GB2065542A - Feeding moulds during filling - Google Patents

Abstract

An apparatus for filling molds with foaming synthetic resin has a fixed mixing head, a turning table (25) for supporting molds and a driving system (26) for the table such that the table is slowed down each time a mold is under the head and is speeded up when it is between molds. The driving system may be a geneva mechanism. <IMAGE>

Description

SPECIFICATION A foaming apparatus The invention is with respect to an apparatus for running liquid foam into molds, having at least one mixing head, a turn-table, and molds placed on said turntable.

In conventional apparatus of this sort, the equally spaced molds are placed along the outer edge of the generally round turntable. The filling of foam into the molds or foaming operation is undertaken by a mixing head, which is moved over and with a given mold at the time of producing foam and running the same into the mold, and when the foaming and filling operation has been completed, it is run back into its starting position so as to be ready for filling the next mold in the same way. Such an apparatus is generally complex, this furthermore being true of the mixing head control system. Furthermore, such a mixing head, which is moved backwards and forwards, is not trouble-free in operation.

One purpose of the present invention is that of designing an apparatus of the sort in question which has a simple driving system and makes possible short filling cycles.

For effecting these and other purposes, an apparatus of the sort noted is characterized n that said mixing head is stationary and the apparatus has a turntable driving unit, which is so designed that, at times of mold filling, the turntable speed is greatly decreased and in that it is stepped up between filling times.

Because the mixing head is stationary, the parts supporting it on the rest of the apparatus may be very simple in design. Furthermore, the lines joining the mixing head with the rest of the apparatus are not moved so that the wear rate in this respect will be slower. Because the turntable with the molds on it is not stopped each time filling takes place, only a lower power rating of the driving unit will be needed. The system does not have to be started up from the stationary condition. Because filling takes place while the table is being slowly turned or "inched", the filling or foaming cycles are much shorter than in the prior art noted. Idle times are decreased to a minimum.

Between the end of filling and foaming operation and the start of the next one, the table is moved at full speed.

A specially simple and useful driving unit for the turntable may take the form of a geneva mechanism producing a changing speed of the turntable ("polygon speed function"). The geneva mechanism is best designed with a geneva wheel with, for example, four evenly spaced slides for driving pins fixed to the table, the wheel and the driving pins then forming the geneva mechanism. Preferably, the pins are fixed under the table and, furthermore, the rest of the geneva mechanism is placed under the table.

Speed control of the geneva wheel is undertaken by a group of cams or the like, fixed to the geneva wheel or its driving shaft, for acting on followers.

An account will now be given of a preferred working example of the invention, to be seen in the accompanying figures.

Figure 1 is a partly sectioned view of a foam-producing and mold-filling apparatus with a geneva driving mechanism, as seen from the side.

Figure 2 is a view looking towards the bottom-side of the geneva mechnism to be seen in Fig.

1.

Figure 3 gives in the form of two graphs the speed of turning of the geneva mechanism of Figs. 1 and 2.

In Fig. 1 a part of the turntable is numbered 25 and is to be seen in chain lines. Molds (not figured) are supported on the table. Under the table 25, which is designed as a round table as is normal in the art and along its edge there are equally spaced driving pins 28, their number equalling the number of molds. These pins are part of a geneva mechanism 26 having a geneva wheel 1 with equally spaced radial slides 27, into which the driving pins are moved on operation (see Fig. 2). The geneva wheel 1 is keyed on shaft 2, which is bearinged in a bearing unit 3 having two ball-bearings, of which one is numbered 12 and which are spaced apart by a distance piece or pipe. At the end of shaft 2, opposite to geneva wheel 1, there is a sprocket wheel 9, which is fixed on the shaft 2 by a key 15 and a threaded pin 16.Sprocket wheel 9 is turned by way of chain 22, joining it up with a driver sprocket wheel 8, which for its part is fixed on driving shaft 13 by key 14. Furthermore, a family of cams 7 is fixed to shaft 13, the cams having followers for working control switches causing, one after the other, timed control functions:~ A-stop-position of round turntable 25 B start of filling/forming I for mold 70 mm in diameter C-speed of V 1 of turntable D-start of filling/foaming 11 for mold 95 mm in diameter E -speed V 2 of turntable F cnd of foaming (safety measure).

Furthermore, two reserve switches and lines X, Y will be seen in Fig. 1. Cams 7 are fixed together and keyed on shaft 13 by way of a threaded pin 23. Shaft 13 is turned by a driving motor through worm gearing. The electric motor 24 gets signals coming from the said switches, which are worked by the cam faces of the group 7 of cams.

With this driving unit. the changes in speed against time will be as in the lower graph of Fig.

3, the desired speed curve being in the form of a broken line. As will be seen from Fig. 3, the foaming/filling takes place at a very low speed of turning of mold turntable 25. Between the foaming/filling times the mold table is moved at full speed, it not being necessary for the turntable to be speeded up from the stationary condition, so that the power rating of the driving unit may be quite low. Furthermore, very much shorter foaming/filling cycles are possible. In this respect, one quarter of a turn of geneva wheel 1 is representative of the center distance between one mold and the next one. The table may have, for example, 126 molds, which may be of different diameters, for example a first mold of 70 mm in diameter, then one 90 mm in diameter, then one 70 mm in diameter and so on in turn.In Fig. 1, "I" is used with respect to a 70 mm diameter mold, while "II" is used for a 95 mm diameter mold. In the working example of Fig. 1, for this reason, molds with different diameters may be filled in one and the same operation. However, naturally, further mold sizes may be used on the turntable, if the cams 7 and the number of switches worked by the cam faces are designed to this end.

As will have become clear, a geneva mechanism is specially simple and trouble-free in operation. It would, however, be possible for the desired speed/angular position, in line with the curve of Fig. 3, to be produced by a servohydraulic system, an electronic motor control, or the like.

In a further development of the design of the invention, followers and control switches for the driving motor 24 may be moved for adjustment of their positions about the cam faces of the cams 7. This makes it possible for the foaming/filling times to be changed. The average speed of the slow and high speed motions is fixed to be in line with the surface speed, which is necessary for the foaming system in question. In this respect, as has been noted, it is possible to have any desired number of speeds, which are preprogrammed, by using the cams for driving the switches in question (potentiometer switches). The lower speed curve of Fig. 3, marked in broken lines, is the product got by compounding the speed changes of the driving unit as caused by the control switches, and the speed changes which are produced by the natural slowfast effect of the geneva mechanism all the time.In the top of Fig. 3, there is a graph, in broken lines, of the speed changes produced by the geneva mechanism when the motor is run at an equal speed ("polygon function").

The points in time L to R are used for: L speed V 2 as controlled by speed potentiometer 1 M speed V 1 as controlled by speed potentiometer 2 N start of foaming/filling 0 middle of mold stop-position P end of foaming Q operation of foam kill cam The two points in time R and S are the times of highest speed as produced by the geneva mechanism, the distance between them being representative of about 360 of motion of the cams and a time equal to 2.85 seconds.

The time between L and M may be adjusted, L being able to be timed so as to zake place earlier. M may be adjusted to take place earlier. The time N-P is fixed by a timer. Q may be timed to take place earlier or later so that it will be seen that the desired changes in speed are the outcome of compounding the changing speed as produced by the geneva mechanism (geneva wheel 1, pins 28) and the change in the speed of turning as controlled by control switches, of motor 24, the motor speed being marked in full lines in the bottom part of Fig. 3.

While foaming/filling is taking place, motor 24 is formed to go on turning shaft 13 and shaft 2, on which geneva wheel 1 is fixed, but at a lower speed V 1. Between the foaming/filling times, the speed of motor 24 is increased up to speed V 2.

Claims (10)

1. An apparatus for running liquid foam into molds, having at least one mixing head, a turntable, and molds placed on said turntable, characterized in that said mixing head is stationary and in that the turntable has a driving unit, which is so designed that at times of filling, the turntable speed is greatly decreased and it is stepped up between filling times.

2. An apparatus as claimed in claim 1, characterized in that the turntable driving unit is in the form of a geneva mechanism producing a changing table speed.

3. An apparatus as claimed in claim 2, in which the geneva mechanism has a geneva wheel with evenly spaced radial slides, as for example four slides, for driving pins joined to said table.

4. An apparatus as claimed in claim 3, in which said pins are placed under said table.

5. An apparatus as claimed in claim 3 or claim 4, in which turning motion of the geneva wheel through the angle between two slides is representative of the center distance between one mold and the next one.

6. An apparatus as claimed in claims 3 to 5, having a group of cams fixed to the geneva wheel or to a driving shaft joined therewith, and cam followers, worked by said cams, for controlling the driving unit of the geneva mechanism.

7. An apparatus as claimed in anyone of claims 1 to 6, characterized in that the turntable is round in outline.

8. An apparatus as claimed in anyone of claims 1 to 6, characterized in that the table is oval in outline.

9. An apparatus as claimed in anyone of claims 6 to 8 having limit switches to be worked by said followers, adjustment of the followers round the cams being possible for adjustment of "full speed" and "inching" ranges of turntable speed, the turntable being inched for filling of the molds, which are supported on the turntable.

10. An apparatus as claimed in claim 1, substantially as described above with reference to and as illustrated in the accompanying figures.