US 3747649 A
Disclosed herein is a chain saw including a breakerless ignition system electrically coupled to a spark plug and including at least one component mounted on the crank cheek of a crankshaft and other components mounted on a crankcase in close proximity to the path of the crank cheek, together with a fan mounted on one crankshaft end portion, a chain sprocket and clutch assembly driven by the other of the crankshaft end portions, and a starter mounted on the chain saw frame and including a clutch having a component mounted on the fan and another component mounted for travel to engage the clutch for starting of the engine.
Claims available in
Description (OCR text may contain errors)
United States Patent [1 1 Densow et al.
[ CRANKSHAFT MAGNETO SYSTEM  Inventors: Ulrich 0. Densow; Lloyd A.
Simmons, both of Peterborough, Ontario, Canada  Assignee: Outboard Marine Corporation,
 Filed: Feb. 8, 1971 ] Appl. No.: 113,322
 U.S. Cl ..30/381, 123/149 D, 123/148 E, 12/179 SE, 123/185 BA  Int. Cl. B271) 17/00, F02p 3/06  Field of Search 123/148, 149, 185, a 123/179; 7418;143/32 R  References Cited UNITED STATES PATENTS 3,581,717 6/1971 Fullerton 143/32 R 2,998,471 8/1961 Jaulmes 123/149 R 3,306,277 2/1967 Gudmundsen. 123/185 BA 3,449,964 6/1969 1 Meyer 123/179 SE 3,447,521 6/1969 Piteo....... 123/149 D 1,838,700 12/1931 Meyer 143/32 R 3,252,452 5/1966 Burkett et'al 123/185 A 11 Jul 24, 1973 2,895,466 7/1959 Mall et al. 123/185 BA 3,134,376 5/1964 Rice 123/185 BA 3,366,099 l/l968 Kaufman 123/185 BA 1,633,863 6/1927 Kelly ct al 74/8 Primary Examiner-Laurence M. Goodridge Assistant Examiner-Cort Flint Attorney-Robert E. Clemency, John W. Michael, Bayard l-l. Michael, Paul R. Puerner, Joseph A. Gemignani, Andrew 0. Riteris, Robert K, Gerling, Spencer B. Michael and Gerrit D. Foster 1  ABSTRACT Disclosed herein is a chain saw including a breakerless ignition system electrically coupled to a spark plug and including at least one component mounted on the crank cheek of a crankshaft and other components mounted on a crankcase in close proximity to the path of the crank cheek, together with a fan mounted on one crankshaft end portion, a chain sprocket and clutch assembly driven by the other of the crankshaft end portions, and a starter mounted on the chain saw frame and including a clutch having a component mounted on the fan and another component mounted for travel to engage the clutch for starting of the engine.
8 Claims, 6 Drawing Figures 1 CRANKSHAFT MAGNETO SYSTEM BACKGROUND OF THE INVENTION The invention relates generally to chain saws and more particularly to chain saws with breakerless ignition systems. Still more particularly, in the past, chain saws have generally included ignition systems which included one or more components carried by a relatively heavy flywheel, as well as other components which, in general, were supported on the engine cylinder. As a consequence, such mounting of ignition components on the engine cylinder diminished the area available for effecting engine air cooling and increased the complexity of the construction of the flywheel which also served as a fan.
SUMMARY OF THE INVENTION The invention provides a chain saw including a breakerless ignition system which is removed from association with a flywheel and which, in part, is provided on a crank cheek of the engine crankshaft and, in part, supported on the crankcase of the engine. In a particular embodiment of the invention, the crank cheek is generally constructed of non-permeable material, i.e., nonmagnetic-flux-conducting material, I for instance aluminum, and includes a core or yoke or a member of permeable material, i.e., magnetic flux conducting material, for instance soft iron, having two pole pieces which are spaced angularly with respect to the crankshaft axis. The permeable yoke or member rotates past a stationary magnet structure supported by the crankcase and including spaced legs cooperable with the pole pieces to periodically completeand interrupt magnetic circuits as the crank cheek rotates relative to the stationary legs. i The invention also provides a chain saw including a relatively lightweight fan structure arranged to supply a stream of cooling air over a finned cylinder which is not encumbered by components of an ignition circuit. In one embodiment of the invention, the fan is arranged in a housing having an intake located to draw incoming air past a fuel tank incorporated in the chain saw so as to cool the fuel tank and thereby to minimize possibility of vapor lock.
Also in accordance with the invention, the fan is arranged to be driven, for engine starting purposes, either by a concentrically located pull rope stator or by forming, at the radially outer end of the fan blades, a gear which cooperates with a tangentially arranged pull rope starter.
One principal object of the invention is the provision of a chain saw which embodies a breakerless ignition system with cooperating components mounted, in part, on the crankcase and extending into the crankcase for cooperation with another component mounted on a crankshaft crank cheek.
Another of the principal objects of the invention is the provision of a saw chain having a lightweight fan which is arranged to deliver a flow of cooling air over an engine cylinder which is unencumbered by mounting of ignition components on the engine cylinder.
Another of the principal objects 'of the invention is the provision of a saw chain having a fan which is arranged to draw incoming air over a fueltank carried by the chain saw.
Another of the principal objects of the invention is the provision of a chain saw including an engine having a crankshaft with oppositely extending end portions, one of which drives a clutch and sprocket assembly and the other of which carries a lightweight fan.
Another of the principal objects of the invention is to provide a smaller and lighter weight chain saw engine, as well as to provide for improved engine cooling.
Another of the principal objects of the invention is the provision of a saw chain having a fan which is constructed, at least in part, of plastic or other relatively lightweight nonrmetallic material.
Other objects and advantages of the invention will become known by reference to the following description and accompanying drawings.
DRAWINGS FIG. 1 is a fragmentary sectional view of a chain saw embodying various of the features of the invention.
FIG. 2 is a fragmentary enlarged schematic view taken generally along line 2-2 of FIG. 1.
FIG. 3 is an end elevational view of the structure shown in FIG. 2.
FIG. 4 is a wiring diagram of the ignition circuit employed in the chain saw shown in FIGS. 1 through 3.
FIG. 5 is a fragmentary sectional view of another embodiment of a chain saw embodying various of the features of the invention. I
FIG. 6 is a view similar to FIG. 5 illustrating another modified chain saw embodying various of the features of the invention.
GENERAL DESCRIPTION Shown in FIG. 1 of the drawingsis a chain saw .11 which embodies various of the features of the invention and which includes a frame 13 which, in part, can constitute a part of the engine block and which has a cutter bar mounting portion 15, a portion comprising a shroud 17, and one or more portions (not shown) for supporting handlesfor hand support of the chainsaw.
Carried either rigidly or through resilient mounts, or constituting a part of the frame 13, is an engine 19 comprising an engine block defining a crankcase 21, together with a single cylinder 23 extending from the crankcase 21 and including a spark plug 25, and a piston 27 operable in the cylinder 23..Iournaled in bearings 29 and 31 in the crankcase 21 is a crankshaft 33 including a crank pin 35 connected through a connecting rod 37 to the piston 27. In addition, the crankshaft 33 includes at least one crank cheek 39 located within the crankcase 21 and including a portion 40 projecting in oppositely extending radial relation from the crank pin 35 with respect to the crankshaft axis 36. The crankshaft 33 also includes at least one end portion 41 shown in dotted outline and extending axially from the crankcase bearing 29. Located exteriorly of the bearing 29 and around the crankshaft 33 is a suitable seal 43. In the specifically disclosed construction shown in FIG. 1, the crankshaft 33 also includes a second crank cheek 45 which, together with the crank check 39, supports the crank pin 35. The crank cheek 45 also includes a projecting portion 47 extending oppositely from the crank pin 35 relative to the crankshaft axis 36. As the cludes a second end portion49 and a second seal 51 exteriorly of the bearing 31.
Any conventional means can be employed for supplying carbureted air to the cylinder 23 through a transfer passage 53 or otherwise in response to piston reciprocation.
The cylinder 23 is also apertures to provide an exhaust port (not shown) which communicates with a muffler 55 mounted by suitable means on the exterior of the cylinder 23 and preferably on a part of the cylinder 23 remote from the shroud frame portion 17.
Except for the muffler mounting arrangement and the spark plug mounting arrangement, the cylinder 23 is substantially otherwise wholly provided with cooling fins 57, there being no other component carried or mounted on the exterior of the cylinder 23 whereby to reduce the area available for providing the cooling fins 57. As a consequence and because of the use of a breakerless ignition system 59, still to be described, the cylinder 23 has superior capability for being air cooled.
The crankshaft end portion 41 is connected to a chain sprocket and clutch assembly 61 which can be of any conventional construction. More particularly, as shown in FIG. 1, the chain sprocket and clutch assembly 61 includes a chain sprocket 63 driven by a centrifugal-clutch 65 which is keyed to the crankshaft end portion 41. While the disclosed construction shows the chain sprocket 63 located outwardly of the clutch 65, the clutch 65 can be located, at least in part, outwardly of the chain sprocket 63 with the sprocket being carried on a clutch hub as generally shown, for instance, in' the US. Irgens Pat. No. 3,144,890 issued Aug. 18, 1964. Proper inertia for idling can be provided,.in addition to providing the crank cheeks with mass, by designing the clutch 65 with a symmetrical clutch driver and clutch shoes..If required, additional inertia can be afforded in the fan.
Alsoas shown in FIG. 1, a cutter bar 67 is mounted on the frame portion in alignment with the chain sprocket 63. Preferably, the frame 13 also includes a removable portion 69 encircling the sprocket and clutch assembly 61 except for an opening for a saw chain (not shown) trained around the chain sprocket 63 and carried by the cutter bar 67.
Mounted on the other or second crankshaft end portion 49 is a lightweight fan 71 which can be constructed of plastic or other lightweight material and which does not carry any ignition components and therefor does not have to be counterweighted.
More specifically, the fan 71 includes a hub 73 with a radially extending relatively thin disc part or member 75 having a plurality of radially and axially extending vanes 77 adapted to direct air through the space between the frame shroud portion 17 and the engine cooling fins 57 to effect engine cooling.
Air is supplied to the fan 71 through a series of openings defined by a series of spaced ribs 81 which support -an axially outwardly located frame portion 83 carrying a pull rope starter 85 which is generally of conventional construction.
The starter 85 includes a cylindrically shaped member 87 movable axially toward the fan 71 and including a serrated end 89 adapted for driving engagement with a clutch component in the form ofa serrated surface 91 on the fan hub 73, whereby to effect engine rotation in response to actuation of the pull rope. If desired, a suitable screen (not shown) can be carried by the frame 13 to prevent entry through the spacesbetween the ribs 81 I and into the fan 71 of solid particles which could be- More particularly, as shown in FIGS. 2, 3, and 4, the
breakerless ignition system 59 comprises a magnetic circuit which is periodically established and interrupted to generate sufficient voltage in cooperation with a breakerless ignition circuit 101 (See FIG. 4) to provide a spark at' the spark plug 25 at the proper times. Still more particularly, the magnetic circuit 101 includes (See FIG. 2) amagnet 103 which is supported at opposite ends ofa pair of legs or arms 105 of flux conducting material, such as soft iron, which legs 105 are carried by a member or housing 107 of non-flux conducting material, such as aluminum or plastic, which member 107 is adapted to be mounted on the crankcase 21 by suitable means such as the screws extending through apertures 109 (See FIG. 3).
In this last regard, the crankcase 21 is apertured and the legs 105 extend through the aperture or apertures into a position closely adjacent to the path of a yoke 111 of flux conducting material, such as soft iron, which yoke 111 is carried on one of the crank cheeks 39 and 45 of the crankshaft 33. The yoke 111 can include two angularly spaced feet or pole pieces 113 and 1 15 which terminate adjacent the periphery of the supporting crank cheek and which travel in a path in close proximity to the adjacent end of the legs 105. As a consequence, upon every rotation of the crankshaft 33, a flux path from the ends of the magnet 103, through the legs 105 and through the yoke 111, is first established and then discontinued as the yoke lll'travels past the ends of the legs 105.
While various ignition circuits can be employed, as
shown in FIG. 4, the ignition circuit 101 includes a voltv age generating coil which includes a center tap 112, which is wound around one of the legs 105, and which is connected, at one end, to the anode 114 of a diode 116. In turn, the cathode 118 of the diode 116 is connected to the anode 120 of an SCR 122 and to one plate 124 of a charge capacitor 126. The cathode 128 of the SCR 122 is connected to the center tap 112 and to one end of the primary winding 130 of an ignition coil 132. The other end of the primary winding 130 is connected to the other plate 134 of the charge capacitor 126. The gate 136 of the SCR 122 is connected to the other end of the voltage generating coil 110. In addition, the ignition coil 132 includes a secondary winding 138 connected to the spark plug 25.
FIGS. 5 and 6 are respectively illustrative of two other chain saws 511 and 61 1 embodying various of the features of the invention. As in the chain saw shown'in FIG. 1, the chain saw 511 includes a frame 513 which supports an engine 519 including an ignition system 559, which engine 519 and ignition system 559 are constructed in essentially the same manner as the engine 19 and ignition system 59 of the chain saw 11. Also as in the chain saw 11, a combination sprocket and clutch assembly 561 is mounted on one end portion 541 of the engine crankshaft 533 and a fan 571 is mounted on the other end'portion 549 of the engine crankshaft 533.
Thefan 571 comprises a hub 573 and a disc part 575 which extends from the hub 573 and is provided on the side thereof adjacent to the crankcase 521 with a plurality of radially and axially extending vanes 577. Air is supplied to the vanes 577 for delivery past the finned outer surface of the cylinder 523 through an inlet 550 to a fan housing 552 which can be regarded as a part ofthe frame 513, which inlet 550 is located in the housing 552 on the side thereof adjacent to the crankcase 521. In this last regard, the frame 513 also supports a fuel tank 560 which can be constructed of plastic or other suitable material and which, at least partially, is located in the path of the stream of air flowing to the inlet 550 of the fan housing 552. More particularly, the fuel tank 560 is housed in a cavity in the frame 513 and the frame includes openings 561 for incoming cooling air, which openings 561 are located to cause at least a part of the incoming air stream to flow past the fuel tank 560. Such operation is vary desirable as it effectively reduces vapor lock problems which can occur in the carburetor system of a chain saw.
The fan 571 also has an outlet area which is located to cause delivery of air from the fan 571 past the cooling fins 557 on the cylinder 523.
Mounted axially of the fan 571 is a conventional pull rope starter 585 which also serves to complete the fan housing 552 and which includes a clutch arrangement for connection with the fan 571 to start the engine 519 in response to actuation of the pull rope.
The chain saw 611 shown in FIG. 6 is constructed in generally the same fashionas the chain saw 511 shown in FIG. 5, except that the construction of the fan and starter are somewhat modified. More particularly, a fan 671 is mounted in a housing 652 having an inlet 650 arwork on the cylinder and piston. Relocation of ignition ranged to draw incoming cooling air at least partially over a fuel tank 660. The fan 671 includes a hub 673 having extending therefrom a series of separate blades or vanes 677 which receive cooling air from the inlet 650 and direct the cooling air past the finned engine cylinder 623. The fan housing 652 includes a removable cover part 654 which extends across or behind the fan 671 on the outer side thereof to complete the fan housing 652 and to assure flow into the fan housing 652 through the inlet 650 and flow outwardly of the fan housing 652 into the area between the frame shroud portion 617 and the cylinder cylnder 623 to effect cooling of the engine 619.
The radially outward and axially outward end of the fan blades 677 are strengthened by connection thereof to a ring gear 670 which cooperates with a pull cord starter 685 which can generally be constructed in accordance with the US. Meyer Pat. No. 3,449,964 is sued June 17, I969. In this regard, the starter 685 includes a pinion 672 engageable with the ring gear 670 and engaged with a gear 674 which is mounted for rotation on the frame 613. The removable cover part 654 is also employed to generally enclose the starter 685.
Chain saws built in accordance with the disclosed invention can be reduced in width and the saw can be symmetrical with respect to a center split line. Ease of magneto servicing as compared to prior devices is provided by removal of ignition components from relatively inaccessiblepositions adjacent to the flywheel. In addition, magneto gap setting is eliminated as the gap between the legs 105 and the pole piece 113 and 115 is fixed by machining of the crankshaft 33 and of the mating faces of the crankcase and ignition components having. Removal of the ignition components from the cylinder, so that only a muffler and spark plug are components from the cylinder also eliminates obstructions to air flow previously caused by cylinder-mounted ignition components and allows forming a greater part of the outer cylinder surface with fins, which fins can have a greater depth and greater heat dissipating capacity without increasing over-all engine size. Removal of the ignition components from the cylinder also facilitates cleaning of the fins. Removal of the ignition and counterweight components from the fan permits fan constructionof lighter material. Such removal also permits fan operation at speeds differing from engine speed and operation with greater speed and efficiency.
The provision of a fan as shown in FIG. 5 with blades which extend axially inwardly toward the engine and consequent drawing of cooling air from the crankcase side of the fan permits the starter to be set flush against the flywheel and also permits incapsulating the starter to protect against dirt. Use of a screened inlet for air which is drawn over the fuel tank permits elimination of rotating screens which have been previously employed.
Various of the features of the invention are set forth in the following claims.
What is claimed is:
1. A chain saw comprising a frame, a single cylinder engine mounted on said frame and having a crankcase, a cylinder extending from said crankcase and having mounted thereon a spark plug, and a crankshaft rotat ably mounted by said crankcase and includinga crank cheek interiorly of said crankcase and opposite end portions extending exteriorly of said crankcase, a chain sprocket and clutch assembly mounted on said frame and driven by one of said end portions, a cutterbar extending from said frame, a cutter chain trained around said sprocket and said cutter bar, a relatively lightweight fan mounted on the other of said end portions, a starter mounted on said frame and including a clutch having a first component mounted on said fan and an other component mounted on said frame for travel to engage said first component for starting of saidengine, and a breakerless ignition system electrically coupled to said spark plug and including a rotary component mounted on said crank cheek and fixed components mounted wholly on said crankcase in close proximity to the path of said crank cheek, whereby to permit cooling of said cylinder unrestricted by mounting thereon of ignition components and to permit mounting of said fan independently of a relatively heavy flywheel.
2. A chain saw in accordance with claim 1 wherein said fan includes a hub mounted on said other crankshaft end portion and a series of blades extending from said hub.
3. A chain saw in accordance with claim 1 wherein said fan comprises a hub mounted on said other crankshaft end portion andincluding a disc portion and a series of blades on said disc portion extending radially and axially toward said crankcase from said disc portion.
4. A chain saw in accordance with claim 1 wherein said fan supports a ring gear in a plane transverse to the axis of said fan and said starter is mounted on said frame and includes means movable into engagement with said ring gear to effect starting of the engine.
5. A chain saw in accordance with claim 1 wherein said fan is of relatively light weight non-metallic material.
6. A chain saw in accordance with claim 1 including a fuel tank carried on said frame and means including said fan for drawing air past said fuel tank and delivering air past said cylinder.
7. A chain saw in accordance with claim 1 wherein said starter is rotatably mounted co-axially with said fan and said other component is movable axially of the axis of fan rotation and relative to a position of engagement with said first component mounted on said fan.
8. A chain saw in accordance with claim 1 wherein legs and connected to said spark plug.