Classifications

• • 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
  • F15B13/0416—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor with means or adapted for load sensing
  • F15B13/0417—Load sensing elements; Internal fluid connections therefor; Anti-saturation or pressure-compensation valves

Definitions

• This invention relates generally to load responsive fluid control valves and to fluid power systems incorporating such valves, which systems are supplied with energy from negative system loads.
• this invention relates to load responsive direction and flow control valves capable of proportional control of negative loads, which maintain a constant pressure differential between negative load pressure and valve outlet pressure.
• this invention relates to pilot operated load responsive controls of direction control valves, which permit variation in the level of control differential between negative load pressure and valve outlet pressure, while this control differential is automatically maintained constant at each controlled level.
• Closed center load responsive direction and flow control valves capable of proportional control of velocity of negative loads, independent of the load pressure, are very desirable.
• Such valves by fluid throttling action, automatically maintain a constant pressure differential between negative load pressure and valve outlet pressure.
• a variable orifice introduced between the negative load and valve outlet, varies the flow supplied from negative load, each
• Another object of this invention is to provide pilot operated load responsive controls of a direction control valve, through which control of negative load can be either accomplished by variation in area of the orifice, between the fluid motor and valve outlet, while the pressure differential across this orifice is maintained constant at a specific level, or by control of pressure differential, acting across this orifice, while the area of the orifice remains constant.
• control input namely modification in the pressure of control signal
• control differential to vary the level of the control differential between negative load pressure and the valve outlet pressure
• this control differential is automatically maintained constant at each controlled level by valve controls receiving low energy control signals to their amplifying stage.
• a load can be controlled in response to either input providing identical control performance, or the variable pressure differential control carl be superimposed on the control action controlling a negative load by variation in the area of the metering orifice. Therefore this control system lends itself very well to an application, in which a manual control input from an operator may be modified by an electronic logic circuit, or a micro-processor.
• Fig. 1 is a diagrammatic representation of a load responsive pilot operated negative load pressure throttling control for adjustment in the level of control differential from a certain preselected level to zero level, with fluid motor and reservoir shown schematically;
• Fig. 2 is a diagrammatic representation of another embodiment of a load responsive pilot operated negative load pressure throttling control for adjustment in the level of control differential from a certain minimum preselected value up to maximum level, with fluid motor and reservoir shown schematically;
• Fig. 3 is a diagrammatic representation ' of another embodiment of the load responsive pilot operated negative load pressure throttling control of Fig. 1, with fluid motor and reservoir shown schematically;
• Fig. 4 is a section view through a four way load responsive direction control valve for control of negative load using the control of Fig. 3 with system pump and reservoir shown schematically;
• Fig. 5 is a diagrammatic representation of manual control input into the load responsive controls of Figs. 1 to 4;
• Fig. 6 is a diagrammatic representation of hydraulic control input into load responsive controls of Figs. 1 to 4;
• Fig. 7 is a diagrammatic representation of electro-hydraulic control input into load responsive controls of Figs. 1 to 4;
• Fig. 8 is a diagrammatic representation of an electro-mechanical control input into load responsive controls of Figs. 1 to 4.
• Fig. 9 is a diagrammatic representation of an electro-mechanical control input into load responsive system of Fig. 3.
• the hydraulic system shown therein comprises a fluid motor 10 subjected to negative load pressure generated by negative load W.
• Supply line 11 connects the fluid motor 10 through variable orifice 12 and line 13 to a differential throttling control, generally designated as 14.
• the differential throttling control 14, composed of throttling section, generally designated as 15 and a signal modifying section, generally designated as 16, comprises a housing 17 having an inlet chamber 18, an outlet chamber 19, a first control chamber 20 and a low pressure chamber 21, all of those chambers being connected by bore 22, slidably guiding a throttling spool 23.
• One end of the throttling spool 23 projects into the first control chamber 20, which communicates through passage 29 with a pilot valve section, generally designated as 30.
• the other end of the throttling spool 23 projects into the low pressure chamber 21, which is connected through passage 31 and line 32 with system reservoir 33.
• a control spring 34 in the first control chamber 20 is _ interposed between the housing 17 and the throttling spool 23.
• the outlet chamber 19 of the throttling section 15 is connected through port 35 and line 32 with a system reservoir 33.
• the pilot valve section 30 is provided with a second control chamber 36, annular space 37 and space 38, connected by bore 39 axially guiding pilot valve spool 40.
• the second control chamber 36 is connected by line 41, orifice 42 and line 43 with downstream of variable orifice 12.
• Space 38 is connected by line 44 with upstream of variable orifice 12.
• Annular space 37 communicates by passage 29 with the first control chamber 20 and by leakage orifice 45, passage 31, port 35 and line 32 with the system reservoir 33.
• the pilot valve spool 40 equipped with metering land 46 and land 47, which define annular space 48, projects into the second control chamber 36, where it engages a spring 49.
• Annular space 48 is connected by passage 50 with passage 31, which in turn is connected to the system reservoir 33.
• the second control chamber 36 is also connected through port 51 with a supply chamber 52, connected by bore 53 with a third control chamber 54 and an exhaust chamber 55.
• Bore 53 slidably guides a control spool 56, equipped with land 57, provided with throttling slots 58 and positioned between the supply chamber 52 and the third control chamber 54, a land 59 separating the supply chamber 52 and the exhaust chamber 55 and flange 60-
• a spring 61 is interposed in the exhaust chamber 55 between the flange 60 of the control spool 56 and the housing 17.
• the exhaust chamber 55 and the third control chamber 54 are selectively interconnected by metering orifice created by a stem 62 guided in bore 63 and provided with metering slots 64.
• the stem 62 is connected to an actuator 65 responsive to external control signal 66.
• FIG. 2 the same components used in Fig. 1 are designated by the same numerals.
• the only difference between the load responsive controls of Figs. 1 and 2 is the phasing of internal components of the differential throttling control 14 of Fig. 1.
• a differential throttling control 67 of Fig. 2 is composed of the throttling section 15, the signal modifying section 16 and the pilot valve section 30 identical to that of Fig. 1.
• the load ' pressure is transmitted through supply line 11, variable orifice 12 and line 13 to the inlet chamber 18 of the throttling section 15.
• FIG. 1 is connected by port 51 with the second control chamber 36, which in turn is connected by line 41, orifice 42 and line 43 to downstream of variable orifice 12, while in Fig. 2 the signal modifying section 16 is connected by port 51 with space 38 which in turn is connected by passage 68 and line 69, orifice 42 and line 11 with the fluid motor 10 upstream of variable orifice 12.
• FIG. 3 the same components used in Fig. 1 are designated by the same numerals.
• the basic load responsive circuit of Fig. 3 with some of the circuit components, including some of the internal components of differential throttling control, generally designated as 70, are the same as those of Fig. 1.
• the second control chamber 36 is connected by port 71 to a chamber 72 of differential valve, generally designated as 73.
• the differential valve 73 comprises a coil 74, retained in the housing, which guides an armature 75 of a solenoid generally designated as 76.
• the armature 75 is provided with a conical surface 77, selectively engageable with sealing edge 78 of flow port 79, connected to downstream of variable orifice 12, by line 80.
• the armature 75 is also provided with venting passage 81 terminating in bore 82, guiding a reaction pin 83.
• the coil 74 is connected by sealed connector 84 to outside of the housing, external control signal being applied to the sealed connector 84.
• the second control chamber 36 is connected by leakage orifice 85, passage 31, port 35 and line 32 to the system reservoir 33.
• the differential throttling control 70 of Fig. 3 was integrated in Fig. 4 into a four way valve assembly, generally designated as 86.
• the four way valve assembly generally designated as 86, comprises a housing 87 having an inlet chamber 88, load chambers 89 and 90 and outlet chambers 91 and 92, interconnected by bore 93, guiding a valve spool 94.
• the valve spool 94 is provided with lands 95, 96 and 97, throttling slots 98, 99, 100 and 101 and signal slots 102 and 103.
• the housing 87 is also provided with load sensing ports 104 and 105 communicating through line 106 with space 39 of
• the inlet chamber 88 is connected by line 110 to a system pump 111 controlled by pump control 112 and supplied with suction fluid from a reservoir 33.
• Load chambers 89 and 90 are connected to the fluid motor 10.
• the stem 62 of the actuator 65 of Figs. 1 to 4 is biased by a spring 112 towards position of zero orifice and is directly operated by a lever 113, which provides the external signal 66.
• the stem 62 of the actuator 65 of Figs. 1 to 4 is biased by a spring 114 towards position of zero orifice and is directly _ operated by a piston 115. Fluid pressure is supplied to the piston 115 from a pressure generator 116, operated by a lever 117.
• the stem 62 of the actuator 65 of Figs. 1 to 4 is biased by a spring 118 towards position of zero orifice and is directly operated by a solenoid 119, connected by a line to an input current control 120, operated by a lever 121 and supplied from an electrical supply source 122.
• the stem 62 of the differential control generally designated as 123, is biased by a spring 124 towards a position, where it isolates the third control chamber 54 from the exhaust chamber 55 and is controlled by a solenoid 125.
• the electrical control signal, amplified by amplifier 126 is transmitted from a logic circuit or a micro-processor 127, subjected to inputs 128, 129 and 130.
• a logic circuit or a micro-processor 131 supplied with control signals 132, 133 and 134, transmits an external digital control signal to a stepping motor 136 of the differential valve 73 or 123 of Figs. 3 and 8 through an amplifier 135.
• the differential throttling control 14 is interposed between the fluid motor 10 and the reservoir 33 and controls the fluid flow and pressure therebetween.
• the differential throttling control 14 is composed of the throttling section 15, the signal modifying section 16 and the pilot valve section 30.
• the throttling section 15 with its throttling spool 23 throttles with throttling slots 27 fluid flow from the inlet chamber 18, connected by line 13, variable orifice 12 and supply line 11 to the fluid motor 10, to the outlet chamber 19, connected by line 32 with the system reservoir 33, to automatically maintain a constant pressure differential across variable orifice 12.
• This control action is accomplished in the following way.
• Fluid from the fluid motor 10 at Pw pressure which is the load pressure, acting upstream of variable orifice 12, is transmitted through line 44 to space 38 where, reacting on the cross-sectional area of the pilot valve spool 40, generates a force tending to move the pilot valve spool 40 downward to connect Pw pressure through annular space 37 and passage 29 to the first control chamber 20 and therefore increase the pressure level in the first control chamber 20.
• Fluid at load pressure P which is the pressure acting downstream of variable orifice 12 is transmitted through line 43 and orifice 42 to the second control chamber 36 where, reacting on the cross-sectional area of the pilot valve spool 40 it generates a force tending to move the pilot
• OMPI valve spool upwards, to connect the reservoir pressure from annular space 48 to annular space 37, passage 29 and to the first control chamber 20 and therefore decrease the pressure level in the first control chamber 20.
• This force due to pressure in the second control chamber 36 is supplemented by the biasing force of the spring 49.
• Increase in pressure level in the first control chamber 20, above the level equivalent to preload of control spring 34, reacting on cross-sectional area of the throttling spool 23, will generate a force tending to move the throttling spool 23 from left to right, in the direction of closing of the flow area through the throttling slots 27 and therefore in direction of increasing the throttling action of the throttling spool 23.
• Leakage orifice 45 connecting the first control chamber 20 through passage 31 and line 32 to the reservoir 33, is used, in a well known manner, to increase the stability of the pilot valve spool 40. If P Mon pressure is equal to P, pressure, which .is the case when the stem 62 is in the position, as shown in Fig. 1, the throttling section 15, by throttling fluid flow from the inlet chamber 18 to the outlet chamber 19, will automatically maintain a constant pressure differential ⁇ P between space 38 and the second control chamber 36 and with ⁇ Py becoming ⁇ p, will also maintain a constant pressure differential across variable orifice 12.
• variable orifice 12 pressure differential ⁇ Py, acting across orifice 12, can be varied by the signal modifying section 16, through the throttling section 15 of the differential throttling control 14, each specific pressure differential ⁇ Py corresponding to a specific constanty flow from the fluid motor 10 irrespective of the variation in the magnitude of the load pressure Pw. Therefore fluid flow from fluid motor 10 can be controlled either by variation in area of variable orifice 12, or by variation in pressure differential ⁇ py, each of those control methods displaying identical control characteristics and controlling flow, which is independent of the magnitude of the load pressure.
• Action of one control can be superimposed on the action of the other, providing a unique system, in which, for example, a command signal from the operator, through the use of variable orifice 12 can be corrected by signal 66 from a computing device, acting through the signal modifying section 16.
• the signal modifying section 16 is, identical to the signal modifying section 16 of Fig. 1 and performs in an identical way,
• Fig. 1 modifies the control signal from the fluid motor 10 and therefore from upstream of the variable orifice 12, instead of modifying the control signal of P 2 pressure, as shown in the system of Fig. 1. Therefore, as can be seen in Fig.
• the load responsive system is similar to that of Fig. 1.
• the throttling section 15 of the differential throttling control 70 together with the pilot valve section 30 of Fig. 3, are identical to that of Fig. 1.
• the differential valve 73 is different from the signal modifying section 16 of Fig. 1, although it performs the same function and provides identical performance.
• the differential valve, generally designated as 73 contains the solenoid, generally designated as 76, which consists of coil 74, secured in the housing and the armature 75, slidably guided in the coil 74.
• the armature 75 is provided with conical surface 77, which, in cooperation with sealing edge 78, regulates the pressure differential ⁇ Px between flow port 79 and the chamber 72.
• the sealed connector 84 in the housing, well known in the art, connects the coil 74 with external terminals, to which the external signal 66 can be applied.
• a solenoid is an electro-mechanical device, using the principle of electro-magnetics, to produce output forces from electrical input signals.
• the force developed on the solenoid armature 75 is a function of the input current. As the current is applied to the coil 74, each specific current level will correspond to a specific force level, transmitted to the armature. Therefore, the contact force between the conical surface 77 of the armature 75 and sealing edge 78 of the housing will vary and be controlled by the input current.
• reaction pin 83 This force is partially balanced by the reaction force, developed on the cross-sectional area of the reaction pin 83, guided in a bore 82, which is connected through venting passage 81 with flow port 79.
• the cross- 0 sectional area of the reaction pin 83 must always be smaller than the area enclosed by sealing edge 78, so that a positive force, due to the pressure differential ⁇ Px, opposes the force developed by the solenoid 76.
• the reaction pin 83 permits use of a larger flow port 5 79, while also permitting a very significant reduction - in the solenoid 76, also permitting the solenoid 76 to work in the higher range of ⁇ Px.
• the second control chamber 36 may be connected by conventional flow control valve with the system reservoir instead of by o leakage orifice 85. Simple leakage orifice 85 is shown in Fig. 3 connecting the second control chamber 36 and passage 31.
• the load responsive system is identical to that as shown in Fig. 3 with 5 identical differential throttling controls being used, but the variable orifice 12 of Fig. 1 was substituted in Fig. 4 by a load responsive four way type direction control valve, generally designated as 86.
• the performance of the control embodiment of Figs. 3 and 4 0 is identical, the only difference being the construction of the variable orifice.
• the differential throttling control and specifically space 39 is connected with the load sensing ports 104 and 105 of the four way valve 86.
• the second control chamber 36 5 is connected through the differential valve 73 with the
• Displacement of the valve spool 94 from its neutral position in either direction first connects with signal slot 102 or 103 load chamber 89 or 90 with load pressure sensing port 104 or 105, while load chambers 89 and 90 are still isolated by the valve spool 94 from the inlet chamber 88 and outlet chambers 91 and 92. Then the load pressure signal is transmitted through load pressure sensing port 104 or 105 and line 106 to space 39, permitting the differential throttling control 70 to react, before metering orifice is open to the load chamber 89 or 90.
• valve spool 94 Further displacement of valve spool 94, in either direction, will create, in a well known manner, through metering slot 98 or 101 a metering orifice between one of the load chambers and the outlet chamber 91 or 92, while connecting the other load chamber, through metering slot 99 or 100 with the inlet chamber 88.
• the metering orifice can be varied by displacement of valve spool 94, each position corresponding to a specific flow level out of one of the load chambers, irrespective of the magnitude of the load controlled by four way valve assembly 86.
• valve spool 94 With valve spool 94 displaced to any specific position, corresponding to any specific area of metering orifice, the flow out of load chambers can be proportionally controlled by the differential throttling control 70 with its differential valve 73, each value of pressure differential ⁇ Py being automatically maintained at a constant level by the throttling section 15 and corresponding to a specific flow level out of one of the load chambers, irrespective of the magnitude of the load controlled by the four way valve assembly 86.
• the ste 62 of the actuator 65 of Figs. 1 and 2 is biased by spring 112 towards position of zero orifice and is directly operated by a lever 113, which provides the external signal in the form of manual input.
• a lever 113 which provides the external signal in the form of manual input.
• the stem 62 of actuator 65 of Figs. 1 and 2 is biased by spring 114 towards position of zero orifice and is directly operated by a piston 115.
• Fluid pressure is supplied, in a well known manner, to the piston 115 from a pressure generator 116, operated by a lever 117. - Therefore the arrangement of Fig. 6 provides the external signal 66 in the form of a fluid pressure signal.
• the stem 62 of the actuator 65 of Figs. 1 to 4 is biased by a spring 118 towards position of zero orifice and is directly operated, in a well known manner, by a solenoid 119, connected by a line to an input current control 120, operated by a lever 121 and supplied from an electrical power source ' 122. Therefore the arrangement of Fig. 7 supplies the external signal 66 in the form of an electric current, proportional to displacement of lever 121.
• the stem 65 of the differential control 123 is biased by a spring 124 towards a position, where it isolates the third control chamber 54 from the exhaust chamber 55.
• the stem 62 is completely pressure balanced, can be made to operate through a very small stroke and controls such low flows, at such low pressures, that the influence of the
• solenoid armature when biased by a spring, is a function of the input current. For each specific current level there is a corresponding particular position, which the solenoid will attain. As the current is varied from zero to maximum rating, the armature will move one way from a fully retracted to a fully extended position in a predictable fashion, depending on the specific level of current at any one instant. Since the forces, developed by solenoid 125 are very small, so is the input current, which is controlled by a logic circuit or a micro-processor 127.
• the micro-processor 127 will then, in response to different types of transducers either directly control the system load, in respect to speed, force and position, or can superimpose its action upon the control function of an operator, to perform required work in the minimum time, with a minimum amount of energy, within the maximum capability of the structure of the machine and within the envelope of its horsepower.
• the control signal from the logic circuit, or the micro-processor 131 which may be of a digital or analog type, is transmitted through an actuator and positions the stem 62 of the differential valve 123 of Fig. 8.
• the actuator will most likely be the stepping motor 136, provided with a lead screw, well known in the art, which will directly position the stem 62 in response to a digital control signal, dispensing with the need for a digital to analog convertor.
• This approach applies equally well to the arrangement of Fig. 3 where the signal 66 can be supplied from a stepping motor which would increase in steps the
• the stem 62 is completely balanced from the force standpoint and requires minimal power levels for its actuation.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Fluid-Pressure Circuits (AREA)
• Control Of Fluid Pressure (AREA)

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• 1981
  • 1981-12-21 WO PCT/US1981/001712 patent/WO1983002305A1/en not_active Ceased
  • 1981-12-21 EP EP19820900472 patent/EP0096031A4/de not_active Withdrawn
  • 1981-12-21 JP JP82500475A patent/JPS58502157A/ja active Pending

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