DE29817711U1 - Drive for a metering device for viscous substances, such as cast resin - Google Patents

Description

Dr.-Ing. ERNST STRATMANN

Patent Attorney
D-40212 Düsseldorf · Schadowplatz 9

10 February 1999

9823 Gm

Process Engineering Hübers GmbH
46395 Bocholt

Drive for a dosing device for viscous substances,
like casting resin

The invention relates to a device for driving a dosing device for viscous substances, such as casting resin, consisting of an evacuable storage container for the substance, optionally equipped with a mixing device, and a dosing pump device associated with this container, the dosing piston of which forms a valve which closes when the piston is pushed into the dosing piston cylinder, as well as drive devices for the piston.

Such a device is already known from DE 38 03 418 A1. The device described therein uses an arrangement in which two storage containers are provided, one for resin, a second for hardener, with each container having an associated dosing pump. The resin or hardener quantities dispensed by the two dosing pumps are mixed in a mixer and then used to cast components.

The disadvantage of the known device is that the dosing can only be carried out in stages, because after carrying out a dosing (or possibly several dosings of smaller quantities) it is necessary to move the dosing piston back again and start dosing again. This return movement means a

Loss of time, which is disadvantageous in modern casting plants with their high throughput rates of components to be cast. The object of the invention is therefore to further develop the device in such a way that this loss of time is eliminated.

The object is achieved in that the metering pump device of one storage container has two metering pumps, the metering pistons of which are each guided with a piston rod in a pressure-tight manner through the lid of the storage container and are each connected to a toothed rack, which are arranged axially displaceably in a common gear housing and can be driven in opposite directions by a drive connected to the housing.

These measures make it possible to bring the other dosing piston into a working stroke while one dosing piston is returning, thus continuously dispensing substances to be dosed.

According to a further development, the two racks are driven by a single common gear, which represents a particularly simple structural embodiment.

In order to save time during maintenance work, a removable coupling element is arranged between the piston rod end and the rack end, because this makes it easier to replace a sleeve or similar wearing material, for example.

According to a further embodiment of the invention, it is advantageous if a check valve is connected downstream of each of the two metering pumps, the outputs of these two metering pumps being led to a common output point for metered substance via a three-way valve.

A servo motor or a stepper motor has proven to be a good drive for the dosing pumps, which can optionally be equipped with a downstream deflection gear, whereby the movement of the servo motor or the stepper motor is preferably controlled by a microprocessor. Such control by the

According to yet another development of the invention, the microprocessor should also have the three-way valve.

It is advantageous if the dosing piston cylinders are arranged in a block that forms the bottom of the storage container, from which the side walls of the storage container also extend. The bottom of the storage container preferably forms two funnel surfaces that open into the upper ends of the cylinders of the dosing pumps. This arrangement also enables a design in which the storage container has a rectangular cross-section, which is particularly space-saving. This space-saving design makes it possible, for example, to arrange two storage containers together on a movable frame. This allows the arrangement to be brought to any location where the substance or mixture of substances to be dispensed is required. Fast availability is also achieved if the check valves are designed as quick-change units. For the same reason, it is advantageous if the piston rods are guided through sleeve inserts in the lid of the storage container, which can be mounted from the outside. This makes it possible to replace the sleeve part, which is subject to wear, without opening the lid. For this purpose, it would be advantageous if, as already described, the coupling piece between the piston rod end and the rack drive end could be removed.

The invention is explained in more detail below using embodiments shown in the drawings.

It shows:

Fig. 1 schematically shows an arrangement showing the device according to the invention

includes;

Fig. 2 shows an axial sectional view of a

Storage tank with two dosing pumps;

Fig. 3 in an axial sectional view, rotated by 90° compared to Fig. 2, a

similar arrangement as Fig. 2, additionally with a mixing device;

Fig. 4 shows in an enlarged axial sectional view the drive of the two

dosing piston;

Fig. 5 in an axial sectional view of the two dosing pistons with

switched check valves and three-way valve;

Fig. 6 a view of two together on a movable frame

assembled dosing devices equipped according to the invention;

Fig. 7 is a top view of the arrangement according to Fig. 6;

Fig. 8 is a left-hand view of the arrangement according to Fig. 6;

Fig. 9 is a sectional view taken along the line A-A of Fig. 5; and

Fig. 10 is a sectional view along the line B-B of Fig. 5.

Fig. 1 shows schematically a first storage container 10, for example for resin, a second storage container 11, for example for hardener, which each form a valve 15, 16 via metering pump devices 13, 14, which closes when the piston is pushed into the metering piston cylinder 17, 18, with a drive unit 21 being provided for each of the metering pumps 13, 14 above the cover 19, which seals the storage container in a pressure-tight manner. As can already be seen from the schematic representation, each storage container 10, 11 has two metering pumps 13, 14, the metering pistons of which are guided in a pressure-tight manner through the cover 19 of the storage container (e.g. 10) and are each connected to a rack 23, 24. The drive of these two racks 23, 24 is preferably carried out by a single common gear 25, which meshes with the two racks 23, 24 and thus leads to a counter-rotating drive of the two piston rods 70, 74 when the gear 25 is driven, for example, by a servo or stepper motor 26.

Fig. 1 also shows that the two metering pumps 13, 14 of the storage container 10 shown on the left in the figure are each followed by a check valve 27, 28, the outputs of which are led via a three-way valve 29 to a common output point (line 30) for the material in the container 10. The structure is completely analogous to that of the storage container 11 shown on the right in Fig. 1, the contents of which are metered out via line 130. The lines 30, 130 are connected, for example, to a mixing stage 31 in order to cast components from there after passing through a static mixer and further metering devices within a vacuum chamber 32, which may be positioned on a mobile plate 33.

If the storage container is filled with a substance that has sedimenting components, a mixing device is necessary, as is shown schematically at 34 with respect to the storage container 10. This is a wing that projects into the storage material and can be set in motion via a drive device 35.

A vacuum device 36 can evacuate the two storage containers 10, 11 and the vacuum chamber 32. The corresponding vacuum lines or valves are shown schematically in Fig. 1. It can also be seen in Fig. 1 that the metering piston cylinders 17, 18 are connected to funnel surfaces 37, 38 and ensure that no material gets stuck in any corners of the container when the metering pumps 15, 16 pump out the stored materials.

A supply line 39, for example, is used to supply material to fill the container 10.

Further construction details are explained in more detail with reference to the following figures. Fig. 2 shows an axial sectional view of a storage container with metering devices according to the invention, with the same reference numbers being chosen for the same components. Of particular interest here is the shape of the container, which consists of a rectangular base block 42 into which cylinders 17, 18 are inserted from below and are held in this position by a plate 44, which also

holds non-return valve blocks 48 and a three-way valve block 50 via clamping brackets 46. The base block 42 is in turn held by supports 52, which can be part of a movable carriage 54, as shown in Fig. 6. This carriage 54 comprises, for example, two arrangements according to Fig. 2, see also the top view of the arrangement according to Fig. 6 in Fig. 7, and it is clear that here the containers are not round, but have a rectangular shape. Walls 56 which are connected to one another (welded or braced to one another) extend from the rectangular base blocks 42 at the edges and which carry a rectangular lid 19 in a pressure-tight manner at their upper end. In the lid 19, as can be seen in Fig. 2, sleeves 58 are provided which can be inserted from the outside and are held by a sleeve holder 60. A piston rod 70 or 74 is inserted through this sleeve. A T-beam piece 62 is screwed onto the cover, which serves as a carrier for a gear block 64 in which, on the one hand, the racks 23, 24 connected to the piston rods 70, 74 are guided in an axially displaceable manner, and on the other hand, the gear 25 meshing with these racks 23, 24 is mounted, which is connected to a drive motor 26 flanged to the block 64 via a deflection gear (not visible here).

As can be seen from Fig. 3, a mounting device 66 can also be mounted on the lid 19, which supports the motor 35 of a mixing device 34, which mixing device 34 extends in a sealed manner through a corresponding opening in the lid 19, the motor 35 being connected to a drive shaft 34 which extends between the two piston drives 70, 74 and is connected to a drive propeller or drive blade 68 and enables the contents of the container 10 to be thoroughly mixed. The blade 68 is advantageously located near the funnel-shaped inlet openings for the two metering pumps and therefore ensures that only well-mixed material is conveyed by these metering pumps.

Fig. 4 shows in greater detail the drive of the metering pump device according to the invention. Of particular interest here is a coupling piece 70 which is located between the upper end 72 of the piston drive rod 74 on the one hand and the

lower end 76 of the rack 24 on the other hand. A long bolt 78 penetrates a central bore 80 in the rack 24, a bore 82 in the coupling piece 71 and is received in a blind threaded bore 84 in the upper end of the piston drive rod 74. The drive bolt 78 holds these three components together. The advantage of this arrangement is that, for example, if the sealing sleeve 58 is worn, it can be replaced without having to dismantle the lid 19 from the container 10. For this purpose, only the bolt 78 needs to be removed, whereupon the flange parts 76 and piston drive rod 74 can be pushed apart, whereupon the coupling piece 70 can then be removed from the inside. The sleeve component 58 can now be pulled upwards off the piston drive rod 74. A new sleeve component can then be pushed back on and, after reinserting the coupling piece 70 and inserting the screw 78, the arrangement can be returned to the operating state.

The shape of the metering piston device running in the piston cylinder, which is clearly visible in Fig. 5, is essentially already known; in this context, reference is made to DT 1 778 396.

The operation of the dosing pump device described is as follows:
It is assumed that the storage container 10 is at least partially filled with material and that this material is already mixed (if, for example, it is resin containing sedimenting materials) or does not require mixing (if it is, for example, hardener). With the position of the pistons 86, 88 shown in Fig. 5, material from the storage container 10 runs along the funnel surface 37, 137 into the area of the cylinder 18, where, with the position of the piston 88 shown on the left in Fig. 5, it can run through this piston and thus flow into the cylinder space 90 located below, including the areas 92, 94, 96 located below, which are formed by the plate 44, the distributor block 98 and the check valve 27 or 28. The filling process continues until all empty spaces are filled.

In the piston devices 86 and 88, a sealing cover 100 is placed on a piston edge, whereby material is not pumped through the piston from above.

can flow through, as was described for the piston device 88 shown on the left in Fig. 5. Nevertheless, material has also accumulated above this cover 100, and it is assumed that material from previous piston strokes is also contained below the cover 100 in the spaces 92, 94, 96. If at this moment the gear 25 according to Fig. 4 is rotated by the motor 26 under the control of a microprocessor device or the like so that it moves in an anti-clockwise direction, the rack 23 meshing with the wheel 25 moves upwards and at the same time the opposite rack 24 moves downwards. First of all, a certain dead motion T must be overcome, which is determined by the distance of the cover 100 from the edge of the piston 86, which can be seen on the left-hand side of Fig. 5. During this piston movement, the cover 100 of the left piston device 88 in Fig. 5 moves towards the corresponding edge of the piston and thereby closes the flow path 104 indicated by arrows between the upper region of the container 10 and the cylinder chamber 90. At the same time, in the right piston arrangement, the cover 100 moves away from the piston 86 and opens up such a flow path. With further movement, which goes beyond the dead path T, the left piston 88 now moves downwards in the cylinder 18 with the cylinder chamber 90 and presses mass or material located there through the regions 92, 94, 96 against the force of the check valve arrangement 27 into the channel 106 and from there to the three-way valve 29, which guides the material in this position shown to an outlet opening 108, where there may be a screw connection to a hose 30, as shown in Fig. 1. While the piston 88 thus moves downwards by a certain amount, mass is displaced according to the piston cross-section and this amount and now reaches the outlet 108. The amount is precisely defined by the path of the piston and can therefore be dosed. In the same period of time, the piston 86 shown on the right in Fig. 5 and in a flow path similar to that of the arrangement on the left, designated 104, moves upwards and during this movement allows material to flow through into the space below the piston device 86. Since this flow occurs without pressure, the check valve below is not opened and material cannot reach the area of the three-way valve 108. The piston movement can be interrupted several times during the downward or upward movement, for example in order to control different amounts during

this time. The downward movement can also be uninterrupted if a large quantity is to be dosed, for example one which exceeds the volume of the piston 90. In this case the left piston will, for example, move to the lower end of the cylinder arrangement shown on the left in Fig. 5 and then stop, while at the same time the right piston reaches an upper position according to Fig. 5. The direction of rotation of the gear 25 is now reversed, i.e. it runs clockwise, whereupon the left piston begins to move upwards and at the same time the right piston downwards. After overcoming the dead distance T again, the described process is repeated, only now the roles are reversed, i.e. the right valve now feeds material downwards to the three-way valve 108, while the left valve enables the piston volume 90 to be filled. During this movement, which now takes place in the opposite direction, material is conveyed again, enabling continuous operation - except for the short dead time of movement by path T.

The double-acting pump described here eliminates waiting times between the filling stroke and the dosing stroke, which can lead to a time saving of more than 50%.

The dead motion caused by the closing path (path T) and any pinion play (play between the teeth of the pinion 25 and those of the racks 23 or 24) can be compensated by the electronic control so that there is no need to fear inaccuracies.

The square shape of the container results in greater compactness and a larger storage volume, while the quickly replaceable check valve arrangement makes handling easier. The double-acting lifting device and the more compact arrangement make it possible to accommodate the entire arrangement on a mobile trolley, so that it can be used for several areas of application or at different locations where resin is processed.

Claims (12)

1. Device for driving a metering device for viscous substances, such as cast resin, consisting of an evacuable storage container ( 10 ) for the substance, optionally equipped with a mixing device ( 68 ), and with a metering pump device ( 13 ) associated with this container ( 10 ), the metering piston ( 88 ) of which forms a valve which closes when the piston ( 88 ) is pushed into the metering piston cylinder ( 18 ), and with drive devices ( 26 ) for the piston, characterized in that the metering pump devices ( 13 ) of the storage container ( 10 ) have two metering pumps ( 13 , 14 ), the metering pistons of which are guided with a piston rod ( 70 , 74 ) in a pressure-tight manner ( 58 ) through the cover ( 19 ) of the storage container ( 10 ) and each with a Racks ( 23 , 24 ) are connected, which are arranged axially displaceably in a common gear housing ( 64 ) and can be driven in opposite directions by a drive ( 26 ) connected to the housing ( 64 ). 2. Device according to claim 1, characterized in that the two racks ( 23 , 24 ) are driven by a single common gear ( 25 ). 3. Device according to claim 1 or 2, characterized in that a removable coupling member ( 71 ) is arranged between the piston rod end ( 72 ) and the rack end ( 76 ). 4. Device according to one of claims 1 to 3, characterized in that the two metering pumps ( 13 , 14 ) are each followed by a check valve ( 27 , 28 ), the outputs of which are led via a three-way valve ( 29 ) to a common output point ( 30 ) for metered substance. 5. Device according to one of claims 1 to 4, characterized in that the drive comprises a servo motor or a stepping motor ( 26 ), optionally with a downstream deflection gear, the movement of which is controlled by a microprocessor. 6. Device according to claim 5, characterized in that the three-way valve ( 29 ) is also controlled by the microprocessor. 7. Device according to one of claims 1 to 6, characterized in that the metering piston cylinders ( 17 , 18 ) are arranged in a block ( 42 ) forming the bottom of the storage container ( 10 ), from which the side walls of the storage container ( 10 ) also extend. 8. Device according to one of claims 1 to 7, characterized in that the bottom ( 42 ) of the storage container forms two funnel surfaces ( 37 , 137 ) which open into the upper ends of the cylinders ( 17 , 18 ) of the metering pumps. 9. Device according to one of claims 1 to 8, characterized in that the storage container ( 10 ) has a rectangular or square cross-section. 10. Device according to one of claims 1 to 9, characterized in that two storage containers ( 10 , 11 ) are arranged together on a movable frame ( 54 ). 11. Device according to one of claims 1 to 7, characterized in that the check valves ( 27 , 28 ) are designed as quick-change units. 12. Device according to one of claims 1 to 7, characterized in that the piston rods ( 70 , 74 ) are guided through sleeve inserts ( 54 ) in the lid ( 19 ) of the storage container ( 10 ), which can be mounted from the outside.