AU2012388831B2

AU2012388831B2 - Method and protective arrangement for linear control and actuator means that are components of a tree harvester of a forestry machine

Info

Publication number: AU2012388831B2
Application number: AU2012388831A
Authority: AU
Inventors: Torbjorn Sikstrom
Original assignee: Komatsu Forest AB
Current assignee: Komatsu Forest AB
Priority date: 2012-08-27
Filing date: 2012-08-27
Publication date: 2017-10-12
Anticipated expiration: 2032-08-27
Also published as: WO2014035300A1; BR112015004094A2; EP2888487A1; EP2888487A4; AU2012388831A1; BR112015004094B1

Abstract

The invention concerns a method and an arrangement to reduce interruptions in operation of linear control means (6) such as a hydraulic cylinder with a cylinder housing (6a) and a piston rod (6b) that is used for the setting displaceable machine elements (2a, 2b) in a tree harvester (1), where the interruptions in operation are caused by splashes of fluid from trees that are being processed in the tree harvester. According to the method, the piston rod (6b) is shielded from the tree (3) that has been taken up into the tree harvester (1) by means of a protective sheath (10) that surrounds the piston rod, where the protective sheath is arranged to accompany the piston rod in its motion in such a manner that the protective sheath surrounds at least partially the cylinder housing (6a) when the control means is located in its compressed condition.

Description

Method and protective arrangement for linear control and actuator means that are components of a tree harvester of a forestry machine

The present invention concerns a method to reduce interruptions in operation of linear control means of the piston rod type, for example hydraulic cylinders, that are used to set displaceable machine elements of tree harvesters of forestry machines, where the function of the said control means can be negatively affected through the influence of splashes from fluids such as resin, sap that is secreted from trees that have been felled and are being processed in the tree harvester. The invention concerns also a tree harvester equipped with such an arrangement and the invention concerns a splash protector.

Tree harvesters are used at forestry machines, and are arranged to carry out the felling of growing trees and the processing of the tree after felling at the worksite in the forest. The tree harvester is attached at the end of a displaceable boom arrangement at the forestry machine, and has the task of gripping an upright tree by means of grippers, and felling it. After cutting, the tree trunk is laid down in an essentially horizontal position and is fed through a trimmer, whereby displacement of the tree through the unit is stopped at certain intervals, at which the tree trunk is cut to the desired lengths by sawing. The trimmer comprises one or several pairs of knives that can be promoted to an active trimming position, in contact with the tree trunk through the influence of hydraulically acting control and actuator means. It is normal that the gripper and the trimmer are so designed that they form a common unit in which the gripper demonstrates gripping arms that can be manoeuvred, which arms are sufficiently sharp at their edges that they can serve at the same time as trimming knives.

For operation of the many moving parts that are components of a tree harvester, not least the trimming knives, linear control and actuator means are normally used of the type known as "hydraulically operated". It should be understood that the expression "linear control means" as it is used in the following concerns any linearly operating control and actuator means at all, of the type that has a piston rod or piston that is mounted in bearings in a housing in a manner that allows displacement and that can move freely during activation of the control means into and out from the housing, for setting the linear operating length of the control means. Attachments for the mounting of the control means are present at the free end of the piston rod and in the housing. It should be remembered that control means of this type may be manufactured for not only electrical operation but also hydraulic operation, or for combinations of these. It is normal that the piston rod during electrical operation forms an anchor at an electrical motor, while the stator winding of the said motor is arranged in the housing. Hydraulically operated control means, which are more commonly used for tree harvesters, comprise in known manner a housing in the form of a cylinder, i.e. a cylinder housing with a piston and a piston rod. Furthermore, connections to a hydraulic drive system are present at the end walls of the cylinder, through the action of which the piston can be caused to move in the cylinder, for setting the operating length of the control means.

It is common for the above-mentioned linear control means that the cylinder has a hole or an opening in one of its end walls, through which the piston rod passes out from the cylinder. The piston rod is guided in a manner that allows sliding in the said opening through what is known as a "piston rod seal". It is highly important for the function of the control means that a good seal is achieved between the cylinder end wall and the piston rod. The principal task of the piston rod seal is thus to prevent leakage of hydraulic medium out from the cylinder, while it also has the task of preventing contaminants from entering the cylinder. It is furthermore important for the function of the control means that the piston rod is not contaminated, and that a protective lubricating film can be maintained at the piston rod.

When working with a tree harvester and during processing of trees, fluids such as resin and sap are secreted from the tree. The said fluids tend to splash, in particular during the trimming operation, onto, among other objects, the piston rod that is a component of the linear control and actuator means that is used to operate the trimming knives of the tree harvester, while the said piston rod is often located in the close vicinity of the working area.

One problem with the said fluids is that they tend to accompany the piston rod into the cylinder through the piston rod seal. The fluids, and in particular the sap, which consists of dissolved nutrient salts and sugar, constitute in the cylinder a contaminant that can not only influence the function of the cylinder in itself, but also, by mixing with the hydraulic agent that is part of the hydraulic circuits of the forestry machine, contaminate the entirety of the hydraulic system. The hydraulic system that is a part of modern forestry machines contains components that are very sensitive to contaminants. Resin is a highly viscous yellow or brown fluid that contains resin components and polysaccharides that can, through splashing from a tree trunk, stick to the piston rod. Such deposits tend to set and form rubber-like layers on the surface of the piston rod. The deposits reduce the ability of the piston rod to move into and out from the cylinder with low friction through the piston rod seal. Furthermore, the set deposits tend to damage or destroy the piston rod seal of the cylinder.

Embodiments of the present invention provide a method that makes it possible to eliminate the problems described above and to reduce the occurrence of interruptions in operation of linear control means of the piston rod type, for example hydraulic cylinders that are used for setting the displaceable machine elements at tree harvesters. Embodiments of the invention provide a tree harvester that mitigates this problem. In some embodiments, the invention also provides a splash protector for a control means of piston rod type at a tree harvester.

In accordance with one aspect, the present invention provides a tree harvester supported by a forestry machine for the felling and processing of trees, the tree harvester comprising a frame that further comprises: - linear control means of piston rod type that demonstrates a cylinder housing and a piston rod, the cylinder housing having: a first fixing lug in the form of a cylinder fixture that is arranged at a rear end part and faces away from the piston rod, and a second fixing lug in the form of a piston rod fixture located at the free end of the piston rod, - grippers for holding a tree, the grippers further comprising: grip arms that operate in pairs, each one of which in order to grip the tree is mounted to pivot at a joint on the machine frame such that it oscillates in a plane that is perpendicular to the longitudinal direction of a tree that has been placed into the tree harvester, each grip arm is provided with a sharp edge in order to serve at the same time as trimming knife, whereby the tree is trimmed through being drawn forwards through the unit with the aid of drawing rollers or wheels that act on opposing sides of the tree, wherein the linear control means is used for the setting of the grip arms and therewith the trimming knives; and wherein the cylinder fixture and piston rod fixture of the linear control means is jointed to pivot at its ends between the two grip arms such that they can be opened and closed by the influence of the linear control means, and thus can be brought into and removed from interaction with a tree that has been inserted into the tree harvester, and wherein the linear control means further comprises: a disposable protective sheath arranged to protect the piston rod from tree fluids; the protective sheath being attached to a holder which is mounted at one end of the piston rod and comprising: a longitudinal slit arranged to guide longitudinal movement of the protective sheath along the cylinder; and a groove-shaped opening arranged to allow the longitudinal movement of the protective sheath along the cylinder by receiving a high pressure line that provides hydraulic fluid to the cylinder in a manner such that, the protective sheath at least partially surrounds the cylinder housing when the linear control means is in its compressed condition; wherein the longitudinal slit and the groove-shaped opening are configured to enable replacement of the protective sheath without disassembling any other component of the linear control means.

The present invention will be described below in more detail with reference to embodiments that are shown in the attached drawings, of which:

Figure 1 shows a perspective view of a part of a tree harvester for a forestry machine according to the invention, at which a protective arrangement is arranged in association with a hydraulic cylinder that is intended for the operation of grippers for the holding of a tree trunk, which grippers serve also as trimming knives when the tree trunk is drawn through the unit,

Figure 2 shows a perspective view of a protective arrangement that is a part of the invention with separated parts and intended to be mounted on the hydraulic cylinder that is a component of the tree harvester that is shown in Figure 1,

Figure 3 shows a cross-sectional view through a protective arrangement that is a part of the invention viewed along the line Ill-Ill in Figure 2, and

Figure 4 shows a transparent view through a part of a protective arrangement that is part of the invention, in an alternative design.

Figure 1 shows schematically a part of a tree harvester 1 of the type that is intended to be supported at the free end of a manoeuvrable boom or arm at a forestry machine. The tree harvester 1 generally comprises a frame (not shown in the drawings) provided with grippers 2 for holding a tree 3, a cutter arrangement (not shown in the drawings) for cutting a tree that is held fast by the gripper 2. The gripper 2 comprises grip arms 2a, 2b that operate in pairs, each one of which in order to grip the tree 3 is mounted to pivot at a joint 4 on the machine frame such that it oscillates in a plane that is perpendicular to the longitudinal direction of a tree 3 that has been placed into the tree harvester. The pivoting action of each arm is illustrated in the drawing, in which the frame is not shown, with a centre line 5, 5' for each arm respectively, for reasons of simplicity.

With reference also to Figure 2, a linear control and actuator means that is a component of the tree harvester 1 and that in this case is constituted by a hydraulic cylinder 6 includes a cylinder housing 6a, a piston rod 6b and a piston rod seal 6c in a forward end section 6d of the cylinder housing that faces towards the piston rod. For the purpose of mounting, the cylinder housing 6a has a first fixing lug in the form of a cylinder fixture 7a that, arranged at a rear end part 6e, faces away from the piston rod, and a second fixing lug in the form of a piston rod fixture 7b located at the free end of the piston rod 6b. With the said cylinder fixture 7a and piston rod fixture 7b the hydraulic cylinder 6 is jointed to pivot at its ends between the two grip arms 2a, 2b such that they can be opened and closed by the influence of the cylinder 6, and thus can be brought into and removed from interaction with a tree 3 that has been inserted into the tree harvester 1. Each grip arm 2a, 2b is provided in known manner with a sharp edge 9 in order to serve at the same time as trimming knife, whereby the tree 3 is trimmed through being drawn forwards through the unit, as is illustrated with an arrow in Figure 1. The drawing operation takes place with the aid of drawing rollers or wheels (not shown in the drawings) that act on opposing sides of the tree. The tree harvester 1 comprises further a cutting arrangement (not shown in the drawings) that comprises a chain saw and is used to cut a tree 3 that is fed forwards through the unit into the desired lengths.

In order to prevent splashes from fluids such as resin, sap and similar that are secreted in an uncontrolled manner from the tree 3 that is being processed in the tree harvester 1 being deposited onto the piston rod, the hydraulic cylinder 6 for the operation of the grip arms and trimming knives 2a, 2b has been equipped with a splash protector that demonstrates a protective sheath 10 with the form of a bowl. This protective sheath 10 is arranged such that it by accompanying the piston rod 6b in its motion protects it from splashes of resin and sap from a tree 3 that has been inserted into the tree harvester 1. The protective sheath 10 has been given such a form relative to the piston rod 6b that the protective sheath essentially surrounds the piston rod 6b and effectively covers it during its working motion into and out from the cylinder housing 6a. The protective sheath 10 in this way accompanies the piston rod 6b in a sufficiently mobile manner that the protective sheath at least partially surrounds the cylinder housing 6a when the cylinder 6 is located in its compressed condition, see Figure 1.

As is made most clear by Figures 2 and 3, the bowl-formed protective sheath 10 includes an extended principally tube-shaped or sheath-shaped body, which forms a jacket with an internal 10a and an external 10b wall surface, see Figure 3. The protective sheath 10 has a longitudinal slit 11 with edge sections 11a, 11b that face each other and that limit between them a groove-shaped opening, the width of which is adapted to form a free compartment against a pressure line 18 on the cylinder housing 6a, and at the same time in this way provide a guide that allows the protective sheath to move in its longitudinal direction relative to the cylinder housing 6a, but prevents the protective sheath from rotating around its longitudinal axis. See also Figure 3, whereby the pressure line 18 and the associated connection at the cylinder housing are suggested with dash-dot lines.

As is made clear by Figures 1 and 2, the protective sheath 10 demonstrates an arcshaped holder 12 of relatively stiff material at one of its ends. This holder may, for example, be manufactured from a blank in the form of a flat rod that has been bent to a U-shape. Suitable material may be constituted by aluminium or steel. The holder 12 is provided with mounting holes 13 and is, in turn, attached through screws 14 or similar, in a manner that allows it to be removed, through the interaction of these screws with corresponding threaded holes 15 in the piston rod head 7b. In its mounted condition, the arced holder 12 extends around a part of the outermost periphery of the piston rod head 7b in which it demonstrates a pair of parallel shanks 12a, 12b that, facing backwards towards the piston rod 6b, extend on opposing sides of the piston rod head 7b, and in which shanks the protective sheath 10 is fixed attached at one of its ends by, for example, pop rivets. The second end of the protective sheath is intended to be supported by the end section 6d of the cylinder housing 6a that faces the piston rod 6b through interaction between the concave inner surface 10a, when viewed in cross-section, of the protective sheath and the convex outer surface, when viewed in cross-section, of the cylinder housing 6a. The protective sheath in the present embodiment is manufactured as a disposable item of a relatively stiff elastic material of plastic. In order to offer the stiffness required and a good guiding action against the forward end wall 6d of the cylinder housing 6a that is facing the piston rod, the protective sheath 10 is provided with a stiffening flange 19.

The present protective arrangement is shown in an alternative embodiment in Figure 4. Similar to the design that is described above, the bowl-formed protective 10 includes an extended principally tube or sheath-shaped body that forms a jacket that protects the piston rod 6b and that accompanies the fixture 7b of the piston rod in its motion. The protective sheath 10 differs from the design described above through it lacking a longitudinal slit 11. The protective sheath is instead designed as a hollow cylinder of continuously surrounding jacket that is so dimensioned that it surrounds not only the cylinder housing 6a and the piston rod 6b, but also a pressure line 18 or similar arrangement that is located on the outer surface of the cylinder housing.

The present invention is not limited to what has been described above and shown in the drawings: it can be changed and modified in several different ways within the scope of the innovative concept defined by the attached patent claims.

Claims

1. A tree harvester supported by a forestry machine for the felling and processing of trees, the tree harvester comprising a frame that further comprises: - linear control means of piston rod type that demonstrates a cylinder housing and a piston rod, the cylinder housing having: a first fixing lug in the form of a cylinder fixture that is arranged at a rear end part and faces away from the piston rod, and a second fixing lug in the form of a piston rod fixture located at the free end of the piston rod, - grippers for holding a tree, the grippers further comprising: grip arms that operate in pairs, each one of which in order to grip the tree is mounted to pivot at a joint on the machine frame such that it oscillates in a plane that is perpendicular to the longitudinal direction of a tree that has been placed into the tree harvester, each grip arm is provided with a sharp edge in order to serve at the same time as trimming knife, whereby the tree is trimmed through being drawn forwards through the unit with the aid of drawing rollers or wheels that act on opposing sides of the tree, wherein the linear control means is used for the setting of the grip arms and therewith the trimming knives; and wherein the cylinder fixture and piston rod fixture of the linear control means is jointed to pivot at its ends between the two grip arms such that they can be opened and closed by the influence of the linear control means, and thus can be brought into and removed from interaction with a tree that has been inserted into the tree harvester, and wherein the linear control means further comprises: a disposable protective sheath arranged to protect the piston rod from tree fluids; the protective sheath being attached to a holder which is mounted at one end of the piston rod and comprising: a longitudinal slit arranged to guide longitudinal movement of the protective sheath along the cylinder; and a groove-shaped opening arranged to allow the longitudinal movement of the protective sheath along the cylinder by receiving a high pressure line that provides hydraulic fluid to the cylinder in a manner such that, the protective sheath at least partially surrounds the cylinder housing when the linear control means is in its compressed condition; wherein the longitudinal slit and the groove-shaped opening are configured to enable replacement of the protective sheath without disassembling any other component of the linear control means.

2. A tree harvester according to claim 1, wherein the protective sheath is made of plastic and the holder is made of aluminium or steel.