Abstract:
A laterally collapsible, user-pushed, four-wheeled rollator, stroller or the like has swiveling front wheels for steering, each mounted in a fork with a vertical post, with a toothed pulley fixed thereto, rotatable in a bearing housing fixed at the front end of right and left side frames. The two swiveling front wheels can swivel to any steering angle but always in unison with each other by virtue of a flexible toothed synchronous belt extending between the toothed pulleys. The interior of each bearing housing closely surrounds each toothed pulley and the belt, preventing any disengagement of the belt from either toothed pulley even when the belt becomes slack when the left and right side frames are folded towards each other. A synchronous chain with sprockets can also be used. Tether means pull the belt/chain rearwardly to a protected position during folding.

Description:
CROSS-REFERENCE TO PRIOR APPLICATIONS 
     This application is a §371 National Stage Application of PCT International Application No. PCT/EP2015/052783 filed Feb. 10, 2015, which claims priority to European Patent Application No. 14155246.3 filed Feb. 14, 2014, each of which are herein incorporated by reference in their entirety. 
     TECHNICAL FIELD 
     Generally, embodiments of the invention relate to collapsible hand-propelled wheeled supports or carriers such as foldable rollators, walkers, pushchairs and strollers. 
     More specifically, different embodiments of the application relate to foldable rollators, walkers, pushchairs and strollers which have two swiveling front caster wheels to steer the assembly when pushed in the desired direction. 
     BACKGROUND 
     Many different types of rollators, walkers, pushchairs and strollers are known in the art. Many have front caster wheels which automatically align themselves in the direction towards which the assembly is pushed from behind. Many assemblies or carriers such as rollators, walkers, pushchairs and strollers are foldable for easy storage and transport in a car for example. Some designs also have means to make the front wheels always point in the same direction. 
     RELATED ART 
     EP 1 028 882 discloses a non-collapsible hand-propelled cart having two pairs of steerable wheels. Each pair of wheels has a tie rod between them to keep the two wheels of each pair pointing in the same direction. There is also a diagonal linkage connecting the two pairs and forcing each pair of wheels to be directed oppositely to the wheels of the other pair, thus facilitating turning using both the front and the rear wheels. 
     EP 2 39 8687 (WO 2010/091513) shows a stroller with free independently swiveling front caster wheels. The stroller is collapsible by folding the top section forward over the bottom section, i.e. about an axis transverse to the longitudinal axis of the stroller. 
     U.S. Pat. No. 4,203,609 discloses a non-collapsible four-wheeled pull-cart, with a pair of front wheels linked to each other to turn in unison and a pair of rear wheels also linked to each other to turn in unision. The front and rear pairs are linked to each other to force the rear pair to turn counter to the front wheels thus making it easier for the cart to turn along an arc. 
     U.S. Pat. No. 3,848,884 describes a collapsible stroller which shows non-swivelable wheels (i.e. fixed in the straight-forward direction). Foldable linkages allow the entire stroller to be folded upwards sliding along a central shaft. 
     WO2006122508 describes a collapsible stroller with two pairs of non-swivelable double wheels. Connecting lateral and longitudinal scissors mechanisms allow the stroller to be collapsed both laterally and longitudinally. 
     FR 2843728 also describes a collapsible stroller with two pairs of non-swivelable double wheels. Connecting lateral and longitudinal scissors mechanisms allow the stroller to be collapsed both laterally and longitudinally. 
     EP0890497 describes a collapsible pushchair having two directionally fixed rear wheels and two independently freely swivelable front wheels. Scissor mechanisms allow folding together of the pushchair both longitudinally and laterally. 
     EP 2 366 372A1 describes a laterally collapsible rollator having a scissors strut assembly between the two frames, but with no synchronous steering of the two front swivel wheels. 
     WO2007101293 discloses a non-collapsible pushcart where the two pivotable wheels on right side are linked by a belt crossed midway so that these two right side wheels swivel counter to each other. The same arrangement is disposed for the left side wheels. This directs the rear wheels counter to the front wheels facilitating arcuate turning. 
     NL1028058 describes a non-collapsible rollator which, the front wheels of which are steered in unison by the two handlebars attached to a central vertical post controlling, via tie bars, each of the front wheels. 
     DE 102004 036 864 A1 discloses a non-collapsable rollator where the two front steering wheels the swivel axles of which are coupled together via a friction belt, which can slip to allow the wheels to accommodate corners or to get back into alignment. 
     GB 364269 A describes a non-collapsable truck or other wheeled frame the front wheels of which are steered by a chain. The entire chain is covered by tubes and housings. 
     DE 19754984 A1 describes a non-collapsable hand lever for adjusting a vehicle seat where two toothed wheels at either end are coordinated by a toothed belt, which is restricted by guide means which prevent the toothed belt from skipping. 
     However, none of the related art discloses or hints at how to achieve the solutions provided by the present invention. 
     OBJECT OF THE INVENTION 
     The present invention intends to solve a complex of difficult-to-reconcile interrelated problems still present in the designs of the prior art:
         1. It is desirable to allow the wheel assembly to be collapsible (foldable) laterally. This permits it to still stand on its wheels and be rolled forward even in the collapsed (folded) storage state, making it easier to handle it in the collapsed state, obviating heavy lifting. Lateral folding keeps the handles at the same level even when being folded together. This is important for a disabled person using a rollator for example.   2. It is desirable to have a hand-pushed wheeled assembly such as a rollator have its caster wheels always swivel in unison. This prevents one of the front wheels from being skewed to one side and halting abruptly the forward progress of the rollator. Synchronous steering also prevents so-called shimmying, which definitely detracts from feel, dependability and steerability. When being pushed at an angle over an obstacle such as a curb, synchronous steering will prevent the wheel first striking the curb at an angle from being forced parallel against the curb thus abruptly braking the entire rollator or stroller. With synchronous steering the friction of the other wheel not yet at the curb will prevent the forward wheel from changing its steering angle as it strikes the curb.   3. This swiveling in unison must always be secure without slippage or skipping, even after being folded up and folded out repeatedly.   4. It is desirable to allow unlimited swiveling of the front wheels (i.e. with no end stop). This allows for easier repeated backward and forward movement as desired.   5. It is desirable to eliminate unnecessary components, and to keep components requiring narrow tolerances to a minimum.   6. Any linkages should be securely protected from the elements.       

     SUMMARY 
     This entire complex of problems listed above finds its solution in the invention as defined in the appended main patent claim. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Embodiments of the invention will now be described in more detail with reference to the appended drawings, wherein: 
         FIGS. 1 a  and 1 b    show side and frontal views respectively of a four-wheeled laterally collapsible (foldable) rollator, which is one embodiment of the present invention. 
         FIG. 1 c    shows the rollator of  FIGS. 1 a  and 1 b    in its collapsed folded-up state. 
         FIG. 2  shows an exploded view of the rollator shown in  FIGS. 1 a    and  1   b.    
         FIG. 3  is a view of the left-hand frame of the rollator. 
         FIGS. 4 a  and 4 b    show the assembled front wheel fork in exploded and unexploded views respectively. 
         FIG. 5  shows in perspective the bearing housing with a toothed belt wheel and a synchronous belt. 
         FIG. 6  shows a cross-sectional view through the bearing housing of  FIG. 5 . 
         FIGS. 7 a  and 7 b    show a folded-out and a folded up view respectively of another embodiment of the present invention using a synchronous chain and a centrally hinged vertical brace frame as struts. 
         FIG. 8  shows in perspective the bearing housing with a sprocket and a synchronous chain. 
         FIGS. 9 a  and 9 b    show a folded-out and a folded up view respectively of another embodiment of the present invention using a tether arrangement pull the belt/chain rearwardly to a protected position during folding. 
         FIGS. 10 a  and 10 b    show a second embodiment of the tether arrangement according to the invention. 
         FIG. 10 c    shows this second embodiment in a perspective view. 
         FIG. 10 d    shows this second embodiment with the wheels and seat removed for better visibility of the tether arrangement. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 a  and 1 b    show side and frontal views respectively of a rollator embodying the present invention.  FIG. 2  shows an exploded view of the entire rollator. The rollator basically has left and right frames,  1  and  2  respectively, each frame being supported on a front wheel  11 ,  12  and a rear wheel  9 ,  10 . The two side frames  1  and  2  are connected both in the folded out and the collapsed state by a scissor frame  3 . The scissor frame  3  comprises two cross pieces  31 ,  32 , articulated to each other at a central pivot point  33 . The lower end of each cross piece  31 ,  32  is hinged to the left or right frame  1  and  2  respectively at  35  and  34  respectively. Towards the upper end of each cross piece  31 ,  32  an extension arm  36  and  37  respectively is hinged at  38  and  39  respectively. The other end of each extension arm  36 ,  37  is hinged to the left or right side frame  1  or  2  respectively, at  40  and  41  respectively.  13  designates a flexible toothed synchronous belt which will be described in more detail below. Thus, the scissor frame  3  can be collapsed bringing the side frames close together for storage, without any detachment of any hinge or pivot point, as shown in  FIG. 1   c.    
     At the very upper end of each cross piece  31 ,  32  there is welded a longitudinal slot piece  42  or  43  respectively. Each slot is designed to hold an end hem, containing a cord or a rod, of a fabric seat  44  stretched between the longitudinal slot pieces  42 ,  43 . The rollator can be used either with or without the fabric seat  44 . The fabric seat  44  collapses as the scissors frame  3  collapses. 
     The scissors frame assembly is also locked against collapse by a small arm and spring mechanism  57  (see  FIG. 1 b   ). This lock engages automatically when the rollator is fully expanded and is released for folding by pulling up on the arm, either directly or via a strap (not shown). 
     As best can be seen in  FIG. 3  showing the left side frame  2 , each frame comprises a horizontal bar  51  and a vertical post  52 . As can be seen in  FIGS. 1 a , 1 a    and  2 , a handlebar assembly  5  is inserted into each post  52  and is adjusted to assume the correct height for the user. As can be seen in these figures each handlebar assembly  5  comprises a brake lever  53  which is coupled via a cable to a brake  54  on the left or right rear wheel  9 ,  10  respectively.  FIG. 3  shows clearly the journal bearing  55 , supporting the axle  58  of the rear wheel  9  or  10 . 
     The forward end of the horizontal bar  51  of each side frame  1  and  2  has a journal bearing housing  21  for the steering post  8   b  of each front wheel fork  8 . This front wheel fork  8  is shown most clearly in  FIGS. 4 a  and 4 b    which show the front wheel fork assembly in exploded and assembled views respectively.  FIGS. 4 a  and 4 b    do not show the journal bearing housing  21  welded to the front of the horizontal bar  51  of each side frame  1 ,  2 . The assembled fork and side frame is only shown in  FIGS. 1 a    and  1   b.    
     The steering post  8   b  is provided with a flat side  22   a  fitting the flat side  22   b  on the interior of a toothed pulley  22 . The steering fork can swivel/rotate as many degrees as desired in the journal bearing housing  21 . It is held in place in the journal bearing housing  21  by a ring cap  26  secured in place by a washer  27  and screws  28  with intermediate ball bearings  24  and ball bearing races  23 ,  25 . 
     A synchronous toothed belt  13  links the two toothed pulleys  22  and thus the forks  8  securely fixed to the pulleys  22 , making sure that the two front wheels  11 ,  12  are always pointing in the same direction. This is important to see to prevent one of the front wheels from skewing off and assuming a position at right angles to the direction of motion of the walker. 
     It is known to steer a wheeled support by pushing it in the desired direction, with freely swivelable front wheels mounted in forks inclined slightly rearwardly. Hopefully, in prior art solutions within dependently freely swiveling front wheels, the two front swivel wheels will steer themselves in the same direction. The present invention insures that as the user steers the rollator by pushing it in the desired direction, both of the front steered wheels will swivel in exactly the same direction. The two front wheel/fork assemblies are otherwise freely unlimitedly swivelable, even multiple rotations and will never reach a rotational end position, where they would be prevented from steering properly, even if the user backs, turns and then proceeds forward. There is no need in the present invention to have any active steering of the front wheels as is the case in NL1028058. 
     One significant problem which the present invention solves is combining lateral collapsibility with a synchronous belt which will never slip or skip in its exact engagement with the toothed pulleys, when repeatedly folding up and folding out the rollator. If one of the pulleys were to slip or skip a few cogs relative to the belt, this would render the rollator unusable, since the front wheels would then be compelled to steer in different directions. This problem is solved by the unique design of the front journal bearing housings  21 . As can be seen in  FIGS. 5 and 6 , showing a perspective view and a cross sectional view respectively of only the journal bearing housing  21 , the toothed pulley  22  and part of the synchronous belt  13 , there is an opening  60  (visible in  FIG. 3  as well) on the lower inside of the housing  21 . The housing  21  thus surrounds in very close proximity the entire portion of the synchronous belt in engagement with the toothed pulley  22 . It is thus physically impossible for the belt  13  to slip in relation to the pulley  22 , even when the belt is collapsed. Beyond holding the pulley always in secure engagement with the synchronous belt  13 , the journal bearing housing also is a journal bearing for supporting the post  8   b  of the swivel fork  8 . The housing  21  can be made to very precise tolerances in a single compact component. This surrounding of the synchronous belt also fulfills another requirement of shielding the pulley from rain and snow. 
     As can be seen in  FIGS. 7 a  and 7 b   , other embodiments of the present invention involve replacing the synchronous toothed belt  13  and toothed pulley arrangement with a synchronous chain  14  and sprockets  29 . Elements corresponding to those in the first embodiment above have received the same reference numerals. See also  FIG. 8  which corresponds to the perspective view of  FIG. 5  but using a synchronous chain  14  and sprockets  29  instead of a belt  13  and toothed pulleys  22 . The sprockets  29  are each fixedly mounted on an individual steering post  8   b , in the manner of the arrangement described above. Otherwise, the arrangement functions exactly as does the toothed belt/toothed pulley arrangement, with the precise tolerances of the inside of the journal bearing housing  21  preventing the chain  14  from ever becoming disengaged from or slipping in relation to the sprockets  29  (see  FIG. 8 ). 
     For embodiments employing either a synchronous toothed belt or a synchronous chain, it is possible to ensure that during the folding up the toothed belt  13  or chain  14  always folds rearwardly between the two side frames, instead of forward where the toothed belt or chain would stick out and possibly become entangled and/or damaged.  FIGS. 9 a  and 9 b    show how this is achieved in one embodiment by having a loose ring or loop  61  around the toothed belt or chain. In this particular embodiment a tether cord  62  is attached at its ends to the longitudinal slot pieces  42 ,  43 . The tether cord  62  passes in this particular embodiment from the one longitudinal slot piece  42  through an eye at strut hinge  35 , through the loop  61 , through a second eye at strut hinge  34  and finally up to longitudinal slot piece  43 . As the two side frames  1  and  2  are folded together, the two longitudinal slot pieces  42 ,  43  will pull the tether cord ends upwards, thereby pulling the toothed belt  13  or the chain  14  rearwards so that it will be protected in the folded up position and will not stick out forwards. 
       FIGS. 10 a , 10 b , 10 c  and 10 d    (wheels and seat removed for visibility) show an alternative embodiment from that shown in  FIGS. 9 a  and 9 b   . Here the loop  61  of  FIGS. 9 a  and 9 b    has been replaced with a rigid rectangular frame  61   a  holding an externally toothed wheel  63  freely rotatably mounted on an axle  64  held in the frame  61   a . The toothed wheel  63  engages the toothed belt  13  and rotates when the front wheels  11 ,  12  are steered together. The interior of the frame  61   a  is dimensioned so as to prevent the toothed belt  13  from ever skipping or slipping over any of the teeth on the toothed wheel  63 , thus always keeping the toothed wheel  63  and the frame  61   a  always exactly centrally placed midway in the belt  13 , however the front wheels  12  and  13  are oriented. The tether cord  62  slips freely through a slot at the rear of the rectangular frame  61   a . As is the case with the previously described tether arrangement, the ends of the tether cord are attached to the longitudinal slot pieces  42 ,  43  fixed to the diagonal struts  31 ,  32 . (most clearly visible in  FIG. 10 d   ). When the two frames  1  and  2  are folded towards each other, the ends of the tether cord  62  are raised with the longitudinal slot pieces  42 ,  43  and the rectangular frame  61   a  and the toothed belt  13  will be pulled backwards in the same manner as described in the preceding paragraph with regard to  FIGS. 9 a  and 9 b   , finally assuming the position shown in  FIG. 10 b   . This embodiment has the advantage of stabilizing the toothed belt as it is pulled rearwardly, and the position of the rectangular frame/toothed wheel will always be midway along the toothed belt in all positions of the wheeled assembly. 
     As can be seen in  FIGS. 7 a  and 7 b    it is possible to replace the scissors strut arrangement with a vertical brace frame  7 . The brace frame  7  consists of two brace frame halves  70 ,  71  that are hinged together in the middle with two hinge brackets  72 ,  73 . A rigid seat  74  is fixedly mounted to the one brace frame half  70 . The brace frame  7  is locked against collapse by a small arm and spring mechanism  75  attached to said seat  74 . This lock engages automatically with the brace frame half  71  when the rollator is fully expanded and is released for folding by pulling up on the arm, either directly or via a strap (not shown). The vertical brace frame  7  can fold rearwards as the rollator is folded up. 
     The person skilled in the art will of course realize that the brace frame arrangement shown in  FIGS. 7 a  and 7 b    can be combined with toothed pulleys and a synchronous belt as well, with or without a tether to pull the chain or belt rearwards as the rollator is folded up. 
     It is also understood that the present invention is not limited to rollators, but encompasses other collapsible wheeled support devices, including push chairs and strollers utilizing swivelable front steering wheels.