Machine with liquid crystal display
BACKGROUND OF THE INVENTION 
     The present invention relates to a power-driven portable machine such as chain saw and, more particularly, to a power-driven portable machine which requires an observation of state of operation of the machine. 
     Hitherto, the evaluation or judgement of the condition or state of operation of power-driven portable machine such as chain saw has been made relying upon the knowledge and experience of the operator. However, in order to fully enjoy the performance of the machine while making most of the operator&#39;s ability and ensuring the safety of the work, it is desirable that the condition or state of operation such as revolution speed of the motor or internal combustion engine, amount of remaining fuel, lubricating condition or the like is observed continuously. 
     To cope with this demand, Japanese patent application No. 157,384/1977 proposes a power-driven portable machine having displaying means for permitting continuous observation of operating condition. 
     SUMMARY OF THE INVENTION 
     The present invention aims at providing an improved power-driven portable machine having displaying means for continuous observation of operating condition of the machine. 
     To this end, the invention provides a power-driven portable machine having a driving assembly including a prime mover and a supporting assembly including handles connected with the driving assembly through vibration damping members, the power-driven portable machine comprising a liquid crystal display device incorporated in a detachable cover member which constitutes a part of the supporting assembly. 
     According to the invention, therefore, it is possible to easily attach the display device not only in the assembling line, i.e. to the new machine but also to existing machines as an optional part. In the case of a trouble or failure in the display device, it can be renewed simply by replacing the cover member of the machine. It is thus possible to execute the work continuously and safely under a good operating condition. 
     Other objects, features and advantages of the invention will become clear from the following description of the preferred embodiment taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of a chain saw as an embodiment of the invention; 
     FIG. 2 is an enlarged bottom plan view of a cover; and 
     FIG. 3 is an enlarged view of a display device. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The invention will be more fully understood from the following description of the preferred embodiment applied to a chain saw, with reference to the accompanying drawings. 
     Referring to the drawings, a chain saw as a power-driven portable machine of the invention has a driving assembly 5 including an internal combustion engine (not shown) and a guide bar 4 along which a saw chain runs. The chain saw further has a supporting assembly 3 which includes a front handle 1, a rear handle 2, a fuel tank 8 and a lubricating oil tank 7 containing a lubricating oil for lubricating the saw chain. The handles 1, 2 and tanks 7, 8 are connected with the driving assembly 5 through the medium of vibration damping members 6, 6, 6, 6 such as of rubber. According to the invention, a liquid crystal type display device 12 is incorporated in, for example, a cover 9 of a carburetor chamber constituting a part of the supporting assembly 3. More specifically, this cover 9 is secured to the upper side of the carburetor chamber by means of fixing screw 10 through an air filter (not shown) and, hence, fixed to the supporting assembly 3. A reference numeral 11 designates an air suction opening to the carburetor chamber. A liquid crystal board 17 and a power source switch S are mounted on the cover 9 to appear to the outside therefrom, while the body of the display device 12 is attached to the lower side of the cover 9 facing the carburetor chamber. The body of the display device 12 includes an electronic circuit 14, battery package 15 as an independent power supply, power switch unit 13 and an antenna or pickup 16 of a contactless tachometer. In FIG. 2, a reference numeral 25 designates terminals for connecting sensors (not shown) which are disposed in the pipes for supplying fuel and lubricating oil. The liquid crystal board 17 exposed to the outside of the cover 9 has a function for displaying states of operation of the machine such as display 19 of the engine speed, display 18 of working hours, warning 20 for remaining fuel and lubricating oil, warning 21 for power of battery as the independent power source. A reference numeral 22 designates a reset button for the working hour display 18. The display device 12 may be installed on other parts than the described cover 9 of the carburetor chamber, e.g. the cover 24 of a recoil starter. 
     Before turning to the daily work, the operator turns the power switch S on so that the engine speed display 19 of the display device 12 starts the continuous display of the engine speed. As the engine speed is increased beyond a speed, e.g. 4,000 r.p.m. at which the centrifugal clutch connects the engine to the saw chain sprocket, the working hour display 18 is turned on to accumulate the actual working hour of the chain saw. During operation, the warning 20 of remaining fuel and lubricating oil informs any shortage of fuel or lubricating oil. It is also possible to know the exhaustion of the battery as the independent power source through the warning 21 of the battery power. 
     If the timing of fuel supply is estimated from the working hour through the working hour display 18, the operator can refuel the machine when a predetermined working hour is reached. In such a case, the operator may reset the working hour display 18 to zero by pressing the reset button 22, so that he can known the timing of next refueling from the working hour display 18. After finishing the daily work, the operator turns the power switch off to save the power of battery. 
     Although the invention has been described through specific terms, it is to be noted here that the described embodiment is not exclusive and various changes and modifications may be imparted thereto without departing from the scope of the invention which is limited solely by the appended claims.