DE2211909A1 - Pneumatic holding unit - Google Patents

Description

PATSNTANWÄLTE ^ '

DMNG. HOSER DIPL-ING. STSLLRECHT M, Se.

plPL-pHYS.PR.GKSSSS3ACH DiPL.-PHYS. HAECKER ¥ STUTTGART-l, UHLANDSTR. 14 c

DId

HA Schlatter AG , 'Schlieren

(Switzerland)

Pneumatic holding unit

The present invention relates to a pneumatic holding unit with at least one piston which can be impacted on one side and is displaceable in a cylinder against the action of a return spring. ι

Such units are mainly used in fixture construction where a desired one is required during a certain period of time Holding force is to be generated, e.g. to hold a workpiece on a work table of a processing machine.

Among other things, three requirements are made of such holding units. First, it should be the one connected to the piston rod At the end of the working stroke, the holding jaw hits the workpiece with as little impact as possible and only then does the full holding force apply to develop. Second, the holding force should, if no longer required,

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Tigt, dismantled as quickly as possible, and the holding jaw start the return stroke as quickly as possible. Thirdly, finally, especially when venting, create as little noise as possible.

The first requirement has so far been met by the pressure build-up in the cylinder during the working stroke, e.g. by means of supply via a throttle point or via a Throttle valve was controlled. The second and third requirements, however, have not yet been met at the same time and optimally fulfill. Either the cylinder was suddenly vented in the interest of a quick return stroke, at the expense of one considerable bang, or by slowly venting the cylinder one aimed at a low noise development and thus took the Disadvantage of a slow pressure reduction in purchase.

It is now a purpose of the present invention to create an assembly of the type mentioned, in which all three of the above requirements can be optimally met.

Accordingly, the invention is based on the object laid out to design the unit in such a way that the return force is independent of the pressure conditions in the cylinder, i.e. independent from the current degree of ventilation can take effect immediately as soon as the unit is disconnected from the pressure source and vented will.

To solve this problem, the proposed unit is characterized according to the invention in that the to the acted upon The cylinder connection leading to the side of the piston can be closed by means of a valve that can be closed by the application medium is, in whose valve body a non-return valve opening in the closing direction is installed, whereby the said valve in the open position connects the pressurized with the non-pressurized side of the piston.

. It follows that as soon as the admission fee; -dium omitted, the valve is still present in the cylinder! Pressure equalization between the pressurized and non-pressurized side

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of the piston occurs, allowing the return force to occur immediately effective to ground.

Further advantages of the subject matter of the invention are based on the following description of an exemplary embodiment can be seen in the drawing. It shows:

1 shows a schematic longitudinal section through a holding unit, and

2 shows a section through part of an embodiment variant.

The holding unit 1 shown in FIG. 1 has a cylindrical housing 2, in one end of which 3 a guide opening 5 provided with a seal 4 for an outwardly extending piston rod 6 is formed. Internally of the housing 2, a cylinder 8 is arranged leaving a dumbbell space 7 free. In the present embodiment, has the cylinder 8 a .sog. Tandem design, i.e. it includes two axially aligned cylinder spaces 9, 10, which are from each other are separated by a partition 11.

In the middle of the partition wall 11, a hub-shaped stop stub 12 is formed, which in turn has a further, with a seal 13 provided guide bore 14 for the piston rod 6.

The tandem installation of the cylinder 8 inevitably leads to the same type of piston. In each of the cylinder spaces 9, 10, a piston plate 15, 16 is mounted so as to be displaceable back and forth. As usual, there is a circumferential seifcig on each piston plate 15, 16 Circumferential seal 17 let in, through which, together with the associated piston head, each of the cylinder spaces acted upon in one and an unoccupied section is divided.

The piston plates 15, 16 sit on the common piston rod 6, in which, between the two piston plates 15, 16, '

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an axial bore 18 with a radial direction to the piston rod outward passages 19 is formed. Bore 18 and ^ urchlüüse 19 thus always connect the acted upon sections of the cylinder spaces 9, 10 with one another.

Between the partition 11 and the unaffected A compression spring 20 is arranged on the side of the piston plate 16, which in the unpressurized state holds the piston in the position shown in the figure.

At one end, the cylinder 8 is on any V / eise attached to the end face 3 of the housing 2, while the cylinder 8 at the other end carries a closing flange 21, in the middle a connection opening 22 is formed. The one over the end flange protruding circumferential edge of this connection opening is designed as a valve seat 23 for a valve plate 24, in the Valve seat 23 facing flat side, a sealing ring 23 corresponding to this is inserted. The valve disk carries on the circumference a seal 29 and is, like a piston head, mounted transversely to itself in a valve chamber 27 which is formed in the other end face 26 of the housing 2. A connection opening 28 leads to the valve chamber 7 at v / elcher the unit shown via a schematically drawn compressed air line 31 and an electromagnetic 3/2-way valve 32 a compressed air source 33 is connected.

While the acted upon sections of the two cylinder chambers 9, 10, as mentioned, via the bore 18 and the passages 19 are always in connection in the piston rod 6, the unloaded sections of the two cylinder grooves are also always connected. For this purpose are in the wall of the cylinder space 9 and the cylinder space 10 in the area of the left in the drawing 16 openings 34, 35 are provided, the associated "cylinder space connect directly to the Piantel room Y.

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Finally, the jacket space 7 is over a small one
Opening 36 is always connected to the ambient air.

The function of the unit shown is
the following. If the valve 32 is switched from the position shown, if the compressed air source 33 is thus connected, then the valve disk 24 is first under the effect of the incoming
Compressed air moved to the left into the closed position on seat 23. As a result, the connection 22 is separated from the jacket space 7. That
Check valve 30 opens and, depending on its permeability, compressed air flows to the sections of cylinder chambers 9, 10 which are acted upon. The pressure build-up that takes place moves the piston head 15, 16 to the left - after the spring force of the spring 20 has been overcome - until the piston head 16 comes to strike the free end face of the stop connector 12. If this state is reached, the pressure in the acted upon sections of the cylinder spaces 9, 10 corresponds approximately to the pressure supplied by the compressed air source.

In this state, the pressure source could be switched off by closing the line 31 or the passage 28. The unit would - if one neglects any leakage losses
pass the piston seals 17 - pause with the piston rod 6 extended because the valve 23-24-25 remains closed. The reason for this is that the surface of the side of the valve disk 24 facing the chamber 27 is larger than the surface of the other side of the valve disk circumscribed by the ring seal 25. :

Since both sides of the valve disk, i.e. that of the chamber 27 and the one facing the connection 22, are subjected to the same pressure are, there is a resultant force acting to the left for the valve disk 24.

Even with minor leakage losses on the piston seals 17, i.e. if there is a slight loss of pressure in the cylinder chambers, the check valve 30 opens to equalize the pressure

between both sides of the valve disc.

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If the return stroke is to be initiated, it is sufficient to bring the valve 32 back into the position shown. So that only the chamber 27, which is opposite to the stroke volume the cylinder spaces 9, 10 has a considerably smaller volume, vented. The check valve 30 closes immediately and the Valve disk 24 moves immediately to the right, whereby valve 23-24-25 is opened. But this takes place over the jacket space 7 and the openings 34, 35 immediately equalize pressure in the cylinder chambers 9, 10 on both sides of the piston head 15, IS instead, so that the spring 20 takes effect immediately, even if the total pressure prevailing in the housing 2 is still considerably higher than the atmospheric pressure of the surroundings.

Regardless of the return stroke of the piston 15, 16, the venting process begins when the poppet valve 23, 24 25 opens of the unit through the opening 36. However, since the permeability of this opening is limited, the entire im The amount of air in the unit expands suddenly, which would lead to the well-known annoying bang Rather, the aggregate takes place slowly, which at best is accompanied by an easily bearable hissing sound. Furthermore will anyone skilled in the art will recognize that even if the venting process of the unit is not yet finished, the next working stroke can start. In practice, one becomes the volume of the shell space 7 in relation to the stroke volume of the cylinder 2 on the one hand and in relation to the permeability of the opening 36 in such a way that that - assuming periodic work strokes - the jacket space 7 acts like an air chamber, so to speak, and through the opening 36 ventilation takes place continuously.

The unit shown has another advantage. Since the return stroke of the piston 15, 16 at a higher pressure than the Atmospheric pressure of the environment occurs, also occurs during the return stroke no suction on the unaffected side of the piston head

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15, 16 on. Accordingly, there is also a guarantee that no contaminants can be sucked in from the environment, which is known to be the lifespan of seals, here the seals 4, 17 and 13 would significantly reduce.

It goes without saying that the invention is not limited to the illustrated tandem design. One thinks on the unit shown, the openings 35 closed, the bore 18 closed, the piston plate 15 away and the Partition 11 shifted to the left and coinciding with the end wall 3, one arrives at an aggregate of approximately the same size in terms of the external dimensions, but with approximately twice the stroke at approximately half strength.

In Fig. 2 a variant is shown in which the valve 23, 24, 25 indirectly, i.e. is servo-controlled.

One recognizes in FIG. 2 a part of the housing 2 in which the cylinder 8 is arranged, leaving the jacket space 7 free is. The end flange 21 of the cylinder 8 is designed as in the embodiment of FIG. 1. The valve disc 24 on the other hand, it is not only mounted so as to be displaceable back and forth in the valve chamber 27, but is also subject to the action a compression spring 40 which tends to move the valve disk 24 to the right in FIG. 2, i.e. in the open position. Besides that a piston extension 41 is formed on the valve plate 24, which in turn is slidably mounted in a piston chamber 42 and through which a passage 43 leading to the check valve 30 leads. On the front side, the piston attachment 41 carries a seal 44, which is intended to interact with the passage 4 &, which is designed as a valve seat 45, into the piston chamber 42.

The passage 46 opens into the inlet 47 to the unit, which is connected directly to the compressed air network.

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A further passage leads from this inlet 47 into the valve chamber 49 of a solenoid valve 50. From this valve chamber 49 leads to a further, always open passage 51 the side of the valve disk 24 facing away from the cylinder 8, i.e. into the valve chamber 27, as well as on that under the action of a Compression spring 53 standing plunger 52 of solenoid valve 50 over - to a passage 54 which opens into the maritime room 7. The front end of the plunger 52 is provided with seals 55, which are intended to open the openings of the passages 48 and 54 into the valve chamber 49 depending on the position of the plunger to close.

The mode of operation of this variant is as follows:

Assume that inlet 47 is connected directly to a source of compressed air and the solenoid valve is not energized.

Accordingly, the plunger 52 is in the extended position and closes the mouth of the with the seal 55 Passage 48 into the valve chamber 49. The passages 51 and 54 are in communication with one another and thus also those of the cylinder remote side of the valve disk 24 on the one hand with that of the cylinder 8 facing side of the valve disk 24. On both sides of the valve disk 24 there is thus the same pressure, which is the compression spring 40 causes the valve disk 24, on the one hand, to lift off the valve seat 23 and, on the other hand, to move the molded piston 41 until the passage 46 is closed by the seal 44. It should be noted at this point that the compression spring 40 is dimensioned in this way is that their force is based on the force of the pressure in the inlet 47 the surface circumscribed by the seal 44 of the piston attachment 41 overcomes. But if the inlet 46 to the piston chamber 42 is blocked, • Also, no compressed air gets into the passage 43 and thus into the cylinder 8. The unit remains in the withdrawn position Position*

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If the solenoid valve 50 is now energized, the plunger becomes 52 is drawn in and thus the passage 48 is opened, while the passage 54 is closed off. Compressed air now flows over the Passage 48, the valve chamber 49 and the passage 51 into the valve chamber 27 of the valve disk 24, in which chamber a Pressure builds up, the effect of which on the much larger free area of the valve disk 24 (compared to that circumscribed by the seal 44 Surface on the piston shoulder 41) is able to overcome the force of the compression spring 40. The valve disk 24 is thus after shifted to the left, i.e. pressed with the seal 25 onto the valve seat 23. At the same time, however, the piston shoulder 41 also lifts from the valve seat from, and the passage 43 thus flows unhindered compressed air from the inlet 47. This becomes the one-way flow control valve 30 is opened, and the pressure build-up which moves the piston, not shown here, takes place in the cylinder 8, as described with reference to FIG. 1. This continues as long as the solenoid valve 50 is energized, i.e. as long as the passage 48 via the chamber 49 with the Passage 51 is connected.

However, as soon as the solenoid valve 50 is de-energized, the passage 48 is closed and the passage 54 is opened. This results in a pressure equalization between the cylinder 8 facing Side of the valve disk 24 and its opposite side. Thus the compression spring 40 comes into play again, which the valve disk 24 lifts off the seat 23 and on the other hand closes off the inlet 46 again. However, this also takes place, as described with reference to FIG. 1, Immediate pressure equalization between the two sides of the working piston via the shell space 7, which immediately leads to the return stroke is initiated.

In contrast to the embodiment according to FIG in this embodiment for initiating the return stroke of the working piston not even the already relatively small one Chamber volume of the valve chamber 27 vented directly into the environment, but also the return stroke of the valve disk 24 is created by creating

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a pressure equalization brought about on both sides. In addition, only a very small control valve is required in the embodiment according to FIG. 2. While in the embodiment according to FIG. 1, the valve 32 has a permeability. ^{7 has} iron, which must be large enough to satisfy the swallowing capacity of the unit in a reasonable time, the solenoid valve 50 only needs to have a nominal width of its passages of a few mm. Accordingly, the solenoid valve 50 can be selected to be so small that it can be integrated as a whole into the end wall 26 of the housing.

By means of a further measure, the low noise level of both embodiments and especially that of FIG. 2 can be increased even further can be increased.

Instead of the vent opening 36, which is called the "air chamber" acting jacket space 7 connects with the outside air, the cylindrical wall of the housing 2 can be wholly or partially a material that is permeable to air to a limited extent, e.g. a felt supported by a framework, made of a fiberglass structure or from a single or multi-layer wire mesh with a very narrow mesh size. This means that all are at the moment of pressure equalization between the two sides of the piston 15, I ^ and des Valve actuator 24 in the shell space 7 occurring pressure surges not directly into the ambient air, but only gradually according to the permeability of the opening 36 or limited permeable housing wall, as described above, drained.

The holding unit described thus ideally fulfills the three requirements mentioned at the beginning at the same time.

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Claims (10)

Claims ί 1) Pneumatic holding unit with at least one unilaterally acted upon and against the effect of a return force piston displaceable in a cylinder, characterized in that the piston (15, 16) leading cylinder connection (22) by means of a through the application medium closable valve (23,24,25) is closable, in the valve body (24) of the same in the closing direction opening non-return valve (30) is installed, said valve in the open position the pressurized with the non-pressurized Side of the piston (15,16) connects. 2. Holding unit according to claim 1, characterized by that the pressurized and the non-pressurized side of the piston (15, 16) via a compensating line that can be released by the valve (23, 24> 25) (7), the interior of which is connected to the outside air via a throttle point (36). 3. Holding unit according to claim 2, characterized in that the compensating line than around the outer wall of the cylinder ' (8) arranged shell space (7) is formed. 4. Holding unit according to claim 1, characterized in that the valve (23,24,25) is a poppet valve and that the Volume of the valve chamber (27) of this poppet valve is a fraction corresponds to the stroke volume of the cylinder (8). 5. Holding unit according to claim 1, characterized in that the check valve (30) is adjustable in the flow direction Throttle valve is formed. 6. Holding unit according to claim 3, characterized in that the cylinder (8) is arranged in one of these, leaving the Msρ 1 ".P ¹ Ir ^ ¹¹¹ Hf ³ S f?) UuI ^0- Gbend.en. Oeiisiise (2) free in its 209843 ^ 0623
6AD ORIGINAL Jt the other end face a guide opening; (5) for the piston rod (6) of the piston is formed. 7. Holding unit according to claims 3 and 4, characterized ' characterized in that on the valve disk (24} of the disk valve (23, 24, 25} a slidably mounted in a slide chamber (42}) Valve piston (41} is integrally formed, which valve piston (41) to it serves, the inlet (43) to the non-return valve (30) from the supply (47) to separate the loading medium, the valve piston (41) is biased in the closing direction. 8. Holding unit according to claim 7, characterized in that that a control valve (50) is provided, which in its one position the side of the valve disk facing away from the cylinder (8) (24) with the feed (47) of the loading medium and in its other position connects the side of the valve plate (24) facing away from the cylinder (8) with the dumbbell space (7). 9. Holding unit according to claims 6 and 8, characterized in that the control valve (50) in one end face (26) of the housing (2) is installed. 10. Holding unit according to dependent claim 2, characterized in that at least 'a part of the outer wall of the Kantelraums (7) is made of a material that is partially permeable to air. 209843/0623 BATH ORIGINAL Blank page