JP2512443Y2 - Gear pump for molten resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a gear pump used in melt extrusion molding of a thermoplastic resin, and particularly when a gear pump is driven by a high resin pressure, a bearing seizure accident An improved molten resin gear pump that does not occur.

[Prior art and its problems] A single-screw extruder is mainly used as a melt-extrusion device for thermoplastic resins. The extruder has three functions: a feeding section, a melting section, and a metering section. When connecting multiple spinning machines to a single extruder, such as synthetic fiber, the amount of polymer supplied to each spinning machine. It is customary in the industry to provide a dedicated metering device, that is, a so-called gear pump, for each spinning device in order to maintain a constant value. On the other hand, in the film production equipment, when the weighting property for molding different polymers into a multi-layered film is emphasized, when the discharge amount is increased greatly, or the stability of the discharge amount is increased, the film thickness fluctuation When the importance is placed on suppression, the extruder's metering ability is insufficient. Therefore, the method of providing the extruder with only the supply / melting function and installing a gear pump at the tip of the extruder to provide the metering function has recently been proposed. It is becoming common because the purpose of obtaining a high extrusion rate and the purpose of stabilizing the discharge state can be satisfied at the same time.

In order to obtain a high extrusion capacity, it is necessary to shorten the metering zone of the extruder and utilize this portion as a melting zone.
Therefore, a screw is designed to meet this condition to enhance the melting capacity, and a gear pump is provided to achieve a high extrusion rate and a constant extrusion state (stable extrusion). Of course,
It is possible to install a highly stable extruder for metering instead of the gear pump, but it is not used so much because it is inferior to the gear pump in terms of equipment cost, occupied space, power cost, maintenance cost and the like.

The gear pump has a relatively narrow clearance between the casing and the gear in order to improve the metering ability and maintain its accuracy.
The amount of leak that occurs inside the pump is suppressed. However,
Narrowing the clearance between the side surface of the gear (a substantially circular surface when viewed from the rotation axis) and the plate-shaped casing allows the gear to rotate at high speed with the aim of achieving high discharge. Plays a role as a pump lubricant, but when the amount of polymer in the clearance decreases, the supply of lubricant is interrupted, which is called the phenomenon of polymer oil film running out in the clearance. This may cause seizure of the bearing.
This risk increases with decreasing clearance. One of the causes of this is that the gear is slightly displaced in the axial direction. In order to prevent the gear from being displaced in the axial direction, it is necessary to provide a restricting means outside the pump, but this is complicated and is not often adopted. If the gear is displaced in the gear pump (for example, if the resin pressure is high, the gear is pushed to the side opposite to the pump block and is likely to be displaced), one of the clearances becomes narrower than in the balanced state (normal position), and As a result of the decrease in the amount of the molten resin, the oil film is broken due to the polymer, which leads to seizure of the bearing portion. This phenomenon tends to occur when the gear pump is operated at a high rotation speed to increase the discharge amount.

Therefore, the size of the gear pump is increased in order to keep the surface pressure of the bearing portion of the gear low, but there is an upper limit in capacity due to restrictions on machining and restrictions on machining. There are 750,800,1300,1500,1800cc / rev, etc. as the capacity that has already been proven, but in order to increase the capacity of existing equipment, it is often dealt with by increasing the rotation speed of the gear pump, which will cause seizure. Not a few things. Occasionally, the difference in lubrication performance depending on the resin viscosity, temperature, or the polymer additive used also promotes seizure. The present invention provides an improved structure for preventing seizure of synthetic resin polymer metering gear pumps.

Generally, a synthetic resin film gear pump uses a 2- or 3-gear type gear pump to suppress the pulsation due to the gear teeth, and the polymer passes through the liquid introduction passage in the pump block that also serves as a gear pump support, and the side surface of the gear. Is introduced immediately after the gear meshing point in the tooth trace direction, moves with the rotation of the gear, and is sent out from the lead-out path immediately before the next meshing point. The surface on the pump block side has ports for introduction and discharge, and the gear is pushed to the side opposite to the pump block due to the pressure loss in the tooth trace direction when the polymer flows in, and moves. On the side of the gear opposite to the pump block side, the clearance decreases and the lubrication polymer becomes insufficient, and the channel resistance increases and the polymer pressure decreases, while on the side of the pump block side gear, the clearance increases and the channel resistance decreases and the polymer pressure decreases. Will be higher. Due to the pressure difference between the both side surfaces of the gear, the gear is pushed to the side opposite to the pump block and seizure occurs due to the high surface pressure.

[Specific Means for Solving Problems] As a result of various investigations to solve this problem, means for making pressures acting on both side surfaces of the gear uniform, strengthening lubrication by the polymer, and improving seizure resistance of the side surface of the gear Devised. Specifically, it is to provide a concave recess in the portion where the gear side surface of the non-pump block side casing is located. The concave recess is provided at a position corresponding to each port of the pump block side casing in order to equalize the pressure on both side surfaces of the gear. Further, the opening area is preferably equal to or larger than the area where the gear side surface is exposed to the port on the pump block side.

The present invention is a gear pump comprising a gear group having two or three gears used when manufacturing a synthetic resin film and a casing covering the gear group, the gear group including a drive shaft. And a driven gear that meshes with the driving gear or two driven gears that mesh with the driving gear and that face each other via the driving gear, and the casing has an introduction path and a discharge path for the molten resin. A pump block side plate (back plate) provided near each meshing position and having a function of pivotally supporting one or two driven gears, and a pump block side plate facing each other through a gear group. A counter pump block side plate (front plate) and a gear case mounted along the tooth surface of each gear. The gear-side surface of the side plate,
A concave recess is provided at a position corresponding to the gear side opening position of the introduction path and the discharge path provided in the pump block side casing, so that the pressure in the gear side direction accompanying the introduction and the extraction of the molten resin is applied to the anti-pump block side plate. It is a gear pump for molten resin, which is an improved point that the pressure on both sides of the gear is balanced by applying the load to the gear.

 The present invention will be described with reference to the drawings.

FIG. 1 is a conceptual diagram showing the present invention. A gear pump having a concave recess on the side opposite to the port, which is a specific structural feature of the present invention in order to equalize the situation where the gear side surface is exposed at the liquid inlet / outlet port and the thrust force generated thereby, is shown. ing.

FIG. 2 shows the overall configuration of the three-gear pump described in the embodiment of the present invention. In the figure, at the position where the back plate and the gear side surface face each other, the liquid introduction path and the liquid discharge path are orthogonal to the drive gear and the driven gear side surface, and the concave recess of the present invention should be implemented. It shows the position of the plate.

FIG. 3 is a side view of the opposite surface of the back plate and the side surface of the gear in FIG. 2 as viewed from the side opposite to the pump block. The introduction port of the circular diameter interferes with the outer shape of the gear, and the side surface of the gear is exposed at the port portion. Indicates the situation.

FIG. 4 is a side view of the opposing surfaces of the front plate and the side surface of the gear in FIG. 2 as viewed from the pump block side, and the concave depression which is a structural feature of the present invention is located at a position corresponding to the port position in FIG. It is an example showing that the shape is provided in consideration of the exposed area of the side surface of the gear on the pump block side and the retention of the polymer.

[Embodiment] An embodiment of the present invention will be described with respect to a three-gear type gear pump for supplying polyethylene terephthalate having a melt viscosity of about 2000 poise. It has been considered that the seizure resistance is limited to a discharge rate of up to about 2 ton / hr due to the sliding speed determined by the rotational speed and the surface pressure determined by the discharge pressure from the performance of the thrust bearing on the side of the conventional gear. Therefore, the concave depression is additionally processed for such a gear pump. The position of the concave depression on the side of the gear opposite to the pump block was set to the position corresponding to the liquid introduction / extraction port on the pump block side of the gear. Regarding the shape of the recess, the pump block side has an opening area equal to the area where the gear side surface is exposed at the liquid inlet / outlet port, and a towing flow occurs due to gear rotation, and deterioration due to retention of molten resin does not occur. It has the same shape and depth. With this improvement, the seizure resistance on the side of the gear has been improved by about 25% in terms of operating discharge rate, enabling operation up to about 2.5 ton / hr.

[Advantage of the Invention] The polymer pressure in the liquid inlet / outlet port of the pump block side casing exerts a thrust force to push the gear to the side opposite to the pump block, while the concave recess is provided to allow the polymer in the port and the gear to move. Through the polymer in the tooth bottom, a reaction force is generated in the polymer in the concave depression having approximately the same pressure, and as a result, the thrust force acting on both sides of the gear can be balanced. This makes the clearance for polymer lubrication provided between the gear side surface and the opposing plate surface uniform at both ends of the gear, and it is possible to form a good lubrication state together.
Therefore, when operating a resin having a high melt viscosity, or when supplying a high discharge amount from the viewpoint of productivity, the gear pump is required to have a high pressurizing ability, which often leads to seizure. By the present invention, seizure resistance can be greatly improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a gear pump showing the concept of the present invention. FIG. 2 is a side view showing the gear pump of the present invention supported by a pump block. FIG. 3 is an end view of the pump block side casing of the gear pump of the present invention. FIG. 4 is an end view of the casing opposite to the pump block of the gear pump of the present invention.

Claims (1)

(57) [Scope of utility model registration request] 1. A gear pump comprising a gear group having two or three gears and a casing covering the gear group,
The gear group is composed of one drive gear having a drive shaft and one or two driven gears meshing with the drive gear, and the casing is provided with a molten resin introduction path and a molten resin discharge path in the vicinity of respective meshing positions. Pump block side plate having a function of axially supporting one or two driven gears, an anti-pump block side plate provided opposite to the pump block side plate via a gear group, and tooth surfaces of each gear In a gear pump provided with a gear case for measuring molten resin, a gear side opening position provided in the pump block side casing on the gear side surface of the plate opposite to the pump block side A concave recess is provided at a position corresponding to, and the pressure in the gear side direction due to the introduction and extraction of the molten resin is also applied to the plate opposite to the pump block side so that the pressure on both sides of the gear is reduced. Improvements and molten resin for gear pump that allowed to balance the.