EP0561308B1

EP0561308B1 - Device with a travelling conveyor and grippers

Info

Publication number: EP0561308B1
Application number: EP93104102A
Authority: EP
Inventors: Robert M. Silva; Frank J. Tomko
Original assignee: Graphic Management Associates Inc
Current assignee: Muller Martini Mailroom Systems Inc
Priority date: 1992-03-17
Filing date: 1993-03-13
Publication date: 1996-07-24
Anticipated expiration: 2013-03-13
Also published as: EP0561308A1; DK0561308T3; DE69303743T2; DE69303743D1; ATE140682T1

Abstract

A selective release for grippers (2) on a conveyor (1), each of which has a movable arm (4) and a stationary arm (3). Arms (3,4) move toward each other to grip a planar product (e.g. a newspaper (50)) therebetween and move away from each other to release the product. The gripper (2) is biased toward the closed position and can be moved into the open position by the application of a release force. A rocker cam (8) is provided which can move into a position whereby it urges the movable gripper arm (4) into the open position and into contact with a retaining cam (18). The retaining cam (18) holds the movable arm (4) in the open position for a period of time sufficient to allow the product to be completely released from the gripper (2). <IMAGE>

Description

The invention presents a device with a conveyor and grippers for holding individual, generally planar products in a traveling direction, each gripper comprising a first gripper arm and a second gripper arm being movable toward each other into a closed gripping position, wherein the gripper arms exert an clamping force on the products, being movable away from one another into an open release position, wherein said grippers release said products, a clamping force of a bias biasing the gripper arms of each gripper towards said closed position is effective. More specifically, the device is intended for use in connection with the conveyance of printed products such as newspapers.
Newspapers come off the press at approximately 75,000 copies per hour. Thereafter, the products themselves, or sections to be inserted therein, must be carried to various pieces of equipment for further processing. It is known from US-A-4 381 056 to use a conveyor with grippers having jaws biased to open. The grippers are held in the closed position by latch means and clamp in the closed position the edge of the newspaper to hold it securely. When the product is to be delivered to the next machine for processing, the latch means are triggered, the latch means release and the grippers spring open.
US-A-4 512 457 presents a conveyor with grippers having jaws. The jaws of the grippers are involved in both rotating and moving toward each other and against the action of a spring. Thus these jaws like those of US-A-4 381 056 are biased toward the open position. Two motions are necessary, axial separation of the jaws of the gripper and rotation thereof about the axis, to release the product. However, since the gripper is biased open, it is necessary to have some means for holding the gripper closed during the vast bulk of its travel.
However, due to the high speed at which the grippers move, coupled with the reaction time of the previous devices, it is difficult to reliably release the papers and deposite them on a belt or other carrier for the next process step.
The present invention is intended to overcome the foregoing difficulties; namely to accurately and reliably open the grippers at the proper point with reaction time allowing to deposite the papers at the proper time and in the appropriate location.
The aim of the invention is realized by a device characterised in

a release force, greater than the clamping force effecting at each gripper (13,14) against the biasing force and moving effected grippers (13,14) into said open position,
at least one rocker cam (8,17) being movable from an inactive into an operative position,
the rocker cam (8,17) in its operative position urging said gripper (13,14) to open and come into contact with at least one retaining cam (18),
the retaining cam (18) being adapted to retain the effected gripper (13,14) in said open position for a period of time sufficient to allow the product to be completely released from the gripper (13,14).

The device of the invention has a short reaction time and is far more efficient than the prior art in that the bias into the closed position allows the gripper to move freely throughout almost all of its path for only at the depositing and pickup points the opening is required. Only when the gripper comes to the pickup or deposit point there is need for a rocker cam to open it.
In essence, the release of the present invention is intended to be used in connection with grippers which clamp a newspaper between a first arm and a second arm. The grippers are spring biased toward the closed position and may be opened by pressure on a release arm connected to the movable gripper arm.
The retaining cam which is adapted to bear against the gripper and hold it in the open position is furthermore effective and useful because it takes with its length a finite amount of time for the product, for example a newspaper, to drop out of the gripper arms. Since the speed is very high (more than 20 copies per second), merely opening the gripper would not allow this to occur. The opening of the gripper against the clamping force together with the features of the rocker arm and the retaining cam allows the device to work accurately and reliable.
The gripper release is actuated by a rocker arm which has an operative position, wherein it urges the gripper into the open position and into contact with the retaining cam, and a closed position, wherein it is inactive and does not cause the gripper to open.
Since the reaction time of the mechanism may be virtually equal to the time between successive grippers, it has been found advantageous to provide means to open every second gripper. Therefore the device comprises a plurality of first grippers sequently followed by a plurality of second grippers, the first grippers alternating with the second grippers. In this way it is in combination with the solenoid activation of the rocker cam possible to activate the release of the grippers selectively.
The opening will be advantageous effected by a selectively solenoid activated movement of the rocker cam. The selective solenoid activation is controllable by switches, located at the depositing and pickup points. The opening action therefore is definite controllable. The possibility of a selective opening of the grippers allows to release them alternately.
Further features of the invention are explained within the description.
In the accompanying drawings, constituting a part hereof, and in which like reference characters indicate like parts,

Figure 1: is a schematic side view of the release of the present invention with some parts omitted for clarity;
Figure 2: is a schematic sectional view from the left side of Figure 1 with some parts omitted for clarity;
Figure 3: is a view similar to that of Figure 1 wherein alternate grippers are released;
Figure 4: is a view similar to that of Figure 2, based on Figure 3;
Figure 5: is a diagrammatic view showing the timing of the various elements of the invention; and
Figure 6: is a schematic representation of the controllers and proximity switches.

DETAILED DESCRIPTION OF THE INVENTION

Referring more specifically to Figures 1 and 2, conveyor 1 is provided with a plurality of grippers 2. Each gripper 2 comprises fixed arm 3, movable arm 4, and a pair of release arms 10, one located on each side of gripper 2.
There are release rollers 15 and 20 mounted on the distal end of release arms 10. To accommodate the ability to release alternate grippers, first alternate grippers 13 have rollers 15 which project to the right as shown in Figure 2. Second alternate grippers 14 have rollers 20 which project to the left as shown in Figure 2. Complementary to rollers 15 and 20 are pairs of rocker cams 8 and 17, actuated by corresponding pairs of solenoids 6 and 7. Each rocker arm 8 and 17 has cam surface 9 thereon.
In operation, as grippers 2 travel along conveyor 1, a signal is given to release certain selected grippers. At the appropriate time, solenoids 6 or 7 are activated, thereby moving rocker cams 8 or 17 into their operative position. If the gripper to be released is one of first alternate grippers 13, solenoids 6 (and hence rocker cams 8) are actuated; on the other hand, if the gripper selected is one of second alternate grippers 14, then solenoids 7 (and hence rocker cams 17) are activated.
In the case of the selected gripper being a first alternate gripper 13, solenoids 6 are activated to cause rocker cams 8 to assume the operative position as shown in full lines in Figure 1. Roller 15, contacting cam surface 9 of rocker cam 8 is forced downward (as shown in Figure 1) and beneath retaining cam 18. As it continues to move, retaining cam 18 holds the gripper open so that paper 50 has an opportunity to drop out.
Because of the high speed of conveyor 1 (necessitated by the press speed), it has been found advantageous to release alternate grippers, thereby doubling the amount of time which the mechanism has in which to assume the operative position and then return to the inoperative position. To facilitate this, as previously indicated, first alternate grippers 13 have rollers 15 extending to the right as shown in Figure 2. Second alternate grippers 14 are provided with rollers 20 which extend in the opposite direction. In Figure 2, the device is shown releasing all of grippers 2. Thus, pairs of solenoids 6 and 7 (and hence rocker cams 8 and 17) are shown in operative position. Roller 15 has just completed its contact with cam surface 9 of rocker arms 8. The other roller 15 is not shown. At the same time, roller 20 on second alternate gripper 14 is approaching cam surface 9 of rocker cam 17. At the point shown, it has not yet been forced downward.
In Figures 3 and 4, the device is shown operating to release alternate grippers. In this case, solenoids 7 and rocker cams 17 are in their inactive positions. Thus, rollers 20 are not contacted by surface 9 and remain in their closed position. They ride on top of cam surface 18 as shown in the leading second alternate gripper 14 in Figure 3. Solenoids 6 have been activated and are, along with rocker cams 8, in their operative positions. Cam surface 9 has contacted rollers 15 (both are shown in Figure 4) and rollers 15 now are held in open position by retaining cam 18. Second alternate grippers 14 may, if desired, be released at a later point in the travel of conveyor 1.
First proximity switches 16 and 51 and second proximity switches 52 and 53 are provided adjacent rocker cams 8 and 17 to detect the presence of rollers 15 and 20. First alternate grippers 13 constitute the odd grippers and second alternate grippers 14 are the even grippers. The control and timing of actuation of solenoids 6 and 7 are shown diagrammatically in Figure 5. Proximity switches 16 and 51, upon registering the presence of an odd gripper send pulses 38, 39, 40, 41, 42, and 43 to the release point control. Proximity switches 52 and 53 send even gripper pulses 24, 25, 26, 27, and 28 to the release point control. Assuming that there is a request to discharge the newspapers from the even grippers, leading edge 29 of gripper pulse 25 is detected by the release point control. Scan time 34 is required for first release point control 54 to recognize that pulse 25 is that of an even gripper. At release point 31, it then signals gripper release control 56 which is programmed so that two conditions must be fulfilled before it is activated. First, it must receive the release point signal from the release point control and, second, it must register the leading edge 30 of the next even gripper pulse 26. Since the scan time of the gripper release control is on the order of 1 millisecond, the reaction time is virtually non existent The fulfillment of the second condition causes the gripper control to activate the release signal 32 and send it to the appropriate solenoids. This signal continues until inactivation point 35. The cycle is repeated as desired. The release of the odd gripper pulses is carried out in exactly the same way. Leading edge 45 of pulse 39 is received by second release point control 55 and scan time 34 is required for recognition. At release point 31, a signal is sent to the gripper control which then awaits the next odd pulse, namely, leading edge 46 of pulse 40. In the same manner as for the release of the even grippers, solenoids 7 are activated by signal 32. They are held in open position until inactivation point 35. The relationship between the various elements of the electronic control system is diagrammed and described in Figure 6.
Thus, the present invention provides a means for selectively releasing grippers, which does not require high speed mechanical equipment which is likely to be unreliable. It is possible to release the newspapers virtually at will and substantially without any misses or errors. They can be released singly, alternately, or entirely as is desired by the operator.

Claims

Device with a conveyor (1) and grippers (13,14) for holding individual, generally planar products (50) in a traveling direction, each gripper (13,14) comprising a first gripper arm (3) and a second gripper arm (4) said first gripper arm and second gripper arm (4) being movable toward each other into a closed gripping position, wherein the gripper arms (3,4) exert an clamping force on the product (50), being movable away from one another into an open release position, wherein said grippers release said products, a clamping force of a bias biasing the gripper arms (3,4) of each gripper (13,14) towards said closed position is effective
characterised in
- a release force, greater than said clamping force effecting at each gripper (13,14) against the biasing force and moving effected grippers (13,14) into said open position,

- at least one rocker cam (8,17) being movable from an inactive into an operative position,

- the rocker cam (8,17) in its operative position urging said gripper (13,14) to open and come into contact with at least one retaining cam (18),

- the retaining cam (18) being adapted to retain the effected gripper (13,14) in said open position for a period of time sufficient to allow the product to be completely released from the gripper (13,14).
Device of claim 1, comprising at least one release arm (10) on each of said grippers (13,14) which is adapted to receive said release force and to transmit said release force to said grippers (13,14).
Device of claim 1, characterised in that said first gripper arm (3) is stationary and said second gripper arm (4) is movable.
Device of claim 2, wherein said release arm (10) has a release roller (15,20) at its distal end, said release roller (15,20) adapted to receive said release force and to transmit said release force to its release arm (10).
Device of claim 2, wherein there is a pair of said release arms (10), one on each side of each gripper (13,14), pairs of said rocker cams (8,17), adapted to bear against each of said release arms (10), and two said retaining cams (18), adapted to retain said release arms (10) and said grippers (13,14) in said open position.
Device of claim 1, comprising actuating cylinders (6,7) adapted to move said rocker cams (8,17) between said operative position and said inactive position.
Device of claim 6, wherein there are pairs of actuating cylinders (6,7) adapted to move said pairs of rocker cams (8,17) between said operative and said inactive position.
Device of any of claims 1 to 7, wherein said grippers (13,14) comprise first grippers (13) which are sequently followed by second grippers (14) and each gripper of said first and second grippers (13,14) comprising release rollers (15,20) on said pairs of release arms (10), one on each side of the grippers (13,14), the release rollers (15) on the release arms of the first grippers (13) projecting in a first direction which is transverse to said traveling direction (20), the release rollers (15) on said release arms (10) of the second grippers (14) projecting in a second direction which is transverse to said traveling direction (20) and different from said first direction, first pairs of the first rocker cams (8) adapted to bear against said first pair of release rollers (15) when in said operative position, and said second pairs of rocker cams (17) adapted to bear against said second pairs of release rollers (20) when in said operative position.
Device of claim 8, wherein said first direction is opposite to said second direction.
Device of claim 8, comprising a proximity switch (16) adjacent said rocker cam (8,17) to sense the presence of said release arm (10) and send a proximity signal to a controller which is adapted to activate actuating cylinder (6,7).
Device of claim 10, comprising proximity switches (16), each adjacent one of said pairs of rocker cams (8), one said proximity switch (16) adapted to sense the presence of each of said release arms (10) and send a proximity signal to a controller which is adapted to activate one of said actuating cylinders (6,7).
Device of claim 10, comprising
- a first proximity switch (16) adjacent one of said first pair of rocker cams (8) and adapted to sence the presence of one of said first pair of release arms (10) and emit a first proximity signal based thereon,

- a second proximity switch (16) adjacent one of said second pair of rocker cams (17) and adapted to sence the presence of one of said second pair of release arms (10) and emit a second proximity signal based thereon,

- a first release point control adapted to receive a first proximity signal and a second proximity signal and to distinguish there between, said first release point control adapted to send a first corresponding signal based on said first proximity signal to a gripper release control,

- said gripper release control adapted to receive said first corresponding signal and receive a first release control signal which directs release of said first gripper (13), said gripper control adapted to send a first operating signal to said first pair of actuating cylinders whereby said first gripper (13) is released.
Device of claim 8, comprising a plurality of said first grippers (13) sequently followed by a plurality of said second grippers (14), said first grippers (13) alternating with said second grippers (14).
Device of claim 12, wherein said first release point control sends said first corresponding signal based on a first proximity signal in advance of the first proximity signal which corresponds to said first gripper (13) to be released.
Device of claim 12, wherein
- a second release point control is adapted to send a second corresponding signal based on said second proximity signal to said gripper release control,

- said gripper release control adapted to receive said second corresponding signal and receive a second release control signal which directs release of said second gripper (14), said gripper control adapted to send a second operating signal to said second pair of actuating cylinders (7) whereby said second gripper (14) is released.
Device of claim 15, wherein said first release point control is adjacent said second release point control.
Device of claim 15, wherein said first release point control and said second release point control are a single release control.
Device of claim 12, wherein said second release point control sends said second corresponding signal based on a second proximity signal in advance of the second proximity signal which corresponds to said second gripper (14) to be released.
Device of claim 1, wherein said rocker cams (8,17) pivot about a point intermediate its ends between said operative position and said interactive position.