United States Patent Irgens [4 June 13, 1972 [54] CHAIN SAW WITH GEAR DRIVE 3,519,037 7/1970 Linkfield ..l43/32 [72] Inventor: Finn T. Irgens, Milwaukee, Wis. mary Examine a1 d R. Schran [73] Assignee: Outboard Marine Corporation, Wau- Attorney-Robert E. Clemency, John W. Michael, Gerritt D. 1 Wi Foster, Bayard H. Michael, Paul R. Puemer, Joseph A. Gemignanio, Andrew 0. Riteris, Spencer B. Michael and [22] Filed: April 3, 1970 Robert K. ceding [21] Appl. No.. 25,526 [5 A S ACT 52 us. Cl. ..143/3211, 74/438 Discbsed herein is ligmweiflh B drive M a 51 lm. Cl ..B27b 17/08 chain saw which includes cmbinatin mini! chain 58 Field of Search ..143/32, 32 A, 32 B; 74/332, P and interim The spmcke i 3 74/438 243, 243 SC ring with a plurality of internal teeth which mesh with the teeth of a pinion gear located within the sprocket and driven [56] References Cited by the engine. The sprocket has through recesses in its periphery to receive the drive tangs of the cutting chain. In NI E S ATES P TENT one embodiment, the chain sprocket is supported in eccentric relation to the output shaft of the engine by a hub located in- I,825, l I t i ly f th i l t th on th p k t 2,409,775 10/1946 Mall et al..... ...l43/32 A l,773,288 8/1930 Valletta ..74/438 X 4 Claims, 5 Drawing Figures CHAIN SAW WITH GEAR DRIVE BACKGROUND OF INVENTION The invention relates to gear drives and more particularly to a gear drive for a chain saw. Chain saws adapted for heavy cutting requirements require a gear drive to reduce the speed of the cutting chain while maintaining a high engine speed and maximum horsepower. Gear drives add weight and bulk to the chain saw, and thus make gear drives unsuitable for the lightweight chain saws.

SUMMARY OF INVENTION The invention provides a compact gear drive for a chain saw which provides adequate power for heavy cutting requirements and which does not appreciably increase the weight of the chain saw. The gear drive includes a combination gear and cutting chain sprocket in the form of a ring which has, along the outer periphery thereof, a plurality of circumferentially arranged recesses which receive and drive the drive tangs of the cutting chain. In addition, the internal surface of the sprocket ring is provided with internal teeth which mesh with the teeth of a pinion gear which is fixedly connected to the drum of a centrifugal clutch and is rotatably supported on the output shaft of the engine. To minimize the size and diameter of the sprocket, the recesses are inwardly open and the pinion gear on the output shaft comprises two sets of axially spaced teeth separated by an annular groove. The drive tangs project through the sprocket ring and are received in the annular groove.

In one embodiment of the invention, the chain sprocket ring is supported in eccentric relation to the axis of the output shaft by a bearing in the fomr of a hub which is located interiorly of the chain saw sprocket and connected to the engine crankcase. The internal teeth of the chain sprocket ring ride on the outer bearing surface of the hub.

It is an object of the invention to provide a compact, lightweight gear drive for a chain saw which utilizes a combination chain saw sprocket and internal gear for transmitting power from the engine output shaft to the cutting chain.

It is a further object of the invention to provide a gear drive for a chain saw which provides the necessary power for heavy cutting requirements and which drive is lightweight, has a minimum of components and requires very little additional space.

Further objects and advantages of the present invention will become apparent from the following disclosure and accompanying drawings in which:

DRAI/VINGS FIG. 1 is a perspective view of a chain saw embodying the gear drive of the invention.

FIG. 2 is a fragmentary sectional view with portions removed of a gear drive in accordance with the invention.

FIG. 3 is an axially enlarged perspective view of the chain saw sprocket ring shown in FIG. 2.

FIG. 4 is a perspective view of the output shaft gear shown in FIG. 2.

FIG. 5 is a plan view with portions removed in partial section of the gear drive shown in FIG. 2.

DETAILED DESCRIPTION In the drawings, FIG. 1 discloses a chain saw which is generally designated 8 and which includes an engine 9 having an output shaft 1 l, and a cutter bar 10 which carries a cutting chain 12. The chain 12 conventionally includes a plurality of drive members or tangs 14 (FIG. 2).

Means are provided for transmitting power from the engine output shaft 11 to the chain 12. In accordance with the invention, such means is in the form of a combination chain saw sprocket and internal gear 18. The chain sprocket 18 is in the form of a ring having, along the outer periphery thereof, a plurality of outwardly open circumferentially arranged recesses 20 which receive and drive the chain. tangs 14. The inside surface 22 of the chain sprocket 18 is provided with a series of internal teeth 24 which mesh with external teeth 26 on a gear 28. The gear 28 is driven by the engine and, in the particularly disclosed construction, is freely rotatably supported on the output shaft 11 by bearings 30 and is fixedly secured to the drum 32 of a centrifugal clutch 34 (FIG. 5).

To minimize the diameter of the sprocket and thus the overall size and weight of the gear drive, the recesses 20 extend through the ring 18 and the teeth 26 of gear 28 are arranged in two spaced rows 26a and 26b (FIG. 4) with the rows separated by an annular groove 36 which receives the bottoms 14a of the tangs 14, as shown in FIG. 5.

In accordance with the invention, means are provided for supporting the sprocket ring 18 in eccentric relation to the axis of the engine output shaft and with the internal teeth in mesh with the gear 28 on the output shaft. In the construction disclosed in FIGS. 2 and 5, the means for mounting the sprocket ring 18 comprises a bearing or hub 38 which has a portion 40 located interiorly of the sprocket 18 and teeth 24. The outer or peripheral surface 41 of hub portion 40 serves as a bearing for the chain sprocket ring 18. The hub portion 40 includes an opening or notch 46 (FIG. 2) through which the teeth 26 or gear 28 project and mesh with the teeth 24.

Means are provided for connecting the hub 38 to the engine 9. As disclosed, the means is in the form of a mounting flange or boss 44 on the engine 9. The hub 38 has a flange 45 (FIG. 5) which is supported on flange 44. The flange 45 is bolted or otherwise secured to the engine 9.

Oil is supplied to the chain 12 for lubrication thereof by means including a passage 47 which extends axially in the hub or bearing 38 and which communicates with another conduit or passage 48 extending radially in the bearing 38 and terminating at the surface 41 in position to supply oil to the recesses or voids 20 which are formed in the combination gear and sprocket l8 and which receive the tangs 14 of the chain 12. As a consequence, oil is supplied to the tangs l4 and from the tangs to the cutter bar 12 and to the chain pivots.

It should be noted that in operation, the chain 12 exerts a pull or force along the bottom edge of the cutter bar 12 in the general direction of arrow A incident to clockwise rotation of the combination gear and sprocket 18. It should also be noted that the pinion or gear 28 is located relative to the combination gear and sprocket 18 so as to locate the line of action or pressure line between the meshed teeth so as to more or less oppose the direction of the arrow A. As a consequence, the loading on the meshed teeth is relatively light and the loading on the bearing is reduced. In addition, the least possible couple is generated around the axis of the output shaft 11.

, Although the disclosed embodiment shows a chain sprocket driven by a gear or pinion supported on the engine output shaft, the drive of the invention can also be employed in other arrangements.

Various of the features of the invention are set forth in the following claims.

What is claimed is:

1. A chain saw comprising an engine, a shaft rotatably supported on said engine and driven by said engine, a chain sprocket in the form of a ring including a plurality of outwardly open circumferentially arranged recesses adapted to receive the drive members of a cutting chain, and internal teeth located on the inside of said ring and including respective inner end surfaces, gear means on said shaft, means for supporting said chain sprocket on said engine in eccentric relation to the axis of said shaft and with said gear means in mesh with said internal teeth, said means for supporting said chain sprocket on said engine comprising a hub mounted on said engine and located interiorly of said sprocket, said hub including a peripheral bearing surface engaged with said inner end surfaces of said internal sprocket teeth and having an opening through which said internal sprocket teeth mesh with said gear means.

2. A chain saw in accordance with claim 1 wherein said gear means includes two spaced rows of teeth separated by an annular groove, said groove being adapted to receive the drive members of the cutting chain.

3. A chain saw in accordance with claim 1 wherein said hub includes an axial passage and a radial passage connected to said axial passage, said radial passage communicating with said recesses in said sprocket to afiord lubrication of the cutting chain 4. A chain saw comprising an engine, a shaft rotatably supported on said engine and driven by said engine, a chain sprocket in the form of a ring including a plurality of circumferentially arranged recesses extending radially through said ring and being both radially inwardly and outwardly open, internal teeth located on the inside of said ring, gear means on said shaft, means for supporting said chain sprocket on said engine in eccentric relation to the axis of said shaft and with said gear means in mesh with said internal teeth, and a saw chain trained around said sprocket and including drive tangs extending through said recesses and projecting from said recesses radially inwardly of said ring.