US3354737A

US3354737A - Chain saw drive sprocket

Info

Publication number: US3354737A
Application number: US459167A
Authority: US
Inventors: Jesse F Wright
Original assignee: Individual
Current assignee: Individual
Priority date: 1965-05-27
Filing date: 1965-05-27
Publication date: 1967-11-28
Anticipated expiration: 1984-11-28

Description

Nov. 28, 1967 J. F. WRIGHT' 3,354,737

CHAIN SAW DRIVE SPROCKET Filed May 27, 1965 Jesse F. Wr/yfif INVENTOR.

zww/d I Arivc" K S United States Patent 3,354,737 CHAIN SAW DRIVE SPROCKET Jesse F. Wright, P.O. Box 284K, Rte. 5, Lufkin, Tex. 75901 Filed May 27, 1965, Ser. No. 459,167 3 Claims. (Cl. 74-243) ABSTRACT OF THE DISCLOSURE A drive sprocket for a chain saw having driving pins engaging the chain at the cutting links and their associated connecting links.

This abstract is neither intended to define the invention of the application which, of course, is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way.

This invention relates generally to power chain saws and more particularly to a sprocket driving means adapted for use with a standard saw chain in a power chain saw.

The usual power chain saw includes an endless link chain having cutter elements projecting outwardly and also having driving or pulling lugs or projections directed inwardly. The driving or pulling lugs are shaped not only to coact with a driving element, such as a toothed sprocket, but also to guide the chain in its longitudinal movement by their engagement within the groove of a guide bar. Because the saw is portable, it is desirable to hold size and weight to a minimum and for this reason the driving element for the endless chain is of as small a diameter as possible. This means that the circumferential path traversed by the chain as it passes around the driving element is along a relatively small radius with the result that the inwardly directed driving or pulling lugs on the chain move into relative proximity to each other during this portion of travel. Because of the relatively small spacing between the driving lugs, a toothed sprocket is employed as the driving element since it may have its teeth tapered in such manner that adequate driving connection :between the sprocket and chain may be effected without undue binding as said chain moves through the circumferential path of relatively small radius.

The toothed drive sprocket has been found satisfactory insofar as permitting the use of a small diameter driving element is concerned but such sprocket has the disadvantage of excessive wear and therefore relatively short life. Such excessive wear is caused by the excessive frictional sliding contact between the sides of the sprocket teeth and the driving or pulling lugs of the chain. Actual experience has shown that the usual drive sprocket must be constantly replaced in a relatively short time.

Other types of driving means have been attempted, particularly roller-type driving sprockets, which eliminated friction because of the freedom of movement but these types have the disadvantage of being comparatively large and heavy.

It is therefore an object of this invention to provide an improved sprocket driving means for a power chain saw in which the device is relatively light and has minimum weight and friction and further coacts with a standard saw chain to transmit the movement from a prime mover to the chain.

Another object of the present invention is to provide a new and improved free pin-type sprocket drive for a chain saw being adaptable to drive a standard saw chain with a minimum of friction thereby minimizing wear.

A further object of the present invention is to provide a drive sprocket for a power chain saw having free pin engagement with the links of the saw chain for driving the saw chain and further providing an annular groove defined by shoulders whereby the guiding links of said chain are guided and partially supported in said groove.

Still another object of the present invention is to provide a drive sprocket for a power chain saw having pins engaging the saw chain wherein such pins are readily removable.

A further object of the present invention is to provide a drive sprocket having pins for engagement with the saw chain positioned loosely in the sprocket whereby pin wear is uniform.

These and other objects of the present invention, together with the construction designed to carry out the invention, will be hereinafter described, together with other features thereof.

The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawings forming a part thereof, wherein an example of the invention is shown, and wherein:

FIGURE 1 is a side elevation of a portable powered chain saw;

FIGURE 2 is an enlarged fragmentary view, partly in section, of the drive sprocket and saw chain and associated parts;

FIGURE 3 is a sectional view taken along line 33 in FIGURE 2; and

FIGURE 4 is a cross-sectional view of another form of drive sprocket of the present invention.

In the drawings the letter A generally designates a portable chain saw which includes a prime mover, such as internal combustion engine 10 having suitable handles 11 attached to the outer casing thereof. The engine 10 is suitably connected to the drive sprocket 12, as hereinafter described in detail, and said sprocket is in driving engagement with portions of the saw chain 13. A guide bar 14, which may be constructed of metal or other materials, extends forwardly from the drive sprocket 13 and may have its outer end rounded to a semicircular form as indicated at 14a. The endless saw chain 13 passes over the driving sprocket 12 and extends around the edge of the guide bar 14, and upon rotation of the sprocket, said chain is moved in a path around the guide bar.

The saw chain 13 used with the present invention is provided with cutting elements or links 15, guiding elements or links 16 and connecting elements or links 17. The cutting links 15 are provided with the usual teeth which do the direct cutting and contact work during operation. It should be noted that the saw chain 13 as illustrated is a standard saw chain which is readily available on the market. The inner side of the connecting links 17 and the cutting links 15 is provided with the arcuate recess 18 which normally would receive the outermost portion of a driving sprocket tooth. However, in the present invention a plurality of pins 19 are mounted in the drive sprocket 12 for engagement with the chain at the position defined by the recess in the links. Thus, approximately one-half of the circumference of the driving pins 19 is received in the recess 18. The driving pins 19 additionally contact the trailing edge of the guiding links 16.

The drive sprocket 12, as shown in FIGURE 3, includes the main body 20 having a central bore 21 to receive a drive shaft 22 therethrough. The sprocket body 20 is provided with radially extending

flanges

22 and 23 which initially define the annular groove 24 into which the inwardly projecting portion of the guiding links 16 extends. The flanges at the outer portion of the groove 24 form the slightly

tapered shoulders

25 and 26 and extend radially outwardly therefrom in parallel relationship to each other to define a larger groove 27 beyond the

shoulders

25 and 26. The flange 23 is extended outwardly at its rearward portion, as at 28, and terminates in cylindrical section 29 which is substantially hollow as shown I for the reasons hereinafter more fully explained.

Holes 30 are drilled in an axial direction through flange 22 and into flange 23 terminating short of the rearmost portion of flange 23. The holes 30 are positioned radially outward. from the center of the body 28 and are spaced circumferentially therearound as best illustrated in FIG- URE 2. The holes 30 are substantially perpendicular to the parallel surfaces defining the larger groove 27 for the reasons hereinafter more fully explained. The diameter of each of the holes 30' is preferably slightly larger than the diameter of the pins 19 to allow the pins 19 a certain degree offreedom of movement when positioned in holes 30. Such freedom of movement will prevent the accumulation of wear on the pins 19 at particular points by distributing the wear uniformly around the pins. The holes 30 extend through flange 22 and allow the pins 19 to be inserted therein from the face 31 of the flange 22. Retaining means, such as annular cover plate 32, is secured to the face 31 of the flange 22 by a plurality of screws 33 to retain the pins 19 in the holes 30. Thus, when a saw chain 13 is in operational engagement with the drive sprocket 12, the pins 19 extend from flange 22 to flange 23 to be able to engage within the recesses 18 of the links and against a portion of a trailing edge of the guiding links 16.

With the drive sprocket 12 positioned on the shaft 22, washer 34 will be positioned over the threaded end of the shaft 22 and engage in the recess portion 35 on the face 31-, and nut 36 will engage the threaded endof shaft 22 to secure drive sprocket 12 in position thereon. Within the interior of the cylindrical section 29 is positioned a clutch assembly 37. Since drive sprocket 12 is not keyed or in any way fixedly secured to the shaft 22, the clutch assembly 37 is provided to transmit the rotation of the shaft to the drive sprocket whereby the saw chain will be driven. The clutch assembly 37 includes the clutch segments 38, theclutch spring 39 and the clutch collar 40. The individual clutch segments 38 are positioned in the recesses in the clutch collar 49. The clutch collar 40 is secured to the shaft 22 by the key 42. The springs 39 engage in the grooves 45 in each of the segments 38 whereby said segments 38 are urged to a position against the bottom of the recess in the collar 40.

Rotation of the shaft 22 by the prime mover will rotate the collar 40 by the direct engagement of'key 42 between the shaft 22 and the collar 40. Rotation of the collar 40 causes clutch segments 38 to rotate, and the centrifugal force created will tend to move the clutch segments 38 radially outwardly against the restraining force of the spring 39. When the speed of rotation of the clutch assembly 37 is sufiicient to create centrifugal force moving clutch segments 38 to a position wherein their outer'surface engages the surface 44 on the interior of cylindrical section 29, the drive sprocket 12 will be then rotated. At any time that the speed of rotation of the clutch assembly 37 is decreased to a point where the spring force overcomes the centrifugal force, the clutch will disengage by the radial inward movement of clutch segments 38 and the drive sprocket 12 will no longer be rotated.v

In FIGURE 4 a modified form of drive sprocket, designated 47, is shown. The drive sprocket 47 is keyed to the shaft 48 by the key 49 and is secured thereon by the washer 50 and the nut 51 threadedly engaging the threaded end of the shaft 48. The drive sprocket 47 is provided with two radially extending

flanges

52 and 53 which de fine an inner groove 54 at the upper end of which the flanges form the

shoulders

55 and 56.

Flanges

52 and 53 extend outwardly beyond the

shoulders

55 and 56 to define an enlarged groove 57. Holes 58 which receive the pins 59 extend through the flange 53 from its face 60 and partially through the fiange'52. Retaining means, such as snap ring 61, is secured in covering relationship to the face 60 by engagement with the groove 62 formed on flange 53 to retain the pins 59 in the holes 58.

In operation when the drive sprocket 12 is rotated through the clutch mechanism 37, the pins 19 engage in the recesses, 18 and partially against the trailing edge of the guiding link 16 to move the saw chain 13 around the guide bar 14. The central portion of the pins 19 engages the guiding link 16 while portions on each side of the central portion of the pins 19 engage in the recesses 18. While the pins 19 are relatively small in diameter, they do have a substantial area of driving engagement with the saw chain 13. Because of the looseness of the pins 19 in the holes 30, the pins 19 will be easily rotated to minimize wear and friction.

Because of the vertical faces of the groove 27 and the perpendicular relationship between such faces and the holes 30, the amount of dirt and trash which can Work into the space between the pins 19 and the holes 30 is minimized. The accumulation of any dirt or trash in the space between the pins 19 and the holes 30 will restrict the freedom of movement of the pins 19. It has been found that the perpendicular relationship between the faces of the secondary groove 27 and the axes of the holes 30 provides the very minimum of dirt collection. The restriction of the freedom of movement of the pins 19 in the holes 38 will greatly accelerate wear on the pins and require their early replacement.

The operation of drive sprocket 47 illustrated in FIG- URE 4 is substantially the same as the operation of drive sprocket. 12 except that sprocket 47 is keyed directly to the shaft 48 by the key 49 and does not include a clutch assembly. In drive sprocket 47 the pins 59 are slightly smaller than the holes 58 in which they reside to allow the pins freedom of rotation therein to minimize friction. The axes. of the holes 58- are substantially perpendicular to the faces of the larger groove 57 to limit the accumulation of trash or dirt in the holes 58.

Since the only point of wear in the drive sprockets of the present invention is the pins, both forms of drive sprocket have provision made for quick and easy replacement of the-pins. In FIGURE 3 the pins 19 are retained in the holes 39 by the retainer ring 32 which is secured to the face 31 of sprocket 12 by the screws 33. In FIG- URE 4 the pins-59 are held in the holes- 58 by the snap ring 61 which is readily removed from engagement with the groove 62. Thus, the pins are readilyreplaceable in both forms of the invention. The pins may be removed from the outer side of the sprocket, as shown in FIGURE 3, or from the innerside of the sprocket, as shown in FIGURE- 4-. Itis contemplated that the number of pinreceiving holes provided in each sprocket could be doubled so that a change of holeswould be available in the eventthe' holesbecame worn or otherwise limited the freedornof movement of the pins.-The freedom of movement of the pins inall forms of the present invention Will greatly minimize friction and therefore reduce wear on the pins.

Itv should be noted: that the grooves 24' and 54 will engage the innermost projection of the links 16 and will maintain the positionof the chain even when the saw is operating on its side. Without this engagement it would be possible for the chain to'rnove to one side or the other of. the sprocket to cause extreme Wear, and without the outward extension of the flanges above the wider grooves 27- and 57- occasionally the chainwould become completely disengaged from the sprocket. The

grooves

24 and 54 will prevent the extra wear by guiding the saw chain in its'movement around the driving sprocket.

As shown in the drawings, the guide links are positioned sufficiently close to the. bottom of the grooves so that they receive support from the groove in the event a pin should fail.

The operation of all' forms of the drive sprocket of the present invention, however, provide the engagement between the drive pins which are loosely positioned in the drive sprocket with the recesses in the cutting and connecting links of the chain saw and with the back edge of the guiding links. The drive sprocket provides a relatively light weight and small driving element for a chain saw whichhasreduced friction and wear. The drive sprocket will coact with a standard saw chain to provide the means of transmitting the rotation to the saw chain from the shaft which connects to the prime mover. The drive sprocket of the present invention provides an eflicient driving means which is light weight and in which the driving pins, the elements having the greatest wear, are readily replaceable.

What is claimed is:

1.. In a portable chain saw including a chain having cutting links, guiding links, and connecting links and a prime mover, the improvement residing in a drive sprocket comprising,

a sprocket body,

a pair of flanges extending radially outward from said body in parallel relation to define an annular groove, and

driving pins extending across said annular groove and engaged in said flanges,

said driving pins adapted to engage said chain to drive said chain,

said driving pins being positioned sufiiciently outward in said groove whereby in operation, each of said pins when driving said chain, would engage a cutting link and its associated connecting link at a point adjacent a guiding link with said guide link coacting with said pin to maintain it in engagement with said cutting link and said connecting link,

said flanges define an inner portion of said groove of suflicient width to receive said guide link, an intermediate portion of said groove of increased width sufiicient to receive the whole width of the chain and an outer portion of said groove of increasing width and of sufficient diameter to prevent inadvertent disengagement of said chain from said drive sprocket.

2. The drive sprocket according to claim 1 wherein,

said driving pins are loosely engaged in said flanges whereby said drive pins are free to rotate with said chain links.

3. In a portable chain saw including a chain having 0 cutting links, guiding links, and connecting links and a prime mover, the improvement residing in a drive sprocket comprising,

a sprocket body, a-pair of flanges extending radially outward from said body in parallel relation to define an annular groove, and driving pins extending across said annular groove and engaged in said flanges, said driving pins adapted to engage said chain to drive said chain, said driving pins being positioned sufliciently outward in said groove whereby in operation, each of said pins when driving said chain, would engage a cutting link and its associated connecting link at a point adjacent a guiding link with said guide link coacting with said pin to maintain it in engagement with said cutting link and said connecting link, said flanges define an inner portion of said annular groove of sufiicient width only to receive said guide links, an intermediate portion of said annular groove having parallel radially extending sides of suflrcient width to receive said chain and across which said pins extend and an outer portion of said annular groove having gradually increasing width and sufficient diameter to provide surfaces maintaining said chain in engagement with said sprocket body.

References Cited UNITED STATES PATENTS 1,526,451 2/1925 Wolf 74-243 2,854,294 9/1958 Bannister 74-243 X 2,884,798 5/1959 Wilson 74-243 3,279,272 10/ 1966 Gudmundsen 74-243 FRED C. MATTERN, J R., Primary Examiner.

DAVID J. WILLIAMOWSKY, Examiner.

I. A. WONG, Assistant Examiner.

Claims

1. IN A PORTABLE CHAIN SAW INCLUDING A CHAIN HAVING CUTTING LINKS, GUIDING LINKS, AND CONNECTING LINKS AND A PRIME MOVER, THE IMPROVEMENT RESIDING IN A DRIVE SPROCKET COMPRISING, A SPROCKET BODY, A PAIR OF FLANGES EXTENDING RADIALLY OUTWARD FROM SAID BODY IN PARALLEL RELATION TO DEFINE AN ANNULAR GROOVE, AND DRIVING PINS EXTENDING ACROSS SAID ANNULAR GROOVE AND ENGAGED IN SAID FLANGES, SAID DRIVING PINS ADAPTED TO ENGAGE SAID CHAIN TO DRIVE SAID CHAIN, SAID DRIVING PINS BEING POSITIONED SUFFICIENTLY OUTWARD IN SAID GROOVE WHEREBY IN OPERATION, EACH OF SAID PINS WHEN DRIVING SAID CHAIN, WOULD ENGAGE A CUTTING LINK AND ITS ASSOCIATED CONNECTING LINK AT A POINT ADJACENT A GUIDING LINK WITH SAID GUIDE LINK COACTING WITH SAID PIN TO MAINTAIN IT IN ENGAGEMENT WITH SAID CUTTING LINK AND SAID CONNECTING LINK, SAID FLANGES DEFINE AN INNER PORTION OF SAID GROOVE OF SUFFICIENT WIDTH TO RECEIVE SAID GUIDE LINK, AN INTERMEDIATE PORTION OF SAID GROOVE OF INCREASED WIDTH SUFFICIENT TO RECEIVE THE WHOLE WIDTH OF THE CHAIN AND AN OUTER PORTION OF SAID GROOVE OF INCREASING WIDTH AND OF SUFFICIENT DIAMETER TO PREVENT INADVERTENT DISENGAGEMENT OF SAID CHAIN FROM SAID DRIVE SPROCKET.