US2991997A - Sensing devices - Google Patents

Description

July 11, 1961 H. B. NILSSON 2,991,997

Filed June 17, 1957 July 11, 1961 H. B. NILSSON 2,991,997

SENSING DEVICES Filed June 17, 1957 3 Sheets-Sheet 2 H. B. NILSSON SENSING DEVICES July 11, 1961 3 Sheets-Sheet 3 Filed June 17, 1957 United States Patent 2,991,997 SENSING DEVICES Herman Bertil Nilsson, Solna, Sweden, assignor to Aktielsiolaget Inventing, Stockholm, Sweden, a corporation of we en Filed June 17, 1957, Ser. No. 666,133 6 Claims. (Cl. 271-57) The present invention relates to a sensing device which is especially well suited for use in those cases where the object to be sensed is itself incapable of producing a strong reaction on the member of the sensing device. In such cases it is often sufficient if one is able to establish whether the object to be inspected is occupying the desired position or not, that is, the number of possible alternatives may be reduced to two. A typical case of this kind is the adaptation in devices for controlling the positioning of a sheet-shaped material on a base, for instance in printing machines, for controlling the positioning of the sheets fed before they are passed on in the machine. Especially when multi-colour printing is concerned, the sheet positioning is a problem which must be solved with the utmost accuracy in order that finished multi-colour print may be acceptable.

The main object of the invention is to provide a sensing device having a sensing element which is easily affected by very small forces, the device being of such a nature that in spite of these small operating forces cflicient makes and breaks are obtained in a switch which can be operated by comparatively large forces in response to the position of the sensing element in relationship to a reference position.

A device according to the invention is characterized by a movable member which is so arranged that it can be brought into such a position that part of it can be actuated by an edge portion of a sheet when this is fed to its position on the base, an electromagnet energized by current impulses timed to the feeding of the sheets, said electromagnet being adapted to provide the required mechanical power for making or breaking of a contact which is component of an electric circuit for stopping the printing machine, or the device for feeding the sheets, when a sheet is delivered to an incorrect place on the base, the movable member having another part which is adapted to cooperate with the unit comprising the electromagnet and the contact in order to render possible or impossible for the electromagnet, when receiving such a current impulse, to make or break the contact.

The invention will be described more in detail hereinbelow with reference to the attached drawings showing in perspective and by way of example various embodiments. FIG. 1 illustrates a first embodiment including an electromagnet of the relay type, FIG. 2 shows a second embodiment also including a magnet of the relay type but operating according to a diiferent principle in order to establish closing of the contacts or breaking of the same in response to the position of the sensing element. FIG. 3 shows a third embodiment having an electromagnet with specially designed, adjacent poles capable of attracting a magnetic element connected with the sensing element. FIG. 4 shows a modification of the embodiment illustrated in FIG. 3, FIG. 5 shows a development of the embodiment according to FIG. 3, and FIG. 6 shows a design chiefly according to FIG. 5 and mounted on a carmen In the various figures of the drawing similar reference numerals designate corresponding elements throughout.

The embodiments shown in the drawings are intended for use in printing machines for sensing of the adjustment of a sheet on a base. The sheet to be fed is intended to cooperate with the sensing elements designated by 3 which are shaped like tongues and can be displaced by the paper sheet from the positions indicated by unbroken lines to the positions indicated by broken lines if the sheet is passed on far enough.

The device according to FIG. 1 is built up on a base plate 1 on which an electromagnet 5 of the relay type is afiixed. One pole of the electromagnet is pivoted to one end of an armature 7, the other end of which cooperating with the other pole of the magnet in such a manner that the armature is attracted to said other pole when the electromagnet is energized.

The sensing elements 3 are pivotally fitted on antifriction bearings 9 by means of a common shaft 11 to which a transmitting bar 13 is fixedly connected at one end. At its opposite end, bar 13 which can be made of a metallic material, is connected with an insulating plate 15 which is adapted so as to pass between a fixed contact 17 and a travelling or resilient contact 19. In order to close the circuit over contacts 17 and 19, contact 19 is actuated by the armature 7 of electromagnet 5 by way of two arms 21 and 23.

When electromagnet 5 is energized, which is done by supplying it with a short current impulse when the sensing device is in operating position, said supply being eifected by means of a contactor governed by the printing machine, contacts 17 and 19 are closed if this action is not prevented by the insulating plate 15. The position of this plate depends on the position of the sensing ele ments 3 which are affected by the paper sheet with a very small force. In the case illustrated, closing of the contacts will take place when electromagnet 5 is energized and the movable members are in the position indicated by unbroken lines. This will occur if the sheet to be inspected is not fed on far enough on the base. Contacts 17 and 19 are connected in an electric circuit which is adapted, possibly via relay switches, to effect stopping of the printing machine, or at least the feeding device for the paper sheets, when contacts 17 and 19 are closed. Hence, this will occur when the movable elements occupy the position indicated by unbroken lines in FIG. 1.

On the other hand, if magnet 5 is energized when sensing elements 3 and plate 15 are in the positions indicated by broken lines, the insulating plate '15 will prevent contacts 17 and 19 from closing so that no stopping of the machine will occur in this position. This device is very simple and reliable.

In FIG. 2 an embodiment is shown of a sensing device in which the sensing element to be actuated by the paper does not cause an insulator to move in between the contacts of the surface but prevents said contacts from closing in another way.

The bar 13 connected with shaft 11 of sensing elements 3 in this instance has been made resilient laterally by inserting a resilient member 14 in the bar. The armature 7 of the relay together with a part -8 attached to it forms a fork through which bar 13 passes. By that means the bar can be controllably afiected laterally by electromagnet 5. The free end 26 of the bar may be adapted to cooperate with a break or make contact as was the arm 21 of FIG. 1. In FIG. 2 a break contact is shown comprising a stationary contact 23a and a resilient contact 24 Which normally touch. The free end 26 of bar 13 projects into the interspace between contacts 23a and 24, said free end being capable of moving up and down in the slot-shaped interspace. Bar 13 is provided with an insulating block 25 which cooperates with a shoulder 27 of a post 22 fixedly connected to the base plate 1. Shoulder 27 is defined in the lower part by the edge 29 below which there is a step 28. The device functions in the following way:

In the position shown of sensing elements 3 they have not been actuated by the sheet fed, for which reason the sheet must have arrived into an incorrect position so that disconnecting or switching-off of the printing machine ought to take place, which is also effected by the device illustrated, as will be disclosed below.

7 When the paper has been fed, electromagnet 5 receives a current impulse from a contactor connected to the machine. Then armature 7 isattracted and brings bar 13 along, the end portion 26 of which protrudes between contacts 23a and 24. In the position shown block 25 will enter the step 28 so that the end portion 26 of the bar takes the resilient contact 24 along, contacts 23a and 24 then breaking. Now the electric circuit to which these contacts belong is arranged in such a manner that it effects switching off of the machine or the device for feeding the sheets when the circuit is broken.

If the sheet is delivered'onto the base in a proper position, it will actuate sensing elements 3 and put them in the position indicated by broken lines in FIG. 2. This causes a vertical swing upwards of bar 13 with its block 25, the latter arriving at a point right opposite shoulder 27. When electromagnet 5 receives its current impulse and attracts its armature 7, the end portion 26 of the bar cannot be taken along laterally as this is prevented by block 25 abutting the stationary shoulder 27. Hence, no breaking of contacts 23a and 24 and switching-01f of the machine is effected which was not supposed to happen either, as the sheet was deliveredto its proper position.

In FIG. 3 an embodiment is illustrated wherein the component electromagnet includes two poles located adjacent one another and enclosing a space in which a magnetic element connected with the sensing elements can move.

Each pole of the magnet 5 includes two shanks 31a, 31b and 33a, 33b, respectively. The space enclosed is denoted by 35 and the magnetic element connected to sensing elements 3 by 37. Said magnetic element is connected with an arm 39 by means of which it is atfixed to the shaft 11 of sensing elements 3. The'magnetic element 37 can occupy two limit positions. In the lower limit position shown, element 37 engages shank 31a. as well as shank 33a of the pole pieces. In the upper limit position the element correspondingly engages shank 3112 as well as shank 33b. Element 37 and the pole pieces are preferably made from soft magnetic material so that the element does not adhere to the pole pieces due to residual magnetism when the electromagnet is not energized.

FIG. 3 also shows a stationary contact 42 and a movable contact 41 cooperating therewith, which contacts normally are separated from each other. The movable contact is positioned in such a way that it can be actuated by the free end of arm 39 when element 37 is att-racted by the upper shanks 31b and 33b of the electromagnet. The device will operate in the following manner:

In the illustrated position of sensing elements 3 a fed sheet has not been passed on far enough. By gravity action. on element 37 or by a suitable, very weak spring force, the element lightly touches the lower shanks 31a and 33a. When the electromagnet receives a current impulse nothing observable will occur. The current pulse only causes element 37 to be more strongly pressed against the lower shanks. The electric circuit, in which contacts 41 and 4-2 are cut in, is adapted in such a way that it effects switching-E of the machine or the device for feeding the sheets if the circuit is not closed in that moment when electromagnet receives a current impulse. Hence, a switching-off will take place in the instance just related.

If a sheet is fed on far enough on the base so as to: move sensing elements 3 to the position indicated by broken lines, the magnetic element 37 will occupy such a; position in the space 35 between the magnet shanks that it will be situated closer to shanks-31b and 331;- than to shanks 31a and33a. When the elcctromagnetafterwards receives a current impulse, element 37 is vigorously attracted to shanks 31b and 33b and presses the movable contact 41 into engagement with the stationary contact 42. At this the circuit to which contacts 41 and 42 are connected does not effect any switching off of the machine.

'In FIG.. 4 a modification is shown of the device according to FIG. 3. A lever 51 is connected with shaft 11 of the sensing elements, the free end of said lever actuating a second lever 53 journalled at 55 and provided at its opposite end with a magnetic element 37 which is situated in the free space 35 between the shanks 31a, 31b and 33a, 33b, respectively, of the pole pieces of magnet 5. A push arm 57 is attached to lever 53 and adapted to cooperate with the insulating stud 59 on a movable contact 63 which cooperates with a stationary, contact 61. Contacts 61 and 63 normally touch and are members of an electric circuit of such a nature that it effects switching-off of the printing machine or the device for feeding the sheets if the contacts are broken. The device will operate in the following manner:

In the'position shown by unbroken lines, a sheet has been delivered to its proper position so as to actuate sensing elements 3. By this action the magnetic element 37 has been set to a position close to the lower shanks 31a and 33aof the magnet, this being effected by levers 51 and 53. When the magnet receives a current pulse, element 37 therefore is attracted to these lower shanks. As for the rest nothing observable will occur.

If sensing elements 3 are in the position indicated by broken lines, the sheet has not advanced far enough. The unit comprising levers 51 and 53 and element 37 can be of such a character that element 37 in this instance occupies a position closer to the upper shanks 31b, 33b than to the lower shanks 31a, 33a. This may also be attained by a suitable, very weak spring load. When electromagnet 5 is energized in such an instance, element 37 is strongly attracted to the upper shanks, push arm 57 then efiecting breaking of contacts 61 and 63 by way of the insulating stud 59 whereupon switchingofi takes lace.

p In FIG. 5 a development of the embodiment according to FIG. 3 is shown. A portion 71 of a transmitting bar 71, 73 is attached to shaft 11 of sensing elements 3, said bar having a second portion 73 which is hinged to portion 71 by means of the hinge 75. Portions 71 and 73 are normally maintained on a level with one another by the action of the spring 77 which holds portion 73 bearing against a stop 79 on portion 71. Portion 73 includes a ferromagnetic element 81 which can move freely in the space 35 of electromagnet 5 in a way as described hereinbefore but it only covers a comparatively small angle when moving downwards according to FIG. 5. When element 81 has reached the limit of this free movement, its back edge 83 will encounter shank 33a of the magnet at point 85'. If the electromagnet is energized, the ferromagnetic element 81 is nevertheless attracted in its entirety to pole pieces 31a and 33a, portion 73 then pivoting about hinge 75 against the action of spring 77. At the same time a push arm 87 attached to portion 73 actuates a movable contact 91 by way of an insulating stud 8? so that the normal resting of said contact 91 against a stationary contact 93 ceases. During this continued turning downwards of portion 73 after element 81 has encountered shank 33a at point 85, portion 71 does not take part in this turning movement, and consequently sensing elements 3 will remain stationary on the whole. If the sensing elements for this reason should be locked in the position-shown, for instance, by a heavy sheet or a plate which is passed on to an incorrect position on the base, this will not prevent contacts 91' and 93 from being actuated upon energizing the magnet, which on the other hand would happen if transmitting bar 71, 73 was rigid and element 81 could move freely in the entire 1 9 35 as according to FIG. 3. In this case sensing elements 3 tend to swing backwards against the delivered sheet or plate when the magnet is energized, and the sheet or plate, if heavy, would form a stop for the sensing elements and thence bar 7-1, 73.

In the embodiment shown in FIG. 6 the base plate 1 is pivotally mounted on pivots 94 in a carrier 95 of a printing machine. The design of the sheet sensing device conforms substantially with the design according to FIG. 5 except that the stop 79 is fitted on portion 73 of the transmitting bar and that the insulating stud 89, which actuates the movable contact 91, is attached directly to the ferromagnetic element 81. The position of sensing elements 3 in relationship to the base can be finely adjusted by means of a rod 96 fitted on plate 1 and which by a spring 97 is held against a helicoidal contact surface 98 of an adjustment member 99 rotatably mounted on carrier 95.

These last-mentioned two embodiments are very reliable and independent of the ease or diificulty with which a sheet or a plate can be displaced on the base after delivery.

The embodiments described above and illustrated in the drawings are not exhaustive concerning the possibilities available for constructing a sensing device having the main features stated in the introductory section of this specification. Common to all alternatives is the fact that the sensing element itself, which is actuated by the sheets fed, is extremely easy to affect and that a contact is included in the device, which contact is designed for a comparatively high contact pressure, an electromagnet or other source of power being provided, capable of causing said contact to close or break. At this the li ht sensing element merely has to bring about such a preadjustment of one or more light parts connected with the source of power or the contact that said source of power when it is put in action will actuate the contact quite difierently depending on the various positions of the sensing element.

The circuit which is arranged for effecting switchingoil of the machine when a sheet has come to an incorrect position may differ in character as would be seen already from the detailed description above. Hence, the component contact may either be a break contact or a make contact which means that the remaining circuit as a matter of course must be designed accordingly in order to bring about the desired effect.

What I claim is:

1. In combination with a printing machine having means for feeding sheets to be printed on a base plate and operable by electric circuit means including a switch; the invention which consists of means for controlling the operation of said switch in accordance with the position of a sheet on said base plate comprising an electromagnet secured to said machine adjacent said base plate, said electromagnet being energized by impulses in timed relationship to the feeding of each sheet, armature means operable by said electromagnet to intermittently operate the contacts of said switch, and sensing means mechanically associated with said switch and pivotally connected to said machine for pivotal movement by an edge of a sheet which is correctly positioned on said base plate to a position preventing operation of said switch contacts by said armature means.

2. Apparatus as defined in claim 1 wherein said sensing means includes an electrically insulating member which is inserted between the switch contacts when a sheet is correctly positioned on said base plate.

3. Apparatus as defined in claim 1 wherein said printing machine includes a stationary stop member secured thereto and further wherein said armature means includes an armature member and a shaft member connected to said armature member normally spaced from said stop means and arranged to operate one of said switch contacts, said sensing means being connected to said shaft member to displace the same to a position adjacent said stop member when a sheet is correctly positioned on the base plate to prevent said shaft member from operating said switch contact.

4. Apparatus as defined in claim 1 wherein said electromagnet is of the relay type having two pole pieces each having a pair of spaced shank portions, the shank portions of one pole piece being opposite the shank portions of the other pole piece, said armature means including an armature having a ferromagnetic portion movable in the space between said shank portions of the pole pieces, said armature normally cooperating with a first shank portion of one pole piece and the associated shank portion of the other pole piece to operate the switch contacts, said sensing means being connected to said armature to displace the same adjacent the other shank portions of the pole pieces when a sheet is correctly positioned on the base plate so that said armature will cooperate solely with the other two shank portions.

5. Apparatus as defined in claim 4, wherein said sensing means includes an arm pivotally connected to said armature about a pivot axis normal to the plane of movement of said armature, and means limiting the pivotal movement of the armature relative to said arm in the direction toward said other pole piece shank portions, whereby catching of the sensing means by a correctly positioned sheet on the base plate will not prevent movement of the ferromagnetic portion of the armature into cooperation with said first shank portion of one pole piece and the associated shank portion of the other pole piece.

6. Apparatus as defined in claim 5 and further including spring means biasing said armature toward said other shank portions against said limiting means relative to said arm, said first shank portion of one pole piece and the associated shank portion of the other pole piece being arranged to cause the movement of the arm and the armature as a unit toward said first shank portion and the associated shank portion to be limited by said first shank portion, the armature subsequently being pivoted relative to the arm against the biasing action of said spring toward said associated shank portion upon energization of said electromagnet.

References Cited in the file of this patent UNITED STATES PATENTS 1,077,818 Eagar Nov. 4, 1913 2,274,738 Potts Mar. 3, 1942 2,357,456 Bryce Sept. 5, 1944 2,579,922 Goldsworthy Dec. 25, 1951 2,788,739 Gillis Apr. 16, 1957 2,793,035 Wroblewski May 21, 1957 2,865,154 Coyne Dec. 23, 1958

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