JPH054615Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a seal ring for a hydraulic cylinder used in an injection molding machine or the like.

(Prior Art) Seal rings can be broadly classified into lip seals made of materials such as rubber or synthetic resin, and piston rings mainly made of cast iron.

Lip seals have very superior sealing performance compared to piston rings, but they are inferior in pressure resistance and heat resistance, and have short lifespans such as wear resistance and weather resistance.Also, because the material is soft, they are easily damaged during assembly. ,
It has drawbacks such as the need for careful handling.

Piston rings are generally not used as sealing materials that require airtightness such as pressure retention because of their poor sealing performance. This is because the material does not have elasticity like lip packing, so at least one part of the ring is
This is because the fluid leaks from the cut portion.

In the seal rings used in hydraulic cylinders for injection molding, a pair of seal rings are fitted onto an inner ring with their openings shifted in position to prevent oil leakage during pressure retention.

(Problem to be solved by the invention) However, even if the openings of each ring are shifted to the farthest positions, due to the very slight rotation of each ring that occurs when the piston operates, 10
When the piston reciprocates about 10,000 times, the split ends naturally overlap and oil often leaks. Furthermore, once the split openings are aligned, the oil that has entered the openings acts as a key, preventing the split openings from shifting again, and the oil gradually leaks from the openings, reducing the holding force.

Coloring is thought to be a means of preventing the seal ring from rotating, but since both use special seal rings and inner rings, special techniques are required when assembling them into the piston. Not only was the ring expensive, but its sealing performance was also unsatisfactory, causing problems.

(Means for solving the problem) This idea was devised in view of the above circumstances, and its purpose is to utilize the advantages of piston rings based on piston rings, and to make the openings of the rings polymerized. Our goal is to provide a new seal ring that does not require any additional work.

The present invention for the above purpose is a seal ring in which a pair of outer rings are provided in parallel on an inner ring with the positions of the openings being shifted, and the inside of the seal ring has a rectangular cross section that extends to the inner ring and two outer rings. A hollow space is formed along the entire circumference in the circumferential direction, and a core body made of an elastic material that contacts each ring is housed and interposed in the hollow space.

(Function) In the seal ring having the above structure, the core made of an elastic material equalizes the pressing force of the outer ring and prevents rotation of each ring, so that the opening of each ring is controlled by the reciprocating movement of the piston. There is no match due to

(Embodiment) As shown in FIG. 1, the seal ring is composed of two outer rings 1 and 2, an inner ring 3, and a core body 4 made of an elastic material interposed inside.

Outer rings 1, 2 and inner ring 3 are
A normal cast iron assembly ring is used, and additional machining is performed to form a groove 5 on the outer circumference of the inner ring, and when aligned with each other on the inner circumference of the outer ring, the groove 5 is placed at the same position in the thickness direction and has the same width. Notches are cut out around the entire circumference so as to form concave grooves 6.

The core body 4 consists of an end ring made of nitrile rubber, and the ring is formed by grooves 5 and 6 over the entire circumferential direction when the outer rings 1 and 2 and the inner ring 3 are combined. The dimensions are such that it fits into a space with a rectangular cross section and is slightly compressed when being filled.

In the drawing, the split positions of each ring are shown close to each other, but in reality, each ring is split on the circumference.
It is assembled so that the positions are shifted by 120 degrees, and the piston 8 is housed in the ring groove 9 of the piston 8 in the cylinder 7 while maintaining this state.

The elastic material used in this embodiment was made of nitrile rubber, but any other oil-resistant elastic material such as fluorocarbon rubber may be used. Also, the hardness
Those with Hs of 60 to 90 are suitable.

Next, the seal ring with the above structure, the normal three-piece ring, one with the split openings shifted by 120 degrees, and the three seal rings with the split openings aligned are sequentially attached to the direct pressure mold clamping device of the injection molding machine. I incorporated it into the test. The results are shown in Figure 3. Before describing the test results, the role of the sealing material of the mold clamping piston in the mold clamping device of an injection molding machine will be briefly explained.

Injection molding machines perform injection filling while strongly clamping and holding the mold, so separate pumps are provided on the mold clamping side and on the injection side to maintain the mold clamping force during injection filling.

However, due to issues such as cost and space, recently a single pump is used in common, and after a strong mold clamping force is generated, the mold clamping cylinder blocks the oil passage to contain the pressure, and supplies pressure oil from the pressure source. After the piston is cut off to hold the pressure, the injection circuit is switched on and injection filling is performed, but in this case, the pressure holding ability is reduced due to leakage from the sealing material of the piston. Further, the holding pressure must be maintained during both the injection and cooling steps.

The time required for both of the above steps is wide, ranging from several seconds to several tens of minutes, and a high pressure of 100 to 175 kg/cm ² is required to maintain the pressure.

The piston is reciprocated at a speed of about 1 m/sec with a mold clamping stroke of about 300 to 1500 mm to open and close the mold. The sealing material for the piston is required to have both high sealing performance and durability, and these conditions are severe.

If leakage occurs in the sealing material, not only will the molded product become defective, but it will also become impossible to mold, and production will stop, so the sealing material for the piston part is considered important.

Test equipment specifications Γ Piston outer diameter: φ360mm Γ Movable stroke: 400mm Γ Hydraulic oil: Showa Ciel Sekiyu Co., Ltd. JH-46 Pressure 140Kg/cm ² Oil temperature 45℃ Γ High-speed mold clamping speed: 950mm/sec Γ High-speed mold opening Speed: 910mm/sec Figure 2 shows how the seal ring is assembled.

Test Results The three types of seal rings described above were sequentially assembled into a mold clamping device having the above specifications, and changes in the pressure inside the cylinder as the pressure retention time elapsed were observed (see Fig. 3).

The seal ring according to the present invention and the three-piece seal ring had almost the same pressure drop after 180 seconds. The reason why the seal ring according to the present invention has a slightly lower pressure drop is thought to be because the pressing force of the outer rings 1 and 2 against the inner surface of the cylinder is equalized by the core body 4 made of an elastic material.

In addition, for a set of 3 seal rings with the split openings combined, it was 26.5Kg/cm ² in 30 seconds and 86.6Kg/cm ² in 180 seconds.
There is a pressure drop, which makes it unusable.

In terms of durability, after 200,000 cycles, the device according to the present invention showed very good results, with no rotation of the opening and no significant difference in holding pressure compared to the initial device.

(Effect of the invention) As described above, this invention forms a space 5 with a rectangular cross section in the inner ring 3 and the two outer rings 1 and 2 all around the circumferential direction inside the seal ring. Since a core body 4 made of an elastic material that contacts each ring is interposed in the hollow space 5, the core body prevents the outer ring from rotating and also from shifting laterally, and as a result, The ties between each ring become tighter, so that the openings will not match up during use. In addition, since it has a split opening, it is easy to assemble into the piston, and since commercially available rings can be used, the cost is not high, and there is no oil leakage that would reduce the holding pressure, making it suitable for injection molding hydraulic cylinders. It has outstanding features.

[Brief explanation of the drawing]

The drawings show one embodiment of the seal ring according to the invention, with FIG. 1 being a partial perspective view, FIG. 2 being a sectional view of the seal ring installed on a piston, and FIG. 3 being a view showing test results. 1, 2... Outer ring, 3... Inner ring, 4... Core body made of elastic material, 5, 6... Concave groove.

Claims (1)

[Scope of utility model registration request] In a seal ring in which a pair of outer rings are provided in parallel on the inner ring with the openings shifted in position, a space with a rectangular cross section extending over the inner ring and two outer rings is formed inside the seal ring in the circumferential direction. A seal ring is formed over the entire circumference of the seal ring, and a core body made of an elastic material is interposed in the hollow space to be in contact with each ring.