WO2008125148A1 - Hydraulic pilot control unit with oscillation damping system - Google Patents

Hydraulic pilot control unit with oscillation damping system Download PDF

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Publication number
WO2008125148A1
WO2008125148A1 PCT/EP2007/053744 EP2007053744W WO2008125148A1 WO 2008125148 A1 WO2008125148 A1 WO 2008125148A1 EP 2007053744 W EP2007053744 W EP 2007053744W WO 2008125148 A1 WO2008125148 A1 WO 2008125148A1
Authority
WO
WIPO (PCT)
Prior art keywords
poppet
pilot control
control unit
upper chamber
damping
Prior art date
Application number
PCT/EP2007/053744
Other languages
French (fr)
Inventor
Mirco Allegretti
Original Assignee
Walvoil S.P.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Walvoil S.P.A. filed Critical Walvoil S.P.A.
Priority to KR1020097023521A priority Critical patent/KR101361019B1/en
Priority to PCT/EP2007/053744 priority patent/WO2008125148A1/en
Publication of WO2008125148A1 publication Critical patent/WO2008125148A1/en

Links

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
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
    • F15B11/028—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the actuating force
    • 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
    • F15B13/042—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by fluid pressure
    • F15B13/0422—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by fluid pressure with manually-operated pilot valves, e.g. joysticks
    • 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
    • F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
    • F15B15/20—Other details, e.g. assembly with regulating devices
    • F15B15/22—Other details, e.g. assembly with regulating devices for accelerating or decelerating the stroke

Definitions

  • TITLE HYDRAULIC PILOT CONTROL UNIT WITH OSCILLATION DAMPING SYSTEM
  • the present invention relates to the field of units for hydraulic pilot control of directional- control valves used in the fabrication of mobile vehicles and particularly relates to a hydraulic pilot control with an oscillation damping system.
  • the pilot control unit is operated by the driver of the mobile vehicle by means of an operating member such as a lever or a pedal.
  • oscillations may have various causes : the uncontrolled actuation of the pilot control unit may be caused by the rolling and vibrations of the mobile vehicle caused by the travel or by the abrupt release of the operating mechanism from any operating position.
  • Object of the present invention is to prevent the above described oscillatory motions, by adding a damping system to the pilot control unit.
  • a further advantage of the invention is that these oscillations are prevented by means of a damping system having a small number of components, hence a lower cost than prior art solutions .
  • FIG. 1 is a cross sectional view of a pilot control unit without any damping system of a typical prior art
  • - Figure 2 is a cross sectional view of a pilot control unit having a damping system according to prior art
  • - Figure 3 is a cross sectional view of one embodiment of the pilot control unit with oscillation damping system object of the present invention
  • FIG. 3a shows a detail of the poppet chamber, particularly in an actuated configuration.
  • FIG. 4 shows a second embodiment of the pilot control unit with oscillation damping system object of the present invention.
  • Such pilot control unit has a casing Ia, with pressure reducing valves operating therein.
  • Each pressure reducing valve is composed of a spool 8, a pressure spring 2 and a poppet 7 and is operated by a push rod 4 , which is in turn actuated by a cam 5 integral with the pilot mechanism 20.
  • Two chambers are formed in the casing Ia: a lower chamber 9 , connected to the pump port P via the pressure line and an upper chamber 6, connected to the discharge port T via the discharge line.
  • Pump port P and discharge port T are situated in the lower portion of the pilot control unit. More specifically, the upper chamber 6 is connected to the discharge port T through a hole 10 in the lower portion of the chamber.
  • a return spring 3 that presses the push rod 4 upward and a pressure spring 2 that transmits the pressing force applied from the poppet 7 to the spool 8.
  • a first drawback of this solution is that, during the above-described actuation, the poppet 7 encounters no resistance as the hydraulic oil with air bubbles contained in the upper chamber 6 is pushed by the poppet 7 itself towards the discharge hole 10, thereby providing no damping effect.
  • the apparatus composed of the poppet 7 , the spool 8 , the spring 2 and the push rod 4 is pushed by the return spring 3 in a direction opposite to the actuation one.
  • This resistance should be very low , in order to not slow down the apparatus composed of the poppet 7 , the spool 8 and the push rod 4 in its return to its neutral position: an excessive resistance would affect a properly safe return to the neutral position.
  • pilot control units that can obviate oscillation problems are already provided; the features of such units are shown in Figure 2.
  • the pilot control shown in Figure 2 has additional damping pistons 1 which operate in combination with the push rods ; additional damping springs 2 have the function of pushing up the damping pistons 1 during the return stroke of the pilot control. Nevertheless, this solution has the disadvantage of increasing the force required to operate the pilot control unit.
  • the present invention has the object of providing a novel pilot control unit that can obviate the above drawbacks , while dramatically reducing fabrication and material costs of prior art solutions.
  • the pilot control unit with damping system has a casing Ia which comprises two chambers , one above the other: a lower chamber 9, connected to the pressure line LP and an upper chamber 6, connected to the discharge line LS.
  • One or more spools 8 slide within the casing Ia and have the function of regulating the pressures at the control ports 12; the spool 8 receives pressurized oil from the lower chamber 9 and discharges oil into the upper chamber 6.
  • Coaxial and concentric springs 2 and 3 are provided in the upper chamber 6; the pressure spring 2 presses the poppet 7 upward against the push rod 4 and the return spring 3 transmits the pressing force applied from the poppet 7 to the spool 8.
  • the poppet 7 , the springs 2 and 3 and a portion of the spool 8 are accommodated in the upper chamber 6.
  • the pilot control unit is driven by actuating the operating member 20 (a lever or a pedal) ; motion is transmitted to the cam 5 which can be displaced, from the neutral position that is shown in Figure 3, in the two directions of arrows Ll and L2 ; arrow Ll corresponds to the actuation stroke and arrow L2 corresponds to the return stroke.
  • the cam 5 operates the push rod 4 , and the latter operates the poppet 7, thereby pressing the pressure spring 2 and operating the spool 8.
  • the upper chamber 6 of the pilot control unit of the present invention is connected to the port T through the discharge hole 11, which is situated in the upper portion of the upper chamber 6, above the poppet 7.
  • Discharge hole 11 and port T are connected through the hole 10, located in the lower portion of the casing Ia of the pilot control unit.
  • the particular position of the hole 11 within the casing Ia allows hydraulic oil to be only discharged when the upper chamber 6 has been filled to a height above the poppet 7 ; this ensures the total filling of upper chamber 6 as well as the easy removal of air bubbles and vapor accumulated in chamber 6 that can be purged through the passage to port T.
  • the cam 5 Upon actuation of the pilot control unit 1 in the direction of arrow Ll, the cam 5 presses the push rod 4 downwards , and the latter operates on the corresponding poppet 7 to press the pressure spring 2, which in turn presses the spool 8 downwards to its operating position.
  • the poppet 7 pushes the hydraulic oil in the upper chamber 6 toward the discharge hole 11; in other words, it forces the hydraulic oil to flow through the clearance between the external diameter of the poppet 7 and the internal diameter 13 of the upper chamber 6, thereby damping the actuation stroke of the pressure reducing valve.
  • the actuation stroke of the poppet 7 ends upon abutment against the casing Ia at the reduced diameter section shown in Figure 3a.
  • a groove 14 is formed to provide communication between the lower and upper portions of the upper chamber 6.
  • the poppet 7 slides within the upper chamber 6 without encountering any resistance by the hydraulic oil , as the poppet 7 may directly push the overlying oil into the discharge hole 11 without forcing it through any clearance, while the hydraulic oil returned by the pilot controlled valve fills the underlying chamber.
  • Figure 4 shows a second embodiment of the pilot control unit with oscillation damping system according to this invention.
  • This embodiment is characterized by the casing Ia being only formed by machine tool processing.
  • upper chamber 6 is put in communication with the discharge T through the holes 11 and 10 and the pressure chamber 9 is itself formed by machine tool drilling.
  • the holes 11 and 9 are isolated from the outside environment by expansion plugs 15.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Servomotors (AREA)

Abstract

The present invention relates to the field of units for hydraulic pilot control of directional-control valves used in the fabrication of mobile vehicles and particularly relates to a hydraulic pilot control with an oscillation damping system. Connections are provided among the chambers in the pilot control unit to provide a damping effect in the actuation stroke, thereby preventing any oscillation: the provision of such connections among the chambers has the function of preventing air stagnation; this arrangement prevents any undamped behavior due to incomplete filling upon installation or to air transported in the hydraulic fluid.

Description

TITLE: HYDRAULIC PILOT CONTROL UNIT WITH OSCILLATION DAMPING SYSTEM
DESCRIPTION
The present invention relates to the field of units for hydraulic pilot control of directional- control valves used in the fabrication of mobile vehicles and particularly relates to a hydraulic pilot control with an oscillation damping system.
The pilot control unit is operated by the driver of the mobile vehicle by means of an operating member such as a lever or a pedal.
The problems of prior art are associated to the oscillatory movements of the operating member and consequently to the fluctuation in the amount of operation of the pilot control.
These oscillations may have various causes : the uncontrolled actuation of the pilot control unit may be caused by the rolling and vibrations of the mobile vehicle caused by the travel or by the abrupt release of the operating mechanism from any operating position.
Besides being a serious operational defect, these oscillations are also a safety problem for operators , as they may cause involuntary and uncontrolled operations of the vehicle on which the pilot control unit is mounted.
Object of the present invention is to prevent the above described oscillatory motions, by adding a damping system to the pilot control unit. A further advantage of the invention is that these oscillations are prevented by means of a damping system having a small number of components, hence a lower cost than prior art solutions .
These objects and advantages are all achieved by the hydraulic pilot control unit with oscillation damping system object of the present invention, which is characterized by what is provided in the below- listed claims. These and other features will be better pointed out by the following description of a few embodiments , which are shown merely as a non-limiting example in the enclosed tables of drawing, in which:
- Figure 1 is a cross sectional view of a pilot control unit without any damping system of a typical prior art;
- Figure 2 is a cross sectional view of a pilot control unit having a damping system according to prior art; - Figure 3 is a cross sectional view of one embodiment of the pilot control unit with oscillation damping system object of the present invention;
- Figure 3a shows a detail of the poppet chamber, particularly in an actuated configuration. - Figure 4 shows a second embodiment of the pilot control unit with oscillation damping system object of the present invention.
With reference to Figure 1, the operating modes of a common prior art hydraulic pilot control unit are shown.
Such pilot control unit has a casing Ia, with pressure reducing valves operating therein.
Each pressure reducing valve is composed of a spool 8, a pressure spring 2 and a poppet 7 and is operated by a push rod 4 , which is in turn actuated by a cam 5 integral with the pilot mechanism 20.
Two chambers are formed in the casing Ia: a lower chamber 9 , connected to the pump port P via the pressure line and an upper chamber 6, connected to the discharge port T via the discharge line.
Pump port P and discharge port T are situated in the lower portion of the pilot control unit. More specifically, the upper chamber 6 is connected to the discharge port T through a hole 10 in the lower portion of the chamber.
Disposed in the upper chamber 6 are a return spring 3 that presses the push rod 4 upward and a pressure spring 2 that transmits the pressing force applied from the poppet 7 to the spool 8.
When the cam 5 is made to tilt by the operation of the pilot mechanism 20, the push rod 4 is pressed downward thus operating on the poppet 7 ; the spool 8 is then pressed downward to its operating position via the pressure spring 2.
A first drawback of this solution is that, during the above-described actuation, the poppet 7 encounters no resistance as the hydraulic oil with air bubbles contained in the upper chamber 6 is pushed by the poppet 7 itself towards the discharge hole 10, thereby providing no damping effect.
During the return stroke, the apparatus composed of the poppet 7 , the spool 8 , the spring 2 and the push rod 4 is pushed by the return spring 3 in a direction opposite to the actuation one.
During such return stroke, the poppet 7 slides within the upper chamber 6 experiencing a resistance against its movement, thereby producing a damping effect; such resistance is due to the fact that the hydraulic oil is forced to move from the upper to the lower part of the upper chamber 6 through the clearance between the external diameter of the poppet 7 and the internal diameter of the upper chamber 6.
This resistance should be very low , in order to not slow down the apparatus composed of the poppet 7 , the spool 8 and the push rod 4 in its return to its neutral position: an excessive resistance would affect a properly safe return to the neutral position.
A further drawback of this prior art pilot control lies in that air bubbles may form in the upper chamber
6 and would considerably reduce the damping effect; as a result, the poppet 7 would not fulfill its damping function during its return stroke.
By the above pilot control configuration, undesired oscillatory movements are only contrasted to a partial extent, whereby the mobile vehicle on which the pilot control unit is mounted may still be operated improperly .
In prior art, pilot control units that can obviate oscillation problems are already provided; the features of such units are shown in Figure 2. The pilot control shown in Figure 2 has additional damping pistons 1 which operate in combination with the push rods ; additional damping springs 2 have the function of pushing up the damping pistons 1 during the return stroke of the pilot control. Nevertheless, this solution has the disadvantage of increasing the force required to operate the pilot control unit.
In view of these prior art problems , the present invention has the object of providing a novel pilot control unit that can obviate the above drawbacks , while dramatically reducing fabrication and material costs of prior art solutions.
The means for obviating such problems will be better explained with Figures 3 and 4 , which show the inventive hydraulic pilot control unit with damping system in a few different embodiments.
With reference to Figure 3 the operation of the pilot control unit with damping system according to the invention is shown.
The pilot control unit with damping system has a casing Ia which comprises two chambers , one above the other: a lower chamber 9, connected to the pressure line LP and an upper chamber 6, connected to the discharge line LS.
One or more spools 8 slide within the casing Ia and have the function of regulating the pressures at the control ports 12; the spool 8 receives pressurized oil from the lower chamber 9 and discharges oil into the upper chamber 6.
Coaxial and concentric springs 2 and 3 are provided in the upper chamber 6; the pressure spring 2 presses the poppet 7 upward against the push rod 4 and the return spring 3 transmits the pressing force applied from the poppet 7 to the spool 8.
The poppet 7 , the springs 2 and 3 and a portion of the spool 8 are accommodated in the upper chamber 6.
The pilot control unit is driven by actuating the operating member 20 (a lever or a pedal) ; motion is transmitted to the cam 5 which can be displaced, from the neutral position that is shown in Figure 3, in the two directions of arrows Ll and L2 ; arrow Ll corresponds to the actuation stroke and arrow L2 corresponds to the return stroke.
The cam 5 operates the push rod 4 , and the latter operates the poppet 7, thereby pressing the pressure spring 2 and operating the spool 8. The upper chamber 6 of the pilot control unit of the present invention is connected to the port T through the discharge hole 11, which is situated in the upper portion of the upper chamber 6, above the poppet 7.
Discharge hole 11 and port T are connected through the hole 10, located in the lower portion of the casing Ia of the pilot control unit.
The particular position of the hole 11 within the casing Ia allows hydraulic oil to be only discharged when the upper chamber 6 has been filled to a height above the poppet 7 ; this ensures the total filling of upper chamber 6 as well as the easy removal of air bubbles and vapor accumulated in chamber 6 that can be purged through the passage to port T.
Upon actuation of the pilot control unit 1 in the direction of arrow Ll, the cam 5 presses the push rod 4 downwards , and the latter operates on the corresponding poppet 7 to press the pressure spring 2, which in turn presses the spool 8 downwards to its operating position.
During such actuation, the poppet 7 pushes the hydraulic oil in the upper chamber 6 toward the discharge hole 11; in other words, it forces the hydraulic oil to flow through the clearance between the external diameter of the poppet 7 and the internal diameter 13 of the upper chamber 6, thereby damping the actuation stroke of the pressure reducing valve.
By adjusting such clearance, several different damping effects may be obtained.
The actuation stroke of the poppet 7 ends upon abutment against the casing Ia at the reduced diameter section shown in Figure 3a. At this stage, to prevent pressure buildup in the chambers underlying the poppet 7, a groove 14 is formed to provide communication between the lower and upper portions of the upper chamber 6. During the return stroke of the pilot mechanism 20 (and therefore of the cam 5) , the apparatus composed of the poppet 7, the spool 8, the pressure spring 2 and the push rod 4 is pushed by the return spring 3 in a direction L2 , opposite to the above actuation direction Ll.
At this stage, the poppet 7 slides within the upper chamber 6 without encountering any resistance by the hydraulic oil , as the poppet 7 may directly push the overlying oil into the discharge hole 11 without forcing it through any clearance, while the hydraulic oil returned by the pilot controlled valve fills the underlying chamber.
This configuration effectively contrasts any undesired continuous oscillation, by damping the actuation motion; the lack of resistance during return to the neutral position ensures an optimized operation of the pilot control unit.
Figure 4 shows a second embodiment of the pilot control unit with oscillation damping system according to this invention.
This embodiment is characterized by the casing Ia being only formed by machine tool processing.
Particularly, upper chamber 6 is put in communication with the discharge T through the holes 11 and 10 and the pressure chamber 9 is itself formed by machine tool drilling. The holes 11 and 9 are isolated from the outside environment by expansion plugs 15.

Claims

1. A pilot control unit (1) having an oscillation damping system, which operates by damping the actuation stroke; comprising a casing (Ia) having two chambers one above the other: a lower chamber (9) , connected to the pressure line (LP) , and an upper chamber (6) , connected to the discharge line (LS) ; one or more spools (8) slide within the body, to control the pressures at the control ports (12) ; coaxial and concentric springs (2) and (3) are provided in the chamber (6) , to press the poppet (7) upward against the push rod (4) and to transmit the pressing force applied from the poppet (7) to the spool (8) respectively, characterized in that the upper chamber (6) is connected to the port (T) through a discharge hole (11) , which is situated in the upper portion of said chamber (6) , above the poppet (7) ; upon actuation of the pilot mechanism (20) , the poppet (7) pushes the fluid in the upper chamber (6) toward the discharge hole (11) , through the clearance between the poppet (7) and the bore (13) ; the upper chamber (6) being always filled with oil, and allowing damping during the actuation stroke.
2. A pilot control unit (1) as claimed in claim 1, characterized in that by adjusting the clearance between the poppet (7) and the bore (13) , several different damping effects may be obtained.
3. A pilot control unit (1) as claimed in claims 1 to 2 , characterized in that the poppet (7) is used as a damping member.
4. A pilot control unit (1) as claimed in claim 1, characterized in that it comprises a lever- or pedal- operated pilot member (20) , for controlling the pilot control unit (1) ; motion is transmitted to the cam (5) ; the cam (5) drives the push rod (4) , and the latter drives the poppet (7) , thereby pressing the spring (2) and driving the spool (8) .
PCT/EP2007/053744 2007-04-17 2007-04-17 Hydraulic pilot control unit with oscillation damping system WO2008125148A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
KR1020097023521A KR101361019B1 (en) 2007-04-17 2007-04-17 Hydraulic pilot control unit with oscillation damping system
PCT/EP2007/053744 WO2008125148A1 (en) 2007-04-17 2007-04-17 Hydraulic pilot control unit with oscillation damping system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2007/053744 WO2008125148A1 (en) 2007-04-17 2007-04-17 Hydraulic pilot control unit with oscillation damping system

Publications (1)

Publication Number Publication Date
WO2008125148A1 true WO2008125148A1 (en) 2008-10-23

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Family Applications (1)

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PCT/EP2007/053744 WO2008125148A1 (en) 2007-04-17 2007-04-17 Hydraulic pilot control unit with oscillation damping system

Country Status (2)

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KR (1) KR101361019B1 (en)
WO (1) WO2008125148A1 (en)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5251660A (en) * 1988-03-31 1993-10-12 Kabushiki Kaisha Komatsu Seisakusho Hydraulic pilot valve unit
EP0716235A2 (en) * 1994-11-10 1996-06-12 Kawasaki Jukogyo Kabushiki Kaisha Hydraulic operated valve

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5215166A (en) 1991-10-30 1993-06-01 Eaton-Kenway, Inc. Mobile stacker for automated storage and retrieval system
JP4181940B2 (en) * 2003-08-01 2008-11-19 カヤバ工業株式会社 Hydraulic buffer with relief valve and vehicle height adjustment function

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5251660A (en) * 1988-03-31 1993-10-12 Kabushiki Kaisha Komatsu Seisakusho Hydraulic pilot valve unit
EP0716235A2 (en) * 1994-11-10 1996-06-12 Kawasaki Jukogyo Kabushiki Kaisha Hydraulic operated valve

Also Published As

Publication number Publication date
KR20100016441A (en) 2010-02-12
KR101361019B1 (en) 2014-02-10

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