NL2002686C2

NL2002686C2 - Apparatus and method for injection molding.

Info

Publication number: NL2002686C2
Application number: NL2002686A
Authority: NL
Inventors: Cornelis Marinus Jagt
Original assignee: I Pac Patents B V
Priority date: 2009-03-30
Filing date: 2009-03-30
Publication date: 2010-10-04

Description

P88026NL00

Titel: Apparatus and method for injection molding.

The invention relates to a molding apparatus for injection molding.

Injection moding apparatus and molds are known in the field.

These normally comprise a first and second mold halves, together defining at least one mold cavity. Plastics material can be brought into the mold 5 cavity, for forming a product. The injection pressure of the plastic injected into the mold cavity will have to be compensated by a press in which the mold is positioned. Especially for larger products and for products with long and/or narrow flow paths for the plastics material in the mold cavity the closure pressure may be high, making a large press necessary, which may 10 be costly and can negatively influence the cycle time for molding a product. Moreover, such press will need relatively much energy.

W02004/024416 describes a mold and method for injection molding, in which at least one movable wall part is provided in the mold cavity, which can be moved from a retracted position to a forward, product 15 forming position, at relatively high speed. In the retracted position of the movable wall part the mold cavity is relatively large, reducing resistance to injection of the plastics material and thus of the pressure needed to keep the mold closed during injection. Still a press is needed to keep the mold closed.

An aim of the present disclosure is to provide an alternative 20 molding apparatus and method for molding.

Another aim of the present disclosure is to provide a molding apparatus or method for injection molding which does not need a separate press for keeping the mold closed.

Still another aim of the present disclosure is to provide a molding 25 apparatus and method for injection molding requiring limited equipment and/or energy.

2

These and other aims can be obtained with a molding apparatus and/or method as claimed and/or described.

In a first aspect a molding apparatus according to this disclosure can be characterised by a first and a second mould part, at least one mold 5 cavity defined by at least said first and second mold parts. A movable wall part is provided for the at least one mold cavity and drive means for driving the movable wall part between a forward position and a retracted position. Mold closure means are provided for closing the mold, wherein the drive means and the mold closure means are functionally coupled to each other, 10 such that upon moving the movable wall part to a forward position the mold closure means apply a closing force to the mold.

In a second aspect a method according to this disclosure for closing a mold having at least two mold parts and at least one mold cavity with at least one movable wall part can be characterized by the movable wall part 15 being moved from a retracted position towards a forward position. Said movement is used for pulling and/or pushing the at least two mold parts together in a closed position.

In order to further describe and elucidate a moulding apparatus and method according to the present disclosure, embodiments will be 20 described hereafter, with reference to the drawings, which show in:

Fig. 1 in side view a molding apparatus;

Fig. 2 in cross sectional side view a first embodiment of a molding apparatus of fig. 1, in a first position;

Fig. 3 in cross section the molding apparatus of fig. 1, in a second 25 position;

Fig. 4 in cross sectional side view a second embodiment of a molding apparatus; and

Fig. 5 in cross sectional view a third alternative embodiment.

In this description only embodiments of a molding apparatus and 30 method are described by away of example. The same or similar parts will 3 have the same or similar reference signs. Any combination of parts of the embodiments described can also be understood as disclosed herein.

In fig. 1 a molding apparatus 1 is shown, comprising a mold 10 having a first mold part 2, a second mold part 3, a lift 4 and an injector 5.

5 Furthermore a control device 6 is provided for operating the molding apparatus 1. In this embodiment the second mold part 3 can be a stationary mold part 3, whereas the first mold part 2 can be a movable mold part 2, which can be lifted from the second mold part 3 by the lift 4. By lifting the first mold part 2 from the second mold part 3 a space between the mold 10 parts 2, 3 can be established, for inserting a robot 7 between the mold parts 2, 3, such as a robot for placing inserts and/or labels in the mold 10 and/or taking out molded products from the mold 10.

The mold 10 comprises at least one mold cavity 8, which is at least partly defined by the first and second mold parts 2, 3. The injector 5 is or 15 can be brought in fluid communication with the mold cavity 8, for example directly or through a valve.

As can be seen in fig. 2 and 3, the mold cavity 8 can have a movable wall part 9, for example in the form of a slide or a piston. The wall part 9 is movable between at least a retracted position, as shown in fig. 2 and a 20 forward position, as shown in fig. 3. In the retracted position of the wall part 9 when the mold 10 is closed the mold cavity 8 has a first volume VI, in the forward position of the wall part 9 the mold cavity 8 has a second volume V2, which is smaller than the first volume VI.

In the embodiment of fig. 2 and 3 the wall part 9 forms a slidable 25 closure of a hydraulic chamber 11, acting as a piston, at a first end 12 of the chamber 11. A seal 13 is provided around the side of the wall part 9 facing the chamber 11, forming a movable seal against the wall 14 of the chamber 11. At the opposite end 15 of the chamber 11a second piston or slide 16 is provided, closing off said second end 15 as a movable wall part. A second 30 seal 17 is provided around said slide 16 forming a slidable seal against the 4 wall 14 of the chamber 11. A channel 18 extends through the second mold part 3 into said chamber 11, for feeding hydraulic fluid into and out off said chamber 11, controlled by the control device 6. Ordinary means such as a pump 19 can be connected to the channel 18 for feeding the hydraulic fluid 5 from and to a storage tank 20. The slide 16 is connected to a plate 21 extending at the side of the second mold part 3 opposite the first mold part 2. A number of rods 22 extend from the plate 21 through the second mold part 3 and the first mold part 2. Clamps 23 are provided around the rods 22 on the first mold part 1, which clamps 23 can be opened and closed around 10 the rods 22, for example electrically, pneumatically or hydraulically, controlled by the control device 6. In the closed position of the clamps 23 lifting of the first mold part 2 off from the second mold part 3 is prevented, whereas when the clamps are opened, the first mold part 2 can be lifted off from the second mold part 3. The clamps 23 can engage the rods 22 for 15 example in indentations, grooves, teeth or the like, indicated by reference sign 24, by way of example. Any means for locking the position of the first mold part 2 relative to the rods 22, at least in the direction away from the second mold part 3 can be used as or in stead of the clamps 23.

At least the hydraulic means 18,19 are comprised in drive means 20 for the movable wall part 9. At least the slide 16, plate 21 and the rods 22 are comprised in closure means for the mold.

A molding apparatus 10 according to fig. 2 and 3 can be used as follows.

With the lift 4 the first mold part 2 is lifted from the second mold 25 part 3 and a product made in the mold cavity 8 is removed by the robot 7, by gravity, if the mold 1 is mounted on a side 25, rotated over e.g. 90 degrees relative to the drawing, or by ejectors or other suitable means. Then the mold 1 is closed by lowering the first mold part 2 onto the second mold part 3 by means of the lift 4, closing the mold cavity 8, and forcing the clamps 23 30 to engage the rods 22, locking the first mold part 2. Then plastics material is 5 injected into the mold cavity 8 by the injector 5, to fill the cavity 8 to a large extend. The volume of plastics material injected is smaller than the volume V2. During or after injection the movable wall part 9 is forced into the direction of the opposite wall of the mold cavity, into the forward position as 5 shown in fig. 3, from a retracted position as shown in fig. 2. To this end hydraulic fluid is forced into the chamber 11 by the hydraulic means, in order to pressurise the movable wall part 9. At the same time the hydraulic fluid acts on the slide 16, forcing this away from the movable wall part 9. This means that the plate 21 and the rods 22 are also moved in a direction 10 away from the first mold part, pulling the first mold part 2 tight against the second mold part 3. In this manner a sufficiently high clamping force can be obtained during movement of the movable wall part 9 toward the forward position. Since the wall part 9 is in the retracted position during at least most of the injection of the plastics material the injection pressure can be 15 relatively low, resulting in a relatively low clamping force for closing the mold during said injection. This can for example be obtained by gravity and/or by the clamps 23 biasing the first mold part 2 onto the second mold part 3. In fig. 2 the distance D1 between the wall part 9 and the slide 16 is disclosed with the wall part retracted, in fig. 3 the larger distance D2 when 20 the slide 16 and wall part 9 are moved away from each other by the hydraulic means. Thus the hydraulic means 18,19, slide 16, plate 21, clamps 23 and rods 22 act as closure means, the hydraulic means 18, 19 as drive means for the wall part 9.

In fig. 2 and 3 the slide 16 and the wall part 9 have the same 25 surface area on which the hydraulic fluid acts. This means that the force exerted on both will be the same. Obviously the surface areas can be varied and can be different for the slide 16 and the wall part 9, in order to vary these forces. Similarly the inertia of the wall part and the plate and slide can be varied, for example by differentiating weight thereof. Thus the speed 30 and acceleration of movement can be varied. In an advantageous manner 6 the speed of the movable wall part can be set relatively high, for example high enough to induce adiabatic heating or frictional heating in the plastics material as a result of the movement of the wall part 9 towards the forward position, such that the temperature of the plastics material is increased 5 again, or at least the temperature reduction is slowed down. Preferably the temperature of the plastics material is increased again, such that the fluidity of the plastics is increased, allowing better filling of the mold cavity 8 at lower pressure than when the mold cavity were to be filled with the same plastics material, having the movable wall part in the forward position 10 constantly. The speed, acceleration, path of travel and timing of the movable wall part 9 can be set by the control device 6. Such method is further elucidated in W02004/024416, incorporated herein by reference.

In fig. 4 an alternative embodiment is shown, in which the first and second mold parts 2, 3 again encloses at least one mold cavity 8. In this 15 embodiment a movable wall part 9 of the mold cavity , for example formed as a forward part of a piston 9A, is carried by a piston rod 30, extending through a bottom end 31 of the chamber 11. At a free end 32 of the piston rod 30 the ends 33 of two levers 34 are pivotably connected, which levers extend into opposite directions and are each carried pivotably by a fixed 20 hinge point 35. The hinge points 35 can be connected to the ground or for example to the second mold part 3. The opposite ends 36 of the levers 34 are pivotably connected to rods 22 connected to the first mold part 2. In this embodiment again the movable wall part 9 can be forced from the retracted position to the forward position by pressurising the chamber 11 by the 25 hydraulic means 18,19. This means that the movable wall part 9 will move into the cavity 8, thereby pulling the piston rod 30 and thus the ends 33 of the levers 34 in the direction of the first mold part 1. This will result in forcing the opposite ends 36 of the levers 34 in the opposite direction, providing for the clamping force for closing the mold 1.

7

In the embodiment of fig. 4 in each rod 22 a spring system 37 is included, which can provide a bias into the closing direction, such that the wall part 9 can first be moved from a retracted position towards a mid position, in which the mold parts are closed with a relatively low clamping 5 force, where after the movable wall part can be moved further to the forward position, increasing the clamping force.

In the embodiment of fig. 4 the mold can be opened by moving the movable wall part toward the end wall 31, moving the rods 22 and thus the first mold part 2 away from the second mold part 3. This means that the 10 hydraulic means can also be used as lift 4.

In fig. 5 a third embodiment is shown, similar to that of fig. 4, wherein the hydraulic means have been replaced by electrical or pneumatic means. In this embodiment the movable wall part 9 is carried by a piston rod 30 which is provided over at least part of its length by screw threads 38. 15 A nut 39 is provided around the piston rod 30, rotatable by a motor 40 and possibly a gear 41. Again levers 34 are pivotable around pivot points 35 and are connected between the piston rod 30 and rods 22. By rotating the nut 39 around the piston rod 30 the levers will be pivoted, depending on the direction of rotation of the nut, either for lifting the first mold part 2 from 20 the second mold part 3 or for pulling the first mold part 2 tight against the second mold part 3. The motor can be any suitable type of motor, such as but not limited to electric, pneumatic, hydraulic or combustion.

In the embodiments of fig. 4 and 5 obviously the pivot points 35 can be placed closer to either end 33, 36, in order to set the distance over which 25 the piston rod 30 is moved relative to the distance over which the rods 22 are moved. In an embodiment the pivot points may be adjustable to this end.

It will be clear that the clamping force can be increased by including force enhancing means between the plate 21 or levers 34 and the 30 first mold part 2, such as for example pulley systems, increasing the closing 8 force by reduced distance of travel. This will be directly clear to any person skilled in the art.

The present disclosure is by no means limited to the embodiments disclosed or discussed. Many variations are possible within the scope of the 5 description and claims. For example a mold can have more than one mold cavity, whereas mold cavities can be exchangeable within the molding apparatus. For each mold cavity more than one movable wall part can be provided, at least one of them having drive means coupled to the closure means for the mold. In the embodiments shown the movable wall part 9 and 10 the slide 16 are provided at opposite ends of one chamber 11. However, they can also be provided in different chambers, interconnected by channels, openings, valves such as throttle valves or the like, leading to the same effects, wherein the openings, channels or valves can influence for example the speed or acceleration of either part and/or the timing of movement 15 thereof. A buffer means can be provided for example in such connecting channel, such that bringing back the plate and/or movable wall part into a starting position may be delayed or slowed down relative to the movement in the opposite direction and/or relative to the other of the slide and movable wall part or vice versa.

20 In an embodiment of figs. 2 - 4 the pump 18 can be used for sucking the hydraulic fluid from the chamber 11, pulling the movable wall part 9 and the slide 16 closer together or moving the movable wall part 9 closer to the end 31. This way the movable wall part 9 can be pulled away from the product formed in the cavity. In stead of the lift 4 as shown in fig. 2 and 3 as 25 a piston system, the clamps 23 could be used for lifting the first mold part from the second mold part. To this end for example the clamps 23 can be made as nuts engaging the rods 22 being provided with external threads. The nuts will be attached rotatably to the first mold art 2, such that when they are rotated around the rods 22 they will move the first mold part 2 30 along the rods 22, towards or away from the second mold part 3. The screw 9 threads will preferably be self braking. The closure means will then provide for the increased clamping force. Other numbers of levers, hydraulic means, plates 21 or the like can be used, whereas more than two mold parts can be combined. S mold according to the description can be a stack mold. The 5 clamps 23 can be positioned on, in or at the plate 21 in stead of on the first mold part, the rods being fixed to the first mold part 2. The piston 16 can be replaced by one or more pistons working side ways, knee-lever systems being provided for pulling the mold parts together when the pistons are moved outward.

10 Combinations of aspects and parts of the embodiments shown and described are also considered to have been disclosed in the present disclosure.

Claims

1. Forming device for injection molding, comprising a first and a second mold part, at least one mold cavity determined by at least said first and second mold parts, wherein a movable wall part is provided for the at least one mold cavity and drive means for driving the movable wall part between a forward position and a retracted position, wherein mold closing means are provided for closing the mold, wherein the drive means and the mold closing means are functionally coupled to each other such that when the movable wall part moves to a forward position, the mold closing means exert a closing force on practice the mold.

2. Forming device as claimed in claim 1, wherein the drive means are fluid-driven and the closing means are fluid-driven.

3. Forming device as claimed in claim 1 or 2, wherein at least one of the drive means and the closing means are hydraulically operated.

4. Forming device as claimed in claim 2 or 3, wherein a transfer structure is connected to the closing means and to the first mold part, while the transfer structure extends at least partly through or along the second mold part, such that a distance away from the first mold part on the transfer structure working force biases the mold in the closed position.

5. Forming device as claimed in any of the foregoing claims, wherein the second mold part is provided at least partly between the first mold part and a transfer part, wherein at least one rod extends through and / or along the second part and along and / or through the first mold part .

6. Forming device as claimed in claim 5, wherein confining means are provided on the or each pull rod, in and / or on the first mold part.

Forming device as claimed in claim 6, wherein the confining means comprise clamping elements.

8. Forming device as claimed in any of the foregoing claims, wherein a lifting device is provided for opening and closing the mold.

9. Forming device as claimed in any of the foregoing claims, wherein the drive means and the closing means are at least partly included in a double-acting piston assembly.

10. Forming device as claimed in any of the foregoing claims, wherein the device comprises means for setting the speed and / or distance for movement of the at least one movable wall part.

11. Forming device as claimed in claim 1, wherein the drive means and / or closing means are motor-driven.

12. Method of closing a mold with at least two mold parts and at least one mold cavity with at least one movable wall part, wherein the movable wall part is moved from a retracted position to a forward position and said movement is used to contracting and / or pushing at least two mold parts in a closed position.

13. Method as claimed in claim 12, wherein said movement is induced by one of the mold parts by hydraulic or pneumatic force and said force is transmitted to the other of the two mold parts for closing the mold.

14. Method according to claim 12, wherein said movement is induced by one motor-driven force in one of the mold parts and said force is transmitted to the other of the two mold parts for closing the mold.

A mold for use with a forming device according to any of claims 1-11 or a method according to any of claims 12-14.