EP2465806B1 - Magnetic grabber - Google Patents

Description

The invention relates to a magnetic gripper for gripping and handling of ferromagnetic workpieces according to the preamble of claim 1.

From the EP 2 085 349 A1 Such a generic magnetic gripper is known. This magnetic gripper comprises a housing, on which a housing bottom is provided, which has an end face facing the workpiece to be gripped. In the housing a movable up and down magnetic piston is provided. On the housing, a connection for a drive fluid for moving the magnetic piston is arranged, so that the magnetic piston is acted upon by a first working pressure and transferred to a working position. In this working position, the magnetic piston is positioned at or near the housing bottom. With a further working pressure of the magnetic piston is again converted into a rest position in a movement space in which the magnetic piston is positioned away from the housing bottom.

It is important in the case of such magnetic grippers that it is automatically detected whether a workpiece has been picked up or not picked up or whether it has been lost during transport. The monitoring takes place via a separately inserted in the magnetic piston detection device, which has a controllable valve with a separate permanent magnet, which is guided in the magnetic piston movable up and down, wherein the holding magnet is anchored in the magnetic piston. This integration of the detection device in the magnetic piston has proven itself in principle, but this detection device requires a large number of individual components. In addition, it is disadvantageous that, with magnetic grippers of small diameter, such a detection device can no longer be integrated into the magnetic piston for reasons of space.

The invention is therefore the object of developing a magnetic gripper of the type mentioned in such a way that a simplification in construction and a saving in the individual components is made possible.

This object is achieved by the features of claim 1. The inventive combination of the holding magnet and the detection device in the magnetic piston simplifies the structure. For this purpose, the holding magnet in the magnetic piston is arranged movable up and down in the magnetic piston and thus simultaneously acts as a detection magnet which opens and closes a valve arrangement of the detection device. It can thereby be achieved that when magnetizing a workpiece and thus gripping a workpiece by the magnetic gripper, the holding magnet is in an active working position and a working pressure of a working fluid of the detection device is maintained. The holding magnet simultaneously closes the valve arrangement in this working position the detection device and acts as a detection magnet for controlling the detection device. As a result, the detection device detects that a component is present on the magnetic gripper. If a component is not gripped by the magnetic gripper, the holding magnet remains in an inactive working position, whereby the valve assembly of the detection device remains open, so that the working pressure drops and the detection device detects that a workpiece is missing or not engaged.

The magnetic piston which can be moved up and down in the magnetic gripper preferably has a recess which is open to the housing bottom and in which the holding magnet is guided movable up and down. As a result, the holding magnet is guided secured in the magnetic piston and can independently perform a lifting movement of the magnetic piston to control the valve assembly of the detection device in response to the presence of a workpiece.

Preferably, the holding magnet is received in a sliding guide in the magnetic piston, so that the holding magnet can be easily transferred into at least one working position. This sliding guide is preferably designed as a pot-shaped reciprocating piston, which is guided in the recess movable up and down. Alternatively, a sliding guide between the holding magnet and the recess of the magnetic piston can be formed.

For the arrangement of the holding magnet in an inactive working position or in an initial position to the magnetic piston is preferably an elastically resilient element, in particular spring element, is provided, through which the holding magnet is pressed into the interior of the recess. As a result, the holding magnet in the magnetic piston assumes a basic position or non-active working position without the action of a vacuum or a magnetic force, in which the valve arrangement is slightly open.

A further preferred embodiment of the invention provides that acts on a front wall portion of the recess, a closure element, by which the elastically resilient element between the holding magnet or the sliding guide and a contact surface of the recess is positioned. As a result, a simple assembly and arrangement of an elastically yielding element is made possible. Likewise, the elastic element in a fatigue can be easily replaced.

The restoring force of the elastically yielding element is preferably greater than the weight of the holding magnet and a valve closing member of the valve assembly or the holding magnet of the sliding guide and valve closure member of the valve assembly and smaller than a magnetic force in the presence of a workpiece. As a result, the starting position or inactive working position of the holding magnet can be adjusted to the magnetic piston in a simple manner, at the same time a transfer is ensured in a working position of the holding magnet. The magnetizing force of the holding magnet, which preferably extends in the surface at least over half of the diameter of the magnetic piston, is substantially greater than the restoring force of the at least one elastically yielding element. As an elastically yielding element spring elements, in particular spring washers, disc springs or other printing elements, can be used.

A further preferred embodiment of the invention provides that in the bottom of the recess of the magnetic piston, a through hole is provided as a valve opening which opens and closes a preferably acting on the holding magnet valve closure member in response to the lifting movement of the holding magnet. In particular, a valve seat of the valve opening is conically formed with preferably a sealing element, in which engages a complementarily designed valve closure member, so that when a lifting movement of the holding magnet from an inactive working position to an active working position, the valve closure member is transferred to a closed position and the preferably conical surface of the valve closure member with the valve opening adjoin one another. As a result, the required closing force for sealing the valve opening can be applied simultaneously via the holding magnet.

Furthermore, in an inactive working position of the holding magnet in the recess of the magnetic piston, the valve closing member is preferably arranged in an open position. Preferably, the valve closure member is attached via an adjustable in height to the holding magnet adjustment mechanism, in particular via a screw thread, so that a corresponding adjustment of the closing movement of the valve closing member can be adapted to the maximum stroke of the holding magnet in the recess in a simple manner.

The detection device preferably has a passage which extends from the valve opening in the bottom of the recess of the magnetic piston in at least one channel portion between the holding magnet or the sliding guide and the bottom of the recess radially outwardly to a loading bore which passes through an outer wall of the recess , As a result, in the absence of a component, a built-up vacuum in the magnetic gripper can be broken down, which is generated to generate a lifting movement of the magnetic piston from a rest position into a working position. If the workpiece is not present on the end face 18 of the magnetic gripper 11 or is located at its immediate vicinity, the holding magnet is not transferred from its rest position to a working position, that is, the valve assembly of the detection device is not closed. Due to this passage, which remains open in the absence of a component, the vacuum can be reduced via an environment-related through-hole in the magnetic gripper, and a control of the detection device recognizes that a component is not present.

A further preferred embodiment of the invention provides that formed between the at least one channel portion and the at least one relief bore an annular channel in the bottom of the recess is. Thus, a small number of channel sections is sufficient to guide the air flowing in via the valve arrangement via the annular channel to the relief bore or to a plurality of relief bores. As a result, a lower production cost is required. In addition, the assembly is simplified because a certain installation direction is taken into account.

Furthermore, the at least one channel section is preferably formed by a groove-shaped recess in the bottom of the recess or in an outer side of the sliding guide or the holding magnet. The arrangement of such a channel section in the holding magnet is provided when a sliding guide is not given, which preferably has a cup-shaped housing and the holding magnet with the exception of the housing bottom facing end face surrounds.

According to a further preferred embodiment of the invention for transferring the magnetic piston in a working position, a negative pressure or vacuum applied as a working pressure, so that the detection device when grasping and handling the workpiece maintains the applied working pressure. As a result, a simple detection due to the conditions prevailing there for detecting and monitoring the magnetic gripper can be made possible. Due to the maintenance of the monitoring principle of the known from the prior art magnetic gripper and a simple conversion of existing magnetic gripper with the advanced holding and detection system is made possible.

Furthermore preferably provided that for transferring the magnetic piston in a working position, a negative pressure or vacuum is applied as the working pressure and the working pressure degrades in the absence, release or storage of the workpiece. This is due in particular to the fact that the retaining magnet is returned to its inactive working position by the resilient element and at the same time the valve arrangement is opened. As a result, ambient air can pass through a through hole leading into the movement space of the magnetic piston flow and pass through the passage to the detection device.

Furthermore, the detection device preferably has a sensor which detects at least one working pressure for transferring the magnetic piston into a working position. This embodiment of the sensor makes it possible that, in the case of a plurality of magnetic grippers provided for handling a workpiece, each individual magnetic gripper can be monitored by a sensor assigned to it, wherein the sensors are preferably arranged in a valve strip remote from the magnetic gripper.

Figur 1

eine schematische Seitenansicht eines Magnetgreifers,

Figur 2

einen schematischen Vollschnitt des Magnetgreifers entlang der Linie I-I in Figur 1 mit einem Magnetkolben in einer Ruhestellung,

Figur 3

einen schematischen Vollschnitt des Magnetgreifers entlang der Linie I-I in Figur 1 mit einem Magnetkolben in einer Arbeitsstellung,

Figur 4a

eine schematische vergrößerte Detailansicht eines Magnetkolbens des Magnetgreifers mit einer darin integrierten Detektionsvorrichtung in einer inaktiven Arbeitsposition,

Figur 4b

eine schematisch vergrößerte Detailansicht des Magnetkolbens des Magnetgreifers mit einer darin integrierten Detektionsvorrichtung in einer aktiven Arbeitsposition,

Figur 5

eine schematische Seitenansicht eines Magnetkolbens und

Figur 6

eine schematische Ansicht von oben auf den Magnetkolben gemäß Figur 5.

The invention and further advantageous embodiments and developments thereof are described in more detail below with reference to the examples shown in the drawings and explained. The features to be taken from the description and the drawings can be applied individually according to the invention individually or in combination in any combination. Show it:

FIG. 1

a schematic side view of a magnetic gripper,

FIG. 2

a schematic full section of the magnetic gripper along the line II in FIG. 1 with a magnetic piston in a rest position,

FIG. 3

a schematic full section of the magnetic gripper along the line II in FIG. 1 with a magnetic piston in a working position,

FIG. 4a

1 is a schematic enlarged detail view of a magnetic piston of the magnetic gripper with a detection device integrated therein in an inactive working position;

FIG. 4b

1 is a schematic enlarged detail view of the magnetic piston of the magnetic gripper with a detection device integrated therein in an active working position;

FIG. 5

a schematic side view of a magnetic piston and

FIG. 6

a schematic view from above of the magnetic piston according to FIG. 5 ,

FIG. 1 shows a schematic side view of a magnetic gripper 11 having a pin 12 in a fastening device 14, for example, to attach this to a robot arm or a handling device. Opposite, a housing bottom 17 is provided on a preferably cup-shaped housing 16, which is bolted to the housing 16, for example. This housing bottom 17 has an end face 18 against which a workpiece 19 to be gripped, which is partially shown, for example, as a ferromagnetic plate, rests.

In FIG. 2 is a sectional view taken along the line II in FIG FIG. 1 of the magnetic gripper 11 shown. In the housing 16, a magnetic piston 21 is guided in a movement space 24 movable up and down. The magnetic piston 21 according to FIG. 2 is provided in a rest position 37, that is, that it is held in an upper position.

The magnetic piston 21 comprises a guide ring 22, to which a seal 23 is assigned, which separates a present above the magnetic piston 21 movement space 24 and a present between the magnetic piston and the housing bottom 17 piston chamber 26. The size of the two spaces 24, 26 determined in inverse proportion to the position of the magnetic piston 21 in the housing 16, ie the rest position 37 according to FIG. 2 and a working position 36 in FIG. 3 , The movement space 24 is via a through hole 27 with the environment in connection. For example, 27 may be provided to protect against contamination of the movement space in the through hole 27. The piston chamber 26 communicates with a connection 31, in particular a pneumatic connection, to which a pressure line 32 is connected. This pressure line 32 leads to a valve bar with a plurality of control valves 30 via the valve bar 33, the individual pressure lines 32 are controlled by control valves 30, each pressure line 32 is preferably associated with a sensor 35 which monitors the working pressure in the pressure line 32. The signals detected by the sensor 35 are forwarded to an evaluation unit for evaluation and also for controlling the magnetic grippers.

For positioning the magnetic piston 21 from the rest position 37 in FIG. 2 in a working position 36 according to FIG. 3 a working pressure, in particular a negative pressure or a vacuum, is applied in the piston chamber 26 via the connection 31. The magnetic piston 21 is sealed by a seal 23 to the housing, so that the piston chamber 26, which is preferably in communication with the pressure line 32, forms a quasi-closed space. Although the valve arrangement 59 of the detection device 41, which is coupled to the holding magnet 34, remains open, this cross-sectionally small opening gap does not affect the lifting movement of the magnetic piston.

By the applied working pressure of the magnetic piston 21 is transferred to a lower position. By magnetizing the workpiece 19, a holding force acts between the holding magnet 34 and the ferromagnetic workpiece 19. Characterized the holding magnet 34 is transferred from an inactive working position 43 in an active working position, whereby the valve assembly 59 is closed. The workpiece 19 is held exclusively by this magnetic holding force and positioned to the housing bottom 17. In this position of the magnetic piston 21 is located in the movement space another working pressure, in particular ambient pressure to. To deposit the workpiece 19, the negative pressure or the vacuum is reduced or introduced pressure pulses in the piston chamber 26, whereby the holding magnet 34 in an inactive working position 43 is pushed back and the valve assembly 59 is opened and the magnetic piston 21 is pressed in a raised position relative to the housing bottom 17, ie in the rest position 37 in accordance FIG. 2 , The movement of the magnetic piston 21 thus takes place in the piston chamber, that is, no large volume flows, compressed air and vacuum must be provided.

To actuate the detection device 41 is the holding magnet 34 of the magnetic piston 21, which simultaneously holds the workpiece 19 by magnetization. The operation and interaction of the holding magnet 34 and the detection device 41 will be described with reference to FIGS FIGS. 4a and 4b discussed, in which the magnetic piston 21 is shown enlarged. In the magnetic piston 21, a recess 45 is provided, which is designed to be open towards the housing bottom 17. In this recess 45, the holding magnet 34 is arranged movable up and down, that is, the holding magnet 34 within the recess 45 can perform a stroke from an inactive working position 43 to an active position 42. The inactive working position 43 is in FIG. 4a shown. The active working position 42 is in FIG. 4b shown.

The holding magnet 34 is preferably received in a sliding guide 47, which is for example cup-shaped as a reciprocating piston. Alternatively, the holding magnet 34 may also be arranged directly in the recess 45. This sliding guide 47 abuts with a peripheral wall 48 on an outer wall 49 of the recess 45 and is thereby guided in the axial direction of movement. For the arrangement of the holding magnet 34 in an inactive working position 43, a resilient element 51 is provided, which engages between an attachable to the outer wall 49 closure member 52 and the sliding guide 47 or its peripheral wall 48 or the holding magnet 34. The closure element 52 is preferably designed detachably as an annular screw element. The resilient element 51 may be formed as a compression spring or a plate spring. Likewise, resilient rubber elements can be used. The slide 47 has in the recess 45 an annular collar 54 which at least partially engages in an annular channel 56 which limits the recess 45. Due to the height of the annular collar 54, a defined inactive working position 43 of the holding magnet 34 in the recess 45 can be determined.

The detection device 41 comprises the valve arrangement 59 with a valve closing member 61 which comprises a holding section 63 which passes through a valve opening 65 in order to engage in a bore 74 arranged in the longitudinal central axis of the sliding guide 47 and the holding magnet 34. Preferably, the holding portion 63 is formed as a screw thread, so that the valve closing member 61 adjustable at a distance to the holding magnet 34 and the closed position of the valve assembly 59 is adapted to the maximum stroke of the holding magnet 34 from an active working position 42 to an inactive working position 43. The valve closure member 61 preferably has a conical head which engages a conical valve seat. In this valve seat, a seal 69 is advantageously provided.

Between the movement space 24 and the chamber space 26, a passage 71 is formed, which is then released, if the detection device 41 is inactive, that is, the holding magnet 34 is disposed in an inactive working position and the valve closure member 61 is lifted relative to the valve opening 65. This passage 71 comprises the valve opening 65 and at least one adjoining channel section 73 which extends radially outwards and merges into at least one relief bore 74 which opens into an annular space 76 which communicates with the pneumatic port 31 and to the piston chamber 26 borders.

In FIG. 5 is a schematic view from the outside on the magnetic piston 21 with its outer wall 49 with at least one relief hole 74 shown.

FIG. 6 shows a schematic view from above of the magnetic piston 21, in the dashed lines is exemplified in the channel section 73, which leads to the relief hole 74. This channel portion 73 may be incorporated as a groove or groove in the bottom of the recess 45 and constitute a connection between the valve opening 65 and the relief hole 74. The annular collar 54 on the sliding guide 47 is interrupted at individual points, so that passages are formed to the annular channel 56, which in turn communicates with at least one relief hole 74.

For the arrangement of the holding magnet 34 in the inactive working position 43, a restoring force of the resilient element 51 is formed such that it is greater than the weight of the holding magnet 34, the slide 47 and the valve closure member 61 or, if a sliding guide 47 is not provided, larger as the weight of the holding magnet 34 and the valve closing member 61 is.

• Der Magnetgreifer 11 wird zum zu handhabenden Werkstück 19 positioniert. Gleichzeitig wird ein Unterdruck oder ein Vakuum in dem Kolbenraum 26 angelegt, so dass der Magnetkolben 21 aus einer Ruhestellung 37 in eine Arbeitsstellung 36 übergeführt wird. Sofern ein Werkstück 19 zum Aufmagnetisieren vorliegt, wird der Haltemagnet 34 aufgrund der wirkenden Magnetkraft aus der inaktiven Arbeitsposition 43 im Magnetkolben 21 in eine aktive Arbeitsposition 42 übergeführt. Gleichzeitig wird dabei die Ventilanordnung 59 geschlossen, so dass der Durchgang 71 für einen Druckausgleich verschlossen ist und das Vakuum oder der Unterdruck somit aufrechterhalten wird. Dadurch wird der Steuerung signalisiert, dass das Werkstück 19 ergriffen und vorhanden ist.

The detection and monitoring of a held by the magnetic gripper 11 workpiece 19 by the detection device 41 is carried out as follows:

• The magnetic gripper 11 is positioned to be handled workpiece 19. At the same time, a negative pressure or a vacuum is applied in the piston chamber 26, so that the magnetic piston 21 is transferred from a rest position 37 into a working position 36. If a workpiece 19 is present for magnetization, the holding magnet 34 is transferred due to the magnetic force from the inactive working position 43 in the magnetic piston 21 in an active working position 42. At the same time, the valve assembly 59 is closed, so that the passage 71 is closed for pressure equalization and the vacuum or the negative pressure is thus maintained. As a result, the control is signaled that the workpiece 19 is gripped and present.

If the workpiece 19 is not engaged, the holding magnet is not transferred from its inactive working position 43 in an active working position 42 and the valve assembly 59 is not closed. In the event that the workpiece 19 is lost after gripping, moves the holding magnet 34 from an active working position 42 due to the restoring force of the resilient member 51 by a return stroke in an inactive position 43 back. In both cases, the passage 71 is open, so that from the movement space 24, a subsequent flow of air and thus a pressure equalization can take place. Due to the pressure difference that occurs, the controller recognizes that the workpiece 19 is no longer present or has not been grasped.

As a result of the lifting movement of the holding magnet 34 in the magnetic piston 21 and the immediate actuation of the valve arrangement 59 of the detection device 41, a further constructive simplification of such a magnetic gripper 21 for detecting and holding ferromagnetic workpieces on magnetic grippers 11 is made possible.

Claims (15)

1. Magnetic grab for grabbing and handling ferromagnetic workpieces (19), comprising a housing (16) on which there is provided a housing bottom (17) having an end face (18) facing the workpiece (19) to be grabbed, and comprising at least one magnetic piston (21) disposed in the housing (16) and at least one connection (31, 27), assigned to the at least one magnetic piston (21), for a drive fluid for moving the magnetic piston (21), so that the magnetic piston (21) is subjected to a first working pressure and is transferred into an operating setting (36), in which the magnetic piston (21) is positioned on or close to the housing bottom (17), and is transferred with a further working pressure into a rest setting (37), in which the magnetic piston (21) is positioned remote from the housing bottom (17), and comprising in the housing (16) a detection device (41), which detects the holding or the non-presence of the workpiece (19) on the end face (18) of the housing (16) and determines a working pressure of a working fluid of the detection device (41) in dependence on an active or inactive operating position (42, 43), characterized in that the magnetic piston (21) has a holding magnet (34) for holding the workpiece (19), which holding magnet faces towards the housing bottom (17) and is movable up and down therein and is simultaneously provided to control a valve arrangement (59) of the detection device (41).
2. Magnetic grab according to Claim 1, characterized in that the magnetic piston (21) has a recess (45), which is configured open towards the housing bottom (17) and in which the holding magnet (34) is guided such that it is movable up and down.
3. Magnetic grab according to Claim 1, characterized in that the holding magnet (34) is accommodated in a sliding guide (47), which is preferably configured as a cup-shaped lifting piston and which guides the holding magnet (34) in the recess (45).
4. Magnetic grab according to one of the preceding claims, characterized in that the holding magnet (34) is held with an elastically resilient element (51) in a starting position or an inactive operating position (43), in which the holding magnet (34) is pressed inside the recess (45).
5. Magnetic grab according to Claim 4, characterized in that the holding magnet (34), in an inactive operating position (43), is arranged set back in relation to an end side of the magnetic piston (21).
6. Magnetic grab according to Claim 4, characterized in that an outer wall (49) of the recess (45) is acted upon, preferably releasably, on the end side by a locking element (52), by which the elastically resilient element (51) is held between the holding magnet (34) or the sliding guide (47) and a contact surface of the locking element (52).
7. Magnetic grab according to Claims 4 to 6, characterized in that a restoring force of the elastically resilient element (51) is greater than the weight force of the sliding guide (47), of the holding magnet (34) and of a valve-closing member (61) of the valve arrangement (59), or of the holding magnet (34) and of the valve-closing member (61), and is less than the magnetic force when a workpiece (19) is present.
8. Magnetic grab according to one of the preceding claims, characterized in that the valve arrangement (59) has a valve opening, which is disposed in the floor of the recess (45) of the magnetic piston (21) and has a valve seat, and a valve-closing member (61), which traverses the valve opening (65) and, with a holding portion (63) arranged preferably thereon, that acts at least upon the holding magnet (34).
9. Magnetic grab according to Claim 8, characterized in that, in an inactive operating position of the holding magnet (34) in the recess of the magnetic piston (21), the valve-closing member (69) is disposed in an opening position.
10. Magnetic grab according to one of the preceding claims, characterized in that the detection device (41) comprises a passage (71), which extends from the valve opening (65), via at least one duct portion (73) between the holding magnet (34) or the sliding guide (47) and the floor of the recess (45), radially outwards up to the at least one relief bore (74), which traverses an outer wall (49) of the recess (45) of the magnetic piston (21).
11. Magnetic grab according to Claim 10, characterized in that, between the at least one duct portion (73) and the at least one relief bore (74), an annular duct (56) is configured on the floor of the recess (45) of the magnetic piston (21).
12. Magnetic grab according to Claim 10 or 11, characterized in that at least one duct portion (73) is provided by a trough-shaped or groove-shaped cavity in the floor of the recess (45), or by an outer side of the sliding guide (47), which outer side faces towards the floor of the recess (45), or by an outer side of the holding magnet (34), which outer side faces towards the floor of the recess (45).
13. Magnetic grab according to Claim 1, characterized in that, for the transfer of the magnetic piston (21) into an operating setting (36), an underpressure or vacuum is applied as a working pressure, and the detection device (41), with a closed valve arrangement (59), maintains the applied working pressure during grabbing and handling of the workpiece (19).
14. Magnetic grab according to Claim 1, characterized in that, for the transfer of the magnetic piston (21) into an operating setting (36), an underpressure or vacuum is applied as a working pressure, and the working pressure decreases via an open valve arrangement (59) while the workpiece (19) is not present, is being released or deposited.
15. Magnetic grab according to Claim 1, characterized in that the at least one working pressure for transferring the magnetic piston (21) out of an inactive operating position (43) into an active operating position (42) is detectable by at least one sensor (35).

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