US3641797A

US3641797A - Stretcher leveling system

Info

Publication number: US3641797A
Application number: US8921A
Authority: US
Inventors: Ronald J Bell; Edward C O'-Neal
Original assignee: American Metal Climax Inc
Current assignee: Cyprus Amax Minerals Co
Priority date: 1970-02-05
Filing date: 1970-02-05
Publication date: 1972-02-15
Anticipated expiration: 1989-02-15

Abstract

A stretcher leveling system having a closed mechanical drive system with the exit roll stand gear train connected to the entrance roll stand gear train through a finite number of fixed gear ratios. A split power transmission train is used for connecting the change gear train with the roll driving gear trains. In one embodiment the change gear train is mechanically connected in series with a differential to reduce the range of stretch which is differential controlled to a small range with a series of fixed gear ratios.

Description

[ 1 Feb. 15, 1972 United States Patent Bell et al.

[54] STRETCHER LEVELING SYSTEM Primary Examiner-Milton S. Mehr AttorneyFowler, Knobbe & Martens ABSTRACT of American Metal Climax, lnc., Riverside, Calif.

A stretcher leveling system having a closed mechanical drive system with the exit roll stand gear train connected to the en- [22] Filed: Feb. 5, 1970 [21] Appl.No.: 8,921

trance roll stand gear train through a finite number of fixed gear ratios. A split power transmission train is used for connecting the change gear train with the roll driving gear trains.

in one embodiment the change gear train is mechanically con- 72/205 72/249 nected in series with a differential to reduce the range of 72 stretch which is difi'erential controlled to a small range with a l series of fixed gear ratios.

[52] US. [51] Int. [58] Field of Search References Cited 17 Claims, 6 Drawing Figures UNITED STATES PATENTS 3,527,078 9/1970 Lowson et PATENTED FEB 1 5 I972 SHEET 3 OF 3 INVENTOR5. POA/ALD .1 BEAL [DH 4K0 6. 071/6221.

POM/LEE ATTOE/VEVS'.

STRETCHER LEVELING SYSTEM This invention relates to an apparatus and process for stretcher leveling strip stock and more specifically to a mechanical power train for use with stretcher leveling ap paratus.

Typically, present stretcher leveling equipment includes an entry roll stand and an exit roll stand of two to four driven rolls at each stand. These stands each have a gearbox which contains the gear train for driving the rolls at that stand. The entry stand gear train is commonly mechanically connected to the exit stand gear train through a differential which controls the speed of the entry stand gears with respect to the speed of the exit stand gears. In this arrangement, a closed loop is achieved in which the operating torque is circulated and the main drive motor need only supply line speed setting and makeup energy to accommodate mechanical losses in the loop. The percent elongation or stretch of the strip is thus dependent upon the relative peripheral roll speeds between entry and exit stand as determined by the differential gearing between the gear stands. The resulting elongation provides a corresponding tensile stress in the strip at a level exceeding the yield strength and thus plastically deforms or elongates the strip by a small percentage as it is drawn through the system. This plastic deformation results in uniform elongation transversely across the strip width and also eliminates nonuniform internal rolling stresses within the strip thereby leveling or flattening the strip.

The differential's function is to maintain a constant percentage elongation of the strip stock passing through the stretcher leveling system by varying the rate of speed of the entrance rolls relative to the speed of the exit rolls. Since the stretcher leveling systems form a closed mechanical loop through the differential, the apparent horsepower of the system is much higher than the actual output of the driving motor. The output of the system is limited by the apparent horsepower, however. While the speed regulation of the differential is effective over a small range of stretch and roll grind down compensation, it loses accuracy for large ranges, on the order of -7 percent stretch, for example.

in the conventional approach, the differential planet carrier is normally hydraulically controlled through a system which has fixed speed losses at a given operating pressure. Thus the output of the hydraulic drive is nonlinear with line speed changes, thereby limiting the accuracy of stretch regulation of the overall system when accelerating to operating speeds or running at low speeds, during splice transport (or passage). No substitute control systems for the hydraulic controls have been able to prevent all deviations from the selected elongation of the system.

A market has now developed for high-capacity, high-quality stretcher leveling systems which are not burdened with the cost and maintenance of excessive auxiliary manual or auto matic control systems and which can maintain a fixed elongation at high roll speeds on the order of 1,500 ft./rnin.

This invention is directed to a system which is relatively low cost, easy to operate and extremely efficient and reliable. Basically the system of this invention includes a fixed ratio change gear train for connecting the entry roll stand gear train with the exit roll stand gear train through a series of change gears which can be shifted to a finite range of gear ratios.

l-leretofore the use of a change gear train with a finite range of fixed gear ratios has not been considered acceptable because of the variations in roll size due to surface grinding of the rolls to maintain a smooth surface finish. This grinding alters the diameters of the rolls by a small amount but at the same time changes the stretch or elongation of the sheet by a significant amount since the elongation is a function of the circumference of the exit and entrance rolls and since for most metals the required elongation is below 3 percent and more normally below about 1 percent to effect stretcher leveling. Thus a small change in the diameter of the rolls can effect a relatively large change in the ultimate elongation of the strip which might alter the physical properties of the strip, reduce the elongation below the elastic limit so that no plastic deformation is effected, or increase the applied stress above the tensile strength of the strip so that failure occurs.

It has now been discovered that for reasonable variations in roll diameters, for example variations up to 3.5 percent difference between the entrance roll diameter and the exit roll diameter, and for sheet elongation of up to 3 percent that a finite range of change ratios for linking the entrance gears with the exit gears can be effected. By using a change gear train to achieve the desired range of change gear ratios, the entrance rolls are fixed in a definite ratio to the exit rolls so that the roll speed of the entrance is maintained at a constant ratio of the roll speed of the exit rolls and the inherent difficulties of using a differential control system are eliminated. For example, such a change gear train does not require the use of an infinitely variable control system to adjust the differential to compensate for roll diameter variation between the entrance rolls and the exit rolls.

The use of a fixed ratio change gear train in the place of a differential has been found to be feasible with the system of this invention by computer analysis of the basic elongation equations which express the elongation as a function of the circumference of the exit roll minus the circumference of the entrance roll over the circumference of the exit roll and the change ratio as a function of the diameter of the exit roll minus the product of the elongation times the diameter of the exit roll over the diameter of the entrance roll or:

Where: RC equals the change ratio; Dex equals the exit diameter; S equals the elongation; and Den equals the entrance roll diameter.

By varying the exit roll diameter from 29.5 to 30 the entrance roll diameter from 29 to 29.7 and the stretch from 0 to 0.035 or 3% percent and computing all permutations of these values, it has unexpectedly been found that the change in roll diameter with respect to the change ratio can be expressed as a family of straight line curves which have change ratios varying from a minimum of 0.963 to a maximum of 1.034. This represents a 0 to 7 percent elongation range. The input values for exit and entrance roll diameters were selected because they represent typical roll grind downs. It has been found empirically that if the differences between the roll diameters get to be greater than these values the rolls must be either relagged with a polyurethane lagging material or the larger of the two rolls must be ground down to match the smaller. Normally the total elongation with strip such as low carbon steels or aluminum rolling alloys can be maintained at less than 3.5 percent with good stretcher leveling characteristics.

Where close control over elongation is required a change gear train may be used in combination with a differential, since the requirements for servo feedback control systems for the difierential can be eliminated when the differential is only required to control a small percentage range of elongation. With this arrangement, the differential is only required to control roll speeds within a fixed range dictated by the change gears. The change gears may be connected to the planet carrier or may be connected to the differential output shaft.

The system of this invention may additionally use a split gear train power transmission between the change gear train and the roll gearing which eliminates excessively large gears and reduces the expense associated therewith. The split train takeoff system has generally not been considered applicable to stretcher leveling systems. By taking power transmission, with a split gear train, the size of the gears required are less than 50 percent of those which would be required if the forces were transmitted through a single pinion gear shaft.

One of the principal features of the basic incorporation of change gears in a stretcher leveling system in accordance with this invention is that the elongation is maintained constant once the desired gear ratio is selected through the change gear train regardless of the roll speeds.

Another feature of the system of this invention is that it operates smoothly, efficiently, and quietly with little or no maintenance or mechanical adjustments necessary.

Another feature of the stretcher leveling system of this invention is that there is a constant elongation imparted to the strip throughout its length which is independent of infinite variable control inaccuracies.

Yet another feature of this invention is that fine control over elongation can be provided for a relatively wide range of material elongations and roll grind down sizes without high control inaccuracies by combining a differential with a change gear train in series combination.

These and other features of this invention will become more readily apparent from the following specification when taken in conjunction with the claims and the appended drawings wherein:

FIG. 1 is a schematic view of the entire control and gearing arrangement for the stretcher leveling system of this invention.

FIG. 2 is a diagrammatic representation of the entrance and exit roll stands showing the strip traveling therethrough;

FIG. 3 is a horizontal section through a change gearbox constructed in accordance with this invention;

FIG. 4 is an overall view of the gear train of the system of this invention;

FIG. 5 is a horizontal section through the entry stand gearbox showing the entry rolls and gear arrangement; and

FIG. 6 is a diagrammatic representation of another embodiment of a stretcher leveling system power train constructed in accordance with this invention.

Referring now to FIG. 1, the overall closed mechanical loop driving mechanism and control for the stretcher leveling system of this invention is schematically shown. An entry stand gearbox 10 is mechanically linked to a change gearbox l4 and to the exit stand gearbox 12. The ratio of change gear linkage between the entrance and exit stand gearbox is fixed at the change gearbox through a controller 16. The drive for the system is supplied by an appropriate power supply such as the DC motor 18. Any other source of torque input for the change gear train such as a hydraulic motor may be used. The DC motor because of its efficiency and operating characteristics is preferred. 9

The roll system is diagrammatically shown in FIG. 2 and comprises an entrance roll stand or bridle 19 including a plurality of driven

rolls

20, 22, 24 and 26 connected to the entry stand gearbox l0 and an exit bridle or roll stand 28 including a plurality of

rolls

30, 32, 34 and 36 which are driven by the motor 18 through the change gearbox l4 and the exit stand gearbox 12. The strip stock 38 which is to be leveled by the system enters the entrance roll stand 19 from a payoff reel (not shown) and is sinuously wound around the entrance rolls 20, 22, 24 and 26. The strip 38 then passes over the exit rolls 30, 32, 34 and 36 and leaves the system. Generally this strip will begin on a payoff roll and be taken up on a large rewind roll (not shown) in the flattened or leveled condition. Several treating processes in addition to the stretcher leveling may be included between the payoff and rewind reels. While the entrance and exit rolls are shown in a generally horizontally spaced configuration it should be understood that any configuration such as vertical stacking of the rolls can be used.

A pinch roll such as pinch roll 40 may be included for controlling the stress applied to the strip when a new strip is being spliced thereto. This is necessary since the splice is too weak to sustain the total required payoff or rewind tension necessary for equilibrium with the high tensions in the stretch zone.

Referring now to FIG. 3, it will be seen that the change gear train in the change gearbox 14 comprises two sets of pinion gears 42, 42' and 44, 44 which are press-fitted on shafts 46 and 48 respectively for rotation with the shafts. Both shafts 46 and 48 are joumaled in the housing 49 of the change gearbox 14. Each of the pinion gears 42, 42' and 44, 44' engage a pair of change gears. The pinion gear 42 engages the change spur gears 50 and 54 and the pinion gear 42' engages the change spur gears 52 and 56. Each of the change gears may be provided with a different number of circumferential gear teeth for effecting different change ratio across the pinion gear shaft 46.

Gears 50 and 52 are mounted on the shaft 55 for rotation about the shaft 55 which is joumaled at its opposite ends in the housing 49 of the gearbox 14. The change gears 49 and 52 are appropriately mounted on the shaft 55 on bearings which are axially fixed but permit the change gears to rotate independent of the shaft.

A shifting collar 58 is splined or keyed on the shaft 55 for axial translation along the shaft and for rotational movement therewith. The shifting collar 58 is provided with circumferentially spaced tabs or clutch jaw members 60 and 61 at its opposite ends. The inwardly facing surfaces of gears 50 and 52 are provided with similar circumferentially spaced clutch jaw members or tabs 62 and 64, respectively, for engaging with the jaw members 60 and 61. Since the shifting collar 58 is splined or keyed on the shaft 55 it rotates with the shaft but can be moved axially along the shaft for engagement with either the jaw members 62 on gear 50 or the jaw members 64 on the gear 52. Thus the shifting collar 58 is essentially a clutch which connects either the gear 50 or the gear 52 into the drive train.

Axial translation of the shifting collar 58 is accomplished by means of a shifting bar 65 (see FIG. 4) which is connected to the shifting collar 58 by means of a shifting band 66 in a circumferential groove 67 axially spaced intermediate the ends of the shifting collar 58.

The circumferentially spaced, radially extending teeth of gears 50 and 52 mesh with the teeth of the pinion gears 42 and 42' respectively. Additionally the teeth of gears 54 and 56 smoothly mesh with the pinion gears 42 and 42' respectively. The gears 54 and 56 are similarly mounted on a shaft 70 for rotation thereon. The shaft 70 also carries a splined or keyed shifting collar 72 with appropriate circumferentially spaced clutch jaw members 74 and 76 at its opposite ends for engaging the inwardly extending clutch jaws 78 and 80 on the gears 54 and 56 respectively. Shafts 55 and 70 also mount, as by welding, press fitting or otherwise, a pair of power transfer spur gears 82 and 84, respectively, for rotation with the shafts. The change ratio over pinion gear shaft 46 is set by axial translation of the shifting collars 58 and 72 into engagement with the jaws on either the gear 50 or gear 52 and with engagement with the jaws on either gear 54 or 56 of the change gears placing the engaged gears in the power train to drive the transfer gears 82 and 84.

The number of teeth on gears 50, 52, 54 and 56 may be varied to provide the appropriate power transmission change ratio required. For example, the desired ratios for the stretcher leveling system of this invention can be obtained by using 96 to 100 gear teeth on these gears as will be discussed. Through this clutching arrangement, four first stage gear ratios are obtainable across the first set of pinion gears 42 and 42'.

The first set of change gears is connected through the power transmission gear 84 fixed on the shaft 70 to the second set of change gears by means of a larger diameter power transmission gear which is fixedly mounted on a shaft 92 for rotation therewith. The shaft 92 is joumaled at each of its ends in the housing 49 of the change gearbox l4 and mounts for rotation thereabout the first set of the second stage change gears. These are circumferentially toothed change gears 94 and 96 which are mounted for rotation on the shaft 92. The teeth of the change gears 94 and 96 mesh with the teeth of the pinion gears 44 and 44' respectively on the joumaled shaft 48. These change gears are also appropriately mounted on hearings or otherwise on the respective shafts for rotation independent thereof.

A shifting collar 98 having circumferentially spaced clutch jaw members 100 and 102 at the opposite ends thereof is splined or keyed to the shaft 92. The clutch jaw members 102 and 100 cooperate with the clutch jaw members 104 on the gear 94 and the members 106 on the gear 96 respectively. Such engagement places one of the change gears 94 or 96 in the gear train by connecting it to the shaft 92 for rotation therewith.

The pinion gears 44 and 44 are also engaged by change gears 110 and 112 respectively which are similarly mounted for rotation on a shaft 114 which is joumaled at its opposite ends in the gearbox housing 49. The shaft 114, as shown in FIG. 3, also carries a splined or keyed shifting collar 116 for rotational movement with the shaft 114 and axial translation along the shaft 114.

The shifting lever 120, as shown in FIGS. 3 and 4, translates the shifting collar 116 into engagement with either the clutch jaw members 130 on the gear 110 or the members 132 on the gear 112. The cooperating clutch jaw members 134 and 136 respectively on the shifting collar 116 engage the jaw members 130 and 132 on the respective change gears to place one of the gears in the drive train for rotating the shaft 114. Four additional change ratios are thus obtained across the pinions 44 and 44' by varying the number of gear teeth on the change gears 94, 96, 110 and 112. The total number of gear ratios available from the change gearbox 14 is thus 16. For a greater number of gear ratios additional pinion shafts and change gears can of course be used. It has been found, however, that elongations within 0.5 percent of those desired can be obtained for the limits discussed herein with the 16 ratio change gear train.

The shaft 114 also serves as the input shaft for operation of the exit stand gear train in gearbox 12 as shown diagrammatically in FIG. 1. The exit stand gear train is connected to the entry stand gear train also through the strip 38 which is being elongated, as shown in FIG. 2, thereby forming a closed mechanical loop.

The driving motor may be a DC motor which preferably is connected to the pinion gear shaft 46 so that the motor can operate at relatively high r.p.m.s in driving this system. The driving source, of course, could be connected to the pinion shaft 14 or to the exit stand gearbox but best efficiency and driving speeds are obtained by driving the shaft 46.

The entire gear train including the shifting mechanisms 120 of the change gear train is best shown in FIG. 4 as are the relative diameters and positioning of the various gears used herein. Each of the shifting collars 58, 72, 98 and 116 are provided with a groove and ring connection to a shifting mechanism 120 as basically shown in FIG. 4 and discussed with respect to the collar 58.

Each of the shifting mechanisms 120 is identical and comprises a flat pivot bar 121 which is pivotally mounted about a pivot pin 122. The shifting handle 124 is mounted on one end of the pivot bar 121 and the upper end of the shifting bar 126 is attached to the opposite end of the pivot bar 121. The lower end of the vertically extending shifting bar 126 is connected to a shifting ring 127 which fits in a groove 129 in the collar 116. Thus, the handles 124 can be used to pivot the bar 121 and thereby axially translate the shifting collars into engagement with the clutch jaw members of one of the two gears 110 and 112 on the shaft 114.

Although the shifting mechanism as shown in FIGS. 3 and 4 is manually operated it should be clear that the mechanism could be programmed so that by merely activating a button indicating the desired ultimate change ratio the shifting collars could be automatically set to the desired condition. For example, a central control panel such as the panel diagrammatically indicated as 18 in FIG. 1 could include a series of activators which are programmed to obtain the desired ratio. These could comprise electrical to hydraulic or pneumatic or electrical operators of the shifting collars to place them in the desired positions.

With continued reference now to FIGS. 3 and 4, it will be seen that the shaft 114 extends out of the change gearbox housing 49 and additionally has two pinion gears 140 and 142 which are keyed or splined into the shaft 114 for limited axial deflection so that they are free to move axially in response to an unbalanced helical gear force and rotate with the shaft. The pinions 140 and 142 form part of the split gear train which transmits power from the driving motor through the change gear train to the roll drive train of the exit gearbox 12 (see FIG. 1). The pinion gear 140 engages the gear teeth ofa larger diameter, circumferentially toothed power transmission gear 144 which is fixedly mounted on one end of a shaft 146 for rotation therewith. A roll neck gear 148 is fixedly mounted at the opposite end of the shaft146 and transfers approximately 50 percent of the input torque from shaft 114 to the rolls by engagement with the gear teeth of a first roll driving gear 150 which is fixedly mounted on a roll shaft 152 for driving the roll 32 which is also fixed to the shaft 152 for rotation therewith. The gear teeth of the roll driving gear 150 also engage the teeth of a second roll driving gear 154 which is fixed on a shaft 156 for driving the roll 30.

The other pinion gear 142 of the split train is fixed to the shaft 1 14 and transfers the other half of the torque input from shaft 114. This torque is transmitted through a circumferentially toothed power transfer and direction-reversing gear 158 which engages the teeth of a second gear 160 mounted on a takeoff shaft 162. The opposite end of shaft 162 has a roll neck gear 164 fixedly mounted thereon for rotation with the shaft 162. The teeth of the gear 164 engage with the teeth of the gear 154 and with the teeth of a third roll-driving gear 166 which is fixedly attached to the roll shaft 168 for driving the roll 34. The teeth of the gear 166 also mesh with the teeth of a fourth roll-driving gear 170 which is mounted on a shaft 172 for driving the roll 36. As can be seen at the exit stand gear train, rolls 30 and 34 rotate in the same direction (clockwise) and the rolls 32 and 36 are rotated in a direction (counterclockwise) opposite to that of the

rolls

30 and 34.

The split gear train power transmission system from the change gear train through shaft 114 and pinion gears 140 and 142 reduces the size requirement for the power transmission gears by about one-half resulting in a considerable savings in capital outlay.

The strip 38 prior to entering the exit rolls 30, 32, 34 and 36 is wound around rolls 20, 22, 24 and 26 ofthe entry stand. The entry stand rolls are connected through a roll-driving gear train and split gear train to the change gear train in a manner similar to the exit stand rolls. The roll 22 is mounted on a shaft which is fixedly attached to a driving gear 182. The teeth of the gear 182 mesh with the gear teeth of a second driving gear 184 mounted on the shaft 186 for driving and being driven by the roll 20. The teeth of the gear 184 mesh with the teeth ofa roll neck gear 188 fixed on a shaft 190 from the split gear train which is connected through gear 192 and intermediate power transfer and direction-reversing gear 194 to the split train pinion gear 196.

The teeth of the roll' neck gear 188 on the shaft 190 also engage the teeth of a roll-driving gear 198 fixedly mounted on a shaft 200 for driving and being driven by the roll 24 (see FIG. 5). The teeth of the roll driving gear 198 mesh with a gear 202 which is mounted on a shaft 204 for driving and being driven by the roll 26. Thus through the entrance stand gear train the

rolls

20 and 24 are rotationally driven clockwise and the

rolls

22 and 26 are rotationally driven counterclockwise.

The teeth of the roll-driving gear 202 to mesh with the teeth of a roll neck gear 206 driven through a shaft 208 by the power transmission gear 210 which engages the gear teeth of the split gear train pinion 212 on the shaft 214. Thus the power transmission from the exit stand through strip 38 and the rolls 20-26 is back to the change gear train through the entry roll gear train by means of a split gear train comprising the roll neck gears 188 and 206 and the driven

shafts

190 and 208. The split train pinion gears 196 and 212 on the shaft 214 drive and are driven by a power transmission gear 216 which is fixedly mounted at the opposite end of the shaft 214. The teeth of the gear 216 engage the teeth of gear 82 on the shaft 54 of the change gear train thereby forming a closed mechanical loop for the stretcher leveling system.

Referring now to FIG. 5 and with continued reference to FIGS. 3 and 4, the split gear train and the entry stand gear box will be discussed in more detail, it being understood that the exit gearbox is of similar construction. The shaft 214 which mechanically connects the entry stand gear train with the change gear train through the pinion gears 196 and 212 is journaled at its

ends

213 and 215 in the housing 217 of the entry stand gearbox 10. The

shafts

190, 195 and 208 which mount the split train power transfer gears 192, 194 and 210 are also journaled in the gearbox 10 for rotation therein. The

pinion gears 196 and 212 are keyed or splined on the shaft 214 for slight axial movement there along and for rotation therewith. The axial freedom permits response to an unbalanced helical gear force. These pinion gears each transmit about 50 percent of the power transmitted along shaft 214 from the change gear train. The roll neck gears 188 and 206 are proximate all of the roll-driving gears in the train and enable the use of relatively small diameter roll-driving

gears

182, 184, 198 and 202 for driving the

shafts

180, 186, 200 and 204 and the

rolls

22, 20, 24 and 26 respectively. As shown in FIG. 5, the roll-driving

shafts

180, 186, 200 and 204 may be journaled near both ends (one shown) in a roll-driving stand 220 for supporting the rolls for rotation therewith.

Since the system forms a closed loop as shown diagrammatically in FIG. 1 and through the gear trains in FIG. 4, the observed horsepower of this system is far greater than the required input horsepower of the driving motor.

For values of elongation from to 7 percent and difference in roll diameter of up to 3.5 percent, it has been found that the gear ratios from 0.096 to 1.036 percent are sufficient as set forth in Table l which shows the position of the clutches or shifting collars in engagement with the change gears based on a change gear tooth distribution as follows:

Number of Teeth TABLE 1 CHANGE GEAR RATlOS It has been found that, with the gearing mechanism arrangement discussed, change ratios within the ranges necessary for compensating for all differences in roll diameters which produce effective stretcher leveling, can be obtained within an error factor of 0.5 percent. This is accomplished by adjusting the change gears so that they increase by about 0.005 in change ratio as the ratio increases from a low of 0.9600 to a high of 1.036. By movement of the shifting collars with shifting levers 120 to all possible combinations of these eight change gear arrangements the desired one of the 16 change ratios is effected. By varying the number of change gears and gear teeth additional change ratios can, of course, be effected, but the arrangements set forth have particular application for use within the practical limitations of the stretcher leveling process for most strip material and roll grind downs. For smaller roll diameters, for example 24-inch rolls, the change ratio may be extended to accommodate roll diameter differences of up to 5 percent.

One of the chief advantages of this system is that once the change gear ratio is selected and the gears engaged the strip elongation is maintained constant regardless of the line speed so that the system is capable of extremely high speeds.

With reference now to FIG. 6, it will be seen that further advantage can be obtained from the combination in series of a differential and a change gear train. This is accomplished by connecting the output shaft from the differential to the input shaft for one of the pinion shafts of the change gear train. By connecting the change gear train in series with a differential, as shown, it is possible to obtain a very close control over the percent of stretch within a series of fixed change ratios and thereby reduce the fixed loss effects of the differential control system. This combination of the differential and the change gear train affords a close precise control of the percent elongation within a narrow range of fixed gear ratios set by the change gear train.

Basically the system, as shown in FIG. 6, comprises the roll gear train at the entry stand gearbox 300, the differential 302 which is connected to the entry stand gearbox through an input shaft 301 and to a change gear train in the change gearbox 304 through the differential output shaft diagrammatically represented as 306. The change gear train is connected to the exit roll gear train in the exit stand gearbox 307 by means of a mechanical connection diagrammatically represented as 308. The driving motor 310 may directly connected to the exit gear train. As discussed previously the input motor may also be connected to the change gear train on one of the pinion shafts.

The differential 302 is provided with a planet carrier drive control motor 314 which is shown diagrammatically in F IG. 6. The control motor 314 drives a planet carrier drive pinion bevel gear 316 which in turn drives a planet carrier bevel gear 318. The gear 318 is fixed to and rotates the planet gear carrier 320 which mounts a conventional bevel planet gear 321 on an inwardly projecting shaft 323 for rotation about the shaft 323 and with the carrier 320 to control the relative speeds of the axially aligned power input and

output bevel gears

322 and 324. This is accomplished by revolving the planet gear 321 with the carrier 320 about the common axis of the

bevel gears

322 and 324 at a controlled speed while the planet gear rotates on the shaft 323. Thus the differential is conventional in that it includes a planet gear carrier driven through a pinion gear by the control motor 314. The planet gear carrier 320 is fixed to the bevel gear 318 for rotation therewith as by welding or other conventional means. Similarly the shaft 323 is fixed to the carrier 320 and planet gear 321 may be journaled thereon.

The change gear train 304 is constructed as shown in FIGS. 3 and 6. In one differential-change gear system the change gear is provided with only one change gear pinion shaft and four change gears three of which have teeth each and one which has 99 gear teeth. Even a single set of change gears such as this reduces the stretch variation controlled by the differential significantly so that percentage stretch losses through the differential control system are similarly reduced. For example, as shown in Table 11, for a typical 1 percent roll grind down, the differential alone, for stretch of up to 1% percent, would have to vary the roll speeds from +l/z percent to 1 percent but with only 1 percent and 0 percent change gear positions the differential control is reduced 40 percent to from percent to 1 percent. The roll speed range variation controlled by the differential is reduced from 21/2 percent to 1% percent. The control inaccuracies are reduced by a similar amount so that the system reliability is increased significantly.

A split gear train such as discussed with respect to F165. 4 and 5 may be incorporated intermediate the entry stand gear box 300 and the differential gear system 302 and between the change gear train in the gearbox 304 and the exit stand gear train. Additionally the relative positioning of the change gear train and the differential gear system can be reversed as long as they are mechanically connected in series. Also the change gear train can be incorporated intermediate the planet carrier 2. A system as defined in claim 1 wherein said clutch means comprise shifting collars mounted on each of said change gear shafts for axial movement along said shafts, said shifting collars having clutch members on the opposite ends thereof and said change gears having inwardly extending mating members thereon for engaging with said shifting collar clutch members whereby said shifting collars operatively connect one of said gears on each of the change gear shafts to said shaft.

TABLE II.DIFFERENTIAL CONTROL WITH A 1% CHANGE GEAR Roll Roll r.p.m. Input r.p.m. Output chg. Roll r.p.m. Roll dis. (percent of difi. gain, difi Chg. gear gear (percent of dia. Stretch, percent (in) full speed) r.p.m. percent r.p.m. r.p.m. gain r.p.m. full speed) (in.)

99.0 990 0 990 1%, position B 1.000 100 41. 58 98. 985 yr 990 1%, position B 1. 000 100 41. 5S 0 101.0 1,010 1 1, 000 0%, position A- 1, 000 100 42. 00 100. 5 100 42. 00

0%. position A It has been found that with a combination differential and simple change gear train, as shown in Table ii, a total spread of 1% percent speed variation in the differential will cover a total range of 04% percent stretch and plus or minus 1 percent roll grinddown compensation. It should be clear that by the use of several change gears in the change gear train an even greater percent variation of stretch and roll grinddown compensation can be obtained with still a small differential control of approximately 1% percent This can be varied to suit the application by proper selection of the change gear ratios. With the combined differential change gear system the losses generally attributed to differential control inaccuracies are maintained at a minimum since the differential controls the roll speeds only within a very small range of variation.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed is:

l. A stretcher leveling system for plastically elongating strip stock comprising:

an entrance roll stand having a plurality of entrance rolls mounted thereat for rotation;

an entrance gear train for driving said entrance rolls;

a change gear train for providing a series of fixed gear ratios;

means for mechanically connecting the entrance gear train with the change gear train;

an exit roll stand having a plurality of exit rolls mounted thereat for rotation;

an exit gear train for driving said exit rolls;

means for mechanically connecting the exit gear train to the change gear train so that said exit gear train is mechanically connected to the entrance gear train through the change gear train in a selected gear ratio set by said change gear train thereby fixing the speed of said exit gear train; and

means connected to said system for driving said rolls,

wherein said strip passes through the entrance roll stand to the exit roll stand to form a closed mechanical power transmission loop;

said change gear train includes: a change gearbox housing; a

pair of pinion gears mounted on a shaft journaled for rotation in the change gear box housing; change gearmounting shafts journaled on the change gearbox housing on opposite sides of said pinion gear shaft and extending substantially parallel thereto; a pair of change gears mounted on each of said mounting shafts for rotation independently thereof, said change gears engaging said pinion gears; and clutch means for drivingly connecting one of said change gears on each of said shafts to the change gear drive train.

3. A system as defined in claim 2 further comprising: means for manually activating said shifting collars for axially translating each of said shifting collars independently along its mounting shaft into engagement with one of said change gears.

4. A stretcher leveling system for plastically elongating strip stock comprising:

an entrance gear train for driving said entrance rolls;

a change gear train for providing a series of fixed gear ratios;

an exit gear train for driving said exit rolls;

means connected to said system for driving said rolls,

said change gear train includes means therein for fixing the gear ratio between said entrance stand and said exit stand at stepped finite values between 0.096 and 1.036.

5. A stretcher leveling system for plastically elongating strip stock comprising:

an entrance gear train for driving said entrance rolls;

a change gear train for providing a series of fixed gear ratios;

an exit gear train for driving said exit rolls;

means connected to said system for driving said rolls,

said means for connecting said change gear train to said entrance gear train and said exit gear train comprises split gear trains.

6. A system as defined in claim 5 wherein each of said split ge lrains includes a single driven sha ft f rom said change gear train and a pair of axially spaced pinion gears mounted on said driven shaft; each of said pinion gears being mechanically connected to the roll-driving gears at the entrance and exit gear train.

7. A system as defined in claim 6 wherein said pinion gears are connected to spaced roll-driving gears for dividing the power transferred between said change gear train and the exit or entrance gear train.

8. A stretcher leveling system for plastically elongating strip stock comprising:

an entrance gear train for driving said entrance rolls;

a change gear train for providing a series of fixed gear ratios including eight change gears and two pinion gear shafts;

means for mechanically connecting the exit gear train to the change gear train so that said exit gear train is mechanically connected to the entrance gear train through the change gear train in a selected gear ratio set by said change gear train in a selected gear ratio set by said change gear train thereby fixing the speed of said exit gear train; and

means connected to said system for driving said rolls, wherein said strip passes through the entrance roll stand to the exit roll stand to form a closed mechanical power transmission loop.

9. A stretcher leveling system as defined in claim 1 further including a differential gear system mechanically connected intermediate the entrance and exit gear trains and comprising a power input means, a power output means and means for varying the speed of the power output means relative to the power input means, said change gear train being connected mechanically to said differential gear system to fix the amount of speed variation required by said varying means.

10. A stretcher leveling system comprising:

an entry roll gear train;

an exit roll gear train;

a differential gear system comprising rotating mechanical input means, rotating mechanical output means, and means for varying the relative rotational speeds of said input means and said output means; and

a change gear train having its input shaft connected to the output shaft of said differential gear system and having its output shaft connected to the input of said exit roll gear train;

the change gear train includes a first shaft having a pair of gear members mounted thereon for rotation independent of the first shaft; a second shaft having a pair of pinion gear members mounted thereon for rotation therewith, said pinion gear members engaging said gear members on said first shaft; a third shaft having a pair of gear members mounted thereon for rotation independent of the third shaft, said gear members engaging the pinion gear members on the second shaft; and clutch means associated with said first and third shafts for operatively connecting select ones of the gear members on said first and third shafts to the respective shaft on which they are mounted for rotation with that shaft, said gear members on said first and third shafts having varying numbers of gear teeth thereon.

11. A stretcher leveling system as defined in claim 10 wherein the gear members on said first shaft each have 100 gear teeth and the gear members on said third shaft have 99 teeth and 100 teeth.

12, A stretcher leveling system as defined in claim 10 wherein said clutch means comprises shifting collars mounted on said first and third shafts intermediate the gear members thereon, said shifting collars being fixedly mounted to the shaft for rotation therewith and being axially translatable along said shafts for engagement with one of the respective gear members on said shaft.

13. A stretcher leveling system as defined in claim 10 wherein said gear members have a variable number of gear teeth thereon for fixing a plurality of gear ratios, the number of teeth being so selected that the differential gear system never requires greater than 1% percent variation of the relative rotational speeds of said input means and said output means for obtaining the desired elongation for stretcher leveling and compensation for roll grinddown.

14. A stretcher leveling system comprising:

an entrance roll stand having a plurality of driven metallurgical rolls therein; an entrance gear train comprising a plurality of rolldriving spur gear members fixedly connected to shafts which mount said metallurgical rolls for rotation therewith, said roll-driving gear train members being mechanically interconnected such that the axes of said gear members are horizontally spaced from each other;

a first split gear train power transmission system having a pair of roll neck gear members engaging spaced ones of said roll-driving gear members, shaft members mounting said roll neck gear members, a single shaft member having a pair of axially spaced pinion gear members thereon, and means for connecting said roll neck gear members to different ones of said axially spaced pinion gear members;

a change gear train comprising a first shaft having a pair of gear members axially spaced thereon and mounted for rotation independent of said first shaft, a second shaft having a pair of pinion gear members thereon, said pinion gear members engaging with the gear members on said first shaft, a third shaft having a pair of gear members mounted thereon for rotation independent of said third shaft, said gear members on the third shaft engaging the pinion gear members on the second shaft and clutch means on said first and second shafts for connecting one of the gear members on each of said first and third shafts into operative engagement with the respective shaft and into the drive train across the second shaft;

means for connecting said first split gear train with said first shaft on said change gear train;

a second split gear train comprising a driving shaft having a pair of axially spaced pinion gear members mounted thereon, a pair of roll neck gear members spaced from each other and means for connecting said roll neck gear members to separate ones of said pinion gear members for dividing the power transmitted from said pinion gear members mounting shaft;

an exit roll stand having a plurality of horizontally spaced exit roll driving gears operatively connected to said exit rolls, spaced ones of said roll-driving gears being con-' nected and driven by said spaced roll neck gears on said second split gear train; and

means for connecting said second split gear train to said change gear train.

15. A stretcher leveling system as defined in claim 14 wherein said change gear train includes a plurality of pinion gear shafts interposed between change gear members for fix ing a plurality of gear ratios and means for drivingly connecting said plurality of pinion shafts so that the final ratio is a product of the several change gear ratios across the plurality of pinion shafts.

16. A stretcher leveling system as defined in claim 14 wherein a differential gear system is mechanically connected in the gear train intermediate said change gear train and one of said roll stands.

17. A stretcher leveling system as defined in claim 16 wherein said differential gear system comprises an input shaft mounting a first bevel gear thereon, an output shaft mounting a second bevel gear thereon, a planet gear for mechanically engaging with said first bevel gear and said second bevel gear and planet gear carrier means for revolving said planet gear about the axes of said bevel gears for varying the relative rotational speeds of said input bevel gear and said output bevel gear.

UNITED STATES PATENT OFFlCE 1 9 CERTlFICfi-JTE OF CORRECTION Patent No. 3,641,797 r Dated Feoruary 15," 197 2 Inventor(s) Ronald J. Bell and Edward c. O'Neal It is certified that error appears in the abovc-identified patent and that said Letters Patent are hereby corrected as shown below:

Title page after "Assigneez" delete "Hunter Engineering Company, a division of American Metal Climax, Inc." and insert-Hunter Engineering Company, Inc.-- Col. 2, line 25, "RC=(Dex=(S DeX))/Den" should be --RC=DeX (S DeX)/Den-; Col. 3, line 70, after "effecting" add -a--; 1

Col. 3, line 74, "49" (2nd occurrence) 'should be '--50--; Col. 6, line 52, "to" should be --also--; a

Col. 6, line 69, after "exit" insert --stand--;

Col. 8, line 27 after "may" insert --be--;

Col. 9, line 1, "136'" should be --3l6--;

Col. ll, line 24, delete line in its entirety.

Signed and sealed this 8th day of August 1972.

(SEAL) Attest:

EDWARQDLFLETQEDERJR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents

Claims

1. A stretcher leveling system for plastically elongating strip stock comprising: an entrance roll stand having a plurality of entrance rolls mounted thereat for rotation; an entrance gear train for driving said entrance rolls; a change gear train for providing a series of fixed gear ratios; means for mechanically connecting the entrance gear train with the change gear train; an exit roll stand having a plurality of exit rolls mounted thereat for rotation; an exit gear train for driving said exit rolls; means for mechanically connecting the exit gear train to the change gear train so that said exit gear train is mechanically connected to the entrance gear train through the change gear train in a selected gear ratio set by said change gear train thereby fixing the speed of said exit gear train; and means connected to said system for driving said rolls, wherein said strip passes through the entrance roll stand to the exit roll stand to form a closed mechanical power transmission loop; said change gear train includes: a change gearbox housing; a pair of pinion gears mounted on a shaft journaled for rotation in the change gear box housing; change gear-mounting shafts journaled on the change gearbox housing on opposite sides of said pinion gear shaft and extending substantially parallel thereto; a pair of change gears mounted on each of said mounting shafts for rotation independently thereof, said change gears engaging said pinion gears; and clutch means for drivingly connecting one of said change gears on each of said shafts to the change gear drive train.

2. A system as defined in claim 1 wherein said clutch means comprise shifting collars mounted on each of said change gear shafts for axial movement along said shafts, said shifting collars having clutch members on the opposite ends thereof and said change gears having inwardly extending mating members thereon for engaging with said shifting collar clutch members whereby said shifting collars operatively connect one of said gears on each of the change gear shafts to said shaft.

4. A stretcher leveling system for plastically elongating strip stock comprising: an entrance roll stand having a plurality of entrance rolls mounted thereat for rotation; an entrance gear train for driving said entrance rolls; a change gear train for providing a series of fixed gear ratios; means for mechanically connecting the entrance gear train with the change gear train; an exit roll stand having a plurality of exit rolls mounted thereat for rotation; an exit gear train for driving said exit rolls; means for mechanically connecting the exit gear train to the change gear train so that said exit gear train is mechanically connected to the entrance gear train through the change gear train in a selected gear ratio set by said change gear train thereby fixing the speed of said exit gear train; and means connected to said system for driving said rolls, wherein said strip passes through the entrance roll stand to the exit roll stand to form a closed mechanical power transmission loop; said change gear train includes means therein for fixing the gear ratio between said entrance stand and said exit stand at stepped finite values between 0.096 and 1.036.

5. A stretcher leveling system for plastically elongating strip stock comprising: an entrance roll stand having a plurality of entrance rolls mounted thereat for rotation; an entrance gear train for driving said entrance rolls; a change gear train for providing a series of fixed gear ratios; means for mechanically connecting the entrance gear train with the change gear train; an exit roll stand having a plurality of exit rolls mounted thereat for rotation; an exit gear train for driving said exit rolls; means for mechanically connecting the exit gear train to the change gear train so that said exit gear train is mechanically connected to the entrance gear train through the change gear train in a selected gear ratio set by said change gear train thereby fixing the speed of said exit gear train; and means connected to said system for driving said rolls, wherein said strip passes through the entrance roll stand to the exit roll stand to form a closed mechanical power transmission loop; said means for connecting said change gear train to said entrance gear train and said exit gear train comprises split gear trains.

6. A system as defined in claim 5 wherein each of said split gear trains includes a single driven shaft from said change gear train and a pair of axially spaced pinion gears mounted on said driven shaft; each of said pinion gears being mechanically connected to the roll-driving gears at the entrance and exit gear train.

8. A stretcher leveling system for plastically elongating strip stock comprising: an entrance roll stand having a plurality of entrance rolls mounted thereat for rotation; an entrance gear train for driving said entrance rolls; a change gear train for providing a series of fixed gear ratios including eight change gears and two pinion gear shafts; means for mechanically connecting the entrance gear train with the change gear train; an exit roll stand having a plurality of exit rolls mounted thereat for rotation; means for mechanically connecting the exit gear train to the change gear train so that said exit gear train is mechanically connected to the entrance gear train through the change gear train in a selected gear ratio set by said change gear train in a selected gear ratio set by said change gear train thereby fixing the speed of said exit gear train; and means connected to said system for driving said rolls, wherein said strip passes through the entrance roll stand to the exit roll stand to form a closed mechanical power transmission loop.

10. A stretcher leveling system comprising: an entry roll gear train; an exit roll gear train; a differential gear system comprising rotating mechanical input means, rotating mechanical output means, and means for varying the relative rotational speeds of said input means and said output means; and a change gear train having its input shaft connected to the output shaft of said differential gear system and having its output shaft connected to the input of said exit roll gear train; the change gear train includes a first shaft having a pair of gear members mounted thereon for rotation independent of the first shaft; a second shaft having a pair of pinion gear members mounted thereon for rotation therewith, said pinion gear members engaging said gear members on said first shaft; a third shaft having a pair of gear members mounted thereon for rotation independent of the third shaft, said gear members engaging the pinion gear members on the second shaft; and clutch means associated with said first and third shafts for operatively connecting select ones of the gear members on said first and third shafts to the respective shaft on which they are mounted for rotation with that shaft, said gear members on said first and third shafts having varying numbers of gear teeth thereon.

12. A stretcher leveling system as defined in claim 10 wherein said clutch means comprises shifting collars mounted on said first and third shafts intermediate the gear members thereon, said shifting collars being fixedly mounted to the shaft for rotation therewith and being axially translatable along said shafts for engagement with one of the respective gear members on said shaft.

13. A stretcher leveling system as defined in claim 10 wherein said gear members have a variable number of gear teeth thereon for fixing a plurality of gear ratios, the number of teeth being so selected that the differential gear system never requires greater than 1 1/2 percent variation of the relative rotational speeds of said input means and said output means for obtaining the desired elongation for stretcher leveling and compensation for roll grinddown.

14. A stretcher leveling system comprising: an entrance roll stand having a plurality of driven metallurgical rolls therein; an entrance gear train comprising a plurality of roll-driving spur gear members fixedly connected to shafts which mount said metallurgical rolls for rotation therewith, said roll-driving gear train members being mechanically interconnected such that the axes of said gear members are horizontally spaced from each other; a first split gear train power transmission system having a pair of roll neck gear members engaging spaced ones of said roll-driving gear members, shaft members mounting said roll neck gear members, a single shaft member having a pair of axially spaced pinion gear members thereon, and means for connecting said roll neck gear members to different ones of said axially spaced pinion gear members; a change gear train comprising a first shaft having a pair of gear members axially spaced thereon and mounted for rotation independent of said first shaft, a second shaft having a pair of pinion gear members thereon, said pinion gear members engaging with the gear members on said first shaft, a third shaft having a pair of gear members mounted thereon for rotation independent of said third shaft, said gear members on the third shaft engaging the pinion gear members on the second shaft and clutch means on said first and second shafts for connecting one of the gear members on each of said first and third shafts into operative engagement with the respective shaft and into the drive train across the Second shaft; means for connecting said first split gear train with said first shaft on said change gear train; a second split gear train comprising a driving shaft having a pair of axially spaced pinion gear members mounted thereon, a pair of roll neck gear members spaced from each other and means for connecting said roll neck gear members to separate ones of said pinion gear members for dividing the power transmitted from said pinion gear members mounting shaft; an exit roll stand having a plurality of horizontally spaced exit roll driving gears operatively connected to said exit rolls, spaced ones of said roll-driving gears being connected and driven by said spaced roll neck gears on said second split gear train; and means for connecting said second split gear train to said change gear train.

15. A stretcher leveling system as defined in claim 14 wherein said change gear train includes a plurality of pinion gear shafts interposed between change gear members for fixing a plurality of gear ratios and means for drivingly connecting said plurality of pinion shafts so that the final ratio is a product of the several change gear ratios across the plurality of pinion shafts.