Cutting – By endless band or chain knife – With means to guard the tension
Patent
1994-11-08
1996-07-09
Peterson, Kenneth E.
Cutting
By endless band or chain knife
With means to guard the tension
30386, B27B 1714
Patent
active
055334326
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a saw assembly comprising a bar mounted in a holder, said holder being pivotable about a shaft; a saw chain running around the bar; a saw motor driving the saw chain; a cylinder to feed the bar in and out during rotation about said shaft; a hydraulic circuit system in which said saw motor and cylinder for feeding in and out are included; a displaceable unit including said bar and mounted on said bar holder to displace the bar in relation to the bar holder in a direction corresponding to the longitudinal centre line of the bar and which is perpendicular to said axis of rotation; and a first hydraulic piston cylinder member which is arranged to be activated by said hydraulic circuit system and displace the unit in relation to the bar holder so that during operation of the saw assembly the bar in the unit automatically stretches the saw chain.
In saw assemblies of the type described above, included in various types of felling aggregates for processors, the saw chain must be stretched in order to reduce the risk of it being Jerked off the bar and to position the chain correctly around the bar. In practice this stretching must be performed manually several times during each work shift. Despite repeated manual stretching the saw chain is frequently jerked off and thrown with considerable force from the felling aggregate. It is often difficult or even impossible to find the saw chain again. An automatic stretching device is known through SU-745 400. This stretching device is in the form of a hydraulic cylinder connected by one end to the bar holder and by the other end to the bar. The clearance normally existing between the constructional elements permits movements of the bar directed perpendicularly to the bar plane. Such movements are not desirable since they may cause the bar to become wedged and break during sawing.
The object of the present invention is to provide a saw assembly which enables automatic stretching of the chain while at the same time allowing the bar to be secured in a controlled manner.
The invention is substantially characterized in that the displaceable unit comprises a block element arranged on the side of the bar holder facing away from the bar, and joined to an inner bar attachment supporting the bar, a small gap thus being formed between opposing surfaces of the bar holder and block element, that the first piston cylinder member is arranged in the block element with its piston rod protruding therefrom to abut against a support surface of the bar holder, and that a second hydraulic piston cylinder member is arranged in the block element, parallel with said shaft, the piston rods of the piston cylinder member being arranged to abut against the bar holder with a predetermined total tension force in order, during normal operation, to fix the movable unit to the bar holder and eliminate the clearance produced by said gap, said tension being less than the stretching force created by the first piston cylinder member, whereby the second piston cylinder member is influenced by the pressure in said hydraulic circuit system.
The invention will be described further with reference to the accompanying drawings.
FIG. 1 is a hydraulic system included in a saw assembly according to the invention.
FIG. 2 is a lateral view of part of a saw assembly according to the invention, including the hydraulic system shown in FIG. 1.
FIG. 3 is an end view of a saw assembly according to FIG. 2 seen from the end of the saw chain.
FIG. 4 is a longitudinal section through the lubricating oil pump included in the hydraulic system according to FIG. 1.
FIG. 5 is an end view of a nipple arranged at the inlet end of the lubricating oil pump according to FIG. 4.
FIG. 6 is an end view similar to that in FIG. 3, of a saw assembly according to a second embodiment of the invention.
The hydraulic circuit diagram illustrated in FIG. 1 comprises two directional valves 1 and 2, which inter alia connect and disconnect two tilt cylinders 3 and a saw motor 4, and a gripping cylinder 5 of a saw assembly,
REFERENCES:
patent: 3279508 (1966-10-01), Ehlen et al.
patent: 4382334 (1983-05-01), Reynolds
patent: 4915317 (1990-04-01), Birch
patent: 5396705 (1995-03-01), Leini
Hultdin Invest AB
Peterson Kenneth E.
Pryor Sean A.
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