DE29713002U1 - Suction gripping device - Google Patents

Description

• V« ·

PRINCE &PARTNERS:" · ^: " ·

PATENTA2STWÄLTE Manzingerweg 7

EUROPEAN PATENT ATTORNEYS D-81241 Munich

EUROPEAN TRADEMARK ATTORNEYS Tel. +49 89 89 69 80

22. Juü 1997

Reinhold Neider
Nordstr. 6

86316 Friedberg

Our reference: N 1064 DE
AI/Ge

Suction gripper

The invention relates to a suction gripping device with a vacuum line, a valve arranged in the vacuum line, which has a valve body which closes the vacuum line in its basic position and releases the vacuum line in its working position, and at least one suction cup with which the device grips a workpiece to be moved and whose interior space delimited by it is in flow connection with the vacuum line.

Moving workpieces using suction grippers simplifies many positioning tasks. Suction grippers are connected to a vacuum pump, which provides the vacuum required to grip the workpieces. Leaks in the suction cups can lead to the vacuum collapsing and the held workpiece being released, which can cause damage. For this reason, vacuum pumps have sometimes been significantly oversized.

To ensure that when several suction cups are attached to a workpiece, a leakage at one suction cup does not lead to a breakdown of the vacuum at all

-2-

Today, all suction cups are usually connected to their own vacuum valve, whereby the vacuum valve is designed to ensure that if the suction cups leak, the vacuum line leading to them is shut off, which guarantees a high level of operational reliability. Suction gripping devices should therefore be designed in such a way that they offer a high level of safety while at the same time having minimal pumping power.

A generic suction gripping device that offers a relatively high level of security against functional failure has a so-called tactile valve. A plunger is arranged inside the suction cup, which opens a valve immediately adjacent to the suction cup when it is placed on the workpiece surface. However, there are limits to the functional reliability of this well-known tactile valve, because if the suction cup is placed on the edge of the workpiece and the plunger is still on the workpiece surface and the valve opens, air flows into the interior via the part of the suction cup that is not on the workpiece surface. As a result, no usable negative pressure can build up in the vacuum system, and operational malfunctions are inevitable.

To avoid this disadvantage, pressure difference controlled valves have been developed in which, for example, a spring presses a sealing body against a valve seat and closes the vacuum line. The vacuum line is always closed when the pump is switched off. A differential pressure is created on the suction side via an adjustable bypass line, which is amplified by a membrane, releases the sealing body from the seat and thereby releases the vacuum line. The membrane serves as a power amplifier, like the brake booster in a vehicle. When closed, however, air is always sucked in via the bypass line, so that a leakage loss occurs which is necessary for the function but reduces the efficiency. Especially when using many such suction gripping devices, e.g. on a suction beam, the throughput of the vacuum pump must be increased considerably due to these numerous individual leakage losses. The cross-sections of the bypass line, which are often kept extremely small to reduce the leakage losses, have the disadvantage that dust particles sucked in from the outside

These holes can easily become clogged, leading to failure of the suction gripper.

The object of the invention is therefore to create a suction gripping device which no longer has any leakage and is characterized by a high level of functional reliability and robustness.

This is achieved in a suction gripping device of the type mentioned at the beginning in that when the suction cup is placed on the workpiece surface, an air volume in the interior enclosed by at least the suction cup and the workpiece surface is displaced in the direction of the valve and moves the valve body into the working position. The invention uses the air volume enclosed when the suction cup is placed on the workpiece surface to switch the valve. The suction gripping device is aligned so that this enclosed air volume acts on the valve body and moves it. When the suction cup is placed on a workpiece edge, the disadvantage of switching the valve, which occurs with tactile valves, no longer occurs, because the air volume is not enclosed in this case and is simply released into the environment via the non-contacting part of the suction cup when the suction cup is placed. This means that there is no internal pressure in the interior and no displacement of the air in the direction of the valve body. The invention is based on the idea that the tightness with which the suction cup is in contact with the surface is checked in advance by generating an overpressure in the interior when the suction cup is in contact with the surface when it is placed on it, so that conversely a vacuum without leakage is also possible.

The suction gripping device according to the invention does not require any differential pressure in the basic position of the valve body, so that functional leakage losses do not occur.

According to the preferred embodiment, the valve body is subjected to force in the direction of its basic position by an elastic spring element and is pressed against its valve seat.

-A-

There are various ways of allowing the enclosed air volume to act on the valve body and switch it. For example, at least part of the air volume or the entire air volume can be pressed against the valve body via an end section of the vacuum line that extends from the interior to the valve body in order to cause it to move into the working position. Furthermore, a pressure chamber can also be provided in the valve alone or in addition to switch the valve body, with at least part of the air volume being pressed into the pressure chamber. The pressure chamber has a movable wall section, for example a membrane, which is in a force-transmitting relationship with the valve body so that when a predetermined chamber pressure is reached, the valve body is moved into the working position. Preferably, however, the enclosed air can exert a force on the valve body both via the end section of the vacuum line and via the pressure chamber in order to move it.

According to the preferred embodiment, the pressure chamber is in flow connection with the interior via a connecting line, whereby a backflow of the air entering the pressure chamber is prevented by a further valve that only allows air flow in one direction. An example of such a further valve is a membrane flap located at the mouth of the connecting line into the pressure chamber.

An opening is provided so that the air flowing into the pressure chamber can also exit again, which also serves to ensure that at least ambient pressure prevails in the pressure chamber. However, so that when the air flows in, it does not immediately flow out again through this opening without causing the valve to switch, the cross-section of the opening is chosen to be smaller than that of the connecting line, so that when the air flows into the pressure chamber, excess pressure is built up. A device can also be provided that opens or closes the opening, whereby the opening should be open when the valve associated with the vacuum line is open, so that pressure equalization between the environment and the pressure chamber can take place more or less quickly.

-5-

In the preferred embodiment, the device is coupled to the movable wall section, for example by providing a tappet attached to the membrane. This embodiment is particularly easy to manufacture.

According to a further design, which is characterized by simple production, the valve body has a closure section that seals against the valve seat and is arranged in an overflow chamber. On the one hand, a section of the vacuum line on the vacuum pump side opens into the overflow chamber, and on the other hand, the end section of the vacuum line that leads to the interior extends from it. The closure section can open and close both openings of the sections of the vacuum line simultaneously, with air flowing towards the vacuum pump via the overflow chamber in the open valve position. In this design, during the switching process, i.e. when the suction gripping device is placed on the workpiece, the displaced air volume presses directly on the closure section.

Furthermore, the invention provides that the valve body consists of two disc-shaped sections and an axial, displaceable axis accommodated in a bearing, which connects the sections, one of which forms the closure section, to one another.

To ensure that the volume of air displaced is as large as possible, an elastic bellows is preferably arranged between the suction cup and the valve. This increases the interior space and, together with the suction cup and the workpiece surface, limits the volume of air. When the suction cup is placed on the valve, the bellows is compressed in the same way as the suction cup, so that the air is forced towards the valve.
30

In particular, if the suction gripping device not only has to lift the workpiece but also move it, positioning problems can arise due to the elastic suction cup 3 and the elastic bellows. To avoid this, the valve is provided with a housing from which a projection protrudes into the bellows. An opening between the bellows and suction cup is aligned in radial and axial extension with the projection so that when the bellows are compressed (when

When the suction cup is placed on the protrusion penetrates the opening and fixes the suction cup in position at the side. This positioning can also serve to create a second interior space, which is assigned to the bellows, in the event that the protrusion seals the opening.

To facilitate the penetration of the projection into the opening, the projection tapers towards its free end.

If the suction cup has a split, circumferential sealing lip with a part extending radially inwards, the pressure in the interior can press on the surface facing the interior, resulting in a self-reinforcing sealing effect.

Further features and advantages of the invention will become apparent from the following description and from the following drawing, to which reference is made.

Fig. 1 shows a longitudinal sectional view through an embodiment of the suction gripping device according to the invention.

Fig. 1 shows a suction gripping device which has a valve 1 and a suction cup 3. The suction cup 3 is integrally connected to a bellows 5 and is spaced from the valve 1 via the bellows 5. The suction cup 3 and the bellows 5 are made of elastic material. An intermediate wall 7 with an opening 9 at the lower end of the bellows separates the bellows and the suction cup from one another.

The valve 1 comprises a valve block 11, into which a central vacuum line 13 is incorporated, which is aligned with the opening 9 and is connected to a vacuum pump in the direction of the arrow. An overflow chamber 15 is arranged in the valve block 11 and is closed off from the outside by a cover 17. The overflow chamber 15 splits the vacuum line 13 into a vacuum pump-side section 19 and an end section 21, with both sections opening into the overflow chamber 15. The vacuum pump-side section 19 connects the vacuum pump to the overflow chamber 15, and the

End section 21 connects the overflow chamber 15 with an interior space 23 in the bellows. The interior space 23 will be discussed in more detail later.

A compression spring 25 is also provided in the overflow chamber 15, which is supported on the one hand on the cover 17 and on the other hand on a disk-like closure section 27 of a valve body 29. The valve body 29 consists of the closure section 27, a section 33 and an axis 31, which is mounted axially displaceably in the valve block 11 and connects the closure section 27 to the opposite, also disk-shaped section 33. The section 33 rests against a displaceable wall section in the form of a membrane 35. The membrane 35 delimits a pressure chamber 37 provided in the valve block 11, opposite the overflow chamber 15. Both chambers are not connected to one another in terms of flow. The pressure chamber 37 is closed off from the outside by another cover 39. The pressure chamber 37 is in flow connection with the interior 23 via a connecting line 41, whereby a valve in the form of a membrane flap 43 acting in one flow direction is provided at the mouth of the connecting line 41 into the pressure chamber 37, which only allows air to flow into the pressure chamber, but not out of it via the connecting line 41. An opening 45 in the cover 39 is aligned with the axis 31. A device for closing the opening 45 in the form of a tappet 47 attached to the membrane 35 releases the opening 45 when the membrane is moved to the right.

Fig. 1 shows the closed state of the valve, i.e. the valve body 29 is in its basic position in which its closure section 27 is pressed against the valve seat by the spring 25. In this position, the closure section 27 closes both the opening of the end section 21 and the vacuum pump-side section 19 to the overflow chamber 15. This simultaneous closing of both sections of the vacuum line 13 can be achieved by the sections ending at the same height when viewed transversely to the axis 31.

On the underside of the valve block 11, which also delimits the interior 23, there is a projection 49 that projects into the interior 23 and tapers conically towards its free end, which is aligned with the opening 9. In its radial and axial extension, it is adapted to the position of the opening 9 and its geometry in such a way that when the bellows is compressed, it penetrates into the opening 9 and fixes the suction cup 3 in position in the radial direction, since the outer wall of the opening 9 rests against the projection 49.

For a better sealing effect, the suction cup 3 has a circumferentially split, circumferential sealing lip 51 with a radially inwardly extending part 53, on whose surface facing the interior 23, as will be explained later, the pressure of the air enclosed when the suction cup is placed on the workpiece acts.

The function of the suction gripping device is explained below. In the closed position of the valve shown, no leakage occurs because the closure section 27 closes off the overflow chamber 15 to the vacuum line 13. When the suction cup 3 is placed on a workpiece surface 55, the suction cup 3 seals the interior 23, which is delimited by the workpiece surface 55, the suction cup 3, the opening 9, the bellows 5 and the underside of the valve block 11, and the air volume contained therein via the sealing lip 51. As the suction gripping device is moved further downwards, the pressure in the interior 23 increases and thus also in the end section 21 and the connecting line 41. The increase in pressure causes part 53 of the sealing lip 51 to press more firmly against the workpiece surface 55 and thus an increased sealing effect. Air flows into the pressure chamber 37 via the opening membrane flap 43 and acts on the membrane 35 and thus also on the valve body 29 via the section 33. An opening force acting to the right is thus exerted on the valve body 29. Likewise, a force is exerted on the closure section 27 via the increasing pressure in the end section 21, which is also directed to the right.

When a switching force defined by the preload force of the spring 25 is exceeded, the valve body 29 is moved to the right, so that the closure section 27 lifts off the valve seat. This immediately creates a negative pressure in the overflow chamber 15 and air is sucked in from the interior 23 via the negative pressure line 13. When the valve is then open, the valve body 29 is in its working position. Although the force exerted to the right on the valve body 29 via the end section 21 is removed when the overflow chamber 15 opens, the pressure in the pressure chamber 37 is high enough to hold the valve body 29 in its working position.

When the valve body 29 is moved into the working position, the tappet 47 is also moved to the right so that it opens the opening 45, which has a smaller cross-section than the connecting line 41. This allows a pressure equalization to slowly occur between the pressure chamber 37 and the environment. The pressure difference between the pressure chamber 37 (at ambient pressure) and the open overflow chamber 15 is also sufficient to hold the valve body 29 in the working position.

When the bellows 5 is compressed, the projection 49 penetrates into the opening 9 and thereby positions the suction cup 3, whereby a laterally precise positioning of the suction cup 3 and the workpiece can be achieved when the workpiece is accelerated laterally in order to deposit it at another location.

The workpiece is simply ejected by blowing compressed air into the vacuum line 13, which also triggers the closing process of the valve.
30

The switching state of the valve can be determined very easily by querying the position of the valve body 29, in particular the closure section 27.

If the pressure in the interior 23 increases due to leaks, e.g. due to wear of the sealing lip 51, the spring 25 pushes the valve body 29 back into the basic position and thus closes the valve leak-free.

If the suction cup 3 does not rest completely on a workpiece surface 55, but on a workpiece edge, the valve does not switch, since the air in the interior then seeks the path with the least resistance out of the interior 23 when the bellows 5 and the suction cup 3 are compressed and leaves the interior 23 via the suction cup 3.

The following are particularly important for the functional reliability of the suction gripper device:
10

a) the dimensioning of the membrane surface 35. The larger this surface, the greater the force acting on it.

b) The design of the spring 25, because it determines the necessary switching force.

c) The volume of the interior, whereby the greatest possible volume difference between the compressed bellows 5 and suction cup 3 and the non-compressed bellows and suction cup is favorable for a strong pressure increase.

The bellows 5 is preferably designed such that it has no internal volume when compressed.

Claims (21)

PRINZ & PARTNER PATENTANWÄLTE Manzingerweg 7 european PATENT attorneys D-81241 Munich EUROPEAN TRADEMARK ATTORNEYS Tel. +49 89 89 69 80 Reinhold Neider Nordstr. 6 86316 Friedberg Our reference: N 1064 DE KI/Ge 22 July 1997 Protection claims 1. Suction gripping device, with a vacuum line (13), a valve (1) arranged in the vacuum line (13), which has a valve body (29) which closes the vacuum line (13) in its basic position and releases the vacuum line in its working position, and at least one suction cup (3) with which the device grips a workpiece to be moved and whose interior space (23) delimited by it is in flow connection with the vacuum line (13), characterized in that when the suction cup (3) is placed on the workpiece surface (55), an air volume in the interior space (23) enclosed by at least the suction cup (3) and the workpiece surface (55) is forced in the direction of the valve (1) and moves the valve body (29) into the working position. 2. Suction gripping device according to claim 1, characterized in that the valve body (29) is subjected to force by an elastic spring element (25) in the direction of its basic position and is pressed against its valve seat. 3. Suction gripping device according to claim 1 or 2, characterized in that via an end section (21) of the vacuum line (13), which extends from the interior (23) to the valve body (29), • * at least part of the enclosed air is pressed against the valve body (29) to cause it to move into the working position. 4. Suction gripping device according to one of the preceding claims, characterized by a pressure chamber (37) in the valve (1) into which at least a part of the air volume is pressed, the pressure chamber (37) having a displaceable wall section which is in a force-transmitting relationship with the valve body (29) so that when a certain chamber pressure is reached, the valve body (29) is moved into the working position. 5. Suction gripping device according to claim 4, characterized in that the wall section is a membrane (35) to which the valve body (29) adjacent. 6. Suction gripping device according to claim 4 or 5, characterized in that the pressure chamber (37) is assigned a connecting line (41) to the interior (23), via which air is introduced into the pressure chamber (37), wherein a further valve is provided which prevents a backflow of air from the pressure chamber (37) in the direction of the suction cup (3). 7. Suction gripping device according to claim 6, characterized in that the further valve is a membrane flap (43) located at the mouth of the connecting line (41) into the pressure chamber (37). 8. Suction gripping device according to one of claims 4 to 7, characterized by an opening (45) in the pressure chamber (37), via which the pressure chamber (37) is connected to the environment, so that at least ambient pressure prevails in the pressure chamber (37). 9. Suction gripping device according to claim 8, characterized in that the cross-sectional area of the opening (45) is smaller than that of the connecting line (41), so that when air flows into the pressure chamber (37) from the interior (23) an overpressure prevails in the pressure chamber (37). 10. Suction gripping device according to claim 8 or 9, characterized in that the opening (45) can be opened and closed by a device, the device opening (45) when the valve associated with the vacuum line (13) is open. 11. Suction gripping device according to claims 4 and 10, characterized in that the device is coupled to the displaceable wall section. 12. Suction gripping device according to one of the preceding claims, characterized in that the valve body (29) has a closure section (27) which rests sealingly on the valve seat and which is arranged in an overflow chamber (15) into which the vacuum pump-side section (19) of the vacuum line (13) opens and from which the end section (21) leading to the interior space (23) extends. 13. Suction gripping device according to claim 12, characterized in that the vacuum pump-side section (19) and the end section (21) are separated from one another by the closure section (27) in the basic position of the valve body (29). 14. Suction gripping device according to one of the preceding claims, characterized in that the valve body (29) has two disc-shaped Sections (27, 33), one of which forms the closure section (27), and an axial, displaceable axis (31) received in a bearing, which connects the disc-shaped sections (27, 33) to one another.
30 15. Suction gripping device according to claims 5 and 14, characterized in that the section (33) of the valve body (29) opposite the closure section (27) rests against the membrane (35). 16. Suction gripping device according to one of the preceding claims, characterized in that an elastic bellows (5) is arranged between the suction cup (3) and the valve (1), which enlarges the interior space (23) and limits the enclosed air volume, whereby the air Compression of the bellows (5) during placement of the suction cup (3) is displaced. 17. Suction gripping device according to claim 16, characterized in that the bellows (5) and the suction cup (3) are connected to one another in one piece. 18. Suction gripping device according to one of the preceding claims, characterized in that the valve (1) has a valve block (11), from which a projection (49) projects into the bellows (5) and an opening (9) between the bellows (5) and the suction cup (3) is coordinated with the projection (49) in radial and axial extent so that when the bellows (5) is compressed, the projection (49) penetrates into the opening (9) and fixes the suction cup (3) laterally in position. 19. Suction gripping device according to claim 18, characterized in that the projection (49) tapers towards its free end. 20. Suction gripping device according to one of claims 16 to 18, characterized in that the bellows has essentially no internal volume in the compressed state. 21. Suction gripping device according to one of the preceding claims, characterized in that the suction cup (3) has a split, circumferential sealing lip (51) with a radially inwardly extending, circumferential part (53), on whose surface facing the interior (23) the pressure in the interior (23) acts.