Abstract:
A suitcase having a telescoping pull handle and a set of spaced apart wheels, between the back panel and bottom wall of the suitcase housing, permits easy movement over a planar surface. A staggered wheel mechanism is pivotally mounted on the back panel of the suitcase for improved mobility of the suitcase over a flight of stairs.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Provisional Application Number: 60895741 
         [0002]    Receipt Date Mar. 20, 2007 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0003]    N/A 
       REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX 
       [0004]    N/A 
       BACKGROUND OF THE INVENTION 
       [0005]    The present invention relates to staggered wheel mechanism to facilitate transporting a traditional wheeled luggage e.g. suitcase over a flight of stairs. The staggered wheel arrangement offers a near linear, continuous, rotary outer surface when in contact with the edge of the steps thus greatly enhancing the mobility of the suitcase over a flight of stairs. The staggered wheel mechanism can also be used on a shopping basket or any other embodiment that requires easy and quick movement over a flight of stairs. 
         [0006]    Traditionally, suitcases have been designed with a set of wheels at the bottom or bottom corners of the suitcase. Wheels permit the suitcase to be easily rolled across a planar surface even by an individual who would not normally be able to physically carry the suitcase from one location to the next. Whilst traditional wheeled luggage greatly enhances mobility over a planar surface an individual is faced with dilemma when they encounter a flight of stairs over which the suitcase has to be transported. Airport and some train/bus station or some other public places have escalators, elevators to facilitate luggage movement from one floor to the next and avoid stairs. However there are greater number of public places and residential places where there is no easy means to move the luggage between two different floors or even to negotiate a few steps. 
         [0007]    Some traditional suitcases come with skids wherein the individual can slide the suitcase over each step. The skids mounted on the back panel of the suitcase rubs against the steps and since the skids are not frictionless it can damage the stairs if made of wood, carpeted or leave marks on the steps. In addition to the gravitational force the user will have to expend additional force to overcome the friction. Secondly when suitcase is pulled over steps in near upright position the back of the suitcase can slam against the stairs as it leaves contact with one step and engages with the next. The friction and jerky movement can lead to additional strain on the hand leading to injury and could also damage fragile articles within the luggage compartment. So a typical rolling suitcase is not well suited for moving luggage up and down a flight of stairs. 
         [0008]    Prior art has been proposed that includes features designed to facilitate easier movement and alleviate the burden of transporting a piece of luggage over stairs. Such solutions are either not practical or have inherent drawbacks that the present invention overcomes 
         [0009]    U.S. Pat. No. 5,575,361 to Chou discloses a wheeled suitcase. Chou&#39;s suitcase places the rollers on the bottom of the suitcase so the suitcase can be easily wheeled over a flat surface but has no means for towing the suitcase up a flight of stairs. 
         [0010]    U.S. Pat. No. 6,041,900 to Sadow et al. discloses a towable article of luggage. Sadow&#39;s improvement places wheels not only on the bottom of the luggage but also on the front face of the luggage. Again such use of additional wheels does not permit towing the suitcase up a flight of stairs. 
         [0011]    U.S. Pat. No. 6,938,740 to Cheryl Gandy discloses a suitcase with a stair roller and brake. Further the rollers are affixed directly to the back of the suitcase housing. In addition such rollers are mounted with or without endless circumscribed belt. Such a solution does make it easier to move a piece of luggage over the stairs in comparison to dragging it up on skids but has the following drawbacks; 
         [0012]    1. If the embodiment uses only bare rollers:
       A. The movement of the suitcase over the steps will be ratty cause of the grooves between two rollers.   B. Depending on the size and spacing of the rollers the edge of the steps may get lodged in the groove formed between adjacent rollers.   C. Because of the grooves between two adjacent rollers a higher initial force will be required to begin the accent and whenever the user stops on the stairs. The article will have to be kept in rapid motion over the flight of stairs to avoid using the extra force.   D. The grooves will cause a higher wear of rollers and thereby the life and reliability of such a roller arrangement will be shorter. The reliability will be compounded by the weight of the article.   E. The size and weight of the roller arrangement can reduce the overall payload.   F. Since the rollers are affixed to the suitcase housing it will slam against the steps, when pulled in an upright position, as it leaves one step and engages with the next. This will further worsen the wear and tear of the rollers.       
 
         [0019]    2. If the embodiment uses rollers with endless belt;
       A. The belt will have to be maintained at correct tension throughout the life of the suitcase due to aging and normal wear else the belt will start to develop some slack. This can lead to dragging of the luggage over the steps instead of neatly rotating over the steps.   B. The part of the endless belt between two wheels will be subjected to pressure by the steps edge causing the belt to loose tension over time.   C. The endless belt will thus need frequent replacements and maintenance   D. The dimensions and weight of the such a roller arrangement with circumscribed endless belt can reduce the overall payload   E. Again since the rollers are affixed to the suitcase housing even with a circumscribed belt the slamming against the steps, when pulled in an upright position, as it leaves one step and engages with the next, now the belt will be subjected to a greater wear and tear.       
 
         [0025]    W.O. Pat. No. 2006/045107 to Michael Yang, Sadow et al. discloses a collapsible spider wheel assembly that could be used on a suitcase and could be used to move the luggage up the stairs but has drawbacks in that the movement will be slow and rattly. It is more suited to be used on handcarts to move heavy loads. 
       BRIEF SUMMARY OF THE INVENTION 
       [0026]    The present invention overcomes the aforementioned problems and drawbacks of prior art and provide a mechanism that would make the embodiment highly maneuverable over a flight of stairs when ascending or descending. 
         [0027]    An article of wheeled luggage having improved mobility characteristics employs a staggered wheel mechanism pivotally mounted on the back panel of the embodiment to easily move and transport it over a flight of stairs. The staggered wheel mechanism consists of two pluraly spaced wheel assemblies and a foldable link structure. Each wheel assembly in turn has two in-line wheel arrays arranged in a staggered fashion in the wheel frame. Such a staggered wheel arrangement creates a near linear, continuous rotary surface which will result in a smoother movement of the luggage article over the stairs. The staggered wheel mechanism can be stowed away in the recesses of the embodiment when not in use. The invention does not employ a braking mechanism since the embodiment can be simply straightened out on the steps to stop the suitcase in mid flight. 
         [0028]    The strengths of the present invention will become readily apparent in the following detailed description and diagrams of one of the preferred embodiment. The preferred embodiment in this case is a suitcase. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0029]    In the drawings like reference numerals denote similar elements throughout the several views 
           [0030]      FIG. 1 : Perspective view of the preferred embodiment, suitcase, with staggered wheel mechanism fully deployed. 
           [0031]      FIG. 2 : Partial side view of the wheel assembly showing a near linear, continuous rotary outer wheel edge. 
           [0032]      FIG. 3 : Perspective view of the suitcase with retracted staggered wheel mechanism and extended telescopic handle. 
           [0033]      FIG. 4 : Perspective view of the suitcase with back panel recesses 
           [0034]      FIG. 5 : Perspective view of the towing apparatus that fits in the back panel recesses of the suitcase 
           [0035]      FIG. 6 : Perspective view of the staggered wheel mechanism partially deployed 
           [0036]      FIG. 7 : Perspective view of the retracted staggered wheel mechanism 
           [0037]      FIG. 8 : Simplified side view of the towing apparatus showing staggered wheel mechanism&#39;s linear outer wheel edge 
           [0038]      FIG. 9 : Partial perspective view showing a wheel frame&#39;s two channels and staggered arrangement of axles in the channels. 
           [0039]      FIG. 10 : Partial top view of the wheel frame 
           [0040]      FIG. 11 : Exploded perspective view of the staggered wheel mechanism 
           [0041]      FIG. 12 : Partial cross-sectional front view shows the pivotal connectivity between the upper link of the link apparatus and suitcase back panel bracket. 
           [0042]      FIG. 13 : Top perspective view of the link apparatus hinge and torsion spring 
           [0043]      FIG. 14 : Exploded perspective view of the wheel assembly 
           [0044]      FIG. 15 : Partial front view of top end of the wheel frame 
           [0045]      FIG. 16 : Perspective view of staggered wheel mechanism with protruding top wheels 
           [0046]      FIG. 17 : Side view of the embodiment on stairs 
           [0047]      FIG. 18 : Simplified partial cross-sectional side view of the sliding latch mechanism area 
           [0048]      FIG. 19 : Simplified perspective view of the sliding latch mechanism area 
           [0049]      FIG. 20 : Exploded perspective view of the sliding latch mechanism 
           [0050]      FIG. 21 : Partial perspective view of mounted pivotal latch mechanism 
           [0051]      FIG. 22 : Exploded perspective view of pivotal latch mechanism 
           [0052]      FIG. 23 : Exploded perspective view of the latch lever mechanism 
           [0053]      FIG. 24 : Perspective view of the staggered wheel mechanism embodied on a shopping cart 
           [0054]      FIG. 25 : Perspective view of suitcase with full-length staggered wheel arrangement. 
       
    
    
       [0055]    The following disclosure describes the invention in connection with one preferred embodiment, the suitcase. 
         [0056]    Furthermore, one should understand that the drawings are not to scale and those graphic symbols, diagrammatic representatives, and fragmentary views, in part, illustrate the embodiment. In certain instances, the disclosure may not include details related to the embodiment itself which are not necessary for an understanding of the present invention. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0057]    With reference now to  FIG. 1 , there is illustrated an article of luggage, suitcase  21 , constructed in accordance with one of the preferred embodiment of the invention. The suitcase  21  is made up of traditional parts; housing, main body wheels  22  and telescopic tube assembly  23 . Also shown in  FIG. 1  is the invention apparatus, staggered wheel mechanism  24  and latch mechanism  25 . 
         [0058]    The suitcase  21  includes generally parallel, spaced apart front and back panel  41  and  42  respectively. The panels  41  and  42  are connected about their periphery by a wall member  43 . The wall member  43  extends between panels  41  and  42  thereby defining the volume of the suitcase. The wall member  43  has a top portion  44 , a bottom portion  45  and side portions  46  and  47 . 
         [0059]    The front panel  41  and the wall member  43  are preferably made of soft, flexible material, such as fabric. A zipper or any other means may be provided on the periphery of the front panel  41  for opening and closing the suitcase  21 . The panels  41 ,  42  and wall member  43  materials, suitable openings into the suitcase, the telescopic tube assembly  23 , main body wheels  22  and placement of handles to carry the suitcase are well known to those skilled in the art. 
         [0060]    For this invention the back panel  42  and bottom portion  45  is made of a suitable rigid, lightweight plastic material, typically used in suitcase construction, to mount the staggered wheel mechanism  24 , the latch mechanism  25  and the telescopic tube assembly  23 . 
         [0061]    Additionally the back panel  42  should be so constructed that it has appropriate recesses  48 A &amp;  48 B to accommodate the staggered wheel mechanism  24  the latch mechanism  25  the telescopic tube assembly  23  and the main body wheels  22  as shown in  FIG. 4 . The depth of the recesses should be appropriate so that the staggered wheel mechanism  24  sits flush in the recess when in a retracted position as is shown in the  FIG. 3 . 
         [0062]    The back panel  42  also has a built in bracket  49  to pivotally mount the top end of the staggered wheel mechanism  24 . Alternately a suitable bracket could be separately affixed to the rear panel  42  for the same purpose. Another alternative would be to do away with the bracket  49  altogether and pivotally mount the top end of the staggered wheel mechanism onto the telescopic tubes  23  similar to what is shown in  FIG. 24  of the shopping basket, using clamps  149  and extended pivot shaft  150   
         [0063]    As shown in  FIG. 5  the telescopic handle assembly  23  comprises of the outer base tubes  51 , the inner telescopic tube  52  and the handle  53 . The outer base tubes  51  telescopically receive the inner telescopic tubes  52  when the handle  53  is retracted. The telescopic handle assembly  23  may have a button  54  on the handle  53  to operate well known interlocking mechanism of the telescopic tubes. The outer base tube  51  of the telescopic handle assembly  23  is mounted in the recess  48 A of the back panel  42  and is firmly held in place by the upper bracket  55  and the bottom bracket  56 . The upper bracket  55  is mounted in the handle recess  48 B, shown in  FIG. 3 , and parallel to the top portion  44  of the wall member  43 . The placement of the upper bracket  55  and its relation vis-á-vis the telescopic tubes are shown in  FIGS. 1 ,  3  &amp;  5 . The upper bracket  55  is suitably secured to the rigid rear panel  42  by means of screws or rivets. The lower end of the outer base tube  51  is placed in the base caps  57 , which are part of the lower bracket  56 , and secured by means of diagonal screws. The lower bracket  56  is mounted on the bottom portion  45  of the wall member  43  by means of rivet or screws. The bottom portion  45  should be suitably shaped for the recesses  48 A and the lower bracket  56 . The lower bracket  56  could also be made as an integral part of the bottom portion  45 . The interlocking, retraction and extension mechanism of the telescopic handle assembly  23  and the corresponding mounting is well known to those skilled in the art. For the purposes of this invention the telescopic handle assembly  23  tubes should be so spaced so as to accommodate the staggered wheel mechanism  24  as shown in  FIGS. 1 &amp; 3 . 
         [0064]    Suitcase  21  also includes a pair of wheels  22  found in a traditional wheeled luggage. The wheels  22  are preferably positioned at the corner junction of back panel  42  and the bottom portion  45  of wall member  43 . As in traditional wheeled luggage the wheels  22  will primarily be used when moving the suitcase  21  over a planar surface. The wheels  22  along with legs (not shown) suitably positioned on the bottom portion  45  support the weight of the suitcase  21  when in the upright, or at-rest, position. 
         [0065]    As shown in  FIG. 1  suitcase  21  further includes the staggered wheel mechanism  24  and the latch mechanism  25 . The staggered wheel mechanism  24  is pivotally connected to both the back panel bracket  49  and the lower bracket  56  to allow movement between the retracted position  FIG. 3  and fully deployed position as shown in  FIG. 1 . Intermediate position is shown in  FIG. 6 . 
         [0066]    As shown in  FIG. 6 ,  8  and  FIG. 11  the staggered wheel mechanism  24  comprises of wheel apparatus  58  and the link apparatus  59 .  FIGS. 9 through 15  show the different views, partial, perspective, exploded, of the staggered wheel mechanism  24 . As shown in  FIGS. 11 ,  14  and  15  the wheel apparatus  58  in turn consists of two spaced apart wheel assemblies  60 , the cross-member  61  and a threaded/non-threaded bolt  62 . 
         [0067]    As shown in  FIG. 14  the wheel assembly  60  in turn comprises of wheel frame  63 , in-line wheels  64  with corresponding axles  65  and cover strip  66 . The wheel frame  63  structure is such that it has two channels  63 A and  63 B running along its length. The wheel frame  63  is preferably fabricated as one single unit with a oval shaped head that has suitable orifices  69  through which the cross-member  61  and the bolt screw  62  can engage. The elongated portion of the oval shaped head is along the length of the wheel frame  63 . The lower end of wheel frame  63  is connected to hinges  77  which in turn are fixed to the lower bracket  56 . The in-line wheels  64  are laid out in an array in each channel  63 A &amp;  63 B of the wheel frame  63 . For clarity the in-line wheels  64  laid out in channel  63 A is designated as wheel array  64 A and in-line wheels  64  laid out in channel  63 B are designated as wheel array  64 B. The wheel arrays  64 A and  64 B are rotatably mounted in their respective channels  63 A and  63 B using axles  65 . As is shown in  FIGS. 9 ,  10  and  15  the height of the outer walls  63 D of the channels  63 A and  63 B should be, when measured from inside the channel, at least 2 mm more than the radius of the wheels to allow free rotation. The midrib,  63 C, of the wheel frame  63  should be, again measured from inside the channel, no more than ¾ of the diameter of the in-line wheels  64 . To mount the axles  65 , cylindrical grooves  67  are made on either side of the midrib  63 C. The grooves through the midrib  63 C can be up to ¾ of its thickness. Also semi-cylindrical grooves  68  are made into the outside walls  63 D of the wheel frame for the second end of the axles  65 . Complementing semi-cylindrical grooves are made into the cover strip  66 . The length of the grooves on the outside wall  63 D and in the cover strip should not be more than half their respective widths. The cover strip  66  is fixed on the outside walls  63 D of the channel  63 A and  63 B by means of screws to secure the axles. 
         [0068]    The axles  65  are spaced equidistant from each other. The distance between any two adjacent axles  65 , from its centre, should be slightly more than the diameter of the wheel  64 . This is so that the edges of the adjacent in-line wheels  64  in wheel arrays  64 A &amp;  64 B have got at least a 1 mm of clearance to freely rotate on its axle  65 . The distance between the edges of the adjacent in-line wheels  64  should kept below 5 mm for smoother movement over the stairs. 
         [0069]    The in-line wheels  64  used in forming the two wheel arrays  64 A &amp;  64 B are of the same diameter and its axles  65  too are also equally spaced apart. However the wheel arrays  64 A and  64 B are mounted in a staggered fashion in their respective channels  63 A &amp;  63 B, as shown in all figures showing staggered wheel mechanism  24 . With this arrangement if wheel array  64 A is laterally moved into channel  63 B, the centers of wheels in wheel array  64 A would fall right in between edges of two wheels of wheel array  64 B and vice-versa. 
         [0070]    The staggered wheel arrangement creates a near linear, continuous rotary edge at the outer edge of the wheels as shown in side views,  FIGS. 2 and 8 . This in turn eliminates the drawbacks of the prior art and leads to easy movement of the wheeled luggage over stairs. 
         [0071]    Further the wheel frame  63  fabrication could be such that the upper ¼ths of its length is slightly tilted outwards for better engagement of the staggered wheel mechanism  24  with the steps whilst ascending. However the wheel frame  63  fabrication could be fabricated without the tilt. 
         [0072]    The two wheel assemblies  60  are joined together at the top end by the cross member  61  and secured using a threaded/non-threaded bolt  62 . Orifices  69  are made at the top end in the wheel frame  63  as shown in  FIG. 14  and  FIG. 15  to interconnect the circular cross-member  61  and the bolt  62  through the wheel frame  63 . To prevent the bolt  62  from getting unscrewed by use over time, due to constant deployment and retraction of staggered wheel mechanism, bolt  62  can be further secured to the cross member  61  by a diagonal screw engaging the cross-member  61  and bolt  62  through the respective orifices  61 A and  62 A. The screw should sit flush within the cross-member  61  orifice  61 A so as to not to impede the link apparatus. To permit assembly a hole or a slot could be made into the eye portion  78  of the lower link  71 . 
         [0073]    As shown in  FIGS. 11-13 , the link apparatus  59  consists of upper link  70  and the lower link  71 . The hinge  72  pivotally connects the lower link  70  to the upper link  71 . The torsion spring  74  mounted in the pivot pin  73  of the hinge  72  enables automatic deployment of the wheel apparatus  58  when the catch  84  in the latch mechanism  25  is raised. The staggered wheel mechanism  24  when stowed away is held in the retractable position by the latching mechanism  25 . 
         [0074]    The upper end of the upper link  70  is pivotally connected to the back panel  42  by a suitable pivot mechanism. In this case a bracket  49 , which could be part of single mould of back panel  42 , is used to pivotally connect the pivot pin  75  as shown in  FIG. 11  and  FIG. 12 . The pivot pin  75  is held in position by a suitable clip  75 A slipped over the groove  76  at either end of the pivot pin  75  from inside the suitcase cavity. 
         [0075]    The lower link  71  is pivotally connected to the cross-member  61  by the eye portion  78 . The cross-member  61  acts as a pivot shaft to the lower link  71 . When the staggered wheel mechanism  24  is fully deployed the two links  70  and  71  will line up and lock in place when in use. To firmly prevent the link apparatus from folding when in use, a simple locking mechanism such as a sliding pin or link plate, on the side of the upper link engaging with the lower link when deployed, could be used. However any suitable, well known, locking mechanisms could be used as part of the link apparatus  59 . 
         [0076]    The lower end of the both the wheel assemblies  60  is pivotally connected to the lower bracket  56  by a suitable pivot mechanism e.g. a bracket with pivot pin or in this case, as shown in the  FIG. 11  by hinges  77 . The lower bracket  56  is rigidly fixed to the bottom portion  45 . Alternately the hinges could be directly fixed to the rigid bottom panel  45 . 
         [0077]    The lower bracket  56  and thereby the staggered wheel mechanism  24  should be so mounted that the outer edge of the in-line wheels  64  and the outer edge of the main body wheels  22  align when staggered wheel mechanism  24  is fully deployed as shown in  FIG. 17 . This arrangement is needed to ensure that the main body wheels  22  of the suitcase  21  do not add a bump to the suitcase movement over the stairs. This arrangement also adds to the overall length of the available wheel apparatus  58 . 
         [0078]      FIG. 16  shows an alternative linkage between the lower link  71  and the cross-member  61 . In the figure the cross-member  61  is rigidly fixed to the back of the wheel frame  63  instead of the top as in earlier figures. A pillow block  79  like structure, which acts as a bracket, is affixed on the back of the wheel frame  63  to hold the cross-member  61  by means of a screw. The pillow block bracket  79  may be separately affixed or fabricated as part of the wheel frame  63 . Another major change is that channels  63 A and  63 B, of both the wheel assemblies  60 , are left open at the top. One wheel, of either wheel arrays  64 A or  64 B of each wheel assembly  60 , depending on the construction, is allowed to protrude out of the channel along its length. This arrangement will be helpful in situation where the wheel apparatus  58  happens to be of shorter length than the distance between two steps edge, creating a possibility of the wheel apparatus  58  getting stuck in the steps. 
         [0079]    The overall dimensions of the staggered wheel mechanism, wheel frame  63 , width of the channels  63 A &amp;  63 B, thickness of the channel walls and back portion, dimensions of axle  65  and in-line wheels  64  will all depend on the shape and size of the embodiment, weight carrying capacity of the embodiment and the materials chosen for the staggered wheel mechanism. Depending on the material chosen for the wheels  64 , preferably polyurethane, the dimensions of wheels  64  and axles  65  should be such that it should be able to bear the anticipated weight of a fully loaded embodiment. Polyurethane properties like elasticity of rubber combined with the toughness and durability of metal makes it suitable to keep the wheel dimensions and overall weight of the staggered wheel mechanism  24  to the minimum. This is turn will not effect the payload capacity and preserve the overall aesthetics of the embodiment. The wheels  64  may be knurled for better gripping. 
         [0080]    The length of the wheel apparatus  58  will also depend more on the average distance between two steps edge and less on the shape and size of the embodiment. The overall length of the wheel apparatus  58  along with wheels  22  should be at least the average distance between edges of two steps so that the top edge of the wheel apparatus does not get caught in the stairs. However for embodiments that do not have sufficient height the staggered wheel mechanism shown in  FIG. 16  is more suitable. This is so because it has wheels  64  at the top end of the wheel apparatus which will continue with the rolling motion even when it would look like possibly getting caught in the higher step. 
         [0081]    It is also of importance to discuss the appropriate length of the link apparatus  59  which in turn determines the deployed rotational angle of wheel apparatus  58 . As per some documents about research there are various configurations of stair steps having different depth and height, and different ratios of the former to the latter, according to conditions of location. The same documents mention that by experiment a baggage cart having an overall length of 90 cm tends to have an inclination of 38 or so with respect to a person 165 cm tall who is drawing the cart by hand on a flat place, 35 or so with respect to a person 180 cm tall, and 43 with respect to a person 150 cm tall. Thus, in almost all cases, the inclination of a baggage cart with respect to a person who is drawing it is within a range of 35 to 43 degrees. However when the suitcase  21  is taken over stairs the desired angle will be dependent on the dimension of the steps, steepness etc. and the document mentions that the angle may vary between 27 to 35 degrees. So the overall length of the link apparatus  59  should be so that the angle formed by the wheel apparatus  58  is around 30 degrees to the wall of the rear panel  42  for easy comfortable pull over the stairs. This is just a suggested angle and it could vary. 
         [0082]    The preferred method of stopping on stairs whilst using the staggered wheel mechanism  24 , for this particular embodiment, i.e. suitcase  21 , is to straighten out the suitcase  21  in the upright position on the steps whilst ascending or descending the stairs. 
         [0083]      FIGS. 18 ,  19  &amp;  20  illustrate a preferred embodiment of the latch mechanism  25  and are well known. The slider latch mechanism  25  comprises of the housing  80  with slider guides  82  and posts  81 . The slider guides  82  engage with vertical flanges  85  on the catch structure  83  and limit it to an up/down vertical movement. The two vertical posts  81  on the housing  80  slidably engage with first, the orifices  87  on the horizontal flange  86  of the catch structure  83  and than with the spring  88 . The spring  88  is held in place by the housing cover  89  which is fixed to the housing by means of screws. In the default position the catch  84  on the catch structure  83  is pushed down by the spring  88  in its relaxed state. The catch  84  in turn engages with the groove  90  on the eye portion  78  of the lower link  71  when the staggered wheel mechanism  24  is in fully retracted position. The luggage handler will have to push the catch  84  up against the force of the spring  88  to disengage it from the groove  90  and deploy the staggered wheel mechanism  24 . To latch in the retracted position the catch  84  will have to be raised or the wheel apparatus will have to be pushed against the latch which in turn will raise the catch  84  portion of the latch mechanism  25 . 
         [0084]      FIGS. 21 ,  22  and  23  illustrate a pivotal latch mechanism. The previous slider latch mechanism  25  illustrated in  FIGS. 18 ,  19  and  20  would require the luggage handler to bend down to disengage the latch and deploy the staggered wheel mechanism. The pivotal latch mechanism attempts to provide a better deployment mechanism wherein the user will not have to bend all the way down. It provides a button  91  that goes through the orifice  92  and engages with the link rod  93 . The link rod  93  has a fork  93 A at the lower end which engages with the crossbar  94  to form a fork joint. The crossbar  94  rests on rear end of the lever  98  and is kept in position on the lever by projection  97 . Additionally the crossbar  94  is kept in position by suitable cavities in the back panel  42 . Projection  97  can be also suitably modified into a loop structure to hold the crossbar  94  in place. The front end of the lever  98  has a projection  99  which acts as a catch and engages with the grooves  96  on the wheel frame  63  because of the force exerted by the torsion spring  101 . The lever mechanism  95  is rigidly fixed to the rear panel  42  by using clamps  102  holding the fulcrum pin  100  on either side. In the default position the projection  99  is held down by the spring force wherein the button  91  is in the raised state. When the button  91  is pushed the staggered wheel mechanism  24  will get deployed as the rear end of the lever  98  will get pushed down thus raising the catch  99 . The button  91  will have to be pushed down momentarily to stow away the staggered wheel mechanism  24  and latch it. 
         [0085]      FIG. 24  shows the staggered wheel mechanism  24  on a shopping basket. Since there is no rigid rear panel the pivot pin  150  is appropriately scaled to pivotally engage with the clamps  150  on the tubes. 
         [0086]    In  FIG. 25  the staggered wheel arrangement is mounted along the full length of the rear panel of the suitcase. In this instance the telescopic handle assembly will have to be made pivotable at the junction of the top portion and the back panel of the suitcase. The back panel recesses will have to be suitably modified to accommodate the full length of staggered wheel. 
         [0087]    The present invention, staggered wheel mechanism, could be suitably exploited for other embodiments.