EP0467890B1 - Process and device for screwing fragile parts - Google Patents

Abstract

A device is useful for screwing fragile parts, in particular for screwing shells, moulds and casting cores, preferably sole and water cooling jacket cores. To facilitate handling of these parts, a gripping device (3) for gripping the parts (1, 2) to be screwed and at least one screwdriver (6) with a screw spindle (10) and a drive device (11) for the screw spindle (10) are provided. In a particularly advantageous embodiment, the screw spindle (10) is elastically mounted in the direction of advance of the screw, i.e. in the axial direction, and possibly also in the radial direction.

Description

The invention relates to a device for connecting parts with low strength, in particular a device for screwing masks, molds, foundry cores, preferably sole and water jacket cores, and a corresponding method.

The connection of parts with low strength is always problematic, since a complicated handling or an expensive conveying of such parts to a nailing or screwing station can lead to the breakage of these parts. To avoid breakage of the parts to be connected, both the screw feed and the tightening torque must also be very low.

Cores from foundry technology are such parts with low strength, so that the problems encountered in practice are explained below using such cores.

In foundry technology, the cores are formed by hand or with the help of core molding machines in special multi-part core boxes or core bushings. The core is generally produced by blowing, plugging and shooting. The individual cores are combined or brought together in separate operations by gluing or nailing, which makes the manufacturing process very cumbersome, labor-intensive and time-consuming (DE-PS 35 26 265 and DE-GM 75 15 919).

The starting point for the device according to the invention or for the method according to the invention is the prior art known from DE-OS 25 22 161. From this document, a method and an apparatus for connecting multi-part, heat-curable foundry cores are known. The foundry cores are connected to one another by means of metal pins, these being knocked into passages and forming an interference fit with the cores.

Furthermore, from DE-OS 34 24 911 a method for screwing a screw into thin-walled sheets and a device for performing the method is known. This is a method for screwing a screw with a self-tapping thread into thin-walled sheets, the screw's pull-out strength being increased by the fact that the screws pull the sheet in a crater-like manner, ie deform it accordingly.

When connecting parts with low strength or when connecting individual cores by nailing or screwing, it has also been found in practice that the material of the parts to be connected breaks easily due to the shear forces that occur.

The present invention is therefore initially based on the object of specifying a device for connecting low-strength parts, in particular for connecting masks, molds, foundry cores, preferably sole and water jacket cores, with which the parts to be combined - without any intermediate handling - can be brought directly from the manufacturing site to the screwing station. The risk of damage to the parts to be connected or even breakage of the material should be considerably reduced. A corresponding procedure is also to be specified.

According to the invention, the above object is achieved in that a gripping device for grasping the parts to be connected and at least one screwdriver and a drive device for the screwdriver are provided. In a particularly advantageous manner, the screw spindle is spring-mounted at least in the screw feed direction.

It was thus initially recognized that a gripping device for grasping the parts to be connected and at least one screwdriver and a drive device for the screwdriver are required for the correct connection of the parts in question. Furthermore, it has been recognized that the material damage or material breakage that frequently occurs when the low-strength parts are screwed together is primarily due to an "coarse" screw feed. This "coarse" screw feed is reduced according to the invention by a resilient mounting of the screw spindle at least in the screw feed direction when the screw counteracts resistance on the material side.

In a particularly advantageous manner, a spring housing is formed for the resilient mounting of the screw spindle between the drive device of the screw spindle and the screw spindle. At least one spring element acting between the drive device and the screw spindle is provided in this spring housing.

So that the feed differences between the feed of the screw spindle and the screw-in speed determined by the speed and the pitch of the thread of the screw to be screwed in are compensated without the contact pressure To affect the screw on the screw and thus on the material of the parts to be screwed, a driving pin is further advantageously provided, which sits on the spring element and thereby represents a link or an operative connection between the spring element and the screw.

Furthermore, it has been recognized that in addition to a "coarse" screw feed, too high a tightening torque can lead to material breakage in the case of parts of low strength. To avoid material breakage, the tightening torque had to be reduced in such a way that tolerance ranges were no longer possible. The screws could be held in place during automatic shooting in by compressed air with clamping jaws, the clamping jaws applying the holding pressure, for example, via leaf springs. However, the tightening torque when pushing the screw head through the clamping jaws and against the locking pressure of the leaf springs would be influenced so strongly that the - even - tightening torque required on the screw could no longer be maintained.

With regard to a limitation of the tightening torque, it is therefore particularly advantageous if the torque of the drive device or of the screwdriver is determined by a preferably adjustable - automatic - shut-off clutch provided in the drive device.

When the screws are automatically shot in, clamping jaws are provided for holding the screws. The holding pressure is generated by means of pneumatic or hydraulic cylinder-piston arrangements. The jaws open to push the screws through.

Now, especially with parts to be connected with low strength, especially brittle parts, particles are loosened when the screw is screwed in, which then gets into the area of the clamping jaws and increases the friction coefficients there or even leads to damage to the clamping jaws According to a further embodiment of the teaching according to the invention, the particles of the parts to be screwed which get into the area of the device during screwing are blown out or sucked away by means of a blow-out device.

So that screws that do not align with the original axis of the screw spindle can also be properly screwed in with the device according to the invention, the screw spindle is also resiliently mounted transversely to the screw feed direction. This creates a slight play of the screw spindle orthogonal to the screw feed direction, as a result of which the screw spindle can tilt slightly.

With regard to the provision of screws to be screwed in, a shooting device for shooting in the screws to be screwed in by the screwdriver is provided, in particular from the point of view of a fully automatic connection of the parts in question. To ensure trouble-free delivery of individual screws to the screw spindle or to the parts to be screwed, the insertion device has a reflection light barrier to monitor and regulate these processes.

Finally, the position of the screwdrivers can be changed by means of spindles, as a result of which the screwdrivers are set to different screwing points.

According to the inventive method for connecting parts with low strength, in particular for connecting masks, Molds, foundry cores, preferably of sole and water jacket cores, are first grasped, the parts to be connected by means of a gripping device and braced together. The parts are then positioned in the work area of a screwdriver. In the case of foundry cores to be screwed, the parts or cores are regularly positioned above one or more screwdrivers. Then one or more screws are shot into the screwdriver. The parts are screwed together, in a particularly advantageous manner to prevent damage to the parts or to avoid brittle fracture, the screw feed, ie the screwing speed, is compensated for by a resilient mounting of the screw spindle without impairing the contact pressure.

To avoid damaging the parts to be connected, the method step of screwing in the screw is advantageously designed such that the torque of the screwdriver is determined or regulated by a preferably adjustable automatic shut-off clutch.

Fig. 1

in einer Seitenansicht, schematisch, ein Ausführungsbeispiel der erfindungsgemäßen Vorrichtung,

Fig. 2

in einer Vorderansicht, schematisch, die Vorrichtung aus Fig. 1,

Fig. 3

in einer Draufsicht, schematisch, die Vorrichtung aus Fig. 1,

Fig. 4

in einer vergrößerten Sprengdarstellung die zu verschraubenden Teile, den Schrauber und die Schraube,

Fig. 5

im Längsschnitt, teilweise und vergrößert, die erfindungsgemäße Vorrichtung und

Fig. 6

im Längsschnitt, schematisch, einen Schrauber der Vorrichtung aus Fig. 5.

There are various other ways of advantageously designing and developing the teaching of the present invention. For this purpose, reference is made to the subordinate claims, on the one hand, and to the following explanation of an exemplary embodiment of the invention with reference to the drawing. In connection with the explanation of the preferred exemplary embodiment of the invention with reference to the drawing, generally preferred configurations and developments of the teaching are also explained. In the drawing shows

Fig. 1

in a side view, schematically, an embodiment of the device according to the invention,

Fig. 2

in a front view, schematically, the device of FIG. 1,

Fig. 3

in a plan view, schematically, the device of FIG. 1,

Fig. 4

in an enlarged explosive view the parts to be screwed, the screwdriver and the screw,

Fig. 5

in longitudinal section, partially and enlarged, the device according to the invention and

Fig. 6

in longitudinal section, schematically, a screwdriver of the device from FIG. 5.

Figures 1 to 3, 5 and 6 show an embodiment of an inventive device of an inventive device for screwing parts 1, 2 with low strength. This is a screwing device for screwing foundry cores, namely sole and water jacket cores 1, 2.

The device according to the invention includes a gripping device 3 for gripping the foundry cores 1, 2 to be screwed, and a screwdriver 6 having a screw spindle 10 and a drive device 11 for the screw spindle 10.

According to the representation in FIG. 6, the screw spindle 10 is spring-mounted at least in the screw feed direction. This is evidently achieved in that for the resilient mounting of the screw spindle 10 between the drive device 11 of the screw spindle 10 and the screw spindle 10, a spring housing 12 with one between the drive device 11 and the screw spindle 10 acting spring element 13 is arranged. A driver pin 14 is seated on the spring element 13.

Furthermore, the torque of the drive device 11 or of the screwdriver 6 is determined by an adjustable automatic shut-off clutch provided in the drive device 11.

For automatic insertion of the screws 5 5 clamping jaws 15 are provided for holding the screws. The required holding pressure is generated by means of pneumatic or hydraulic cylinder-piston arrangements 16. The clamping jaws 15 only open for pushing through the screws 5.

Particles of the parts 1, 2 to be screwed, possibly reaching the area of the device during screwing, are blown out by means of a blow-out device 17 or sucked off by means of a suction device.

In the figures, it is not shown that the screw 10 can also be resiliently mounted transversely to the screw feed direction, so that screws 5 can also be easily screwed in, which are not aligned with the original axis of the screw 10.

1 and 5 indicate that a shooting device 4 is provided for shooting in the screws 5 to be screwed in by the screwdriver 6. The shooting device 4 can have a separating device (not shown in the figures) for separating the screws 5.

The mode of operation of the device according to the invention is described below. The parts 1, 2 or the sole core 1 and the water jacket core 2 are plugged together or joined and gripped by means of the gripping device 3 and braced together. Then the clamped parts 1, 2 are brought over the screwdriver 6. A screw 5 or screws 5 are then pneumatically injected into the clamping jaws 15 by means of the shooting device 4 through the transport hoses 8. The parts 1, 2 are then screwed together. The respective screw position of the spindle 10 can be specified via an adjusting spindle 7. The screw spindles 10 with drive motor 11, spring housing 12, spring 13 and driving pin 14 are used for the gentle screwing of the parts 1, 2, the screw feed or screwing speed being balanced without the contact pressure of the screw spindle 10 on the screw 5 being impaired. The screws are held by the clamping jaws 15, which can be actuated via the pneumatic cylinder 16. For the sake of a complete illustration, reference numbers 18, 19 refer to ball bearings and a bearing bush.

Finally, it should be emphasized here again that the teaching according to the invention deals with the connection of parts of low strength. The screwing of foundry cores has only been used here as an example.

Claims (13)

1. Device for connecting parts (1, 2) of low strength, in particular for connecting masks, moulds, casting cores, preferably base and water jacket cores, characterised in that a gripper device (3) for grasping the parts (1, 2) to be connected and at least one screwing device (6) for screwing the parts together comprising a screw spindle (10) and a drive device (11) for the screw spindle (10) are provided; in that the screwing device (6) is arranged such that it can be adjusted by means of spindles (7); and in that the screw spindle (10) is mounted so as to be resilient at least in the screwing advance direction.
2. Device according to Claim 1, characterised in that a spring housing (12) having at least one spring component (13) acting between the drive device (11) and the screw spindle (10) is disposed between the drive device (11) of the screw spindle (10) and the latter such that the screw spindle (10) is mounted resiliently.
3. Device according to Claim 2, characterised in that the spring component (13) is in the form of a pressure spring.
4. Device according to Claim 2 or 3, characterised in that a carrier bolt (14) is mounted on the spring component (13).
5. Device according to any one of Claims 1 to 4, characterised in that the torque of the drive device (11) or of the screwing device (6) is determined by an automatic cut-off coupling which is provided in the drive device (11) and can preferably be regulated.
6. Device according to any one of Claims 1 to 5, characterised in that the screw (5) to be screwed in is monitored by a detecting light scanner (20), preferably a reflective light scanner.
7. Device according to any one of Claims 1 to 6, characterised in that clamping jaws (15) are provided for holding the screws (5) when they are automatically fired in; in that the holding pressure is generated by means of pneumatic or hydraulic cylinder-piston arrangements (16); and in that the clamping jaws (15) open in order for the screws (5) to be pushed through without impairing the centring of the screws.
8. Device according to any one of Claims 1 to 7, characterised in that particles of the parts (1, 2) to be screwed together reaching the area of the device during the screwing process (5) are blown out by means of a blow-out device (17) or are sucked out by means of a suction device.
9. Device according to any one of Claims 1 to 8, characterised in that the screw spindle (10) is also mounted resiliently transversely to the screwing advance direction such that screws (5) which are not aligned with the original axis of the screw spindle (10) can be inserted.
10. Device according to any one of Claims 1 to 9, characterised in that a firing apparatus (4) is provided for firing in the screws (5) to be screwed in by the screwing device (6).
11. Device according to Claim 10, characterised in that the firing device (4) comprises a separating device for separating the screws (5).
12. Process for connecting parts (1, 2) of low strength, in particular for connecting masks, moulds, casting cores, preferably base and water jacket cores, characterised by the following method steps:

    - grasping and bracing of the parts (1, 2) to be connected by means of a gripping device (3);

    - positioning of the parts (1, 2) in the operating area of a screwing device (6); and

    - firing screws (5) into the screwing device (6) and screwing together the parts (1, 2), wherein the advance of the screw, ie, the velocity at which it is screwed in, is compensated by a resilient mounting of the screw spindle (10) without impairing the contact pressure.
13. Process according to Claim 12, characterised in that, when a screw (5) is screwed in, the torque of the screwing device (6) is determined or regulated by an automatic cut-off coupling which can preferably be regulated.

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