Woodworking – Feeder or presser
Reexamination Certificate
2000-02-09
2001-04-10
Bray, W. Donald (Department: 3725)
Woodworking
Feeder or presser
C083S435110, C144S002100, C144S003100, C144S039000, C144S369000, C144S246100, C144S248500, C144S357000
Reexamination Certificate
active
06213176
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a device for working of tree trunks to produce squared timbers from them with a machining center, with a feed section which is located in front of the machining center viewed in the machining direction, and with a delivery section which viewed in the machining direction is located after the machining center, and with grippers which can be moved relative to the machining center on carriages in the feed section for pushing the tree trunks to the machining center.
DESCRIPTION OF THE RELATED ART
UP 5 28 490 A discloses a device for working of tree trunks with a machining center, with a feed section and a delivery section in which there is a gripper for supplying the tree trunks to the machining center.
SUMMARY OF THE INVENTION
The object of the invention is to make available a device of the initially mentioned type with which with a high throughput and with a structural length of the device which is as short as possible at the same time tree trunks can be machined by trimming, for example into square beams, square beams with bevelled edges or into the octagonal beams.
This object is achieved using a device which is characterized by the fact that at least two grippers are fork tongs, that each gripper has two sides which are joined to one another to swivel around a common axis which is located underneath the axis of the machining center, that the sides of the grippers are supported to swivel on extension arms which point downward from the carriages, that the grippers can be closed by swivelling their sides concentrically to the center axis of the machining center, and that the tree trunks are held by the sides of the gripper with an axis which lies essentially in the axis of the machining center.
In the device of the invention tree trunks are supplied to the machining center, for example using chain conveyors, the feed section and from the feed section. In the machining center the tree trunks are worked into squared timber of the shape and dimensioned as desired at the time. For example square beams, square beams with oblique edges, square beams with rough edges or for example octagonal beams can be produced.
In the feed section of the device of the invention there are movable, tong-like grippers with which the tree trunks are supplied to the machining center. The grippers can be set up such that they hold a tree trunk during feed into the machining center, it being guaranteed by the shape and design of the grippers that the grippers close concentrically to the center axis of the machining center and guide the tree trunk independently of its diameter, such that the axis of the tree trunk is essentially in the axis of the machining center.
The sides of the gripper which engage the tree trunk are supported to swivel around one axis which can have a distance as large as possible from the axis of the machining center, so that the parts of the sides of the gripper which engage the tree trunks move along a circular path with a large radius so that in the affected area of motion of the sides of the gripper the deviation from linear motion is negligibly small.
To open and close the sides of the grippers hydraulic cylinders can engage the sides formed lengthwise via levers.
The grippers (there are at least two such grippers) are mounted on carriages. The carriages can move preferably on a bed. Here an embodiment is preferred in which only the gripper which is farther from the machining center is coupled to a drive, for example a rack-and-pinion gear, since the other gripper is moved along the bed by engagement with the tree trunk which is supplied to the machining center. In one practical embodiment it is preferably provided that the carriages can move on guide rails which are provided on a bed-shaped frame.
Reliable movement of the fork tongs of the grippers arises in the invention when there is a hydraulic cylinder which engages the sides via two push rods to adjust the sides of the grippers.
In another embodiment the sides of the grippers have V-shaped recesses with edges which can be placed against the tree trunk to be held. Here it is preferred if the center of the surface which is bounded by the V-shaped recesses in the sides of the grippers is in the axis of the machining center. In this embodiment it can be provided that the lower edges of the V-shaped recesses are longer than their upper edges. It is advantageous when the lower, longer edges of the V-shaped recesses in the sides of the grippers, especially when the latter are placed against the tree trunk, can overlap one another, for which the sides of the grippers are supported offset laterally for example on the carriages or the sides can be made bent at right angles.
In the invention it can be provided that the sides of the grippers, especially on their upper edges, carry optionally driven reversible rolls for a tree trunk. This embodiment makes it possible to turn a tree trunk which has been placed on the still closed grippers such that it assumes the position which is most favorable for producing beams in the machining center. For example, the tree trunk is turned until deformities or curves of the tree trunk which are present anyway have been set into a favorable position. These optionally driven rollers can also be located in the area of the lower edges of the V-shaped recesses in the sides of the grippers.
To achieve automatic closing of the grippers, it can be provided that an operating lever is assigned to at least one of the grippers in the area of its bit which is formed by the V-shaped recesses in the sides and the lever triggers actuation of the hydraulic cylinder to close the grippers. In doing so it can still be provided that the operating lever is connected to a valve which joins the hydraulic cylinder of the gripper to a storage tank for the hydraulic fluid.
Preferably the grippers are positioned in the initial position in which they are supplied with a tree trunk such that they grasp the tree trunk to be worked in the area of its ends. Automatic triggering of advance of the tree trunk after it is inserted into the grippers can take place for example such that the increase of pressure in the hydraulic medium which actuates the actuating cylinder for the gripper sides after closing of the grippers—if therefore one tree trunk is held by the grippers—is used in order to open a pressure-dependent valve which triggers the drive for the advance motion for the gripper carriages.
Here it is preferable if the advance motion begins with a time delay so that enough time remains to position the cutting tools according to the desired machining result.
In one embodiment of the invention it is provided that a feed drive for positioning the grippers in the direction to the machining center is assigned to at least one of the two carriages.
One economical embodiment arises when solely the carriage which carries the gripper which is located farther from the machining center is coupled to a feed drive.
Automatic interruption or shutdown of the advance of the gripper arises when a sensor is assigned to the gripper which is nearer the machining center and when the gripper or its carriage runs against the machining center, the sensor causes the sides of this gripper to be released from the tree trunk. In addition, it can be provided that a sensor is assigned to the carriage which carries the gripper which is located farther from the machining center and when the carriage runs against the carriage of the gripper which is located nearer the machining center, the sensor shuts down the feed for this carriage.
As soon as the gripper which is located nearer the machining center has reached the feed-side end of the machining center, for example a spring-loaded test finger triggers the opening of this gripper and the gripper remains stationary with the opened sides which therefore do not further engage the tree trunk near the machining center (inlet side). Guidance of the tree trunk now is assumed by the machining center itself and the gripper which is farther from the machining center cont
Sanborn Dale
Wolf Johann
Bray W. Donald
Young & Thompson
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