DE102021108874B4 - Pneumatic cylinder unit and transport device equipped with it in an irradiation facility - Google Patents

Abstract

Pneumatic cylinder unit (1) with
- a cylinder tube (2) with at least one compressed air connection (5a),
- a piston (3) which can be moved inside the cylinder and is attached to the rear end of a piston rod (4),
- wherein the piston (3) is sealed against the cylinder tube (2) by means of at least one piston ring (6) which lies in an annular groove (7) of the piston (3),
- wherein the piston rod (4) is sealed relative to a cylinder head (2.1) of the cylinder tube (2) in its rod opening (2a) by means of at least one rod seal (8) and/or is guided by means of at least one rod guide (9),
- wherein the rod seal (8) and/or rod guide (9) consists of inorganic material, and
- wherein at least one end, preferably at both axial ends, of the interior of the cylinder tube (2) is provided with an axially acting damping element (14) which serves to brake the piston (3) at the end of its travel, characterized in that
- the damping element (14) is designed as a damping sleeve (14),
- the damping sleeve (14) is fixed in the cylinder tube (2) in a floating manner in the radial direction and its axial movement is limited by a snap ring (16) inserted in the inner wall of the cylinder tube (2),
- the piston (3) has a piston extension (17a, b) which protrudes in the axial direction (10), in particular is centric, and which is designed to axially immerse itself tightly into the inner circumference of the damping sleeve (14) and thereby close the regular connection to the adjacent working chamber connection (5a, b), and
- a bypass (54a+55a, 54b+55b) between each of the working chambers and the associated working chamber connection (5a, b), the cross-section of which can be adjusted by means of a regulating screw (19a, 19b).

Description

I. Area of application

The invention relates to the use of pneumatic cylinder units with the aim of maximum service-free operating time under radioactive irradiation.

II. Technical Background

Working cylinder units, especially pneumatic cylinders, are required not only in nuclear power plants, but also in other irradiation facilities, for example a sterilizer in which surgical instruments are sterilized using gamma radiation from a cobalt source, for example.

In general, pneumatic cylinder units are available, for example, from KR 10 2017 0 140 599 A which discloses a pneumatic cylinder with a piston attached to a piston rod and guide elements for guiding the piston rod. Furthermore, DE 84 01 902 U1 Another pneumatic cylinder unit is known, wherein annular grooves are provided in a guide element of the piston rod, in which static and dynamic seals are arranged in order to seal the piston rod against the cylinder tube.

In addition, the documents DE 196 10 809 A1 , DE 10 2007 001 619 A1 , DE 10 2017 001 720 A1 , DE 198 41 792 A1 and EP 2 589 842 A1 mentioned.

Radioactive radiation causes organic compounds such as plastics to be destroyed very quickly by embrittlement, which is why plastic seals or plastic sliding rings on such working cylinder units have to be replaced at very short intervals. The regular cost and personnel expenditure for removing and installing the working cylinders, usually pneumatic cylinders, which are used up to 50 times in such systems and which are all replaced - sometimes only as a precaution - for safety reasons to avoid unwanted downtime, is very high, not only because of the downtime of the system but also because of the extensive procurement of spare parts for seals, the keeping of replacement cylinders and the regular assembly work to replace the destroyed seals.

For the same reason, hydraulic cylinders are generally not used as working cylinder units, since even organic hydraulic oil would very quickly be adversely affected in its consistency by radioactive radiation and the working cylinder units / hydraulic cylinders would no longer be functional.

Even the use of compressed air, which usually contains oil - which is usually used to lubricate pneumatically operated elements at sliding friction points - is disadvantageous, since the oil content of the compressed air also changes in consistency and in particular solidifies due to the radioactive radiation, and instead of a reduction, an increase in the sliding friction on the affected pneumatic elements occurs.

It is therefore usually necessary that in such pneumatic cylinder units operated with oil-containing compressed air under radioactive radiation, the internal metal parts must also be cleaned of cracked oil ash residues when the destroyed plastic seals are replaced - usually after less than 2000 operating hours.

III. Description of the invention

a) Technical task

The object of the present invention is to provide a pneumatic cylinder unit which contains as few organic compounds as possible in order to achieve drastically extended service intervals of the pneumatic cylinder unit and to reduce the effort for assembly and spare parts provision, as well as to significantly extend the trouble-free availability of an irradiation system in which such a pneumatic cylinder unit is used, preferably to at least one year.

b) Solution of the task

This object is achieved by the features of claims 1, 9 and 12. Advantageous embodiments emerge from the subclaims.

• - Zylinderrohr,
• - darin dicht verschiebbarer Kolben,
• - abdichtender Kolbenring im Kolben,
• - einer Stangendichtung in der Stangenöffnung des Zylinderkopfes

wird diese Aufgabe dadurch gelöst, dass die Dichtungen und/oder die Stangenführung aus einem anorganischen Material bestehen, da anorganische Materialien wesentlich beständiger gegenüber radioaktiver Strahlung, insbesondere Gamma-Strahlung sind und damit diese Bauteile weniger schnell versagen.Regarding the pneumatic cylinder unit with the usual main components

• - cylinder tube,
• - piston that can be moved tightly inside,
• - sealing piston ring in the piston,
• - a rod seal in the rod opening of the cylinder head

This task is solved by the seals and/or the rod guide being made of an inorganic material, since inorganic materials are much more resistant to radioactive radiation, especially gamma rays. and thus these components fail less quickly.

The cylinder itself is usually made of metal, mostly steel.

Preferably, the piston and/or a piston ring also consists of an inorganic material, which is also to be understood as pure carbon - i.e. not a carbon compound -, for example in the crystalline form as graphite, in particular if a component such as a piston or a piston ring consists predominantly of pure carbon, namely at least 90% by weight, better at least 95% by weight, better at least 98% by weight.

Due to the self-lubricating properties of carbon or graphite, this has the additional advantage that the piston can rest against the inner circumference of the cylinder tube during operation without the piston and/or cylinder tube wearing out too quickly. This is particularly advantageous for pneumatic cylinder units that are used horizontally, as is often the case with horizontal transport devices.

The annular gap between the piston and the cylinder tube cannot be chosen to be too narrow, as it is necessary to ensure that the piston slides in the tube with as little friction as possible during the working stroke. Therefore, instead of the plastic seal previously used, the seal between the two pressure chambers is achieved by a spring-loaded piston ring fitted in a groove in the piston circumference. The difference between the outer circumference of the piston and the inner circumference of the cylinder tube is preferably between 0.2 mm and 0.05 mm, better between 0.15 mm and 0.10 mm.

For this reason, the cross-section of the piston ring to the ring groove that accommodates it is also dimensioned in such a way that the radial depth of the ring groove is greater than the piston ring, so that, especially when the pneumatic cylinder unit is operated horizontally, the piston ring can completely disappear into the ring groove on the underside, i.e. it is guided floatingly in the ring groove, in particular the piston groove, and its outward-directed spring effect ensures the seal by resting against the inner wall of the cylinder tube, while the piston can slide easily with its outer side on the inner circumference of the cylinder tube without mechanical pressure.

If, according to a first variant, the piston ring consists of an inorganic, resilient material, usually metal, it can, as is known, be a ring slotted at only one circumferential point, which - in the relaxed state - has a larger outer diameter than the inner diameter of the cylinder tube and also the outer diameter of the piston, and, due to its internal stress, seals sufficiently against the cylinder tube where it protrudes radially beyond the piston.

It is preferably made of a metal that is softer than the cylinder tube on its inner peripheral surface, whereby the piston is then preferably made of brass or bronze, to which carbon in particular can be added in order to achieve a self-lubricating effect. The carbon content is then very low, but at least 1% by weight, preferably 3% by weight, preferably 5% by weight, but generally not more than 10% by weight.

A second variant consists in the material of the piston ring consisting predominantly of carbon, namely 90% by weight, preferably 95% by weight, preferably 98% by weight, which then largely prevents the occurrence of wear on the inner peripheral wall of the cylinder tube, but requires a different design due to the lack of elasticity and residual stress.

Such a piston ring is preferably manufactured as a closed ring, the outside diameter of which is equal to or only slightly smaller than the inside diameter of the cylinder tube, and is then broken or cut into several segments at two or more circumferential points. The undersize is at most 0.5 mm, preferably at most 0.3 mm, preferably at most 0.2 mm, preferably at most 0.1 mm.

If this split piston ring, in particular a graphite ring, consists of two parts and cannot produce a natural spring force by compression as in the case of a slotted piston ring with radial oversize made of an elastic material such as metal, springs are used on the two ring segments in the installed state, which press the ring segments, in particular two, outwards against the inner surface of the cylinder tube.

Instead of a sliding bush, a recirculating ball longitudinal guide is preferably used as a rod guide in the cylinder tube head, in which the axial retraction and extension of the piston rod only causes rolling friction, so that hardly any wear occurs even on the rolling elements and/or a cage and/or the raceways for the rolling elements made of an inorganic material such as metal, in particular hardened steel.

Of course, additional lubrication, such as that provided by the oil component of oil-containing compressed air used to drive the pneumatic cylinder, is advantageous, but the Parts of this oil, which is virtually "burned" by the radioactive radiation, are also detrimental to this type of rod guide. Therefore, synthetic, non-organic lubricants with adjustable viscosities, such as silicone oils, can be used instead of organic oils.

Conventionally, the rod guide can again consist of a sliding bushing, but made of an inorganic material such as metal, then a softer metal than that of the outer peripheral surface of the piston rod.

Preferably, the material of such a sliding bushing also has a carbon content of at least 1% by weight, better at least 3% by weight, better at least 5% by weight, but preferably not more than 10% by weight in order to improve the sliding properties of such a sliding bushing.

Alternatively, the sliding bushing can also consist predominantly of pure carbon, namely at least 90% by weight, better at least 95% by weight, better at least 98% by weight,

To ensure a good seal between the piston rod and this sliding bushing, the gap between them should have a very tight tolerance, if possible less than 0.1 mm, preferably less than 0.07 mm, preferably between 0.05 mm and 0.06 mm.

In order to prevent the piston rod from jamming in the cylinder head, this sliding bush can be provided with a radially protruding collar, for example, which is pressed axially against the cylinder head by a spiral spring, whereby the sliding bush and thus the piston rod are guided in a floating manner in the radial direction and yet tightly against the cylinder head.

There can also be an additional piston ring on the rod guide, which is then preferably accommodated in a ring groove that is located in the inner circumference of the rod opening and which, when relaxed, naturally has a smaller inner diameter than the outer diameter of the piston rod. Here too, the ring groove should preferably have a greater radial depth than the width of the piston ring in the radial direction, so that the piston rod can also lie directly against the sliding bush.

This piston ring on the rod guide can be designed and manufactured in a similar way, including in its relationship to the receiving ring groove, as previously described for the piston ring of the piston.

Since the pneumatic cylinder unit is preferably only moved back and forth between two end positions, and for this purpose both working chambers, i.e. on each of the two sides of the piston, are equipped with a working chamber connection - which can be optionally pressurized with compressed air or vented to the environment - the piston should be dampened at the end of the movement path in order to strike the respective front end plate of the cylinder with only a small force.

For this purpose, according to the invention, an axially acting damping element is provided at one or preferably at both axial ends of the interior of the cylinder, for example a damping sleeve, into which parts of the piston or the piston rod can extend and into which piston extensions protruding with a precise sliding fit at both piston ends retract when approaching the respective end position.

At the moment the respective piston extension is immersed in the respective damping sleeve, the regular respective working chamber connection is blocked and the remaining air volume of the respective working chamber can only flow out to the working chamber connection via a lateral bypass channel, whereby the bypass volume flow and thus the speed of the piston in this damping area can be adjusted using a regulating screw. In this way, damping can be achieved without organic wearing parts.

According to the invention, the damping element is attached to the cylinder tube in a floating manner in the radial direction.

With regard to an irradiation system, such as a sterilizer, which in addition to a radiation source also has a pneumatic cylinder unit, for example as part of a transport device for transporting the products to be sterilized into or through the sterilizer, the object is achieved in that the pneumatic cylinder unit is designed as described above in order to enable a long maintenance-free operating time of the at least one pneumatic cylinder unit and thus of the entire irradiation system.

The pneumatic cylinder unit will often have to be installed horizontally in the irradiation system, i.e. with a main extension direction that takes a smaller angle to the horizontal than to the vertical, which means that the piston resting with its underside on the cylinder tube is hardly avoidable due to gravity.

However, if the contact surface between the piston and the cylinder tube is large enough, this will only result in a low surface pressure and thus low wear if the piston is made of a material that allows good sliding, such as pure carbon or graphite. This is especially true if the piston is installed vertically.

With regard to the method for operating a pneumatic cylinder unit and an irradiation system equipped therewith, this object is achieved in that the compressed air with which the pneumatic cylinder is driven contains oil in order to lubricate the ball bearing guides in particular, but preferably the oil contained in the compressed air is an inorganic oil, for example silicone oil.

This reduces the friction of the balls in the recirculating ball bearing guides and yet such an inorganic oil can withstand radioactive radiation for a relatively long time.

If there is no rod guide to be lubricated, oil-free compressed air can be used.

• - zunächst als umlaufend geschlossener Ring hergestellt wird,
• - anschließend der Kolbenring in mindestens zwei Segmente zerbrochen wird,
• - danach die Segmente unter Anordnung eines federnden Elementes, insbesondere Federn zwischen dem Boden der aufnehmenden Ringnut (7) und dem Kolbenring in die Nut eingelegt wird.

With regard to the method for producing a pneumatic cylinder unit, this object is achieved in that the, in particular each, piston ring

• - is initially manufactured as a circumferentially closed ring,
• - the piston ring is then broken into at least two segments,
• - then the segments are inserted into the groove with a resilient element, in particular springs, arranged between the bottom of the receiving ring groove (7) and the piston ring.

The component consisting primarily of carbon, such as a piston, is preferably manufactured by mixing carbon with pitch, then forming the component from it and, after hardening, converting the pitch into carbon.

This conversion of pitch into carbon can be achieved by sintering under pressure.

c) Examples of implementation

• 1a, b: die Pneumatikzylinder-Einheit in Seiten- und Frontansicht,
• 2a: einen Längsschnitt durch die Pneumatikzylinder-Einheit der 1a, b
• 2b: eine Ausschnittvergrößerung und Verkürzung ausgehend von 2a,
• 2c: einen Querschnitt durch die Pneumatikzylinder-Einheit an der Stelle des Kolbenringes,
• 3: eine Prinzip-Darstellung eines Sterilisators.

Embodiments according to the invention are described in more detail below by way of example. They show:

• 1a , b: the pneumatic cylinder unit in side and front view,
• 2a : a longitudinal section through the pneumatic cylinder unit of the 1a , b
• 2b : a detail enlargement and shortening starting from 2a ,
• 2c : a cross-section through the pneumatic cylinder unit at the location of the piston ring,
• 3 : a schematic diagram of a sterilizer.

As the 1a , b in connection with 2a show, the pneumatic cylinder unit 1 consists of a cylinder 2, which is made of two square end plates 2.1, 2.2, between which a cylinder tube 2.3 is clamped in the axial direction, wherein the clamping takes place by means of tension rods 21 protruding into the corners of the square end plates 2.1, 2.2.

One end plate 2.2, the cylinder head, has a rod opening 2a through which the piston rod 4 can extend outwards, to the inner end of which the piston 3 is attached, which - see 2a - can be moved tightly inside the cylinder 2 in the axial direction 10, the longitudinal direction of the cylinder 2, by supplying the working spaces 20a, b present in front of and behind the piston 3 in the interior of the cylinder with compressed air, which takes place via the working space connections 5a, b, which are arranged in the end plates 2.1, 2.2 and can be controlled to be supplied with compressed air p or vented to the environment U.

In contrast to a hydraulic cylinder, a pneumatic cylinder unit 1 such as the present one may well have a small amount of leakage, since small amounts of escaping compressed air are generally acceptable and only slightly increase the operating costs for driving the pneumatic cylinder unit 1.

Therefore, the piston 3 is sealed against the inner circumference of the cylinder tube 2 with only a single piston ring 6, accommodated in an annular groove 7, which, however, results in only a small transfer of compressed air from the currently pressurized working chamber 20b into the other, currently vented, working chamber 20a, especially since the piston 3 has a relatively large extension in the axial direction of at least 0.5 times, better 0.75 times, better 1.0 times, the piston diameter, which already makes it difficult for compressed air to pass through.

Likewise, in the inner circumference of the rod opening 2a of the cylinder 2, more precisely the cylinder head 2.2, an annular groove 7' can also be formed, in which a piston ring 6' is arranged, which with its inner circumference on the outer circumference of the piston rod 4, just as the outer circumference of the piston ring 6 rests on the inner circumference of the cylinder tube 2.

Nevertheless, both piston rings 6, 6' have a cross-section which is smaller in the radial direction than the depth of the ring groove 7, 7' in which it is accommodated, so that - especially when the pneumatic cylinder unit 1 is arranged horizontally as shown - the piston 3 and the piston rod 4 can certainly rest on the underside of the inner circumference of the cylinder tube 2 and / or the rod opening 2a.

For this reason, at least the piston 3 consists of a material that has good sliding properties compared to that of the cylinder tube 2, in particular of carbon, in particular graphite, or a material with a high graphite content.

In the case of the piston rod 4, direct contact with the rod opening 2a is avoided as far as possible by using a rod guide 9 between the piston rod 4 and the rod opening 2a, which guides the piston rod 4 radially.

To avoid sliding friction, these can be ball-type longitudinal guides 12, one of which is 2b shown in the enlargement and of which at least three should be arranged distributed around the circumference of the rod opening 2a.

In a design shown in Figure 1, the rolling elements 12a held in a cage, usually balls 12a, roll around a rod running in the longitudinal direction 10, here a rod 12b with rounded ends, primarily in the longitudinal direction 10, which roll on the outside of the ball longitudinal guide 12 - directly or indirectly - on the inner circumference of the rod opening 2a and on the inside on the outer circumference of the piston rod 4.

In a second design (not shown), there is no rotation around the central rod 12b, but instead the balls of each of the two longitudinal rows of balls are returned to the starting point of the next rolling insert at the end of their axial rolling path in the longitudinal direction 10 through a return channel in the adjacent component, in particular the cylinder head 2.1. This results in an endlessly revolving insert of a finite number of balls in every direction of movement of the piston rod.

Such ball longitudinal guides 12 are preferably arranged axially outside the ring groove 7' and the piston ring 6' arranged therein.

However, the rod guide 9 can also - instead or in addition - be a sliding bush 13 arranged in the inner circumference of the rod opening 2a, which preferably consists of a material with good sliding properties such as bronze or brass and in whose inner circumference the piston rod 4 rests and is guided with very tight tolerances. The sliding bush 13 is pressed axially from the inside to the outside against a shoulder in the cylinder head 2.2 by a spring 15, here a spiral spring 15, and is thereby sealed against it.

In order to give the piston rod 4 a small freedom of movement in the axial direction and to prevent jamming, the sliding bush 13 can move radially along this shoulder, i.e. is mounted in a floating manner.

In order to ensure that the piston 3 does not hit the opposite end of the cylinder 2, i.e. the end plate 2.1 or 2.2 there, too hard when compressed air is applied to one of the working chambers 20a, b, a damping element 14 in the form of a damping sleeve 14 is arranged in the sides of the end plates 2.1, 2.2 facing the interior of the cylinder 2, which has such a large inner circumference that one of the piston extensions 17a, b projecting axially beyond the piston 3 on both sides can dip into this inner circumference of the damping sleeve 14 before the piston 3 hits the end face of the damping sleeve 14 and thus the end plate 2.1 or 2.2.

• Dieser Arbeitsraum-Anschluss 5a, b der dem Außenumfang der Grundplatte 2.1 bzw. 2.2 angeordnet ist, steht über einen radialen sowie einen damit in Verbindung stehenden axialen Kanal in dieser Endplatte mit einer Zentralmündung 22 in der dem Innenraum des Zylinders zugewandten Stirnfläche der jeweiligen Endplatte 2.1, 2.2 in Verbindung.

Braking of the piston 3 at the end of its respective movement path, i.e. before it hits the respective base plate, is achieved by a controlled venting of the working chamber, here 20a, which is not pressurized with compressed air during the movement, via its working chamber connection 5a:

• This working space connection 5a, b, which is arranged on the outer circumference of the base plate 2.1 or 2.2, is connected via a radial and a connected axial channel in this end plate to a central opening 22 in the end face of the respective end plate 2.1, 2.2 facing the interior of the cylinder.

As long as the connection from this central opening 22 to the working chamber connection 5a, b is open, the venting is not impaired and the piston 3, which is pressurized with compressed air p on the other side, very quickly approaches the end plate 2.1 which is currently connected to the environment at the working chamber connection 5a.

However, there is a damping sleeve 14 in the central mouth 22, and a piston extension 17a, b is arranged at each front end of the piston 3, the outer circumference of which fits tightly into the inner circumference of the damping sleeve 14.

Towards the end of the axial movement path of the piston 3, the piston extension 17a is immersed tightly into the damping sleeve 14, whereby the connection from the working chamber connection 5a or 5b to the mouth to the working chamber is closed.

Air from the working chamber to be vented, e.g. 20a, can then only flow via a bypass to the working chamber connection 5a, which consists of an axial bore 54a, which opens into the working chamber away from the damping sleeve 14 in the inner face of the end plate, as well as a radial bore 55a in the corresponding end plate 2.1, which intersects with it and is connected to it.

This radial bore 55a is on the one hand connected to the working chamber connection 5a independently of the piston position by opening into the adjoining radial channel, and it opens with the other end into the circumferential surface of the end plate, e.g. 2.1.

From there, a regulating screw, e.g. 19a, is screwed in, which reduces the transition from the axial bore 54a to the radial bore 55a to an adjustable extent depending on the screw-in depth of the regulating screw 19a.

Since the remaining cross-section is much smaller than the cross-section of the central opening 22, the venting can only take place much more slowly from the time the piston extension 17a enters the damping sleeve 14, whereby the piston 3 is slowed down before it hits the corresponding end plate, e.g. 2.1

In addition, the mouth 54.1 of the axial bore 54a or b in the end face towards the cylinder interior can be arranged such that it is partially covered by the piston 3, in particular a shoulder of the piston 3 resting on the end plate, which causes an additional reduction of the volume flow into this mouth shortly before the piston 3 rests on the corresponding end plate 2.1, 2.2.

The damping sleeve 14 is mounted in a radially floating manner and is only positioned radially by the piston extension 17a or 17b which is immersed in it, which is why corresponding run-in slopes, possibly alternately, on both the damping sleeve 14 and the piston extension 17a, b, are advantageous. In the axial direction, the damping sleeve 14 is positioned between a corresponding shoulder in the end plate and a snap ring 16 which is also inserted in the end plate.

On the cylinder head side, between the piston rod guide 9 and the damping sleeve 14, there is also a sealing sleeve that can be moved tightly on the outer circumference of the piston rod 4, which is pressed by a spiral spring 15 away from the damping sleeve 14 against a corresponding shoulder in the end plate 2.2 there, which is located between the rod guide 9 and the axial channel to the working chamber connection 5b there and is intended to minimize the escape of compressed air from the adjacent working chamber 20b through the rod guide 9.

• Wenn dieser beispielsweise aus Graphit besteht, kann aufgrund mangelnder Elastizität keine Vorspannung zur Anlage nach radial außen an dem umgebenden Zylinderrohr 2.3 durch Herstellung mit Übermaß und anschließendes Durchtrennen des Kolbenringes an nur einer Stelle, wie bei Kolbenringen aus Metall üblich, erreicht werden.

2c shows a cross-section of the piston ring 6 in the installed state:

• If the piston ring is made of graphite, for example, due to a lack of elasticity, it is not possible to achieve a preload for radially outward contact with the surrounding cylinder tube 2.3 by manufacturing it with an oversize and then cutting the piston ring at only one point, as is usual with metal piston rings.

Instead, in this case, the piston ring 6 is manufactured as a circumferentially closed ring and then broken into two approximately semicircular segments 6a, b, which are then inserted separately into the circumferential groove 7, adjacent to one another in the circumferential direction, in the piston 3.

For the preload radially outward against the cylinder tube 2.3, these segments 6a, b must be preloaded.

This can be done, for example, by means of a wave spring 18a - i.e. a corrugated narrow strip of springy, sufficiently elastic sheet metal - between the bottom of the circumferential groove 7 and the respective segment 6a, b, as shown on the right segment 6b.

The advantage is that such a wave spring 18a can also be inserted in the circumferential direction along the entire circumference of the circumferential groove 7 and presses against the piston ring 6 from the inside over the entire circumference. A radial tolerance must be provided between the outer diameter of the piston ring and the inner diameter of the surrounding cylinder tube in order to avoid jamming and breaking of the less elastic graphite piston ring.

Alternatively - as shown on the left segment 6a - a compression spring 18b, in particular a spiral spring 18b, guided in e.g. a radial piston bore, can press against e.g. the approximately central region of the segment 6a in the circumferential direction from the inside, best by means of a pressure piece adapted to the inner circumferential contour of the segment 6a and also guided in the piston bore between the compression spring 18b and the segment 6a.

• In einem von einer dicken Beton-Umhüllung 59 umgebenen Sterilisator 50, dem Stahlbeton-Strahlungsbunker mit dem bestrahlten Raum 56 darin, befindet sich eine Strahlungsquelle 51, beispielsweise eine Kobalt-Quelle, die radioaktive Strahlung in den bestrahlten Raum 56 hinein abgibt.

The 3 shows a typical application of such a pneumatic cylinder unit 1, which can do without organic material:

• In a sterilizer 50 surrounded by a thick concrete casing 59, the reinforced concrete radiation bunker with the irradiated room 56 therein, there is a radiation source 51, for example a cobalt source, which emits radioactive radiation into the irradiated room 56.

At approximately both ends of the room 56, there is a permanently open feed opening 56a on the one hand and a discharge opening 56b on the other in a wall, where the escape of radioactive radiation is ensured by a reinforced concrete angle attached to the opening in the wall of the bunker - which can be seen, for example, when viewed from above - which covers the corresponding opening with one leg in the exit direction and creates a permanent, insurmountable barrier for the radioactive radiation. This prevents the opening and closing of movable gates and thus the short-term escape of radiation into an unprotected environment.

In the side view of the 3 this angled shape of the chicanes 56a, 56b is not visible. The dwell time in the bunker required for sterilization by means of radiation is achieved by a transport device 52, here in the form of a horizontally running sliding section, in particular functioning according to the pilgrim step method, or any other suitable transport device 52.

Through the loading chicane 56a, a container 53 filled with products P to be sterilized can be placed on the initial area of the transport device 52 and this can be moved further, and the next container 53 can be placed behind it.

At the end of the transport path, the container 53, the contents of which are sterilized after this period of time, is removed through the output chicane 56b.

In a basically known pilgrim step sliding section, the transported goods, here the containers 53, rest on two storage strips that run across the entire transport section in the transport direction 52' and are spaced apart from one another. Next to or in between - also in the transverse area of the containers 53 - there are lifting strips 58 that are approximately the same length, the top of which is located under the top of the storage strips in the initial state, so that the containers 53 then rest on the storage strips.

By means of one or more of the pneumatic cylinder units 1, the lifting bars 58 are raised synchronously via a pilgrim step drive 57 so that they rest on the underside of the containers 53, lift them off the storage bars, move one step - which preferably corresponds approximately or at least to the length of a container 53 - in the transport direction 52' with the containers 53 resting on them and place them further forward on the storage bars by sinking. The lifting bars 58 then move back to their starting position in a lowered position without contact with the containers 53.

This creates a free space at the beginning of the container row in the bunker with the length of a new container to be introduced through the feeding chicane 56a.

Thus, when viewed from the side, the lifting bars follow, for example, a circumferential, circular, rectangular or even elliptical path with the aid of the at least one working cylinder unit 1 which actuates the pilgrim step drive 57.

It is also possible to move the containers 53 to or from another level (not shown) of the transport device 52 using a working cylinder unit 1.

REFERENCE SYMBOL LIST

1

pneumatic cylinder unit

2

cylinder

2.1

end plate

2.1

end plate, cylinder head

2.3

cylinder tube

2a

rod opening

3

Pistons

4

piston rod

5a, b

workspace connection

6, 6'

piston ring

7, 7'

ring groove

8

rod seal

9

rod guide

10

axial direction, longitudinal direction

11

transverse direction

12

ball longitudinal guide

13

sliding bushing

14

damping element, damping sleeve

15

Feather

16

snap ring

17a, b

piston extension

18a, b

spring, wave spring, spiral spring

19a, b

adjusting screw

20a, b

workspace

21

tie rods

22

central mouth

50

irradiation facility

51

radiation source

52

transport device

52'

transport direction

53

container

54

axial bore

54a

mouth

55

radial threaded hole

56

sterilization chamber, irradiated room

56a

loading opening, loading chicane

56b

distribution opening, distribution chicane

57

pilgrim step drive

58

lifting bar

59

concrete casing

p

compressed air

P

product

Claims (13)

Pneumatic cylinder unit (1) with - a cylinder tube (2) with at least one compressed air connection (5a), - a piston (3) which can be moved inside the cylinder tube and which is fastened to the rear end of a piston rod (4), - the piston (3) being sealed off from the cylinder tube (2) by means of at least one piston ring (6) which lies in an annular groove (7) of the piston (3), - the piston rod (4) being sealed off from a cylinder head (2.1) of the cylinder tube (2) in its rod opening (2a) by means of at least one rod seal (8) and/or being guided by means of at least one rod guide (9), - the rod seal (8) and/or rod guide (9) being made of inorganic material, and - an axially acting damping element (14) being present at at least one end, preferably at both axial ends, of the interior of the cylinder tube (2), which serves to dampen the piston (3) at the end to slow down its travel, characterized in that - the damping element (14) is designed as a damping sleeve (14), - the damping sleeve (14) is attached in the cylinder tube (2) in a floating manner in the radial direction and its axial movement is limited by a snap ring (16) inserted in the inner wall of the cylinder tube (2), - the piston (3) has a piston extension (17a, b) which protrudes in the axial direction (10), in particular is central, which is designed to axially immerse itself tightly in the inner circumference of the damping sleeve (14) and in the process close the regular connection to the adjacent work space connection (5a, b), and - a bypass (54a+55a, 54b+55b) between each of the work spaces and the associated work space connection (5a, b), the cross section of which can be adjusted by means of a regulating screw (19a, 19b). Pneumatic cylinder unit according to claim 1 , characterized in that the piston (3) consists predominantly of inorganic material, in particular pure carbon, in particular graphite, in particular at least 90% by weight, better at least 95% by weight, better at least 98% by weight. (Rod guide:) Pneumatic cylinder unit according to one of the preceding claims, characterized in that the rod guide (9) is a ball-recirculating longitudinal guide (12). Pneumatic cylinder unit according to one of the preceding claims, characterized in that - the rod guide (9) is a sliding bush (13) made of a soft metal, in particular brass or bronze, - in particular the material of the sliding bush (13) has a carbon content of at least 1.0 % by weight, better 3.0 % by weight, better 5.0 % by weight. Pneumatic cylinder unit according to one of the preceding claims, wherein - a piston ring (6') is present in the inner circumference of the rod opening (2a), - the piston ring (6') in the relaxed state has a smaller inner diameter than the outer diameter of the piston rod (4), characterized in that - the ring groove (7') has a greater radial depth than the piston ring. (Piston:) Pneumatic cylinder unit according to one of the preceding claims, - wherein the piston ring (6) in the relaxed state has a larger outer diameter than the inner diameter of the cylinder tube (2), characterized in that - the annular groove (7) has a greater radial depth than the piston ring (6) and/or - the piston ring (6, 6') consists of a soft metal, in particular brass or bronze. Pneumatic cylinder unit according to one of the preceding claims, characterized in that - the piston ring (6) consists of at least two separate segments (6a, b), - which are prestressed in particular in the direction out of the receiving annular groove (7), in particular by means of springs (18), which are preferably made of metal. Pneumatic cylinder unit according to one of the preceding claims, characterized in that - the material of the piston ring (6, 6') has a proportion of pure carbon of at least 90% by weight, better 95% by weight, better 98% by weight. Irradiation system (50), in particular sterilizer (50), with - a radiation source (51), - a transport device (52) for transporting products to be sterilized (P), in particular containers (53) with products to be sterilized (P) therein, through the irradiated space (56), - at least one pneumatic cylinder unit (1) as part of the transport device (52) in the irradiated space (56), characterized in that the at least one pneumatic cylinder unit (1) is designed according to one of the preceding claims. irradiation facility according to claim 9 , characterized in that all pneumatic cylinder units (1) are designed according to one of the preceding claims. irradiation facility according to claim 9 or 10 , characterized in that the at least one pneumatic cylinder unit (1) is arranged horizontally. Method for producing a pneumatic cylinder unit according to one of the Claims 1 - 9 , characterized in that - each piston ring (6, 6') is manufactured as a circumferentially closed ring, - the piston ring (6, 6') is then broken into at least two segments (6a, b), - the segments (6a, b) are then inserted into the groove (7) with a resilient element, in particular springs (23), arranged between the bottom of the receiving ring groove (7) and the piston ring (6), and - at least the piston (3) is manufactured as a component by mixing carbon with pitch, then forming the component from it and, after hardening, converting the pitch into carbon. procedure according to claim 12 , characterized in that - the component formed from pitch and carbon is sintered under pressure, thereby converting the pitch into carbon.

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