Patent EA-000903-B1 (EA)
Title: System for controlling tension of a backing material in a tufting machine
Inventor: MCGOWAN OLIVER W
IPC: B65H23/192
Filed: 1998-01-15
Abstract: 1. A tufting machine for inserting yarn in a backing material, comprising:  a pair of advancing rollers with a first advancing roller for feeding the backing material into the tufting machine and a second advancing roller for removing the backing material from the tufting machine;  a load measuring unit for measuring an actual value of tension generated along the backing material between the pair of advancing rollers and for generating a tension signal representing the actual value of tension;  a drive motor for rotating one advancing roller of the pair of advancing rollers;  a drive circuit for generating a driving signal for driving the drive motor;  a monitoring unit for monitoring a condition of the other advancing roller of the pair of advancing rollers and for generating a condition signal; and  a controller for receiving the tension signal from the load measuring unit and for receiving a predefined value of tension, wherein the controller generates a control signal based on the tension signal from the load measuring unit and the predefined value of tension;  wherein the drive circuit generates the driving signal by combining the condition signal from the monitoring unit and the control signal from the controller, the driving signal causes the drive motor to rotate the one advancing roller so that the actual value of tension measured by the load measuring unit becomes substantially equal to the predefined value of tension; and wherein the monitoring unit includes a position encoder coupled to the other advancing roller and a frequency analog converter for converting an output signal of the position encoder to an analog signal that represents a speed of the other advancing roller.  2. The tufting machine as set forth in claim 1, wherein the pair of advancing rollers comprises an entry pin roller and an exit pin roller. 3. The tufting machine as set forth in claim 1, wherein the load-measuring unit comprises a strain gauge. 4. The tufting machine as set forth in claim 3, wherein the strain gauge is positioned at an entrance to the tufting machine. 5. The tufting machine as set forth in claim 1, wherein the drive motor drives the first advancing roller. 6. The tufting machine as set forth in claim 1, wherein the drive motor controls a speed of rotation of the one advancing roller. 7. The tufting machine as set forth in claim 1, wherein the monitoring unit determines the condition of speed of the other advancing roller. 8. The tufting machine as set forth in claim 1, wherein the controller generates the control signal based on a difference between the output from the load measuring unit and the predefined value of tension. 9. The tufting machine as set forth in claim 1, wherein the controller includes an input interface for receiving the predefined value of tension. 10. The tufting machine as set forth in claim 1, wherein the controller includes an output interface for displaying the actual value of tension on the backing material. 11. An apparatus for controlling a machine-direction tension in an advancing web of carpet primary backing material passing through a tufting machine, comprising:  means for advancing the web of carpet primary backing material through the tufting machine;  means for measuring the machine-direction tension in the advancing web of carpet primary backing material and  means for controlling the advancing means so that the measured machine-direction tension remains substantially equal to a predetermined quantity of tension as the web of carpet backing material is being advanced through the tufting machine;  wherein the advancing means comprises a first pin roller driven by a first drive motor for introducing the web of carpet backing material into the tufting machine and a second pin roller driven by a second drive motor for removing the web of carpet backing material from the tufting machine; and wherein the controlling means comprises: a position encoder for tracking a rotation of the second pin roller; a frequency analog converter for receiving an output from the position encoder and for generating an analog speed signal representing a speed of rotation of the second pin roller; a controller for generating a control signal based on a comparison between the measured machine-direction tension from the measuring means and the predetermined quantity of tension; and a drive circuit for generating a drive signal for driving the first drive motor, wherein the drive circuit producing the drive signal based on a combination of the analog speed signal from the frequency analog converter and the control signal from the controller. 12. The apparatus as set forth in claim 11, wherein the controlling means controls one of the drive motors, first or second, so that the web of carpet backing material has the predetermined quantity of tension. 13. The apparatus as set forth in claim 11, wherein the measuring means comprises a strain gauge for measuring the machine-direction tension in the web of carpet backing material. 14. The apparatus as set forth in claim 11, wherein the controlling means controls the advancing means so that a first speed at which the web of carpet backing material is introduced into the tufting machine is slower than a second speed at which the web of carpet backing material is removed from the tufting machine.