JPS6148637B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gear pump for pumping highly viscous materials.

A gear pump is a device that pumps fluid at a fixed amount and at a constant pressure. In the past, gear pumps were mainly used to pump low-viscosity fluids such as oil and water, but recently there have been attempts to use gear pumps for polymeric materials such as synthetic resins, which become highly viscous fluids in their molten state. being done. For example, in extrusion molding and injection molding, gear pumps are used as a means to extrude polymer materials that have been kneaded and melted or become molten during the polymerization process because they are more compact than screw extruders and have higher quantitative performance. It is being used in place of extruders.

By the way, in the general gear pump used for the above-mentioned low-viscosity fluid, the outer periphery of a pair of pumping gears that mesh with each other is brought into close contact with the casing, and the fluid to be pumped is pumped by the suction force generated by the rotation of the gears. Therefore, if the material to be pumped has a high viscosity, it is difficult to get into the tooth groove of the gear. This tendency is particularly noticeable when a highly viscous material is supplied from the kneading machine in a rope shape and does not fill the gear pump inlet side.
Pumping becomes difficult.

Therefore, as a gear pump used for high viscosity materials, as shown in Japanese Patent Application Laid-open No. 129249/1983,
Near the material outlet, the inner surface of the casing is brought into close contact with the outer periphery of each pumping gear in a small area as possible, and as the material moves, a tooth gap is gradually formed between the outer periphery of each gear and the inner surface of the casing upstream of this close contact area. A space is provided to make it easier to get into the gear, and a pair of nip rolls are installed upstream of the gear to hold the rope-like high-viscosity material and feed it onto the gear. However, even with this structure, if the highly viscous material supplied to the gear pump contains air bubbles, it is difficult to degas the air bubbles. That is, in the above gear pump, the pair of Nipro rolls are
The two nip rolls and the two nip rolls are arranged so as to correspond to each other with a relatively small interval so that the high viscosity material can be sandwiched and fed between the two nip rolls in a sealed state with the inner surfaces of both sides of the casing. The space between the pumping gear and the pumping gear is filled with material and pressurized. In this case, when the material is drawn between the two nip rolls, some deaeration is performed due to the compressive force of the two nip rolls, but since it is necessary to feed the required amount of material, there is no sufficient deaeration effect. It's difficult. On the other hand, the air bubbles contained in the high viscosity material after passing through both nip rolls cannot pass between both nip rolls because a clamping pressure greater than the pressure on the downstream side is applied between both nip rolls. The material gets mixed in with the material filling the space between the pumping gear and the pumping gear.
As described above, since deaeration is not performed downstream of the Nipprol, and the deaeration by the Nipprol is insufficient, air bubbles remain in the material discharged from the gear pump, which may deteriorate the quality of materials such as synthetic resins. It was hot.

In view of these circumstances, the present invention provides a gear pump for extruding highly viscous materials that can efficiently pump polymeric materials such as molten resins and can significantly improve the deaeration effect.

That is, the present invention includes a pair of pumping gears that mesh with each other, and a casing that surrounds both gears, and has a material inlet side space above the gears and a material outlet side space below the gears in the casing. ,
In the gear pump for extruding a high viscosity material, the rope-shaped high viscosity material supplied to the material inlet side space is sent to the material outlet side space by the pumping gear and discharged from this space. A seal portion is formed on the inner surface of the casing in the vicinity of the casing, and a seal portion that is in close contact with the tips of the teeth of each of the gears is formed, and a predetermined range of the outer periphery of each of the gears on the upstream side of the seal portion and the inner surfaces of the casing on both sides opposite thereto. , a material compression space whose width becomes narrower as it approaches the seal portion, and a space for feeding high-viscosity material to each material compression space is formed near the upstream end of each material compression space above and outside of each gear. Feed rolls, the roll axis of which is parallel to the axis of each of the gears, and a distance between each roll and each of the corresponding gears is approximately the same as the width of the upstream end of the material compression space, Moreover, the two rolls are arranged such that there is a distance between them that is sufficiently larger than the thickness of the rope-like high-viscosity material.

Embodiments of the present invention will be described below with reference to the drawings.

In FIGS. 1 and 2, 1 and 1' are a pair of pumping gears that mesh with each other, and 2 is a casing that surrounds both gears 1 and 1'. Both pumping gears 1 and 1' are rotatably supported by the casing 2 via shafts 11 and 11', respectively, in a state in which they mesh with each other and are arranged at predetermined positions in the casing 1. By being interlocked and connected to an external gear drive device, they are rotated in opposite directions in the directions indicated by arrows A and A'.

The casing 2 has a material inlet side space 21 above the gears 1 and 1' that communicates with the material inlet 21a.
A material outlet side space 22 communicating with a material discharge port 22a is provided below both gears 1 and 1'. Further, seal portions 23, 23' that are in close contact with the tips of the teeth of each gear 1, 1' are provided on the inner surface of the casing 2 near the material outlet side space 22, corresponding to the outer periphery of each of the gears 1, 1'. It is being These seal portions 23, 23' block communication between the upstream side and the downstream side at this portion, so that the material that has entered the tooth groove of each gear 1, 1' is quantitatively transferred to the material outlet side space 22. The seal portions 23 and 23'
The formation range of is made small. Material compression spaces 24, 24' are formed between the outer periphery of each of the gears 1, 1' and both inner surfaces of the casing 2 on the upstream side of the seal portions 23, 23'. The spaces 24, 24' are intended to allow the material to gradually enter the tooth grooves of the gears 1, 1' while being compressed as the highly viscous material moves along the outer periphery of the gears 1, 1'. The material inlet side space 21
It is formed so that the width becomes narrower as it approaches the seal portions 23, 23'.

In addition, each gear 1 in the casing 2,
Feed rolls 3, 3' for feeding highly viscous material to the spaces 24, 24' are arranged near the upstream end of the material compression space above and outside the space 24, 24', respectively. Both rolls 3, 3' have their respective shafts 31, 3
1' is parallel to the shafts 11, 11' of gears 1, 1', and the axis is located outward from the outer end of each gear 1, 1', and high viscosity is formed between both rolls 3, 3'. In order to prevent a clamping force from acting on the material, they are spaced apart from each other at a distance sufficiently larger than the thickness of the rope-like high viscosity material (molten resin 10) supplied from the kneader 6 or the like as described later. Further, as shown in the enlarged sectional view of FIG. 3, the distance l between each roll 3, 3' and each gear 1, 1' is
The width should be about the same as the upstream end of 4', and usually about 10 to 30 mm to suit the feed action. Both rolls 3 and 3' are connected to the casing 2, respectively.
By being rotatably supported on the shaft and interlockingly connected to a roll drive device (not shown),
As shown in FIG.
24'. Reference numerals 25 and 25' designate material scraping seal parts that come into sliding contact with the outer peripheries of the rolls 3 and 3'.

The material intake port 21a of this gear pump is connected, for example, to the discharge port 61 of the kneader 6 via the chute 5, and the chute 5 is provided with an exhaust hole 51 connected to a vacuum pump (not shown).

Next, the molten resin 1 containing air bubbles is passed from the kneader 6.
The operation of this gear pump will be explained in the case where 0 is supplied to the gear pump in the form of a rope. The rope-shaped molten resin 10 falling onto the pumping gears 1, 1' moves outward along both the gears 1, 1', and closes to the upstream ends of the material compression spaces 24, 24'. Due to the feed action of the feed rolls 3 and 3', the space 2 is expanded as shown by arrow C.
4, 24'. Then, the space 2
Inside 4, 24', as it approaches the seal portions 23, 23', the spaces 24, 24' narrow and the pressure increases, compressing the molten resin 10.
When the bubbles in the molten resin 10 are subjected to compressive force, they move to the low pressure side. Therefore, due to the compressive action in the spaces 24, 24', the bubbles move from the spaces 24, 24' to the upstream side as shown by the broken arrow D. The material flows backward into the material inlet side space 21, and is discharged to the outside from the exhaust hole 51 of the chute 5.

In this case, the feed rolls 3, 3' assist the compression and deaeration of the molten resin 10 in the spaces 24, 24', and do not prevent air bubbles flowing back from the spaces 24, 24' from passing through. Achieve the effect of Qi. That is, as in the past, a pair of nip rolls that clamp the high viscosity material are provided above the pumping gear, and the space between the nip rolls and the pumping gear is filled with the high viscosity material to fill this area. If pressure is applied from the nip rolls, air bubbles will be prevented from flowing back between the nip rolls. In contrast, in the present invention, both feed rolls 3, 3' are spaced apart from each other with a sufficiently large interval, there is no material clamping action between both rolls 3, 3', and each roll 3, 3' is individually The highly viscous material is fed into the material compression spaces 24, 24' in correspondence with the gears 1, 1'. Further, the material compression spaces 24, 24' are the seal portions 23,
23', that is, the downstream side, the width becomes narrower, and the feed rolls 3, 3' and gears 1,
1' is approximately the same as the widest part of the upstream ends of the spaces 24, 24', so the pressure generated between the feed rolls 3, 3' and the gears 1, 1' is Material compression space 24, 2 downstream from this
4'.

Therefore, when the bubbles are pushed back and flow back due to the large compression pressure generated in the material compression spaces 24, 24',
The passage of air bubbles is not obstructed either between the feed rolls 3, 3' and the gears 1, 1', or between both the feed rolls 3, 3', and air is effectively degassed. The higher the rotation speed of the feed rolls 3 and 3', the more the material compression space 2
The pressure on the lower end side of 4, 24' increases, and the material is highly compressed accordingly, thereby increasing the degassing effect and making it possible to achieve a high degree of degassing.

After degassing in the material compression spaces 24, 24' in this way, the molten resin that has entered the tooth grooves of the gears 1, 1' passes through the seal parts 23, 23' and enters the material outlet side space 22. The material is fed and discharged from the material discharge port 22a at a fixed amount and at a constant pressure.

FIG. 4 shows another embodiment of the gear pump of the present invention. In this embodiment, in addition to the structure shown in the basic embodiment, a pair of nip rolls are installed in the material inlet side space 21 above the feed rolls 3, 3' to sandwich the polymeric material and feed it onto the pumping gears 1, 1'. 4, 4' are arranged. However, these nip rolls 4, 4' do not fill the space between the nip roll and the gear with material under pressure, as is the case with the conventional gear pump mentioned above, but instead they simply draw in the rope-shaped molten resin 10 and fill the space between the nip roll and the gear. This is to facilitate feeding onto the feed rolls 1 and 1', and is arranged with a constant spacing between the inner surface of the casing 2 and the feed rolls 1 and 1'. Therefore, the air bubbles flowing back from the material compression spaces 24, 24' escape into the chute 5 through the feed rolls 3, 3' and between the inner surface of the casing 2 and the nip rolls 4, 4', and are discharged from the exhaust hole 51.

As explained above, according to the gear pump of the present invention, the high viscosity material is fed into the material compression space between each gear and the inner surfaces of both sides of the casing by the feed rolls disposed above and outside each pumping gear. At the same time, both feed rolls are arranged so as to increase the compression force of the material in the space and not to prevent the escape of air bubbles that flow backward due to the deaeration effect due to the compression force in the space. In addition to being able to pump viscous materials well,
It enables highly efficient deaeration of highly viscous materials containing bubbles, and can significantly improve product quality.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional front view showing one embodiment of the gear pump of the present invention, Fig. 2 is a sectional view taken along the - line in Fig. 1, Fig. 3 is an enlarged sectional view of the main parts, and Fig. 4 is a separate view. FIG. 1, 1'... Pumping gear, 2... Casing, 21... Material inlet side space, 22... Material outlet side space, 23, 23'... Seal portion, 24, 2
4'... Material compression space, 3,3'... Feed roll.

Claims (1)

[Claims] 1 A pair of pumping gears that mesh with each other,
a casing surrounding both the gears, a material inlet side space above the gear in the casing, a material outlet side space below the gear, and a rope-shaped high viscosity material supplied to the material inlet side space. In the gear pump for extruding high viscosity materials, the pumping gear sends the material to the material outlet side space and discharges it from this space. A material compression space is formed between a predetermined area of the outer periphery of each of the gears on the upstream side of the seal portion and inner surfaces on both sides of the casing opposing the seal portion, the width of which becomes narrower as the distance approaches the seal portion. At the same time, a feed roll for feeding a high viscosity material to each material compression space is provided near the upstream end of each material compression space above and outside each of the above gears, the roll axis of which is parallel to the axis of each of the above gears. , a distance between each roll and each of the corresponding gears is approximately the same as the width of the upstream end of the material compression space, and
A gear pump for extruding a highly viscous material, characterized in that the rolls are arranged with a distance sufficiently larger than the thickness of the rope-shaped high viscosity material.