Sewing – Special machines – Embroidering
Reexamination Certificate
1998-06-22
2001-03-27
Nerbun, Peter (Department: 3741)
Sewing
Special machines
Embroidering
C112S275000, C112S475010
Reexamination Certificate
active
06205940
ABSTRACT:
A Microfiche Appendix consisting of 2 sheets (150 total frames) of microfiche is included in this application, the contents of which are hereby incorporated herein by reference. The Microfiche Appendix contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the Microfiche Appendix, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever.
FIELD OF THE INVENTION
This invention generally relates to controlling the operation of carpet tufting machines, and more particularly, to a system for controlling the stopping position of the needle bar of a tufting machine in a preset carpet stitch pattern.
BACKGROUND OF THE INVENTION
A tufting machine produces carpet through the use of a needle bar assembly containing a plurality of needles. The needles stitch yarn for producing the carpet while one or more needle bars move in a side-to-side motion. At a first position (i.e., “home” position), the needle bar is disposed at a starting location within the carpet stitch pattern. At a second position, the needle bar may be displaced horizontally to the right while stitching the carpet. At a third position, the needle bar may again be displaced to the right. After a series of such steps and stitches of the carpet pattern, the needle bar is displaced horizontally in the opposing direction. After a number of steps have been completed, for example 22 steps, the needle bar will have returned to the home position in the carpet stitch pattern. The above process is repeated to produce tufted loop carpeting. In one common technique, the carpet produced by this process has a series of zig-zag edges due to the horizontal left and right displacement of the needle bar. This horizontal displacement helps alleviate some of the defects produced in the manufacture of the carpet, or creates a desired visual appearance.
During normal operation, a tufting machine operates by rotating a main drive shaft at about 450 to 1150 revolutions per minute. The main drive shaft is coupled either directly or indirectly to the needle bar(s) that stitches the carpet. A programmable logic controller (“PLC”) and an inverter drive are commonly used to control the starting and stopping (i.e., drive motion) of the tufting machine. A repeating carpet pattern may be created by a shifting needle bar action produced by a mechanical shifter, hydraulic shifter or other linear displacement mechanism to produce the desired carpet pattern. An encoder detecting system may be employed to track the position of the needle bar assembly within the needle stroke. A count of the steps taken within each pattern can then be communicated by the encoder to a controller. Each time the needle bar completes a pattern cycle, the controller counting the steps is reset.
In the event of yarn breakage or other error condition, the operator of the tufting machine can engage a stop button, or another stop mechanism (i.e., end out detectors) can be engaged, to halt the machine. When the stop signal is received, the operation of the tufting machine typically ramps down to approximately sixty revolutions per minute. This speed is commonly referred to as the “jogging speed” of the machine. Due to the physical momentum introduced by the size of a tufting machine, it may take a series of individual steps for the machine to slow down to reach the jogging speed. For example, where a carpet pattern includes 22 steps and the operator hits the stop button at step
4
, it may take 15 steps before the machine reaches the jogging speed. At the jogging speed, therefore, the machine will have progressed to step
19
in the carpet pattern. After reaching the jogging speed, the tufting machine is braked for needed repair or maintenance of the carpet.
When restarting the machine, a defect may be produced along a given line in the carpet because the tension and feeding of the carpet at that line may result in yarn being tighter or looser than before. To reduce the risk of such a defect, the prior art discloses a method of stopping the needle bar at a given height (i.e., relative position of the drive shaft) within the needle stroke. This technique only alleviates some of the risks of a defect. If the machine is stopped at a point which is far away from a preset stop position, defects may also arise even if the needle bar is stopped at the height taught by the prior art. The prior art thus lacks the advantage of stopping the tufting machine at or about a predetermined step in the stitch pattern such as, for example, the next desired stop position, with a minimum number of jog steps, while at the same time stopping the needle bar at a given height within the needle stroke.
It is therefore an object of the invention to stop a carpet tufting machine at a preset stop step in the carpet pattern.
It is also an object of the invention to stop the needle bar of a carpet tufting machine at the next predetermined stop position and at a certain orientation of mainshaft rotation.
It is a further object of the invention to employ a programmable logic controller and encoder to stop a tufting machine at the next home position.
It is yet another object of the invention to minimize the number of jog steps prior to halting the needle bar at the predetermined stop step.
SUMMARY OF THE INVENTION
In view of the above, a system and method are provided for controlling the stopping point of a tufting machine at a preset stop step in a carpet stitch pattern. According to the system of the invention, a tufting machine for forming pile carpet is provided. The tufting machine includes a frame, a main drive shaft housed within the frame and a series of tufting needles mounted on a reciprocating needle bar assembly connected to the main drive shaft so as to be moveable between raised and lowered conditions. The tufting machine also includes a controller configured to the main drive shaft to control the stopping position of the needle bar assembly at a preset stop step in the carpet stitch pattern. A brake coupled to the main drive shaft is included for stopping the main drive shaft at a predetermined position in the carpet stitch pattern in response to the control means. In the preferred embodiment, the predetermined position is the home position and the tufting machine is slowed to a jogging speed prior to stopping the needle bar.
A method for controlling the stopping point of a tufting machine includes the step of receiving a signal to stop the tufting machine. The tufting machine is then slowed, and the needle bar is stopped at a predetermined stop position within the carpet stitch pattern. In the preferred embodiment of the invention, the predetermined stop position is the home position and the tufting machine is slowed to a jogging speed prior to stopping the needle bar.
In another aspect of the invention, the number of jog steps or jog time required before the tufting machine can be stopped is minimized by controlling the deceleration of the main drive shaft. The deceleration is delayed, from receipt of a stop signal, to a time or position when only a minimum number of jog steps are required before the drive shaft is braked to stop at the predetermined stop step.
According to the present invention, defects created by the stopping and starting of a tufting machine can be reduced or eliminated. By locating the stop position of the needle bar at a preset position in the carpet stitch pattern, fewer defects are created once the tufting machine resumes operation. If a defect is created, however, it is less likely to be detected or observed if located at the same position of the carpet stitch pattern every time the machine is stopped and restarted because the severity of the defect may be reduced. By controlling the location where the needle bar is stopped or halted in response to a need for repair or maintenance of the carpet, the appropriate tension for the yarn used in making the carpet can be properly controlled.
These and other features and advantages o
Morgan Douglas L.
Vaughan William N.
Brinks Hofer Gilson & Lione
Nerbun Peter
Shaw Industries, Inc.
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