JP2001030253A - Endless belt and mold structure thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily produce an endless belt of which the peripheral length is 3.2 times or less the width thereof. SOLUTION: The inner mold 13 of a casting mold 10 is set to a split system consisting of a first split mold 56, a toothed mold 55 and a second split mold 56 and split into two parts after molding to demold a product. By this constitution, a core wire-containing endless belt of which the peripheral length is 3.2 times or less the width thereof and which comprises a polyurethane elastomer and has a toothed part provided to the inner peripheral surface thereof can be easily molded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an endless belt having a toothed portion on an inner peripheral surface of a belt main body in which a core wire is buried and having a small ratio between a belt width and a peripheral length, and a metal suitable for molding the same. It concerns the mold structure.

[0002]

2. Description of the Related Art Endless belts are used for power transmission and conveyance. In the endless belts, a core wire is buried in order to ensure dimensional accuracy of the belt circumferential length, and one end of the inner circumferential surface in the width direction is provided. A timing belt having a toothed portion in a portion is also known.

As a method of manufacturing a cored timing belt having a toothed portion on a part of the inner peripheral surface, a core wire and unvulcanized rubber are wound around the inner peripheral surface of a vulcanizing mold. A vulcanization molding method of molding by pressure vulcanization, or a molding method in which a core wire is wound around the inner mold, and a casting material such as liquid rubber is injected and cured between the inner mold and the outer mold to form the molding. It has been known.

[0004] In any of the molding methods, a toothed molded portion for molding the toothed portion is set on the outer peripheral surface of the inner mold in view of the relationship with the embedding position of the core wire for ensuring the accuracy of the circumferential length. In order to make it possible to remove the molded product from the mold, the toothed molding portion is set over the entire length of the inner mold in the mold axial direction, and the endless belt that has been removed is turned over once, leaving the toothed portion. After the other portions were polished and removed to form a flat belt portion, the molded product was again inverted to obtain a finished product.

[0005]

By the way, in recent years, product dimensions have been diversified, and there has been a demand for supply of products having a short circumferential length despite the large belt width. In order to respond to such a demand, when an attempt is made to manufacture a toothed belt with a core having a small ratio between the belt width and the circumference by a conventional manufacturing method, the elongation in the circumferential direction is regulated by the presence of the core. Therefore, a situation has arisen in which the toothed portion cannot be polished upside down after molding.

[0006]

Means for Solving the Problems The present inventors have paid attention to the above-mentioned problems, and have formed a mold structure of an endless belt having a toothed portion on a part of an inner peripheral surface, particularly, a structure of a casting mold. As a result of diligent examination of, a part of the inner mold is equipped with a toothed mold,
If the inner mold has a divided structure with at least one end in the mold axis direction of the toothed molding die as a boundary, one of the surfaces of the rising portion in the mold axis direction of the toothed portion is open at the time of division, It has been found that the belt can be easily removed, and it is not necessary to turn over the toothed portion after molding as in the related art.

The split structure of the inner mold can be applied to the case where the toothed portion is formed on the entire or a part of the inner peripheral surface, but is particularly effective when the toothed portion is formed partially. Also,
In the case where the toothed portion is partially formed, the position and the number of the toothed portion can be applied irrespective of the position and the number of the toothed portion. In general, a toothed portion is formed at the center position in the belt width direction in consideration of the effect and the transmission efficiency. Accordingly, corresponding to this, a form in which the toothed mold is disposed in the central region of the inner mold in the mold axial direction can be exemplified.

[0008] The casting mold structure generally has a deaeration hole formed at an upper side surface of the cavity at a position substantially symmetrical with respect to an injection port formed below, and a control valve for opening and closing the deaeration hole is provided.
At the time of injection of the casting material under pressure, open the deaeration hole and discharge the air in the cavity together with the casting material to the outside,
It is designed to prevent the entrapment of air in the casting material.

[0009] However, in the above mold structure,
Since the injection port is located at one location below the cylindrical cavity and the deaeration hole is also formed only at one location at the top of the cavity, the rising speed of the casting material in the cavity is limited by the injection port at the peripheral surface of the cavity. Side speed increases,
It will rise in an uneven state. Therefore, the casting material easily embraces air, and when the casting material is filled in the entire cavity and the casting material is fused, a so-called flow mark is easily formed.

[0010] The flow mark is based on the fact that the casting material does not rise uniformly in the circumferential direction of the cavity.
First, by forming a ring-shaped groove at the entrance of the cavity communicating with the injection port, and second, by forming a ring-shaped groove at the cavity outlet portion communicating with the overflow hole of the casting material also serving as a deaeration hole. The casting material can be uniformly raised on the peripheral surface of the cavity.

Furthermore, thirdly, by adopting means for closing the overflow hole lightly with a control valve at the time of injection of the casting material under pressure, the flow rate can be reduced as compared with the case where the overflow hole is opened at the time of the injection of the casting material. The mark has been resolved. this is,
It is considered that the compression / expansion motion of the air confined in the cavity works in a direction to promote leveling by the weight of the casting material. The air pressure in this case is 1 kg / cm
Good results were obtained at about 2 (gauge pressure).

As a measure for lightly tightening the control valve, a spring for biasing the control valve in the valve closing direction is provided, and the biasing force is controlled to such an extent that the air pressure can be obtained and the casting material is allowed to overflow. It was set appropriately to the extent of opening.

As the casting material, various materials can be selected according to the use of the endless belt, and chloroprene rubber,
Examples thereof include liquid rubber such as butadiene rubber and liquid thermosetting resin. Above all, a polyurethane elastomer having excellent properties such as mechanical properties, chemical resistance, and abrasion resistance is preferably used as an endless belt.

The above casting mold structure can be applied to any endless belt regardless of the presence or absence of a core wire, but forms an endless belt containing a core wire which is restricted in elongation in the circumferential direction and cannot be turned over. It is preferably applied to a mold structure.

When the core wire is embedded, the core wire may be wound around the cavity surface of the inner mold at the time of casting, the casting material may be injected into the cavity under pressure and hardened, and embedded in the main body of the belt. If the core material is brought into close contact with the cavity surface, the injected material is not completely involved in the core wire, and the core wire may be exposed after molding. Therefore, by forming a plurality of long ridges (so-called pips) in the cavity surface of the inner mold in the belt width direction in parallel at intervals along the cavity surface, the contact between the cavity surface and the core wire is in a point contact state. It is advantageous to prevent the core wire from being exposed if the casting material goes around the groove between the ridges. In this case, if the tooth tip surface of the toothed part is the pip forming position, in the formed toothed part, only a pip mark remains in the tooth space,
Does not affect the performance of the toothed part.

The above casting mold structure is not limited to the one having a small ratio between the belt width and the perimeter, and can be applied to the molding of endless belts of various dimensions. As a result of also examining the relationship between the belt width and the perimeter of difficult endless belts, it was found that when the belt perimeter was less than or equal to 3.2 times the belt width, it was difficult to turn over. Therefore, the above casting mold structure is optimally applied to the manufacture of an endless belt with cored teeth having a belt circumference of 3.2 times or less the belt width.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front view of an endless belt, and FIG. 2 is a plan view of the same. As shown in the figure, the endless belt 1 of the present embodiment has a large number of vacuum through-holes 3 formed in a belt main body 2 made of urethane elastomer in order to convey a photographic printing paper while sucking the photographic printing paper. A core wire 4 made of a cord body such as glass fiber, steel fiber, or aramid fiber is embedded in the belt main body 2, and a toothed portion 5 is provided at the center of the inner peripheral surface of the belt more than other flat belt portions 6. It protrudes inward.

The endless belt 1 has a circumference L equal to or less than 3.2 times the belt width D and is difficult to turn over and reverse after molding.
The circumference is set to 340 mm with respect to mm.

FIG. 3 is a sectional view showing an example of a casting mold structure for molding the endless belt. As shown in FIG.
In the casting mold structure 10, an outer mold 12 and an inner mold 13 are detachably mounted on a bottom plate 11, and a pressure injection means 14 for casting material is provided.

The bottom plate 11 is formed with a fitting hole 16 for fitting the lower small-diameter portion of the inner mold 13 and a ring-shaped peripheral wall 17 for fitting the outer mold 12 around the hole. A lower clamp mechanism 18 for fixing the outer mold 12 is provided at two or three outer positions.

The lower clamp mechanism 18 has a clamp piece 19 having a flange-shaped clamp at the upper end of the cylindrical boss.
And a bolt hole 2 formed in the bottom plate 11 through the boss.
0, and a flange 22 formed on the lower outer surface of the outer die 12 is sandwiched between the clamp piece 19 and the upper surface 11a of the bottom plate 11 to thereby form the outer die 1
2 is fixed to the bottom plate 11. A ring-shaped groove 26 is formed on the inner upper surface of the peripheral wall 17 of the bottom plate 11 at a position below the cavity 25 formed between the outer die 12 and the inner die 13.
7 is formed to penetrate downward.

The outer mold 12 has a cylindrical shape, and the flange 22 is formed on the lower outer side. An O-ring 29 for sealing between the outer mold 12 and the inner surface of the peripheral wall 17 is provided on the lower outer peripheral portion. Installed. A ring-shaped recess 30 is formed in the lower inner peripheral surface of the outer mold 12, and cooperates with the ring-shaped groove 26 of the bottom plate 11 to make the casting material easily wrap around in the circumferential direction. In the upper part of the outer mold 12, an overflow hole 32 which also serves as a tapered deaeration hole whose diameter is expanded outward is penetrated at a position substantially symmetrical with the injection port 27, and correspondingly, the overflow hole 32 is formed in the inner peripheral surface of the outer mold 12. Is formed with a ring-shaped concave portion 33 for facilitating the circulation of air and the casting material in the circumferential direction.

FIGS. 4A and 4B are enlarged views of the control valve, wherein FIG. 4A shows the valve open state, and FIG. 4B shows the valve closed state. As shown in FIG. 4, outside the overflow hole 32, a control valve 34 for opening and closing the hole is provided. The control valve 34 has a wedge-shaped valve body 3 at the tip of a rod-shaped member 35 having a thread formed on the outer peripheral surface.
Numeral 6 is provided so as to be movable in a radial direction orthogonal to the mold axis, and a rod-shaped member 35 is screwed into a bracket 37 provided on the outer peripheral portion of the outer die 12 so as to be movable in the radial direction.

A guide rod 38 which is movable inside the rod 35 is fixed to the rear end of the valve body 36. A coil spring 39 provided in the recess 35a at the front end of the rod 35 is provided with a bottom surface of the recess and the valve body 36. , And urges the valve body 36 in the valve closing direction (radially inward). A stopper 40 is fixed to the rear end of the guide rod 38. A knob 42 also serving as a stopper is fixed to the rear end of the rod-shaped member 35.

As shown in FIG. 3, an upper clamp mechanism 45 for fixing the inner mold 13 is provided above the outer mold 12. The upper clamp mechanism 45 has an inner mold 13
And a clamp bolt 50 which is screwed into a bolt hole 49 of a bracket 48 fixed to the outer peripheral portion of the outer die 12 through a through hole 47 of the clamp piece 46. .

As shown in FIG. 3, the inner die 13 includes a cylindrical second split die 54 for forming the flat belt portion 6 and a toothed portion 5 from the lower side to the upper side with respect to the center axis 53. A cylindrical toothed forming die 55 to be formed, a cylindrical first split die 56 to form the flat belt portion 6, and a cylindrical fixing nut 57 for fixing these to the central shaft 53 are sequentially fitted. It has a structure.

The toothed forming die 55 is formed with an irregular tooth shape surrounding the toothed portion 5 to form the tooth shape of the toothed portion 5, and has an outer diameter smaller than that of the first and second split dies 56 and 54. It has a small diameter. Both end faces in the axial direction of the toothed mold 55 are
Tapered surfaces 55a and 55b tapering toward the central axis are formed, and these tapered surfaces and end tapered surfaces 54a and 56 of the first split mold 56 and the second split mold 54 are formed.
a is closely related. The toothed forming die 55 is provided with a plurality of mounting bolts 60 that penetrate the toothed forming die 55 from the bottom side and reach the first split die 56 at a plurality of locations in the circumferential direction.
Is connected to the first split mold 56.

The second split mold 54 penetrates the first split mold 56 and the toothed mold 55 in the axial direction of the mold, and the second split mold 5
4 and is connected to the first split mold 56 and the toothed mold 55 by mounting bolts 62. The second split die 54 and the toothed forming die 55 are positioned by positioning pins 65 provided around the second split die 54 and the toothed forming die 55.

The fixing nut 57 is screwed into a male screw section engraved on the upper portion of the central shaft 53. The first split mold 56 and the toothed forming die 55 are arranged in the axial direction of the central shaft 53. Are fixed to the central shaft 53 by a stepped portion 63 and a fixing nut 57 at an intermediate position between the two.

The outer mold 12 is provided on the outer periphery of the upper part of the first split mold 56.
In the second split mold 54, an O-ring 67 for sealing the gap between the bottom plate 11 and the fitting hole 16 is attached to the outer periphery of the lower small diameter portion 54a. ing.

FIGS. 5A and 5B are cross sectional views of the cavity. FIG. 5A shows a toothed portion, and FIG. 5B shows a flat belt portion.
As shown in the figure, on the outer peripheral surfaces of the first split mold 56, the second split mold 54, and the toothed mold 55, a plurality of sharp ridges 70 extending in the mold axial direction are arranged at intervals along the circumferential direction. In this case, the outer peripheral surface of the inner mold and the core wire 4 are brought into contact with each other in a point contact state, and the casting material 73 is wrapped around the groove 71 between the spikes 70. Also in the toothed mold 55, a spike 70 is formed on the top of the groove forming part 74 that forms the tooth groove of the toothed part 5.
Are formed.

As shown in FIG. 3, the pressure injection means 14 comprises a casting material storage container 75 which is open upward, and a piston 76 whose lower part is fitted to this storage container 75 and whose upper part is fixed to the bottom plate 11.
And a cylinder 77 for pushing up the storage container 75, and the casting material 73 in the storage container 75 is attached to the piston 76.
The supply hole 78 that supplies the gas to the injection port 27 is formed through.

Next, a method of manufacturing the endless belt 1 using the casting mold will be described. Liquid casting material 7
3, the liquid polyurethane is stored in the storage container 75, and the core wire 4 is spirally wound around the inner mold 13.
The outer mold 3 and the outer mold 12 are fitted in a gas-liquid tight manner to form a cavity 25 therebetween, which is fitted to the bottom plate 11 and fixed to the bottom plate 11 by the lower clamp mechanism 18. Outer die 1
The inner mold 13 and the inner mold 13 are heated, and the control valve 34 above the outer mold 12 is closed.

In this state, when the casting material in the container 75 is pushed up at a predetermined pressure, the casting material 73 is
Through the ring-shaped groove 26 of the bottom plate 11 and the ring-shaped concave portion 30 of the outer die 13 to go around the entire region of the inner die 13 in the circumferential direction, and rise inside the cavity. At this time, since the control valve 34 is in the closed state, the air in the cavity 25 performs a compression / expansion motion as the casting material rises, thereby promoting leveling of the casting material by its own weight. Therefore, the casting material 73 rises in the cavity 25 in a state that is almost horizontal.

When the casting material 73 approaches the overflow hole 32, the air inside the cavity passes through the ring-shaped concave portion 33 at the upper part of the outer mold 12 together with the casting material 73 and reaches the overflow hole 32. Control valve 34
Is moved in the valve opening direction against the urging force of the coil spring 39. Further, the casting material 73 containing air bubbles is also discharged from the overflow hole 32 by the pressure. When the number of bubbles in the discharged casting material 73 is reduced, the bar-shaped member 35 is screwed in, and the overflow hole 32 is closed. In this state, the container 75 is further pushed up to keep the inside of the cavity at a predetermined pressure, and is heated until the casting material 73 is hardened.

After the curing is completed, the pressure in the cavity 25 is lowered by lowering the storage container 75, and then the operation proceeds to the demolding operation.
In the demolding operation, first, after the upper clamp mechanism 45 is released, the mounting bolt 62 is removed, and the first split mold 56 and the toothed mold 55 are pulled out together with the central shaft 53 upward. Next, the lower clamp mechanism 18 is released, and the second split mold 54 is released.
At the same time, after removing the outer mold 12 from the bottom plate 11, the second split mold 54 is pulled out from below. Finally, the molding belt 1 attached to the inner peripheral surface of the outer mold 12 is removed and removed.

As described above, in the present embodiment, the inner mold 13
Is divided, and the toothed forming die 55 is pulled out together with the first split die 56 so as to be separable from the second split die 54, so that the inner peripheral surface of the belt projects more inward than the flat belt portion 6. Even if it has the toothed portion 5, it can be easily removed from the mold, and even if it is an endless belt having a small ratio between the belt width and the circumferential length, it can be formed without being inverted after forming.

Further, since a plurality of ridges 70 which are in point contact with the core wire 4 are formed on the outer peripheral surface of the inner mold 13, the casting material 73 wraps around the groove 71 between the ridges, and the core wire is formed after molding. 4 can be prevented from being exposed.

Also, in the casting mold structure, the presence of the ring-shaped grooves 26 and the ring-shaped recesses 30 and 33 causes
It becomes easier for the casting material 73 to wrap around the cavity periphery,
Further, since the overflow hole 32 is closed by the control valve 34 with the coil spring 39 when the casting material is injected, the leveling of the casting material by its own weight is promoted by the compression / expansion motion of air. That is, a so-called flow mark can be eliminated.

FIG. 6 shows the case where the overflow hole is opened when the casting material is injected (FIG. 6A) and the case where the control valve 34 is closed as in the present embodiment (FIG. 6B). )) Is a diagram showing the results of confirming the rise of the casting material. In both figures (a) and (b), about 1
Liquid polyurethane heated to 00 ° C was used. (FIG. 6
In (a), while the degree of rise of the casting material is extremely different in the circumferential direction of the cavity, a flow mark is easily generated.
In (b), since it rises in a substantially horizontal state, it can be understood that a flow mark is hardly generated.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that many modifications and changes can be made within the scope of the present invention. For example, in the present embodiment, an example in which the pressure injection means is arranged below the mold is shown. However, in a mode in which the casting material can be injected under pressure, the installation place such as a horizontal position is limited. Not something. The upper and lower clamp mechanisms 18 and 45 are also provided with the outer mold 1.
Various structures can be adopted as long as they can fix the base 2 to the bottom plate 11 and the outer mold 12 to the inner mold 13.

[0042]

As is apparent from the above description, according to the present invention, an endless belt with a core wire having a toothed portion on a part of an inner peripheral surface thereof using a casting mold using a split type inner mold. , It is possible to easily manufacture even an endless belt whose belt circumference, which is difficult to turn over, is 3.2 times or less with respect to the belt width.

[Brief description of the drawings]

FIG. 1 is a front view of an endless belt according to an embodiment of the present invention.

FIG. 2 is a plan view of the same.

FIG. 3 is a sectional view showing a mold structure for cast molding of an endless belt.

FIGS. 4A and 4B are enlarged views of the control valve, wherein FIG. 4A shows an open state and FIG. 4B shows a closed state.

5A and 5B are enlarged cross-sectional views of the cavity, wherein FIG. 5A shows a toothed portion, and FIG. 5B shows a flat belt portion.

FIGS. 6A and 6B show the results of experimentally confirming the ascending state of the casting material when the overflow hole is opened during the injection of the casting material and when the overflow hole is opened during the injection of the casting material, respectively. It was done.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Endless belt 2 Main belt 3 Through hole 4 Core wire 5 Toothed part 6 Flat belt part 10 Casting mold 12 Outer mold 13 Inner mold 14 Pressure injection means 27 Injection 32 Overflow hole 34 Control valve 53 Center shaft 54 Second Of the mold 55 Toothed mold 56 First divided mold 73 Casting material

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) F16G 1/28 F16G 1/28 ZE // B29K 75:00 105: 08 B29L 29:00 (72) Invention Person Akira Mizoguchi 172 Ikezawa-cho, Yamatokoriyama-shi, Nara Prefecture Unita Nara Factory F-term (reference) 4F202 AA42 AA45L AC05 AG16 AM36 CA01 CB01 CB11 CK07 CK25 CK75 CL28 CL42 CL47 4F204 AA42 AA45L AC05 AG16 EB03 EB03 EF03 EB01 EF49 EK10 EK17

Claims (7)

[Claims] The present invention relates to a mold for forming an endless belt with a core wire having a toothed portion in a part of an inner peripheral surface of a belt main body in a width direction of the belt, wherein a toothed forming die is provided in a part of the inner die. A molding die structure for an endless belt in which the inner die has a divided structure with at least one end in the axial direction of the toothed molding die as a boundary. 2. The molding die structure for an endless belt according to claim 1, wherein said toothed molding die is arranged in a central region in the axial direction of said inner die. 3. An endless belt molding die structure, wherein an injection port for pressurizing and injecting a flowable casting material is provided at a lower portion of a cavity between an inner die and an outer die. A molding die structure for an endless belt provided with a control valve with a spring for urging the overflow hole in a valve closing direction at the time of pouring a casting material into an overflow hole formed at an upper portion of the cavity. 4. The mold structure according to claim 1, wherein
A molding die structure for an endless belt provided with the die structure according to claim 3. 5. An endless belt in which a core wire is buried in a main body made of an elastomer, a toothed portion is formed in a part of an inner peripheral surface, and a circumferential length is set to 3.2 times or less of a belt width. 6. The endless belt according to claim 1, wherein said belt main body is made of a urethane elastomer. 7. An endless belt formed by molding the endless belt according to claim 5 or 6 using the mold according to claim 1.