EP0786599A2 - Fluid pressure operating means with a cylinder and a plunger piston - Google Patents

Abstract

The plunger piston (3) can be withdrawn from the passage bore (13) in the abutment and from the sealing ring (8), without dismantling the abutment. The abutment is formed as a sliding body, and forms a diametrical dove-tail connection with the end of the cylinder (1). When in inserted position, the abutment is locked by the piston relative to the cylinder. The dove-tail connection has two diametrically opposite slide rails, which are inserted into complementary cross grooves (9, 10) in the cylinder. The sliding body has a ring groove (16) with stripper ring.

Description

The invention relates to a pressure medium drive with a cylinder with a cylinder chamber, a radially guided piston, a sealing ring and an exchangeable abutment with a through hole for the piston and with a contact surface for the sealing ring.

Such pressure medium drives, which are generally designed as hydraulic drives, are required in large numbers, for example for industrial trucks such as forklifts, etc. There is an abutment at the end of the cylinder, which at least partially also serves as a guide for the plunger. This abutment also absorbs the axial forces of the sealing ring.

From DE 36 35 010 A1 it is known in a generic pressure medium drive to pass a rack, which is connected to a piston, through an abutment, namely through a work space end piece, each with an inner and an outer seal, and the abutment by a radially preloaded , a circlip consisting of a round wire in the cylinder to be determined. Since the piston has a larger diameter than the rack, the rack cannot be pulled out of the abutment. Rather, the retaining ring must be inserted into the narrow annular gap between the toothed rack and the cylinder by means of a tool and, in the event of a repair, also removed from the annular gap. Manufacturing and repair are therefore complex, and the round wire is a weak point for extremely high working pressures for numerous applications.

From US 33 91 612 it is known to connect a piston seal with a larger cross-section to the piston of a hydraulic motor by means of a dovetail connection to the piston. In order to be able to establish and release this connection, a radial opening is provided in the cylinder wall, which is closed by a cover with screws that can only be released by a tool. The piston itself must remain in the cylinder until the piston seal is removed; nothing is disclosed about pulling out of the bore of an abutment. Regarding a closure wall located at the end of the cylinder, which can be referred to as an abutment, it is stated that this is also inserted and removed through an identical radial opening in the cylinder wall. A seal change and the associated design are complex, especially since no extruded profiles can be used to manufacture the cylinder. In addition, the radial mounting shafts for the seals with their lids represent marked weak points in relation to high pressures.

All known types of fastening are either indefinite or complex, taking into account that such pressure medium drives are required in large numbers.

The invention is therefore based on the object of specifying a pressure medium drive which can be produced simply and using fewer parts is, in which the abutment has a precise fit and the sealing ring is easily replaceable.

• a) der Kolben als Tauchkolben ausgebildet ist, der ohne Demontage des Widerlagers aus der Durchtrittsbohrung und aus dem Dichtungsring herausziehbar ist,
• b) das Widerlager als Schiebekörper ausgebildet ist und mit dem Ende des Zylinders eine diametrale Schwalbenschwanzverbindung bildet und daß
• c) das Widerlager in eingeschobener Lage durch den Kolben gegenüber dem Zylinder arretiert ist.

The problem is solved in the pressure medium drive specified at the outset according to the invention in that

• a) the piston is designed as a plunger which can be pulled out of the through bore and out of the sealing ring without dismantling the abutment,
• b) the abutment is designed as a sliding body and forms a diametrical dovetail connection with the end of the cylinder and that
• c) the abutment is locked in the inserted position by the piston relative to the cylinder.

It is particularly advantageous if the dovetail connection has two diametrically opposed sliding strips which are inserted into complementary transverse grooves in the cylinder.

It is also advantageous if the piston is guided in a guide ring inserted into the cylinder chamber and if the sealing ring is arranged between the guide ring and the sliding body, in particular if the guide ring consists of a lubricious plastic and is arranged in a stepped bore in the cylinder chamber.

In the subject matter of the invention, only a small number of parts are required, of which the abutment assumes a precise fit in the open end of the cylinder, takes over at least part of the piston guidance, ensures precise support for the sealing ring and enables its replacement in a simple manner. Special Sleeves and threaded holes at the cylinder end are not required, as are no additional sealing plates and no sealing rings.

The plunger itself serves in a surprisingly simple way as a locking device for the sliding body; no further fasteners are required. As long as the plunger is pushed into the cylinder piston, the sliding body cannot be pushed out of the transverse grooves in the cylinder. If the plunger is pulled out of the cylinder, the sliding body can be pushed out of the transverse grooves perpendicular to the longitudinal axis of the cylinder, so that the sealing ring can then be pulled out of its stepped bore without special tools and replaced with a new sealing ring. The sliding body can also be reused as often as required.

It is particularly advantageous in the course of an embodiment of the invention if the sliding body has a rectangular outline in the axial direction of view (which is also to be understood as a square outline) and if the sliding strips are arranged on two opposite sides of the rectangle.

In the course of a further embodiment of the invention, it is again particularly advantageous if the sliding body is provided with an annular groove within the through bore for the plunger, into which a scraper ring is inserted.

This scraper ring can also be easily levered out of the ring groove and replaced with a new one. As long as the wiper ring is reusable, it remains in the sliding body and can be inserted into the transverse grooves again after the sealing ring has been replaced, whereupon it is locked again by the plunger.

Further advantageous embodiments of the subject matter of the invention emerge from the remaining subclaims.

Two exemplary embodiments of the subject matter of the invention are explained in more detail below with reference to FIGS. 1 to 8.

Figur 1

einen teilweisen Axialschnitt durch einen vollständigen Druckmittelantrieb,

Figur 2

eine stirnseitige Ansicht des Gegenstandes nach Figur 1 in Richtung des Pfeils II,

Figur 3

das linke Ende von Figur 1 in vergrößertem Maßstab,

Figur 4

einen Axialschnitt durch den Schiebekörper entlang der Linie IV-IV in Figur 5,

Figur 5

eine Ansicht des Schiebekörpers nach Figur 4, in Richtung des Pfeils V,

Figur 6

einen Axialschnitt durch einen doppelseitigen Druckmittelantrieb gemäß Figur 1, wie er beispielsweise für sogenannte Seitenschiebereinrichtungen für Gabeln von Gabelstaplern verwendet werden kann,

Figur 7

eine Explosionsdarstellung des Gegenstandes nach den Figuren 1 bis 5 im Zusammenhang mit einem Doppelzylinder nach Figur 6 und

Figur 8

eine Variante des Gegenstandes nach Figur 1 in Explosionsdarstellung.

Show it:

Figure 1

a partial axial section through a complete pressure medium drive,

Figure 2

2 shows an end view of the object according to FIG. 1 in the direction of arrow II,

Figure 3

the left end of Figure 1 on an enlarged scale,

Figure 4

5 shows an axial section through the sliding body along the line IV-IV in FIG. 5,

Figure 5

3 shows a view of the sliding body according to FIG. 4, in the direction of arrow V,

Figure 6

2 shows an axial section through a double-sided pressure medium drive according to FIG. 1, as can be used, for example, for so-called side shift devices for forks of forklift trucks,

Figure 7

an exploded view of the object according to Figures 1 to 5 in connection with a double cylinder according to Figure 6 and

Figure 8

a variant of the object of Figure 1 in an exploded view.

1 shows a cylinder 1 with a cylinder chamber 2, in which a plunger 3 is arranged, which is also referred to as a plunger. Due to a difference in diameter between the cylinder chamber 2 and the plunger 3, an annular gap 4 is formed, into which a connection bore 5 opens for a hydraulic line, not shown.

The end of the cylinder chamber 2 is slightly enlarged in diameter, and a guide ring 6 is used in this extension, which is made of a good sliding plastic, such as polyamide. This extension is followed by a stepped bore 7 into which a sealing ring 8 is inserted, which is designed in the manner shown as a groove or lip ring.

This stepped bore 7 is in turn connected to two mutually parallel transverse grooves 9 and 10, which have a prismatic cross section and run across the entire cylinder 1, i.e. are open at both ends. In the direction of the end of the cylinder 1, these transverse grooves 9 and 10 are each delimited by a claw 11 which runs parallel to the respective transverse groove 9 and 10 and forms a sliding fit with each.

In the transverse grooves 9 and 10, a sliding body 12 is inserted in the diametrical direction, which has a through bore 13 for the plunger 3. As can be seen from Figure 1, the sliding body 12 forms an abutment for the sealing ring 8, which is in the direction of the cylinder opening under the pressure of the hydraulic fluid, which is up to 300 bar, but this value does not represent a critical upper limit.

As can be seen from FIG. 2, the sliding body 12 can be pushed out in both directions according to the double arrow 14 perpendicular to the axis A. In the axial direction, however, the sliding body 12 is reliably held by the transverse grooves 9 and 10 or by the claws 11.

As can additionally be seen from FIG. 3, the sliding body 12 has a contact surface 15 for the sealing ring 8 and, on the opposite side within the through bore 13, an annular groove 16 (FIG. 4) for receiving a wiper ring 17. This wiper ring can be reused depending on the findings; it does not require a metal frame, since the sliding body 12 also takes on this function. As can be seen particularly from FIG. 3, the scraper ring 17 is held in all directions by the walls of the annular groove 16 and by the plunger 3; However, after pulling out the plunger 3, it can easily be levered out or rolled out.

As can be seen from FIGS. 4 and 5, the sliding body 12 has a rectangular outline in the axial viewing direction according to the arrow V, two mutually parallel sliding strips 18 and 19 being arranged on two opposite sides of the rectangle R, which likewise have a prismatic cross section and are arranged and formed complementary to the transverse grooves 8 and 9. This results in a type of dovetail connection between the sliding body 12 and the cylinder 1, which ensures an extremely exact fit of the sliding body 12.

• 1. Tauchkolben herausziehen,
• 2. Schiebekörper 12 seitlich aus den Quernuten 9 und 10 herausschieben,
• 3. Dichtungsring 8 und ggf. auch Abstreifring 17 auswechseln,
• 4. Schiebekörper 12 von der Seite her wieder einschieben und
• 5. Tauchkolben in axialer Richtung einschieben.

FIG. 6 also shows a double cylinder 20 with two cylinder chambers 2a and 2b, which are separated from one another by a partition wall 21. The two cylinder chambers 2a and 2b can be acted upon independently of one another by two connection bores 5a and 5b. Since such a plunger requires an external stop to limit the stroke, such pressure medium drives are preferred, however not exclusively, used in so-called side shift devices with a side shift frame 22, the upper part of which, like the plungers 3a and 3b, are shown in broken lines in FIG. By alternately acting on the two plungers 3a and 3b, the sideshift frame 22 can be shifted by the dimension "s" on both sides. For example, when the plunger 3a is pushed out further, the plunger 3b is pushed back by an identical amount. In any case, however, the side shift frame 22, which forms the necessary stops, prevents the plungers 3a and / or 3b from escaping. After removing the sideshift frame 2, the sealing rings 8 and possibly also the wiper rings 17 can be replaced as follows:

• 1. Pull out the plunger,
• 2. Push the sliding body 12 sideways out of the transverse grooves 9 and 10,
• 3. Replace sealing ring 8 and, if necessary, wiper ring 17,
• 4. Push the sliding body 12 in again from the side and
• 5. Insert the plunger in the axial direction.

The idea of the invention can be used both in cylinders with a rectangular or square outer contour (FIG. 7) and in cylinders which have, for example, an outer cylinder surface (FIG. 8). In FIGS. 7 and 8, identical parts are provided with the same reference symbols. In FIG. 8, the cylinder 1 according to FIG. 1 is replaced by a cylinder 23 with a cylindrical outer surface which has a corresponding wall thickness in order to enable the transverse grooves 9 and 10 and the sliding strips 18 and 19 to have a sufficient length.

Claims (7)

Pressure medium drive with a cylinder (1, 23) with a cylinder chamber (2, 2a, 2b), with a radially guided piston (3, 3a, 3b), a sealing ring (8) and an exchangeable abutment (12) with a through hole (13 ) for the plunger (3, 3a, 3b) and with a contact surface (15) for the sealing ring (8), characterized in that a) the piston (3, 3a, 3b) is designed as a plunger which can be pulled out of the through bore (13) and out of the sealing ring (8) without dismantling the abutment (12), b) the abutment (12) is designed as a sliding body (12a) and forms a diametrical dovetail connection (9/18 and 10/19) with the end of the cylinder (1, 23) and that c) the abutment (12) is locked in the inserted position by the piston (3, 3a, 3b) relative to the cylinder (1, 23). Pressure medium drive according to claim 1, characterized in that the dovetail connection (9/18 and 10/19) has two diametrically opposed sliding strips (18, 19) which are inserted into complementary transverse grooves (9, 10) in the cylinder (1, 23). Pressure medium drive according to claim 1, characterized in that the sliding body (12) has a rectangular outline in the axial viewing direction, and that the sliding strips (18, 19) are arranged on two opposite sides of the rectangle (R). Pressure medium drive according to claim 1, characterized in that the sliding body (12) is provided within the through bore (13) with an annular groove (16) into which a wiper ring (17) is inserted. Pressure medium drive according to claim 1, characterized in that the piston is guided in a guide ring (6) inserted into the cylinder chamber (2, 2a, 2b) and that the sealing ring (8) is arranged between the guide ring (6) and the sliding body. Pressure medium drive according to claim 4, characterized in that the guide ring (6) consists of a slidable plastic. Pressure medium drive according to claim 4, characterized in that the sealing ring (8) is arranged in a stepped bore (7) of the cylinder chamber (2, 2a, 2b).

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