DE29714022U1 - Pneumatic cylinder - Google Patents

Description

PATENT AND LAWYERS MEINKE, DABRINGHAUS AND PARTNEER GbR

ADMISSIONED AT THE EUROPEAN PATENT AND TRADEMARK OFFICE EUROPEAN PATENT AND TRADEMARK ATTORNEYS*

PATENT ATTORNEYS'

JULIUS MEINKE, dipl.-ing. WALTER DABRINGHAUS. dipl.-ing. JOCHEN MEINKE, dipl.-ing.

LAWYER

THOMAS MEINKE

WESTENHELLWEG 44137 DORTMUND

TELEPHONE (0231) 14 50 FAX (0231) 14 76

PO BOX 10 46 45

14 022.1 ⁴⁴⁰⁴⁶ Dortmund, 2 5 . Feb. 1998

DRESDNER BANK AG DTMD. Account no. 1 148 047 (bank code 440 800 SO) POSTBANK DORTMUND. Account no. 542 02-463 (bank code 440 100 46)

FILE NO. 1/1338 9 JM/B

Registrant: Thomas Bikowski, Hördemannshof 24, 44359 Dortmund

"Pneumatic cylinder"

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'Pneumatic cylinder'

The invention relates to a pneumatic cylinder with a housing and a piston with a piston rod that can be moved pneumatically between two end positions, wherein at least one proximity switch designed as a reed switch is arranged on the outside of the housing for detecting an end position of the piston.

Such pneumatic cylinders, which are often small in size and have a pressure range of 1.2 to 10 bar, for example, are well known. They are used in a variety of ways, particularly in automation technology, to handle simple, position-accurate lifting or positioning tasks.

To control these cylinders, it is necessary to measure the respective end position of the cylinder piston, for which so-called proximity switches are used, which are designed as reed switches. Such a reed switch is closed when a magnetic field on the piston (e.g. permanent magnet on the piston) is approached and thereby emits an electrical signal. If the piston with its magnetic field is in the end position, the reed switch triggers an electrical control signal accordingly. In order to obtain a process-safe switching signal,

Especially with smaller cylinder pistons, which have a weaker magnetic field, the reed switch must be optimally adjusted, i.e. the reed switch must be located centrally above the magnetic field.

The reed switch must be attached to the outside of the pneumatic cylinder's housing in the most precise position possible, but this is very time-consuming and complicated. At present, the cylinder is first moved to an end position. To query this end position, a reed switch provided for this purpose must be manually moved back and forth on the housing surface in order to locate the switching limits, i.e. to detect the edges of the magnetic field. The middle of the two switching limits thus determined is then assumed to be the switching center and the reed switch is positioned accordingly. This procedure is very complicated and inaccurate.

EP 0 044 287 A1 discloses a pneumatic cylinder with complex mechanically actuated display means, i.e. not a generic pneumatic cylinder with a reed switch as a proximity switch. DE 44 10 363 A1 discloses a pneumatic cylinder with capacitive sensors as display elements, but this pneumatic cylinder also does not contain any reed switches. The sensors of this cylinder can hit the cylinder head's mounts.

The object of the invention is to provide a simple and precise way of activating a proximity switch designed as a reed switch in such pneumatic cylinders, in particular of small design.
to be able to position.

This object is achieved according to the invention in a pneumatic cylinder of the type described at the outset in that a stop is provided on the housing for fixing the reed switch.

With the invention it is surprisingly easy
possible to fix the reed switch precisely to the housing of the pneumatic cylinder without complicated and
The stop may already be mounted at the factory, as in
In almost all applications, the reed switch is intended to detect the respective end position of the cylinder piston. The end positions are determined independently of the stroke length from the fixed stops of the cylinder cover. This means that the distance
from the switching center to the cylinder cover is the same for all cylinders of the same type, regardless of the cylinder stroke. It is therefore possible to provide the corresponding stop at the factory. Of course, it is also possible to equip existing pneumatic cylinders with a stop
to retrofit.

According to a first advantageous embodiment, it is provided that the stop is detachably attached to the housing. This solution is particularly intended if retrofitting of existing pneumatic cylinders is to be carried out.

The stop is particularly preferably designed as a locking element. By simply moving the reed switch along the housing, the reed switch then automatically locks into its exact fixing position.

Alternatively, the stop can be designed as a mounting hole. The reed switch can then simply be screwed into place on the cylinder using a screw.

In principle, it is also advantageous for the stop to be designed as an integral part of the housing.

To simplify handling, it can be advantageous to provide an additional optical display on the housing, which is designed like a marking. This can make setting even easier.

The invention is described below with reference to the drawing.

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example, explained in more detail. This shows in:

Fig. 1 shows a longitudinal section of a pneumatic cylinder according to the state of the art,

Fig. 2 shows a longitudinal section through a pneumatic cylinder according to the invention with stop,

Fig. 3 shows a longitudinal section through a pneumatic cylinder according to the invention in another embodiment and

Fig. 4 shows a side view of another embodiment of a pneumatic cylinder according to the invention.

A pneumatic cylinder is designated with 1 throughout the figures. This pneumatic cylinder has a housing 2 in which a piston 3 with piston rod 4 is arranged so that it can be moved in the longitudinal direction. The piston is suitably mounted and sealed in the housing 2, this is not important in detail, seals are designated with 5. Pressure medium inlets and outlets 6 and 7 are provided to actuate the piston 3 in one direction or the other within the housing 2.

To detect the end positions of the piston, proximity switches are used, which are designed as so-called reed switches.

Such a reed switch is marked 8. This reed switch is closed when it approaches a magnetic field; this magnetic field, marked 9, is part of the piston 3.

The pneumatic cylinder 1 must therefore be equipped with such a reed switch 8, whereby according to the illustration in Figure 1, the reed switch 8 is positioned on the outside of the housing 2 after the piston 3 has been moved to an end position. In order to query this end position, the reed switch 8 is moved on the outside of the housing in order to detect the switching limits, i.e. the edges of the magnetic field 9. The center thus devised between the two switching limits or edges of the magnetic field 9 is then assumed to be the switching center and the reed switch 8 is attached to the housing 2 accordingly. Obviously, this setting is complex and inaccurate.

The inventive design according to Figures 2 to 4 is based on the knowledge that the end positions of the cylinder piston 3 result from the fixed stops of the cylinder cover, regardless of the stroke length, i.e. the distance S from the switching center M of the magnetic field 9 to the cylinder cover is the same for all cylinders of the same type, regardless of the cylinder stroke. Taking this knowledge into account, the invention now provides that a

A correspondingly positioned stop 10 is provided for fixing the reed switch 8. This stop 10 can be designed in different ways.

In the embodiment according to Figure 2, the stop 10 is designed as a mounting bracket that is suitably attached to the housing 2. This stop 10 has indicated mounting holes 11 so that the reed switch 8 can be positioned precisely by screwing in the appropriate mounting screws.

In the embodiment according to Figure 3, two stops are provided, namely a fixed stop 10' and a hook-shaped stop 10'' with a locking element 12. In this embodiment, the reed switch 8 arranged on the left in Figure 3 must be brought into contact with the fixed stop 10' and then fastened; in the embodiment shown in the right half of Figure 3 with locking element 12, the reed switch 8 can simply be moved into the area of the stop 10'' and then automatically locks into the correct position.

Figure 4 shows a further or additional embodiment, which shows the possibility of supplementing the stop with an optical marking 13.

Of course, the invention is not limited to the embodiments shown. Other embodiments are possible without departing from the basic idea. For example, the stop can also be designed as an integral part of the housing 2 and the like.

Claims (6)

Expectations; 1. Pneumatic cylinder with a housing and a piston between two end positions of a pneumatically movable piston with a piston rod, wherein at least one proximity switch designed as a reed switch is arranged on the outside of the housing for detecting an end position of the piston, characterized in that a stop (10) for fixing the reed switch (8) is provided on the housing. 2. Pneumatic cylinder according to claim 1, characterized in that the stop (10) is detachably attached to the housing (2). 3. Pneumatic cylinder according to claim 2, characterized in that the stop (10) is designed as a locking element. 4. Pneumatic cylinder according to claim 2, characterized in that the stop (10) is designed as a fastening bore. 5. Pneumatic cylinder according to claim 1, characterized in that the stop (10) is designed as an integral part of the housing (2). 6. Pneumatic cylinder according to claim 1 or one of the following, characterized in that an optical display (13) is additionally provided on the housing (2).