The invention relates to a method for removing a moulded article from between the mould parts of an injection moulding machine by means of a gripping member, which gripping member is inserted to between the mould parts, whereafter the moulded article is gripped and removed from between the mould parts and dropped to a collection spot or the like.

The invention also relates to an apparatus for removing a moulded article from between the mould parts of an injection moulding machine, which apparatus comprises a base for fixing the apparatus to the injection moulding machine, an arm and a gripping member attached thereto, which gripping member is designed for gripping the moulded article, as well as an actuator for shifting the arm and the gripping member to between the mould parts and away therefrom. The moulds employed in Injection moulding machines can be used for moulding one or several moulded articles, i.e. the plastic products proper. The fluid plastic material is pressed through a nozzle and via the mould channel of a two-part mould into the product moulds. When the mould parts are released from each other, an amount of moulded plastic is set both in the moulding channel and the product moulds. The waste pieces in the mould channels and the plastic products proper are detached in connection with their removal from the mould, if the mould is so designed. The finished products and the waste pieces are dropped from the mould to the same heap or collection receptable. They can be separated either manually, which is a time-consuming job, or by means of equipment particularly designed for this purpose. The waste pieces are then fed into a crushing mill, and the crush is mixed to the raw material to be reused. In order to eliminate manual work and the

separating procedure in general, it is advantageous to remove the waste pieces from the moulding channels with the aid of a gripping member, i.e. a so-called manipulating device, which is arranged in a movable arm. One such device is introduced in the German patent application DE-A1 3 013 198.

The said device is installed on top of the moving platen of an injection moulding machine. It comprises a vertical guide bar, a slide moving supported by this guide, a control arm which is connected in between the stationary platen and the slide, an auxiliary arm which is attached to the slide at the middle and turnably in the motional direction of the platen, so that the control arm is attached to the first end thereof and that a gripping arm, provided at the end with a gripping member, is attached to the second end of the auxiliary arm, the gripping arm being turnable in perependicular direction to the motion of the platen. By means of the control arm, the slide, together with the auxiliary and gripping arms plus the gripping .member, is positively moved to in between the mould parts in order to remove the waste piece from the mould channel and to transfer it to the removal shaft arranged next to the injection moulding machine. The stages of operation of the said device are the following: during the opening stroke of the mould, the auxiliary arm, moved by the slide and the control arm, is shifted down to between the mould parts; when the gripping member is placed down to the level of the waste piece, it grips the waste piece; at the beginning of the closing stroke of the mould, the control arm presses the auxiliary arm and the gripping arm and turns the waste piece out of the mould channels, whereafter the slide, the auxiliary arm and the gripping arm and member start to rise up from between the mould parts; during the rising motion, the gripping arm is turned to the side by means of a mechanical guide, and the waste piece is dropped into the

removal shaft.

The.device which is shortly described above contains several members which are movable with respect to each other, wherefore it is complicated and expensive to manufacture. Moreover, the device encumbers the installation of the mould. It requires constructional changes in the injection moulding machine as well as a lot of free space. Furthermore, the adjusting of the device so that it works in the desired fashion takes time. In connection with every change of mould, the device must also be readjusted.

In the prior art there are also known both all- round robots and manipulators which are used for instance in the task of releasing the moulded article from the mould of the moulding machine, or shifting an article from one place to another in general.

One such mechanism is introduced in the Brittish patent publication GB 1 194 612. The mechanism is designed for releasing soft, flexible plastic products from the mould of the injection .moulding machine after the moulding. Generally ready-moulded articles are released from the mould by means of an ejector rod, but with soft plastic products there is the danger of damaging the product. The said mechanism comprises a rectangular support frame which is turnably installed to the platen attached to one half of the mould; an extraction member which is installed, adjustably as regards the position, to the support arm of the support frame, a hydralulic cylinder in connection with the base for moving both the support frame and the extraction member connected thereto by means of lever arms to the operational position to between the mould halves and away therefrom, as well as a hydraulic actuator for pressing the extraction member to grip one or several moulded articles and to release the grip when the article is detached from the mould.

The above described mechanism is installed on top of the housing of the injection molding machine, in

similar fashion as the waste piece extractor introduced in the German application. The installation of this mechanism presupposes changes in the injection moulding machine; the generally used protecting hood, which is drawn over the mould members for the duration of the moulding, must be provided with a substantial extension at the top, and in addition to this, owing to the cumbersome structure and relatively large size of the mechanism, its base must be at several points attached to the housing of the injection moulding machine. The cumbersome nature of the structure is due, among other things, to the fact that the mechanism is designed to extract several moulded articles from the parallel partial moulds of the mould structure, wherefore its width Is remarkable, and also to the fact that the employed actuators are hydraulic cylinders connected to lever arms or the like. In order to remove the waste pieces from the mould channels, the" ^* mechanism is provided with a separate device, and it is not even suggested that the mechanism for extracting ready-moulded articles or a similar device should be used for this purpose.

All-round robots and manipulators are extremely expensive, and their installation to be used in connection with injection moulding machines is a troublesome process. Moreover, they should be reprogrammed nearly always when the mould is changed.

The purpose of the present invention is, among other things, to eliminate the above described drawbacks and to provide a method and apparatus where the moulded articles, and particularly waste pieces, can be removed from the mould channels of injection moulding machines in a simple fashion, quickly and economically. This is achieved by the characteristic novel features of the invention, which are enlisted in the appended patent claims 1-4 as regards the method, and in the patent claims 5-11 as regards the apparatus.

In the method of the present invention, the

removal of a moulded article from between the mould members of an injection moulding machine is carried out by means of a gripping member which is turned around a stationary axis in such a fashion that the trajectory of the gripping member forms a circle orbit, and so that the said stationary axis is arranged in connection with the moving platen of the injection moulding machine; the trajectory of the gripping member is directed towards the mould space of the other mould half, where the moulded article is being formed, so that the ejecting motion of the moulded article meets it at a sharp angle; and a) the turning of the gripping member along the trajectory to between the mould members is started at a predetermined moment during the opening stroke of the mould; b) the gripping member is turned to the immediate vicinity of the moulded article and pressed to engage it at the latest when the mould members are located at the determined maximum distance from each other; c) a force of a suitable strength is directed to the gripping member in order to turn it out from between the mould members so that the turning of the gripping member along the trajectory starts immediately when the moulded article is begun to be pushed out of the mould space, and when the moulded article is at least partly released of the mould; d) the location of the gripping member is detected immediately when the gripping member has, in its motion along the trajectory, reached a point where it has turned out from between the mould members, and e) the detection of the location is utilized in the controlling of the closing of the mould so that if the detection takes place, the mould is closed, and if not, the mould is not closed and the moulding process is interrupted; f) the gripping member is opened and the moulded article is dropped at a collection point, when the turning

of the gripping member along the trajectory has passed the said point of detection and most advantageously reached a predetermined point, whereafter the above described stages a - f can be repeated after the mould is closed and the following moulding operation has been carried out.

Among the advantages of the method and apparatus of the present invention let us point out the clear stages of operation and simple trajectories, simple and light structure, security in operation, easiness in the installation without extensive changes in the injection moulding machine, rapid adjustability to be operated with correct timing and good accuracy after the changing of a mould, easiness in the maintenance, variability within the scope of the basic structure of the apparatus to be suited in-different injection moulding machines as an extractor of moulded articles and/or waste pieces, and in addition to these, a remarkable reduction in the manufacturing costs in comparison wi.th any prior art extractors of moulded articles and waste pieces in particular. The apparatus of the present invention is light and concentrated in structure, wherefore the masses to be moved can be rapidly accelerated and slowed down again. Thus the apparatus becomes swift in motion and it is unnecessary to slow down the operational stages or movements of the mould members of the injection moulding machine, wherefore the extracting apparatus does not increase the production time or cycle per product. The currently used extractors of moulded articles are realized with metal structures. The apparatus of the present invention can be partly realized with plastic elements. The injection-moulded plastic members are more economical than metal members, when the production series are large and correspond to the costs of manufacturing the mould. With the aid of plastic parts, the structure of the apparatus can be made even lighter, so that the required movements can be made really rapid. According to the method of the present invention, the

apparatus picks the moulded article from between the mould members of the injection moulding machine during the opening and detention strokes of the mould, whereafter it immediately returns from the interior of the mould members to the exterior thereof, when the closure stroke of the mould is about to start. Irrespective of security precautions of the apparatus, it may happen - due to a human error, electric disturbance or the like - that the arm of the apparatus complete with the gripping member is caught in between the closing members of the mould. If the apparatus is made of plastic, the risk of damage to the mould is remarkably smaller than with a metal device. Tn addition to this, the plastic members of the apparatus can be designed in a fairly free fashion. Thus the moulded articles can be extracted even from relatively troublesome moulds, where control pins, cores and other such parts hinder the motions. An effective spare parts maintenance is easily arranged; the user can always keep in store a few plastic or the like spare parts such as the arms with their gripping members..

In the production with an injection moulding machine, the aim is to minimize the down time passed for instance in the installation of the mould. The installation of an extractor of moulded articles for each injection moulding machine in connection with the changing of the mould takes time. The apparatus of the present invention is economical in price, so that a number of these can be purchased per each injection moulding machine. The apparatus can be tied to the mould, i.e. it can be already fixed to the mould or be easily fixable thereto. In that case extra time for installation is not needed when the mould is being changed. If there are two extracting apparatuses to be used per each injection moulding machine, one can be set for a coming production series of moulded articles, while the other operates together with the current production series.

In the following the invention and its

advantages are explained in detail with reference to the appended drawings, where

Figure 1 is a schematical illustration of an extracting apparatus of moulded articles for an injection moulding machine according to the present invention;

Figure 2 is an illustration of a similar extracting apparatus, seen in partial cross-section along the line 1-1 of figure 1;

Figure 3 is a schematical illustration of how the apparatus of the invention is installed at an oblique angle on a plane perpendicular both to the plane parallel to the shift rail of the injection moulding machine and to the vertical plane;

Figure 4 is a schematical illustration of how the apparatus of the invention is installed at an oblique angle on a plane perpendicular to the plane at right angles to the shift rail of the injection moulding machine;

Figure 5 illustrates a fastening support whereby the extracting apparatus can be .fastened to the injection moulding machine; and

Figure 6 illustrates a structure of the arm of the extracting apparatus.

A preferred embodiment of the apparatus applying the method of the invention is seen in figures I and 2. The illustrated parts of the injection moulding machine are the stationary platen 1, the heating cylinder 2, the nozzle 3 and the fastening plate 4a, the first, mould member 4, and respectively the moving platen 5, movable along guide bars (not illustrated in the drawing), the fastening plate 6a and the second mould member 6 attached thereto. The mould members 4, 6 are provided, at respective spots, with one or several mould cavities 7a, 7b proper and the mould channels 8a, 8b connected to the nozzle 2 and leading to the mould cavities 7a, 7b. In connection with the moulding, the moulded articles 50 proper are formed in the mould cavities 7a, 7b, and the

waste piece 9 is formed in the mould channels 8a, 8b. In general the mould cavities and the mould channels can all be called mould spaces.

The extracting apparatus of a moulded article, particularly a waste piece, comprises the base 10 for fastening the apparatus to the moving platen 5 of the injection moulding machine or to a member connected thereto, the arm 11 and the gripping member 12 attached thereto, and an actuator for turning the arm and the gripping member to between the mould members 4, 6 and away therefrom.

The actuator is a pneumatic turning member 13. It comprises a chamber 14 which has an at least partly circular or annular encasing and is provided with the turning axis 15 in the middle. A stationary flap .16 or a segment and a movable flap 17 are fitted in the said chamber 14. The flaps 16, 17 extend over the cross- sectional plane of the chamber, from the middle axis to the circumference of the encasing. The movable flap 16 is connected to the turning axis 15. and the turning axis further to the arm 11. In addition to this, the chamber 14 is provided with positionally adjustable limiters 18, 19, whereby the angle of the rotational motion of the movable flap 16, i.e. the rotational angle -^ can be set to a predetermined size. On both sides of the stationary flap 16 there are connected the pressure air channels 20, 21, and these are further connected, via the first control valve 22, to the pressure air supply 28 such as a compressor or the like. With the aid of the control unit 23, which in simplest form is an adjustable timer, the control valve 22 and thus the flow of pressure air into one of the channels 20, 21 is regulated according to whether the movable flap 17 and the axis 15 are desired to turn clockwise or counterclockwise. When pressure air is fed into the turning member 13 via the channel 20, the flap 17 and the axis 15 are turned counterclockwise, and in this case the arm 11 is turned out from between the

mould members 4, 6, from position D to position C. When pressure air is fed into the turning member 13 via the channel 21, everything occurs In the opposite direction, and the arm 11 turns to between the mould members, from position C to position D. The position C of the arm 11 is marked by dotted lines in figure 1.

In connection with the turnable arm 11 there is installed the pneumatic cylinder 24. The piston 25 of this cylinder is connected to the gripping member 12, and the cylinder space 26 is connected, via another control valve 27, to the pressure air supply 28. The cylinder 24 is advantageously single-acting, in which case it contains the return spring 29. It is clear that a double-acting cylinder can also be employed in this connection. The jaws 12a, 12b of the gripping member 12 (figure 2) are pressed together and opened according to how pressure air is fed into the cylinder space 25 or let out therefrom. The second control valve 27 is adjusted in similar fashion as the first - either from the common control unit 23, or by means of for instance a separ.ate timer.

In connection with the base 10 there is arranged an indicator or a detector of the position of the arm 11, i.e. the detector 30. Its position with respect to the turning member 13 is adjustable. The detector 30 is an optoelectric, electromagnetic or similar member, whereby the arm 11 is spotted immediately when it or a member connected to it is turned into the effective field of the said detector. The detector ^' 30 is arranged in such a position in relation to the turning member 13 and the mould members 4, 6, that the turning of the arm 11 and the gripping member 13 out of reach of the mould members is thereby registered. The detector 30 is connected to the control unit 23 and/or to the control logic 42 of the injection moulding machine. The purpose of the detector is to secure that the arm 11 along with the gripping member 12 is not in any circumstances caught In between the mould members 4, 6.

The moulding spaces 7b and 8b of the injection moulding machine are provided with pins or rods whereby the moulded articles are pushed out of the mould and the channels. Generally such ejectors 31, 32 are connected to the moving platen 5. They are rods parallel to the guide bars along which the platen 5 is moved and are permanently fixed to the housing of the injection moulding machine. When the moving platen 5 is shifted sufficiently far away from the stationary mould member 4, the ejectors 31, 32 push the bottoms of the mould pieces existing in the mould cavities 7b and in the mould channels 8b outwards, so that they are ejected out of the mould cavities 7b and the mould channels 8b and are thereafter dropped down. The ejectors 31, 32 can also be operated with the aid of a separate actuator such as a hydraulic cylinder.

The waste piece 9 is in form a pin-like object 9b provided with one or several stems 9a. The stems 9a are formed in the mould channels 8a, 8b, which lead to one or several mould cavities 7a, 7b. The pin 9b in turn is formed in between the nozzle 3 and the moving platen 5 as an elongate piece directed outwards of the movable mould member 6.

The removing of the waste pieces 9 from the injection moulding machine is carried out so that by means of one back-and-forth turning motion C→D→C of the arm

11 and during this motion, all procedures connected to the removal are performed. The turning motion of the arm 11, and particularly the trajectory of the gripping member 12, is so directed to the moulding channels 8b of the injection moulding machine, in which channels the waste piece 9 is formed, that the direction A (figure 1) of the thrusting motion created by the ejector 32 and directed towards the waste piece 9 is roughly equal to the trajectory of the gripping member 12, i.e. the direction B of the turning motion, or intersects it at the sharp angle α.

The pin 9b of the waste piece 9 is relatively

long, and during the extraction stage after the moulding it is still warm and flexible. The gripping member 12 is designed to grip the pin most advantageously at its middle area before the beginning of the ejecting stroke. The turning motion of the arm 11 outwards from between the mould members begins before the start of the ejecting stroke, in which case the pin 9b may yield and be partly bent. Thus the intersection angle may be surprisingly large, advantageously however < 45°. The limit for the size of the intersection angle α is set above all by the depth of the moulding channels 8b: the deeper into the mould member 6 the moulding channels 8b extend, the smaller must the intersection angle α be. Typically the depth of the moulding channels is within the range of 4...10 mm, in which case the Intersection angle ot may be 45° or even larger. The waste piece 9 must be released from the mould channels 8b before the sideways distance of the arm 11 has remarkably grown owing to the turning ^* motion. Otherwise the waste piece 9 may be torn into pieces and parts thereof may remain in the moulding channel 8b.

In principle the Injection moulding machine is operated so that first the mould members 4, 6 are pressed together, whereafter hot fluid plastic material is pressed from the heating cylinder 2 through the nozzle 3 and via the mould channels 8a, 8b into the mould cavities 7a, 7b. Then the mould pieces are allowed to be cooled and set for a moment, whereafter the mould is opened, i.e. the mould members 4 and 6 are drawn apart. The moulded articles 50 are removed from the mould cavities 7a, 7b, and the waste pieces 9 are extracted from the mould channels, whereaftsr the mould members 4, 6 are again pressed together and the above described procedure is repeated.

The waste pieces 9 are removed from the mould channels 8b In the following manner during one above described operational cycle of the injection moulding machine. When the mould members 4, 6 start moving apart,

/FI87/00044

the turning motion of the arm 11 is started from position C towards position D by opening, with the aid of the control valve 22, the channel 21 from the pressure air supply 28 to the first side of the movable flap 17 of the turning member 13. The exact moment of time for starting the turning motion with respect to the opening of the mould is adjustable by means of the control unit 23, the timer and/or the control logic 42 of the injection moulding machine. In principle the adjusting is carried out so that when the mould members 4, 6 are sufficiently far apart, the arm 11 is just about to slip in between them. Accordingly the arm 11 is turned from position C to position B to between the mould members 4, 6 during their opening stroke. Before the mould is completely open, the arm 11 has already reached the immediate vicinity of the waste piece 9. With the aid of the second control valve 27, the pressure air supply 28 is now connected, via the channel 29, to the pneumatic cylinder 24. This presses the jaws 12a, 12b of the gripping member 2 around the tail 9b of the waste piece 9. The second control valve 27 is in principle controlled in similar fashion as the first, with the aid of the control unit 23, the timer and/or the control logic 42 of the injection moulding machine. Thus the gripping member 12 engages the waste piece 9 before the ejectors 32 are set in operation.

Thereafter the first control valve 22 immediately receives the command from the control unit 23 or the like to connect, via the channel 20, the pressure air supply 28 to the second side of the movable flap 17 of the turning member 13. The arm 11 together with the gripping member 12 and the waste piece 9 is now ready to start turning from position D towards position C. The power which turns the arm 11 by means of the turning member 13 out from between the mould members is adjusted (or it can be adjusted for example by regulating the pressure from the pressure air supply 28) to be so low

that the waste piece 9 is not torn under the tensile strain before it is ejected, but on the other hand the same power is so high that the arm 11 is ready to turn immediately after the waste piece has been released or is being released from the mould channels 8b.

When the ejectors 32 are set in operation, they start pushing the moulded articles 50 and the waste pieces 9 out of the mould spaces. Immediately after the waste piece is released from the mould channels 8a at the beginning of the ejecting stroke, the arm 11 together with the gripping member 12 and the waste piece 9 performs the turning motion from position D to position C. At the same time the moulded articles are dropped to a collection receptable or the like placed under the moving platen 5. It is also pointed out that the motion of the arm 11 is remarkably swifter than the pushing motion of the ejector 32.

Immediately after the moulded articles 50 proper and the waste pieces 9 are released from the mould cavities 7b and the mould channels 8b, the closing stroke of the mould is started again. At this stage the arm 11 together with the gripping member 12 and the waste piece 9 is already turning out from between the mould members 4, 6. When it has passed the point G on its trajectory, the detector 30 registers the arm and informs, via the control unit 23 (or directly) the control logic 42 of the injection moulding machine that the mould can be closed. If for some reason the arm 11 is not able to turn out from between the mould members 4, 6 during the cycle, the detector 30 informs the control logic 42 of the injection moulding machine that the mould members cannot be closed, and the operation is interrupted. Thus the damaging of the expensive mould members, owing to a disturbance in operation or the like, is avoided. When the arm 11 has turned to the position C, the second control valve 27 closes the channel to the pressure air supply 28 and connects the channel 26a to the

open air according to the command from the timer of the control unit 23 or the like. The spring 29a of the pneumatic cylinder 24 opens the jaws 12a, 12b of the gripping member 12, and the waste piece 9 drops into the collection spot 41. Simultaneously the pressure air supply to the turning member 13 via the first control valve 22 is stopped. Now the system is in stand-by position, waiting for the next moulding cycle.

The above described pneumatic turning member 13 is not easily replaced by a hydraulic or pneumatic cylinder. The reason for this is that there is not enough space in the vicinity of the moving platen 5 or the second mould member 6 for an elongate actuator, such as the said cylinders among others are. On the other hand, they are also too slow to generate swift turning motions.

The pneumatic turning member 13 comprises the chamber 14, which is in shape a circle, a ring or a part thereof, such as a circular segment or arc; the turning axis 15, which is arranged on the middle axis of the chamber; a member fitted in the phamber, such as the flap 17 or the like, which in cross-sectional area at least roughly corresponds to the cross-sectional area of the chamber 14, so that to the chamber, at least on one side of the said member 17, there Is connected the channel 20, 21, wherethrough the pressure air or corresponding pressurized gas can be conducted into the chamber, by means of which pressure air the chamber and the member such as the flap 17 can be turned, with respect to each other, around the middle axis 14 of the chamber. As is apparent from the above description, either the chamber 14 or the flap 17 or a similar member can be arranged to turn around the middle axis, whereas the second part is permanently fixed to the base 10. In that case the arm 11 is naturally attached to the turnable part of the turning axis 15. The turning member 13 can be single-acting, which means that only one pressure channel is connected to the chamber. The turning motion to one

direction is created by means of pressure air, and the returning motion to the opposite direction is created by means of for instance a counterspring. The rotation angle is determined on the basis of the shape of the chamber; it may be nearly 360< or smaller. The size of the rotation angle can be limited either by limiting the chamber length in the circumferential direction, or by arranging suitable obstructions in the chamber, whereby the turning motion of the flap or the like is limited to stay within the desired range. This variation was illustrated in the embodiment of figure 1.

It is pointed out that the pneumatic turning member 13, and particularly its turning axis 15 or its middle axis, are permanently fixed to place. The turning axis 15 of the turning member remains in place with respect to the moving part 6 of the mould and the platen 5. On the other hand It is to be noted that the places of the turning member 13 and the turning axis 15 can be changed, or the place can be chosen as desired, and simultaneously the inclination qr angle of the turning axis 15 with respect to the middle axis E-E of the injection moulding machine can be suitably chosen.

In the above described embodiment of the present invention the turning axis 15 of the arm 11 of the apparatus is perpendicular to the shift rail E-E of the injection moulding machine. It is also possible to incline the turning axis 15 in relation to the shift rail E-E. In figure 3 the apparatus and particularly the turning axis 15 are positionioned at an oblique angle 0,, on a plane perpendicular to the plane parallel to the shift rail E-E of the injection molding machine and to the vertical plane F-F. In figure 4 the apparatus and its turning axis 15 are positioned, on a vertical plane, at an oblique angle 8 _a with respect to the plane H-H which is perpendicular to the shift rail E-E of the injection moulding machine. Naturally a combination of the examples of figures 3 and 4 is also possible. The advantage of

inclining the apparatus and its turning axis 15 is that in that case the apparatus can be installed nearer to the moving platen 5 or the mould member 6, so that the arm 11 can be made shorter and consequently lighter. By means of this arrangement, the apparatus can also be fitted to a smaller space than in the case of the embodiment with a vertical turning axis, which was illustrated in figure 1.

The apparatus of the present Invention can be attached, according to the priciple illustrated in figure 3, to the arched fastening support 34 by means of a suitable slide 33 or the like, as is apparent from figure 5. In that case the angle 0.. can be adjusted. The fastening support 34 can be attached either directly or with the aid of the auxiliary support 35 to the platen 5 or to the mould member 6. The radius R of the curvature of the fastening support 34 corresponds to the distance of the support 34 from the shift rail or middle axis E-E of the injection moulding machine. Now, when the length of the arm 11 is suitable, the gripping member 12 can always be turned along the middle axis .E-E, and it can be used for gripping the waste piece 9 irrespective of the place where the apparatus is attached on the fastening support 34 with the aid of the slide 33.

Let us observe more closely the embodiment of figure 4. The turning motion of the arm 11 and the gripping member 12 takes place on a plane which intersects, at an oblique angle 0 _a the shift rail E-E. Now the intersection point of the trajectory of the gripping member 12 and the shift rail Ξ-Ξ must be located in front of the movable mould member 6 at a point where the tail of the waste piece can easily be gripped by means of the gripping member. Thus the trajectory C-D of figure 1, which - when the injection moulding machine is observed from the top - is circular in form, becomes elliptical and is illustrated by the dotted lines K in figure 1.

An advantage of this arrangement is for example that the opening distance a of the mould members 4, 6 does

not have to be as long as In the above described embodiments. Thus the apparatus of the invention can be fitted Into a fairly narrow space. Another advantage is that by means of the gripping member 12, a better grip of the waste piece 9 is obtained than in the apparatus according to the previous embodiment. The jaws of the gripping member 12 are set to meet the stem of the pin 9b of the waste piece 9, in which case the grip is secure and the extraction succeeds even more reliably than before. The size of the inclination angle _a is naturally determined according to the same principles as the size of the above explained intersection angle. Consequently the inclination angle _£ Is advantageously ≤45<>.

It is advantageous to place the turning axis 15 of the arm 11 and thus the turning member 13, with respect to the mould members 4, 6, so that it is always located outside the distance a of the mould members 4, 6 or outside the pressing seam of the together-pressed mould members, at the distance c from the front edge of the mould part 6 movable in the direction of the axis E-E.

This means that the line between the intersection point of the trajectory of the gripping member 12 and the shift rail C-D, i.e. the gripping point D, and the turning axis 15, meets the shift rail E-E at the angle 3 _A which is smaller than 90<>. The advantage of this solution is that the extension of the trajectory of the arm 11 and the gripping member 12 In the direction of the shift rail E-E is reduced in comparison to the alternative where the angle 3 is for instance 90° or larger. Here again the main issue is the opening distance between the mould members 4, 6 and the extraction of the moulded article from the mould and from between the mould members with the maximum speed. The limit for the distance of the turning axis 15, i.e. for the distance c, is set by the growth of the mass of the arm 11; the longer the distance c, the longer and heavier the arm will be as a whole, and the heavier the arm, the greater the moment of inertia.

The arm 11 of the apparatus may be a straight, elongate member, which at its first end is attached to the axis 15 of the turning member 13, and which at the second end is provided with the gripping member 12. Advantageously, however, the arm 11 is formed of an arched and/or flexed member, as is illustrated for instance in figures 1 and 2. This solution is recommendable particularly if the turning axis 15 is located outside the distance a of the mould members 4, 6. If a straight arm 11 were employed, it could be possible that the gripping member 12 provided at its end would not reach sufficiently close to the waste piece 9 on the shift rail E-E of the injection moulding machine, because the edge of the mould 6 would obstruct the turning motion of the arm 11. But if the arm 11 were provided with a flexure 11a or a bend, the turnign to behind the edge of the mould member succeeds well, as is apparent from figure 1.

It is pointed out that the apparatus of the invention is relatively small in size. All essential parts thereof, such as the arm 1,1, the gripping member 12, the turning member 13, the cylinder 24 and the control valves 22, 27 can be realized as structural elements of a small size. The distance between the turning axis 15 and the gripping member 12, which in practice means the working range of the apparatus, is in most practical applications 25 cm at the most. In that case the apparatus can still be fitted within the protecting hood of the injection mopulding machine, and any structural changes in the injection moulding machine itself or in its protective equipment are not needed.

The small size of the apparatus of the invention means that the base of the apparatus can be attached directly to the mould. This may be carried out, with the aid of the base 10', directly to the movable mould half 6, as is illustrated by the dotted lines in figure 1. If the moulds are already provided with the waste piece extracting apparatuses of the invention, the changing of

the moulds is considerably speeded up. All electric and pneumatic couplings of the moulds can be made according to the agreed rules. Thus it would be unnecessary to separately detach the extracting apparatus of the injection moulding machine and thereafter reinstall it in connection with every mould change. As a result of the suggested procedure, the effective working time of the machine and the mould would be remarkably prolonged. The current mould changes of several hours would be reduced to a few minutes.

The arm 11 of the apparatus of the present invention can be realized as a sheath-like form or as a U- beam structure as is apparent from figure 2. The employed material can be aluminium, plastic or other such light and durable material.

One preferred embodiment of the arm 11 is illustrated in figure 6. Here the pneumatic cylinder 24, which runs the gripping member 12, is formed as an essential part of the arm 11. The arm 11, the space 26 of the cylinder 24 and the aperture.36 for the rod 37 of the cylinder piston 25 are advantageously manufactured all during the same working cycle, suitably of plastic such as polypropene or reinforced thermoplast. The space of the cylinder 26 can at the end be closed by means of a threaded pin 38. Between the threaded pin 38 and the piston 25 there is placed the spring 39. The pressure air supply is connected, via the control valve and the pressure air channel 26a, to the space 26. The first jaw 12a of the gripping member 12 is stationary, and the second jaw 12b is turnably journalled to the arm 11 at the point 40. One end 36 of the arm 36 is connected, turnably or flexibly, to the second jaw 12b. When pressure air is conducted via the channel 26a to the space 26, the spring 39 is pressed together, urged by the piston 25, and the piston rod 37 turns and presses the second jaw 12b against the first jaw 12a. When a workpiece lies in between, it is tightly pressed in between the jaws 12a, 12b of the

gripping member 12. When the supply of pressure air into the space 26 is cut off and the space 26 is connected to the open air, the spring 39 returns the piston 25 to its initial position and the jaws 12a, 12b are opened. By forming the arm 11 and the pneumatic cylinder

24 into a unit of the above described type, it can be manufactured economically and rendered as a light, compact and reliably operating uniform component, which is extremely well suited to be an essential part of the extracting apparatus of the invention.

The arm 11 illustrated in figure 6 is in principle formed of two straight pieces lib and lie, which are roughly at right angles to each other. It is clear that the arm can also be different in form, for instance straight, arched or a combination of these two.

In the above specification, the method and apparatus of the invention are described mainly in connection with the removal of waste pieces. It is, however, maintained that both the method and the apparatus are equally well suited for extracting moulded articles proper from the mould. Generally the workpieces proper are allowed to be dropped from the mould, because their number may be more than one, and only the waste piece is extracted and shifted apart so that it is not mixed with the said moulded articles.

Above the invention has been explained mainly with reference to one preferred embodiment thereof. However, it is naturally clear that the invention can be modified in many ways within the scope of the appended patent claims. For example, in the above description the turning axis of the turning member of the apparatus and the turning axis of the arm are one and the same axis. These axes can also be separated and placed at a distance from each other, and power transmission can be arranged therebetween for instance by means of band pulleys and band or some other similar arrangement.