WO2011142835A1 - Système de mise à niveau de plate-forme - Google Patents

Système de mise à niveau de plate-forme Download PDF

Info

Publication number
WO2011142835A1
WO2011142835A1 PCT/US2011/000859 US2011000859W WO2011142835A1 WO 2011142835 A1 WO2011142835 A1 WO 2011142835A1 US 2011000859 W US2011000859 W US 2011000859W WO 2011142835 A1 WO2011142835 A1 WO 2011142835A1
Authority
WO
WIPO (PCT)
Prior art keywords
platform
height
cylinders
hydraulic fluid
cargo loader
Prior art date
Application number
PCT/US2011/000859
Other languages
English (en)
Inventor
David Mercer
Original Assignee
John Bean Technologies Corporation
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 John Bean Technologies Corporation filed Critical John Bean Technologies Corporation
Publication of WO2011142835A1 publication Critical patent/WO2011142835A1/fr

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64F—GROUND OR AIRCRAFT-CARRIER-DECK INSTALLATIONS SPECIALLY ADAPTED FOR USE IN CONNECTION WITH AIRCRAFT; DESIGNING, MANUFACTURING, ASSEMBLING, CLEANING, MAINTAINING OR REPAIRING AIRCRAFT, NOT OTHERWISE PROVIDED FOR; HANDLING, TRANSPORTING, TESTING OR INSPECTING AIRCRAFT COMPONENTS, NOT OTHERWISE PROVIDED FOR
    • B64F1/00—Ground or aircraft-carrier-deck installations
    • B64F1/32—Ground or aircraft-carrier-deck installations for handling freight
    • B64F1/322—Cargo loaders specially adapted for loading air freight containers or palletized cargo into or out of the aircraft

Definitions

  • the present invention is directed to a platform leveling system for maintaining at least two opposite sides of a moveable platform level during use.
  • the platform leveling system is used to maintain the platform of an aircraft cargo loader level during lifting and lowering of the platform.
  • One type of prior art aircraft cargo loader comprises a loading platform which is supported on a frame by a pair of scissors.
  • the platform is lifted and lowered relative to the frame by a pair of hydraulic lift cylinders.
  • Each cylinder comprises a cylinder body which is connected to the frame and a piston rod which is movably supported in the cylinder body.
  • a roller is connected to the top of each piston rod and a lift chain having a first end connected to the platform and a second end connected to the frame is trained over the roller.
  • the height of the platform is directly related to the height of the piston rods. Consequently, when the piston rods are extended the platform is raised relative to the frame, and when the piston rods are retracted the platform is lowered relative to the frame.
  • an aircraft cargo loader which comprises a frame; a platform which is supported for vertical movement relative to the frame, the platform comprising at least first and second opposite sides; first and second hydraulic cylinders for lifting and lowering the first and second sides relative to the frame; at least one sensor for generating signals representative of the height of the first side relative to the height of the second side; and a controller for controlling the flow of hydraulic fluid to and from the first and second cylinders.
  • the controller controls the flow of hydraulic fluid to or from at least one of the first and second cylinders in response to the signals generated by the at least one sensor in order to maintain the first and second sides level.
  • an operator in operation of the cargo loader an operator directs the lifting and lowering of the first cylinder and the controller controls the flow of hydraulic fluid to or from the second cylinder in order to maintain the second side level with the first side.
  • the cargo loader may comprise a first valve for controlling the flow of hydraulic fluid to and from the first cylinder and a second valve for controlling the flow of hydraulic fluid to and from the second cylinder, the first and second valves being controlled by the controller.
  • each of the first and second valves may comprise a four-way three-position valve.
  • the cargo loader may comprises a third valve which is connected between the first and second cylinders and which in the event of a failure of the at least one sensor opens to allow hydraulic fluid to flow between the cylinders.
  • the at least one sensor comprises a first sensor for generating a first signal representative of the height of the first side relative to the frame and a second sensor for generating a second signal representative of the height of the second side relative to the frame.
  • each of the first and second sensors may comprise a magnetostrictive linear position (MLP) sensor.
  • MLP magnetostrictive linear position
  • each of the first and second cylinders comprises a piston rod which is connected to a piston that is slidably received in a cylinder body
  • each MLP sensor may comprise a sensor head which is fixed in position relative to the cylinder body; a position magnet which is fixed in position relative to the piston rod; and a sensor pipe which extends from the sensor head through the position magnet.
  • the position of the position magnet relative to the sensor head is representative of the height of the corresponding first or second side relative to the frame.
  • the cylinder body comprises a cylinder barrel having an end which is closed by a cap
  • the sensor head may be mounted to the cap
  • the position magnet may be mounted to the piston
  • the sensor pipe may extend axially through the position magnet and the piston rod.
  • the controller determines the actual speed at which the platform is being lifted or lowered based on at least one of the first and second signals.
  • the controller may control the flow of hydraulic fluid to or from the first and second cylinders in order to maintain the actual speed at which the platform is being lifted and lowered approximately equal to a desired lift or lower speed.
  • the controller may control the flow of hydraulic fluid to or from the first and second cylinders in order to adjust the actual speed at which the platform is being lifted and lowered depending on the height of at least one of the first and second sides relative to the frame.
  • the present invention also provides a novel method for maintaining the platform of an aircraft cargo loader level in use, the platform being supported for vertical movement relative to a frame and having first and second opposite sides which are raised and lowered by corresponding first and second hydraulic cylinders.
  • the method comprises the steps of communicating hydraulic fluid to or from the first and second cylinders in order to lift or lower the platform; generating signals representative of the height of the first side relative to the height of the second side; and controlling the flow of hydraulic fluid to or from at least one of the first and second cylinders in response to the signals in order to maintain the first and second sides at approximately the same height during lifting and lowering of the platform.
  • the flow of hydraulic fluid to the first cylinder is manually controlled and the flow of hydraulic fluid to the second cylinder is automatically controlled in response to the signals in order to maintain the height of the second side approximately the same as the height of the first side during lifting and lowering of the platform.
  • the step of generating signals representative of the height of the first side relative to the height of the second side comprises generating a first signal representative of the height of the first side relative to the frame and generating a second signal representative of the height of the second side relative to the frame.
  • the method comprises the step of determining the actual speed at which the platform is being lifted or lowered based on at least one of the first and second signals.
  • the method may also comprise the step of controlling the flow of hydraulic fluid to or from the first and second cylinders in order to maintain the actual speed at which the platform is being lifted and lowered approximately equal to a desired lift or lower speed.
  • the method may comprise the step of controlling the flow of hydraulic fluid to or from the first and second cylinders in order to adjust the actual speed at which the platform is being lifted and lowered depending on the height of at least one of the first and second sides relative to the frame.
  • Figure 1 is a perspective view of an exemplary cargo loader comprising a first embodiment of the platform leveling system of the present invention
  • Figure 2 is a partial cross sectional view of the lift cylinder component of the platform leveling system shown in Figure 1 ;
  • Figure 2A is a partial cross sectional view of an alternative embodiment of the lift cylinder component of the platform leveling system shown in Figure 1 ;
  • Figure 3 is a schematic drawing of the hydraulic circuit of the platform leveling system shown in Figure 1 ; and Figure 4 is a perspective view of an exemplary cargo loader comprising two alternative embodiments of the platform leveling system of the present invention.
  • the platform leveling system of the present invention has wide application to a variety of equipment, such as cargo loaders, conveyors and lift tables.
  • the invention is particularly useful in aircraft cargo loaders which comprise a cargo platform that can be raised and lowered relative to a vehicle frame by two or more hydraulic lift cylinders.
  • the cargo loader of this embodiment includes a rear platform 12 which is supported by a pair of rear scissors 14 on a cargo loader frame 16.
  • the rear platform 12 is raised and lowered relative to the frame 16 by left and right hydraulic lift cylinders 18 and 20.
  • Each cylinder 18, 20 comprises a cylinder body 22 which is connected to the frame 16 and a piston rod 24 which is movably supported in the cylinder body in a conventional manner.
  • a roller 26 is connected to the top of each piston rod 24, and a lift chain 28 having a first end connected to the platform 12 and a second end connected to the frame 16 is trained over the roller.
  • the height of the platform 12 is directly related to the height of the piston rods 24.
  • the platform 12 During operation of the cargo loader 10, it is important that the platform 12 remain level at all times as cargo is being lifted and lowered.
  • the lift cylinders In certain prior art cargo loaders in which the lift cylinders are positioned on the left and right sides of the platform, maintaining the platform level in certain situations, such as when the load is positioned off center, may be difficult.
  • the cylinders are connected in parallel to their source of hydraulic fluid and therefore exert an equal force on the left and right sides of the platform.
  • the cylinders will not be able to maintain the piston rods at the same height.
  • the platform leveling system maintains the piston rods 24 at the same height when the cylinders 18, 20 are activated to raise and lower the platform 12.
  • the platform 12 will remain level at all times during operation of the cargo loader 10.
  • the platform leveling system maintains the piston rods 24 at the same height by individually controlling the left and right cylinders 18, 20 in response to signals representative of the height of the left and right sides of the platform 2 relative to the frame 16.
  • These left and right side position signals may be provided by any of a number of conventional sensors, such as linear or rotary encoders which are operatively connected between the platform 12 and the frame 16 adjacent each of the cylinders 18, 20.
  • each of the left and right side position signals is generated by a respective magnetostrictive linear position sensor which is embedded in a corresponding cylinder 18, 20.
  • MLP magnetostrictive linear position
  • the cylinder 20 is identical to the cylinder 18 and therefore does not need to be described separately.
  • the piston rod 24 is connected to a piston 32 which is slidably received within a cylinder barrel 34 that forms a portion of the cylinder body 22 shown in Figure 1 :
  • the end of the barrel 34 is closed by a cap 36 to which an end piece 38 is secured, such as by bolts 40.
  • the barrel 34 is connected to a source of hydraulic fluid through a port 42 which extends through the cap 36.
  • a suitable MLP sensor 30 for use in the present invention is the
  • the MLP sensor 30 includes a sensor head 44 which is fixed in position relative to the cylinder body 22, a ring-shaped position magnet 46 which is fixed in position relative to the piston rod 24, and a sensor pipe 48 which is connected to the sensor head and extends through the position magnet and the piston rod 24 to approximately the opposite end of the cylinder body.
  • the sensor head 44 may be mounted in a corresponding bore in the cap 36 and retained in position by the end piece 38 and/or a retainer screw 50.
  • the end piece 38 is omitted and the sensor head 44 is simply mounted in a corresponding bore in the cap 36 and retained in position by the retainer screw 50.
  • the position magnet 46 may be mounted in a
  • the MLP sensor 30 uses a time-based magnetostrictive position sensing principle to determine the distance of the position magnet 46 relative to the sensor head 44.
  • the sensor head 44 generates a current pulse which travels along a waveguide located in the sensor tube 48. This current pulse generates a first magnetic field which interacts with a second magnetic field generated by the position magnet 46. The momentary interaction of these two magnetic fields produces a strain pulse which travels back along the waveguide and is detected by the sensor head 44.
  • the sensor head 44 measures the elapsed time between the generation of the current pulse and the detection of the strain pulse and uses this elapsed time to calculate the distance between the sensor head and the position magnet 46.
  • the MLP sensor 30 in the left cylinder 18 is a measure of the height of the left side of the platform 12 relative to the frame 16 and can therefore be used as the left side position signal.
  • the output of the MLP sensor 30 in the right cylinder 20 is a measure of the height of the right side of the platform 12 relative to the frame 16 and can therefore be used as the right side position signal.
  • the MPL sensors 30 may be calibrated by simply setting the left and right side position signals equal when the platform is verified by an external measuring device to be level.
  • the platform leveling system includes means responsive to the left and right side position signals for adjusting the hydraulic flow to or from at least one of the cylinders 18, 20 in order to maintain the left and right sides of the platform 12 at the same height.
  • one of the cylinders, say cylinder 18, is designated a master cylinder and moves as directed by the operator
  • the other cylinder, in this case cylinder 20 is designated a slave cylinder
  • the flow adjusting means adjusts the hydraulic flow to or from the slave cylinder in order to maintain the height of the right side of the platform 12 equal to the height of the left side of the platform.
  • the flow adjusting means in accordance with one embodiment of the invention comprises a suitable controller, such as a
  • the PLC 52 controls two solenoid valves 54, 56.
  • Each solenoid valve 54, 56 may be a four-way three-position valve which in a first position connects a corresponding cylinder 18, 20 with a source of hydraulic fluid, such as a pump 58, in a second position connects the, cylinder with a sump 60, and in a third position disconnects the cylinder from both the pump and the sump.
  • the first or master valve 54 is positioned in a first hydraulic line 62 extending between the pump 58 and the master cylinder 18.
  • the second or slave valve 56 is positioned in a second hydraulic line 64 which extends between the pump 58 and the slave cylinder 20.
  • the cylinders 18 and 20 are connected by a third hydraulic line 66 which is normally closed by a by-pass valve 68.
  • the PLC 52 receives the left and right side position signals from the MLP sensors 30 and compares these signals to determine if a difference exists between the height of the left and right sides of the platform 12. If a difference exists, the PLC 52 applies this difference as an error signal to the slave valve 56 in order to adjust the flow of hydraulic fluid to or from the slave cylinder 20 to thereby bring the height of the right side of the platform level with that of the left side of the platform. For example, if the difference between the left and right side position signals indicates that the right side of the platform is lower than the left side of the platform, the PLC 52 will open the slave valve 56 an amount sufficient to raise the right side to the level of the left side. Similarly, if the difference between the left and right side position signals indicates that the right side of the platform is higher than the left side of the platform, the PLC 52 will close the slave valve 56 an amount sufficient to lower the right side to the level of the left side.
  • This same operation can be performed to maintain the left and right sides of the platform 12 level during raising and lowering of the platform.
  • the platform 12 is raised by moving the valves 54, 56 to their first position in order to open the lines 62, 64 connecting the pump 58 to the cylinders 18, 20.
  • the platform 12 may then be lowered by moving the valves 54, 56 to their second position in order to connect the cylinders 18, 20 to the sump 60.
  • the amount the valves 54, 56 are opened in each of these positions determines the lift and lower speed of the platform 12.
  • the PLC 52 will compare the left and right side position signals and, if a difference between these signals exists, apply the difference to the slave valve 56 in order to bring the right side to the level of the left side. For example, if during raising of the platform 12 the right side is lower than the left side, the PLC 52 will open the slave valve 56 an additional amount sufficient to bring the right side level with the left side as the platform is moving. Similarly, if during lowering of the platform 12 the right side is lower than the left side, the PLC 52 will close the slave valve 56 an additional amount sufficient to bring the right side level with the left side as the platform is moving.
  • the platform leveling system may be used to control the lift and lower speed of the platform 12.
  • the lift and lower speed is adjusted by varying the amount the valves 54, 56 are opened.
  • the platform leveling system addresses this problem by determining the actual lift and lower speed from the derivative of the left and right side position signals. The PLC 52 then adjusts the valves 54, 56 in order to maintain a desired speed.
  • the platform leveling system of the present invention may be used to automatically adjust the speed of the platform 12 as it is being raised or lowered.
  • the platform leveling system may adjust the valves 54, 56 to slow down the platform 12 as it is nears its fully lowered or fully raised position and to speed up the platform in between these positions.
  • the platform leveling system may be used to enable or disable certain functions when the platform 12 reaches a predetermined height.
  • the platform leveling system comprises two level sensors 70, each of which is mounted on a corresponding scissor 14 at approximately the same longitudinal distance from the frame 16.
  • each level sensor 70 provides a corresponding left or right side position signal which the PLC 52 uses to control the valves 54, 56 in the manner described above in order to maintain the left and right sides of the platform 12 level.
  • the platform leveling system comprises a single level sensor 72 mounted under approximately the center of the platform 12.
  • the level sensor 72 provides both the left and right side position signals which the PLC 52 uses to control the valves 54, 56 in the manner described above in order to maintain the left and right sides of the platform 12 level.
  • the level sensors 70, 72 may be, e.g. , mercury switches, inclinometers or accelerometers.
  • the platform leveling system is used with a cargo loader having four lift cylinders, each of which is located near a corresponding corner of the platform.
  • the platform leveling system employs two sensors or sets of sensors, one for detecting the difference in height between the left and right sides of the platform and one for detecting the difference in height between the front and back of the platform.
  • the first set of sensors may comprise two MLP sensors 30 mounted as described above, and the second set of sensors may comprise a single tilt sensor 72 mounted in approximately the center of the platform.
  • one of the cylinders is designated as a master cylinder, the remaining cylinders are designated as slave cylinders, and the PLC controls the valves for each of the slave cylinders in a manner described above in order to maintain the left side level with the right side and the front level with the back.
  • the platform leveling system of the present invention may also include means for disabling the system in the event of, e.g. , a failure of the system.
  • the by- pass valve 68 connecting the cylinders 18 and 20 is opened. This will equalize the pressure in the cylinders 18, 20 and cause the cargo loader 10 to operate in a manner similar to the prior art cargo loader described above.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Fluid-Pressure Circuits (AREA)

Abstract

L'invention concerne un système de mise à niveau de plate-forme pour un chargeur de fret aérien, ledit système comprenant des premier et second vérins hydrauliques destinés à lever et abaisser des premier et second côtés correspondants de la plate-forme, au moins un capteur destiné à générer des signaux indiquant la hauteur du premier côté par rapport à la hauteur du second côté, et un dispositif de commande destiné à réguler l'écoulement de fluide hydraulique vers les premier et second vérins et depuis ces derniers en réponse aux signaux générés par le ou les capteurs, afin de maintenir le niveau des premier et second côtés.
PCT/US2011/000859 2010-05-13 2011-05-13 Système de mise à niveau de plate-forme WO2011142835A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US39560910P 2010-05-13 2010-05-13
US61/395,609 2010-05-13
US39598410P 2010-05-19 2010-05-19
US61/395,984 2010-05-19

Publications (1)

Publication Number Publication Date
WO2011142835A1 true WO2011142835A1 (fr) 2011-11-17

Family

ID=44914632

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2011/000859 WO2011142835A1 (fr) 2010-05-13 2011-05-13 Système de mise à niveau de plate-forme

Country Status (1)

Country Link
WO (1) WO2011142835A1 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017030551A1 (fr) * 2015-08-17 2017-02-23 John Bean Technologies Corporation Chargeur pour aéronef
CN107915168A (zh) * 2017-11-24 2018-04-17 广东浩翔机械制造有限公司 可互换型同轴自动微调的升降装置及其安装方法
CN109941619A (zh) * 2019-03-12 2019-06-28 中国船舶重工集团应急预警与救援装备股份有限公司 一种带可翻转滚道的运输平台
CN110160416A (zh) * 2018-04-16 2019-08-23 北京机电工程研究所 托弹架拆卸装置及技术准备车
WO2023036202A1 (fr) * 2021-09-10 2023-03-16 威海广泰空港设备股份有限公司 Dispositif de mise à niveau automatique pour une plate-forme de transport, et chargeur

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2764869A (en) * 1954-08-19 1956-10-02 Origins Inc Means for synchronizing the travel of two or more traveling work elements
US4312619A (en) * 1979-07-19 1982-01-26 Fmc Corporation Aircraft cargo loading method and apparatus
US4662809A (en) * 1985-09-27 1987-05-05 Fmc Corporation Automatic level device
US5150049A (en) * 1991-06-24 1992-09-22 Schuetz Tool & Die, Inc. Magnetostrictive linear displacement transducer with temperature compensation
US5992562A (en) * 1996-01-26 1999-11-30 Jlg Industries, Inc. Scissor lift control apparatus

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2764869A (en) * 1954-08-19 1956-10-02 Origins Inc Means for synchronizing the travel of two or more traveling work elements
US4312619A (en) * 1979-07-19 1982-01-26 Fmc Corporation Aircraft cargo loading method and apparatus
US4662809A (en) * 1985-09-27 1987-05-05 Fmc Corporation Automatic level device
US5150049A (en) * 1991-06-24 1992-09-22 Schuetz Tool & Die, Inc. Magnetostrictive linear displacement transducer with temperature compensation
US5992562A (en) * 1996-01-26 1999-11-30 Jlg Industries, Inc. Scissor lift control apparatus

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017030551A1 (fr) * 2015-08-17 2017-02-23 John Bean Technologies Corporation Chargeur pour aéronef
CN108137169A (zh) * 2015-08-17 2018-06-08 卓缤科技贸易公司 飞行器用升降机
CN108137169B (zh) * 2015-08-17 2022-01-04 Jbt航空技术公司 飞行器用升降机
US11465775B2 (en) 2015-08-17 2022-10-11 JBT AeroTech Corporation Loader for aircraft
CN107915168A (zh) * 2017-11-24 2018-04-17 广东浩翔机械制造有限公司 可互换型同轴自动微调的升降装置及其安装方法
CN110160416A (zh) * 2018-04-16 2019-08-23 北京机电工程研究所 托弹架拆卸装置及技术准备车
CN109941619A (zh) * 2019-03-12 2019-06-28 中国船舶重工集团应急预警与救援装备股份有限公司 一种带可翻转滚道的运输平台
WO2023036202A1 (fr) * 2021-09-10 2023-03-16 威海广泰空港设备股份有限公司 Dispositif de mise à niveau automatique pour une plate-forme de transport, et chargeur

Similar Documents

Publication Publication Date Title
NL2017114B1 (en) Lifting system for lifting a vehicle with indirect height measurement and method therefor
EP2947209B1 (fr) Ensemble de levage amélioré destiné à un véhicule de travail
EP2982639B1 (fr) Système de stabilité latérale
CN106661894B (zh) 实现悬臂弹跳减少以及防止液压系统中的非指令运动的方法和设备
US9932215B2 (en) Lift arm suspension system for a power machine
WO2011142835A1 (fr) Système de mise à niveau de plate-forme
EP2839171B1 (fr) Système de commande à transmission d'énergie par fluide pour équipement de manipulation de charge mobile
EP1300595B1 (fr) Système hydraulique avec commande électronique pour abaisser une flèche dans une situation d'urgence
CN201784598U (zh) 支腿式工程机械及其液压控制系统
US8504251B2 (en) Interference prevention control device of a machine
CN102192206A (zh) 一种液压动态同步控制与位置补偿系统
GB2440810A (en) Control valves
US20180170733A1 (en) Industrial truck having a control unit for regulating the movement of a hydraulic cylinder, and method for controlling the same
US20140174550A1 (en) Fault isolation & decontamination procedures for electrohydraulic valves
US20090043461A1 (en) Method and device for longitudinally balancing an agricultural vehicle
EP2711332A1 (fr) Véhicule avec descente de chariot sollicitée
CN112064699A (zh) 基于油缸行程位移的铲斗自动调平控制方法和系统
FI118469B (fi) Menetelmä ja laitteisto nosturin toimilaitteen ohjaamiseksi
CN106762936A (zh) 一种液压支架试验加载台移动梁升降液压缸同步控制系统
CN110616758B (zh) 挖掘机节能控制系统
CN208218342U (zh) 一种防止叉车货叉高位误操作的控制系统
US11668296B2 (en) Hydraulic system and method for controlling the speed and pressure of a hydraulic cylinder
EP3789338B1 (fr) Systèmes de décharge de pression hydraulique variable et procédés pour un véhicule de manutention de matériaux
KR101190054B1 (ko) 출력 조절형 카고 크레인 및 그의 출력 조절 방법

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 11780929

Country of ref document: EP

Kind code of ref document: A1

DPE1 Request for preliminary examination filed after expiration of 19th month from priority date (pct application filed from 20040101)
NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 11780929

Country of ref document: EP

Kind code of ref document: A1