Abstract:
An electrical device comprising a housing for electrical circuitry, the housing defining a cavity opening to the exterior of the device. The cavity includes a first and second fixing arrangement capable of mechanically interlocking with a power connection insert to fix the power connection insert in position. The power connection insert provides a power cable or power connector that couples the electrical circuitry to an external electrical power supply for the device. The use of different power connection inserts allows a wide range of connector types to be provided using a single design of the housing.

Description:
[0001]    The present invention relates to an electrical device. Preferred embodiments relate to power tools and gardening equipment such as lawn mowers, trimmers, hedge trimmers, string trimmers and the like. 
       BACKGROUND OF THE INVENTION 
       [0002]      FIG. 1  shows an example of an electrical device  1 , which in this example is an electrically powered string trimmer  1  as known in the prior art. The string trimmer  1  has a cutting end  2  which has a rotating string or strings for cutting grass, etc. At the other end, the string trimmer  1  has a handle  3  by which the operator can manipulate the device. The handle  3  has a power connection  4  by which electrical power can be supplied to the string trimmer  1 . 
         [0003]      FIG. 2  shows a detailed view of the handle  3  of the string trimmer  1 . In this example, the power connection  4  takes the form of a socket  5  formed in the housing  6  of the handle  3 . A power cable  7  has a corresponding plug  8  for plugging into the socket  5 . The operator of the trimmer  1  connects the other end of the power cable  7  to a suitable mains electricity outlet to provide power to the trimmer  1 . 
         [0004]    Different countries have different standards and safety regulations governing the arrangement of plugs/sockets and the provision of electrical power to electrical devices. Furthermore, many countries have specific regulations governing the provisioning of power to power tools and other equipment where there is a risk of accidentally severing the electrical power cable  7 .  FIGS. 3 to 5  show three examples of different ways in which a power connection can be made to an electrical device  1  which are used in various countries. 
         [0005]    In  FIG. 3 , a socket  5  in the form of a male connector comprising a protruding body portion  5 A and conducting pins  5 B which extend from the body portion  5 A. The power cable  7  has a plug  8  in the form of a female connector for mating with the male connector of the socket  5 . The plug  8  comprises a body portion  8 A having holes  8 B for receiving the pins  5 B of the socket  5 . The plug also has a shell portion  8 C which extends beyond the body  8 A and forms a receptacle in which the body portion  5 A is received when the two are mated. This helps make a mechanical connection between the two parts. This also shields the pins  5 B when the plug  8  and socket  5  are engaged. Such an arrangement is common for example in various European countries. 
         [0006]    In  FIG. 4 , the socket  5  of the device is a male connector comprising a receptacle  5 C within which the male pins  5 B are positioned. The power cable  7  has a plug  8  in the form of a female connector for mating with the male connector of the socket  5 . The plug  8  comprises a body portion  8 A having holes  8 B for receiving the pins  5 B of the socket  5 . The body portion  8 A is received in the receptacle  5 C when the two parts mate. This arrangement helps make a secure mechanical connection between the two parts as well as shielding the pins  5 B. Such an arrangement is common for example in the United States of America. 
         [0007]    In  FIG. 5 , the device has the cable  7  fixedly attached to the housing, i.e. there is no plug and socket arrangement to allow the cable to be connected/disconnected from the device by the operator. Such an arrangement is common for example in the United Kingdom. 
         [0008]    It should be noted that in this document the convention is followed of referring to the connector on the electrical device as the “socket” and the connector on the power cable which moves to connect with the device as the “plug”. Also, the connector with protruding pins is known as the “male” connector and the connector with holes for receiving those pins is known as the “female” connector. Thus, the convention which is sometimes seen of always referring to the connector with the protruding pins as the plug is not necessarily followed herein. The terminology of plug/socket and male/female connector used herein is intended to be a convenient way of referring to the connector parts of the power cable/device and is not intended to be limiting unless specifically stated. 
         [0009]    The proliferation of different arrangements for making a power connection to a device  1  creates a problem for manufacturers of such devices  1  in that to sell the device in different countries often requires redesigning the part of the device that deals with the power connection. In particular, the housing  6  of the device  1  is commonly manufactured from moulded thermoplastic or suchlike and is arranged according to the particular power connection that is required for that device  1 . Thus, the manufacturer must have different tooling for manufacturing the housing of the tool for different countries. This is expensive and inconvenient for manufacturers. 
         [0010]    According to a first aspect of the present invention, there is provided an electrical device, the device comprising: a housing; electrical circuitry in the housing, wherein the walls of the housing define a cavity having a first end that is open to the exterior of the device and a second end that is inside the housing, the housing having a first fixing arrangement at the first end of the cavity and a second fixing arrangement at the second end of the cavity, wherein the first and second fixing arrangements are each capable of fixing a power connection insert in position; and, a power connection insert fixed by either the first or second fixing arrangement, wherein the power connection insert and that fixing arrangement are constructed and arranged to mechanically interlock with each other, wherein the power connection insert provides a power cable or power connector, said power cable or power connector being electrically connected to said electrical circuitry such that external electrical power can be supplied to the device via the power cable or power connector. 
         [0011]    By appropriate design of the insert and appropriate positioning of the insert in either the first or second fixing arrangement of the housing, the invention allows a wide range of connector types to be provided using a single design of housing. Having two fixing arrangements with different positions allows connectors to be formed using appropriate inserts that can protrude beyond the housing and that can use the cavity to provide shielding for the connection formed when a plug is plugged into that connector. Alternatively a power cable insert can be used where it is not desired to provide a connector at the device. This allows the device to be provided with an appropriate power connection type for most if not all territories in which the device may be sold. This allows manufacturers to keep down costs of manufacturing by having a single design of housing for their product, which reduces tooling costs, and which is also simple to assemble. The design can also be extended to provide different connector types if new connector types are developed in the future by designing appropriate new inserts. The invention is therefore also relatively future proof. 
         [0012]    Preferably at least one fixing arrangement is such that there is no straight line path between the insert and the interior of the housing. This helps prevent dust, debris, etc from penetrating the housing. Potentially water can be prevented from penetrating by watertight fit between the housing and insert or by adding seals. 
         [0013]    Preferably at least one fixing arrangement is a slot defined by the walls of the housing extending around part or all of the periphery of the cavity. Preferably the insert has a flange which fits into the slot to fix the insert in place. Preferably both fixing arrangements are defined by slots defined by the walls of the housing extending around the periphery of the cavity. These provide a secure way of fixing the insert into position which is simple to manufacture and assemble. 
         [0014]    Preferably the first slot has a wider width that the second slot. Generally, the first slot should be wider than the cavity, so that the cavity is accessible, whereas the second slot may be smaller than the width of the cavity, which allows a smaller insert to be used to fit into the second slot. 
         [0015]    Preferably the cavity is open or has a hole at its second end through which electrical connection is made between the insert and the electrical circuitry. Generally the electrical circuitry to which a power connection needs to be made will be accommodated within a compartment in the housing. Having an open ended cavity or a hole in the cavity allows electrical wires to be passed from the insert to the electrical circuitry. 
         [0016]    Preferably the shape of the cavity is adapted to receive and mate with the body of a standard format connector plug. This can help retain the plug in a socket formed in the device by the appropriate insert. 
         [0017]    In an embodiment, the insert is fixed to the second fixing arrangement, the insert having connector pins which extend into the cavity to form a connector. Thus, a socket is formed in the device by the cavity and insert to which a connector plug can be inserted to make electrical connection to the device. This arrangement can be used to provide for example a connector suitable for use in the United States of America, e.g. the connector known as NEMA 1-15 (North American 15 A/125 V ungrounded). 
         [0018]    In an embodiment, the insert is fixed to the first fixing arrangement, the insert having a body portion that extends beyond the housing, the insert having connector pins which extend beyond the body portion to form a connector. This arrangement can be used for example to provide a connector suitable for various European countries, e.g. the connector known as the CEE 7/16 (Europlug 2.5 A/250 V ungrounded). 
         [0019]    Preferably, the shape of the body portion of the insert is adapted to be received and mate with a shell of a standard format connector plug. This forms a connector in the device having an extending portion which can mate with part of a connector plug to keep the plug in place. 
         [0020]    In an embodiment, the insert is fixed to the first fixing arrangement, the insert having a body with a power cable fixed thereto, the power cable extending through the body into the housing and being connected to the electrical circuitry. This can provide a means of providing power to the device without using a connector at the device suitable for use for example in the United Kingdom. 
         [0021]    Preferably, the housing is formed in two parts which attach together to form the cavity. The housing may be formed in two halves which come together along their central plane to form the housing and to form the cavity. Thus, insert can be sandwiched between the parts of the housing as they are attached together, allowing a convenient method of manufacturing the device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: 
           [0023]      FIG. 1  shows an electrical device as known in the prior art; 
           [0024]      FIG. 2  shows a detailed view of the handle area of the device of  FIG. 1 ; 
           [0025]      FIGS. 3 to 5  show examples of electrical power connections between a power cable and a device; 
           [0026]      FIG. 6A  shows a sectional view of an example of a housing for an electrical device according to an embodiment of the present invention, and  FIGS. 6B to 6D  show examples of power connection inserts for use with the housing of  FIG. 6A ; 
           [0027]      FIG. 7  shows in cross section the insert of  FIG. 6B  installed with the housing of  FIG. 6A ; 
           [0028]      FIG. 8  shows in cross section the insert of  FIG. 6C  installed with the housing of  FIG. 6A ; 
           [0029]      FIG. 9  shows in cross section the insert of  FIG. 6D  installed with the housing of  FIG. 6A ; 
           [0030]      FIGS. 10 to 12  show detailed views of the arrangements of  FIGS. 7 to 9  respectively. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]      FIG. 6A  shows in cross section a housing  6  for part of an electrical device  1 . The electrical device  1  may be any sort where electrical power is provided to the device  1  by a power cable, such as, but not limited to, power tools and garden equipment such as lawnmowers, trimmers, etc. In the present example, the housing  6  forms part of a handle  3  for a device  1 , such as the handle of a string trimmer as shown in  FIGS. 1 and 2 . 
         [0032]    The housing  6  has walls that define a cavity  11  in the housing  6 . The cavity  11  is generally tubular in shape and in this example is generally cylindrical, having a first end  12  which is open to the outside of the device  1  so the cavity  11  is externally accessible, and a second end  13  which is inside of the housing  6  adjacent to another compartment of the housing  6 . Preferably there is a hole in the housing  6  at the second end  13  of the cavity  11  to allow wires to pass from the cavity to the interior of the housing  6  for connection to the power circuitry of the device  1 . 
         [0033]      FIGS. 6B to 6D  show examples of power connection inserts  20 ,  30 , and  40 . As described in more detail in the following description, any of these may be received and held in position in the cavity  11 . According to the type of insert, the insert may be positioned either at the first end of the cavity or the second end of the cavity as will be described. 
         [0034]    The housing  6  has fixing arrangements to fix the inserts in position in the cavity  11  by enabling a mechanical interlock to be made between the inserts and the housing  6 . In the example of  FIGS. 6A , the fixing arrangements are provided by a first circumferential slot  14  defined by the walls of the housing  6  adjacent the first end of the cavity  11 , and a second circumferential slot  15  is defined by the walls of the housing  6  adjacent the second end  13  of the cavity  11 . The first circumference slot  14  has a larger diameter than the second slot  15 . The inserts  20 ,  30 , and  40  shown in  FIGS. 6B ,  6 C and  6 D each have a body  21 ,  31  and  41  with a protruding circumferential flange  22 ,  32  and  42  which is received in one of the slots  14 , 15  of the cavity  11 , thereby forming a mechanical interlock between the insert and the housing  6 , in order to hold the insert in position. 
         [0035]    The housing  6  is preferably formed in at least two parts to aid assembly of the device  1 . In the preferred example, the housing is in two halves (one half being shown in  FIG. 6A ) which are fixed together by fasteners so that the housing  6  forms the cavity  11  and fits about the insert (shown most clearly in  FIGS. 10 to 12 ). 
         [0036]      FIG. 6B  shows an insert  20  for providing a connector of the type which is suitable for use for example in the USA. The body  21  of the insert  20  has two conductor pins  23  extending from it. The body  21  has a circular flange  22  projecting radially outwards which fits into the second slot  15  in the housing  6 .  FIGS. 7 and 10  show the insert  20  received within the cavity  11 . As can be seen from  FIG. 7 , the rear portions of the pins  24  are connected by wires  25  to the power circuitry of the device  1 . Thus, the cavity  11  and the projecting pins  23  form a socket which can receive a plug  8  of the type shown in  FIG. 4  to enable electrical connection to be made to the device  1 . The connector thus formed can be a NEMA 1-15 (North American 15 N125 V ungrounded) type in which the pins  23  have the form of two flat parallel non-coplanar blades. The inside surface of the cavity  11  preferably has a shape which closely receives the body of the plug  8  to avoid the plug working loose when the device  1  is in operation. 
         [0037]      FIG. 6C  shows an insert  30  for providing a connector of the type which is suitable for use for example in various European countries known as the CEE 7/16 (Europlug 2.5 A/250 V ungrounded). The body  31  has two conductor pins  33  extending therethrough. The body  31  is generally cylindrical and has a circular flange  32  projecting radially outwards from its rear end which fits into the first slot  14  in the housing  6 .  FIGS. 8 and 11  show the insert  30  received within the housing  6 . As can be seen, when so positioned, the cylindrical portion of the body  31  of the insert  30  extends outwards from the housing  6  of the device  1 . As can be seen from  FIG. 8 , the rear portions  34  of the pins  33  are connected by wires  35  to the power circuitry of the device  1  inside the housing  6 . Thus, body  31  and the projecting pins  33  form a socket which can mate with a plug  8  of the type shown in  FIG. 5  to enable electrical connection to be made to the device  1 . The body  31  of the insert preferably has a shape which closely fits the shell part of the plug  8  to avoid the plug working loose when the device  1  is in use. 
         [0038]      FIG. 6D  shows an insert  40  suitable for use in for example the United Kingdom. This insert  40  comprises a body portion  41  having a circular flange  42  projecting radially outwards from its rear end which fits into the first slot  14  in the housing  6 . The body  41  has a power cable  43  passing therethrough and may optionally have a strain relief grommet  44  attached to its outer face to support and protect the power cable  43 .  FIGS. 9 and 12  show the insert  40  received within the housing  6 . As can be seen from  FIG. 9 , once it passed through the body of the insert  40 , the cable  43  connects to the power circuitry of the device  1  inside the housing  6 . The wires of the cable  44  may be connected by a screw junction box  45  to enable easy connection and/or replacement of the cable  44  in case of damage. Thus, the insert  40  provides a power cable to enable electrical connection to be made to the device  1 . 
         [0039]    Thus, the manufacturer of the electrical device can manufacture a housing  6  to a single design and by using the appropriate inserts  30 , 40 , 50 , can provide a wide range of different power couplings to adapt the device to different requirements or the different standards of different countries. 
         [0040]    As the skilled person will appreciate, the present invention is not limited to the particular examples of connector show and described herein. Other connector types can be provided using the schemes outlined herein. For example, the inserts could be adapted to be grounded to the housing where the housing is made of a metal, and/or to have earth wire. 
         [0041]    Different fixing arrangements could be used to fix the inserts  20 ,  30  and  40  to the housing  6 . For example, the housing  6  could have projections and the insert  20 ,  30  and  40  could have corresponding holes in its body to receive the projections, or visa versa. The projections can extend all the way around the circumference of the insert  20 ,  30  and  40  or be at discrete intervals. The insert  20 ,  30  and  40  and the walls of the housing  6  defining the cavity  11  can be keyed to prevent misinsertion or misalignment of the insert  20 ,  30  and  40  in the cavity  11 . The walls of the housing defining the cavity  11  could be keyed to the plug  8  to prevent the plug  8  being misinserted or to aid alignment when plugging in the plug  8 . 
         [0042]    It is preferred however that the interlock between the housing  6  and insert  20 ,  30  and  40  is such that there is no straight line path into the housing between the housing and the insert to help prevent debris and/or moisture entering the housing  6 . 
         [0043]    Embodiments of the present invention have been described with particular reference to the example illustrated. However, it will be appreciated that variations and modifications may be made to the examples described within the scope of the present invention.