GB2064415A

GB2064415A - Mould Closing and Locking Arrangement

Info

Publication number: GB2064415A
Application number: GB8037289A
Authority: GB
Original assignee: Umformtechnik Herbert Warnke VEB
Current assignee: Umformtechnik Herbert Warnke VEB
Priority date: 1979-11-29
Filing date: 1980-11-20
Publication date: 1981-06-17
Also published as: FR2470674B1; CS268756B1; BG37256A1; AT378500B; SE8008383L; DD146406A1; GB2064415B; SE434357B; DE3034024C2; DE3034024A1; IT8050255A0; IT1145296B; FR2470674A1; ATA460580A; SU1287975A1

Abstract

In a method for actuating a mould closing and locking arrangement of an injection moulding machine or a metal pressure casting machine, having a movable mould mounting platen and a fixed mould mounting platen, the movable platen is moved into the closure position by means of pressure cylinders, locking being effected simultaneously with the traverse stroke into the closure position. During the traverse stroke into the closure position, when the end of each of four columns (29) attached to the movable platen abuts a cover (34) of a clamping bush (31), a hydraulic locking cylinder (14) is pressurised after the displacement of the opening piston 46 inside a cylinder 7 has displaced working fluid in the direction of the locking cylinder (14). On completion of the locking stroke the mould closure stroke is caused by a cam, attached to the piston rod of the locking cylinder 14, actuating a switch so that the pressure chamber 17 of a closure cylinder (47) is pressurised. For the removal of the moulding the opening cylinder 7 and the locking cylinder 14 are simultaneously actuated. <IMAGE>

Description

SPECIFICATION Method and Hydraulic Circuit Arrangement for Injection Moulding This invention relates to a method and hydraulic circuit arrangement for actuating the mould closing arrangement of plastics injection moulding machines, in which the mould mounting platens are locked to one another before the mould closure and clamping force is applied. The invention is applicable in a similar manner to metal pressure casting machines.

Injection moulding machines are known which have a movable and a fixed mould mounting platen and in which the movement of the movable platen is effected by separately arranged, relatively long-stroke working cylinders, locking being effected simultaneously by locking elements mounted for constrained movement, with a superimposition of rotational and translational movement. Unlocking is effected synchronously with the opening stroke of the mould. Such locking arrangement is known from German Democratic Republic Patent 133 635.

Columns mounted rotationally fast and axially adjustably in a movable mould mounting platen have at their ends, which enter into the fixed mould mounting platen, annular segment-shaped outer dogs which during the traverse stroke into the closure position engage clamping bushes constrainedly guided in the fixed mould mounting platen.

The clamping bushes, which in such case act as locking elements, have inner annular segment shaped dogs and are constrainedly controlled by a cam and pin follower system. During the travel of the movable mould mounting platen into the closure position, the outer dogs on the columns pass through the inner dogs of the bush, which they displace in the axial direction. Due to the constrained guidance by means of the cam and follower system the bush is moved axially by the length of the mould closure stroke and is rotated through an angle in order to lock the outer dogs to the inner dogs. Then the short-stroke closure cylinders are brought in without interrupting the traverse.

Such locking arrangement has the following disadvantages. The cam and follower systems for the bushes are very liable to wear. Furthermore, the relatively long stroke of the large-area closure piston which is due to the characteristics of the cam and follower system and is required only for the locking operation is very unfavourable, i.e. it means that a very large amount of hydraulic liquid in the closure system must be displaced and sucked back, so that the final part of the stroke of the mould mounting platen is considerably decelerated. Moreover, for this reason relatively long guide and sealing surfaces are required.

It is an object of the invention to provide a mould closing arrangement with wear-resistant locking elements which ensure that the locking time is not disadvantageous to the total cycle time of the injection moulding machine.

The problem which the invention aims at solving is to provide a method enabling the mould closure and locking operation and also the mould unlocking and opening operation to be effected in a continuous operation, the passive stroke of the closure piston which is required to initiate the locking operation being shortened, the mechanical constrained guidance of the locking elements being eliminated, and a hydraulic circuit arrangement being provided for carrying out the method.

Accordingly, the present invention consists in a method of closing and locking the mould mounting platens of injection moulding machines, in which the movable mould mounting platen is moved into the closure position by long-stroke low pressure cylinders, locking being effected simultaneously with the traverse stroke into the closure position, columns having at their ends for rotary coupling suitable outer dogs which engage clamping bushes in which a matching profile in the form of inner dogs is disposed, each clamping bush being attached to the piston of a closure cylinder, the closure force being applied by shortstroke high pressure cylinders arranged on the fixed mould mounting platen and co-operating with the end of the columns, and after the cooling of the moulding unlocking is effected simultaneously with the opening stroke of the piston in an opening cylinder, characterised in that during the traverse stroke into the closure position, when the end of each column of a clamping bush abuts a cover, a hydraulic locking cylinder is pressurised after the displacement of the opening piston inside the opening cylinder has displaced working fluid in the direction of the locking cylinder, and on completion of the locking stroke the closure force is applied by a cam attached to the piston rod of the locking cylinder actuating a switch which simultaneously operates directional valves, so that the pressure chamber of the closure cylinder is pressurised, and for the removal of the moulding the opening cylinder and the locking cylinder are simultaneously actuated by the respective pressure chambers of the opening cylinder, and the locking cylinder being simultaneously pressurised, after the directional valves have been changed over.

The hydraulic circuit arrangement for carrying out the method comprises a pressure flow generator, a first directional valve disposed downstream of the pressure flow generator which valve is connected via a first line, which divides on the one hand to a second directional valve and on the other hand to a third directional valve, a second line extending from the first directional valve to a working fluid reservoir, a connection being provided to the locking cylinder via the second directional valve and two further lines, a connection being provided via the third directional valve and two further lines to the closure and opening cylinders, the closure cylinder being connected on the one hand via a seventh line and a fourth directional valve to an equalising reservoir connected to said fluid reservoir, and on the other hand via an eighth line, the third directional valve, ninth line and a non-return valve to said fluid reservoir, the first and third directional valves being actuated simultaneously via a switch operated by the piston rod of the locking cylinder. Advantageously, the individual clamping bushes are interconnected via a linkage which is actuated via a pivot joint by means of the locking cylinder.

In order that the invention may be more readily understood, reference is made to the accompanying drawings, which illustrate diagrammatically and by way of example an embodiment thereof, and in which:~ Figure 1 is an overall view of a mould closure unit with two mould mounting platens and cantilever mounted columns.

Figure 2 is a cross-section through the locking elements, taken on the line A-A of Figure 1, Figure 3 is a cross-section through the locking elements, taken on the line B-B of Figure 2, Figure 4 shows the hydraulic circuit arrangement associated with the method according to the invention, and Figure 5 shows a locking device having a linkage for interconnecting the locking elements.

Figures 1, 2, 3 and 5 illustrate the application of the method according to the invention to a mould closure unit having two mould mounting platens 26 and 27, and four force transmitting columns 29 mounted cantilever fashion. The platen 26 is arranged to be displaceable on a base frame 25 by means of traverse cylinders 28. The columns 29 are constructed as clamping bolts and are disposed axially adjustable by means of column nuts 36 in the movable platen 26, for adoption to the mould part installation spacing.

Each column 29 has at its end facing the fixed platen 27 segmental outer dogs 30 adapted for coupling with complementary elements in the platen 27. The columns 29 are further secured - against rotation by a key 44 which is axially displaceable in a groove 45 of a bush 43 which is rigidly connected to the movable mould mounting platen 26.

Disposed on the fixed mould mounting platen 27 are clamping bushes 31 which effect mould locking operation and have inner dogs 38. Fitted on to the clamping bush 31 is a retaining ring 32 connected via a screwed connection to a cover 34 bounding the clamping bush 31. The cover 34, shaped like a segment of a circle, forms a unit with the retaining ring 32, the clamping bush 31 and a closing piston 18.

Disposed in the zone of the flat surface of the cover 34 formed by the chord and at right angles to the column 29 is the piston rod 35 of a hydraulic locking cylinder 14, the piston rod 35 being connected to the clamping bush 31 so as to transmit an eccentrically acting force to the clamping bush 31. Attached to the piston rod 35 is a cam 51 by means of which a switch 50 disposed on the casing of an opening cylinder 7 is actuated in dependence on travel of the piston rod 35. Disposed immediately downstream of the closure piston 18 is an opening piston 46 which is operable on one side by the pressure medium in the chamber 6 of the opening cylinder 7. The closure piston 18 and the opening piston 46 are interconnected by the cover 34 and the clamping bush 31 with the retaining ring 32.The pressure line 8 of the pressure chamber 6 of the opening cylinder 7 is connected selectively via a combination of directional valves 11, 9, 1 and lines 2, 8, 10, 12, 1 3 to the locking cylinder 14 or to a pressure flow generator in the form of a pump 3. The pressure chamber 17 of the closing cylinder 47 is connected selectively via lines 22, 10, 2 and the combination of directional valves 9, 1 1 to the pressure flow generator 3 and via the line 19 and the directional valve 20 to an equalising reservoir 21.

The operation of the method according to the invention will now be briefly described. In the opening position for the removal of the moulding the movable mould mounting platen 26 and the fixed mould mounting platen 27 are at the largest possible distance apart.

In this inoperative position of the closure system the pump 3 sucks working fluid from a reservoir 5 and delivers it via line 2, the directional valve 1 (operational position I) and line 4 unpressurised back to the reservoir 5. The pressure chamber 17 of the closure cylinder 47 is connected via the line 19 and the interposed directional valve 20 (operational position I) to the equalising reservoir 21 and is therefore unpressurised. A non-return valve 24 prevents the working fluid in the cylinder chamber 17 from running away via the line 22, the directional valve 9 (operational position I) and line 48 to the reservoir 5.The pressure chamber 6 of the opening cylinder 7 and the pressure chamber 40 of the locking cylinder 14 are connected via lines 8, 10, 1 2, 1 6 and the combination of directional valves 1 (operational position 1), 9 (operational position I) and 11 (operational position I) jointly via a pressure-limiting valve 15 to the reservoir 5 and are therefore under a pre-stressing pressure, so that an opening force corresponding to the prestressing pressure of the pressure-limiting valve 15 is maintained In the pressure chambers 6 and 40. For a further injection moulding operation the traverse cylinders 28 are pressurised, so that the movable mould mounting platen 26 with the columns 29 attached thereto move in the direction of the fixed mould mounting platen 27.

The segment-shaped outer dogs 30 formed at the ends of the columns 29 entering into the fixed mould mounting platen 27 move into the clamping bushes 31. As they do so the outer dogs 30 move along the grooves extending axially in the clamping bush 31, whereafter the end faces of the columns 29 abut the inner surface of the cover 34 which closes the clamping bush 31.

Then a force is transmitted by the kinetic energy, by which the movable mould mounting platen 26 is moved, via the end face of the column 29 to the cover 34 against which the opening piston 46 of the opening cylinder 7 bears. Consequently the working fluid is forced out of the pressure chamber 6 and flows via line 8 and directional valve 9 (operational position I) into line 10, from which the pressurised liquid flows via operational position ll of the directional valve 11 into lines 12, 13 to the locking cylinder 14. Due to the circuit produced at the directional valve 11 for a working cylinder with one-sided piston rod 35, the piston rod 35 is moved out of the cylinder 14, so that as a a result of the connection of the piston rod 35 to the clamping bush 31 the latter is rotated through a predetermined angle.As a result the outer dogs 30 of the column 29 and the inner dogs 38 of the clamping bush 31 come to lie one behind the other. The movable mould mounting platen 26 has therefore been locked positively to the fixed mould mounting platen 27 in one continuous operation, synchronously with the traverse into the closure position. The working fluid not required for this operation is removed via lines 8, 10, 1 6 and the combination of directional valves 9 (operational position I) and 1 (operationai position I) and the pressure-limiting valve 15 to the reservoir 5. This ensures that the clamping bush 31 is reliably locked by the locking cylinder 14 to the outer dogs 30 of the column 29, and the traverse is not interrupted by the locking operation, thus allowing a continuous transition to the build up of closure force.This is ensured by the feature that the cam 51 attached to the piston rod 35 of the locking cylinder 14 actuates the switch 50 immediately after the locking stroke has been effected. The switch 50 is connected by circuitry to the directional valves 1, 9 each of which is moved into the operation position II for this purpose.

The pressure chamber 17 of the one-sidedly operable closure piston 18 is connected via line 1 9 and directional valve 20 (operational position I to the equalising reservoir 21, which is connected via line 49 to the reservoir 5, to ensure constant equalisation of the varying volume of working fluid. The closure force is built up by the pressure flow generator 3 delivering pressurised liquid via the directional valve 1 into line 10, the liquid passing on the one hand via the directional valve 9 and line 22 into the pressure chamber 17 of the closure piston 18, and on the other hand via the directional valve 11 and lines 12, 13 into the pressure chambers 37, 40 of the locking cylinder 14. The pressure of the pressure flow generator 3 is limited by the pressure-limiting valve 23.The volume of pressurised liquid displaced from the pressure chamber 6 of the opening cylinder 7 passes via line 8 and directional valve 9 to line 48, and via non-return valve 24 to the reservoir 5.

The non-return valve 24 prevents the closure cylinder 47 from running empty.

After the injection moulding operation and the cooling of the moulding, the pressure chamber 6 of the opening cylinder 7 is pressurised from the pressure flow generator 3 via lines 2, 10, 8 and the combination of the directional valves 1 (operational position ll) and 9 (operational position I).

At the same time in one continuous operation the pressure chamber 40 of the locking cylinder 14 is pressurised for the purpose of unlocking via the lines 2, 1 0, 12 and the combination of directional valves 1 (operational position II) and 11 (operational position I). The pressure flow generator 3 delivers pressurised liquid via line 2 and directional valve 1 (operational position II) to the line 10, which is connected on the one hand via the directional valve 9 (operational position I) to the line 8 extending to the pressure chamber 6 of the opening cylinder 7, and on the other hand via the directional valve 11 (operational position I to the line 10 extending to the locking cylinder 14.In this circuit the opening piston 46 displaces the closure piston 18 into the left-hand end position (as viewed in Figure 2) and simultaneously the locking cylinder 14 effects unlocking, so that the clamping bush 31 is rotated into the starting position, and the outer dogs 30 of the column 29 can be moved back through the axially extending grooves 33 of the clamping bush 31. The clamping bush 31 is therefore unlocked in one continuous operation with the opening stroke, without any idle periods.

The working fluid displaced from the unlocking cylinder 14 during unlocking is supplied unpressurised via line 13 and directional valve 11 to the reservoir 5. With the object of economising in technical equipment, the following is suggested in connection with the locking mechanism proposed by the invention. The necessary locking devices are operatively connected via a linkage which actuates all four locking devices simultaneously and operates as shown in Figure 5. The necessary locking devices, i.e. the clamping bushes 31, are actuated simultaneously by one locking cylinder 14 via a linkage 41. The locking cylinder 14 is connected via a pivot point 42 to the linkage 41 and locks all four clamping bushes 31 to the columns 29 and unlocks them therefrom.

For the sake of completeness it should be pointed out that the description relates respectively to one locking unit, i.e. to clamping bush 31, and also to one closure cylinder 47 and one opening cylinder 7 each associated with a respective column 29.

In accordance with the arrangement and operation of the method and hydraulic circuit arrangement according to the invention when applied to injection moulding machines of a given known construction, four opening cylinders 7 and closure cylinders 47, and also four associated clamping bushes 31, which are preferably actuated by one locking cylinder 14, are required to correspond to the number of columns 29. The four opening cylinders 7 and closure cylinders 47, which each co-operate with a clamping bush 31 acting as a locking element, are interconnected via parallel circuits. This enables all four opening cylinders 7 and closure cylinders 47 and the associated clamping bushes 31 (locking elements) to operate smoothly and synchronously.

Claims

1. A method of closing and locking the mould mounting platens of injection moulding machines, in which the movable mould mounting platen is moved into the closure position by long-stroke low pressure cylinders, locking being effected simultaneously with the traverse stroke into the closure position, columns having at their ends for rotary coupling suitable outer dogs which engage clamping bushes in which a matching profile in the form of inner dogs is disposed, each clamping bush being attached to the piston of a closure cylinder, the closure force being applied by shortstroke high pressure cylinders arranged on the fixed mould mounting platen and co-operating with the end of the columns, and after the cooling of the moulding unlocking is effected simultaneously with the opening stroke of the piston in an opening cylinder, characterised in that during the traverse stroke into the closure position, when the end of each column abuts a cover of a clamping bush, a hydraulic locking cylinder is pressurised after the displacement of the opening piston inside the opening cylinder has displaced working fluid in the direction of the locking cylinder, and on completion of the locking stroke the closure force is applied by a cam attached to the piston rod of the locking cylinder actuating a switch which simultaneously operates directional valves, so that the pressure chamber of the closure cylinder is pressurised, and for the removal of the moulding the opening cylinder and the locking cylinder are simultaneously actuated by the respective pressure chambers of the opening cylinder, and the locking cylinder being simultaneously pressurised, after the directional valves have been changed over.

2. A hydraulic circuit arrangement for carrying out the method claimed in claim 1, comprising a pressure flow generator, a first directional valve disposed downstream of the pressure flow generator which valve is connected via a first line, which divides, on the one hand to a second directional valve and on the other hand to a third directional valve, a second line extending from the first directional valve to a working fluid reservoir, a connection being provided to the locking cylinder via the second directional valve and two further lines, and a connection being provided via the third directional valve and two further lines to the closure and opening cylinders, the closure cylinder being connected on the one hand via a seventh line and a fourth directional valve to an equalising reservoir connected to said fluid reservoir, and on the other hand via an eighth line, the third directional valve, ninth line and a nonreturn valve to said fluid reservoir, the first and third directional valves being actuated simultaneously via a switch operated by the piston rod of the locking cylinder.

3. A device for carrying out the method claimed in claim 1, characterised in that the clamping bushes are interconnected by a linkage actuated via a pivot joint by the locking cylinder.

4. A method of closing and locking the mould mounting platens of injection moulding machines, substantially as herein described with reference to the accompanying drawings.

5. A hydraulic circuit arrangement for closing and locking the mould mounting platens of injection moulding machines, substantially as herein described with reference to and as shown in Figure 4 of the accompanying drawings.