US3419263A

US3419263A - Sheet feeder

Info

Publication number: US3419263A
Application number: US648077A
Authority: US
Inventors: William H Weidman
Original assignee: Harris Intertype Corp
Current assignee: Harris Graphics Corp
Priority date: 1967-06-22
Filing date: 1967-06-22
Publication date: 1968-12-31
Anticipated expiration: 1985-12-31

Description

Dec. 31, 1968 w. H. WEIDMAN 3,419,263

SHEET FEEDER Filed June 22, 1967 Sheet I IIIIIIIIIA .I)

INVENTOR. W/LL/AM H. Wf/DMAN IIITORNEXS' Dec. 31, 1968 w, H. w mM N 3,419,263

SHEET FEEDER Filed June 22, 1967 Sheet 2 of 2 INVENTOR.

W/lL/AM H WE/DMAN United States Patent 3,419,263 SHEET FEEDER William H. Weidman, Maple Heights, Ohio, assignor to Harris-Intertype Corporation, Cleveland, Ohio, a corporation of Ohio Filed Jane 22, 1967, Ser. No. 648,077 17 Claims. (Cl. 271-26) ABSTRACT OF THE DISCLOSURE The control for the sheet feeder includes a valve means which operates to control the application of vacuum from a rotary timing valve to sheet feeding apparatus. The rotary timing valve is in communication with a vacuum pump and interrupts and applies vacuum to the sheet gripping means of the sheet handling apparatus in a timed sequence corresponding to the sequence of operation of the sheet feeder. The valve means is connected between the rotary valve and the sheet gripping means and includes a valve member which is movable between an open position in which the rotary timing valve is in vacuum connection with the sheet gripping means of the sheet feeder and a closed position wherein communication is blocked. During operation of the feeder the rotary timing valve is continuously rotated and the sheet feeding can be interrupted by moving the valve member to its closed position. The valve member is vacuum responsive and can only be moved to its closed position when the timing valve is not applying a vacuum to the sheet gripping means so that the feeding operation cannot be interrupted in the middle of a cycle. The valve means further includes a vacuum operated electrical switch which opens and prevents energization of a solenoid which moves the valve member to its open position when the timing valve is in its vacuum applying phase of its cycle of operation.

The present invention relates to a control for a sheet feeder and particularly to a control for controlling the application of vacuum to the vacuum operated mechanism of the sheet feeder.

Known sheet feeders have sheet gripping means operated by vacuum to grip the top sheet of a stack of sheets and feed the sheet to sheet processing equipment such as a printing press or the like. The sheet feeders are controlled so that during one phase of the operation vacuum is applied to the sheet gripping means to grip the sheet and feed it from the stack. After the sheet has been moved the required extent, the vacuum is discontinued to release the sheet from the sheet gripping mechanism. A rotating timing valve controls the application of suction to the sheet gripping means. To stop or start the feeding cycle it has been necessary for the operator to observe the feeder and actuate the switch for the vacuum pump to establish or interrupt the vacuum application at the appropriate time in the feeding cycle to insure that the feeder does not jam or otherwise cause a malfunction of the feeder or the associated equipment. The on-off switch for the pump had to be located so that the operator could view the feeder which operates the switch. The operator had to go to the switch location and wait until the feeder entered the appropriate phase in the cycle of operation before operating the switch. This is time consuming for the operator and also requires training to know when to actuate the switch.

Accordingly it is an important object of the present invention to provide a new and improved control for the sheet feeder which permits the start and stop button for the vacuum pump to be located at one or more areas convenient to the operator and further permits the operator to actuate the switch at any time without regard to the phase of the sheet feeding operation which the feeder is in and the control operates to start or stop the application of vacuum from the timing valve to the sheet feeder only when the feeder is in the proper phase of its cycle of operation.

Another object of the present invention is to provide a new and improved control for a sheet feeder having valve means in the vacuum communication system between the rotary timing valve and the sheet gripping means of the feeder which is operable to establish communication through the system only when the rotary timing valve is in a non-vacuum application phase of its cycle of operation so that vacuum cannot be applied to the sheet gripping means except when the gripping means is ready to commence a new feed cycle.

Yet another object of the present invention is to provide a new and improved control for a sheet feeder, as noted in the preceding paragraph, and which control includes a vacuum operated switch which is communicated with the timing valve through the valve means when the valve means is in a position to block vacuum application to the gripping means and if the timing valve is in a vacuum applying phase of the cycle, vacuum acts to open contacts of the switch and prevents energization of the control mechanism for actuating the valve means.

A further object of the present invention is the provision of a new and improved control for a sheet feeder in which valve means controls communication between a rotary timing valve and sheet gripping means of the sheet feeder and which is operable to shut off the vacuum only when the timing valve is not in its vacuum applying phase of its operation to insure that vacuum is applied to the sheet gripping means until it has completed a sheet feeding operation.

A still further object of. the present invention is the provision of a new and improved control for a sheet feeder, as noted in the next preceding paragraph, and in which the valve means includes a port which is in communication with the rotary timing valve and which port is engaged by a port closing member carried by the movable valve member of the valve means when the valve means is in a vacuum communicating position and the valve member cannot be shifted to block communication as long as vacuum is being applied to the port closing member by the rotary timing valve.

Another object of the present invention is the provision of a new and improved control for a sheet feeder having valve means which operates in conjunction with a rotary timing valve to apply vacuum and blow down pressure successively to the sheet gripping means of the sheet feeder to effect feeding of the sheets from the stack to the sheet processing equipment and the valve means can be energized at any time without regard to the phase of operation of the timing valve but which will not operate to interrupt the vacuum to the sheet gripping means until the timing valve is in the blow down phase of operation at which time the valve means will be permitted to close and block further communication between the timing valve and the sheet gripping means.

These and other objects will become apparent from the following detailed description of the preferred embodiment of the invention taken in conjunction with the drawings forming a part thereof and in which:

FIG. 1 is a diagrammatic view of a control for a sheet feeder embodying the present invention;

FIG. 2 is a fragmentary view of the control shown in FIG. 1 and showing parts in a different operative setting;

FIG. 3 is a view similar to FIG. 2 but showing parts in yet other operative setting; and

FIG. 4 is an elevational view with part shown in section of the control for the sheet feeder embodying the present invention.

The illustrated embodiment of the present invention provides a relatively simple and reliable control for a sheet feeder which is actuatable at any time by an operator and which operates to establish or discontinue vacuum to the sheet gripping means at an appropriate time in the cycle of operation of the feeder. The control embodying the present invention is applicable for controlling various types of feeding devices but it is herein disclosed for controlling a sheet feeder of the type shown diagrammatically in FIG. 1.

Referring to FIG. 1, the sheet feeder is indicated generally by reference numeral and includes an elevatable platform 12 which supports a stack of sheets and moves vertically incrementally as the top sheet of the stack is successively fed from the stack by a well known sheet feeding means 14. The sheet feeding means 14 is shown diagrammatically and comprises a plurality of pick-up suckers 16 which are supported for vertical reciprocating movement relative to the top sheet of the stack. At start-up of a sheet feeding cycle of operation, the pick-up suckers 16 move down into engagement with the trailing end of the sheet. Suction is applied to the pick-up suckers 16 just prior to engaging the sheet and the suckers 16 move the sheet vertically into engagament with a plurality of forwarding suckers 18. As the sheet moves into engagement with the forwarding suckers 18, the suction to the pick-up suckers 16 is shut off and suction is directed to the forwarding suckers 18 just prior to engaging the sheet to effect transfer of the sheets from the pick-up to the forwarding suckers.

Thhe forwarding suckers 18 are supported for general horizontal reciprocating movement and move the gripped sheet relative to the stack to position the leading edge of the sheet in the nip between the driven

pinch rolls

20 and 22. As the pinch rolls 20 and 22 engage the sheet, the suction to the forwarding suckers 18 is shut ofi. The sheet is fed onto a feed board 24 by the

rolls

20 and 22 where it is subsequently delivered to sheet processing equipment, such as a printing press.

When the sheet is released from the forwarding suckers 18, the forwarding suckers 18 return to their initial position shown in FIG. 1 as the pick-up suckers 16 commence another feeding cycle.

A rotary timing valve 26 controls the application of vacuum to the pick-up suckers 16 and forwarding suckers 18 in the proper sequence during the sheet feeding cycle. The rotary timing valve 26 comprises a valve body 28 and a valve member arranged to rotate within the valve \body 28. The valve 26 is connected to a vacuum pump P by suitable pressure conduit means 29 which communicates the vacuum pump P and the valve member 30. The valve member 30 is rotated by a driven shaft 31 (FIG. 4) in timed relation to the movement of the sheet feeding suckers 16, 18 and provides for communicating the pump P and the pick-up suckers 16 and forwarding suckers 18 in proper sequence during the sheet feeding cycle.

The valve member 30 includes a vacuum area 32 which is connected to the conduit means 29 through suitable passageways, not shown. The valve housing 28 has two pairs of

passageways

34 and 36 which are connected respectively to the pick-up suckers 16 and forwarding suckers 18 through suitable pressure conduit means 38 and 40 respectively. When the vacuum area 32 is in communication with the passageways 34, suction is applied to the pickup suckers 16. This provides vacuum for the pick-up suckers 16 to grip the trailing end of the sheet and lift it into engagement with the forwarding suckers 18. As the end of the sheet is brought into engagement with the forwarding suckers 18, vacuum area 32 clears passageways 34 and shuts off vacuum to the pick-up suckers 16. As

the trailing end of vacuum area 32 moves out of communication with the passageways 34-, the leading end thereof is in communication with passageways 36 to apply vacuum to the forwarding suckers 18.

The valve member 30 also has a blow-down area 42 which is connected to a suitable source of air under pressure and when communicated with the suckers 16 and 18 provides positive separation of the gripped sheet from the suckers. Valve member 30 rotates clockwise as viewed in FIG. 1 and blow-down area 42 follows the vacuum area 32 into communication with the passageways 34 and applies air pressure to the pick-up suckers 16 to positively separate the sheet from pick-up suckers 16 as it is transferred to the forwarding suckers 18. The blow-down area 4-2 also follows the vacuum area 32 into communication with the passageways 36 to provide air under pressure to the forwarding suckers 18 after the forwarding suckers have moved the leading end of the sheet into the

pinch rolls

20 and 22 to positively separate the sheet from the forwarding suckers 18.

From the foregoing it should be apparent that the rotary timing valve 26 is timed in relation to the movement of the sheet feeder 10 and in particularly in relation to the sheet feeding means 14 to correlate the application of suction and pressure to the pick-up suckers 16 and forwarding suckers 18 during a feeding cycle of operation. After the top sheet of the stack has been fed into

pinch rolls

20 and 22, platform 12 moves upward to present the next top sheet of the stack in proper relationship to the sheet feeding means 14 to be fed during the next cycle of operation of the feeder.

In certain printing installations sheet feeding can be temporarily interrupted without shutting off the sheet feeder. This can be accomplished by interrupting the vacuum to the pick-up suckers. Without vacuum, the pick-up suckers will move through their described feeding cycle but will not grip and feed a sheet. The vacuum must be shut off at the appropriate time in the sheet feeding cycle or the sheet feeder 10 may malfunction. For example, if the vacuum is shut off after the pick-up suckers 16 have started to lift the trailing edge of a sheet up toward the forwarding suckers, the pick-up suckers 16 would drop the sheet back onto the stack. If the dropped sheet is out of alignment with the stack, it will be out of proper alignment with the sheet gripping means 14 and with the pinch rolls 20 and 22 when it is subsequently fed and could possibly jam and shut down the press. The press may also be shut down if the misaligned sheet is fed and due to its misalignment would not register properly with the press. Thus, it can be seen that the vacuum can be shut off only after the pick-up suckers 16 have completed their phase of the cycle of operation.

It is also important to re-apply the vacuum to the suckers at the appropriate time in the cycle of operation of sheet gripping means 14. This is particularly important in a high speed sheet feeder in which the sheet delivery is interrupted by shutting off the vacuum to the suckers while the suckers continue to move through their cycle of operation. An example of such a feeder is disclosed in the co-pending application of Robert K. Nortion SN 605,339 assigned to the same assignee as the present application. In such a high speed feeder, the suckers move rapidly and if the sheet delivery commences by applying vacuum to the pick-up suckers 16 after they begin moving away from the sheet, the vacuum may lift the sheet from the stack. But in view of the high speed movement of the suckers, the sheet would not be drawn into engagement with the suckers and will drop back onto the stack perhaps out of alignment. When subsequently fed, the sheet may be jam or would be arranged so that it would not register properly with the press causing the press to shut down.

The present invention provides control means for controlling the shut-olf and application of vacuum to the sheet feeder 10 and which control means can be actuated at any time in the cycle of operation by a control signal generated by an automatic control system of the type disclosed in the said Norton application or by an operator depressing a manually operated switch 46 provided at any location convenient for the operator. The control means operate upon receipt of the control signal to start up or shut-off the vacuum only at the appropriate time in the feeding cycle. The illustrated embodiment of the control means comprises valve means 50 disposed in conduit means 38 communicating the timing valve 26 and the pick-up suckers 16.

The valve means 50 is responsive to the timing Valve 26 and in particular to the vacuum and

pressure areas

32 and 42 of valve member 30 to start up and stop vacuum application to the pick-up suckers 16 only when the pick-up suckers 16 have completed their phase of the sheet feeding cycle. Valve means 50 does not affect the application of vacuum to forwarding suckers 18 because it is only necessary to control the application of vacuum to the pick-up suckers 16 to control the sheet feeding. If the pick-up suckers 16 have no vacuum, they will not transfer a sheet to the forwarding suckers 18.

Valve means 50, best shown in FIG. 4, comprises a valve body 52 having a central bore 54. The bore 54 slidably receives a valve member 56 which controls communication through the valve 50. In the illustrated embodiment, the valve bady 52 has a pair of

inlet ports

58 and 60 which communicate the central bore 54 with the timing valve 26 through conduit means 38. The disclosed timing valve 26 provides for the application of vacuum and air blast to the suckers through two separate conduits; a separate line is provided for each of two pairs of pick-up suckers 16 which is the preferred pick-up sucker arrangement. The part of the rotating valve member 30 illustrated diagrammatically in FIG. 1 is duplicated to provide second line of communication between the pump and suckers. However, any desired number of lines of communication can be provided as required by the nature of the sheet feeder and valve means 50 can be constructed to control the selected number of lines. Since valve means 50 must accommodate two lines of communication, conduit means 38 includes

conduits

38a and 38b which are connected with the

inlet ports

58 and 60 respectively. The valve body 52 further has outlet ports 62 and 64 which communicate the bore 54 with the pairs of pick-up suckers 16 through the continuation of

conduits

38a and 38b.

The valve member 56 which is in the nature of a spool valve has an exposed end 56a connected to a suitable actuator, such as a solenoid 66. Energization of solenoid 66 moves the valve 56 from its closed position shown in FIGS. 1 and 3 wherein flow through the valve is blocked to its open position shown in FIGS. 2 and 4 and wherein flow through the valve is established. With the valve member 56 in its open position, reduced or necked portions 56b and 560 formed thereon are aligned with

openings

58 and 62 and openings 60 and 64, respectively, in the valve body 52 to establish flow through the valve and communicate the pick-up suckers 16 with the timing valve 26. The valve member 56 is biased to the left as viewed in FIG. 4 or the right or the right as viewed in FIGS. 1-3 toward its closed position by spring means 68 acting between one end of the valve body 52 and an abutment formed on the valve member 56.

The solenoid 66 is energized by the manually actuated switch 46 which also energizes pump P. When valve member 56 is in its open position as a result of energization of solenoid 66, vacuum is applied to the pick-up suckers 16 each time the vacuum area 32 of the rotary valve moves into communication with the passageways 34. Hence when the vacuum area 32 communicates with the pair of passageways 34 of the timing valve 26, vacuum is directed to the pick-up suckers 16 through valve means 50 so that the suckers can pick up the trailing end of the sheet and move it upward into engagement with the forwarding suckers 18. As the vacuum area 32 passes beyond the passageways 34, the vacuum to the pick-up suckers 16 is discontinued and the vacuum is applied to the forwarding suckers 18 as the vacuum area 32 communicates with the pair of passageways 36. At this time the blowdown area 42 communicates with the passageways 34 and provides an air blast to the pick-up suckers 16 for positively separating the sheets from the pick-up suckers 16.v

After the forwarding suckers 18 have moved leading edge of the sheet into engagement with the pinch rolls 20 and 22, the blow-down area 42 will be in communication with the passageways 36 to effect a positive separation of the sheet from the forwarding suckers 16 and whereafter the forwarding suckers 18 return to their initial position.

In the event it is not desired to feed a sheet at a particular time, the operator depresses the off button 46b of the switch 46 which shuts off the pump P and de-energizes the solenoid 66. The switch 46 may be located away from the feeder 10 since the operator may actuate the switch 46 without viewing the sheet feeding means 14. When the solenoid 66 is de-energized, spring 68 tends to shift the valve member 56 to its closed position. This action will not occur unless the timing valve is in a proper phase of its cycle of operation. The valve member 56 has a sucker member 70 mounted on the exposed end 56a thereof and which moves with the valve member 56. The sucker member 70 cooperates with an axially extending port 72 in the valve body 52 and which communicates the inlet port 58 to atmosphere. When the valve member 56 is in its open position as shown in FIG. 2, the sucker member 70 blocks or covers one end of the axially extending ports 72. The sucker member 70 is fixedly secured in any suitable manner to the valve member 56 and consequently as long as there is vacuum acting on the sucker member 70, the spring 68 cannot shift valve member 56 to its closed position.

Vacuum is applied to sucker member 7 0 when vacuum area 32 communicates with passageways 34 as shown in FIG. 2. Hence valve member 56 cannot be shifted to its closed position as long as vacuum is being directed to inlet port 58 by timing valve 26. This prevents interrupting the vacuum to the pickup suckers 16 while the pick-up suckers 16 are in the middle of the feeding cycle. The vacuum will not be interrupted until the blow-down area 42 communicates with passageways 34 and a blast of air is directed through the inlet port 58 to vent port 72. The air pressure discontinues the vacuum holding the valve member 56 open and spring 68 moves the sucker member 70 and connected valve member 56 to its closed position to block communication between the

ports

58 and 62 and ports 60 and 64- as shown in FIGS. 1 and 3. Hence the pick-up suckers 16 will be permitted to finish their feeding cycle and the vacuum will not be shut off until they complete a cycle of operation. However, if solenoid 66 is de-energized when the vacuum area 32 is not applying a vacuum to inlet port 58, the spring 68- will shift the valve member 56 to its closed position.

In the event off-button 46b of switch 46 is depressed when the vacuum area 32 is in communication with passageways 34 as shown in FIG. 2, the pump P will be shut off immediately but sufiicient vacuum will be provided by pump drift after shut-off to maintain vacuum in the system until area 32 clears passageways 36. Thus the feeding cycle can be completed once the pick-up suckers 16 grip a sheet.

The Valve means 50 also prevents application of vacuum to pick-up suckers 16 unless the timing valve 26 is in position to begin a new cycle of operation. The valve means 50 includes a vacuum responsive switch means 72 which prevents energization of the solenoid 66 when the vacuum area 32 of timing valve 26 is in communication with passageways 34. The switch 72 includes a body member 74 which is in the form of a cylinder having a central opening or bore 76 therein. The bore 76 receives a piston member 78 for reciprocation therein. The piston member 78 is biased to the left as viewed in FIG. 4 or to the right as shown in FIGv 2 outwardly of the cylinder 74 by spring means 80 acting between an abutment member 82 closing one end of the cylinder 74 and a shoulder portion 84 formed on the piston member 78. The spring 80 biases a contact plate 86 carried on the free end of the piston member 78 into engagement with a pair of contacts 88. When the contact plate 86 engages the contacts 88 and timing valve member 30 is in the position shown in FIG. 1, depressing the start button 46a of the switch 46 directs current to the solenoid 66 and the solenoid moves the valve member 56 into its open position.

If the operator depresses the start button 46a for the pump P and solenoid 66 when the vacuum area 32 is in communication with passageways 34 in the valve housing 28 as shown in FIG. 3, suction is applied to the piston member 78 in the cylinder 74 and breaks the electrical connection between plate 86 and contacts 88. Suction is directed to piston member 78 through passageway 90 which communicates inlet port 60 with bore 76 when valvemember 56 is in its closed position. In the described operational set-up shown in FIG. 3, the reduced area 560 of the valve member 56 is in position to communicate the inlet port 60 with passageway 90. When the valve member 56 is positioned as described, vacuum is applied to the piston member 78 and the piston member 7 8 will move to the left as viewed in FIG. 3 and assume the position thereof shown in FIG. 3 to break contact between the plate 85 and the contacts 88. When the contact plate 86 is out of contact with the contacts 88, the solenoid 66 cannot be energized.

As the vacuum area 32 moves out of communication with the passageways 34 in the timing valve 26, the spring 80 will move the contact plate 86 into engagement with the connectors 88 and the solenoid 66 will be energized to move the valve member 56 to its open position. The described movement of the piston rod 78 by spring means 80 is aided by the air blast provided when the blow-down area 42 communicates with the passageway 34. This will assure a good electrical contact between the contact plate 86 and contacts 88.

Once the valve member 56 establishes communication between the pick-up suckers 16 and the pump P it cannot be interrupted until the blow-down area 42 communicates with passageways 34 to shift the sucker members 78 away from the vent port 72 as described hereinbefore.

Having described my invention, I claim:

1. A control for a sheet feeder having sucker means which successively moves the top sheet of a stack of sheets relative to the stack during a part of a cycle of operation comprising timing valve means in communication with a vacuum pump and being in condition during said part of said cycle to communicate said sucker means with said vacuum pump and upon completion of said part of said cycle to efiectively terminate communication of said sucker means with said vacuum pump, and control means for interrupting communication between said sucker means and said timing valve means including first means actuatable at any time during said cycle and second means responsive to said first means and having a part movable to interrupt communication between said timing valve means and said sucker means only when said timing valve means is not in said condition to communicate vacuum to said sucker means.

2. A control for a sheet feeder as defined in claim 1 wherein said second means comprises control valve means in communication with said timing valve means and said sucker means and including said part and means for moving said part in response to said first means to block communication through said control valve means only when said timing valve means is not applying vacuum to said control valve means.

3. A control for a sheet feeder as defined in claim 1 wherein said second means comprises control valve means having a valve body in communication with said timing valve means and with said sucker means, a valve member including said part movable relative to said valve body between open and closed positions to respectively establish and block fiow through said valve body, a vacuum responsive member on said valve member and means for applying vacuum to said vacuum responsive member when said timing valve means is applying vacuum to said valve body and said valve member is in said open position to prevent movement of said valve member to said closed position as long as said timing valve means is applying said vacuum to said valve body.

4. A control for a sheet feeder as defined in claim 1 wherein said timing valve means during said part of said cycle of operation is in condition to communicate said sucker means with air under pressure and said second control means includes a member operatively connected to move said part in response to air pressure and means for directing air pressure to said air pressure responsive member when air pressure is directed to said sucker means to move said part if said first means has been actuated.

5. A control for a sheet feeder as defined in claim 4 wherein said second control means further includes actuator means for shifting said part and said first means includes a switch for energizing said actuator means.

6. A control for a sheet feeder as defined in claim 1 wherein said control means further includes means for establishing communication between said timing valve means and said sucker means, vacuum responsive switch means in circuit with said means for establishing communication, and means communicating said vacuum responsive switch means with said timing valve means when communication is interrupted between said timing valve means and said sucker means to open said switch means and prevent said means for establishing said communication from establishing said communciation when said timing valve means is in said condition to communicate vacuum to said sucker means.

7. A control for a sheet feeder having sucker means or successively moving the top sheet of a stack of sheets relative to the stack during a part of a cycle of operation comprising timing valve means in communication with a vacuum pump and being in condition during said part of said cycle to communicate said sucker means and said vacuum pump and upon completion of said part of said cycle to effectively terminate communication of said sucker means with said vacuum pump, and control means for establishing communication between said sucker means and said timing valve means including first means actuatable at any time during said cycle of operation for initiating operation of said control means and second means responsive to said first means and including a part movable to establish said communication only when said timing valve means is not in said condition to communicate vacuum to said sucker means.

8. A control for a sheet feeder as defined in claim 7 wherein said second means includes a vacuum operated switch means which is opened upon application of vacuum thereto to prevent operation of said second means and means for communicating said vacuum operated switch with said timing valve means when said timing valve means is in said condition to prevent movement of said part as long as said timing valve means is in said condition.

9. A control for a sheet feeder as defined in claim 8 wherein said first means comprises a switch and said second means comprises control valve means in communication with said timing valve means and said sucker means and including said part, actuator means for moving said part, and means providing a circuit for said switch, said actuator and said vacuum operated switch and operable upon operation of said switch to energize said actuator only when said vacuum operated switch is closed.

10. A control for a sheet feeder as defined in claim 8 wherein said timing valve means during said part of said cycle of operation is in condition to communicate said sucker means with air under pressure and means for directing air under pressure to said vacuum operated switch when said timing valve means is in condition to communicate said sucker means with air under pressure and communication between said timing valve means and said sucker means is not established to effect closure of said vacuum operated switch and permit said part to be moved when said first means is actuated.

11. A control for a sheet feeder as defined in claim 7 wherein said control means further includes means for moving said part of said second means to block communication between said timing valve means and said sucker means, vacuum responsive means operatively connected to said part and means for communicating said vacuum responsive means with said timing valve means when said part of said second means is in position to establish communication and operable to prevent operation of said means for moving said part to block communication through said control means when said timing valve means is in condition to apply vacuum to said control means.

12. A control for a sheet feeder having a plurality of sucker means which cooperate to successively move the top sheet of a stack of sheets relative to the stack comprising timing valve means in communication with a vacuum pump and in condition during a cycle of operation to communicate said sucker means with said vacuum pump in a timed relationship to the sequence of operation of said sucker means, control valve means in communication with said timing valve means and said sucker means and having a valve member movable between first and second positions to establish and interrupt communication between said sucker means and said timing valve means, respectively, and means for moving said valve member from one of said positions to another of said positions only when said timing valve means is not in said condition to communicate said vacuum pump and said sucker means.

13. A control for a sheet feeder as defined in claim 12 wherein said means for moving said valve member includes a vacuum responsive member operatively connected to said valve member, means communicating said vacuum responsive member with said timing valve means when said valve member is in said first position to prevent said valve member from moving to said second position as long as said timing valve means is in said condition.

14. A control for a sheet feeder as defined in claim 13 wherein said vacuum responsive member includes a sucker which closes one end of a port in communication with said timing valve means when said valve member is in said first position, and prevents movement of said valve member to said second position from said first position as long as vacuum is being applied to said sucker from said timing valve means.

15. A control for a sheet feeder as defined in claim 14 wherein said timing valve means during said cycle of operation is in condiiton to communicate said sucker means with air under pressure and means for moving said valve member includes actuator means conditioned for permitting movement of said valve member to said second position and means for directing air pressure to said sucker when said timing valve means is in condition to communicate said sucker means with air pressure to effect movement of said valve member to said second position upon conditioning of said actuator means.

16. A control for a sheet feeder as defined in claim 12 in which said means for moving said member includes a power operated actuator means operatively connected to said valve member, and a vacuum responsive switch means in the power circuit for said actuator means and communicated with said timing valve means when said valve member is in said second position, said vacuum responsive switch means being operable to break the circuit to said actuator means and prevent movement of said valve member to said first position as long as said timing valve means is in said condition.

17. A control for a sheet feeder as defined in claim 16 wherein said vacuum responsive switch means includes a switch member which is communicated by said valve member with said timing valve means when said valve member is in said second position, and said switch member being responsive to a vacuum applied thereto from said timing valve means to break the power circuit to said actuator means.

References Cited UNITED STATES PATENTS RICHARD E. AEGERTER, Primary Examiner.