Abstract:
A walk behind working machine has a frame having a forward end portion and a rear end portion, a prime mover mounted on the frame, a pair of drive wheels mounted on the frame for undergoing rotation, and a power transmission mechanism for transmitting rotational power from the prime mover to the drive wheels. A running clutch is adapted to be placed in an engaged state in which rotational power is transmitted to the drive wheels and in a disengaged state in which rotational power is not transmitted to the drive wheels. A pair of operating handles extend from the rear end portion of the frame. A single grip/clutch lever serves as a grip handle for being gripped by an operator to maneuver the working machine and as a clutch lever manually operable to selectively place the running clutch in the engaged state and the disengaged state. The grip/clutch lever is pivotally mounted on distal end portions of the operating handles to undergo pivotal movement in forward and rearward directions of the frame between a rearward stop position having a first forward tilt and in which the running clutch is in the disengaged state and a forward operating position having a second forward position greater than the first forward position and in which the running clutch is in the engaged state.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a walk behind working machine operated by an operator walking behind the machine and gripping a grip portion of a handle of the machine. 
     BACKGROUND OF THE INVENTION 
     One example of walk behind working machines is known from, for example, Japanese Utility Model Publication No. SHO-58-32578 entitled “A SELF-PROPELLED LAWNMOWER”. The known lawnmower is described below with reference to FIG. 23 hereof. 
     When cutting a lawn  201  with the walk behind lawnmower  200 , an operator  204  shifts a clutch lever  207  in a direction as shown by an arrow from a position, shown in a phantom line, while gripping a grip  206  of a handle  205  under a condition where a cutter in a housing  203  is rotated by an engine  202 . With such an operation, a running clutch, interposed between the engine  202  and rear wheels  208 , is coupled to enable drive power of the engine  202  to be delivered to the rear wheels  208 . Rendering the lawnmower  200  to be self-propelled with the rear wheels  208  and front wheels  209  allows the cutter to cut the lawn  201 . 
     Normally, the running clutch used in the lawnmower employs a dog-clutch. The dog-clutch is arranged such that sliding a shifter in a case toward a worm gear causes clutch teeth of the shifter to be brought into mating engagement with worm teeth of the worm gear to assume a coupled state. Such a dog-clutch is instantaneously operated from an uncoupled state to the coupled state. For this reason, when the operator  204  shifts the clutch lever  207  in the direction as shown by the arrow from teh position shown by the phantom line while gripping the grip  206  of the handle  205 , the clutch is apt to be instantaneously brought into the coupled state to cause the lawnmower  200  to rapidly start off at an initial speed V1. When this occurs, since the operator  204  holds the grip  206 , rapid taking off of the lawnmower  200  causes the operator  204  to be pulled from the lawnmower  200 . Therefore, in order to have the walk behind lawnmower  200  to start off smoothly, the operator must start walking in synchronism with the coupling operation of the clutch. 
     However, if the operator  204  begins to walk at a low speed, a forward movement of the lawnmower  200  is interrupted, causing the rear wheels  208  of the lawnmower  200  to slip or causing the front wheels  209  to lift up as shown by the arrow. As a result, there are some instances where the grass  201  is caused to be laid down or to be torn off and where the cutter tends to be lifted up due to lifting up of the front wheels  209 . Thus, it is difficult to cut the grass  201  with a high quality finish using the walk behind lawnmower during the taking off period of the walk behind lawnmower  200 . 
     Because of the reasons described above, in order to allow the walk behind lawnmower  200  to start off in a suitable manner, it is required for the operator to predict the speed at which the lawnmower takes off, thereby requiring skilled handling of the walk behind lawnmower  200  in order to cut the grass  201  with a desired finish. For this reason, an attempt has heretofore been made with a view to providing a walk behind lawnmower, which is enabled to carry out a smooth taking off, into practical use. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a walk behind working machine which has excellent operability during a take-off operation to achieve a desired smooth take-off. 
     According to a first aspect of the present invention, there is provided a walk behind working machine which comprises: a machine body; a drive source mounted on the machine body; right and left drive wheels carried on a rear portion of the machine body and driven by actuation of the drive source; a running clutch provided between the right and left drive wheels and coupled to the drive source such that it allows use in a slipping phase; operating handles extending rearward from the machine body; and a grip/clutch lever mounted on the handles swingably between a forward position and a rearward position, the grip/clutch lever being connected to the running clutch via a clutch cable such that the running clutch is coupled when the grip/clutch lever is shifted to the forward position, and is uncoupled when the grip/clutch lever is shifted to the rearward position, whereby the working machine is capable of traveling in the clutch slipping phase during the course of shift of the grip/clutch lever between the forward and rearward positions. 
     By thus bringing the grip/clutch lever into a clutch slipping phase during its forward pushing, the walk behind working machine starts running at a low speed. In this instance, since the operator merely walks forward while applying the forward pushing force onto the grip/clutch lever, it is possible for the operator to handle the walk behind working machine in a natural motion, making it possible to have the walk behind working machine start off smoothly. For this reason, it is possible to cut grass with the walk behind working machine in a high quality finish from the start of work. 
     In addition, the walk behind working machine may start off at a low speed during the operator&#39;s forward pushing operation of the grip/clutch lever, allowing the operator to follow the start-off movement of the walk behind working machine in a natural motion. 
     Further, since the grip/clutch lever serves as both a clutch lever and a handle grip as a result of it being rendered capable of handling the machine body by gripping the grip/clutch lever, it is possible to perform a clutch operation with the grip/clutch lever gripped. Accordingly, it is possible to save troublesome steps for removing one hand from the handle grip with the clutch lever handled with the removed hand as required in the conventional working machine, with a resultant decrease in the operator&#39;s load. 
     In a preferred form, the grip/clutch lever includes stoppers mounted to proximal ends thereof for restricting fore and aft movements of the grip/clutch lever beyond the forward and rearward positions. The stoppers are thus separated from the grip of the grip/clutch lever during a handling operation of the grip/clutch lever, thereby avoiding interference of the operator&#39;s hand with the stoppers. 
     Desirably, the grip/clutch lever further includes a hold lever mounted to the handles forwardly of the grip/clutch lever so that by gripping the grip/clutch lever and the hold lever together as the grip/clutch lever is tilted or swung toward the hold lever until it comes to the forward position, the grip/clutch lever is retained at the forward position. By thus tilting the grip/clutch lever to the forward position while gripping the grip/clutch lever together with the hold lever, the grip/clutch lever is retained at the forward position. Since the grip/clutch lever is retained at the forward position by merely gripping the grip/clutch lever together with the hold lever, it is possible for the grip/clutch lever to be retained at the forward position in a further simplified manner. 
     The hold lever is swingable between a forward stationary position and a rearward gripping position so that when the hold lever is gripped together with the grip/clutch lever at the forward position, the hold lever is retained at the gripping position and when the hold lever is released from the gripped state, it is returned to the stationary position. Thus, since the hold lever is arranged to have the capability of tilting between the forward stationary position and the rearward gripping position, gripping the hold lever and the grip/clutch lever together causes the hold lever to be retained at the gripping position for thereby allowing the grip/clutch lever to be retained at the forward position. On the other hand, there is an instance where it is desired for the hold lever to be kept at the forward position by continuously pushing the grip/clutch lever forward without gripping the hold lever. In such a case, since the hold lever is rendered capable of returning to the stationary position, it is possible for the operator&#39;s hand to be precluded from interfering with the hold lever during continuous forward pushing movement of the grip/clutch lever. Thus, the presence of the capability for tilting the hold lever enables the operation for retaining the grip/clutch lever at the forward position to be carried out in the two different modes. As a result, a suitable operating method can be selected from the two different modes in accordance with the working status of the walk behind working machine, with the result that the maneuverability or operability of the walk behind working machine is further improved. 
     With the stopper mounted to the proximal end of the hold lever for restricting the fore and aft movements of the hold lever at the stationary position and the gripping position, it becomes possible to separate the stopper from the grip of the hold lever to thereby prevent the operator&#39;s hand from interfering with the stopper during the handling operation of the hold lever. 
     According to a second aspect of the present invention, there is provided a walk behind working machine which comprises: a machine body; a drive source mounted on the machine body; right and left drive wheels carried on a rear portion of the machine body and driven by actuation of the drive source; a running clutch provided between the right and left drive wheels and coupled to the drive source such that it allows use in a slipping phase; operating handles extending rearward from the machine body; a grip/clutch lever mounted on the handles swingably between a forward position and a rearward position, the grip/clutch lever being connected to the running clutch via a clutch cable such that the running clutch is coupled when the grip/clutch lever is shifted to the forward position, and is uncoupled when the grip/clutch lever is shifted to the rearward position; and a hold lever mounted on the handles forwardly of the grip/clutch lever, the grip/clutch lever and the hold lever being spaced a predetermined distance from each other when the grip/clutch lever, after it is swung toward the hold lever until it comes to the forward position, is gripped together with the hold lever. 
     Thus, by swinging the grip/clutch lever to the forward position, the running clutch is brought into the slipping phase, thereby enabling the walk behind working machine to start off at a low speed. That is, the operator may advance forward while applying a pushing force to the grip/clutch lever. This allows the operator to handle the walk behind working machine in a natural motion, thereby enabling the walk behind working machine to start off in a smooth manner. 
     In addition, merely tilting the grip/clutch lever to the forward position compels the walk behind working machine to start off at a low speed. As a result, the operator is allowed to follow the start off operation of the walk behind working machine in a natural motion. 
     Further, by gripping the grip/clutch lever to allow the machine body to be handled, the grip/clutch lever may commonly serve as the clutch lever and the handle grip, permitting the clutch operation to be performed with the grip/clutch lever retained in the gripped state. Consequently, it is possible to save troublesome steps, which would be required in the conventional working machine, for removing one hand from the handle grip and for handling the clutch lever with the removed hand. 
     When the walk behind working machine ascends a sloped hill in an exemplary case, large drive power is required. When the walk behind working machine travels in a non-working state, it is desired that the working machine advances at a high speed. To this end, as described above, when the grip/clutch lever, remaining at the forward position, is gripped with the hold lever, the grip/clutch lever is so constructed as to be separated from the hold lever by a given distance. For this reason, strongly gripping the grip/clutch lever and the hold lever enables the grip/clutch lever to be strongly urged toward the hold lever. With such an action, a strong urging force can be applied to the running clutch, thereby enabling the slipping phase to be adjusted into a less slipping state. Therefore, the drive power of the walk behind working machine is increased depending on the working status while allowing the working machine to travel at a higher speed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Certain preferred embodiments of the present invention will be described in detail below, by way of example only, with reference to the accompanying drawings, in which: 
     FIG. 1 is a side view of a walk behind working machine according to a first embodiment of the present invention; 
     FIG. 2 is an enlarged cross-sectional view of a portion  2  shown in FIG. 1; 
     FIG. 3 is a cross-sectional view taken along line  3 — 3  of FIG. 2; 
     FIG. 4 is a perspective view illustrating handles and levers, etc., forming part of the first embodiment; 
     FIG. 5 is a side view of the handles and levers, shown in FIG. 4, as assembled; 
     FIG. 6 is a partial cross-sectional view, wherein a central area covering the levers, etc., is shown in cross section, illustrating a right handle and the levers; 
     FIG. 7 is a side view illustrating a condition wherein a brake lever is tilted from a rest position shown in FIG. 5 to a brake-releasing position; 
     FIG. 8 is a partial cross-sectional view illustrating a condition wherein the brake lever and a grip/clutch lever are tilted from a condition shown in FIG. 7 to an operating position; 
     FIG. 9 is a side view illustrating an action of forces imparted to the grip/clutch lever under the condition shown in FIG. 8; 
     FIG. 10 is a view illustrating a condition wherein the walk behind working machine according to the first preferred embodiment cuts a grass; 
     FIG. 11 is a perspective view illustrating a walk behind working machine according to a second embodiment wherein levers, etc., are mounted to handles; 
     FIG. 12 is an exploded perspective view of the handles and the levers, etc., shown in FIG. 11; 
     FIG. 13 is a side view of the handles and the levers, etc., shown in FIG. 11; 
     FIGS. 14A to  14 C are views illustrating operations of stoppers associated with respective levers, etc., shown in FIG. 11; 
     FIG. 15 is an operational view illustrating a condition wherein the grip/clutch lever is tilted with the brake lever from the state shown in FIG. 13 to the brake-releasing position; 
     FIG. 16 is an operational view illustrating a condition wherein the grip/clutch lever is tilted with the brake lever from the state of FIG. 15 to the operating position; 
     FIG. 17 is an operational view illustrating a condition wherein three levers including the brake lever, the grip/clutch lever and the hold lever are gripped with a hand from the condition shown in FIG. 16; 
     FIG. 18 is a perspective view illustrating handles and respective levers, etc., of a walk behind working machine according to a third embodiment of the present invention; 
     FIG. 19 is a perspective view illustrating handles and respective levers, etc., of a walk behind working machine according to a fourth embodiment of the present invention; 
     FIG. 20 is a perspective view illustrating handles and respective levers, etc., of a walk behind working machine according to a fifth embodiment of the present invention; 
     FIG. 21 is an operational view illustrating a condition wherein the hold lever is gripped from the condition of FIG. 20 with a given distance spaced from the grip/clutch lever; 
     FIG. 22 is a perspective view illustrating handles and respective levers, etc., of a walk behind working machine according to a sixth embodiment of the present invention; and 
     FIG. 23 is a side view of a conventional walk behind working machine. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 to  10  show a walk behind working machine of a first preferred embodiment of the present invention. In FIG. 1, the walk behind working machine  10  includes a machine body  11  whose fore and aft distal ends have right and left front wheels  12  and right and left rear wheels (running wheels)  13  (with only one of the front wheels and one of the rear wheels being shown in a side view of FIG.  1 ). An engine (primer mover)  14  is fixedly mounted on an upper area of the machine body  11 . The engine has an output shaft  15  having a lower distal end mounted with a cutter  16  via a clutch/brake (not shown). A drive pulley  17   a , which delivers a drive power to the rear wheels  13 , is fixedly mounted on an intermediate part of the output shaft  15 . A belt  18  is wound between the drive pulley  17   a  an an input pulley  17   b . Th rear wheels  13  are connected to an input shaft  19 , which is mounted to the input pulley  17   b , via a transmission  20 . 
     In the walk behind lawnmower  10 , operating the engine  14  allows the rear wheels  13  and the cutter  16  to rotate, permitting the front and rear wheels  12 ,  13  to travel while cutting a lawn with the cutter  16 . When this takes place, an operator walks while following the walk behind lawnmower  10  and gripping a grip/clutch lever  70  and a brake lever  60 . 
     The walk behind lawnmower  10  of the present invention is of the type which includes a running clutch  30  (see FIG. 2) which is mounted in a drive system (transmission  20 ) which interconnects the input shaft  19  to the rear wheels  13  and has right and left handles  50 ,  51  which extend rearward from a rear end portion of the machine body, with the grip/clutch lever  70  being carried with the right and left handles  50 ,  51  to allow the running clutch  30  to be coupled or uncoupled. The running clutch  30  is contained in the transmission  20 . 
     Also, the walk behind lawnmower  10  includes a throttle control lever  25  mounted in the close proximity to a rear distal end portion  50   a  of the left handle  50  for controlling an engine speed, with the grip/clutch lever  70  and the brake lever  60  being carried with the rear distal end portions  50   a ,  51   a  of the right and left handles  50 ,  51  for tilting movement to control a clutch and a brake of the cutter. A lawn receiver box  26  receives the lawn cut by the cutter  16 . 
     In FIGS. 2 and 3, the transmission  20  is comprised of a transmission case  21  by which the input shaft  19  is supported for rotational movement, with a pinion  22   a  formed at a distal end of the input shaft  19  being located in the transmission case  21  and held in meshing engagement with a bevel gear  22   b , and a drive-wheel drive shaft  23  disposed in the transmission case  21  for rotational movement and associated with the running clutch  30 . 
     The running clutch  30  includes a clutch shifter  32  slidably mounted on the rear-wheel drive shaft  23  via a pin  31  fixedly mounted to the drive shaft  23 . An outer circumferential periphery of the clutch shifter  32  is formed with a recessed portion  32   a  in which claws  33   a ,  33   a  of a clutch cam  33  is operatively located. The clutch cam  33  is mounted in the transmission case  21  by means of a support pin  34  for tilting movement. A clutch lever  35  is coupled to the support pin  34 . Connected to the clutch lever  35  is a front distal end  36   a  of a clutch cable  36 . A rear distal end  36   b  of the clutch cable  36  is connected to a lower distal end  56   c  of an arm  56  shown in FIG.  1 . 
     When pulling the clutch cable  36  in an arrow shown in FIG. 2, the clutch lever  35  is operated to tilt in a rear surface direction of FIG. 2 to cause the support pin  34  to be rotated clockwise. Clockwise rotation of the pin  34  allows the clutch cam  33  to tilt for thereby permitting the clutch shifter  32  to slide in a front surface direction of FIG. 2 (i.e. in a rightward direction in FIG.  3 ). 
     Referring to FIG. 3, a distal end of the clutch shifter  32  has a cone-shaped portion. A peripheral surface  37   a  of the cone-shaped portion  37  is able to be brought into contact with a lining  38  fixedly mounted in a hub  39  of the bevel gear  22   b . The bevel gear  22   b  is mounted on the rear-wheel drive shaft  23 . Thus, by pulling the clutch cable  36  in the direction as shown by the arrow in FIG. 2, the clutch cam  33  is pivoted to allow the clutch shifter  32  to slide toward the bevel gear  22   b  in the direction as shown by the arrow such that the peripheral surface  37   a  of the cone-shaped portion  37  is brought into contact with the lining  38 . With such a structure, the running clutch  30  can be used in a slipping phase or state. 
     The term “slipping phase” used herein refers to a state wherein a slipping condition or half-connected state is normally maintained between the peripheral surface  37   a  of the cone-shaped portion  37  of the clutch shifter  32  and the lining  38  of the bevel gear  22   b . Rendering the clutch to be maintained in the slipping phase or state compel a rotational force of the bevel gear  22   b  remaining at a side of the engine  14  (see FIG. 1) to be delivered to the cone-shaped portion  37 , located at the side of the rear wheels  13  (see FIG.  1 ), under a controlled state. Consequently, it is possible for the walk behind working machine to start off at a low speed. 
     Also, the running clutch  30  is of a wet-type clutch which is internally filled with lubricating oil to enable the periphery surface  37   a  of the cone-shaped portion  37  and the lining  38  fixedly mounted to the hub  39  of the bevel gear  22   b  to resist the slip condition in an extended period of time. 
     FIG. 4 shows the brake lever  60  and the grip/clutch lever  70 , to be mounted to a handle body defined by right and left handles  50 ,  51 , which form an important feature of the walk behind lawnmower of the first preferred embodiment of the present invention. 
     The walk behind lawnmower  10  has a structure wherein a connecting pipe  53  transversely extends between and is connected to respective rear distal ends  50   a ,  51   a  of the right and left hands  50 ,  51 . Inserted through the connecting pipe  53  is a retainer rod  54  which has right and left distal end portions  54   a ,  54   b  which protrude outward from the connecting pipe  53  and which are held in mating engagement with right and left mounting bores  61   a ,  61   b , respectively, with right and left proximal ends  70   a ,  70   b  of the grip/clutch lever  70  being held in abutting engagement with right and left distal edges  54   c ,  54   d  of the retainer rod  54 , respectively. Right and left bolts  72 ,  72  are inserted through mounting apertures  71   a ,  71   b  of the right and left proximal ends  70   a ,  70   b , respectively, and are screwed into threaded bores  73 ,  73  of the right and left distal edges  54   c ,  54   d , thereby permitting the brake lever  60  and the grip/clutch lever  70  to be mounted on the retainer rod  54  for swinging movement in fore and aft directions. 
     The brake lever  60  is constructed of a substantially U-shaped gripping rod  62 , and right and left mounting plates  63 ,  64  fixedly secured to right and left ends of the gripping rod  62 . The left mounting plate  63  has the mounting bore  61   a  through which the left distal end portion  54   a  of the retainer rod  54  is enabled to be inserted, and a protruding end  65  to which a rear end  66   a  of the brake cable  66  is fixedly secured. On the other hand, the right mounting plate  64  has the mounting bore  61   b  through which the right distal end portion  54   b  of the retainer rod  54  is enabled to be inserted, and a stopper segment  67  for retaining the brake lever  60  in a braked position P 3  (see FIGS.  5  and  6 ). 
     A return spring  69  engages a left distal end of the connecting pipe  53 , and has one end  69   a  which is hooked to a rear distal end  50   a  of the left handle  50  and the other end  69   b  which is hooked to the left distal end of the gripping rod  62 , thereby urging the brake lever  60  in the rearward braked position P 3  (see FIG.  5 ). 
     The grip/clutch lever  70  is substantially formed in the same configuration as the brake lever  60  and has a U-shaped gripping pipe  75  with right and left proximal ends  70   a ,  70   b  which are formed with the mounting apertures  71   a ,  71   b , respectively, a cable arm  76  mounted to the left end of the gripping pipe  75 , and a stopper arm  77  mounted to the right end (i.e. of the proximal end) of the gripping pipe  75 . A central area of the gripping pipe  75  has a gripping portion  75   a . The proximal end of the cable arm  76  has the mounting apertures  71   a , and a distal end thereof has a connecting pin  78 . The proximal end of the stopper arm  77  has the mounting apertures  71   b , with a distal end of the stopper arm  77  having a stopper segment (stopper)  79   a  for retaining the grip/clutch lever  79  at a stop position (remaining at a rear position) P 1  (see FIG. 5) and an operating stopper segment (stopper)  79   b  for retaining the grip/clutch lever  70  in an operative position (remaining at a front position) P 2  (see FIG.  8 ). 
     A right distal end  53   a  of the connecting pipe  53  engages a return spring  55 , which has one end  55   a  engaging a rear end  51   a  of the right handle  51  and the other end engaging the right proximal end  70   b  of the grip/clutch lever  70 , thereby urging the grip/clutch lever  70  in the rearward stop position P 1  (see FIG.  5 ). 
     A dog-legged arm  56  is pivotally mounted to the left handle  50  in the vicinity of a rear distal end  50   a  thereof via a mounting pin  57 . An upper distal end  56   a  of the arm  56  is formed with an elongated slot  56   b  which engages the connecting pin  78 , with a lower distal end  56   c  being connected to a rear distal end  36   b  of the clutch cable  36 . 
     FIGS. 5 and 6 show conditions wherein the brake lever  60  and the grip/clutch lever  70  are pivotally mounted for rocking movements in fore and aft directions about the retainer rod  54 . 
     In FIG. 5, the mounting bores  61   a  and  61   b  of the brake lever  60  are fitted on the right and left distal end portions  54   a ,  54   b  (with the distal end portion  54   b  being not shown) of the retainer rod  54  inserted through the connecting pipe  53  integrally connected to the respective rear distal ends of the handles  50 ,  51 . The grip/clutch lever  70  is located outwardly of the brake lever  60 , with the right and left proximal ends  70   a ,  70   b  of the grip/clutch lever  70  being mounted to the right and left distal ends  54   c ,  54   d  (see FIG. 4 for the right distal end) of the retainer rod  54  by means of the right and left bolts  72 ,  72 . With such an arrangement, the brake lever  60  and the grip/clutch lever  70  are rendered to pivot about the center of the retainer rod  54 . 
     Further, FIG. 5 shows a condition wherein the arm  56  is pivotally mounted to the left handle  50  in the vicinity of the rear distal end  50   a  thereof for rocking movements, and the connecting pin  78  is fitted to the elongated slot  56   b  of the upper end  56   a  to cause the arm  56  to be connected to the grip/clutch lever  70  via the cable arm  76  and where the rear distal end  36   b  of the clutch cable  36  is secured to the lower end  56   c  of the arm  56 . 
     In addition, FIG. 5 shows a condition wherein the left mounting plate  63  of the brake lever  60  has the protruding end  65  to which the rear end  66   a  of the brake cable  66  is secured. 
     In FIG. 6, the return spring  55  is fitted to the right distal end  53   a  of the connecting pipe  53 , and has the one end  55   a  engaging the rear distal end  51   a  of the right handle  51  and the other end  55   b  engaging the right proximal end  70   b  of the grip/clutch lever  70 . With such an arrangement, the grip/clutch lever  70  is urged toward the rear stop position P 1  with the action of the return spring  55  to compel the stopper segment  79   a  to be brought into abutting contact with the rear distal end  51   a  of the right handle  51  to enable the grip/clutch lever  70  to be retained in the rear stop position P 1 . 
     On the other hand, when shifting the grip/clutch lever  70  to the front operating position P 2  (see FIG.  8 ), the operating stopper segment  79   b  is brought into abutting contact with the rear distal end  51   a  of the right handle  51 , thereby retaining the grip/clutch lever  70  in the front operating position P 2 . The operating position P 2  will be described below in detail with reference to FIG.  8 . 
     Thus, the grip/clutch lever  70  is formed at its lower end with the stopper segments  79   a ,  79   b  which restrict the fore and aft movements of the grip/clutch lever  70 . As a consequence, when operating the grip/clutch lever  70 , it is possible for the operator&#39;s hand to be precluded from interfering with the stopper segments  79   a ,  79   b , thereby improving the maneuverability or operability of the grip/clutch lever  70 . 
     Further, this drawing shows a condition where rendering the stopper segment  67  of the brake lever  60  to be brought into contact with the right handle causes the brake lever  60  to be retained in the rear braking position P 3 . 
     Now, the operation of the brake lever  60  and the grip/clutch lever  70  is described with reference to FIGS. 7 to  9 . 
     First, when cutting the grass with the lawnmower, the operator touches the brake lever  60  as seen in FIG.  5  and then shifts the brake lever  60  about the retainer rod  54  from the braking position P 3  as shown by arrow {circle around ( 1 )} in a swung fashion. When this takes place, the brake cable  66  is pulled with the protruding end  65  of the brake lever  60  in a direction as shown by an arrow {circle around ( 2 )}. 
     Then, in FIG. 7, the brake lever  60  is tilted to the brake-releasing position P 4  until it is brought into abutting contact with the grip/clutch lever  70 . Tilting the brake lever  60  to the brake-releasing position P 4  causes the brake for the cutter  16  (see FIG. 1) to be released, with the clutch for the cutter  16  being turned on to initiate rotation of the cutter  16 . 
     Under such a condition, the operator&#39;s hand  80  applies a pushing force F 1  onto the grip/clutch lever  70  in a horizontal direction. When this occurs, the hand  80  is applied to the grip/clutch lever  70  by its own weight F 2 . Accordingly, a resultant composite force F, i.e. the pushing force F 1  and the own weight F 2 , is applied in a direction as shown by an arrow. The composite force F is substantially aligned in an orientation wherein the grip/clutch lever  70  is tilted about the center of the retainer rod  54 . Consequently, applying the pushing force F 1  to the grip/clutch lever  70  with the operator causes the grip/clutch lever  70  to be tilted about the center of the retainer rod  54  from the stop position P 1  as shown by an arrow {circle around ( 3 )} in an efficient fashion. The brake lever  60 , which remains at the brake-releasing position P 4 , is tilted together with the lever  70  about the center of the retainer rod  54  as shown by the {circle around ( 3 )}. 
     Tilting the grip/clutch lever  70  as shown by the {circle around ( 3 )} causes the arm  56  to be tilted about the shaft of the mounting pin  57 , pulling the clutch cable  36  in a direction as shown by an arrow {circle around ( 4 )}. With such an action, the clutch cable  36  shown in FIG. 2 is pulled in a direction as shown by the arrow to allow the clutch lever  35  to be tilted in the upper surface direction of FIG. 2, thereby shifting the clutch shifter  32  in a direction as shown by the arrow shown in FIG. 3 via the clutch cam  33 . 
     Thereafter, when the grip/clutch lever  70  is tilted to a given position, the cone-shaped surface  37   a  of the clutch shifter  32  is brought into contact with the lining  38  to cause the running clutch  30  to be brought into the slipping state. Thus, the walk behind lawnmower  10  is allowed to start off in a forward direction at the low speed. 
     In FIG. 8, the grip/clutch lever  70  is tilted to the operating position P 2 , and the brake lever  60  is also tilted to the operating position P 5  together with the grip/clutch lever  70 . The operating stopper segment  79   b  of the grip/clutch lever  70  is brought into abutting contact with the rear distal end of the right handle  51  to cause the grip/clutch lever  70  to be held stationary at the front operating position P 2  and to cause the brake lever  60  to be held stationary at the operating position P 5 . 
     Thus, the right proximal end  70   b  (see FIG. 4) of the grip/clutch lever  70  has the stopper arm  77  formed with the stopping and operating stopper segments  79   a ,  79   b  for restricting the fore and aft movements of the grip/clutch lever  70 . Therefore, since the respective stopper segments  79   a ,  79   b  are enabled to be separated from the grip portion  75   a  of the grip/clutch lever  70 , it is possible for the operator&#39;s hand  80  to be prevented from interfering with the stopper segments  79   a ,  79   b  during operation of the grip/clutch lever  70 . This results in a highly improved operability of the grip/clutch lever  70 . 
     In FIG. 9, tilting the grip/clutch lever  70  to the operating position P 2  causes the cone surface  37   a  of the clutch shifter  32  to be surely brought into contact with the lining  38  such that the running clutch  30  is brought into a coupled or connected state, allowing the walk behind lawnmower  10  shown in FIG. 1 to travel in the forward direction. When this takes place, the brake for the cutter  16  (shown in FIG. 1) is released while the clutch for the cutter  16  remains coupled, with the cutter  16  remaining in a rotating condition. Accordingly, the walk behind lawnmower  10  is enabled to travel forward while enabling the cutter  16  to cut the grass. 
     Also, in the first preferred embodiment, as shown in FIG. 8, it is so constructed that bringing the operating stopper segment  79   b  of the grip/clutch lever  70  into abutting engagement with the rear distal end  51   a  of the right handle  51  allows the grip/clutch lever  70  to remain stationary at the operating position P 2  while the running clutch  30  (see FIG. 3) is held in the connected state, the present invention is not limited thereto and it may be modified such that it is possible for the grip/clutch lever  70  to reach the operating position P 2  to cause the running clutch  30  to be brought into the connected state before the operating stopper segment  79   b  of the grip/clutch lever  70  is brought into abutting engagement with the rear distal end  51   a  of the right hand  51 . In this case, the cone surface  37   a  of the clutch shifter  32  shown in FIG. 3 is brought into pressured contact with the lining  38  such that the grip/clutch lever  70  is held stationary at the operating position P 2 . 
     FIG. 10 shows a traveling state of the walk behind lawnmower  10  with the running clutch  30  shown in FIG. 3 remaining in the slipping state. 
     Due to the slipping state of the running clutch  30 , the walk behind lawnmower  10  starts off at the low speed V. During this movement, since the operator&#39;s hand  80  applies the pushing force F 1  to the grip/clutch lever  70  and the brake lever  60  in the forward direction and in a horizontal direction, i.e., in a traveling direction of the walk behind lawnmower  10 , it is possible for the operator to manipulate the walk behind lawnmower  10  in a natural motion. This results in a smooth start-off of the walk behind lawnmower  10  to allow the same to cut the grass in a high quality finish. 
     Further, the presence of the slipping phase of the running clutch  30  performed during a time interval in which the grip/clutch lever  70  is forced forward allows the operator to move following the start-off movement of the walk behind lawnmower  10  in the natural motion during the start-off period of the walk behind lawnmower  10 . As a result, the walk behind lawnmower  10  may be operating in a simple manner. 
     In addition, during working operation of the walk behind lawnmower  10 , adjusting (i.e. applying a force in strength and weakness) the forward pushing force of the grip/clutch lever  70  enables the working speed of the walk behind lawnmower  10  to be adjusted in an easy fashion in dependence on a working status. 
     On the other hand, when it is desired to shift the traveling direction of or to move the walk behind lawnmower  10  rearward, the grip/clutch lever  70  and the brake lever  60  are first pulled rearward, tilting these components to the stop position P 1  and the brake-releasing position P 4  (sown in FIG.  7 ), respectively. During such tilting movement, the stopping stopper segment  79   a  (shown in FIG. 6) of the grip/clutch lever  70  is brought into abutting contact with the rear distal end  51   a  of the right handle  51 , thereby restricting further tilt of the grip/clutch lever  70 . Under this circumstance, the running clutch  30  shown in FIG. 3 is turned off, rendering the rear wheels  13  to be freely moveable. Accordingly, the operator may shift the traveling direction of or to move the walk behind lawnmower  10  rearward while retaining the grip/clutch lever  70  and the brake lever  60  in their gripped states. 
     Further, it is constructed such that the grip/clutch lever  70  also serves as the grip of the handles  50 ,  51  in combined use. Accordingly, it is possible to save troublesome efforts to manipulate the clutch lever while gripping the grip of the handles that would be otherwise required in the conventional working machine. Thus, operation is simplified to enable the operator&#39;s load to be minimized. 
     Now, a description is made for a spring force of the spring force (shown in FIG. 6) of the grip/clutch lever  70 . 
     If the return spring  55  of the grip/clutch lever  70  is settled to have an excessively large spring force, the grip/clutch lever  70  encounters a difficulty in a smooth returning operation owing to a quick restoring movement of the spring during a restoring movement from the operating position P 2  (see FIG. 9) to the stop position P 1  (see FIG.  6 ). For this reason, when taking the restoring movement of the grip/clutch lever  70  from the operating position P 2  to the stop position P 1  into consideration, it is preferred that the spring force of the returning spring  55  is limited to some extents. 
     However, where the spring force of the return spring  55  is excessively small, it is highly likely that the grip/clutch lever  70 , when applied with only a small force (i.e., downward force F 1 ), is tilted or pivoted forward from the stop position P 1 . 
     To this end, the brake lever  60  is arranged such that it includes the return spring  69 , whose spring force is combined with the spring force of the return spring  55  (see FIGS.  6  and  7 ), whereby, when only a suitable operating force is applied, the grip/clutch lever  70  and the brake lever  60  are tilted forward. With such an arrangement, the grip/clutch lever  70  may be smoothly restores from the operating position P 2  to the stop position P 1  and the grip/clutch lever  70  may be precluded from unintentionally tilting forward from the stop position P 1 , resulting in further improved operability. 
     Also, in the first preferred embodiment, although a description has been made in conjunction with the brake lever  60  associated with the return spring  69 , it is possible to provide a return spring in the vicinity of the clutch/brake of the cutter  16  in stead of the return spring  69 . 
     Thus, in a case where, in stead of the return spring  69 , the return spring is provided in the clutch/brake remaining at one side of the cutter  16 , it seems that it is difficult for the brake lever  60  to be smoothly restored from the brake-releasing position P 4  to the brake position P 3 . 
     However, during restoring movement of the grip/clutch lever  70  from the operating position P 2  to the stop position P 1  with the action of the return spring  55 , the brake lever  60  is restored from the operating position P 5  (see FIG. 8) to the brake-releasing position P 4  (see FIG. 7) together with the grip/clutch lever  70  with the spring force of the return spring  55 . 
     The brake lever  60 , which is restored to the brake-releasing position P 4 , is subjected to an inertial force to be tilted rearward with the spring force of the return spring  55  for the grip/clutch lever  70 , with the inertial force being utilized to enable the brake lever  60  to be restored from the brake-releasing position P 4  to the brake position P 3  (see FIG. 5) in a smooth fashion. 
     Also, in the first preferred embodiment, although it is so constructed such that, when the running clutch  30  (see FIG. 3) is held in the slipping state, in the course of swinging movement or shifting of the grip/clutch lever  70  from the stop position P 1  (see FIG. 5) to the operating position P 2  (see FIG.  9 ), to allow the grip/clutch lever  70  to reach the operating position P 2 , the running clutch  30  is coupled, it may be also constructed such that, under a condition wherein the grip/clutch lever  70  remains stationary at the operating position P 2 , the running clutch  30  is continuously maintained in the slipping state. 
     Further, it may be so constructed such that, before bringing the operating stopper lever  79   b  of the grip/clutch lever  70  into abutting engagement with the rear distal end  51   a  of the right handle  51 , the grip/clutch lever  70  is moved to the operating position P 2  to operate the running clutch  30  in the slipping phase. In such a case, pressing the cone surface  37   a  of the clutch shifter  32  shown in FIG. 3 against the lining  38  allows the grip/clutch lever  70  to remain stationary at the operating position P 2 . 
     Thus, the presence of the structure wherein the running clutch  30  is held in the slipping phase under the condition wherein the grip/clutch lever  70  is held stationary at the operating position P 2  enables the cutter  16  (shown in FIG. 1) to cut the grass while allowing the running clutch  30  of the walk behind lawnmower  10  to remain in the slipping state to keep traveling state of the front and rear wheels  12 ,  13 . 
     With such a walk behind lawnmower  10  thus constructed, it is possible to obtain the same results as those obtained in the first preferred embodiment. 
     Also, it is so constructed such that the surface  37   a  of the cone  37  and the lining  38  of the hub  39  resist slippage in a long period of time to allow the running clutch  30  shown in FIGS. 2 and 3 to have capability of performing the grass cutting operation under the slipping state. 
     Now, a lever structure of a second preferred embodiment is described in conjunction with FIGS. 11 to  17 . Also, the same component parts as those of the first preferred embodiment bear the same reference numerals as used therein and a detailed description of the same is herein omitted. 
     In FIG. 11, a walk behind lawnmower  80  has the lever structure wherein a connecting pipe  86  transversely extends between right and left handles  82 ,  83  in the vicinities of rear distal ends  82   a ,  83   a  thereof, with the rear distal ends  82   a ,  83   a  being formed with boss portions  84 ,  85 , respectively, to which a hold lever  90 , a brake lever  100  and a grip/clutch lever  110  are mounted with right and left fixture bolts  87 ,  88  for swinging movement. 
     The hold lever  90  is located in a forward position, with the brake lever  100  being positioned in a rearward position and with the grip/clutch lever  110  being located between the hold lever  90  and the brake lever  100 . 
     Also, the right and left handles  82 ,  83  are arranged to extend rearward of the machine body  11  (see FIG. 1) like the handles  50 ,  51  in the first preferred embodiment shown in FIG.  1 . 
     In FIG. 12, the hold lever  90  is comprised of a substantially U-shaped gripping pipe  91 , right and left boss portions  92 ,  93  mounted to right and left distal ends of the gripping pipe  91 , and a stopper arm  94  mounted to the right boss portion  93 . The gripping pipe  91  is composed of a member having a central portion (gripping portion)  91   a  formed in a substantially elliptical shape in cross section, with each of right and left distal ends being formed into a circular shape. 
     The left boss portion  92  of the hold lever  90  is located outward of the left boss portion  84  secured to the left handle (handle)  82 , with a left retainer bolt  87  being fitted through the left boss portions  92 ,  84 . Also, the left boss portion  93  of the hold lever  90  is located outward of the left boss portion  85  secured to the right handle (handle)  83 , with a right retainer bolt  88  being fitted through the left boss portions  93 ,  85 . Thus, the hold lever  90  is mounted to the rear distal ends of the right and left handles  82 ,  83  for swinging movements. 
     The stopper arm  94  is composed of a plate which protrudes forward from the right boss portion (i.e., proximal end)  93  of the hold lever  90  and which has an upper central area formed with a resting stopper segment (i.e., stopper)  94   a  and a lower distal end formed with a gripping stopper segment (i.e., stopper)  94   b  for retaining the hold lever  90  at a rearward gripping position L 7  (shown in FIG.  13 ). 
     Also, it is possible to construct such that the hold lever  90  is retained at a forward resting position L 6  with an own weight of the hold lever  90  without mounting the return spring  95 . 
     The brake lever  100  is comprised of a gripping rod  101  formed in the substantially same U-shape as the gripping pipe  91  of the hold lever  90 , and right and left mounting plates  102 ,  103  secured to right and left distal ends of the gripping rod  101 . The left mounting plate  102  has a mounting bore  102   a  which is able to fit the left retainer bolt  87 , with a protruding end  102   b  being formed with a bore  102   c  to which a rear distal end  66   a  of a brake cable  66  is fixed. The right mounting plate  103  has a mounting bore  103   a  which is able to fit to the right retainer bolt  88  and a stopper segment  103   b  for retaining the brake lever  100  at a brake position L 3  (shown in FIG.  13 ). 
     The left mounting plate  102  of the brake lever  100  is located inward of the left boss portion  84  secured to the left handle  82 , with the retainer bolt  87  being fitted to the mounting bore  102   a  of the left mounting plate  102 . Further, the right mounting plate  103  of the brake lever  100  is located inward of the right boss portion  85  secured to the right handle  83 , with the retainer bolt  88  being fitted to the mounting bore  103   a  of the right mounting plate  103 . With such an arrangement, the brake lever  100  is mounted to the rear distal ends of the right and left handles  82 ,  83  for swinging movement. 
     The grip/clutch lever  110  is comprised of a gripping pipe  111  formed in the substantially the same U-shape as the gripping pipe  91  of the hold lever  90 , a cable arm  112  fixed to a left distal end of the gripping arm  111 , and a stopper arm  115  fixed to a right distal end (proximal end) of the gripping pipe  111 . The gripping pipe  111  has a central portion formed with a gripping portion  11   a . Mounting bores  113  are formed in a left distal end of the gripping pipe  111  and a proximal end of the cable arm  112 , and mounting bores  116  are formed in a right distal end of the gripping pipe  111  and a proximal end of the stopper arm  115 . 
     The cable arm  112  is composed of a plate which protrudes forward from the left distal end of the gripping pipe  111  and which includes a member which has a distal end formed with a connecting pin  114  which protrudes outward. 
     The stopper arm  115  is composed of a plate which protrudes forward from the right distal end (a proximal end) of the gripping pipe  111 , and has a lower distal end formed with a resting stopper segment (stopper)  115   a  to maintain the grip/clutch lever  110  at the stop position (remaining at the rear position) L 1  (shown in FIG. 13) and an upper distal end formed with an operating stopper segment (stopper)  115   b  for maintaining the grip/clutch lever  110  at the operating position (remaining at the forward position) L 2  (shown in FIG.  13 ). 
     The left distal end of the grip/clutch lever  110  is located inside the left distal end of the brake lever  100 , with the mounting bore  113  being fitted to a threaded portion  87   a  of the left retainer bolt  87 . Also, the right distal end of the grip/clutch lever  110  is located inside the right distal end of the brake lever  100 , with the mounting bore  116  being fitted to a threaded portion  88   a  of the right retainer bolt  88 . Then, right and left nuts  89   a ,  89   b  are screwed to the right and left retainer bolts  87 ,  88 , respectively. Thus, the grip/clutch lever  110  is swingably mounted to rear distal ends of the right and left handles  82 ,  83 . 
     The return spring  116  is fitted to the right boss portion  85  of the right handle  83  and has one end  116   a  engaging the rear distal end  83   a  of the right handle  83  and the other end  116   b  engaging the right proximal end of the grip/clutch lever  110 . Thus, the grip/clutch lever  110  is urged toward the rear stop position L 1  with the spring force of the return spring  116 . 
     Located in an area between the left boss portion  84  of the left handle  82  and the connecting pipe  86  is a dog-legged arm  117  which is mounted with a mounting pin  118  for tilting movement. The arm  117  has an upper distal end  117   a  formed with an elongated slot  117   b  for fitting the connecting pin  114  and a lower distal end  117   c  formed with a bore  117   d  to which a rear distal end  36   b  of the clutch cable  36  is fixedly secured. 
     FIG. 13 shows a condition where the connecting pipe  86  is connected to the respective rear distal ends  82   a ,  83   a  of the right and left handles  82 ,  83  and the hold lever  90 , the brake lever  100  and the grip/clutch lever  110  are mounted to the right and left boss portions  84 ,  85  with the right and left retainer bolts  87 ,  88  for swinging movement. 
     The grip/clutch lever  110  is composed of a member which is tiltable between the stop position (the rearward position) L 1  and the operating position (the forward position) L 2 . 
     The connecting pin  114  protrudes from the cable arm  112  of the grip/clutch lever  110  and is inserted through the elongated slot  117   b  of the arm  117 . With such an arrangement, tilting the grip/clutch lever  110  from the stop position (the rearward position) L 1  to the operating position (the forward position) L 2  causes the arm  117  to rotate counterclockwise about the shaft of the mounting pin  118  to enable the clutch cable  36  to be pulled rearward. 
     The brake lever  100  is composed of a member which is swingable between the brake position L 3  and the operating position L 5 . Swinging the brake lever  100  from the brake position L 3  to the forward brake-releasing position L 4  causes the brake lever  100  to be brought into abutting contact with the grip/clutch lever  110 . In such a position, the brake for the cutter is brought into the released condition while keeping the clutch for the cutter in the coupled condition. 
     The left mounting plate  102  of the brake lever  100  is formed with the protruding end  102   b , which has a bore  102   c  to which a rear distal end  66   a  of a brake cable  66  is secured. With such an arrangement, swinging the brake lever  100  from the brake position L 3  to the operating position L 5  causes the brake cable  66  to be pulled rearward. 
     The hold lever  90  is composed of a member which is tilting between the stationary position L 6  and the gripping position L 7 . The hold lever  90  serves as a member which retains the grip/clutch lever  110  at the operating position (forward position) L 2 . Also, an example of using the hold lever  90  is described below. 
     FIGS. 14A to  14 C are views for illustrating the basic sequence of operations of the respective stoppers and the levers of the walk behind working machine of the second preferred embodiment. 
     In FIG. 14A, when the grip/clutch lever  110  remains at the stop position (rearward position) L 1 , the resting stopper segment  115   a  of the stopper arm  115  is held in the abutting contact with the right handle  83 , thereby retaining the grip/clutch lever  110  at the stop position (rearward position) L 1 . Then, shifting the grip/clutch lever  110  from the stop position L 1  to the operating position (forward position) L 2 , which is shown by a dotted line, causes the operating stopper segment  115   b  of the stopper arm  115  to be brought into abutting contact with the right handle  83  for retaining the grip/clutch lever  110  at the operating position (forward position) L 2 . 
     The grip/clutch lever  110  is comprised of the proximal end (lower end portion) provided with the resting stopper segment  115   a  and the operating stopper segment  115   b  for restricting the fore and aft movements of the grip/clutch lever  110 . Consequently, during operation of the grip/clutch lever  110 , it is possible for the operator&#39;s hand from interfering with the resting stopper segment  115   a  and the operating stopper segment  115   b , with a resultant highly improved operability of the grip/clutch lever  110 . 
     In FIG. 14B, when the brake lever  100  remains at the rearward, brake position L 3 , the stopper segment  103   b  of the right mounting plate  103  is held in abutting contact with the right handle  83 , thereby retaining the brake lever  100  at the brake position L 33 . Then, shifting the brake lever  100  from the brake position L 3  to the forward, operating position L 5 , whish is shown by a dotted line, causes the brake lever  100  to be brought into abutting contact with the grip/clutch lever  110 . Since, in this instance, the grip/clutch lever  110  is retained at the operating position L 2 , the brake lever  100  is retained at the operating position L 5 . 
     In FIG. 14C, when the hold lever  90  remains at the stationary position L 6 , the resting stopper segment  94   a  of the stopper arm  94  is held in abutting contact with the right handle  83 , thereby retaining the hold lever  90  at the stationary position L 6 . The, shifting the hold lever  90  from the stationary position L 6  to the rearward, gripping position L 7  as shown by a dotted line, the gripping stopper segment  94   b  of the stopper arm  94  is brought into abutting contact with the right handle  83 , thereby retaining the hold lever  90  at the gripping position L 7 . 
     The hold lever  90  is comprised of the proximal end (lower end portion) provided with the resting stopper segment  94   a  and the gripping stopper segment  94   b  for restricting the fore and aft movements of the hold lever  90 . Consequently, since the resting stopper segment  94   a  and the gripping stopper segment  94   b  are enabled to be separated from the gripping portion  91   a  of the hold lever  90 , it is possible for the operator&#39;s hand  120  from interfering with the resting stopper segment  94   a  and the gripping stopper segment  94   b  during the operation of the hold lever  90 . This results in a highly improved operability of the hold lever  90 . 
     Now, the operations of the brake lever  100 , the grip/clutch lever  110  and the hold lever  90  are described in conjunction with FIGS. 15 to  17 . 
     First, in FIG. 13, the operator&#39;s hand is placed on the brake lever  100  and the brake lever  100  is shifted in the swinging movement from the brake position L 3 , which is an operative braking position, in a direction as shown by an arrow a about the axes of the right and left retainer bolts  87 ,  88 . With such a shifting movement, eh brake cable  66  is pulled in a direction as shown by an arrow b with the protruding end  102   b  of the left mounting plate  102 . 
     In FIG. 15, the brake lever  100  is swung to the brake-releasing position L 4  until it abuts against the grip/clutch lever  100 . Swinging the brake lever  100  to the brake-releasing position L 4  causes the brake for the cutter  16  (shown in FIG. 1) to be released while keeping the clutch for the cutter  16  in the coupled state to rotate the cutter  16 . 
     Further, the operator7s hand  120  applies the pushing force F 3  onto the grip portion  111   a  of the grip/clutch lever  110  in the horizontal direction. When this takes place, the own weight F 4  of the hand  120  is applied to the grip/clutch lever  110 . This causes the composite force F 5 , that is, the pushing force F 3  combined with the own weight F 4 , is applied in a direction as shown by an arrow. This composite force F 5  is substantially aligned in an orientation wherein the grip/clutch lever  110  is tilted about the centers of the right and left retainer bolts  87 ,  88  of the grip/clutch lever  110 . Consequently, applying the pushing force F 3  to the grip/clutch lever  110  from the operator enables the grip/clutch lever  110  to be efficiently tilted about the centers of the right and left retainer bolts  87 ,  88  from the stop position L 1  in a direction as shown by an arrow c. During such a tilting movement, the brake lever  100 , which remains at the brake-releasing position L 4 , is tilted about the centers of the right and left retainer bolts  87 ,  88  together with the grip/clutch lever  110  in a direction as shown by the arrow c. 
     Tilting the grip/clutch lever  110  in the direction as shown by the arrow c causes the arm  117  to pivot about the axis of the mounting pin  118  in a direction as shown by an arrow d, thereby pulling the clutch cable  36  in a direction as shown by an arrow e. With such a movement, the clutch cable  36  shown in FIG. 2 is pulled in the direction as shown by the arrow, causing the clutch lever  35  to pivot in the surface direction of FIG. 2 such that the clutch shifter  32  is shifted in a direction as shown by an arrow in FIG. 3 via the clutch cam  33 . 
     Then, if the grip/clutch lever  110  is tilted to a given position, the cone surface  37   a  of the clutch shifter  32  shown in FIG. 3 is brought into contact with he lining  38  to cause the running clutch  30  to be brought into the slipping state. Therefore, the walk behind lawnmower  10  is initiated to start moving in the forward direction at the low speed. 
     During such a movement, the presence of the pushing force F 3  applied to the grip/clutch lever  110  and the brake lever  100  in the forward direction with the operator&#39;s hand  80  for pushing the walk behind lawnmower in the horizontal direction, i.e. in the forward direction enables the operator to operate the walk behind lawnmower in the natural motion. Thus, like in the first preferred embodiment, the walk behind lawnmower is enabled to start off in the smooth manner, thereby allowing the same to cut the grass in a high quality finish. 
     Further, rendering the running clutch  30  to remain in the slipping phase in the course of the forward movement of the grip/clutch lever  110  enables the operator to follow the taking-off movement of the walk behind lawnmower in the natural motion during the taking-off operation thereof. As a result, like in the first preferred embodiment, it is possible for the walk behind lawnmower to be simply operated. 
     In FIG. 16, the grip/clutch lever  110  is tilted to the operating position L 2  and the brake lever  100  is tilted together with the grip/clutch lever  110  to the operating position L 5 . Swinging the grip/clutch lever  110  to the operating position L 2  causes the cone surface  37   a  of the clutch shifter  32  to be surely brought into contact with the lining  38  to allow the running clutch  30  to be brought into the engaged or connected state. Under such a condition, if the operator extends the finger  121  of the hand  120 , the finger  121  reaches the gripping portion  91   a  of the hold lever  90 . Under this circumstance, bending the finger  121  as shown by an arrow f enables the hand  120  to grip the gripping portion  91   a  of the hold lever  90 . As a result, the hold lever  90  is enabled to swing rearward as shown by an arrow g. 
     Also, the presence of the gripping portion  91   a , which is collapsed into the substantially elliptical shape in cross section, of the hold lever  90  enables the finger  121  to readily hook the hold lever  90 . With such an arrangement, it is possible for the gripping portion  91   a  of the hold lever  90  to be gripped with the finger  120  in a further simplified manner. 
     In FIG. 17, gripping the gripping portion  91   a  of the hold lever  90  with the hand  120  to tile the hold lever  90  to the gripping position L 7  causes the gripping stopper segment  94   b  to be brought into abutting contact with the right handle  83 . As a consequence, the hold lever  90  is retained at the gripping position L 7 , thereby restricting a further rearward movement of the same. On the other hand, the presence of the operating stopper segment  115   b  of the grip/clutch lever  110  held in abutting contact with the right handle  83  restricts the grip/clutch lever  110  from being shifted forward from the operating position L 2 . Accordingly, gripping the hold lever  90  and the grip/clutch lever  110  together enables the grip/clutch lever  110  to be retained at the operating position (forward position) L 2 . When this occurs, since the brake lever  90  is also gripped with the hand  120 , the brake lever  100  remains in the abutting engagement with the grip/clutch lever  110 , enabling the brake lever  100  to be retained at the operating position L 5 . 
     Tilting the grip/clutch lever  110  to the operating position L 2  causes the cone surface  37   a  of the clutch shifter  32  to be surely brought into contact with the lining  38  to render the running clutch  30  to remain in the connected state, allowing the walk behind lawnmower  10  shown in FIG. 1 to start off forward at a given speed. During such a movement, the brake for the cutter  16  (shown in FIG. 1) is released while the clutch for the cutter  16  remains coupled, with the cutter  16  remaining in a rotating condition. Thus, it is possible for the cuter  16  to cut the grass while allowing the walk behind lawnmower  10  to travel in the forward direction. 
     In accordance with the second preferred embodiment, by merely gripping the grip/clutch lever  110  together with the hold lever  90 , since the grip/clutch lever  110  is enabled to be retained at the operating position (forward position) L 2 , it is possible to retain the grip/clutch lever  110  at the operating position L 2  in a simple fashion. As a result, it is possible to further improve the operability of the walk behind lawnmower, with a resultant further improvement in a convenience for using the walk behind lawnmower. 
     On the other hand, like in the first preferred embodiment, there is a need where the operating position L 2  is retained by continuously pushing the grip/clutch lever  110  in the forward direction without gripping the hold lever  90 . In such a case, allowing the hold lever  90  not to be gripped enables the hold lever  90  to be retained at the stationary position L 6  (see FIG.  16 ), thereby precluding the operator&#39;s hand  120  from interfering with the hold lever  90  during the forward, continuous pushing movement of the grip/clutch lever  110 . 
     Thus, the presence of a structure wherein the hold lever  90  is arranged to be tiltable enables the operation of the grip/clutch lever  110  to be retained at the operating position L 2  to be carried out in two methods. 
     That is, it is possible to carry out the above operation in a method for retaining the grip/clutch lever  110  at the operating position L 2  by gripping the hold lever  90  and a method for retaining the grip/clutch lever  110  at the operating position L 2  by pushing the same in the forward direction. Thus, since it is possible for a suitable operating method to be selected from the two kinds of operating methods depending on working conditions of the walk behind lawnmower, the walk behind lawnmower may have a further improved operability, with a resultant further improvement in the convenience for using the same. 
     Now, a description is made on how to steer or to move the walk behind lawnmower  10  rearward. Gripping the grip/clutch lever  110  while gripping the hold lever  90  enables the grip/clutch lever  110  to be retained such that is not tilted in the fore and aft directions. As a result, under a condition where both the grip/clutch lever  110  and the hold lever  90  remain in the gripped states, it is possible to steer or to move the walk behind lawnmower  10  shown in FIG.  1 . When steering or moving the walk behind lawnmower  10  rearward, of course, like in the first preferred embodiment, the running clutch may also be rendered uncoupled to enable free rotation of the rear wheels  13 . In such a case, after releasing the gripping state of the hold lever  90 , the grip/clutch lever  110  and the brake lever  100  may be pulled rearward such that they are tilted to the stop position L 1  and the brake-releasing position L 4  (shown in FIG.  15 ), respectively. When this occurs, the resting stopper segment  115   a  (see FIG. 14A) of the grip/clutch lever  110  is brought into abutting contact with the right handle  83  to restrict a further tilting movement of the grip/clutch lever  110 . Under this condition, the running clutch  30  is rendered uncoupled to enable free rotation of the rear wheels  13 . Consequently, the operator may steer or move the walk behind lawnmower rearward while keeping the grip/clutch lever  110  and the brake lever  100  in the gripped states. 
     Further, like in the first preferred embodiment, the grip/clutch lever  110  is so constructed as to commonly serve as the grip for the right and left handles  82 ,  83  in a combined use. Thus, it is possible for saving a labor to manipulate the clutch lever while gripping the grip of the handles that would be required in the conventional working machine. This results in a simplified operation with an decrease in the operator&#39;s load. 
     Now, a structure related with levers and handles of a walk behind lawnmower of a third preferred embodiment is described with reference to FIG.  18 . 
     In the third preferred embodiment, the walk behind lawnmower  130  includes right and left hold levers  131 ,  135  in place of the holding lever  90  (shown in FIG. 11) of the second preferred embodiment, with other component parts being identical with those of the second preferred embodiment and bearing the same reference numerals as those of the second preferred embodiment for omitting the description of the same. 
     In FIG. 18, the left hold lever (hold lever)  131  is composed of a left dog-leg shaped gripping pipe  132 , with its distal end mounted with a left boss portion  92  to which a stopper arm  133  is fixed. The left gripping pipe  132  is composed of a member having a distal end formed in a substantially elliptical shape in cross section and a proximal end portion formed in a circular shape in cross section. 
     The left boss portion  92  of the left hold lever  131  is located outside the left boss portion  84  fixed to the left handle  82 , with the left retainer bolt  87  being fitted to both the left boss portions  92 ,  84 . Thus, the left hold lever  131  is mounted to the rear distal end of the left handle  82  for swinging movement. 
     The stopper arm  133  is composed of a plate which protrudes forward from the left boss portion  92  of the left hold lever  131  and which has an upper central area formed with a resting stopper segment  133   a  for retaining the left hold lever  131  at the forward stationary position L 6  (see FIG. 13) and a lower distal end formed with a gripping stopper segment  133   b  for retaining the left hold lever  131  at the rearward gripping position L 7  (see FIG.  13 ). The stopper arm  133  is composed of a member formed in a symmetric relation with respect to the right and left of the stopper arm  94  of the second preferred embodiment. 
     The right hold lever (hold lever)  135  is composed of a left dog-leg shaped gripping pipe  136 , with its distal end mounted with a right boss portion  93  to which a stopper arm  134  (which is identical with that of the second preferred embodiment) is fixed. The right gripping pipe  136  is composed of a member having a distal end formed in a substantially elliptical shape in cross section and a proximal end portion formed in a circular shape in cross section. The right boss portion  93  of the right hold lever  135  is located outside the right boss portion  85  fixed to the right handle  83 , with the right retainer bolt  88  being fitted to both the right boss portions  93 ,  85 . Thus, the right hold lever  135  is mounted to the rear distal end of the right handle  83  for swinging movement. 
     The stopper arm  94  is composed of the plate which protrudes forward from the right boss portion  93  of the right hold lever  135  and which has the upper central area formed with the resting stopper segment  94   a  for retaining the right hold lever  135  at the forward stationary position L 6  (see FIG. 13) and the lower distal end formed with the gripping stopper segment  94   b  (see FIG. 14B) for retaining the right hold lever  135  at the rearward gripping position L 7  (see FIG.  13 ). 
     In accordance with the third preferred embodiment, when tilting the grip/clutch lever  110  to the operating position L 2  shown in FIG. 16 while shifting the brake lever  100  to the operating position L 2 , like in the second preferred embodiment, the right and left hold levers  131 ,  135  may be gripped together with the grip/clutch lever  110  and the brake lever  100 , or either one of the right and left hold levers  131 ,  135  may be gripped. Thus, like in the second preferred embodiment, it is possible to retain the grip/clutch lever  110  at the operating position L 2  shown in FIG.  17 . As a result, it is possible in the third preferred embodiment to have the same advantages as those obtained in the second preferred embodiment. 
     Further, in accordance with the third embodiment, forming the hold lever of the second preferred embodiment into two separate pieces, i.e. the right and left hold levers  131 ,  135  enables the hold levers  131 ,  135  to be formed in a compact shape. For this reason, it is easy to handle and an assembling work can be performed in a simplified manner. 
     Now, a structure related with levers and handles of a walk behind lawnmower of a fourth preferred embodiment is described with reference to FIG.  19 . 
     The walk behind lawnmower  140  includes only the right hold lever  135  among the right and left hold levers  131 ,  135  of the third preferred embodiment shown in FIG. 18, with the other component parts being identical with those of the third preferred embodiment and bearing the same reference numerals as those of the same to omit a description of the same. 
     In accordance with the fourth preferred embodiment, when tilting the grip/clutch lever  110  from the stop position L 1  shown in FIG. 15 to the operating position L 2  shown in FIG. 16 while shifting the brake lever  100  to the operating position L 5 , the right hold lever  135  may be gripped together with the grip/clutch lever  110  and the brake lever  100 . Thus, like in the second preferred embodiment, it is possible to retain the grip/clutch lever  110  at the operating position L 2  shown in FIG.  16 . As a result, it is possible in the fourth preferred embodiment to have the same advantages as those obtained in the second preferred embodiment. 
     Further, in accordance with the fourth embodiment, the right hold lever  135  may have a simplified shape, making it possible to reduce the cost of the right hold lever  135 . In addition, according to the fourth preferred embodiment, since the right hold lever  135  may be formed in a compact structure, it is easy to handle and an assembling work can be performed in a simplified manner. 
     Now, a structure related with levers and handles of a walk behind lawnmower of a fifth preferred embodiment is described with reference to FIGS. 20 and 21. 
     In the second preferred embodiment described in conjunction with FIGS. 15 to  17 , although it is constructed such that the running clutch  30 , shown in FIGS. 2 and 3, is brought into the slipping state in the course of tilting movement of the grip/clutch lever  110  from the stop position L 1  to the operating position L 2  and is operative to be brought into the connected state when the grip/clutch lever  110  reaches the operating position L 2 , the fifth preferred embodiment is so arranged such that the running clutch  30  is maintained in the slipping state under a condition where the grip/clutch lever  110  remains stationary in the operating position L 2 . 
     When tilting the grip/clutch lever  110  from the stop position L 1  in the second preferred embodiment shown in FIG. 2 to the operating position L 2 , the brake lever  100  is tilted together with the grip/clutch lever  110  to the operating position L 5 . 
     As seen in FIG. 20, when the grip/clutch lever  110  is tilted to the operating position L 2 , the cone surface  37   a  of the clutch shifter  32  is brought into contact with the lining  38  such that the running clutch  30  is brought into the slipping state. Therefore, the walk behind lawnmower  10  shown in FIG. 1 is enabled to start off forward at the low speed. 
     Upon operation of the cone surface  37   a  of the clutch shifter  32  into contact with the lining  38 , the grip/clutch lever  110  is rendered stationary at the operating position L 2 . In this event, the operating stopper segment  115   b  (see FIG. 21) of the grip/clutch lever  110  is held out of abutting engagement with the right handle  83 . 
     Now, under a condition where the grip/clutch lever  110  is tilted to the operating position L 2 , since the operator applies the pushing force F 3  to the grip/clutch lever  110  and the brake lever  100  with the hand  120  in the forward direction, i.e. in the horizontal, namely, in the forward traveling direction of the walk behind lawnmower, the operator is enabled to operate the walk behind lawnmower in the natural motion. Accordingly, like in the first and second preferred embodiments, it is possible for the walk behind lawnmower to start off in a smooth fashion to cut the grass in a high quality finish. 
     Further, rendering the running clutch  30  operative to remain in the slipping state when the grip/clutch lever  110  is tilted to the operating position L 2  enables the operator to follow the taking-off movement of the walk behind lawnmower in the natural motion during taking-off operation of the walk behind lawnmower. As a result, like in the first and second preferred embodiments, it is possible to operate the walk behind lawnmower in a simple fashion. Under such a circumstance, the operator may extend the finger  121  of the hand  120  such that the finger  121  reaches the gripping portion  91   a  of the hold lever  90 . From this condition, when bending the finger  121  as shown by an arrow h, the hand  120  is enabled to grip the grip portion  91   a  of the hold lever  90 . Thus, it is possible to tilt the hold lever  90  in a rearward direction as shown by an arrow j. 
     Also, forming the grip portion  91   a  of the hold lever  90  in a shape to have the substantially elliptical in cross section enables to provide an ease for the hand  120  to grip the grip portion  91   a  of the hold lever  90 . 
     In FIG. 21, gripping the gripping hand  91   a  of the hold lever  90  with the hand  120  to tile the hold lever to the gripping position L 7  causes the gripping stopper segment  94   b  to be brought into abutting contact with the right handle  83 . Consequently, the hold lever  90  is retained at the gripping position L 7  for restricting a further tilting movement in the rearward direction. When this occurs, since the cone surface  37   a  of the clutch shifter  32  shown in FIG. 3 is held in contact with the lining  38 , the grip/clutch lever  110  is enabled to be rendered stationary at the operating position L 2  in a continuous fashion. Thus, the running clutch  30  shown in FIG. 3 remains in the slipping state. 
     Gripping the hold lever  90  and the grip/clutch lever  110  together enables the grip/clutch lever  110  to be rendered stationary at the operating position L 2  (,i.e. in the forward position). Under this circumstance, a given distance S is left between the grip/clutch lever  110  and the hold lever  90 . In this instance, since the brake lever  100  is gripped with the hand  120 , the brake lever  100  is continuously held in an abutting contact with the grip/clutch lever  110 , thereby enabling the brake lever  100  to be retained in the operating position L 5 . Thus, it is possible to cut the grass with the cutter  16  (see FIG. 1) while permitting the walk behind lawnmower to travel with the rear wheels  13  with the running clutch  30  remaining in the slipping state. 
     In such a manner, the walk behind lawnmower of the fifth preferred embodiment may have the same advantages as those of the first and second preferred embodiments. 
     Also, the running clutch  30  shown in FIGS. 2 and 3 are constructed such that the surface  37   a  of the cone  37  and the lining  38  of the hub  39  resist the slipping condition in a long period of time to enable cutting operation of the grass while maintaining the running clutch  30  in the slipping phase. 
     In addition, in accordance with the fifth preferred embodiment, since there is the given distance S maintained between the grip/clutch lever  110  and the hold lever  90 , adjusting (in strength and weakness) the gripping force for the grip/clutch lever  110  and the hold lever  90  enables the traveling speed of the walk behind lawnmower to be easily adjusted for thereby providing a further improved operability. More particularly, it is desired for the waking type lawnmower to be driven with an increased drive power during ascending a slope and to be moved at a higher speed during traveling in a non-working condition. Accordingly, strongly gripping the grip/clutch lever  110  and the hold lever  90  and strongly pushing the grip/clutch lever  110  toward the hold lever  90  enables the cone surface  37   a  of the clutch shifter  32  shown in FIG. 3 to be strongly brought into pressured contact with the lining  38 . With such an arrangement, adjusting the running clutch  30  into the slipping phase with less slippage to cause the drive power of the engine  14  to be efficiently delivered to the rear wheels  13  allows the walk behind lawnmower to travel at a higher speed. 
     Also, when the walk behind lawnmower ascends the sloped hill, the walk behind lawnmower is applied with a force compelling the same to descend the slope with its own weight. When this takes place, strongly pushing the grip/clutch lever  110  in the forward direction instead of strongly gripping the grip/clutch lever  110  and the hold lever  90  enables the cone surface  37   a  of the clutch shifter  32  to be strongly brought into pressured contact with the lining  38 . With such a movement, like in a case where the grip/clutch lever  110  and the hold lever  90  are strongly gripped, the running clutch  30  is adjusted into the slipping state with less slippage such that the drive power of the engine  14  can be more efficiently delivered to the rear wheels  13 . 
     Lastly, a structure related with levers and handles of a walk behind lawnmower of a sixth preferred embodiment is described with reference to FIG.  22 . The walk behind lawnmower  150  of the sixth preferred embodiment shown in FIG. 22 has a feature wherein a hold lever  153  is fixed at the gripping position L 7  (see FIG.  13 ), with other features bearing the same structure as that of the fifth preferred embodiment shown in FIGS. 20 and 21. 
     The walk behind lawnmower  150  of the sixth preferred embodiment is composed of the right and left handles  82 ,  83 , whose rear distal ends are mounted with right and left boss portions  151 ,  152  which include outwardly extending protruding segments  151   a ,  152   a , respectively, to which right and left distal ends of the hold lever  153  are welded to fix the hold lever  153  at the gripping position L 7 . 
     The hold lever  153  has a gripping portion which is formed in the same substantially U-shaped configuration as the gripping pipe  91  (which forms a component part of the hold lever  90 ) of the fifth preferred embodiment. 
     In accordance with the sixth preferred embodiment, when tilting the grip/clutch lever  110  to the operating position L 2  shown in FIG. 20 while shifting the brake lever  100  to the operating position L 5 , it is possible for the grip/clutch lever  110  to rest at the position distanced from the hold lever  151  by the given space S like in the fifth preferred embodiment shown in FIG.  21 . Under this condition, gripping the hold lever  153  together with the grip/clutch lever  110  and the brake lever  100  enables the running clutch  30  shown in FIG. 3 to be maintained in the slipping state as in the fifth preferred embodiment. As a result, in accordance with the preferred embodiment, adjusting (in strength and weakness) the gripping force for the grip/clutch lever  110  and the hold lever  153  like in the fifth preferred embodiment enables the working speed of the walk behind lawnmower  10  (see FIG. 1) to be finely adjusted in an easy manner, with a resultant improvement in the operability. 
     Further, in accordance with the sixth preferred embodiment, fixing the hold lever  153  makes the machine simplified in structure. 
     In the illustrated preferred embodiments described above, although walk behind working machine of the present invention has been exemplarily discussed in conjunction with the lawnmowers  10 ,  80 ,  130 ,  140 ,  150 , the working machine of the present invention may be applied to other types of working machineries. 
     Also, in the above preferred embodiments, although the running clutch  30  has been discussed with reference to an example wherein the cone type clutch is employed, other types of clutches may also be employed. As a main point, the clutch may be of any type which is operable to be brought into the slipping state. 
     The present disclosure relates to the subject matters of Japanese Patent Application No. 2000-403381, filed Dec. 28, 2000, and Japanese Patent Application No. 2001-223318, filed Jul. 24, 2001, the disclosures of which are expressly incorporated herein by reference in their entireties.