DE102006008900A1 - Pneumatic actuator for an active hood of a motor vehicle comprises a lock with non-contact zones formed on the periphery of the lock to form a contact with the wall of holes - Google Patents

Abstract

Pneumatic actuator comprises a lock (31) with non-contact zones (42) formed on the periphery of the lock to form a contact with the wall of holes. Preferred Features: A front section of the lock facing the operating gas which drives the lock is free from non-contact zones. The lock has a multi-corned cross section and the holes have a round cross-section.

Description

The The present invention relates to a pneumatic actuator for an active Hood of a motor vehicle.

Under An active hood is understood to mean a bonnet in the event of an accident is automatically raised by one or more actuators to the distance between the hood and underlying, hardly deformable Parts of the vehicle to enlarge and so possibly one a pedestrian striking the hood extended Deformation path available to deliver. So should be avoided that the pedestrian with a speed on the non-deformable body parts bounces, the too life-threatening Cause injury can.

The actuators for such a hood can be driven in different ways. For example, describe DE 197 12 961 A1 and DE 103 31 018 A1 mechanical actuators driven by springs. In DE 197 12 961 A1 a compression spring acts on the one hand on the body of a vehicle and on the other hand on an elongated hinge support, which is anchored at one end by a hinge and at another end by a releasable latch on the body and carries handlebars of a multi-joint hinge, which movement to open and close lead the hood. A disadvantage of these known mechanical actuators is that they require strong and correspondingly heavy springs to store the energy needed for a quick lifting of the hood.

One favorable relationship from weight to available Power is through the use of pneumatic, in particular pyrotechnically powered by igniting a propellant charge To reach actuators. However, pyrotechnic actuators have the problem that the gas pressure driving them only at the moment of Lifting the hood available is. Under normal operating conditions, the cylinder is one Actuator depressurized, and a possible play of the piston in relation on the cylinder in the unpressurized state transfers to the hood, if this is held only by actuators of this type. It is therefore Constructions with destructible bridges have been proposed under normal operating conditions intact stay and anchor the hood securely and without play to the body, but destroyed in an accident be used to allow a lifting of the hood. The destroying the bridges Required energy must be simultaneous with the energy to lift the hood available what a correspondingly powerful source of energy required power. About that In addition, the destruction includes the bridges irreversible damage to the overall construction, so that expensive after each actuation of the actuators Repairs are required even if the hood in an accident, the trigger led the actuators has otherwise been affected in any way.

It There is therefore a need for a pneumatic actuator for an active Hood, the one without the help of destructible bridges a firm hold the Hood on the bodywork is able to convey.

In an unpublished one Patent application of the ACTS GmbH, Sailauf, is a pneumatic actuator for one active hood described, the without the use of destructible bridges a firm hold of the hood to the body can convey by a piston attached to a cylinder of the actuator between a rest position and an extended position out is movable, can be fixed in the rest position by a bolt, which engages in a bore of the piston and a bore of the cylinder.

If such an actuator reversed after triggering and continue to use it is not excluded that by the at the release of the Actuator occurring hot, aggressive gases the surface of the bolt and the leader Drilling is attacked. If thereby the mobility of the bolt is too severely restricted, could It happens that the latch is blocked, and the actuator is the hood can not raise. It is therefore desirable to have one lockable pneumatic actuator, in which the unlocking even after multiple tripping still reliable works.

One Such actuator is defined in claim 1. While with an actuator with positively in the bores of the piston and the cylinder engaging latch, in particular a bar of cylindrical shape, in principle every point of the bar surface can come into contact with the wall of a bore and the contact zones the more extended the more precisely the cross sections of bars and Holes are aligned with each other are in the bolt according to the invention determined by the shape of its circumference non-contact zones, with the wall of the holes can not come into contact. The Expansion of areas, on which the bolt and the walls of the holes can touch is thereby reduced, and accordingly the danger of a Sticking of the bolt is reduced upon actuation of the actuator.

Preferably, the contact zones are formed by elongated, narrow ribs formed by depressions acting as the non-contact zones are separated from each other.

Especially The latch can have a polygonal cross-section, while the Holes have a round cross-section.

Around to prevent working gas from entering the actuator when the actuator is triggered Non-contact zones unused past the latch is preferably a facing the movement of the bolt driving working gas Front portion of the bolt free of non-contact zones.

A different possibility, to prevent sticking of the latch is to at least this a portion of its circumference in the direction of the release position tapered to the locking position Give shape. This shape causes a tiny Displacement of the bolt in the direction of the release position is sufficient to the friction between the bolt and the walls of the holes considerably to reduce. It is sufficient Therefore, a comparatively low pressure of the working gas to the To set the bolt in motion.

in the as in the other case, the piston and the bolt are preferably drivable by a same source of pressurized gas.

Conveniently, locks the bolt in the locked position, a gas inlet line of the cylinder, leaving in a working chamber of the cylinder, the the movement of the piston drives, no pressure can be built up, as long as the bolt is not moved and the gas inlet pipe releases.

Preferably extends the gas inlet pipe along the holes. In other words the holes themselves are part of the gas inlet line.

About one Canal extending from the downstream End of the bore of the piston extends to a bottom surface of the cylinder, arrives after displacement of the bolt in the release position working gas to the bottom of the cylinder and push out the piston.

Preferably the working chamber is divided into an antechamber and a main chamber, wherein the free cross section of the antechamber is smaller than that of the main chamber is and the bore in an engaging in the antechamber locking projection of the piston is formed. This allows a secure locking of the piston at the same time low stroke of the bolt between the Locking position and the release position.

If the locking projection the free cross section of the antechamber fills in at least part of their length can be prevented that pressurized working gas in significant amount in the main chamber passes and on the cross section pressure on the piston exerts before this completely is unlocked.

A attached to one end of the bolt, covering the holes Shoulder can serve as a stop on the one hand, the locking position determines the bolt, on the other hand, when operating the actuator working gas, which over the non-contact zones flow past the latch, pressure on the shoulder exercise and thereby contribute to the unlocking.

Around to prevent being in a side chamber in which the shoulder is displaceable guided is, on actuation of the actuator builds up a back pressure, which makes unlocking difficult, can be provided that the secondary chamber communicates with the environment.

Around to allow a reversal of the piston after actuation Preferably, the bolt is reversible in its release position lockable. Therefor can be a blocking body be provided, which, when the latch in the release position is located between a blocking position in which he returns the Bolt locked in the locked position, and a sunk Position is movable, in which he returns the bolt to the locked position allows.

Of the blocking body can be located at the bottom of the antechamber.

Of the blocking body preferably has a first pressing surface on which in the release position of the bolt rests the end face and flush with a surface of the Piston is, on which the bore opens. When the latch is out of the Bore displaced is, the piston can extend, with the surface on which the bore opens to slides along the front of the bolt. Together with the away movement the piston can be the locking body move up, and the frontal area the bolt comes to lie on the first Andrückfläche.

A second pressing surface of the Locking body pushes in the Blocking position of the lock body against the circumference of the bolt, so that the locking body does not pass the bolt can.

A third pressing surface of the Block body beats in the locked position of the piston on the piston and places so in this Position the position of the locking body firmly.

Further features and advantages of the invention will become apparent from the following description of embodiments with reference to the accompanying figures. Show it:

1 1 a motor vehicle with a hood held by actuators in a raised position;

2 a perspective exploded view of an actuator according to the invention;

3 a schematic section through the actuator of 2 ;

4 a perspective view of the bolt used in the actuator according to a first embodiment;

5 the bolt according to a second embodiment;

6 according to the bolt 4 or 5 lockable piston;

7 the bolt according to a third embodiment; and

8th according to the bolt 7 lockable piston.

1 schematically shows a motor vehicle with a hood 1 passing through adjacent to the front or rear edge of the hood 4 . 2 arranged actuators 5 . 3 in one opposite a normal position in which they are with adjacent body parts 6 is flush, raised position is held. The hood 1 is solely by the actuators 3 . 5 supported.

2 shows a perspective exploded view of one of the two rear actuators 3 , It includes an elongated cylinder 7 , the two mounting flanges for mounting the cylinder 7 on a rigid frame of the motor vehicle carries. At a lower end of the cylinder 7 is a gas inlet flange 9 with inlet opening 10 arranged. A gas generator carrier 11 is provided to be gas tight at the inlet flange 9 to be attached. The gas generator carrier 11 has chambers for three gas generators 12 on that with the inlet opening 10 are connected. In a passage between each chamber and the inlet opening 10 can each have a destructible partition wall, not shown in the figure, in the gas generator carrier 11 be attached, which ruptures when the gas generator 12 is ignited in the associated chamber, but a in their assigned chamber accommodated gas generator 12 protects against it, by the explosion of a gas generator 12 to be lit in an adjacent chamber.

One from the cylinder 7 opposite side of the gas generator carrier 11 to be mounted cover 13 includes an electronic ignition circuit, each on receipt of a firing command via a signal cable 14 one of the gas generators 12 ignites.

The actuator of 2 is thus able to three movements of the hood 1 drive before it is used up and needs to be replaced.

It is obvious that also more or less than three gas generators 12 in the gas generator carrier 11 can be accommodated. However, the number of gas generators will generally not be greater than five or six, as the number of hood deployment movements to be expected is limited during the life of a motor vehicle.

In principle, a gas generator carrier with a single gas generator in question, which then every time after a list of the hood 1 would have to be replaced while the cylinder itself could remain in the vehicle. An exchange of generator carrier, then after each installation of the hood 1 would be required, but would require significant safety precautions, which are difficult to ensure in a car repair shop.

One at an upper end 16 of the cylinder 7 emerging piston rod 18 is threaded at its tip. The thread is intended to fit in a hinge carrier 19 to be screwed, to which a handlebar or, in the preferred case of a one-hinged hinge, a fixed to the hood 1 attached hinge part 17 is articulated. A buffer piece 20 made of hard rubber or another slightly elastically deformable material with a central bore 21 is intended to be on the piston rod 18 fitted and in the rest position of the actuator between the hinge carrier 19 and the front side 16 of the cylinder to be pinched and deformed. This is the piston rod 18 at rest in the cylinder 7 locked, as will be described in more detail below. The deformation of the buffer piece 20 is strong enough to have a restoring force of the buffer piece 20 greater than any under normal operating conditions, when driving or when opening and closing the hood 1 , force acting on the hood. Thus, under normal operating conditions, there is no additional deformation of the buffer piece 20 instead, that is, the hinge carrier 19 is effectively immovable with respect to the cylinder 7 and the body that carries it.

3 shows the cylinder 7 of the 2 in an axial section. An internal chamber 23 of the Zy Linders 7 is divided into a main chamber 24 and an atrium 25 , which are each of cylindrical shape and coaxial with each other. The free diameter of the antechamber 25 is significantly smaller than that of the main chamber 24 , A hole 26 extends between the antechamber 25 and the inlet opening 10 ,

The piston rod 18 hangs together with a piston 22 , who in his rest position shown in the figure at the bottom of the chamber 23 located. The in 6 in a perspective view shown piston 22 includes a piston plate 27 that is the cross section of the main chamber 24 fills, and one of the piston plate 27 down into the antechamber 25 in projecting pins 28 , In an upper area of the antechamber 25 , between the mouth of the hole 26 in the antechamber 25 and the main chamber 24 , the cone fills 28 the cross section of the antechamber 25 out. A peak 29 of the pin 28 is semi-cylindrical in cross-section and lies with its curved outer side close to the wall of the antechamber 25 around the mouth of the hole 26 at. One with the hole 26 aligned bore 30 intersperses the top 29 of the pin 28 ,

A in the figure half in side view, half in section shown latch 31 is in the hole 30 slidably received. A front end 32 of the bolt 31 grabs the hole 26 one. One at the opposite foot of the bolt 31 protruding ring flange 33 is in a chamber 34 slidably received, the at the bore 26 diametrically opposite side of the antechamber 25 is formed. One in the chamber 34 housed compression spring 35 holds the bar 31 in the position shown, in which the annular flange 33 on a shoulder of the chamber 34 is applied.

At the bottom of the antechamber 25 , below the top 29 of the pin 28 , is a blocking body 36 arranged. The locking body 36 has a stepped top with a first horizontal pressing surface 38 in the configuration shown by a compression spring 37 against the top 29 is pressed, as well as a vertical pressing surface 39 and another horizontal pressing surface 40 , whose function will be described below in connection with the unlocking process and the reversing of the actuator.

In the case of actuation of the actuator pressure gas escapes from the gas generator 12 into the hole 26 and press against the front 32 of the bolt 31 , The bolt 31 give way under pressure until he drills the hole 30 in the cone 28 has left. Now the gas flows through the holes 26 . 30 free in the antechamber 25 and acts on the underside of the pin 28 , The piston 22 evades the pressure of the gas upwards, since he with the exit of the bolt 31 out of the hole 30 is unlocked. Simultaneously with the piston 22 the blocking body moves 36 under the pressure of the spring 37 upwards until it comes through the contact of the horizontal stop surface 40 with the latch 31 is stopped.

As soon as the top 29 of the pin 28 starts, the antechamber 25 to leave, compressed gas flows from the antechamber 25 in the main chamber 24 and thus acts on the entire cross-sectional area of the piston 22 and drives the piston with great force upwards.

It would also be conceivable embodiment in which the chamber of the cylinder is not divided, the pin 28 deleted and instead one to the hole 30 homologous bore is formed in the piston plate itself. The embodiment shown in the figure, however, has a number of advantages. For a more compact design is achieved because the chamber 34 into which the latch 31 evades the unlocking, not laterally on the cylinder housing must survive. Another advantage is that any leak gas that passes through the bore 26 Coming around bypassing the hole 30 of the pin 28 directly into the antechamber 25 passes, only on the small cross-sectional area of the antechamber 25 Can exert pressure on the piston, which could complicate the unlocking. Furthermore, a short movement of the bolt is sufficient 31 to release the piston, so that a significant delay of the hood lift is prevented by the unlocking process.

After lifting the hood 1 the gas pressure builds up in the chamber 23 Gradually, and the spring 35 tends to the bolt 31 in his in 3 repel the position shown. However, the locking position is not reached; instead, the spring pushes 35 only the front side 32 of the bolt 31 against the vertical pressure surface 39 of the locking body 36 ,

Therefore, the bolt provides 31 also no obstacle when the piston 22 is later pushed back to its original position. The summit 29 of the pin 28 can the front side 32 of the bolt 31 happen, finally hits the pressure surface 38 and drives the locking body 35 so far down until the hole 30 with the latch 31 Aligns and the latter, driven by the spring 35 , again the hole 30 happens and a little way into the hole 26 presses. The actuator is now ready to be triggered again.

4 shows the bar 31 in a detailed perspective view. The bolt 31 is intended to drill into 26 . 30 to engage the same, each circular cross-section is but in turn not exactly circular in cross-section, but has the shape of a circle with a smaller radius than that of the holes 26 . 30 , of which several are in the longitudinal direction of the bolt 31 extending flat ribs 41 protrude. The height of the ribs 41 is chosen as small as needed to make a contact between the ribs 40 lying cylindrical segment-shaped surface areas 42 of the bolt 31 with the wall of the hole 26 respectively. 30 sure to rule out. The possible contact surface between the bolt 31 and the wall of the holes 26 . 30 where the bolt 31 is therefore limited to the apex surfaces of the ribs 41 , To minimize this contact area, the width of the ribs is 41 only a small fraction of the width of the intervening areas 42 ,

The surface areas 42 limit along with the indicated by a dashed line walls of the holes 26 . 30 Channels through which compressed gas into the antechamber 25 can reach even before the bolt 31 the hole 30 has left. Due to the low height of the ribs 40 However, the cross-section of these channels is small and the pressure drop occurring therein is large, so that a pressure that could significantly complicate the unlocking, before the escape of the bolt 31 out of the hole 30 not in the antechamber 25 can build up.

An alternative embodiment of the bolt 31 is in 5 shown. Here are the ones between the ribs 41 in the peripheral surface of the bolt recessed surface areas 42 significantly lower than the bar of the 4 but they do not extend to the front 32 of the bolt. This is formed by a circular disc, with little tolerance in the holes 26 . 30 is fitted. Although the contact surfaces on which the edge of the disk touches the bores are larger in the circumferential direction of the disk, the tighter the tolerance, the overall contact surface remains small due to the small thickness of the disk.

A third embodiment of the invention will be described with reference to 7 and 8th explains, each one a bolt 31 ' and a piston to be locked by the latch 22 ' demonstrate. The bolt 31 ' can be understood here as the intersection of a through the ring flange 33 foot formed to the front 32 of the bolt 31 towards slightly tapered truncated cone 44 and one flattened on two sides, to the truncated cone 44 coaxial cylinder, the two projecting over the lateral surface of the truncated cone flat ribs 45 and a bridge connecting the two ribs 46 at the front 32 forms.

The piston 22 ' includes a piston plate 27 and one of the piston plate 27 downwardly projecting pins 28 through which the bore 30 extends. The hole 30 is complementary to the bolt 31 essentially frusto-conical and with the ribs 45 receiving grooves 47 shaped of which in 8th only one is visible. The lower groove 47 is by a score 48 with the underside of the pin 28 connected. The width of the notch 48 is at least as big as the bridge 46 , and their depth at least as large as the supernatant of the bridge 46 over the face 32 ,

In the locked position is the bolt 31 ' in the direction of the arrow 49 into the hole 30 introduced and lies form-fitting on the walls of the hole 30 at. It is sufficient upon actuation of the actuator, a small displacement of the bolt 31 ' to the truncated cone 44 the contact with the walls of the hole 30 Lose it, leaving the latch 31 ' slightly further is movable. About the out of the shift of the bolt 31 ' resulting gaps between the truncated cone 44 and the walls of the hole 30 but still no gas in the antechamber 25 get there, because the pin 28 this fills in on their entire cross section and the notch 48 through the lower rib 45 the bolt is hidden. Only when the bar 31 against the direction of the arrow 49 shifted so far that the truncated cone 44 the hole 26 has completely left, can gas at the top of the jetty 46 over by the notch 48 flow. At the same time, however, is the piston 22 ' unlocked, the jetty 46 the notch happens 48 , and the piston 22 ' lifts.

To enable a reversal of the actuator, the bolt 31 ' and the piston 22 ' according to 7 . 8th with the same locking body 35 as based on 3 described, interact. The cone shape facilitates the re-engagement of the bolt when reversing 31 ' into the hole 30 , It is not necessary that the bolt 31 ' into the hole 30 Immediately engages to an end position in which the walls of the bolt and the bore touch on their entire circumference, because if any engagement between the bore 30 and bars 31 ' took place, later movements of the piston 22 ' , eg due to vibration during driving, wind load on the hood 1 or one on the hood 1 supporting person, to that the bolt 31 ' over time into the hole 30 engages and finally reaches the end position.

According to a fourth embodiment, which is a simplification of the third embodiment, are on the bolt 31 ' Ribs 45 and the jetty 46 omitted, ie the bolt comprises only the truncated cone 44 and the ring flange 33 , and the hole 30 is purely conical. The lateral surface of the truncated cone 44 and / or the wall of the bore 30 can be slightly convex in axial section to the contact surface between the piston 22 ' and bars 31 ' in the locked state to limit to a circumferential sealing line. A passage of gas into the chamber 23 or their antechamber 25 is then no longer excluded once the bar has moved slightly under the pressure of the working gas, but with a suitable design of the cone angle, the gas passing through be so small that it does not significantly hamper the release of the piston.

1

Engine Hood

2

edge

3

actuator

4

edge

5

actuator

6

body part

7

cylinder

8th

mounting flange

9

gas inlet flange

10

inlet port

11

Gas generator carrier

12

inflator

13

cover

14

signal cable

15

16

front

17

hinge part

18

piston rod

19

hinge support

20

buffer piece

21

drilling

22

piston plate

23

chamber

24

main chamber

25

antechamber

26

drilling

27

piston plate

28

spigot

29

top

30

drilling

31

bars

32

front end

33

annular flange

34

chamber

35

compression spring

36

blocking body

37

compression spring

 38 39, 40

pressing surface

41

rib

42

surface area

44

truncated cone

45

rib

46

web

47

groove

48

score

49

arrow

Claims (19)

Pneumatic actuator ( 3 . 5 ) for an active hood ( 1 ), with a cylinder ( 7 ), one on the cylinder ( 7 ) guided between a rest position and an extended position movable piston ( 22 ) and a bolt ( 31 ), which in the rest position of the piston ( 22 ) between a locking position in which it is in a bore ( 30 ) of the piston ( 22 ) and a hole ( 26 ) of the cylinder ( 7 ) and contact zones ( 41 ) on the circumference of the bolt ( 31 ) a wall of the bore ( 30 ) of the piston ( 22 ) or the bore ( 26 ) of the cylinder ( 7 ) in a release position in which it is a movement of the piston ( 22 ), is pneumatically driven, characterized in that at the periphery of the bolt ( 31 ) Non-contact zones ( 42 ), for which contact with the wall of the bores ( 26 . 30 ) is excluded. Pneumatic actuator according to claim 1, characterized in that the contact zones ( 41 ) are formed rib-shaped. Pneumatic actuator according to claim 1 or 2, characterized in that the movement of the bolt ( 31 ) driving working gas facing end portion ( 32 ) of the bolt ( 32 ) is free of non-contact zones. Actuator according to one of the preceding claims, characterized in that the bolt ( 31 ) has a polygonal cross-section and the holes ( 26 . 30 ) have a round cross-section. Pneumatic actuator ( 3 . 5 ) for an active hood ( 1 ), with a cylinder ( 7 ), one on the cylinder ( 7 ) guided between a rest position and an extended position movable piston ( 22 ) and a bolt ( 31 ' ), which in the rest position of the piston between a locking position, in which he in a bore ( 30 ) of the piston ( 22 ' ) and a hole ( 26 ) of the cylinder ( 7 ) and contact zones ( 44 . 45 ) on the circumference of the bolt ( 31 ' ) a wall of the bore ( 30 ) of the piston ( 22 ) or the bore ( 26 ) of the cylinder ( 7 ) in a release position in which it is a movement of the piston ( 22 ), is pneumatically driven, characterized in that the bolt ( 31 ' ) on at least one part ( 44 ) of its circumference is tapered in the direction from the release position to the locking position. Pneumatic actuator according to one of the preceding claims, characterized in that the piston ( 22 . 22 ' ) and the bolt ( 31 . 31 ' ) by a same compressed gas source ( 12 ) are drivable. Pneumatic actuator according to one of hergehen claims, characterized in that the bolt ( 31 . 31 ' ) in the locking position, a gas inlet line ( 26 . 30 ) of the cylinder ( 7 ) blocked. Pneumatic actuator according to claim 7, characterized in that the gas inlet line ( 26 . 30 ) along the holes ( 26 . 30 ) runs. Pneumatic actuator according to one of the preceding claims, characterized by a channel extending from the downstream end of the bore ( 30 ) of the piston ( 22 ) extends to a bottom surface of the cylinder. Pneumatic actuator according to one of Claims 1 to 8, characterized by a channel ( 48 ) extending from the upstream end of the bore ( 30 ) of the piston ( 22 ' ) extends to a bottom surface of the cylinder. Pneumatic actuator according to one of the preceding claims, characterized in that a working chamber ( 23 ) of the cylinder ( 7 ), in which the piston ( 22 . 22 ' ) is movable, an antechamber ( 25 ) and a main chamber ( 24 ), wherein the free cross-section of the antechamber ( 25 ) smaller than that of the main chamber ( 24 ) and the bore ( 30 ) in an engaging in the antechamber locking projection ( 28 ) of the piston ( 22 . 22 ' ) is formed. Pneumatic actuator according to claim 11, characterized in that the locking projection ( 28 ) the free cross-section of the antechamber ( 25 ) fills at least part of its length. Pneumatic actuator according to one of the preceding claims, characterized in that the bolt ( 31 . 31 ' ) at one end a shoulder ( 33 ), which bore ( 30 ) covered. Pneumatic actuator according to claim 13, characterized in that the shoulder ( 33 ) in a secondary chamber ( 34 ) is slidably guided, which communicates with the environment. Pneumatic actuator according to one of the preceding claims, characterized in that the bolt ( 31 . 31 ' ) is reversibly lockable in the release position. Pneumatic actuator according to claim 15, characterized by a blocking body ( 36 ) of when the bolt ( 31 ) is in the release position, between a blocking position, in which he a return of the bolt ( 31 ) is locked in the locking position, and a lowered position in which he is the return of the bolt ( 31 ) in the locking position permits. Pneumatic actuator according to claim 16, characterized in that the blocking body ( 36 ) a first pressing surface ( 39 ), in which in the release position of the bolt ( 31 ) whose end face is present, and that the first pressing surface ( 39 ) flush with a surface of the piston ( 22 ) to which the bore ( 29 ) opens. Pneumatic actuator according to claim 17, characterized in that the blocking body ( 36 ) a second pressing surface ( 40 ), which in the blocking position of the blocking body ( 36 ) against the circumference of the bolt ( 31 ) presses. Pneumatic actuator according to claim 17 or 18, characterized in that the blocking body ( 36 ) a third pressing surface ( 38 ), which in the locked position of the piston ( 22 ) on the piston ( 22 ) strikes.