US3287015A

US3287015A - Detecting device for the sheet feeder of a printing press

Info

Publication number: US3287015A
Application number: US426943A
Authority: US
Inventors: Presuss Friedrich; Ruckert Walter
Original assignee: Roland Offsetmaschinenfabrik Faber and Schleicher AG
Current assignee: Roland Offsetmaschinenfabrik Faber and Schleicher AG
Priority date: 1964-04-23
Filing date: 1965-01-21
Publication date: 1966-11-22
Anticipated expiration: 1983-11-22
Also published as: SE318895B; CH434306A; GB1094863A; DE1204243B

Description

Nov. 22, 1966 F, PREUSS ET AL 3,287,015

DETECTING DEVICE FOR THE SHEET FEEDER OF A PRINTING PRESS Filed Jan. 21, 1965 2 Sheets-Sheet .L

FIG. 8

INVENTORS FRIEDRICH gsuss WALTER RUCKEET ATTORNEYS 22, 1966 F. PREUSS ET AL 3,287,015

DETECTING DEVICE FOR THE SHEET FEEDER OF A PRINTING PRESS Filed Jan. 21. 1965 2 Sheets-Sheet 2 62 38K L kzg a =n 0 wa i -J FIG.

INVENTORJ FR/EDIPIcl-l PREUSS WALTER RUCKERT A TTORNEYS United States Patent 3,287,015 DETECTING DEVICE FOR THE SHEET FEEDER OF A PRINTING PRESS Friedrich Preuss, Neu-Isenburg, and Walter Riickert,

Offenbach (Main), Germany, assignors to Roland Ottsetmaschinenfabrik Faber & Schleicher AG, Offenbach (Main), Germany, a firm of Germany Filed Jan. 21, 1965, Ser. No. 426,943 Claims priority, application Germany, Apr. 23, 1964, R 37,758 14 Claims. (Cl. 271-57) The invention relates to a detecting device for use with a sheet printing press for detecting the absence of sheets consecutively fed by a sheet feeder from a stack of sheets to the forward stops of the press and also for detecting the occurrence of doubled-up sheets in the feed path. More particularly, the invention relates to a detecting evice of the general kind above referred to which includes two detectors spaced apart from each other in the direction of the feed path. Each of the two detectors generates a signal which is indicative of the thickness of the sheet material detected by the respective detector and these signals are compared as to the differential between the two detected thickneses of the sheet material. In the event the differential between the two signals exceeds a predetermined value, a control signal is generated causing the press to be stopped or otherwise controlled in a conventional fashion. Sheet feeders for presses to be practical should be capable of handling all sheet sizes between a maximum and a minimum size and also sheets of widely different gauges.

the range of each detector during each cycle of the press and for the other limit size, up to three sheets. Consequently the signal produced by each detector changes each time the leading edge and the trailing edge passes a detector. The signals change additionally each time the size of the fed sheets is changed. As a result a very short.

detecting time may be available during each cycle of the press and such short detecting time may affect the reliability of the detecting device.

It is a broad object of the invention to provide, particularly for overlap feeding devices, a novel and improved detecting device including two detectors, which device at any moment during normal feed operation probes the same number of sheets within the range of each detector, independent of the dimensions of the sheets.

A more specific object of the invention is to provide a novel and improved detecting device including two detectors which does not need to be specifically adjusted for the gauge of the sheets to be supervised or the dimensions thereof, thereby greatly simplifying the operation of the detecting device.

Another more specific object of the invention is to provide a novel and improved detecting device which is operative during the full cycle of the printing press, thereby assuring that the feed of sheets is continuously superv-ised.

Still another more specific object of the invention is i to provide a novel and improved detecting device which is capable of distinguishing between heavy gauges of sheet material and lighter gauges, in that the detecting either roller from a predetermined position.

"ice

device generates a control signal at greater difierentials between the signals produced by the detectors when heavy gauge sheets are fed than sheets of lighter gauge. This has the advantage that the detecting device always responds at approximately the same percentage of a departure from the correct thickness of the sheet material, for instance due to the presence of a doubled-up sheet, irrespective of the gauge of the sheet material to be supervised. If the detecting devices would be operated always with the same absolute sensitivity and such sensitivity would be adjusted according to the lightest gauge, the device, when used for carboard might produce a control signal in response to thickness variations that are within the tolerance range for such heavy material.

The aforementioned objects, features and advantages and other objects, features and advantages which will be pointed out more fully hereinafter are attained by arranging the two detectors of the device at a distance from each other which is equal to the spacing of the trailing edges of adjacent overlapping sheets forming the train of overlapping sheets moving along the feed path, or equal to an integral mulitple of said spacing.

The invention also contemplates providing in one of the detectors two probes, the distance of which in the direct-ion of the sheet travel firom the other detector is larger and smaller respectively by substantially the same amount as the aforesaid spacing of the sheets from each other in said train of sheets whereby the detector including the two probes transmits a signal for comparison with the signal of the other detector only when'the signal produced by the two probes are approximately equal.

In the event the sheets to be supervised are not accurately cut or not cut at all, the detecting device tends to respond, since with such irregular sheets the same number of sheets is not necessarily present when the leading edge and the trailing edge respectively of the sheets passes the two detectors. Another result of inaccurately cut sheets or uncut sheets would be that the aforesaid Overlap spacing between adjacent sheets would be changed. By providing the aforedescribed two probes in one of the detectors such fa-ut-ly indications due to inaccurately or uncut sheets are avoided.

The invention further contemplates providing for each detector a stationar-ily mounted roller, which coacts with a yieldably supported roller whereby the axial distance between the two coacting rollers constitutes a measure of the thickness of the sheet material between the rollers. Such an arrangement is simple and rugged and hence reliable in operation.

The invention also provides coupling the yieldably supported rollers of the two detectors by a yieldable linkage which operates a switch in response to a displacement of Such operation of the switch may be utilized to initiate suitable control operations. A switch control of this kind is reliable and can be conveniently serviced.

The invention further contemplates providing means for intermittently lifting the yieldable rollers of the two detectors to insure a free run-in of the leading edges of the sheets thereby assuring that the sheets reach the feed table of the press in a wrinkle-free condition.

To obtain the aforementioned automatic dilferentiation between different gauges of sheet material to be supervised, the invention provides that the yieldable roller of the detector including the two probes is supported on one arm of a bell crank lever, the other arm of which mounts two lugs which are disposed at different distances from the pivot axis of the lever. These lugs coact with switch rected and cross each other.

contacts which are displaced substantially parallel to each other by a displacement of the yieldably supported roller of the other detector. Such control assembly is simple and rugged and can be conveniently checked when in operation.

The invention also provides for the purpose of differentiating between different sheet gauges that each of the yieldably supported rollers of the two detectors is mounted on a pivotal lever. The two levers are oppositely di- Each lever carries at one end a switch which coacts with a preferably adjustable abutment part on the other lever to effect operation of switches initiating control functions in predetermined angular positions of the two levers in reference to each other. a I

The invention further contemplates utilizing the variable spacing between two coacting rollers, which as previously pointed out, is indicative of the thickness of the sheet material passing between the rollers, for operating a mechanical-electrical converter preferably with a nonlinear characteristic. With such an arrangement a sensitivity of the detecting device variable as a function of the gauge of the sheet material to be supervised, is obtained by purely electrical means.

For detecting devices which detect the thickness of the sheet material capacitatively -by comparing two obtained capacitance values in a suitable bridge, the invention contemplates providing across the bridge output terminals a circuit component which produces a control signal in response to a predetermined and preferably adjustable imbalance of the bridge. If the bridge is designed with a linear characteristic, the detecting device responds to the same differential between the signals of the detectors irrespective of the gauge of the sheet material to be supervised.

In the accompanying drawing several preferred embodiments of the invention are shown by way of illustration and not by way of limitation.

In the drawing:

FIG. 1 is a diagrammatic elevational side view of the detecting device according to the invention coacting with the feed table of a printing press,

FIG. 2 is a fragmentary detail view of FIG. 1 on an enlarged scale,

FIG. 3 is a plan view of FIG. 2,

FIG. 4 is a side view of FIG. 2,

FIG. 5 is a diagram of the control circuit controlled by the device of FIG. 1,

FIG. 6 is an elevational side view of a modified detecting device having two probes in one of the detectors of the device, 7

FIG. 7 is a fragmentary view of FIG. 6 on an enlarged scale,

FIG. 8 is a diagram of the operational movements of some of the components of the detecting device according to FIG. 6,

FIG. 9 is a diagram of the control circuit controlled by the device of FIG. 6,

FIG. 10 is a diagrammatic elevational view of another modification of the detecting device,

FIG. 11 is a detail view of part of FIG. 10 in a different operational position of the detecting device,

FIG. 12 is a diagram of the operational movements of slrame of the components of the device according to FIG.

FIG. 13 is a fragmentary diagrammatic view of a detecting device using capacitative detectors,

FIG. 14 is fCiICUit diagram for a detecting device using capacitative detectors,

FIG. 15 is a fragmentary view showing a modification of the detectors for detecting devices as shown in FIGS. 1 to 12; and

FIG. 16 is a graph showing the characteristics of a detector according to FIG. 15.

Referring first to FIGS. 1 through 4 in detail, FIG. 1

shows a stack 3 of sheets from which sheets 1, such as paper sheets, are successively withdrawn by a suitable pick-up device shown as a suction cup 2. The individual sheets are placed with overlap upon a feed table 4 on which they are transported in the form of a continuous train of overlapping or shingled sheets to the front markers 6 of a diagrammatically indicated printing press 7. The lifting and the transport of the sheets are assumed to be conventional and do not constitute part of the invention. The conveyor 5 includes a roller 8 which coacts with a roller 9 mounted on an arm of a three-arm lever 10. Several rollers 9 may be provided, and roller 8 may extend across the width of table 4. A second arm 10a of the lever coacts by means of a cam follower 13 with a unidirectionally rotated cam disk 11 whereby the rollers 9 are intermittently lifted in reference to roller 8 to permit a free and smooth run-in the leading edge of Sue-. cessive sheets 1. A loaded spring 12 may be provided or equal .to an integral multiple of the spacing, the socalled overlap spacing. A rod 18 links arm 10b of lever 10, which arm is substantially normal to the plane of table 4, to the arm 16a of lever 16, which arm is also substantially normal to the plane of table 4. As can best be seen in FIG. 2, an elongated slot 19 in rod 18 engaged by a bolt 101 permits a limitedangular movement of lever arm 16a in reference to rod v1'8. An extension20 of lever arm 16a mounts on eachside a lug 102 coacting with

switches

21 and 22 supported on rod 18. The positions of

switches

21 and 22 in reference to rod 18 and thus in reference to extension 20 and the lugs thereon may be adjusted by set screws 103 engaging slots 102a in rod 18 or by other suitable means.

When the feed of sheets operates normally there are always two sheets between rollers 8, 9 and

rollers

14, 15 as it is shown. Lever arm 16a is adjusted so that lugs 102 thereon will not operate either one of switches 21 105. Solenoid 104 should be visualized as constituting part of a conventional control circuit system which. may stop the press, or initiate another appropriate control action.

As it is evident, the sensitivity of the detector may be adjusted by varying the spacing of

switches

21 and 22 in reference to lugs 102 on the extension 20 of lever arm 16a.

As has been previously described, roller 9 is intermittently lifted by the action of cam disk 11. Such lifting of the roller causes a movement of rod 18 towards the left and thus an operation of switch 22 and also a lifting of roller 15. To prevent an energization of solenoid .104

and the initiation of control functions due to such energization when the roller 9 is lifted by disk 11, as part of the normal function of the detecting device, a normally closed switch 23 is provided in the connection between solenoid 104 and source of current 105. Switch 23 is controlled by an extension 24 of lever arm 10a and opened whenever cam disk 11 acts upon follower 13, thereby rendering ineffective the closing of switch 22.

Referring now to the embodiment of FIGS. 6, 7, 8 and 9, the detecting device according to these figures comprises two probes in one of the two detectors of the device. The roller pairs 25, 26 and 27, 28 of FIG. 6 correspond functionally to

rollers

14 and 15 of FIG. 1. The distance A is again equal to the overlap spacing of the train of sheets. The spacing between

roller

25, 26 and roller 8, 9 is greater than the distance A by a distance which is equal to the distance by'which the spacing between rollers 27, 28' and rollers 8, 9 is smaller than the

distance A. Rollers

8, 9, 25, 26, 27 and 28 may extend across the entire width of table 4.

Roller 9 is supported on one arm of a pivotal threearm lever 29, an arm 30 of which pivotally supports one end of a rod 31. The other end of rod 31 is linked to a lever 32, the other end of which is pivotally mounted about a stationary pivot point 32a. Roller 26 is supported by a bell crank lever 33 and roller 28 by a bell crank lever 34. Loaded tension springs 35 and

35a urge rollers

26 and 28 respectively toward

rollers

25 and 27 respectively. The arms 33a and 34a of

levers

33 and 34 respectively are approximately normal to the plane of table 4 and mount lugs 36, 36a and 37, 37a respectively.

p The positions of these lugs are adjustable, for instance by eccentrically mounting the lugs on rotatable supports as is shown in FIG. 7. The lugs coact with

electric switches

38, 38a and 39, 39a respectively.

The distance of

lugs

36, 36a from the pivot axes of

levers

33 and 34 respectively is smaller by a predetermined distance than the length of

lever arms

30 and 32 and the distance between

lugs

37 and 37a from the pivot axes of

lever

33 and 34 respectively is larger by the same amount. The point 40 in FIG. 7 signifies the point at which rod 31 is linked to lever 30.

The aforedescribed ratios of distances result in the paths of movements diagrammatically indicated in FIG. 8. The eccentric lugs 36, 36a and 37, 37a are adjusted in accordance with the desired detecting sensitivity to wit: so that the

switches

38, 38a and 39 39a are closed only after a predetermined movement of lever arms 33a and 34a in reference to rod 31. More specifically, the lugs may be so adjusted that for thin paper the

lugs

36 and 37 must move into the positions indicated at 136 and 137 respectively to efiect operation of

switches

38 and 39 respectively. Line 41 indicates the positions in which the lugs will operate the switches. The dotted lines in FIG. 8 indicate the required movements for a heavy gauge of paper or cardboard. The line 41 has moved into the dotted line position 41 and the point 40 into the position 40. Accordingly, the

switches

38 and 39 are operated when point 36' has moved into the position 236 and point 37' into the position 237. As it is evident, the distance between point .36 and point 236 and between point 37' and point 237 are greater than the distances from point 36 to point 136 and from point 37 to point 137. Accordingly, the absolute detecting sensitivity is correspondingly reduced for heavier gauges of sheet material. The aforedescribed geometric proportions can be conveniently so adjusted that the relative detecting sensitivity remains approximately the same for each gauge of the sheet material. Accordingly, the detecting device will respond only when a sheet is missing or sheets are doubled up but not to tolerances in gauge which are acceptable for heavier types of cardboard and are in the order of magnitude of the gauge of very thin paper.

As it is shown in FIG. 9, switches 38 and 38a are connected in series so that the energizing circuit for solenoid 106 through source of current 107 is closed only when both switches are closed at the same time. Solenoid 106 should again be visualized as being connected to or constituting part of a suitable control circuit for the press. Similarily, switches 39 and 39a are connected in series so that both of these switches must also be simultaneously closed to establish the energizing circuit for solenoid 106.

To neutralize the closing of

switches

39 and 39a when

rollers

9, 26 and 28 are intermittently lifted by the action of cam disk 11 to provide for a free run-in of the sheets, a normally closed switch 23a is opened by lever 30 whenever lever 29 is pivoted by the coaction between cam disk 11 and follower 13.

Referring now to the detecting device according to FIGS. 10, 11 and 12, these figures shows a device in which

rollers

42, 43 correspond to rollers 8, 9 of FIG. 2;

rollers

44, 45 correspond to

rollers

25, 26 and

rollers

46, 47 correspond to

rollers

27, 28. Roller 43 is supported on a lever 48; roller 44 on a lever 49 and roller 46 on a lever 50. As it is shown in the figures, levers 48, 49 and 50 are two-arm levers pivotal about pivot axes 48a, 49a and 50a. The levers extend in opposite directions and cross each other. The free ends of the levers support

switches

51, 52, 53 and 54 respectively. These switches are operable by engagement with preferably

adjustable abutment members

55, 56, 57 and 58 on

levers

49, 48, 50 and 48.

Rollers

44, 45 and 46, 47 are disposed side by side adjacent to each other. Tension springs 55, 60 and 61

urge rollers

43, 44 and 46 toward the

respectiv counter rollers

42, 45 and 47.

If, as desired, the same number of sheets is present between

rollers

42, 43; 44, 45; and 46, 47, switches 51 through 54 are spaced apart from the respective abutments 55 through 58. However, if sheets are doubled up between rollers 42 and 53, the angular position of lever 48 in reference to lever 49 changes accordingly thereby causing operation of switches 52 and 54 by engagement with

abutment portions

56 and 58. As a result the control circuit means are activated in the manner described in connection with FIG. 9. Similarly, switches 51 and 53 are operated when a sheet is missing between

rollers

42 and 43.

Adjustment of abutment members 55 through 58 may be effected in any suitable and conventional manner, for instance by providing set screws or eccentric lugs of the kind shown in FIG. 7 and described in connection therewith.

A unidirectionally rotating cam disk 62 acts upon a pivotally mounted bell crank lever 63 by means of a cam follower 65. A tension spring 64 acting upon lever 63 urges follower 65 toward the cam disk. A rod 66 linked to arm 63a of lever 63 couples the lever arm with two

bars

67 and 68 which, in turn, coact with

levers

48, 49 and 50 by means of rollers 69 and 70 respectively. As it is evident, rotation of cam disk 62 will cause an intermittent lifting of

levers

48, 49 and 50 to provide for a free run-in of the leading edges of the sheets between the respective rollers to assure a substantially wrinklefree transport of the sheets. A special switch to prevent generation of a control signal when the levers are lifted, such as

switches

23 and 23a, is not necessary in this arrangement since the intermittent lifting of

levers

48, 49 and 50 separates switches 51 through 54 from the respective abutment members 55 through 58.

The automatic variation of the sensitivity of the detecting device in accordance with the specific gauge of the sheet material to be supervised is apparent from the diagram of FIG. 12 in which are shown the movement performed by switch 51 and its abutment member 55. The full lines represent the positions for thin sheets and the dotted lines for heavy gauge sheet material, such as heavy cardboard. As it is apparent, the requirement movement of the point representing abutment member 55 to the point representing switch 51 is considerably shorter than the distance between point 55' and point 51'. As is also apparent, the sensitivity of the device is the higher the closer levers 48 approach parallel positions.

FIG. 13 shows diagrammatically an arrangement in which the previously described coacting pairs of rollers are replaced by capacitative detecting means. According to the figure, electrodes 108 in the form of metal plates are inserted in a feed table 4a. Each of the plates coacts with a second plate electrode 110 and 111 respectively.

7 The

electrodes

108, 110 and 109, 111 are so spaced from each other that the sheets to be fed can freely pass between the .electrodes. The two pairs of electrodes each con- 1 stitute a capacitor, the capacitance value of which is controlled by the total thickness of the sheet material passing therebetween. The distance between the two capacitors is again equal to the distance A representing the spacing between adjacent sheets. As it is evident, the sheet material constitutes a dielectric for the capacitors and hence the capacitance values will accurately reflect the number of superimposed sheets or the absence of sheets.

The two capacitance values obtained with the arrangement according to FIG. 13 are compared in suitable comparing means such as the four-arm bridge shown in FIG. 14. The two capacitors are included in two arms of the bridge and each of the two other arms includes an

adjustable capacitor

112 and 113 respectively. The bridge is connected to a high frequency source of current 114, or any other suitable source of current and is adjusted by means of

capacitors

112 and 113 so that the bridge is in balance when, as desired, the same number of sheets passes

capacitors

108, 110 and 109, 111. However, if one of the capacitors detects a different number of sheets, the bridge is in imbalance and a voltage is now present at

points

115, 116. This voltage is fed to an amplifier 118 connected to a source of current 117 and controlling a solenoid 119 which constitutes part of the control circuit as described in connection with FIGS. 5 and 9.

The arrangement of FIG. 15 uses a mechanical-electrical converter for obtaining control signals corresponding to the spacing between rollers 120 and 121 which, as previously described, is controlled by the thickness of the sheetrnaterial passing between the rollers.

The converter comprises a suitably connected exciter coil 122 in which a core of varying cross sectional outline, such as a conical core 123, is lengthwise displaceable. As it is evident, the conical shape of the core gives a non-linear characteristic to the converter. The core is coupled to an arm 125 pivotal at one end about a stationary pivot 124 and supporting at the other end a roller 121. The counter roller 120 is suitably secured to a feed table 40 for instance by means of a bracket 126. The general function of the device according to FIG. 15 is evident from FIGS. 1, 6, and 11. As it is also evident, a converter such as shown in FIG. should be provided as previously described for two pairs of rollers spaced at the distance A representing the overlap spacing between adjacent sheets.

The signals obtained from the two converters may be compared in a bridge circuit of the kind shown in FIG. 14, though of course designed for signals of the kind delivered by an inductive converter.

FIG. 16 shows a graph in which the abscissa X indicates the gauge of the sheet material, such as paper, and the ordinate Y the induction of coil 120. As it is evident, roller 21 is lifted higher by a heavy gauge than by a light gauge whereby the peripherally smaller portion of core 123 enters more deeply into coil 122. FIG. 16 shows that the change in the induction of coil 122 is less for a heavy gauge in response to a given change in the total thickness of the sheet material than for a light gauge. Accordingly, the bridge comparing the signals obtained from the two converters will operate a control solenoid, such as solenoid 119, when heavy gauge sheets are used, at larger departures from a reference value than when light gauge sheets are used.

While the invention has been described in detail with respect to certain now preferred examples and embodiments of the invention it will be understood by those skilled in the art after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention, and it is intended, therefore, to cover all such changes and modifications in the appended claims.

8 What is claimed as new and desired to be secured by Letters Patent is:

1. In a detecting device for detecting the absence of sheetsand the presence of doubled-up sheets fed in the form of a train of overlapping sheets to a printing press,

said detecting device comprising two detectors disposed spaced apart in the direction of the sheet travel, each of said detectors being arranged to detect the thickness of the sheet material passing the same and to generate a sig I control signal in response to a differential above a pre:

determined value between said compared signals, and con trol circuit means activated by said electric control signal.

2. A detecting device according to claim 1 wherein each of said detectors comprises a pair of coacting rollers for feeding said sheets therebetween, one of said rollers of each pair being yieldably supported, the spacings between the rotational axes of each of said pairs of rollers being indicative of the total thickness of the sheet mate rial passing between the rollers of the respective pair.

3. A detecting device according to claim 1 wherein each of said detectors comprises a pair of coacting rollers for feeding said sheets therebetween, one of said rollers being yieldably supported, the spacings between the rotational axes of each of said pairs of rollers being indicative of the total thickness of the sheet material passing between the rollers of the respective pair, and comprising lifting means coacting with one of said yieldable rollers to lift the same intermittently for opening the respective detector to provide a free run-in for the leading edges of the sheets.

4. A detecting device according to claim 1 and comprising adjustment means responsive to the gauge of the fed sheets and controlling said comparing means to produce a control signal in response to a differential which is greater for sheet gauges above a predeterminedvalue than for sheet, gauges below said predetermined value.

5. A detecting device according to claim 1 wherein one of said detectors comprises two probes for detecting the thickness of sheet material at two points spaced apart in the direction of the sheet travel, the spacing of one of said probes from the other detector being larger than the overlap spacing of the sheets in said train of sheets by a predetermined amount and the spacing of the other of said probes from said other detector being smaller than said overlap spacing by approximately the same amount, the two probes producing a signal for comparison with the signal produced by said other detector when both probes detect substantially the same thickness of sheet material passing the probes.

6. A detecting device according to claim 1 wherein eachof said detectors comprises a pair of coacting rollers for feeding said sheets therebetween, one of the rollers being yieldably supported, the spacings between the rotational axes of each pair of rollers being indicative of the total thickness of the sheet material passing between the rollers of the respective pair, and comprising two mechanicalelectrical converts having a non-linear characteristic, each of said converters being coupled with the yieldable roller of one pair for generating an output signal corresponding to the spacing of the rollers of the respective pair, said output signals being fed to said comparing means.

7. A detecting device according to claim 6 wherein each of said converters is an inductive converter including an exciter coil and a tapered cone lengthwise slidable in said coil.

8. A detecting device according to claim 1, wherein each of said detectors comprises a capacitance means having two spaced apart electrodes for passing the sheets therebetween, the thickness of the passing sheet material controlling the capacitance value of the respective capacitance means, and wherein said comparing means comprise -a bridge circuit including said capacitance means for generating a control signal in response to a predetermined imbalance'of said bridge circuit.

9. In a detecting device for detecting the absence of sheets and the presence of doubled-up sheets fed in the form of a train of overlapping sheets to a printing press, said detecting device comprising two detectors disposed spaced apart in the direction of the sheet travel, each of said detectors being arranged to detect the thickness of the sheet material passing the same and to generate a signal corresponding to the detected thickness, the spacing between the two detectors being equal to an integral multiple of the overlap spacing of the sheets within said train of sheets, comparing means comparing said signals and producing an electric control signal in response to a diiferential above a predetermined value between said compared signals and control circuit means activated by said control signal.

10. In a detecting device for detecting the absence of sheets and the presence of doubled-up sheets fed in the form of a train of overlapping sheets to a printing press, said detecting device comprising two detectors disposed spaced apart in the direction of the sheet travel, each of said detectors being arranged to detect the thickness of the sheet material passing the same, the spacing between the two detectors being equal to the overlap spacing of the sheets within said train of sheets, each of said detectors including a pair of coacting rollers for feeding sheets therebetween, one of said rollers of each pair being yieldably supported, the spacings between the rotational axes of each of said pairs of rollers being indicative of the total thickness of the sheet material passing between the rollers of the respective pair and a linkage coupling the two yieldable rollers of said detectors, said linkage being displaceable in response to a differential in the positions of the two yield-able rollers in reference to the respective other roller of each pair, a control circuit means, and switch means operated in response to a positional differential above a predetermined value, said switch means when operated activating said control circuit means.

11. A detecting device according to claim wherein said linkage comprises a pivotal arm coupled to one of said yieldable rollers, the angular position of said arm being controlled by the position of said yieldable roller in reference to the other roller of the pair, and a rod coupled to the other yieldable roller and crossing said arm at an angle, said rod being lengthwise displaceable in reference to said arm according to the position of said other yieldable roller in reference to the respective other roller, and wherein said switch means comprise two switches disposed on said rod on opposite sides of said arm, displacement of the arm and the rod in reference to each other above a predetermined value operating either one of said switches depending upon the direction of displacement of the arm and the rod in reference to each other.

12. In a detecting device for detecting the absence of sheets and the presence of doubled-up sheets fed in the form of a train of overlapping sheets to a printing press, said detecting device comprising two detectors disposed spaced apart in the direction of the sheet travel, each of said detectors being arranged to detect the thickness of the sheet material passing the same, the spacing between the two detectors being equal to the overlap spacing of the sheets within said train of sheets, each of said detectors including a pair of coacting rollers for feeding said sheets therebetween, one of said rollers of each pair being yieldably supported, the spacings between the rotational axes of each of said pairs of rollers being indicative of the total thickness of the sheet material passing between the rollers of the respective pair, a bell crank lever pivotal about a rotational axis, one arm of said lever mounting the yieldable roller of one of said detectors and the other arm mounting two lugs disposed at different distances from the rotational axis of said lever, the angular position of said lever being controlled by the spacing between the two rollers of said one detector, a lengthwise displaceable rod coupled with the yieldable roller of the other detector for displacement of said rod in response to a variation of the spacing between the two rollers of the other detector, a control circuit means, and a pair of switches supported on said rod each disposed adjacent to one of said lugs, either one of said switches being operated by the respective lug in response to a change in the position of the lever and the rod in reference to each other above a predetermined value, operation of one of said switches activating said control circuit means.

13. In at detecting device for detecting the absence of sheets and the presence of doubled-up sheets fed in the form of a train of overlapping sheets to a printing press, said detecting device comprising two detectors disposed spaced apart in the direction of the sheet travel, each of said detectors being arranged to detect the thickness of the sheet material passing the same, the spacing between the two detectors being equal to the overlap spacing of the sheets within said train of sheets, one of said detectors including two probes for detecting the thickness of the sheet material at two points spaced apart in the direction of the sheet travel, the spacing of one of said probes from the other detector being larger than the overlap spacing of the sheets in said train of sheets by 'a predetermined amount and the spacing of the other of said probes from said other detector being smaller than said overlap spacing by approximately the same amount, the two probes producing a signal for comparison with a signal produced by said other detector when both probes detect substantially the same thickness of sheet material passing the probes, each of said probes including a pair of coacting rollers for feeding sheets therebetween, one of said rollers of each pair being yieldably supported, the spacings between rotational axis of each pair of rollers being indicative of the total thickness of the sheet material passing between the rollers of the respective pair, a pair of bell crank levers, each of said levers being pivotal about a rotational axis, one arm of each of said levers mounting the yieldable roller of one of said probes and the other arm of each lever mounting two lugs disposed at difierent distances from the rotational axis of the respective lever, the angular position of each of said levers being controlled by the spacing between the two rollers of the respective probes, a lengthwise displaceable rod coupled with the yieldable roller of the other detector for displacement of said rod in response to a variation of the spacing between the two rollers of said other detector, 21 control circuit means, and two pairs of switches supported on said rod, the two switches of each pair being disposed adjacent to the lugs on the other arm of the respective lever, either one of said switches of both pairs being operated in response to a change in the positions of the respective lever and the rod in reference to each other above a predetermined variation, operation of one of the switches of either pair activating said control circuit means.

14. In a detecting device for detecting the absence of sheets and the presence of doubled-up sheets fed in the form of a train of overlapping sheets to a printing press, said detecting device comprising two detectors disposed spaced apart in the direction of the sheet travel, each of said detectors being arranged to detect the thickness of the sheet material passing the same, the spacing between the two detectors being equal to the overlap spacing of the sheets within said train of sheets, each of said detectors including a pair of coacting rollers for feeding said sheets therebetween, one of said rollers of each pair being yieldably supported, the spacings between the rotational axis of each pair of rollers being indicative of the total thickness of the sheet material passing between rollers of the respective pair, a pair of pivotally mounted levers, one end of each of said levers mounting one of the yieldable rollers, the angular positions of said levers being controlled by the spacings between the yieldable References Cited by the Examiner rollers and the respective other rollers, said levers cross UNITED STATES PATENTS mg each other, a sw1tch mounted at the other end of each 7 lever, the switch on each one of said levers being oper- 2,274,738 3/1942 Pqtts 261 57 X able by engagement with the respective other lever in 5 216801614 6/1954 Glbson' -271 57 predetermined angular positions of the levers in reference to each other, and a control circuit means, operation of M. HENSON WOOD, JR., Primary Examiner. either one of said switches activating said control circuit J N ERLICH Assistant Exam,-ner means.

2,940,754 6/1960 Stoothofi 27157 X'

Claims

1. IN A DETECTING DEVICE FOR DETECTING THE ABSENCE OF SHEETS AND THE PRESENCE OF DOUBLE-UP SHEETS, FED IN THE FORM OF A TRAIN OF OVERLAPPING SHEETS TO A PRINTING PRESS, SAID DETECTING DEVICE COMPRISING TWO DETECTORS DISPOSED SPACED APART IN THE DIRECTION OF THE SHEET TRAVEL, EACH OF SAID DETECTORS BEING ARRANGED TO DETECT THE THICKNESS OF THE SHEET MATERIAL PASSING THE SAME AND TO GENERATE A SIGNAL CORRESPONDING TO THE DETECTED THICKNESS, THE SPACING BETWEEN THE TWO DETECTORS BEING EQUAL TO THE OVERLAP SPACING OF THE SHEETS WITHIN SAID TRAIN OF SHEETS, COMPRISING MEANS COMPARING SAID SIGNALS AND PRODUCING AN ELECTRIC CONTROL SIGNAL IN RESPONSE TO A DIFFERENTIAL ABOVE A PREDETERMINED VALUE BETWEEN SAID COMPARED SIGNALS, AND CONTROL CIRCUIT MEANS ACTIVATED BY SAID ELECTRIC CONTROL SIGNAL.