FI13127Y1 - Arrangement in a pneumatic cylinder - Google Patents

Abstract

An arrangement in a pneumatic cylinder, which pneumatic cylinder has a rear end (2), a front end (4) and a pressure space (11) therebetween, in which pressure space (11) is arranged a reciprocating movable in the pressure space (11) piston (20) with a piston rod (5) whose free end is arranged to project out of the pressure space (11) through a structure (17) in the front end (4) which guides the piston rod (5), between which guide structure (17) and the piston rod (5) has a clearance (25) for discharging the pressure medium from the pressure space during the movement of the piston rod (5), and that the pneumatic cylinder further has a first pressure medium flow channel (9) leading to a first side of the piston (20) and a second pressure medium flow channel (12) leading to a second side of the piston (20), and structures which dampen the reciprocating movement of the piston (20) at the extreme ends of the movement and which include at least a first damping element (16) and a second damping element (22), and the structures which dampens the piston (20) reciprocating movement at the extreme ends of the movement includes a first structure (24) for limiting the amount of outlet during damping and a second structure (18) for limiting the amount of outlet during damping, and the pneumatic cylinder has a sealing arrangement (6) adapted to prevent the pressure medium from flow out of the pneumatic cylinder through the clearance (25) when the piston rod (5) and the load moved therefrom are in their innermost extreme position, characterized in that the sealing arrangement (6) comprises a first abutment surface (6b) in the front end (4), a second abutment surface (6c) moving together with the piston rod (5) and an elastic sealing element (6a) between the abutment surfaces. In addition, the protection requirements 2-15.

Description

ARRANGEMENT IN A PNEUMATIC CYLINDER

TECHNICAL FIELD OF THE INVENTION The invention relates to an arrangement in a pneumatic cylinder as set out in the preamble of claim 1.

BACKGROUND OF THE INVENTION Preferably, the pneumatic cylinders according to the invention are used, inter alia, in industrial plants producing sawn timber, i.e. in sawmills for short periods, for rapidly lowering the rotating saw blade to the sawing position and for rapidly raising it out of the sawing position. At this point of use, a pneumatic cylinder which makes very fast reciprocating movements is referred to, inter alia, as a trimmer cylinder. The pneumatic cylinders of the invention can also be used for many other purposes.

In order to function properly, the trimmer cylinder must be very fast, durable and maintenance-free. In addition, the trimmer cylinder must be able to withstand mechanical stress from the outside and must not be sensitive to dirt, such as resin in sawmills. In addition, one of the most important requirements for a fast and reciprocating trimmer cylinder is that the end damping of the trimmer cylinder must be particularly good. The problem with the prior art pneumatic cylinders acting as trimmer cylinders is that they have to be adjusted very often in order to operate at zero. In particular, damping adjustment is very important and must be done too often with current cylinders. If the adjustment is not made often enough, the cylinders will break 7 or will not work as desired. The need for adjustment is mainly due to the wear and tear of the elastic seals in the cylinder, which require grease lubrication, during operation. In this case, the functions to be adjusted include end damping and = 30 stroke speeds. In addition, the operating pressure on the cylinder N must often be adjusted for successful adjustment. These adjustments are laborious and difficult to make and time consuming because there are often many parallel trimmer cylinders and the need to adjust individual trimmer cylinders is often at different times. In addition, the problem with the prior art pneumatic cylinders acting as trimmer cylinders is that their commissioning requires an experienced person. Attempts have been made in the present solutions to solve the problem, for example, by connecting several other valves in addition to the main valve to control the damping of the trimmer cylinders used in sawmills. The damping is then adjusted by throttling the air outlet with the valves. However, additional valves increase costs and complicate the design of the cylinder unit and make it more susceptible to failure. In addition, additional valves increase the need for maintenance and adjustments. The structure and fasteners of the cylinders have also been strengthened to solve the durability problem. This also increases costs and puts extra weight on the structures. In addition, one problem is that current solutions do not make it easy to increase production speeds, as they are already at the extreme limits of cylinder durability.

OBJECT OF THE INVENTION The object of the present invention is to reduce or even eliminate the above-mentioned problems in the prior art. In this case, it is an object of the present invention to provide a reliable and as maintenance-free arrangement as possible in a pneumatic cylinder, in particular in a trimmer cylinder used in sawmills. Such an arrangement can be implemented, for example, by removing as many wearing and lubricating seals as possible from the structure and / or by changing the sealing material to one that does not require lubrication. In addition, it is an object of the invention to provide such an arrangement in a pneumatic cylinder, in particular in an N trimmer cylinder, in which the rapid damping of the movement of the piston can be effectively adjusted and thus harmful pressure spikes can be prevented. In this case, a sudden backward movement at the end of the movement of the piston rod, for example due to the pressure spike of the trimmer cylinder, can be effectively prevented. Such a movement could momentarily change the position of the saw blade, for example, so that the sawing result on the fast-moving wood material would not be as desired.

DESCRIPTION OF THE INVENTION In order to achieve the above-mentioned objects, the arrangement according to the invention in a pneumatic cylinder is characterized by what is stated in the claim.

1 in the characteristic part. Other embodiments of the invention are characterized by what is set forth in the other claims.

A typical pneumatic cylinder of the arrangement according to the invention comprises a rear end, a front end and a pressure space therebetween, in which pressure a reciprocating piston is arranged in the pressure space, comprising a piston rod whose free end extends out of the pressure space through a piston rod guide at the front end. The pneumatic cylinder further comprises a first flow passage of the pressure medium leading to the first side of the piston and a second flow passage of the pressure medium leading to the second side of the piston, and structures for damping the reciprocating movement of the piston at the extremes. Preferably, there is a clearance between the piston rod guide structure and the piston rod to direct the pressure medium out of the pressure space during the movement of the piston rod.

One of the great advantages of the solution according to the invention is that the movement of the piston of the pneumatic cylinder according to the invention can be very fast and still the damping of the movement works reliably. Check valves placed in the structure facilitate the rapid movement of the piston. The advantage of fast movement is that production speeds can be increased without the equipment suffering. Another advantage is that the pneumatic cylinder according to the invention is easy to commission and the need for maintenance is low. In this case, the service interval is long compared to the solutions according to the prior art. One advantage is also that the damping of the piston movement can be effectively adjusted and thus harmful pressure spikes can be prevented. In this case, it is possible to effectively prevent, for example, a sudden backward movement due to the pressure spike of the N trimmer cylinders, i.e. a rebound, at the end of the movement of the piston rod. In this way, for example, trimmer cylinders used in sawmills provide a more secure sawing result. A further advantage is that during the negative stroke of the piston, i.e. the entry & movement of the piston rod, dirt can be effectively prevented from entering the pneumatic cylinder S to block the structures. Another advantage is that the structure according to the invention = 30 does not cause significant friction in the movement of the piston or the piston rod. In this case, the sealing and bearing structure is also almost wear-free and maintenance-free. Another advantage is that the fastening structure of the rear end bracket of the cylinder partially dampens the mechanical knocks of the cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail by way of example with reference to the accompanying schematic and simplified drawings, in which Figure 1 shows one pneumatic cylinder according to the invention in a simplified and side view and the piston rod Fig. 3 shows a simplified and side sectional view of the cylinder part of the pneumatic cylinder shown in Fig. 1, and Fig. 4 shows a simplified sectional view of the pneumatic cylinder shown in Fig. , the flow restrictor operating during the damping of the pneumatic cylinder according to the invention, enlarged, simplified and viewed from the side, and the cross-section Fig. 6 shows a detail of another preferred flow restrictor operating during the damping of a pneumatic cylinder according to the invention.

OF O OF

O o

O

I a a

O

O 5

OF O

Enlarged, simplified, side and sectional view of Fig. 5, Fig. 7 shows the pneumatic cylinder shown in Fig. 1 in simplified and side view and partially sectioned and the piston rod fully extended, Fig. 8 shows the pneumatic cylinder shown in Fig. 1 in simplified and side view FIG. and the piston rod almost retracted, Fig. 11 shows a detail of a preferred sealing of the piston rod of a pneumatic cylinder according to the invention in an enlarged, simplified and side view; Fig. 12 shows a detail of a preferred mounting of the rear end of a pneumatic cylinder according to the invention in an enlarged, simplified and side view and a cross-section, Fig. 13 shows a further preferred pneumatic cylinder according to the invention in a simplified and side view almost retracted, N Fig. 14 - shows another preferred pneumatic cylinder 5 according to the invention in simplified and side view and partially cross-sectioned and o piston rod almost retracted and 7 Fig. 15 - shows another preferred pneumatic cylinder E according to the invention in simplified and side view and partially sectioned piston rod almost retracted. = 30

N DETAILED DESCRIPTION OF THE EXAMPLES OF THE FIGURES In the figures, the structure of the pneumatic cylinder is simplified and not all components may be shown. In addition, for the sake of clarity, the valve structures and part of the pressure medium flow passage are only symbolically drawn in the figures. The pressure medium used is a gas, preferably air, hereinafter referred to as any suitable pressure medium.

Figure 1 shows a pneumatic cylinder according to the invention, preferably used as a trimmer cylinder for sawmills, in a simplified and side view with the piston rod 5 almost retracted. Preferably, the pneumatic cylinder comprises a cylinder part bracket 1, a rear part 2 of the cylinder part, a cylinder tube 3, a front end 4 of the cylinder part, a piston rod 5, a front arrangement 4 for sealing , adjusting members, bearings and possible seals not shown in Figure 1. Figures 2-6 show the pneumatic cylinder shown in Figure 1 in a simplified and side view and in partial section. In Fig. 2, the pneumatic cylinder is shown assembled and the piston rod 5 almost retracted. Figure 3 shows only the cylinder part without the piston part partly in section and Figure 4 shows only the piston part with its components and partly in section. Figures 5 and 6 show a first and a second structure limiting the amount of flow leaving during damping, i.e. a first flow restrictor 24 and a second flow restrictor.

18. Figures 5 and 6 are particularly simplified so that the clearances 24a and 18a of the flow restrictors are clearly visible in the figures. N The rear end 2 and the front end 4 of the cylinder part are hermetically connected to each other preferably by a cylindrical cylinder tube 3 containing a space of movement or pressure 11 of the piston 20. The rear end 2 has a first flow passage 9 In addition, the flow channel 9 is connected to the pressure space 11 through a non-return valve 10, a damping-adjustable flow path 14a, a constant flow path 14b and a first damping element 16 = 30 through a central channel 16a. For damping control, in connection with the damping adjustable N flow paths 14a, there is a damping control member 14 for adjusting the maximum pressure of the air flow leaving during the damping phase. The damping is adjusted according to the invention by adjusting the maximum pressure of the air flow. Medium

the hub 16a is located in a cylindrical and protruding damping element 16 extending coaxially with the piston 20 inside the pressure space 11 towards the rear end 4 towards the front end 2. The central axis of the piston 20 has a cylindrical bore for the damping element 16 16 outer diameter.

The damping space 23 of the first damping element extends inside the piston 20 and the piston rod 5, the diameter of the damping space 23 of the damping element being smaller than the diameter of the damping space 23 of the damping element.

When the piston rod 5 is in its fully retracted position, the damping element 16 extends into the damping space 23 of the damping element.

Near the open end of the damping space 23 of the first damping element, the damping space 23 of the damping element has a first structure 24, i.e. a first flow restrictor 24, which may advantageously be a separate damping ring, but may also be a short damping element 23 an annular projection extending towards the central axis and having a diameter smaller than the other diameter of the damping space 23 of the damping element.

In this case, the protrusion as the first flow restrictor 24 is preferably of the same material as the piston 20. The first flow restrictor 24 forms a throttling point between the damping element 16 and the damping space 23 of the first damping element to limit the air flow during the damping phase of the piston 20.

The flow can also be suitably limited without a separate projection, by appropriately dimensioning the diameter N of the damping element of the damping element, as shown in Fig. 9. 5 25 o The extension of the first damping element 16 inside the piston 20 allows a short construction length of the 7 pneumatic cylinders.

Preferably, the inner diameter of the first flow restrictor 24 is larger than the outer diameter of the first damping element 16 so that there is a narrow clearance 24a between the inner diameter of the flow restrictor 24 N and the outer diameter of the damping element 16 for air flow, the damping element 16 not being in contact with 24. In this case, the first damping

the element 16 is arranged to run non-contact in the first damping space 23 of the damping element with respect to the first flow restrictor 24.

Correspondingly, the front end 4 of the pneumatic cylinder has a second flow channel 12, which is preferably connected via a cylinder connection to a source of compressed air, for example a compressor.

In addition, the second flow passage 12 is connected to the pressure space 11 through a check valve 13, a damping adjustable flow path 15a, a constant flow path 150 and a damping space 19 of the second damping element.

For damping control, in connection with the damping adjustable flow path 15a, there is a damping control member 15 for adjusting the maximum pressure of the air flow leaving during the damping phase.

In this case, too, the damping is adjusted by adjusting the maximum pressure of the air flow.

The damping space 19 of the damping element is further connected to a structure 17 at the front end 4 extending from the end surface of the front end, guiding the piston rod 5, such as a bore in which the piston rod 5 is arranged to move.

Hereinafter, the shorter term drilling 17 will also be used.

The constant flow paths 14b and 15b allow and ensure a controlled and final release of pressure when the movement of the cylinder stops.

The adjustable flow path that regulates the pressure does not relieve the pressure to the O level, because the control members 14 and 15 close when the pressure drops below the set level.

N Near the end 5 of the second damping element deflection space 19 opening into the pressure space 11, the damping element deflection space 19 has a second structure 18 limiting the flow o during damping, i.e. a second flow restrictor 18, which may preferably be a a short annular projection extending towards the central axis of the damping element deflection space 19 and having a diameter equal to or smaller than the other diameter of the damping element deflection space 19.

In this case, the flow restrictor 18 is preferably of the same material N as the front end 4. The second flow restrictor 18 forms a throttling point between the extension of the piston rod 5, i.e. the outer diameter of the second damping element 22 and the damping space 19 of the second damping element.

The operative structure can also be provided without a separate damping ring or protruding throttling point by suitable mutual dimensioning of the damping space 19 of the second damping element 22 and the second damping element, so as to provide a suitably flow-limiting clearance, as shown later in FIG. Preferably, the inner diameter of the second flow restrictor 18 is larger than the outer diameter of the second damping element 22 so that a narrow clearance 18a is left between the inner diameter of the flow restrictor 18 and the outer diameter of the damping element 22 for air flow, the damping element 22 not in sealing contact with the second damper. is arranged to run non-contact during damping in the deflection space 19 of the damping element with respect to the second flow restrictor 18.

The actual piston 20 is suitably smaller in cylindrical outer diameter than the inner diameter of the cylinder tube 3. In addition, the piston 20 is sealed to the cylinder tube 3 by a lubrication-free seal 21, which is preferably made of, for example, PTFE material. At the base of the piston there is a shoulder-like extension extending towards the outlet end of the piston rod 5, i.e. towards the free end, which acts as a second damping element 22 having a diameter 20 larger than the diameter of the rest of the damping element 22 towards the free end of the piston rod 5. The free end of the second damping element 22 has a chamfer 22a which, at the beginning of the damping step, allows a soft and substantially non-contact passage of the damping element 22 through a second flow restrictor 18 at the free end of the damping space 19 of the second damping element. The first damping element 16 with its central channel 16a, the first damping element deflection space 23 and the first flow restrictor 24, and the second damping element 22, the second damping element deflection space 19 and the second flow restrictor 18 S form a reciprocating motion of the piston 20 of the pneumatic cylinder according to the invention = 30 damping the main structures. Preferably, said structures for damping the reciprocating movement of the piston 20 at the extremities also comprise flow paths 14a, 14b, 15a and 15b with their control members 14 and 15. the common cross-sectional area of the flow paths 14a, 14b and 16a participating in the damping of the movement of the piston 20 from the pressure space 11 to the first flow channel 9.

Correspondingly, the cross-sectional area of the flow path of the non-return valve 13 between the pressure space 11 and the second flow channel 12 is preferably larger than the common cross-sectional area of the flow paths 15a, 15b and clearance 18a involved in damping the piston flow from the pressure space 11 to the second flow channel 12.

In connection with the free end of the piston rod 5 there is further a sealing arrangement 6, which preferably comprises an annular sealing element 6a, a first abutment surface 6b and a second abutment surface 6c, between which abutment surfaces 6b and 6c are arranged by the piston rod 5.

The sealing element 6a is preferably of elastic material and is arranged to close the air leakage of the cylinder when the piston rod 5 is in its fully retracted position at the end of the negative stroke.

The first abutment surface 6b is immobile relative to the cylinder part and is preferably in the front surface of the front end 4 of the cylinder.

Correspondingly, the second abutment surface 6c is arranged to move with the piston rod 5.

In the exemplary embodiments according to the figures, the second abutment surface 6c is in a separate flange 7 attached to the piston rod 5, but it may also be in the end surface 4N of the front end 4 of the holder 8 of the piston rod 5, as shown later in Fig. 13.

The abutment surfaces 6b and 6c are opposite to each other and the sealing element 6a is between the abutment surfaces 6bo and 6c.

In the exemplary embodiments, the sealing element 6a is attached to the second mating surface 6c, but may just as well be attached to the first mating surface 6b & or may be a detachable, freely floating structure on the piston rod 5, making it easier to replace it than .

The service interval of the sealing element 6a is extended when the speed of the inlet movement is limited pneumatically by the structure 24a. In the solution according to the invention, the sealing after the negative movement of the piston 20 takes place when the load attached to the piston rod 5 or following the movement of the piston rod 5 has reached the desired negative stroke position by the force of the movement of the piston 20. In this case, the sealing abutment surface 6c and the load moved by the piston rod 5 move simultaneously. Figures 7 and 8 show a pneumatic cylinder according to the invention in situations where the piston 20 and the piston rod 5 are in two different extreme positions. In Fig. 7, the piston rod 5 is completely outward in its extreme position and the second damping element 22 is in the second damping element deflection space 19. As the piston 20 moves, air escapes from the narrow gap 25 inside the cylinder. the first damping element 16 is in the first damping space 23 of the piston rod damping element. narrow clearance 25.

Figures 9 and 10 show two different preferred embodiments of the invention. In the structure according to Fig. 9, the piston 20 and the piston rod 5 are provided with a sliding bearing. In this case, the piston 20 is mounted on the inner surface of the cylinder tube 11 by means of one or more, preferably lubrication-free, sliding bearings 26 and the piston rod o 5 is mounted on the inner surface of the bore 17 of the front end 4 by means of one or more, preferably lubrication-free, sliding bearings 27. By means of the bearings, the radial movement of the piston 20 and the piston rod 5 is obtained very precisely, the clearance 18a between the damping space 23 of the first damping element 23 and the first damping element 16 and also between the inner surface of the damping space 19 could be reduced so that separate outflow-restricting structures, i.e. flow restrictors 18, 24, are not necessarily required, but the small clearance 18a, 24a itself acts as an outflow-limiting structure. The structure can operate without the actual flow restrictors 18, 24 even when the piston 20 and the piston rod 5 do not have a plain bearing. In the structure according to Fig. 10, a separate structure 28 restricting the amount of outgoing air flow is arranged close to the end surface 4a of the front end 4, i.e. a third flow restrictor 28, which may advantageously be a separate sealing ring, but may also be short. an annular protrusion extending towards the central axis and having a diameter smaller than the other diameter of the bore 17. In this case, the protrusion 28 as the outflow restricting structure is preferably of the same material as the front end 4. The third flow restrictor 28 forms a throttling point between the outer diameter of the piston rod 5 and the bore 17 to restrict the outflow of air from the pressure space 11 and / or the damping element.

However, the inner diameter of the third flow restrictor 28 is 25 times larger than the outer diameter of the piston rod 5 at the bore 17. In this case, there is a small leak in the clearance 25 of the piston rod 5 and the third flow restrictor 28 during the impact. In the solution in which the flow restrictor 28 is a separate ring, the ring is arranged to float freely on the piston rod 5, so that the ring does not act as a bearing for the piston rod 5 and thus does not wear very easily.

Preferably, the third flow restrictor 28 is also adapted to act as a wiper to wipe away the material and loose debris N adhering to the inwardly moving piston rod 5. The compressed air discharged from the clearance 25 is adapted to enhance the wiping effect. Preferably, the third flow restrictor 28 is metal or plastic. Fig. 11 shows an enlarged detail of the sealing of the piston rod 5 of a preferred pneumatic cylinder according to the preferred invention in a simplified and S side view and in cross-section. This solution has an otherwise similar construction to the solution according to Fig. 10, but here the piston rod 5 is additionally provided with a plain bearing 27, of which only one is shown, but there can also be several in parallel. The plain bearing 27 can have a plurality of circumferences so that end gaps are left between the parts, through which the compressed air compressed into the clearance 25 from the second damping element damping space 19 can easily travel out of the pressure space 11 between the third flow restrictor 28 and the piston rod 5.

In this embodiment, the third flow restrictor 28 is a ring disposed in an annular recess 31 in the end face of the front end 4, which is axially locked in place by a locking ring 30 on its outer end side and sealed from its pressure end side As mentioned above, the separate ring acting as a flow restrictor 28 is adapted to run freely on the piston rod 5 so that the outer diameter of the ring is smaller than the inner diameter of the recess 31 by the desired clearance. In this case, the piston rod 5 does not rub against the third flow restrictor 28, so that neither of them wears out and their service life is long. The structure corresponding to Fig. 11 can also be without a plain bearing 27, as shown in Fig. 10.

Figure 12 shows a detail of a preferred fastening of the rear end 2 of a pneumatic cylinder according to the invention in a simplified and side view and in cross-section. The bracket 1 of the cylinder part is fastened to the rear end 2 by means of a fastening flange 32 so that the bracket 1 can move damped by the impacts of the piston 20. The bracket 1 is a separate element, the mounting hole of which has a resilient damping ring 34 and in addition the part inside the rear end 2 of the bracket 1 has resilient damping pads 35 and 36 arranged to operate in both directions of impact of the piston 20. The damping pad 35 is adapted to receive the shock caused by the stopping of the outward movement of the piston 20 and the damping pad 36 is adapted to receive the shock caused by the stopping of the inward movement of the piston 20.

T a S The rear surface of the rear end 2 has a cylindrical recess 2a in which a flange-like extension 1a inside the rear = 30 end 1 of the bracket 1 is placed. Correspondingly, the end surface on the rear end 2 side of the fixing flange 32 has a recess corresponding to the recess 2a and a central hole smaller than the recess, through which a shank portion smaller than the extension 1a of the bracket 1 is arranged.

An annular damping pad 35 is placed in the recess 2a of the rear end 2 and in the recess of the mounting flange 32 between the flange-like extension 1a and the mounting flange 32 to press the bracket 1 towards the bottom of the rear end recess 2a.

Correspondingly, the end surface on the rear end 2 side of the bracket 1 has a cylindrical recess 1b in which a damping pad 36 is placed to press the bracket 1 away from the bottom of the recess 2a of the rear end. There is an axial clearance between the end surface of the rear end 2 of the bracket 1 and the bottom of the cylindrical recess 1b, within which limits the bracket 1 can move during its damping movement without touching the rear end 2 and the mounting flange 32. with nuts.

Fig. 13 shows another preferred pneumatic cylinder according to the invention in a simplified and side view, as well as a partial cross-section and the piston rod 5 almost retracted. This is a very simple functional solution without any adjustments and abrasive dynamic seals on the outer diameter or piston rod 5 of the piston 20. In this solution the rear end 2 has only a first flow channel 9 and a non-return valve 10 with flow paths between the first flow channel 9 and the pressure space 11 respectively, at the front end there is only a second flow channel 12 and a non-return valve 13 with flow paths between the second flow channel 12 and the pressure space 11 and a second damping element deflection space 19 and a bore 17 for the passage of the piston rod 5. The rapid movement N of the piston 20 can also be achieved with this simplified structure, in which the flow into the pressure space 11 takes place mainly through the non-return valves 10, 13 and their flow paths o. At the beginning of the movement, a small flow also takes place through the clearances 24a or 18a.

This solution differs from the previously mentioned solutions in that the first damping element 16 is on the opposite side of the piston rod 5 to the piston 20 and the first damping element deflection space 23 is located at the rear end 4 N in connection with the first flow channel 9. In the first damping space 23 of the damping element 23, only the clearance 24a between the damping space 23 of the first damping element and the first damping element 16 now acts as a structure limiting the amount of flow leaving during damping, but there may be other flow restrictors 24 already earlier.

The structure of the second damping element 22 and the damping space 19 of the second damping element with its flow limiters and clearances is preferably similar to that shown in the description of the structure according to Fig. 9, but it can also be similar to the structure shown in the solutions of any other figure.

Furthermore, one difference with the above solutions is that in this solution the seal 21 of the piston 20 is not an abrasive seal on the outer circumference of the piston, but the annular seal 21 is divided into two parts on each side of the piston 20 so that the piston 20 is sealed by movement of the piston 20. at both extremes.

One preferred structure is shown in Figure 13, where the seal 21 of the first side of the piston 20 is on the end face 4 of the rear end 4 of the piston 20 and the seal 21 of the second side of the piston 20 is on the surface 11 of the pressure chamber 11 of the front end 4.

For the sake of clarity, only the cutting surface of each of the piston seals 21 is shown in Fig. 13, but not the part of the semicircle behind the cutting plane.

Equally, the piston seals 21 could each be in the piston 20 at each end face of the piston, or one at the front end 4 as shown in Figure 13 and one at the rear end 2, or one at the rear end 2 and the other at the front end 4 of the piston 20.

N The solution according to Fig. 13 also shows the structure of the free end 5 of the piston rod 5, which is different from that previously shown.

However, the structure could just as well be similar to that previously described.

The solution shown in Fig. 13 does not have a different flange for the second abutment surface 6c, but the abutment surface 6 ¢ is in connection with the bracket 8 of the piston rod 5.

In addition, the sealing element 6a S is now attached to the first abutment surface 6b at the front end 4.

The sealing element 6a could just as well be fixed to the second abutment surface 6c or it could be a detachable structure floating on the piston rod 5. Fig. 14 shows another preferred pneumatic cylinder according to the invention in a simplified and side view, as well as a partial cross-section and the piston rod 5 almost retracted. This solution is also without any abrasive dynamic seals on the outer diameter of the piston 20 or on the piston rod 5. This solution is otherwise substantially similar to the solution according to Fig. 13, but the constant flow paths involved in damping the movement of the piston 20 and the damping flow paths with adjusting members 14, 15. In addition, the annular seals 21 of the piston 20 are located in a different place than in the solution according to Fig. 13. In the solution according to FIG. For the sake of clarity, only the cutting surface of each of the piston seals 21 is shown in Fig. 14, but not the part of the semicircle behind the cutting plane.

Fig. 15 shows another preferred pneumatic cylinder according to the invention in a simplified and side view, as well as a partial cross-section and the piston rod 5 almost retracted. This solution is also without any abrasive dynamic seals on the outer diameter of the piston 20 or on the piston rod 5. This solution is otherwise substantially similar to the solution according to Fig. 13, N but a different sealing structure of the piston 20 is shown here. The annular seals 21 of the piston 20 are different and are located in a different place than in the solution according to Fig. 13. In the solution according to FIG. extends beyond the end plane of the piston 20. N In addition, the seals 21 are arranged so that there is a clearance between them and the inner surface of the pressure space 11. In this case, the seals 21 do not rub against the inner surface of the pressure space 11 as the piston 20 moves, and there is a clearance 20a between the piston 20 and the inner surface of the pressure space 11 as the piston moves.

For the sake of clarity, only the cutting surface of each of the piston seals 21 is shown in Fig. 15, but not the part of the semicircle behind the cutting plane.

In the solution according to FIG.

Furthermore, the solution according to Fig. 15 differs from the other solutions shown in that the sealing element 6a of the sealing arrangement 6 is now a detached structure floating on the piston rod 5.

The sealing element 6a could just as well be similar to one of the sealing elements 6a described above or also to a different structure.

In the construction according to Figs.

The piston 20 is thus arranged to move non-contact in the pressure space 11, whereby during the movement of the piston 20 the clearance 20a is unsealed and the pressure medium leaks through the clearance 20a.

Such an unsealed clearance 20a is advantageous for the longevity of the structures, since the seals 21 do not rub against the inner surface of the pressure space 11 and thus heat it.

Likewise, non-abrasive seals do not wear out so quickly.

In all the above-mentioned and other solutions according to the invention, there can advantageously be said clearance 20a or the like between the piston 20 and the inner surface of the pressure space 11, and the sealing of the piston 20 can be effected by the seals 21 only in the extreme positions of the piston movement. One of the main ideas of the arrangement according to the invention is to remove as many abrasive dynamic seals as possible from the structure of the pneumatic cylinder, preferably from the piston 20 and the piston rod 5.

At the same time, the friction caused by the seals is removed, which may change as the external temperature of the cylinder changes and also as the cylinder ages.

This reduces the need for adjustment.

The pneumatic cylinder structure according to the invention does not have a seal between the piston rod 5 and the structure used to guide the piston rod which is in sealing contact with the piston rod 5. The piston rod 5 is thus arranged to move substantially non-contact in the bore 17 of the front end that air is leaking outwards from the clearance 25 between the piston rod 5 and the bore 17 of the front end. This leak is also good because it helps to remove the dirt stuck to the piston rod 5. In the arrangement according to the invention, this leakage is only blocked at the end of the inlet movement of the piston rod 5 by an elastic sealing element 6a, which is long-lasting because it is not subjected to abrasion, such as prior art piston rod seals.

Preferably, the piston 20 is also arranged to move substantially non-contact in the pressure space 11 and the sealing of the piston 20 is effected only at the extremes of movement of the piston 20.

The control of the damping of the movement of the piston 20 at the end of the movement of the piston 20 is carried out in the arrangement according to the invention by means of a spring-loaded pressure relief valve, i.e. the previously mentioned damping control element 14, 15. Thus, in order to adjust the damping, the arrangement according to the invention adjusts the maximum pressure of the air flow, while in the prior art solutions the size of the flow opening, i.e. the flow itself, is generally adjusted.

In the arrangement according to the invention, the movement of the piston 20 is controlled by using one or more such valves, by means of which pressure can be applied to and released from the pressure space 11 of the cylinder. One preferred solution is to use a 5/2 valve. In this case, the pressure is applied alternately to the second flow channel 12 at the front end 4 of the cylinder and to the first flow channel 9 at the rear end 2, each of which branches into two flow paths.

The first branching flow path of the rear end 2 comprises a non-return valve 10, through which pressure is applied to the pressure space 11 of the cylinder. This second branch of the first flow channel 9 is also joined by a constant-hole constant flow path 14b connected to the cylinder pressure space 11 and a damping adjustable flow path 14a comprising a maximum damping pressure control member 14 such as a control valve.

When a gaseous pressure medium, such as air, is passed through the first flow passage 9 at the rear end 2 to the pressure space 11 of the cylinder, a small amount of pressure medium also passes through the constant flow paths 14b and the clearance 24a of the first damping element 16. After some movement of the piston 20 of the cylinder, the central channel 16a acting as a flow path passing through the space of the first damping element 16 opens completely. As the piston 20 moves backward when the second flow passage 12 is pressurized, the pressure is initially released without restriction through the central passage 16a of the first damping element 16 until the damping element 16 restricts flow, thereby simultaneously releasing a small amount of pressure through the constant flow paths 14b. After the first damping element 16 restricts the flow, the pressure begins to rise in the pressure space 11. When the pressure in the pressure space 11 has risen to the desired level, the pressure relief valve 14 opens and the flow of pressure medium passes into the first flow channel 9 - from. The elevated pressure in the pressure space 11 between the piston 20 and the rear end 2 limits the movement of the mass moved by the piston 20 and thus also the pneumatic cylinder, e.g. the blade of the circular saw, appropriately preventing mechanical stress at the end of the impact.

N Correspondingly, the first branching flow path of the front end 4 comprises a non-return valve 5 25 13, through which the pressure is conducted to the cylinder pressure space 11. The second branch of the second flow channel 12 in the front end 4 also extends into the cylinder pressure space 11 through the second damping element deflection space 19. This second & branch of the second flow passage 12 is also joined by a constant-hole constant flow path 15b connected to the cylinder pressure space 11 and a damping adjustable flow path 15a comprising a maximum damping pressure control member 15 such as a control valve = 30. The non-return valve 13 of the front end 4 with its flow and the structures 15, 15a, 15b, 18, 18a and 19 damping the reciprocating movement of the piston 20 at the extremes of operation operate in substantially the same way as the corresponding structures of the rear end 2 mentioned above. The simplified structure shown in Figures 13 and 15 does not have the aforementioned flow paths 14a, 14b, 15a and 15b or control valves 14, 15. through. In addition, a small amount of pressure medium can also pass through the clearance 24a of the first damping element 16.

Respectively, in the structure shown in Figs. At the same time, a small amount of pressure medium is also discharged through the clearance 18a of the damping space 19 of the second damping element. When the piston 20 has moved such a distance towards the rear end 2 that the second damping element 22 has moved out of the second damping element 19 of the damping element, the pressure is released into the pressure space 11 freely through the damping space 19 of the second damping element.

It will be apparent to those skilled in the art that the various embodiments of the invention are not limited to the examples set forth above, but may vary within the scope of the protection requirements set forth below. Thus, for example, the structure of a pneumatic cylinder, with its ends, pressure spaces, pistons, flow paths, dampers, seals and adjusting members, may be different from that shown in the figures. Likewise, the alternative structures described above may be incorporated into the structure in various ways.

= a It is also clear to a person skilled in the art that the constant flow path mentioned in the exemplary applications 5 5 leading from the pressure state to the flow path of the adjustable damping S can also be an adjustable flow path. In this case, it is advantageous to adjust, for example, the size of the cross-sectional area of said flow path. It will also be apparent to one skilled in the art that the placement of the piston seals may be different from that described above. The seals can be on the inner circumference of the pressure space, for example so that the abutment surface in the piston can also be something other than a straight face, for example a bevel, a rounding or even a surface extending to the outer circumference of the piston. It is advantageous in this case that during the movement of the piston the clearance between the piston and the inner circumference of the pressure space is unsealed.

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Claims (15)

PROTECTIVE REQUIREMENTS An arrangement in a pneumatic cylinder, which pneumatic cylinder has a rear end (2), a front end (4) and a pressure space (11) therebetween, in which pressure space (11) is arranged one in the pressure space (11) front and reciprocating piston (20) with a piston rod (5) whose free end is arranged to project out of the pressure space (11) through a structure (17) in the front end (4) which guides the piston rod (5), between which guide structure (17 ) and the piston rod (5) there is a winch (25) for discharging the pressure medium from the pressure space during the movement of the piston rod (5), and that the pneumatic cylinder further has a first pressure medium flow channel (9) leading to a first side of the piston ( 20) and a second pressure medium flow channel (12) leading to a second side of the piston (20), and structures which dampen the reciprocating movement of the piston (20) at the extreme ends of the movement and which at least include a first damping element (16) and a second damping element (22), and the structures which dampen the piston ns (20) movement back and forth at the extreme ends of the movement includes a first structure (24) for limiting the amount of outlet during damping and a second structure (18) for limiting the amount of outlet during damping, and the pneumatic cylinder has a sealing arrangement (6) which is arranged to prevent the pressure medium from flowing out of the pneumatic cylinder through the clearance (25) when the piston rod (5) and the load moved therefrom are in their innermost extreme position, characterized in that the sealing arrangement (6) comprises a first abutment surface (6b) in the front end (4), a second abutment surface (6c) which moves together with the piston rod (5) and an elastic sealing element (6a) between the abutment surfaces. N N 25 Arrangement according to protection claim 1, characterized in that between the first construction (24) which limits the amount of outlet during the damping and the first> damping element (16) there is a clearance (24a), and that between the second Take There is a clearance (18a) in the structure (18) which limits the amount of outlet during the damping and the second damping element (22). Arrangement according to protection claim 1 or 2, characterized in that the sealing element (6a) is arranged to be pressed between the abutment surfaces (6b) and (6c) when the piston rod (5) is in its innermost extreme position. Arrangement according to protection requirements 1, 2 or 3, characterized in that the sealing element (6a) is placed as a floating structure on the piston rod (5). Arrangement according to one of the preceding protection requirements, characterized in that the structures which dampen the movement of the piston (20) back and forth at the extreme ends of the movement comprise pressure medium flow paths (14a, 14b, 15a and 15b) with control means (14 and 15). Arrangement protection requirement 5, characterized in that in connection with the flow path with adjustable damping (14a, 15a) for adjusting the damping there is a damping adjusting means (14, 15) for adjusting the maximum pressure of the pressure medium flow which is removed in the damping step. Arrangement according to one of the preceding protection requirements, characterized in that the pressure medium flow from the clearance (25) between the piston rod (5) and the structure (17) which controls it is limited by a flow restrictor (28). NN 25 8. Arrangement according to any one of the preceding protection claims 5 - 7, characterized in that the pressure medium flow path (14b) in the arrangement is a constant flow path which> via the flow path with adjustable damping (14a) in the rear end (2) has a connection. Partition from the pressure chamber (11) to the first flow channel (9). S = 30 Arrangement according to any one of the preceding protection claims 5 - 8, characterized in that the pressure medium flow path (15b) in the arrangement is a constant flow path which via the flow path with adjustable damping (15a) in the front end (4) has a connection. from the pressure chamber (11) to the second flow channel (12). Arrangement according to one of the preceding protection requirements, characterized in that between the pressure space (11) and the flow channel (9, 12) to ensure a quick start of the piston (20) there is a counter-valve (10, 13) with flow paths which allows a pressure medium flow in the direction of the pressure space (11) and which prevents it from the pressure space (11) to the flow channel (9, 12). Arrangement protection claim 10, characterized in that the cross-sectional area of the counter-valve (10) flow path is larger than the common cross-sectional area of the flow paths (14a, 14b), which leads from the pressure space (11) to the first flow channel (9) and which participates in the damping of the movement of the piston (20), and in the middle channel (16a) of the first damping element (16), and that the cross-sectional area of the flow path of the counter valve (13) is larger than the common cross-sectional area of the flow paths (15a, 15b) leading from the pressure space (11) to the second flow channel (12) and which participates in the damping of the movement of the piston (20), and of the clearance (18a). Arrangement according to one of the preceding protection requirements, characterized in that the inner surface of the piston (20) and the pressure space (11) have a clearance (20a) which, during the movement of the piston (20), lets through a pressure medium leakage and which in both extreme positions the movement of the piston (20) is arranged to be sealed by the seals (21). N Arrangement according to one of the preceding protection requirements, characterized in that the pressure space (11) of the pneumatic cylinder for sealing the piston (20) has at least 2 two annular seals (21), the first of which is arranged to be sealed against the first front surface of the piston (20). when the piston (20) is in its innermost extreme position and of which the other is Take S = 5 arranged to be sealed against the second front surface of the piston (20) when the piston (20) is in its extreme extreme position. Arrangement according to one of the preceding protection requirements, characterized in that the rear end (2) of the pneumatic cylinder has a bracket (1) which, by the action of the stroke of the piston (20), is arranged to move in relation to the rear end (2). Arrangement protection claim 14, characterized in that the bracket (1) is mounted on the rear end (2) of the pneumatic cylinder by means of a damping element (35, 36) such that the first damping element (35) is arranged to dampen the strength of the piston ( 20) outward strokes and the second damping element (36) is arranged to damp the strength of the inward stroke of the piston (20). N N O N N <Q O I a a O O 5 N O N 5