US3613471A - Counterbalancing means for cutoff knives - Google Patents

Abstract

A KINEMATIC OR QUADRIC CHAIN TYPE ADJUSTABLE SPEED KNIFE DRIVING MECHANISM IS PROVIDED WITH A COUNTERBALANCING MEANS FREELY ROTATED ON THE SHAFT WHICH DIRECTLY DRIVES THE KNIFE BARS. THE DRIVE ARMS OR LINKS FOR THE KNIFE BARS AND THE COUNTERBALANCING MEANS ARE DRIVEN AT SPEEDS WHICH VARY CYCLICALLY WITHIN EACH REVOLUTION OF THE KNIFE BAR, WITH THE ARM DRIVING THE COUNTER BALANCING LINK ARRANGED TO PUSH THE COUNTERBALANCE WHILE THE ARM DRIVING THE KNIFE BARS IS ARRANGED TO PULL THE KNIFE CRANK. THE DRIVING PINS CONNECTING THE COUNTERBALANCE AND KNIFE CRANK TO THE INPUT POWER SOURCE ARE SPACED APART BY AN ANGULAR DISTANCE IN THE ORDER OF 60-90 DEGREES, WITH THE PIN FOR THE COUNTERBALANCE DRIVE ARM LEADING THE PIN FOR THE KNIFE BAR DRIVE ARM.
D R A W I N G

Description

Oct. 19, 1971 A. F. SHIELDS COUNTERBALANCING MEANS FOR CUTOFF KNIVES Filed 001;. 20, 1969 3 Sheets-Sheet 1 A. F. SHIELDS COUNTERBALANCING MEANS FOR CUTOFF KNIVES Oct. 19, 1971 3 Sheets-Sheet 2 Filed Oct. 20, 1969 w m Rm a my N r W Q? m M M M W M 6 m a y MW WM. 6 r 4/ 0 w 0 5 i J r. m m a 5 MM 6 XKNuQNmS Oct. 19, 1971 A. F. SHIELDS COUNTERBALANCING MEANS FOR CUTOFF KNIVES Filed Oct. 20, 1969 3 Sheets-Sheet 5 R. m m V W /A' 35/67 fly/62M United States Patent US. Cl. 74-393 15 Claims ABSTRACT OF THE DISCLOSURE A kinematic or quadric chain type adjustable speed knife driving mechanism is provided with a counterbalancing means freely rotated on the shaft which directly drives the knife bars. The drive arms or links for the knife bars and the counterbalancing means are driven at speeds which vary cyclically within each revolution of the knife bar, with the arm driving the counter balancing link arranged to push the counterbalance while the arm driving the knife bars is arranged to pull the knife crank. The driving pins connecting the counterbalance and knife crank to the input power source are spaced apart by an angular distance in the order of 60-90 degrees, with the pin for the counterbalance drive arm leading the pin for the knife bar drive arm.

This invention relates to an improvement of the structure shown in my U.S. Pat. 3,176,565 issued Apr. 6, 1965 for a Counterbalancing Means for Cutoff Knives. More particularly, this invention relates to novel counterbalancing means for an adjustable transmission which produces cyclically varying speeds to drive knife bars in a manner such that a web travelling at uniform speed will not buckle or rip as it is cut transversely into sheets.

There are many machine applications in which it is necessary to produce cyclically varying speeds with a transmission which is readily adjustable to the speed pattern within a cycle. One such application is manufacturing corrugated sheets of corrugated board in which the web material, after having passed through the corugating machines, is fed at a continuous predetermined speed through a cutting mechanism which cuts the material at different predetermined lengths. The cutting mechanism usually comprises a pair of knives mounted on individual rotating drums or bars, one drum located above and one drum located below the sheet to be cut so that the knives cyclically engage and cut the sheet material.

The length of sheet cut by the knives depends upon the time taken for the knives to complete each revolution or cycle. Accordingly, in order to change the lengths of the sheets, the r.p.m. of the knife drums is changed. However, during the cutting interval, it is essential that the speed of the knives shall be equal to or substantially in synchronism with the linear movement of the sheet material in order to prevent either buckling of the sheet which would occur if the knives move too slowly, or rip ping of the sheet which would occur if the knives move too fast.

The device of my aforesaid Pat. 3,176,565 secures synchronism between the knives and the moving web by employing the principle of a kinematic or quadric chain having four turning pairs. Of necessity there is a certain amount of backlash and play associated with the gears and pivoted connections of the device. The cyclically variable speed which is necessary to bring the knife blades up to the paper speed during the cutting sets up heavy forces tending to vibrate the mechanism. This leads to sheet length variations due to the fact that slack and blacklash are not taken up to the same degree for each cutting operation. In order to overcome this difficulty, means are provided for producing a force to counterbalance the ice forces tending to send the system into vibration. The cyclically variable load induced by the linkages which drive the knife bars is counterbalanced by a similar cyclically variable load induced by the drive to a counterbalancing crank which may drive a counterbalance-wheel. The elements of the counterbalancing system are so proportioned and arranged that the system uses the same inertial moment averaged over a cycle as the knife bar assembly and its driving elements.

A typical machine for cutting sheets in size ranges between 50 and 200" long is provided with knife bar drums of 14 diameter. For such a typical machine constructed in accordance with teachings of my aforesaid Pat. 3,176,- 565, the counterbalancing means consists of a rotating weight freely mounted upon the drive shaft for the knife bars, with the driving pivots for the counterbalancing weight and the knife bar dri-ve arm being spaced apart. While this arrangement was imminently satisfactory for shorter length sheets, counterbalancing effectiveness deteriorated as sheet length increased.

In order to improve counterbalancing performance while cutting relatively long length sheets without deteriorating performance while cutting shorter sheets, the instant invention provides a device in which the drive pivots for the counterbalance and knife bars are spaced apart by an angle falling in the range of 6090, with the counterbalance drive pivot leading the knife bar drive pivot. In addition, the knife bar drive arm is driven in tension, while the counterbalance drive arm is driven in compression. This arrangement results in a structure in which the counterbalance weight is rapidly decelerating during the period immediately preceding cutting when the knife bars are accelerating. The overall effect is to obtain smooth operation over an extended range of sheet length sizes.

Accordingly, a primary object of the instant invention is to provide a novel counterbalancing means for transmissions which produce adjustable cyclically variable speed patterns.

Another object is to provide an improved simple link means which produces a cyclically variable counterbalancing moment to offset the tendency for vibration in a drive system for cutoff knives adapted to operate over a relatively wide range of sheet lengths.

Still another object of this invention is to provide a novel counterbalancing means, for a kinematic or quadric chain drive, which secures synchronism between the cutoff knife and moving web over an extended range of sheet lengths.

These objects as well as other objects of this invention will become readily apparent after reading the following description of the accompanying drawings in which:

FIG. 1 is a perspective, in schematic form, of a cutoff knife drive system incorporating a counterbalancing means constructed in accordance with teachings of the instant invention.

FIG. 2 is a velocity diagram for the drive system of FIG. 1.

FIG. 3 is a rear elevation of a cutoff knife and transmission embodying the principles illustrated in FIG. 1.

FIGS. 4, 5 and 6 are cross-sections taken through lines 44, 5-5 and 6-6, respectively, of FIG. 3 looking in the directions of the respective arrows.

FIG. 7 is a side elevation of the mechanism of FIG. 3, looking in the direction of arrows 7-7 of FIG. 3.

Referring to FIG. 1, shaft 1, driven from any suitable source of power, drives the Reeves 2 through which adjustable speeds are obtained on output shaft 3 which is connected by chain belt 4 to shaft 5 determining the fixed center of my mechanism. Secured by any suitable means to the shaft 5 is pinion 6 meshing with gear 7 keyed to a shaft 8 which rotates turning link 9. Turning link 9 carries moving pivot pins 10 and 102. Pin 10 carries connecting arm or link 11 arranged to rotate with respect to the turning link 9 on the pin 10. Connecting link 11 is also rotatably mounted at its opposite end to pin 12, through which it carries a second rotatable link 13 which in turn is fastened at its opposite end, as by a keyway 14, to knife carrying shaft 15 which carries drum or bar 16 on which is mounted the knife 17.

Gear 18, carried at one end of drum 16, meshes with gear 19 which is secured to and drives knife drum carry ing shaft 20 on which is mounted drum 21 carrying knife 22. As drums 16 and 21 rotate in a counterclockwise and clockwise direction respectively and the corrugated board 23 coming from a single facer or double backer (not shown) is fed between the drums by feed rolls 24 and 25, cutting knives 17 and 22 cyclically engage and cut strip material 23 which is being fed forward by feed rollers 24 and 25 driven through sprocket and chain mechanism 26, 27 and 28 by shaft 1 from a source of power (not shown).

Referring now again to the kinematic chain including rotating link 9, connecting link 11 and rotating link 13, it will be seen that as the power from the Reeves unit 2 drives the shaft and through it pinion 6 and gear 7, the rotation of the shaft 8 causes a rotation of the rotating link 9. As link 9 rotates it acts as a crank to drive connecting link 11 in tension. Inasmuch as the distance between the pins and 12 is fixed, as crank mechanism 9 rotates, a corresponding movement of link 11 at pin 12 must occur.

This movement of pin 12 by link 11, in turn, drives the second rotating link 13, rotating the shaft 15. Thus, the result of this quadric or double crank movement is to produce a rotation of the pin 10 about the shaft 8 as a center and the rotation of the pin 12 about the shaft as a center.

Inasmuch as the shaft 8 is rotating at a constant speed from the power supplied by the Reeves drive 2, the pin 10 will also rotate at a constant speed. The actual rotation of pin 10 may of course be resolved into two components:

(1) the component in the direction of the connecting link 11 and (2) at right angles to this latter direction. It is this former component which will produce the actual momentary velocity of pin 12.

By this arrangement a constant velocity of link 9 produces a variable velocity of link 13 during each cycle as explained in detail in my US. Pat. No. 2,202,872. During each revolution of link 13 there is a time when the link at a predetermined displacement has a linear velocity synchronous with the movement of the sheet material. This synchronous movement of the driven link and sheet at a predetermined angular displacement obtains irrespective of the speed of rotation of the constant speed driven link. The speed of the latter is changed by the Reeves drive as already explained in order to change the period of each cycle of both the driving and driven link so as to change the size of sheet cut. Notwithstanding this change in speed of the driven link however, this latter link will move at synchronous speed with the sheet at a predetermined angular displacement thereof which in turn is fixed as the cutting position at which the knives engage the sheet material for cutting.

In order to insure that the synchronous speed occurs at a predetermined angular displacement of the driven link, the adjustments of the constant speed link must be made through a predetermined arcuate path. The mechanism for accomplishing this includes the electrical control motor 31 which through worm 32 and worm gear 33 drives shaft 34 carrying, for rotation therewith, worm 35. Worm 35 meshes with gear sector 36, mounted through the arm 39 on the shaft housing 41. As worm gear sector 36 is turned through an angle, it in turn carries gear 7 and the shaft 8 which is pivoted about the center of shaft 5.

Gear sector 36, which is attached to the housings for both shafts 8 and 5, thereby moves shaft 8 along an arcuate path about shaft 5 as a center while maintaining a fixed distance therebetween. This results in a change in the distance between the centers of shafts 8 and 15 and thereby changes the length effect therebetween so that the rate of acceleration and deceleration for each cycle is changed.

Also carried on shaft 34 is a worm 42 meshing with worm gear 43 which rotates shaft 44 on the other end of which is carried an indicator 45. By means of indicator 45 the angular rotation that the motor 31 should transfer to the shaft 34 for any predetermined adjustment of Reeves drive 2 is predetermined so as to stop motor 31 when the necessary adjustment has been obtained. Automatic adjustment of the connecting links for each change in Reeves drive 2 produced for different lengths of a sheet material also occurs. This is accomplished by extending shaft 34 to worm 46 which meshes with worm gear 47 driving shaft 48 which in turn, through screw 48 and fork 51, adjusts the belt of Reeves drive 2 corresponding to the adjustment made by the motor of the adjusting mechanism. It will be understood that the construction of the Reeves drive adjusting mechanism is such that as sheet length is varied the cut-off mechanism will automatically be adjusted to bring the knife blades to the speed of the web at the time of cutting, with this knife blade speed being the maximum speed during each revolution of the knife carrying drum.

The cyclically variable speed of driven shaft 15 which imparts variable speed to the cutting knife mechanism tends to impart vibration to the mechanism hereinbefore described. Vibration will result in inaccuracies occurring during the cutting operation so that the sheet lengths will be non-uniform. In order to overcome the tendency of the mechanism to vibrate, a counterbalancing means is provided.

This counterbalancing means comprises moving pivot pin 102 on rotating arm 9. Pin 102 is connected to one end of link 103, whose other end is connected through pin 104 to the free end of link 105. The other end of link 105 is mounted upon shaft 15 so as to be freely rotatable thereabout. Thus, as driving shaft 8 is rotated at uniform speed a cyclically varying counterbalancing force will be applied to shaft 15 through the coaction of links 9 and 105 interconnected by compressioned link 103, in a manner similar to the manner in which shaft 15 is driven through the cooperation of links 13 and 9 connected by tensioned link 11.

In order to provide a more effective counterbalance, counterbalance-wheel 106 (indicated in phantom) is connected to arm 105 and is positioned concentric with output shaft 15. The combination of arm 105 and wheel 106 possesses the same rotative inertia as the knife drums 16, 21.

The arms 9, 13 and 105 and driving links 11 and 103 are so arranged and proportioned that during the cutting interval arms 13 and 105 are angularly displaced in such a manner that the force on shaft 8, which results from driving arm 13, is counter-balanced by a force in the opposite direction which results from the counterbalancing arm 105.

This is illustrated graphically in FIG. 2, in which the velocity curve B for counterbalance 105, 106 is superimposed on the velocity curve C for knife drums 16, 21. Cutting of web 23 by knives 17, 22 takes place when drums 16, 21 are at maximum speed, illustrated in FIG. 2 as being point A on curve C. It is noted that the slope of curve C is rising most rapidly as point A is being approached. Thus, knife drums 16, 21 are accelerating fast est in the period immediately preceding the cutting of web 23. During this period the slope of the counterbalance curve B shows a rapid decrease in velocity, or rapid deceleration. The rapid acceleration of knife drum 16, 21 in the interval immediately preceding cutting of Web 23 combined with rapid deceleration of counterbalance 105,

106 during this same period results in extremely smooth 7 operation. By spacing the velocity peaks on curves B and C approximately 70 apart, particularly smooth operation is obtained for a relatively wide range of sheet lengths. Relatively superior smooth operation over an extended range of sheet lengths is obtainable by spacing the velocity maximums apart by angular distances in the range of between 60 and 90.

The spacing in time between points A and D of maximum velocity is a function of the angular spacing between drive and counterbalance drive arm pivot pins 10 and 102. Such angular spacing is measured along an are about intermediate shaft 8 as a center, with such are extending between lines radiating from shaft 8 and intersecting pivot pins 10 and 102. It is also noted that the direction of rotation for turning link 9 is such that pivot pin 102 is in a position leading pivot pin 10.

FIGS. 3 through 7 illustrate a physical structure embodying the principles previously described in connection with FIG. 1. In order to correlate the elements of FIGS. 3 through 7 to the elements of FIG. 1, the former, where practical, are the same as the latter followed by a lower case a.

Thus, in the embodiment of FIGS. 3 through 7 chain belt 4a drives a gear keyed to fixed center 5a journaled for rotation in bearing means (not shown) carried by frame upright 301. Shaft 5a is keyed to pinion 6a, whose teeth are in mesh with the internal teeth of gear 7a.

Disk 9a is mounted for rotation about stub shaft 8a mounted on carrier 41a and located laterally by nut 8b, received by threaded formations at one end of shaft 8a. Carrier 41a is shaped as a circular segment having gear teeth 36a along the arcuate edge thereof. Gear teeth 36a are in engagement with worm 35a suitably mounted to bearings (not shown) carried by frame upright 301. R- tation of worm 35a is effective to pivot carrier 41a about fixed center a and in so doing pivot the center 8a of drive disk 9a about fixed center 5a. Thus, it is seen that center 8a is adjustable, or movable, in an arcuate path about the fixed center of input shaft 5a.

Pin 10a secures one end of connecting link 11a to disk 9:: at a point along its periphery. The other end of link 11a is connected through pin 12a to one end of drive link 13a, which is keyed to fixed output shafts 15a journaled for rotation in bearings (not shown) carried by frame upright 302.

Pin 102a secures one end of connecting link 1030 to disk 9a at a peripheral point thereof removed substantially 70 (FIGS. 4 and 5) from pin 10a. The other end of link 103a is connected through pin 104a to counterbalancing link 105a near its outer end, while the inner end of link 105a is freely mounted for rotation about output shaft 15a. counterbalance-wheel 106a is mounted to the outer end of link 105a in a position concentric with shaft 15a. It is noted that drive link 13a is disposed between counterbalancing link 105a and the web 305 of wheel 106a.

The machine frame is provided with another upright 303 extending parallel to uprights 301 and 302. Drums 16a and 21a carrying knives 17a and 22a, respectively, are mounted to shafts 15a and a extending between uprights 302 and 303. Shaft 15:: carries gear 18a, whose teeth are in mesh with the teeth of gear 19a keyed to shaft 20a. Drums 16a and 21a are angularly related in a manner such that knives 17a and 22w mesh along the path of sheet material fed between drums 16a and 21a.

As explained in detail in my aforesaid Pat. 2,202,872, the mounting of movable center 8a for arcuate movement about fixed center 5a enables the speed pattern at output shaft 150 to be varied over a wide range, yet in each case the maximum speed of shaft 15a will occur at a point A (FIG. 2) in the cycle when knives 17a and 22a are in mesh. In like manner, the speed pattern for counterbalancing link 105a will automatically adjust to conform with the speed pattern for output shaft 15a.

Although there have been described preferred embodi- 6 ments of this novel invention, many variations and modifications will now be apparent to those skilled in the art. Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the appending claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. An adjustable transmission for transforming a constant speed input to a cyclically varying output, said transmission comprising an input shaft, an output shaft, an intermediate shaft, means defining a path of movement for said intermediate shaft relative to said input and said output shaft, means for operating said intermediate shaft to a selected point along said path, a first link one end of which is in driving engagement with said output shaft, a second link one end of which is freely mounted to said output shaft, connecting means joining said links at the other ends thereof to said intermediate shaft in a manner such that said links are rotated in the same direction by a driving force applied at said input shaft with each of said links completing a revolution in equal time intervals for all revolutions; said intermediate shaft being positionable along said path to operate said connecting means in a manner such that the distances between said other ends of said links and said intermediate shaft shift within each revolution of said intermediate shaft whereby said first link rotates said output shaft at a speed which varies within each revolution of said output shaft and said second link applies a counterbalancing force to said output shaft at a cyclically varying rate, said connecting means including first and second pivots to which the respective first and second links are connected, said pivots being spaced apart by an angular distance in the range of 60 to degrees measured along an are drawn about said intermediate shaft as a center and extending between lines which radiate from said intermediate shaft through each of said pivots.

2. A transmission as set forth in claim 1, in which said second pivot is in a position leading said first pivot as said intermediate shaft rotates.

3. A transmission as set forth in claim 1, in which said angular distance is substantially 70 degrees.

4. A transmission as set forth in claim 2, in which said pivots define axes parallel to and laterally spaced from said intermediate shaft, said pivots being driven in unison about said intermediate shaft as a center.

5. A transmission as set forth in claim 4, in which the connecting means also includes a drive arm and a counterbalance, said drive arm pivotally connected at opposite ends thereof to said first pivot and said first link, said counterbalance pivotally connected at spaced locations thereof to said second pivot and said second link.

6. A transmission as set forth in claim 5, in which the drive arm is pulled and the counterbalance is pushed during rotation of said intermediate shaft.

7. A transmission as set forth in claim 6, in which said angular distance is substantially 70 degrees.

8. A transmission as set forth in claim 6, constituting part of a mechanism for cutting a traveling web, said mechanism also including a knife means driven by said output shaft to transform said web into sheets by cutting said web transverse to its direction of travel, said first link being accelerated for a period during which said knife means approaches its web engaging position, said second link being decelerated during said period.

9. A mechanism as set forth in claim 8, in which said angular distance is substantially 70 degrees.

10. A mechanism as set forth in claim 7, in which there is a common drive means rotating said input shaft at uniform speed throughout each revolution thereof, and moving said web linearly past said knife means at uniform speed, said uniform speed being adjustable.

11. A transmission for transforming a constant speed input to a cyclically varying output, said transmission comprising a drive shaft, an output shaft, a first link, one

end of which is in driving engagement with said output shaft, a second link, one end of which is freely mounted to said output shaft, connecting means joining said links at the other ends thereof to said drive shaft in a manner such that said links are rotated in the same direction by a driving force applied at said drive shaft with each of said links completing a revolution in equal time intervals for all revolutions; said output shaft and said drive shaft being laterally offset whereby the distances between said other ends of said links and said drive shaft shift within each revolution of said drive shaft with said first link rotating said output shaft at a speed which varies within each revolution of said output shaft and said second link applying a counterbalancing force to said output shaft at a cyclically varying rate, said connecting means including first and second pivots to which the respective first and second links are connected, said pivots being spaced apart by an angular distance in the range of 60 to 90 degrees measured along an arc drawn about said drive shaft as a center and extending between lines which radiate from said drive shaft through each of said pivots.

12. A transmission as set forth in claim 11, in which said second pivot is in a position leading said first pivot as said drive shaft rotates.

13. A transmission as set forth in claim 11, in which said angular distance is substantially 70 degrees.

14. A transmission as set forth in claim 11, in which said pivots define axes parallel to and laterally spaced from said drive shaft, said pivots being driven in unison about said drive shaft as a center, said connecting means also including a drive arm and a counterbalance, said drive arm pivotally connected at opposite ends thereof to said first pivot and said first link, said counterbalance arm pivotally connected at spaced locations thereof to said second pivot and said second link, during rotation of said drive shaft one of said drive arm and said counterbalance being pushed and the other of said drive arm and said counterbalance being pulled.

15. A transmission as set forth in claim 14, in which there is an input shaft, means connecting said input shaft and said drive shaft, whereby driving power for said drive shaft is supplied through said input shaft, means mounting said drive shaft for movement along an arcuate adjustment path about said input shaft as a center.

References Cited UNITED STATES PATENTS 3,003,380 10/1961 Moser et al. 74-393 X 3,292,989 12/1966 Zahn 74393 X LEONARD H. GERIN, Primary Examiner US. Cl. X.R. 83-324

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