US 4,361,960 A · Chain saw bar with automatic tensioning

Abstract

A chain saw guide bar assembly (30) having improved automatic chain tensioning, vibration damping and lubrication properties, and related lubrication methods are provided. A nose guide member (34) rotatably carrying an idler sprocket (34.1) is mounted to an elongate primary guide bar member (32) for reciprocal longitudinal movement relative thereto. Biasing spring members (50, 51) acting on force-imparting surfaces (60.4, 60.5), are protectively enclosed within an internal cavity (33) of the primary guide member and bias the nose guide member with predetermined tensioning force in the longitudinal direction against an endless cutting chain (40). An interchangeable force block member (60) enables preselection of the desired chain tension force. Damping finger members (32.35, 32.36, 50, 51) cooperatively absorb vibratory forces transmitted through the guide bar. Oil passageways (32.33, 32.34, 39) longitudinally extend through the guide bar to provide complete lubrication of the biasing means, the idler sprocket and other moving parts of the bar assembly and to provide improved lubrication of the cutting chain at a position adjacent the juncture of the two guide members comprising the bifurcated guide bar. Method steps for lubricating the cutting chain and the idler sprocket from oil transmitted through the length of the guide bar are also provided.

Claims32

Dependent claims

A chain saw guide bar assembly for use with a chain saw of the type of having an endless toothed chain, a frame, a drive sprocket rotatably mounted on said frame and supporting said chain, means for mounting said guide bar assembly to said frame such that said chain is guided by and moves along the periphery of said guide bar assembly in response to rotation of said drive sprocket;

said guide bar assembly comprising:
(a) a bifurcated guide bar, comprising:
(i) an elongate primary guide member having a proximal end configured for mounting to the frame adjacent the drive sprocket and an oppositely disposed distal end, whereby said primary guide member when mounted to said frame extends from said frame in cantilevered manner toward said distal end;
(b) means for movably connecting said nose guide member to said primary guide member at said distal end thereof for movement with respect thereto substantially only in the axial direction of said primary guide member;
whereby the chain will operatively move along the outer peripheries of the primary and the nose guide member;
(c) biasing means enclosed within said bifurcated guide bar for automatically applying uniform predetermined tensioning forces to the cutting chain by controllingly urging said nose guide member primarily in the axial direction away from the distal end of said primary guide bar member;
wherein said biasing means is shielded from the external environment of said bifurcated guide bar during operation thereof;
and
(d) means for preventing accummulation of sawdust and foreign matter during operation of said bar assembly that would impede the relative operative movement of said primary and nose guide members and the operation of said biasing means, whereby said uniform predetermined tensioning forces to the cutting chain are maintained.

6 more elements

said guide bar assembly comprising:
(a) a bifurcated guide bar, comprising:
(i) an elongate primary guide member having a proximal end configured for mounting to the frame adjacent the drive sprocket and an oppositely disposed distal end, whereby said primary guide member when mounted to said frame extends from said frame in cantilevered manner toward said distal end;
(b) means for movably connecting said nose guide member to said primary guide member at said distal end thereof for movement with respect thereto substantially only in the axial direction of said primary guide member;
whereby the chain will operatively move along the outer peripheries of the primary and the nose guide member;
and
(c) biasing means enclosed within said bifurcated guide bar for automatically applying uniform predetermined tensioning forces to the cutting chain by controllingly urging said nose guide member in the axial direction away from the distal end of said primary guide bar member;
wherein said biasing means is shielded from the external environment of said bifurcated guide bar during operation thereof;
and wherein said biasing means includes:
(i) a force block member removably insertable within one of said guide members, said force block member defining a force-imparting bearing surface;
and
(ii) a spring member operatively disposed to reactively engage said bearing surface and to urge said primary and said nose guide members in a direction away from each other in response thereto.

9 more elements

An improved chain saw guide bar assembly for use with a chain saw of the type having an endless articulated chain having a plurality of cutting teeth serially connected by interconnecting link members, a frame, a drive sprocket rotatably mounted on said guide bar assembly to said frame such that said chain is guided by and moves along the periphery of said guide bar assembly in response to rotation of said drive sprocket, in a manner such that the interconnecting chain links slideably engage the periphery of said guide bar assembly;

said guide bar assembly comprising:
(a) a bifurcated guide bar, comprising:
(i) an elongate primary guide member having a proximal end configured for mounting to the frame adjacent the drive sprocket and an oppositely disposed distal end, whereby said primary guide member when mounted to said frame extends from said frame in cantilevered manner toward said distal end;
(ii) a nose guide member configured to form an operative extension of said primary guide member at said distal end thereof;
(b) means for movably connecting said nose guide member to said primary guide member at said distal end thereof for movement with respect thereto substantially only in the axial direction of said primary guide member;
whereby the chain will operatively move along the outer peripheries of the primary and the nose guide members;
(c) biasing means enclosed within said bifurcated guide bar for automatically applying uniform predetermined tensioning forces to the cutting chain by controllingly urging said nose guide member in the axial direction away from the distal end of said primary guide bar member;
wherein said biasing means is shielded from the external environment of said bifurcated guide bar during operation thereof;
(d) oiling means within said guide bar assembly for lubricating said cutting chain adjacent the distal end of said primary guide bar member as the chain returns to the drive sprocket, wherein said oiling means is further characterized by said primary guide bar member being configured to define:
(i) an oil inlet port adjacent the proximal end of said primary guide bar member, suitable for receiving a charge of lubricating oil from a source external of said guide bar assembly;
(ii) an oil passageway operatively connected to said inlet port and extending through said primary guide bar member to the distal end thereof;
and
(iii) an oil outlet port adjacent the distal end of the primary guide bar member and operatively opening into said oil passageway, for enabling oil passing through said passageway to flow under the force of gravity onto said underlying chain;
whereby those surfaces of said chain links that slideably engage the periphery of the guide bar assembly are lubricated just prior to engagement of the cutting teeth carried by those links with an object being cut thereby during normal cutting operations;
and
(e) means within said primary guide bar member operatively connected with said oil passageway for maintaining a positive pressure of said oil within said passageway and for ejecting a charge of said oil flowing through said passageway out of said oil inlet port.

13 more elements

An improved method for lubricating an idler sprocket of a chain saw guide bar assembly of a portable chain saw of the type having an endless toothed chain, a frame, a drive sprocket rotatably mounted on said frame and supporting said chain, an elongate guide bar assembly extending between first and second ends, an idler sprocket mounted for rotation adjacent said second end of the guide bar assembly, said guide bar assembly being of a type having an internal oil passageway extending through said guide bar assembly from an oil inlet port adjacent said first end thereof to an oil outlet port adjacent said idler sprocket and being bifurcated into primary and nose guide members connected by connecting means reciprocally mounted for longitudinal movement within said internal oil passageway, means for mounting the primary guide bar member at its first end to the frame such that the guide bar assembly extends in cantilevered manner toward said second end thereof and such that the chain is guided by and moves along the periphery of the guide bar assembly and over the idler sprocket in response to rotation of said drive sprocket, said method comprising the steps of:

(a) introducing a charge of lubricating oil into the internal oil passageway of the guide bar assembly through the oil inlet port adjacent the first end of the guide bar;
(b) causing the introduced oil to travel through the oil passageway, the length of the guide bar and through that oil outlet port adjacent the second end thereof;
(c) directing the oil passing through the oil outlet port to flow into lubricating engagement with the idler sprocket;
and
(d) maintaining a positive oil pressure within said oil passageway for preventing entry of sawdust or foreign matter into said oil passageway and for preventing accummulation of such sawdust or foreign matter that would inhibit operation of said connecting means.

2 more elements

Dependencies are inferred from the claim text.

Chain saw bar with automatic tensioning

Life of this patent

Chain saw bar with automatic tensioning

Life of this patent

Abstract

Claims32