FR2523109A1 - MAT TILT INDICATOR FOR LIFT TRUCK - Google Patents

Abstract

THE DRIVER OF A TROLLEY OR OTHER HANDLING VEHICLE 11 CONTAINING A TILTING MAST 12 IS ALERT WHEN THE TILT OF THE MAST EXCEEDS A CERTAIN LIMIT BY TEMPORARY SLOWING OF THE SPEED OF THE TILT MOVEMENT OF THE MAST. THE RETURN MOVEMENT OF THE MAST 12 MAY NOT BE PREVENTED. THE DRIVER IS ADVISED IN A SAFE MANNER WHEN MAT 12 REACHES A PREDETERMINED LIMIT, BUT THE TILT MOVEMENTS OF THIS CONTINUE WHEN NECESSARY, FOR EXAMPLE TO PASS VEHICLE 11 UNDER AN OBSTACLE. IN VEHICLES WHERE THE MAT 12 IS INCLINED BY HYDRAULIC MOTORS 20, THE AUTOMATIC REDUCTION OF THE TILT SPEED OF THE MAT CAN BE ACHIEVED BY A VALVE WHICH TEMPORARILY INTRODUCES A UNIDIRECTIONAL CIRCULATION RESTRICTION IN THE CIRCULATION PATH BETWEEN THE FLUID CIRCULATION PATH 20 AND A SOURCE OF PRESSURIZED FLUID, THE VALVE BEING ACTIVATED BY A TILT DETECTION MECHANISM.

Description

The present invention relates generally to vehicles

  comprising a tilting mast for supporting and transporting loads, and more particularly relates to a device which informs the

  driver of the vehicle that the mast has reached a predefined inclination

  finished. The mast of a forklift or the like is generally more or less vertical while a load is received or deposited, and is tilted back towards the body of the vehicle, in order to retain the load, during transport movements. unexpected mast forward

  beyond a few degrees from the vertical, during operations

  carrying a load, may cause the load to drop

  forks or other components holding it The stability of the vehicle

  This could be affected, especially when the mast tilt is considerable when the load is supported at a certain level.

height along the mast.

  Consequently, it is customary to provide mechanisms for limiting

  ter the tilting movement on forklifts and the like in order to stop the forward tilting of the mast at a position slightly beyond the vertical, such as a forward tilt of three degrees, for example A To this end, various mechanical stops or mechanisms which stop the operation of the motors can be used.

  hydraulics generally used to tilt the mast.

  Now there are circumstances in which an appreciable degree

  tilting the mast forward may be desirable or even necessary

  This is how it may be necessary to tilt the mast forward to allow the vehicle to pass under a relatively low air obstacle. Lowering the mast by tilting forward may also be desirable when the vehicle is towed or transported. on the platform of a truck or other means of transport A forward tilt may also be necessary to deposit loads at high locations, such as openings in stacks of containers, under certain conditions Cases where a tilt forward mast is necessary become more frequent with the arrival of what is called all-terrain forklifts which have relatively high masts and which can be designed to operate on uneven surfaces, such

  than construction sites or the like.

  In many prior forklifts, of which the mechanism described in US Patent No. 3,386,603 to HD Rueb of June 4, 1968 is an example, the mast cannot be tilted forward beyond the predetermined limit unless that the driver stops the vehicle, dismantles and detaches or removes the components of the

  tilting motion So some drivers may inadvertently

  or deliberately do not reassemble the tilt movement limitation mechanism before resuming work Consequently,

  such a driver is no longer alerted to the fact that the normal incline limit

  naison forward is almost to be exceeded during the following operations. The provision of a system by which the driver could,

  if necessary, deactivate the mechanism limiting the tilting movement.

  its forward of the mast would only result in sensitive complicating-

  the whole and would not prevent the deactivation system from being left in action either accidentally or voluntarily, in order to avoid the need for repeated actuation during the following operations Acoustic or optical devices, such as as vibrators or indicator lights, to alert the operator when the tilt

  forward of the mast exceeds a predetermined limit, is not a solution

  preferred, given the large number of other optical devices

  or acoustic that are usually present on a forklift.

  In addition, indicators like this require a lot of maintenance and are

  as easy to intentionally disconnect However, it would be advantageous

  tagging to have another system signaling to the driver that the mast

  began to tilt forward.

  The present invention aims to remedy the above drawbacks

  and provide a solution to the problems it poses.

  According to one aspect of the present invention, a vehicle for

  handling of loads comprising a tilting mast, means for

  carry a load on the mast and motor means to tilt the mast

  between a first and a second position is further provided with a

  positive deceleration to slow the mast tilt movement, and a tilt sensor to detect the mast tilt and actuate the retarder in response to movement of the mast in a predetermined range of positions between the first

and the second position.

  The invention very safely alerts the driver of the vehicle.

  riot elevator or other when the mast which supports the loads reaches a predetermined inclination, by a temporary slowing down of the speed

  tilt movement The mast tilt can then continue

  vre, if necessary, without any additional action on the part of the

  conductor, that is to say, without having to dismantle or disconnect a met

  Any mechanism This device is not likely to be left inadvertently inactive and can be arranged to make deliberate deactivation extremely difficult. The device could, if necessary, be designed to slow down only the speed of inclination of the mast during its movement. tilt forward but not during

  back movement along the same part of the range of inclinations.

  This avoids delaying the return movement.

  Other characteristics and advantages of the invention will emerge

  of the description which will be given below with reference to the drawings

annexed in which:

  Figure 1 is a side view of the front part of a cha-

  industrial elevator riot equipped with a first embodiment of the present invention;

  Figure 2 is an axial section through a reducing valve.

  tilt speed used in the embodiment of the invention shown in Figure 1 and which also shows some

  elements of the fluid circuit which are shown in schematic form

  FIG. 3 shows certain elements of the embodiment of FIG. 2 in displaced positions which correspond to another stage of operation; Figure 4 shows the device of Figure 3 at a still different operating stage; Figure 5 is a schematic view of another embodiment of the present invention; and, Figure 6 is an elevational view of part of the structure

  in Figure 5, taken along line VI-VI.

  Referring first to FIG. 1, it should be noted that a large number of vehicles for handling loads, such as the

  industrial forklift It describes belowhave a vertical mast

  cal 12 on which the loads are supported The mast 12 can be connected to the chassis or body 13 of the vehicle by a joint 14 located near its base and which allows it to pivot both forwards and backwards relative to the vertical position shown Means 16 provided to support the load on the mast 12 can take very diverse forms

-2523109

  and, in the present example, comprise a carriage 17 from which extend forks 18 intended to be applied against a load, the

  carriage can move vertically along the mast 12 -

  In the embodiment shown, the motor means 19 intended to pivot the mast 12 are constituted by two extensible and retractable fluid cylinders 20 of which only one is visible on the

  Figure 1, these cylinders being mounted between the mast and the body 13 of the vehicle

  cule The cylinders 20 could for example be calculated to allow

  an inclination of the mast about 12 'back and about 450 in -

  forward relative to the vertical, although these limits may be different in other vehicles The mast 12 only tilts forward a few degrees during handling operations, but a

  some possibility of tilting forward has been provided in order to

  put some special operations, like for example a lowering

  from the mast when the vehicle needs to pass under aerial obstructions.

  The various components described above of the forklift 11, including components such as the mast 12, the articulation 14, the carriage 17, the forks 18 and the slewing cylinders 20 could, where appropriate, be a known type and therefore need not be described further. According to the present invention, the forklift It is in

  additionally provided with a tilt indicator 21 intended to alert the

  conductor when the tilting movement brings the mast 12 into a predetermined part of the range of its tilting movements, temporarily slowing down the speed of the tilting movement In the embodiment shown, a device 21 slows down the movement of the mast 12 when it has tilted forward from 0 to 50, that is to say along the first part of the total angle of 45 which it can tilt forward, well that this device can be designed to slow down the speed

  tilt to any other part of the total tilt range

  However, as may be desirable in other commercial vehicles.

  Referring to Figure 2, it can be seen that the inelinai-

  sound 21 includes a slowing device 22 intended to temporarily slow down the tilting movement of the mast 12 and a detection device 23 for detecting the tilting of the mast and actuating the tilting slowing device in response to a movement of the mast in a

  predetermined range of positions.

  The orifice 24 of the end close to the rod and the orifice 26 of the end close to the head of the tilt cylinders 20 are connected respectively to a source of pressurized fluid 27 by conduits 28 and 29 and by a control valve 31 in order to transmit a pressurized fluid to one of the selected conduits, at the same time discharging the fluid from the other conduit, and which also ensures selective blocking of the two conduits in order to immobilize the cylinders 20 and, starting from the mast 12, when desired In this embodiment, the speed reducer 22 comprises a member 32 for reducing the flow of fluid between the source 27 and the cylinders 20 More precisely, a

  flow reduction valve 33 is interposed in the conduit 28 abou-

  weaving at the rod ends of the cylinders 20 in this particular example.

  In the embodiment of the invention shown, the flow reduction valve 33 comprises a casing 34 having a stepped bore 36 in which a slide 37 moves axially. Ports 38 and 39, located on either side of the central region of the bore 36, communicate respectively with the motor orifices 24 and of the control valve 31 and, in fact, delimit between them a part of the duct 28 The slide 37 has two annular grooves 41 and 42 spaced apart by a central bearing 43 A spring 44 urges the drawer towards a first position, shown in FIG. 2, in which the orifices 38 and 39 are interconnected by the groove 42 The drawer 37 can move in the bore 36 to a second position, shown in the Figure 3, in which the central bearing 43 blocks the holes 38 and 39 and thus blocks the duct 28, the slide can be moved even further to a third position shown in Figure 4 in which the second groove 41 re-establishes the communication between the two orifices of the valve In the third position shown in FIG. 4, the drawer abuts against a step 46 provided in the bore 36,

  which hampers the continuation of its axial movement.

  Referring to FIG. 2, it can be seen that an actuating rod 47 extends outside the casing of the drawer 37 along the axis of the bore 36 in order to allow movement of the drawer between

  different positions described above.

  In this exemplary embodiment of the invention, the tilt detector 23 comprises a tension spring 48 fixed between the actuating rod 47 and the mast 12 The length of the spring 48 is sufficient for it to be relaxed when the mast 12 is tilted back and so that it begins to be stretched when the mast arrives vertically The elastic modulus of the tension spring 48 is substantially greater than

  that of the internal spring 44 of the flow reduction valve 33.

  Thus, a certain inclination in front of the mast 12 has the effect of

  override the spring 44 and move the slide 37 rather than substantially relax the tension spring 48 Consequently, during the first part of its inclination forward, the mast 12 moves the valve

  flow reduction 33 to its second position and then to the third.

  In order to produce a relatively narrow circulation path between the control valve 31 and the ports 24 of the cylinders 20 when the flow restriction valve 33 is in its second position, the ports 38 and 39 are connected through a flow restriction member. flow or throttle 49 In this example, throttle 49 is calculated to reduce the flow of fluid between about a quarter and a fifth of that which occurs when valve 33 is opened, although other degrees of reduction in flow can be used In this embodiment, the temporary reduction in the tilting speed of the mast 12 is only necessary when the latter is tilting forward, and it is preferable that the return movement of the mast is not slowed down A

  To this end, a member 50 has been provided to prevent the device from slowing down.

  22 to intervene during return movements More preci-

  a non-return valve 51 is also connected between the orifices 38 and 39 of the valve, in parallel on the throttle 49 The valve 51 is oriented so as to deflect the fluid around the throttle 49

  when the latter flows from the control valve 31 to the orifices 24.

  The flow reduction valve 33 could take other specific forms, while fulfilling the functions described above. For example, the throttle 49 and / or the valve 51 could be incorporated in the central bearing 43 of the drawer 37, instead of being placed somewhere else as shown diagrammatically in the drawing The tilt sensor 23 could also take other forms, while essentially fulfilling the same functions Figures 5 and 6 illustrate a second embodiment of the invention o these components

have been changed.

  More specifically, with reference to FIG. 5, it can be seen that the mast 12 a, the tilt cylinders 20 a, the source of pressurized fluid 27 a and the control valve 31 a can be identical to the components.

  correspondents of the first embodiment which has just been described.

  However, a modified flow reduction valve 33 a is present in the duct 28 a between the control valve 31 a and the orifices

252 3109

  neighboring the rod end 24 has tilt cylinders 20 a In this second embodiment, the flow reduction valve 33 a is a two-position valve, having a first position allowing free circulation between the valve control 31 a and the tilt cylinders 20 a, and a second position in which this circulation path is relatively restricted An internal spring 52 urges the valve 33 a to its first position, that is to say to the position of free circulation The valve 33 a has an actuating rod 47 a which can be moved axially in order to move the valve to its second position or restricted circulation position, against

the force of the spring 52.

  The modified inclination detector 23 a of the embodiment of FIG. 5 comprises a lever 53 extending from one side of the mat 12 a to the actuating rod 47 a and an intermediate point of which is articulated at the

  body 13 has of the forklift by a pivot 54 which allows it to move

  cer in a vertical plane The actuating rod 47 a of the flow reduction valve 33 a is lowered through an opening 56 made in the rear end of the lever 53, a nut and a washer 57 being threaded on the lower end of the rod 47 a, directly under the lever 53 Thus, a downward movement of the rear end of the lever 53 results in a displacement of the valve 33 a towards its second position or position for reducing flow, at against the force of the internal spring 52, which slows the extension of the cylinders

tilt 20 a.

  A compression spring 58 is threaded on the rod 47 a between the lever 53 and the underside of the casing 34 a of the flow reduction valve 33 a The spring 47 has a smaller elastic constant than that of the internal spring 52 of the valve 33 a so that in the absence of an additional force acting on the lever 53, the latter is held in the position shown in FIG. 5 and the valve 33 a remains in its first position The valve 33 a can be moved to its second position or flow restriction position, by an upwardly directed force acting on the end of the lever 53 adjacent to the

mast 12 a.

  Now considering Figures 5 and 6 together, it can be seen that a cam 59 is fixed to the side of the mast 12 a and that a touch 61 extends a short distance laterally from the adjacent end of the lever 53 in position to come into contact with the upper cam surface 62 when the mast 12 a tilts forward from its vertical position The cam 59 rises by tilting towards the rear of the mast 12 a so as to push back the touch 61 upwards when the mast tilts forward from the vertical This rotates the lever 53 by moving the flow limitation valve 33 a to its second position or restricted flow position The cam surface 62 is quite long to hold the touch 61 in the raised position while the mast 12 a passes along the initial part of the range of its tilting movements forward In this example, the cam 59 is calculated and is mounted to move the valve 33 has at its second position or flow restriction position when the inclination of the mast 12 has reached vertical or 0 and to hold it in this position until the forward inclination of the mast exceeds 5 It is quite obvious that the cam 59 and the touch 61 can be formed and mounted to operate the flow limiting valve 33 a during different parts of the range of inclinations of the

mast, when desired.

  During the operation of the first embodiment of the

  vention, shown in Figures 1 to 4, the speed reducer 22 remains inoperative during the periods during which the mast 12 is

  strictly vertical or tilted back towards the body 13 of the vehicle.

  Under these conditions, the tension spring 48 of the tilt detector 23 is sufficiently relaxed so that the internal spring 44 of the flow reduction valve 33 can hold the slide 37 on the right side,

  as seen in Figure 2 In this position, the limit valve

  flow rate 33 allows free circulation of the fluid in the duct 28 through the groove 42 The inclination of the mast -12 can progress at speed

  chosen by the driver by acting on the control valve 31.

  Referring now to Figure 3, we see that when the mast 12 tilts forward beyond the strictly vertical position or O 'tilt, the spring 48 is stretched and pulls the drawer 37 towards the left, according to FIG. 3 Therefore, the central bearing surface 43 of the drawer 37 blocks the orifices 38 and 39 The flow of fluid which is then discharged from the tilt cylinder into the conduit 28 is forced to pass through the throttle 49 , which slows down its circulation and results in a corresponding slowing down of the forward tilting speed of the mast 12 When the mast 12 reaches a certain forward tilt, of about 5 in this particular example, the spring 48 has enough pulled the drawer 37 to the left, according to FIG. 4, to restore a free circulation path through the second groove 41 of the valve drawer The continuation of the tilting movement of the mast 12 beyond the point at which its drawer has reached at its extreme left position, as shown entered in FIG. 4, results in an extension of the tension spring 48 Thus, the continuation of the forward tilt of the mast 12 a continues, in the present example from approximately 50 to approximately 450, at a speed relatively high determined by the setting of the

  control valve 31 by the driver.

  Consequently, it can be seen that the invention provides the driver with a positive and reliable signal when the mast initially reaches the area of its forward inclinations by temporarily slowing down the speed.

  of its forward tilt movement.

  In this embodiment, the tilting speed of the mast 12 is not slowed down at any stage of its return movement or tilting backwards although the flow reduction valve 37 can block the orifices 38 and 39 at a certain stage of the return movement, circulation in the duct 28 takes place, at this time, in the opposite direction to that corresponding to the forward tilt movement so that the non-return valve 51 opens in allowing free

  circulation around the throttle 49.

  A similar temporary slowing down of the tilting speed in front of the mast, during the tilting movement corresponding to the same part of the range of mast tilting is achieved by the second

  embodiment of the invention shown in Figures I and 6.

  Between the maximum degree of inclination behind the mast 12 a and its strictly vertical position, the touch 61 is not in contact with the cam 59 Under these conditions, the lever 53 is held in the horizontal position shown in FIG. 5 by the internal spring 52 of the

  flow reduction valve 33 a and by compression spring 58.

  Thus, the valve 33 a is in its first position in which the tilting movements of the mast 12 a, in one direction or the other, can be carried out at the speed chosen by the driver by means of

the control valve 31 a.

  When the forward tilting movement of the mast 12 a continues beyond the vertical or the position of O, the surface 62 of the cam 59 comes into contact with the touch 61 and pushes the latter

  upwards This has the effect of pivoting the lever 53 by pulling the

  actuation age 47 has downward against the force of the internal spring 52 so that the valve moves to its second position or position of

  flow restriction, in which the speed of action of the information cylinders

  clinching 20 a is slowed down 1 When the forward inclination of the mast 12 a continues even more, beyond about 5 in the present example, the cam touch 61 leaves the end of the cam surface 62, which allows the internal spring 52 to return the flow reduction valve 33 a to its first position Thus a free path is again restored

  circulation between the control valve 31 a and the tilt cylinders

  its 20 a, and the forward tilting movement of the mast 12 a is thus accelerated at the speed chosen by the driver by means of the valve

31 a.

  During the backward movement of the mast 12 a from 5 to 0, the touch 61 is temporarily pushed downwards by the lower face 63 of the cam 59 This has the effect of pivoting the lever 53

  in the opposite direction from its movement during the in-

  forward tilting The flow limiting valve 33 a is not influenced by the pivoting of the lever 53 during the return movement of the mast 12 a, which simply compresses the spring 58 without modifying the position of the rod. actuation 47 a of the valve Thus, as in the case of the first embodiment, the temporary slowing down of the speed of inclination of the mast to a predetermined part of the range of inclinations thereof only occurs during the inclination towards

the front of the mast 12 a.

  The return movement of the mast 12 a can continue at full

  speed of the fact that the underside of the range 59 constitutes a joint

  With the lever 53 and the spring 58, a device 50 a which prevents the intervention of the retarding device 22 a during the movement.

back.

  It can therefore be seen that the invention provides a device whose action is very positive and which unequivocally alerts the driver to the arrival

  mast in the first part of the range of its forward inclinations.

  The driver can then interrupt this forward tilt when it is desirable, but he can also continue it if necessary without

late and effortless.

  It goes without saying that many modifications can be made to the embodiments shown and described, without going out for

as much within the scope of the invention.

Claims (8)

  1 Load handling vehicle (11) comprising a tilting mast (12, 12 a), means (16) for supporting a load on the mast (12, 12 a) and motor means (19) for tilting the mast ( 12, 12 a) in a direction between a first and a second position respectively, and for tilting the mast (12, 12 a) in an opposite direction between a first and a second position respectively, characterized in that it comprises a device deceleration device (22, 22 a) to slow down the tilting movement of the mast (12, 12a) an inclination detector (23, 23a) to detect the tilting of the mast and actuate the deceleration device (22, 22 a) in response to movement of the mast (12, 12 a) in a predetermined range of positions between the first and second positions and in the direction mentioned first and means (50,  50 a) to prevent the operation of the retarding device (22, 22 a) when the mast (12, 12 a) returns passing in the predetermined range of positions during its movement in the opposite direction.   2 vehicle according to claim 1, characterized in that the predetermined range of mast positions (12, 12 a) is located between the first and second positions and in that the tilt sensor (23, 23 a) deactivates the device deceleration (22,22 a) after passing the mast in the predetermined range of positions in the mentioned direction first.   3 Vehicle according to claim 1, characterized in that the motor means (19) comprise at least one fluid motor (20, 20 a) connected to the mast (12, 12 a), a source of pressurized fluid (27,27 a) and a control valve (31,31 a) for selectively transmitting the fluid between the source (27, 27 a) and the motor (20,20 a) at a selectable flow, and in that the deceleration device ( 22, 22 a) comprises means (32.32 a) for decreasing the flow rate of the circulation of the fluid between the source (27.27 a) and the motor (20.20 a) while the retarding device (22, 22 a) is actuated by the tilt detection device (23, 23 a).   4. Vehicle according to claim 3, characterized in that the means (32, 32 a) for reducing the flow rate comprise a flow reduction valve (33, 33 a) having a first position in which the fluid can circulate between the source (27, 27 a) and the fluid motor (20, 20 a) at a determined flow rate established by the control valve (31, 31 a) and a second position in which the fluid circulates between the source (27, 27 a ) and the fluid motor (20, 20 a) at a reduced flow rate through a relatively restricted circulation path, and in that the route detector   (23, 23 a) moves the flow restriction valve (33, 33 a) by its first   first position at the second position in response to a movement of the mast   (12, 12 a) in the predetermined range of positions.   Vehicle according to claim 1, characterized in that the load handling vehicle (11) is a forklift, the mast (12, 12 a) being inclined towards the outside of the forklift (11) when it is in its first position position and inclined inward, towards the forklift (11), when it is in its second position, the predetermined range of mast positions (12, 12 a) being between the first position and a position in which the mast (12, 12 a) east oriented vertically.   6 Load handling vehicle comprising a tilting mast (12, 12 a), means (16) for supporting a load on the mast (12, 12 a), and at least one fluid tilt cylinder (20, 20 a) connected to the mast (12, 12 a), a source (27, 27 a) of pressurized fluid, and means (31, 31 a) for selectively establishing a fluid circulation path between the cylinder (20, 20 a) and the source (27, 27 a), characterized in that it comprises a flow restriction valve (33, 33 a) interposed in the circulation path (28, 28 a) and having a first position in which a stream of fluid flows in the path (28, 28 a) at a first flow, and a second position in which the fluid flows in the path (28, 28 a) at a relatively lower flow, and in that a tilt sensor (23, 23 a) is provided to move the restriction valve   flow (33, 33 a) from its first position to the second position in response   when the mast (12, 12 a) passes through a predetermined part of the range of its inclinations.   7 Vehicle according to claim 6, characterized in that the predetermined part of the tilt range of the mast is an intermediate part of the range, and in that the flow restriction valve (33) has a third position in which the fluid flows between the source (27) and the fluid motor (20) at a greater flow rate than in the second position thereof, and in that the tilt sensor (23) moves the flow restriction valve (33) in its third position   after the mast has passed through the intermediate part of the inclination range   nons. 8 Vehicle according to claim 7, characterized in that the flow restriction valve is biased towards the first position   and comprises an actuating element which can be moved on a pre-   first distance in order to transfer the valve to its second position and which can be moved over a second greater distance in order to transfer the valve to its third position, and in that the tilt sensor   includes a tension spring mounted between the mast and the action element-   The tension spring can be relaxed in response to conti-   change in the inclination of the mast after the latter has passed through the   intermediate part of the inclination range.   9 Vehicle according to claim 6, characterized in that it comprises a throttle (49) interposed in the circulation path (28), at the second position of the flow restriction valve (33), and a   unidirectional valve (51) for short-circuiting the circulation path   tion around the constriction (49) when traffic along the path   (28) takes place in a certain direction.   Vehicle according to claim 6, characterized in that the inclination detector (23 a) comprises a cam (59) fixed to the mast (12 a), a cam touch (61) placed to come into contact with the cam (59 ) and to be moved by it when the mast (12 a) is inclined in the predetermined part of the range of inclinations, and in that means (53, 57, 47 a) are provided for transmitting the movement of the cam touch (61) to the flow restriction valve (33 a) in order to transfer it   at its second position in response to movement of the cam touch (61).   11 Vehicle according to claim 10, characterized in that the means (53, 57, 47 a) for transmitting the movement of the cam feeler (61) to the flow restriction valve (33 a) comprise an articulated lever (53) extending near the path of movement of the cam (59) when the mast (12a) is inclined in the predetermined part of the range of inclinations, the cam including means (62) for pivoting the lever (53 ) in a first direction when the mast enters the predetermined part of the range of inclinations from one side, and means (63) for pivoting the lever (63) in the opposite direction when the mast (12 a) enters the predetermined part of the range of inclinations from the opposite side, means (47 a, 57, 58) being further provided for transferring the flow restriction valve (33 a) to its second position only in response to pivoting of the lever (53) in the first position. 12 Forklift comprising a tilting mast (12, 12 a), means (16) for supporting a load on the mast (12, 12 a), a fluid motor means (19) for tilting the mast (12, 12 a ) between a first position and a second position, a source of pressurized fluid (27, 27 a), a control valve (31, 31 a) for controlling the circulation of the fluid between the source (27, 27 a) and the drive means (19) at a selected high flow rate, a flow restriction valve (33, 33 a) for reducing the selected circulation rate, and means (23, 23 a) for detecting the position of the mast and actuating the valve flow restriction (33, 33 a) in response to the finding that the mast (12, 12 a) is placed in   a predetermined range of positions between the first and second positions.