Interstand tension regulator for a multistand rolling mill

Claim 2

In the method for controlling the gauge of strip material issuing from a tandem rolling mill by varying tension in the strip material between two stands of the mill through control of the speed of one of said two stands and wherein the transfer function relating interstand tension between said two stands to the operating speeds of the two stands is dependent upon the cross-sectional area of the strip between the two stands and the speed of the first of said two stands in the tandem mill, the steps of: generating a first electrical signal proportional to actual tension between said two stands, generating a second electrical signal proportional to desired tension between said two stands, generating a third electrical signal which varies as a function of the gauge of the strip material at the output of the last of said two stands in the tandem mill, comparing said first, second and third signals to derive an error signal for varying the speed of one of said stands, and modifying said error signal as a function of the cross-sectional area of the strip between said two stands and the speed of said first of the two stands to compensate for changes in said transfer function.

Claim 3

The method of claim 1 wherein said error signal is modified by steps including multiplying the error signal by the speed of the first of said two stands and dividing the product thus derived by the cross-sectional area of the strip material between said two stands.

Claim 4

The method of claim 1 including the step of controlling tension in the strip material between said two stands of the mill at low speed without materially modifying said error signal.

Claim 5

The method of claim 1 wherein said two stands comprise the last two stands in the tandem rolling mill, said first of the two stands comprising the next to the last stand in the tandem rolling mill.

Claim 6

In the method for controlling the gauge of strip material issuing from a tandem rolling mill by varying tension in the strip material between two stands of the mill through control of the speed of one of the two stands and wherein the transfer function relating interstand tension between said two stands to the operating speeds of said two stands is: T ((AE''/V4)/1 + ((L/V4) (E''/E)) S) (V5- V4) where T is interstand tension between said two stands, L is the distance between said two stands, A is the strip cross-sectional area between said two stands, V4 is the speed of the first of said two stands in the tandem rolling mill, V5 is the speed of the last of said two stands in the tandem rolling mill, E is the strip modulus of elasticity of the strip material, E'' is the apparent modulus of elasticity, and S is the Laplace operator, the steps of: generating an electrical signal proportional to actual tension between said two stands, generating an electrical signal proportional to desired tension between said two stands, compAring said actual and desired signals to derive an error signal for varying the speed of the last of said two stands, and modifying said error signal in accordance with the transfer function: Kx (1 + ((L/V4) (E''/E)) S/(A(E/V4)) S ) where Kx is a constant.

Claim 7

In the method for controlling the gauge of strip material issuing from a tandem rolling mill by varying tension in the strip material between two stands of the mill through control of the speed of one of the two stands and wherein the transfer function relating interstand tension between said two stands to the operating speeds of said two stands is: T ((AE''/V4)/1 + ((L/V4) (E''/E)) S) (V5- V4) where T is interstand tension between said two stands, L is the distance between said two stands, A is the strip cross-sectional area between said two stands, V4 is the speed of the first of said two stands in the tandem rolling mill, V5 is the speed of the last of said two stands in the tandem rolling mill, E is the strip modulus of elasticity of the strip material, E'' is the apparent modulus of elasticity, and S is the Laplace operator, the steps of: generating an electrical signal proportional to actual tension between said two stands, generating an electrical signal proportional to desired tension between said two stands, compAring said actual and desired signals to derive an error signal for varying the speed of the last of said two stands, and modifying said error signal in accordance with the transfer function: Kx (1 + ((L/V4) (E''/E)) S/(A(E/V4)) S ) where Kx is a constant.

Claim 8

The method of claim 5 wherein said error signal is modified in circuitry having said transfer function, and including the steps of generating electrical signals proportional to A and V4 and applying said signals to said circuitry.

Claim 9

In apparatus for controlling the gauge of strip material issuing from a tandem rolling mill by varying tension in the strip material between two stands of the mill through control of the speed of one of said two stands and wherein the transfer function relating interstand tension between said two stands to the operating speeds of said two stands is represented by: T ((AE''/V4)/1 + ((L/V4) (E''/E)) S) (V5 - V4) where T is the interstand tension between said two stands, L is the distance between said two stands, A is the strip cross-sectional area between said two stands, V4 is the speed of the first of said two stands in the tandem rolling mill, V5 is the speed of the last of said two stands in the tandem rolling mill, E is the apparent modulus of elasticity, and S is the Laplace operation, the combination of means for generating an electrical signal proportional to actual tension between said two stands, means for generating an electrical signal proportional to desired tension between said two stands, means for comparing said actual and desired signals to derive an error signal for varying the speed of one of said two stands, means for controlling the speed of said last of the two stands, and circuitry for applying said error signal to said speed controlling means, said circuitry having the transfer function: Kx (1 + ((L/V4) (E''/E)) S/(A (E/V4)) S ) where Kx is a constant.

Claim 10

In apparatus for controlling the gauge of strip material issuing from a tandem rolling mill by varying tension in the strip material between two stands of the mill through control of the speed of one of said two stands and wherein the transfer function relating interstand tension between said two stands to the operating speeds of said two stands is represented by: T ((AE''/V4)/1 + ((L/V4) (E''/E)) S) (V5 - V4) where T is the interstand tension between said two stands, L is the distance between said two stands, A is the strip cross-sectional area between said two stands, V4 is the speed of the first of said two stands in the tandem rolling mill, V5 is the speed of the last of said two stands in the tandem rolling mill, E is the apparent modulus of elasticity, and S is the Laplace operation, the combination of means for generating an electrical signal proportional to actual tension between said two stands, means for generating an electrical signal proportional to desired tension between said two stands, means for comparing said actual and desired signals to derive an error signal for varying the speed of one of said two stands, means for controlling the speed of said last of the two stands, and circuitry for applying said error signal to said speed controlling means, said circuitry having the transfer function: Kx (1 + ((L/V4) (E''/E)) S/(A (E/V4)) S ) where Kx is a constant.

Claim 11

The apparatus of claim 7 including means for generating an electrical signal proportional to V4, means for generating an electrical signal proportional to A, said circuitry incorporating means for multiplying said error signal by said signal proportional to V4, and means for dividing the product derived by multiplication by said signal proportional to A.

Claim 12

The apparatus of claim 8 wherein said means for multiplying is included in a signal channel including an integrating operational amplifier for applying said error signal to the input of said multiplying means.

Claim 13

The apparatus of claim 9 including a second channel in shunt with said first channel, the second channel including a proportional operational amplifier, the outputs of said channels being summed and applied to said means for dividing by a signal proportional to A.

Claim 14

The apparatus of claim 10 including a signal channel in shunt with said multiplying means whereby a portion of the signal at the output of said integrating operational amplifier is applied directly to said summing point.