Patent Publication Number: US-8539636-B2

Title: Surface treating appliance

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of United Kingdom Application No. 0918022.5, filed Oct. 15, 2009, the entire contents of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a surface treating appliance. 
     BACKGROUND OF THE INVENTION 
     Surface treating appliances such as vacuum cleaners are well known. The majority of vacuum cleaners are either of the “upright” type or of the “cylinder” type (also referred to canister or barrel machines in some countries). An upright vacuum cleaner typically comprises a main body containing dirt and dust separating apparatus, a pair of wheels mounted on the main body for maneuvering the vacuum cleaner over a floor surface to be cleaned, and a cleaner head mounted on the main body. The cleaner head has a downwardly directed suction opening which faces the floor surface. The vacuum cleaner further comprises a motor-driven fan unit for drawing dirt-bearing air through the suction opening. The dirt-bearing air is conveyed to the separating apparatus so that dirt and dust can be separated from the air before the air is expelled to the atmosphere. The separating apparatus can take the form of a filter, a filter bag or, as is known, a cyclonic arrangement. 
     In use, a user reclines the main body of the vacuum cleaner towards the floor surface, and then sequentially pushes and pulls a handle which is attached to the main body of the cleaner to maneuver the vacuum cleaner over the floor surface. The dirt-bearing air flow drawn through the suction opening by the fan unit is conducted to the separating apparatus by a first air flow duct. When dirt and dust has been separated from the air flow, the air flow is conducted to a clean air outlet by a second air flow duct. One or more filters may be provided between the separating apparatus and the clean air outlet. 
     An example of an upright vacuum cleaner with improved maneuverability is shown in WO2009/030885. This upright vacuum cleaner comprises a barrel-shaped rolling assembly located at the lower end of the main body for engaging the floor surface to be cleaned, and which rolls relative to the main body for allowing the main body to be rolled over the floor surface using the handle. The rolling assembly is rotatably connected between a pair of ducts which each extend to one side of the main body. The main body of the vacuum cleaner houses separating apparatus for separating dirt from a dirt-bearing air flow drawn into the cleaner head. To increase the stability of the vacuum cleaner, and to make efficient use of the space within the rolling assembly, the motor-driven fan unit for drawing dirt-bearing air into the suction opening is located within the rolling assembly. 
     A yoke extending about the external periphery of the rolling assembly connects the cleaner head to the main body. The yoke is pivotably connected between the ducts to allow the main body to be reclined relative to the yoke between an upright position and a reclined position for maneuvering the vacuum cleaner over a floor surface. The pivot axis of the yoke is substantially co-linear with the rotational axis of the rolling assembly. The cleaner head is connected to the forward, central part of the yoke by a joint which permits the yoke to be rotated relative to the cleaner head. These connections allow the main body to be rotated about its longitudinal axis, in the manner of a corkscrew, while the cleaner head remains in contact with the floor surface. As a result the cleaner head may be pointed in a new direction as the main body is rotated about its longitudinal axis. As the main body is pushed over the floor surface using the handle, the vacuum cleaner moves forward along the direction in which the cleaner head is pointed, thereby allowing the vacuum cleaner to be smoothly and easily maneuvered over the floor surface. 
     The vacuum cleaner comprises a stand for supporting the main body in its upright position, and which is moveable relative to the main body to a retracted position to allow the vacuum cleaner to be maneuvered over the floor surface when in its reclined position. The stand is moveable from the supporting position to the retracted position automatically in response to a force being applied to the main body to recline the main body from its upright position. The stand comprises a pair of wheels on to which the vacuum cleaner may be reclined to allow the vacuum cleaner to be transported rapidly, for example, between rooms with the stand in its supporting position. 
     The vacuum cleaner also comprises an upright lock for locking the cleaner head in a fixed position with respect to the main body when the stand is in the supporting position. The upright lock is automatically released when the main body is moved to a reclined position. The upright lock allows the vacuum cleaner to be reclined on to the wheels of the stand and moved without the cleaner head falling towards the floor. The upright lock may be arranged to provide a resistance to the movement of the stand to its retracted position, thereby reducing the risk of accidental movement of the stand to its retracted position. 
     SUMMARY OF THE INVENTION 
     The present invention provides an upright surface treating appliance comprising a main body comprising a user operable handle, a stand moveable relative to the main body between a supporting position for supporting the main body in an upright position, and a retracted position, the stand comprising at least one surface-engaging rolling member for allowing the appliance to be rolled along a surface using the handle when, with the stand in its supporting position, the body is reclined rearwardly from its upright position, and a stand retaining mechanism for releasably retaining the stand in the supporting position and from which the stand is releasable upon application of a force to the main body, the stand retaining mechanism comprising means for increasing the force required to release the stand when the body is reclined rearwardly from its upright position. 
     The provision of means for increasing the force required to release the stand when the body is reclined rearwardly from its upright position can further reduce the risk of the stand being released accidentally from the supporting position when the main body is reclined and rolled along a surface using the rolling member of the stand. 
     The means for increasing the force required to release the stand is preferably arranged to increase the force required to release the stand depending on the angle by which the body is reclined rearwardly from its upright position. In a preferred embodiment, the means for increasing the force required to release the stand is arranged to increase the force required to release the stand when the body is reclined rearwardly from its upright position by an angle of at least 10°, and preferably at least 20°. 
     The stand retaining mechanism preferably comprises a stand locking member which is moveable relative to the main body from a first position to a second position to release the stand. The stand locking member is preferably arranged to engage a part of the stand to retain the stand in its supporting position. For example, the stand locking member may comprise a surface for engaging part of the stand. This surface may be conveniently located on a protrusion extending outwardly from the side of the stand locking member. This surface, or other engaging means of the stand locking member, is preferably arranged to allow relative movement between said part of the stand and the stand locking member depending on the magnitude of a torque applied to one of the stand locking member and the stand. Where the engaging means comprises a surface of the stand locking member, the surface is preferably inclined or otherwise shaped to permit the part of the stand to move along the surface depending on the magnitude of a torque applied to the stand by the yoke. This can provide for a relatively smooth release of the stand from its supporting position. 
     The part of the stand is preferably located on one of the two supporting arms of the stand. In a preferred embodiment, the part of the stand comprises a pin which extends outwardly from one of two supporting arms of the stand to engage a surface of the stand locking member. 
     The means for increasing the force required to release the stand preferably comprises a moveable member which is moveable from a stowed position to a deployed position, in which it is located within a path along which the locking member moves from its first position to its second position, depending on the angle by which the body is reclined rearwardly from its upright position. The moveable member may be moveable mechanically between its stowed position and its deployed position, but is preferably moveable between its stowed position and its deployed position under gravity. In this latter case, the moveable member may comprise a rolling element which rolls between its stowed position and its deployed position depending on the angle by which the body is reclined rearwardly from its upright position. The moveable member may be moveable between its stowed and deployed positions along a track which, when the main body is in its upright position, is inclined so that the deployed position is located above the stowed position. This track is preferably inclined by an angle of at least 20° to the horizontal when the main body is in its upright position. 
     The means for increasing the force required to release the stand preferably comprises resilient biasing means towards which the moveable member is urged by the locking member as the locking member moves to its second position when the moveable member is in its deployed position. The resilient biasing means preferably comprises a spring, which may be in the form of a helical compression spring or a leaf spring and which is arranged to resist the movement of the moveable member theretowards and so increase the force required to move the stand locking member. The locking member preferably comprises a fin having a curved surface for engaging the moveable member when the moveable member is in its deployed position. The curved surface of the fin can direct the moveable member gradually towards the resilient biasing means with movement of the stand locking member. 
     In addition to the resilient biasing means, the stand retaining mechanism preferably further comprises biasing means for applying a force to the locking member which resists movement thereof from its first position. This can provide a resistance to the release of the stand from its supporting position when the main body is in its upright position. The biasing means is preferably in the form of a spring, and is preferably arranged to apply a force to one end of the locking member. The stand locking member is preferably pivotably moveable between its first and second positions about a pivot axis, with the pivot axis being preferably located at or towards an end of the locking member. In this case, the biasing means is preferably arranged to act on the other end of the locking member to resist its movement about the pivot axis. 
     The stand retaining mechanism is preferably carried by the main body, and may be located within a housing of the main body. To reduce the number of components forming the main body, the stand retaining mechanism may be conveniently carried by a casing housing a fan unit of the appliance, which may be located between wheels of the appliance to lower the center of gravity of the appliance. 
     The appliance preferably comprises separating apparatus for separating dirt from a fluid flow. The separating apparatus is preferably in the form of a cyclonic separating apparatus having at least one cyclone, and which preferably comprises a chamber for collecting dirt separated from the air flow. Other forms of separator or separating apparatus can be used and examples of suitable separator technology include a centrifugal separator, a filter bag, a porous container or a liquid-based separator. 
     The term “surface treating appliance” is intended to have a broad meaning, and includes a wide range of machines having a head for travelling over a surface to clean or treat the surface in some manner. It includes, inter alia, machines which apply suction to the surface so as to draw material from it, such as vacuum cleaners (dry, wet and wet/dry), as well as machines which apply material to the surface, such as polishing/waxing machines, pressure washing machines, ground marking machines and shampooing machines. It also includes lawn mowers and other cutting machines. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a front perspective view, from the left, of an upright vacuum cleaner; 
         FIG. 2   a  is a right side view of the vacuum cleaner, with the main body of the vacuum cleaner in an upright position, and  FIG. 2   b  is a right side view of the vacuum cleaner, with the main body in a fully reclined position; 
         FIG. 3  is a rear view of the vacuum cleaner; 
         FIG. 4  is a bottom view of the vacuum cleaner; 
         FIG. 5   a  is a front vertical cross-sectional view through the center of a spherical volume V defined by the wheels of the support assembly of the vacuum cleaner, and  FIG. 5   b  is a section along line K-K in  FIG. 5   a , but with the motor inlet duct omitted; 
         FIG. 6   a  is a front perspective view, from the left, of the yoke of the vacuum cleaner, and  FIG. 6   b  is a front perspective view, from the right, of the yoke; 
         FIGS. 7   a ,  7   b  and  7   c  are a sequence of left side views of the motor casing and the stand retaining mechanism of the vacuum cleaner, illustrating the release of the stand from the retaining mechanism as the main body is reclined, and  FIG. 7   d  is a similar side view illustrating the movement of the stand retaining mechanism as the main body is returned to its upright position; 
         FIG. 8  is a rear perspective view, from the left, of the cleaner head of the vacuum cleaner; 
         FIG. 9   a  is a perspective view of a change over arrangement of the vacuum cleaner, and  FIG. 9   b  is an exploded view of the change over arrangement; 
         FIG. 10   a  is a vertical cross-sectional view of the change over arrangement when mounted on the motor casing, and with the change over arrangement in a first angular position relative to the motor casing, and  FIG. 10   b  is a similar cross-sectional view as  FIG. 10   a  but with the change over arrangement in a second angular position relative to the motor casing; 
         FIG. 11   a  is a front perspective view, from the left, of part of the vacuum cleaner, with the main body in its upright position and the separating apparatus removed,  FIG. 11   b  is a similar view as  FIG. 11   a  but with the upper yoke section omitted,  FIG. 11   c  is a similar view as  FIG. 11   a  but with the main body in a reclined position,  FIG. 11   d  is similar view as  FIG. 11   c  but with the upper yoke section omitted, and  FIG. 11   e  is a vertical cross-sectional view illustrating the position of the shield relative to the motor casing; 
         FIG. 12  is a front perspective view, from the right, of the motor casing and the motor inlet duct of the vacuum cleaner; 
         FIG. 13  is a perspective view of the stand of the vacuum cleaner; 
         FIG. 14   a  is an exploded view of the lower housing section of the yoke, the motor casing and the components of a retaining mechanism for locking the angular position of the cleaner head relative to the yoke, and  FIGS. 14   b  to  14   d  are left side cross-sectional views of the components of  FIG. 14   a  when assembled and illustrating the movement of a locking member of the retaining mechanism from a deployed position to a stowed position; 
         FIGS. 15   a  to  15   d  are a series of right side views of the vacuum cleaner, with various parts of the vacuum cleaner omitted, illustrating the movement of the stand between a supporting position to a retracted position as the main body is reclined, and  FIG. 15   e  is a similar side view during the return of the main body to its upright position; 
         FIGS. 16   a  to  16   d  are a series of left side views of the motor casing of the vacuum cleaner, illustrating the movement of the change over arrangement from the first angular position to the second angular position; 
         FIGS. 17   a  and  17   b  are similar views as  FIGS. 7   a  and  7   b  when the vacuum cleaner is reclined by around 45° about the stabilizer wheels of the support; and 
         FIG. 18  illustrates schematically the release of the cleaner head by the cleaner head retaining mechanism when the cleaner head is subjected to a rotational force relative to the yoke. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 to 4  illustrate an upright surface treating appliance, which is in the form of an upright vacuum cleaner. The vacuum cleaner  10  comprises a cleaner head  12 , a main body  14  and a support assembly  16 . In the  FIGS. 1 ,  2   a ,  3  and  4 , the main body  14  of the vacuum cleaner  10  is in an upright position relative to the cleaner head  12 , whereas in  FIG. 2   b  the main body  14  is in a fully reclined position relative to the cleaner head  12 . 
     The cleaner head  12  comprises a housing  18  and a lower plate, or sole plate  20 , connected to the housing  18 . The sole plate  20  comprises a suction opening  22  through which a dirt-bearing air flow enters the cleaner head  12 . The sole plate  20  has a bottom surface which, in use, faces a floor surface to be cleaned, and which comprises working edges for engaging fibers of a carpeted floor surface. The housing  18  defines a suction passage extending from the suction opening  22  to a fluid outlet  24  located at the rear of the housing  18 . The fluid outlet  24  is dimensioned to connect to a yoke  26  for connecting the cleaner head  12  to the main body  14  of the vacuum cleaner  10 . The yoke  26  is described in more detail below. The lower surface of the cleaner head  12  can include small rollers  28  to ease movement of the cleaner head  12  across the floor surface. 
     The cleaner head  12  comprises an agitator for agitating dirt and dust located on the floor surface. In this example the agitator comprises a rotatable brush bar assembly  30  which is mounted within a brush bar chamber  32  of the housing  18 . The brush bar assembly  30  is driven by a motor  33  (shown in  FIG. 5   b ) located in a motor housing  34  of the housing  18 . The brush bar assembly  30  is connected to the motor  33  by a drive mechanism located within a drive mechanism housing  36  so that the drive mechanism is isolated from the air passing through the suction passage. In this example, the drive mechanism comprises a drive belt for connecting the motor  33  to the brush bar assembly  30 . To provide a balanced cleaner head in which the weight of the motor  33  is spread evenly about the bottom surface of the sole plate  20 , the motor housing  34  is located centrally above, and rearward of, the brush bar chamber  32 . Consequently, the drive mechanism housing  36  extends into the brush bar chamber  32  between the side walls of the brush bar chamber  32 . 
     It will be appreciated that the brush bar assembly  30  can be driven in other ways, such as by a turbine which is driven by an incoming or exhaust air flow, or by a coupling to the motor which is also used to generate the air flow through the vacuum cleaner  10 . The coupling between the motor  33  and brush bar assembly  30  can alternatively be via a geared coupling. The brush bar assembly  30  can be removed entirely so that the vacuum cleaner  10  relies entirely on suction or by some other form of agitation of the floor surface. For other types of surface treating machines, the cleaner head  12  can include appropriate means for treating the floor surface, such as a polishing pad, a liquid or a wax dispensing nozzle. 
     The main body  14  is connected to a support assembly  16  for allowing the vacuum cleaner  10  to be rolled along a floor surface. The support assembly  16  comprises a pair of wheels  40 ,  42 . Each wheel  40 ,  42  is dome-shaped, and has an outer surface of substantially spherical curvature. Annular ridges  41  may be provided on the outer surface of each wheel  40 ,  42  to improve grip on the floor surface. These ridges  41  may be integral with the outer surface of each wheel  40 ,  42  or, as illustrated, may be separates members adhered or otherwise attached to the outer surface of each wheel  40 ,  42 . Alternatively, or additionally, a non-slip texture or coating may be provided on the outer surface of the wheels  40 ,  42  to aid grip on slippery floor surfaces such as hard, shiny or wet floors. 
     As shown most clearly in  FIGS. 5   a  and  5   b , the outer surfaces of the wheels  40 ,  42  (that is, excluding the optional ridges  41 ) at least partially delimit a substantially spherical volume V. The rotational axes R 1 , R 2  of the wheels  40 ,  42  are inclined downwardly relative to an axis A passing horizontally through the center of the spherical volume V. Consequently, the rims  40   a ,  42   a  of the wheels  40 ,  42  provide the lowest extremity of the wheels  40 ,  42  for making contact with a floor surface  43 . A ridge  41  may be formed or otherwise provided at each rim  40   a ,  42   a . In this example, the angle θ of the inclination of the rotational axes R 1 , R 2  is around 8°, but the angle θ may take any desired value. 
     The wheels  40 ,  42  are rotatably connected to the yoke  26  that connects the cleaner head  12  to the main body  14  of the vacuum cleaner  10 , and so the yoke  26  may be considered to form part of the support assembly  16 .  FIGS. 6   a  and  6   b  illustrate front perspective views of the yoke  26 . In this example, to facilitate manufacture the yoke  26  comprises a lower yoke section  44  and an upper yoke section  46  connected to the lower yoke section  44 . However, the yoke  26  may comprise any number of connected sections, or a single section. The lower yoke section  44  comprises two yoke arms  48 ,  50 . A wheel axle  52 ,  54  extends outwardly and downwardly from each yoke arm  48 ,  50 . The longitudinal axis of each wheel axle  52 ,  54  defines a respective one of the rotational axes R 1 , R 2  of the wheels  40 ,  42 . Each wheel  40 ,  42  is rotatably connected to a respective wheel axle  52 ,  54  by a respective wheel bearing arrangement  56 ,  58 . End caps  60 ,  62  mounted on the wheels  40 ,  42  inhibit the ingress of dirt into the wheel bearing arrangements  56 ,  58 , and serve to connect the wheels  40 ,  42  to the axles  52 ,  54 . 
     The lower yoke section  44  also comprises an inlet section  64  of an internal duct, indicated at  66  in  FIG. 10   a , for receiving a dirt-bearing air flow from the cleaner head  12 . The internal duct  66  passes through the spherical volume V delimited by the wheels  40 ,  42  of the support assembly  16 . The fluid outlet  24  of the cleaner head  12  is connected to the internal duct inlet section  64  in such a manner that allows the fluid outlet  24  to rotate about the internal duct inlet section  64 , and thus allows the cleaner head  12  to rotate relative to the main body  14  and the support assembly  16 , as the vacuum cleaner  10  is maneuvered over a floor surface during floor cleaning. For example, with reference to  FIG. 8  the fluid outlet  24  of the cleaner head  12  comprises at least one formation  65  for receiving the internal duct inlet section  64 . The fluid outlet  24  of the cleaner head  12  may be retained on the internal duct inlet section  64  by a snap-fit connection. Alternatively, or additionally, a C-clip or other retaining mechanism may be used to releasably retain the fluid outlet  24  of the cleaner head  12  on the internal duct inlet section  64 . 
     With reference again to  FIG. 10   a , the internal duct  66  further comprises an internal duct outlet section  68  connected to the main body  14  of the vacuum cleaner  10 , and a flexible hose  70  which extends between the wheels  40 ,  42  of the support assembly  16  to convey a dirt-bearing air flow to the internal duct outlet section  68 . The internal duct outlet section  68  is integral with a first motor casing section  72  of a motor casing  74  housing a motor-driven fan unit (indicated generally at  76  in  FIG. 5   a ) for drawing the airflow through the vacuum cleaner  10 . As also shown in, for example  FIGS. 5   a  and  12 , the motor casing  74  comprises a second motor casing section  78  which is connected to the first motor casing section  72 , and which defines with the first motor casing section  72  an airflow path through the motor casing  74 . The axis A passes through the motor casing  74  so that the central axis of the fan unit  76 , about which an impeller of the fan unit rotates, is co-linear with the axis A. 
     A number of parts of the main body  14  of the vacuum cleaner  10  are also integral with the first motor casing section  72 , which is illustrated in  FIG. 7   a . One of these parts is an outlet section  80  of a hose and wand assembly  82  of the main body  14 . The hose and wand assembly outlet section  80  has an air outlet  80   a  which is angularly spaced from the air outlet  68   a  of the internal duct outlet section  68 . With reference again to  FIGS. 1 ,  2   a  and  3 , the hose and wand assembly  82  comprises a wand  84  which is releasably connected to the spine  86  of the main body  14 , and a flexible hose  88  connected at one end thereof to the wand  84  and at the other end thereof to the hose and wand assembly outlet section  80 . The spine  86  of the main body  14  preferably has a concave rear surface so that the wand  84  and the hose  88  may be partially surrounded by the spine  86  when the wand  84  is connected to the main body  14 . Cleaning tools  90 ,  92  for selective connection to the distal end of the wand  84  may be detachably mounted on the spine  86  of the main body  14 , or the distal end of the hose  88 . 
     The motor casing  74  is connected to the base of the spine  86  of the main body  14 . The spine  86  of the main body  14  comprises a user-operable handle  94  at the end thereof remote from the support assembly  16 . An end cap  95  is pivotably connected to the upper surface of the handle  94  for covering the distal end of the wand  84  when the wand  84  is connected to the spine  86  to inhibit user contact with this end of the wand  84  when the wand  84  is connected to the spine  86 . A power lead  96  for supplying electrical power to the vacuum cleaner  10  extends into the spine  86  though an aperture formed in the spine  86 . Electrical connectors (not shown) extend downwardly within the spine  86  and into the spherical volume V delimited by the wheels  40 ,  42  to supply power to the fan unit  76 . A first user-operable switch  97   a  is provided on the spine  86  and is arranged so that, when it is depressed, the fan unit  76  is energized. The fan unit  76  may also be de-energized by depressing this first switch  97   a . A second user-operable switch  97   b  is provided adjacent the first switch  97   a . The second switch  97   b  enables a user to control the activation of the brush bar assembly  30  when the main body  14  of the vacuum cleaner  10  is reclined away from its upright position, as described in more detail below. An electrical connector  98   a  for supplying electrical power to the motor  33  of the brush bar assembly  30  is exposed by an aperture  99  formed in the upper yoke section  46 . The electrical connector  98   a  is arranged to connect with an electrical connector  98   b  extending rearwardly from the cleaner head  12 . As described in more detail below, power is not supplied to the motor  33  of the brush bar assembly  30  when the main body  14  of the vacuum cleaner  10  is in its upright position. 
     The main body  14  further comprises separating apparatus  100  for removing dirt, dust and/or other debris from a dirt-bearing airflow which is drawn into the vacuum cleaner  10 . The separating apparatus  100  can take many forms. In this example the separating apparatus  100  comprises cyclonic separating apparatus, in which the dirt and dust is spun from the airflow. As is known, the separating apparatus  100  can comprise two or more stages of cyclone separation arranged in series with one another. In this example, a first stage  102  comprises a cylindrical-walled chamber and a second stage  104  comprises a tapering, substantially frusto-conically shaped, chamber or, as illustrated, a set of these tapering chambers arranged in parallel with one another. As illustrated in  FIGS. 2   a  and  3 , a dirt-bearing airflow is directed tangentially into the upper part of the first stage  102  of the separating apparatus  100  by a separating apparatus inlet duct  106 . The separating apparatus inlet duct  106  extends alongside, and is connected to, the spine  86  of the main body  14 . 
     Returning again to  FIG. 7   a , the separating apparatus inlet duct  106  is connected to an inlet duct inlet section  108  which also forms an integral part of the first motor casing section  72 . The inlet duct inlet section  108  has an air inlet  108   a  which is angularly spaced from both the air outlet  68   a  and the air outlet  80   a  along a circular path P defined by the first motor casing section  72 . A changeover valve  110  connects the air inlet  108   a  to a selected one of the air outlet  68   a  and the air outlet  80   a . The change over arrangement  110  is illustrated in  FIGS. 9   a  and  9   b . The changeover valve  110  comprises an elbow-shaped valve member  112  having a first port  114  and a second port  116  located at opposite ends of the valve member  112 , with the valve member  112  defining an airflow path between the ports  114 ,  116 . Each port  114 ,  116  is surrounded by a respective flexible seal  118 ,  120 . 
     The valve member  112  comprises a hub  122  which extends outwardly from midway between the ports  114 ,  116 . The hub  122  has an inner periphery  123 . The hub  122  is mounted on a boss  124 . The boss  124  is also integral with the first motor casing section  72  and, as illustrated in  FIG. 7   a , is located at the center of the circular path P. The first motor casing section  72  thus provides a valve body of the changeover valve  110 , within which valve body the valve member  112  is rotatable. 
     The boss  124  has a longitudinal axis L passing through the center of the circular path P, and which is substantially parallel to the axis A passing through the motor casing  74 . The outer surface of the boss  124  is profiled so that the boss  124  is generally in the shape of a tapered triangular prism, which tapers towards the tip  124   a  of the boss  124  and which has rounded edges. The size and shape of inner surface  123  of the hub  122  is substantially the same as those of the outer surface of the boss  124  so that the inner surface  123  of the hub  122  lies against the outer surface of the boss  124  when the valve member  112  is mounted on the boss  124 . 
     The valve member  112  is rotatable about the longitudinal axis L of the boss  124  between a first angular position and a second angular position relative to the motor casing  74 . In the first angular position, shown in  FIG. 10   a , the airflow path defined by the valve member  112  connects the hose and wand assembly  82  to the separating apparatus inlet duct  106  so that air is drawn into the vacuum cleaner  10  through the distal end of the wand  84 . This is the position adopted by the valve member  112  when the main body  14  of the vacuum cleaner  10  is in its upright position. The conforming profiles of the inner surface  123  of the hub  122  and the outer surface of the boss  124  means that the valve member  112  can be accurately aligned, both angularly and axially, relative to the motor casing  74  so that, in this first position of the valve member  112 , the first port  114  is seated over the air outlet  80   a  so that the seal  118  is in sealing contact with the hose and wand assembly outlet section  80 , and the second port  116  is seated over the air inlet  108   a  so that the seal  120  is in sealing contact with the inlet duct inlet section  108 . In this first position of the valve member  112 , the body of the valve member  112  serves to isolate the cleaner head  12  and the internal duct  66  from the fan unit  76  so that substantially no air is drawn into the vacuum cleaner  10  through the suction opening  22  of the cleaner head  12 . 
     In the second angular position, as shown in  FIG. 10   b , the airflow path connects the internal duct  66  to the separating apparatus inlet duct  106  so that air is drawn into the vacuum cleaner  10  through the cleaner head  12 . This is the position adopted by the valve member  112  when the main body  14  is in a reclined position for floor cleaning. In this second position of the valve member  112 , the body of the valve member  112  serves to isolate the hose and wand assembly  82  from the fan unit  76  so that substantially no air is drawn into the vacuum cleaner  10  through the distal end of the wand  84 . The mechanism for moving the valve member  112  between the first and second positions, and its actuation, is described in more detail below. 
     Returning to  FIG. 5   a , the main body  14  comprises a motor inlet duct  130  for receiving an airflow exhausted from the separating apparatus  100  and for conveying this airflow to the motor casing  74 . As previously discussed, the fan unit  76  is located between the wheels  40 ,  42  of the support assembly  16 , and so the motor inlet duct  130  extends between the wheels  40 ,  42  of the support assembly  16  to convey the airflow from the separating apparatus  100  to the fan unit  76 . 
     In this example the airflow is exhausted from the separating apparatus  100  through an air outlet formed in the bottom surface of the separating apparatus  100 . The airflow is conveyed from the second stage  104  of cyclonic separation to the air outlet of the separating apparatus  100  by a duct passing through, and co-axial with, the first stage  102  of cyclonic separation. In view of this, the motor inlet duct  130  can be substantially fully accommodated within the spherical volume V delimited by the wheels  40 ,  42  of the support assembly  16 . With reference now to  FIG. 11   a , the upper yoke section  46  has an external surface  46   a  which is located between the wheels  40 ,  42 , and which has a curvature which is substantially the same as that of the outer surfaces of the wheels  40 ,  42 . The upper yoke section  46  thus serves to further delimit the spherical volume V, and, in combination with the wheels  40 ,  42  provides a substantially uninterrupted spherical appearance to the front of the support assembly  16 . As shown also in  FIGS. 6   a  and  6   b , the upper yoke section  46  comprises an aperture  132  in the form of a slot through which a motor inlet duct inlet section  134  protrudes so that the air inlet of the motor inlet duct  130  is located beyond the external surface  46   a  of the upper yoke section  46 . The motor inlet duct inlet section  134  comprises a spigot  136  upon which the base of the separating apparatus  100  is mounted so that the air inlet of the motor inlet duct  130  is substantially co-axial with the air outlet of the separating apparatus  100 . 
     A manually-operable catch  140  is located on the separating apparatus  100  for releasably retaining the separating apparatus  100  on the spine  86  of the main body  14 . The catch  140  may form part of an actuator for releasing the separating apparatus  100  from the spine  86  of the main body  14 . The catch  140  is arranged to engage with a catch face  142  located on the spine  86  of the main body  14 . In this example, the base of the separating apparatus  100  is movable between a closed position and an open position in which dust and dirt can be removed from the separating apparatus  100 , and the catch  140  may be arranged to release the base from its closed position when the separating apparatus  100  is removed from the main body  14 . Details of a suitable catch are described in WO2008/135708, the contents of which are incorporated herein by reference. A mesh or grille  144  may be located within the motor inlet duct inlet section  134 . The mesh  144  traps debris which has entered the motor inlet duct  130  while the separating apparatus  100  is removed from the main body  14 , and so prevents that debris from being conveyed to the motor casing  74  when the fan unit  76  is activated, thereby protecting the fan unit  76  from large foreign object ingress. 
     The separating apparatus inlet duct  106  comprises a hinged flap  107  which is manually accessible when the separating apparatus  100  is removed from the main body  14  to allow the user to remove any items which may have entered the separating apparatus inlet duct  106  while the separating apparatus  100  is removed from the main body  14 , and to allow the user to remove blockages from the changeover valve  110 . 
     The nature of the separating apparatus  100  is not material to the present invention and the separation of dust from the airflow could equally be carried out using other means such as a conventional bag-type filter, a porous box filter or some other form of separating apparatus. For embodiments of the apparatus which are not vacuum cleaners, the main body can house equipment which is appropriate to the task performed by the machine. For example, for a floor polishing machine the main body can house a tank for storing liquid wax. 
     With reference now to  FIGS. 5   a  and  12 , to facilitate manufacturing the motor inlet duct  130  comprises a base section  146  connected to the second motor casing section  78 , and a cover section  148  connected to the base section  146 . Again, the motor inlet duct  130  may be formed from any number of sections. The base section  146  and the cover section  148  together define an airflow path extending from the motor inlet duct inlet section  134  to an air inlet  150  of the second motor casing section  78 . The yoke arm  50  is pivotably connected to the cover section  148  of the motor inlet duct  130 . The outer surface of the cover section  148  comprises a circular flange  152 . The circular flange  152  is orthogonal to the axis A passing through the center of the spherical volume V, and arranged so the axis A also passes through the center of the circular flange  152 . The inner surface of the yoke arm  50  comprises a semi-circular groove  154  for receiving the lower half of the circular flange  152 . A yoke arm connector  156  is located over the upper end of the yoke arm  50  to secure the yoke arm  50  to the cover section  148  while permitting the yoke arm  50  to pivot relative to the cover section  148 , and thus relative to the motor casing  74 , about axis A. The yoke arm connector  156  comprises a semi-circular groove  158  for receiving the upper half of the circular flange  152 . 
     The yoke arm  48  is rotatably connected to the first motor casing section  72  by an annular arm bearing  160 . The arm bearing  160  is illustrated in  FIGS. 5   a  and  14   a . The arm bearing  160  is connected to the outer surface of the first motor casing section  72 , for example by means of bolts inserted through a number of apertures  162  located on the outer periphery of the arm bearing  160 . 
     The arm bearing  160  is connected to the first motor casing section  72  so that it is orthogonal to the axis A, and so that the axis A passes through the center of the arm bearing  160 . The outer periphery of the arm bearing  160  comprises a first annular groove  163   a . The upper end of the yoke arm  48  is located over the arm bearing  160 . The inner surface of the yoke arm  48  comprises a second annular groove  163   b  which surrounds the first annular groove  163   a  when the yoke arm  48  is located over the arm bearing  160 . A C-clip  164  is housed between the grooves  163   a ,  163   b  to retain the yoke arm  48  on the bearing  160  while permitting the yoke arm  48  to pivot relative to the arm bearing  160 , and thus the motor casing  74 , about axis A. 
     Returning to  FIG. 7   a , the first motor casing section  72  comprises a plurality of motor casing air outlets  166  through which the airflow is exhausted from the motor casing  74 . This airflow is subsequently exhausted from the vacuum cleaner  10  through a plurality of wheel air outlets  168  formed in the wheel  40  located adjacent the first motor casing section  72 , and which are located so as to present minimum environmental turbulence outside of the vacuum cleaner  10 . 
     As is known, one or more filters are positioned in the airflow path downstream of the first and second stages  102 ,  104  of cyclonic separation. These filters remove any fine particles of dust which have not already been removed from the airflow by the stages  102 ,  104  of cyclonic separation. In this example a first filter, referred to as a pre-motor filter, is located upstream of the fan unit  76  and a second filter, referred to as a post-motor filter, is located downstream from the fan unit  76 . Where the motor for driving the fan unit  76  has carbon brushes, the post-motor filter also serves to trap any carbon particles emitted from the brushes. 
     The pre-motor filter may be located within the separating apparatus  100 , between the second stage  104  of cyclonic separation and the air outlet from the separating apparatus  100 . In this case, the pre-motor filter may be accessed by the user when the separating apparatus  100  has been removed from the main body  14 , for example by disconnecting the first stage  102  from the second stage  104 , or when the base of the separating apparatus  100  has been released to its open position. Alternatively, the pre-motor filter may be located within a dedicated housing formed in the motor inlet duct  130 . In this case, the pre-motor filter may be accessed by removing the wheel  42  located adjacent the cover section  148  of the motor inlet duct  130 , and opening a hatch formed in the cover section  148 . 
     The post-motor filter, indicated at  170  in  FIG. 5   a , is located between the first motor casing section  72  and the wheel  40  so that the airflow passes through the filter  170  as it flows from the motor casing air outlets  166  to the wheel air outlets  168 . The post-motor filter  170  is in the form of a dome-shaped pleated filter. Details of a suitable pleated filter are described in our application no. PCT/GB2009/001234, the contents of which are incorporated herein by reference. The filter  170  surrounds the axle  52  upon which the wheel  40  is rotatably mounted. The filter  170  is located within a frame  172  which is releasably connected to a filter frame mount  174  by a manually releasable catch  175 . The filter frame mount  174  may be conveniently connected to the first motor casing section  72  by means of the bolts used to connect the arm bearing  160  to the first motor casing section  72 . The filter frame mount  174  comprises a pair of apertured sections  176  which are inserted within apertures  178  formed in the first motor casing section  72  to ensure that the filter frame mount  174  is correctly aligned with the first motor casing section  72 . These sections  176  also assist in suppressing noise generated by the motor of the fan unit  76 . An annular seal  179   a  is located between the outer surface of the first motor casing section  72  and the filter frame mount  174  to inhibit the leakage of air therebetween. Additional annular seals  179   b ,  179   c  are provided between the filter frame mount  174  and the frame  172 . 
     The filter  170  may be periodically removed from the vacuum cleaner  10  to allow the filter  170  to be cleaned. The filter  170  is accessed by removing the wheel  40  of the support assembly  16 . This wheel  40  may be removed, for example, by the user first twisting the end cap  60  to disengage a wheel mounting sleeve  41  located over the end of the axle  52 . As illustrated in  FIG. 5   a , the wheel mounting sleeve  41  may be located between the axle  52  and the wheel bearing arrangement  56 . The wheel  40  may then be pulled from the axle  52  by the user so that the wheel mounting sleeve  41 , wheel bearing arrangement  56  and end cap  60  come away from the axle  52  with the wheel  40 . The catch  175  may then be manually depressed to release the frame  172  from the filter frame mount  174  to allow the filter  170  to be removed from the vacuum cleaner  10 . 
     The support assembly  16  further comprises a stand  180  for supporting the main body  14  when it is in its upright position. With reference to  FIG. 13 , the stand  180  comprises two supporting legs  182 , each supporting leg  182  having a stabilizer wheel  184  rotatably attached to an axle extending outwardly from the lower end of the supporting leg  182 . 
     The upper end of each supporting leg  182  is attached to the lower end of a relatively short body  188  of the stand  180 . As illustrated in  FIG. 4 , the body  188  of the stand  180  protrudes outwardly from between the wheels  40 ,  42  of the support assembly  16 , and so protrudes outwardly from the spherical volume V. The stand  180  further comprises two supporting arms  190 ,  192  extending outwardly and upwardly from the upper end of the body  188  of the stand  180 . The supporting arms  190 ,  192  of the stand  180  are located within the spherical volume V, and so cannot be seen in  FIGS. 1 to 4 . The upper end of each supporting arm  190 ,  192  comprises a respective annular connector  194 ,  196  for rotatably connecting the stand  180  to the motor casing  74 . The annular connector  194  is located over a cylindrical drum  198  formed on the outer surface of the first section  72  of the motor casing  74 , and which is also illustrated in  FIG. 15   a . The annular connector  194  is retained on the motor casing  74  by the arm bearing  160 . The annular connector  196  is located over the motor casing air inlet  150 . An annular bearing  199  is positioned between the second motor casing  78  and the annular connector  196  to enable the annular connector  196  to rotate relative to the motor casing  74 , and to retain the annular connector  196  on the motor casing  74 . 
     Each of the annular connectors  194 ,  196  is rotatably connected to the motor casing  74  so that the annular connectors  194 ,  196  are orthogonal to the axis A, and so that the axis A passes through the centers of the annular connectors  194 ,  196 . As a result, the stand  180  is pivotable relative to the motor casing  74  about the axis A. 
     The stand  180  is pivotable relative to the motor casing  74 , and therefore relative to the main body  14  of the vacuum cleaner  10 , between a lowered, supporting position for supporting the main body  14  when it is in its upright position, and a raised, retracted position so that the stand  180  does not interfere with the maneuvering of the vacuum cleaner  10  during floor cleaning. Returning to  FIG. 13 , an over-center spring mechanism is connected between the motor casing  74  and the stand  180  to assist in moving the stand  180  between its supporting and retracted positions. Depending on the relative angular positions of the motor casing  74  and the stand  180 , the over-center spring mechanism either urges the stand  180  towards its supporting position, or urges the stand  180  towards its retracted position. The over-center spring mechanism comprises a helical torsion spring  200  having a first end  202  connected to the supporting arm  192  of the stand  180  and a second end  204  connected to the second motor casing section  78 . The biasing force of the torsion spring  200  urges apart the ends  202 ,  204  of the torsion spring  200 . 
     As discussed in more detail below, when the main body  14  is in its upright position the wheels  40 ,  42  of the stand assembly  16  are raised above the floor surface. Consequently, and as indicated in  FIGS. 2   a  and  3 , when the main body  14  of the vacuum cleaner  10  is in its upright position the load of the vacuum cleaner  10  is supported by a combination of the cleaner head  12  and the stabilizer wheels  184  of the stand  180 . The raising of the wheels  40 ,  42  of the support assembly  16  above the floor surface can enable the cleaner head  12  and the stand  180  to provide maximum product stability when the main body  14  is in an upright position by ensuring that the cleaner head  12  and the stand  180  contact the floor surface rather than one of those components in combination with the wheels  40 ,  42  of the support assembly  16 . 
     With reference now to  FIG. 7   a , the vacuum cleaner  10  comprises a stand retaining mechanism  210  for retaining the stand  180  in its supporting position when the main body  14  is in its upright position so that the wheels  40 ,  42  may be maintained above the floor surface. This stand retaining mechanism  210  comprises a stand locking member  212  located within an open-sided housing  214  formed on the outer surface of the first motor casing section  72 . The housing  214  comprises a base  216 , two side walls  218 ,  220  each upstanding from an opposite end of the base  216 , and an upper wall  222  extending between the top surfaces of the side walls  218 ,  220 . A first end  224  of the stand locking member  212  is in the form of a hook, the tip  228  of which is lodged against the base of a curved ridge  230  upstanding from the base  216  of the housing  214 . A first helical compression spring  232  is located between a second end  234  of the stand locking member  212  and the base  216  of the housing  214 . The compression spring  232  urges the second end  234  of the stand locking member  212  in an upward (as illustrated) direction so that the second end  234  of the stand locking member  212  engages the upper wall  222  of the housing  214 . A ridge  236  may be located on, or integral with, the upper wall  222  of the housing  214  for engaging a groove  238  formed on the upper surface of the stand locking member  212  to inhibit sideways movement of the stand locking member  212  within the housing  214  when the stand locking member  212  is in the position illustrated in  FIG. 7   a.    
     The stand locking member  212  comprises a protrusion  240  extending outwardly from the side surface thereof, away from the motor casing  74 . In this example the protrusion  240  is in the form of a generally triangular prism having side surfaces which define a first side face  242 , a second side face  244  angled relative to the first side face  242 , and a third side face  246  angled relative to both the first and second side faces  242 ,  244 . The first side face  242  is concave, whereas the second and third side faces  244 ,  246  are generally planar. 
     The stand  180  comprises a stand pin  250  which extends inwardly from the supporting arm  190  for engaging the protrusion  240  of the stand retaining mechanism  210 . The weight of the main body  14  acting on the stand  180  tends to urges the stand  180  towards its raised, retracted position, against the biasing force of the torsion spring  200 . This causes the stand pin  250  to bear against the first side face  242  of the protrusion  240 . The force applied to the protrusion  240  by the stand pin  250  tends to urge the stand locking member  212  to rotate clockwise (as illustrated) about the tip  228  of its hooked first end  224  towards the position illustrated in  FIG. 7   b . However, the biasing force of the compression spring  232  is chosen so that the stand locking member  212  is maintained in the position illustrated in  FIG. 7   a , against the force applied to the protrusion  240  by the stand pin  250 , when the main body  14  is in its upright position so the stand  180  is retained in its supporting position by the stand retaining mechanism  210 . 
     With reference now to  FIGS. 14   a  and  14   b , the vacuum cleaner  10  further comprises a mechanism  280  for retaining the cleaner head  12  in a generally fixed angular position relative to the yoke  26  when the main body  14  is in its upright position. This allows the cleaner head  12  to support the main body  14 , along with the stand  180 , when the main body  14  is in its upright position. In the event that the cleaner head  12  was able to rotate relative to the yoke  26 , and thus the main body  14 , when the main body  14  is in its upright position there is a risk that the vacuum cleaner  10  may topple over, for example when the wand  84  is disconnected from the spine  86  of the main body  14 . 
     This cleaner head retaining mechanism  280  retains the cleaner head  12  in its generally fixed angular position relative to the yoke  26  by inhibiting the rotation of the cleaner head  12  about the internal duct inlet section  64  of the yoke  26 . The cleaner head retaining mechanism  280  comprises a cleaner head locking member  282  which is moveable relative to the cleaner head  12  between a deployed position, in which rotation of the cleaner head  12  relative to the yoke  26  is generally inhibited, and a stowed position. The movement of the locking member  282  between its deployed and stowed positions is described in more detail below. The locking member  282  is slotted into a locking member housing  284  which is connected to the inner surface of the lower yoke section  44 . The locking member housing  284  comprises a conduit  286  which is disposed between the internal duct inlet section  64  and the hose  70  of the internal duct  66  so that a dirt-bearing airflow flows through the conduit  286  as it passes from the internal duct inlet section  64  to the hose  70 . The locking member housing  284  further comprises a pair of grooves  288  for receiving ribs  290  formed on the sides of the locking member  282  to allow the locking member  282  to slide along the locking member housing  284 . A pair of fingers  292  extends forwardly from the front surface of the locking member  282 . When the locking member  282  is in its deployed position, the fingers  292  protrude through an aperture  294  located between the lower yoke section  44  and the upper yoke section  46 , as illustrated in  FIGS. 6   a  and  6   b , and into a groove  296  located on the upper surface of a collar  297  extending about the fluid outlet  24  of the cleaner head  12 , which is shown in  FIG. 8 . When the locking member  282  is in its stowed position, the locking member  282  is substantially fully retracted within the spherical volume V delimited by the wheels  40 ,  42  of the support assembly  16 . 
     When the main body  14  is in its upright position, the locking member  282  is urged towards its deployed position by an actuator  298 . The actuator  298  is located between a pair of arms  300  extending outwardly from the outer surface of the first motor casing section  72 . Each side of the actuator  298  comprises a rib  302  which is slotted into, and moveable along, a track  304  formed on the inner side surface of a respective one of the arms  300 . When the main body  14  is in its upright position, the actuator  298  is urged towards the locking member  282  by a helical compression spring  306  located between the actuator  298  and the outer surface of the first motor casing section  72 . A curved front face  308  of the actuator  298  is urged against a conformingly curved rear face  310  of the locking member  282  to force the fingers  292  through the aperture  294  and into the groove  296  on the collar  297  of the cleaner head  12 . 
     A catch  312  restricts the movement of the actuator  298  away from the motor casing  74  under the action of the spring  306 . The catch  312  is preferably arranged so that the actuator  298  is spaced from the end of the catch  312  when the main body  14  is in its upright position so that the actuator  298  is free to move both towards and away from the motor casing  74 . A second helical compression spring  314  is located between the lower yoke section  44  and the locking member  282  to urge the locking member  282  away from the groove  296  located on the upper surface of a collar  297 , and so urge the rear face  310  of the locking member  282  against the front face  308  of the actuator  298  when the main body  14  is in its upright position. The biasing force of the spring  306  is greater than the biasing force of the spring  314  so that the spring  314  is urged into a compressed configuration under the action of the spring  306 . 
     In use, when the main body  14  is in its upright position the valve member  112  of the changeover valve  110  is in its first position, as illustrated in  FIG. 10   a , so that when the user depresses the first switch  97   a  to activate the fan unit  76  a dirt-bearing airflow is drawn into the vacuum cleaner  10  through the distal end of the wand  84 . The dirt-bearing airflow passes through the hose and wand assembly  82  and is conveyed by the valve member  112  of the changeover valve  110  into the separating apparatus inlet duct  106 . The dirt-bearing airflow is conveyed by the separating apparatus inlet duct  106  into the separating apparatus  100 . Larger debris and particles are removed and collected in the chamber of the first stage  102  of cyclonic separation. The airflow then passes through a shroud to a set of smaller frusto-conically shaped cyclonic chambers of the second stage  104  of cyclonic separation. Finer dust is separated from the airflow by these chambers of the second stage, and the separated dust is collected in a common collecting region of the separating apparatus  100 . An airflow is exhausted from the air outlet formed in the base of the separating apparatus  100 , and is conveyed to the motor casing  74  by the motor inlet duct  130 . The airflow passes through the motor casing  74  and the fan unit  76 , and is exhausted from the motor casing  74  through the motor casing air outlets  166 . The airflow passes through the post-motor filter  170  before being exhausted from the vacuum cleaner  10  through the wheel air outlets  168 . 
     The main body  14  of the vacuum cleaner  10  is moveable between an upright position, illustrated in  FIG. 2   a , and a fully reclined position, illustrated in  FIG. 2   b . In this example, when the vacuum cleaner  10  is located on a substantially horizontal floor surface  43  with both the wheels  28  of the cleaner head  12  and the stabilizer wheels  184  of the stand  180  in contact with the floor surface, the longitudinal axis M of the spine  86  of the main body  14  is substantially orthogonal to a horizontal floor surface  43  when the main body  14  is in its upright position. Of course, the main body  14  may be inclined backwards or forwards slightly towards the floor surface  43  when in its upright position. 
     The rotational attachment of the yoke  26  and the stand  180  to the motor casing  74  allows the main body  14 , which includes the motor casing  74 , the hose and wand assembly  82 , the spine  86  and the motor inlet duct  130 , to be rotated about the axis A relative to the cleaner head  12 , and the yoke  26 , wheels  40 ,  42  and stand  180  of the support assembly  16 . The axis A may thus also be considered as a pivot axis about which the main body  14  may be reclined away from its upright position. Consequently, as the main body  14  is reclined from its upright position to its fully reclined position the bottom surface of the cleaner head  12  may be maintained in contact with the floor surface. In this example, the main body  14  pivots by an angle of around 65° about the pivot axis A as it is reclined from its upright position to its fully reclined position. 
     The main body  14  is reclined when the vacuum cleaner  10  is to be used to clean a floor surface. The rotation of the main body  14  of the vacuum cleaner  10  from its upright position is initiated by the user pulling the handle  94  of the main body  14  towards the floor surface while simultaneously pushing the handle  94  downwardly, along the longitudinal axis M of the spine  86  of the main body  14 , both to increase the load bearing on the stand  180  and to maintain the bottom surface of the cleaner head  12  in contact with the floor surface. This action causes the stand  180  to move slightly relative to the motor casing  74 , against the biasing force of the torsion spring  200 , so that the wheels  40 ,  42  of the support assembly  16  engage the floor surface. This reduces the load acting on the stand  180 , due to the load on the vacuum cleaner  10  now being borne also by the wheels  40 ,  42  of the support assembly  16 , and so enables the stand  180  to be raised subsequently to its retracted position, as described in more detail below. 
     As the main body  14  is reclined relative to the floor surface, the motor casing  74  rotates about the axis A, relative to the support assembly  16 . Initially, the stabilizer wheels  184  of the stand  180  remain in contact with the floor surface. Consequently the force acting between the protrusion  240  of the stand locking member  212  and the stand pin  250  increases. The increase in this force is due to both the increased load acting on the stabilizer wheels  184  and the application of a torque to the main body  14 . As the user continues to recline the main body  14  towards the floor surface, the torque applied to the main body  14  increases. Eventually, the force acting between the protrusion  240  and the stand pin  250  becomes sufficiently high as to cause the stand locking member  212  to pivot about the tip  228  of its hooked first end  224 , against the biasing force of the compression spring  232  acting on the second end  234  of the stand locking member  212 . This in turn causes the first side face  242  of the protrusion  240  to slide along the stand pin  250  as the main body  14  is reclined further by the user. 
     Once the stand locking member  212  has pivoted to a position at which the stand pin  250  is located at the upper edge of the first side face  242 , as illustrated in  FIG. 7   b , the stand locking member  212  can now be rapidly moved beneath the stand pin  250  under the action of the torque applied to the main body  14  by the user. This is because the second side face  244  of the protrusion  240  is angled so as to not impede relative movement between the stand pin  250  and the stand locking member  212 . This relative movement between the stand pin  250  and the stand locking member  212  is also assisted by the action of the compression spring  232  urging the second end  234  of the stand locking member  212  back towards its raised position as the second side face  244  of the protrusion  240  slides beneath the stand pin  250 . When the stand pin  250  and the stand locking member  212  are in the relative positions illustrated in  FIG. 7   c , the stand pin  250  has become released from the stand retaining mechanism  210 . In this example, the stand  180  becomes released from the stand retaining mechanism  210  when the main body  14  has been reclined from its upright position by an angle of around 5 to 10°. However, due to the user both pulling and pushing the handle  94  downwardly to release the stand  180  from the stand retaining mechanism  210 , the stand  180  becomes released when the motor casing  74  has been rotated relative to the stand  180  by a slightly greater angle. 
     Once the stand  180  has been released by the stand retaining mechanism  210 , the main body  14  can be reclined fully towards the floor surface by the user while maintaining the bottom surface of the cleaner head  12  in contact with the floor surface. The main body  14  is preferably arranged so that its center of gravity is located behind the stabilizer wheels  184  of the stand  180  once the stand  180  has become disengaged from the stand retaining mechanism  210 . Consequently, the weight of the main body  14  tends to assist the user in reclining the main body  14  towards its fully reclined position. 
     Following its release from the stand retaining mechanism  210 , the stand  180  does not automatically move to its retracted position. Instead, as the main body  14  is reclined towards its fully reclined position following the release of the stand  180  from the stand retaining mechanism  210 , initially the stabilizer wheels  184  of the stand  180  remain in contact with the floor surface, and so the main body  14  continues to pivot about axis A relative to the stand  180 . As discussed above, the over-center spring mechanism comprises a torsion spring  200 , and this torsion spring  200  is connected between the stand  180  and the motor casing  74  so that the spacing between the ends  202 ,  204  of the torsion spring  200  varies as the main body  14  is pivoted about axis A. In this example, this spacing reaches a minimum, and so the torsion spring  200  is at its over-center point, when the main body  14  has been reclined by an angle of around 30° from its upright position.  FIGS. 15   a  and  15   b  illustrate the relative positions of the stand  180  and the motor casing  74  when the main body  14  is in its upright position, and when the main body  14  has been reclined so that the torsion spring  200  is at its over-center point, respectively. 
     As the main body  14  is reclined beyond the position illustrated in  FIG. 15   b , the biasing force of the torsion spring  200  urges the first end  202  of the torsion spring  200  away from the second end  204  of the torsion spring  200 . This results in the automatic rotation of the stand  180  about the axis A to its raised, retracted position, as illustrated in  FIG. 15   c , in which the stabilizer wheels  184  are raised above the floor surface. A first stand stop member  260  located on the motor casing  74  engages the supporting arm  192  of the stand  180  to inhibit movement of the stand  180  beyond its retracted position, and so, in combination with the torsion spring  200 , serves to maintain the stand  180  in a fixed angular position relative to the motor casing  74 . 
     The biasing force of the torsion spring  200  subsequently maintains the stand  180  in its retracted position relative to the motor casing  74  when the main body  14  is reclined from its upright position by an angle which, in this example, is in the range from 15 and 65°. We have found that, during floor cleaning, the main body  14  of the vacuum cleaner  10  tends to be inclined at an angle within this range as it is maneuvered over a floor surface, and so generally the torsion spring  200  will prevent the stand  180  from moving away from its retracted position during a floor cleaning operation.  FIG. 15   d  shows the relative positions of the stand  180  and the motor casing  74  when the main body  14  is in its fully reclined position. In this position, the stabilizer wheels  184  are able to contact the floor surface, and thus may assist in maneuvering of the vacuum cleaner  10  over the floor surface when the main body  14  is in its fully reclined position, for example for cleaning beneath items of furniture. 
     As the main body  14  is reclined from its upright position, the cleaner head  12  is released by the cleaner head retaining mechanism  280  to allow the cleaner head  12  to rotate relative to the yoke  26  as the vacuum cleaner  10  is subsequently maneuvered over the floor surface during floor cleaning. As mentioned above, the actuator  298  of the cleaner head retaining mechanism  280  is retained between the arms  300  extending outwardly from the motor casing  74 , whereas the engagement between the ribs  290  of the locking member  282  and the grooves  288  of the locking member housing  284  retains the locking member  282  on the yoke  26 . Consequently, as the main body  14  is reclined the motor casing  74  rotates about axis A relative to the yoke  26 , which results in the actuator  298  moving upwardly relative to the locking member  282 . 
     As the main body  14  is reclined, the front face  308  of the actuator  298  slides over the rear face  310  of the locking member  282 . A series of grooves may be formed on the rear face  310  of the locking member  282  to reduce frictional forces generated as the front face  308  of the actuator  298  slides over the rear face  310  of the locking member  282 . Due to the conformingly curved shapes of the front face  308  of the actuator  198  and the rear face  310  of the locking member  282 , the locking member  282  remains in its deployed position while the front face  308  of the actuator  298  maintains contact with the rear face  310  of the locking member  282 . 
     In this example the front face  308  of the actuator  298  maintains contact with the rear face  310  of the locking member  282  until the main body  14  has been reclined by an angle of around 7°. This means that the angular position of the cleaner head  12  relative to the yoke  26  remains fixed while the stand  180  is retained in its supporting position by the stand retaining mechanism  210 . The relative positions of the locking member  282  and the actuator  298  when the main body  14  has been reclined by around 7° are shown in  FIG. 14   c . With continued reclining of the main body  14  from its upright position, the front face  308  of the actuator  298  becomes disengaged from the rear face  310  of the locking member  282 . The biasing force of the spring  306  urges the actuator  298  away from the motor casing  74  and against the catch  312 , as shown in  FIG. 14   d . Under the action of the spring  314 , the locking member  282  begins to move along the locking member housing  284 , away from its deployed position, as the main body  14  is reclined, resulting in the retraction of the fingers  292  from the groove  296  formed in the outer collar  297  of the fluid outlet  24  of the cleaner head  12 . 
     As also shown in  FIGS. 14   a  and  14   b , the actuator  298  comprises a curved, lower drive face  318  which is inclined by an angle of around 30 to 40° to the front face  308  of the actuator  298 . The locking member  282  comprises a conformingly curved upper driven face  320 , which is inclined at an angle of around 30 to 40° to the rear face  310  of the locking member  282 . The purpose of the drive face  318  and the driven face  320  is to allow the locking member  282  to be subsequently returned to its deployed position, as described in more detail below. Under the action of the spring  314 , the driven face  320  of the locking member  282  slides over the drive face  318  of the actuator  298  as the main body  14  is reclined. Grooves may also be formed in the driven face  320  to reduce frictional forces generated as the driven face  320  slides over the drive face  318 . 
       FIG. 14   d  illustrates the relative positions of the locking member  282  and the actuator  298  when the locking member  282  has moved to its stowed position, in which the fingers  292  of the locking member  282  are fully retracted from the groove  296  formed in the outer collar  297  of the fluid outlet  24  of the cleaner head  12  to allow the cleaner head  12  to rotate relative to the yoke  26 . In this example the locking member  282  reaches its stowed position once the main body  14  has been reclined by an angle of around 15° from its upright position, that is, before the stand  180  is moved to its retracted position by the over-center spring mechanism. As the main body  14  is reclined further, the drive surface  318  becomes spaced from the driven surface  320 , allowing the spring  314  to maintain the locking member  282  in its stowed position, in which it is urged against the stop member  316  located at the rear of the locking member housing  284 . 
     The movement of the stand  180  from its supporting position to its retracted position actuates the movement of the valve member  112  of the changeover valve  110  from its first position to its second position. Returning to  FIGS. 9   a  and  9   b , the changeover valve  110  further comprises a valve drive  340  for rotating the valve member  112  between its first and second positions. The valve drive  340  comprises a body  342 , a first pair of drive arms  344  and a second pair of drive arms  346 . Each pair of drive arms  344 ,  346  extends outwardly from the body  342 , with the first pair of drive arms  344  being located diametrically opposite the second pair of drive arms  346 . Within each pair, the drive arms  344 ,  346  are spaced apart to define an elongate slot  348 ,  350 . The ends  352 ,  354  of each pair of drive arms  344 ,  346  protrude inwardly so that each slot  348 ,  350  has a region of reduced width located remote from the body  342 . A further slot  355  extends radially inwardly from the outer periphery of the body  342 . 
     The valve member  112  comprises a pair of diametrically opposed driven arms  356  extending outwardly from the side thereof located opposite to the hub  122  (only one of the shafts  356  is visible in  FIGS. 9   a  and  9   b ). Each driven arm  356  is arranged to be received between a respective pair of drive arms  344 ,  346  by a snap-fit connection so that each driven arm  356  is moveable within a respective slot  348 ,  350  but is retained therein by the ends  352 ,  354  of the drive arms  344 ,  346  defining that slot  348 ,  350 . Each driven arm  356  has a head  358  which is locally enlarged to prevent the driven arms  356  from sliding out of the slots  348 ,  350 . This arrangement enables the drive arms  344 ,  346  of the valve drive  340  to rotate the driven arms  356  of the valve member  112  about the longitudinal axis L of the boss  124  while permitting the valve member  112  to move towards and away from the valve drive  340 . 
     A helical compression spring  360  is located between the valve member  112  and the valve drive  340 . One end of the spring  360  is located over a boss  362  located within a recess  364  located centrally in the body  342  of the valve drive  340 , while the other end of the spring  360  is located within a central recessed portion (not shown) of the outer surface of the valve member  112 . 
     The valve drive  340  is rotatably connected to a cover plate  366  by a connector pin  368  which extends through an aperture  370  formed in the cover plate  366 . In assembly, the valve member  112  is located on the boss  124  of the motor casing  74  so that the valve member  112  is in its first position. The valve drive  340  is then connected to the valve member  112 , with the spring  360  disposed therebetween, with the slot  355  oriented so that the mouth  355   a  of the slot  355  is located below the center of the drive member  340 . The cover plate  366  is then connected to the valve drive  340  using the connector pin  368  so that the valve drive  340  can rotate relative to the cover plate  366 , and secured to the first motor casing section  72  by screws  372  which are inserted through apertures  374  in the cover plate  366  and screwed into the motor casing  74 . When the valve member  112 , valve drive  340  and the cover plate  366  are located on the motor casing  74 , both the valve member  112  and the valve drive  340  may be rotated about the longitudinal axis L of the boss  124 . Due to the connection of the valve drive  340  to the cover plate  366 , the biasing force of the spring  360  urges the valve member  112  towards the boss  124  located on the motor casing  74 . 
     The movement of the valve member  112  between its first and second positions is actuated by the stand  180  as the main body  14  is reclined from its upright position. While the stand  180  is in its supporting position, the longitudinal axis L of the hub  124  orbits about the pivot axis A of the main body  14  towards the stand  180  as the main body  14  is reclined. As shown in  FIG. 13 , the supporting arm  190  of the stand  180  comprises a valve drive pin  380  extending inwardly from a raised section  382  of the supporting arm  190 . With reference now to  FIG. 16   a , the valve drive pin  380  is spaced from the valve drive  340  when the main body  14  is in its upright position. The valve drive pin  380  is positioned on the supporting arm  190  so that as the main body  14  is reclined towards the floor surface, the valve drive pin  380  enters the slot  355  formed in the body  342  of the valve drive  340 , through the mouth  355   a  thereof. In this example, the valve drive pin  380  enters the slot  355  once the main body  14  has been reclined by an angle of around 9° from its upright position. The relative positions of the valve drive pin  380  and the valve drive  340  when the main body  14  has been reclined by this amount are shown in  FIG. 16   b . As the main body  14  is reclined further from the upright position, the relative movement between the motor casing  74  and the stand  180  causes the valve drive  340  to be rotated about the longitudinal axis L of the boss  124  by the valve drive pin  380 , which in turn causes the valve member  112  to be rotated from its first position towards its second position, as illustrated in  FIG. 16   c.    
     The valve drive  340  rotates about the longitudinal axis L of the hub  124  until the valve drive pin  380  eventually leaves the slot  355 , as shown in  FIG. 16   d . In this example, the valve drive pin  380  leaves the mouth  355   a  of the slot  355  when the main body  14  has been reclined by an angle of around 25 to 30° from its upright position. Following this rotation of the valve drive  340  about the longitudinal axis L of the hub  124 , the valve member  112  has been rotated about an angle of 120° from its first position to its second position, as also shown in  FIG. 10   b , although the angle of rotation of the valve member  112  may be any desired value depending on the arrangement of the motor casing  74 . The entire movement of the valve member  112  from its first position to its second position thus occurs while the stand  180  is in its supporting position. 
     The tapered, triangular profiles of the outer surface of the boss  124  and the inner surface  123  of the hub  122  assist in breaking the seals that the valve member  112  makes with the hose and wand assembly outlet section  80  and the inlet duct inlet section  106  when the valve member  112  is in its first position. This reduces the amount of torque required to rotate the valve member  112  to its second position, particularly when an airflow is being drawn through the changeover valve  110 . As the valve member  112  is urged away from its first position through the rotation of the valve drive  340  by the valve drive pin  380 , due to the tapered triangular profiles of the outer surface of the boss  124  and the inner surface  123  of the hub  122  the movement of the valve member  112  has two different components: (i) a rotational movement about the longitudinal axis L of the boss  124  with the valve drive  340 , and (ii) a translational movement along the longitudinal axis L of the boss  124  towards the valve drive  340 , against the biasing force of the spring  360 . It is this translational movement of the valve member  112  along the boss  124  that facilitates the breaking of the aforementioned seals. 
     This combination of translational and rotational movements of the valve member  112  relative to the boss  124  continues until the valve member  112  has been rotated about the longitudinal axis L of the boss  124  by around 60°. At this point, the valve member  112  has moved along the longitudinal axis L of the boss  124  by a distance which in this example in the range from 5 to 10 mm. The further movement of the valve member  112  as it is moved to its second position now has the following two different components (i) a rotational movement about the longitudinal axis L of the boss  124  with the valve drive  340 , and (ii) a reverse translational movement along the longitudinal axis L of the boss  124 , away from the valve drive  340 , under the biasing force of the spring  360 . 
     In the second angular position of the valve member  112  relative to the motor casing  74 , the airflow path defined by the valve member  112  connects the internal duct  66  to the separating apparatus inlet duct  106  so that air is drawn into the vacuum cleaner  10  through the suction opening  22  of the cleaner head  12 . As shown in  FIG. 10   b , in this second position of the valve member  112  the first port  114  is now seated over the air inlet  108   a  so that the seal  118  is in sealing contact with the inlet duct inlet section  108 , and second port  116  is seated over the air outlet  68   a  so that the seal  120  is in sealing contact with the internal duct outlet section  68 . In this second position of the valve member  112 , the body of the valve member  112  serves to isolate the hose and wand assembly  82  from the fan unit  76  so that substantially no air is drawn into the vacuum cleaner  10  through the wand  84  of the hose and wand assembly  82 . Again, the conforming profiles of the inner surface  123  of the hub  122  and the outer surface of the boss  124  means that the valve member  112  can be accurately aligned, both angularly and axially, relative to the motor casing  74  when in its second position. When compared to  FIG. 10   a ,  FIG. 10   b  illustrates the compression of the hose  70  of the internal duct  66  as the main body  14  moves from its upright position to a reclined position. This is due to the movement of the internal duct outlet section  68 , which is connected to the motor casing  74 , towards the internal duct inlet section  64 , which is connected to the yoke  26 . 
     Returning to  FIG. 16   d , the valve member  112  and the valve drive  340  are each shaped to define a groove or recess  384 . The recess  384  is arranged so that the valve drive pin  380  can move along the outer surface of the valve member  112  and the valve drive  340  in the event that the valve member  112  has been moved manually to its second position while the main body  14  is in the upright position. 
     The movement of the stand  180  from its supporting position to its retracted position also enables the motor of the brush bar assembly  30  to be energized. As the stand  180  is moved to its retracted position, the supporting arm  192  actuates a brush bar activation switch mechanism (not shown) mounted in a switching housing  390  located on the second motor casing section  78 . The actuation of this switch mechanism is preferably through contact between the switch mechanism and a switch actuating portion  392  of the annular connector  196  of the supporting arm  192  of the stand  180  as the stand  180  moves to its retracted position. For example, the switch mechanism may comprise a spring-loaded cam which is engaged by the switch actuating portion  392  of the stand  180  and urged against a switch of the switching mechanism as the stand  180  is rotated towards its retracted position. Alternatively, this switch may be actuated by a magnetic, optical or other non-contact actuation technique. The actuation of the switch preferably occurs as the stand  180  is moved towards its retracted position by the over-center spring mechanism. Upon actuation, the switch is placed in a first electrical state in which power is supplied to the motor  33  of the brush bar assembly  30  to enable the brush bar assembly  30  to be rotated within the brush bar chamber  32  of the cleaner head  12 . The vacuum cleaner  10  is preferably arranged so that rotation of the brush bar assembly  30  is started upon actuation of the switch. Depending on the nature of the floor surface to be cleaned, the user may choose to de-activate the motor  33  by de-pressing the second switch  97   b . During cleaning, the motor  33  of the brush bar assembly  30  may be selectively re-activated or de-activated as required by depressing the second switch  97   b.    
     In use, with the main body  14  is in a reclined position and the valve member  112  of the changeover valve  110  is in its second position, a dirt-bearing airflow is drawn into the vacuum cleaner  10  through the suction opening  22  of the cleaner head  12  when the user depresses the first switch  97   a  to activate the fan unit  76 . The dirt-bearing airflow passes through the cleaner head  12  and the internal duct  66  and is conveyed by the valve member  112  of the changeover valve  110  into the separating apparatus inlet duct  106 . The subsequent passage of the airflow through the vacuum cleaner  10  is as discussed above when the main body  14  is in its upright position. 
     Returning to  FIG. 5   a , the main body  14  comprises a bleed valve  400  for allowing an airflow to be conveyed to the fan unit  76  in the event of a blockage occurring in, for example, the wand and hose assembly  82  when the main body  14  is in its upright position or the cleaner head  12  when the main body  14  is in a reclined position. This prevents the fan unit  76  from overheating or otherwise becoming damaged. The bleed valve  400  is located in the lower portion of the motor inlet duct inlet section  134 , and so is located within the spherical volume V delimited by the wheels  40 ,  42  of the support assembly  16 . The bleed valve  400  comprises a piston chamber  402  housing a piston  404 . An aperture  406  is formed at one end of the piston chamber  402  for exposing the piston chamber  402  to the external environment, and a conduit  408  is formed at the other end of the piston chamber  402  for placing the piston chamber  402  in fluid communication with the motor inlet duct inlet section  134 . 
     A helical compression spring  410  located in the piston chamber  402  urges the piston  404  towards an annular seat  412  inserted into the piston chamber  402  through the aperture  406 . During use of the vacuum cleaner  10 , the force F 1  acting on the piston  402  against the biasing force F 2  of the spring  410 , due to the difference in the air pressure acting on each respective side of the piston  404 , is lower than the biasing force F 2  of the spring  410 , and so the aperture  406  remains closed. In the event of a blockage in the airflow path upstream of the conduit  404 , the difference in the air pressure acting on the opposite sides of the piston  402  dramatically increases. The biasing force F 2  of the spring  410  is chosen so that, in this event, the force F 1  becomes greater than the force F 2 , which causes the piston  404  to move away from the seat  412  to open the aperture  406 . This allows air to pass through the piston chamber  402  from the external environment and enter the motor inlet duct  130 . 
     Turning now to  FIGS. 11   a  to  11   e , a shield  414  is connected to the motor casing  74  for inhibiting the ingress of dirt into the spherical volume V delimited by the wheels  40 ,  42  of the support assembly  16  when the main body  14  is in a reclined position. The shield  414  is connected to the motor casing  74  using one or more of the bolts or other fixing means which are used to connect the motor inlet duct  130  to the motor casing  74 . The shield  414  has an upper surface  414   a  which has a substantially spherical curvature. The radius of curvature of the upper surface  414   a  of the shield  414  is only slightly smaller than that of the upper surface  46   a  of the upper yoke section  46 . The shield  414  has a curved upper end  416  which partially surrounds the motor inlet duct inlet section  134 , and a lower end  418  which terminates above the arms  300  of the first motor casing section  72 . The shield  414  also provides a housing for one or more of the electronic components of the vacuum cleaner  10 , such as a circuitry for driving the motor  33  of the brush bar assembly  30  and/or the fan unit  76 . 
     With reference to  FIGS. 11   a  and  11   b , when the main body  14  is in its upright position the upper yoke section  46  is located over the shield  414 , and so the shield  414  is hidden from view. As the main body  14  is reclined from its upright position to, for example, the reclined position illustrated in  FIGS. 11   c  and  11   d  in which the stand  180  is in its retracted position, the motor casing  74  rotates about axis A relative to the yoke  26 . Consequently, the shield  414  rotates relative to the upper yoke section  46 . This results in the exposure of part of the shield  414 . Due to the spherical curvature of the outer surface  414   a  of the shield  414 , there is minimal disruption to the spherical appearance of the front of the support assembly  16  as the main body  14  is reclined from its upright position. 
     With the main body  14  in a reclined position and the stand  180  in its retracted position, the vacuum cleaner  10  can be moved in a straight line over a floor surface by simply pushing or pulling the handle  94  of the main body  14 . With the pivot axis A of the main body  14  substantially parallel to the floor surface, both of the wheels  40 ,  42  engage the floor surface, and so rotate as the vacuum cleaner  10  is maneuvered over the floor surface. The pivotal mounting of the yoke  26  to the main body  14  allows the bottom surface  20  of the cleaner head  12  to be maintained in contact with the floor surface as the main body  14  is maneuvered over the floor surface. Returning to  FIG. 5   a , the bottom surface of the lower yoke section  44  comprises a pair of raised ribs  419 . Each rib  419  comprises a curved lower surface. The radius of curvature of the lower surface of each rib  419  is slightly smaller than that of the inner surfaces of the wheels  40 ,  42 . Each rib  419  is sized so that the lower surface thereof is spaced from the inner surface of its respective wheel  40 ,  42  when the main body  14  is in its upright position so that the wheels  40 ,  42  are raised above the floor surface. When the main body  14  is reclined, depending on the load applied to the vacuum cleaner  10  the rims  40   a ,  42   a  of the wheels  40 ,  42  may deform radially inwardly so that the inner surfaces of the wheels  40 ,  42  engage the lower surfaces of the ribs  419 . This prevents excessive deformation of the wheels  40 ,  42 . When a heavy load is applied to the main body  14 , the curved lower surfaces of the ribs  419  can present a curved surface over which the inner surfaces of the wheels  40 ,  42  slide as the vacuum cleaner  10  is maneuvered over the floor surface. 
     To change the direction in which the vacuum cleaner  10  moves over the floor surface, the user twists the handle  94  to rotate the main body  14 , in the manner of a corkscrew, about its longitudinal axis M, shown in  FIGS. 2   a  and  3 . With the cleaner head  12  free to rotate relative to the yoke  26 , the bottom surface  20  of the cleaner head  12  can be maintained in contact with the floor surface as the main body  14 , together with the yoke  26  and the wheels  40 ,  42 , is rotated about its longitudinal axis M. As the main body  14  rotates about its longitudinal axis M, the cleaner head  12  rotates relative to the yoke  26  so as to turn in the direction in which the handle  94  has been twisted by the user. For example, twisting the handle  94  in a clockwise direction causes the cleaner head  12  to turn to the right. The pivot axis A of the main body  14  becomes inclined towards the floor surface which results, in this example, in the wheel  40  becoming spaced from the floor surface. The curved outer surface of the wheel  42  rolls over the floor surface, and so still provides support for the main body  14 , while the wheel  42  continues to rotate about its rotational axis R 2  to turn the vacuum cleaner  10  to its new direction. The extent to which the handle  94  is twisted by the user determines the extent to which the cleaner head  12  turns over the floor surface. 
     When the user wishes to return the main body  14  of the vacuum cleaner  10  to its upright position, for example upon completing floor cleaning, the user raises the handle  94  so that the main body  14  pivots about the pivot axis A towards its upright position. As mentioned above, when the main body  14  is in its upright position the longitudinal axis M of the main body  14  is substantially vertical when the vacuum cleaner  10  is located on a horizontal floor surface. As the main body  14  is raised to its upright position, the motor casing  74  rotates about the axis A, and thus moves relative to the yoke  26 . When the main body  14  reaches its upright position, the lower surfaces  300   a  of the arms  300  of the cleaner head retaining mechanism  280 , which are connected to the motor casing  74 , engage the upper surfaces  287   a  of a pair of columns  287  upstanding from the locking member housing  284 , which is connected to the yoke  26 , and which prevent the main body  14  from moving relative to the yoke  26  beyond its upright position. 
     As the main body  14  is returned to its upright position, the stand  180  is automatically moved towards its supporting position. Returning to  FIGS. 13 and 15   a , the main body  14  comprises a gear lever  420  which has a body  422  which is rotatably connected at the center thereof to the inner surface of the yoke arm  50  for rotation about axis B which is spaced from, and preferably substantially parallel to, the pivot axis A. The gear lever  420  further comprises a lever arm  424  and a gear portion  426 . The lever arm  424  and the gear portion  426  each extend radially outwardly from the body  422  of the gear lever  420 , the lever arm  424  being located diametrically opposite to the gear portion  426 . The gear portion  426  comprises a plurality of teeth  428  which mesh with teeth  430  located on the outer periphery of the annular connector  196  located at the upper end of the supporting arm  192  of the stand  180 . 
     As the main body  14  is raised from its fully reclined position, initially the biasing force of the torsion spring  200  maintains the stand  180  in its retracted position relative to the motor casing  74  and so the motor casing  74  and the stand  180  initially rotate together about the pivot axis A of the main body  14 . The intermeshing of the teeth  428  of the gear lever  420  with the teeth  430  of the stand  180  causes the gear lever  420  to rotate in a first rotational direction relative to the yoke  26 . When the main body  14  has been raised so that the main body  14  is inclined at an angle of around 15° from the upright position, a drive pin  440  located on the second motor casing section  78  engages the lever arm  424  of the gear lever  420 , as illustrated in  FIG. 15   d . With further raising of the main body  14  towards its upright position, and thus rotation of the main casing  74  relative to the yoke  26 , the drive pin  440  drives the gear lever  420  to rotate in a second rotational direction which is reverse to the first rotational direction. Due again to the intermeshing of the teeth  428  of the gear lever  420  with the teeth  430  of the stand  180 , the rotation of the gear lever  420  in this reverse direction causes the stand  180  to start to rotate relative to the main casing  14 , away from its supporting position and against the biasing force of the torsion spring  200 . The gear ratio between the gear lever  420  and the stand  180  is at least 1:3, and preferably around 1:4 so that with each subsequent 1° pivotal movement of the main body  14  about its pivot axis A towards its upright position the stand  180  rotates around 4° relative to the motor casing  74  towards its supporting position. 
     The relative rotation between the main casing  14  and the stand  180  reduces the spacing between the ends  202 ,  204  of the torsion spring  200 . This spacing now reaches a minimum, and so the torsion spring is at its over-center point, when the main body  14  has been raised so that, in this example, it is at an angle in the range from 1 to 5° from its upright position. As the main body  14  is raised further from this position, the biasing force of the torsion spring  200  urges the first end  202  of the torsion spring  200  away from the second end  204  of the torsion spring  200 . This results in the automatic rotation of the stand  180  towards its supporting position so that the stabilizer wheels  184  of the stand  180  engage the floor surface. 
     As mentioned above, when the main body  14  is initially in its upright position and the stand  180  is in its supporting position the wheels  40 ,  42  of the support assembly  16  are raised above the floor surface so that the vacuum cleaner  10  is supported by a combination of the stabilizer wheels  184  of the stand  180  and the rollers  28  of the cleaner head  12 . To return the vacuum cleaner  10  to this configuration the user is required to push the handle  94  of the main body  14  so that the main body  14  leans forward, beyond its upright position, by an angle which is preferably no greater than 10°. This prevents the center of gravity of the vacuum cleaner  10  from moving beyond the front edge of the bottom surface of the cleaner head  12 , which in turn prevents the vacuum cleaner  10  from toppling forward, under its own weight, during this forward movement. This forward movement of the vacuum cleaner  10  causes both the cleaner head  12  and the main body  14  of the vacuum cleaner  10  to pivot about the front edge of the bottom surface  20  of the cleaner head  12 , both raising the wheels  40 ,  42  from the floor surface and providing sufficient clearance between the vacuum cleaner  10  and the floor surface for the stand  180  to be urged by the torsion spring  200  beyond its supporting position until the front surface  450  of the body  188  of the stand  180  engages the rear surface  452  of the lower yoke section  44 . The rear surface  452  of the lower yoke section  44  may be considered to provide a second stand stop member of the vacuum cleaner  10 . The angular spacing about the pivot axis A between this second stand stop member and the first stand stop member  260  is preferably around 90°. 
     As the stand  180  is urged towards the rear surface  452  of the lower yoke section  44  by the torsion spring  200 , the stand pin  250  engages the third side face  246  of the protrusion  240  of the stand locking member  212 . The torque that has to be applied to the main body  14  by the user in order to move the stand pin  250  relative to the protrusion  240  as the stand  180  is urged towards the second stand stop member is significantly less than that which is required to release the stand  180  from the stand retaining mechanism  210 . The inclination of the third side face  246  of the protrusion  240  is such that the subsequent relative movement between the motor casing  74  and the stand  180  causes the stand locking member  212  to pivot upwardly about the ridge  238  of the housing  214  to allow the stand pin  250  to slide beneath the third side face  246  of the protrusion  240 . As illustrated in  FIG. 7   d , the spring  232  of the stand retaining mechanism  210  tends to be pushed away from the side wall  220  of the housing  214  as the stand locking member  212  pivots about its second end  234 , with the result that the spring  232  affords only a relative small resistance to the movement of the stand locking member  212  in comparison to when the user requires the stand  180  to be released from the stand retaining mechanism  210 . This allows the stand pin  250  to slide along the third side face  246  of the protrusion  240  under the biasing force of the torsion spring  200  alone. Once the stand pin  250  has moved beyond the left end (as illustrated) of the third side face  246 , the spring  232  returns the stand locking member  212  to the position illustrated in  FIG. 7   a  so that the stand  180  is again retained in its supporting position by the first side face  242  of the protrusion  240 . The main body  14  may now be returned to its upright position by the user so that the stabilizer wheels  184  contact the floor surface. Due this final movement of the stand  180  relative to the motor casing  74 , the wheels  40 ,  42  of the support assembly  16  are spaced from the floor surface when the stabilizer wheels  184  engage that floor surface. 
     The rotation of the stand  180  back to its supporting position causes the switch actuating portion  392  of the annular connector  196  of the supporting arm  192  to push the spring-loaded cam of the brush bar activation switch mechanism against the switch of the switching mechanism. The actuation of the switch preferably occurs as the stand  180  is moved towards its supporting position by the over-center spring mechanism. Upon re-actuation, the switch is placed in a second electrical state in which power is no longer supplied to the motor  33  for driving the brush bar assembly  30 . 
     The rotation of the stand  180  back to its supporting position also causes the valve member  112  of the changeover valve  110  to be driven back to its first position through engagement between the valve drive pin  380  of the stand  180  and the valve drive  340 . The movement of the valve member  112  from its second position to its first position is the reverse of its movement from the first position to the second position. The symmetry of the profiles of the outer surface of the boss  124  and the inner surface  123  of the hub  122  means that the torque required to subsequently return the valve member  112  to its first position is substantially the same as the torque required to move the valve member  112  to the second position. 
     Simultaneously with the movement of the stand  180  to its supporting position, the locking member  282  of the cleaner head retaining mechanism  280  is returned to its deployed position. Returning to  FIGS. 14   b ,  14   c  and  14   d , when the main body  14  is raised so that it is inclined at an angle of around 15° to its upright position the drive face  318  of the actuator  298  re-engages the driven face  320  of the locking member  282 . As the main body  14  continues to move towards its raised position, under the action of the spring  306  the actuator  298  pushes the locking member  282  back towards its deployed position, against the biasing force of the spring  314 . With the cleaner head  12  angularly positioned relative to the yoke  26  so that the groove  296  on the cleaner head  12  is aligned with the aperture  294  of the yoke  26 , the fingers  292  of the locking member  282  re-enter the groove  296  to lock the angular position of the cleaner head  12  relative to the yoke  26 . Once the main body  14  has been raised so that it is inclined at an angle of around 7° to its upright position, the locking member  282  has been urged back to its deployed position by the drive face  318  of the actuator  298 , as shown in  FIG. 14   b . The locking member  282  is maintained in its deployed position through the engagement between the front face  308  of the actuating member  298  and the rear face  310  of the locking member  282 . 
     In the event that the groove  296  on the cleaner head  12  is not correctly aligned with the aperture  294  of the yoke  26 , there is a risk that the end of at least one of the fingers  292  of the locking member  282  will engage the end of the collar  297 . This will prevent the fingers  292  from re-entering the groove  296  with further raising of the main body  14  towards its upright position. In the event that the user continues to raise the main body  14  to its upright position, the biasing force of the spring  306  is chosen so that it will compress to allow the actuating member  298  simultaneously to move towards the motor casing  74  along the tracks  304  of the arms  300  and to slide over the now stationary locking member  282 . This prevents permanent damage to one or more of components of the cleaner head retaining mechanism  280 , the motor casing  74  and the cleaner head  12 . Once the main body  14  has moved relative to the cleaner head  12  so that the aperture  294  and the groove  296  are aligned, the biasing force of the spring  306  will urge both the actuator  298  and the locking member  282  away from the motor casing  74  so that the locking member  282  moves to its deployed position. 
     When the main body  14  is in its upright position, the vacuum cleaner  10  may be maneuvered over a floor surface by pulling the handle  94  downward so that the vacuum cleaner  10  tilts backwards on the stabilizer wheels  184  of the stand  180 , raising the bottom surface of the cleaner head  12  from the floor surface. The vacuum cleaner  10  can then be pulled over the floor surface, for example between rooms of a building, with the stabilizer wheels  184  rolling over the floor surface. This maneuvering of the vacuum cleaner  10  when in this orientation relative to the floor surface is hereafter referred to as “wheeling” of the vacuum cleaner  10  over the floor surface so as to differentiate this movement of the vacuum cleaner  10  from that taking place during floor cleaning. We have observed that a user tends to tilt the vacuum cleaner by an angle of at least 30°, more usually by an angle in the range from 40 to 60°, to place the handle  94  of the main body  14  at a comfortable height for pulling the vacuum cleaner  10  over a floor surface. The shape of the stabilizer wheels  184  aids a user in guiding the vacuum cleaner  10  between rooms. In this example the face of each stabilizer wheel  184  which is furthest from the supporting leg  182  is rounded to provide smooth running on a variety of floor surfaces. 
     The stand retaining mechanism  210  is preferably arranged to increase the force required to release the stand  180  from the stand locking member  212  when the vacuum cleaner  10  is reclined for wheeling over a floor surface. This can reduce the risk of accidental movement of the stand  180  to its retracted position relative to the motor casing  74  as the vacuum cleaner  10  is wheeled over the floor surface, which could result in the sudden, and inconvenient, “bumping” of the vacuum cleaner  10  down on to the floor surface. 
     Returning to  FIGS. 7   a  to  7   c , the base  216  of the housing  214  is inclined relative to the horizontal, in this example by an angle of at least 20°, when the main body  14  is in its upright position so that the base  216  slopes downwardly towards the side wall  218  of the housing  214 . The base  216  comprises a relatively short wall  460  upstanding therefrom between the side walls  218 ,  220  of the housing  214 . A ball bearing  462  is located on the base  216 , between the side wall  220  and the wall  460  of the housing  214  so that the ball bearing  462  rolls, under gravity, against the wall  460  of the housing  214 . The stand locking member  212  further comprises a fin  464  depending downwardly between the first end  224  and the second end  232  thereof. The fin  464  comprises a relatively straight first side surface  466  and a curved second side surface  468 . The wall  460  of the housing  214  and the fin  464  of the stand locking member  212  are arranged so that, as the stand locking member  212  pivots about the tip  228  of its first end  224  between the positions illustrated in  FIGS. 7   a  and  7   b  when the main body  14  is reclined from its upright position, the first side surface  466  of the fin  464  does not contact the ball bearing  462 . 
       FIGS. 17   a  and  17   b  illustrate the orientation of the motor casing  74  when the vacuum cleaner  10  has been tilted backwards on to the stabilizer wheels  184  of the stand  180  for wheeling over the floor surface. The rotation of the motor casing  74  results in the base  216  of the housing  214  now sloping downwardly towards the side wall  220  of the housing  214 , which causes the ball bearing  462  to roll under gravity away from the wall  460 . The motion of the ball bearing  462  is checked by a side surface of a piston  470  located within a piston housing  472  forming part of the housing  214  of the stand retaining mechanism  210 . A compression spring  474  located within the piston housing  472  urges the piston  470  towards the wall  460  and against an annular seat of the piston housing  472 . The seat of the piston housing  472  is shaped so as to allow the ball bearing  462  to enter the piston housing  472 , against the biasing force of the spring  474 . 
     In the event of a force being applied to the stand  180  as the vacuum cleaner  10  is wheeled over the floor surface which would tend to cause the stand  180  to rotate towards its retracted position, the increased force acting between the stand pin  250  and the protrusion  240  of the stand locking member  212  can cause the stand locking member  212  to rotate about the tip  228  of its first end  224 , against the biasing force of the spring  232 . The fin  464  of the stand locking member  212  and the piston housing  472  are arranged such that before the stand pin  250  is released by the stand locking member  212 , the curved second side surface  468  of the fin  464  contacts the ball bearing  462  so as to urge the ball bearing  462  against the piston  470 . The biasing force of the spring  474  acting on the piston  470  resists the movement of the ball bearing  462  into the piston housing  472 , which in turn increases the resistance to the rotation of the stand locking member  212  about the tip  228  of its first end  224 . Thus, in order to release the stand  180  from the stand retaining mechanism  210  the force applied to the stand pin  250  must now be able be sufficiently large as to move the stand locking member  212  to the position illustrated in  FIG. 17   b  against the biasing forces of both springs  232 ,  474  of the stand retaining mechanism  210 . 
     With the locking member  282  of the cleaner head retaining mechanism  280  in its deployed position, the cleaner head  12  is prevented from rotating relative to the yoke  26  as the vacuum cleaner  10  is wheeled over the floor surface. When the vacuum cleaner  10  is tilted on to the stabilizer wheels  184  of the stand  180  the weight of the cleaner head  12  urges the rear surface  452  of the lower yoke section  44  against the front surface  450  of the body  188  of the stand  180 . However, as the movement of the stand  180  relative to the motor casing  74 , and so the main body  14 , is restrained by the stand retaining mechanism  210 , the stand retaining mechanism  210  thus serves also to restrain the rotation of the yoke  26  relative to the main body  14  as the vacuum cleaner  10  is wheeled over the floor surface. The stand retaining mechanism  210  and the cleaner head retaining mechanism  280  thus serve to inhibit rotation of the cleaner head  12  relative to the main body  14  about two substantially orthogonal axes, respectively the pivot axis A and the axis of rotation of the cleaner head  12  relative to the yoke  26 , as the vacuum cleaner  10  is wheeled over the floor surface, which rotation could otherwise obstruct the movement of the vacuum cleaner  10 . 
     In the event that the cleaner head  12  is subjected to an impact, or its movement with the main body  14  of the vacuum cleaner  10  is restricted by engagement with an item of furniture or the like, as the vacuum cleaner  10  is wheeled over the floor surface, then the cleaner head  12  can be released for movement relative to the main body by the stand retaining mechanism  210  or the cleaner head retaining mechanism  280  as appropriate to prevent any part of the vacuum cleaner  10  from breaking. 
     As a first example, if the cleaner head  12  is subjected to an impact in a direction opposite to that in which the vacuum cleaner  10  is being pulled over the floor surface, then the force of the impact will be transferred to the stand  180  through the engagement between the rear surface  452  of the lower yoke section  44  and the front surface  450  of the body  188  of the stand  180 . Depending on the magnitude of this force, the force acting between the protrusion  240  on the stand locking member  212  and the stand pin  250  may increase sufficiently so as to cause the stand pin  250  to be released from the stand restraining mechanism  210 . This can now enable both the stand  180  and the yoke  26  to pivot about the pivot axis A of the main body  14 , thereby allowing the cleaner head  12  to move relative to the main body  14 . In the event that the magnitude of the force of the impact is insufficient to release the stand  180  from the stand retaining mechanism  210 , then the force of the impact can be absorbed through compression of the springs  232 ,  474  of the stand locking mechanism  210 . 
     As a second example, if the cleaner head  12  is subjected to an impact which causes the cleaner head  12  to rotate about its axis of rotation relative to the yoke  26 , then the side of the groove  296  formed in the collar  297  of the cleaner head  12  would be urged against the side surface of one of the fingers  292  of the locking member  282 . With reference to the sequence of images (i) to (iv) of  FIG. 18 , the locking member  282  is preferably formed from resilient material to allow that finger  292  of the locking member  282  to bend towards the other finger  292  under the bending force applied thereto by the collar  297  of the cleaner head  12 . Depending on the force of the impact the edge  296   a  of the groove  296  can move along the side surface of the bent finger  292 , thereby pushing the locking member  282  away from the groove  296  against the biasing force of the spring  306 . If the magnitude of the force of the impact is sufficiently high as to push the fingers  292  of the locking member  282  fully from the groove  296 , then the cleaner head  12  is free to rotate relative to the yoke  26  under the force of the impact. The connection between the electrical connectors  98   a ,  98   b  is preferably a push-fit connection to allow this connection to be broken upon relative rotation between the cleaner head  12  and the yoke  26 .