US2024433A

US2024433A - Apparatus for the manufacture of the grooved rolls as used in pilger rolling mills

Info

Publication number: US2024433A
Application number: US758740A
Authority: US
Inventors: Davidson Graham
Original assignee: Stewarts and Lloyds Ltd
Current assignee: Stewarts and Lloyds Ltd
Priority date: 1934-08-22
Filing date: 1934-12-22
Publication date: 1935-12-17
Anticipated expiration: 1952-12-17

Description

. 1' 17, 1935. G. DAVIDSON 2,024,433 APPARATUS FOR THE MANUFACTURE OF THE GROOVED ROLLS AS USED IN PILGER ROLLING MILLS Filed D80. 22, 1934 4 Sheets-Sheet l Dec. 17, 1935. D V N 2,024,433

APPARATUS FOR THE MANUFACTURE OF THE GROOVED ROLLS AS USED IN PILGER ROLLING MILLS Filed Dec. 22, 1934 4 Sheets-$heet 2 Dec; 17, 1935. G, vmso I 2,024,433

APPARATUS FOR THE MANUFACTURE OF THE GROOVED ROLLS AS USED IN PILGER ROLLING MILLS Filed Dec. 22, 1934 4 Sheets-Sheet 3' 9 E0 1; O Q 15 11 12 1s ss- O O V O I o O O J I 10 v o O o o v 1g 0 o o o \w 0 as? 25 B6 27 21 3 1520672571 Ora/26072 3640562 5072 Dec. 17, 1935. G, DAVIDSON 2,024,433

APPARATUS FOR THE MANUFACTURE OF THE GROOVED ROLLS AS USED IN PILGER ROLLING MILLS Filed 'Dec. 22, 1.934- 4 Sheets-Sheet 4 Cir Patented Dec. 17, 1935 APPARATUS FOR THE MANUFACTURE OF THE GROOVED ROLLS AS USED IN PIL- V GER ROLLING MILLS Graham Davidson, Wishaw, Scotland, assignor to Stewarts and Lloyds Limited, Glasgow, Scotland Application December 22, 1934, Serial No. 758,740

' In Great Britain August 22, 1934 20 Claims.

This invention relates to apparatus, such, for instance, as set forth in the specification of Bookers Patent No. 1,499,633, used in the cutting of the v grooves of the rolls of pilger rolling mills for the manufacture of weldless tubes from hollow blooms.

In the well known Becker apparatus the cutting tool of a lathe machine is actuated by mechanism in such manner that a compound motion is given to it, this motion combining two rectilinear motions at an angle to each other, one being of a uniform speed and the other of variable speed, together with a swinging motion, the composite motion imparted to the tool producing on the roll the inclined flanks having a variable angle to the axis of rotation of the roll while a circularly curved profile between the flanks and having eccentrically ascending and descending portions, as regards rotation of the roll about its axis, is produced by the combination of a swinging motion with a rectilinear motion at a variable speed. The last mentioned rectilinear motion of the tool is effected by means of a control cam driven at constant speed. The groove as made by the Becker lathe is found to be somewhat disadvantageous in practice as rolls of the Becker profile do not give the most uniform stressing of the material of the hollow bloom being acted on due to the fact that the accumulation of material at the sides or fins, effected during the rolling process, are not drawn out equally to the adjacent parts having less material, the consequence being that the tubes produced are not as perfect as they might be, being liable to variations in the wall thickness and to small undulations in the material. r

In the rolls as made in a Becker machine the bellmouth, rolling or finishing pass, relief and gap parts of the groove are all bound by definite angles bearing a definite relationship irrespective of the diameter of the roll and, as the production of the mill is proportional to the lengths of the bellmouth and rolling pass which together with the relief make up the working portion? or working pass it means that in the case of small diameter rolls there is the further disadvantage that the mill production is not so large as it might be.

The object of this invention is to operate the tool of the lathe in such a manner that a pilger roll can be out on a Becker, or like, lathe of a profile which will allow for the accumulated material as aforesaid being so allowed for that during the pilgering in the rolling mill of the hollow bloom into the finished tube, the tube material will be much more uniformly stressed and better drawn out than heretofore, and therefore better tubes produced.

According to our invention, we provide mechanism whereby the control cam can be driven at a variable speed, that is to say, can be accelerated and decelerated during its motion, and this is done in such a manner as to cause the tool to cut the roll groove of a profile which renders the roll capable of stressing the material of the bloom during the rolling operation more uniformly and drawing it out better than heretofore, thereby giving better results than formerly. The amount of acceleration and deceleration can be varied to suit requirements by an adjustable part of the mechanism.

The effect of accelerating the control cam is that the tool, when cutting the roll, is moved into the bellmouth of the roll groove earlier than if the cam had been rotating, as usual, at constant speed, the acceleration and consequently the advancement of the tool preferably increasing, as the tool swings across the section, from zero at the inner edge of a fiat to maximum at the root of the groove and then correspondingly decreasing from the root to the inner edge of the other fiat.

The cycle of acceleration and deceleration is timed to correspond with the time taken by the tool to move round the groove from one fiat edge to the other.

The acceleration and deceleration has no effect during the action of the concentric part of the control cam so that no deepening occurs in the finishing pass of the roll, and the action throughout the relief angle is negligible as the gradient there is very gradual.

In accordance with a further feature of the invention, the second mentioned disadvantage is avoided by injecting a further alternate acceleration and deceleration into the cam motion, said acceleration and deceleration being timed so that a complete cycle thereof occurs during each revolution of the roll. Thus the working portion of the roll can be made a maximum length irrespective of the roll diameter and full production can therefore be obtained through the life of a roll.

The mechanism is characterized by the combination of two different so-called correcting motions for the drive of the control cam, the motion for correcting it during the cross sectional shaping of the bell mouth of the groove comprising a cycle of alternate acceleration and deceleration imparted to the cam drive during each swing of the tool from the inner edge of one flat to the inner edge of the other, and the motion for correcting it to vary the length of working portion of the groove comprising a cycle of alternate acceleration and deceleration imparted to the control cam drive during each revolution of the roll.

The two correcting motions may be imparted by means of a double epicyclic gear in the cam drive, comprising two elements controlled respectively with reference to the rotational speed of the roll and the traversing speed of the tool from one inner flat edge to the other.

The said elements may be controlled by variable-throw cranks driven from the control cam drive.

In order that the nature of the invention may be clearly understood, one embodiment of how the invention may be put into practice in connection with a standard Becker lathe will now be described, but merely by way of example, and with reference to the accompanying drawings, wherein:--

Fig. 1 shows diagrammatically the tool and associated mechanism of the Becker lathe and the roll in position therein.

Fig. 2 is a plan of a pilger roll as obviously produced by this lathe.

Fig. 3 shows the groove profile as corrected by the mechanism in accordance with the invention.

Fig. 4 is a front view showing diagrammatically part of a Becker lathe with an attachment in accordance with the invention.

Fig. 5 is an end view corresponding to Fig. 4.

Fig. 6 is a sectional plan view of the attachment to a larger scale.

Fig. '7 is a corresponding elevation.

Fig. 8 is a part elevation to a larger scale of the ratchet mechanism in Fig. '7.

Fig. 9 shows diagrammatically the driving motor end of the Becker lathe.

Referring to the drawings wherein the same numerals or letters denote the same parts throughout, in Fig. 9, 40 denotes the driving motor driving through gearing M the roll 4 shown mounted in the lathe and also driving the spindle 8. As shown diagrammatically in Fig. 4 the earn 3 is driven by the bevel gearing 4| on shaft 42 which is driven from the extended sleeve 9a through the intermediary of gearing 43 and a differential gear inside a casing 45, the latter being controlled to compensate for the effect of the swinging movement of the tool with reference to the cam 3. The swinging movement of the tool, which is a slow movement, is obtained by means of a worm wheel 44 connected to the cross slide and driven by a worm which is driven through gearing from the gear box of the slide rest. In Fig. 1, I denotes the cutting tool mounted on slide 2 which as the pilger roll rotates, is moved out and in in known manner by the rotatable cam 3 and the cam slot 3a to give to the pilger roll 4 the cross sectional profile as shown. The slide 2 and cam 3 are mounted on a swivelling base 5 by means of which the swinging motion is imparted to the tool.

The finishing pass, the bellmouth, the gap and the relief of the pass ofthe roll are indicated by the angles X, W, Z, and Y which they respectively subtend at the centre of the roll (Fig. 1).

In Fig. 2, the lateral flats are denoted by 6 and the arcuate groove by 1.

Referring to Fig. 6, the known control cam 3 (Fig. 1)-of the Becker lathe-4s normally driven from a spindle running at constant speed. An

extension 8 (Fig. 6) is made to this spindle and a sleeve 9 fitted on the outside thereof is connected to bevel gears (not shown) driving the control cam. The bevel gears previously were keyed direct to the spindle, but when the spindle was extended and the sleeve 9 put on, the key was removed so that the gears might rotate freely with the sleeve independently of the extended spindle, hereinafter called spindle 8. The sleeve 9 is rigidly keyed to a sleeve 9a movable 10 freely on the spindle 8 (Fig. 6) and terminating in a pinion II. Keyed on the shaft 8 is a pinion ID. The pinions I0 and II are the same size. On the spindle 8 runs a loose disc I2 with stubaxles I3 carrying planet wheels I4, I5 which engage respectively with the above-mentioned two pinions I0, Ii. On the outside of the planet wheels I4, I5 are two internally toothed rings I6, I! gearing respectively with said wheels and loosely mounted respectively on the spindle 8 and the sleeve 9a of the pinion II.

The above forms a double epicyclic unit and its action is as follows:

For one clockwise revolution of the pinion I 9 (holding the rings I6, I! stationary), the planet wheel I4 is turned in an anti-clockwise direction, and since it revolves itself on the teeth of its outer ring I6 it will drag the disc I2 round in a clockwise direction. This disc will then drag the axle of the second planet wheel l5 round in a clockwise direction, and this planet wheel will rotate itself in an anti-clockwise direction against the teeth of its outer ring I! and will therefore force the pinion II round in a clockwise direction. If (as shown) the two pinions I0, I I are of the same 5 size, the planet wheels I4, I5 of the same size, and the rings I 6, I! of the same size, then, for one clockwise revolution of the pinion I 0, there is one clockwise revolution of the pinion i I provided the rings I6, I! are held stationary. If the ring I6 is allowed to move freely, then the planet wheel I4 will merely rotate on its axle without moving the disc I2 and consequently no motion will be imparted to the pinion II and the cam 3 will remain stationary.

Thus it will be seen that, while the pinion is rotating uniformly with the driving spindle 8 of the control cam 3, it is possible to alter the motion of the second or driven pinion II by controlling the motion of the said ring IE5, the other ring I! meanwhile being held stationary.

Similarly, if the ring I6 is held stationary the motion of the driven pinion I I can still be altered by controlling the movement of the ring I! so that there are two independent sources of control over the motion of the driven pinion H which, as aforesaid, is connected with the control cam 3 of the lathe.

By moving the rings I6, I! simultaneously any motions imparted to the rings will be combined into a resultant motion which will be imparted to the driving sleeve of the control cam through the driven pinion I I.

The motion imparted to the ring I! is given by rotation of a disc I8 through a connecting rod I 9 connected, at one end, to the ring I! and, at the other, to a square-headed crank-pin 2i adjustable in the diametral slot 2|. By putting the crank pin 20 at the centre of the disc I8 no motion is imparted to the ring I7, but by placing the crank pin at the extreme end of the slot 2I the maximum oscillatory movement is imparted to the ring I I. As the ring I1 acts on the tool to cause deepening of the bellmouth W of the roll groove as the roll rotates the disc I8 is timed 7 to give one complete revolution as the tool I cuts across the roll section from the inner edge of one fiat to the inner edge of the other (from A to B, Fig. 3). The effect of this, at a section across the bellmouth W, is to deepen the groove by varying the curve gradually'from the usual almost semi-circular arcuate shape as shown in full lines, Fig. 3, to the shape part oval shape, which is not now per se, indicated in dotted lines, by relatively displacing the jaw curves through certain angles against the direction of rotation of the rolls. The finishing pass X, which is concentric with 'the axis of the roll, is not deepened owing to the fact that the angular motion of the cam 3 has been retarded in the concentric portion, and so does not impart any transverse radial motion to the tool during the machining of the finishing pass. This is a very slow motion, and is accomplished through reduction gearing, the action of which will be explained later.

The motion of the ring I6 is obtained in exactly the same way from another slotted disc 22, connected to the said ring through connecting rod 59a, by locating the crank pin 20a, in the slot 21a at predetermined positions between the centre of the disc and the periphery. The essential difference is that the disc 22 makes one revolution for each turn of the roll in the lathe. The connections to the rings l6 and I! are made in the same way. In Fig. 6 the connecting rods are broken off. a

Thus, it will be seen that there is a constant oscillatory motion imparted to the ring it .of a frequency equal to the number of revolutions per minute of the roll being machined, which motion causes alternate accelerations and decelerations of the same frequencyin the control cam, and, superimposedon this is a slow oscillatory motion injected by means of the ring I! which is oscillated by means of the connecting rod 19 and associated mechanism timed over the complete radial traverse of the tool round the curved portion. of the cross section of the roll.

The result is the production of a roll with a groove of improved shape giving a constant working length with a bellmouth corrected as indicated by the dotted line in Fig. 3 to accommodate the accumulation of material which is unavoidable in any Pilger process due to the necessary lateral relief of the rolls.

The improved rolls materially increase the rate of tube production and definitely eliminate most of the non-uniformity in the tube walls. Further, the rolls enable thin gauge tubes to be rolled without the well-known crescent shaped marking and splitting of the material because they allow of a much more uniform fiowof-mate-V rial through the working pass of the rolls.

It must be noted that the attachment apparatus in accordance with the invention does not interfere in any way with the gradual lessening of the relief angle B (Fig. 3) from the beginning of the bellmouth W to the beginning of the rolling or finishing pass which is accomplished by a special mechanism already in the standard Becker lathe.

The motion of the disc l8.controlling the deepening effect is accomplished by gearing down from the driving spindle 8 which runs at constant speed, through the

gear wheels

24, 25, 26 on to an externally toothed ring 21 bolted to the disc 22. Round the circumference of the disc 22 are bolted six cams 28 which actuate the roller follower 29 mounted in a forked member 30 of bell crank shape which is pivoted about the axis 3i and carries the spring-urged pawl 32'engaging the ratchet wheel 33. The follower E9 is urged into engagement with the cams by means of the spring-urged abutment 34 and the ratchet wheel is locked against retrograde movement by means of the spring-urged detent35.

As a guard against an over-swing on the forward movement of the ratchet'a small brake pad is allowed to rub on the side surface of the said ratchet wheel 33. I

Further, as it may be necessary sometimes to adjust the angular position of the disc IS with relation to the rest of the mechanism, a clutch is embodied which disengages wheel 36 from 3? by sliding the former along a feather key on its shaft. 7

The ratchet wheel 33 drives the disc 18 through

gear wheels

36, 31, 38 and toothed ring 39 which is bolted to said disc I8. The reason for the mechanism being constructed in this way is because the travel of the Becker lathe tool across the roll is controlled by a ratchet capable of altering the cross feed according to whether 1,25

2, 3 or more teeth are taken in one sweep of the pawl. To correspond with this it is necessary to put on 1, 2,3 or more cams on the disc 22. V

This portion of the attachment is capable of adjustment so that further variations which may be desired can be made in the shape of the cross section of the roll by the following method:-

Suppose the number of teeth for the cross feed on the Becker lathe is three, then normally three cams 28'would be put on the disc 22, but it is also possible for the first sixth part of the cross travel to put on two cams, for the second sixth part three cams, and for the third sixth part four cams, for the fourth sixth part four cams, for the fifth sixth part three cams, and for the last 4 sixth part two cams. It is to be noted that this refers to the circular part of the travel between the inner edges of the flats, thus giving a groove with a smaller root curve than if three cams had been used for the entire travel.

It will be seen from the foregoing that a number of roll cross sections can be effected with this mechanism.

In Fig. 7 six cams are shown on the disc 22 being removably secured by set pins.

With a Becker lathe provided with our invention it is not only possible to lengthen the working portion or pass of the rolls, but, also, when using extra large diameter rolls, to shorten the pass to suit the maximum stroke of the air cylinder of the Pilger mill for returning the mandrel bar and bloom between the rolls at each revolution thereof.

The mechanism hereinbefore described, while specially applicable to lathe machines of the Becker type, is also applicable to other lathe machines working on the same or similar principle.

I claim:

V 1. In a lathe for shaping the grooves of pilger rolls, including means for rotating a roll, a cutting tool and a cam for moving said tool out and in with reference to the roll; mechanism for imparting timed acceleration and deceleration to said cam. v

2. In a lathe for shaping the grooves'of pilger rolls, includ ng means for rotating a roll, a cutting tool, a rotating control cam for moving said tool out and in with reference to the roll, driving means for the cam and means for imparting an arcuate swinging motion to the tool; correcting mechanism in said driving means for imparting timed acceleration and deceleration to said cam so that the ordinary arcuate cross section of the curved part of the groove can be varied by deepening it at the part known as the bellmouth.

3. In a lathe for shaping the grooves of pilger rolls, including means for rotating a roll, a cutting tool, a rotating control cam for moving said tool out and in with reference to the roll, driving means for the cam and means for imparting an arcuate swinging motion to the tool; correcting mechanism in said driving means for imparting a cycle of acceleration and deceleration to said cam during each swing of the tool.

4. In a lathe for shaping the grooves of pilger rolls, including means for rotating a roll, a cutting tool, a rotating control cam for moving said tool out and in with reference to the roll, driving means for the cam and means for imparting an arcuate swinging motion to the tool; correcting mechanism in said driving means for imparting a cycle of acceleration and deceleration to said cam during each revolution of the roll.

5. In a lathe for shaping the grooves of pilger rolls, including means for rotating a roll, a cuting tool, a rotating control cam for moving said tool out and in with reference to the roll, driving means for the cam and means for imparting an arcuate swinging motion to the tool; a correcting mechanism in said driving means for imparting a cycle of acceleration and deceleration to said cam during each swing of the tool and a further correcting mechanism in said driving means for imparting a cycle of acceleration and deceleration to said cam during each revolution of the roll.

6. In a lathe for shaping the grooves of pilger rolls, including means for rotating a roll, a cutting tool, a rotating control cam for moving said tool out and in with reference to the roll, driving means for the cam and means for imparting an arcuate swinging motion to the tool; a correcting mechanism in said driving means for imparting a cycle of acceleration and deceleration to said cam during each swing of the tool, a further correcting mechanism in said driving means for imparting a cycle of acceleration and deceleration to said cam during each revolution of the roll and means interconnecting said correcting mechanisms whereby the former is controlled from the latter.

7. In a lathe for shaping the grooves of pilger rolls, including means for rotating a roll, a cutting tool, a rotating control cam for moving said tool out and in with reference to the roll, driving means for the cam and means for imparting an, arcuate swinging motion to the tool;

an epicyclic gear in said driving means and means for controlling said gear so as to impart a cycle of acceleration and deceleration to said cam during each swing of the tool.

8. In a lathe for shaping the grooves of pilger rolls, including means for rotating a roll, a cutting tool, a rotating control cam for moving said tool out and in with reference to the roll, driving means for the cam and means for imparting an arcuate swinging motion to the tool; an epicyclic gear in said driving means and means for controlling said gear so as to impart a cycle of acceleration and deceleration to said cam during each rotation of the roll.

9. In a lathe for shaping the grooves of pilger rolls. including means for rotating a roll, a cutting tool, a rotating control cam for moving said tool out and in with reference to the roll, driving means for the cam and means for imparting an arcuate swinging motion to the tool; an epicyclic gear in said driving means and means for 5 controlling said gear so as to impart a cycle of acceleration and deceleration to said cam during each swing of the tool, a further epicyclic gear in said driving means and means for controlling said gear so as to impart a cycle of ac- 10 celeration and deceleration to said cam during each rotation of the roll, and means interconnecting said control means.

10. In a lathe for shaping the grooves of pilger rolls, including means for rotating a roll, a cut- 15 ting tool, a rotating control cam for moving said tool out and in with reference to the roll, a power drive for the cam and means for imparting an arcuate swinging motion to the tool; an epicyclic gear in said drive, a variable throw-crank 0 connected at its reciprocating end to an element of said gear and means for rotating said crank once for every revolution of the roll.

11. In a lathe for shaping the grooves of pilger rolls, including means for rotating a roll, a cut- 25 ting tool, a rotating control cam for moving said tool out and in with reference to the roll, a power drive for the cam and means for imparting an arcuate swinging motion to the tool; an epicyclic gear in said drive, a variable-throw crank 0 connected at its reciprocating end to an element of said gear and means for rotating said crank once during each swing of the tool.

12. In a lathe for shaping the grooves of pilger rolls, including means for rotating a roll, a cut- 5 ting tool, a rotating control cam for moving said tool out and in with reference to the roll, a power drive for the cam and means for imparting an arcuate swinging motion to the tool; an epicyclic gear comprising a sun, wheel, a planet wheel and 40 a rotatable ring member engaging said planet wheel; a rotating member, means for driving said member from said drive, so that the member rotates once for each rotation of the roll, a connecting rod attached to said ring member and a 5 radially adjustable connection on said rotating member for said rod.

13. In a lathe for shaping the grooves of pilger rolls, including means for rotating a roll, a cutting tool, a rotating control cam for moving said i tool out and in with reference to the roll, a power drive for the cam and means for imparting an arcuate swinging motion to the tool; an epicyclic gear comprising a sun wheel, a planet wheel and a ring member engaging said planet wheel; a rotating member, means for driving said member from said drive so that it rotates once during each swing of the tool, a connecting rod attached to said ring member and a radially adjustable connection on said rotating member for said rod.

'14. In a lathe for shaping the grooves of pilger rolls, including means for rotating a roll, a cutting tool, a rotating control cam for moving said tool out and in with reference to the roll, a drive for the cam and means for imparting an arcuatc 5 swinging motion to the tool; an epicyclic gear in said drive comprising a sun pinion, a planet wheel and a toothed ring member engaging the same; and means for imparting a complete oscillation to said ring member during each rotation of the roll. I

15. In a lathe for shaping the grooves of pilger rolls, including means for rotating a roll, a cutting tool, a rotating control cam for moving said tool out and in with-reference to the roll, a drive ing cam for moving said tool in and out with ref- 7 erence to the roll during each revolution of the roll, a drive for the cam and means for imparting a slow, arcuate swinging motion to the tool; a double epicyclic gear in said drive, each gear comprising a sun wheel, a planet wheel and a rotatable ring member; means for imparting a complete oscillation to one ring member during each rotation of the roll and means for imparting a complete oscillation to the other ring memher during each swing of the tool. i

17. In a lathe for shaping the grooves of pilger rolls, including means for rotating a roll, a rotating cam for moving said tool in and out with reference to the roll during each revolution of the roll, a drive for the cam and means for imparting a slow, arcuate swinging motion to the tool; a double epicyclic gear in said drive each com prising a toothed sun wheel, a planet wheel and a rotatable toothed ring engaging said planet Wheel; a control element for each ring comprising a rotating slotted disc, a connecting rod, an adjustable connection for an end of said rod in said slot and a connection for the other end to the respective ring; gearing between said drive and one of said discs which is rotated once for each rotation of the roll, and reduction gearing between said disc and the other disc for rotating the latter once during each swingof the tool.

18. In a lathe for shaping the grooves of pilger rolls, including means for rotating a roll, a rotating cam for moving said tool in and outwith reference to the roll during each revolution of the roll, a drive for the cam and means for imparting a slow arcuate, swinging motion to the tool; a double epicyclic gear in said drive each comprising a toothed sun wheel, a planet wheel 5 and a rotatable toothed ring engaging said planet wheel; 'a control element for each ring comprising a rotating slotted drive, a connecting rod, an adjustable connection for an end of said rod in said slot and a connection for the other end to 10 the respective ring; gearing between said drive and one of said discs which is rotated once for each rotation of the roll, reduction gearing between said first disc and the other disc, spaced removable cams on said first disc and pawl and ratchet means operated by said cams for driving said reduction gearing so that said second disc is rotated once during each swing of the'tool.

19. Correcting mechanism for the cam drive of a Becker lathe, comprising epicyclic gear means and cyclic control means operated by the drive itself for imparting a cycle of acceleration and deceleration timed over each revolution of the roll and a cycle of acceleration and deceleration timed over each swing of the tool.

20. Correcting mechanism for the control cam drive of a Becker lathe, comprising a double epicyclic gear, each including a toothed sun wheel,

a toothed planet wheel,- and a toothed rotatable ring; a control element for each ring including a rotatable and diametrally slotted disc, a connecting rod connected to the respective ring and an adjustable connection in the slot for said rod, gearing for driving one of said disc members from the control cam drive, spaced cams on said disc, a removable mounting for said cams, a pawl and ratchet mechanism driven by said cams and gearing between said mechanism and the other disc, said gearing being driven by said pawl and ratchet mechanism.

GRAHAM DAVIDSON.