DE102022112811A1 - Plasticizing and/or injection unit of a plastics processing machine - Google Patents

Abstract

The invention relates to a plasticizing and/or injection unit (1) of a plastics processing machine, comprising a screw cylinder (2) with an internal cylindrical surface (3) and a screw cylinder located in the screw cylinder (2) and rotating relative to the screw cylinder (2) around an axis ( a) rotatably arranged screw (4), a non-return valve (5) being arranged at one axial end of the screw (4) in order to enable the flow of plasticized plastic material in one direction (R1) and in the opposite direction (R2) at least to complicate. In order to achieve a sufficient effect without moving parts in such a plasticizing and/or injection unit, the invention provides that the non-return valve (5) has a cylindrical base body (6), in the outer circumference (7) of which there is a flow channel (8). for plasticized plastic material, the flow channel (8) consisting of a number of adjoining channel sections (13), each channel section (13) having a first sub-channel (9) and a second sub-channel (10), the first sub-channel (9 ) and the second partial channel (10) are connected in parallel and the two partial channels (9, 10) are fluidly connected to one another at two adjacent meeting points (11, 12), the first partial channel (9) being between the two meeting points (11, 12). has lower flow resistance than the second sub-channel (10).

Description

The invention relates to a plasticizing and/or injection unit of a plastics processing machine, in particular an injection molding machine, comprising a screw cylinder with an internal cylindrical surface and a screw located in the screw cylinder and rotatably arranged about an axis relative to the screw cylinder, with one at one axial end of the screw Non-return valve is arranged to enable the flow of plasticized plastic material in one direction and at least to make it more difficult or to prevent it in the opposite direction.

In plasticizing and/or injection units of this type, as are typically used in injection molding machines, non-return valves are usually used at the axial end of the screw. Their task is to prevent the plastic melt from flowing back from the antechamber of the plasticizing cylinder into the screw flights during the injection process. During dosing, the flow of melt from the screw towards the antechamber must be possible.

It is not absolutely necessary that the backflow of melt is absolutely prevented; In many applications it is only necessary that the backflow remains low and reproducible in order to ensure sufficient process or component consistency.

Non-return valves are constantly flooded with the plasticized plastic material, so that they are subject to relatively high levels of wear due to the abrasive effect of the plastic material. It would therefore be desirable to forgo a non-return valve.

In the EP 3 294 519 B1 A procedure for operating an injection molding machine is described, in which a non-return valve is dispensed with. However, this requires a relatively complex procedure.

As a rule, non-return valves with mechanically moving parts are used to enable closing and opening during the individual process steps. The most common type in this regard is the three-part ring non-return valve. It consists of the tip, the shut-off ring and the stop ring. The shut-off ring can move between the tip and the stop ring and thus open or close the flow path like a valve. Special solutions for such non-return current barriers reveal the DE 297 01 495 U1 , the DE 100 59 615 A1 , the DE 199 59 495 C1 and the DE 102 55 953 B3 .

The invention is based on the object of designing the non-return valve in a plasticizing and/or injection unit of the type mentioned in such a way that it works as wear-free as possible and still has a sufficient effect, i.e. H. prevents or makes more difficult the flow of plasticized plastic material in the opposite direction mentioned. The aim is in particular for the non-return valve to work without moving parts.

The solution to this problem by the invention is characterized in that the non-return valve has an at least partially cylindrical base body, in the outer circumference of which at least one flow channel for plasticized plastic material is incorporated, the at least one flow channel consisting of a number of adjoining channel sections, each channel section has a first sub-channel and a second sub-channel, the first sub-channel and the second sub-channel being connected in parallel and the two sub-channels being fluidly connected to one another at two adjacent meeting points, the first sub-channel having a lower flow resistance between the two meeting points than the second sub-channel.

The lower flow resistance of the first sub-channels is preferably achieved by the fact that the plasticized plastic material experiences the smallest possible directional deflection from a straight direction when flowing through the first sub-channels, which is defined by the course of the flow channel. The directional deflection from the straight direction is preferably always less than 45°, particularly preferably less than 30°.

The higher flow resistance of the second sub-channels is preferably achieved in that the plasticized plastic material experiences a directional deflection from the stated straight line direction as it flows through the second sub-channels, which is at least 150° in sections, preferably at least 180°.

Said straight direction is therefore to be understood as meaning that the flow channel, possibly after unwinding from the cylindrical base body of the non-return valve, has an extension that is largely straight or linear.

With this specification, the design of a so-called Tesla valve (see below) is realized, which according to the invention is used in a non-return valve of a plasticizing and/or injection unit of a plastics processing machine.

The at least one flow channel preferably extends helically around the cylindrical base body of the non-return valve. In this case it is preferably provided that in the side view of the base body the angle of the helix to the axis is at least 30°.

A further preferred embodiment of the invention provides that a plurality of flow channels arranged parallel to one another are formed in the cylindrical base body of the non-return valve. These several flow channels arranged parallel to one another can be designed in the manner of a multi-start thread in the cylindrical base body of the non-return valve. Particularly preferably, the plurality of flow channels arranged parallel to one another are arranged equidistantly around the circumference of the base body of the non-return valve.

The at least one flow channel preferably has at least five, preferably at least ten channel sections arranged one behind the other, each of which has the two partial channels arranged parallel to one another.

The cylindrical outer circumference of the base body is (professionally) tolerated in relation to the inner cylindrical surface of the screw barrel in such a way that, on the one hand, the mobility, i.e. H. the relative rotation and the relative axial displacement between the screw cylinder and the non-return valve ensure that, on the other hand, no significant amount of plastic melt can flow through the remaining gap between the internal surface of the screw cylinder and the outer circumference of the base body during operation of the plasticizing and / or injection unit. The melt is therefore practically exclusively guided through the flow channels.

The plasticizing and/or injection unit is preferably designed as a push screw unit in which the screw is axially displaced relative to the screw cylinder for the purpose of injecting the melt.

Advantageously, the non-return valve according to the invention has no moving individual parts, so that production is correspondingly inexpensive.

The invention uses the principle of the so-called Tesla valve, which is in the US 1,329,559 A is described, to which express reference is made. As a result of the above-described and defined design of the sub-channels, in which a sub-channel of the first type described and a sub-channel of the second type described are connected in parallel and thus form a channel section, a large number of which are arranged in series one behind the other, a check valve effect is generated, in which the flow resistance in one flow direction is significantly lower than in the other flow direction. The backflow of melt is thus prevented or hindered without moving parts and passively via the geometry of the flow channels.

• 1 zeigt schematisch den Radialschnitt durch eine Plastifizier- und/oder Einspritzeinheit mit Schneckenzylinder, Schnecke und Rückstromsperre,
• 2a, 2b und 2c zeigt die (von der Schnecke demontierte) Rückstromsperre, wobei diese in drei Seitenansichten dargestellt ist, bei denen die Rückstromsperre jeweils um ihre Achse a um einen gewissen Winkel gedreht wurde,
• 3 zeigt zwei benachbart angeordnete Fließkanäle, die in den Außenumfang des Grundkörpers der Rückstromsperre eingearbeitet sind, und
• 4 zeigt noch einmal die Rückstromsperre, wobei schematisch die Abwicklung des Fließkanals vom zylindrischen Grundkörper der Rückstromsperre dargestellt wurde.

An exemplary embodiment of the invention is shown in the drawings.

• 1 shows schematically the radial section through a plasticizing and/or injection unit with screw cylinder, screw and non-return valve,
• 2a , 2 B and 2c shows the non-return valve (dismantled from the screw), which is shown in three side views, in which the non-return valve was each rotated about its axis a by a certain angle,
• 3 shows two adjacently arranged flow channels, which are incorporated into the outer circumference of the base body of the non-return valve, and
• 4 shows the non-return valve again, with the development of the flow channel from the cylindrical base body of the non-return valve shown schematically.

In 1 a plasticizing and/or injection unit 1 is schematically sketched, which has a screw cylinder 2 with an internal cylindrical surface 3. A screw 4 is arranged in the screw cylinder 2, at one axial end of which a non-return valve 5 is arranged (screwed).

The screw cylinder 2 or the screw 4 have an axis a. Along this, the screw 4 can be axially displaced relative to the screw cylinder 2 in order to inject plasticized plastic melt into an injection molding tool (not shown). So that during dosing, melt flows in the direction of R1 (see. 1 ) can flow, which collects in the screw anteroom, but so that the plastic material collected in the screw anteroom does not flow back in the direction of R2 during injection, the non-return flow barrier 5 is provided. The non-return valve is concentric to axis a, so that this is also the axis of the same.

The specific embodiment according to a preferred exemplary embodiment of the invention results from the synopsis of 1 with the 2 until 4 .

The non-return valve 5 has a cylindrical base body 6 which has a cylindrical outer circumference 7.

Flow channels 8 are incorporated into the outer circumference 7 of the base body. At the in 2 In the exemplary embodiment shown, a single flow channel 8 runs helically around the outer circumference 7 of the base body 6. In the 2a , 2 B and 2c The non-return valve 5 is shown in different positions relative to the axis a, so that it can be seen that the flow channel 8 extends from the front (left) end of the base body 6 to the rear (right) end of the same and in a helical shape around the outer circumference 7 runs around.

Alternatively, several flow channels 8 running parallel to one another can also be provided; in this respect it will be up 3 Referenced, where two parallel flow channels 8 are shown. The flow channels 8 generally have a straight direction G, ie a direction that extends essentially linearly and is conveyed into the plastic melt.

In this respect it will be up 4 Reference is made, where the development of the flow channel 8 from the base body 6 is shown schematically. The stated straight line direction G and the angle α which this direction includes with the axis a are entered.

Each of the flow channels 8 has a structure that best suits them 3 emerges. The flow channels 8 consist of a number of channel sections 13 one behind the other (ie connected in series) (see Fig. 3 ). The channel sections 13 each consist of a first sub-channel 9 and a second sub-channel 10, the two sub-channels 9, 10 being arranged parallel to one another. In the straight direction G, the two partial channels 9, 10 come together at two adjacent meeting points 11 and 12 and are fluidly connected to one another here.

How out 3 results, the first sub-channels 9 are designed essentially straight, ie when plastic melt flows through the first sub-channels 9, the flow of the material is only slightly deflected from the straight direction G. In 3 In this regard, the angle β is entered, which indicates the direction of deflection from the straight direction G and which should always be smaller than 45°.

However, the second sub-channels 10 are shaped in such a way that the plastic melt experiences a significantly greater deflection as it flows through the second sub-channels 10. In this regard, reference is made to the angle γ, which is in 3 is registered. This angle is in the exemplary embodiment 3 approximately 150°, which means that with the corresponding flow the plastic melt practically or largely reverses its flow direction in order to then exert a braking effect on the material flow at the point of contact with the first partial channel 9.

Flows accordingly - according to the illustration below 3, p . the arrows shown - the material in the first direction R1, the melt can pass through the flow channel 8 largely undisturbed. However, according to the illustration above, it flows into 3, p . the arrows shown - the material in the second direction R2, the aforementioned accumulation or braking effect occurs, so that the flow resistance through the flow channel 8 is significantly greater. According to the invention, this is used for the functionality of the non-return valve.

At the meeting points 11 of the first and second partial channels arranged parallel to one another (see Fig. 3 , above) the flow is divided and redirected. The flow resistance of the flow channel becomes higher the more channel sections 13 are arranged in series one behind the other.

In 4 The above-mentioned angles β and γ are also entered again in the development of the flow channel 8.

The proposed non-return valve 5 can therefore completely dispense with moving parts. The backflow of the melt (in the direction of R2) is regulated or prevented exclusively passively by the design of the geometry of the flow channel and in particular the first and second sub-channels 9, 10.

By arranging a large number of channel sections 13 arranged one behind the other, the desired effect is increased, so that in one direction (direction R2) an effective loading or prevention of the material flow is achieved.

According to the preferred embodiment of the non-return valve shown, the principle of the Tesla valve is used, but an advantageous adaptation is made to the present application of the non-return valve and in particular to the shear-thinning flow behavior of plastic melts.

In order to be able to continue to use the available installation space of existing non-return valves, the space available for the number of repeating geometry segments, ie channel sections, is limited. In order to solve this problem, as already explained above, the flow channel 8 is introduced into the base body 6 in a helical shape (ie helically). This is in 2 (and again in 4 ) indicated where the angle α is entered, which in the side view the straight direction G includes with the axis a. As a result, the entire effective length of the flow channel 8 is extended accordingly (which is good in 4 can be seen); A larger number of channel sections 13 can be arranged one behind the other (in a row).

In order to increase the flexibility in the design of the flow channel, it is also possible to arrange several flow channels parallel to one another in the manner of a multi-start thread on the outer circumference of the base body of the non-return valve. This is explained schematically 3 Referenced, where two parallel flow channels 8 are illustrated.

The individual flow channels 8 are preferably arranged equidistantly around the outer circumference of the base body.

For example, three, four, five or six flow channels 8 running parallel to one another can be arranged.

With the flexibility that can be achieved in this way, it is possible to efficiently design variants of the proposed non-return valve 5 so that they are optimally adapted to a specific type of plastic.

List of reference symbols:

1

Plasticizing and/or injection unit

2

screw cylinder

3

internal cylindrical surface

4

Snail

5

Non-return valve

6

cylindrical base body

7

Outer circumference of the base body

8th

Flow channel for plasticized plastic material

9

first sub-channel

10

second sub-channel

11

first meeting point

12

second meeting point

13

Canal section

a

axis

R1

first direction of flow of plasticized plastic material

R2

second direction of flow of plasticized plastic material

G

Straight direction

α

Angle of the helix to the axis a

β

Angle of directional deflection from the straight direction in the first sub-channel 9

γ

Angle of the directional deflection from the straight direction in the second sub-channel 10

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 3294519 B1 [0005]
• DE 29701495 U1 [0006]
• DE 10059615 A1 [0006]
• DE 19959495 C1 [0006]
• DE 10255953 B3 [0006]
• US 1329559 A [0019]

Claims (10)

Plasticizing and/or injection unit (1) of a plastic processing machine, in particular an injection molding machine, comprising a screw cylinder (2) with an internal cylindrical surface (3) and a screw cylinder located in the screw cylinder (2) and relative to the screw cylinder (2) about an axis ( a) rotatably arranged screw (4), a non-return valve (5) being arranged at one axial end of the screw (4) in order to enable the flow of plasticized plastic material in one direction (R1) and in the opposite direction (R2) at least to make it more difficult, characterized in that the non-return valve (5) has an at least partially cylindrical base body (6), in the outer circumference (7) of which at least one flow channel (8) for plasticized plastic material is incorporated, the at least one flow channel (8). a number of adjacent channel sections (13), each channel section (13) having a first sub-channel (9) and a second sub-channel (10), the first sub-channel (9) and the second sub-channel (10) being connected in parallel and the two Sub-channels (9, 10) are fluidly connected to one another at two adjacent meeting points (11, 12), the first sub-channel (9) having a lower flow resistance between the two meeting points (11, 12) than the second sub-channel (10). Plasticizing and/or injection unit Claim 1 , characterized in that the lower flow resistance of the first sub-channel (9) is achieved in that the plasticized plastic material experiences the smallest possible directional deflection (β) from a straight line direction (G) as it flows through the first sub-channel (9). of the flow channel (8) is defined. Plasticizing and/or injection unit Claim 2 , characterized in that the directional deflection (β) from the straight direction (G) is always less than 45°, preferably less than 30°. Plasticizing and/or injection unit according to one of the Claims 1 until 3 , characterized in that the higher flow resistance of the second sub-channel (10) is achieved in that the plasticized plastic material experiences a directional deflection (γ) from the straight direction (G) as it flows through the second sub-channel (10), which is caused by the course of the flow channel (8) is defined, which is at least 150° in sections, preferably at least 180°. Plasticizing and/or injection unit according to one of the Claims 1 until 4 , characterized in that the at least one flow channel (8) extends helically around the cylindrical base body (6) of the non-return valve (5). Plasticizing and/or injection unit Claim 5 , characterized in that in the side view of the base body (6), the angle (α) of the helix to the axis (a) is at least 30°. Plasticizing and/or injection unit according to one of the Claims 1 until 6 , characterized in that a plurality of flow channels (8) arranged parallel to one another are formed in the cylindrical base body (6) of the non-return valve (5). Plasticizing and/or injection unit Claim 7 , characterized in that the several flow channels (8) arranged parallel to one another are designed in the manner of a multi-start thread in the cylindrical base body (6) of the non-return valve (5). Plasticizing and/or injection unit Claim 7 or 8th , characterized in that the plurality of flow channels (8) arranged parallel to one another are arranged equidistantly around the circumference of the base body (6) of the non-return valve (5). Plasticizing and/or injection unit according to one of the Claims 1 until 9 , characterized in that the at least one flow channel (8) has at least five, preferably at least ten channel sections (13) arranged one behind the other.

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