WO2016079653A1

WO2016079653A1 - Pneumatic cylinder with damper sleeve

Info

Publication number: WO2016079653A1
Application number: PCT/IB2015/058846
Authority: WO
Inventors: Sebastian BICELLI; Dario Braga; Fabio BOTTARELLI; Vladimir Morozov
Original assignee: Camozzi S.P.A. Societa' Unipersonale
Priority date: 2014-11-18
Filing date: 2015-11-16
Publication date: 2016-05-26
Also published as: CN107250569A; CN107250569B; EP3221596A1; EP3221596B1

Abstract

A pneumatic cylinder (100) comprises a piston, axially mobile inside a casing. The pneumatic cylinder comprises at least one damper sleeve (10) suitable to reduce the intensity of the impact that occurs when the piston (20) arrives in abutment against the head (104, 105) of the casing. The damper sleeve (10) is provided with a front portion (14) provided with a plurality of through holes (60), extending in a radial direction, and a tapered wall (143) with a wall thickness which decreases toward a front end (144) of the damper sleeve (10). When the piston (20) approaches the end-stroke position, the pressurised air escapes towards the duct (108) through the holes (60) and a vent space (80) defined between the stem (21) of the piston (20) and an inner wall (141) of the front portion (14) of the sleeve (10).

Description

DESCRIPTION

"Pneumatic cylinder with damper sleeve"

[0001] This invention relates to a pneumatic cylinder provided with means of self-damping the piston.

[0002] A pneumatic cylinder, provided with a piston movable with reciprocating motion inside a casing, is generally provided with a damping means to ensure a reduction in the intensity of the impact that occurs when the piston arrives in frontal support in a suitable seat formed in the head of the casing.

[0003] The known damping means include damper sleeves, made of resilient material, applied to the piston head.

[0004] An example of such damper sleeves is described in patent EP2047116, wherein on the head of the piston rod is provided at least one sleeve provided, on the outer surface, with damping grooves extending in the longitudinal direction. When the piston approaches the end-stroke position, the air compressed between the piston and a sealing element housed in the cavity of the head, reduces the intensity of the impact of the piston and, through the damping grooves, exits towards suitable openings made in the head of the casing. The geometry of the grooves then determines a discharge law of the air that allows the controlled slowing of the piston.

[0005] However, it has been noted that the realisation of damping grooves on the outer surface of the damper, sleeve has a number of disadvantages:

[0006] - the solidity of the sleeve is compromised: a groove, for example V-shaped, involves a reduction of the section in the axial direction and represents a point of weakening of the structure of the sleeve;

[0007] - the repeatability of the sleeve is compromised: even small variations of inclination of the grooves can significantly change the discharge law of the air that allows the controlled slowing of the piston;

[0008] - possibility of variation of the discharge law at high pressures: high pressure can cause deformation of the sealing element (housed in the head cavity of the casing) , which can, at least partially, close the grooves and change the discharge law of the air that allows the controlled slowing of the piston.

[0009] In the field, there is a particularly felt need to reduce the set-up times related to the adjustment of the damping screw. The need is therefore felt to realise cylinders able to function properly in an increasingly broader range of pressures, loads and speeds without resorting to manual adjustments.

[0010] The purpose of this invention is to meet this need.

[001 1] Said purpose is achieved with a pneumatic cylinder and damper sleeve respectively according to claim 1 and 14. The dependent claims describe preferred embodiments of the invention.

[0012] The characteristics and the advantages of a pneumatic cylinder and damping sleeve according to the invention will, in any case, be evident from the following description of its preferred embodiments, provided by way of non-limiting example, with reference to the accompanying figures, wherein:

[0013] Figure 1 shows a pneumatic cylinder provided with a damper sleeve according to this invention, in a first end-stroke position;

[0014] Figures 2 to 6 show the piston head provided with a pair of damper sleeves according to this invention, in advancement up to the end-stroke position;

[0015] Figure 7 shows a pneumatic cylinder' provided with a damper sleeve according to this invention, in a second end-stroke position;

[0016] Figure 8 shows a perspective view of half-piston and damper sleeve according to this invention, in an embodiment variant;

[0017] Figures 9 and 10 show respectively a sectional view and a top view of the half-piston and damper sleeve of Figure 8;

[0018] Figure 11 shows a perspective view of the half- piston and damper sleeve according to this invention, in a further embodiment variant;

[0019] Figures 12 and 13 show respectively a sectional view and a top view of the half-piston and damper sleeve of Figure 11.

[0020] Figure 14 shows a pneumatic cylinder provided with a damper sleeve according to this invention, in a further embodiment variant .

[0021] With reference to the accompanying figures, reference number 100 indicates a pneumatic cylinder provided with at least once damper sleeve 10.

[0022] I^'n particular, Figure 1 shows a linear double-acting pneumatic cylinder.

[0023] The pneumatic cylinder 100 comprising a casing or jacket 103, cylindrical, inside which is housed a piston 20, axially mobile along the axis X. The piston 20 is fixed to a stem 21. As shown in Figure 3, the piston 20 comprises a first portion or front half-piston 20' and a second portion or rear half-piston 20' ' .

[0024] The operating principle consists in introducing pressurised air into one of the two chambers 102,102' defined inside the casing 103, so that the air pushes on one face of the piston 20 and makes it move inside the casing 103.

[0025] The casing 103 defines a front head 104 and a rear head 105, each provided with an abutment wall 106,107 for abutment with the piston head 20 in an end-stroke position and, in particular, respectively with the front half-piston 20' rear half-piston 20''.

[0026] In operation, in the opposite chamber 102 ' to the chamber 102 in which air is introduced under pressure, it is necessary to discharge the air present, which would tend to brake the movement of the piston 20. This phenomenon of braking the piston is exploited through the definition of an optimum air discharge law that, exiting, allows a controlled slowing of the piston 20.

[0027] Both the front head 104 and the rear head 105 are provided with a chamber 112,113 for housing the sleeve connected to the piston 20, respectively to the front half-piston 20' and to the rear half-piston 20' ' .

[0028] Both the front head 104 that the rear head 105 are provided with a duct 108,109 for connection with specific pneumatic lines (not shown) for feeding the fluid (air or gas) to the inside of the casing 103. In particular, the duct 108,109 is in fluid communication with the respective front chamber 102' or rear chamber 102 through the chamber 112,113 for the housing the sleeve connected to the piston 20.

[0029] When the fluid (for example, air) is passed through the duct 109 of the head 105 in the chamber 102, the piston 20 moves in the direction of the head 104 (up to the end-stroke position shown in Figure 1). Similarly, when the fluid is passed through the duct 108 of the head 104 in the chamber 102', the piston 20 is moved backwards towards head 105 (up to the end-stroke position shown in Figure 7 ) .

[0030] The pneumatic piston 100 comprises several gaskets that prevent the leakage of air from one chamber to the other as well as to the outside.

[0031 ] Both the front head 104 that the rear head 105 are therefore provided with at least one annular outer gasket 110,111, housed in a suitable cavity formed in a wall of the respective seat 106,107.

[0032] In addition, the piston 20 is provided with at least one annular inner gasket 26, housed in a suitable cavity formed on the body of the piston. Preferably, the piston 20 is provided with a front inner gasket and a rear inner gasket .

[0033] In order to reduce" the impacts between the piston 20 and the heads 104,105, impacts that tend to ruin the pneumatic cylinder and create annoying noises, suitable damper means 10 are provided.

[0034] In the embodiment variant shown in the figures, the sleeve 10 is in one piece with the piston 20 and, in particular, a first sleeve 10 is in one piece with the front half-piston 20' and a second sleeve 10 is in one piece with the rear half-piston 20' ' .

[0035] In a variant, shown in Figure 14, the piston 20 and the sleeve 10 are separate elements. In this variant, the sleeve 10 is fixable to the piston 20 and, in particular, a first sleeve 10 is fixable to the front half-piston 20' and a second sleeve 10 is fixable to the rear half-piston 20 ' ¹.

[0036] The damper sleeve 10 allows reducing the intensity of the impact that occurs when the piston 20 arrives in abutment against the cylinder head 104,105.

[0037] Preferably, the pneumatic cylinder 100 is provided with a pair of damper sleeves 10 provided on both sides of the piston 20. The presence of a pair of sleeves 10 allows damping the piston 20 in both the outbound position, in the chamber 102', and return position, in the chamber 102.

[0038] In the end-stroke positions, shown in Figures 1 and

7, the outer gasket 110,111 realises a seal against the respective damper sleeve 10.

[0039] Preferably, the half-piston 20 ',20^{1 1} is provided with an annular seat 11, for housing an inner gasket 26.

[0040] Preferably, as shown in Figures 8 to 10, the sleeve

10 has an ogival shape, bevelled at the front.

[0041] Preferably, the sleeve 10 comprises a main body 12, extended in the axial direction, and provided with a through opening 13.

[0042] The main body 12 comprises a front portion 14, substantially cylindrical, suitable to be housed in the chamber 112,113 of the head 104,105.

[0043] The main body 12 comprises a further rear portion 15, which protrudes radially with respect to the front portion 14.

[0044] In the embodiment variants shown in Figures 8 to 13, wherein the sleeve 10 is in one piece with the piston 20, the further rear portion 15 defines the half-piston 20',20''. In said variant, the further rear portion 15 that defines the half-piston is provided with a seat 11 for ^'housing an inner gasket 26.

[0045] In the embodiment variant of Figure 14, the further rear portion 15 is substantially a flange or edge.

[0046] Advantageously, the front portion 14 is provided with a wall 143 defined, in the radial direction, by an inner face 141 and an outer face 142. The outer face 142 is substantially parallel to the axis X and the inner face 141 is inclined by an angle ?.

[0047] Advantageously, the wall 143 of the front portion 14 is tapered, with a wall thickness that decreases towards a front end 144 of the damper sleeve 10.

[0048] Advantageously, the front portion 14 defines a frusto-conical front opening with a greater conicity towards the front end 144 of the damper sleeve 10.

[0049] Preferably, the sleeve 10 is provided with a plurality of through holes 60 that extend in the radial direction, provided in correspondence of the front portion 14.

[0050] In the embodiment variant shown in Figure 8, the holes 60 are arranged in line in the axial direction X.

[0051 ] In the embodiment variant shown in Figure 11, the holes 60 are distributed circumferentially on the front portion 14.

[0052] Preferably, the longitudinal distance D (in the direction X) between two consecutive holes is variable. Preferably, the distance D increases towards a front end 144 of the damper sleeve 10, as shown in the variants of Figure 8 and 11.

[0053] Preferably, the holes 60 are equal, and have the same diameter.

[0054] In the embodiment variant of Figure 10, the holes 60 are^' equal, have the same diameter, and are positioned at a variable distance D. Preferably, the distance D increases towards a front end 144 of the damper sleeve 10.

[0055] In a further embodiment variant, the holes have a different diameter and are positioned at an equal distance D. The distance D between the holes remains unchanged from the interior towards a front end 144 of the damper sleeve 10.

[0056] In a still further embodiment variant, the holes have a different diameter and are positioned at a variable distance D.

[0057] In use, the tapered wall 143 of the front portion 14 of the sleeve 10 allows defining a vent space 80 for the pressurised air, defined between the stem 21 and the inner wall 141 of the sleeve 10. The holes 60 provide passage for venting the pressurised air.

[0058] Preferably, on the one hand, the front portion 14 of the sleeve extends axially beyond the head of the stem 21. Advantageously, this configuration allows defining a particularly ample vent space 80 for the pressurised air.

[0059] As shown in Figure 3, when the piston 20 approaches the end-stroke position, the outer gasket 110 and the inner gasket 26 sealingly close the chamber 102 ' . The residual air pressure trapped in the chamber 102 ' allows damping the impact of the piston 20. It is important that the residual pressurised air can escape from the chamber 102' through the duct 108. Advantageously, the holes 60 and the vent space 80 (between the stem 21, or the nut screwed on the stem, and the sleeve 10) provide an outlet for the pressurised air towards the duct 108.

[0060] As shown in Figures 4 and 5, as the piston 20 approaches the end-stroke position, the holes 60 and the vent space 80 provide an escape route for the pressurised air .

[0061 ] The size of the holes 60, the number of holes 60, the distance D between the holes 60, the angle ? and the thickness of the tapered wall 143 of the front portion 14 influence the damping behaviour of the compressed gas and thus define the discharge law of the air that allows the controlled slowing of the piston.

[0062] Advantageously, the tapered wall 143, with a wall thickness that decreases towards a front end 144 of the damper sleeve 10, favours the passage of air through the holes 60.

[0063] Advantageously, a damper sleeve 100 provided with a tapered wall 143 allows obtaining a free passage for the air (vent space 80) without throttling the flow.

[0064] Advantageously, a damper sleeve 100 provided with a tapered wall 143 always allows obtaining a free _^passage for the air (vent space 80) even in case of deformations of the outer gasket 110,111.

[0065] Advantageously, a damper sleeve 100 provided with tapered wall 143 and holes 60 allows the air to flow out smoothly, from the narrower conical part to the wider part, with no load losses.

[0066] Advantageously, a damper sleeve 10 provided with tapered wall 143 and of holes 60 facilitates the expulsion of air without compromising the ogival section.

[0067] Innovatively, a pneumatic cylinder provided with a damper sleeve according to this invention is able to function properly in a wide range of speeds, pressures and loads .

[0068] To the forms of embodiment of the pneumatic cylinder and damper sleeve according to the invention, a technician in the field, to satisfy contingent requirements, may make modifications, adaptations and replacements of members with others functionally equivalent, without departing from the scope of the following claims. Each of the characteristics described as belonging to a possible form of embodiment can be achieved independently from the other embodiments described.

Claims

1. Pneumatic cylinder (100), comprising:

- a piston (20), attached to a stem (21) and axially mobile inside a casing (103) along an axis X, said piston (20) being provided with at least one inner gasket (26);

- a cylindrical casing (103), comprising a front head (104) and a rear head (105), each head (104, 105) being provided with a chamber (112, 113) for the housing of a

sleeve (10) of the piston (20) in an end-stroke position, a duct (108,109) for the supply of pressurised air inside the housing (103), an outer annular gasket (110, 111), housed in a cavity made in a wall of the chamber (112, 113);

- at least one damper sleeve (10), engaged with the piston (20), suitable to reduce the intensity of the impact which occurs when the piston (20) comes into abutment against the head (104, 105), said sleeve (10) comprising a front portion (14) provided with a plurality of through holes (60) extending in the radial direction, and a tapered wall (143) with a wall thickness which decreases toward a front end (144) of the damper sleeve (10) ,

wherein when the piston (20) approaches the end-stroke position, the pressurised air trapped between the outer gasket (110,111) and the inner gasket (26) escapes towards the duct (108) through the holes (60) and a vent space (80) defined by the inner wall (141) of the front portion (14) of the sleeve (10) .

2. Pneumatic cylinder (100) according to claim 1, wherein the front portion (14) defines a frusto-conical front opening with a greater conicity towards the front end (144) of the damper sleeve (10).

3. Pneumatic cylinder (100) according to claim 1 or 2, wherein the tapered wall (143) is defined, in the radial direction, by the inner face (141) and by an outer face (142), and wherein the outer face (142) is substantially parallel to the axis X and the inner face (141) is inclined by an angle a.

4. Pneumatic cylinder (100) according to any of the previous claims, wherein the holes (60) are distributed cxrcumferentially on the front portion (14).

5. Pneumatic cylinder (100) according to any of the claims from 1 to 3 , wherein the holes (60) are positioned in a line in an axial direction X.

6. Pneumatic cylinder (100) according to any of the previous claims, wherein the longitudinal distance D between consecutive holes (60) is variable.

7. Pneumatic cylinder (100) according to claim 6, wherein the longitudinal distance D between consecutive holes (60) increases towards the front end (144) of the damper sleeve ( 10 ) .

8. Pneumatic cylinder (100) according to any of the claims from 1 to 5, wherein the longitudinal distance D between the holes remain unchanged towards the front end (144) of the damper sleeve 10.

9. Pneumatic cylinder (100) according to any of the previous claims, wherein the holes (60) are the same and have the same diameter.

10. Pneumatic cylinder (100) according to any of the claims from 1 to 8 wherein the holes have different diameters .

11. Pneumatic cylinder (100) according to any of the previous claims, provided with a pair of damper sleeves

(10) .

12. Pneumatic cylinder (100) according to any of the previous claims, wherein the piston (20) and the sleeve (10) are separate elements.

13. Pneumatic cylinder (100) according to any of the claims from 1 to 11, wherein the sleeve (10) is in one piece with the piston (20) .

14. Damper sleeve (10) for a pneumatic cylinder comprising a front portion (14) extending along a longitudinal axis X and provided with a plurality of through holes (60) extending in a radial direction and a tapered wall (143) with a wall thickness which decreases toward a front end (144) of the damper sleeve (10).

15. Damper sleeve (10) according to claim 14, wherein the longitudinal distance D between the holes (60) increases towards the front end (144) of the damper sleeve (10) .