JP2740700B2 - Gear pump for molten resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear pump used for pressurizing a molten resin between a kneader and a pelletizer, for example, in a kneading and granulating apparatus.

[0002]

2. Description of the Related Art A gear pump of this kind is designed to melt molten resin at a temperature of 200 to 300.degree.
The pressure is raised to a high pressure of 300 kg / cm ² and supplied to the pelletizer, which is a high temperature and high pressure specification. In this high-temperature and high-pressure pump, a journal bearing using a molten resin film instead of an oil film is used between the pump housing and the gear rotor. That is, by supplying the resin from the gear portion to the clearance between the shaft portion of the gear rotor and the journal bearing body, the shaft portion is supported while being lubricated with the resin.

However, when the shaft of the gear rotor is lubricated with a molten resin, depending on the type of the resin, it is subjected to an excessive shearing force in the clearance and thermally deteriorated. May degrade quality. Therefore, there is known a gear pump in which a discharge path communicating with a clearance is provided in a pump housing, and the thermally deteriorated resin is constantly discharged to the outside from the discharge path to prevent a decrease in product quality (for example, a gear pump). See JP-A-58-120889 and JP-A-60-77784.

[0004]

However, in the above-mentioned prior art, the pump housing is provided only with a discharge path for always discharging the molten resin in the clearance to the outside, so that the resin in the clearance is thermally degraded. All of them are discharged to the outside even if they are not, so that there is a disadvantage that the material yield and the pump efficiency are deteriorated.

On the other hand, in order to solve the above-mentioned inconvenience, conventionally, an on-off valve and a flow control valve are provided in the discharge path to shut off or restrict the discharge of resin to the outside. Since the resin in the clearance is blocked or throttled from flowing into the discharge path, the molten resin in the clearance stays and accelerates thermal deterioration.

In view of such circumstances, the present invention allows a molten resin that has not been thermally degraded to be returned to the suction port without staying in the clearance, thereby reducing the material yield and the pump efficiency without deteriorating the product quality. The purpose is to prevent deterioration.

[0007]

In order to achieve the above object,
The present invention has taken the following technical measures. That is, the present invention provides a pump housing 3 having a suction port 1 and a discharge port 2.
A pair of gear rotors 6 having a gear portion 4 and a shaft portion 5 are rotatably arranged in a meshing state with the gear portion 4, and a gear is provided between the journal bearing body 30 of the pump housing 3 and the shaft portion 5 of the gear rotor 6. In the gear pump for molten resin having a clearance 7 into which the resin flows from the portion 4, a recovery path 8 for returning the resin supplied to the clearance 7 to the suction port 1 is provided. A switching valve 19 is provided which can be switched between a direction in which the resin from the nozzle 7 is returned to the suction port 1 and a direction in which the resin is discharged to the outside (claim 1).

In this case, it is preferable that the switching valve 19 be made of a martensitic stainless steel material for the reasons described below.

[0009]

The molten resin that has flowed into the clearances 7A and 7B from the gear portion 4 acts as a journal bearing between the shaft portion 5 and the journal bearing body 30, passes through the recovery path 8 having the switching valve 19, and flows through the suction port 1. Returned to That is, when the resin is thermally degraded in the clearances 7A and 7B, the resin is drained to the outside without returning to the suction port 1 by setting the switching valve 19 to the discharge direction. When the resin is not thermally degraded, the switching valve 19 is set in the return direction to return the resin to the suction port 1 (claim 1).

In this case, regardless of whether the switching valve 19 is set in the discharge direction or the return direction, the clearance 7 is not changed.
Since the molten resin in A and 7B always flows into the recovery path 8, the molten resin is prevented from staying in the clearances 7A and 7B. Therefore, clearances 7A, 7
B, the thermal deterioration of the molten resin is effectively prevented, and the switching valve 19 is normally used when the resin is not thermally deteriorated.
Is set in the return direction, the resin is collected in the recovery path 8.
The sound can be returned to the suction port 1 through the port, so that sound resin can be reused.

On the other hand, the switching valve 19 always has a sliding portion. Usually, the sliding portion is made of a copper-based material (for example, bronze).
Is used. However, it is known that when such a copper-based material comes into contact with a certain kind of resin (for example, polypropylene), the resin deteriorates. Therefore, the present invention recommends that the switching valve 19 be made of a martensitic stainless metal material (claim 2).

In this case, since the resin is prevented from deteriorating when passing through the switching valve 19, it is possible to reuse the returned resin even with a material such as polypropylene which is easily degraded with respect to a specific metal.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. 3, the kneading and granulating apparatus 20 includes a kneading machine 21.
, A gear pump 22 and a pelletizer 23, and supplies a resin material, an additive, and the like into a chamber 25 from a supply port 24 of the kneading machine 21, and includes two rotors 26 arranged in parallel.
Then, the molten resin is pressurized by the gear pump 22 from the outlet 27 and fed to the pelletizer 23.

1 to 3, a gear pump 22 has a pair of gear rotors 6 arranged in a pump housing 3. The pump housing 3 has a pair of left and right journal bearings 30 disposed in a body 29 and side plates 31 disposed on the left and right sides thereof and fixed to the body 29.
The suction port 1 is formed on the side, and the discharge port 2 is formed on the pelletizer 23 side. Reference numeral 32 denotes a heating heating panel.

The pair of gear rotors 6 each have a gear portion 4 and a shaft portion 5 integrally formed, and the gear portions 4 mesh with each other. The shaft portions 5 on both sides of the gear portion 4 are inserted into the journal bearing body 30. Clearances 7A and 7B are formed between the left and right side surfaces of the gear portion 4 and the outer peripheral surface of the shaft portion 5 with the journal bearing body 30, and a portion of the molten resin (for example, a discharge amount of 0. 1 to 3%), and the shaft portion 5 and the journal bearing body 30 constitute a journal bearing. One gear rotor 6 is connected to a driving device via a coupling 33.

A groove for increasing the amount of resin entering the clearance 7A is formed on the inner peripheral surface of the journal bearing body 30 facing the clearance 7A so as to increase the amount of resin supplied to the clearance 7A. May be. At each end of the clearances 7A on the side plate 31 side, a pressure drop is prevented by a seal ring 34 provided on the shaft portion 5, and the clearances 7A communicate with the recovery path 8.

The recovery passage 8 passes through a switching valve 19 provided on the side plate 31 for each shaft portion 5 and is assembled into a member 36 from two switching valves 19 attached to each side plate. Connected to 1. The switching valve 19 is a three-way valve having, in addition to the return path 17 communicating with the suction port 1, a discharge path 18 for draining resin, rotates a valve body 19 </ b> A constituting a sliding portion thereof. By doing
The return path 17 and the discharge path 18 are switched.

The valve body 19A is formed of, for example, SUS420 (Tufftride), and the sleeve 19B is formed of SUS40.
3 (tufftride), which is a martensitic stainless metal material that does not deteriorate the passing resin and can prevent seizure between the valve body 19A and the steve 19B. The valve body 19A and the sleeve 1
The material of 9B may be composed of a different combination of other martensitic stainless steels. When the switching valve 19 adjusts the rotation of the valve body 19A, the amount of the returned resin is changed, and the switching resin 19 is applied to the journal bearing. The amount of supplied resin can be adjusted.

[0019]

As described in detail above, according to the present invention,
In addition to simply discharging the thermally degraded molten resin to the outside,
Since the molten resin that has not been thermally degraded can be returned to the suction port 1 through the recovery path 8, the clearance 7A,
It is possible to improve the material yield by reusing sound resin while effectively preventing thermal deterioration due to stagnation of the molten resin in 7B (claim 1).

Further, according to the present invention, since the switching valve 19 is formed of a martensitic stainless metal material,
It is possible to effectively prevent a resin that is easily degraded with respect to a certain specific metal such as polypropylene from deteriorating when passing through the switching valve 19, and it is possible to increase the types of resin that can be returned to the suction port 1 and reused. (Claim 2).

[Brief description of the drawings]

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

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3 is a partially sectional explanatory view showing the entire kneading and granulating apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 suction port 2 discharge port 3 pump housing 4 gear section 5 shaft section 6 gear rotor 7 clearance 8 recovery path 17 return path 18 discharge path 19 switching valve

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-85276 (JP, A) JP-A-62-255671 (JP, A) Real opening 60-77784 (JP, U)

Claims (2)

(57) [Claims] 1. A pair of gear rotors (6) having a gear part (4) and a shaft part (5) in a pump housing (3) having a suction port (1) and a discharge port (2). )
The journal bearing body (30) of the pump housing (3) and the gear rotor (6) are rotatably arranged in an engaged state.
Gear pump of the shaft portion (5) and the molten resin resin from the gear portion (4) formed a clearance (7) that flows between the
In the above, the resin supplied to the clearance (7) is
A recovery path (8) for returning to (1) is provided, and a tree from the clearance (7) is provided in the recovery path (8).
The direction of returning the fat to the suction port (1) and discharging the resin to the outside
Closable switching valve switching in either direction of (1
Gear pump the molten resin, wherein the kite is provided with 9). (2) Switching valve (19) is martensitic
Characterized by being formed of stainless metal material
The gear pump for molten resin according to claim 1.