Abstract:
A battery pack suitable for handheld appliance, the battery pack including a plurality of cells and a circuit board associated with the cells, wherein a power terminal is associated with the circuit board and configured to transmit power to an appliance, in use, the battery pack further including a momentary switch operatively connected to the circuit board and movable between closed and open positions by an actuator wherein, when in the open position the power terminal is configured by the circuit to a power delivery state and, when in the closed position, the power terminal is configured by the circuit to a power disabled state.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of United Kingdom Application No. 1202349.5, filed Feb. 10, 2012, and United Kingdom Application No. 1210139.0, filed Jun. 8, 2012, the entire contents of which are incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The invention relates to a battery pack, and particularly a battery pack suitable for use in a battery-powered appliance such as a handheld vacuum cleaner. 
       BACKGROUND OF THE INVENTION 
       [0003]    There are various types of vacuum cleaners available on the market, and these can be categorized generally into “cylinder” vacuum cleaners, “upright” vacuum cleaners, “handheld” vacuum cleaners and “stick” vacuum cleaners, also known as “stick-vacs”. 
         [0004]    In order to provide portability, it is common for handheld vacuum cleaners and stick-vacs to be cordless whereby power is supplied to such devices by way of a battery pack. 
         [0005]    An example of a known handheld vacuum cleaner is shown in WO2010/109215 and is marketed internationally by the Applicant under the product name DC34. Here, a handheld cleaning appliance includes a removable battery pack which is generally slab-like in form with an upstanding pillar that is receivable in a dock opening in the end of a handle of the vacuum cleaner. The upper end of the pillar includes electrical terminals that connect to an electrical connector within the handle of the vacuum cleaner. In this way, power in the battery pack can be transferred to the motor of the vacuum cleaner. A trigger switch is provided on the handle and is arranged to actuate an electronic controller internal to the vacuum cleaner in order to turn the vacuum cleaner on and off. 
         [0006]    An arrangement as described in WO2010/109215 requires suitable electronic switching means internal to the vacuum cleaner, and it is desired to simplify the switch mechanism and also to improve the assembly of the battery pack. 
       SUMMARY OF THE INVENTION 
       [0007]    Against this background, from a first aspect, the invention provides a battery pack suitable for handheld appliance, the battery pack including a plurality of cells and a circuit board associated with the cells, wherein a power terminal is associated with the circuit board and configured to transmit power to an appliance, in use, the battery pack further including a momentary switch operatively connected to the circuit board and movable between closed and open positions by an actuator wherein, when in the open position the power terminal is configured by the circuit to a power delivery state and, when in the closed position, the power terminal is configured by the circuit to a power disabled state. 
         [0008]    Such an arrangement provides significant benefits in operation. In the power disabled state, in which the momentary switch is in a closed position, a very small amount of travel of the actuator results in the momentary switch transitioning from a closed position to an open position, such that the circuit board sets the battery pack into a power delivery state. The short travel required to activate the device appears almost instantaneous to the user. Following activation, the actuator is then able to move through a much larger amount of travel, preferably in the order of 5 mm to 10 mm, without affecting the state of the momentary switch. Therefore, this allows a user to alter finger position on the trigger member without inadvertently turning the machine off. In effect, therefore, the invention provides a light action trigger, but guards against the machine toggling on and off when the user&#39;s finger shifts position on the trigger during use, thereby improving ergonomics. 
         [0009]    In a second aspect, the invention provides a battery pack suitable for a handheld appliance, the battery pack including a plurality of cells and a circuit board associated with the cells, wherein the plurality of cells and the circuit board are contained within a housing, wherein the housing is defined by first and second separable housing sections which are engageable with one another to form the housing, wherein the circuit board includes an illuminable element that the circuit board is configured to illuminate to indicate the status of the battery pack, wherein the illuminable element forms part of the external surface of the battery pack. The illuminable element therefore fixes one of the housing sections relative to the circuit board and so serves as a locating feature during assembly. Furthermore, since the illuminable element is fixed directly to the circuit board, the circuit board is braced against movement within the battery pack. 
         [0010]    In a third aspect, the invention provides a battery pack suitable for a handheld appliance, the battery pack including a plurality of cells and a circuit board associated with the cells, wherein the plurality of cells and the circuit board are contained within a housing, wherein the housing is defined by first and second separable housing sections which are engageable with one another to form a complete housing, wherein the circuit board includes an illuminable element that the circuit board is configured to illuminate to indicate the status of the battery pack, wherein the illuminable element forms part of the external surface of the battery pack and is located intermediate the first and second housing parts. 
         [0011]    Preferably the illuminable element is a light pipe. 
         [0012]    Preferably, the light pipe has first and second ends that extend transversely across the battery pack and engage the housing on opposing sides thereof by protruding through respective apertures in the housing. This arrangement firmly locks the circuit board and cells against multi-axial movement within the battery pack. 
         [0013]    Since the illuminable element is effectively sandwiched between the first and second parts of the housing, the element serves as a locating feature for the housing sections during assembly. A benefit of this is that components of the circuit board, for example power terminals, can be referenced from the illuminable element as a datum position which improves manufacturability. Furthermore, since the illuminable element is held in a fixed position relative to the housing, the circuit board is supported by the element and held rigidly against mechanical shocks to the battery pack. 
         [0014]    Further optional and/or preferred features are set out in the dependent claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    So that it may be more readily understood, embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which: 
           [0016]      FIG. 1  is a perspective side view of a handheld vacuum cleaner in which a battery pack in accordance with an embodiment of the invention is incorporated; 
           [0017]      FIG. 2  is a side view of the vacuum cleaner in  FIG. 1  with a section of the handle cut away; 
           [0018]      FIG. 3  is a perspective side view of the handheld vacuum cleaner in  FIG. 1  but with the operating trigger/switch in a second position; 
           [0019]      FIG. 4  is a side view of the vacuum cleaner, as in  FIG. 2 , but with the operating trigger in the second operating position; 
           [0020]      FIG. 5  is a perspective view of the battery pack removed from the handheld vacuum cleaner; 
           [0021]      FIG. 6  is a perspective view of the battery pack in  FIG. 5 , but from a reversed angle; 
           [0022]      FIG. 7  is a perspective view of the battery pack, like that in  FIG. 5 , but with a forward portion of the battery pack housing removed to show internal detail of the battery pack; 
           [0023]      FIG. 8  is a view identical the same as that in  FIG. 7 , but with the switch unit in a second operating position; 
           [0024]      FIG. 9  is a perspective view of the battery pack, like that in  FIG. 6 , but with a rear portion of the battery pack housing removed to show internal detail of the battery pack, 
           [0025]      FIG. 10  is a perspective view of a battery pack of an alternative embodiment of the invention; and 
           [0026]      FIG. 11  is a view from above of the battery pack in  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    Referring firstly to  FIGS. 1 and 2 , a handheld vacuum cleaner  2  has a main body  4  which houses a motor and fan unit, an outer housing of which is indicated generally at  6 . The motor and fan unit  6  is located above a generally upright handle or grip portion  8 . The lower end  8   a  of the handle  8  supports a generally slab-like battery pack  10 . A set of exhaust vents  12  are provided on the main body  4  for exhausting air from the handheld vacuum cleaner  2 . 
         [0028]    The main body  4  supports a cyclonic separating apparatus  14  that functions to remove dirt, dust and other debris from a dirt-bearing airflow drawn into the vacuum cleaner by the motor and fan unit. The cyclonic separating apparatus  14  is attached to a forward part  4   a  of the main body  4  and an air inlet conduit/nozzle  16  extends along a longitudinal axis X-X from a forward portion of the cyclonic separating apparatus  14  that is remote from the main body  4 . The air inlet nozzle  16  is configured so that a suitable brush tool can be mounted to it and includes a catch  18  for securely holding such a brush tool when the tool is engaged with the inlet. The brush tool is not material to the present invention and so is not shown here. An elongate extension tube or wand (not shown) may also be mounted to the air inlet nozzle  16  to extend the cleaning reach of the vacuum cleaner. 
         [0029]    The cyclonic separating apparatus  14  is located between the main body  4  and the air inlet nozzle  16  and has a longitudinal axis Y-Y which extends in a generally upright direction so that it is substantially orthogonal with the longitudinal axis X-X of the inlet nozzle  16 . The handle  8  extends along an axis Z-Z that lies at a shallow angle to the axis Y-Y and which, in the exemplary embodiment is approximately 10 degrees, although any angle from orthogonal to about 20 degrees is suitable. 
         [0030]    The handle  8  is oriented in a pistol-grip formation which is a comfortable interface for a user since it reduces stress on a user&#39;s wrist during cleaning. The cyclonic separating apparatus  14  is positioned close to the handle  8  which also reduces the moment applied to the user&#39;s wrist when the handheld vacuum cleaner  2  is in use. The handle  8  carries an on/off switch arrangement in the form of a trigger member  20  for turning the motor and fan unit  6  on and off. In use, the motor and fan unit draws dust laden air into the vacuum cleaner  2  via the air inlet nozzle  16 . Dirt and dust particles entrained within the air flow are separated from the air and retained in the cyclonic separating apparatus  14 . The cleaned air is ejected from the rear of the cyclonic separating apparatus  14  and conveyed by a short duct section  22  to the motor and fan unit  6  located within the main body  4 , and is subsequently expelled through the air outlets  12  which may also include a fine particle filter by way of a final filtering stage to remove micro-contaminants from the airflow that exits the cleaner. 
         [0031]    It should be noted at this point that although the cyclonic separating apparatus described here is cyclonic, this is not essential to the invention and other separating apparatus are viable, for example other bagless-type separating apparatus which feature a fibrous filter element in a whirl-chamber to separate contaminants from the airstream, or even a bagged-type separating apparatus as is known in the art. The precise configuration of the cyclonic separating apparatus is not material to the present invention and so will not be described in detail here. However, one particular configuration of cyclonic separation that is suitable is described in the Applicant&#39;s co-pending application GB2475312A. 
         [0032]    Turning now to  FIG. 2 , there is shown a side view of the handheld vacuum cleaner  2  in  FIG. 1  but with a portion of the outer skin of the handle cutaway so the interior of the handle can be seen and, in particular, the on/off trigger arrangement. 
         [0033]    The battery pack  10  has a generally rectangular block-like base portion  23 . An upstanding post or pillar portion  24  extends upwardly at an angle of approximately 80° to the plane of the base portion  23 , although it should be noted that the precise angle of inclination does not form part of the invention. The handle  8  is tubular in cross section with a generally oval shape that complements the cross section of the pillar  24  of the battery  10 . Therefore, the pillar  24  of the battery  10  is receivable by the open lower end  8   a  of the handle  8  so that the battery pack  10  may be docked onto the vacuum cleaner  2 . 
         [0034]    An upper end of the pillar  24  includes electrical terminals that connect to corresponding electrical connectors housed in the interior of the handle  8  and which lead to an electronic control module (not shown) that is interfaced to the motor and fan unit. Electrical power is therefore transmitted from the battery pack  10  to the motor and fan unit  6  via the electrical connectors. 
         [0035]    The pillar  24  also includes a mechanically actuated switch unit  26  that is oriented so as to extend upwardly from the top face of the pillar  24 . The switch unit  26  includes an actuator  28  and is operated by an end of the trigger member  20 , as will now be described. 
         [0036]    The trigger member  20  takes the form of a bell crank having a first end  20   a  in the form of an actuating finger that is engageable with the battery switch unit  26  and a second end  20   b  that provides a contact face for the trigger member  20  and which protrudes through a forwardly facing aperture  30  in the handle  8 . The contact face  20   b  of the trigger is seen clearly in  FIG. 1  extending through the aperture  30 . A plate-like finger rest  32  extends forwardly from the handle  8  at a position just below the aperture  30  and provides a means to prevent a user&#39;s finger from slipping off the trigger member  20  in use. It also allows a user to grasp the handle without actuating the trigger, during carrying for example. 
         [0037]    The trigger member  20  is biased into a non-actuating position by a biasing means which in this element is a spring element  34  that extends between a spring retaining member  36  provided on the rear of the contact face  20   b  and a spring abutment member  38  provided in the handle  8 . The spring element  34  therefore biases the trigger member such that the contact face  20   b  protrudes from the aperture  30  in the handle and the actuating finger  20   a  is spaced from the actuating switch unit  26  of the battery pack  10 . When the trigger member  20  is in this position, the motor and fan unit  6  does not operate. Expressed another way, the trigger arrangement takes the form of a so-called ‘dead man&#39;s trigger’ which will only operate the vacuum cleaner whilst it is being depressed by a user. 
         [0038]    In order to operate the vacuum cleaner  2 , a user depresses the trigger member  20  to an operating position, which is shown in  FIGS. 3 and 4 . In this position, the activating finger  20   a  of the trigger member  20  engages the activating switch unit  26  of the battery pack  10  which initiates power supply to the electronic control module of the motor and fan unit  6  thereby operating the vacuum cleaner. Also, in this position the contact face  20   b  of the trigger member  20  recedes into the trigger aperture  30  on the handle  8  so that it lies substantially flush with the adjoining portions of the handle  8 . 
         [0039]    The battery pack  10  will now be described in more detail with reference to  FIGS. 5 to 9 , in which the battery pack  10  is separated from the appliance and in which the interior components of the battery pack  10  are shown in detail. 
         [0040]    As has been mentioned, the battery pack  10  generally comprises a block-like base portion  23  and a pillar portion  24  that extends upwardly away from the base. These portions of the battery pack  10  are defined by a two-part housing  40 . 
         [0041]    The housing  40  serves to contain the operational components of the battery pack  10 , the major parts being a cell assembly  42  and the switching unit  26  as has been referred to above. The cell assembly  42  comprises a plurality of cells  44  (six in this embodiment) which are cylindrical in form and mounted in a cell block or cage  46  in parallel so that their longitudinal axes are transverse to the long axis ‘A’ of the battery pack  10 . A circuit board  48  is mounted to the cell block  46 , which may be a plastics material, and carries all the necessary electronics required to control the delivery of power from the cells  44  to electrical terminals  50  of the battery pack, and to control the recharging of the cells. It should be noted that the electrical terminals are mounted directly to the circuit board  48  and extend upwardly away therefrom—this provides the terminals with a rigid mounting point and does not require a dedicated connector block to be coupled to the housing in some manner. Ends of adjacent cells  44  having opposite polarity are connected by cell connectors  52 , two of which are show in  FIG. 7 , and the cell connectors  52  are linked to the circuit board  48  by voltage monitoring tabs  54  by which means the control circuitry is able to monitor the voltages on individual cells. Power take-off tabs  55  are provided on the first and last cells in the group and it will be seen that the power take-off tabs  55  are relatively thick compared to the voltage monitoring tabs  54  in order to cope with high current values. The circuit board  48  is mounted on top of the cell block  46  and, in this embodiment extends along its longitudinal axis ‘A’ in parallel therewith. Since the housing  23  defines a close fit with the cells, an elongated protrusion or ‘hump’  55  is provided on the housing which stands proud of the remainder of the battery pack and so provides additional internal volume to accommodate the circuit board  48 . A longitudinal rib  57  extends along the upper surface of the hump  55  and provides a means to strengthen the engagement with the vacuum cleaner. The exact form of the circuit board  48  design is not central to the invention and so will not be described in detail. 
         [0042]    The two-part housing  40  is defined by first and second housing sections  56 ,  58 . The housing is split so that each of the sections  56 ,  58  defines a part of the block-like base portion  23  or ‘cell housing’ and a part of the pillar portion  24 . The first housing section  56  is shown to the right in  FIGS. 5 to 7 , and the second housing section  58  is shown on the left. Accordingly, the split line  60  between the first and second sections  56 ,  58  can be seen running substantially vertically along the base portion  23  and the pillar portion  24 . 
         [0043]    The pillar portion  24  contains the switch unit  26  of the battery pack  10 , as has been generally described above. In more detail, the switch unit  26  comprises the actuator  28  and a momentary switch  64  that is connected to the circuit board  48 . In this embodiment, the momentary switch  64  is a miniature snap-action switch as is generally known in the art as a microswitch. 
         [0044]    In the position shown in  FIG. 7 , the battery pack  10  is in a power disabled state, so that the circuit board  48  does not deliver a voltage to the terminals  50  of the battery pack. In this state, a contacting part  28   a  of the actuator  28  protrudes upwardly from the pack, more specifically the upper surface of the pillar  24 —this is the position also shown in  FIG. 2 . The end of the actuator  28  distal from the contacting part  28   a  defines an actuating part  28   b  which in the form of a right-angled leg which extends underneath the momentary switch  64 . In this position, since the contact part  28   a  of the actuator  28  is urged upwardly by a spring element (not shown) the actuating part  28   b  is engaged with the momentary switch  64 , so that the momentary switch  64  is in a closed position. 
         [0045]      FIG. 8  shows the battery pack  10  in a power delivery state. In this state, the contact part  28   a  of the actuator  28  has been pressed downward and so is recessed into the pillar  24 . Accordingly, the actuating part  28   b  of the actuator  28  is moved out of contact with the momentary switch  64 , so that the momentary switch  64  is set to an open position. The circuit board  48  electronics are configured to detect the opening of the momentary switch  46  and trigger power delivery to the terminals  50  of the battery pack. 
         [0046]    Such an arrangement of the actuator  28  and the momentary switch  64  has significant benefits in operation. In the power disabled state illustrated in  FIG. 7 , in which the momentary switch  64  is in a closed position, a very small amount of travel of the actuator  28  results in the momentary switch  64  transitioning from a closed position to an open position, such that the circuit board  48  sets the battery pack into a power delivery state. 
         [0047]    As the switch unit  26  is operated mechanically by the trigger member  20 , the short travel required to activate the device appears almost instantaneous to the user. Following activation, the actuator  28  is then able to move through a much larger amount of travel, in the order of 5 mm to 10 mm, without affecting the state of the momentary switch  26 . Therefore, this allows a user to alter finger position on the trigger member  20  without turning the machine off. In effect, therefore, the invention provides a light action trigger, but guards against the machine toggling on and off when the user&#39;s finger shifts position on the trigger during use. The ergonomics of the vacuum cleaner are improved as a result. 
         [0048]    The battery pack  10  of the invention also includes a feature to assist in its assembly, as will now be explained. The circuit board  48  includes a status indicator  70  which is operable in use to illuminate in various circumstances, for example when the battery charge level is low, and when the battery pack is being charged. 
         [0049]    In this embodiment, the status indicator  70  is an illuminable element in the form of a light pipe that is surface-mounted to the circuit board  48  in the region of the pillar portion  24 . Here, the light pipe  70  is secured in place on the circuit board by a screw  72  that passes through a central boss  74 , although it will be appreciated that the light pipe  70  may be affixed to the circuit board  48  by other techniques, such as using an epoxy. Alternatively, the light pipe  70  could include a projecting feature, such as a stud, that is press-engaged with a complementary-shaped recess in the circuit board. The light pipe  70  is located on top of a light emitting diode  75  (shown in  FIG. 9 ) that is secured to the circuit board  48  underneath the light pipe  70 . 
         [0050]    The light pipe  70  may be manufactured from any suitable materials known in the art, such as glass or, more preferably, an optical grade plastic such as polycarbonate. 
         [0051]    The light pipe  70  is bar-like in shape and extends transversely across the circuit board  48  in a direction that is generally perpendicular to the longitudinal axis A of the battery pack  10 , and therefore generally in parallel with the cells  44 . The light pipe  70  has first and second ends  76 ,  78 , each of which protrudes through the housing  40  at a point towards the base of the pillar portion  24 . The light pipe therefore forms part of the external surface of the battery pack  10 . It should be noted here that a single light source is split via the light pipe two ways so as to provide an indicator on either side of the battery pack. 
         [0052]    The ends  76 ,  78  of the light pipe  70  serve to position correctly the first and second sections  56 ,  58  of the housing  40 . For this purpose, each end of the light pipe  70  includes a first abutment surface  80  that is engageable with a corresponding abutment surface  81  of the first housing section  56 , and a second abutment surface  82  which is engageable with a corresponding abutment surface  83  of the second housing section  58 . It should therefore be appreciated that the ends  76 ,  78  of the light pipe  70  are in a position so as to sit intermediate the first and second housing parts, that is to say, on the split line  60  of the two-part housing  40 . 
         [0053]    In this embodiment, the light pipe ends  76 ,  78  are rectilinear, preferably rectangular, and fit into a complementary-shaped cut-out in the first housing section  56 . This ensures a close fit between the light pipe  70  and the housing sections  56 ,  58 . However, the light pipe ends  76 ,  78  could be alternative shapes, for example circular or oval, and still provide the necessary abutment surface for the housing sections  56 ,  58 . Furthermore, both the first and second housing sections  56 ,  58  may include cut-outs to define a suitably shaped aperture for the light pipe ends. 
         [0054]    Since each of the first and second housing sections  56 ,  58  abut up against the light pipe  70 , the light pipe serves as a locating feature for the housing sections during assembly. 
         [0055]    This increases the rigidity of the battery pack housing  40  as a whole, and ensures that the housing sections  56 ,  58  are properly positioned with respect to the cells. Furthermore, since the light pipe  70  is held in a fixed position relative to the housing, since it is sandwiched between the housing sections  56 ,  58 , the circuit board  48  is supported by the rigidly held light pipe. This increases its resilience to mechanical shock and reduces the need for other fastening means (epoxies, for example) to join the circuit board  48  securely to the cell block  46 . Also, since the light pipe engages with the housing, and the light pipe is attached securely to the circuit board, the light pipe serves as a datum point for the terminals of the circuit board so that they are positioned precisely within the pillar portion  24  of the housing. 
         [0056]    The skilled person would be aware that various modifications could be made to the specific embodiments described above without departing from the broad concept of the invention as defined by the claims. 
         [0057]    For example, although the specific embodiment includes a light pipe  70  having two ends  76 ,  78 , both of which protrude from the split line  60  between the first and second housing sections  56 ,  58  of the battery pack  10 , a similar effect could be achieved if the light pipe  70  only had one protruding part. Similarly, it is not essential that the light pipe  70  protrude from the housing  40  at a location close to the base of the pillar  24 , although this location has been found to be convenient in this embodiment. In principle the status indicator  70  could protrude from the housing  40  at any point along the split line  60  between the first and second housing sections  56 ,  58 . 
         [0058]    A further embodiment is shown in  FIGS. 10 and 11 . This embodiment is substantially the same as the embodiments described above so only the differences will be described here. 
         [0059]    In this embodiment, the ends  76 ,  78  of the light pipe  70  extend to the surface of the battery pack housing as in previous embodiments. However, the ends of the light pipe do not sit on the split line  60  between the first and second housing sections  56 ,  58 . 
         [0060]    Instead, the ends  76 ,  78  of the light pipe sit in a complementary shaped aperture defined in the first housing section  56 , that is to say an aperture defined wholly by one of the housing sections instead of being defined partly by each housing section. Such an arrangement provides the same benefits as in previous embodiments, chief of which is to provide a secure mounting point to position the circuit board and the battery pack relative to the battery pack housing. 
         [0061]    During assembly, the first housing section is received onto the cell block and the housing deforms slightly to enable the light pipe ends  76 ,  78  to snap-fit into their respective apertures. The light pipe ends  76 ,  78  therefore engage the housing section  76  at two opposed points and so brace the circuit board against movement along multiple axes. In this embodiment, therefore, the light pipe serves to hold the circuit board in a fixed position relative to the housing, and also acts as a datum point for the components of the circuit board, for example the power terminals, relative to the housing.