Abstract:
A method and apparatus for retarding rotation of at least one wheel, the apparatus including at least one braking member, a latch member secured to the braking member and movable between a first position and a second position, and a latch actuating member arranged to determine the position in which the latch member is positioned. The braking member is movable into a braking position in which rotation of the at least one wheel is retarded when the latch member is in the second position.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method and apparatus for providing a latching mechanism. In particular, but not exclusively, the present invention relates to a latching mechanism which can be used to determine when a braking member should or should not operate to retard rotation of a wheel of a castor secured to a vehicle or some other movable object. 
     2. The Prior Art 
     There are many instances known in which vehicles, or other such means of transportation, which are provided with one or more wheels should have their movement inhibited or prevented. A known way for achieving this is to provide a brake mechanism on one or more of the wheels. When motion of a vehicle or object is to be slowed or stopped, a signal is transmitted to a brake which is applied. The application of the brake retards rotation of a wheel. 
     Many different types of braking mechanism are known and the manner in which braking is achieved is often dependent upon the type of vehicle which is to be slowed or stopped. 
     It will be understood that embodiments of the present invention are generally applicable in the sense that they can be adapted to retard rotation of one or more wheels of any type of means of transportation or object which is provided with the facility to move. However, the present invention is particularly well suited to retarding rotation of at least one wheel of a castor for a shopping cart. Shopping carts, sometimes referred to as shopping trolleys, are well known and are provided by supermarkets or other retail establishments for shoppers to transport goods to be purchased in a very convenient manner. However, supermarkets are known to have a problem in that from time to time shopping carts may be removed from the premises by unauthorised personnel. Such removal costs retail businesses money to either replace or locate the trolleys and return them to a desired location. 
     Shopping carts are typically provided with four castors, each of which includes one or two wheels arranged to rotate about a common axis between forks. The forks are connected at a common point to the shopping cart. 
     Many methodologies and apparatus have been suggested in the past for avoiding the unauthorised removal of shopping carts. Some of these involve the inclusion of a braking assembly in at least one castor of the shopping cart. However, such braking assemblies can be costly to produce and are prone to failure from time to time. Another problem is that the environment in which the shopping cart operates is a relatively inhospitable environment. For example, shopping carts are often pushed or pulled over very uneven surfaces where a jarring motion may be transferred into the castor of the shopping trolley. This makes parts within the castor prone to failure and can cause a brake to invalidly deploy or unset. 
     Some known braking assemblies for wheels include a latch-like assembly in which a latch can be positioned in one of two positions. In a first position a brake operates to brake a wheel, thus retarding rotation of the wheel. In another position the brake is not applied. Many known latching assemblies are prone to failure either because of the environmental harshness noted above or because unauthorised personnel will attempt to disable the latch mechanism. 
     In this sense latching mechanisms per se are known for a whole host of different applications. As such these latching mechanisms are arranged to select one or more states. Once a state of a latch is selected, this determines operation of some machinery or other component parts in the apparatus where the latch mechanism is located. However, many types of latch mechanism are complex which makes them costly to produce and maintain or means that they are prone to failure. It will be understood that whilst embodiments of the present invention are described by way of example with respect to a latching mechanism applicable to select a braking state for a wheel of a shopping cart, embodiments of the present invention are generally applicable to circumstances where a latch mechanism is required to select one or more states of operation of particular equipment. 
     It is an aim of the present invention to at least partly mitigate the above-mentioned problems. 
     It is an aim of embodiments of the present invention to provide a latching mechanism in which a position of a latch member is determined using a very convenient method which is relatively cheap to produce and is not prone to error. 
     It is an aim of embodiments of the present invention to provide a method and apparatus for retarding rotation of a wheel of a castor of the type which can be secured to a vehicle or other object to be moved. Preferably the wheel is a wheel of a castor of a shopping trolley. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention there is provided an apparatus for retarding rotation of at least one wheel, comprising:
         at least one braking member;   a latch member secured to said braking member and movable between a first position and a second position; and   a latch actuating member arranged to determine the position in which said latch member is positioned; wherein   said braking member is movable into a braking position in which rotation of said at least one wheel is retarded when said latch member is in said second position.       

     According to a second aspect of the present invention there is provided a method for retarding a wheel, comprising the steps of:
         providing a braking member to which is secured a latch member, said latch member being movable between a first and second position;   selecting a position for said latch member via a latch actuating member; and   moving the braking member into a braking position thereby retarding rotation of the wheel when said latch member is in said second position.       

     According to a third aspect of the present invention there is provided an apparatus for providing a latching mechanism, comprising:
         a latch member movable between a first position and a second position; and   a latch actuating member arranged to determine a position of said latch member; wherein   at least one of said latch member and/or said latch actuating member comprises a magnetic element.       

     Embodiments of the present invention provide an apparatus and method for retarding the rotation of at least one wheel in a relatively simple and efficient manner. This is achieved by latching a braking member in one of two positions. In a first position a braking member used to prevent or reduce rotation of a wheel is non-engageable and thus a wheel can move freely. When a latch is moved to a second position movement of the vehicle, such as a shopping cart, will itself power the movement of the braking member into a braking position which will retard either fully or partially further motion of the wheel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will now be described hereinafter, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  illustrates a castor; 
         FIG. 2  illustrates another view of a castor; 
         FIG. 3  illustrates a non-braking position of a braking member; 
         FIG. 4  illustrates a braking position of a braking member; 
         FIG. 5  illustrates transmission of a set and unset signal; 
         FIG. 6  illustrates parts of a castor; 
         FIG. 7  illustrates a latching mechanism in a non-deployed state; 
         FIG. 8  illustrates a latching mechanism in a deployed state; 
         FIGS. 9A ,  9 B and  9 C illustrate an inner surface of a wheel; 
         FIG. 10  illustrates a compartment in a castor housing; 
         FIG. 11  illustrates a latch actuator; 
         FIG. 12  illustrates how wheels are connected together; 
         FIG. 13  illustrates power supply in a castor; and 
         FIG. 14  illustrates motion of a castor on a travelator. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the drawings like reference numerals refer to like parts. 
       FIG. 1  illustrates a side view of a castor  10 . The castor includes two wheels  11  held between forks  12  and able to rotate about a common wheel axis A. It is to be understood that the present invention is not restricted to use of two wheels. Rather, the invention is generally applicable to castors including one or more wheels. A braking member  13  includes a brake foot  14  at an end region  15  of an arm thereof. It will be understood that castors of this type have many potential uses such as, for example, facilitating movement of shopping carts where castors  10  of this type would be located in the four underside corners of the shopping cart. However, such castors may be applied generally to the underside of very many different types of equipment or vehicles such as, for example, on hospital equipment, furniture or office equipment. 
       FIG. 2  illustrates another view of the castor  10 . Here the two forks  12   1 ,  12   2  may more clearly be seen to bridge the wheels  11 . In particular in  FIG. 2 , the castor can be seen to include two wheels  11   1 ,  11   2  which are both arranged to rotate about a common wheel axis A. The two wheels are secured to the forks of the castor by a nut  20  and corresponding bolt  21 . A first end of each fork  12  is secured to the nut and bolt whilst the other ends of the forks form a fork body  22  towards the top of the castor. A securing pin  23  which is threaded is located at the top of the castor so that the castor can be secured to a target object such as an item of furniture or a vehicle. Other securing mechanisms may be used. 
     The wheels  11   1 ,  11   2 , are arranged side by side and separated by a central housing  24 . The housing  24  is connected to the top of the castor by a rigid connecting piece  25 . In this sense the housing and forks are rigidly secured to a further object by the connecting member  23  and the two wheels will rotate independently with respect thereto. The housing  24  has a groove  26  along part of the circumference which enables the braking foot  14  connected to the arm of the braking member to move from its non-braking position shown in  FIG. 2  downwardly until the braking foot separates the wheels of the castor from the ground surface  27 . 
       FIG. 3  illustrates the braking foot  14  in a non-braking mode of operation whilst  FIG. 4  illustrates the brake foot in a braking position. In the braking position the foot  14  is rotated downwardly from the position shown in  FIG. 3  until the foot is juxtaposed between the running surface  27  and the wheel  11 . It will be understood that in this position a user pushing the object to which the castor is connected (not shown) will be hindered considerably in movement. 
       FIG. 5  illustrates deployment of the braking foot  14  from a braking position to a non-braking position. This occurs when a sensor  50  on the castor body detects a control signal. For example a wireless signal from a transmitter  51 . The remote transmitter  51  transmits a first signal  53  which operates to initiate braking when a vehicle or other object to which the castor is connected moves from zone X to zone Y as shown in  FIG. 5 . This operation will be described in more detail hereinafter. The transmitter  51  also transmits a second signal  52  which is detected by the sensor  50  when the castor moves from zone Y to zone X. As the castor moves over an interface between the zones, the signal  52  is received by the sensor  50  which releases the braking mechanism to thus unlock the braking mechanism. In this sense a user is able to move an object to which the castor is connected within zone X but as soon as movement from zone X to zone Y occurs the braking mechanism retards rotation of at least one of the wheels  11  so that movement of the object becomes impossible or very difficult. 
       FIG. 6  illustrates the separate parts of the castor in more detail. As may be seen each wheel  11  is formed from a respective wheel body  60  formed from rigid plastic or metal or some other rigid material. Each wheel is substantially circular in cross section and is generally disk-like. About the edge of each wheel  11  is a high friction surface  61  such as rubber which helps ensure the wheels run smoothly over a running surface. Each wheel  11  has an inner side  62  and an outer side  63 . The inner side  62  is recessed. 
     The bolt  20  extends all the way through the two wheels and the wheel housing  24 . A dust cover  64  prevents the ingress of dust onto the axle of the wheel which might hinder rotation of the wheels. The dust cover may also act as a string guard. 
     A spindle  65 , which is a generally cylindrical element, is also located along the common axis of the wheels in a coaxial manner from end to end. A further dust cover/string guard  66  is located on the outer side  63   2  of the wheel  11   2  and the threaded end  67  of the bolt  20  is secured with nut  21 . The forks  12  (sometimes referred to as the horns) are secured to the nut and bolt so that the wheels  11  will rotate about the axis A. 
     As illustrated in  FIG. 6 , the wheel housing  24  is a substantially cylindrical housing having an H-shaped cross section. The outer wall  68  is supported by a central plate  69 . The central plate  69  separates two sides of the housing and each side provides a respective compartment C 1 , C 2  in which further equipment of the castor may be located. 
       FIG. 7  illustrates a first compartment C 1  of the housing.  FIG. 7  illustrates the housing  24  without the wheel  11   1 . A circular rim  70  defines an open mouth of the housing and the braking member  13 , including the braking foot  14 , is shown in more detail. The braking member includes an arm  71  secured at a first end  15  to the brake foot. The arm extends into a hip region  72  which is arranged to rotate about the axis A. The hip region  72  of the brake includes an extension  73  which is secured to a first end of a biasing spring  74 . The extension, hip, arm and foot may be integrally formed. The remaining end of the biasing spring  74  is secured in a fixed position with respect to the housing. In this way the spring operates to urge the braking arm and hip in an anti-clockwise direction thus urging the braking foot  14  upwardly away from a running surface. This is in a non-braking mode of operation. A latch member  76  is pivotally secured to the braking hip and includes a magnet  77  and braking arm  78 . The latch member  76  is pivotable about a pivot point  79 . The magnet is arranged to present a predetermined pole, for example north, outwards in the direction of the circumferential edge of the wheel housing. 
     A latch actuating member  80  which is formed from an elongate body is also pivotable between stops  81  and  82 . The latch actuator includes a further magnetic element  83 . The magnet  83  is arranged along a lower contact surface of the latch actuator  80 . Thus one side of the actuator is magnetised generally with a first pole of the magnet whilst a remainder side of the actuator is magnetised generally according to the remaining pole. As illustrated in  FIG. 7 , when the latch actuator  80  is pivoted anti-clockwise until it abuts with end stop  82 , the end at which the second magnet is located is a substantial distance away from the latch  76 . In this position the latch is arranged such that the latch is repelled downwardly by virtue of the north pole of the magnet  77  on the latch being presented to the matching north pole end of the actuator magnet  83 . In this way whilst the magnet  77  is arranged extending away from the latch/actuator contact surface of the latch the magnet  83  is arranged along the corresponding surface of the actuator thus revealing north and south poles. 
       FIG. 8  illustrates a further setting of the latch and latch actuator in which the latch actuator  80  is pivoted clockwise until it abuts with a second end stop  81 . In this position the south pole of the magnet  83  is more closely presented to the north pole facing out from the magnet  77 . The magnets are thus arranged so as to be attracted with a significant strength and thus the latch  76  is attracted towards the end of the latch actuator  80 . This moves the latch into a second and activated position. In this position the latch arm  78 , which extends outwardly from the latch body in a direction out of the page shown in  FIGS. 7 and 8 , moves from a first position in which it is radially proximate to the central axis A to a second position in which the radial distance from the central axis is increased. 
       FIGS. 9A ,  9 B and  9 C illustrate the inner side  62   1  of the first wheel  11   1  (not shown in  FIGS. 7 and 8 ) in more detail. It will be noted that the annular recess inside the wheel includes one toothed region  90 . One such region is sufficient but having a plurality of such regions means that braking occurs more promptly when required. The toothed region is formed from a substantially circular wall  91  which extends outwardly from a central flat zone  92 . The wall  91  has a V-shaped portion  93  with the apex of the V-shaped tooth having an engaging lip  94 . Each wall region  91  provides a distance R 1  which is greater from the central axis than a corresponding radius R 2  in a region where the toothed region is located. As will be understood by those skilled in the art when the arm  78  of the latch  76  is in the first position, as illustrated in  FIG. 9B , the arm is relatively speaking close to the axis. In this sense the arm has a distance from the axis A around R 3 . As such the arm in this position does not engage with a toothed region  90  on the inside of the first wheel. However, when the latch actuator  80  is rotated to move closer to the latch  76 , the magnetic forces of attraction pull the latch  76  about its pivot point  79  into a position in which the arm  78  is radially further away from the axis A. As the wheel rotates a toothed region  90  will thus come into contact with the arm. This is illustrated in  FIG. 9C . The arm  78  will in fact engage with an abutment surface  94  of one of the toothed regions. As the wheel  11  continues to move, the abutment of the surface  91  drives the braking member by virtue of the fact that the latch  76  is connected to the brake. The drive causes the braking arm  71  in a clockwise direction against the biasing force of the spring  74 . Movement of the wheel caused by a user pushing thus drives the braking foot into a braking position. 
     When a brake is to be disengaged, for example, when the castor passes back into an authorised zone and thus receives a reset signal from the remote transmitter, the latch actuator  80  is rotated until it hits the first abutment  82 . This moves the south pole of the magnet  83  away from the north pole of the magnet  77 . The north pole of the magnet  83  is then effectively presented again to the north pole of the magnet  78  of the latch which causes the latch to be biased away from the latch actuator. This moves the latch arm  78  radially towards the wheel axis A thus disengaging the arm from a previously engaged toothed region. The biasing forces of the spring  74  then acts to return the braking arm into a non-braking position thus enabling the wheel to continue onwards unretarded. 
     It will be understood that the above-described embodiments include a magnetic element in both the latch actuator  80  and latch  76 . However, it will also be understood that only one of the actuator and latch need have such a magnetic element. For example, the actuator could include a magnet and the body of the latch  76  could be wholly or substantially metallic. In this way the magnet would attract the metallic body in much the same way as the two magnets are attracted. It will also be understood that more than one magnet could be used on any one of the latch or latch actuator. As an alternative, magnets could be arranged so as to repel each other when in an ‘unlock’ configuration in which case a biasing member, such as a spring (not shown) would be employed to tend to drive the latch into a braking position with the magnetic forces of repulsion being used to overcome this biasing force to disengage the brake. 
       FIG. 10  illustrates a reverse side of the housing  24  to that shown in  FIGS. 7 and 8 . The housing wall  68  ends in a second rim  100  which defines an open mouth of the housing. This open mouth defines the second compartment C 2  referred to with respect to  FIG. 6 . 
       FIG. 11  illustrates a section through line Z-Z shown in  FIG. 10 . The actuator  80  pivots about pivot point B and is connected from the first compartment C 1  side to the second compartment C 2  side of the housing by a drive shaft  101 . The drive shaft  101  extends from the latch actuator through the central plate  69  of the castor housing where it is connected to a rotating ear  102 . As the rotating ear  102  moves from right to left this rotates the drive shaft  101  which causes a corresponding rotation of the latch actuator  80 . The rotating ear  102  is driven by a first solenoid unit  103  and a second solenoid unit  104 . In this sense the movement of the switch is created by two opposing solenoids. Solenoids are only able to hold their position when they have power running through them. Due to the very limited availability of power in the castor it is preferable to pulse the solenoids to move from the first to a second position and then use a second solenoid to pulse back to the first position. The plunger  105  of the first solenoid is connected to the plunger  106  of the second solenoid  104  by a connector  107  which is generally U-shaped. In this sense a pulse may be driven into the coil of the first solenoid  103  to extend the plunger thus extending the connected plungers from left to right in  FIG. 10 . This causes a corresponding counter clockwise rotation of the rotating ear  102  and thus the latch actuator  80  is driven into the braking position. When a non-braking position is desired a pulse is driven into the solenoid  104  thus moving the rotating ear towards the left hand side of  FIG. 10  thus driving the latch actuator away from the latch mechanism. Having oppositely facing solenoids thus provides an electrically efficient mechanism. When more power is available only one such solenoid unit is needed. It will be appreciated that other methods of driving the latch may be envisaged. For example, one or more motors could be used. 
       FIG. 10  also illustrates how power may be generated in the castor, in particular in one of the compartments C 2 . The power generating includes use of a drive belt which extends about an outer rim surface of a central drive ring  109 . This drive ring  109  rotates as the wheels of the castor rotates as will be described hereinafter and the rotation of the drive ring is transferred to the drive belt  108 . The drive belt is also connected to a further drive ring  110  which forms a drive ring connected to a rotor of a generator unit. As the drive belt  108  is turned by rotation of the central drive ring  109 , the drive ring  10  is rotated in a corresponding manner. This rotates a rotor in the power generating unit. The rotor includes a magnetic element which is surrounded by a coil. As the magnet rotates within the coil current is induced in the wires of the coil and this current forms the basis of power for the castor. The power may be stored in a rechargeable battery (not shown) carried by the castor or may be used directly to provide power to the braking mechanism as afore-mentioned. Alternatively, the power may be transmitted through the castor up through the connecting fixing  23  into the object to which the castor is connected where the power may be utilised for a variety of different reasons. 
     It will be understood that embodiments of the present invention can use power generation on the castor as a wake-up signal for the on board (or rather on-castor) circuitry. In this way a power saving protocol can be implemented with power down taking place a predetermined time after power is generated and power on occurring when it is determined that power is being generated. 
       FIG. 12  illustrates a cross section through the castor in more detail and helps clarify how the drive belt  108  is secured to the drive ring  109 . The drive ring  109  forms a substantially circular rim to a connecting piece  120 . The connecting piece  120  includes a substantially cylindrical sleeve section  121  which includes at a first end thereof a crenulated contact surface  122  which includes raised and lower portions. The inner surface  62   1  of the wheel body  60   1  has mating crenulations including extensions and recesses. The end of the connector sleeve  121  and wheel body  60   1  can thus be interlocked so that movement of the wheel  60   1  transfers into movement of the connecting cylinder  121  of the connector  120 . A further end of the connecting cylinder  121  also includes similar crenulations which are provided to mate with corresponding crenulations on the inner surface  62   2  of the second wheel  11   2 . In this way movement of the second wheel  11   2  is transferred into rotation of the rotating sleeve  121 . A further advantage of connecting the wheels to the connector  120  in this manner is that both wheels will thereby be forced to move together. In this sense one wheel cannot move independently of the other. This has the advantage that since the braking mechanism is only applied to one wheel of the castor, the other wheel is automatically retarded. This avoids the possibility of one wheel being able to continue to turn even though the other wheel is retarded. As an alternative the wheels may be secured to the connecting piece by other techniques such as welding or gluing. 
     The cylindrical connecting sleeve  121  and its crenulations are integrally formed with the drive ring  109  which extends outwardly from the second end region of the connector  120 . The outer surface  123  of the drive ring  109  includes an indented channel in which the drive belt  108  runs. In this way the connection of the two wheels so as to move in a common manner has the advantage that if only one of the wheels is in contact with the ground and caused to rotate, that rotation will provide drive to the drive ring and thus to the drive belt. 
       FIG. 13  illustrates how the generating unit  130  can be electrically connected to the solenoids  103  and  104  and to a further electrical housing  131  which is arranged on the castor and which holds a castor PCB  132  which is connected to a sensor  50  to receive the remote signals which cause the setting or unsetting of the brake. A wireless signal from a remote transmitter is advantageously focused by a lens  133  which remains uncovered at all times when the castor is connected to a vehicle or object. The lens  133  focuses the received signal onto the sensor  50  and the PCB then controls operation of the solenoids to deploy or unset the braking member as appropriate. Power for the on-board circuitry and components is powered by the generating unit  130 . It will be understood that embodiments of the present invention can utilise more than one generating unit on a castor. Referring to  FIG. 10 , the ghost location  134  is provided to optionally house a second generating unit and it will be appreciated that if this is utilised the drive belt  108  would also be extended over the slave drive ring  110  of the further generating unit. 
     Use of the sleeve generally located around the central shaft of the wheel and having teeth which locate permanently into corresponding teeth of the wheel has a number of advantages. In particular, consistent drive can always be maintained without damaging the spindle of the stepper motor of the generating unit due to the flexible nature of the belt and the central nature of the drive through the sleeve. Use of the sleeve also means that the castor is relatively easy to assemble, service and resistant to ingress of dirt. 
       FIG. 14  illustrates how embodiments of the present invention can be utilised in a manner compatible with use of castors on shopping carts in an environment where the shopping carts are to be held in place on a travelator or escalator in a retail environment. Each wheel  140   1 ,  140   2  of the castor includes a central slot  141   1 ,  141   2  which is sized to encompass upwardly extending walls  142  on an upper surface of the travelator. When this occurs the bottom part of the housing between the wheels includes an engagement surface  143  which contacts an upper surface  144  of multiple walls. This disengages the wheels from the running surface and effectively locks the shopping cart in place whilst on the travelator. 
     Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of the words, for example “comprising” and “comprises”, means “including but not limited to”, and is not intended to (and does not) exclude other moieties, additives, components, integers or steps. 
     Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. 
     Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.