DE29900349U1 - Working device - Google Patents

Description

G 18103 - leml 30 November 1998

FESTO AG & Co. 73734 Esslingen

Work device ·

The invention relates to a working device, in particular a crust cup device, with a working cylinder which has a working body which separates two working spaces from one another and which can be driven by controlled fluid exposure to the first working space to a first lifting movement and by controlled fluid exposure to the second working space to a second lifting movement in the opposite direction.

A working device of this type is disclosed in DE 197 09 648 Al. It is a crust breaking device that is used to prevent the formation of a crust on the surface of the melt during the production and/or further processing of liquid metal material, and in particular aluminum material, or to break up the crust so that additives and aluminum oxide can be added to the melt from time to time. In the known case, the crust breaking device contains a fluid-operated working cylinder arranged above the melt, the working body of which has a downward-facing surface towards the melt.

piston rod, which has an impact section on the front side. In order to break up the crust, the working body is caused to make a first stroke movement starting from a retracted starting position by applying fluid to a first working chamber, during which the piston rod hits the crust by means of an impact section provided on it, e.g. a hammer, and pierces it. The return stroke from this extended working position to the retracted starting position takes place by applying fluid to the second working chamber of the working cylinder.

Due to the high heat of the molten metal, the piston rod or its impact section becomes damaged or worn over time. The replacement that is then required impairs metal processing, so that maintenance intervals that are as long as possible are aimed for. The present invention therefore has the task of creating a working device of the type mentioned at the beginning, which, when used as a crust breaker, enables the working body to return to the retracted starting position as quickly as possible.

To solve this problem, according to the characterizing part of patent claim 1, it is provided that a fluid reservoir is present which is fed with a working fluid during the first stroke movement and releases working fluid into the second working chamber during the second stroke movement.

In this way, a conventional first stroke movement of the working body is still possible, whereby this

set in connection with a crust breaker device, the part is immersed in the molten metal after piercing the crust. The second stroke movement in the opposite direction, which in this case is a return stroke movement, can, however, take place considerably faster because the second working chamber is fed with the working fluid stored in the fluid reservoir and under a correspondingly high pressure, which, at least initially, causes a greatly accelerated second stroke movement. If the working device is used as a crust breaker device, the residence time of the relevant section of the working body in the molten metal can be considerably reduced and the entire service life of the cylinder and the impact section can thus be extended.

Advantageous further developments of the invention emerge from the subclaims.

The working fluid fed into the fluid reservoir during the first stroke movement is expediently branched off directly from the first working chamber or from a first fluid channel leading to the first working chamber. In this way, a separate supply line is saved and the filling of the fluid reservoir can take place automatically during the first stroke movement. In this context, it is particularly advantageous if the fluid reservoir is connected to a channel connecting the two working chambers of the working cylinder and/or the fluid channels leading to these working chambers, which is referred to below as an acceleration channel because it is connected to the

Fluid storage enables the aforementioned accelerated lifting movement of the working body.

In order to obtain the required connection of the fluid reservoir with the two working chambers or fluid lines, suitable control means are expediently connected to the acceleration channel. These control means can contain a check valve connected between the fluid reservoir and the first working chamber or the first fluid line, which opens in the direction of the fluid reservoir and closes in the opposite direction. In this way, the fluid reservoir is automatically filled when fluid is applied to the first working chamber, while emptying towards the first working chamber is excluded.

The control means preferably also contain a control valve which is connected between the fluid reservoir and the second working chamber or the second fluid channel leading to it and which can selectively interrupt or release the connection between the fluid reservoir and the second working chamber or the second fluid channel. In this way, the control valve can be used to specify the time at which the second working chamber is fed from the fluid reservoir. It is expediently provided that the control valve simultaneously controls the connection between a working fluid source and the first working chamber, so that a coordinated connection of the working chambers takes place and the specification of the two stroke movements corresponds as desired to the controlled connection with the fluid reservoir.

Advantageously, the first section of the acceleration channel connecting the fluid reservoir to the control valve is connected to the working fluid source. In this way, the second working chamber is always connected to both the fluid reservoir and the working fluid source at the same time. This enables a particularly economical mode of operation that saves pressure medium. The design can be such that the volume of working fluid accumulated in the fluid reservoir is sufficient to quickly remove the working body from the molten metal and thus achieve a high speed at the start of the second stroke. However, if the working body has covered a certain stroke section so that it is removed from the molten metal when used as a crust breaker, there is no longer any particular reason to also carry out the remaining stroke at high speed. The volume of fluid stored in the fluid reservoir can thus be limited to an amount that ensures the required high speed during the desired stroke section, while the subsequent remaining stroke is slowed down by the working fluid supplied directly via the working fluid source. The savings can be made particularly effective if a pressure control device is connected to the connection between the working fluid source and the acceleration channel, in particular a pressure regulator without secondary venting, which reduces the working pressure and accordingly the amount of fluid supplied.

The reversal of the stroke movement direction is expediently effected by a limit switch, in particular a pneumatic or electrical one, which responds to a predetermined position of the working body.

The fluidic circuit of the working cylinder is expediently carried out in such a way that a throttle check valve is connected to the first fluid channel leading to the first working chamber, while in the second fluid channel leading to the second working chamber there is a releasable check valve that can be released by the pressure prevailing in the first fluid channel leading to the first working chamber. The latter fulfills a safety function because the first stroke movement of the working body is interrupted if a pressure drop occurs in the supply line to the first working chamber.

Preferably, the working cylinder and the other components of the working device are combined to form a structural unit, whereby the fluid reservoir can also be a component of the working cylinder. For example, the fluid reservoir could be formed by a chamber in the wall of the housing of the working cylinder, which is formed during extrusion of the housing.

The invention is explained in more detail below with reference to the accompanying drawings, in which:

Fig. 1 in schematic representation the inventive

Appropriate working device for a

typical use as a crust breaking device, and

Fig. 2 the working device from Fig. 1 in

Circuit diagram-like representation to explain the individual components and their function.

Figure 1 shows a working device 1 designed as a crust breaker, which is installed above a container 2 in which an aluminum melt 3 is located. The latter tends to form a crust in the area of its surface 4 due to its cooling, which is broken up by the working device 1. By means of time intervals, the crust breaker also ensures that the opening in the surface of the melt required for dosing does not become blocked. Only when the crust has broken up is it possible to add additives and aluminum oxide to the aluminum melt 3.

To simplify the illustration, only one fluid-operated working cylinder 5 belonging to the working device 1 is shown in Figure 1, which is also shown schematically in Figure 2. It has a housing 6, via which it is fixed to a suitable holder 7 in such a way that its longitudinal axis 8 is oriented vertically.

A working body 12 is guided on the housing 6 so that it can be moved linearly in its longitudinal direction. In the embodiment, it contains a working body 12 arranged inside the housing 6 and

a first and a second working chamber 13, 14 axially separated by a piston 15, which is connected to a piston rod 16, which protrudes from the front end of the housing 6 pointing downwards in Figure 1. Its free end is designed as a butt section 17 or is provided with such a section.

The first working chamber 13 communicates with a first fluid channel 18, while the second working chamber 14 is connected to a second fluid channel 19. The second working chamber 14 is the one through which the piston rod 16 passes, the first working chamber 13 is the opposite working chamber arranged at the back in the housing 6.

Through the controlled supply and discharge of a working fluid, in particular compressed air, with respect to the two working spaces 13, 14, the working body 12 can be driven to a linear lifting movement in opposite axial directions. The working body 12 can be moved from the retracted starting position shown in Figure 2 and depicted in solid lines in Figure 1 and the extended working position indicated in dash-dotted lines in Figure 1.

In the retracted starting position, the first working chamber 13 has its minimum volume and the second working chamber 14 has its maximum volume. The extension movement starting from this position is referred to as the first stroke movement 22. The oppositely oriented return movement is referred to as the second stroke movement 23; it begins when the

first working chamber 13 has its maximum volume and the second working chamber 14 has its minimum volume.

From Figure 2 it can be seen that the piston rod 16 or the impact section 17 provided on it is arranged in the retracted starting position at a distance above the surface 4 of the aluminum melt 3. During the first stroke movement 22 the piston rod 16 extends from the housing 6 and plunges with its impact section 17 into the aluminum melt 3, penetrating any metal crust that may be present in the area of the surface 4. The extended working position indicated by a dot-dash line is then present, which is followed as immediately as possible and at least initially at high speed by the second stroke movement 23 back in the direction of the retracted starting position.

In the further explanations, reference is made in more detail to Figure 2.

The working device 1 contains a control valve 24, which in the exemplary embodiment is designed as a 5/2 switching valve, to which the first and second fluid channels 18, 19 are connected separately. Furthermore, the control valve 24 is connected to a working fluid source P via a feed channel 25 and communicates with a vent channel 26 leading to a pressure sink R and in particular to the atmosphere. In a working device 1 that is not operated with a gaseous but with a hydraulic working fluid, the vent channel would be a relief channel leading to a tank.

The working device 1 further contains a channel referred to as an acceleration channel 27, which connects the first fluid channel 18 to the second fluid channel 19 and into which a fluid reservoir 32 and control means 28 are connected. The control means 28 enable a controlled connection of the fluid reservoir 32 to the first fluid channel 18 and the second fluid channel 19.

One of the control means 28 is formed by the control valve 24, to which not only the second fluid channel 19 but also a first section 34 of the acceleration channel 27 is connected. In this way, the control valve 24 is located between the fluid reservoir 32 and the second fluid channel 19 leading to the second working chamber.

Further control means 28 in the form of a check valve are located in the second section 35 of the acceleration channel 27 connecting the fluid reservoir 32 to the first fluid channel 18, the orientation being such that the check valve 33 allows fluid flow in the direction of the fluid reservoir 32, but prevents it in the opposite direction.

This preferred connection ensures that the fluid reservoir 32 is supplied with a working fluid during the first stroke movement 22 of the working body 12 and releases working fluid into the second working chamber 16 during the second stroke movement 23. This makes it possible to ensure that the second stroke movement 23 is at least initially accelerated or takes place at high speed and thus the working body

12 after immersion in the aluminium melt 3 it can be quickly removed from it.

The control valve 24 can be moved optionally into the first switching position shown in Fig. 2 and a second switching position. Switching to the second switching position occurs when the working body 12 is to be caused to perform the first lifting movement 22. The required switching movement is brought about in the exemplary embodiment by a pilot valve 36, which is operated electrically, for example, and switches the control valve 24 into the second switching position against the force of an auxiliary spring 38 with a fluidic control signal 37 indicated by dashed lines.

In the second switching position, the feed channel 25 is connected to the first fluid channel 18, so that pressure medium is fed into the first working chamber 13, which acts on the piston 14 in the extension direction. To save pressure medium, a preferably adjustable throttle 42 can be connected to the first fluid channel 18, which is bypassed during the return stroke of the piston 15 by a parallel-connected check valve 43, the throttle 42 and the check valve 43 expediently being part of a combined throttle check valve 41.

In the second switching position of the control valve 24, the second fluid channel 19 is also connected to the pressure sink R. This allows pressure medium displaced by the piston 15 to be vented from the second working chamber 14.

In order to obtain a safety function, a releasable check valve 44 is inserted into the second fluid channel 19. It normally allows fluid flow in the direction of the second working chamber 14, while preventing flow in the opposite direction. However, there is a fluid signal connection 45 between the releasable check valve 44 and the first fluid channel 18, so that the releasable check valve 44 is unlocked when the desired operating pressure prevails in the first fluid channel 18. In this way, it is ensured that when the first working chamber 13 is pressurized with fluid, the releasable check valve 44 is opened and pressure medium can flow out of the second working chamber 14 to the pressure sink R.

During the first stroke movement 22, the fluid reservoir 32 is fed with working fluid from the first fluid channel 18 via the check valve 33, whereby a fluid volume accumulates which is under a pressure that corresponds to the feed pressure supplied by the working fluid source P and is, for example, 6 bar. In contrast, in the first working chamber 13 there is a pressure reduced by the throttle 42 of, for example, in the order of magnitude between 1 and 2 bar, which enables a fluid-saving first stroke movement 22.

If the working body 12 encounters increased resistance when it comes into contact with the crust of the molten metal, the pressure in the first working chamber 13 increases to a maximum of

the food pressure is applied, which certainly ensures that the crust that has formed breaks through.

Once the working body 12 has reached its extended working position, it actuates a limit switch 46, which is expediently integrated into the working cylinder 5, which causes the control valve 24 to switch back to the first switching position. The limit switch 46 can be an electrical or, as in the embodiment, a fluidic limit switch.

In the embodiment, the limit switch 46, designed in the manner of a valve, is located in a control channel 47 that connects the feed channel 25 to an actuating device of the control valve 24. This connection is normally interrupted and is only released when the limit switch 46 is actuated by the working body 12, so that the control valve 24 receives a hold-back pulse. At the same time, the pilot valve 36 can receive a switching pulse via a connected second control line 48, so that it returns to the basic position and the actuating signal 37 is removed.

If the control valve 24 assumes the first switching position shown in Figure 2, the feed channel 25 is blocked. At the same time, the first fluid channel 18 is connected to the pressure sink R and the connection from the first section 34 of the acceleration channel 27 to the second fluid channel 19 is switched through. This has the consequence that the fluid accumulated in the fluid reservoir 32 and preferably under the

Working fluid under feed pressure suddenly flows into the second working chamber 14, which means that the second stroke movement 23 takes place at least initially at a high speed. As a result, the working body 12 is moved out of the aluminum melt 3 very quickly.

At the same time, the first working chamber 13 is vented via the first fluid channel 18 and the control valve 24.

In order to reduce fluid consumption to a minimum, the working device of the embodiment is designed so that the volume stored in the fluid reservoir 32 is only sufficient to effect a partial stroke of the second stroke movement 23, the length of which is at least large enough that the working body 12 is pulled out of the aluminum melt 3 at the end of this initial partial stroke. The remaining stroke can then run at a lower speed to save fluid. This is achieved by the second section 34 of the acceleration channel 27 being connected to the feed channel 25 by a bridging channel 49, with a pressure control device 50 being connected to the bridging channel 49, which enables a pressure setting such that the secondary pressure on the output side is lower than the primary pressure on the inlet side and corresponds to the feed pressure. The pressure control device 50 is in particular a pressure regulator without secondary venting.

If the pressure in the fluid reservoir 32 has thus fallen to the secondary pressure set in the pressure control device 50, then a supply of working fluid takes place.

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working fluid into the second working chamber 14, the fluid flow through the feed channel 25, the bridging channel 49, a partial area of the first section 34 of the acceleration channel 27, the control valve 24 and the second fluid channel 19. This ensures the complete return stroke of the working body 12 into the retracted starting position.

In addition, an emergency valve 53 can be provided which can be operated in an emergency to switch the control valve 24 to the first switching position. It is connected in the connection between a working fluid source P and the control line 47, whereby the connection can be made with an OR valve 55.

In the practical design of the working device, all of the components shown in Figure 2 within a dash-dotted frame 54 are expediently combined to form a structural unit, whereby the fluid lines, the valves and the fluid reservoir can be attached to the working cylinder 5 and/or at least partially integrated into it. The entire device is therefore very easy to handle and install.

It should also be added with regard to the fluid reservoir 32 that, with a corresponding design of the control means 28, it could also be directly connected to the working chambers 13, 14, in particular if it is integrated into the housing 6 of the working cylinder 5, as is recommended for a housing 6 designed as an extruded part.

Claims (17)

G 18103 - leml 30 November 1998 FESTO AG & Co. 73734 Esslinqen Working device Claims 1. Working device, in particular a crust breaking device, with a working cylinder (5) which has a two working
sraums (13, 14) separating working bodies (12) which is controlled by fluid exposure of the
first working space (13) to a first lifting movement (22)
and can be driven by controlled fluid loading of the second working chamber (14) to a second stroke movement (23) directed in the opposite direction, characterized in that a fluid reservoir (32) is provided which is fed with a working fluid during the first stroke movement (22) and during
the second stroke movement (23) releases working fluid into the second working chamber (14). 2. Working device according to claim 1, characterized in that during the first lifting movement (22) in the
Fluid reservoir (32) fed working fluid directly from
the first working space (13) or from a space belonging to the first working chamber (13) is branched off. 3. Working device according to claim 2, characterized in that the fluid reservoir (32) is part of an acceleration channel (27) connecting the two working spaces (13, 14) and/or the fluid channels (18, 19) leading to them. 4. Working device according to claim 3, characterized in that control means (28) are connected to the acceleration channel (27) which control the connection of the fluid reservoir (32) to the two working spaces (13, 14) or the fluid channels (18, 19) leading to them. 5. Working device according to claim 4, characterized in that the control means (28) contain a check valve (33) inserted between the fluid reservoir (32) and the first working chamber (13) or the first fluid line (18), opening in the direction of the fluid reservoir (32) and closing in the opposite direction. 6. Working device according to claim 4 or 5, characterized in that the control means (28) contain a control valve (24) connected between the fluid reservoir (32) and the second working chamber (14) or the second fluid channel (19) leading to it, which can interrupt or release the connection between the fluid reservoir (32) and the second working chamber (14) or the second fluid channel (19) depending on the switching position. 7. Working device according to claim 6, characterized in that the control valve (24) simultaneously controls the connection between a working fluid source and the first working chamber (13). 8. Working device according to claim 7, characterized in that the control valve (24) is designed in such a way that in a second switching position it interrupts the fluid connection between the fluid reservoir (32) and the second working chamber (14) and at the same time establishes the fluid connection between the working fluid source and the first working chamber (13), while in a first switching position the previously interrupted connection is released and the previously released connection is interrupted. 9. Working device according to one of claims 6 to 8, characterized in that the first section (34) of the acceleration channel (27) present between the fluid reservoir (32) and the control valve (24) is connected or connectable to the working fluid source. 10. Working device according to one of claims 6 to 9, characterized in that the first section (34) of the acceleration channel (27) present between the fluid reservoir (32) and the control valve (24) is connected to the output of a pressure control device (50) connected on the input side to the working fluid source. ·· 11. Working device according to claim 9 or 10, characterized in that the volume of the fluid reservoir (32) is matched to the maximum volume of the second working space (14) in such a way that the working fluid stored in the fluid reservoir (32) alone is not able to completely effect the second lifting movement (23) of the working body (12). 12. Working device according to one of claims 1 to 11, characterized in that the reversal of the direction of stroke movement of the working body (12) is effected by a limit switch (46) responding to a specific position of the working body (12). 13. Working device according to one of claims 1 to 12, characterized in that a throttle check valve (41) is inserted into the first fluid channel (18) leading to the first working chamber (13). 14. Working device according to one of claims 1 to 13, characterized in that a releasable check valve (44) is inserted into the second fluid channel (19) leading to the second working chamber (14), which check valve can be releasably opened by the pressure prevailing in the first fluid channel (18) leading to the first working chamber (13). 15. Working device according to one of claims 1 to 14, characterized in that the fluid reservoir (32) is a component of the working cylinder (5). • tr ··
r. 5 -· 16. Working device according to one of claims 1 to 15, characterized in that its components and the working cylinder (5) are combined to form a structural unit. 17. Working device according to one of claims 1 to 16, characterized in that the working body (12) contains a piston (15) and a piston rod (16) connected to the piston and having a butt section (17) at the end.