Patent Grant
5005621
This application is related to copending application Ser. No. 278,778, filed Dec. 2, 1988, now abandoned, and the disclosure thereof is incorporated herein by reference. This invention relates to improvements in rotating drum debarkers for removing bark from logs and similar roundwood, particularly long roundwood. More particularly, the invention relates to improved reinforcing ring and log lifter arrangements which reduce flailing of logs and improve the movement or flow of long logs into and through the drum, when fed from a conveyor or inclined chute in front of the drum, but which also work well with any length logs. Rotating drum debarkers of the type having lifters in the form of circumferentially spaced apart projections extending inwardly from the inner surface of the drum shell are well known. A typical debarking drum takes the form of a relatively thin cylindrical shell with the lifters welded to the inside of the shell, and with slots in the wall of the shell in the regions between the lifters for discharging removed bark from the drum. The lifters extend the length of the shell and serve to stiffen and reinforce the shell. A typical lifter takes the form of a length of U, V, or L shaped angle iron or channel with the ends of both its legs welded to the inside of the shell so the tip or peak of the lifter points toward the axis of the drum. A stiffening or reinforcing ring is secured to each end of the drum, and the ends of the lifters are usually welded to the inner side surfaces of these rings. Thus, the lifters cooperate with the shell and the reinforcing rings to provide a beam reinforced skin structure which is quite strong even though the shell skin or side wall of the drum is relatively thin. In the past, roundwood was cut to relatively short lengths for drum debarking because the short lengths were easy to handle with the available equipment. The trend today is toward debarking of tree length logs, to enable obtaining as much usable lumber as possible, and to provide long lengths which can be chipped more efficiently for pulpwood use, where the logs after debarking, are found to be unsuitable for use as lumber. In the past, the reinforcing ring provided at the inlet and outlet ends of the drum had an inside diameter less than the diameter of the circle defined by the tips of the lifters, and covered the ends of the lifters. Logs entering the drum could then roll on the inside of the ring before engaging the lifters, and the ring at the outlet end served the additional purpose of providing a dam to restrict the flow of logs from the drum in order to provide more time in the debarking drum for debarking. Such a drum arrangement is not satisfactory for use with long roundwood fed, for example, by a conveyor or chute in front of the drum, either to a single drum debarker, or to a debarker with two drums, one downstream of the other, which are rotated in the same or in opposite directions during debarking. Long logs partly in the drum tend to roll around the inlet ring so their trailing ends flail and gyrate, and some gyration and clogging occurs at the outlet. In a two drum arrangement the logs sometimes roll and sometimes slip on the rings at the discharge end of the first drum and the inlet end of the second drum, with resulting decreased debarking efficiency. In accordance with the invention, it has been found that flailing and gyration of the trailing ends of logs fed part way into the debarking drum from a conveyor in front of the drum can be decreased by providing means adjacent the inlet of the drum for intermittently engaging and displacing logs inwardly away from the inside surface of the drum. These means can take the form of inwardly projecting portions of the lifters and/or the reinforcing ring adjacent the inlet of the drum. It has been found, in accordance with one aspect of the invention, that improved debarking of logs fed from a conveyor or chute in front of the drum is obtained where the reinforcing ring at the drum inlet and/or outlet has an inside diameter greater than the free inside diameter of the drum, i.e. the diameter of a circle passing through the tips or radially innermost portions of the log lifters, so that the lifters are exposed to engage and agitate logs entering and leaving the drum. It has been found, in accordance with another aspect of the invention, that improved debarking is obtained where the reinforcing ring at the inlet and/or outlet of the drum has an inside diameter greater than the free inside diameter of the drum, but less than the inside diameter of the drum shell, so that at least portions of the lifters are exposed at the inlet and outlet to agitate and displace logs entering and/or leaving the drum. It has further been found, according to the invention, that the rings of existing drums can be modified for improved debarking by cutting away or scalloping the reinforcing rings at the inlet and/or outlet of the drum, so that the diameter of the ring between lifters is greater than the diameter of a circle passing through the log engaging portions of the lifters, but less than the inside diameter of the drum shell. For a new drum being constructed, it is preferred to cut the ends of the lifters at an angle so they slope outwardly toward the inside of the drum shell, particularly at the inlet end of the drum. However, where the ring (or rings) of an existing drum is modified by scalloping the ring, good infeed and discharge are obtained, with minimal flailing of the logs, or clogging at the outlet. It is preferred, in accordance with the invention to make the reinforcing ring of a larger outside diameter than the outside diameter of the drum. It is thus an object of the invention to provide an improved reinforcing ring arrangement for a drum debarker in which the reinforcing ring adjacent at least one end of the drum has an inside diameter greater than the free inner diameter at the peaks of the lifters. It is another object to provide an improved reinforcing ring arrangement for a drum debarker in which the reinforcing ring adjacent at least one end of the drum has an inside diameter larger than the free inner diameter at the peaks of the lifters, but smaller than the inside diameter of the shell of the drum. Another object is a reinforcing ring and lifter arrangement in which the inside of the reinforcing ring adjacent at least one end of the drum is scalloped in the regions between selected adjacent lifters. Another object is a reinforcing ring and lifter arrangement in which the ends of the lifters diverge at the ends of the drum and slope outwardly from the peaks of the lifters toward the inner surface of the drum, and can be welded to the rings. A further object is a reinforcing ring and lifter arrangement in which the ends of the lifters are cut at an angle and are covered with sloping plates. Another object is a method of modifying an existing drum by removing portions of the reinforcing ring between lifters, and if required, adding a reinforcing ring to the outside of the drum, adjacent the inlet and/or outlet to further strengthen the drum. Another object is a debarking drum having means adjacent the inlet thereof, for displacing logs fed from a conveyor in front of the drum away from the inner surface of the drum inlet. Another object is a method and apparatus for enhancing the flow of logs into and through a debarking drum by agitating the logs as they pass through the inlet of the drum. Another object is a method and apparatus enhancing the flow of logs from a debarking drum by agitating the logs as they pass through the outlet of the drum. Another object is a method and apparatus for removing long logs from a debarking drum by agitating the logs as they pass through the outlet of the drum and pulling partly discharged logs from the drum with a conveyor at the outlet of the drum. Another object is a method and apparatus for removing long logs from a debarking drum by pulling partly discharged logs through the outlet of the drum with a conveyor which slopes away from the outlet of the drum, either with or without agitating the logs as they pass through the outlet of the drum. Another object is a two drum debarking apparatus having debarking drums in accordance with one or more of the above objects. Other features and advantages of the invention will become apparent from the drawings and the detailed description which follows.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3020943 | Hjartsater | Feb 1962 | |
| 3262477 | O'Brien | Jul 1966 | |
| 3286747 | Delcellier | Nov 1966 | |
| 3301289 | Hanson | Jan 1967 | |
| 3783918 | Simpson | Jan 1974 | |
| 4374533 | Svensson | Feb 1983 | |
| 4774987 | Sepling | Oct 1988 |
