GB2218035A

GB2218035A - Injection moulding press

Info

Publication number: GB2218035A
Application number: GB8910515A
Authority: GB
Inventors: Adelio Grasselli
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-05-06
Filing date: 1989-05-08
Publication date: 1989-11-08
Anticipated expiration: 2009-05-08
Also published as: KR970011568B1; IT1219271B; IT8867418A0; FR2630962A1; GB2218035B; DE3914846A1; ES2014076A6; CA1329686C; KR890017064A; GB8910515D0

Description

0 2',"'i '18 0 3 5 1 M&C FOLIO: 230P58690 INJECTION MOULDING PRESS

WANGDOC: 1427P The present invention relates to presses for the injection moulding of plastics materials in general, e.g. thermoplastics, polyesters, and elastomers. The aim of the invention is improved operative performance of such presses, at the same time restricting manufacturing costs.

As is known, large moulding presses comprise a basic structure which supports a fixed plate, associated with a fixed half-mbuld, and a mobile plate, slidable on three or more support columns having parallel axes, associated with a mobile half-mould; hydraulic means for moving the mobile plate: locking means for the mobile plate when the mould is closed; injecting means; reaction means: at least one hopper with dosing means for feeding a plasticizing cylinder having a nozzle communicating with the inside of the mould through its fixed part; and means for extracting the moulded parts on termination of each operating cycle.

Known means are used to active the mobile plate, such as: pistons and relative hydraulic cylinders. which may or may not cooperate with mechanical means. integrated 2 with means for temporarily locking the mould in the closed position; jointed mechanisms; or other mixed devices, including hydraulic closing means and locking mechanisms.

Furthermore. semi-automatic or completely automatic presses are known. Such presses are provided with known automatic control means which, one the operator has fixed the operating conditions and activated the press. allow the press to repeat the first cycle indefinitely, including the automatic expulsion of the moulded part.

For the continuous functioning of these machines, other than supplying the feed hopper(s), maximum precision of the moulds and of the complex mechanisms constituting the machine is necessary, as well as accurate and costly maintenance.

The present invention provides a semi-automatic, automatic, or nonautomatic press which comprises hydraulic cylinders, cooperating with rescindable groove mechanical means, able to guarantee blocking of the mobile plate and relative half-mould joined to said plate. in a perfect closed position with respect to the half-mould coupled to the fixed plate and with respect to the hydraulic reaction cylinders parallel to the columns along which the mobile plate is slidable.

ZI 3 Preferred and optional features are set forth in claims 2 et seq. The hydraulic cylinders may be supported by a frame which replaces the usual counter-reaction plate. thereby eliminating the space taken up by the plate and making more room, in the longitudinal sense, for an expulsion mechanism for ejecting the moulded part.

The extremities of the columns. preferably three or more. may be linked to the fixed member by means of corresponding piston heads, having a short run in single stroke hydraulic cylinders, which can be activated in the injection phase, thereby guaranteeing that the position of the moulding comples, subjected to a high level of stress generated by the inside pressure of the mould in the operating phase. cannot be altered.

In a preferred embodiment, additional hydraulic cylinders have pistons which are screw adjustable with respect to their corresponding shafts, the free end of each shaft fixed to pushing means which start up on termination of the moulding cycle so as to supply an initial unlocking and opening push to the mould.

The invention will be described further, by way of example, with reference to the accompanying schematic drawings, on a variable scale, in which:

4 Figure 1 is a side view of a preferred embodiment of the press according to the invention; 55.

Figure 1A is a plan view of the press; Figures 2. to 4 are part--:sectioned plan views which illustrate the press at three different operating phases; Figures 5 and 6 are part-sectioned plan views, on a larger scale, which highlight some details of the press in different operating conditions:

Figure 7 is a section on line VII-VII in Figure 5; and Figure 8 is a section on line VIII-VIII in Figure 6.

With reference to Figure 1, the press comprises a base 1 supporting the following main organs: a hopper 2; a plasticizing and feed group 3, provided with an injecting nozzle 4 which passes through a fixed plate 7 and enters a fixed part or halfmould 5 (Figures 2 to 8); columns 11, in this case four in number, symmetrically coupled, coaxial with double stroke reaction cylinders 50; a mobile plate 9 to which a mobile part 6 of the mould is linked; and a support 12 for approach and return cylinders 29.

As shown in Figures 2 to 8, the half-mould 5 is fixed to the fixed plate 7, which has an inlet 8 for the nozzle 4 (Figures 3, 5) for input into the closed mould,.when the half-mould 6 (linked to the mobile plate 9), due to the action of pistons 43, associated with shafts 44 linked to the plate 9. is in the (closed) position shown in Figures 4 and 6 with respect to the fixed part 5. The mobile plate 9 is slidably mounted on the cylinders 50 with the interposition of bushings 48. Figures 2, 7, and 8 show centering bushings 31 for the respective columns 11. A known mechanism 10 is associated with the mobile plate 9, for the expulsion of the moulded part.

The approach and return cylinders 29, parallel to the columns 11, pass through the fixed support 12, which can advantageously assume the structure of a frame of quadrangular or other suitable geometric shape, so as to eliminate any waste of space in a longitudinal sense. so that the expulsion mechanism 10 is able to make wide longitudinal movements for stripping the moulded part. Nuts 13 protected by castings 14 (Figures 7, 8) are screwed on the columns 11 for the exact adjustment of the position of the support 12.

The extremities lla of the columns 11 are linked to the fixed plate 7 by means of single stroke pistons 17 6 k running in cylinders 18; packings 19. 20 guarantee the sealing between piston 17. cylinder 18 and the extremity lia of each column. Each cylinder 18 is associated with the fixed plate 7 and is fed with fluid under pressure. by means.of a suitable duct 22 (Figures 5, 6). A single stroke. push piston 23. in contact with the extremity lla of each column 11. is fed by a suitable duct 27. On the sleeve of each reaction cylinder 50 there is perimetrical recess 32 with one edge 33 at 900 to the axis of the corresponding cylinder and the opposide edge 34 diverging radically outwards. Locking means are mounted on the mobile plate 9, each locking means comprising a couple of semi-collars 35 (Figures 5 to 8) slidably mounted on paralled rods 37, at least one of which. 37a is associated with double stroke pistons 38 running in corresponding hydraulic cylinders 39 fed by suitable ducts (not shown). The rods 37 are fixed to the plate 9; the semi-collars 35 slide along the rods 37, 37a.

Pistons 43, with shafts 44 connected. at 45, to the mobile plate 9, are mounted in the double stroke approach and return cylinders 29. connected at 46, 47 to intake and discharge ducts for the fluid under pressure.

A couple of cylinders 51, each having an axis paralled to the longitudinal axis of the press. are fixed to the p- 7 plate 7, only one of which can be seen in Figure 6. A piston 52 is mounted in each cylinder 51, this piston having a run limited by the height of the cylinder; the free end of the piston shaft 53 is provided with pushers which act against the mobile plate 9 at 54.

The use and working of the machine as described below.

In an initial stage the mobile plate 9 is moved away from the fixed plate 7 (Figure 2). The pistons 43, in the corresponding cylinders 29. are in an end-of-run position.

At the second stage, after input of fluid under pressure into the circuit of the machine, the pistons 43 move the mobile plate 9 towards the fixed plate 7 and the parts 5. 6 of the mould gradually come together (Figures 3, 5) until closest approach of the plates 7 and 9 is obtained (Figures 4, 6). The sliding of the plate 9, with respect to the sleeves of the cylinders 50, is facilitated by the prescence of the bushings 48 fixed to the plate 9; these bushings are. obviously, longer than the width of the recesses 32, so as to avoid jamming. At the same time the piston 23, activated, rests on the bottom of the cylinder 18 keeping the piston 17 in the end of the run position with the respect to said cylinder.

8 At the third stage, the mobile plate 9 is locked by means of the closure of the semi-collars 35 causec by the activation of the hydraulic cylinders 39. The semi-collars 35 enter the recesses 32 in the sleeves of the reaction cylinders 50.

At the fourth stage, fluid under pressure through the duct 22 activates the piston 17, which stabilizes the relative positions of the fixed plate 7 and the columns 11, avoiding any, minimal, movement of the parts 5 and 6 of the mould.

The injection phase follows. for example forming a part "All (Figure 6) and, finally the stage at which the mould opens and the part is expelled (Figure 2). Once the part is expelled, the machines returns to the starting condition, ready for another operating cycle.

On termination of the injection cycle, the initial push for detaching the parts 5, 6 of the mould is supplied by the couple of short run pistons 52 running in the cylinders 51. The consequent opening of the mould and the initial position of the machine is obtained due to the action of the double stroke hydraulic approach and return cylinders 29, fed by ducts 46, 47 activating the pistons 43, the shafts. 44 of which are fixed to the k 1 1 9 mobile plate 9.

The initial detachment of the parts 5. 6 of the mould by the pistons 52 allows one to restruct the power and consequently the size of the hydraulic cylinders 29. resulting in considerable economy of hydraulic fluid (oil) and an optimal sequence of the phases of the operating cylce of the machine.

Obviously the press is furnished with a plurality of known mechanisms, such as end-of-run switches, thermostats, and safety devices to interrupt the operating cycle, at any phase. in case of any unforeseen faults that may arise when the machine is running.

The advantages deriving from the above-described press can be summarized as follows:

elimination of the reaction plate and consequently wider longitudinal movement of the expulsion means:

improved accessibility to the expulsion mechanism:

terminal bearing of the support columns with respect to the fixed plate. with the intermediary of a fluid bearing, under pressure, so as to prevent any deformation of the fixed plate; considerable reduction in the overall length of the machine due to the frame shape of the support 12, replacing the reaction plate. and which can be crossed by the jexpulsion means; support means for the support columns not subject to any bending stress; possibility of choosing the most suitable materials to build the organs of the machine, according to the reduced stress to which some organs are subjected due to the particular architecture of the press; an example of this is the double stroke cylinders 29. which are subject to compression (rather than to tracti.on which necessitates the use of materials having a high resistance to stress).

Although the description and the drawings refer to the example of a horizontal presses. the invention is not limited to such a structure and does not exclude vertical presses having the characteristics described and any other similar presses within the scope of the claims.

E "7 01 i

Claims

1. A press for the injection mouling of plastics materials, in general, comprising support guide columns, having one extremity linked to a fixed member for carrying a fixed mould part, a mobile member for carrying a mobile mould part complementary to the fixed mould part, the mobile member being slidable along the columns, double-stroke piston-and- cylinder devices for moving the mobile member towards and away from the fixed member, and mechanical means. preferably activated by hydraulic means. for locking the position of the mobile member when the mould is closed.

2. A press as claimed in claim 1, in which the locking means comprise locking elements. preferably semi-collars. the locking elements being associated with hydraulic actuating means which force the locking elements to engage in recesses in the guide columns along which the mobile member runs.

3. A press as claimed in claim 1 or 2, in which the locking means are mounted on the mobile member itself.

4. A press as claimed in any preceding claim, in which one of the fixed and mobile members carries a short-stroke hydraulic piston-and-cylinder device which 12 acts on the other member to push the closed parts of the mould apart after moulding.

5. A press as claimed in any preceding claim. including double stroke hydraulic reaction cylinders.

6. A press as claimed in any preceding claim, in which the extremities of the columns fixed to the fixed member are associated with hydraulic piston-and-cylinder devices actuable to stabilize and lock their relative position during injection moulding.

7. An injection moulding press substantially as described with reference to. and as shown in, the accompanying drawings.

Published 1989 at The Patent Office, State House, 66 71 High HoCnern, London VrCIR4TP. Further copies maybe obtamed from The Patent Office. Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd- St Mary Cray, Kent, Con. 1187 1 1 09