Patent Description:
In industrial plants for the production and assembly of motor vehicles there is the need to handle and move motor-vehicle body shells being defined or already partially assembled through the welding stations and the subsequent processing stations so as to complete assembly according to the sequence imposed in the design stage.

The current production lines are, however, conceived in a substantially rigid way as regards movement of mobile frames or pallets for carrying motor-vehicle body shells in so far as the movement is exclusively entrusted to floor conveying systems, which automatically position the mobile frame in the processing station.

The operations of positioning and geometrical referencing are hence characterised by an extremely high precision and repeatability. To provide a simplified picture of the situation, known solutions are conceived in such a way that the system for handling the mobile frames and the system for positioning thereof have levels of positioning precision that are substantially comparable or in any case compatible with one another.

However, the inventors have noted how significant advantages could be achieved from rethinking of the production-line structures and in particular from elimination of underground structures and of structures arranged in an overhead position in so far as this is likely to reduce the requirements of the industrial building that houses the plant, consequently widening the choice of buildings.

In particular, by so doing, there is no longer the need to carry out civil works for laying underground line structures necessary for operation of the floor conveyors, and likewise the need to choose or erect buildings the vaults of which are able to support a high load at the nodes.

In the perspective of redesigning an industrial installation assuming elimination of underground or embedded structures, a very interesting possibility is constituted by the movement of mobile frames for supporting motor-vehicle body shells by means ofautonomous handling and movement devices, such as the so-called AGVs (Automated Guided Vehicles), which can transport the mobile frames/pallets through the plant following pre-set paths and can likewise position the pallets in a processing station.

The prior art offers in this regard an extremely large number of examples of motor-vehicle production lines in which the pallets for supporting motor-vehicle body shells are moved via AGVs. In known solutions, generally each AGV transports a single pallet throughout the processing cycle that the body shell is to undergo.

If the use of handling and movement solutions based upon AGVs on the one hand makes it possible to do without the civil works for laying underground the system for moving and guiding the floor conveyors, on the other hand it presents levels of performance in terms of positioning precision that are far inferior. This performance gap is mainly due to the fact that an automatic handling and movement device such as an AGV suffers from very poor repeatability as regards the operation of entry into a fixed station and its positioning therein. Hence, the mobile frame (pallet) carried by the vehicle in question arrives in the station with a positioning error that is one or two orders of magnitude higher than the errors allowed for proper execution of the processing operations on the vehicle body shell.

In addition, since in known solutions each vehicle is generally associated to one and only one mobile frame/pallet, the number of automated vehicles to be used in the plant may reach levels such as to render impracticable an efficient management of the paths, in addition to increasing considerably the investment necessary for equipping an industrial installation.

The object of the present invention is to solve the technical problems mentioned previously. In particular, the object of the invention is to provide a system for positioning a mobile frame with respect to a fixed frame - the latter being associated to a processing station - that will enable operation with very small positioning tolerances compatible with the processing operations carried out on a motor-vehicle body shell, albeit using a low-precision handling and movement device.

The object of the present invention is achieved by a positioning system, a receiving element, a processing station, and a method having the features of the attached claims, which form an integral part of the technical disclosure provided herein in relation to the invention.

The invention will now be described with reference to the annexed drawings, which are provided purely by way of non-limiting example and in which:.

The reference number <NUM> in <FIG> designates as a whole a system for positioning a mobile frame with respect to a fixed frame according to the invention. The system <NUM> comprises a receiving element <NUM> configured for connection to one of the mobile frame and the fixed frame, and a pin <NUM> configured for connection to the other of the mobile frame and the fixed frame. The pin <NUM> is configured for coupling within the receiving element <NUM> in an engagement direction defined by a main axis Z2 of the receiving element <NUM>.

In particular, the axis Z2 is a longitudinal axis of an orifice O of the receiving element <NUM>, where the term "longitudinal" is here to be understood only with reference to the receiving element <NUM> and not with reference to the cartesian system X-Y-Z that is represented in the figures, which is consistent in all figures and applies to a processing station according to the invention. The system X-Y-Z identifies the three notable spatial directions: longitudinal direction (X), transverse direction (Y), vertical direction (Z).

With reference to <FIG>, <FIG>, the receiving element <NUM> comprises a first ring of rollers <NUM> and a second ring of rollers <NUM>, where the two rings of rollers <NUM>, <NUM> are preferably arranged so as to be centred on the axis Z2 and in such a way that the rollers of the first ring <NUM> alternate with the rollers of the second ring <NUM> so that a roller <NUM> of the first ring is comprised between two rollers <NUM> of the second ring, and vice versa.

The rollers of the ring <NUM> have an axis of rotation γ8, whilst the rollers of the ring <NUM> have an axis of rotation γ10, where the axes of rotation γ8 and γ10 belong to planes orthogonal to the main axis Z2 and preferably belong to one and the same plane XY orthogonal to the axis Z2. In some embodiments, the axes γ8 belong to a first plane orthogonal to the axis Z2, whereas the axes γ10 belong to a second plane orthogonal to the axis Z, set at a longitudinal distance from the first plane (for example, in the view of <FIG> the plane to which the axes γ10 belong is above the plane to which the axes γ8 belong).

The rollers <NUM> and the rollers <NUM> functionally come to define the orifice O, as may be clearly seen in <FIG>. In this way, the orifice O has a pseudopolygonal shape that derives from the arrangement of the peripheral (rolling) surfaces of the rollers <NUM>, <NUM> (and consequently of the axes γ8 and γ10) in a position tangential to respective circumferences.

In particular, with reference to <FIG>, the rollers of the first ring <NUM> have peripheral (rolling) surfaces set tangential to a first circumference C8 centred on the axis Z2, whereas the outer surfaces of the rollers of the second ring <NUM> are set tangential to a second circumference C10, once again centred on the axis Z2, where the diameter of the circumference C8 is smaller than the diameter of the circumference C10.

Moreover, with reference to <FIG>, the axes γ8 are arranged in a position tangential to a circumference C8*, whereas the axes γ10 are arranged in a position tangential to a circumference C10*, having a diameter larger than that of the circumference C8*.

Since the rollers <NUM>, <NUM> preferably have the same diameter, in view of the circumstances referred to above, their radial protrusion within the orifice O is greater for the rollers <NUM>, whereas the rollers <NUM> are arranged with the peripheral (rolling) surfaces set further back than the surfaces of the rollers <NUM>, for reasons that will become clear in the ensuing description. Moreover, on account of the preferably alternating arrangement of the rollers <NUM>, <NUM>, an alternation of radial protrusions of the peripheral (rolling) surfaces is obtained.

In the preferred embodiment of the invention illustrated herein, the first ring of rollers comprises four rollers <NUM> set at equal angular distances apart (hence at <NUM>°, with a crosswise arrangement) and the second ring of rollers likewise comprises four rollers <NUM> set at equal angular distances apart (hence at <NUM>°, with a crosswise arrangement). The two rings have the preferred alternating arrangement of the rollers <NUM>, <NUM>, where the first ring of rollers <NUM> and the second ring of rollers <NUM> are arranged angularly staggered by <NUM>° with respect to one another. In this way, the rollers <NUM>, <NUM> are arranged at regular intervals of <NUM>° about the axis Z2.

In the above arrangement, as may be seen in <FIG>, the rings of rollers <NUM> and <NUM> are in effect arranged in such a way that the respective axes γ8, γ10 - when prolonged - give rise to an octagonal shape, and moreover pseudo-octagonal is the shape defined in plan view by the envelope of the peripheral (rolling) surfaces of the rollers <NUM>, <NUM> facing one another so as to define the orifice O (which hence itself has the pseudo-octagonal shape).

It should on the other hand be noted that the same alternation of protrusions of the outer surfaces of the rollers <NUM>, <NUM> may be obtained also in a different way. For instance, it is possible to arrange the axes γ8, γ10 tangential to one and the same circumference and vary the protrusion simply by providing the rollers <NUM> with a diameter larger than that of the rollers <NUM>.

With reference to <FIG> and to <FIG>, <FIG>, and <FIG>, the pin element <NUM> comprises a first, tapered, portion <NUM> and a second, cylindrical, portion <NUM>, which develop coaxially sharing a longitudinal axis Z4 of the pin (the term "longitudinal" is here understood with reference to just the pin, and not to the reference system XYZ of the figures). The tapered portion <NUM> preferably has a conical geometry, which terminates at a first (free) end R14, and extends for an axial length L14 as far as the cylindrical portion <NUM>.

The cylindrical portion <NUM> develops for an axial extension L16, and the ratio L14/L16 is sized in such a way that, when the pin <NUM> is completely within the orifice O, the rollers of the first ring <NUM> bear upon the cylindrical surface <NUM>, slightly above the interface with the surface <NUM> (see <FIG>). The ratio L14/L16 depends upon the amount of the positioning error that it is required to recover (as likewise upon the number of rollers <NUM>, <NUM>). The dimension L16 depends upon the length necessary for engaging the rollers <NUM>, <NUM> and upon the overall height of the receiving element <NUM>. The size of the rollers <NUM>, <NUM> depends upon the load to be withstood during introduction of the pin <NUM>.

It is to be borne in mind that in alternative embodiments the tapered portion <NUM> may exhibit a different geometry that envisages a reduction of diameter towards the end R14 of the pin <NUM>. For instance, parabolic profiles or even circular profiles with a large radius may be envisaged.

The pin element <NUM> is configured for being connected to the fixed frame or to the mobile frame at a second end H4 that is adjacent to the cylindrical portion <NUM>, whereas the end R14 constitutes the free end of the pin <NUM> configured for encountering, first, the orifice O and the rollers of the rings <NUM>, <NUM> in the engagement direction Z2.

With reference to <FIG>, designated as a whole by <NUM> is a processing station according to a preferred embodiment of the invention. The station <NUM> comprises a fixed frame <NUM> and a mobile frame <NUM> (the so-called pallet), where the mobile frame can be selectively coupled to and removed from the fixed frame <NUM>. The longitudinal direction X, the transverse direction Y, and the vertical direction Z apply directly to the station <NUM> and to the frame <NUM>. As regards the frame <NUM>, if it is referenced with respect to the same reference system, the directions are the same, whereas, if a local cartesian triad is considered, then the local directions of the frame <NUM> coincide with those X-Y-Z of the frame <NUM> and of the station <NUM> - as will be seen - only when the frame <NUM> is positioned on the frame <NUM> and coupled thereto.

The mobile frame/pallet <NUM> can be picked up from the frame <NUM> and can be released thereon (according to the needs and/or the step of the processing cycle considered) by means of a handling device V, illustrated schematically in <FIG>. Preferentially, the handling device V is a so-called AGV.

With reference to <FIG>, the fixed frame <NUM> is a frame fixed on the floor configured for supporting the mobile frame <NUM>. The fixed frame <NUM> comprises a first lateral bank <NUM>, a second lateral bank <NUM>, and a plurality of supports <NUM>, which are configured for supporting the mobile frame <NUM> when it is rested on the lateral bank <NUM>, <NUM> and are configured for providing a position reference for the frame <NUM> along the vertical axis Z with respect to the floor (reference Z = <NUM>).

The supports <NUM> are carried by brackets <NUM>, <NUM>, <NUM>, which basically differ for the type of equipment with which they are provided. With reference to <FIG>, the brackets <NUM> are vertical supporting brackets and, as such, are equipped with just the support <NUM> for sustaining the frame <NUM> vertically.

The bracket <NUM> is a bracket for providing a triaxial position reference in so far as it comprises a support <NUM> configured for providing the position reference along the vertical axis Z and a receiving element <NUM> configured for providing the position reference along the longitudinal axis X and the transverse axis Y, as will be described in detail in what follows. The rollers of the first ring <NUM> and the rollers of the second ring <NUM> have the preferred arrangement illustrated in <FIG>, with four rollers <NUM> at <NUM>° with respect to one another, and four rollers <NUM> at <NUM>° with respect to one another, and staggered by <NUM>° with respect to the rollers <NUM>.

The bracket <NUM> is, instead, configured for providing a biaxial position reference in so far as it carries a support <NUM> for vertical positioning, and a further receiving element <NUM> is configured for being engaged by a pin <NUM>' carried by the mobile frame <NUM>. The pin <NUM>' is illustrated in <FIG> in combination with the receiving element <NUM>, and all the references identical to those already used designate the same objects. It will thus be noted how the pin <NUM>' has exactly the same shape as the pin <NUM>, with the addition of two flattened areas F set in diametrally opposite positions and aligned along the longitudinal axis X, in such a way that the pin <NUM>' and the rollers of the receiving element <NUM> bear upon one another only in the transverse direction Y when the pin <NUM>' is located in the orifice O. The flattened area F extends for an axial length LF that covers at least the entire length L16, and optionally part of the length L14.

With reference to <FIG>, the handling device V is preferably, as has been mentioned, an AGV configured for autonomous movement of the frame <NUM> on the floor (for this reason the device V will frequently be referred to , in an interchangeable way, as "vehicle V"), which is carried for this purpose on the back of the vehicle V. The back of the vehicle V corresponds to a top portion of the vehicle itself, which is configured for receiving the frame <NUM> and - for reasons that will be clarified in what follows - for vertical movement of the frame <NUM>.

With reference to <FIG>, the frame <NUM> comprises two longitudinal members <NUM>, which extend in a longitudinal direction X, and a plurality of cross members <NUM>, some of which carry supports <NUM> oriented along the vertical axis Z for supporting a motor-vehicle body shell. The longitudinal member <NUM> is configured for resting on the side <NUM> of the fixed frame <NUM>, on which the brackets <NUM> and <NUM> are provided, and is equipped for this purpose with a pin <NUM> and a pin <NUM>' in longitudinally spaced positions. The pins <NUM> and <NUM>' are covered by a shield <NUM>.

As may be seen in <FIG>, when the pin element <NUM> or <NUM>' is received in the respective receiving element <NUM>, <NUM>', the shield <NUM> completely envelops the receiving element so as to prevent exposure thereof to the outside environment.

Moreover, in a preferred embodiment, the frame <NUM> and the handling device V are themselves equipped with a positioning device <NUM>, where in particular the receiving element <NUM> is located in a position set upside down on the frame <NUM>, whilst the pin <NUM> is located on the vehicle V, with the end R14 facing upwards. The device <NUM> for coupling between the vehicle V and the frame <NUM> makes it possible to keep the vehicle V and the frame <NUM> coupled together during movement of the vehicle V, and likewise makes it possible to assist the operations of taking-up of the frame <NUM> by the frame <NUM>, and release of the frame <NUM> on the frame <NUM>. Moreover, once again preferentially, the vehicle V is equipped with a release device comprising, for example, a roller or ball platform that enables relative movement of the frame <NUM> with respect to the vehicle V at the (mechanical) interface between them, rendering the former floating during the transients of picking-up and release. An example of release device that can be applied to the vehicle V and/or to the frame <NUM> is illustrated in <FIG> (position) and 6D (detail). The release device in question is associated to the reference FL and comprises a plurality of rolling elements BB here provided as idle balls. In the embodiment illustrated here, the vehicle V is equipped with four units FL (arranged in the proximity of four opposite corners of the vehicle V) with five balls BB each arranged quincuncially, as illustrated in <FIG>. Preferably, the balls BB are carried by a supporting plate SP, which also carries the seats for the balls BB and is in turn preferably mounted in a seat specifically provided on the vehicle V. It is to be borne in mind, however, that the number and arrangement of the units FL and of the balls BB may be varied according to the needs, and it is likewise possible to set the release devices FL on the frame <NUM> (with the balls BB oriented towards the vehicle V) or else again it is possible to adopt hybrid arrangements in which a part of the release devices FL is set on the vehicle V, while another part is set on the frame <NUM>.

At a general level, falling within the scope of the invention is provision of a release device at the interface between the handling device V (whatever this may be) and the mobile frame <NUM> that is handled by the handling device V. The release device preferably comprises one or more rolling elements that can enable the relative movement required at the interface itself, and may be provided both on the mobile frame <NUM> and on the handling device V (even in combination, as has been seen).

This means that, when the handling device V is provided as automated guided vehicle, it may in the limit be of a completely conventional type, i.e., without the release device. The latter may be installed on board the frame <NUM> in the form, for example, of arrays of rolling elements.

In addition, for certain applications, even not necessarily linked to the motor-vehicle sector (for example, the logistics industry and the mass-distribution industry), in the case where the load weighing upon the frame <NUM> is low, the release device may be obtained even without the use of rolling elements, but relying upon one or more sectors or elements made of a material with low coefficient of (sliding) friction.

With the aid of <FIG>, <FIG>, and <FIG>, there now follows a description of a sequence of coupling between the mobile frame <NUM> and the fixed frame <NUM>, in which a position referencing of the frame <NUM> with respect to the frame <NUM> is simultaneously carried out in the processing station <NUM>.

With reference to <FIG> and <FIG>, the handling device (vehicle) V is configured for picking up the mobile frame <NUM> from the fixed frame <NUM> or releasing it thereon in the station <NUM> so as to position in the station a motor-vehicle body shell that is to undergo processing operations, for example welding. Thanks to the provision of the positioning system <NUM>, it is possible to position the vehicle body shell accurately relative to the processing station <NUM> (i.e., to the frame <NUM>) in a completely automatic and purely mechanical way.

In particular, with reference to the positioning system <NUM>, the handling device V is configured for providing a coupling of the pin element <NUM>, <NUM>' within the corresponding receiving element <NUM> at the moment of release of the mobile frame <NUM> on the fixed frame <NUM>, and for enabling extraction of the pin element <NUM>, <NUM>' from the corresponding receiving element <NUM> at the moment of picking-up of the mobile frame <NUM> from the fixed frame <NUM>.

Since the engagement directions Z2 are oriented along the vertical axis Z, this is physically achieved by a vertical movement (i.e., a movement comprising at least one vertical component) of the mobile frame <NUM> with respect to the fixed frame <NUM>.

For this reason, as has been mentioned, the vehicle V is substantially configured as a vertically mobile platform so as to assist the variations in height of the frame <NUM> necessary to complete the operations referred to above. During vertical movement of the frame <NUM>, the aforesaid variations in height also enable disengagement or engagement of the pin <NUM> on the vehicle V with respect to the receiving element <NUM> on the frame <NUM>.

With reference to <FIG> and <FIG>, the fixed frame <NUM> comprises an entry section IN, an exit section OUT, and a lay-by area P (indicated schematically by a dashed and dotted line), set between the entry section IN and the exit section OUT and between the lateral bank <NUM>, <NUM>. It should be noted that the terms "entry section" and "exit section" only correspond to a functional specification. The vehicle V may enter the station in any direction of travel, so that it may happen that what functionally corresponded to an "entry section" in a previous working cycle, may become an "exit section" for a subsequent working cycle.

The lay-by area P is understood as an area of manoeuvre for the handling device/vehicle V, i.e., an area in which the handling device/vehicle V arrives, parks, or in general interacts for the time necessary to release the frame <NUM> on the frame <NUM> or to pick up the frame <NUM> from the frame <NUM>, and from which it moves away, exiting through the exit section OUT.

As may be seen in <FIG>, when the operation to be carried out is release of the mobile frame <NUM> (which is carrying a motor-vehicle body shell, here not illustrated to facilitate vision of the other components) on the fixed frame <NUM>, the handling device/vehicle V enters the lay-by area P through the entry section IN.

The automatic guiding system of the handling device/vehicle V is configured so that it will stop in the lay-by area P, positioning the mobile frame <NUM> with respect to the fixed frame <NUM> in such a way that the pin <NUM> comes to be located substantially in a position corresponding to the orifice O of the respective receiving element <NUM>, and the pin <NUM>' comes to be located substantially in a position corresponding to the orifice O of the respective receiving element <NUM>.

The back of the vehicle V is in this step held in a raised position with respect to the frame <NUM>, and in particular in a position such that the bottom ends of the frame <NUM> are above the level of the supports <NUM> and the pins <NUM>, <NUM>' are located above the level of the receiving elements <NUM>. Otherwise, even just entry of the vehicle V into the lay-by area P would be impossible, as likewise positioning of the frame <NUM> in the required preliminary position.

With reference to <FIG> and <FIG>, on account of the (relatively) poor precision of positioning of the handling device/vehicle V with respect to the frame <NUM>, even if positioning of the frame <NUM> on the handling device/vehicle V presents high repeatability, the frame <NUM> arrives with the pins <NUM>, <NUM>' misaligned with respect to the engagement direction Z2 of the corresponding receiving element. Without the positioning device <NUM>, release of the frame <NUM> on the frame <NUM> would occur with the former in a position completely out of tolerance along the transverse axis Y and along the longitudinal axis X (along Z the reference is in any case provided by the supports <NUM>, but this is clearly not sufficient).

In this regard, <FIG> and <FIG> illustrate a possible starting condition of the operations of release of the mobile frame <NUM> on the fixed frame <NUM>, in particular a condition in which the handling device V has reached the lay-by area P with a positioning such that the axis Z4 of the pin <NUM> presents a longitudinal deviation ΔX and a transverse deviation ΔY with respect to the axis Z2 of the receiving element <NUM> (even though not illustrated for reasons of economy, a very similar situation arises also for the pin <NUM>': the deviations may, of course, be different but the situation is conceptually the same).

With reference to <FIG> and <FIG>, the frame <NUM> is moved in the vertical direction Z reducing its height and bringing it up to the frame <NUM>.

This facilitates entry of the pin <NUM> into the orifice O of the receiving element <NUM>, and entry of the pin <NUM>' into the orifice O of the further receiving element <NUM>.

In this regard, the presence of a double ring of rollers, i.e., the ring <NUM> and the ring <NUM>, facilitates the operations of positioning, ruling out the risk of any sticking. In fact, with reference to <FIG>, the tapered portion <NUM> can easily bear upon the rollers of the first ring <NUM> and/or the rollers of the second ring <NUM> according to the longitudinal and transverse deviations, causing the frame <NUM> to shift in the longitudinal direction and/or in the transverse direction to nullify the deviations ΔX and ΔY as the vertical movement of descent of the frame <NUM> proceeds.

The deviations ΔX', ΔY', which may be seen in <FIG>, are of a small amount as compared the deviations ΔX and ΔY in so far as the pin <NUM> is guided by a roller <NUM> and/or by a roller <NUM> towards the position of alignment between the axes Z2 and Z4.

According to the invention, the rollers of the first ring <NUM> are configured for providing the final longitudinal and transverse positioning, and if need be for guiding the pin <NUM> during the transient of release of the frame <NUM>, whereas the rollers of the ring <NUM>, which are radially set further back, are configured only for facilitating the operations of centring of the pin <NUM> during the transient of release, but do not intervene in the final positioning in so far as they are radially set further back. In other words, during the transient both of the rings of rollers may be active for facilitating as much as possible centring of the pin <NUM> in the orifice O, whereas in the final coupling condition of the pin <NUM> in the orifice O just the rollers <NUM> intervene (or rather interact).

Precisely for this reason, the embodiment represented the figures is to be deemed preferred, where the rollers <NUM> (four in number) are aligned in pairs in the longitudinal and transverse directions, whereas the rollers <NUM> are aligned along the directrices at <NUM>° with respect to the transverse and longitudinal directions so as to function as further guides in the case of recovery of deviations ΔX, ΔY with components of the same order of magnitude in both directions (X and Y).

If the handling device/vehicle V is provided with the aforementioned release device, when the frame <NUM> is released on the frame <NUM> and the handling device V is progressively relieved of the weight of the frame <NUM>, it is possible to enable a relative movement, in a transverse direction and/or in a longitudinal direction, between the frame <NUM> and the handling device V, which assists recovery of the deviations ΔX and ΔY.

Also the ensemble formed by the receiving element <NUM> and the pin <NUM> set at the interface between the frame <NUM> and the vehicle V assists release of the frame <NUM> and recovery of the deviations ΔX and ΔY, in any case maintaining a minimal condition of (mobile) constraint between the vehicle V and the frame <NUM> as release proceeds so as to prevent any sudden movements of the frame <NUM> with respect to the vehicle (which become more likely if a release device is provided).

Quite simply, contrary to what occurs at the interface between the frame <NUM> and the frame <NUM>, as the frame <NUM> passes from being supported by the vehicle V to being supported by the frame <NUM>, the pin <NUM> on the vehicle V progressively releases from the receiving element <NUM> on the frame <NUM>, being guided without any sticking by the two rings of rollers <NUM>, <NUM>.

The final coupling condition may be seen in <FIG>, where it may be noted how, at the end of the relative movement between the tapered portion <NUM> and the rollers <NUM>, <NUM> that has led to alignment of the axes Z2, Z4, it is the cylindrical portion <NUM> that lies between the rollers <NUM>, <NUM> and bears upon them, with the rollers <NUM> that bear upon the surface of the portion <NUM> in diametrally opposite positions (net of any inevitable fitting play) along the axis X and along the axis Y, thus enabling extremely precise positioning of the frame <NUM> with respect to the frame <NUM> both in the transverse direction and in the longitudinal direction. In particular, the pair of rollers <NUM> aligned in the direction X positions the frame <NUM> longitudinally, whereas the pair of rollers <NUM> aligned in the direction Y positions the frame <NUM> transversely.

Simultaneously with the sequence of <FIG>, the same sequence of operations applies, with the necessary changes, also to the pin <NUM>' and the corresponding receiving element <NUM>, with the sole exception due to the fact that in this case the final condition of coupling between the pin <NUM>' and the receiving element <NUM> does not envisage contact with the rollers <NUM> in the longitudinal direction on account of the flattened areas F so as to prevent conditions of statically indeterminate longitudinal constraint for the frame <NUM> with respect to the frame <NUM>. In a transverse direction, instead, there is no static indeterminacy in the constraint since the pins <NUM> and <NUM>' are located at opposite ends of the frame <NUM> so that it is necessary to fix the position of one end and the other end in the transverse direction.

It should moreover be noted that in the final coupling condition the receiving element <NUM> and the pin <NUM> do not support any weight in the vertical direction since the supporting and vertical-positioning function is entrusted solely to the supports <NUM>.

Once the process of release is concluded with the condition illustrated in <FIG>, the handling device V can resume its movement from the lay-by area P and abandon the station <NUM> through the exit section OUT.

In the reverse operation, i.e., that of picking up of the frame <NUM> from the frame <NUM> by the vehicle V, the latter enters through the entry section IN, positions itself in the lay-by area P underneath the frame <NUM>, and progressively raises its top surface in order to take up progressively the weight of the frame <NUM>.

In this case, the presence of the release platform and of the aforesaid positioning system <NUM> between the frame <NUM> and the vehicle V enables compensation in the opposite direction of the differences of positioning between the device V and the frame <NUM> when the latter is supported by the frame <NUM>. As always, it is the vehicle V that enters the station <NUM> with a non-optimal position with respect to that of the frame <NUM> (which is here no longer a target position, but an actual position): if in the release operation the frame <NUM> has to compensate for the deviations with respect to a target position on the frame <NUM>, in the picking-up operation the frame <NUM> has to compensate for the deviations with respect to the position of coupling to the vehicle V, in particular with respect to the position of coupling to the pin <NUM> on the vehicle V.

In this regard, now it is the pin <NUM> on the vehicle V that progressively engages the receiving element <NUM> on the frame <NUM>, while the pins <NUM> and <NUM>' progressively release from the receiving elements <NUM> and <NUM>' on the frame <NUM>. In this step, it is the pin <NUM> on the vehicle V with the respective receiving element <NUM> on the frame <NUM> that functions as centring element, while the pins <NUM> and <NUM>' at opposite ends of the frame <NUM> remain fundamentally passive or practically passive.

Once again, in the case where it is present, the release device on the vehicle V further assists the relative movements between the frame <NUM> and the vehicle V, this time, however, being in a more burdensome condition since the load on the vehicle V increases as the operation proceeds.

Thanks to the positioning system <NUM> according to the invention, it is hence possible to reconcile the needs and performance of positioning of objects that are even very different from one another, in a completely automatic and purely mechanical way, without any need for interventions other than simple actions of picking-up and release of the frame <NUM> itself. It hence becomes possible to exploit the extreme flexibility afforded by handling devices, such as AGVs, within a plant: the paths of flow of the frames <NUM> can be established with greater flexibility as compared to what is obtained with pit-type movement and handling equipment, and can benefit from a greater flexibility in the layout of the industrial plant.

The shape of the pin <NUM> and provision of a double ring of rollers, where one of the two rings performs only functions of lead-in/centring of the pin (the ring <NUM>) and the other ring performs both the lead-in function and the function of position referencing (the ring <NUM>), ensures that, whatever the misalignment between the axes Z4 and Z2, this can be recovered and nullified without sticking of any sort, and without any need for external corrections, in a completely automatic and purely mechanical way.

On the other hand, it should be noted, the configuration of pins/receiving elements here illustrated can be combined in any way according to the needs. For instance, the receiving elements fixed to the frame <NUM> and aimed at enabling coupling with the pins <NUM> and <NUM>' on the frame <NUM>, can be shifted on the frame <NUM> in homologous positions, and the pins <NUM>, <NUM>' can consequently be mounted on the frame <NUM>. Also the receiving element on the frame <NUM> in a central position for coupling with the pin <NUM> on the vehicle V may be installed on the vehicle V, and the pin may be accordingly repositioned on the frame <NUM>. Hybrid schemes may also be used, in which the frame <NUM> has the pin <NUM> and the receiving element <NUM> designed for coupling with the pin <NUM>' on the frame <NUM>, or vice versa.

This in practice opens to the possibility of creating industrial installations in which movement of the frames <NUM> may be performed on floors without pits or embedded structures for housing guide equipment, thus ideally making it possible to implement an industrial installation in any building that is provided with a roof, including a prefabricated building not expressly conceived for housing an industrial assembly installation.

The reference number <NUM> in <FIG> designates as a whole a system for positioning a mobile frame with respect to a fixed frame according to a further embodiment of the invention. The system <NUM> comprises a receiving element <NUM> configured for connection to one between the mobile frame <NUM> and the fixed frame <NUM>, and a pin <NUM> configured for connection to the other between the mobile frame <NUM> and the fixed frame <NUM>. The pin <NUM> is configured for coupling within the receiving element <NUM> in a engagement direction defined by a main axis Z202 of the receiving element <NUM>.

In particular, the axis Z202 is a longitudinal axis of an orifice O of the receiving element <NUM>, where the term "longitudinal" is here to be understood only with reference to the receiving element <NUM> and not with reference to the cartesian system X-Y-Z that is represented in the figures, which is consistent in all the figures and - as has been said - applies to the processing station <NUM>. With reference to <FIG>, <FIG>, the receiving element <NUM> comprises a single ring of rollers <NUM> centred around the axis Z202.

The rollers of the ring <NUM> have an axis of rotation γ208, where - by comparison with the receiving element <NUM> - the axes of rotation γ208 lie on a circumference C208*, which is homologous with respect to the circumference C8, and belong to planes orthogonal to the main axis Z202, and preferably belong to one and the same plane XY orthogonal to the axis Z202.

The rollers <NUM> come to define functionally the orifice O, as may be clearly seen in <FIG>. In this way, the orifice O has a pseudopolygonal (here pseudo-octagonal) shape that derives from the arrangement of the peripheral (rolling) surfaces of the rollers <NUM>, in a position tangential to a circumference C208 centred on the axis Z2 and homologous with respect to the circumference C8.

Since the rollers <NUM> have the same diameter, their radial protrusion within the orifice O is constant: this is the main difference with respect to the receiving element <NUM>.

In the preferred embodiment of the invention illustrated here, the ring of rollers comprises four first rollers <NUM> set at equal angular distances apart (hence at <NUM>°, with a crosswise arrangement) and four second rollers <NUM> set at equal angular distances apart (hence at <NUM>°, with a crosswise arrangement), where the arrangement of the first rollers is staggered by <NUM>° with respect to the arrangement of the second rollers about the axis Z202.

In the above arrangement, as may be seen in <FIG>, the rollers <NUM> are in effect arranged in such a way that their respective axes γ208 - when prolonged - give rise to an octagonal shape, and moreover pseudo-octagonal is the shape defined in plan view by the envelope of the peripheral (rolling) surfaces of the rollers <NUM> that face one another to define the orifice O (which hence itself has the pseudo-octagonal shape, as already mentioned).

With reference to <FIG> and to <FIG>, <FIG>, <FIG>, the pin <NUM> comprises a first, tapered, portion <NUM> and a second, prismatic, portion <NUM>, which develop coaxially sharing a longitudinal axis Z204 of the pin (the term "longitudinal" is here understood with reference to just the pin, and not to the reference system XYZ of the figures). The tapered portion <NUM> preferably has a conical geometry that terminates at a first (free) end R214, and extends for an axial length L214 as far as the prismatic portion <NUM>. The prismatic portion <NUM> has a polygonal cross section having a shape homologous with respect to the arrangement of the rollers <NUM>. In the embodiment illustrated here, the portion <NUM> comprises four faces 216C orthogonal to one another and orthogonal in pairs with respect to the axis X and to the axis Y, and four faces 216P, which are also orthogonal to one another and orthogonal in pairs to the bisectrices of the quadrants of the plane XY. The faces 216C are hence arranged alternating with the faces 216P. The envelope of the faces 216C and 216P is an irregular octagonal shape in which (<FIG>, <FIG>, <FIG>) the distance between the faces 216C and 216P varies about the axis Z204 according to the face considered. In particular, a radial distance AC associated to the faces 216C has a length greater than a radial distance AP associated to the faces 216P. In other words, the faces 216P have a radial protrusion smaller than the one that they would have in the case where they formed part of a regular octagonal shape, and in any case such that - with reference, in particular, to <FIG> -, when the pin <NUM> is completely within the orifice, the faces 216P do not touch the peripheral surfaces of the rollers <NUM> facing them. The prismatic portion <NUM> develops for an axial extension L216, and the ratio L14/L16 is sized in such a way that, when the pin <NUM> is completely within the orifice O, the rollers <NUM> bear upon the cylindrical surface <NUM>, slightly above the interface with the surface <NUM> (see <FIG>). As already noted in regard to the system <NUM>, the ratio L214/L216 depends upon the degree of the positioning error that it is required to recover (as likewise upon the number of rollers <NUM>). The dimension L216 depends upon the length necessary for engaging the rollers <NUM> and upon the overall height of the receiving element <NUM>. The size of the rollers <NUM> depends upon the load to be sustained during introduction of the pin <NUM>.

It is to be borne in mind that in alternative embodiments the tapered portion <NUM> may exhibit a different geometry that envisages a reduction in a diameter towards the end R14 of the pin <NUM>. For instance, parabolic profiles or also circular profiles with a wide radius may be envisaged.

The pin element <NUM> is configured for being connected to the fixed frame or to the mobile frame at a second end H4 that is adjacent to the prismatic portion <NUM>, whereas the end R214 constitutes the free end of the pin <NUM> configured for encountering, first, the orifice O and the rollers <NUM> in the engagement direction Z202.

Hence, it may be stated that the embodiments <NUM>, <NUM> present the common characteristic of a receiving element <NUM>, <NUM> that has at least one ring of rollers, which develops about a longitudinal axis Z2, Z202 and defines the orifice O, and where a distance (in the radial direction) between peripheral surfaces of the rollers of the at least one ring and the pin <NUM>, <NUM> when the latter is received (in particular completely received) in the orifice O varies around the main axis Z2, Z202. In addition, in both embodiments <NUM>, <NUM>, when the pin <NUM>, <NUM> is received (in particular, completely received) in the orifice O, there exists at least one area of contact between a roller of the at least one ring of rollers <NUM>, <NUM> or <NUM> and the second portion <NUM> (cylindrical portion), <NUM> (prismatic portion) of the pin <NUM>, <NUM>.

In the case of the coupling system <NUM>, the variation in the radial distance is due to the different radial protrusion of the rollers of the rings <NUM>, <NUM> and in particular to the tangency of the rolling surfaces thereof to concentric circumferences C8, C10 that have a different diameter. Hence, the at least one area of contact referred to above will correspond to an area of contact between a roller of the ring <NUM> and the portion <NUM>. Instead, in the case of the coupling system <NUM>, the variation is due to the different radial protrusion of the surfaces 216P, 216C with respect to the axis Z204, and in particular to the difference of length between the distance AP and the distance AC. Hence, the at least one area of contact will correspond to an area of contact between a face 216C and a roller <NUM> facing it.

The system <NUM> is able to equip a station <NUM>, or may be used in all the applications referred to in the corresponding description (including non-automotive applications), in a way similar to what has been described for the system <NUM>. For the purposes of completeness of the present description, with the aid of <FIG> an operating sequence that involves the positioning system <NUM> will now be described.

With reference to <FIG> and <FIG>, on account of the (relatively) poor precision of positioning of the handling device/vehicle V with respect to the frame <NUM>, even if positioning of the frame <NUM> on the handling device/vehicle V presents high repeatability, the frame <NUM> arrives with the pin <NUM> misaligned with respect to the engagement direction Z202 of the corresponding receiving element. Without the positioning device <NUM>, release of the frame <NUM> on the frame <NUM> would occur with the former in a position completely out of tolerance along the transverse axis Y and along the longitudinal axis X (along Z the reference is in any case provided by the supports <NUM>, but this is clearly not sufficient). As regards the pin <NUM>', this can equip the frame <NUM> (coupled to the receiving element <NUM>) also in the case where the first pin is a pin <NUM>, but it is possible to envisage a pin <NUM>' coupled to the receiving element <NUM>, where the faces 216C aligned along the axis X and orthogonal thereto are further set back, for example until there is a radial distance from the axis Z204 equal to the distance AP or even shorter.

In this regard, <FIG> and <FIG> illustrate a possible starting condition of the operations of release of the mobile frame <NUM> on the fixed frame <NUM>, in particular a condition in which the handling device V has reached the lay-by area P with a positioning such that the axis Z204 of the pin <NUM> presents a longitudinal deviation ΔX and a transverse deviation ΔY with respect to the axis Z2 of the receiving element <NUM> (even though not illustrated for reasons of economy, a very similar situation arises also for the pin <NUM>', <NUM>': the deviations may, of course, be different but the situation is conceptually the same).

This facilitates entry of the pin <NUM> into the orifice O of the receiving element <NUM>, and entry of the pin <NUM>'/<NUM>' into the orifice O of the further receiving element <NUM>/<NUM>.

In this regard, the presence of the prismatic portion <NUM>, in combination with the tapered portion <NUM>, facilitates the operations of positioning, ruling out any risk of sticking. In fact, with reference to <FIG>, the tapered portion <NUM> may conveniently bear upon the rollers <NUM> - both the ones facing the surfaces 216P and the ones facing the surfaces 216C - according to the longitudinal and transverse deviations, causing the frame <NUM> to shift in the longitudinal direction and/or the transverse direction to nullify the deviations ΔX and ΔY as the vertical movement of descent of the frame <NUM> proceeds.

The deviations ΔX', ΔY', which may be seen in <FIG>, are of a small amount as compared the deviations ΔX and ΔY in so far as the pin <NUM> is guided by one or more rollers <NUM> towards the position of alignment between the axes Z202 and Z204.

According to the invention, the faces 216C are configured for providing the final longitudinal and transverse positioning, and if need be for guiding the pin <NUM> during the transient of release of the frame <NUM>, whereas the faces 216P, which are radially set further back, do not intervene in the final positioning in so far as they are not configured for contacting the rolling surfaces of the rollers <NUM> facing them.

In other words, during the transient both of the arrangements of rollers <NUM> may be active, both the arrangement with the rollers aligned in pair in the directions X and Y or the arrangement with the rollers aligned along the bisectrices of the quadrants of the plane X-Y, as well as the tapered portion <NUM>, whereas in the final coupling condition of the pin <NUM> within the orifice O just the rollers facing the faces 216C (centring faces) intervene (or rather interact), and the faces 216P prevent - thanks to their position - any contact all around the axis Z202, which could otherwise generate sticking or interference.

Quite simply, contrary to what occurs at the interface between the frame <NUM> and the frame <NUM>, as the frame <NUM> passes from being supported by the vehicle V to being supported by the frame <NUM>, the pin <NUM> on the vehicle V progressively releases from the receiving element <NUM> on the frame <NUM>, being guided without any sticking by the rings of rollers <NUM>.

The final coupling condition may be seen in <FIG> and <FIG>, where it may be noted how, at the end of the relative movement between the tapered portion <NUM> and the rollers <NUM> that has led to alignment of the axes Z2, Z4, it is the cylindrical portion <NUM> that lies between the rollers <NUM>, with the faces 216P that bear upon them in diametrally opposite positions (net of any inevitable fitting play) along the axis X and along the axis Y, thus enabling extremely precise positioning of the frame <NUM> with respect to the frame <NUM> both in the transverse direction and in the longitudinal direction. In particular, the pair of rollers <NUM> aligned in the direction X positions the frame <NUM> longitudinally, whereas the pair of rollers <NUM> aligned in the direction Y positions the frame <NUM> transversely.

Simultaneously with the sequence of <FIG>, the same sequence of operations applies, with the necessary changes, also to the pin <NUM>'/<NUM>' and the corresponding receiving element <NUM>/<NUM>, with the sole exception due to the fact that in this case the final condition of coupling between the pin <NUM>'/<NUM>' and the receiving element <NUM>/<NUM> does not envisage contact between the pin <NUM>'/<NUM>' and the rollers <NUM>, <NUM> in the longitudinal direction on account of the flattened areas F or of the faces set further back so as to prevent conditions of statically indeterminate longitudinal constraint for the frame <NUM> with respect to the frame <NUM>. In a transverse direction, instead, there is no static indeterminacy in the constraint since the pins <NUM> and <NUM>'/<NUM>' are located at opposite ends of the frame <NUM> so that it is necessary to fix the position of one end and the other end in the transverse direction.

In this regard, now it is the pin <NUM> on the vehicle V that progressively engages the receiving element <NUM> on the frame <NUM>, while the pins <NUM> and <NUM>'/<NUM>' progressively release from the receiving elements <NUM> and <NUM>'/<NUM> on the frame <NUM>. In this step, it is the pin <NUM> on the vehicle V with the respective receiving element <NUM> on the frame <NUM> that functions as centring element, while the pins <NUM> and <NUM>'/<NUM>' at opposite ends of the frame <NUM> remain fundamentally passive or practically passive.

Finally, with reference to <FIG>, these illustrate three possible arrangements of the coupling systems <NUM>, <NUM> on the mobile frame <NUM> in the light of the considerations set forth in the foregoing description.

As has been seen, the need is to prevent statically indeterminate constraint schemes: this results in constraining globally three degrees of freedom in the plane XY in at least two points (three at the most). In the solution already described, which corresponds to the scheme represented in <FIG>, two positioning systems according to the invention are aligned along a single directrix parallel to a long side L of the frame <NUM>, where a first positioning system <NUM>, <NUM> (also identified by the Roman numeral I) imposes the position reference along the co-ordinates X and Y at what in <FIG> is the right-hand top corner (indicated by the combined reference X, Y) and a second positioning system <NUM>, <NUM> (identified by the Roman numeral II) imposes the position reference just in the direction Y (once again as represented by the reference Y). Hence, the first positioning system constrains two degrees of freedom, whereas the second positioning system constrains just one degree of freedom (the positioning system represented with a dashed outline identified by the Roman numeral III is the one at the interface with the handling device V).

According to the scheme of <FIG>, the distribution of the constraints on the degrees of freedom is the same (two and one, respectively), but in this case the positioning system I, which blocks two degrees of freedom, is set at the opposite end of a short side l as compared to the case of <FIG>, with the same arrangement as in <FIG> of the second positioning device II along the side l, in an opposite end position.

Finally, according to the scheme of <FIG> the positioning systems I, II are arranged aligned along an axis parallel to a short side l. In this case, the distribution of the constrained degrees of freedom is the same (two and one), but the system II imposes the position reference along the axis X.

Claim 1:
A receiving element (<NUM>) for a positioning system (<NUM>) of a mobile frame (<NUM>) relative to a fixed frame (<NUM>), the receiving element (<NUM>) comprising:
- an orifice (O) having a main axis (Z2) defining an engagement direction,
- a first ring of rollers (<NUM>) and a second ring of rollers (<NUM>), each of the rollers of the first ring (<NUM>) and of the second ring (<NUM>) having axis of rotation (γ8, γ10) belonging to a plane orthogonal to said main axis (Z2), the first ring of rollers (<NUM>) and the second ring of rollers (<NUM>) defining said orifice (O), and
the receiving element being characterized in that:
- the peripheral surfaces of the rollers (<NUM>) of the first ring are arranged tangential to a first circumference (C8) having a centre on said main axis (Z2),
- the peripheral surfaces of the rollers of the second ring (<NUM>) are arranged tangential to a second circumference (C10) having a centre on said main axis (Z2), and
- the diameter of the first circumference (C8) is lower than the diameter of the second circumference (C10).