Patent Publication Number: US-2022232766-A1

Title: Working machine

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Chinese Patent Application No. 202110087072.4 filed on Jan. 22, 2021, the entire contents of which are hereby incorporated by reference into the present application. 
     TECHNICAL FIELD 
     This disclosure herewith relates to a working machine. 
     BACKGROUND 
     Japanese Patent Application Publication No. 2013-000029 describes a working machine. The working machine is operable using electric power supplied from a battery pack, and is used in a state of being in contact with a ground. The working machine includes a battery pack receptacle to which the battery pack can be attached. 
     SUMMARY 
     When a long workable time is required for the working machine disclosed in Japanese Patent Application Publication No. 2013-000029, a power supply having a rated capacity larger than a rated capacity of the battery pack is used instead of the battery pack. There are various types of power supplies having different housing shapes. The present specification discloses a technique in which a plurality of types of power supplies having different housing shapes can be used in a working machine. 
     A working machine disclosed herein may be configured to operate with electric power supplied from a first power supply or a second power supply and configured to be used in a state of being in contact with a ground. Each of the first power supply and the second power supply may comprise a battery cell; a housing configured to house the battery cell; a power cable extending from the housing and configured to discharge electric power; and a connector disposed at an end of the power cable. The housing of the first power supply and the housing of the second power supply may have different shapes from each other. The working machine may comprise a power supply receptacle to which either the first power supply or the second power supply is configured to be detachably attached; and a connector coupler configured to be coupled with the connector. 
     In the above configuration, the working machine can be used with the first power supply being attached to the power supply receptacle, or the working machine can also be used with the second power supply having a housing shape different from that of the first power supply being attached to the power supply receptacle. Due to this, a plurality of types of power supplies having different housing shapes can be used for a working machine. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a working machine  2  to which a first power supply  28  according to an embodiment is attached. 
         FIG. 2  is a cross-sectional view of vicinity of a cutting blade  16  of the working machine  2  according to the embodiment. 
         FIG. 3  is a perspective view of a power supply receptacle  26  according to the embodiment. 
         FIG. 4  is a perspective view of the first power supply  28  in a state where a first upper housing  40  according to the embodiment is closed. 
         FIG. 5  is a perspective view of the first power supply  28  in a state where the first upper housing  40  of the embodiment is open. 
         FIG. 6  is a perspective view of vicinity of a connector coupler  48  of the working machine  2  according to the embodiment. 
         FIG. 7  is a cross-sectional view of a key insertion part  54  according to the embodiment. 
         FIG. 8  is a perspective view of vicinity of the key insertion part  54  in a state where a cover  50  according to the embodiment is closed. 
         FIG. 9  is a cross-sectional view of vicinity of a third machine-side engagement part  98  in a state where the first power supply  28  of the embodiment is attached to a power supply receptacle  26 . 
         FIG. 10  is a cross-sectional view of vicinity of a first machine-side engagement part  94  in a state where the first power supply  28  of the embodiment is attached to the power supply receptacle  26 . 
         FIG. 11  is a perspective view of the third machine-side engagement part  98  according to the embodiment. 
         FIG. 12  is a cross-sectional view of the vicinity of the third machine-side engagement part  98  when the first power supply  28  according to the embodiment is attached to the power supply receptacle  26 . 
         FIG. 13  is a perspective view of the working machine  2  to which a second power supply  30  according to the embodiment is attached. 
         FIG. 14  is a perspective view of the second power supply  30  according to the embodiment. 
         FIG. 15  is a top view of the second power supply  30  in a state where a second upper housing  152  according to the embodiment is removed. 
         FIG. 16  is a cross-sectional view of the vicinity of the third machine-side engagement part  98  in a state where the second power supply  30  according to the embodiment is attached to the power supply receptacle  26 . 
         FIG. 17  is a cross-sectional view of vicinity of a second machine-side engagement part  96  in a state where die second power supply  30  according to the embodiment is attached to the power supply receptacle  26 . 
     
    
    
     DETAILED DESCRIPTION 
     Representative, non-limiting examples of the present disclosure will now be described in further detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the present disclosure. Furthermore, each of the additional features and teachings disclosed below may be utilized separately or in conjunction with other features and teachings to provide improved working machines, as well as methods for using and manufacturing the same. 
     Moreover, combinations of features and steps disclosed in the following detailed description may not be necessary to practice the present disclosure in the broadest sense, and are instead taught merely to particularly describe representative examples of the present disclosure, furthermore, various features of the above-described and below-described representative examples, as well as the various independent find dependent claims, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings. 
     All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or toe claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter. 
     In one or more aspects of the present teachings, the first power supply may further comprise a first specific engagement part, disposed on the housing of toe first power supply. The second power supply may further comprise a second specific engagement part disposed on the housing of die second power supply. The power supply receptacle may comprise a first machine-side engagement part disposed at a position corresponding to the first specific engagement part and engageable with the first specific engagement part to fix the first power supply to the power supply receptacle; and a second machine-side engagement part disposed at a position corresponding, to the second specific engagement part and engageable with the second specific engagement part to fix the second power supply to the power supply receptacle. 
     In the above configuration, die first power supply can be firmly fixed to the power supply receptacle, and the second power supply can be firmly fixed to the power supply receptacle. 
     In one or more aspects of the present teachings, each of the first power supply and the second power supply may further comprise a common engagement part disposed on die housing. The power supply receptacle may further comprise a third machine-side engagement part disposed at a position corresponding to the common engagement part of each of both the first and second power supplies and engageable with the common engagement part to fix either the first power supply or the second power supply to die power supply receptacle. 
     In the above configuration, the third machine-side engagement part is engageable with the common engagement part of the first power supply and also is engageable with the common engagement part of the second power supply. Thus, the configuration of the power supply receptacle can be prevented from becoming complicated. 
     Embodiment 
     A working machine  2  according to an embodiment will be described with reference to  FIGS. 1 to 17 . As shown in  FIG. 1 , the working machine  2  is a lawn mower. The working machine  2  is operable using power supplied from a first power supply  28  or a second power supply  30  described later. The working machine  2  is used in a state of being in contact with a ground. The working machine  2  comprises a body unit  4 , a grass collector unit  6 , and a handle unit  8 . The body unit  4  includes four wheels  10  that are in contact with the ground. The grass collector unit  6  is detachably attached to a rear end of the body unit  4 . The handle unit  8  is connected to a rear upper portion of the body unit  4 . When a user stands behind the working machine  2  and holds an upper portion of the handle unit  8  with both hands and pushes the handle unit  8  forward, the wheels  10  rotate and the body unit  4  moves forward along the ground. Hereinafter, a direction in which the wheels  10  rotate and the body unit  4  moves along the ground will be referred to as a front-rear direction, a direction orthogonal to the ground will be referred to as an up-down direction, and a direction orthogonal to the front-rear direction and the up-down direction will be referred to as a left-right direction. 
     As shown in  FIG. 2 , the body unit  4  comprises a deck  12 , a drive shaft  14 , a cutting blade  16 , a fan  18 , a motor receptacle  20 , a motor for cutting blade (cutting blade motor)  22 , and an ECU (not shown). A lower surface of the deck  12  has an opening in a substantially cylindrical shape toward the ground. An opening  12   a  having a substantially circular shape is defined on an upper surface of the deck  12 . A space inside the deck  12  communicates with a duct (not shown) that has a port toward a rear side of the body unit  4 . When the grass collector unit  6  (see  FIG. 1 ) is attached to the rear end of the deck  12 , the space inside the deck  12  communicates with a space inside the grass collector unit  6  via the duct. The drive shaft  14  extends substantially along the up-down direction. The cutting blade  16  and the fan  18  are disposed in the space inside the deck  12 . The cutting blade  16  is fixed to a lower end of the drive shaft  14 . The cutting blade  16  extends from the drive shaft  14  in a direction substantially orthogonal to the up-down direction. The fan  18  is fixed to the drive shaft  14  at a spot higher than the cutting blade  16 . As the drive shaft  14  rotates, the cutting blade  16  rotates, by which grass on the ground is cut. When the drive shaft  14  rotates, the fan  18  rotates by which a flow of air traveling from the opening on the lower surface of the deck  12  toward the duct is generated in the space inside the deck  12 . Due to this, the grass cut by the cutting blade  16  is sucked up by the fan  18  and delivered to the grass collector unit  6  via the duct. 
     The motor receptacle  20  is fixed to the upper surface of the deck  12 . The motor receptacle  20  has the cutting blade motor  22  fixed thereto. The cutting blade motor  22  is, for example, a brushless motor. The cutting motor  22  is configured to rotate the drive shaft  14 . The ECU includes, for example, an inverter circuit (not shown) including a plurality of switching elements (not shown) and a control circuit (not shown) configured to control operations of the plurality of switching elements. The ECU controls operation of the cutting blade motor  22  by controlling electric power supplied to the cutting blade motor  22  from the first, power supply  28  or the second power supply  30 , which are to be described later. 
     The working machine  2  further comprises a power supply receptacle  26  shown in  FIG. 3 . As shown in  FIG. 2 , the power supply receptacle  26  is fixed to the motor receptacle  20 . The power supply receptacle  26  covers the cutting blade motor  22  from above. Either the first power supply  28  (see  FIG. 1 ) or the second power supply  30  (see  FIG. 13 ) can be selectively attached to the power supply receptacle  26 . Specifically, when the first power supply  28  is attached to the power supply receptacle  26 , the second power supply  30  cannot be attached to the power supply receptacle  26 , and when the second power supply  30  is attached to the power supply receptacle  26 , the first power supply  28  cannot be attached to the power supply receptacle  26 . First, the first power supply  28  wilt be described below. 
     The first power supply  28  shown in  FIG. 4  is a part of a backpack battery in which a frame for carrying, on user&#39;s back, a shoulder belt, and a waist belt are attached to the first power supply  28 . The user can carry the backpack battery by wearing the shoulder belt on the shoulders and the waist belt on the waist. The first power supply  28  comprises a first housing  32 , four first battery packs BP (see  FIG. 5 ), a first power cable  34  (see  FIG. 1 ), and a first connector  36  (see  FIG. 1 ). The first housing  32  includes a first lower housing  38  and a first upper housing  40 . When the first power supply  28  is attached to the power supply receptacle  26 , a lower surface  38   a  of the first lower housing  38  faces the power supply receptacle  26 . As shown in  FIG. 5 , four battery receptacles  42  are disposed in the first lower housing  38 . The first battery pack BP is detachable from/attachable to each battery receptacle  42 . A plurality of battery cells (not shown) is accommodated in each first battery pack BP. The battery cells include, for example, lithium ion batteries. Bach first battery pack BP has, for example, a rated voltage of 18 V and a rated capacity of 108 Wh. In a state where the four first battery packs BP are attached to the battery receptacles  42 , the rated voltage of the first power supply  28  is 18V or 36V, and the rated capacity is 436 Wh. Due to this, the working machine  2  can be used for long hours by using the first power supply  28 . A weight of the first battery pack BP is, for example, 0.6 kg, and in a state where the four first battery packs BP are attached to the battery receptacles  42 , a weight of the first power supply  28  is, for example, 7 kg or more. The first upper housing  40  is openably attached to the first lower housing  38 . In a state where the first upper housing  40  is opened, the first battery packs BP can be attached to and detached from the battery receptacles  42 . On the other hand, in a suite where the first upper housing  40  is closed, lire first battery packs BP are disposed in an internal space defined by the first lower housing  38  and the first upper housing  40 . Due to this, the four first battery packs BP are housed inside the first housing  32 . 
     As shown in  FIG. 4 , a first grip  44  is attached to a front end of the first lower housing  38 . The first grip  44  is configured to be gripped by the user. Due to this, the user can easily cam the first power supply  28  by gripping first grip  44 . 
     The first power cable  34  shown in  FIG. 1  is configured to discharge power of the first battery packs BP. The first power cable  34  extends from a rear end of the first housing  32 . The first power cable  34  is routed along a right surface of the power supply receptacle  26 . A guide tor routing (cable hook)  46  is disposed on the right surface of the power supply receptacle  26 . The first power cable  34  extends forward and below the routing guide  46 , then extends upward on a front side of the routing guide  46 , and then extends rearward and above the routing guide  46 . Due to this, the first power cable  34  is routed around the routing guide  46 , by which the first power cable  34  can be suppressed from loosening. 
     As shown in  FIG. 6 , the first connector  36  is disposed at an end (tip) of the first power cable  34 . The first connector  36  is configured to be inserted into the connector coupler  48  disposed on the right surface of the power supply receptacle  26 . The connector coupler  48  is disposed behind the routing guide  46 . A cover  50  is attached above the connector coupler  48  openably and closably. The cover  50  is biased in a direction of closing the connector coupler  48  by a biasing member  52  (see  FIG. 8 ). In a state where the cover  50  is opened, since the connector coupler  48  is exposed, the first connector  36  can be inserted into the connector coupler  48 . When the First connector  36  is inserted into the connector coupler  48 , power of the first battery pack BP becomes ready to be supplied to the working machine  2 . On the other hand, as shown in  FIG. 8 , in a state where the cover  50  is closed, since the connector coupler  48  is closed by the cover  50 , the first connector  36  cannot be inserted into the connector coupler  48 . In addition, in a state where the cover  50  is closed, the cover  50  can suppress liquid from entering the connector coupler  48 . 
     As shown in  FIG. 6 , a key insertion pan  54  is disposed more on the rear side than the connector coupler  48  is. The key insertion part  54  comprises a key insertion base  56 , a waterproof wall  58 , a lid member  60 , and a biasing member  62 . The key insertion base  56  has an upper surface  56   a  orthogonal to the up-down direction and a key insertion port  56   b  arranged on the upper surface  56   a . The upper surface  56   a  is disposed more on the upper side than (higher than) the connector coupler  48  is. As shown in  FIG. 7 , a lock-off key  64  can be inserted into the key insertion port  56   b  along the up-down direction. When the lock-off key  64  is inserted into the key insertion port  56   b  in a state where the first connector  36  is inserted into the connector coupler  48 , a conduction plate  66  disposed below lire lock-off key  64  comes into contact with a conduction part  68  disposed inside the power supply receptacle  26 . The conduction part  68  is disposed between the first battery packs BP and the cutting blade motor  22  in an electric circuit. Due to this, the first battery packs BP and the cutting blade motor  22  are electrically connected to each other. The cutting blade motor  22  can thus be driven by the electric power supplied from the first battery packs BP. On the other hand, when the lock-off key  64  is removed from the key insertion port  56   b  in the state where the first connector  36  is inserted into the connector coupler  48 , the conduction plate  66  does not contact the conduction part  68  anymore (i.e. separates from the conduction plate  66 ). Due to this, the first battery packs BP and the cutting blade motor  22  are electrically disconnected from each other. Due to this, the power from the first battery packs BP is not supplied to the cutting blade motor  22 , and the cutting blade motor  22  cannot be driven. Furthermore, the configuration using the lock-off key  64  may not be limited to the configuration of the present embodiment, but may also be applicable to a case where another power supply source is used, for example, a case where the first battery packs BP are directly mounted to the power supply receptacle  26 , a case where power is supplied from an external power supply to the working machine  2  via a power cable, or the like. 
     The lock-off key  64  has a know port  70  on its upper portion. The knob port  70  penetrates the lock-off key  64  in its thickness direction. In a state where the lock-off key  64  is inserted into the key insertion port  56   b , the knob port  70  is located more on the upper side than (higher than) the upper surface  56   a . By inserting a finger into the knob port  70 , the user can easily pull out the lock-off key  64  upward from the key insertion port  56   b.    
     As shown in  FIG. 6 , the waterproof wall  58  protrudes upward from the upper surface  56   a . The waterproof wall  58  surrounds the key insertion port  56   b . Due to this, even when liquid is present on the upper surface  56   a  outside the key insertion port  56   b , entry of the liquid into the key insertion port  56   b  can be suppressed. 
     The lid member  60  is attached to the key insertion base  56  so as to be openable and closable more on the rear side than the key insertion port  56   b  and the waterproof wall  58 . The lid member  60  is biased in a closing direction (that is, direction in which an abutting surface  60   a  of the lid member  60  approaches to face an upper surface  56   a  of the key insertion base  56 ) by the biasing member  62 . As shown in  FIG. 7 , in a state where the lid member  60  is closed, a closed space  72  is defined by the lid member  60  and the upper surface  56   a . The lock-off key  64  inserted into the key insertion port  56   b  and the waterproof wall  58  are disposed in the closed space  72 . In the state where the lid member  60  is closed, the abutting surface  60   a  abuts on the upper surface  56   a  so as to surround the waterproof wall  58 . Due to this, in the state where the lid member  60  is closed, entry of liquid into the closed space  72  can be suppressed. 
     As shown in  FIG. 4 , the first power supply  28  further includes two first common engagement parts  76  and two first specific engagement parts  78 . The two first common engagement pans  76  are disposed at a rear portion of the lower surface  38   a  of the first lower housing  38 . The two first common engagement parts  76  are arranged side by side in the left-right direction. Each first common engagement part  76  includes an engagement recess  80  and a first common engagement pawl  82 . The engagement recess  80  is recessed upward from the rear portion of the lower surface  38   a  of the first lower housing  38 . As shown in  FIG. 9 , the first common engagement pawl  82  is separated from a bottom surface  80   b  of the engagement recess  80 . The first common engagement pawl  82  extends rearward from a side surface  80   a  of the engagement recess  80 . The first common engagement pawl  82  is inclined downward from the side surface  80   a . Due to this, the engagement recess  80  opens rearward. 
     As shown in  FIG. 4 , the two first specific engagement parts  78  are arranged on the lower surface  38   a  of the first lower housing  38 . The two first specific engagement parts  78  are disposed more on the front side than the two first common engagement parts  76  are. The two first specific engagement parts  78  are arranged side by side in the left-right direction. Each first specific engagement part  78  includes an engagement recess  86  and two first specific engagement pawls  88 . The engagement recess  86  is recessed upward from vicinity of the front end of the lower surface  38   a  of the first lower housing  38 . One of the engagement recesses  86  is connected to a right surface  38   b  of die first lower housing  38 , and the oilier of the engagement recesses  86  is connected to a left surface  38   c  of the first lower housing  38 . As shown in  FIG. 10 , the first specific engagement pawls  88  are connected to a side surface  86   a  of the engagement recess  86  and extend in a direction separating away from the side surface  86   a . The first specific engagement pawls  88  are disposed apart from a bottom surface  86   b  of the engagement recess  86 . 
     Next, the power supply receptacle  26  shown in  FIG. 3  will be described. The power supply receptacle  26  comprises a base member  92 , two first machine-side engagement parts  94 , a second machine-side engagement part  96 , and two third machine-side engagement parts  98 . The base member  92  has a reference surface  92   a  The reference surface  92   a  faces upward. When the first power supply  28  is attached to the power supply receptacle  26 , the reference surface  92   a  faces the lower surface  38   a  of the first lower housing  38 . 
     The two first machine-side engagement parts  94 , the second machine-side engagement part  96 , and the two third machine-side engagement parts  98  are disposed on the reference surface  92   a . The two first machine-side engagement parts  94  are arranged side by side in the left-right direction. Each first machine-side engagement part  94  comprises a machine-side engagement recess  102  and a first machine-side engagement pawl  104 . The machine-side engagement recess  102  is recessed downward from the reference surface  92   a . One of the machine-side engagement recesses  102  is connected to a right surface of the base member  92 , and the other of the machine-side engagement recesses  102  is connected to a left surface of the base member  92 . Each first machine-side engagement pawl  104  is swingably attached to the base member  92 . As shown in  FIG. 10 , each first machine-side engagement pawl  104  includes a swing shaft  104   a , a holding part  104   b , and a pawl part  104   c . The swing shaft  104   a  extends in the front-rear direction. The swing shaft  104   a  is attached to the base member  92  in the machine-side engagement recess  102 . The holding part  104   b  is connected to the swing shaft  104   a . The holding part  104   b  is held when the user operates the first machine-side engagement pawl  104 . By holding and directly operating the holding part  104   b , the user can cause the first machine-side engagement pawl  104  to swing around the swing shaft  104   a  extending in the front-rear direction. The pawl part  104   c  extends from the holding part  104   b  in a direction substantially orthogonal to the holding part  104   b . The pawl part  104   c  is disposed apart from the swing shaft  104   a.    
     As shown in  FIG. 3 , the second machine-side engagement part  96  is disposed more on the front side than the two first machine-side engagement parts  94  are. In the left-right direction, the second machine-side engagement part  96  is disposed near a center of the base member  92 . The second machine-side engagement part  96  comprises a rear wall  99 , two side walls  100 , and a horizontal wall  101 . The rear wall  99  extends upward from the reference surface  92   a . An upper surface of the rear watt  99  is inclined frontward and downward (see  FIG. 17 ). The two side walls  100  extend upward from the reference surface  92   a . One of the side walls  100  is connected to a right end of the rear wall  99 , and the other of the side walls  100  is connected to a left end of the rear wall  99 . The two side walls  100  extend to a spot more frontward than the rear wall  99 . The horizontal wall  101  extends frontward from a front surface of the rear wall  99 . In the up-down direction, the horizontal wall  101  is connected to the rear wall  99  in vicinity of a center of the rear wall  99  (see  FIG. 17 ). A rigid end of the horizontal wall  101  is connected to the one side wall  100 , and a left end of the horizontal watt  101  is connected to the other side wall  100 . 
     The two third machine-side engagement parts  98  are disposed more on the rear side titan the two first machine-side engagement parts  94  and the second machine-side engagement part  96 . The two third machine-side engagement parts  98  are arranged side by aide in the left-right direction. Bach third machine-side engagement part  98  comprises a machine-side engagement recess  106 , an engagement member  108 , an auxiliary member  110 , a swing shaft  112  (see  FIG. 11 ), and a biasing member  114  (see  FIG. 11 ). The machine-side engagement recess  106  is recessed downward from the reference surface  92   a . As shown in  FIG. 3 , the engagement member  108  protrudes upward from the reference surface  92   a . The engagement member  108  is constituted of, for example, a metal material or a resin material. As shown in  FIG. 11 , the engagement member  108  comprises a lower engagement part  118 , a rear engagement part  120 , and an upper engagement pan  122 .  FIG. 11  illustrates postures of the engagement member  108 , the auxiliary member  110 , the swing shaft  112 , and the biasing member  114  when located at an initial position. The lower engagement part  118  extends in the front-rear direction. The rear engagement part  120  is connected to a rear end of the lower engagement part  118 . The rear engagement part  120  extends in the up-down direction. An upper end of the rear engagement part  120  is disposed more on the upper side titan (higher than) an upper end of the lower engagement part  118 . An insertion bole  124  penetrating the rear engagement part  120  in the left-right direction is defined in a rear lower part of the mar engagement part  120 . The upper engagement, part  122  extends frontward from an upper part of a front surface of the rear engagement part  120 . The upper engagement part  122  gradually becomes thinner toward the front side. As shown in  FIG. 9 , when the engagement member  108  is located at the initial position, the upper engagement part  122  and an upper half of the rear engagement part  120  protrude upward from the reference surface  92   a.    
     As shown in  FIG. 3 , the auxiliary members  110  protrude upward from the reference surface  92   a . Each auxiliary member  110  is made of, for example, a metal material or a resin material. A strength of the auxiliary members  110  is lower than a strength of the engagement members  108 . As shown in  FIG. 11 , each auxiliary member  110  comprises a lower auxiliary part  126  and an upper auxiliary part  128 . The lower auxiliary part  126  is disposed between a right wall  120   a  and a left wall  120   b  of the rear engagement pan  120 . The lower auxiliary part  126  extends upward. An upper end of the lower auxiliary part  126  is disposed slightly more on the upper side than (higher than) the upper end of the rear engagement part  120 . The upper auxiliary part  128  extends frontward front the upper end of the lower auxiliary part  126 . A length of the upper auxiliary part  128  in the up-down direction gradually increases from the upper end of the lower auxiliary part  126  toward the front side, and then ends up being constant. Although not shown, when the auxiliary member  110  is located at the initial position, the upper auxiliary part  128  and an upper half of the lower auxiliary part  126  protrude upward from the reference surface  92   a.    
     The swing shaft  112  is inserted into the insertion hole  124  defined in the rear engagement part  120  and an insertion hole (not shown) defined in the lower auxiliary part  126 . Due to this, the engagement member  108  and the auxiliary member  110  are swingably supported by the base member  92  via the swing shaft  112 . The engagement member  108  is movable relative to the auxiliary member  110 . As shown in  FIG. 9 , the swing shaft  112  is attached to the base member  92  in the machine-side engagement recess  106 , and both ends of the swing shall  112  protrude outward from the base member  92 . Retainer members  132  (see  FIG. 11 ) are attached to both ends of the swing shaft  112 , respectively. The retainer members  132  suppress detachment of the swing shaft  112  from the base member  92 . 
     As shown in  FIG. 11 , the biasing member  114  is, for example, a torsion spring. The biasing member  114  has the swing shaft  112  inserted therethrough. The biasing member  114  biases the auxiliary member  110  toward the initial position. When the lower auxiliary part  126  is in contact, with the rear engagement part  120 , the engagement member  108  is biased toward the initial position by biasing force of the biasing member  114 . 
     Next, an operation of attaching the first power supply  28  to the power supply receptacle  26  will be described. The user inserts die first common engagement pawls  82  into corresponding spaces between the lower engagement part  118  and the upper engagement part  122  of each of the engagement members  108  in a state where the first power supply  28  is tilted with respect to the reference surface  92   a  of the base member  92 . Due to this, without the engagement members  108  being directly operated by the user, the upper engagement parts  122  are inserted into the engagement recesses  80  of the first common engagement parts  76 , by which the first common engagement parts  76  are engaged with the third machine-side engagement parts  98 . As shown in  FIG. 12 , when the first common engagement pawls  82  abut on the rear engagement parts  120  of the engagement members  108 , the engagement members  108  swing rearward around the swing shafts  112 , and take postures inclined with respect to the reference surface  92   a . In addition, the upper auxiliary parts  128  of the auxiliary members  110  abut on the first lower housing  38  of the first power supply  28  and swing rearward around the swing shafts  112 , without being directly operated by the user. 
     Next, the user lays down the first power supply  28  in the tilted state toward the reference surface  92   a  to bring the lower surface  38   a  of the first lower housing  38  into contact with the reference surface  92   a . As shown in  FIG. 9 , the upper surfaces of the lower engagement parts  118  and the upper surfaces of the upper engagement parts  122  abut on the first lower housing  38 , swing forward around the swing shafts  112 , and return to the initial positions. On the other hand, the auxiliary members  110  swing frontward while being in contact with the first lower housing  38  by the biasing force of the biasing members  114 , but does not return to the initial positions shown in  FIG. 3 . 
     Next, the user directly operates the holding parts  104   b  of the first machine-side engagement pawls  104  to cause the first machine-side engagement pawls  104  to swing in a direction going toward the first lower housing  38 . Thereafter, as shown in  FIG. 10 , the user causes the pawl parts  104   c  of the first machine-side engagement pawls  104  to engage with the first specific engagement pawls  88 . Due to this, the first power supply  28  is fixed and attached to the power supply receptacle  26  without the lower surface  38   a  of the first lower housing  38  floating from the reference surface  92   a.    
     When the first power supply  28  is to fie removed from the power supply receptacle  26 , the user directly operates the holding parts  104   b  of the first machine-side engagement pawls  104  to cause the first machine-side engagement pawls  104  to swing in a direction separating away from the first lower housing  38 . Thereafter, the user tilts the first power supply  28  in a direction separating away from the reference surface  92   a , and pulls out the upper engagement parts  122  from the engagement recesses  80 . Due to this, the engagements between the first common engagement parts  76  and the third machine-side engagement parts  98  are released without the engagement members  108  and the auxiliary members  110  being directly operated by the user. Further, the auxiliary members  110  swing frontward by the biasing force of the biasing members  114 . When the auxiliary members  110  abut on the engagement members  108 , both the engagement members  108  and the auxiliary members  110  swing frontward by the biasing force of the biasing members  114  and return to the initial positions shown in  FIG. 3 . 
     Next, the second power supply  30  will be described. As shown in  FIG. 13 , the second power supply  30  is attachable to the power supply receptacle  26 . The second power supply  30  is a part, of a backpack battery m which a frame for carrying on user&#39;s back, a shoulder belt, and a waist belt are attached to the second power supply  30 . A weight of the second power supply  30  is, for example, 7 kg or more. As shown in  FIG. 14 , the second power supply  30  comprises a second housing  140 , two cell holders  142  (see  FIG. 15 ), a second power cable  144 , and a second connector  146 . A shape of the second housing  140  is different from the shape of the first housing  32 . The second housing  140  comprises a second lower housing  150  and a second upper housing  152 . When the second power supply  30  is attached to the power supply receptacle  26 , a lower surface  150   a  of the second lower housing  150  faces the reference surface  92   a  of the base member  92 . The second lower housing  150  is fixed to the second upper housing  152  using, screws (not shown). 
     As shown in  FIG. 15 , a second grip  154  is swingably attached to a front end of the second lower housing  150 . The second grip  154  is gripped by the user in a raised state. Doe to this, the user can easily carry the second power supply  30  by gripping the second grip  154 . 
     The two cell holders  142  are housed inside the second housing  140 . In  FIG. 15 , the second upper housing  152  is removed to facilitate understanding of a positional relationship between the two cell holders  142 . The two cell holders  142  are arranged side by side in the left-right direction. The ceil holders  142  house a plurality of battery cells (not shown). The battery ceils include, for example, lithium ion batteries. A rated voltage of the second power supply  30  is, for example, 18V or 36V, and a rated capacity is 416 Wh. Due to this, the working machine  2  can be used for long hours by using the second power supply  30 . 
     The second power cable  144  is configured to discharge power of the cell holder  142 . The second power cable  144  extends from a rear end of the second housing  140 . Although not shown, since the second power cable  144  is shorter than the first power cable  34 , in a state where the second power supply  30  is attached to the power supply receptacle  26 , the second power cable  144  is not routed around the muting guide  46  (see  FIG. 1 ) arranged on the right surface of the power supply receptacle  26 . 
     The second connector  146  is disposed at an end (tip) of the second power cable  144 . The second connector  146  is insertable (out be plugged) into the connector coupler  48  (see  FIG. 6 ) disposed on the right surface of the power supply receptacle  26 . 
     As shown in  FIG. 14 , the second power supply  30  further includes two second common engagement parts  156  and a second specific engagement part  158 . The two second common engagement parts  156  are disposed at a rear pair of the lower surface  150   a  of the second lower housing  150 . Each second common engagement pan  156  includes a second common engagement pawl  160  and a plurality of reinforcing members  162 . As shown in HG  16 , each second common engagement pawl  160  extends rearward from the rear part of the second lower housing  150 . The second common engagement pawl  160  is inclined downward from the rear pan of the second lower housing  150 . Each of the reinforcing members  162  is connected to the rear pan of the second lower housing  150  and a lower surface of its second common engagement pawl  160 . The pluralities of reinforcing members  162  prevent the respective second common engagement pawls  160  from being damaged, for example when external force in the up-down direction is applied to the second common engagement pawls  160 . 
     As shown in  FIG. 14 , the second specific engagement part  158  is disposed at a front end of the second lower housing  150 . The second specific engagement part  158  is disposed more on the front side than the two second common engagement pans  156  arc. As shown in  FIG. 17 , the second specific engagement part  158  includes a second specific engagement pawl  166 , a swing shaft  168 , an operation member  170 , and a biasing member  172 . The second specific engagement pawl  166  extends frontward and downward from the swing shaft  168  extending in the left-right direction, is then bent and extends downward, and is further bent and extends rearward. The swing shaft  168  extends along the left-right direction and is attached to the second lower housing  150 . The operation member  170  is connected to an upper end of the swing shaft  168 . The operation member  170  is biased toward its initial position by the biasing member  172 . The operation member  170  is exposed from the second lower housing  150 . Thus, the operation member  170  can be operated by the user. 
     Next, an operation of attaching the second power supply  30  to the power supply receptacle  26  will be described. The user inserts the second common engagement pawls  160  shown in  FIG. 14  into corresponding spaces between the lower engagement part  118  and the upper engagement part  122  of each of the engagement members  108  in a state where the second power supply  30  is tilted with respect to the reference surface  92   a  of the base member  92 . Due to this, the second common engagement parts  156  are engaged with the third machine-side engagement parts  98 , respectively. When the second common engagement pawls  160  abut on the rear engagement parts  120  of the engagement members  108 , similarly to when the first power supply  28  is attached to the power supply receptacle  26 , the engagement members  108  swing rearward around the swing shafts  112  and take inclined postures with respect to the reference surface  92   a . The auxiliary members  110  abut on the second lower housing  150  and swing backward around the swing shafts  112 . 
     Next, the user lays down die second power supply  30  in the tilted state toward the reference surface  92   a  to bring the lower surface  150   a  of the second lower housing  150  into contact with the reference surface  92   a . As shown in  FIG. 16 , the upper surfaces of the lower engagement parts  118  abut on the second lower housing  150 , swing frontward around the swing shafts  112 , and return to the initial positions shown in  FIG. 3 . On the other hand, the auxiliary members  110  swing frontward while being in contact with the second lower housing  150  by the biasing force of die biasing members  114 , but do not return to the initial positions shown in  FIG. 3 . 
     In addition, when the second power supply  30  in the tilted state is laid down toward the reference surface  92   a  and the second specific engagement pawl  166  thereby abuts on an upper surface of the rear wall  99  of the second machine-side engagement part  96 , the second specific engagement pawl  166  swings in a first direction around the swing shaft  168 . In  FIG. 17 , the first direction is equal to a clockwise direction. As shown in  FIG. 17 , when a tip of the second specific engagement pawl  166  moves to a spot lower than die horizontal wall  101 , the second specific engagement pawl  166  swings in a second direction around the swing shaft  168  by biasing force which the operation member  170  receives from the biasing member  172 , by which the second specific engagement pawl  166  engages with the horizontal wall  101 . Due to this, the second power supply  30  is fixed and attached to the power supply receptacle  26  without the lower surface  150   a  of the second lower housing  150  floating from the reference surface  92   a . The second direction is a direction opposite to the first direction. 
     When the second power supply  30  is to be removed from the power supply receptacle  26 , the user pushes in the operation member  170  with a finger. Due to this, the second specific engagement pawl  166  swings in the first direction, and the engagement between the second specific engagement pawl  166  and the horizontal wall  101  is released. In this state, the user tilts the second power supply  30  in the direction separating away from the reference surface  92   a , and pulls the second common engagement pawls  160  out of the respective spaces between the lower engagement part  118  and the upper engagement part  122  of the engagement members  108 . As a result, the engagement between the second common engagement parts  156  and the third machine-side engagement parts  98  is released without the engagement members  108  and the auxiliary members  110  being directly operated by the user. In addition, both the engagement members  108  and the auxiliary members  110  swing frontward by the biasing force of the biasing members  114  and return to the initial positions shown in  FIG. 3 . 
     (Effect) 
     The working machine  2  disclosed herein is configured to operate with electric power supplied from the first power supply  28  or the second power supply  30  and configured to be used in a state of being in contact with a ground. The first power supply  28  comprises the battery cells; the first housing  32  configured to house the battery cells; the first power cable  34  extending from the first housing.  32  and configured to discharge electric power; and the first connector  36  disposed at the end of the first power cable  34 . The second power supply  30  comprises the battery cells; die second housing  140  configured to house the battery cells; the second power cable  144  extending from the second housing  140  and configured to discharge electric power; and the second connector  146  disposed at the end of the second power cable  144 . The first housing  32  of the first power supply  28  and the second housing  140  of the second power supply  30  have different shapes from each other. The working machine  2  comprises the power supply receptacle  26  to which either the first power supply  28  or the second power supply  30  is configured to be detachably attached; and the connector coupler  48  configured to be coupled with either the first connector  36  or the second connector  146 . 
     In the above configuration, the working machine  2  can be used with the first power supply  28  being attached to the power supply receptacle  26 , or the working machine  2  can also be used with the second power supply  30  having a housing shape different from that of the first power supply  28  being attached to the power supply receptacle  26 . Due to this, a plurality of types of power supplies  28 ,  30  having different housing shapes can be used for the working machine  2 . 
     The first power supply  28  further comprises the first specific engagement parts  78  disposed on the first housing  32 . The second power supply  30  further comprises the second specific engagement part  158  disposed on the second housing  140 . The power supply receptacle  26  comprises the first machine-side engagement parts  94  disposed at the positions corresponding to the first specific engagement parts  78  and engageable with the first specific engagement parts  78  to fix the first power supply  28  to the power supply receptacle  26 ; and the second machine-side engagement part  96  disposed at the position corresponding to the second specific engagement part  158  and engageable with the second specific engagement part  158  to fix the second power supply  30  to the power supply receptacle  26 . 
     In the above configuration, the first power supply  28  can be firmly fixed to the power supply receptacle  26 , and the second power supply  30  can be firmly fixed to the power supply receptacle  26 . 
     The first power supply  28  further comprises the first common engagement parts  76  disposed on the first housing  32 . The second power supply  30  further comprises the second common engagement parts  156  disposed on the second housing  140 . The power supply receptacle  26  further comprises the third machine-side engagement parts  98  disposed at the positions corresponding to both the first common engagement parts  76  and the second common engagement parts  156  and engageable with either the first common engagement parts  76  or the second common engagement parts  156  to fix either the first power supply  28  or the second power supply  30  to the power supply receptacle  26 . 
     In the above configuration, the third machine-side engagement parts  98  are engageable with the common engagement parts  76  of the first power supply  28  and also is engageable with the common engagement parts  156  of the second power supply  30 . Thus, the configuration of the power supply receptacle  26  can be prevented from becoming complicated. 
     The engagement member(s)  108  according to an embodiment may be swingable about swing shaft(s), and its auxiliary member(s)  110  may be swingable about another swing shaft(s). 
     The strength of the engagement members  108  according to one embodiment may be equal to or less than the strength of the auxiliary members  110 . 
     The working machine  2  according to one embodiment is not limited to a lawn mower, and may be, for example, a carrier, a cultivator, a sweeper for sweeping a floor, a vacuum cleaner, or a lifting device.