FR2869284A1 - Transport trolley chassis for e.g. workshop, has guiding bearings maintaining guiding carrier wheel rotating around rotation axis, and switching units to switch guiding bearing between inhibition and functional guiding states - Google Patents

Abstract

The chassis (2) has guiding bearings maintaining a guiding carrier wheel (41) rotating around a rotational axis (310) which extends along an extension line to a preset azimuth orientation. Switching units (65, 311) are provided to switch the guiding bearing (31) between an inhibition state and a functional guiding state, in the functional position of the chassis.

Description

The present invention relates to an object transport trolley

  any, and more precisely its chassis.

  The problem at the origin of the invention concerned precisely the transport of raw materials in a workshop and their distribution to various workstations.

  A workshop generally has a considerable area, so it is desirable to optimize the raw material distribution paths to the various stations from a common store. A basic solution is to make star links from the store, dragging or pushing each time a truck filled. One can, at best, if the passage corridors allow, try to drag in parallel a second carriage, to carry out a second delivery. This solution is not always possible and it is also inconvenient during transport.

  Moreover, there is the problem of guiding the carriage during its transport, because it must be able to be driven along the traffic corridors, that is to say without making lanes but being able to take the turns. In addition, once out of the corridor passage and delivered in the station area, however, the carriage must be able to follow an irregular path to access the desired location, which is not always very accessible. It must then be able to pivot on itself without effort or be able to follow a broken line trajectory, that is to say with sharp angles and no longer curves. This constraint is obviously antinomic with that related to the guidance in the corridor. The same kind of problem arises for a caddy in a department store.

  The present invention aims to propose a solution to this problem of controlling the degrees of freedom of the movements of the carriage.

  To this end, the invention relates to a carriage chassis equipped with a plurality of at least one first idler bearing means arranged to maintain a first idler wheel in azimuth bearing orientation relative to the chassis in the operative position, characterized in that it comprises at least one first guide bearing means arranged to maintain a first rotary guide bearing wheel about a first axis of rotation extending along a predetermined azimuthal orientation line, and provision is made for Chassis guidance mode switch means arranged for, in the operative position of the chassis, under the action of guide mode switching control means, switching the first guide bearing means between a muting state and a functional state guidance.

  Thus, the carriage, once the chassis equipped wheels to form a trolley, can rest in unguided mode on only one or more idle wheels.

  In this case, among the three conventional degrees of freedom in rotation offered to a moving body around three orthogonal axes XYZ, the carriage then has a total degree of freedom in rotation on itself, around a vertical axis Z of position whatever, that is to say crossing or not the carriage.

  In addition, among the three degrees of freedom in translation along these three axes, the carriage has two degrees of freedom in horizontal translation along the X, Y axes since it can roll on the ground in any desired azimuthal direction.

  In guided mode, the first guide wheel becomes functional and the azimuth direction of the axis of the first guide wheel imposes, or at least promotes, a bearing azimuthal direction perpendicular to this axis, due to the coefficient of friction of the first guide wheel on the ground, which opposes changes in azimuthal direction. The degree of freedom in translation along the Y axis, arbitrary, is lost or at least weakened.

  Likewise, in guided mode, the degree of freedom in rotation about the vertical axis Z is reduced by the fact that, as the first guide wheel in practice rests on the ground in a non-pointwise manner, its coefficient of friction s' opposes, on the one hand, somewhat to its pivoting on the spot, and, on the other hand, this same coefficient of friction provides a resistant torque against any lateral translation in an arc that would scrape the first guide wheel on the floor when the carriage is pivoted. This therefore requires that the lever arm of the pivoting friction torque is minimal, that the vertical axis Z of pivoting occupies a specific position, and precisely that it passes substantially through the contact surface of the guide wheel with floor.

  It will be noted that the chassis, in minimum configuration, comprises only two first bearings, mutually different types defined above, respectively allowing and prohibiting the azimuthal pivoting, the function of ground support of the frame being ensured permanently by at least one of these first two different bearings, but the azimuth guidance function being optional.

  The lift polygon can therefore be reduced to an elementary support surface of a single first wheel, of one type or the other, if the first different bearings are rendered mutually exclusive. The support polygon is only reduced to a support line if the first two different levels can be simultaneously functional in guide mode or, if not, if only a third is provided. wheel of any type. This is still the case with such a support line if the first two wheels, respectively associated with the first bearings operating in mutually exclusive mode, are each of large width or each in the form of twin wheels on the same axle. The user may therefore be obliged to hold the carriage to prevent it from tipping over. However, it can also be expected that the carriage is supported for this purpose, against any tilting front and rear or side, on a previous or next carriage, which thus ensures the locking of the last two degrees of freedom in rotation.

  As explained in detail below, the functional position of a first wheel with controlled support, associated with a bearing of one or the other type, can be performed by tilting the frame, to select another polygon of lift, by the relative pivoting thus caused the direction of the force of gravity with respect to the frame. However, it can be expected that the bearings are movable in height so that the first guide wheel comes to reach tangentially, respectively "drill", the plane of the levitation polygon tangent to the idle wheel or wheels and thus attenuates, respectively inhibits , the support function of the idler wheel, to become a carrier in replacement, with then a guide.

  It will be noted that the concept of the invention, which is intended here to protect, relates to the bearing means, and not to the wheels themselves, which constitute only a conventional means, with mutually identical diameters or no.

  In one embodiment, the guide mode switching means is arranged to specifically make one of the first bearing means from the group consisting of the first idle bearing means and the first guide bearing means and inhibiting the specific azimuthal guidance function, respectively of azimuth-free slewing orientation, of the other first bearing means.

  This is the switching mode with exclusive operation of a single, as desired, first different bearing means. In such a case, the entire load of the frame in the area of the first guide bearing means is supported by it, so that the associated guide wheel is pressed to the ground and thus ensures the best guidance.

  The slide guiding mode switching means may furthermore be arranged so that, in the operative position of the chassis, it is possible to move one of the first bearing means of said group in height with respect to a floor surface beneath the frame. It is thus possible to lift the associated wheel off the ground and thus to inhibit the specific function of the bearing means considered.

  In such a case, at least one of the first bearing means of said group can be mounted so that, under the action of the switching control means of the guide mode, the first idler wheel or the first associated guide wheel it is able to maintain can ensure, optionally, a local ground clearance of the adjustable frame between a retracted position of rest, non-functional, ground clearance value less than a ground clearance value of the other first wheel associated with said group, and a functional deployment position, for which the first wheel of the first movable bearing provides a ground clearance value at least equal to that of the other wheel associated with said group. This is for example the first guide bearing means which is movable.

  The guide wheel can be provided vertically movable to achieve or "drill", the plane of the support polygon or the crazy wheels, this fictitious plane can however be pivotable if it is the first idler wheel that can approach the chassis and thus allow the guide wheel, then can be fixed ground clearance, to find tangent or even cut by the plane of the lift polygon, and thus becoming functional complement or replacement of the first idler wheel . Note that the guide wheel may be outside the support polygon defined by the or the idlers.

  The first crazy bearing means may be substantially on the extension line of the first axis of rotation. In particular then, a second crazy bearing means may be substantially on the extension line of the first axis of rotation.

  The three corresponding wheels are thus substantially collinear, and the direction of the inequality of the respective guard height values of the first competing wheels, respectively crazy and guide, can be inverted as desired, or canceled in the limit case, so that to obtain or not the guidance.

  In another embodiment, the mode switching means are arranged to tilt the chassis by a determined elevation angle, in operative position, about a ground bearing line defined from an alignment between a second idler bearing means, arranged to maintain a second idler, and third idler bearing means arranged to hold a third idler, to move the first idle bearing means away from the ground and to bring the first guide bearing, located, with respect to the bearing line on the ground, on an opposite side with respect to a side where the first idler bearing means is located.

  The various bearing means can therefore be of fixed height relative to the chassis, that is to say a ground clearance of the chassis of a given value, so that the chassis, with its bearing bearings, can constitute an indeformable assembly, of which the guiding function switching is ensured by the global switching mentioned above.

  This tilting can for example be controlled by a piston or additional bearing means mounted movable in height, under the action of operating means such as a lever, at a front end of the frame, to push upwards this end of the frame and thus tilt towards the opposite polygon of levitation, for example rear. Forward tilting can be achieved by a single piston or additional idler bearing means mounted at the rear. Alternatively, each of the first two bearing means 2869284 may be provided movable in height to provide the desired pulse intended to tilt the carriage, the first bearing means thus temporarily active, possibly returning thereafter to its position in height relative to chassis, so as not to disturb the desired operating mode. As a further variant, it may also be envisaged that the second and third idler bearing means, which occupy an intermediate position serving as the tilting axis of the chassis, are mounted movable in translation forward / backward in order to shorten one of the two levitation polygons they limit to the benefit of the other and thus cause the desired changeover.

  The first idler wheel can thus be lifted from the ground to one end of the frame, while the first guide wheel comes to rest at the opposite end.

  In such a case, the guiding mode switching means can be arranged to pivot the frame, in the tilted position, by an additional tilt angle around substantially the first guide bearing means, so as to also move the ground away from the ground. second and third idle bearing means and to support the chassis on the ground through a second guide bearing means arranged to maintain a second guide wheel with rotation axis substantially parallel to the axis of rotation of the first wheel of guide.

  The carriage thus has, in total, a succession of three polygons or segments of lift lines which, in side view, are aligned in a very open U, the first with only crazy bearing means, the third with only means guide bearing, and the second obviously having both types of bearing means.

  When the first guide wheel is functional, the carriage thus also tends to rest on the second and third idlers, so to be stable, if its load is evenly distributed. In particular, it is interesting that the second and third idler bearing means are front bearings, because then the first guide bearing means are at a greater distance from a preceding guide carriage, which is thus easier to guide and specific.

  In still another embodiment, the first idle bearing means is mounted at a first chassis end, a second idle bearing means arranged to hold a second idler wheel, and a third idle bearing means arranged to maintain a third idler, of permanent ground supports, are mounted at an opposite end, and, in an intermediate zone, the first guide bearing means is arranged to provide a switchable ground support with a bearing of the first idle bearing, the extension line of the axis of rotation of the first guide wheel being closer to the first follower bearing means than the second and third follower bearing means.

  In guide mode, the carriage thus naturally rests on the second and third idler bearing means and on the first guide bearing means, without significant risk that it takes a tilted position, simultaneous support on only the first two means bearing, of different types. Guiding the carriage by another guide carriage is thus easier because, the active levitation polygon is well defined, it can be chosen that it relates to the front portion of the carriage, so the towed end.

  In an advantageous embodiment, the guiding mode switching control means are provided for controlling an angular locking means of the first idler bearing means in a given azimuthal direction relative to the frame, thereby to inhibit the specific function thereof. transforming the first crazy bearing means into said first guide bearing means. The switching control means of the guide mode then preferably comprise a manual lever control mechanism of the type of a brake handle.

  The first bearing means is bifunctional and switchable to present, at any time, only one of its two mutually exclusive specific functions, crazy azimuth rotation or otherwise blocking in a given azimuthal direction. This avoids a duplication of the first two wheels respectively associated with the two first bearing means of different types, the first wheel can thus be unique and therefore always remains a support wheel. The ground support function, nonspecific as common to both types of bearing means, is therefore permanently ensured by the same first wheel.

  It will be noted that the azimuthal direction defined by the angular locking means may be predetermined, that is to say defined by construction, or it may be provided a possibility of adjustment of this azimuthal direction by the user, at each switching fashion. In the first case, it is for example a needle which is inserted into a cavity, of determined position, formed in a rotary vertical axis carrying the wheel through a stirrup or equivalent. In the second case, a ring of such cavities may be provided, offering a plurality of angular indexing positions, or a brake pad with a return spring in a given direction.

  The switching control means of the guide mode advantageously comprise a mobile linkage, connecting with another carriage, mounted movably between a folded position, rest, and a deployed functional position, traction. However, it may be provided that the drawbar has a fixed direction of extension, for example horizontal, and that the moving part is summarized to a coupling sensor to another carriage, for example a tensile force sensor.

  It is therefore unnecessary to provide specific and exclusive mode switching control means, since the drawbar is bi-functional, that is to say it constitutes a sensor of the desired operating mode and that it ensures due to its functional position, the appropriate switching control.

  The drawbar may be provided for, during its movement, rotate, through a connection kinematic, a height adjustment stirrup belonging to that of the bearing means which is movable, as provided in one of the embodiments of the present invention. -above.

  The pivoting of the drawbar forward, from a rest position for example folded laterally horizontally or raised vertically against the front of the frame, is converted into a downward movement of the wheel of the movable bearing.

  The linkage kinematics optionally comprises a means for adjusting the stroke of the movable bearing, for example a screw coupled to a nut for connecting two sections of adjustable length operating rod, or a longitudinal rack device coupled to a setting pinion. .

  The drawbar is preferably associated with return means to the rest position. It is therefore easy to provide that the drawbar folds to a rest position in which it is pressed against the frame, that is to say, it automatically has a minimal amount of space as soon as it is released.

  The return means advantageously comprise a gas cylinder having a predetermined return time constant. This avoids any risk of sudden return, likely to injure the user, while ensuring a desired return force to return to the rest position.

  It can be provided that, if the drawbar is movable in a predetermined rotation range, the jack is connected to it so that, when moving to the deployed position of the drawbar, against a return force to the retracted position exerted by the jack, said restoring force has a direction which comes to cut a pivot axis of the drawbar so that the restoring force is converted into a restoring force to the deployed position. This locks the drawbar in the functional position.

  The invention will be better understood with the aid of the following description of a chassis truck according to the invention, with reference to the appended drawing, in which: FIG. 1 is a schematic perspective view of the truck, and Figures 2 and 3 are each a schematic side view of the carriage of Figure 1, with a guide wheel respectively raised from the ground and supported thereon.

  FIG. 1 represents a carriage 1 comprising a chassis intended here for the transport of parcels, for example in a workshop or a station. The chassis has for this purpose essentially a lower frame 2, here rectangular and carrying a not shown grid floor, horizontal in the operative position, for receiving packages. Two vertical frames 3, 4, with not shown grid, close here the front ends, right in Figure 1, and rear of the frame.

  For the simplicity of the present disclosure, and in particular the indication of the extension directions of the various constituent elements, the carriage 1 is supposed to be in the functional position as shown, that is to say resting on a plane floor, with therefore the frame 2 extending in a horizontal plane. Of course, the explanations would remain valid, with the necessary transposition, in the case of a different orientation.

  Two pairs of support bearings, respectively rear 11, 12 and front 13, 14, are mounted idly, in azimuthal rotation, under respective corner regions of the frame 2 and are respectively associated with two pairs of idler wheels 21, 22 and 23, 24, which are rotatably mounted by respective horizontal axes such as the wheel axle 110 of the idle bearing 11, shown in Figures 2 and 3. The two pairs of idlers 21 to 24 are here identical and the two idlers of each pair are here of the same diameter. The idle wheels 21 to 24 thus defining, by their respective points of support on the ground, a rectangle of crazy levitation, represented directly by the ground in FIG.

  To ensure the freedom of azimuthal mad rotation, the horizontal axis 110, carrying the idler wheel 21, is itself carried by the ends of the two branches of an inverted U-shaped stirrup which extend in front of two opposing sectors. 21. The horizontal base of the U is integral with a pin 119, vertical axis, pivotally mounted in azimuth in a vertical passage 118 formed in the frame 2 or in an insert for this purpose. A lower mouth of the passage 118 also constitutes a horizontal plane support bearing of the frame 2 on the stirrup 111, and thus ultimately of bearing on the idler wheel 21 through the horizontal carrier axis 110. The explanation below is above is for other crazy bearings 12 to 14.

  As shown in the drawing of Figures 2 and 3, the stirrup 111 has an asymmetric triangular profile, so that the ground support zone of the idler wheel 21 is away from the vertical axial direction of the mounting stud 119, which allows the idler 21 to take, when moving the carriage, a retracted position to maintain or take the desired instantaneous orientation.

  The idle wheels 21 to 24 are therefore strictly guided in azimuth by the stirrup that holds them, such as the stirrup 111, and it is actually the latter which is mounted crazy and which thus confers this property to the so-called crazy wheel associated 21 to 24.

  The frame 2 is further secured to two guide bearings 31 and 32, on the right and on the left, respectively associated with guide wheels 41 and 42, occupying, on either side of the frame 2, an intermediate position on the length.

  The guide bearing 31 comprises a U-shaped stirrup 311 of the same kind as the stirrup 111, and having a horizontal axis 310 for supporting the guide wheel 41, but the stirrup 311 is pivotally mounted on the frame 2 around a horizontal axis. In other words, the vertical passage 119 with the pin 118 of the idle bearing 11 is equivalent, in the guide bearing 31, the same kind of mounting but turned 90 degrees, that is to say an axis or horizontal nipple 319 secured to the U-shaped base of the stirrup 311 and pivotally mounted in a horizontal passage 318 of the frame 2, or an insert for this purpose. The carrier axis 310, with a fixed direction relative to the frame 2, thus defines, to 90 degrees, the azimuth guidance direction.

  The stirrup 311 can pass, by pivoting, from a folded position (FIG 2), that is to say back to the frame 2, and here to the rear, in which the guide wheel 41 is located above the rectangle of crazy levitation defined by the idle wheels 21 to 24, to an extended position, the guide wheel 41 then touching (FIG 3), or cut, the rectangle of crazy levitation, so that thus at least its low point, of support to the ground, reaches the rectangle of levitation or even passes under it. The return movement in the folded position is also possible. Nothing would prevent the guide wheel 41 is then completely under the rectangle crazy levitation. The guide wheel 41 can thus be turned off or in use, by adjusting the distance of the horizontal bearing axis 310 with respect to the frame 2 and therefore also with respect to the rectangle of crazy levitation, that is to say the height from the ground.

  A switching mechanism of the carriage guide mode, i.e. the position of the stirrup 311, together with its counterpart of the left guide bearing 32, will now be exposed, as well as a mechanism for order it.

  The guiding mode switching control mechanism, that is to say with or without an azimuthal guiding mechanism, comprises a drawbar 51 rotatably mounted, by an end articulated on a horizontal axis 50, in front of the frame 2 between a folded position, rest (Fig 2), for which the drawbar 51 is raised against the front frame 3, and a functional position, traction (Fig 3), for which the drawbar 51 extends substantially horizontally . An opposite free end has a hook or a millet (FIG 1) hanging on the back of another carriage, identical or conventional.

  An operating link 65 is articulated, by a rear end, on one of the branches of the pivoting stirrup 311, and hingedly mounted, by a front end, at an intermediate point of the drawbar 51. As a result, the drawdown towards the front of the drawbar 51, moving into a horizontal functional position, causes a pull of the operating rod 65 which rotates the stirrup 311 from its rest position, here folded back, to its operative position here substantially vertical. The caliper of the left bearing 31 is likewise controlled by another rod. Alternatively, the stirrups of the two bearings 31 and 32 are mutually coupled in tilting, for example by the wheel axle 310, then common to the two wheels 41, 42.

  It may be provided that the rod 65 consists of two rods coupled end to end in a lengthwise adjustable manner, for example by a threaded portion coupled to a nut facing rotatably mounted on a shoulder of a ring-shaped bulge .

  Alternatively, the stirrup 311 can occupy an advanced resting position, and then the stirrup 311 must then have an additional operating lever arm, at the top part above the pivot axis 319, coupled to the operating link 65, in order to compensate for the initial kinematic inversion due to the advanced rest position.

  In this example, the drawbar 51 comprises, in the lower part, a rear lateral arm 52 fixed with respect to the rest of the drawbar 51, arm 52 which is here in the form of a stick with a generally horizontal extension and open downwards in the folded position, The axis 50 extends here over all the width of the frame 2 and is rotatably mounted on two bearings visible in Figure 1, to carry two arms 52, laterally opposed and twinned. As shown in FIG. 3, the arms 52 are here borne by the articulating end of the drawbar 51, constituting in fact the axis 50. The coupling of the operating rod 65 on the drawbar 51 is effected by done on the associated arm 52, right. When pivoting to the horizontal position of the drawbar 51, the arm 52 considered recovers forward and thus pulls the rod 65 maneuver.

  The advantage of the presence of arms 52 on the right is that, at the beginning of its straightening movement from its horizontal position, it has a substantially vertical trajectory, that is to say substantially perpendicular to the horizontal movement of the rear end. of the operating rod 65, which is slightly inclined to the horizontal. As a result, the amplitude of the substantially horizontal initial traction displacement of the latter is very small.

  Conversely, according to the principle of conservation of work, the corollary is that it results in a force-enhancing effect, that is to say that the force exerted by an operator to initially tilt the tiller 51 from its raised position is is found amplified at the coupling between the operating rod 65 and the stirrup 311. The operator therefore has no particular effort to exercise.

  At the end of pivoting of the drawbar 51 horizontally, this force-amplifying effect of the arm 52 no longer exists, but the operator can then press with the foot or with both hands on the drawbar 51 to complete the maneuver by the the effect of its own weight, by bringing the guide wheels 41, 42 into firm contact with the ground, that is, until the rear idlers 23 and 24 are raised, or less than a portion of the support load of the frame 1 is transferred to the guide bearings 31 and 32 with the associated guide wheels 41 and 42. The final uprising, more or less pronounced, the mass of the truck by the wheels 41 and 42 can be carried out, as indicated above, by simply exerting the weight of the operator on the drawbar 51. Note further that the final pivoting movement of the stirrup 311 tends to a deployed position which is here vertical, so that the movement of the horizontal axis 310 carrier of the guide wheel 41, has essen tially a horizontal component, therefore associated with a vertical component of very reduced descent. As it is this vertical component which corresponds to the work of lifting the mass of the carriage, one benefits from an effect of force amplification, corollary of the reducing effect of vertical displacement, according to the principle explained above.

  The restoring movement of the drawbar 51 in the raised rest position is here controlled by a quasi-vertical gas jack 60 connecting a point at the midpoint of the fixed front frame 3 to the drawbar 51, and precisely here to the left arm 52.

  In the folded position of the drawbar 51, that is to say with the arm 52 extending horizontally, the jack 60, working here in thrust, has a state of rest or near-rest, deployed. On the other hand, when the drawbar 51 is in the low position, the arm 62 occupying its upright position, the piston 60 is compressed. As shown in FIG. 3, the expansion thrust direction of the jack 60 then passes substantially through the axis 50, and even passes at the front thereof, which has a locking effect in the horizontal functional position of the drawbar 51, since the cylinder 60 will begin to redeploy after passing its deployment force line at the front of the axis 50. To raise the drawbar 51, the operator has only to raise it from the angle necessary for the thrust force of the cylinder 60 to return to the rear of the axis 50, and then this force can be exerted freely to rotate a quarter of a turn the arm 62, and therefore globally the tongue 51, to its rest position. The stirrup 311 is thus maintained in the raised position. The transfer of gas between a chamber under pressure and a vacuum chamber is effected through a calibrated passage introducing a controlled flow braking of the gas and thus determining a time constant for the return of the drawbar 51, which allows avoid any risk of injury to the operator.

  Alternatively, it may be provided that the drawbar 51 carries, at its free end, a horizontal bar for pulling or pushing and guiding the carriage 1, serving as a handlebar, that is to say determining a T-shape, in L or even U. The axis 50 may if necessary be located substantially at the height of the handlebar. Alternatively, the handlebar can be fixed and carry a mechanism of the kind handbrake bicycle lever, lever possibly continuing 2869284 20 by a brake bar parallel to the bar handlebar, to switch the state of the caliper 311 possibly a sheathed cable. If however it is the guided mode which is the most used, the guide bearings 31, 32 will then be of fixed height position and it will be the crazy bearings at one end, 11, 12 or 13, 14, which will be lowered in order to take off from the ground the guide bearings 31, 32.

  Such an arrangement of the switching mechanism can also be used for a caddy or a pram. For a carriage 1 as described above, it can be integrated in a train of such carriages pulled by an operator with a trolley if necessary and, once arrived at a destination, the operator uncouples the desired carriage and the individually gripped by the handle bar by actuating the above control mechanism, that is to say "disengagement" functional guide bearings 31, 32 by lowering idle bearings, for example the bearings 11, 12. On conceives that it is also possible to have, in the absence of control, a support on only guide bearings, the guide bearings 31, 32 being for example then located at the rear and further duplicated to the before the carriage 1, and in this case all the idle bearings 11 to 14 are switchable in height to temporarily replace the guide bearings, possibly adjacent respectively.

  As a further variant, all the guide bearings 31, 32 may be omitted, the idle bearings 11 to 14 being then completed by a brake mechanism, as mentioned at the beginning, in which a brake pad blocks the rotation of the pin 119. in the passage 118, thus fixing a determined azimuthal direction, but variable from one time to the next, for the rotation of the idler 21. Preferably, each idle bearing 11 to 14 is equipped likewise. The advantage of such a solution is that it does not require lifting the carriage 1. A return spring, equivalent to the cylinder 60, is provided to return the pad in the spaced apart position or in contact with the pin 119, and the Brake handle mechanism acts against the spring. 2I2

Claims (18)

claims   A carriage frame (2) equipped with a plurality of at least one first idler bearing means (11) arranged to hold a first idler bearing wheel (21) in azimuth bearing orientation relative to the frame. (2) in operative position, characterized in that it comprises at least one first guide bearing means (31, 32) arranged to maintain a first guide carrier wheel (41) rotatable about a first axis of rotation {310) extending along a predetermined azimuth orientation extension line, and means (65, 311) for guiding frame mode switches (2) arranged for, in the operative position of the frame (2), under the action of switching control means of the guide mode (51, 52), switching the first guide bearing means (31) between a muting state and a guiding functional state.   The frame of claim 1, wherein the guide mode switching means (65) is arranged to specifically make the one (11, 31), as desired, first bearing means among the group consisting of the first follower bearing means (11) and the first guide bearing means (31), and inhibiting the azimuthal, or azimuth-wise, slewing orientation specific function of the other first bearing means (31, 11).   The chassis of claim 2, wherein the chassis guide mode switching means (65,311) is arranged to move in height relative to a ground surface in the operating position of the chassis (2). 2869284 23 under the frame (2), one of the first bearing means to said group (11, 31).   4. Chassis according to claim 3, wherein at least one of the first bearing means of said group (11, 31) is movably mounted so that under the action of the switching control means of the guide mode (51 , 52), the first idler wheel (21) or the first associated guide wheel (41) that it is able to maintain can provide, as desired, a local ground clearance of the frame (2) adjustable between a retracted position of rest, non-functional, ground clearance value less than a ground clearance value of the other first wheel associated with said group (11, 31), and a deployment functional position, for which the first wheel (21, 41) of the first movable bearing (11, 31) provides a ground clearance value at least equal to that of the other wheel associated with said group (11, 31).   5. Chassis according to claim 4, wherein it is the first guide bearing means (31) which is movable.   Chassis according to one of claims 1 to 5, wherein the first idler bearing means is substantially on the extension line of the first axis of rotation (310).   The chassis of claim 6, wherein a second idler bearing means is substantially on the extension line of the first axis of rotation.   8. Chassis according to one of claims 1 to 6, wherein the mode switching means are arranged to tilt the frame (2) a given elevation angle, in operative position, around a support line on the ground defined according to an alignment between a second idler bearing means, arranged to maintain a second idler wheel, and a third idler bearing means, arranged to maintain a third idler wheel, so as to move away from the ground the first means of bearing fool and bring closer to the ground the first guide bearing means, located, relative to the bearing line on the ground, an opposite side with respect to a side where is the first means of crazy bearing.   The chassis of claim 8, wherein the guide mode switching means is arranged to pivot the frame (2), in the tilted position, by an additional tilt angle about substantially the first guide bearing means ( 31), also to move the second (13) and third (14) idle bearing means away from the ground and to press the frame (2) to the ground through a second guide bearing means arranged to hold a second wheel guide carrier with rotation axis substantially parallel to the axis of rotation of the first guide wheel.   10. Chassis according to one of claims 1 to 7, wherein the first follower means (11) is mounted at a first frame end (2), a second follower bearing means (13), arranged to maintain a second idler wheel (23), and a third idler bearing means (14), arranged to maintain a third idler wheel (24), of permanent ground supports, are mounted at an opposite end, and in an intermediate zone the first guide bearing means (31) is arranged to provide a switchable ground support with a bearing of the first idler bearing (11), the extension line of the axis of rotation (310) of the first idler wheel. guide (41) being closer to the first idler bearing means (11) than second and third idler bearing means (13, 14).   Chassis according to one of claims 1 to 10, wherein the guide mode switching control means (51, 52) are provided for controlling an angular locking means of the first idler bearing means (11) in accordance with a azimuth direction determined relative to the frame (2), thereby to inhibit the specific function and transform the first crazy bearing means (11) into said first guide bearing means (31).   The chassis of claim 11, wherein the guide mode switching control means (51, 52) includes a lever-type manual control mechanism such as a brake handle.   13. Chassis according to one of claims 1 to 12, wherein the switching control means of the guide mode comprise a drawbar (51, 52) for connection with another carriage, mounted movably between a folded position, resting , and a deployed functional position, traction.   14. Chassis according to claims 4 and 13 together, wherein the drawbar (51, 52) is provided for, during its movement, rotate, through a connection kinematic (65), a stirrup (311) for adjusting height belonging to that of the bearing means (11, 31) of claim 2 which is movable.   Chassis according to claim 14, wherein the linkage kinematics (65) comprises a stroke adjustment means of the movable bearing (11, 31).   16. Chassis according to one of claims 13 to 15, wherein the drawbar (51, 52) is associated with means (60) for returning to the rest position.   17. The frame of claim 16, wherein the biasing means comprises a gas cylinder (60) having a predetermined return time constant.   Chassis according to claim 17, wherein the drawbar (51, 52) being movable in a predetermined range of rotation, the jack (60) is connected thereto so that, when moving to the extended position of the drawbar (51, 52), against a restoring force towards the folded position exerted by the jack (60), said restoring force has a direction which cuts a pivot axis (50) of the drawbar ( 51) so that the restoring force is transformed into a restoring force towards the deployed position.