Carrier or lubricant ring and hydraulic cylinder with such a ring

Abstract

Lubrication ring designed for installation in a hydraulic cylinder (100) with a cylinder tube (104), a displaceable piston rod (102) and a piston (106) arranged on the piston rod (102) in order to supply an inner cylinder surface (108) of the cylinder tube (104) with lubricant, comprising: - a carrier ring (10) having an outer ring surface (20a, 20b; 22) for sliding along the inner cylinder surface (108) of the cylinder tube (104) of the hydraulic cylinder (100) and an inner cavity (124), - a receiving material (30) present in the inner cavity (124) of the carrier ring (10) which is designed to receive and slowly release a lubricant, and - at least one through-hole (24) which is made in the outer ring surface (22) and which allows the lubricant received in the receiving material (30) to escape from the inner cavity (124) onto the inner cylinder surface (108).

Description

Technical FieldThe present invention relates to a carrier or lubricant ring which is designed for installation in a hydraulic cylinder with a cylinder tube, a displaceable piston rod and a piston arranged on the piston rod.In particular, such a hydraulic cylinder is a so-called single-acting hydraulic cylinder, in which hydraulic oil is fed into a first chamber in order to displace the piston rod in the cylinder tube within a second chamber filled with air, for example.The lubricant ring has the function of supplying lubricant to an inner cylinder surface of the cylinder tube. The lubricant film is intended to protect the inner surface of the cylinder from corrosion and to ensure the sealing effect of possible further seals arranged on the piston.The present invention further relates to a hydraulic cylinder having one or more such lubricant rings.BackgroundIn particular in the case of single-acting hydraulic cylinders, a felt ring is often arranged on the so-called dry side of the piston, which felt ring is impregnated with lubricant such as, for example, hydraulic oil. As is known, single-acting hydraulic cylinders have a one-way connection. The piston rod moves when hydraulic oil or gas is fed into the first chamber separated by the piston, also called a hydraulic chamber. In order to reverse the expansion or piston rod displacement, a counter pressure is necessary. If such a single-acting cylinder is not equipped with a spring for this purpose, an external counterforce is applied, for example in the form of a weight. In both cases, however, ambient air enters a second chamber which is separated from the hydraulic chamber by the piston.On the piston of the single-acting hydraulic cylinder, one or more seals are provided which ensure that the hydraulic fluid necessary for extending the piston rod remains in place and does not enter the dry region, i.e. the second chamber.Slow, stable discharge of the lubricant from the felt ring is intended on the one hand to protect the inner cylinder surface of the second chamber of the hydraulic cylinder from corrosion. On the other hand, the at least one seal of the piston arranged adjacent to the grease-impregnated felt ring is to be supplied with a lubricant film. Only the lubricant film allows the sealing effect of the piston seals.The felt material used hitherto is indeed well suited to store lubricant and to deliver it slowly to the inner cylinder surface towards which the piston and thus the felt ring moves. However, in practice it has been found that individual threadlike components of the felt material become detached from the felt ring as the period of use of the hydraulic cylinder increases and pass under the sealing lips of the seals. This can lead to leakage at the sealing lips. As a result, hydraulic oil of the hydraulic cylinder reaches the second chamber of the hydraulic cylinder and is possibly pushed outwards by the air filter present there.Due to the detached filamentary felt particles of the felt ring, the felt ring gradually loses contact with the cylinder inner surface and, as a result, the discharge of hydraulic oil to the cylinder inner surface stops. Due to this, drying effects occur on the cylinder inner surface and the one or more sealing lips of the associated seals wear very quickly.If the hydraulic cylinder with the fibrous felt ring is now not actuated for a longer period of time, i.e. one or more days, the inner surface of the cylinder corrodes. By sucking in warm or moist air, moisture may in fact possibly deposit on the colder inner surface of the cylinder. The rust formed by the condensed moisture destroys the sealing lips of the at least one seal on the piston upon further actuation of the hydraulic cylinder. Due to the damaged sealing lips, hydraulic oil can enter the second chamber, which oil is pressed outwards during the movement of the piston rod by an air filter which is in flow communication with the second chamber. This not only disables the air filter, but also disables the hydraulic cylinder. Repair is complicated and expensive.The present invention is directed to the elimination or at least mitigation of one or more of the foregoing disadvantages.SUMMARY OF THE INVENTIONAccording to a first aspect of the present invention, a lubricant ring is disclosed that is configured for installation in a hydraulic cylinder having a cylinder tube, a movable piston rod and a piston arranged on the piston rod, in order to supply lubricant to an inner cylinder surface of the cylinder tube. The lubricant ring according to the invention comprises a carrier ring having an outer ring surface for sliding along the cylinder inner surface of the cylinder tube of the hydraulic cylinder and an inner cavity. In the internal cavity of the carrier ring there is a receiving material which is designed for receiving and slow dispensing of a lubricant. In the outer ring surface, at least one through hole is present, which allows the lubricant accommodated in the receiving material to exit from the inner cavity onto the cylinder inner surface.The present invention is based on the idea of interposing a material having suitable sliding properties which satisfies the function between the receiving material which delivers a lubricant and the inner cylinder surface which is to be wetted with the lubricant, in order to reduce or even completely eliminate the problems which arise in the prior art owing to felt particles which are detached during the sliding movement of the known felt ring.For the first time, according to the invention, a separate carrier ring is present which holds the lubricant-storing material but prevents direct contact of this receiving material with the cylinder inner surface of the cylinder tube. At least the surface parts of the carrier ring that are in sliding contact with the cylinder inner surface or the entire carrier ring is made of a material optimized for the sliding movement. In other words, compared with the prior art, the function of sliding and the function of receiving and gradually discharging the lubricant are separated from each other. The "perforation" of the carrier ring outer surface nevertheless allows a suitable lubricant discharge onto the cylinder inner surface without damage to the sealing lips of the adjacent seals occurring as a result of material particles of the receiving material becoming detached.An exemplary embodiment of a lubricant ring according to the invention has a plurality of through holes distributed over a part of the outer ring surface. This allows optimized supply of lubricant to the cylinder inner surface and at the same time also limits the production cost for the through-holes.A further exemplary embodiment of a lubricant ring according to the invention has the plurality of through holes distributed over the entire outer ring surface, in particular they are uniformly distributed over the surface facing the cylinder inner surface. Thus, optimum formation of a lubricant film on the cylinder inner surface can be achieved.In a further exemplary embodiment of a lubricant ring according to the invention, a larger number of through-holes is arranged on an upper ring half of the outer ring surface than on a lower ring half of the outer ring surface.In this way, in the case of a horizontally installed hydraulic cylinder, it is better ensured that lubricant stored in the receiving material, such as oil, does not escape more quickly and frequently or exclusively at the lower ring half of the cylinder inner half.In a further exemplary embodiment of a lubricant ring according to the invention, the through-holes have different bore diameters. This allows a more specific distribution of the lubricant to specific, for example more highly loaded, segments of the cylinder inner surface.The shape of the lubricant ring and the number and size or the position of the bores can be adapted according to the installation position of the cylinder.In an advantageous embodiment, the present invention may also be based on the basic idea that the diameters and the number of through-holes are suitably selected in accordance with the diameter and the stroke of the cylinder, i.e. the larger the diameter of the hydraulic cylinder-and thus the cylinder inner diameter-the larger the number of through-holes and possibly also the bore diameter.In an advantageous embodiment of the present invention, the width of the oil-supplying carrier ring is preferably selected as a function of the cylinder diameter and the stroke and the desired operating conditions, such as number of stroke cycles, ambient temperature and cylinder installation position.In the case of larger cylinders, a plurality of lubricant rings may also be necessary in order to sufficiently wet large cylinder tube surfaces with oil and to provide sufficient oil to large sealing lip peripheries for sealing function and for preventing sealing lip wear.In order to make more lubricant available to the carrier ring or lubricant ring for a long operating period of the hydraulic cylinder than is possible by the predefined holding capacity of the holding or storage material, cavities can be created, in particular drilled, in the piston or in the piston rod, which cavities can be closed off from the outside but have at least one connection toward the carrier ring. Thus, refilling of the receiving material with lubricant such as oil is possible from the outside without the carrier ring having to be removed.By a suitable configuration of an air filter which is connected to the second chamber and an air outlet, for example valve-controlled, the air intake negative pressure can be controlled and the quantity of oil emerging from the carrier ring can thus be influenced in a suitable manner.In a further exemplary embodiment of a lubricant ring according to the invention, the carrier ring consists of a plastic material such as PTFE or other similar materials, which have suitable sliding properties and wear resistance. Materials which can be used as material for the carrier ring are in principle good sliding, low-wear sliding, oil-resistant and up to approximately 120° C. temperature-resistant materials, i.e. in particular polyamide (PA, nylon), polyoxymethylene (POM, acetal), polyetheretherketone (PEEK), polyphenylsulfide (PPS) or variants modified therefrom, such as nylon with silicone or teflon.In a further exemplary embodiment of a lubricant ring according to the invention, the carrier ring consists of a plurality of joined parts which are preferably joined together in a releasable manner. Furthermore, the plurality of parts of the carrier ring are preferably mechanically detachably connected to one another by a latching or plug connection. This configuration simplifies the production and the introduction of the receiving material.In a further exemplary embodiment of a lubricant ring according to the invention, the through-holes have a diameter equal to or greater than 0.5 mm, in particular 0.8 mm or 1.0 mm. On the one hand, this makes possible the stable distribution of the lubricant to the inner cylinder surface, and on the other hand, the manufacture of such a carrier ring is also possible at low cost.In another exemplary embodiment of a lubricant ring according to the invention, the ratio of the diameter of a through hole to the inner diameter of the cylinder inner surface is equal to or greater than 1 / 100, in particular greater than 1 / 48, experiments have shown that the distribution of the lubricant and the formation of a lubricant film are improved.In another exemplary embodiment of a lubricant ring according to the invention, the receiving material is an oil-absorbing or oil-adsorbing material, such as felt, nonwoven, polymer batt or foam, polypropylene mat, coke fiber, flaxseed, flax or other elastic materials with chemical additives which bind oil and slowly release it again. Preferably, a felt- or sponge-like material is also used, as has also been used hitherto in the form of a ring, i.e. now a felt ring which is impregnated with oil and is arranged within the carrier ring.In a further exemplary embodiment of the present invention, the carrier ring is open at both end faces so that the carrier ring can be inserted into a matching annular groove in the piston without having to be excessively stretched. The open carrier ring preferably has a somewhat larger outer diameter than the inner diameter of the cylinder tube, so that the ring always bears easily against the cylinder tube as a result of a memory effect.In a further exemplary embodiment of the present invention, the ring outer side of the carrier ring is curved inward, i.e. concave, so that the bearing surface or sliding friction surface is not too large and thus the heat generation on the carrier ring by sliding friction remains suitably low when the hydraulic cylinder is actuated.The design of the carrier ring can be adapted to the oil storage materials. For example, in the case of felt, the carrier ring is open on the inside and is covered only laterally and on the outer diameter.In a further exemplary embodiment of a lubricant ring according to the invention, a lubricating oil is provided as lubricant, with which the receiving material is impregnated in the carrier ring. In particular, all lubricants known hitherto for lubricating and forming a lubricating film can be used.A further exemplary embodiment of a lubricant ring according to the invention provides that a continuous transverse slot is present. On the one hand, this facilitates the insertion of a felt ring impregnated with oil into the carrier ring by the carrier ring being expanded somewhat with the use of force. The widening is of course also dependent on the material properties of the carrier ring. On the other hand, the transverse slot and its gap width also facilitate insertion into the piston.According to another aspect of the present invention, a hydraulic cylinder is disclosed that includes a cylinder tube, a piston rod slidably disposed in the cylinder tube, and a piston disposed on the piston rod. In addition, at least one lubricant ring disclosed herein is arranged on the piston.As in the prior art, this lubricant ring according to the invention makes it possible to discharge lubricant over a long period of time through the at least one through hole onto the cylinder inner surface and thus to form a lubricant film at each stroke of the hydraulic cylinder. However, the carrier ring reduces the risk that particles of the receiving material, such as felt in particular, separate and reach the inner cylinder surface. As a result, the sealing lips of the at least one seal arranged on the piston are not damaged. The operational reliability of the hydraulic cylinder is thus substantially improved and the downtime is consequently reduced.As already mentioned above, such a hydraulic cylinder is in particular a single-acting hydraulic cylinder. Lubricant rings according to the invention can, however, also be used in principle in other types of hydraulic cylinders which have a drying side to which no hydraulic oil is allowed to pass.Brief Description of the DrawingsThe following drawings illustrate exemplary embodiments of the present invention. It shows: FIG. 1 is a perspective view from obliquely above of a lubricant ring according to the invention; FIG. 2 is a right side view of the lubricant ring according to FIG. 1 ; FIG. 3 is a front view of the lubricant ring according to FIG. 2 ; FIG. 4 is a sectional view of the lubricant ring according to FIG. 2 ; FIG. 5 shows a detailed illustration "C" of an outer section according to FIG. 4 ; FIG. 6 shows a detail view "D" of the lubricant ring according to FIG. 2 ; and FIG. 7 shows a longitudinal section of a hydraulic cylinder according to the prior art.DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTIONThe following is a detailed description of exemplary embodiments of the present invention. The accompanying drawings merely illustrate the basic construction of these exemplary embodiments and are not intended to limit the scope of the appended claims.At the outset, for better understanding of the technical environment of the present invention, a hydraulic cylinder 100 according to the prior art is explained in more detail with reference to FIG. 7.The single-acting hydraulic cylinder 100 shown in FIG. 7 and known from the prior art comprises a cylinder tube 104, a piston rod 102 mounted displaceably therein and a piston 106 fastened to the piston rod 102 by means of a threaded pin 112. The piston rod 102 is guided over a plug 110 at a front end of the cylinder tube 104. A first chamber 120 is provided between the plug 110 and the piston 106. The chamber 120 is charged with hydraulic oil via a hydraulic connection 120.The piston 106 slides on a cylinder inner surface 108 of the cylinder tube 104 and creates a second chamber 124 in the cylinder tube 104.The piston 106 is provided with a guide ring 114 and a seal 116 arranged next to it, the sealing lips of which seal the first chamber 120 from the second chamber 124. It should be noted that the seal 116 is only schematically illustrated here.In a circumferential groove of the piston 106, a felt ring 118 known per se (only shown schematically here) is arranged, which is impregnated with lubricating oil. With each stroke of the piston rod 102 or a displacement of the piston 106 by hydraulic oil fed under pressure into the chamber 120, a lubricant film is produced on the cylinder inner surface 108 in order to lubricate the sealing lips of the seals 114, 116.For the sake of good order, it should also be noted that at the front end of the piston rod 102 there is a threaded connection piece 130, on which a workpiece or the like to be moved can be attached. The hydraulic cylinder 100 can be fastened via a fastening eye 132 at a suitable location of a machine or the like.When pressurized hydraulic oil is introduced into the first chamber 120 via the hydraulic port 122, the piston 106 shifts to the right in the initial position shown in FIG. 7 and pulls the piston rod 102 into the cylinder tube 104. In order to return the piston rod 102 to its initial position again, the hydraulic oil pressure in the connecting line to the chamber 120 is released, while, for example, an external tensile force such as a weight force pulls the piston rod to the left again. External air can be sucked into the chamber 124 filtered via a filter connection 126 via an air filter 128 arranged on the filter connection.Upon each relative displacement of the piston 106 in the cylinder tube 104, lubricating oil is discharged from the oil-impregnated felt ring 118 to the cylinder inner surface 108 and the sealing lips of the seal 116 are lubricated. However, there is the problem that, as mentioned at the beginning, individual fiber particles of the felt ring 118 are viewed under the sealing lips of the seal 116 and here through. Consequently, it may happen that, during each stroke, hydraulic oil passes from the first chamber 120 into the second chamber 124. This hydraulic oil can thereby enter the air filter 128 and damage or even destroy it. Furthermore, any moist air may precipitate on the cylinder inner surface 108 of the cylinder tube 104, which leads to corrosion and rust formation due to the deficient lubrication film. This grid can in turn further damage the sealing lips of the seal 116.The carrier ring 10 according to the invention shown in FIG. 1 has a ring shape interrupted by a transverse slot 26. As can be seen in particular from the side view of FIG. 2, the transverse slot 26 is formed on the left-hand ring half of the carrier ring 10. As can be seen, for example, in the further FIGS. 3 and 4, the transverse slot 26 has a "Z" shape.The outer side 18 of the carrier ring 10 is formed in the present exemplary embodiment of the invention by two rectilinear contact surfaces 20 a, 20 band an intermediate concave outer surface 22.Over the entire concave outer surface 22, a plurality of through-holes 24 are distributed, preferably in a regular distribution pattern. The through holes 24 extend through the wall of the carrier ring 10.As can be seen from the sectional view of FIG. 4, a felt ring 30 can be inserted inside the carrier ring. The felt ring 30 or any alternative material body 30 impregnated with lubricant is preferably provided with the same transverse gap as the carrier ring 10.Industrial applicabilityDuring operation of the hydraulic cylinder 100, hydraulic oil is introduced with pressure into the first chamber 120 via the hydraulic oil connection 122. This moves the piston 106 to the right from the position shown in FIG. 7. During the "life" and particularly during the sliding operation of the piston 106, lubricating oil passes from the felt ring 30 via the through holes 24 into the cavity bounded by the concave outer surface 22 and the cylinder inner surface 108 and forms a lubricating film on the cylinder inner surface 108.This lubricating film lubricates the sealing lips of the seals 116 and ensures their sealing function with respect to the hydraulic oil fed under pressure into the first chamber 120. At the same time, wetting of the cylinder inner surface 108 with lubricant is ensured even if the piston is displaced back into its original position to the left-see FIG. 7-by introducing compressed air into the second chamber 124.During the retracting and extending movement of the piston rod 102, the piston 106 moves relative to the cylinder inner surface 108, and during these sliding movements, lubricating oil constantly passes from the felt ring 30 through the through holes 24 onto the cylinder inner surface 108. As can be seen in particular in the representations of FIGS. 3-5, the outer surface 22 has a concavely curved surface 22, which is adjoined by sliding surfaces 20 a, 20 b. These sliding surfaces 20 a, 20 bare designed to slide along the cylinder inner surface 108 in an optimized manner by the material selection of the carrier ring 10. The inward curvature of the outer surface 22 forms a "depot" for lubricant such as oil leaking from the material 30, and a lubricating film is continuously maintained during the sliding movements of the piston 106.List of reference characters10 Carrier ring 12 Sliding wall 14 Carrier ring inner wall 16 Inner hollow space 18 Outer side of the carrier ring 20 a, b Contact surfaces 22 Concave outer surface 24 Through holes 30 Receiving material such as felt for lubricant such as e.g. oil 100 Hydraulic cylinder / single-acting 102 Piston rod 104 Cylinder tube 106 Piston 108 Cylinder inner surface 110 Closure plug 112 Threaded pin 114 Piston guide ring 1116 Seal 118 Hollow space for receiving a lubricant ring 120 First chamber 122 Hydraulic oil connection 124 Second chamber 126 Filter connection piece 128 Air filter 130 Threaded connection piece 132 Fastening eye

Claims

A lubricant ring configured for installation in a hydraulic cylinder (100) having a cylinder tube (104), a movable piston rod (102) and a piston (106) arranged on the piston rod (102), for supplying lubricant to an inner cylinder surface (108) of the cylinder tube (104), comprising: - a carrier ring (10) having an outer ring surface (20a, 20b; 22) for sliding along on the cylinder inner surface (108) of the cylinder tube (104) of the hydraulic cylinder (100) and having an inner cavity (124), - a receiving material (30) present in the inner cavity (124) of the carrier ring (10) and designed for receiving and slow discharging of a lubricant, and - at least one through hole (24) introduced in the outer ring surface (22) and allowing the lubricant received in the receiving material (30) to exit from the inner cavity (124) onto the cylinder inner surface (108).The lubricant ring according to claim 1, wherein a plurality of through holes (24) are distributed over a part of the outer ring surface (22).Lubricant ring according to claim 2, wherein the plurality of through holes (24) are distributed, in particular evenly distributed, over the entire outer ring surface (22).The lubricant ring according to claim 2 or 3, wherein a larger number of through holes (24) are arranged on an upper ring half of the outer ring surface (22) than are present on a lower ring half of the outer ring surface (22).The lubricant ring according to any one of claims 2 - 4, wherein the through holes (24) have different bore diameters.Lubricant ring according to one or more of the preceding claims, wherein the carrier ring (10) consists of a plastic material, e.g. PTFE or PTFE or similar materials, which have matching sliding properties and wear resistance, in particular polyamide (PA, nylon), polyoxymethylene (POM, acetal), polyetheretherketone (PEEK), polyphenylene sulfide (PPS) or variants modified therefrom, such as nylon with silicone or teflon.Lubricant ring according to one or more of the preceding claims, wherein the carrier ring (10) consists of several joined parts.The lubricant ring of claim 7, wherein the plurality of parts of the carrier ring (10) are detachably connected to each other.Lubricant ring according to claim 8, wherein the plurality of parts of the carrier ring (10) are mechanically detachably connected to one another by a snap-in or plug-in connection.Lubricant ring according to one or more of the preceding claims, which one or more through holes (24) have a diameter equal to or greater than 0.5 mm, in particular 0.8 mm or 1.0 mm.Lubricant ring according to one or more of the preceding claims, in which the ratio of the diameter of a through hole (24) to the inner diameter of the cylinder inner surface (108) is equal to or greater than 1 / 100, in particular 1 / 48.Lubricant ring according to one or more of the preceding claims, in which the receiving material (30) is a felt-like or spongy material.Lubricant ring according to one or more of the preceding claims, in which the lubricant is a lubricating oil, in particular a hydraulic oil or lubricating oil as was used in the prior art.Lubricant ring according to one or more of the preceding claims, in which the carrier ring (10) has a continuous transverse slot (26).Hydraulic cylinder (100) having: - a cylinder tube (104), - a piston rod (102) which is arranged displaceably in the cylinder tube (104), - a piston (106) which is arranged on the piston rod (102), and - a lubricant ring which is arranged on the piston (106), according to one or more of the preceding claims.The hydraulic cylinder (100) of claim 15, wherein the hydraulic cylinder is a single-acting hydraulic cylinder (100) in which the piston (106) divides the cylinder cavity into a first chamber (120) to be supplied with hydraulic oil and a second chamber (124).Hydraulic cylinder according to Claim 15 or 16, in which an air filter (128) is arranged in a filter connection piece (126) which is fluidically connected to the second chamber (124).

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