JPH09131765A - Molding equipment of rubber member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively suppress the development of weldlines and orientational property by a comparatively simple structure. SOLUTION: A tubular cavity part 16 is composed of a plurality of molds including a first mold 12 and a second mold 14. At the same time, a plurality of gate parts 11 are radially formed at positions inward away from the extension line of the cavity part 16. At the same time, the cavity part 16 and a plurality of the gate parts are connected with each other through nearly L- shaped connecting parts 17. By forming a well part of rubber member, a throttled part 19, at which a course of flowing rubber member is contracted, and an enlarged part 20, at which the course is enlarged, in the order named from the gate part side at each connecting part 17, the development of weldlines and orientational property in a molded rubber member can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber member molding apparatus, and more particularly to an improvement of a cylindrical conductive rubber member molding apparatus used as a charging member of an electrophotographic copying machine.

[0002]

2. Description of the Related Art Generally, an electrophotographic copying machine of this kind is composed of, for example, a photosensitive drum, a developing drum, a fixing drum, and various electrodes around the photosensitive drum. In copying by this apparatus, first, when a charge is applied to a photosensitive drum by a charging electrode and exposure is performed, an electrostatic latent image is formed on the drum by the charge according to the intensity of light, and the opposite polarity charge is formed there. The toner is supplied and attached from the developing drum to form a visible image,
Copying is performed by transferring this onto the conveyed paper by the charging of the transfer electrode.

By the way, in the transfer portion of the above-mentioned apparatus, for example, a rubber member, carbon black (channel black or furnace black), metal powder, carbon fiber, oxides such as zinc oxide and aluminum oxide, and the like. A conductive rubber member obtained by appropriately mixing an electric resistance adjusting agent such as a reoxidant is used, and is molded by, for example, a molding device shown in FIGS. 5 to 8.

In the figure, reference numeral 1 is a first plate, for example, a spindle-shaped sprue 2 is formed so as to penetrate through a central portion thereof. An injection system including an injection nozzle of a rubber member (not shown) is coupled to one opening 2a of the sprue 2, and the other opening 2b is provided with, for example, eight runners 3 communicating with the opening. -Radially formed along the ting surface. This first play
The second plate 4 is fixed to the runner portion side of the runner 1, and eight holes 5 are formed in the portion corresponding to the tip portion of the runner portion 3. A temperature adjusting mechanism is provided inside the second plate 4 for controlling the conductive rubber member to, for example, 70 to 100 ° C., which does not cause a crosslinking reaction. Specifically, for example, it is configured by an oil circulation path set to a predetermined temperature.

The above-mentioned second plate 4 has a third plate.
Toe 6 is fixed, and hole 7 is formed in a portion corresponding to hole 5. The third plate 6 is made of, for example, a heat insulating member such as asbestos, and is for alleviating the thermal influence from the first and second molds described later. A fourth plate 8 is fixed to the third plate 6, and a hole 9 is formed in a portion corresponding to the hole 7. In addition, inside the plate 8, first and
A cooling mechanism is provided to mitigate the thermal influence of the second mold on the second plate 4. Specifically, for example, it is configured by a circulation path through which air passes. A bushing 10 is fitted in each of the holes 5, 7, 9 and a gate portion 11 for guiding the conductive rubber member is formed inside the bushing 10.

The first plate 1 is attached to the above-mentioned fourth plate 8.
2 is fixed, and the gate portion 11 of the fourth plate 8 is fixed.
A gate portion (11) is formed in the portion corresponding to. A cylindrical hollow portion 13 is formed on the extension of the gate portion 11.
Are formed. In the hollow portion 13 of the first mold 12, a substantially cylindrical second mold 14 is arranged so that a predetermined space is formed in the peripheral portion thereof. This second
The mold 14 is fixed to the third mold 15 and is configured to be movable in the axial direction with respect to the first mold 12. A substantially cylindrical cavity portion 16 is formed in a portion surrounded by the molds 12, 14, and 15. Then, these molds have a built-in heating means for promoting the crosslinking reaction of the conductive rubber member.
Controlled to ~ 170 ° C.

Molding of a cylindrical conductive rubber member by this molding apparatus is performed as follows. First, the first mold 12
Then, the second and third molds 14 and 15 are clamped so that the second mold 14 is housed in the hollow portion 13 of the first mold 12. As a result, the cavity portion 16 is formed in the portion surrounded by each mold. In this state, the second plate 4 has a temperature at which the conductive rubber member does not undergo a crosslinking reaction (for example, 70 ° C.), and each mold has a temperature at which the crosslinking reaction is accelerated (for example, 150 to 170 ° C.). Is set to. Next, the conductive rubber member in a fluid state is attached to the sprue 2, runner portion 3, gate portion 11 of the first plate 1.
It is injected into the cavity portion 16 via. After the injection, it is cured by heating from each mold, and a cylindrical conductive rubber member is molded. The conductive rubber member present in the gate portion 11 of the second plate 4 maintains fluidity because it does not undergo a crosslinking reaction. Next, the second and third molds 14 and 15 are moved to separate the second mold 14 from the first mold 12. The cured conductive rubber member is taken out from the cavity portion 16 while being stuck to the second mold 14. At this time, the gates of the third and fourth plates 6 and 8
The conductive rubber member in the cured state existing in the belt portion 11 is taken out together with the conductive rubber member in the cavity portion 16. After that, the tubular conductive rubber member is removed from the second mold 14 and the gate portion is removed to complete the molding.

[0008]

The conductive rubber member is adjusted to have a desired electric resistance by the above-mentioned electric resistance adjusting agent. The shape of the gate portion, the number of gate portions, and the rubber are used. Weld lines and orientation may occur in the cylindrical conductive rubber member formed by the fluidity of the member, and the electric resistance value may become non-uniform.

As described above, the non-uniform electric resistance value is caused by the reversal development of the development on the photosensitive drum, and in the apparatus employing the contact belt transfer or roller transfer, the visible image on the photosensitive drum is transferred to the transfer member. When the (toner image) is transferred, the transfer current becomes unstable because the volume resistivity of the toner is in the region of 10 ⁶ to 10 ¹⁰ Ω · cm, which is difficult to stabilize in the semiconductive region level. Image defects are likely to occur.

In particular, in the case of the gate structure shown in FIG. 8, since the bottom inner wall surface 11a of the gate portion 11 is formed at a right angle to the extension direction of the cavity portion 16, the weld is performed. Lines are likely to occur, the orientation of the rubber member changes at the weld line portion, and the electric resistance tends to be non-uniform, resulting in a problem that a high-quality product cannot be obtained.

Therefore, as shown in FIG. 9, the inner wall surface 11a
Although an attempt was made to form the inclined surface of the rubber member, although the flow of the rubber member was improved, the weld line was still generated and the uniformity of the electric resistance value could not be improved.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a rubber member molding apparatus capable of effectively suppressing generation of weld lines and orientation with a relatively simple structure.

[0013]

Therefore, in order to achieve the above-mentioned object, the present invention forms a cylindrical cavity portion with a plurality of molds including a first mold and a second mold, and The gate portion is formed at a position displaced inward from the extension line of the cavity portion, and the cavity portion and the gate portion are connected through a substantially L-shaped connecting portion. Second
In the invention, the connecting portion is formed with a reservoir portion of the rubber member and a throttle portion in which the flow path of the rubber member is reduced in order from the gate portion side.

According to a third aspect of the present invention, a cylindrical cavity portion is formed by a plurality of molds including the first and second molds, and the cavity portion is formed inward from the extension line of the cavity portion. A plurality of gate portions are radially formed at deviated positions, and the cavity portion and the plurality of gate portions are connected via a substantially L-shaped connecting portion, and the gate portion is connected to the connecting portion. The present invention is characterized in that a reservoir portion of the rubber member, a narrowed portion in which the flow path of the rubber member is reduced, and an enlarged portion in which the passage is expanded from the narrowed portion are formed in that order from the side of the rubber member. It is characterized in that the pool portion is arranged on the extension line of the gate portion.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to FIGS. The same parts as those of the conventional example shown in FIGS. 5 to 9 are designated by the same reference numerals, and detailed description thereof will be omitted.

The characteristic part of the present invention is that the first and second molds 1 are
Cylindrical cavity 16 with a plurality of molds including 2, 14
And the gate portion 11 is formed at a position displaced inward from the extension of the cavity portion 16, and the cavity portion 16 and the gate portion 11 are connected to each other in a substantially L-shaped connecting portion 1
That is, they are connected via 7.

The connecting portion 17 is, for example, a rubber member reservoir portion 18 formed on an extension line of the gate portion 11, a narrowing portion 19 in which the flow path of the rubber member is reduced, and a passage extending from the narrowing portion 19. And an enlarged portion 20 in which an inner wall surface 20a is provided with an inclined surface (20a) toward the cavity inlet portion 16a.
It is composed of

According to this embodiment, since the gate portion 11 is formed at a position displaced inward by, for example, about 10 mm from the extension line of the cavity portion 16, the rubber member is separated from the gate portion 11 by the cavity. It becomes a turbulent flow by the time it flows to the part 16. Therefore, no visible weld line is generated in the molded rubber member, and the electric resistance value can be made uniform.

In particular, at the connecting portion 17, the sump portion 1
8, the opening length of the diaphragm portion 19 is a, the length from the center of the gate portion 11 to the inner wall of the cavity portion 16 is L, the horizontal length of the inclined surface 20a is 1, and the connecting portion is If the height of the cavity portion including H is H and the height of the inclined surface 20a including the throttle portion 19 is h, and the following relations are satisfied between them, the rubber member has a large shearing force at the throttle portion 19. The expanded portion 20 mixes them, and the shearing force applied to the rubber member is relaxed by the expanded portion 20 to flow into the cavity portion 16 from the gate portion 11. For this reason, after the mixing of the rubber members is promoted by the narrowed portion 19, the stress applied at that time is relaxed by the enlarged portion 20, so that a tubular conductive rubber member having uniform electric resistance is obtained. It is what is done.

Formula 1 0.45 ≦ a / A ≦ 0.9 Formula 2 0.25 ≦ l / L ≦ 0.6 Formula 3 0.01 ≦ h / H ≦ 0.1 However, in Formula 1, a / When A <0.45, the flow resistance in the throttle becomes large and rubber scoring occurs. On the contrary, when a / A> 0.9, the throttle effect decreases and the electrical resistance of the product becomes uneven. Will occur. In Equation 2, when 1 / L <0.25, the volume of the rubber reservoir becomes small and the shearing force relaxation effect becomes poor, resulting in uneven resistance. Conversely, when 1 / L> 0.6.
In this case, a part of the rubber member flows into the enlarged portion before the narrowed portion approaches the gate portion and the rubber member is filled in the reservoir portion, and a uniform product cannot be obtained. Furthermore, in the formula 3, when h / H <0.01, the volume of the enlarged portion becomes small and the relaxation of the shearing force becomes insufficient, resulting in uneven resistance. Conversely, when h / H> 0.1, the enlargement occurs. The volume of the part becomes too large, and the loss of the rubber member becomes large, resulting in poor economy. Therefore, in order to obtain a high quality product, it is desirable to satisfy the above formula.

FIG. 3 shows another embodiment of the present invention, in which the basic construction is the same as that of the molding apparatus shown in FIGS. A different point is that a plurality of sprues 2 are provided on the first plate 1 and the tip of a runner portion 23 branched from the sprue 22 of the plate 21 is located on each sprue 2. A plurality of groups of gate parts 1 branched from each of the sprues 2 into second to fourth plates 4, 6 and 8.
1 is formed, the first to third molds 12, 14, 15
That is, a plurality of cavities 16 are formed in. According to this structure, a plurality of rubber members can be molded at the same time, and productivity can be improved.

The present invention is not limited to the above-mentioned embodiment at all, and the rubber member can be applied to other than conductive ones, for example, a rubber belt for conveying paper sheets, a rubber roll and the like. Further, the number of gate parts can be set to other than eight. Further, the detailed configuration of the molding apparatus can be appropriately changed in consideration of manufacturability, assemblability, and the like.

[0023]

EXAMPLE Next, the molding apparatus shown in FIGS.
An experimental example using FIG. 9 will be described. First, a rubber member, an electric resistance adjusting agent and the like are mixed based on the mixing ratio shown in FIG. 4 and supplied to the injection system. Fluidity is imparted within the range of 70 to 100 ° C., and a cylindrical conductive rubber member is molded by each molding device. The volume resistivity of 72 portions of the rubber member 5 cm from the upper end is measured at intervals of 5 ° in the circumferential direction, and the maximum value and the minimum value are obtained. As a result of evaluating each molded product from the difference in volume specific resistance value log (Ω _max −Ω _min ), 0.7 is obtained for the product of the present invention by the molding device shown in FIGS. It was 2.3 in Example 1 and 1.8 in Conventional Example 2 using the molding apparatus shown in FIG. This volume specific resistance value difference of 1 or less is excellent in uniformity of electric resistance and is desirable,
It was confirmed that the product of the present invention was further excellent in uniformity.

[0024]

As described above, according to the present invention, the cylindrical cavity portion is formed by a plurality of molds including the first and second molds, and the inner side of the extension line of the cavity portion is inward. Since the gate portion is formed at a position deviated from the position and the cavity portion and the gate portion are connected through a substantially L-shaped connecting portion, the rubber member is injected into the cavity portion in a turbulent state. can do. Therefore, no visible weld line is formed in the molded rubber member. In particular, when it is applied to a conductive rubber member, the occurrence of weld lines and orientation can be suppressed, and the electric resistance value can be made uniform.

Further, by forming a pool portion, a narrowed portion, and an enlarged portion in the connecting portion, it is possible to enhance the uniformity of electric resistance of the conductive rubber member by applying and relaxing the shearing force to the rubber member. In particular, excellent copy images can be obtained when applied to an electrophotographic copying machine.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention.

FIG. 2 is an enlarged view of a connecting portion shown in FIG.

FIG. 3 is a side sectional view showing another embodiment of the present invention.

FIG. 4 is a view showing a mixing ratio of a rubber member.

FIG. 5 is a side sectional view of a conventional example.

FIG. 6 is a bottom view of the first plate shown in FIG.

7 is a sectional view taken along line XX of FIG.

FIG. 8 is an enlarged view of the gate portion shown in FIG.

9 is an enlarged view of another example of the gate portion shown in FIG.

[Explanation of symbols]

 1 1st plate 2,22 sprue 3,23 runner part 4 2nd plate 6 3rd plate 8 4th plate 11 gate part 12 1st metal mold 13 hollow Part 14 Second mold 15 Third mold 16 Cavity part 16a Cavity inlet part 17 Connecting part 18 Reservoir part 19 Drawing part 20 Enlarged part 20a Sloping surface

Claims (4)

[Claims] 1. A cylindrical cavity part is formed by a plurality of molds including a first mold and a second mold, and a gate part is provided at a position displaced inward from an extension line of the cavity part. An apparatus for molding a rubber member, characterized in that it is formed and the cavity portion and the gate portion are connected via a substantially L-shaped connecting portion. 2. The rubber member according to claim 1, wherein the connecting portion is formed with a reservoir portion of the rubber member and a throttle portion having a reduced flow path of the rubber member in this order from the gate portion side. Molding equipment. 3. A cylindrical cavity portion is formed by a plurality of molds including a first mold and a second mold, and a plurality of gates are arranged at positions displaced inward from an extension line of the cavity part. Parts are formed in a radial shape, and the cavity part and a plurality of gate parts are connected to each other through a connecting part having a substantially L shape, and the connecting part has a rubber member pool part from the gate part side, An apparatus for molding a rubber member, characterized in that a narrowed portion in which the flow path of the rubber member is reduced and an enlarged portion in which the path is enlarged from the narrowed portion are sequentially formed. 4. The rubber member molding apparatus according to claim 2, wherein the pool portion of the rubber member is arranged on an extension line of the gate portion.