Patent Abstract:
A device for starting an internal combustion engine comprising a first clutch member attachable to the engine, and a second clutch member attachable to a portable drive means, wherein the first and second clutch members are engageable so that the drive means transmit force through the clutch members so as to turn and start the engine, and wherein, once the engine starts, the first and second clutch members automatically disengage from each other and wherein at least one of the first and second clutch members retracts. Preferably at least one of the first and second clutch members comprises resilient biassing means against retraction. A preferred embodiment relates to a lawnmower comprising such a device.

Full Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a device for starting an internal combustion engine.  
       BACKGROUND OF THE INVENTION  
       [0002]     Many internal combustion engines are not provided with a starter motor and must instead be started by an external force. Often, a rope or handle must be manually used to turn over the engine in order to start it.  
         [0003]     However, this suffers from a number of disadvantages. Firstly, the action of manually starting an internal combustion engine can require a substantial force which a user, for example, an elderly person, may be unable to supply. It may also be necessary to repeat the exercise of turning the engine over several times before the engine starts. This is exacerbated under certain conditions, such as cold weather, where an even greater force is needed to start the engine. Another situation where problems arise is when an engine has been stored without fuel. Although known engines can include means to prime the engine with fuel before starting, the engine may still be difficult to start. Also, even when a person is able to turn over the engine, there remain the danger of injury caused by kick-back from the motor.  
         [0004]     There have been proposed a number of devices for assisting in the starting of internal combustion engines. Some of these relate to the use of an electric drill to turn over the engine. However, none of these proposed methods or devices is believed to overcome all of the existing problems in order to provide a convenient and easy way to start an internal combustion engine.  
         [0005]     There exists therefore a need for an improved apparatus for starting an internal combustion engine.  
       SUMMARY OF THE INVENTION  
       [0006]     According to the present invention there is provided a device for starting an internal combustion engine comprising a first clutch member attachable to the engine, and a second clutch member attachable to a portable drive means, wherein the first and second clutch members are engageable so that the drive means transmit force through the clutch members so as to turn and start the engine, and wherein, once the engine starts, the first and second clutch members automatically disengage from each other and wherein at least one of the first and second clutch members retracts.  
         [0007]     Preferably, at least one of the first and second clutch members comprise resilient biasing means against retraction.  
         [0008]     Conveniently, at least one of the first and second clutch members is resiliently biased by a spring.  
         [0009]     Advantageously, the second clutch means is suitable for attachment to a portable drill.  
         [0010]     Preferably, the first clutch member is suitable for attachment to a lawnmower engine.  
         [0011]     Conveniently, the first clutch member is retractable.  
         [0012]     Advantageously, the second clutch member is retractable.  
         [0013]     Preferably, the retractable clutch member remains retracted when the clutch members disengage.  
         [0014]     Conveniently, one of the clutch members is slidably mounted on a shaft.  
         [0015]     Advantageously, the clutch member is prevented from rotating about the shaft.  
         [0016]     Preferably, the first and second clutch members comprise a dog clutch.  
         [0017]     According to another aspect of the present invention, there is provided a lawnmower comprising a first clutch member attached to an internal combustion engine wherein the first clutch member may engage with a second clutch member attached to a portable drive means so that the drive means transmit force through the clutch members so as to turn and start the engine, and wherein, once the engine starts, the first and second clutch members automatically disengage from each other and wherein at least one of the first and second clutch members retracts. 
     
    
       [0018]     The invention will now be described, by way of example, with reference to the accompanying drawings in which:  
         [0019]      FIG. 1  is a side view of a lawnmower and a starting device of the invention;  
         [0020]      FIG. 2  is a side view of part of the starting device of the invention;  
         [0021]      FIG. 3  is a side view of a lawnmower and a starting device of the invention engaged with a lawnmower engine before the engine has started;  
         [0022]      FIG. 4  is a view corresponding to  FIG. 3  after the engine has started;  
         [0023]      FIG. 5  is a side view of a lawnmower and an alternative embodiment of the device of the invention; and  
         [0024]      FIG. 6  is a perspective view of part of an alternative embodiment of the clutch members of the invention. 
     
    
       [0025]     While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as described by the appended claims.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0026]     A lawnmower is shown generally at  10  and is of conventional construction. It comprises a main body  12 , four wheels  14 , a handle  16  and an engine indicated generally at  18 .  
         [0027]     A first clutch member  20  is attached to the flywheel of the engine  18 . The first clutch member  20  comprises a substantially circular disc with an upstanding annular wall. The annular wall defines a series of asymmetric notches. There is also provided an electric drill  22  in the chuck of which is mounted a starting device indicated generally at  24 . The construction of the first and second clutch members can be more easily understood with reference to  FIG. 2 . The starting device  24  comprises a shaft  28  extending from the drill bit of the drill  22 . Fixed on the shaft  28  is located a substantially circular disc  30 . The disc  30  supports a coil spring  32  extending away from the drill  22 . Towards the end of the shaft  28  there is mounted a second clutch member  26 . The second clutch member  26  is of similar configuration to the first clutch member  20  and has complementary asymmetric notches.  
         [0028]     A notch of the first clutch member  20  as attached to a lawnmower will now be described. A first wall is directed substantially perpendicularly to the axis between the first clutch member and the lawnmower and thus defines the distal edge of the notch. A second wall is directed towards the lawnmower substantially parallel with the axis between the first clutch member and the lawnmower. A third wall, of shorter length than the first wall, is directed substantially parallel with the first wall, defining the proximal edge of the notch. A fourth wall is directed away from the lawnmower towards the distal end of the clutch member at an angle away from the first wall. The notch thus tapers away from a smaller width at the proximal edge to a greater width at the distal edge. This pattern is repeated around the annular wall of the first clutch member to define a regular series of notches. The second clutch member is provided with a corresponding complementary set of notches which mesh together with the notches in the first clutch member.  
         [0029]     The second clutch member  26  is slidably mounted upon the shaft  28  but is prevented by rotation about the shaft  28 . The spring  32  biases the second clutch member  26  towards the end of the shaft  28  but allows the second clutch member  26  to move some distance towards the disc  30 .  
         [0030]     As shown in  FIG. 3 , in use, the drill  22  and apparatus  24  are aligned with the first clutch member  20  and the second clutch member  26  is brought into contact with the first clutch member  20 . The complementary asymmetric notches of the first and second clutch members  20  and  26  mate together. The notches are shaped so as to allow the drill  22  to efficiently transmit drive through to the engine  18 . Thus, once the first and second clutch members are engaged and the drill  22  is switched on, the engine  18  is forced to turn over, as will be explained below.  
         [0031]      FIG. 5  shows a further embodiment of the invention with the positions of the first and second clutch members  20 ′ and  26 ′ being reversed with respect to the embodiment shown in  FIG. 1 . In this embodiment, the first clutch member  20 ′ is attached to the drill  22 . The starting arrangement  24 ′ is attached to the engine  18 . Once the first and second clutch members  20 ′ and  26 ′ are engaged and the drill  22  is turned on, the engine  18  is turned over as explained above. Again, if the engine turns the second clutch member  26 ′ faster than the first clutch member  20 ′, they will automatically disengage, with the second clutch member  26 ′ being forced down towards the engine  18 .  
         [0032]     Once the engine  18  starts, the drill  22  and apparatus  24  may be pulled away from the clutch member  20 . However, if the engine  18  forces the first clutch member  20  to turn at a rate faster than that of the second clutch member  26 , the asymmetric shape of the notches in the first and second clutch members forces them apart. The second clutch member  26  would be thrown away from the engine  18  towards the drill  22  to reach the situation shown in  FIG. 4 . Thus, the distance between the drill  22  and the second clutch member  26  has decreased. In other words, the second clutch member  26  has retracted. The axial shock of this movement is absorbed by the spring  32 , reducing the force passed to the user of the drill  22 . After retraction, the second clutch member  26  would be pushed back away from the drill  22  by the spring  32 . The drill  22  and attached arrangement  24  can then be safely withdrawn away from the engine  18 .  
         [0033]     In an alternative embodiment, there is provided a catch on the shaft  28  which allows the second clutch member  26  to travel towards the disc  30  to reach the position shown in  FIG. 4 , but prevents the return of member  26  towards the terminus of the shaft  28 . Thus, in this embodiment, if the second clutch member  26  is thrown from the first clutch member  20  the shock is absorbed by the spring  32  and second clutch member is safely retained by the catch away from the engine  18 . In other words, the second clutch member  26  undergoes retraction without immediately moving back away from the drill  22 . The user may return the second clutch member  26  to its initial position by releasing the catch. Thus any injury or shock caused by the kick-back from the motor  18  to the user of the drill  22  is prevented.  
         [0034]      FIG. 5  shows a further embodiment of the invention with the positions of the first and second clutch members  20 ′ and  26 ′ being reversed with respect to the embodiment shown in  FIG. 1 . In this embodiment, the first clutch member  20 ′ is attached to the drill  22 . The starting arrangement  24 ′ is attached to the engine  18 . Once the first and second clutch members  20 ′ and  26 ′ are engaged and the drill  22  is turned on, the engine  18  is turned over as explained above. Again, if the engine turns the second clutch member  26 ′ faster than the first clutch member  20 ′, they will automatically disengage, with the second clutch member  26 ′ being forced down towards the engine  18 . In this embodiment, the first clutch member  20  undergoes retraction towards the engine  18 . In an alternative embodiment, means may be provided to prevent the immediate return of the retracted clutch member to its initial position.  
         [0035]     It is to be appreciated that numerous forms and configuration of the first and second clutch members could be used which allow them to automatically disengage once the engine has started.  
         [0036]      FIG. 6  shows an alternative arrangement of a first clutch member  40 , comprising a diametrically extending bar, and a second clutch member  42 , comprising an annular wall defining two asymmetric notches. If the first clutch member  40  is brought into contact with the second clutch member  42  and is turned in one direction, drive may be transmitted as described above. If the first clutch member is turned in the other direction, the members automatically disengage from each other.  
         [0037]     Although the invention has been described in relation to the starting of a lawnmower, it is to be appreciated that it is also applicable to other engines. For example, the invention also applies to chainsaws, strimmers, outboard engines, generators, compressors and other such devices.  
         [0038]     The above specification provides a complete description of the invention. Since many embodiments of the invention can be made to work without departing from the spirit and scope of the invention, the invention resides in the appended claims.

Technology Classification (CPC): 5