SE544677C2

SE544677C2 - Method for adjusting the tightness of a saw chain of a chain saw, a chain saw and a harvester head

Info

Publication number: SE544677C2
Application number: SE2150192A
Authority: SE
Inventors: Paavo Alhainen
Original assignee: Kesla Oyj
Priority date: 2020-04-01
Filing date: 2021-02-24
Publication date: 2022-10-11
Also published as: SE2150192A1; FI129870B; FI20205332A1

Abstract

The invention relates to adjusting the tightness of the saw chain of a chain saw (100) in a harvester head. The method comprises the steps of controlling a first actuator in the pivot body (110) of the chain saw (100) by means of hydraulic pressure, and based on this, moving the guide bar (120) with respect to the pivot body (110) in order to adjust the tightening of the saw chain, whereby once the tightness reaches a predefined value, the second actuator of the pivot body is further controlled so that the guide bar is secured against the pivot body. The invention further relates to a chain saw and a harvester head.

Description

Method for adjusting the tightness of a saw chain of a chain saw, a chainsaw and a harvester head Field of the invention The present invention relates to a method for tightening a saw chain, a chain sawand a harvester head as set out in the preambles of the independent claims.

Background of the invention Mechanical harvesting systems, such as harvesters, are often equipped with a har-vester head or a multifunctional part with a chain saw for sawing timber. Adjustingthe tightness of the saw chain employed in the chain saw in an appropriate manneris essential for ensuring the faultless function of the chain saw during sawing. Thesaw chain may loosen in use due to stretching or warming, for example. A loosesaw chain may then increase the risk of the chain saw becoming detached from theguide bar or the premature failure of the saw chain. On the other hand, if the sawchain is tightened too much, wear of the saw may be accelerated, thus adding tothe maintenance need of the chain saw. Therefore, the function of the saw chainneeds to be monitored and the tightness of the saw chain readjusted when neces- sary.

In previously known solutions, adjusting the tightness of the saw chain is generallycarried out by moving the guide bar with respect to the drive sprocket actuating therotation of the saw chain. In previously known solutions, this has been implementedby way of fixedly attaching the guide bar to a separate slide, which is moved bymeans of hydraulics with respect to the pivot body in the harvester head in order totighten the saw chain. However, the previously known solutions turn out compli-cated to implement as well as taking up much space.

Summary of the inventionThe aim of the invention is to solve the above-mentioned problems and to provide a method for adjusting the tightness of a saw chain. In addition, the invention aims toprovide a new and innovative chain saw and harvester head. The above goals are achieved with the invention characterized by that which is defined in the independ- ent claims.

A typical chain saw of the invention comprises a pivot body, a guide bar arrangedmovably on the pivot body, a saw chain arranged on the guide bar, a guide barpress arranged on the pivot body and a motor, as well as a drive sprocket arrangedon the same shaft with the motor, which motor is adapted to move the saw chainarranged on the guide bar via the drive sprocket. The invention is characterized inthat the chain saw further comprises an arrangement comprised of a first actuatorand a second actuator, which arrangement is adapted to move the guide bar be-tween the pivot body and the guide bar press with respect to the pivot body both inthe direction of the plane of the guide bar surface and in the direction of the planeof the normal of the guide bar surface.

In one embodiment of the invention, the above-mentioned arrangement is imple-mented by two separate actuators controlled with hydraulic pressure, of which thefirst actuator is a piston cylinder arrangement and the second actuator is a screwpiston arrangement. The surface area ratio of the actuators is preferably propor-tioned so that they may function simultaneously, whereby as the first actuatormoves the guide bar for adjusting the saw chain tightness, the second actuator maysimultaneously move the guide bar towards the pivot body.

Further, the invention relates to a method for adjusting the tightness of the sawchain of a chain saw, wherein the method comprises the following steps: - receiving hydraulic pressure in a pivot body and directing the received hy-draulic pressure to a piston cylinder arrangement in the pivot body; - based on control of the piston cylinder arrangement, moving a guide barwith respect to the pivot body towards the pivot body and away from thepivot body; - while moving the guide bar, directing the guide bar between the pivot bodyand guide bar press side of a guide bar press facing the pivot body,defining a space for the guide bar arranged therein in a central part of ascrew piston arrangement such that grooves in the central part receivegrooves in the guide bar;identifying the tightness of the saw chain, and once the tightness of the saw chainreaches a predefined value, controlling the screw piston arrangement by means ofhydraulic pressure in order to secure the guide bar against the pivot body.

The invention further relates to a harvester head with a chain saw according to theembodiments of the invention.

The insight of the invention is that in adjusting the tightness of the saw chain, it isnot necessary to use a slide or any such arrangements or mechanisms that wouldrequire the use of e.g. slide guides. The advantages of the present invention com-pared to previously known solutions are thus lower manufacturing costs and a re-duced need for space in the pivot body in the direction of the motor shaft. In addi-tion, the tightening force applied to the guide bar can be controlled more reliablycompared to previously known solutions.

Other preferred embodiments of the invention are described in the independentclaims.

Brief description of drawings Next, the invention is described in more detail with reference to the accompanyingfigures, in which FIGURE 1 shows an exploded view of a chain saw according to an embodimentof the invention; FIGURE 2 shows an assembly view of the embodiment shown in figure 1; FIGURE 3 shows a chain saw according to an embodiment of the invention.

Detailed description of the invention Figure 1 shows an exploded view of the chain saw according to an embodiment ofthe invention. Figure 2 shows an assembly view of the embodiment shown in figure1. A chain saw herein refers to a chain saw for use in harvesting machines, i.e.harvesters or tractors, attached to the frame of a harvesting machine, harvesterhead or a multifunctional part arranged in a harvesting machine. The chain saw isdriven by a motor fitted thereto rotating the saw chain arranged in the guide bar ofthe chain saw via a shaft.

The chain saw 100 shown in figures 1 and 2 comprises a pivot body 110, a guidebar 120 movably arranged on the pivot body, a saw chain arranged on the guidebar (not shown in figures 1 and 2), a guide bar press 140 arranged on the pivotbody, and a motor (not shown in figures 1 and 2) and a drive sprocket (not shownin figures 1 and 2) fitted on the same shaft therewith, wherein the motor is adaptedto move the saw chain arranged on the guide bar via the drive sprocket. The chainsaw 100 further comprises a first actuator, which in this embodiment is a piston cyl-inder arrangement 170, and a second actuator, which in this embodiment is a screwpiston arrangement 180, the two of which constitute an adjustment arrangementcontrolled with hydraulic pressure.

The pivot body 110 of the chain saw 100 is fitted with a first opening 111 for thedrive sprocket shaft, and a second opening 112 for the screw piston arrangement.Further, around the opening 112 for the screw piston arrangement, there is an in-dentation, wherein the diameter of the indentation is greater than the diameter ofthe opening 112. The openings 111, 112 are preferably arranged such that theircentral axes are parallel to the normal of the plane of the guide bar. The front edgeof the pivot body further comprises an opening 113 facing the tip of the guide barfor the piston cylinder arrangement.

Opposite the pivot body, there is a guide bar press 140 with an opening 141. Theguide bar press is arranged such that it is positioned between the circumference de-fined by the first opening 111 and the front edge of the pivot body, whereby theside of the pivot body facing the guide bar press and the side of the guide bar pressfacing the pivot body define a space for a guide bar 120 arranged therein. When thefront edges of the guide bar press and pivot body are aligned, such as in figure 1,the opening 112 for the screw piston arrangement in the pivot body is aligned withthe opening 141 in the guide bar press, allowing the screw piston arrangement tobe fitted through both the opening 112 in the pivot body and the opening 141 in theguide bar press.

The screw piston arrangement 180 (the second actuator) is implemented such thatit comprises a T-shaped moving part with a base 181 and a sleeve-Iike portion 182that is narrower than the base, below the base, as well as a stationary part 183connected to the moving part, the lower part of which is threaded. The screw pistonarrangement 180 further comprises a central part 184, wherein on opposite sides ofthe central part, there are grooves for the guide bar.

Between the pivot body 110 and the guide bar press 140, there is an elongatedguide bar 120 arranged to be movable. The guide bar is equipped with a movablesaw chain at the edge 120' of the guide bar. The guide bar extends in its longitudi-nal direction along the line defined by the centers of the opening 111 and opening112 to beyond the front edge of the pivot body and the guide bar press, wherebythe longitudinal direction of the guide bar is away from the pivot body. The guidebar is equipped with a dent 121 located at a distance from the edge of the guidebar, and with an elongated groove 122 extending to a distance from the edge of theguide bar towards the tip of the guide bar in the longitudinal direction of the guidebar.

The piston cylinder arrangement 170 (the first actuator) shown in figure 1 is imple-mented such that it comprises a moving part and a stationary part 172. The pistoncylinder arrangement further comprises a lever 173, wherein the first end of thelever is connected fixedly, or alternatively, removably, for example by means of anut or a screw, to the moving part of the piston cylinder arrangement, and the sec-ond end of the lever is arranged in the dent 121 in the guide bar. The lever may bee.g. L-shaped or Z-shaped. In figure 2, the stationary part 172 of the piston cylinderarrangement is arranged in the opening 113 in the pivot body 110 such that themoving part of the piston cylinder arrangement is able to move in the direction ofthe surface of the plane of the guide bar in opposite directions with respect to thestationary part 172 and the pivot body 110 based on control of the piston cylinderarrangement.

When assembling the chain saw, the pivot body 110 and the guide bar press 140are arranged against each other such that their front edges are facing the sameway, and the openings 112 and 141 are aligned. The screw piston arrangementis led through the openings 112 and 141 in the pivot body and the guide bar press,whereby the base 181 of the screw piston arrangement abuts the indentationaround the opening 112 in the pivot body. The screw piston arrangement extendsthrough the pivot body and the guide bar press such that the threaded lower part183 extends to a distance from the bottom of the guide bar press 140. The guidebar 120 is brought between the pivot body and the guide bar press and installedsuch that the grooves in the central part of the screw piston arrangement and theelongated groove 122 of the guide bar are aligned. The grooves in the screw pistonarrangement are positioned against the edges of the groove 122 in the guide bar,directing the guide bar between the pivot body and the guide bar press. Thethreaded lower part 183 of the screw piston arrangement is fitted with a base plate191 and a nut 192 threaded in place such that the pivot body and the guide barpress are tightened against each other and the guide bar remains between the pivotbody and the guide bar press upon tightening. The tip of the guide bar thus facesaway from the pivot body. Once the nut (and base plate) are tightened onto thebottom of the guide bar press, a clearance remains between the guide bar and thepivot body, thus keeping the guide bar in place, but also allowing guide bar to bemoved during use of the chain saw when sufficiently high hydraulic pressure is usedin controlling the piston cylinder arrangement.

Figure 3 shows a chain saw of an embodiment of the invention. The chain saw 100comprises a pivot body 110, a guide bar 120 arranged movably on the pivot body, asaw chain arranged on the guide bar (not shown in figure 3), a guide bar press 140fitted on the pivot body, and a motor 150 and a drive sprocket 160 fitted on thesame shaft therewith, wherein the motor is adapted to move the saw chain ar-ranged on the guide bar via the drive sprocket. The chain saw further comprises anadjustment arrangement comprised of a first actuator, herein a screw piston ar-rangement, and a second actuator, herein a piston cylinder arrangement, controlledwith hydraulic pressure (the actuators are not shown in figure 3).

Adjusting the tightness of the chain saw of the invention can be carried out eitherautomatically or manually, for example by an operator. At the starting point, saidactuators can be pressureless, whereby the guide bar slides at first freely towardsthe pivot body, for example for changing or maintenance of the saw chain. Whenadjusting the tightness of the saw chain is started, the hydraulic pressure producedin an external pressure source, such as a harvester or tractor, starts to increase.The hydraulic pressure is received at the pivot body, wherein the received pressureis directed further into a valve and through channels in the pivot body to a first ac-tuator controlling the displacement of the guide bar. As a result of the control of thefirst actuator, the guide bar begins to move with respect to the pivot body. As theguide bar moves away from the pivot body, the distance between the tip of theguide bar and the pivot body grows, whereby the saw chain around the guide bartightens as a result of the displacement of the guide bar. When the saw chain hastightened sufficiently, reaching a predefined value identifiable in the chain saw bymeans of e.g. a pressure regulator in connection therewith, the hydraulic pressure isdirected by means of the valve to a second actuator tightening the guide baragainst the pivot body and securing the guide bar onto the pivot body.

When adjusting the tightness of the saw chain, both of said actuators may be con-nected in parallel to the same hydraulic pressure or their function and the timing oftheir function can be adjusted by means of a valve, for example a sequence valve.This can be carried out, for example, by adjusting or changing the control of the ac-tuators when pressure at either of the actuators reaches a desired or predefinedpressure value. The surface area ratio of the first actuator and the second actuatoris preferably proportioned so that at the same pressure, they may operate simulta-neously, whereby, for example, as the first actuator moves the guide bar, the sec-ond actuator may simultaneously tighten the guide bar towards the pivot body andthe guide bar press.

It is to be understood that the above description and the drawings related theretoare intended only for illustrating the present invention. The invention is thus notlimited to the embodiment presented above or defined in the claims, rather it is ob-vious to a person skilled in the art that the invention can be modified in many wayswithin the scope of the inventive idea presented in the accompanying claims.

It is obvious to a person skilled in the art that as technology advances, the inventiveconcept may be implemented in many ways. Further, it is obvious to a personskilled in the art that the described embodiments may be combined with other em- bodiments in various ways.

Claims

1. A method for adjusting the tightness of the saw chain of a chain saw, charac-terized in that the method comprises the steps of: - receiving hydraulic pressure in a pivot body (110) and directing the receivedhydraulic pressure to a piston cylinder arrangement (170) in the pivot body(110); - based on control of the piston cylinder arrangement (170), moving a guidebar (120) with respect to the pivot body ( 110) towards the pivot body andaway from the pivot body; - while moving the guide bar (120), directing the guide bar (120) between thepivot body (110) and guide bar press side of a guide bar press (140) facingthe pivot body ( 110),defining a space for the guide bar (120) arranged therein in a central part(184) of a screw piston arrangement (180) such that grooves in the centralpart (184) receive grooves (122) in the guide bar (120); - identifying the tightness of the saw chain, and once the tightness of the sawchain reaches a predefined value, controlling the screw piston arrangement(180) by means of hydraulic pressure in order to secure the guide bar (120)against the pivot body (110).

2. The method according to claim 1, characterized in that the method com-prises the steps of:- while the piston cylinder arrangement and the screw piston arrangement(170, 180) are in a pressureless state, moving the guide bar towards thepivot body (110).

3. The method according to claim 1, characterized in that the method com-prises the steps of:- controlling the piston cylinder arrangement and the screw piston arrange-ment (170, 180) with a sequence valve.

4. The method according to claim 1, characterized in that the method com-prises the steps of:- adjusting the hydraulic pressure with a pressure regulator, and- based on the adjusted hydraulic pressure, determining a predefined valueaccording to which the tightness of the saw chain is adjusted.

5. The method according to any one of the preceding c|aims 1 to 4, character-ized in that the above-mentioned steps are carried out automatically.

6. The method according to any one of the preceding c|aims 1 to 4, character-ized in that the above-mentioned steps are carried out manually by an operator.

7. A chain saw (100), comprising a pivot body (110), a guide bar (120) arrangedmovably on the pivot body, a saw chain arranged on the guide bar, a guide barpress (140) arranged to be connected to the pivot body, a motor (150) and a drivesprocket (160) arranged on the same shaft therewith, wherein the motor is adaptedto move the saw chain arranged on the guide bar via the drive sprocket, and an ar-rangement comprised of a first actuator (170) and a second actuator (180) adaptedto move the guide bar (120) between the pivot body (110) and the guide bar press( 140) with respect to the pivot body both in the direction of the plane of the surfaceof the guide bar and in the direction of the normal of the surface of the guide bar,characterized in that the first actuator is a piston cylinder arrangement ( 170)with a part moving in a first and second direction opposite one another and a sta-tionary part (172) fitted to the pivot body (110), as well as a lever (173), whereinthe first end of the lever (173) is connected to the moving part of the piston cylin-der arrangement ( 170) and the second end of the lever (173) is connected to theguide bar (120), and the second actuator is a screw piston arrangement (180) witha part fitted through the pivot body (110) and the guide bar press (140) moving in athird and a fourth direction opposite one another, the part comprising a base (181)to be positioned against the pivot body (110), a stationary part (183) to be posi-tioned against the guide bar press (140), a sleeve-like portion (182) below the base,and a central part (184) with grooves on opposing sides, which grooves receivegrooves (122) in the guide bar (120) and direct the guide bar (120) between thepivot body (110) and the guide bar press (140) when adjusting the tightness of thesaw chain by hydraulic pressure directed to the piston cylinder arrangement (170)controlling the displacement of the guide bar towards the pivot body and away fromthe pivot body, and by hydraulic pressure directed to the screw piston arrangement(180) securing the guide bar against the pivot body.

8. The chain saw according to claim 7, characterized in that the chain saw(100) comprises a pressure regulator.

9. The chain saw according to claim 7, characterized in that the chain saw( 100) is adapted to carry out the method steps according to any one of the preced-ing claims 1 to 6 while using the chain saw (100).

10. A harvester head, characterized in that the harvester head comprises a chainsaw (100) according to any one of the preceding claims 7 to 9.