US2567578A - Quick return mechanism for bed and cylinder presses - Google Patents

Description

P 1951 A. w. RANGER 2,567,578

QUICK RETURN MECHANISM FOR BED AND CYLINDER PRESSES Filed Dec. 5, 1947 s Sheets-Shed 1 Sept. 11 1951 A. w. R 'ANGER 5 5 QUICK RETURN MECHANISM FOR BED AND CYLINDER PRESSES Filed Dec. 5, 1947 a 7 s Sheets-Sheet '2 171 912 for I Ari/Earl W/ZZ Sept. 11, 1951 w, RANGER I 2,567,578

QUICK RETURN MECHANISM FOR BED AND CYLINDER PRESSES Filed Dec. 5, 194' 3 SheetS Sheet s Patented Sept. 11, 1951 QUICK RETURN MECHANISM FOR BED AND CYLINDER PRESSES Arthur 'Wi1lard Ranger, Brighton, England Application December 5, 1947, Serial No. 789,803

In Great Britain December 5, 1946 The invention relates to printing machines of the flat bed type, and more particularly to single revolution non-stop cylinder machines.

' It was suggested many years ago to reciprocate the bed by one mechanism 01f the main driving shaft and to rotate the impression cylinder by another mechanism only, also driven off the main shaft. Th mechanisms suggested, however were notcapable of being used in a modern machine running at high speeds.

When it is considered that the impression cylinder had to rotate at varying speeds during each revolution and the large and heavy cylinders in use at the time of this old suggestion it is obvious that the momentum of the heavy rotating mass would render any variable speed of rotation at high speed impracticable unless it would be possible to provide some effective means to absorb the shocks set up.

When a toothed rack is provided on the forme bed meshing with a toothed wheel on the impressioncylinder as in an ordinary stop cylinder flat bed machine the shocks due to the variations in speed of the cylinder can be transferred to the mechanism employed for reciprocating the forme bed which is provided with suitable bufier devices for cushioning the changes in the speed and direction of movement of the forme bed, and in addition the cylinder is fitted with brakes to retard the momentum towards the end of the printing stroke.

In the specification of my application Serial No. 653,068 and now Patent No. 2,542,705, a machine is described in which the printing cylinder is rotated during the printing period by a rack on the forme bed meshing with a toothed wheel on the printing cylinder. The printing cylinder is 1'0- tated during the non-printing period by means of a train of gears oif the main shaft of the machine which drives the mechanism for reciprocating the bed, so that, not only does the cylinder continue to rotate in synchronism with the bed during the non-printing period, but the peripheral speed of the toothed wheel on the cylinder is equal to the speed of the rack at the moments of reengagement and disengagement.

According to the present invention, the rack and toothed wheel drive between the bed and'the cylinder is dispensed with, and the complete rotation of the cylinder, during the printin and non-printing periods, is efiected by means of a train of gearing off the main shaft, while still ensuring that the cylinder rotates in synchronism with the reciprocation of the bed, and is rotating with a peripheral speed equal to the speed of the bed during the printing period.

The gearing from the main shaft includes gears 1 Claim. (Cl. 101282) of such form as to impart the requisite rotational movement to the printing cylinder during the printing period and to complete the rotation ofthe cylinder during the non-printing period. Each of the specially formed gear wheels may be briefly described as an oval gear wheel, that is one the pitch line of the teeth of which is an oval, being neither completely circular nor trulyelliptical, but may be said to be composed of sections of varying radii drawn from varying foci, so proportioned as to rotate the cylinder with'a suitably varying speed in synchronism with a complete reciprocation of the bed and so that during the printing period it is moving at the same speed as the bed.

The printing machine according to the invention is intended to be run at very high speeds, i. e. several thousands of revolutions of the impression cylinder per hour. As the bed is reciprocated by mechanism imparting a quick returnmotion to the bed,-the form of the gear wheels referred to above can be such as to avoid abrupt changes in velocity and the required rotation of the cylinder can be effected smoothly in spite of the momentum of the impression cylinder.

It will be appreciated that during part of acomplete revolution the cylinder is moving at the same speed as the forme bed, corresponding to the printing period, and that the remainder of the revolution of the cylinder has to be completed during the non-printing period, i. e. while the bed finishes its forward movement and makesits return movement to a position ready for the next printing period.

It is desirable that during the printing periodthe bed speed shall be reduced as much as is practicably possible, but the rotational speed of the cylinder during the corresponding non-printing period must be slower still to allow for the viding for an adequately long printing period or length of printing forme.

For instance, with an impression cylinder of 12 diameter weighing 300 lbs., with most of its weight near the periphery, it is possible to rotate it at 4,000 to 5,000 revolutions per hour without requiring any auxiliary controlling device for the cylinder such as brakes. The section of pitch line of each of the specially formed gear wheels, corresponding to the printing period, may comprise for example and the other section /5 of the complete ovalpitch line.

The actual form of the gear wheels required can be calculated and plotted mathematically.

In the accompanying drawings:

Figure 1 is a side sectional elevation of a printing machine with the improvements applied, other details of the machine well known in the art being omitted for the sake of clearness, the section being taken on il, Figure 2.

Figure 2 is an end sectional elevation on 22, Figure 1.

Figure 3 is a plan corresponding with Figure 1.

Figure 4 is a side view of the train of gears for driving the impression cylinder.

- Figures 5 and 6 are, respectively, a diagram and a graph to be used in calculating and plotting the pitch lines of the oval gears.

In the example of machine illustrated the impression cylinder l is fixed on a shaft 2 carried in bearings 3, 4, fixed on the main frame 5 of the machine. 1

A forme bed 8 slides to and fro on rollers 9 on guide rails Hi. It is reciprocated by a quick return driving mechanism of a type well known in the art. It comprises a slotted lever II which is fulcrumed on a shaft l2 and has a slot 13 in which slides a block l4 pivotally mounted on a crank pin [5 on a gear wheel 15 fitted on a shaft IL The shaft I1 is rotated from a main driving shaft 18 through a pinion I9 meshing with the gear wheel H5. The slotted lever H has a driving pin 20 pivotally fitted to one end 2| of a connecting rod 22, the other end forming a bearing for a pin 6 carrying a toothed wheel 23 which meshes with a rack 24 and with a rack l fixed to the underside of the reciprocating bed 8.

,This mechanism, as is well known, imparts an increased stroke to the bed, namely twice the movement of the wheel 23 and, moreover, the return stroke, to the right hand in Figure 1, is quicker than the forward stroke, to the left hand, which corresponds with the impression or printing stroke.

The movement of the bed 8 during each stroke is not uniform, that is to say, the bed starts from a momentarily stationary condition, increases in speed, then decreases and ends in a stationary condition.

This quick return driving mechanism is similar to that described in specification to application Serial No, 653,068. It may be provided with a buffer. Similarly the guide rails l may be supported on the frame and be raised and lowered relatively to the impression cylinder, and other details may be provided as described in that specification. These parts and details are not described herein as they form no essential part of the present invention.

The impression cylinder I has a peripheral impression surface 34 the remainder of the periphery of the cylinder being removed or relatively depressed to form a gap as usual to allow the forme on the bed 8 to return without contact with the cylinder.

The shaft 2 of the impression cylinder I has a gear wheel 25, Figure 4, fixed to it, which meshes with a gear wheel 26 fixed to a gear wheel 21, these two gear wheels rotating freely on a stub shaft 28 which is fixedly mounted on the frame 5. The gear wheel 21 meshes with a gear wheel 29 rotating freely on a stub shaft 30 fixedly mounted on the frame 5. The gear wheel 29 meshes with a gear wheel 3| fixed on the shaft H.

The impression cylinder I is rotated continuously by the main driving shaft [8 through the gears l9, l6 and the shaft [1 and thence through the train of gear wheels 3|, 29, 26 and 25.

In order that the impression cylinder I shall be rotated in synchronism with the reciprocating forme bed 8, and so that the impression surface 34 shall move at the same speed as the forme bed 8 while pressing the sheet of paper on to the forme on the forme bed 8 during the printing period and at the required variable speed during the remainder of its revolution, the gear wheels 25 and 26 are specially formed. For convenience they are referred to herein, and in the appended claims forming part of this specification, as oval wheels. The pitch lines for the teeth of these oval wheels are neither circular nor elliptical but are composed of sections of varying radii drawn from varying foci, so proportioned as to rotate the cylinder with a suitably variable speed in synchronism with a complete reciprocation of the forme bed.

The pitch lines of the oval gears may be derived mathematically.

For the purpose of indicating the principle the effect of the connecting rod can be ignored and the bed movement be considered as indicated in the diagram Figure 5.

Therefore the movement of bed for any given value of 0 will be Difierentiating with respect to time gives the velocity of the bed at any given movement of crank from B. D. C. (bottom dead centre).

inches Wt h 2rh cos wt Inches/See The angular velocity of cylinder at any point during printing period will be To find the radius of the cylinder driving gears at any given value of 0 during printing period.

Distance traveled by bed=2y, from (1) Angle turned by cy11nder=a 2TB Velocity of bed=v, from (2) Angular velocity of cylinder=w from (3) RatiO=w /co P Radius of cylinder gear-rc-m Example where find re and rd when 6=135 and 180 i f 8.68 for 135; 0 for 180 x/386 190 cos 0 I O I O- O a- 79 24 for 135 0 for 180 .0874X140Xc0s 0J386-190 cos 0- 6 of the train of gears 25, 26, 21, 29 and 31 or of the mechanism for reciprocating the bed 8.

I claim:

A printing machine comprising, in combination, a frame, a flat forme bed mounted for reciprocation on said frame, power drive means on said frame, quick return drive mechanism driven by said power drive means for reciprocating said bed through a relatively slow variable speed impression stroke and a relatively fast variable speed return stroke, an impression cylinder rotatably mounted on said frame above the path of said bed for cooperation with said bed during an impression period intermediate the ends of the impression stroke of the bed, and cylinder drive means on said frame and operated from said power drive means to drive said cylinder one revolution for each cycle of O. 6.26 .137 radlans/sec. for 135 .1635 radians/sec. for 180 rd=l0rc=6.1 for 135; 6.52 for 180 =3.9" for 135; 3.48 for 180 Any number of points can be found in this Way and the periphery of the gears during the printing period can be marked out accurately. During the non-printing period these points can be found graphically.

The absence of the usual rack and gear wheel drive between the forme bed and the impression cylinder enables a greater width of printing surface to be utilised for the same width of bed.

It also reduces cost of manufacture and fitting and further permits of higher printing speeds being adopted.

If desired, a registering device between the forme bed and the impression cylinder may be provided, for instance such as indicated in Figure 4, a few teeth 35 on the impression cylinder being adapted to mesh with a few teeth 36 on the bed 8, at the beginning of the printing period, so as to avoid any possibility of slight error occurring due to wear or back lash in the gearing =.8556"/sec. for 1.02/sec. for

bed movement, said cylinder drive means includ ing a first oval gear wheel journalled on said frame and driven from said power drive means at a constant speed, and a second oval gear wheel fixed with said cylinder and constantly meshing with said first oval gear wheel to drive said cylinder in synchronism with the reciprocation of said bed and at a continuously variable speed with a variable relatively slow speed between said impression periods and at a variable relatively fast speed in registry with the bed through each impression period during which it is driven at the same speed and at the same rate of acceleration and deceleration as that of said bed during the start and throughout to the end of each impression period, whereby said cylinder is driven at one revolution for each cycle of bed movement and at a continuously variable rate through each revolution thereof and without abrupt changes of cylinder speed.

ARTHUR WILLARD RANGER.

REFERENCES 1 CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 98,087 Montague Dec. 21, 1869 131,702 Potter Sept. 24, 1872 1,137,383 Colburn Apr. 27, 1915

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