EP2960026A1

EP2960026A1 - Feeding device for axial feed of log

Info

Publication number: EP2960026A1
Application number: EP15173154.4A
Authority: EP
Inventors: Jonas Ljung
Original assignee: Soderhamn Eriksson AB
Current assignee: Usnr AB
Priority date: 2014-06-24
Filing date: 2015-06-22
Publication date: 2015-12-30
Anticipated expiration: 2035-06-22
Also published as: EP2960026B1; SE1450780A1; SE538240C2

Abstract

A feeding device comprising a support (8) having feed cylinders (2,3,4) arranged in a free end of a respective supporting arm (5,6,7) and driven in rotation, wherein the supporting arms in a supported end are journalled in the support on shafts (9,10,11) extending in parallel with each other and pivotable about the shafts between a home position and a pivoted work position, and wherein the supporting arms are mutually connected to each other via a system of articulated links (13,16,19) and by means of the links forced to pivot jointly about their respective shafts, and a movement damping element (20,20',200), which is separate from the support, is integrated in the system of links and independently from the support configured to brake the return movement of the supporting arms from the pivoted position.

Description

Technical field of the Invention

The present invention relates to a feeding device configured for feeding a log in the length direction of the log. More precisely, the invention relates to a feeding device of the kind comprising a support having a through opening and feed cylinders adjoining the opening, which feed cylinders are angularly distributed and which are individually arranged in a free end of a respective supporting arm and driven in rotation, and wherein the supporting arms in a supported end are journalled in the support on shafts extending in parallel with each other and pivotable about the shafts between a home position and a pivoted work position, and wherein the supporting arms are mutually connected to each other via a system of articulated links and by means of the links forced to pivot jointly about their respective shafts.

Background and prior art

Feeding devices of this type are used in barking machines of rotation ring type of the kind comprising a stationary machine support and a rotor rotatably journalled in relation to the support and having a central hole for passing the logs. Usually one feeding device is located on the upstream side of the support for feeding the logs into the machine, while another corresponding feeding device is located on the downstream side of the support for outputting the barked log. A number of pivotable machining tools are mounted to the rotor, the machining tools being equipped with replaceable elements that can be pressed against the surface of the log in order to peel off the bark.
Feeding devices for barking machines have the function of feeding the logs in a quick and powerful way without the logs slipping in the contact with the feed cylinders. The feed cylinders are for this purpose typically arranged with friction increasing elements, for instance in the form of projecting pins or the like, at the envelope surface thereof. The feed cylinders must by the same cause be distinctly pressed against the logs but at the same time indulgently follow irregularities in the surface of logs having varying dimensions.
It is customary that the feeding speed through a feeding device at barking machines is in the range of a couple of meters per second or more. It is thereby realized that the feed cylinders and the links are exposed to high dynamical loads and rapid adjustment movements when a log enters the feeding device and leaving the feeding device, respectively.
A feeding device of this kind in known from the applicants earlier Swedish Patent having publication number SE 517517 C2 . Distinguishing for this feeding device is that a holding down mechanism in the form of a compressible bellows is arranged between the support and a link that is part of the link system. The bellows is arranged to be compressed and expanded depending on the pivoting movement of the feed cylinders and has the function to generate a holding down force that secure the vital contact between the feed cylinders and the envelope surface of the log. A shock absorber having the function of damping the movement of the feed cylinders in connection with the log leaving the feed cylinders is configured to work between the support and a link that is part of the link system.
In the known feeding device considerable dynamical loads in the form of shocks and vibrations are transferred to the support in connection with the log entering and leaving the feeding device, respectively. These shocks and vibrations cause a great strain on the holders of the shock absorber and on the support.

Brief description of the Invention

The present invention aims at obviating above mentioned disadvantages of the known feeding device.
In brief, the object is attained by means of a feeding device of the initially defined type, wherein a movement damping element, that is separate from the support, is integrated in the link system and independently from the support configured to brake the return movement of the supporting arms from a pivoted position. Thereby the risk of wear or fatigue caused by shocks and vibrations that otherwise are transferred to the support are removed or essentially reduced.
As previously mentioned the feeding device comprises a support having a through opening and feed cylinders adjoining the opening, which feed cylinders are angularly distributed and which are individually arranged in a free end of a respective supporting arm and driven in rotation, and wherein the supporting arms in a supported end are journalled in the support on shafts extending in parallel with each other and pivotable about the shafts between a home position and a pivoted work position, and wherein the supporting arms are mutually connected to each other via a system of articulated links and by means of the links forced to pivot jointly about their respective shafts. The system of links comprises bar-shaped links that are connected between the supporting arms, which links in each end are articulately connected to a respective supporting arm, as well as a carrier that is inserted between the links and articulately connected in relation to the links. In one embodiment of the invention the movement damping element is operatively connected between the carrier and one of said two links.
For this purpose the link in question presents a bracket that is directed outwards seen from the feeding path and serving as a first holder for the movement damping element. According to the same embodiment the carrier can take the shape of a bracket that is directed outwards seen from the feeding path and acting as a moment arm pivoting together with the supporting arm and serving as a second holder for the movement damping element.
In the feeding device there is arranged a holding down element operative to generate a holding down force by which the feed cylinders are pressed against the surface of the feeding log. This holding down element may for instance be realized in the form of a resilient bellows, such as a air filled bellows, arranged to operate between the system of links and the support.
In different embodiments of the invention a holding down element in the form of a mechanical spring, a gas spring or a hydraulic spring is integrated in the movement damping element.

Brief description of the drawings

Embodiments of the invention are described herein below with reference to the accompanying drawings, in which

Fig. 1 is a schematic illustration of a feeding device in the home position seen from an input side or an output side,
Fig. 2 is a corresponding view disclosing a partly modified feeding device in operational mode, and
Fig. 3 discloses a part of the hydraulics of one embodiment of the invention.

Detailed description of preferred embodiments

A feeding device 1 for feeding a log in the length direction of the log usually comprises three feed cylinders 2, 3 and 4 which are supported in the free end of a respective supporting arm 5, 6 and 7 which in a supported end are pivotably journalled in a machine support/stand 8. The supporting arms are journalled on shafts 9, 10 and 11 which extend in parallel to each other and essentially in the feeding direction of the log through the feeding device. The shafts 9-11 are evenly distributed angularly about an opening 12 through the support, and may by other words be said to be located at the tips of an isosceles triangle. The feed cylinders 2-4 are driven in rotation R in order to, by means of the envelope surfaces thereof being in tangential contact with a log, feeding the log through the opening 12. An imaginary feeding path through the feeding device is defined in this way by means of the feed cylinders and their envelope surfaces that are tangentially oriented in relation to the feeding path. The letter C in the drawings stand for a centre of the feeding path.
The feed cylinders may via a chain and gear drive transmission be jointly driven by an individual driving device, but may alternatively be individually driven by separate driving devices that are arranged in the respective supporting arm or feed cylinder.
Supporting arms and corresponding feed cylinders are mutually connected via a system of links that are articulately connected to the supporting arms 5-7. The link system comprises more precisely a first link 13 that is pivotably journalled about pivots 14 and 15 arranged at the supporting arms 5 and 6, respectively. A second link 16 is in the corresponding way pivotably journalled about pivots 17 and 18 arranged at the supporting arms 6 and 7, respectively. The links 13 and 16 are mainly bar-shaped and may present bendings in order to admit that the feed cylinders are pivoted outwards in overlapping relationship with the links 13 and 16 (as illustrated in Fig. 2). A third link 19 is pivotably journalled about pivots 15 and 17 in relation to the links 13 and 16. The third link 19 acts as a carrier for a movement damping element 20 in a way that will be described in more detail below.
The supporting arms and the feed cylinders of the feeding device are freely pivotable about their respective shafts 9-11 and may by means of the location of the pivots 14-15 and 17-18 on the supporting arms and in relation to the fulcrum of the shafts 9-11 be balanced such that no significant turning forces normally effects the feeding device in its home position. In order to secure the necessary engagement of the feed cylinders with the outside of the log a holding down force is applied to the link system, which force in the embodiment according to Fig. 1 is generated by means of a spring element 21. The spring element 21 may as is shown in Fig. 1 be supported by a bracket 22 arranged on the support in order to act between the support 8 and a link 16 that is part of the system of links. The spring element 21 may be constituted by a known gas filled bellows or by a so-called air spring.
Thus far, the described feeding device 1 essentially corresponds to the feeding device known from SE 517517 C2 .
The feeding device 1 is distinguished from the known feeding device in an essential way, and more precisely by means of the arrangement of the movement damping element 20 in the feeding device.
The design of the movement damping device 20 may be of the known type that comprises a piston that is axially displaceable in a cylinder and that divide the cylinder in a first and a second chamber, both filled with hydraulic liquid. The chambers communicates with each other via a return check valve that admit in principle an unhindered flow from one chamber to the other and that by means of a flow restricting choke brakes the return flow for a more slow movement of the piston in the return direction. The movement damping element 20 acts in this way to dampen the movement of the feed cylinders in connection with a log leaving the feeding device while the supporting arms and feed cylinders pivot back to the home position before the next log arrives at the feeding device.
The movement damping element 20 is in the feeding device 1 arranged integrated in the link system and thus independently from the support operative to brake the return movement of the supporting arms to the home position according to Fig. 1, from the work position according to Fig. 2, wherein the supporting arms are pivoted outwards from the centre C of the feeding path in radial directions. For this function the movement damping element 20 is in one end thereof articulately journalled in a bracket 23 configured on the carrier 19 and serving as a first attachment point 24 for the movement damping element. In the opposite end the movement damping element 20 is articulately journalled in a bracket 25 configured on the second link 16 and serving as a second attachment point 26 for the movement damping element. Arranged in this way the movement damping element 20 is only activated/compressed as a result of the mutual pivoting movement of the links. More precisely the movement damping element 20 is activated or "charged" by means of reduction of the distance between the attachment points 24 and 26 as a result of the mutual turning of the carrier 19 and the link 16 in opposite turning directions about the pivot 17, during outwards pivoting of the supporting arms. In the corresponding way the braking force is internally adopted in the link system during extension of the distance between the attachment points 24 and 26 as a result of the mutual turning of the carrier 19 and the link 16 in inverted directions.
A modified embodiment of the above described feeding device is illustrated in Fig. 2. In this embodiment the spring element 21 has been deleted and is exchanged by a spring 27 that is merged with the movement damping element 20'. In general meaning the movement damping element 20' can be compared to a spring leg having a spring and a shock absorber in combination. The spring 27 may be constituted by a mechanical spring such as a coil spring, but may alternatively be constituted by an air spring or a spring filled with another compressible gas. In the modified embodiment the spring element that provides the necessary holding down force against the surface of the log is configured to act between the link 16 and the carrier 19, and is in other words like the movement damping element 20, 20' integrated in the link system.
An advantageous embodiment, the combined spring and movement damping element 20, 20' comprises a double cylinder 200 that is schematically disclosed together with the accompanying hydraulic in Fig. 3. The double cylinder 200 is in the corresponding way as the movement damping element 20 and 20' integrated in the link system of the feeding device, and may like these be arranged to act between the link 16 and the carrier 19.
The double cylinder 200 comprises a piston 201 having a piston rod 202 that is adjustable for adjusting the total length of the double cylinder and the distance between the link 16 and carrier 19 in this embodiment. For this function the piston 201 is served by a hydraulic circuit 203 that via a valve 204 regulates the volume of the two communicating cylinder chambers 205 and 206 which are separated by the piston 201 that is axially moveable in the double cylinder. Hereby the size of the opening between the feed cylinders 2-4 can be set to a home position or pre-opening position that is adapted to the thickness of the logs in question.
The double cylinder 200 thereto comprises a piston 207 having a piston rod 209 that presents the double functions of on the one hand dampen the return movement of the feed cylinders to the home position when a log leaves the feeding device, and on the other hand applying a holding down force that increase the contact pressure of the feed cylinders against the log during feeding through the feeding device. For this function the piston 207 is served by a hydraulic circuit 209 that via a valve 210 distribute the hydraulic liquid amongst the two communicating cylinder chambers 211 and 212 which are separated by the piston 207 that is axially moveable in the double cylinder. More precisely, the hydraulic circuit 209 comprises a non-return valve 213 that admit hydraulic liquid to unhindered flow from the chamber 211 to the chamber 212 via the valve 210 when the piston 207 moves in the direction from right to left in the drawings, as a result of the feed cylinders are pivoted outwards by the log entering between the feed cylinders. When the log leaves the feeding device and the feed cylinders are pivoted back, the piston 207 moves in the opposite direction, the hydraulic liquid pass back from the chamber 212 to the chamber 211 via the adjustable choking 214. Thereby the flow is braked and the movement of the feed cylinders is damped.
An accumulator 215 is connected in order to raise the working pressure in the hydraulic circuit 209 and applies a pressure that acts against the greater piston area of the piston 207 that is thereby biased in the direction from left to right in the drawings. Hereby the double cylinder 200 exercises a holding down force to the link system and to the feed cylinders 2-4. The size of the accumulator pressure may as an example be set to ca 3-3,8 MPa, the higher pressure being applied on the feeding side of the feeding device. The invention is of course not limited to this pressure range that is only given as an example. For completeness it shall be mentioned that the letter references P and T refer to connection conduits from a pump and to a tank, respectively. Other components that are needed for hydraulic medium supply and safety systems are left out from the drawings because their arrangement is not crucial for the invention and thereby does not demand for any detailed description.
In this context it shall be mentioned that the double cylinder 200 in an eminent way may be maneuvered to open the feeding device in connection with service. By corresponding setting of the valves 204 and 210 both pistons 201 and 207 may when needed be displaced to their outer end positions for maximum turning outwards of the feed cylinders 2-4, in order to offer the best possible access during service of the feeding device.
Without departing from the inventive idea an alternative embodiment of the feeding device may comprise that the movement damping element instead is mounted to act between the carrier 19 and the first link 13. Where appropriate the flow regulating valve may be realized having inverted function and configured to cause a braking of the movement of the link system during compression of the piston/cylinder unit.
In both embodiments the object to remove or essentially reduce the disadvantages of wear and fatigue caused by shocks or vibrations transferred to the support is fulfilled.

Claims

A feeding device for feed of log in the length direction of the log, comprising a support (8) having a through opening (12) and feed cylinders (2,3,4) adjoining the opening, which feed cylinders are angularly distributed and which are individually arranged in a free end of a respective supporting arm (5,6,7) and driven in rotation (R), and wherein the supporting arms in a supported end are journalled in the support on shafts (9,10,11) extending in parallel with each other and pivotable about the shafts between a home position and a pivoted work position, and wherein the supporting arms are mutually connected to each other via a system of articulated links (13,16,19) and by means of the links forced to pivot jointly about their respective shafts, characterized in that a movement damping element (20,20',200), which is separate from the support, is integrated in the system (13,16,19) of links and independently from the support configured to brake the return movement of the supporting arms to the home positions, wherein the movement damping element (20',200) is provided with a holding down element (27,215) operatively arranged between the links in the system (13,16,19) of links to apply a holding down force to the feed cylinders (2,3,4).
The feeding device according to claim 1, wherein the system of links comprises links (13,16) that are articulately connected between the supporting arms as well as a carrier (19) that is inserted between the links and articulately connected in relation to the links, characterized in that the movement damping element (20,20',200) is operatively connected between the carrier (19) and one of said links (16).
The feeding device according to claim 2, characterized in that the link (16) in question presents a bracket serving as an holder (26) for the movement damping element (20,20',200).
The feeding device according to claim 2 or 3, characterized in that the carrier (19) is constituted by a bracket serving as a moment arm pivoting together with the supporting arm (6), wherein the moment arm serving as a holder (24) for the movement damping element (20,20',200).
The feeding device according to claim 1, characterized in that the movement damping element (20') presents an integrated holding down element (27) in the form of a spring element.
The feeding device according to claim 1, characterized in that the movement damping element is constituted by a hydraulically driven double cylinder (200) comprising a piston (207) that is effected by a hydraulic holding down element (215) in the form of an accumulator.
The feeding device according to any preceding claim, characterized in that the movement damping element is a hydraulically driven double cylinder (200) comprising a piston (201) that is adjustable for setting a pre-opening position between the feed cylinders (2,3,4).