US 3036607 A
Description (OCR text may contain errors)
May 29, 1962 P. v. RAURA 3,036,607
METHOD AND DEVICE FOR CENTERING IRREGULARLY FORMED, SUBSTANTIALLY CYLINDRICAL WORKPIECES, SUCH AS LOGS Filed June 25. 1959 INVENTOR:
PENTTI VALD R RAURA Attorney United States Patent 3,036,607 METHOD AND DEVICE FOR CENTERING IRREG- ULARLY FORMED, SUBSTANTIALLY CYLIN- DRICAL WORKPIECES, SUCH AS LOGS Pentti Valdemar Raura, Kristinehamn, Sweden, assrgnor to Aktiebolaget Furuplywood, Kristinehamn, Sweden, a Swedish joint-stock company Filed June 25, 1959, Ser. No. 822,959 Claims priority, application Sweden July 1, 1958 2 Claims. (Cl. 144-209) This invention relates to a method and a device for centering irregularly formed workpieces, such as logs, which are to be treated, e.g. turned, around a predetermined center line.
When veneer is to be turned from wood logs, a center line for the log is, as a rule, determined by the eye in connection with fixing the workpiece in the lathe with help of mechanical lifting appliances or manually. Certain simple hand tools are also used for finding this center line. However, in some cases, for certain kinds of wood, a center line is used which is displaced in relation to the geometrical center line of the log, substantially with a view to obtaining certain wood-technical effects.
The logs which are cut from a trunk, obtain a form which very nearly can be described as a truncated cone, which complicates the centering. When the trunk, as often occurs, is crooked also the log will, to a certain extent, suffer from this drawback. Furthermore, there may also be other formal defects, viz. root folds and great surface and bark damages. As already mentioned, one has, by the eye, tried to pay regard to these errors when fixing the log in a veneer lathe. The intention is to obtain the greatest possible yield from the log, i.e. to obtain a log of cylindrical form when turning and with the least possible waste of material, and thus the greatest possible quantity of whole, single veneer.
The device described below is designed in such a mannor that at the same time as it lifts the log into the veneer lathe, it automatically determines the desired center line and corrects the errors usually occurring in logs, such as crookedness, conicity and great surface defects.
The invention is substantially characterized in that the center is determined in two cross sections located at a certain distance from the ends of the workpiece, starting from three points on the periphery of each cross section, raising the workpiece while it is supported at two points so that the center of each cross section follows a definite line and, when the center has reached a definite position, stopping the workpiece by means of an impulse supplied by a feeling member when said feeling member which is displaced in dependence upon the lifting movement and in the opposite direction, travels towards the workpiece and forms the third point on the periphery of the cross section.
Furthermore, the invention relates to a device for finding the center, which is characterized by two independent lifting devices, each supporting the workpiece at a definite distance from the ends of the workpiece, and each comprising a feeling member adapted to be actuated by the workpiece and guided by the respective lifting device, said feeling member stopping the movement of the lifting device when the workpiece has reached the desired position. Each lifting device may be provided with a lifting member which is designed as an arm on which the workpieces rest, and thus serves as a magazine. That part of the lifting member which supports the workpiece, is so designed that the circle center determined by the supporting points and the third point is located in a definite position. If there are errors in the workpiece which the device does not pay regard to, the centering is cor- 3,036,607 Patented May 29, 1962 rected by raising or lowering the common center point of the lifting and feeling members. When the feeling member has reached its highest position, it is turned for removal of the core and for replacing of the lathe tool. A feed device located on the arm feeds a workpiece one at a time.
An embodiment of the invention will be hereinafter described, reference being bad to the accompanying drawing, in which- FIG. 1 is a lateral elevation of the device,
FIG. 2 an end view,
FIG. 3 a plan view, and
FIG. 4 a feed device.
The workpiece 1 is placed on two spaced arms 2 whereafter it slides, by its own weight, along the arms towards a feed device comprising a part 3 which is so designed that it feeds a workpiece when it is actuated by a force P through a bar 5. A force F is, through bars 6, transmitted to the arms 2 so that the latter raise the workpiece and the movement of the arms is transmitted by link arms 7, 8 and 9 to a bar 11 guided by rollers 10. On said bar 11 there is fixed a feeling member 12 provided with a cross piece 13 which is tangential to the periphery of the workpiece. The impulse supplying part or cross piece 13 of the feeling member 12 acts as a contact element which is operatively connected to the means for moving arms 2 and is arranged to stop the lifting movement of the said arms at contact with the workpiece 1. With regard to quality defects the centering may be controlled by raising or lowering the lifting and feeling members. This takes place by means of a bar 14 which actuates a bellcrank lever 15 in such a manner that the link arm 8 mounted thereon can be displaced in the vertical direction.
Fundamentally, the device determines the center points in two cross sections of the log if the cross section is circular. In reality the cross sections are slightly elliptical or irregular, but in practice this is of no importance because the device determines the center, starting from three different tangent lines to the periphery of the cross section. When the shape of the log is a straight truncated cone, its center line is obtained by determining the center points in two cross sections taken arbitrarily on the log. If the shape of the log is a curved truncated cone, its center line is found with sufficient exactness by determining the center points in two cross sections located at a fourth of the total length of the workpiece from each end.
The lifting movement is obtained either hydraulically, pneumatically or electrically or in some other suitable manner or by these methods in combination.
The device is preferably remote-controlled so that the machine operator starts the lifting movement while the centering itself and the return movement of the device take place automatically.
What I claim is:
1. A device for centering workpieces having a substantially cylindrical, but irregular, cross section in a lathe, comprising two independent lifting devices, each of said lifting devices comprising an arm which is pivotally supported at one end and which, at the other end, is shaped such that it will support a substantially cylindrical workpiece at two points on the periphery of the workpiece and at a definite distance from the ends of the workpiece, said pivotally mounted arms being adapted to support additional workpieces and thus serve as a magazine for feeding workpieces to the lathe, and each lifting device also comprising a feeling member, lever means connecting each of said feeling members to the respective lifting device, the construction and arrangement being such that each feeling member is displaced 3 downward when the lifting device lifts the workpiece through an arcuate path, and is so actuated by said workpiece that, when the feeling member contacts the workpiece, it supplies an impulse which stops the lifting movement when the workpiece is centered in the lathe.
2. A device as claimed in claim 1, characterized by a feed device arranged on the arm for feeding a workpiece one at a time.
References Cited in the file of this patent