AU606498B2 - Platen guide - Google Patents

Description

606498 Form COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-62 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Appi'cation Number: Lodged: Class Int. Class Colmlete Specification Lodged: SAccepted: Published: Priority: r Relatad Art: a a n, IC .J U Namde of Applicant: Address of Applicant: Actual Inventor: Address for Service: TO BE COMPLETED BY APPLICANT JAMES ENGINEERING SERVICES PTY. LTD.

2 Janet Street, Campbelltown, State of South Australia, Commonwealth of Australia MALCOLM BARRY JAMES Care of R.K. MADDERN ASSOCIATES, 345 King William Street, Adelaide, State of South Australia, Commonwealth of Australia Complete Specification for the Invention entitled: "PLATEN GUIDE" The following statement is a full description of this invention, including the best method of performing it known to me. us.

1 i I iii- i l- r ~311 This invention relates to a platen guide which is useful for guiding the platen (saddle) of an injection moulding machine.

Some injection moulding machines comprise a fixed platen at one end, an actuating ram mounted on a head frame at the other end, a plurality of guide bars which .4, are parallel with one another but spaced from one another g joining the fixed platen and head frame, and a movable platen which is slidable over the guide bars. There are usually four guide bars, and the movable platen is provided with four parallel bushes which engage 4' respective guide bars. The die halves for the moulding machine are carried respectively on the fixed and movable platens.

In order to achieve rigidity the guide bars are large in diameter, quite often in the order of four or six inches, and even when the bushes are in perfect condition and perfectly aligned, there can be a significant clearance, because of the necessary tolerance between the bushes and the bars. When wear takes place this clearance can vary considerably. In addition to this however there is also the difficulty that sometimes the load which is imparted under operating conditions is not necessarily completely concentric, and tilting of the movable platen can take place. As a result, the platens cannot be relied on to provide alignment of the die halves.

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This difficulty has been widely recognised, and use is frequently made of interengaging surfaces between the die halves which will assist in alignment of those halves, the interengaging surfaces sometimes being guide pins and bushes, and sometimes heel plates or blocks, but there are nevertheless many iistances where such interengaging surfaces are not able to reliably correct the misalignment to a satisfactory degree. In performing their alignment function, the interengaging surfaces are subjected to forces which result in wear of those surfaces. The rate of this wear becomes higher as the

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misalignment of the platens increases. Maintenance of the dies to rectify this wear is expensive and timeconsuming. When the wall thickness of the moulded part is small, commonly known as a "thin wall moulding", misalignment becomes a matter of very great importance and a high rejection rate is likely to occur.

The main object of this invention is to provide improvements whereby a movable platen can be accurately guided, and remain at right angles to the guide bars for its entire travel, and in one embodiment of this r invention the movable platen is provided with a plurality of guide brackets, each guide bracket being securable to a platen and carrying at least one guide member which engages an upper surface of a guide bar.

With this invention, the effective clearance between the movable platen and the guide bar is very much reduced -3 Li 3 r.

or entirely eliminated. Even if the guide bars are worn, the likelihood of tilting of the movable platen is considerably reduced by this invention, since the guide members can be made to directly contact the guide bars.

The guide members are preferably part-bushes, but can be rollers.

SWith this invention, it becomes an easy matter to provide adjustment means so that contact occurs and there is no clearance, and the incidence of both wear and tilting can be reduced because of wider load distribution.

The arrangement can be either included in original equipment or can be retro-fitted to original equipment for relatively low cost. It should be noted also that even large diameter rods can be subject to some sag which is most undesirable, and in all instances, but particularly where the guide brackets include additional bearing elements (part-bushes), the load distribution 0 can be so improved that the effect of sag can also be substantially reduced.

An embodiment of the invention is described hereunder in some detail with reference to and as illustrated in the accompanying drawings in which: Fig. 1 is a side elevational representation of an injection moulding machine to which platen guides are attached, Fig. 2 is a plan of a part-bush type guide, 44 I 4( -1C~orJ C

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I Fig. 3 is a side elevation of Fig. 2, and Fig. 4 is an end elevation of Fig. 3.

V In Fig. i, a typical injection moulding machine comprises a head frame 11 and a fixed platen 12, these being held together by four parallel spaced bars 13. The bars 13 are accurately machined bars, and these support guide bushes 14 of a movable platen 15 which is controlled by an actuating ram 16 carried by the head frame 11. The invention is not limited to use on a machine having this configuration.

In most instances the invention utilises a partbush and to provide the additional guide bracket, and Figs. 2, 3 and 4 illustrate a platen guide 20 comprising a part-bush 21 of suitable bearing bronze (for example phosphor bronze or aluminium bronze) on a saddle 22.

The saddle 22 is secured by bolts 23 to the movable platen Attachment is by pivot pins 24 extending between 1 side wings 25 and through saddle 22, and bolts 26 bear downwardly on pivot pins 24 to provide an adjustment means between the saddle and the part-bushes so that any wear can be compensated for by simple adjustment.

While the bush arrangement is generally preferred, the invention also includes embodiments wherein use is made of rollers.

The above described embodiment assumes the machine configuration includes a platen 15 which can accommodate I i upper and lower saddles 22. In many instances however, the platen 15 will not accommodate elongate saddles, and each saddle 22 needs to be replaced by two brackets each of which is shape in elevation, one arm of each 'L' being clamped to a vertical face of the platen and the other arm pivotally supporting a part bush 21 as otherwise described and illustrated herein. (The 'L' shape is shown at the lower portion of Fig. i.) In some instances rollers may be required in lieu of the preferred part-bush arrangement described above.

In one roller assembly, a guide comprises a central bridge plate which overlies the movable platen, and is secured thereto through a pair of wing bars (these being necessary because of the possible need to secure them to the platen on respective sides of the guide bars).

Each end of the bridge plate supports a respective roller which is preferably shaped to fit the shape of the guide bar and is carried on an eccentric shaft itself locked to a quadrant which can be pivoted about one of the eccentric axes, being guided by a guide pin and secured with a clamping bolt, the surfaces of the arcuate slot bearing against the pin and bolt. By this means the effective elevation of axis of rotation of each respective roller can be varied.

The second guide would normally be used as an alternative to the first guide, although in some -6- Ii

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instances it can be used in conjunction therewith. It simply comprises a bracket which can be secured to a face of the movable platen and which engages an inner surface of a guide bar. Adjustment can be achieved if this is required by any adjustment means including shims, o< adjustment screws or the like, but again in this 000oooo o 00 embodiment use is made of an eccentric shaft which can o D S a vary the height of the roller.

oo 0° °o In either or both cases, the bush or roller mounting P 0 o 10. heights are very carefully adjusted so that the bushes are as parallel as possible with respect to the guide 0oo bars on which they slide, and to achieve this some 00 o- pressure is necessarily imparted to the rollers. It may 000000 be noted that this need not be great, so that excessive wear on the guide bars need not necessarily occur.

o a The device may also be mounted at the side of the oo0000oo 0oo o guide bar to control horizontal alignment. It can also 01 0 be mounted to operate on the undersides of the guide bars.

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Claims (7)

1. 2. A platen guide according to claim 1 wherein each said guide bracket is a saddle and further comprising retention means r(taining a pair of said guide members one at each end of the saddle.
2. 3. A platen guide according to claim i wherein each said guide bracket has an shape in side elevation, the vertical arm of the being securable to a vertical face of the machine platen, and further comprising retention means retaining a said guide member to the horizontal arm of the
3. 4. A platen guide according to either claim 2 or claim 3 wherein each said reL(ntion means comprises a pivot pin joining a said bracket and a said guide member. A platen guide according to claim 4 wherein each said retention means further comprises a threaded adjustment member threadably engaging a said bracket member and bearing against said pivot pin.
4. 6. A platen gutde according to any preceding claim wheroin each said guide member comprises a part-bush which, when in use, depends from a said guide bracket 5 and sl
5. 7. A each s concav mouldi 5 a m -page is sli C S~ S a s o 41 contig a It a said g wings apertu a 15 that E a load or all bar tI
6. 8. 2 with 3 1 (u Is -a- 6. and slidably engages an upper surface of a said guide bar. 7. A platen guide comprising a-plurality of guide members, each said guide member comprising a part-bush having a concave face complementary to the shape of a guide bar of a moulding machine and a pair of spaced upstanding wings, a plurality of guide brackets, means securing each said guide bracket to a platen which is slidable over said guide bar, said upstanding wings of each said guide member being o 9t contiguous with sides of a said guide bracket, lb a suspension pin extending through apertures in each said guide bracket and also through apertures in said side wings contiguous with that bracket, one or more of said apertures being elongate in a vertical direction, and a threaded adjustment member threadably engaging that said guide bracket and bearing against said pin to apply a loading on those said contiguous side wings such that part or all of the weight of said platen is imparted to said guide bar through the relevant part-bush. 8. A platen guide substantially as hereinbefore described with reference to and as illustrated in the J
7. 9- t t 0 Sr r_ accompanying drawings DATED this 26th day of January, 1989. JAMES ENGINEERING SERVICES PTY. LTD. By its Patent Attorneys, R.K. MADDERN ASSOCIATES. t I CC 0 1.