Automatic press roll control

Details Automatic press roll control Automatic press roll control

2001-03-14

2003-06-03

Bray, W. Donald (Department: 3725)

Woodworking

Process

Including monitoring of operation

C144S116000, C144S117100, C144S242100, C144S248200, C144S248400, C144S402000, C198S781060

Reexamination Certificate

active

06571839

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates generally to planers and infeed tables. More specifically, this invention relates to position and pressure control of planer and infeed table press rolls.
A planer provides a smooth finish on up to four sides of rough lumber that has been produced by a saw mill. Referring to
FIG. 1
, a typical high speed, high production planer
10
includes multiple press rolls
20
. The press rolls
20
drive the wood through high speed blades, called “cutter heads,” which cut a smooth surface on the wood. These press rolls
20
must be accurately positioned in order to appropriately engage wood being fed into the planer
10
. The press rolls
20
must also apply a significant amount of downward force on the wood passing underneath them to create the traction required to push the wood through the planer's cutting heads.
A common way to provide positional and pressure control over the press rolls
20
is to use either a stacked hydraulic cylinder
30
or a jack screw and spring (not shown). These methods, however, do not provide position or force indication and require manual intervention when the roll
20
position or tension forces need to be adjusted. As a result, using these methods, the force exerted on the wood is difficult to accurately control and adjusting the pressure settings during operation is unreliable. In addition, these prior designs allow excessive forces to be experienced by the components in the press roll tower assembly
21
during operation, resulting in undue wear and premature failure of the roll tower
21
components.
The ideal function of an infeed table is to present a continuous ribbon (end to end) of wood into the planer
10
. Referring to
FIG. 2
, a typical infeed table
110
also includes multiple press rolls
120
. The center press rolls are arranged in a powered hold down
124
. Referring to
FIGS. 1 and 2
, in operation, wood transitions horizontally into the deck area
126
of the infeed table
110
, where it is grabbed by the first set of press rolls
122
, called “pineapple rolls,” and directed lengthwise towards a planer entrance
12
(see FIG.
1
). The feed rolls
120
on the table run faster than the press rolls
20
in the planer
10
to allow the wood to “butt up” end to end before entering into the planer
10
through its entrance
12
. Unfortunately, conventional infeed tables, such as infeed table
110
, require operator intervention to adapt to various board thicknesses. Conventional infeed tables also lack a reliable way to control the position and pressure of the press rolls.
Referring to
FIG. 3
, a conventional hydraulic actuation system for modifying the position and pressure of the press roll
20
of
FIG. 1
includes a double hydraulic cylinder
30
and various control components. Four way directional control valves
34
are provided for each cylinder. A flow control valve
37
and a dual pilot operated check valve
33
are mounted inline with the four way directional control valve
34
for the bottom cylinder. A pressure reducing valve
35
is mounted inline with the four way directional control valve for the top cylinder. An accumulator
32
and pump
39
are also provided. Fluid flow is directed between the bottom
38
and top
36
of each cylinder to control actuation of the press roll
20
.
SUMMARY OF THE INVENTION
One aspect of the present invention is to enable a press roll assembly that provides reliable control over press roll position and pressure.
Another aspect of the present invention is to enable a press roll assembly that automatically adapts to various board thicknesses.
According to the foregoing aspects of the present invention, a press roll assembly includes a press roll adapted to exert a pressure on wood passing through a device, such as a planer or an infeed table. A controller is configured to control a position of the press roll and the pressure exerted by the press roll. A position sensor senses the position of the press roll and transmits a signal corresponding to that position to the controller. A pressure sensor measures the pressure being exerted by the press roll and transmits a signal corresponding to that pressure to the controller. A press roll actuator, preferably comprising a single hydraulic cylinder and hydraulic servo valve, can also be provided to move the press roll based on electrical signals from the controller. The press roll assembly of this invention can be automated to automatically adjust the position of the press roll and the pressure exerted by the press roll on wood. A planer or infeed table preferably comprises a plurality of these press roll assemblies, wherein each of the press roll assemblies can be independently controllable.
A method of automatically controlling a position and pressure of a press roll is provided by another aspect of this invention. The position of the press roll is sensed and the position can then be automatically and dynamically adjusted toward a desired position. The desired position can be based on user-defined set points. The desired position can also be automatically determined based on sensed board thickness. Similarly, the pressure being exerted by the press roll is sensed and the pressure can then be automatically and dynamically adjusted toward a desired pressure.
Upgrading an existing device, such as a planer or infeed table, to provide automatic control of press roll position and pressure is accomplished by retrofitting the existing device with a force and position controller. A position sensor is also provided to measure the position of the press roll and to communicate the position of the press roll to the controller. A pressure sensor is provided to measure the pressure exerted by the press roll on wood travelling through the device and to communicate the measured pressure to the controller. A communications interface is provided to permit communication between the controller and existing circuitry. The existing circuitry, for example, could be a Programmable Logic Controller (PLC) and an Operator Interface, including both a Human Machine Interface (HMI) and switches.
Once configured, the force and position controller can control the position and pressure of the press roll based on signals received from the position and pressure sensors. Pressure and position adjustment of the press rolls can be accomplished, for instance, through use of an actuator that adjusts the position and pressure of the press roll based on controller signals. In a preferred embodiment, the actuator comprises a single hydraulic cylinder and a servo valve, wherein the servo valve is arranged in electrical communication with the controller. dr
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing objects, features, and advantages of the present invention will become more readily apparent from the following detailed descriptions of various preferred embodiments, made with reference to the following figures, in which:
FIG. 1
is a side elevation view, with cutaways, of a planer according to the prior art.
FIG. 1A
is a side elevation view, with cutaways, of a planer according to one aspect of the invention.
FIG. 1B
is an enlarged perspective view of a hydraulic cylinder attached to a press roll for adjusting the position and pressure of the press roll.
FIG. 2
is a side elevation view of an infeed table according to the prior art.
FIG. 2A
is a side elevation view of an infeed table according to another aspect of this invention.
FIG. 3
is a somewhat schematic illustration of an actuation system for adjusting a position of and pressure exerted by a press roll according to the prior art.
FIG. 3A
is a somewhat schematic illustration of an actuation system for adjusting a position and pressure exerted by a press roll according to yet another aspect of this invention.
FIG. 4
is a block diagram of an electrical control system for the planer of
FIG. 1A
according to a further aspect of this invention.
FIG. 5
is a block diagram of an electrical control system for the infeed table of
FIG. 2A
according to a still further aspect of th

Affiliated with

Also associated with

Rating

Automatic press roll control does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Automatic press roll control, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Automatic press roll control will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3089716