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WO1983003089A1 - Indicateur par reduction de vitesse de l'inclinaison d'un mat - Google Patents

Indicateur par reduction de vitesse de l'inclinaison d'un mat Download PDF

Info

Publication number
WO1983003089A1
WO1983003089A1 PCT/US1982/000297 US8200297W WO8303089A1 WO 1983003089 A1 WO1983003089 A1 WO 1983003089A1 US 8200297 W US8200297 W US 8200297W WO 8303089 A1 WO8303089 A1 WO 8303089A1
Authority
WO
WIPO (PCT)
Prior art keywords
mast
flow
valve
fluid
positions
Prior art date
Legal status (The legal status 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 status listed.)
Ceased
Application number
PCT/US1982/000297
Other languages
English (en)
Inventor
Jerry L Reeves
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
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 Individual filed Critical Individual
Priority to PCT/US1982/000297 priority Critical patent/WO1983003089A1/fr
Priority to CA000417981A priority patent/CA1178250A/fr
Priority to GB08235966A priority patent/GB2116518B/en
Priority to FR8303622A priority patent/FR2523109B1/fr
Publication of WO1983003089A1 publication Critical patent/WO1983003089A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66F—HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD
    • B66F17/00—Safety devices, e.g. for limiting or indicating lifting force
    • B66F17/003—Safety devices, e.g. for limiting or indicating lifting force for fork-lift trucks

Definitions

  • This invention relates generally to vehicles which have a tiltable mast for supporting and carrying loads and more particularly to apparatus which informs the vehicle operator when the mast arrives at a predetermined inclination.
  • the mast of a lift truck or the like is usually more or less upright as a load is being received or deposited and is tilted backward towards the body of the vehicle, to retain the load, during load carrying operations. Inadvertent forward tilting of the mast beyond a few degrees from vertical during load carrying operations can cause a loss of the load from the forks or other load engaging components. Stability of the vehicle may be adversely affected particularly if there is a substantial amount of forward tilt at a time when a load is being supported at an elevated location along the mast.
  • tilt motion limiting mechanisms of various kinds on lift trucks or the like may variously be mechanical stops or mechanisms which stop operation of the fluid motors that are typically used to tilt the mast.
  • These may variously be mechanical stops or mechanisms which stop operation of the fluid motors that are typically used to tilt the mast.
  • Forward tilting of the mast may be needed to enable travel of the vehicle under a low overhead obstacle.
  • Lowering of the mast by forward tilting may also be desirable when the vehicle is being towed or transported on the bed of a truck or other conveyance.
  • Forward tilt may also be necessary in order to deposit loads at elevated locations, such as openings in stacks of containers, under some conditions. Instances where forward tilting of the mast may be necessary have become more common with the advent of so called rough terrain lift trucks which typically have high masts and which may be designed to operate on uneven surfaces such as at construction sites or the like.
  • Providing of an override system with which the operator could optionally inactivate the forward tilt motion limiting mechanism would add substantial structural complication and the override system could itself be left activated either by accident or purposely in order to avoid a need for repeated actuations during subsequent work operations.
  • Audible or visual indicators such as buzzers or indicator lamps for alerting the operator when the mast is tilted forwardly past a predetermined inclination are not a preferred solution in view of the large number of other audible and visual indicator devices which are typically present on a lift truck. Indicators of this kind require considerable maintenance and are also readily susceptible to intentional disconnection. It would be advantageous to use some other system to signal the operator when the mast enters the forward tilt range of movement.
  • the present invention is directed to overcoming one or more of the problems as set forth above.
  • a load handling vehicle having a tiltable mast, means for supporting a load on the mast and motor means for tilting the mast between a first and a second position is further provided with speed reducing means for slowing tilting movement of the mast and inclination sensing means for detecting the inclination of the mast and actuating the speed reducing means in response to movement of the mast into a predetermined range of mast positions between the first and second positions.
  • the invention very reliably alerts the operator of a lift truck or the like when a load supporting mast reaches a predetermined inclination by a temporary slowing of the rate of tilting movement.
  • the tilting of the mast may then be continued if that is desired without additional actions on the part of the operator such as disconnection or removal of motion limiting mechanisms.
  • the apparatus is not susceptible to being inadvertently left in an inactivated condition and can be arranged to render deliberate inactivation extremely difficult.
  • the apparatus may, if desired, be arranged to slow the rate of mast tilt only during forward tilting movement but not during the return movement of the mast through the same portion of the range of mast inclinations. This avoids delay in the return movement.
  • Figure 1 is a side elevation view of the forward portion of an industrial lift truck equipped with a first embodiment of the present invention.
  • Figure 2 is an axial section view of a tilt speed restrictor valve of the embodiment of the invention depicted in Figure 1 further including certain associated fluid circuit elements which are shown in schematic form.
  • Figure 3 depicts certain elements of the embodiment of Figure 2 in shifted positions which occur at another stage of operation.
  • Figure 4 depicts the structure of Figure 3 at still another stage of operation.
  • Figure 5 is a diagrammatic view of an alternate embodiment of the present invention.
  • Figure 6 is an elevation view of a portion of the structure of Figure 5, taken along line VI-VI. Best Modes for Carrying Out the Invention
  • FIG. 1 of the drawings many load handling vehicles such as the industrial lift truck 11 of this embodiment have an upwardly extending mast 12 on which loads are supported.
  • the mast 12 may be connected to the frame or body 13 of the vehicle through a pivot coupling 14 situated near the base of the mast to provide for tilting of the mast both forwardly and backwardly from the vertical orientation shown in the drawing.
  • Means 16 for supporting a load on the mast 12 may take a variety of forms and in this example includes a carriage 17 with forwardly extending forks 18 for engaging a load, the carriage being vertically movable along the mast 12.
  • Motor means 19 for causing tilting movement of mast 12 in this embodiment include a pair of fluid operated extensible and retractable tilt cylinders 20 of which a single cylinder appears in Figure 1, the cylinders being connected between the mast and body 13 of the vehicle.
  • the fluid cylinders 20 may for example be sized to provide for a range of mast inclinations from about 12° of backward tilt to about 45° of forward tilt relative to vertical although these limits may be different in other vehicles.
  • the mast 12 is not tilted forward beyond a few degrees during many load handling operations but the forward tilt capability is present to enable certain specialized operations such as lowering of the mast when that is necessary to travel the vehicle under overhead obstacles.
  • the lift truck 11 is further provided with tilt indicator means 21 for alerting the operator when tilting motion moves the mast 12 into a predetermined portion of the range of mast inclinations by temporarily slowing the rate of tilting motion.
  • tilt indicator means 21 slows the mast 12 motion as the mast tilts forwardly through the initial, 0° to 5°, part of the total 45° range of forward inclinations although the apparatus may be arranged to slow the rate of tilting at any other portion of the total range of inclinations as may be desirable in other load carrying vehicles.
  • the tilt indicator means 21 includes tilt speed reducing means 22 for temporarily slowing tilting movement of the mast 12 and inclination sensing means 23 for detecting the inclination of the mast and actuating the tilt speed reducing means in response to movement of the mast into a predetermined range of mast positions.
  • the rod end and head end ports 24 and 26 respectively of the tilt cylinders 20 are connected to a source of pressurized fluid 27 through flow lines 28 and 29 respectively and through control valve means 31 for transmitting pressurized fluid to a selected one of the flow lines while discharging fluid from the other flow line and which also provides for selective blocking of both flow lines to immobilize the cylinders 20 and thus the mast 12 when that is desired.
  • the speed reducing means 22 in this embodiment includes flow reducing means 32 for reducing the rate of fluid flow between source 27 and tilt cylinders 20.
  • a flow restrictor valve 33 is situated in flow line 28 to the rod ends of the cylinders 20 in this particular example.
  • the flow restrictor valve 33 of this particular embodiment of the invention has a housing 34 with a stepped bore 36 in which a valve spool 37 is disposed for axial movement.
  • Valve ports 38 and 39 situated at opposite sides of the central region of bore 36 are communicated with motor ports 24 and control valve 31 respectively and in effect define a portion of the flow line 28 therebetween.
  • Spool 37 has a pair of annular grooves 41 and 42 spaced apart by a central land 43.
  • a spring 44 biases the spool towards a first spool position, depicted in Figure 2, at which valve ports 38 and 39 are intercommunicated by spool groove 42.
  • Spool 37 may be shifted axially in bore 36 to a second position, depicted in Figure 3, at which the central land 43 blocks valve ports 38 and 39 and thus flow line 28 and may be shifted still further to a third position depicted in Figure 4 at which the other spool groove 41 again intercommunicates the two valve ports.
  • the spool abuts a step 46 in bore 36 which blocks further axial movement of the spool.
  • a valve actuator rod 47 extends from spool 37 out of housing 34 along the axis of bore 36 to provide for shifting of the spool between the above described positions.
  • the inclination sensing means 23 in this example of the invention includes a tension spring 48 connected between actuator rod 47 and mast 12.
  • Tension spring 48 has a length sufficient to cause the spring to be relaxed when the mast 12 is tilted backwardly but to begin a state of tension as the mast reaches a vertical orientation.
  • the spring constant of tension spring 48 is substantially greater than that of the internal biasing spring 44 of flow restrictor valve 33.
  • valve ports 38 and 39 are communicated through a flow restriction 49.
  • restriction 49 is sized to reduce the rate of flow to about one fourth to one fifth of the rate of flow which occurs when valve 33 is open although other degrees of flow reduction may be used.
  • the temporary reduction of the rate of tilting of mast 12 is needed only when the mast is being tilted in the forward direction and it is preferable that the return motion of the mast not be slowed.
  • means 50 are provided for preventing operation of the speed reducing means 22 during the return motion.
  • a one way flow valve or check valve 51 is also connected between valve ports 38 and 39 in parallel relationship with the flow restriction 49. The check valve 51 is oriented to bypass fluid around the flow restriction 49 when the fluid flow is directed from control valve 31 to valve ports 24.
  • the flow restrictor valve 33 may have other specific forms while still accomplishing the above described functions.
  • the flow restriction 49 and/or the check valve 51 may be built into central land 43 of valve spool 37 instead of being located elsewhere as depicted schematically in the drawings.
  • the inclination sensing means 23 may also take other forms while accomplishing essentially similar functions.
  • Figures 5 and 6 illustrate a second embodiment of the invention with modified components of these kinds.
  • the mast 12a, tilt cylinders 20a, pressurized fluid source 27a and control valve 31a may all be. similar to the corresponding components of the first described embodiment.
  • a modified flow restrictor valve 33a is present in the flow line 28a between control valve 31a and rod end ports 24a of tilt cylinders 20a.
  • Flow restrictor valve 33a in this second embodiment, is a two position valve having a first position providing an unrestricted flow path between control valve 31a and tilt cylinders 20a and having a second position at which the flow path is relatively restricted.
  • An internal valve spring 52 biases flow restrictor valve 33a to the first or unrestricted position.
  • the valve 33a has an actuator rod 47a which may be moved axially to shift the valve to the second or flow restricting position against the force of biasing spring 52.
  • the modified inclination sensing means 23a of the embodiment of Figure 5 includes a lever 53 extending from one side of mast 12a to actuator rod 47a and which is pivoted at an intermediate point to the body 13a of the lift truck by a pivot coupling 54 which provides for pivoting movement of the lever in a vertical plane.
  • Actuator rod 47a of flow restrictor valve 33a extends downwardly through an opening 56 in the back end of lever 53 and a threaded nut and washer 57 are engaged on the lower end of the actuator rod 47a immediately below the lever 53.
  • downward motion of the back end of the lever 53 will shift the flow restrictor valve 33a to the second or flow restricting position against the biasing force of the internal valve spring 52 and thereby slow the rate of extension of tilt cylinders 20a.
  • a compression spring 58 is disposed coaxially around valve actuator rod 47a between lever 53 and the underside of the housing 34a of flow restrictor valve 33a.
  • Spring 47a has a smaller spring constant than the internal biasing spring 52 of flow restrictor valve 33a so that, in the absence of an additional force acting on the lever 53, the lever is held in the position depicted in Figure 5 and the flow restrictor valve 33a remains at the first position.
  • the valve 33a may be shifted to the second or flow restricting position by upward force acting on the end of lever 53 which is adjacent mast 12a.
  • a cam plate 59 is secured to the side of mast 12a and a cam follower pin 61 extends sidewardly a short distance from the adjacent end of lever 53 in position to be contacted by the upper cam surface 62 as the mast 12a is tilted forwardly from a vertical orientation.
  • the cam plate 59 slopes upwardly towards the back of mast 12a to force cam follower pin 61 upwardly as the mast 12a tilts forward from vertical. This pivots lever 53 to shift flow restrictor valve 33a to the second or flow restricting position.
  • the upper cam surface 62 is of sufficient length to hold the cam follower pin 61 in the elevated position as the mast 12a tilts through an initial portion of the range of forward mast inclinations.
  • cam 59 is sized and positioned to shift the valve 33a to the second or flow restricting position as the forwardly tilting mast 12a reaches the upright or 0° orientation and to hold the valve in that shifted position until the forward tilt of the mast passes 5° of forward tilt.
  • the cam 59 and follower 61 may be shaped and located to actuate the flow restrictor valve 33a during different portions of the range of mast inclinations where that is desirable.
  • the speed reducing means 22 remains inactive during periods when the mast 12 is strictly upright or tilted backward towards the vehicle body 13. Under these conditions, tension spring 48 of the inclination sensing means 23 is relaxed sufficiently that the internal biasing spring 44 of flow restrictor valve 33 may hold spool 37 to the right as viewed in Figure 2. At that position, the flow restrictor valve 33 provides an unrestricted flow path 28 via valve groove 42. Tilting of the mast 12 may proceed at rates selected by the operator by adjustment of control valve 31.
  • the invention functions to give a positive and reliable signal to the operator when the mast first enters the forward tilt portion of the range of mast inclinations by temporarily reducing the rate of the forward tilting movement.
  • lever 53 is held in the horizontal position depicted in Figure 5 by the internal biasing spring 52 of flow restrictor valve 33a and by the compression spring 58.
  • the flow restrictor valve 33a is at the first position at which tilting motions of the mast 12a, in either direction, may proceed at the rate selected by the operator's setting of the control valve 31a.
  • cam follower pin 61 is temporarily forced downward by the undersurface 63 of cam 59. This pivots lever 53 in an opposite direction relative to the lever movement during forward tilting.
  • the flow restrictor valve 33a is unaffected by the pivoting of lever 53 during the return motion of the mast 12a which simply compresses compression spring 58 without affecting the position of valve actuator rod 47a.
  • the tem'porary slowing of the rate of mast tilting movement at a predetermined portion of the range of mast inclinations occurs only during forward tilting of the mast 12a.
  • Return movement of the mast 12a may proceed at full speed as the undersurface 63 of cam 59 in conjunction with lever 53 and spring 58 constitute means 50a for preventing operation of the speed reducing means 22a during the return movement.
  • the invention in any of its embodiments very positively and unmistakably alerts the operator when the mast first enters the forward portion of the range of mast inclinations.
  • the operator may then terminate the forward tilting when that is desirable but may also continue the forward tilting, if necessary, without any delay or diversion of effort to enable the continued forward tilting.

Landscapes

  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Geology (AREA)
  • Mechanical Engineering (AREA)
  • Structural Engineering (AREA)
  • Forklifts And Lifting Vehicles (AREA)

Abstract

L'opérateur d'un chariot élévateur ou d'un autre véhicule de transport de charges (11) ayant un mât inclinable (12, 12a) est averti lorsque le mât (12, 12a) s'incline au-delà d'une certaine orientation prédéterminée par un ralentissement temporaire de la vitesse de l'inclinaison. Le retour en arrière du mât (12, 12a) peut être libre. L'opérateur est averti de façon sûre lorsque le mât (12, 12a) atteint une limite prédéterminée, mais il peut continuer à l'incliner si nécessaire dans certains cas comme par exemple faire passer le véhicule (11) sous des obstacles aériens. Dans des sytèmes où le mât (12, 12a) est incliné par des moteurs à fluide (20, 20a), la réduction automatique de la vitesse de l'inclinaison peut être réalisée par une soupape (33, 33a) qui introduit temporairement une restriction d'écoulement à sens unique (49) dans la conduite d'écoulement du fluide (28, 28a) entre les moteurs (20, 20a) et la source (27, 27a) de fluide pressurisé, la soupape (33, 33a) étant actionnée par un mécanisme détecteur de l'inclinaison (23, 23a).
PCT/US1982/000297 1982-03-08 1982-03-08 Indicateur par reduction de vitesse de l'inclinaison d'un mat Ceased WO1983003089A1 (fr)

Priority Applications (4)

Application Number Priority Date Filing Date Title
PCT/US1982/000297 WO1983003089A1 (fr) 1982-03-08 1982-03-08 Indicateur par reduction de vitesse de l'inclinaison d'un mat
CA000417981A CA1178250A (fr) 1982-03-08 1982-12-17 Indicateur-ralenti-seur du degre et de la vitesse d'inclinaison d'un mat de levage
GB08235966A GB2116518B (en) 1982-03-08 1982-12-17 Load handling vehicle with tiltable mast
FR8303622A FR2523109B1 (fr) 1982-03-08 1983-03-04 Indicateur d'inclinaison de mat pour chariot elevateur

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1982/000297 WO1983003089A1 (fr) 1982-03-08 1982-03-08 Indicateur par reduction de vitesse de l'inclinaison d'un mat

Publications (1)

Publication Number Publication Date
WO1983003089A1 true WO1983003089A1 (fr) 1983-09-15

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ID=22167851

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1982/000297 Ceased WO1983003089A1 (fr) 1982-03-08 1982-03-08 Indicateur par reduction de vitesse de l'inclinaison d'un mat

Country Status (4)

Country Link
CA (1) CA1178250A (fr)
FR (1) FR2523109B1 (fr)
GB (1) GB2116518B (fr)
WO (1) WO1983003089A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0157213A1 (fr) * 1984-03-08 1985-10-09 Krupp MaK Maschinenbau GmbH Dispositif amortisseur de fin de course
FR2599016A1 (fr) * 1986-05-21 1987-11-27 Jungheinrich Kg Chariot elevateur equipe d'un portique monte basculant.
US4930975A (en) * 1987-03-20 1990-06-05 Nissan Motor Company, Limited Control for load carrier for industrial vehicle
FR2723933A1 (fr) * 1994-08-08 1996-03-01 Linde Ag Chariot elevateur equipe d'un mat de levage et recevant un moyen de reception de charge mobile en montee et en descente

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2390595B (en) 2002-07-12 2005-08-24 Bamford Excavators Ltd Control system for a machine
WO2008135039A2 (fr) * 2007-05-08 2008-11-13 UNIVERSITÄT KARLSRUHE (TH) FORSCHUNGSUNIVERSITÄT-GEGRüNDET 1825 Procédé et dispositif pour chariots élévateurs
GB2471134B (en) 2009-06-19 2012-10-10 Bamford Excavators Ltd Speed sensitive longitudinal load moment control of a working machine
US9090432B2 (en) 2012-08-04 2015-07-28 Serverlift Corporation Lift with lifting mast collision control apparatus

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3386603A (en) * 1965-08-16 1968-06-04 Champ Corp Mast tilt safety device for lift trucks
US3530766A (en) * 1969-01-09 1970-09-29 Ware Machine Works Inc Control mechanism for automatically restricting the flow of fluid in a conduit leading to hydraulically actuated means
US4138928A (en) * 1977-02-11 1979-02-13 Ware Machine Service Inc. Fluid actuated apparatus

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1250698A (fr) * 1969-01-21 1971-10-20

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3386603A (en) * 1965-08-16 1968-06-04 Champ Corp Mast tilt safety device for lift trucks
US3530766A (en) * 1969-01-09 1970-09-29 Ware Machine Works Inc Control mechanism for automatically restricting the flow of fluid in a conduit leading to hydraulically actuated means
US4138928A (en) * 1977-02-11 1979-02-13 Ware Machine Service Inc. Fluid actuated apparatus

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0157213A1 (fr) * 1984-03-08 1985-10-09 Krupp MaK Maschinenbau GmbH Dispositif amortisseur de fin de course
FR2599016A1 (fr) * 1986-05-21 1987-11-27 Jungheinrich Kg Chariot elevateur equipe d'un portique monte basculant.
US4930975A (en) * 1987-03-20 1990-06-05 Nissan Motor Company, Limited Control for load carrier for industrial vehicle
FR2723933A1 (fr) * 1994-08-08 1996-03-01 Linde Ag Chariot elevateur equipe d'un mat de levage et recevant un moyen de reception de charge mobile en montee et en descente

Also Published As

Publication number Publication date
GB2116518B (en) 1985-09-18
FR2523109A1 (fr) 1983-09-16
CA1178250A (fr) 1984-11-20
GB2116518A (en) 1983-09-28
FR2523109B1 (fr) 1987-01-30

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