US3029675A

US3029675A - Device for severing continuously moving strip at predetermined locations

Info

Publication number: US3029675A
Application number: US636800A
Authority: US
Inventors: Alexander Raymond; Schupan Fred Arnold; Abbott James
Original assignee: Kendall Co
Current assignee: Kendall Co
Priority date: 1957-01-28
Filing date: 1957-01-28
Publication date: 1962-04-17
Anticipated expiration: 1979-04-17

Description

April 1962 R. ALEXANDER ETAL 3,029,675

DE 012 FOR SEVERING TINUO Y M us STRIP AT PREDETER NED L TION Filed Jan. 28, 1957 2 Sheets-Sheet 1 APrll 1962 R. ALEXANDER ETA]. 3,

DEVICE FOR SEVERING CONTINUOUSLY MOVING STRIP AT PREDETERMINED LOCATIONS Filed Jan. 28, 1957 2 Sheets-Sheet 2 4 WEB kg m @curme ecu awe/v. r/wch'.

J7 m T W 0 1/01. 7465 W? sol/ecz- United States Patent 3&2? 675 DEVZCE F61 SEVERWG CQNEINUUUSLY MQV- ING S'ERil AT PREDEEERMHQED LOQATMENS Raymond Aierander and Fred Arnoid Schupan, Framrngham, and .lames Ahhott, Sherhorn, Mass, assignors to The Kendall Company, Eoston, Mass, a corporatron of Massachusetts Filed Jan. 28, 12357, Ser. No. 636,8tlfi 8 iliairns. (Cl. 83-75) This invention relates to register cutting apparatus adapted for the cutting of strip material at predefined locations spaced longitudinally of the strip.

In many cutting processes wherein a long strip of matenal is to be cut into relatively short sections whose lengths are defined by a special characteristic of the material recurring at fixed intervals, a problem is often created by the fact that the longitudinal spacings of the intervals are non-uniform. This problem is an especially severe one where the intervals deviate from a nominal value in more or less random fashion, and where each cut must be made accurately, within relatively close tolerance limits.

It is an object of the present invention to provide register cutting. apparatus which meets all of these requirements and which in addition is especially designed for applications requiring relatively high speed operation. One such application is the cutting of certain textile webs along transverse bars defined by abrupt changes in thickness of the web at randomly varying intervals of from 18 to 24 inches. Although the details of the apparatus will be described in this environment, in view of the fact that the apparatus is adapted to operate at rates as high as 75 cuts per minute along lines within /s inch from the centers of the bars, the fitness of the apparatus for many other allied applications will be apparent.

The novel features of the invention together with further objects and advantages thereof will become apparent from the illustrative embodiment shown in the accompanying drawings and described in detail hereinafter.

In the drawings:

FIG. 1 is a perspective view of the register cutting apparatus according to the present invention;

FIG. 2 is a side View in elevation of a device for sensing the locations where cuts are to be made;

FIG. 3 is a front view in elevation of the device of FIG. 2;

FIG. 4 is a schematic diagram of the electronic computer employed in the apparatus to derive error voltages for control of the speed of the apparatus; and

FIG. 5 is a schematic diagram of relay circuits ancillary to the computer of FIG. 4.

With reference first to FIG. 1, it will be observed that the strip or web of material to be out has been designated by the numeral 11, and the locations or bars defining the required spacing intervals between cuts have been designated 12. The web 11 moves continuously in a longitudinal direction according to the invention, and to produce such longitudinal travel of the web there is shown by way of example a pair of feed rolls 13 and 14 driven by a motor 15. Disposed at a fixed station beyond the feed rolls, is a cutter roll 16, provided with two diametrically opposed cutting knives 17 whose circumferential spacing is equal to the nominal spacing between the bars 12. A bed for the knives is afforded by an anvil roll 18 which is directly driven from the feed roll 13. As shown, bevel gears 21 and 22., mounted on a common shaft 23, provide the driving connection to the anvil roll, but it will be appreciated that these are merely illustrative of the fact that the speed of the anvil roll is by any convenient means permanently synchronized with the speed of the feed rolls and hence the speed of the web.

The cutter roll 16, on the other hand, is adapted to be driven at a variable rate of speed relative to the lineal speed of the Web in order to correct for each spacing interval of the bars 12, which is different from the nominal spacing value. To this end, a hydraulic motor 24 is operatively connected to the cutter roll, as by a shaft 25, and a pump 26 is provided to supply fluid under pressure to the hydraulic motor. Connected in the line between the pump 26 and the motor 24 is a two-stage electro-hydraulic valve 27 which controls the how of pressure fluid to the motor and hence its speed. A standard torque motor type valve having a substantially proportional response characteristic has been found to operate satisfactorily in this environment, the speed of the motor 24- being very nearly, therefore, in direct proportion to the magnitude of the current applied to the valve. A voltage to produce this current is derived in a computeer 28 which is coupled to the valve through an amplifier 29. The latter is a conventional push-pull direct current amplifier incorporating an oscillator for small amplitude oscillatory movement of the valve at approximately 400 cycles per second.

To supply the computer with information indicative of projected positional errors between each projected line of cut and the center of the corresponding oncoming bar, according to the invention there is geared to the cutter roll shaft 25 a first direct current tachometer generator 31, and there is geared to the anvil roll a second direct current tachometer generator 32. The output Signals or voltages from the tachometer generators represent the speeds of the cutter roll and the Web, respectively. In addition to these velocity signals, there are also fed to the computer, timing or location signals to indicate the arrival of the cutter roll at predetermined angular positions, and the arrival of the bars at a fixed station in advance of the cutter roll. The arrival of each bar is sensed by a device 33 incorporating a switch SW which is adapted to be actuated in response to a sudden change in the thickness of the web. Since such a change occurs at the bars, it followsthat switch SW will be momentarily actuated at intervals corresponding to the times of arrival of the bars at the station where the device is located. Specifically, it is located in advance of the cutter roll axis a distance approximately equal to the shortest bar spacing for which the apparatus is designed to compensate. Location signals to represent the arrival of the cutter roll at predetermined angular positions are produced by a switch SW actuated by a cam 34. Cam 34 is mounted on a shaft 25' adapted to run at twice the speed of the cutter roll shaft 25 and has a single abrupt lobe which defines these angular positions when in contact with the switch SW Cam 34 is oriented so that switch SW will. be actuated at the same time as switch SW when an oncoming bar spacing is encountered which is precisely equal to the nominal spacing value aforementioned. Finally, a reset cam 35 is provided on the shaft 25' in addition to the cam 34. Cam 35 also has a single abrupt lobe which is oriented so that a switch SW will be actuated shortly following each cutting interval.

The character of the error voltage applied to the valve 27 and the manner in which it is derived by the computer 23 will now be described with reference to FIGS. 4 and 5. With reference first to FIG. 4, it will be observed that the tachometer generators 3'1 and 32 are oppositely connected through load resistors 41 and 42, respectively, to a circuit which is adapted to provide voltages which are integral functions of the output voltages from the tachometer generators. In particular, this integrating circuit is formed with a capacitor 43 and resistors 44, one for each of the tachometer generators as shown. Connected in parallel relation to the integrating circuit across the respective tachometer generator load circuits is a pair of switching circuits. The switching circuit associated with tachometer generator 32 is comprised of normally open relay contacts K and normally closed relay contacts W connected in series with one another. The switching circuit associated with tachometer generator 31 is seen to comprise normally closed relay contacts K and normally open relay contacts W likewise con nected in series with one another. Relay contacts K and K are adapted to be actuated together, that is, they are actuated by a common coil, and the same is true for the relay contacts W and W The result of this arrangement is that the output signals or voltages from both tachometer generators will be applied to the integrating circuit when all the contacts K K W and W are either in their normal conditions as shown, or in an actuated condition. If only the relay contacts K and K are actuated, however, only tachometer generator 31 will be connected to theintegrating circuit, since relay contacts K and W will then be effective to by-pass the signal from tachometer generator 32 with respect to the integrating circuit. Contrariwise, actuation of relay contacts W and W alone, effectively bypasses the signal from tachometer generator 31 so that only the signal from tachometer generator 32 is applied to the integrating circuit.

Coupled to the integrating circuit, that is, across the capacitor 43, there is provided a filter

network including resistors

45 and 46 and a capacitor 47. As shown, each of these elements is disposed in series relation with one another across the capacitor 43, the output voltage from the filter network being developed across resistor 4e and capacitor 47. This output or error voltage is applied to the amplifier 29 which, in turn, is coupled to the electrohydraulic valve described in connection with FIG. 1. As will be apparent to those skilled in the art, the purpose of the filter network is to improve the stability of the overall system at certain critical frequencies.

FIG. 5 illustrates diagrammatically the circuit for actuating the relay contacts K K W and W As shown in FIG. 5, there is associated with the contacts K and K an actuating coil K which is connected across a suitable energizing source through the switch SW There is also provided a holding circuit for the coil K which is formed with one section of the normally closed switch SW and a normally open contact K actuated in common with contacts K and K Similarly, contacts W and W are actuated by a coil W connected across the energizing source through the switch SW there being associated with the relay coil W a normally open contact W The latter, in combination with another section of the switch SW forms a holding circuit for the coil W. Accordingly, once either of the coils K and W have been energized by the momentary closure ofswitches SW and SW respectively, they will be held energized so long as switch SW remains closed. When the switch SW opens, however, both coils will be deenergized simultaneously.

The operations of the apparatus will be described first for the case where the oncoming spacing interval between the bars defining the next section of the web to be cut is equal to the nominal spacing value. It will be assumed that at the time of the preceding cut, and immediately thereafter, the respective speeds of the cutter roll and of the web itself are substantially the same. That this is so, will become apparent as the description of the operation proceeds. Thus, owing to the relation established between the position of the sensing device 33 and the setting of the cam 34, switches SW and SW will be actuated simultaneously after the previous cut has been made. As a result, relay contacts K K W and W will be actuated and, once actuated, they will remain so by virtue of the operation of the respective holding circuits associated with the relay coils K and W. It follows that both the tachometer generators 31 and 32 will then be coupled to the integrating circuit to provide an output voltage which is an integral function of any difference in voltage which may arise as a result of relative speed variations between the tachometer generators. Since the tachometer voltages reflect the lineal speed of travel of the web on the one hand, and the circumferential speed of the cutter roll on the other, the output voltage from the integrating circuit will reflect projected positional errors between the oncoming knife and the bar to be cut. If, for example, tachometer generator 32 runs at a faster speed momentarily than tachometer generator 31, indicating that the oncoming bar will arrive too soon, it will be seen that the resulting error voltage will be positive. Since the sense of the valve is such that its opening increases in response to a positive voltage, the speed of hydraulic motor 24 will be increased so as to correct for such positional deviation. Conversely, a relative increase in speed of the tachometer generator 31 will result in a negative voltage being applied to the integrating circuit, and an integral function thereof being applied to the valve, so that speed of the motor will be decreased. In other words, the apparatus, according to the invention, maintains the relative speeds of the web and the cutter roll closely synchronized throughout the cutting interval in this assumed case, so that when the cut occurs, the line of cut will correspond very closely to the center line of the bar. After the cut has been made, switch SW is actuated, deenergizing the coils K and W, and restoring the relay contacts K K W and W to their normal conditions. It will be seen that this does not affect the relations of the tachometer generators to the integrating circuit, however.

Assuming that the oncoming spacing interval between bars is greater than the nominal spacing value, so that under existing speed conditions the cut would be made too soon, what happens is that switch SW is actuated before SW The cutter roll may be thought of as leading the web under this assumed condition. As a result, only the relay contacts K and K will be actuated at first, and only the cutter roll tachometer generator 31 Will be operative on the integrating circuit. Accordingly, a definite time integral of the tachometer voltage, de-limited by the interval between the actuation of the switches SW and SW will be produced. This voltage represents the positional error between the bar and the knife caused by the greater than nominal spacing of the bar from the cut bar preceding it. Since the voltage is negative, motor 24, and hence the cutter roll, will be slowed down.

In this regard, it will be observed that once relay coil W is energized, and tachometer generator 32 is also operative on the integrating circuit, the decrease in speed of the cutter roll will result in a positive voltage being applied to the integrating circuit due to the relatively higher speed of the tachometer 32. Thus, as the knife slows down to meet the bar, the previously established negative charge on the capacitor 43 will be reduced, and ultimately neutralized, indicating that no further correction in the cutter roll speed need be applied for proper registry of the knife with the oncoming bar, at least insofar as the increased bar spacing is concerned. Rather the computer functions for the remainder of the cutting interval to keep the cutter roll in synchronism with the Web and to correct only for relatively small positional errors arising from minor speed variations as in the first assumed case. At the precise instant of cut, the cutter roll speed will be very nearly equal to the web speed so that no puckering of the material takes place.

Finally, if it be assumed that the oncoming section to be cut is shorter than a nominal length section, switch SW will be actuated before switch SW As a result, only the web tachometer 32 will be operative on the integrating circuit at first, and the error voltage developed thereby will be positive to reflect the amount the cutter roll must be advanced to catch up with the web. After the error voltage has been established, both tachometer generators will be coupled to the integrating circuit and, as before, the efiect of the cutter roll tachometer 31 will be to reflect the progress of the correction applied on the basis of the initial error voltage. Once the correction has been made, very nearly synchronous operation will follow for the remainder of the cutting interval. &

FIGS. 2 and 3 illustrate in detail a sensing device 33 which has been found to be especially Well-suited for use with certain textile materials. As shown, this sensing device includes a bed 51 provided with a pair of guide rails 52 which, in combination, are adapted to mount a supporting frame 53 for the sensing elements and to permit positional adjustments thereof with respect to the bed.- The sensing elements themselves are constituted by a pair of

rollers

54 and 55, the former being rotatably mounted in a fixed block 56, and the latter being mounted for pivotal as well as rotational movement. To this end, there is provided a pivot arm 57, at one end pivoted about a pin 58, and at its other end provided with a shaft 59 mounting the roller 55. Disposed above the roller 55 is the switch SW and its associated plunger 61. As shown, the orientation of the switch is such that the plunger 61 projects downwardly into registry with the shaft 59, against which it is urged by the internal bias of the switch. 7

Normally, the plunger 61 will be caused to assume an upward position due to the pasage of the main body of the web 11 between the rollers. When the rollers encounter the bars 12, however, which are thinner than the main body of the material, roller '55, and hence the plunger, will be permitted to 'fall sufficiently to reverse the condition of the switch. These operations will, of course, recur in the apparatus of the invention at intervals determined by the spacing of the bars and the speed of the web. Although the above described thickness sensing device is preferred for the illustrative application described herein, it will be apparent to those skilled in the art that in the case of different types of material, a somewhat different type of sensing device may be preferable. In fact, since the apparatus of the present invention is in no way dependent upon any special kind of sensing device, it will also be equally applicable to those applications where the cutting intervals are defined merely by printed indicia such as register marks. In such case, a conventional photocell sensing device might be substituted for the device 33 described herein.

Similarly, it will be appreciated that the apparatus might optionally be .arranged to vary the speed of the web rather than the speed of the cutter roll in order to produce the required registry between the knives and the bars. Various modifications of this nature that take advantage or" the novel features of the invention will no doubt occur to those skilled in the art and, therefore, the invention should not be deemed to be limited to the illustrative embodiment described herein by way of example. Rather, the invention should be deemed to be limited only by the scope of the appended claims.

What is claimed is:

1. Apparatus for severing strip material at locations spaced longitudinally of the strip at intervals defined by indicia on the strip, comprising a feed mechanism for continuously feeding the strip longitudinally past spaced first and second stations, means to sense the arrival at said first station of a said location, a cutter repetitively movable into and out of cutting engagement with said strip at said second station, means to move said cutter, means for producing a first velocity signal responsive to the speed of said strip, means for producing a second first station, means for producing a second location signal upon arrival of said cutter at the position in its travel corresponding to the position of the strip when said location is at said first station, switching means responsive to said location signals for interrupting one only of said velocity signals upon occurrence of a corresponding one of said location signals and terminating such interruption upon occurrence of the other location signal, circuit means for combining said velocity signals into an error signal, and means for varying the relative speed of said cutter and strip in accordance with variations in said error signal to tend normally to keep the motion of said cutter in synchronism with the motion of said strip while operating said means to move said cutter to out said strip only upon arrival at said second station of a said location.

2. Apparatus as claimed in claim 1, further including means responsive to movement of said cutter to cut said strip effective to reset said switching means.

3. Apparatus as claimed in claim 1 wherein said circuit means produces an error signal which is directly pro portional to the time integral of the difference between said velocity signals.

4. Apparatus as claimed in claim 3, further including means responsive to movement of said cutter to out said strip effective to reset said switching means.

5. Apparatus as claimed in claim 3 wherein said first and second stations are spaced apart a distance approximately equal to the minimum of said intervals.

6. Apparatus as claimed in claim 3 wherein said outter is a rotatable cutter movable along a circular path. 7. Apparatus as claimed in claim 3 wherein said cutter is a rotatable cutter movable along a circular path and wherein said first and second stations are spaced apart a distance approximately equal to the minimum of said intervals, and further including means responsive to movement of said cutter to out said strip efiective to reset said switching means.

8. Apparatus for severing strip material at locations spaced longitudinally of the strip at irregular intervals defined by indicia on the strip, comprising a feed mechanism for continuously feeding the strip longitudinally past first and second stations, spaced apart a distance approximately equal to the minimum of said intervals, Photoelectric means to sense the arrival at said first station of the next oncoming said location, a rotatable cutter movable along a circular path into and out of cutting engagement with said strip at said second station, a hydraulic motor to rotate said cutter, a source of pressure fluid to drive said motor, an electro-hydraulic valve coupled between said source and said motor to control the flow of pressure fluid to the motor, a first direct current tachometer generator driven in timed relation with said feed mechanism for producing a first velocity signal responsive to the speed of said strip, a second di rect current tachometer generator driven in timed relation with said cutter for producing a second velocity signal responsive to the speed of said cutter, means operated by said sensing means for producing a first location signal upon arrival of said next location at said first station, means for producing a second location signal upon arrival of said cutter at the position in its travel corresponding to the position of the strip when said next location is at said first station, a switching circuit connected in parallel relation to said first generator, a switching circuit connected in parallel relation to said second generator, each of said switching circuits including normally open relay contacts in one circuit and normally closed relay contacts in the other circuit adapted to be simultaneously actuated in response to one of said location signals and including normally closed relay contacts in said one circuit and normally open relay contacts in said other circuit adapted to be simultaneously actuated in response to the other of said location signals, whereby said switching circuits interrupt one only of said velocity signals upon occurrence of the corre- "I sponding one of said location signals and terminate such interruption upon occurrence of the other location sig- 'nal, said generators being oppositely connected to circuit means for combining said velocity signals into an error signal which is directly proportional to the time integral of the difference between said velocity signals, means for controlling said valve to vary the speed of said cutter in accordance With variations in said error signal to tend normally to keep the motion of said cutter in synchronism with the motion of said strip while operating said means to rotate said cutter to cut said strip only upon arrival at said second station of a said location, and means responsive to movement of said cutter to cut said strip effective simultaneously to restore said contacts to their normal conditions.

References Cited in the file of this patent UNITED STATES PATENTS 2,002,374 King May 21, 1935 2,249,190 Thompson July 15, 1941 2,583,580 Ludwig Jan. 29, 1952 2,599,430 Beuerman June 3, 1952 2,648,380 SOcke Aug. 11, 1953 2,648,381 Engel Aug. 11, 1953 2,751,982 Schlemmer June 26, 1956