GUIDE BAR FOR POWER CHAIN SAWS

CROSS REFERENCE AND RELATED APPLICATION

The present application claims the benefit of US provisional application 61/027,466 filed on February 10, 2008, the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to guide bars for chain saws and more particularly to improving the durability of guide bars for power chain saws, such as chain saws for cutting hard materials such as concrete and reinforced concrete.

BACKGROUND AND PRIOR ART

A power chain saw such as a concrete cutting chain saw has several concerns, whereas one of the main concerns is the durability of the chain and the durability of the guide bar. Concrete cutting chain saws have been considered to require a substantial drive motor, e.g. ranging from a low of about 5 horsepower motor to as high as 9 horsepower motor or more. Having high power on the one hand and high cutting resistance on the other, concrete cutting generates a vast amount of wear due to the grinding process and heat and dust generated. Hence, improving the durability of the chain and the guide bar is a major concern of a concrete cutting chain saw.

Typically, in power chain saws such as concrete cutting chain saws, the chain and the chain guide bar are disposable, that is, the chain and the chain guide bar are replaced after a few hours of accumulated work. Hence, it is desirable to maximize the life span of the chain and the guide bar. It is further desirable to have a guide bar whit a life span that is at least as long as the life span of the coupled chain.

A very high degree of wear resistance is required as a crucial requirement from the guide bars for proper performance. Two common practices, which requiring special manufacturing steps, are used in prior art: a) Local induction hardening of the perimeter, using a medium carbon constructional steel. b) "Stellite" cladding of the wear area, on an ordinary steel body. The term "Stellite" as used herein refers to generic trademark for wear resistant high- cobalt base alloys.

Typically, prior art guide-bars have a steel body of proper length and have appropriately sized guiding slots along the perimeter, in which the cutting chain is guided. Figure 1 illustrates a prior art guide bar 10 for a concrete cutting chain saw. Guide bar 10 includes rim 20, rounded portion 30 of the rim and sprocket 40 disposed at the radial center of rounded portion 30 of rim 20. One solution of prior art guide bars is to use hardened steel, such as carbon constructional steel. The manufacturing by local hardening of carbon constructional steel guide bars being expensive, in some prior art guide bars "Stellite" cladding of the wear area, such as at the guide bar rim, is used on an ordinary steel body. However, this is still an expensive solution.

Another factor in the deterioration of guide bars for concrete cutting chain saws is the durability of rounded portion 30 of rim 20. US Patent 6186136, given to Ian Osborne, provides a guide bar 10 coupled to a chain (not shown) that moves rapidly along a slot at rim 20 as well as at rounded rim portion 30, and applying a wear force to rim 20 and to rounded portion 30 of rim 20. US Patent 6397475, given to Karl-olov Pettersson et al, provides a guide bar 10 coupled to a chain that runs rapidly along a slot at rim 20 as well as at rounded rim portion 30, whereas the links of the moving chain push teeth 45 and thereby rotating sprocket 40 about axis 42, and thereby improving the durability of rounded rim portion 30. As the chain moves on rim 20, the chain applies force vector 50 on sprocket 40. Force vector 50 is a radial force which is transferred to the bearing of sprocket 40. Typically, there is a manufacturing tolerance which gives the moving parts (spherical or cylindrical) some freedom to move inside the bearing housing. Typically, the force vector 50 is transferred to two of the multiple moving parts (spherical or cylindrical) and thereby causing an accelerated deterioration of the two moving parts absorbing force vector 50. Force vector 50 also increases the wear force applied to rounded portion 30 of rim 20, which in turn increases force vector 50, which in turn increases the wear force applied to rounded portion 30 of rim 20, and so on and so forth.

Thus there is a need for and it would be advantageous to have a guide bar for power chain saws such as concrete cutting chain saws that will have a longer life span by lessening the wear at the rounded portion 30 of a guide bar 10.

The pitch between teeth 45 of sprocket 40 is fixed. It is therefore desirable to have a guide bar that is not coupled only to chains with a particular pitch between the

chain links, but a guide bar that can be coupled to various chains irrespective of the pitch between the chain links.

The term "austenitic manganese steel" as used herein refers to a steel grade which has outstanding wear resistance capabilities, in the as-supplied state. This steel is known as "austenitic-manganese", "Hadfield", "K700", X120Mnl2, W. No. 1.3401, and other names, according to various standards and trade names. Numerous variations of austenitic manganese steel exist. For example, the chemical composition of standard "W. No. 1.3401" steel includes 1.12 wt% Carbon, 12.25 wt% Mn, 0.33 wt% Si, and 0.22 wt%Cr. The remainder is iron, in an "austenitic solution" heat treated state. Other austenitic manganese steels having essentially the same or better properties have the following chemical composition: from 0.6 to 1.8 wt% Carbon, from 7 to 16 wt% Mn, with any addition of at least one of the following: 0-3 wt% Ti, Cr, B, V, Zr, and/or N, each element alone or in any combination thereof. The remainder is iron.

SUMMARY OF THE INVENTION

The principal intentions of the present invention include providing a guide bar for power chain saws, such as concrete cutting chain saws, whereas the guide bar includes a toothless front pulley, which includes a four-point bearing and dirt trapping grooves. The guide bar is preferably made of wear-resistant austenitic manganese steel.

According to the teachings of the present invention there is provided a guide bar for operatively holding and guiding the chain of power chain saws, the guide bar including: a) a housing body having a front end and a back end, wherein the housing body includes two sides, wherein each of the sides are affixed to each other in an assembled state, the two sides being substantially a reverse image of each other; and b) a pulley assembly, wherein the pulley assembly includes two discs and a body, wherein the two discs and the body form a four-point bearing in an assembled state of the pulley assembly.

In a working state, the housing body holds the pulley assembly, firmly.

In some embodiments of the present invention, the four-point bearing is a four- point-bearing-roller. The four-point-bearing-roller includes roller balls housed between two V-grooves formed by the tλvo discs and the body of the pulley assembly.

In some embodiments of the present invention, the four-point bearing is a four- point-bearing-roller. The four-point-bearing-roller includes roller balls housed between two concave grooves formed respectively by the two discs and the body of the pulley assembly.

According to further teachings of the present invention, the discs of the pulley assembly, further includes circumferential grooves that operatively trap particles of debris.

According to further teachings of the present invention, the housing body further includes a carrying portion that includes an elongated leading portion and a stopper portion. The elongated leading portion, include two substantially parallel edges. The pulley assembly includes two anchoring legs that form substantially parallel inner edges. The distance between the parallel edges of the elongated leading portion is substantially the same as the distance between the parallel inner edges of the anchoring legs. Thereby, the inner edges of the anchoring legs can slide over the edges of the elongated leading portion with substantially no tolerance between the inner edges of the anchoring legs and the edges of the elongated leading portion. An aspect of the present invention is to enable quick replacement of the pulley assembly without having to replace the guide bar as a whole. When assembling the pulley assembly into the housing body, the pulley assembly is inserted through an opening at the front end of the housing body. The inner edges of the anchoring legs slide inwardly over the edges of the elongated leading portion until the ends of the anchoring legs reach the edges of the stopper portion.

The four-point-bearing-roller has both lateral and radial stress bearing capability, a property absent in the prior art, used by other guide-bars manufacturers. In other manufacturers' designs, only the radial forces are handled by the bearing, while lateral forces are burdened on plain rubbing on the side steel plates. Therefore, the four-point-bearing-roller design is saving power on the cutting engine, by not wasting it on internal wear between the chain, the pulley and the guide bar itself.

An aspect of the present invention is to provide a guide bar for power chain saw, such as concrete cutting chain saw, wherein at least a portion of the guide bar is made of austenitic manganese steel Austenitic manganese steel also represents a manufacturing shortcut, by avoiding additional steps of hardening, tempering, straightening, cladding and flat grinding necessary in other manufacturers processes

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become fully understood from the detailed descπption given herein below and the accompanying drawings, which are given by way of illustration and example only and thus not limitative of the present invention, and wherein

FIG 1 (pπor art) illustrates a prior art guide bar for a concrete cutting chain saw,

FIG 2 illustrates a guide bar for power chain saws, according to embodiments of the present invention, FIGs 3a and 3b illustrate the guide bar shown m Figure 2, whereas Figure 3a shows one side of the housing body and the front pulley assembly, and Figure 3b shows the complementing side of the housing and the front pulley assembly,

FIG 4a is a side view illustration of front pulley assembly of guide bar shown m Figure 2, FIG 4b is a cross section W-W, front view illustration of front pulley assembly shown in Figure 4a,

FIG 4c is a top view illustration of front pulley assembly shown in Figure 4a, FIG 5 illustrates the body of the front pulley assembly shown in Figures 4a-4c,

FIG 6a is a front view illustration of one of the two symmetrical discs of pulley of the front pulley assembly shown in Figures 4a-4c,

FIG 6b is a side view illustration of the disc shown m Figure 6a, FIG 7 illustrates the details of window Y shown in Figure 4b, FIG 8 illustrates the details of window Z shown in Figure 5, and

FIG. 9 is a perspective view illustration of the front pulley assembly shown in Figures 4a-4c.

FIG. 10 illustrates a guide bar for power chain saws, according to preferred embodiments of the present invention; FIG. 1 Ia is a side view illustration of front pulley assembly of the guide bar shown in Figure 10;

FIG. 1 Ib is a cross section A-A, front view illustration of front pulley assembly shown in Figure 11a;

FIG. 1 Ic is a top view illustration of front pulley assembly shown in Figure 11a; FIG. 12 illustrates the body of the front pulley assembly shown in Figures 1 Ia-I Ic;

FIG. 13a is a front view illustration of one of the two symmetrical discs of pulley of the front pulley assembly shown in Figures 1 Ia- lie;

FIG. 13b is a side view illustration of the disc shown in Figure 13a; FIG. 14 illustrates the details of window B shown in Figure l ib; FIG. 15 illustrates the details of window C shown in Figure 12;

FIG. 16 is a perspective view illustration of the front pulley assembly shown in Figures 1 Ia-I Ic, with one disc removed for illustrative purposes only.

FIG. 17 illustrates the details of window D shown in Figure 15;

FIG. 18 illustrates a guide bar for power chain saws of the guide bar shown in Figure 1O ₅ whereas one side of the housing body is removed for illustrative purposes only, in a working state;

FIG. 19 illustrates an exploded view of the guide bar shown in Figure 18; and

FIG. 20 illustrates the guide bar shown in Figure 18, in an intermediate assembly state.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different

forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided, so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The methods and examples provided herein are illustrative only and not intended to be limiting.

By way of introduction, the principal intentions of the present invention include providing a guide bar for power chain saws, such as concrete cutting chain saws, whereas the guide bar includes a toothless front pulley, which includes a four- point bearing and dirt trapping grooves. The guide bar is preferably made of wear- resistant austenitic manganese steel. Austenitic manganese steel also represents a manufacturing shortcut, by avoiding additional steps of hardening, tempering, straightening, cladding and flat grinding necessary in other manufacturers processes.

Reference is now made to the drawings. Figure 2 illustrates guide bar 100 for power chain saws, such as concrete cutting chain saws, according to embodiments of the present invention. Guide bar 100 includes a body 110 and a rotating front pulley 140 at the front end of guide bar 100, which is can rotate about axis 142. The chain of the chain saw (not shown) performs penetration cuts into rigid matters such as concrete walls, including reinforced concrete walls. The chain runs over rim 120 of body 110, as in prior art chain saws. However, contrary to prior art chain saws, the chain does not go over the rounded front rim of body 110, but rather on rim 141 of front pulley 140, thereby avoiding the deterioration of the front rim. In embodiments of the present invention body 110 of guide bar 100 includes an assembly of three steel layers, whereas the two outer layers HOa and HOb are preferably made of the above austenitic manganese steel. In-between, an arrangement is laid out of machined parts, made of a simple material, such as soft steel or other suitable sheet stock. The intermediate layers keep the two outer layers HOa and HOb at the correct spacing as well as serves as water conduits to pre-determined exit ports, to cool, lubricate and flush the whole device during work.

Reference is also made to Figures 3a and 3b, which illustrate guide bar 100, whereas Figure 3a shows one side (HOa) of housing body HO and front pulley

assembly 160, and Figure 3b shows the complementing side (HOb) of housing body 110 and front pulley assembly 160 When assembled, side HOa of housing body 110 and side HOb of housing body 110 are affixed together by any attaching mechanism, including screws and nuts, spot welding or any other suitable method One pulley side 140a is affixed to the other pulley side 140b by any attaching mechanism, including screws 147b and nuts 147a, spot welding or any other suitable method

Reference is now made to Figure 4a which is a side view illustration of front pulley assembly 160 of guide bar 100 shown in Figure 2 Reference is also made to Figure 4b which is a cross section W-W, front view illustration of front pulley assembly 160 shown m Figure 4a, and to Figure 4c which is a top view illustration of front pulley assembly 160 The whole pulley assembly 160 is a separate entity, which provides guide bar 100 with an elongated life span, with respect to prior art guide bars

A key element in achieving the elongated life span is the four-point-beaπng- roller which is designed to keep the thickness of pulley 140 within the typical 5mm requirement The four-pomt-beaπng- roller provides "zero clearance ^' ' or otherwise stated "pre-stressed" assembling of this type of bearing This property stems from its conceptual design which, when properly realized, gives the bearing a contact area approaching half of the race circumference and thereby a much lower contact pressure is achieved, improving significantly the bearing lifespan

The four-pomt-beaπng-roller has both lateral and radial stress capacity, a property absent in the prior art, used by other guide-bar manufacturers In other manufacturers' designs, only the radial forces are handled by the bearing, while lateral forces are burdened on plain rubbing on the side steel plates Therefore, the four- pomt-beaπng-roller design is saving power on the cutting engine, by not wasting it on internal wear between the chain, the pulley and the guide bar itself

Reference is also made to Figure 5 which illustrates body 162 of the front pulley assembly 160, to Figure 6a which is an illustration a front view of one of the two symmetrical discs of pulley 140 and to Figure βb which is a side view illustration of disc 140 shown m Figure 6a Body 162 includes outer annular portion 163 and anchoring legs 169 Anchoring legs 169 are designed to affix front pulley assembly 160 to body 110 of guide bar 100 Anchoring legs 169 are appropriately engineered to

provide a balanced amount of strength and stiffness to pulley assembly 160. Furthermore, it incorporates an essential cooling conduit 167, directing cooling water to the bearing, which is needed to keep the bearing working temperature at levels compatible with the materials used. Annular portion 163 has an outer radius Tbz, an inner radius ^ ₁ , and a groove depth radius r _b2 - Groove 164 is a V-groove that serves as the outer race of the bearing of front pulley assembly 160. Each of symmetrical discs 140 has an outer radius of r _d 3, an inner radius r _c io, an inner V-groove radius r _t n, an outer V-groove radius r _d2 and a body groove radius r _d4 . When assembled together, annular portion 163 of body 162 fits into groove 143 whereas rbs is substantially equal to r _d4 and ^ ₁ is substantially equal to r _d2 . Slope 145, coupled with slope 145 of the other disc 140, form another V- groove, opposing V-groove 164 of annular portion 163 and serves as the inner race of the bearing of front pulley assembly 160. V-grooves 145 and 164 serve as the housing of the balls of the bearing. Reference is also made to Figure 7 which illustrates the details of window Y shown in Figure 4b, and to Figure 8 which illustrates the details of window Z shown in Figure 7. Pulley assembly 160 is a separate entity, which provides guide bar 100 elongated life span, with respect to prior art guide bars. Slopes 145a, and 145b form a V-groove and together with V-groove 164 provide a rhombus housing for roller balls 180, whereas each ball 180 touches each slope of each V-groove (145, 164) at one point only (182). Referring also to Figure 9, which is a perspective view illustration of front pulley assembly 160, roller balls 180 are viewed disposed inside V-groove 164. When implementing the four-points-bearing-roller concept, a full row of roller balls 180 is filled in, with appropriate greasing. The size of each roller ball 180 is such that the external radius of roller balls 180 is brought into intimate contact with the slopes of V-grooves 145 and 164, thus realizing a closed structure.

When the chain saw is operating, V-groove 164 is static while V-groove 145, being part of pulley discs 140, rotated by the chain, thereby V-grooves 145 roll over roller balls 180 which roll with V-groove 145. Typically, roller balls 180, body 162 and discs 140 are treated with hardening procedures to increase their durability to abrasion. While in prior art bearings used in front end sprockets only radial forces are applied to the moving parts (spherical or cylindrical), roller balls 180 of the present invention have both radial and tangential forces applied to, which stabilizes pulley 140

motion. Typically, the 4-points- bearing has substantially no clearance between balls 180 and V-grooves 145 and 164, and wear force vector 50 applied by the operating chain onto the bearing is applied to nearly half the number of roller balls 180 (and not only on two at the time as in prior art), thereby substantially increasing the life span of roller balls 180.

The inner radius (rao) of pulley 140 is substantially sealed, thereby occluding the entrance of abrasive debris and thus, eliminating the accelerated wear expected in working in such a harsh environment, as in concrete cutting.

Optionally, discs 140 further include circumferential grooves 149. During work, the centrifugal forces act in accelerating outwards particles trying to get into pulley 140. Circumferential grooves 149 serve as traps to the particles of debris in order to minimize the penetration of debris from the inner side of pulley 140 and thereby hinder the seepage of debris to the bearing.

Reference is now made to Figure 10, which illustrates guide bar 200 for power chain saws, such as concrete cutting chain saws, according to preferred embodiments of the present invention. Guide bar 200 includes a body 210 and a rotating front pulley 240 at the front end of guide bar 200, which is can rotate about axis 242. The chain of the chain saw (not shown) performs penetration cuts into rigid matters such as concrete walls, including reinforced concrete walls. The chain runs over rim 220 of body 210, as in prior art chain saws. However, contrary to prior art chain saws, the chain does not go over the rounded front rim of body 210, but rather on rim 241 of front pulley 240, thereby avoiding the deterioration of the front rim.

Reference is also made to Figure 11a which is a side view illustration of front pulley assembly 260 of guide bar 200 shown in Figure 10. Reference is also made to

Figure lib which is a cross section A-A, front view illustration of front pulley assembly 260 shown in Figure l la, and to Figure l ie which is a top view illustration of front pulley assembly 260. The whole pulley assembly 260 is a separate entity, which provides guide bar 200 with an elongated life span, with respect to prior art guide bars.

A key element in achieving the elongated life span is the four-point-bearing- roller which is designed to keep the thickness of pulley 240 within the typical 5mm

requirement. The four-point-bearing-roller provides "zero clearance" or otherwise stated ''pre-stressed" assembling of this type of bearing. This property stems from a conceptual design that gives the bearing a contact area having a much lower contact pressure, improving significantly the bearing lifespan. The four-point-bearing-roller has both lateral and radial stress capacity, a property absent in the prior art, used by other guide-bar manufacturers. In other manufacturers' designs, only the radial forces are handled by the bearing, while lateral forces are burdened on plain rubbing on the side steel plates. Therefore, the four- point-bearing-roller design is saving power on the cutting engine, by not wasting it on internal wear between the chain, the pulley and the guide bar itself.

Reference is also made to Figure 12 which illustrates body 262 of the front pulley assembly 260, to Figure 13a which is an illustration a front view of one of the two symmetrical discs of pulley 240 and to Figure 13b which is a side view illustration of disc 240 shown in Figure 13a. Body 262 includes outer annular portion 263 and anchoring legs 269. Anchoring legs 269 are designed to affix front pulley assembly 260 to body 210 of guide bar 200. Anchoring legs 269 are appropriately engineered to provide a balanced amount of strength and stiffness to pulley assembly 260. Gap 267 is fitted to a complimentary segment of body 210.

Annular portion 263 has an outer radius r _b s, an inner radius rt,i and a groove depth radius fø. Groove 264 is a concave groove that serves as the outer race of the bearing of front pulley assembly 260. Each of symmetrical discs 240 has an outer radius of 1^3, an inner radius r _c io and a groove depth radius ^ ₁ . Groove 245 is a concave groove that serves as the inner race of the bearing of front pulley assembly 260. Grooves 245 and 264 serve as the housing of the roller balls of the bearing. Reference is also made to Figure 14 which illustrates the details of window B shown in Figure lib, to Figure 15 which illustrates the details of window C shown in Figure 14 and to Figure 17 which illustrates the details of window D shown in Figure 15. Pulley assembly 260 is a separate entity, which provides guide bar 200 elongated life span, with respect to prior art guide bars. Concave groove 245 together with concave groove 264 provide rhombus housing for roller balls 280, whereas each ball 280 touches the slope of concave grooves 245 and 264 at four points (282), altogether. Referring also to Figure 16, which is a perspective view illustration of front pulley

assembly 260, wherein one disc is removed for illustrative purposes only, such that roller balls 280 can be viewed being disposed inside concave groove 264. When implementing the four-points-bearing-roller concept, a full row of roller balls 280 is filled in, with appropriate greasing. The size of each roller ball 280 is such that the external radius of roller balls 280 is brought into intimate contact with the surface of concave grooves 245 and 264, thus realizing a closed structure.

When the chain saw is operating, concave groove 164 is static while concave groove 245, being part of pulley discs 240, rotated by the chain, thereby concave groove 245 rolls over roller balls 280 which roll with concave groove 245. Typically, roller balls 280, body 262 and discs 240 are treated with hardening procedures to increase their durability to abrasion. While in prior art bearings used in front end sprockets only radial forces are applied to the moving parts (spherical or cylindrical), roller balls 280 of the present invention have both radial and tangential forces applied to, which stabilizes pulley 240 motion. Typically, the four-points-bearing has substantially no clearance between balls 280 and concave grooves 245 and 264, and wear force vector 50 applied by the operating chain onto the bearing is applied to nearly half the number of roller balls 280 (and not only on two at the time as in prior art), thereby substantially increasing the life span of roller balls 280.

The inner radius (rao) of pulley 240 is substantially sealed, thereby occluding the entrance of abrasive debris and thereby, eliminating the accelerated wear expected in working in such a harsh environment, as in concrete cutting.

Reference is now made to Figure 18, which illustrates a guide bar for power chain saws of guide bar 200, whereas one side of housing body 210 is removed for illustrative purposes only, in a working state. Reference is also made to Figure 19, which illustrates an exploded view of guide bar 200, and to Figure 20, which illustrates guide bar 200 in an intermediate assembly state.

An aspect of the present invention is to enable quick replacement of pulley assembly 260 without having to replace guide bar 200 as a whole. Anchoring legs 269 of pulley assembly 260 has gap 267 (Figure 12) between the two anchoring legs. Housing body 210 includes carrying portion 290 which includes substantially parallel, elongated leading portion 292 and stopper portion 294. Edges 295 of stopper portion 294 are designed to stop inwardly movement of pulley assembly 260 when being

assembled and in operating state. Width 297 of elongated leading portion 292 substantially fits the dimension of gap 267. When assembling pulley assembly 260 into housing body 210, pulley assembly 260 is inserted through an opening at front end 212 of housing body 210, wherein the substantially parallel inner edges 268 of anchoring legs 269 slide over edges 298 of elongated leading portion 292, in direction 265. Pulley assembly 260 is pushed into housing body 210 until the ends of the legs of anchoring legs 269 reach edges 295 of stopper portion 294. Preferably end 296 of elongated leading portion 292 is rounded to ease the insertion of pulley assembly 260 onto carrying portion 290 of housing body 210.

The invention being thus described in terms of several embodiments and examples, it will be obvious that the same may be varied in many ways Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art.