FR2726100A1 - PILOT CONTROL DEVICE EQUIPPED WITH A HYDRAULICALLY ACTUABLE MAIN CONTROL DISTRIBUTOR - Google Patents

Abstract

In said device, the pilot pressure, prevailing in a control chamber (16, 17) of a main control valve (15), can be reduced to a smaller value compared to the pilot pressure prevailing at an outlet control (12) of a pilot control valve (11).

Description

PILOT CONTROL DEVICE EQUIPPED WITH A DISTRIBUTOR OF

  HYDRAULICALLY ACTUABLE MAIN CONTROL

  The present invention relates to a pilot control device fitted to a main control distributor.

  hydraulically actuated, comprising an adjustable distributor

  pilot control line, provided with a control output at which a pilot pressure prevails which can be preset by a signal

  inlet, and through which a control chamber of the dispenser

  main control unit can be requested.

  In construction machines, such as, for example,

  jumpers or cranes it is known to apply to devices

  pilot control operating, in particular, on the basis of

  direct control pressure transmitters, input signals which can be modified manually and are converted, by said pilot control apparatus, into pilot pressures whose value depends on the input signal. In the main control valve, a control slide is stressed by the pilot pressure considered and is moved, opposing the force of one or more return spring (s), until a

  balance is established between the force proportional to the pressure

  elastic force. A cross section of com-

  request is open with a different value, in said distribution

  main valve, depending on the pilot pressure and therefore

  quent, of the stroke of the control drawer. In the case of a

  control with volume flow regulation ("load-

  sensing ", or with load detection), the pressure drop

  producing through the opening cross section of the distri-

  main striker is kept constant by regulation of a variable displacement pump. There is then a correlation

  fixed, independent of the load, between the pre-

  established manually and the speed of the working movement. The speed range of the working movement corresponds to the stroke

  manual operation of a lever on the pilot control unit.

  Modern construction machinery must necessarily have both good aptitude for precise control and high working speeds. Since the lever travel on the pilot control device is limited for ergonomic reasons, the ability to control precisely becomes lower as the maximum working speed has to

  to be great. The aptitude for precise control is certainly improved.

  improved, in the low speed range, thanks to a progressive appearance of the characteristic curves both of the pilot control device and of the opening cross section in the main distributor, but the ability to control

  nevertheless degrades in the upper speed range.

  The subject of the invention is a pi-

  lot with the characteristics mentioned in the introduction, perfect

  such that the ability to control a movement

  work is improved in the low speed range

  ses, good command skills should also be pos-

  sible in the higher speed range.

  According to the invention, this object is achieved thanks

  to a pilot control device which has the characteristics

  ticks set out in the preamble to this memo, and in which the pilot pressure prevailing in the control chamber

  of said main distributor, can be reduced up to a

  their smaller compared to the pilot pressure prevailing at the control output of the pilot control distributor. In a pilot control device according to the invention, it is therefore possible, just like in control devices.

  pilot control known so far, to solicit a cham-

  control valve of the main control valve by the pilot pressure prevailing at the control output of the pilot control valve. Thus, with regard to high speeds of the working movement, no modification occurs.

  compared to known devices. However, the com-

  control of the main distributor can also be requested by a pilot pressure which is reduced compared to the pressure prevailing at the control output of the control distributor

  pilot. The full stroke of the lever, on the

  pilot demand, then corresponds to a smaller range of the

  control opening cross section in the dispenser

  principal, and therefore at a smaller range of speeds of the working movement. A very sensitive command is then

  possible in this speed range.

  Advantageously, to limit complexity,

  the pilot pressure prevailing in the control chamber of the

  main control valve can be reduced, taking into account a minimum pilot pressure necessary at the start of the adjustment of a control member of said main distributor, in fixed relation to the pilot pressure prevailing at the

  pilot control distributor control output.

  To bring about the reduction, it is for example possible to use a proportional pressure valve, installed in parallel with a distributor. This valve is in action when

  the dispenser is closed. Said valve remains without any

  fluence if the dispenser is open.

  However, it proves to be less expensive to allow a reduction of the pilot pressure, prevailing at the control output of the pilot control distributor, via a

  pressure divider with two throttles, between the

  which can be taken the reduced pilot pressure compared

  at the pilot pressure prevailing at the control output of the

  pilot control stopper, and among which a first

  this is located in a first branch of the pressure divider, located between the sampling point and the control outlet of the pilot control distributor, and a second

  constriction is found in a second branch of said divi-

  sor, located between the sampling point and a tank. Preferably, to switch from the normal pilot command, during

  which the pressure prevailing at the control output of the

  pilot control stopper also prevails in the control chamber of the main control distributor, on precise control during which the pilot pressure, prevailing in the control chamber of said main distributor, is reduced compared to the pilot pressure prevailing at the control output from the pilot control valve, a flow of control oil is allowed through the second throttle. To this end, a

  dispenser comprising an isolation position and a posi-

  tion of through circulation is conveniently located in the second branch of the pressure divider, in series with

  the second throttle. When this distributor occupies the posi-

  isolation, no control oil can flow to the tank through the second throttle. The pressure prevailing in the control chamber of the main control distributor then corresponds to the pressure prevailing at the control output of the pilot control distributor at least when a balance of forces is established on the control member of said main distributor. , and when this control member is at rest. In this case, you should no longer take into account a small circulation of oil resulting from a leak from the main distributor, and causing a small fall.

  pressure through the first throttle.

  Several pilot control distributors are authorized

  all present in mobile work devices, in order to be able to activate several consumers individually

  hydraulic. A pressure divider is respectively displayed.

  assigned to these multiple pilot control distributors. Enjoyed-

  therefore pressure dividers are present. However, from an economic point of view, it is favorable that the latter

  throttles of multiple pressure dividers be con-

  jointed connection, via a check valve

  respective return, to a distributor who precedes them on the supply side

  see, the non-return valves opening in the direction of said device

  tributor. Thus, a single distributor is present for most

  pilot distributors and for several di-

  pressure sights. The non-return valves guarantee

  no control oil flows through the second struts

  regulations, that is to say that each hydraulic consumer can be activated individually and that the pressure, prevailing in a control chamber, corresponds to the pilot pressure prevailing at the control output of a pilot control distributor. The control drawer of an order distributor

  main is normally maintained, by one or more res-

  reminder spell (s), in a rest position in which a preload must still be imposed on said spring (s). As a result, minimum pilot pressure is required to

  initiate movement of the control drawer. This pressure pi-

  minimum lot occurs, on the pilot control lever ac-

  manually operable, by an inert stroke that said lever

  must first traverse until a movement of tra-

  vail takes place. A pressure limiter allows to give the plate

  inert, in "precise control" functional mode, exactly the same value as in normal functional mode. Said limiter

  pressure can advantageously be interposed between the reservoir

  see and the second throttle of a pressure divider. A

  single pressure relief valve can also advantageously

  geuse, be arranged in series with several second throttles

  ment. The invention will now be described in more detail, by way of non-limiting example, with reference to the drawing on

  which the single figure illustrates a pi-

lot according to the invention.

  We can distinguish, in the drawing, two hydraulic devices

  ques 10 pilot control, both operating on the basis of pressure reducers 11 direct control, one of which is illustrated symbolically in each pilot control device. Each pilot control unit has a number

  total of four pilot control distributors 11 and, in con-

  sequence, four control outputs 12. Distributors 11

  can be adjusted by means of a lever 13

  pilot control can be deflected in four directions, from

  shot from a middle position in which a pressure of reserve

  see reigns at all control outputs 12 of a device 10.

  Depending on the deviation of the lever, said distributors

  regulate a pilot pressure determined at the output 12 correspond-

  laying. Pilot control devices of the type described are

  universally known and are illustrated in detail, e.g.

  ple, in the technical sheet RD 64 555 / 03.89 of the company

  Mannesmann Rexroth GmbH, Lohr / Main, so that comments

  more specific in this regard do not seem necessary.

  The pilot control apparatuses 10 activate

  tion of the control drawers 14 from several distributors of

  main control 15, one of which is shown in the drawing.

  In this main distributor 15, a respective control chamber 16 or 17, provided with a control connection 18, is located at each end of the drawer 14. The chamber 16 is larger than

  chamber 17 and receives two return springs 19 and 20 preloaded

  which are arranged coaxially to each other and center the drawer 14 in a middle position from which it

  can be moved in opposite directions, in counter

  rant the force of said springs 19 and 20.

  The main control distributor 15 has two connections 25 and 26 of a consumer appliance, or working connections, to which two respective conduits of

  work 28 and 29 leading to a hydraulic cylinder 27. The two rac-

  working edges 25 and 26 can be isolated when the drawer

  control 14 occupies the middle position. When moving

  drawer 14 from the middle position, one of the

  working ropes is connected to a pressure source, by the in-

  end of an opening section depending on the size

  displacement, and the other working fitting is connected to a

to serve.

  A control conduit 30 gains each connection of com

  18 of the main distributors 15, led by the

  median from which a pilot pressure prevailing between a first fixed throttle 31 and a second fixed throttle 32 of a pressure divider can be taken. The first fixed constriction 31 is interposed between a sampling point 33 and an outlet

  12 of a distributor 11 of pilot control. A class

  pet non-return valve 34, installed in series with each fixed throttle 32, opens in the direction of a collecting duct 35 common to all the fixed throttles 32. A distributor 40 has

  a rest position in which it isolates the collecting duct

  35. It can be brought, by an electromagnet 41, to a po-

  switching position in which said conduit 35 is connected

  strung, via said distributor 40, at the input

  a pressure relief valve 42 whose outlet is relieved in di-

  rection of a reservoir 43. The limiter 42 is adjusted to a pressure corresponding to the minimum pilot pressure, from which there is a movement of the control slide 14

  a main control valve 15.

  The electromagnet 41 is connected, via a control conductor 44, to an electric switch not shown in detail, integrated in one of the two devices 10

  pilot control, and can be actuated by means of a button

  push-button 45 housed in the pilot control lever 13.

  The electromagnet 41 is energized as long as the button-

  pusher 45 is depressed, so that the passage through the

  dispenser 40 is open. The distributor 40 falls back to its po-

  rest position when the push button 45 is released. This-

  the electrical switch can just as easily

  sister in a bistable switch whose switching position

  tion varies with each push of the push button 45.

  Using the pilot control device described, the device

  two hydraulic consumers can be used in two ways

  functional modes. When the distributor 40 takes its position

  tion of rest and isolates the collecting duct 35, it develops in a control chamber, during a displacement of the control lever 13, a pressure corresponding essentially to the pressure prevailing at the control output 12 of the distributor 11 pilot control which is actuated by the displacement of said lever 13. In fact, the distributor 40 prevents an oil circulation, directly to the reservoir, via

  the corresponding fixed throttle 32; and check valves

  return 34 prevent oil circulation until the tank

  see, via the fixed throttle 32 corresponding

  in addition to other fixed throttles 32,

  fixed bearings 31 located downstream of the pilot control distributors which are not actuated, and of said pilot control distributors which are not actuated. If necessary, a leak through the control slide 14 can cause a small circulation of oil through the fixed throttle 31 located at

  downstream of the pilot control distributor which is precisely activated

  and therefore also a pressure drop occurs

duisant said choke.

  An actuation of the distributor 40 results in switching to a precise command. Two cases must then be distinguished. As long as the pressure prevailing at the control output 12 of a pilot control valve 11 is lower than the pressure at which the pressure relief valve 42 is adjusted, no control oil can flow until

  reservoir 43 via the fixed throttle 32 cor-

  respondent. The pressure prevailing in a respective control chamber 16 or 17 therefore corresponds, essentially, to the pressure prevailing at the control output 12. When the pressure prevailing at the output 12 exceeds the pressure set on the limiter 42, and at this stage only, said limiter opens so that a flow of control oil flows up to

  reservoir 43, using the fixed throttle 31 corresponding

  dant, the associated fixed throttle 32, a non-return valve 34, the distributor 40 and the limiter 42. There is now reign at the sampling point 33 between the two throttles 31, 32, and therefore in a respective control chamber 16 or 17, a pressure between the pilot pressure at the control output 12, and

  the pressure set on the limiter 42. The value of this pressure

  sion depends on the opening sections of the fixed throttles 31 and 32. The pressure limiter 42 allows the movement of the control slide 14 to start, in functional mode

  precise control, when the lever 13 undergoes the same movement-

  only in normal functional mode. The difference between the

  pilot pressure prevailing at a control output 12, and the pressure

  sion set on the limiter 42, is in fixed relation with the diff-

  reference between the pilot pressure taken at point 33, and the

  pressure set on said limiter 42. Thus, when moving

  integrally of a control lever 13, the pressure prevailing in a control chamber 16 or 17 respectively is lower than in normal functional mode, so that the control slide 14 is also displaced by a distance lesser. The

  full lever travel is therefore available on the app.

  similar 10 pilot control, for controlling a small range of speeds of the working movement, making it possible

a sensitive command.

  O10 Several pilot control distributors can also

  They can be easily activated when the mode is

  "precise control" is engaged. There is no mutual influence of the pilot pressures at the points of

direct debit 33.

  It goes without saying that many modifications can-

  can be made to the device described and shown, without

depart from the scope of the invention.

-R E V E N D I CATIONS -

  1. Pilot control device fitted to a dispenser

  main control actuator (15) hydraulically actuated, comprising an adjustable pilot control distributor (11), provided with a control output (12) at which a pilot pressure prevails which can be preset by an input signal, and by which a control chamber (16, 17) of the distributor

  main control (15) can be activated, device

  characterized by the fact that the pilot pressure prevailing in the control chamber (16, 17) of said main distributor (15) can be reduced to a smaller value compared to

  the pilot pressure prevailing at the control output (12) of the device

pilot control tributor (11).

  2. Device according to claim 1, characterized by

  the fact that the pilot pressure prevailing in the control chamber

  demand (16, 17) of the main control valve (15) can be reduced, taking into account a minimum pilot pressure

  necessary at the start of the adjustment of a control member (14) of the

  said main distributor (15), in fixed relation to

  the pilot pressure prevailing at the control output (12) of the device

pilot control tributor (11).

  3. Device according to claim 1 or 2, characterized by a pressure divider provided with two throttles (31,

  32), between which the pilot pressure can be taken

  that is relative to the pilot pressure prevailing at the control output (12) of the pilot control distributor (11), and among which a first throttle (31) is located in a first branch of the pressure divider, situated between the point of direct debit (33) and the control outlet (12) of the distributor

  (11) for pilot control, and a second throttle (32) is found

  ve in a second branch of said divider, located between the

  sampling point (33) and a reservoir (43).

  4. Device according to claim 3, characterized by

  the fact that a distributor (40), comprising an iso-

  Lely and a through circulation position, is located in the second branch of the pressure divider, in series

with the second throttle (32).

  5. Device according to claim 4, characterized by

  the fact that the distributor (40) can be actuated by means of

  medial of an electromagnet (41). 6. Device according to claim 4 or 5, characterized

  by the presence of several pid control distributors (11)

  lot, to which a pressure divider (31, 32) is respectively-

  mentally affected; and by the fact that the second throttles (32)

  multiple pressure dividers are connected together

  dice, via a non-return valve (34) respec-

  tif, to a distributor (40) which precedes them on the tank side, the

  non-return valves (34) opening in the direction of said distribution

(40).

  7. Device according to any one of the claims

  3 to 6, characterized in that a pressure relief valve (42) is interposed between the reservoir (43) and the second throttle

(32) of a pressure divider.

  8. Device according to claims 6 and 7, character-

  operated by a single pressure relief valve (42), arranged in series

  with several second throttles (32).