GB1577125A - Drive for bridle rolls - Google Patents

Description

(54) IMPROVEMENTS IN DRIVE FOR BRIDLE ROLLS (71) We, THE HEAD WRIGHTSON MACHINE COMPANY LIMITED, a British company, of The Friarage, Yarm, Cleveland, England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to drives for sets of bridle rolls utilised for applying tension to continuous metal strip being processed, or for isolating sections of strip at different tensions.

Such bridle roll sets normally consist of two or more rolls, normally of the same diameter, around which the strip passes along a sinuous path so as to ensure frictional contact between the rolls and the strip.

Clearly, the torque applied to or sustained by the rolls in order to generate the desired tension differential across the bridle roll set must be shared between the rolls, and obviously also the strip at the higher tension end of the set will be stretched as compared with its state at the low tension end, this stretching being distributed due to the sharing of torque between the rolls. As a result of this elongation of the strip as it passes over successive rolls, the latter must be driven at incrementally differing speeds if the desired torque is to take place, and furthermore, slippage of the strip relative to the surface of the rolls is to be minimised.

Such slippage is highly undesirable since it is liable to damage the surface of the strip.

Various proposals have been made in the past for overcoming this difficulty. According to one prior proposal which is the subject of our Patent No. 1,394,083, a bridle roll arrangement comprises a plurality of bridle rolls arranged to provide a sinuous path for strip to be entrained therearound, a primary drive shaft supplying drive to the plurality of rolls, a drive system connecting said shaft to said rolls and including differential gear boxes associated with all or all but one of said bridle rolls, each of said differential gear boxes being provided with a secondary drive adapted to adjust its output speed, a torque meter associated with each of said bridle rolls and at least one comparator for comparing the output of the torque meters and controlling the secondary drives of the differential gear boxes so as to maintain the torque delivered to the bridle rolls in a predetermined relationship.

While this prior arrangement operates very satisfactorily, it is a complicated arrangement and is expensive to install and operate because of the large number of torque meters required and because of the associated control circuitry. We have now developed a bridle roll arrangement which is an improvement of that the subject of our Patent No. 1,394,083.

According to the present invention, we provide a bridle roll arrangement comprising a plurality of bridle rolls arranged to provide a sinuous path for entrainment by metal strip being processed, a primary drive shaft supplying drive to the plurality of rolls and a drive system connecting said primary drive shaft to the rolls and including differential gear boxes associated with all or all but one of said bridle rolls, each of said differential gear boxes being provided with a secondary drive adapted to adjust its output speed, a torque meter associated with one only of said bridle rolls for determining the torque applied to that roll and control means for varying the torque applied by each of said secondary drives in proportion to the output torque measured by the said torque meter.

The invention is now described by way of example with reference to the accompanying diagrammatic drawings, in which: FIGURE 1 shows in plan a strip pro cessing apparatus incorporating two sets of bridle rolls.

FIGURE 2 shows the arrangement of the bridle rolls in each set, and FIGURE 3 is a view of a strip processing apparatus corresponding to Figure 1 and showing a control apparatus in more detail.

Referring to the drawings, a drag or entry bridle has two upper rolls 1 and 4 and two lower rolls 2 and 3 and a tension or exit bridle is provided with two upper rolls 5 and 8 and two lower rolls 6 and 7. Between the bridles is a treatment unit X in which a continuous metal strip is treated while under tension, the bridles generating the necessary tension in the strip and isolating this tension from adjacent equipment. As can be seen from Figure 2, the strip passes in a sinuous path over each roll in each bridle and the two bridles are similar, their rolls being numbered in the sequence the strip passes over them.

The two bridles are driven in known manner by a main drive in the form of an electric motor M driving two drive shafts D and E through a primary gear box F.

The primary gear box F includes an adjustable differential enabling the speeds between the shafts D and E to be varied, hence giving rise to a corresponding difference in the mean speeds of the outputs of the two secondary gear boxes G and H driven by the shafts D and E. The secondary gear boxes G and H are used to distribute the drive from shafts D and E to the individual rolls 1-8 of the two bridles in known manner.

As shown, each of the four output shafts of the gear boxes G and H is used as the main drive to a differential gear box J1-J8 although normally the differential gear boxes J4 and J5 would be dispensed with (see Fig. 3) so that an output from the respective secondary gear boxes G and H could drive the bridle rolls 4 and 5 directly.

A high strip tension is generated by virtue of the speed difference between the rolls of the drag and tension bridles, this tension being exactly sufficient to provide, in conjunction with the treatment unit X, an elongation in the strip compensating for the difference in peripheral velocity of the rolls 4 and 5, assuming that there is no slipping.

The change in strip tension as the strip passes over successive rolls in each of the bridles causes stretching or contraction of the strip, and a certain amount of slip will take place between the strip and at least some of the bridle rolls. It is generally desirable to minimise the amount of slip which takes place and this can be achieved by distributing the torque applied to each of the bridle rolls within a bridle in a predetermined manner.

Tn the construction shown, each of the differential gear boxes J1-J8 is provided with a secondary drive M1-M8 although, as previously described, gear box J4 and J5 and their associated secondary drives M4 and M5 are not essential. Each of the secondary drives is in the form of an electric motor and the drive from the secondary drives of each bridle is in a predetermined ratio dependant upon the torque supplied to the bridle roll 4 of the drag bridle and bridle roll 5 of the drive bridle respectively.

For this purpose, a torque meter T is provided for the bridle rolls 4 and 5 and the reading from each of the meters T is fed into a controller C. It must be appreciated that each controller C controls the amount of current supplied to the secondary drives in each bridle in a predetermined ratio dependant upon the torque at the main bridle rolls in each bridle. Hence, the correct distribution of load on each bridle roll can be obtained merely by feeding the currents to the secondary drive motors in a definite proportion dependant upon the measured torque in each of the main rolls of each bridle.

In the particular form shown on Figure 3, the output from the torque meter T4 is fed to attenuators Al, A2 and A3. The attenuators are associated with the correspondingly numbered rolls and have attenuation factors corresponding to the ratio of torque required to be transmitted by roll 4 and by the associated numbered roll.

The outputs from the attenuators are fed to comparator circuits C1, C2 and C3 respectively. Feedback signals il, i2, and i3, which are signals proportional to the amount of current supplied from thyristor regulators TR1, TR2 and TR3 respectively to the secondary motors M1, M2 and M3 are also applied to the comparators. Any deviation of a motor current from the value required to maintain the correct torque distribution will result in an error signal from the associated comparator.

This error signal is applied to the phase control of the appropriate thyristor regulator so as to correct the error.

A signal Z is applied to the comparators during acceleration or deceleration of the apparatus to compensate for the acceleration or deceleration of the small motors Ml, M2, M3, M6, M7 and M8 being different from that of the main motor M, and an alternative signal Y is applied to the thyristor regulators for use during threading of the strip, or when the apparatus is operated at low speed with negligible tension in the strip.

In these circumstances the output from the torque meter T will be very small and the control signals from the attenuators will be ineffective.

The control of the exit bridle will be similar to the entry bridle shown.

Having regard to the provisions of Section 9 of the Patents Act 1949, attention is directed to the claims of Patent No.

1,389,963.

WHAT WE CLAIM IS: 1. A bridle roll arrangement comprising a plurality of bridle rolls arranged to provide a sinuous path for entrainment by metal strip being processed, a primary drive shaft supplying drive to the plurality of rolls and a drive system connecting said primary drive shaft to the rolls and including differential gear boxes associated with all or all but one of said bridle rolls, each of said differential gear boxes being provided with a secondary drive adapted to adjust its output speed, a torque meter associated with one only of said bridle rolls for determining the torque applied to that roll and control means for varying the torque applied by each of said secondary drives in proportion to the output torque -measured by the said torque meter.

2. A bridle roll arrangement as claimed in claim 1 wherein the output of said torque meter is used as a reference for controlling the secondary drives of said differential gearboxes.

3. A bridle roll arrangement as claimed in claim 1 or claim 2 wherein the bridle roll associated with said torque meter is not associated with a differential gearbox.

4. A bridle roll arrangement as claimed in claims 2 or 3 wherein the output from said torque meter is applied as an input to a plurality of attenuators corresponding to the number or the number less one of said rolls, the outputs from each attenuator being passed as one input to an associated comparator circuit, a second input to the comparator circuit being provided by a signal corresponding to the speed of rotation of one of said bridle rolls, the output from said comparator being used to control the speed of rotation of that bridle roll.

5. A bridle roll arrangement as claimed in claim 4 wherein the said secondary drive associated with said differential gear-boxes comprises an electric motor and wherein the said second input is a signal corresponding to the current applied to the particular motor and wherein the said output of the comparator controls the said current.

6. A bridle roll arrangement substantially as described herein with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. directed to the claims of Patent No. 1,389,963. WHAT WE CLAIM IS:

1. A bridle roll arrangement comprising a plurality of bridle rolls arranged to provide a sinuous path for entrainment by metal strip being processed, a primary drive shaft supplying drive to the plurality of rolls and a drive system connecting said primary drive shaft to the rolls and including differential gear boxes associated with all or all but one of said bridle rolls, each of said differential gear boxes being provided with a secondary drive adapted to adjust its output speed, a torque meter associated with one only of said bridle rolls for determining the torque applied to that roll and control means for varying the torque applied by each of said secondary drives in proportion to the output torque -measured by the said torque meter.

2. A bridle roll arrangement as claimed in claim 1 wherein the output of said torque meter is used as a reference for controlling the secondary drives of said differential gearboxes.

3. A bridle roll arrangement as claimed in claim 1 or claim 2 wherein the bridle roll associated with said torque meter is not associated with a differential gearbox.

4. A bridle roll arrangement as claimed in claims 2 or 3 wherein the output from said torque meter is applied as an input to a plurality of attenuators corresponding to the number or the number less one of said rolls, the outputs from each attenuator being passed as one input to an associated comparator circuit, a second input to the comparator circuit being provided by a signal corresponding to the speed of rotation of one of said bridle rolls, the output from said comparator being used to control the speed of rotation of that bridle roll.

5. A bridle roll arrangement as claimed in claim 4 wherein the said secondary drive associated with said differential gear-boxes comprises an electric motor and wherein the said second input is a signal corresponding to the current applied to the particular motor and wherein the said output of the comparator controls the said current.

6. A bridle roll arrangement substantially as described herein with reference to the accompanying drawings.