Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B66—HOISTING; LIFTING; HAULING
  • B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
  • B66C23/00—Cranes comprising essentially a beam, boom, or triangular structure acting as a cantilever and mounted for translatory of swinging movements in vertical or horizontal planes or a combination of such movements, e.g. jib-cranes, derricks, tower cranes
  • B66C23/62—Constructional features or details
  • B66C23/72—Counterweights or supports for balancing lifting couples
  • B66C23/78—Supports, e.g. outriggers, for mobile cranes
  • B66C23/80—Supports, e.g. outriggers, for mobile cranes hydraulically actuated
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B13/00—Details of servomotor systems ; Valves for servomotor systems
  • F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
  • F15B13/04—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor
  • F15B13/0401—Valve members; Fluid interconnections therefor
  • F15B13/0402—Valve members; Fluid interconnections therefor for linearly sliding valves, e.g. spool valves

Definitions

• This invention relates to a device in pilot-con ⁇ trolled non-return valves for hydraulic mechanisms of the type incorporating in its cylinder a reciprocable piston having at least one piston rod and dividing the interior of the cylinder into first and second chambers which are connectible via first and second conduits to a pump and a tank via a directional valve, e.g.
• a slide valve which in one of two alternative, operative setting positions, on the one hand, enables feeding hydraulic oil or fluid to one of the chambers while oil is evacuated from the other, and in an inoperative, closing position, on the other hand, interrupts the communication between the cylinder and the pump and tank, the non-return valve being provided between the cylinder and the directional valve and comprising a spring-biased valve member, e.g.
• a ball or cone which is applicable against a seat and serves, when in a first operational state, to allow oil to flow in the direction of the first chamber of the cylinder, but preclude flow in the opposite direction to prevent the piston from moving into the cylinder, as well as a pilot piston integrated in a housing and serving, when in another operational state when the oil pressure in the second chamber starts exceeding a certain limit or threshold value, to remove the valve member via a pin or pin-like part from the associated seat so as to permit oil to flow through the first conduit in a direction away from the first chamber for evacuating this chamber.
• FIG. 1 schematically illustrates a hydraulic cylinder mechanism with associated directional and non ⁇ return valves of a general design
• FIG. 2 is an enlarged longitudinal section of a main non-return valve designed in accordance with the invention, to which also the hydraulic cylinder is shown schematically connected
• FIG. 3 schematically illustrates an alternative embodi- ment of the invention.
• reference numeral 1 generally designates a hydraulic cylinder mechanism, 2 a directional valve in the form of a slide valve, and 3 a main non-return valve.
• the cylinder 4 of the mechanism 1 comprises in conven ⁇ tional manner an axially reciprocable piston 5 having a piston rod 6.
• the piston rod 6 is schematically shown provided with a foot plate 7 at its free end.
• the piston 5 divides the cylin ⁇ der 4 into two chambers, namely a first chamber 8 and a second chamber 9.
• the first chamber 8 will also be refer ⁇ red to hereinafter as the piston side of the cylinder, while the chamber 9 is referred to as the piston-rod side.
• the inven ⁇ tion does not preclude the possibility of providing the piston 5 with two piston rods, e.g. two piston rods hav ⁇ ing different diameters on opposite sides of the piston, although in practice only one piston rod is normally used for the piston.
• a first conduit generally designated 10
• a second conduit generally designated 11
• a pump schematically illustrated, is designated 12 and a tank is designated 13.
• the directional valve 2 serves to distribute the oil flow from the pump 12 alter- natingly to the cylinder chambers 8, 9 while the return flows therefrom are led back to the tank 13.
• the directional valve 2 generally is in the form of a slide valve comprising a rod-like slide member 14 which is axially movable back and forth in a bore provided in a block 15.
• the valve 2 is illustrated highly schematically in Fig. 1.
• the slide member or rod 14 has a number (here two) of grooves or recesses 16 cooperating with a number of ports 17, 18, 19, 20 and 21 provided in the block.
• the ports 18 and 20 are connected to the conduits 10 and 11, respectively.
• the port 19 is connected to a feed conduit or duct 22, which is connected to the pump 12.
• the ports 17, 21 are connected to the tank 13 via one or more return conduits or ducts 23.
• the port 21 is also connected to the conduit 11 via a drain passage 24 having the nature of a constriction or throttle.
• the slide member 14 is shown in an inoperative, closing position, in which it precludes all communication between the cylinder 4, on the one hand, and the pump 12 and the tank 13, on the other hand. However, by moving the slide member 14 axially to a suitable position, oil from the pump 12 can be caused to flow to either the chamber 8 or the chamber 9 while evacuating the other chamber.
• the port 19 will be opened and permit oil to flow from the pump 12 to the first chamber 8, more specifically through the conduit 10 via the main non-return valve 3.
• the port 20 is opened and allows oil from the second chamber 9 to flow back to the tank 13.
• the directional valve 2 is gene ⁇ rally connected to far more components in a hydraulic system than only a single hydraulic cylinder.
• the directional valve may also serve to direct oil flows as desired to several hydraulic cylinders included in a vehicle crane.
• the valve block 15 has as many pairs of ports with associated conduits as the number of hydraulic cylinders or functions.
• the non-return valve in- eludes a valve member 25 which, in this case, is in the form of a ball biased by a spring 26 and engaging a seat 27 in a passage through a schematically illustrated block or housing 28.
• the valve ball 25 divides the first con ⁇ duit 10 into two portions 10', 10", of which the first extends between the first cylinder chamber 8 and the non ⁇ return valve, while the second extends between the non ⁇ return valve and the directional valve. It will be appre ⁇ ciated that the ball 25, when acted on only by the spring 26, permits oil to flow in one direction only, namely in the direction of the first chamber 8.
• the housing 28 fur ⁇ ther accommodates a pilot piston 29 which in known manner is biased by a spring 30 and which is provided with a pin or pin-like part 31 which, when the pilot piston 29 is acted on by an oil pressure overcoming the force exerted by the spring 30, serves to lift the ball 25, i.e. to remove it from the seat 27 with a view to allowing oil to flow in a direction away from the first chamber 8 through the conduit 10.
• the hydraulic system illustrated in Fig. 1 is substantially previously known.
• the pilot piston 29, designed in accordance with the invention divides the conduit 11 into two conduit por ⁇ tions 11*, 11", as will be discussed in more detail below.
• Such a division of the conduit extended from the piston-rod side of the cylinder into two particular por ⁇ tions or sections is not known in conventional non-return valves for support-leg cylinders. Background of the Invention and Prior Art When a hydraulic cylinder of the type described above is used for operating a support leg it is of vital importance that the piston of the cylinder can always be reliably held in a given setting position.
• the support leg If the support leg is retracted to its inoperative initial position, it is important that it be retained in this position so that the lower, movable telescopic tube of the leg does not start sliding out during travel. If the support leg is in an operative state with its foot plate engaging the sup ⁇ porting surface, it is also important that the piston be retained in its given, current position, for, whether the piston tends to move into or out of the cylinder, the stability of the crane supported by the support legs is jeopardised. An especially adverse situation is when the piston tends to move into the cylinder, thereby shorten- ing the support leg.
• a serious drawback of previously known hydraulic systems or devices for adjusting support legs is that there may occur in different parts of the hydraulic sys ⁇ tem amounts of excess oil or oil-pressure imbalance tend- ing to set the cylinder piston in motion in an uncontrol ⁇ led and undesired manner.
• One reason for such uncontrol ⁇ led piston movements is to be found in the directional valve, especially when this is a slide valve. Even if the measurement accuracy of the slide member and the sur- rounding valve block is excellent, it is impossible to prevent oil leakage between different ports in the valve. This takes place also at relatively low oil pressures in the system. Assume that oil leaks into the port 18 (see Fig. 1) when the slide member is in its inoperative, closing position for retaining the piston 5 in a given, stationary state.
• the present invention aims to overcome the above- mentioned drawbacks and make it possible, in a given set ⁇ ting position, to reliably retain the piston in a hydrau- lie cylinder, especially a hydraulic cylinder for operat ⁇ ing support legs, while obviating the risk of bursting.
• the invention is based on the insight that it is not pos ⁇ sible in practice to take any additional measures in the slide valve or directional valve that would eliminate with certainty oil leakage between different ports.
• a basic object of the invention thus is to design the part of the hydraulic system which is separate from the slide valve in such a manner that the piston of the cylinder is not set in motion uninten ⁇ tionally or in an uncontrolled manner as a result of oil leakage between the ports of the slide valve.
• Another object is to obviate the risk of oil-pressure rises in the system as a result of temperature variations in the surroundings of the cylinder.
• Yet another object of the invention is to realise the aimed-at piston-retaining function with the aid of simple and inexpensive means, which should be incorporable in the hydraulic system in a convenient manner without appreciably affecting the external design of the hydraulic cylinder.
• the invention is based on the idea of dividing, with the aid of a valve means that provides an additional valve or closure function, the second conduit extending between the piston-rod side of the cylinder and the directional valve into two portions, of which a pri- mary portion can be maintained pressurised while a secon ⁇ dary portion can be maintained substantially unpressur- ised, there being further provided in or in association with the conduits at least one drain passage enabling drainage of leaking excess oil which tends to set the piston in uncontrolled motion.
• substantially unpressurised should be inter- preted such that in the secondary portion of the second conduit there may very well, in practice, exist a certain residual pressure (the conduit portion concerned is not evacuated), but this residual pressure, if any, is negligible compared with the working pressures normally prevailing in the other portions of the conduits.
• the invention can be implemented in several alternative ways.
• the above- mentioned valve means is integrated with the pilot piston of the main non-return valve, more specifically by being designed as a portion of the piston itself.
• the valve means concerned it is also possible within the scope of the invention to arrange the valve means concerned separate from the main non-return valve. This embodiment is however more expen ⁇ sive and requires more space than the preferred embodi ⁇ ment.
• the addi ⁇ tional valve or closure function characteristic of the invention, is integrated in the pilot piston 29. More specifically, the lower end of the piston 29 is formed with a conical portion 32, which cooperates with a seat 33 formed in the housing 28. The piston portion 32 and this seat separate the conduit portions 11', 11" from each other.
• the pilot piston 29 see Fig.
• a secondary non-return valve 34 which, on the one hand, prevents oil from flowing from the second con ⁇ duit 11 into the space 35 in the housing 28, in which the piston 29 is movable back and forth and in which the spring 30 is mounted, and which, on the other hand, enables evacuation of excess oil which originates from the first conduit 10 and has penetrated into the space or the spring chamber 35.
• Such excess oil can be drained from the conduit 10, more specifically its portion 10" via a drain passage 36, which is schematically illustrat ⁇ ed in Fig. 1 by a bore, having a constriction, in the housing or block 28.
• Fig. 2 shows more clearly than the schematic illustration of Fig.
• the secondary non-return valve 34 is a spring- biased ball which is placed in a bore extending axially through the pilot piston 29 and having two distinct por ⁇ tions 37, 37' of different diameter. More specifically, this bore has a relatively narrow portion 37 opening in the spring chamber 35, and a larger portion 37' opening in the secondary portion 11" of the conduit 11, the tran ⁇ sition between the bore or duct portions 37, 37' forming a seat for the ball 34 of the non-return valve.
• the spring 38 of the valve ball is maintained in place by a dismountable screw sleeve 39.
• the housing 28 is designed as a cartridge or cartridge-like construction which, in addition to the substantially cylindrical wall 28', has a base 28" and a top or cover 28'".
• the base 28" is inte ⁇ grally formed with the cylinder wall 28' while the cover 28'" is dismountable by being screwed in the upper end of the cylinder wall 28' .
• the valve cartridge 28 in turn is integrated in an outer shell or casing, which is not shown in Fig. 2 but the inside of which is intimated at 40.
• the cartridge 28 of the non-return valve is integrated in the hydraulic cylinder 4, although this is schematically illustrated separate from the cartridge. More specifically, the cartridge is incorporated in the end wall of the cylinder opposite to the piston rod 6.
• the valve member 25 is in the form of a cone having a conical portion which engages in the seat 27.
• the valve cone 25 has a stem 41 which is separate from the pin 31 of the pilot piston 29.
• a thin spring 42 connected to the stem 41 holds the valve cone in place when this is not affected by other external forces.
• the drain passage 36 schematically shown in Fig. 1 may in practice be embodied in different ways.
• One con- ceivable way is to intentionally provide a dimensional difference between the circumferential surface of the valve stem 41 and the inside of the bore in the top or cover 28'" through which the stem is movable, so that oil from the conduit portion 10" can flow between the space 35 and the secondary portion 10" of the conduit 10 via the resulting annular passage which, despite being nar ⁇ row, is penetrable by the oil.
• Another way is to provide a fine bore 36' in the cylinder wall 28' of the car ⁇ tridge, the conduit 10 being so designed in the casing surrounding the cartridge that oil can flow between the spring chamber 35 and the conduit portion 10".
• the oil can flow in both directions through the drain passage depending on the function of the sys ⁇ tem.
• the oil flow takes place in a direction into the spring cham ⁇ ber 35.
• flow takes place in a direc ⁇ tion out of the chamber 35 more precisely in the case when the piston 29 has been lifted off the seat 33 by oil from the channel portion 11'.
• the pilot piston 29, in the area between the conical portion 32 and the part of the piston which is sealing against the inside of the cylinder wall 28' of the cartridge has a recess 43 which is defined at the top by an annular abutment surface 44.
• annular abutment surface 44 Adjacent the seat 33, there is a. similar, planar and annular abutment 33'. The outer diameter of the abutment surface 44 always exceeds the inner diameter of the abutment surface 33' of the seat.
• the directional valve is reversed so that the pump 12 can feed oil out into the conduit 11 at the same time as the port 18 is opened so that oil can flow back from the chamber 8 through the conduit 10.
• the pilot piston 29 will move upwards so that the oil can pass freely through the conduit portion 11' to the chamber 9 of the piston-rod side.
• the pilot piston lifts the valve member 25 so that oil from the first chamber 8 can pass freely through the conduit 10 back to the directional valve and thence to the tank 13.
• the secondary non-return valve 34 pre ⁇ vents oil from flowing into the spring chamber 35 of the cartridge 28.
• Fig. 1 the slide member 14 occupies a closing position, in which it should not be possible to feed oil out into the system from the pump 12.
• both the conduit portion 10' of the piston side and the con- duit portion 11' of the piston-rod side are pressurised, while the conduit portions 10" and 11" may be substan ⁇ tially unpressurised.
• the support leg is locked in a given position. It cannot be retracted because of the valve member 25 of the main non-return valve. Nor can it be extended unless the counterpressure at the pilot piston 29 is overcome.
• a valve means 45 which divides the second conduit 11 into two portions 11', 11" is separate from the main non-return valve 3 and disposed between this and the cylinder 4.
• the means 45 is in the form of a third valve or non-return valve (here exemplified as a spring- biased ball) which acts in a first direction and coope- rates with a fourth valve in the form of a non-return valve 46 (also a spring-biased ball) which acts in the opposite direction.
• the fourth non-return valve 46 is disposed in a by-pass 47 between the primary conduit por ⁇ tion 11' and the secondary conduit portion 11".
• the spring 45' of the valve ball 45 is a sturdy spring designed to perform a counterpressure function against the oil pressure in the conduit portion 11' , while the spring 46' for the ball 46 is thin and merely serves to hold this valve ball in position without performing any counterpressure function.
• each of the ports 18 and 20 in the slide valve 2 is drained via drain passages 48, 49.
• the flow of oil is pressed through the valve 45 against the action of the counter- pressure spring 45' while the valve 46 is closed.
• the support leg is shortened, the flow is pressed without any resistance through the valve 46 while the valve 45 is closed.
• the valve 45 ensures that tempera ⁇ ture increases cannot cause any major pressure increases in the cylinder than what is determined by the spring 45' of the valve ball.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• General Engineering & Computer Science (AREA)
• Actuator (AREA)
• Fluid-Pressure Circuits (AREA)
• Forklifts And Lifting Vehicles (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20390429

Family Applications (1)

Country Status (3)

Cited By (1)

Citations (2)

• 1993
  • 1993-06-28 SE SE9302215A patent/SE500456C2/sv not_active IP Right Cessation
• 1994
  • 1994-04-15 WO PCT/SE1994/000335 patent/WO1995000762A1/en active Application Filing
  • 1994-04-15 AU AU69012/94A patent/AU6901294A/en not_active Abandoned

Patent Citations (2)

Also Published As

Similar Documents

Legal Events