Abstract:
An open center recoil starter in a small internal combustion engine having a blower housing, a flywheel, and a crankshaft. The open center recoil starter generally includes an annular cover mounted to the blower housing and defining an airway into the blower housing and the engine. The open center recoil starter also includes an annular mechanism for engaging the flywheel, thereby rotating both the flywheel and the crankshaft to start the engine.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates to small internal combustion engines such as those used with lawnmowers, lawn tractors, and other lawn and garden implements. In particular, the present invention relates to a new recoil starter for such engines. 
     2. Description of the Related Art 
     Typically, implements with small internal combustion engines include a manually-operable recoil starter for engine starting. The recoil starter includes a handle and rope pull assembly which is manually pulled by an operator to rotate the flywheel and crankshaft in order to begin reciprocation of the piston as well as actuation of the ignition assembly to start the engine. 
     The pulleys of prior recoil starters are usually restrictive in the center to airflow, allowing only an annular air opening around the outer recoil region. The pulley construction necessitates that air entering the engine must be directed around the pulley, thus the pulley restricts airflow into the engine. To compensate for the restricted airflow, prior methods, such as elevating the pulley assembly to create a small area for air to enter beneath the pulley, were implemented. However, the engines which incorporate these methods may still experience restricted airflow since a maximum amount of air is not drawn into the engine through the small area. 
     What is needed is a recoil starter having a construction which allows a maximum amount of air to easily enter the engine for improved engine cooling. 
     SUMMARY OF THE INVENTION 
     A centerless recoil starter is provided which is used with a small internal combustion engine having a blower housing, a flywheel, and a crankshaft. The centerless recoil starter generally includes an annular cover mounted to the blower housing and defining an airway into the blower housing and the engine and also includes an annular starter mechanism for engaging the flywheel, thereby rotating both the flywheel and the crankshaft to start the engine. 
     The annular starter mechanism for engaging the flywheel includes an annular ring within a track around the airway having engagement elements, such as pulley dogs, therein to engage posts on the flywheel. The pulley dogs have a retracted position during normal engine operation and an extended position for engaging the posts during engine starting. Also included is a spring which retracts the rope and pulley thus causing the pulley dogs to rotate back to their retracted position. 
     An advantage of the inventive recoil starter is that airflow to the engine is unrestricted. With the recoil starter having a substantially open center, air is freely able to enter the blower housing and the engine to provide less restrictive airflow to the engine. 
     The present invention provides an internal combustion engine, including a crankcase having a crankshaft rotatably disposed therein, a flywheel mounted to the crankshaft externally of the crankcase, a blower housing attached to the crankcase and having an opening disposed generally above the flywheel, and an annular recoil starter mechanism attached to the blower housing and disposed around the opening to define a center airway therethrough into the blower housing. The annular recoil starter mechanism selectively engages the flywheel to rotate the flywheel and the crankshaft to start the engine. 
     The present invention further provides an internal combustion engine, including a crankcase having a crankshaft rotatably disposed therein, a flywheel mounted to the crankshaft, a blower housing attached to the crankcase, and an annular recoil starter mechanism attached to the blower housing and disposed around an opening in the blower housing generally above the flywheel. 
     The present invention also provides an implement having a small internal combustion engine including a frame, an engine connected to the frame and having a crankshaft disposed therein, a flywheel mounted to the crankshaft, and an annular recoil starter mechanism attached to the housing and disposed around an opening in the housing generally above the flywheel. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a perspective view of a lawnmower having a centerless recoil starter in accordance with the present invention, the recoil starter being shown partially cut away; 
     FIG. 2 is an exploded view of the recoil starter of FIG. 1, viewed from above; 
     FIG. 2A is an enlarged view of the first annular ring of the recoil starter of FIG. 2; 
     FIG. 3 is an exploded view of the recoil starter of FIG. 1, viewed from below; 
     FIG. 4 is a sectional view through a diameter of the recoil starter of FIG. 1, the recoil starter shown attached to the blower housing of a lawnmower; and 
     FIG. 5 is an enlarged sectional view through a diameter of the recoil starter of FIG.  4 . 
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one preferred embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
     DETAILED DESCRIPTION 
     Referring first to FIG. 1, a centerless recoil starter is shown as part of implement  10 , or more specifically, lawnmower  12 . Lawnmower  12  includes engine  14  having crankcase  16 , deck  18 , and handle  24  attached to deck  18 . Centerless recoil starter  26  is attached to blower housing  28  in such a manner that starter cover  30  is fixed to blower housing  28  by the connection of flange  32  to blower housing  28 , thereby preventing rotation of starter cover  30 . As part of starter  26 , starter cover  30  surrounds the elements of starter  26  and includes open center area  34  through which air is able to easily enter engine  14 . Flywheel  36  is affixed to crankshaft  38  in a known manner, by nut  40 . Crankshaft  38  is rotatably disposed in crankcase  16 , and is attached to a piston (not shown) by a connecting rod (not shown) in a known manner. Blower housing  28  includes opening  29  therein, disposed above flywheel  36 , through which air may enter blower housing  28 . 
     With reference to FIGS. 2 and 3, starter cover  30  includes slot  42  within inner circumferential surface  44 , and aperture  46  within protrusion  48  of outer circumferential surface  50 . Additionally, inner circumferential surface  44  defines open center area  34 . First annular ring  74  includes upper surface  54  and rim surface  62  having slot  64  therein, also shown in FIG.  2 A. Coil spring  66 , disposed between starter cover  30  and first annular ring  74  and resting on upper surface  54 , has first end  68  received in slot  64  and second end  70  being in slot  42  of starter cover  30 , thereby connecting starter cover  30  and first annular ring  74 . 
     Referring again to FIGS. 2 and 3, annular pulley ring  74  further includes groove  80  in outer circumferential surface  82  thereof for containing pulley rope  84 . Pulley rope  84  is wound around annular ring  74 , in groove  80 , multiple times and emerges through aperture  46  where pulley rope  84  terminates in handle  86  abutting flat surface  88  of protrusion  48 . The opposite end of pulley rope  84  is inserted through hole  90  in annular ring  74 . Pulley rope  84  terminates in knot  92  which is maintained in slot  60  to connect pulley rope  84  to first annular ring  74 . Annular ring  74  further includes lower surface  94 , which abuts upper surface  96  of second annular ring  98 . 
     Second annular ring  98  retains engagement elements, such as pulley dogs  100 , in a corresponding number of recesses  102  which form bearing surfaces for pulley dogs  100  and which have pivot pins  104  integrally formed therein. Pulley dogs  100  may pivot in a limited manner around pivot pins  104  (FIG.  5 ). Within inner circumference  106  of annular ring  98  are engagement members formed as flywheel posts  108 , which are cast with flywheel  36 . Although flywheel  36  is positioned beneath blower housing  28 , flywheel posts  108  extend upwardly above blower housing  28  to engage pulley dogs  100 . 
     Referring now to FIGS. 4 and 5, a sectional view of starter  26 , attached to blower housing  28 , is shown. FIG. 5 shows an enlarged sectional view of recoil starter  26 , circled in FIG.  4 . Protruding feet  110  are formed in lower surface  112  of second annular ring  98  and are slidably disposed in shallow groove  114  of bottom track  116 , thereby allowing annular ring  98  to rotate. Bottom track  116  is disposed within blower housing  28  and above flywheel  36 . Bottom track  116  may be formed with blower housing  28  or constitute a separate part which is then attached to blower housing  28 . Pulley dogs  100  pivot around pins  104 , to engage flywheel posts  108 . Pulley dogs  100  also include projections  118  that are received in arcuate grooves  120  on lower surface  94  of annular ring  74 . Arcuate grooves  120  are not concentric with the axis of crankshaft  38  and force pulley dogs  100  to swing inward during recoil starter  26  operation. 
     In operation, an operator grasps pulley rope handle  86  and pulls pulley rope  84 . This action causes annular rings  74  and  98  to rapidly rotate and to cause pulley dogs  100  to swing inwardly, due to the cam action of arcuate grooves  120  and causing projections  118  to move inward, to a maximum projection distance where pulley dogs  100  engage flywheel posts  108  to rotate flywheel  36  for engine starting. Concurrently, coil spring  66  contracts due to its attachment to stationary starter cover  30  and rotating annular ring  74 ; when annular ring  74  rotates, first end  68  of coil spring  66  also rotates while second end  70  remains stationary, thereby contracting coil spring  66 . 
     After rope  84  is pulled to its furthest extent and the engine is started, release of tension on rope  84  by the operator allows coil spring  66  to unwind, thereby causing annular rings  74  and  98  to rotate in an opposite direction and to return to pre-starting positions. After the engine starts, flywheel  36  rotates much faster than annular rings  74  and  98 . This difference in rotational speeds causes flywheel posts  108  to contact the back of pulley dogs  100 , thereby causing pulley dogs  100  to swing back outward to a pre-starting position in which pulley dogs  100  are disposed radially outward of flywheel post  108 . Furthermore, arcuate grooves  120  force pulley dogs  100  into a retracted position when ring  74  rotates in an opposite direction due to the camming action of grooves  120  causing projections  118  to move outwardly. Engine operation then continues in a known manner. 
     While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.