Stroller frame, particularly for transporting a child

A frame for a child's stroller which includes two rear arms and a single front arm which are joined to one another with the two rear arms spaced on opposite sides of a front to rear median vertical plane (P) of the frame and wherein wheels are pivotally mounted to each of the arms so as to be movable between first deployed positions wherein an axes of rotation of the wheels extend transversely to the plane (P) and a second compact storage position wherein the axes of rotation of the wheels extend parallel with respect to the plane (P), and wherein the wheels connected so as to be moved simultaneously between the two positions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a stroller frame. It relates in particular to the field of strollers for transporting a very young child.

2. Brief Description of the Related Art

To push a stroller on the ground, its frame is typically equipped with wheels or casters. The invention deals in particular with the so-called “three-wheel” stroller frames, that is to say, stroller frames provided, at the front, with a single wheel or a single pair of twinned wheels, whereas, at the rear of the frame, there are distinctly provided two wheels or two pairs of twinned wheels, respectively on the left and right sides of the frame. This type of stroller frame is highly appreciated because it gives the stroller a particularly pleasing overall appearance, with a sporty look, which is particularly attractive to a young clientele, as well as for the fact that having the frame press on the ground in three areas forming the vertices of a forward-pointing triangle makes the frame extremely easy to handle. This type of stroller frame is thus recognized for its good rolling behavior on country paths and bumpy ground, particularly in cities where strollers have to negotiate sidewalks, staircases, etc.

However, the existing three-wheel stroller frames have a major drawback associated with their bulk: this type of frame makes it essential, for comfort and safety reasons, to provide for the wheels to have a relatively large diameter. Given these conditions, some users forego the purchase of this type of stroller frame because it is so difficult to stow away and transport when the stroller is not in use, and to load in and unload from transport vehicles.

In the field of so-called conventional strollers, unlike the three-wheel strollers, that is to say, in the field of strollers with a “four-wheel” frame, frames are known that allow for the two front wheels and the two rear wheels to be retracted, particularly for the purposes of stowing away the stroller. For example, in the recent document WO-A-2007/025551, the front and rear wheels of one and the same left or right side of a stroller can be simultaneously moved, relative to the frame of the stroller, from an extended service position, in which the wheels are extended vertically to roll on the ground, to a retracted storage position, in which the wheels are extended horizontally to be flattened against the frame. Other examples of four-wheel stroller frames that are retractable in this way are provided by the older documents FR-A-525 797, U.S. Pat. No. 2,429,763 and U.S. Pat. No. 4,659,096.

In practice, the teaching relating to four-wheel stroller frames cannot, however, be transposed to a three-wheel stroller frame because of the specific structure of this frame essentially consisting of a single front arm and two rear arms, respectively left and right. Thus, WO-A-03/097466 proposes a stroller frame of which the three wheels can be moved from an extended service position to a retracted storage position, but only in a way that is both successive, that is to say one wheel after the other, and complicated, that is to say after several manual actions on the part of the user in several different areas of the stroller frame.

SUMMARY OF THE INVENTION

The aim of the present invention is to propose a “three-wheel” stroller frame of the type discussed hereinabove, of which all the wheels can be retracted quickly, simply and easily.

To this end, the subject of the invention is a stroller frame particularly for transporting a child, comprising:two rear arms and a single front arm, which are fixedly joined to one another and respectively provided with at least one wheel bearing on the ground,means of moving the rear and front wheels relative to their respective arms, suitable for simultaneously moving all the wheels between, respectively, an extended service position, in which the rotation axes of all the wheels extend substantially perpendicularly to the same antero-posterior median plane of the frame, and a retracted storage position, in which the rotation axes of all the wheels extend substantially parallel to this plane, the antero-posterior distance between the rear wheels and the front wheel or wheels then being smaller than when the wheels are in their extended position, anda specific handle for manually driving the movement means, arranged at the front end of the front arm.

The idea on which the invention is based is to exploit the particular structure of the “three-wheel” stroller frame to provide the user with a practical control handle, that specifically makes it possible to retract all the wheels. By virtue of this handle, the user is able to easily and quickly apply a driving force that the movement means, incorporated in the frame, transmit mechanically, in the front region of the frame, to the front wheel or to the twinned front wheel train, and, in the rear region of the frame, to the two rear wheels or to the two twinned rear wheel trains, respectively left and right. This handle enables the user to preferentially apply a driving torque to the input of the movement means advantageously with one hand. The mechanical nature of the arms, of the movement means and of the handle makes the stroller frame robust and reliable, the relative movement between the wheels and the arms being precise, rapid and reproducible.

When the wheels are in their retracted storage position, the bulk of the frame is significantly reduced, both in the direction in which the bodies of the wheels and the frame are then arranged in superposed planes, and in the antero-posterior direction of the frame because of the convergence toward the front of the rear wheels.

By positioning the control handle at the front end of the frame, this handle can be grasped manually by the user, quickly and easily. This handle then forms, with respect to the user, a reference element with regard to the mechanical positioning of the moving components of the stroller: depending on the drive action that the user imposes on this handle, all the wheels of the stroller are retracted or extended at the same time, being respectively accompanied by a “shortening” or an “elongation” of the frame, that is to say a bringing-together or a distancing of the rear wheels relative to the front wheel, by virtue of the action of the movement means.

Furthermore, the front handle makes it possible, when the wheels are in their retracted storage position, to lift the frame from the ground, for example to load it in a car trunk, or to pull it on the ground. Moreover, according to an advantageous feature of the stroller frame according to the invention, when the wheels are in their retracted position, the rear wheels extend substantially in the same plane perpendicular to the antero-posterior median plane of the frame and are able to roll on the ground in this same plane. This way, when the wheels are retracted, the rear wheels are able to rest in line on the ground, which enables the stroller to be stabilized vertically, to be very easily pulled or pushed laterally by virtue of the handle which is then situated at the top of the frame, particularly for the purposes of stowage in a closet or similar, in the manner of a baggage trolley. In practice, the user can then control the retraction of the wheels so that the rear wheels remain pressed on the ground while they are being retracted, whereas it progressively straightens the frame vertically, with its front end directed upward. In this way, the retraction of the wheels automatically results in the frame being converted to a stable vertical stowage position.

Other advantageous features of the stroller frame according to the invention, taken in isolation or in all technically possible combinations, are specified in the dependent claims2to15.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The figures show a frame2of a stroller intended to transport a very young child, by being pushed on the ground S by an adult. As represented very diagrammatically inFIG. 1only, this stroller comprises, in addition to the frame2, a mounting4to which is, in this case, added and fixed a seat6in which the transported child is sat, it being noted that, in the interests of clarity of the drawing, the child is not shown. In a variant that is not represented, the seat6is replaced by a bed, making it possible to transport the child lying down, or by another similar transport element that is nonlimiting of the present invention. In practice, the mounting4can have extremely diverse structures, including or not including components that are articulated relative to one another, it being understood that each of these structures is supported by the frame2in an articulated and/or removable manner, in particular for the purposes of folding and/or storing the stroller in periods during which said stroller is not used to transport the child.

For convenience, the rest of the description is oriented toward the stroller frame2when the latter is in its service configuration illustrated inFIGS. 1 and 2, so that the terms “upper” and “top” designate a direction directed away from the ground S and corresponding to the top portion ofFIG. 1, whereas the terms “lower” and “bottom” designate an opposite direction. Similarly, the terms “front” and “rear” should be interpreted relative to the normal direction of advance of the stroller, that is to say the direction in which this stroller is normally pushed, so that the front corresponds to the right hand portion ofFIG. 1and the top portion ofFIGS. 2 to 4. Similarly, the terms “left” and “right” are defined relative to the direction of advance of the stroller, so that they respectively designate the left-hand and right-hand portions ofFIGS. 2 and 4.

The frame2comprises a non-articulated rigid framework which includes a single front arm12, two left14G and right14D rear arms and a central section16. The arms12,14G and14D each have an essentially tubular shape extending lengthwise overall in the antero-posterior, or front to rear, direction of the frame2. The front arm12is rectilinear over its entire length, whereas the left14G and right14D rear arms converge toward one another toward the front so that each of these arms consists of a rectilinear rear portion14G1,14D1, centered on a longitudinal axis X14G-X14G, X14D-X14Dand extended toward the front by a bent portion14G2,14D2in the direction of the section16. The left14G and right14D rear arms are advantageously symmetrical to one another relative to an antero-posterior, or front to rear, median vertical plane P of the frame2, this plane passing through the central longitudinal axis X12-X12of the front arm12.

The central section16comprises a partially hollow rigid main body to which are joined the rear end of the front arm12and the respective front ends of the rear arms14G and14D by leading inward. In the example considered in the figures, the arm12is made of a single piece with the body of the section16whereas the rear arms14G and14D are added and fixed to this body, with an external capping fitted, particularly for esthetic purposes.

To push the stroller1on the ground S, the frame2is provided with three wheels bearing on the ground, namely a front wheel20and two rear wheels, respectively left22G and right22D, designed to rotate about respective rotation axes Y20-Y20, Y22G-Y22G, Y22D-Y22D. In practice, each of these wheels can have various embodiments, as much regarding its outer peripheral portion201,22G1,22D1intended to roll on the ground, which may, for example, consist of a rubber sheath or a tubed tire, as with regard to its discoid central body202,22G2,22D2, possibly open-worked or spoked, the central geometrical axis of which corresponds to the rotation axis Y20-Y20, Y22G-Y22G, Y22D-Y22D.

As can be clearly seen inFIGS. 1 and 4, and as represented in more detail inFIGS. 5 to 7, the front wheel20is connected to the front arm12by, in succession, a rigid leg30and a mechanical articulation assembly32. More specifically, the wheel body202is mounted to rotate about the axis Y20-Y20on a hub formed by a longitudinal end301of the leg30, said leg extending lengthwise in a direction radial to this axis. The arm12is provided internally with a shaft34which extends over the entire length of the arm, being centered on its axis X12-X12. For mechanical strength reasons, the outer diameter of this shaft34is fitted to the inner diameter of the arm12. The front end341of the shaft34is prolonged forward, outside the arm12, by an end fitting36supporting the articulation assembly32. Here, the end fitting36is rigidly linked to the shaft end341, being of a single piece with this end, and is conformed in a hollow sphere truncated both on the side from which the leg30extends and on the opposite side. Inside this sphere formed by the end fitting36, a pivot articulation38is arranged between this end fitting and the end302of the leg30, opposite the wheel20: this articulation38allows free pivoting of the end302relative to the end fitting36and therefore relative to the shaft34about an axis Z-Z that is substantially perpendicular to the axis X12-X12. In this way, in particular when the stroller frame2is rolling on the ground S, the leg30and, by that, the front wheel20, can pivot about the axis Z-Z, the top edge of the end302then sliding against the bottom face of the end fitting36, whereas, in the longitudinal direction of the leg30, said leg and the end fitting36are fixedly linked to one another.

The pivot articulation38can be neutralized inasmuch as it can be mechanically immobilized. In the exemplary embodiment illustrated in detail inFIGS. 5 and 6, this immobilization is obtained by a pin40that can be accommodated in a complementary recess42delimited at the end302of the leg30, in the top edge of this end: as long as the pin40is outside the recess42, as inFIG. 6, the leg30and the end fitting36are free to pivot relative to one another about the axis Z-Z, whereas, when the pin40is inserted into the recess42as inFIG. 5, the leg30and the end fitting36are rigidly linked to one another, so that the rotation axis Y20-Y20then extends orthoradially to the axis X12-X12, as inFIGS. 1 to 4.

The movement of the pin40is controlled by a push finger44, with the interposition of an overtravel spring46partially housed in a bush48mounted to slide in the end fitting36in the direction of movement of the pin40. Under the action of the spring46, the push finger44is pressed, unlike the pin40, against a plate50fixedly joined to the end fitting36, in this case by screws, while extending overall in its truncation plane opposite the leg30. The finger44is rigidly linked to a trim52mounted on the end fitting36so as to rotate about an axis Z52-Z52both perpendicular to the plate50and passing through the center of the sphere formed by the end fitting36.

By rotating the trim52about the axis Z52, the user drives, over a corresponding travel, the finger44which, because of its variable thickness in a direction peripheral to this axis, acts on the immobilizing pin40: in the configuration illustrated inFIG. 5, the position of the trim52about the axis Z52-Z52is such that a significant thickness of the finger44is interposed between the plate50and the bush48, whereas, in the configuration ofFIG. 6, the position of the trim is such that a lesser thickness of the finger44is interposed, a spring54then returning the pin40in the direction opposite to the recess42.

To facilitate handling of the trim52, and for esthetic purposes, this trim has an external cap521, contained within the spherical jacket defined by the end fitting36. Similarly, as can be clearly seen inFIGS. 5 and 6, it will be noted that the end302of the leg30is conformed in a spherical cap contained within the abovementioned jacket, so that the assembly of this end301of the end fitting36and of the trim52gives an overall ball shape, with a visual “signature” effect, specific to the stroller frame2, as can be clearly seen inFIG. 7in which the external cap521is represented by faint lines to reveal the interior of the trim.

Advantageously, a light source is arranged between the plate and an open-work internal cap522of the trim52, so as to have a visual warning lamp. Detailed modalities for producing such a lamp are given in WO-A-2006/111656 to which the reader can refer.

Moreover, as can be clearly seen inFIGS. 1 to 7, the end fitting36is prolonged, forward, by a handle60rigidly linked to the end fitting, while being, for example, directly of a piece with the end fitting. Advantageously, this handle60is in the shape of a bow, the elongate main body62of which is situated on the front side of the end fitting36, extending along the front end portion of the end fitting and in a direction that is overall peripheral to the end fitting while providing between them sufficient space for the user to be able to insert his fingers therein in order to grasp the body62. At its longitudinal ends, the body62is rigidly linked to the lateral sides of the end fitting36by legs64converging toward one another in the direction of the end fitting36.

At the back of the frame2, the bodies22G2and22D2of the wheels22G and22D are respectively connected to the rectilinear parts14G1and14D1of the arms14G and14D according to arrangements described hereinbelow in detail for the right side of the stroller, it being understood that the arrangements of the left side can be deduced by symmetry relative to the plane P and incorporate components which, in the figures, notablyFIG. 10, bear the same numeric references as the right side, but followed by the letter G instead of the letter D.

As represented in more detail inFIGS. 8 and 9, the body22D2of the right wheel22D is mounted to rotate about the axis Y22D-Y22Don a hub formed by a longitudinal end70D1of a leg70D extending lengthwise in a direction radial to this axis. Its end70D2opposite to the wheel body22D2is, in the longitudinal direction of the leg, fixedly linked to a sleeve72D which both coaxially surrounds the rectilinear part14D1of the arm14D and extends partially protruding behind this part. Advantageously, the link between the leg70D and the sleeve720is articulated about a tilting axis74D parallel to the rotation axis Y22D-Y22D, thus enabling the leg70D to oscillate about this axis relative to the sleeve, with interposition of a visco-elastic pad76D for damping purposes. The rear wheel22D is thus suspended relative to the framework by the oscillating leg700, which makes the rolling of the stroller very comfortable for the child being transported, even if the surface condition of the ground S is poor. This suspended structure of the rear wheels22G and22D also makes it possible to avoid the need for a rigid axle directly linking these two rear wheels through the space between the rear of the arms14G and14D. The adult pushing the stroller can then walk comfortably, without the risk of banging his leg when striding.

The sleeve72D is rigidly linked to a link block78D arranged coaxially inside both the sleeve72D and the rectilinear part14D1. In the exemplary embodiment considered here, the sleeve72D and the link block78D are linked to one another at their rear end. The link block78D is mounted to move inside a tubular slide80D interposed coaxially between the link block and the rectilinear part14D1. The link block78D is provided with helical external ribs78D1which wind around the longitudinal axis of the link block, whereas the internal face of the slide80D delimits complementary helical grooves80D1in which the ribs are received. This way, the link block78D is able to move inside the slide80D by a helical movement centered on the axis X14D-X14D.

The driving of the link block78D relative to the slide80D is controlled by a pulling and pushing cord82D. The rear end of this cord82D is provided with a small end fitting82D1which is essentially spherical and thus able to rotate freely on itself with the rest of the cord82D inside a head84D that is both fixed to the front end of the link block78D and fixedly linked to the cord82D in the longitudinal direction of this cord.

The cord82D extends toward the front inside the arm14D, the running part of this cord being received in a sheath86D fixedly wedged inside the arm. In particular, the rear end of this sheath is wedged in a fixed front end fitting80D2of the slide80D, which is passed through from side to side by the cord82D.

As represented in more detail inFIGS. 11 to 13, the respective front ends82D2and82G2of the cords82D and82G are fixed to one and the same control wheel88rigidly assembled at the rear end342of the shaft34. More specifically, the control wheel88is centered on the axis X12-X12, whereas the rear ends82D2and82G2of the cords82D and82G are fixed in areas of the control wheel88that are diametrically opposite relative to the axis X12-X12.

The handle60controls the movement of the wheels20,22G and22D relative to the framework2. More specifically, if we consider that the wheels are initially in their service position ofFIGS. 1 and 2, that is to say, in an extended position relative to the framework, enabling them to roll on the ground S, with their rotation axis Y20-Y20, Y22G-Y22Gand Y22-Y22Dall perpendicular to the plane P, driving the shaft34to rotate on itself about the axis X12-X12by virtue of the corresponding manipulation of the handle60by a user gripping the body62, as indicated by the arrow R inFIGS. 1 and 2, and this over an angular travel of 90° C., results in the combined retraction of the three wheels as explained hereinbelow. In other words, to do this, the user grasps the handle60and applies a driving torque of a quarter turn about the axis X12-X12.

At the front of the frame2, rotating the front end341of the shaft34results in a corresponding rotation, over an angular travel of 90°, of the end fitting36and, through that, of the leg30and of the wheel body202. The wheel20then switches from its position ofFIGS. 1 and 2to its position ofFIGS. 3 and 4, in which its rotation axis Y20-Y20extends parallel to the plane P, it being noted that, during this retraction of the wheel, the pivot articulation38may be immobilized by virtue of the immobilizing pin40previously inserted into the recess42, as explained above.

At the rear of the stroller frame2, rotating the rear end342of the shaft34results in a 90° rotation about the axis X12-X12of the control wheel88, which then switches from its position ofFIG. 11to that ofFIG. 12. The cords82D and82G are then pulled over an identical travel, causing the link blocks78D and78G to be pulled forward inside their slide80D and80G, fixed relative to the arm14D and14G. The link blocks78D and78G then describe respective helical travels, combining a forward translation movement and a 90° rotation respectively about axes X14D-X14Dand X14G-X14G. The result of this is that the rear wheels22D and22G change from their position ofFIGS. 1 and 2to their retracted position ofFIGS. 3 and 4, in which the rotation axes Y22D-Y22Dand Y22G-Y22Gextend parallel to the plane P, it being noted that the rear wheels remain symmetrical to one another relative to the plane P throughout their retraction.

The bodies22D2and22G2of the rear wheels22D and22G then extend overall in one and the same plane perpendicular to the plane P, allowing the frame2to roll on the ground S by rotation of the two rear wheels about their axis Y22D-Y22D, Y22G-Y22G. If necessary, the stroller frame2is then locked in this configuration by an ad hoc immobilizing means, such as a locking pin. The stroller frame2can then be moved stably in the manner of a baggage trolley with its front arm12and the handle60directed upward, so that this handle can be grasped by the user to move the stroller frame in order to stow it vertically, by rolling it into a closet for example. In a particularly practical manner, it will be understood that, when the user grasps the handle60when the wheels are extended and he operates this handle to retract the wheels as described above, the user concomitantly uses this handle to straighten the frame of the stroller vertically so as to automatically bring the frame to its stable position bearing on its rear wheels.

Furthermore, because of the helical travel of the retraction movement of the rear wheels22G and22D, it will be understood that the distance Δ between the rotation axis Y20-Y20of the front wheel20and the rotation axis Y22D-Y22D, Y22G-Y22Gof each rear wheel22D,22G varies by the antero-posterior dimension of the part of the link blocks78D and78G retracted inside their corresponding slide80D,80G, which may in practice be as much as 40 mm. Consequently, the overall antero-posterior dimension of the stroller frame2is reduced by Δ when the wheels are retracted.

Obviously, the control by the handle60of the 90° rotation of the shaft34in the reverse direction to that considered above, when the wheels20,22D and20G are initially retracted, results, through a transmission of reverse movements, in the concomitant extension of these three wheels.

Optionally, a longitudinal part of each cord82D,82G is advantageously made of a metal alloy with shape memory, such as the alloy based on nickel and titanium, marketed by the company NIMESIS (France), so that this cord part is able to be twisted, or even folded without damage, by transverse elastic deformation, when the user controls the retraction or the extension of the wheels when said retraction is inadvertently prevented, for example, following the wedging of a wheel against a wall. In this way, damage to the rest of the cord is avoided, which could have damaging consequences for the correct transmission of the pulling and pushing forces that must normally be provided by this cord.

FIGS. 13 and 14show a variant embodiment of the link blocks78D and78G and the slides80G and80D of the stroller frame2. The corresponding arrangements of this variant are described in detail hereinbelow for the left side of the stroller frame2, it being understood that the arrangements of the right side can be deduced by symmetry relative to the plane P.

Thus, according to this variant ofFIGS. 13 and 14, the link block78G and the slide80G are replaced respectively by a link block78G′ and a slide80G′. The arrangement, within the stroller frame2, and the function of this link block78G′ and of this slide80G′ are similar to the arrangement and the function of the link block78G and of the slide80G: in particular, the link block78G′ is arranged coaxially inside the sleeve72G as diagrammatically represented inFIG. 15, while being rigidly linked to this sleeve72G at their rear end, whereas the slide80G′ is fixedly arranged inside the rectilinear part14G1of the arm14G, also as shown inFIG. 15.

The link block78G′ and the slide80G′ are mainly distinguished from the link block78G and from the slide80G by arrangements relating to the guiding of the link block78G′ inside the slide80G′ by an overall helical movement centered on the axis X14G-X14Gof the arm14G. In practice, by replacing the helical ribs and grooves used in the embodiment ofFIGS. 1 to 12, the tubular wall of the slide80G′ is passed through, from side to side, by two diametrically opposite slots80G′1, symmetrically relative to the axis X14G-X14G. Each groove80G′1includes, along its length, a helical front end part80G′2, centered on the axis X14G-X14G, and a rectilinear rear end part80G′3, parallel to this axis. When the link block78G′ is assembled inside the slide80G′, each of these grooves80G′1receives one of the longitudinal ends of a transfixing locking pin78G′1rigidly linked to the link block78G′, extending perpendicularly to the axis X14G-X14G, one of the longitudinal ends of this locking pin78G′1being visible inFIG. 14, with the reference78G′2. The width of each groove80G′1is fitted to that of the ends78G′2of the locking pin78G′1, so that, during the relative movement between the link block78G′ and the slide80G′, the corresponding movement successively consists of a first helical sub-movement, when the ends78G′2of the locking pin78G′1pass through the helical part80G′2of the grooves80G′1and a second rectilinear sub-movement when the abovementioned ends pass through the rectilinear part80G′3of the grooves.

Thus, by cooperation between the locking pin78G′1and the helical parts80G′2of the grooves80G′1, the antero-posterior guidance between the link block78G′ and the slide80G′ by a helical movement, substantially as for the embodiment ofFIGS. 1 to 12, is restored. Furthermore, by cooperation between the locking pin78G′1and the rectilinear parts80G′3of the grooves80G′1, the relative angular position between the link block78G′ and the slide80G′ is fixed: this configuration corresponds to the extreme rear placement of the link block78G′ relative to the slide80G′, as shown inFIG. 14, that is to say to the configuration in which the rear wheels22G and22D are extended. The mechanical strength of these wheels in the extended configuration is thus enhanced.

Advantageously, this mechanical strength is reinforced by the presence, on the outer surface of the link block78G′, of a crenellated ring78G′3comprising a plurality of axial ribs78G′4which are distributed on the outer periphery of the link block and that are conformed to be received in a complementary manner in axial grooves80G′4hollowed out in the internal face of the slide80G′, in this case at the rear end of this slide. By appropriate dimensioning, these ribs78G′4and these grooves80G′4are progressively axially geared to one another when the locking pin78G′1passes through the rectilinear parts80G′3of the grooves80G′1, from the front end of these rectilinear parts to their rear end. The forces then applied to an ad hoc locking means, immobilizing the stroller frame2with its wheels in extended configuration, thus remain limited and supported by this immobilizing means, without damage.

By way of optional advantageous arrangement, not represented in detail in the figures, the helical parts80G′2of the grooves80G′1are prolonged forward by rectilinear groove parts that do not need to be as long as the rear rectilinear parts80G′3and that make it possible to stabilize the relative angular position between the link block78G′ and the slide80G′ when the corresponding rear wheel22G is retracted, by being folded back against the framework10as explained above. The resistance to the forces then applied to the duly folded stroller frame2is enhanced.

FIGS. 15 and 16represent another variant embodiment of the stroller frame2which, apart from what has just been described with regard toFIGS. 13 and 14, is distinguished from the embodiment described with regard toFIGS. 1 to 12essentially by the structure, detailed hereinbelow, of the driving means of the link blocks78D and78G or78D′ and78G′ relative to their corresponding rear arm14D and14G, and, incidentally, by slight contour modifications to certain components associated with these rear arms, without, however, these slight modifications inducing significant structural and functional differences.

Thus, rather than drive each link block78D,78G by the pulling and pushing cord82D or82G as described with regard toFIGS. 8 and 9, the variant ofFIGS. 15 and 16provides for the use of an actuator in the form of a semi-rigid rod82D′ or82G′, it being noted that only the rod82G′ associated with the left rear arm14G can be seen inFIGS. 15 and 16. Moreover, the corresponding arrangements for the left side of the stroller frame2are described in more detail hereinbelow, it being understood that the arrangements of the right side can be deduced by symmetry relative to the plane P.

Thus, with regard toFIGS. 15 and 16, the semi-rigid rod82G′ links in movement the link block78G′ and the rear end342of the shaft34. To this end, the rear end82G′1of this rod is fixedly joined to a front end head84G′ of the link block78G′, in this case by having a bulbous shape, received and retained in a complementary recess delimited inside the head84G′. Advantageously, the head84G′ is fixed relative to the link block78G′ by the transfixing locking pin78G′1.

The running part82G′2of the semi-rigid rod82G′ is received in a sheath86G′ that is functionally similar to the sheath86G: this sheath86G′ is thus fixedly incorporated inside the arm14G with, in particular, its rear end wedged in a fixed front end fitting80G′5of the slide80G′ whereas this end fitting is passed through from side to side by the rod82G′. The flexibility of the running part of the rod82G′2is exploited, on the one hand, to adapt the overall longitudinal profile of the rod82G′ to the bent part14G2of the arm14G, by bending this profile, and on the other hand, to support, without damage, a slight twist of the rod82G′, associated with the helical movement of the link block78G′. The result of this last aspect is that the mechanical link between the rod82G′ and the link block78G′ does not have to be as sophisticated as that between the cord82G and the link block78G, in particular without the need for a small spherical end piece to be provided at the rear end of this cord.

As an example, to obtain sufficient flexibility of the running part of the rod82G′2, while guaranteeing sufficient force transmission by this running part of the rod, in a longitudinal direction of the latter, this running part82G′2has a cross-shaped transversal section and is made of a synthetic material such as nylon.

The front end82G′3of the rod82G′ is rigidly provided with an insert82G′4, for example overmolded with the front end of the rod, as represented inFIG. 16. At its end opposite to the rod82G′, this insert82G′4is fixed to a control wheel88′, arranged at the rear end342of the shaft34and functionally similar to the control wheel88shown inFIGS. 11 and 12. In the exemplary embodiment considered inFIG. 16, the control wheel88′, centered on the axis X12-X12, is provided, in diametrically opposite areas relative to this axis, with two protruding spheres88G′1and88D′1, designed to be respectively received, in the manner of a ball joint, in a complementary shell82G′5rigidly borne by the insert82G′4of the rear end of the corresponding left rod82G′ or right rod82D′.

Thus, as for the control wheel88, the rotation of the control wheel88′ by the shaft34, over a 90° travel centered on the axis X12-X12, results, depending on the direction of this rotation, in the semi-rigid rods82G′ and82D′ being pulled forward or pushed backward in order to actuate the movement of the link blocks78G′ and78D′ inside their slide80G′ and80D′. By comparison with the cords82G and82D, the actuating rods82G′ and82D′ have the advantage of being standard mechanical components that are widely available on the market, which support, without damage, the transmission of the forces needed to extend and retract the rear wheels22G and22D.

FIGS. 16 to 19show yet another variant embodiment of the stroller frame2, which specifically relates to the mechanical link between the rear end342of the shaft34and the control wheel88or88′, this variant being applied here to the control wheel88′ and thus detailed hereinbelow in this context. Rather than rigidly joining this control wheel to the rear end342of the shaft34, as in the embodiment considered inFIGS. 1 to 12, a horseshoe-type spring90is interposed between them in order to limit the intensity of the torque transmitted between the control wheel88′ and the shaft end342.

More specifically, this spring90is conformed to grip, in a manner centered on the axis X12-X12, a bush343that is rigidly linked to the shaft end342and to the central region88′1of the control wheel88′: the stiffness of the spring90is engineered to immobilize the relative rotation of the bush343and the region of the control wheel88′1about the axis X12-X12, as long as the intensity of the torque transmitted between these two pieces is below a predetermined limit value, as represented inFIG. 18. In this way, if a relative torque, about the axis X12-X12, between the shaft34and the control wheel88is applied with an intensity above the abovementioned limit value, the spring90is deformed elastically to allow a relative free rotation of the shaft34on itself and of the control wheel88′ on itself, as represented inFIG. 19.

In this way, when the user retracts or extends the wheels of the stroller frame2by the handle60, when this retraction or this extension is inadvertently prevented at one of the rear wheels22G and22D, for example following the jamming of this wheel against a wall, the kinematic resistance of this wheel induces, on the control wheel88′, a torque differential about the axis X12-X12relative to the shaft34: if the intensity of this torque differential is above the abovementioned limit value, the user continues rotating the shaft34without the corresponding force being transmitted to the control wheel88′ and to the rods82G′ and82D′ by virtue of the spring90, thus avoiding damage to this control wheel and these rods.

Various arrangements and variants of the stroller frame2described hitherto can also be considered. A few examples are given below:each wheel20,22D and22G or at least one of these wheels can be equipped with a rotation immobilizing means in order to immobilize the stroller frame2on the ground S for the purpose of parking for a certain time;the front wheel20and/or each of the rear wheels22D and22G can be replaced by a twinned pair of wheels, or even a twinned wheel train;moreover, to link the front wheel20to the arm12, the leg30may be replaced by a fork, the two branches of which extend either side of the wheel body202;optionally, the rotation of the shaft34by the handle60when retracting or extending the wheels can be transmitted, by appropriate arrangements, to the structure4of the stroller, in particular in order to respectively assist in the folding and the opening of this structure relative to the frame; and/oralso optionally, the structure of the stroller frame2can be reinforced by a cross-member rigidly linking the rear arms14D and14G, in particular in their rectilinear part14D1and14G1; for example, the opposite ends of such a cross-member are fixedly joined to the respective fixed caps that externally clamp the arm parts14D1and14G1, as partially represented inFIG. 15, in which the abovementioned cross-member is referenced92.