FI127044B

FI127044B - Mute

Info

Publication number: FI127044B
Application number: FI20145719A
Authority: FI
Inventors: Stefan Bergquist
Original assignee: Hultdin System Ab
Priority date: 2013-08-27
Filing date: 2014-08-14
Publication date: 2017-10-13
Also published as: NZ628700A; FI20145719A; SE537941C2; SE1350982A1

Description

DAMPING DEVICE

DESCRIPTION TECHNICAL FIELD

The present invention relates to a harvester head having an actuator for feeding-out and returning a pivotal saw assembly in a harvester.

Said actuator may also be used for feeding out and returning a pivotal saw assembly in for example a felling head, grapple saw, delimber, or fire wood machine, etc.

BACKGROUND ART

Such an actuator for a harvester head is disclosed in US 6,158,322 (Omberg), where a saw assembly for a harvester has a saw chain running around a bar and a chain sprocket; a bar holder pivotally journalled on the saw assembly stand; a saw motor driving the chain sprocket; and a device for feeding a bar out and in. The feeding-out and feeding-in device preferably is a hydraulic cylinder mounted on the stand and having a piston rod. The movements of the piston rod are transmitted to the pivotal bar holder by means of a pivotally journalled first toothed wheel which is joined to the bar holder and has a toothed wheel rim cooperating with the piston rod, which is in the form of a rack.

Such an actuator for a harvester head is also disclosed in US 5,802,946 (Leini), where a drive mechanism of minimal vertical height for a chain saw, particularly in timber harvesting vehicles, includes a drive motor, a holder with a clamping mechanism for clamping a chain saw guide bar, a bearing assembly allowing the holder to rotate in relation to the motor and a swivel device to convey liquid from the motor to the guide bar through closed channels and grooves. The bearing assembly and the swivel device have openings having sufficiently large inner diameters such that the bearing assembly and the swivel device fit around the motor, thereby avoiding the need for mounting those elements on top of one another. A torque drive device includes a hydraulic cylinder, i.e. a hydraulically operated piston and cylinder assembly, for rotating the bar holder.

In both of the two prior art designs referred to above, in course of time, there is some risk of material failure through exhaustion due to an impact when the saw assembly returns to its retracted end position.

SUMMARY OF THE INVENTION

The object of the present invention is to prevent such an impact or at least considerably reduce its harmful effects.

In a harvester head of the kind stated in the first paragraph above, this object is achieved in accordance with the present invention in that the harvester head comprises a shock absorber for absorbing an impact upon an arrival of said saw assembly at a home position. A shock absorber absorbs so much of the impact, that the impact no longer has any harmful effect. Consequently, this will permit an operator to work faster, as the time required for the return stroke of the saw assembly can be reduced considerably, because the feeding of a tree trunk through the harvester head to the next cutting position cannot be carried out until the return stroke of the pivotal saw assembly is completed, so that the pivotal saw assembly does not block the passage of the tree trunk. The faster the return stroke can be carried out, the more time is saved and the more the productivity can increase, but the faster the pivotal saw assembly moves during its return stroke, the heavier an impact against a stop will be. Thus, the provision of a shock absorber makes it possible to use higher return speeds than up to now possible and thereby increase the productivity.

The shock absorber may be mounted to absorb the impact of the pivotal saw assembly against a stop provided in a housing of the harvester head, but preferably the shock absorber is included in the actuator. Thereby, the stopping of the return movement of the pivotal saw assembly at its start and rest position will not in course of time damage the attachment of the pivotal saw unit to the housing of the harvester head.

The shock absorber may be hydraulic or pneumatic, but preferably it is mechanical. A mechanical shock absorber is simple and cost-efficient, and it is also less sensitive to temperature changes between summer and winter conditions, for example.

Preferably, the actuator includes a member that is axially movable between two end positions, one of which corresponds to a completely returned saw assembly, and the axially movable member has one end engaging a pivotal member for the feeding-out and the returning of the pivotal saw assembly.

In a preferred embodiment, said pivotal member is a toothed rotary wheel and said axially movable member is a piston rod having one end shaped as a rack for cooperation with the toothed wheel for the feeding-out and the returning of the pivotal saw assembly. Thereby, the length of the torque arm (radius arm) does not change, and in addition, all parts are contained in a single unit and the piston rod is shielded so as to permit a higher degree of utilization of the grip-harvester than what is the case with prior art actuators, where the piston rod isn’t shielded.

The shock absorber preferably comprises a spring holder mounted in an axial bore in the piston rod. The spring holder has a head and a shank, and the head projects axially from an axial end surface of the piston rod. The shank is surrounded by at least one compression spring compressed between the head and a bottom of the bore. Thereby, the only component that has to be modified in view of the incorporation of the shock absorber is the piston rod.

Suitably, the axial bore is displaced radially from a longitudinal axis of the piston rod. Thereby, the bore does not require an increased diameter of the piston rod in spite of being located in the rack-shaped portion of the piston rod.

It is preferred that the spring holder is locked to the piston rod by means of a crosswise extending pin, and one of the head and the piston rod has a crosswise extending bore for the pin dimensioned to permit the pin to move diametrically in the crosswise extending bore in the axial direction of the spring holder. Thereby, the spring holder can perform a restricted axial movement in relation to the piston rod due to compression and relaxation of the compression spring in order to absorb a shock.

Although helical compression springs may be used, said at least one compression spring preferably is a stack of Belleville washers. Belleville washers are cost-efficient and easy to build in.

The Belleville washers suitably are arranged in a plurality of consecutive stacks with alternating opposed orientation. Thereby, it is easy to adapt the spring to the expected force and to get a desired damping length.

It is also preferred that the shank has an end provided with a threaded axial bore, said at least one spring extends along the entire length of the shank, and a screw having a head of slightly larger diameter than a diameter of the shank is screwed into the threaded bore to keep said at least one spring on the shank during mounting of the shock absorber. Thereby, it is possible to pre-mount the Belleville washers on the screw to form a spring package, and no washer will be dropped on mounting or demounting the package in the actuator.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in more detail with reference to preferred embodiments and the appended drawings.

Fig. 1 is a schematic view from above, partially in cross-section, of a preferred embodiment of a saw assembly for a harvester head and illustrates its feeding-out and returning device for a saw bar in a partly fed-out position, and also a built-in lubricating oil pump.

Fig. 2 is a perspective view of a piston rod included in the feeding-out and returning device and having a shock absorber.

Fig. 3 is an end view of the piston rod of Fig. 2.

Fig. 4 is a longitudinal cross-sectional view of the piston rod taken along line IV-IV of Fig. 3.

Fig. 5 shows an encircled portion marked by circle V of Fig. 4 on a larger scale.

Fig. 6 is a side view of the shock absorber used in the piston rod of Figs. 2-5.

Fig. 7 is a longitudinal cross-sectional view of the shock absorber taken along line VII-VII of Fig. 6.

Fig. 8 is a schematic view from above, partially in cross-section, of another embodiment of a saw assembly for a harvester head and illustrates its feeding-out and returning device for a saw bar.

MODE(S) FOR CARRYING OUT THE INVENTION

Fig. 1 shows schematically parts of a saw assembly 13 mounted in a so-called saw box, which is intended for inclusion in a harvester. The saw assembly comprises 13 a stand 1, a bar holder 2 and a bar 3 mounted on the bar holder 2 with the aid of suitable bar attachments and assembly devices so that a displaceable unit is formed including said bar 3. A saw chain 4 runs around the bar 3 and a chain sprocket (not shown), which is driven by a saw motor (not shown) located under a cover 50. The saw motor is rigidly secured inside the stand 1. The bar holder 2 is pivotally journalled in relation to the stand 1 to be turned in controlled manner about an axis 10 coinciding with the central axis of the saw motor.

The displaceable unit is thus mounted on the bar holder 2 so that the bar 3 can be displaced in relation to the holder 2 in a direction corresponding to the longitudinal centre line 11 of the bar 3 and which is perpendicular to the pivot axis 10. A first hydraulic piston cylinder (not shown) is arranged in one of the bar attachments to be activated by a hydraulic circuit system of the saw assembly via a directional valve and a connection comprising an outer pipe 12 for displacement of the unit in relation to the bar holder 2 so that, during operation of the saw assembly, the bar 3 in the unit automatically keeps the saw chain 4 taut. A second hydraulic piston cylinder (not shown) is arranged in one of the bar attachments to act in parallel with the axis of pivot 10 in order to press against the bar holder 2 in a controlled manner to flexibly secure the movable unit to the bar holder 2. The other piston cylinder is also affected by the pressure in said hydraulic circuit system via said outer pipe 12.

The saw assembly 13 comprises a device 14 for controlled feeding of the bar 3 out and returning it by turning the bar holder 2 about the pivot axis 10. The feeding-out and returning device 14 comprises a hydraulic piston and cylinder actuator 17 having a piston cylinder 18 situated behind the bar 3, seen in its direction of movement, and parallel to the bar 3 when this is in its initial position prior to a sawing operation. The hydraulic actuator 17 has a piston rod 19 having an end portion shaped as a rack, its side facing the axis of pivot 10 being provided with a section having a plurality of teeth 20 - twelve teeth in the embodiment shown. Hydraulic fluid is supplied to and removed from two pressure chambers 21, 22 provided in the piston cylinder 18 via pipes 23, 24 connected to a hydraulic circuit system of the saw assembly via a directional valve (not shown), which pressure chambers 21, 22 are defined by a piston 25 carried by the piston rod 19. The feeding-out and retracting device 14 also comprises a toothed wheel 26 with a rim 27, with which the rack of the piston rod 19 of the hydraulic actuator is in engagement. The toothed wheel 26 is rigidly joined to the bar holder 2 to form a unit therewith, which can be turned about the pivot axis 10.

The saw assembly 13 also comprises a lubricating oil pump 38, arranged to provide the saw chain 4 with lubricating oil when the bar 3 is fed out. In the embodiment shown, the lubricating oil pump is built into the hydraulic actuator 17 itself in order to form an integrated unit therewith and be served thereby. The lubricating oil pump 38 comprises a central, longitudinally extending pump chamber 39 inside the piston rod 19 in the end portion attached to the piston 25 and facing the piston cylinder 18, and also a central pipe 40 extending through the piston cylinder 18 and into said pump chamber 39, so that one end is always situated in the pump chamber 39. The pump chamber 39 is closed off from the pressure chamber 21 of the hydraulic actuator 17 by means of suitable sealing elements 41 comprising a sealing ring 42. The hydraulic actuator 17 is closed at the end facing away from the piston rod 19 by means of a valve housing 43 in which said central pipe 40 extends for rigid assembly therein. The pump chamber 39 is supplied with lubricating oil from a lubricating oil tank 44 via an outer pipe 45, a first channel 46 in the valve housing 43 and the central pipe 40. Lubricating oil is pumped out from the pump chamber 39 via the central pipe 40, a second channel 47 in the valve housing 43 and an outer pipe 48 connected to an inlet 49 in a cover 50 of the saw motor. The first and second channels 46, 47 in the valve housing 43 are provided with non-return valves 51, 52, respectively. It will be understood that lubricant is pumped out of the pump chamber 39 when the piston rod 19 is moved towards the valve housing 43 in order to commence a sawing operation, the volume of the pump chamber 39 being reduced as a result of a larger part of the central pipe 40 being located within the pump chamber 39. When the saw bar 3 is returned by the piston rod 19 being moved in the opposite direction, the volume in the pump chamber 39 increases to a corresponding degree since a smaller part of the central pipe 40 is located within the pump chamber 39. Due to the reduced pressure now created in the pump chamber 39 the lubricant will be sucked into the pump chamber 39 from the lubricating oil tank 44 via pipe 45, channel 46 with its opened non-return valve 51 and the central pipe 40. From the inlet 49 the lubricant is conveyed to the saw chain 4 via connections (not shown) in the saw motor, the toothed wheel 26, the bar holder 2, and a conduit 53 having its orifice close to the saw chain 4.

In prior art designs there is, in course of time, some risk of material failure through exhaustion due to an impact when the saw assembly 13 after having performed a cutting operation returns to its end position, i.e. start or rest position. The hydraulic actuator includes an axially movable member that has one end engaging a wheel for feeding-out and returning of the pivotal saw assembly 13, and to prevent such an impact or at least considerably reduce its harmful effects, the hydraulic actuator 17 comprises a shock absorber for absorbing an impact upon an arrival of an axially movable member of the actuator at an end position that corresponds to a home saw assembly 13. A shock absorber absorbs so much of the impact, that the impact no longer has any harmful effect.

Although other embodiments are conceivable, in the preferred embodiment illustrated in Figs. 2-7, the axially movable member of the hydraulic actuator 17 is the piston rod 19, which is axially movable between two end positions, one of which corresponds to a completely returned saw assembly 13, and said member having one end engaging a wheel for the feeding-out and the returning of the pivotal saw assembly 13. The piston rod basically is a rod having a round cross-section. At one end it is shaped for permitting attachment of the piston 25 and also has a bore constituting the pump chamber 39. At its other end it has an end portion provided with the teeth 20 and forming a rack, which engages the toothed wheel 26. This latter end of the piston rod 19 also has an end face 70, which in the shown preferred embodiment is provided with a stepped bore 71 for housing a shock absorber 190, which prevents the end face 70 of the piston rod 19 from abutting a wall portion of the stand 1 when the saw assembly 13 after a cutting operation returns to its end position. A shock absorber absorbs so much of the impact, that the impact no longer has any harmful effect. Of course, if desired, it is also possible to place the shock absorber at other positions exposed to abutting forces on arrival of the saw assembly 13 to its start or rest position after a cutting operation. The shock absorber 190 could be mounted on the peripheral surface of the piston rod 19 or in the wall of the stand 1 or even in a connection between the piston rod and the wheel for pivoting the saw assembly 13, for example.

The shock absorber 190 could also be located inside the cylinder 18 of the hydraulic actuator 17, e.g. in pressure chamber 22. Even though the shock absorber 190 may be hydraulic or pneumatic, it preferably is mechanical. A mechanical shock absorber is less sensitive to changes in temperature between summer and winter conditions.

Preferably, in the preferred embodiment shown in the drawings, the shock absorber 190 comprises a spring holder 191 mounted in the stepped axial bore 71 in the piston rod 19. The spring holder 191 has a head 192 and a shank 193, and the head 192 projects axially from the axial end face 70 of the piston rod 19. The shank 193 is surrounded by at least one compression spring 194 compressed between the head 192 and a shoulder 72 of the stepped bore 71. Thereby, the only component that has to be modified in view of the incorporation of the shock absorber 190 is the piston rod 19.

As is best shown in Figs. 3 and 4, the stepped axial bore 71 is displaced radially from a longitudinal axis of the piston rod 19. Thereby, the bore 71 does not require an increased diameter of the piston rod 19 in spite of being located in the rack-shaped portion of the piston rod 19.

It is preferred that the spring holder 191 is locked to the piston rod 19 by means of a crosswise extending pin 195 (Fig. 5), and one of the head 192 and the piston rod 19 has a crosswise extending bore 196 for the pin 195 dimensioned to permit the pin 195 to move diametrically in the crosswise extending bore 196 in the axial direction of the spring holder 191. Thereby, the spring holder 191 can perform a restricted axial movement in relation to the piston rod 19 due to compression and relaxation of the compression spring 194 in order to absorb a shock. In a preferred embodiment, the head 192 projects axially a distance of about 1 mm from the end face 70 of the piston rod 19. In other words, the shock absorber 190 has a shock absorbing length of about 1 mm.

Although helical compression springs may be used, said at least one compression spring 194 preferably is a stack 197 of Belleville washers. A Belleville washer is a type of spring shaped like a washer. It has a frusto-conical shape which gives the washer a spring characteristic. Some properties of Belleville washers include: high fatigue life, better space utilization, low creep tendency, high load capacity with a small spring deflection, and possibility for high hysteresis (damping) by stacking several Belleville washers on top of each other in the same direction. Multiple Belleville washers may be stacked to modify the spring constant or amount of deflection. Stacking in the same direction will add the spring constant in parallel, creating a stiffer joint (with the same deflection). Stacking in an alternating direction is the same as adding springs in series, resulting in a lower spring constant and greater deflection. Mixing and matching directions allow a specific spring constant and deflection capacity to be designed.

The Belleville washers suitably are arranged in a plurality of consecutive stacks 197,198 with alternating opposed orientation of the washers. In the preferred embodiment shown in Figs. 6 and 7, there are five stacks, each one containing 23 Belleville washers, and all washers in a stack have the same orientation, but the orientation in each stack is opposed to that in an adjacent stack. Thereby, it is easy to adapt the spring to the expected force and to get a desired damping length.

It is also preferred that the shank 193 has an end provided with a threaded axial bore, said at least one spring 194 extends along the entire length of the shank 193, and a screw 199 having a head of slightly larger diameter than a diameter of the shank 193 is screwed into the threaded bore to keep said at least one spring 194 on the shank 193 during mounting of the shock absorber 190. Thereby, it is possible to pre-mount the Belleville washers on the screw to form a spring package, and no washer will be dropped on mounting or demounting the package in the actuator.

The present invention is not restricted to the most preferred embodiment shown in Figs. 1-7 and described above but can be modified within the scope of the appended claims. As an example, shown in Fig. 8, a pivotal member, e.g. an arm 26’ or other lever, may be substituted for the toothed wheel 26 that is engaged by the axially movable member 19 for the feeding-out and the returning of the pivotal saw assembly 13. However, the toothed wheel 26 is preferred as it will give a constant torque, while an arm 26’ or other lever will give a varying torque during the feeding-out of the pivotal saw assembly 13. Further, although not shown, if an arm 26’ or other lever is used for pivoting the saw assembly 13, then the mechanical shock absorber may be a cushioning member of suitable rubber or plastic, for example, that is fixed to said arm or lever or to the stop provided in the housing of the harvester head. Further, the pivoting of the saw assembly 13 may also be carried out by the rotor of a motor, which then constitutes the actuator 17.

INDUSTRIAL APPLICABILITY

The harvester head of the present invention is applicable for performing a felling and cross cutting operation in a harvester.

Claims

Harvester assembly having an actuator (17) for dispensing and returning a rotatable saw (13) into a harvester, characterized in that said harvester assembly includes a shock absorber (190) for absorbing a shock upon the arrival of said sawmill (13) to a home location.

Harvester assembly according to claim 1, characterized in that the shock absorber (190), to allow a rapid return stroke of the saw (13), which is inactive during most of the return stroke and active only at one last stage of the return stroke.

Harvester assembly according to claim 1 or 2, characterized in that the shock absorber (190) is included in the actuator (17).

Harvester assembly according to any one of claims 1-3, characterized in that the shock absorber (190) is mechanical.

Harvester assembly according to any one of claims 1-4, characterized in that said actuator (17) comprises an element (19) which is axially movable between two end positions, one of which corresponds to a fully retracted saw (13), and wherein said axially movable element (19) has an end which engages a rotatable element (26) for the output and return of the rotatable saw (13).

Harvester assembly according to claim 5, characterized in that said rotatable element is a toothed rotating wheel (26) and said axially movable element is a piston rod (19) having an end formed as a rack for interaction with the toothed rotating wheel (26). for the output and return of the rotatable saw (13).

Harvester assembly according to claim 6, characterized in that the shock absorber (190) comprises a spring holder (191) mounted in an axial hole (71) in the piston rod (19), said spring holder (191) having a head (192) and a shaft (193), said head (192) projecting axially from an axial end surface (70) of the piston rod (19), said shaft (193) being surrounded by at least one compression spring (194) compressed between the head (192) and a the bottom (72) of the axial hole (71).

Harvester assembly according to claim 7, characterized in that the axial hole (71) is displaced radially from a longitudinal axis of the piston rod (19).

Harvester assembly according to claim 7 or 8, characterized in that the spring holder (191) is secured to the piston rod (19) by means of a transverse pin (195) and that either the head (192) or the piston rod (19) has a transverse hole (196). ) for the pin (195) which is sized to allow the pin (195) to move in the diameter direction of the transverse bore (196) in the axial direction of the spring holder (191).

Harvester assembly according to any one of claims 7-9, characterized in that said at least one compression spring (194) is a stack of (197) of Belleville washers.

Harvester assembly according to claim 10, characterized in that the Belleville washers are arranged in a plurality of successive stacks (197, 198) in alternating opposite directions.

Harvester assembly according to any of claims 7-11, characterized in that the shaft (193) has an end provided with a threaded hole, said at least one spring (194) extending along the entire length of the shaft (193) and wherein screw (199) having a head with a slightly larger diameter than a diameter of the shaft (193) is screwed into the threaded hole to retain said at least one spring (194) on the shaft (193) when mounting the shock absorber (190).