DE2414873A1 - PISTON CYLINDER ARRANGEMENT - Google Patents

Description

PATENT Attorney DIPL.-ING. GERHARD SCHWAN

OFFICE: 8000 MUNICH 83 ELFENSTRASSE 32

27 March 1974

72-MHI-493

24H873

EATON CORPORATION 100 Erieview Plaza, Cleveland, Ohio 44114, V.St.A.

Piston cylinder assembly

The invention relates generally to an overload protection device for use in vehicles and particularly relates to a piston-cylinder assembly for such vehicles.

The relevant technology has already dealt with the problem on various occasions, vehicles such as forklifts, lift trucks, pallet trucks and the like from tipping over (U.S. Patents 2,774,437, 2,767,394, and 3,059,701). Among other things, the circumstance exploited that the force that overturned the truck or the like seeks, is related to the force exerted on the push rod of one of the piston-cylinder assemblies, by means of which the mast is pivoted. One of the solutions assumes that the force acting on the push rod is directly related to the difference in pressures in the cylinder located pressure medium is on opposite sides of the piston of the existing piston-cylinder arrangement. the Working medium pressures prevailing on both sides of the piston are transmitted to a valve that responds to pressure, which is a prevents further pivoting when the torque that the

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TELEPHONE: 0811/6012039 CABLE: ELECTRICPATENT MUNICH

Seeks to tip over a lift truck or the like, has reached a dangerous level (US-PS 3 OO7 593). In order to be able to utilize the pressure difference principle effectively, a pressure other than zero must be transmitted from the piston side on which the greatest working medium pressure prevails. In the case of the known device (US Pat. No. 3,007,593), this is not taken into account. There the piston can rest against the end of the cylinder while the mast is pivoting, whereby the working medium _{pressure prevailing on this side of the piston becomes zero 5} so that the pressure-sensitive valve no longer responds correctly.

The invention is suitable for facilities such as counterbalance vehicles with a mast, boom, boom or other primary load link that is opposed to a frame or chassis by means of a piston-cylinder arrangement is movable interconnecting the primary load member and the frame, an arrangement being provided which senses the difference in pressures on opposite sides of the piston and sends a pressure difference signal to a Appropriate device transmitted to prevent further adjustment of the piston relative to the cylinder.

According to the invention, the forms through one end of the cylinder through the protruding piston or push rod of the piston-cylinder arrangement together with the cylinder an annular channel, which includes the push rod and with the outer space of the cylinder and with the chamber located in the cylinder on the push rod side of the piston is in communication. Funds are available

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see which seal the annular Καησχ when the piston is near is a cylinder end to include between the piston and the one end of the cylinder pressure medium and to prevent contact between the piston and the cylinder tail _s thereby ensuring that a positive pressure signal from the piston side to the Transmission to the pressure detection device is available. A resilient ring seal encompassing the rod is attached to one side of the piston and projects over the piston toward one end of the cylinder to encompass and seal the annular opening as the piston approaches one end of the cylinder.

According to a further feature of the invention, the annular Channel or passage with a pressure medium receiving Channel of a pressure medium circuit are brought into connection; another channel that connects to the outside of the cylinder and the Pressure medium in the chamber on the push rod side is in constant communication, is formed in the cylinder to generate a pressure signal to be transmitted to the pressure detection device. The other channel and the annular channel form separate different ones Passages from the chamber located at the push rod end of the cylinder to the space outside the cylinder.

The invention is shown below on the basis of a preferred exemplary embodiment explained in more detail. The attached drawings show: - -

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-A-

Figure 1 is a schematic representation of a hydraulic circuit with a piston-cylinder arrangement designed according to the invention and

Figure 2 is a sectional side view of one half of a piston-cylinder arrangement according to the invention.

1O

Figure 1 shows a hydraulic circuit / with a line 12, the one Pump 14 connects to a container 16. The pump 14 is connected to one connection of a reversing valve 2O via a line tied together. Another connection of the reversing valve 20 is connected to the container 16 via a line 22. Lines 24 and 26 are connected to further connections of the reversing valve 20. In one switching position of the reversing valve, the Line 18 to line 26 and line 22 to line 24 associated. In a second position, the line 18 comes with the line 24 and the line 22 with the line 26 in connection. In a third switch position, the line 18 connected to line 22.

A piston-cylinder assembly 28 has a piston 30, the one has an annular side 32 which delimits a first chamber 34 in the cylinder 36, and which is provided with a full-surface side 38 which helps to delimit a second chamber 40 in the cylinder. The line 24 and a line 41 are with the first and second chambers 34 and 40, respectively, via a first and a second end portion 42 and 44 in connection. A push rod

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is connected to the annular side 32 of the piston 30 and projects outwardly through a seal 48 from the first end portion 42 of the cylinder 36. A resilient seal 5O is attached to the annular side of the piston 3O and protrudes from this side. When the piston 30 approaches the first end section 42, the seal 50 closes the line 24 so that no pressure medium can pass from the first chamber 34 into the line 24.

A valve 52 has a valve piston 54 which is displaceable within a substantially cylindrical space 56 between a first and a second position. The valve piston 54 is provided with two end parts 58 and 60 which are rigidly connected to one another via a section 62 of reduced diameter. The end portions are slidingly engaged with the cylindrical wall of the space 56. The end part 58 is provided with an annular side 64 which also delimits a first chamber 66 within the space 56, while the end part 6O has a full-surface side 68 which helps delimit a second chamber 70 in the space 56. Two axially spaced apart annular spaces 86 and 88 are located between the chambers 66 and 70. Lugs 72 are attached to the annular side 64; they can come into contact with one surface of a wall 74 which separates the chamber 66 from a spring chamber 76 provided in the valve 52. One end of a rod 78 is attached to the end part 58 and extends through an opening in the wall 74 into the spring chamber 76. A ring seal 8O

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engages around the rod 78 and provides a separation between Chamber 66 and Spring Chamber 76. A preloaded compression spring 82 encompasses the rod 78 within the spring chamber 76. One end the compression spring rests against the wall 74, while the other end of the compression spring with a circular disc 84 is in contact, which is attached to the other end of the rod 78.

The valve piston 54 is shown in Figure 1 in the first position. The annular spaces 86 and 88 are connected to one another via the annular space surrounding the central section 62. Will When the valve piston 54 is displaced into the second position, the cylindrical jacket surface of the end part 58 seals the annular spaces 86 and 88 against each other. The lines 26 and 41 are in communication with the annular spaces 86 and 88, respectively. The valve piston 54 allows as long as it is in the first position, pressure medium can pass from the line 26 around the central section 62 to the line 41. If, on the other hand, the valve piston 54 is in the second position, the pressure medium flow from the line 26 is reduced by the Central section 62 interrupted around the line 41. Another line 90 is with the annular space 86 and the line 26 in Link. A one-way check valve 92 is located in the line 90; the pressure medium only reaches the line 26 from the annular space 86 leaves.

The pressures prevailing in the chambers 34 and 40 are passed through lines 94 and 96 transferred to the chambers 66 and 7O. The Ver-

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ratio between the surface of the annular side 32 and the The area of the full-surface side 38 of the piston is equal to that Ratio between the area of the annular side 64 and the surface of the full-surface side 68 of the valve piston 54. The Displacement of the valve piston 54 is caused by the preload and the spring stiffness of the compression spring 82 as well as by the difference the pressures of the pressure medium in the chambers 34 and 40 are determined. The preload of the spring depends on the maximum tensile force, which is to act on the push rod 46 before the valve piston 54 begins to move from the first to the second position. The stiffness of the spring is increased by the additional pressure increase determined, which is desired for the transition of the valve piston 54 from the fully open to the fully closed position.

When the on the annular side 64 by the pressure of the "pressure medium force exerted in the chamber 66 exceeds the resultant of the forces exerted by the pressure of the pressure medium in the chamber 70 are exerted on the full-surface side 68 and by the bias of the compression spring 82, the valve piston 54 begins to move to the left in Figure 1 towards the second position. As the amount exerted on the annular side 64 increases Force against the force acting on the full-surface side 68 is reached. A point at which the end part 58 den Annular space 86 separates from the annular space 88.

The piston 30 would be against the first end 42 of the cylinder 36 would apply that exerted on the annular side 32

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Force can be transmitted directly to the first end of the cylinder; as a result, the working medium pressure in the chamber 34 would increase Zero. In such a case, the valve piston 54 would no longer respond to the tensile force exerted on the push rod 46, because the pressure of the pressure medium in the chamber 66 would also become zero. The seal 5O prevents this from happening by it blocks the line 24 and traps a certain amount of pressure medium between the piston 3O and the first end 42. the The seal is compliant to prevent significant pressure transfer from the piston to the first end of the cylinder. As a result of that a certain amount of pressure medium is trapped between the piston and the first end of the cylinder, lead to increases in the push rod 46 exerted tensile force to corresponding increases in the pressure of the pressure medium in the chamber 34, whereby the Pressure of the pressure medium in the chamber 66 increases accordingly.

The piston-cylinder arrangement 28 is illustrated in detail in FIG. It has an annular housing part 98 which delimits a space 100 by means of the first and the second End portion 42 and 44 is complete. The piston 30 is in sliding engagement with the space-defining inner surface of the Housing part 98 and has flexible seals 99 which prevent the passage of pressure medium between the chambers 34 and 40. The push rod 46 has a shoulder 102 which rests against the piston 30. A nut 104 is on the push rod 46 screwed on to hold the push rod and piston together. Resilient seals 1O6 in the first end section

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are arranged, include the push rod 46. The end portion 42 is provided with a ring plate 108 connected to the body of the end portion 42 via screws 110, of which only one is shown and the one in the circumferential direction around the push rod 46 are arranged distributed around. An annular opening 112 in plate 108 defines an annular passage therebetween the push rod 46 and the plate 108, which communicates with the chamber 34 and an annular space 114 in the first end portion 42 stands. The annular space 114 is in turn connected to the line 24. Ring seals 116 are located between the plate and the body of the first end portion 42 to provide a passage to prevent pressure medium between these two components. The line 94 communicates with the chamber 34 via one through the first End portion 42 extending through passage 117 in connection. As shown in Figure 2, the passage 117 must be so arranged be that it cannot be shut off by the piston 30.

On the annular side of the piston 30 there is an annular space 118, which is bounded by the outer surface of a truncated cone. The annular space 118 is concentric with the rod 46; be Cross-section widens in Figure 2 from left to right. At the left end of the annular space 118 there is an enlarged one Annular groove with a conical outer surface 12O, which widens from right to left in the figure and which is at the end of the the surface delimiting the annular space 118 begins. A compliant annular seal 122 is corresponding to the conical outer

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surface 120 formed and lies next to the piston 3O against the cylindrical outer surface 128 of the push rod 46, the other The end of the seal 122 protrudes outwardly from the outer surface 130 of the Piston 3O away into the chamber 34 and has a plate-shaped Opening 132 which converges outward from left to right in FIG. 2 and that of the outer surface of a truncated cone is formed. The plate-shaped opening 132 ends at one circular outer edge 134. The diameter of the outer edge is larger than the diameter of the annular opening 112 in FIG of plate 1O8. The cylindrical outer surface 136 of the annular Seal 122 is spaced from the wall of the conical annulus 118.

In operation, the reversing valve 20 is adjusted so that on the one hand the lines 18 and 26 and, on the other hand, the lines 22 and 24 are connected to one another. This is pressure medium in the Chamber 40 introduced and discharged from chamber 34; The piston 3O is shifted to the right in FIG. When the piston 30 arrives in a position near the end 42, the outer edge 134 of the gasket 122 lies against the surface 138 of the plate 1O8, causing the annular passage 112 against the chamber 34 is sealed. After the passage 112 has been sealed, no pressure medium can flow out of the chamber 34; another Adjustment of the piston 3O to the right in FIG. 2 only leads to an increase in pressure in the chamber 34. The seal 122 can under give in to the force due to the adjustment of the piston to the right and is finally compressed in such a way that

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that their shape partially adapts to the annular space 118. As a result of the over the outer surface13O of the piston 30 in the direction of the End portion 42 protruding part of the seal 122 comes the Outer surface 13O of the piston 3O, however, at no time the surface 138 of the cylinder 36 in contact. After yourself the ring seal 122 partially adapted to the shape of the annular space 118 has, the remaining one protruding beyond the outer surface 13O becomes Part of seal 122 between surfaces 130 and 138 pressed together. The seal 122 lies under the influence the radial forces generated by the pressure in the chamber 34 Pressure medium are exerted firmly against the push rod 46. If the piston 30 is to move to the left in FIG. 2, the reversing valve is brought into the position shown in FIG. Pressure medium is applied via line 24 against the seal 122 pressed. The seal 122 gives way and lets pressure medium in enter chamber 34. At the same time can be located in the chamber 4O Pressure medium via the line 41 and either past the central section 62 or through the check valve 92 reach the line 26 and the container 16.

The hydraulic circuit of Figure 1 can be used in the same way are like part of that illustrated in U.S. Patent 3,07,593 and described hydraulic circuit. For example, in the case of an arrangement according to FIG. 3 of this patent specification, this can be the case valve 52 described can be used instead of the valve 16 present there, while instead of the known swivel cylinder 6 the piston-cylinder assembly 28 according to the invention can be provided.

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Claims (8)

24U873 - 12 claims ί1 J Pressure medium-actuated piston-cylinder arrangement for use in a pressure medium circuit with a pressure medium supply channel and a pressure medium receiving channel, characterized by a housing with a housing part arranged between a first and a second end part, which together with the end parts delimits a space, one housed within this space and with the housing part slidingly engaged piston dividing the space into first and second chambers, the first chamber being partially delimited by the first end part, a rod connected to the piston and protruding from the space through the first end part, the first end part and the rod delimiting therebetween an annular passage which can constitute a single connection between the first chamber and the pressure medium receiving channel, as well as by a sealing arrangement which seals the annular passage when the piston is near but spaced apart from the first end portion to confine a certain amount of pressure medium in the first chamber between the piston and the first end portion and to prevent contact between the piston and the first end portion. 2. Piston-cylinder arrangement according to claim 1, characterized in that that the sealing arrangement is a resilient member comprising the rod, one end of which engages the piston and its other end away from the piston in the direction 409841/0330 24U873 protruding onto the first end portion of the housing, the outer Portion of the other end of the resilient member is sized to include the annular passage. 3. Piston-cylinder arrangement according to claim 1, characterized by Means defining a further passage in the housing, that of the first chamber and the space outside the housing communicates and is arranged so that it is included with Pressure medium quantities comes into contact. 4. Piston-cylinder arrangement, characterized by a housing with one arranged between a first and a second end part Housing part which, together with the end parts, defines a cavity, one housed within this cavity and piston engaging the housing portion between the cavity defining surfaces of the end portions is adjustable, a rod connected to the piston and protruding from the cavity through the first end part, which together with the first end part defines an annular passage which communicates with the cavity and with the space outside of the housing is in communication, as well as by an annular resilient member comprising the rod, one of which End engages the piston and the other end of which projects away from the piston towards the first end portion and comes into contact with the cavity defining surface of the first end portion when the piston is in a predetermined Distance from the first end part, with the other A09841 / 0330 End of the resilient member has such a cross-section that it communicates with the cavity part of the comprises annular passage and maintains a certain amount of pressure medium between the piston and the first end portion, when the other end of the resilient member comes into contact with the first end portion, in this way an immediate To prevent contact between the piston and the first end portion. 5. Piston-cylinder arrangement according to claim 4, characterized in that that the piston forms an annular opening, the resilient member has a substantially cylindrical shape and that one end of the resilient member is provided with an annular shoulder which is connected to the annular opening of the Piston is engaged. 6. piston-cylinder arrangement according to claim 4, characterized in that that the piston delimits a conical opening, the largest cross-sectional area of which is near the end face of the piston which is facing the surface of the first end portion delimiting the cavity, and that the resilient member has a has a substantially cylindrical outer surface which is concentric with and in the region of the conical opening, so that a contact between the other end of the resilient member and the first end part a compression of at least one Nes portion of the resilient component and a deflection of the same into the conical opening results. 4098-1 / 0330 2AH873 7. Piston-cylinder arrangement according to claim 4, characterized in that that a plate-shaped opening is provided at the other end of the flexible component, the annular passage Has circular shape and the other end of the resilient component is provided with a circular outer edge, the diameter of which is larger than the diameter of the annular passage and which is the outer limit of the plate-shaped opening forms. 8. Piston-cylinder arrangement according to claim 4, characterized by means in the housing one with the first chamber and limit the space outside the housing communicating passage separated from the annular passage and is arranged to communicate with the space between the piston and the first end portion. 409841/0330 Lee rs ei te