Pressure-medium actuated linear unit

A pressure medium linear unit for handling devices for industrial manufacture includes a housing block, at least one operating cylinder for at least one piston, at least one piston rod, at least one guide rod, and guide elements for at least one piston rod and at least one guide rod. The housing block accommodates the at least one operating cylinder for the at least one piston and the guide elements for the at least one piston rod and the at least one guide rod. The housing block is a modular unit and includes a guide unit and a drive unit releasably connected with the guide unit, one behind the other, to form a compact unit in the direction of linear movement. The guide rod and the piston rod are arranged in an axially parallel manner. The end of the guide rod at the end of the drive can be moved within the drive unit. If the guide rod is moved into the drive unit, the drive unit extends at least over the moved-in length of the guide rod. The guide unit includes the guide elements for the piston rod and the guide rod.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention is based on a pressure-medium actuated linear unit. 
2. Background Information 
In the case of a familiar linear unit (EP-B1 017 779), the drive unit is 
located in a housing block which is equipped with end flanges at both end 
faces, in which the guide elements for the piston rod and the guide rod 
are accommodated. This design necessitates that the guide rod and the 
piston rod must be guided out of the housing block on both sides. This 
arrangement makes it impossible for the linear unit to be designed as a 
compact unit. 
In the case of another familiar linear unit (EP-A1 309 613), the guide 
elements for the piston rods and the guide rods, as well as the pressure 
medium drive, are integrated in a uniform housing block. For the various 
areas of application, linear units with differing stroke lengths are 
required. For the purpose of realising the various stroke lengths, apart 
from the guide rods and pistons rods, the length of the housing block must 
also be varied. Thus for the various stroke lengths, requiring high 
production depth, only small batch production is possible. 
SUMMARY OF THE INVENTION 
In contrast, the linear unit in accordance with this invention, with the 
characterising features of the main claim, has the advantage that a 
compact modular construction is possible. A further advantage is the fact 
that all significant function elements which require a high production 
depth are integrated into the guide unit, by which means the manufacturing 
batch size can be increased. 
Through the measures listed in the dependent claims, further advantageous 
developments of the linear unit described in the main claim are possible. 
It is particularly advantageous to employ a constant length for all stroke 
lengths of the guide unit. A further advantage is in the manufacture of 
the guide unit and the drive unit from one extruded profile, with the 
extruded sections respectively containing the passages for the piston rod 
and the guide rod. It is furthermore expedient if the extruded part of the 
drive unit contains a further hole as a pressure medium path. A design 
which is advantageous for a compact construction consists of the fact that 
two guide rods are provided, which are connected with one another in the 
region of the drive unit by means of a connecting element. A further 
expedient design form consists in the drive unit being equipped with end 
position switches which are damped by a surface which is connected to the 
guide rod.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The linear unit represented in FIG. 1 consists of a guide unit 10, a drive 
unit 11, a piston rod 12, two guide rods 14, and an operating cylinder 15 
in which a piston 13 is guided which is connected to the piston rod 12. 
The ends of the piston rod 12 and the ends of the two motion guide rods 
14, which project from the guide unit 10, are fixed to a common operating 
yoke 22. The further structural elements of the linear unit, such as for 
example a gripper device, are fitted on the operating yoke 22. 
The housing block of the guide unit 10 and of the drive unit 11 are each 
manufactured from an extruded section 50 or 60 (FIG. 2 and FIG. 3). The 
extruded section 50 (FIG. 3) of the guide unit 10 has various cavities 40 
to 44. Here, cavity 42 serves for the passage of the piston rods 12, and 
the cavities 43 and 44 respectively serve for the passage of the two guide 
rods 14. The drive unit housing 11 likewise has a cavity 45, which is 
arranged in alignment with cavity 42 of the guide unit 10. Profile 60 
(FIG. 2) of the drive unit 11 has laterally open recesses 46, 47 for each 
of the two guide rods 14, whereby the profile 60 assumes an open form. For 
the purpose of achieving a closed housing, the profile 60 is laterally 
equipped with a protective cover plate 61, which is provided with 
snap-type connections which latch into the profile 60. 
The guide unit 10 and the drive unit 11 are arranged end on to each other 
in the direction of the linear movement, and are coupled in a manner to 
allow for separation from each other. For this purpose, further holes are 
provided in the profiles 50 and 60, which serve as clearance and tapped 
holes for the connecting screws. In the current design example, both 
profiles 50 and 60 are connected, for example, by four Allen screws which 
are inserted through the profile 50 of the base body 10 and are screwed 
into the threaded holes of the drive unit 11. 
On the end face of the profile 50, the guide unit 10 is equipped with an 
end plate 20, which contains the corresponding passages for the piston rod 
12 and the two guide rods 14. The end face of the profile 60 of the drive 
unit 11 is closed by an end plate 21. 
In the guide unit 10, a guide bush 16 for the piston rod 12, and two guide 
bushes 17 for each guide rod 14 are fitted. The guide bushes 17 are, for 
example, linear ball races which are inserted at the two end faces of the 
profile 50, into the cavities 43 and 44. The cavity 45 of the drive unit 
11 forms the operating cylinder 15 for the pneumatic drive. The guide bush 
16 is inserted into a further bush 18, which has a collar 24. The bush 18 
is inserted into the end face of the guide unit 10, which is connected to 
the end face of the drive unit 11, in such a way that the collar 24 closes 
off the operating cylinder 15 from the guide unit 10 with an air-tight 
seal. The translationally moved piston rod 12 is additionally equipped, in 
the bush 18, with a seal 25 which encloses the piston rod 12. To form the 
operating cylinder 15, the end plate 21 is mounted on the profile 60 in 
such a way that it seals off the cavity 45 in an air-tight manner. 
In order to drive the piston 13, the operating cylinder 15 is equipped with 
a compressed air connection in the region of each of the two end faces. In 
the current drawing, only the compressed air connection 32 is shown, which 
is set into the end plate 21 and which supplies compressed air to the 
operating cylinder 15 at the right-hand end face. At the side of the 
operating cylinder 15, opposite this compressed air connection 32, a 
further compressed air supply, not shown, is fed into the operating 
cylinder 15. This compressed air connection is led into the operating 
cylinder 15 by means of a hole 33 drilled into the profile 60. The 
pressure medium line 33 is equipped with a transverse hole which extends 
into the operating cylinder 15. The compressed air connection for the 
pressure medium line 33 is made through the end plate 21, in a manner 
similar to the pressure medium connection 32. 
The movement direction of the piston 13 is controlled by a pneumatic valve, 
which is located outside the drive unit 11 and which is not shown in the 
drawing. 
The two guide rods 14 which project into the drive unit 11 are rigidly 
connected to each other within the drive unit 11 by means of a connecting 
element 28. This ensures that the guide rods 14 do not cant in their 
guides. The design of the laterally open profile 60 makes it possible to 
accommodate the connecting element 28 within the drive unit. 
In order to set the stroke of the linear unit, two inductive end position 
switches 36, 37 are provided, which are damped by a surface 38, for 
example a sheet metal strip, which is firmly connected with the guide rods 
14. 
For setting the stroke length, the end position switches 36, 37 are 
located, axially movable, in a groove 48 of the profile 60. The electrical 
connection of the two inductive end position switches 36, 37 is made via 
two connections 23 provided at the end plate 21. 
To limit the stroke length, two adjustable limit stops 29a, b and 30a, b 
are additionally provided, with each limit stop part 29a or 30a being 
allocated a damping medium 29b or 30b respectively. The damping media 29b 
and 30b are inserted in the passages 40 or 41 of the profile 50. 
Due to the guide unit 10 being equipped with all guide elements for the 
piston rod 12 and the two guide rods 14, all the functions which require a 
precise manufactured length are integrated in the guide unit 10. Thus it 
is possible to use, for the various stroke lengths, a guide unit 10 of 
uniform length, requiring length variation only in the case of the drive 
unit 11, the piston rod 12, the two guide rods 14 and the protective cover 
61. Apart from the pneumatic drive described, equipping the linear unit 
with a hydraulic drive is equally conceivable.