WO2009007053A1

WO2009007053A1 - Gri pping device having two sucker heads and a mechanical gripper

Info

Publication number: WO2009007053A1
Application number: PCT/EP2008/005421
Authority: WO
Inventors: Marko Schreiber; Andreas Wolf
Original assignee: Mars Incorporated
Priority date: 2007-07-09
Filing date: 2008-07-03
Publication date: 2009-01-15
Also published as: DE102007031847B3

Abstract

A gripping device (1) for an industrial robot for picking up and putting down soft objects (27), especially pieces of food, such as meat, fruit or small fish, with two spaced apart sucker heads (12), between which is disposed a mechanical gripper, having two gripping arms (8) which are pivotably mounted about one or two spaced apart, parallel swivel axes (10), and with a bearing surface (26) disposed between the sucker heads (12) and between the gripping arms (8).

Description

GRIPPING DEVICE HAVING TWO SUCKER HEADS AND A MECHANICAL GRIPPER

The invention relates to a gripping device for an industrial robot for picking up and putting down soft objects, especially delicate pieces of food, such as meat or vegetables or parts intended as a decoration for food products, such as shrimps or small fish.

In the case of handling procedures carried out by robots involving phases of picking up, moving and placing in position or putting down, the aim is to have clock times that are as short as possible, as a result of which in the movement phase, rapid acceleration and accordingly high inertia forces act on the objects picked up, but also on the gripping device itself, and the processes of picking up and releasing have to be performed in very short times. Known gripping technologies therefore cannot readily be used for the purpose mentioned.

The problem of the invention is to create a gripping device with which soft objects, especially delicate pieces of food, can be picked up, moved and put down by an industrial robot at high speed, without the objects themselves or their outward appearance being damaged or impaired.

This problem is solved in accordance with the invention by a gripping device for an industrial robot for picking up and putting down soft objects, especially delicate pieces of food, such as meat, fruit or small fish, with two spaced apart sucker heads, between which is disposed a pair of mechanical grippers, the two gripping arms of which are pivotably mounted about one or two spaced apart, parallel swivel axes, and with a bearing surface disposed between the sucker heads and between the gripping arms, preferably provided with a surface structure.

It may be provided that the sucker heads are formed as drilled holes opening into the bearing surface.

Alternatively, it may be provided that the sucker heads are held resiliently in indentations in the bearing surface. In this context, it is possible that the sucker heads may be formed completely or partially as bellows. The sucker heads may be resiliency mounted perpendicularly to one extension plane of the bearing surface.

In an unloaded state, the sucker heads may project above the bearing surface and may be capable of being depressed in the direction of the bearing surface in operation as a result of a suction force and/or the pressing force of an object to be picked up.

The sucker heads may have longitudinal axes located in a central longitudinal plane of the gripping device.

The swivel axis (axes) may be disposed parallel to a central longitudinal plane of the gripping device.

It may preferably be provided that the gripping arms are loaded pneumatically in a first direction, such as by compressed air, and by the resilient force of a spring in a second direction.

It is convenient for the first direction to be a release direction and the second direction a gripping direction.

The gripping arms may have gripper arm ends adapted to the shape of an object to be gripped.

In addition, it may be provided that the sucker heads can be connected via separate lines to a vacuum source and optionally to a source of overpressure.

A switching means is conveniently provided, which makes it possible to load the sucker heads optionally with a partial vacuum or with overpressure.

The gripping arms may be mounted on a gripper body, which is mounted, together with the sucker heads, on an integral base body. In addition, a carrier may be formed on the base body in order to attach it to a robot arm, such as in the form of a clamping cone or a cylindrical clamping sleeve. Pneumatic connections may be disposed on the base body for the sucker heads.

Further advantages and features of the invention will become clear from the following description of a preferred embodiment, reference being made to a drawing in which

Figures Ia and Ib show two side views of a gripping device in accordance with the invention, partially in section, before a gripping process,

Figures 2a and 2b show the gripping device according to Figures Ia and Ib in corresponding views in a first gripping phase,

Figures 3a and 3b show the gripping device in a second gripping phase, and

Figure 4 shows a connection diagram for the sucker heads.

The gripping device 1 shown in the drawing consists of an integral base body 2, which may be made of plastic or metal, for example, and which is shown in Figures Ib, 2b and 3b partially in a section view. Attached to the base body or formed integrally with it is a carrier 4, wherein the carrier 4 may be formed as a cylindrical sleeve or clamping sleeve as shown, or as a conical clamping sleeve, for attaching the gripping device to a robot arm (not shown) in order to carry out handling processes with a phase of picking up, moving and putting down with accurate positioning in each case.

Mounted on the base body 2 is a gripper body 6, with two gripping arms 8 coming out of it which are pivotably mounted on the gripper body 6, on parallel swivel axes 10. The swivel axes run spaced apart and parallel to a central longitudinal plane 11 of the gripping device.

The base body 2 has a mounting portion 2a and a bearing portion 2b running substantially transverse thereto, in which two sucker heads 12 are disposed, spaced apart from one another, on both sides of the gripping arms 8. Each sucker head 12 is disposed in a cylindrical indentation 14 of the bearing portion 2b and consists of a tubular portion 16 and a bellows-shaped portion 18 adjacent to it. The tubular portion 16 is inserted in a hole 19 in the base body 2 or is firmly joined to it, whereas the bellows-shaped portion 18 is elastic, soft and movable and is guided in the longitudinal direction along the longitudinal axis 20 of the indentation 14 and through the hole 19. In this way, a free suction edge 22 of the bellows-shaped portion 18 can be moved as far as an extension plane 24 of a bearing surface 26 of the bearing portion 2b, as is shown in Figures 2 and 3, for example.

The flexibility of the bellows-shaped portions 18 and thus their force/distance behaviour ("spring rate") is selected such that, when a rated partial vacuum of, for example, 0.3, 0.5 or 0.8 bar is applied and when the opening surface is closed in the region of the free suction edge 22 the bellows-shaped portion 18 is pressed together solely on the basis of the force of the external air pressure, preferably at least up to the level of the extension plane 24, so that an object picked up which only weighs a small amount is drawn into the region of the bearing surface 26 solely by the effect of the partial vacuum.

The bearing surface 26 is flat in the example shown, but it could equally well be curved or domed. It is provided with a structured surface, in this case with ribbing, which can be arranged in one or more directions at an angle to one another, in order to create a non-positive contact as soon as it comes into contact with an object to be picked up.

Adjoining the holes 19, connections 30 are provided for connecting to flexible lines 32, in order to connect a vacuum source (not shown) to the sucker heads. The sucker heads 12 are connected separately, i.e. with relatively long lines, proceeding from the connections 30, which are then only connected to a common vacuum line in the region of the robot arm. The advantage of this separate connection is that any defect in a sucker head, such as clogging or a lack of coverage because an object has been grasped incorrectly, does not have a direct effect on the other sucker head. Any foreign body penetrating a suction body and partially or completely closing it would first have to move as far as the region of a common junction point between the two suction lines and a vacuum line before it could have a disturbing influence on the other sucker head.

Fig. 4 shows a different embodiment of a separate connection means for the two sucker heads 12. One line 32 in each case joins a connection 30 to a reverse valve 34, the slide 36 of which makes it possible to apply compressed air, negative pressure or a vacuum, as desired, to the line 32.

The lines 32 are not exclusively lines for applying negative pressure, but also for applying overpressure, so that it is possible not only to pick up an object, but also to put it down more quickly by means of a pressure pulse. In this case too, the mobility of the sucker heads thanks to the bellows-shaped portions has a positive effect, because when pressure is applied, the bellows- shaped portions tend to move away from the bearing surface 26 and to move out of the indentations 14, as a result of which the release of the object from the bearing surface 16 is additionally supported.

The gripping arms 8 are biased by a compression spring 38 in the closed or retaining position illustrated in Figure 3a and are moved into the open position illustrated in Figures Ia and 2a by overpressure in an arrangement not illustrated in detail, which is located within the gripper body 6, said overpressure being delivered to connections 42 via corresponding lines 40 (supply and bleed lines). An on-off valve 44 makes it possible to connect the line 40 to a source of compressed air. By means of a corresponding setting or by adjusting the spring rate of the compression spring 38, it is possible to achieve an appropriate retaining force in the closed state without the objects picked up being excessively deformed or damaged.

At their free ends, the gripping arms 8 are designed to be adapted in shape with regard to the objects to be picked up, so that damage to the objects or excessive pressing by the gripping arms can be avoided as far as possible.

Since, as has been mentioned, both a partial vacuum and preferably also overpressure are used for a complete gripping cycle, it is convenient for the partial vacuum required to be generated dynamically from a source of compressed air. This can be done, for example, in that a source of compressed air with about 5 to 8 bar is provided. In order to deliver a pressure pulse to the sucker heads, the compressed air, optionally mediated by a pressure reducer, is fed to the connections 30. In order to generate a partial vacuum, e.g. 0.3, 0.5 or 0.8 bar, the compressed air is, for example, guided through a Venturi tube, and the partial vacuum required is generated in this way. In the embodiment according to Fig. 4, the two reverse valves 34 may be connected to a common compressed air line via initially one pressure line each and to a common negative pressure via initially one vacuum line each, or alternatively, in order to ensure a completely independent supply of negative pressure for each sucker head and for each reverse valve, a separate negative pressure generator, such as a Venturi tube or the like, can be provided.

When picking up an object, it is convenient first to grasp the object solely with the sucker heads 12, with the gripping arms 8 open (Figures 2a, b), and, as described, to move the object towards the bearing surface 26 either by a partial vacuum alone or additionally with a continued movement of the gripping device as a whole, whereupon the gripping arms 8 are then closed (Figures 3a, b), in order to provide additional lateral support in the case of rapid movements.

List of reference numerals

Gripping device

Base body a Mounting portion b Bearing portion

Carrier

Gripper body

Gripping arm 0 Swivel axis 2 Sucker head 4 Indentation 6 Tubular portion 8 Bellows-shaped portion 9 Hole 0 Longitudinal axis (of 14) 2 Suction edge 4 Extension plane 6 Bearing surface 7 Object 8 Central longitudinal plane 0 Connection 2 Line 4 Reverse valve 6 Slide 8 Compression spring 0 Line 2 Connection 4 On-off valve

Claims

1. A gripping device (1) for an industrial robot for picking up and putting down soft objects (27), especially pieces of food, such as meat, fruit or small fish, with two spaced apart sucker heads (12), between which is disposed a pair of mechanical grippers, the two gripping arms (8) of which are pivotably mounted about one or two spaced apart, parallel swivel axes (10), and with a bearing surface (26) disposed between the sucker heads (12) and between the gripping arms (8).

2. The gripping device as claimed in claim 1, characterised in that the sucker heads (12) are formed as holes (19) opening into the bearing surface (26).

3. The gripping device as claimed in either of claims 1 or 2, characterised in that the sucker heads (12) are held resiliently in indentations (19) in the bearing surface (26).

4. The gripping device as claimed in any of the preceding claims, characterised in that the sucker heads (12) are formed in a bellows shape.

5. The gripping device as claimed in any of the preceding claims, characterised in that the sucker heads (12) are held perpendicularly to an extension plane (24) of the bearing surface.

6. The gripping device as claimed in any of the preceding claims, characterised in that, in an unloaded state, the sucker heads (12) project above the bearing surface (26) and are capable of being depressed in the direction the bearing surface (26) in operation as a result of a suction force and/or the pressing force of an object to be picked up (27).

7. The gripping device as claimed in any of the preceding claims, characterised in that the sucker heads have longitudinal axes (20) located in a central longitudinal plane (28) of the gripping device.

8. The gripping device as claimed in any of the preceding claims, characterised in that the swivel axis (axes) (10) is (are) disposed parallel to a central longitudinal plane (28) of the gripping device (1).

9. The gripping device as claimed in any of the preceding claims, characterised in that the gripping arms (8) are loaded pneumatically in a first direction, and by the resilient force of a spring (38) in a second direction.

10. The gripping device as claimed in claim 8, characterised in that the first direction is a release direction and the second direction is a gripping direction.

11. The gripping device as claimed in any of the preceding claims, characterised in that the gripping arms (8) have gripper arm ends adapted to the shape of an object to be gripped (27).

12. The gripping device as claimed in any of the preceding claims, characterised in that the sucker heads (12) can be connected via separate lines (32) to a vacuum source.

13. The gripping device as claimed in any of the preceding claims, characterised in that a switching means (34) is provided, which makes it possible to load the sucker heads (12) optionally with a partial vacuum or with overpressure.

14. The gripping device as claimed in any of the preceding claims, characterised in that the gripping arms (8) are mounted on a gripper body (6), which is mounted, together with the sucker heads (12), on an integral base body (2).

15. The gripping device as claimed in any of the preceding claims, characterised in that a carrier (4) is formed on the base body (2) in order to attach it to a robot arm.

16. The gripping device as claimed in any of the preceding claims, characterised in that pneumatic connections (30) are disposed on the base body (2) for the sucker heads (12).