stepped surface of the main body is formed on a part of the circumferential direction of the outer circumferential surface of the bar body, excluding the side facing the downstream hole.

7. The end face of the bar body portion to which the hydraulic cylinder is coupled functions as an auxiliary stepped surface located on the return direction side of the main body stepped surface. The screen changer according to claim 6, wherein the auxiliary stepped surface is formed over the entire circumferential surface of the outer circumferential direction of the bar body portion.

8. The screen changer according to claim 7, wherein the auxiliary stepped surface forms a gap between the outer surface of the joint and the inner surface of the insertion hole that is larger than the gap width between the outer surface of the bar body formed by the main stepped surface and the inner surface of the insertion hole.

9. The screen changer according to claim 1 or claim 5, wherein the corner portion formed by the outer peripheral surface of the bar body and the stepped surface of the body is acute.

10. The screen changer according to claim 3 or claim 7, wherein the corner portion formed by the outer peripheral surface and the auxiliary stepped surface of the bar body is acute.

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