WO1992018305A1

WO1992018305A1 - Gas spring for barking machines

Info

Publication number: WO1992018305A1
Application number: PCT/SE1992/000245
Authority: WO
Inventors: Börje Persson; Lennart Magnusson; Per-Åke Wiklund
Original assignee: Söderhamns Verkstäder Ab
Priority date: 1991-04-23
Filing date: 1992-04-15
Publication date: 1992-10-29
Also published as: AU1674992A; DE4291090C2; SE468311B; DE4291090T1; SE9101219D0; SE9101219L

Abstract

A gas spring for barking machines comprises at least one elastic cushion or bellows (12, 12') which is filled with gas and operates between a stationary abutment (13) on a rotor of the machine and a supporting plate (15) connected to a driver means (18) of a tool shaft (9) by an articulation (17). The supporting plate (15) is connected to a control means (19) which is laterally removed from the articulation (17) and which engages, and is movable back and forth along, a guide means (20), the control means (19) and the articulation (17) being compelled to move jointly towards and away from the abutment while guiding the supporting plate substantially parallel to the abutment.

Description

GAS SPRING FOR BARKING MACHINES

Field of the Invention

This invention relates to a gas spring for barking c 5 machines comprising a stator and a rotor to which are connected a number of pivotable processing tools each arranged on a shaft which is rotatably mounted in the rotor and which, via a torque-transmitting driver means, is operable by the gas spring to keep the tool yieldably

10 applied against a log passing through the machine in operation, said gas spring comprising at least one elastic cushion which is filled with gas and operates between a stationary abutment on the rotor, e.g. a peripheral wall, and a movable supporting plate directly

15 or indirectly connected to the driver means of the tool shaft by an articulation which describes an arcuate path of movement when the shaft is rotated. Description of the Prior Art

In gas springs of this type, it is of the utmost

20 importance that the supporting plate for the elastic cushion(s) filled with gas is maintained substantially parallel to the opposing abutment, regardless of the degree of compression, and shows no tendency to pivot drastically about the associated articulation. If the

25 supporting plate were to pivot considerably relative to the articulation, and thus be sharply inclined relative to the centre axis of the cushions, the latter would become deformed. As a result, the cushions would no longer function satisfactorily and be rapidly worn. It

30 should here be pointed out that a gas spring of this type operates extremely rapidly, since the individual process¬ ing tool connected to and operated by the spring has to f. follow the irregular circumferential surface of a log being longitudinally fed at considerable speed through

35 the machine. To prevent the supporting plate from pivot¬ ing about the associated articulation, the prior art provides a construction in which the underside of the supporting plate is equipped with an angular arm which projects laterally from the articulation and whose free end is articulated to one end of a link, the opposite end of which is articulated to an attachment on an internal cylinder wall of the rotor. More precisely, the angular arm projects from the articulation on that side which is opposite to the tool shaft. During its pivotal movements, the supporting plate is so positively guided by the angular arm and the link in relation to the back-and- forth movable driver means on the tool shaft that it is maintained substantially parallel to the abutment of the spring cushions, regardless of the pivotal position of the driver means. In practice, this construction is, however, impaired by the inconvenience that the articula- tions of the link are unable to withstand the severe strain caused by the extremely rapid movements back and forth of the shaft and the driver means. Consequently, articulations of this type have a short service life. Although the articulations are inexpensive, it takes quite a long time to replace them. Thus, the short service life of the articulations results in costly and recurrent stoppages. Object of the invention

The present invention aims at obviating the above inconveniences and providing a gas spring whose different components function satisfactorily for a long time. A basic object of the invention is, therefore, to dispense with the previously-required link and associated articu¬ lations and provide a gas spring in which the control means for the supporting plate are not affected by the rapid movements taking place. Summary of the invention

According to the invention, this object is achieved by a gas spring which is characterised in that the supporting plate is connected to a control means which is laterally removed from the articulation and which engages, and is movable back and forth along, -a guide means, said control means and said articulation being compelled to move jointly towards and away from the abutment while * guiding the supporting plate substantially parallel to

) said abutment.

5 According to the invention, the control means advantageously is a rotatable roller. Conveniently, the guide means is composed of two spaced-apart plates projecting from the peripheral wall of the rotor radially into the rotor, said control means being arranged on a 10 projection which juts out sideways from the supporting plate. Brief description of the drawings

In the drawings, Fig. 1 is a longitudinal section of a machine housing, 15 showing the upper half of a stator forming part of a barking machine which also includes a rotor, Fig. 2 is a cross-section of the upper half of the rotor of the machine, illustrating a gas spring according to the invention which is mounted in the 20 machine and occupies a first operating position, and Fig. 3 is a similar cross-section illustrating the gas spring in a second operating position. Description of the preferred embodiment 25 Fig. 1 shows a stator 1 which comprises a substan¬ tially vertical, annular end wall 2 and, rigidly connected thereto, a cylinder wall 3 defining a central opening 4 through which the logs are longitudinally fed. A rotor 5 is rotatably mounted on the outside of the cylinder wall 30 3. This rotor is composed of front and rear end walls 6 i and 7 which are interconnected by a peripheral, outer cylinder wall 8, thereby forming a rigid unit. Between the two end walls 6, 7 extends a rotatably mounted shaft 9 whose one end projects through the front end wall 6 and 35 supports a processing tool 10. This tool is an arcuate arm whose free end may support a releasable cutting or processing means. To keep the tool arm 10 resiliently applied against a log (not shown) passing through the opening 4, a gas spring 11 is provided inside the rotor 5.

Figs 2 and 3 illustrate the gas spring 11 which in this case includes an elastic bellows which is filled with gas and comprises two cushion-like elements 12, 12'. One end of the bellows construction is applied against an abutment in form of a bottom 13 of a seat 14 in the cylinder wall 8 of the rotor. The opposite end of the bellows construction is applied against a supporting plate 15. On the underside of this plate is provided a support member 16 which, by an articulation 17, is connected to a driver means 18 which is non-rotatably connected to the tool shaft 9. The driver means, which projects a short distance perpendicular to the tool shaft, serves as a torque-transmitting arm converting the axial expansive force of the gas spring 11 into a torque acting on the shaft 9 and at all times striving to pivot the tool shaft 10 towards an inner end position or into contact with a log passing through the opening 4. The bellows is filled with gas, e.g. air, initially having a fairly moderate pressure, e.g. 3 or 4 bar. Naturally, the gas pressure increases when the bellows is compressed owing to the tool arm 10 being swung outwards.

It should be observed that the tool arm 10 is, in Fig. 2, shown in an inner end position in which the bellows is maximally expanded. In Fig. 3, on the other hand, the tool arm 10 is outwardly swung to an outer end position in which the bellows is maximally compressed.

According to the invention, the supporting plate 15 is connected to a control means 19 which is laterally removed from the articulation 17 and which engages a guide means 20. This guide means is advantageously composed of two spaced-apart plates 21, 21' projecting radially from the inside of the cylinder wall 8. These plates define an elongate gap 22. In practice, the control means 19 advantageously is a roller rotatably mounted on the free end of a projection 23 which juts out in the extension of the supporting plate 15 (see Fig. 3). The projection 23 may be either a simple finger or a fork whose two prongs

* grip one guide plate 21 and jointly support a shaft for 1 the roller 19. ⁱ 5 The distance between the articulation 17 and the control means 19 is always the same, these two components being rigidly interconnected. When the articulation 17 moves along its arcuate path about the shaft 9, the control means or roller 19 will, therefore, positively

10 guide the supporting plate 15 so that the latter is kept in a position substantially parallel to the abutment 13 and does not pivot drastically about the articulation. As illustrated in Figs 2 and 3, the supporting plate 15 is, in its two end positions, slightly inclined relative to an

15 axial line through the bellows construction, but this slight inclination is fully acceptable, since it does not cause any substantial deformation of the bellows. Conveniently, the bellows is made of rubber. It goes without saying that the invention is not

20 restricted to the embodiment described above and shown in the drawings. Thus, it should be emphasised that the gas spring is shown together with a barking machine having a special, and preferred, mechanism for setting the barking tools in different stand-by positions. However, the gas

25 spring according to the invention is not restricted to use in this particular type of barking machines, but may be used in all machines encompassed by the preamble to appended claim 1. It should be added that the described gas spring can be modified in many ways as to the position

30 and the design of the guide means and the control means. Thus, the guide means may, in some machines, be provided on an inner cylinder wall of the rotor and be arranged in another direction than the radial one. Thus, the control means may be disposed on an auxiliary arm projecting

35 obliquely inwards from the underside of the supporting plate, and engage an inclined guide means in the area between the bellows and an inner cylinder wall of the rotor.

Claims

1. A gas spring for barking machines comprising a stator (1) and a rotor (5) to which are connected a number of pivotable processing tools (10) each arranged on a shaft (9) which is rotatably mounted in the rotor and which, via a torque-transmitting driver means (18), is operable by the gas spring (11) to keep the tool yieldably applied against a log passing through the machine in operation, said gas spring comprising at least one elastic cushion or bellows (12, 12') which is filled with gas and operates between a stationary abutment (13) on the rotor, e.g. a peripheral wall, and a supporting plate (15) connected to the driver means (18) of the tool shaft by an articulation (17) which describes an arcuate path of move¬ ment when the shaft is rotated, c h a r a c t e r i s e d in that the supporting plate (15) is connected to a control means (19) which is laterally removed from the articulation (17) and which engages, and is movable back and forth along, a guide means (20), said control means (19) and said articulation (17) being compelled to move jointly towards and away from the abutment (13) while guiding the supporting plate substantially parallel to said abutment.

2. A gas spring as claimed in claim 1, c h a r a c ¬ t e r i s e d in that the control means is a rotatable roller (19).

3. A gas spring as claimed in claim 1 or 2, c h a - r a c t e r i s e d in that the guide means (20) is composed of two spaced-apart plates (21, 21') projecting from the peripheral wall (8) of the rotor radially into the interior of the rotor, said control means (19) being arranged on a projection (23) which juts out sideways from the supporting plate (15).