US3809389A

US3809389A - Sheet feeding apparatus for printing presses

Info

Publication number: US3809389A
Application number: US00314338A
Authority: US
Inventors: A Wirz
Original assignee: Heidelberger Druckmaschinen AG
Current assignee: Heidelberger Druckmaschinen AG
Priority date: 1971-12-18
Filing date: 1972-12-12
Publication date: 1974-05-07
Anticipated expiration: 1991-05-07
Also published as: DE2163083B2; CH543439A; IT975238B; DE2163083C3; DE2163083A1

Abstract

Sheet feed apparatus for printing presses in which sheets are lifted from a stack and transported to a sheet feed device includes a carrier operable between a pick-up position and a feed position. The carrier includes a carrier bar having a central section and two outer sections rotatably mounted relative to the central section. Suction grippers are mounted on the two outer sections and also a suction gripper may be mounted on the central section. A slide bar means is provided for varying the travel pattern of the outer suction grippers such that the latter are operable to align a sheet as the sheet is transported from the stack towards the sheet feed device.

Description

Mute States atent [111 3,809,389 Wirz May 7, 1974 [541 igfffigg ggg g FOR FOREIGN PATENTS OR APPLICATIONS 1,177,652 9/1964 Germany 271/93 [75] Inventor: Arno Wirz, Bammental, Germany [73] Assignee: Heidelberger Druckmaschinen Prima'y 'f Blunk Amiengeseuschafl, Heildelberg, Assistant Exammer-Bruce H. Stoner, Jr. Germany Attorney, Agent, or Firm-Herbert L. Lerner [22] Filed: Dec. 12, 1972 [57] ABSTRACT [21] Appl- 314,338 Sheet feed apparatus for printing presses in which sheets are lifted from a stack and transported to a [30] Foreign Application Priority D t sheet feed device includes a carrier operable between Dec 18 I971 Gama 1 2,6308} a pick-up position and a feed position. The carrier iny cludes a carrier bar having a central section and two [52] U S Cl 271/91 271/60 271/93 outer sections rotatably mounted relative to the cen- [51] a 9/14 tral section. Suction grippers are mounted on the two [58] Fieid 90 107 outer sections and also a suction gripper may be mounted on the central section. A slide bar means is provided for varying the travel pattern of the outer [56] References Cited suction grippers such that the latter are operable to align a sheet as the sheet is transported from the stack UNITED STATES PATENTS towards the sheet feed device. 2,995,360 8/1961 Simpson 271/107 3,360,262 l2/I967 Kekopoulos et al. 271/60 x 8 Claims, 4 Drawlng Flgllres 'MWTEM 7 291 4 $809389 SHEET 1 BF 3 all FIG: 2

1 SHEET FEEDING APPARATUS FOR PRINTING PRESSES The invention relates to a sheet feeding device for printing machines and more particularly .to a sheet feeding device, having conveyor suction grippers for lifting sheets from a stack in which the height of the stack can be adjusted by pneumatically or electrically operated means. The, conveyer suction grippers pick up the top sheet from the stack and carry it in one direction toward further sheet transport means. The conveyor suction grippers are pivotally mounted on a carrier bar which has imparted thereto an oscillatory movement by means of an eccentric or cam drive and which is. guided rectilinearly by a slide bar arrangement.

It is an object of the present invention to align a sheet, which is gripped by the conveyer suction grippers in such a manner'during the feeding movement that the exact placement of the front edge of the sheet against the front stops isassured in that the front edge of the sheet does not arrive askew.

From the German Patent 1, 177,652 a sheet feeding device is known in which two suction grippers are suspended by a shaft having an oscillatory motion and which are guided parallel to the surface of the pile of sheets by means of a control cam. One of the suction grippers is pivoted with respect to the other and is adjustable by means of an adjustable control lever, whereby a lead or lag of the suction surface of the pivoted suction gripper relative to the other one may be obtained during the feeding motion. The lead or lag of the one suction gripper relative to the other causes alignment of the sheet being gripped and lifted from the pile during the feeding motion toward the further sheet transport means.

Such alignment means can advantageously be used for smaller sheet sizes. For large sheet sizes, however, the tilting of the gripped sheet about one of the two suction grippers has a very detrimental effect in that the sheet is also moved in its central region, during its alignment, that is the sheet moves forward or back in its entirety. This displacement of the sheet in'or toward the transport direction can cause registration differences in the case of relatively large .corrections,'particularly with the larger sheet sizes, or make necessary an adjustment of the suction head relative to the machine.

To avoid this disadvantage, in a further sheet feeding device according to German Patent 1,786,029, the tube carrying the conveyer suction device is pivoted at its center about a vertical axis and is rigidly connected with a lever, the free end of which slides in a U-shaped guide bar which can be adjusted at an angle relative to the direction of travel. Because the two conveyer suction devices can pivot about a vertical axis, the sheet is rotated during its alignment in such a manner that its front edge assumes the desired position without a detrimental displacement of the sheet in the transport direction.

However, this known sheet feeding device has another disadvantage. For processing sheets of larger size, at least a third suction gripper must be attached on the conveyer bar, in order to prevent excessive sagging of the sheet being transported. Otherwise, the blower air would be prevented from separating the sheet properly from the pile and from carrying it forward, so that its front edge cannot be reliably gripped by the sheet transport means which passes the sheet on. The arrangement of a third suction gripper at the center of the tube carrying the two conveyer suction gripper, however, interferes with the support of the tube, which must be located at that position.

In the case of larger size sheets, the conveyer suction grippers must furthermore be provided at a greater distance from the rear edge, which leads to a large overhang of the support and guidance members of the carrier tube of the conveyer suction grippers. If, however, the vertical axis of the carrier tube support were displaced on the center line of the sheet, a lateral dislocation would occur in the alignment of the sheet to be transported and depending on the size of this displacement, the registration of the sheet would also be impaired.

it is an object of the invention to provide a sheet feeding device which processes large sheet sizes in a reliable manner and which makes possible the alignment of the front edge of the sheet during the feeding or transport movement without displacement of the transported sheetin the transport direction or laterally thereto.

The present invention overcomes the aforementioned prior art disadvantages by providing at the cen ter of the carrier bar a conveyer suction gripper which is held in vertical position by a slide bar during the oscillatory movement of the carrier bar. The carrier bar is divided into three sections, the outer sections being rotatable or pivotably mounted on the center section of u the carrier bar and each outer section carrying an additional conveyer suction gripper. Each of the pivoted outer sections is guided by a pivoted slide bar, and the two pivoted slide bars can be adjusted by a positioning device to the same angle in opposite directions.

If both adjustable slide bars are swung from their null or neutral positions, one of the outer conveyer suction grippers executes an additional oscillating motion in the transport direction, and the other, outer conveyer suction gripper executesan oscillatory movement of the same magnitude but in the opposite direction. The transported sheet thereby rotates about the vertical axis of the middle-suction gripper, which is designed as a drop or gravity gripper. Practically no lateral or longitudinal displacement of the transported sheet occurs.

In further advantageous embodiment of the present invention drive holder means are pivoted at the free end of an oscillating crank of an eccentric drive, such drive holder means extending in the direction of the sheet transport and being guided along a straight line path by the slide bar. The carrier bar of the conveyer suction gripper is arranged at the free end of the drive holder means. This device permits the reliable processing of the largest sheet sizes as the distance of the conveyer suction grippers from the rear sheet edge is substantially greater than that which can be chosen with conventional suction heads.

In a preferred embodiment of the invention the slide bars are provided in the form of U-shaped guide rails which extend in the direction of the sheet transport and which have an arc-like curvature. The arc-like curva-.

ture compensates for the influence which the crank oscillation might otherwise have on the vertical movement and guidance of the conveyer suction grippers, which tends to be accentuated or amplified because of for the invention are set forth in the appended claims.

Although the invention is illustrated and described in relationship to specific embodiments, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and rang of equivalents of the claims.

The construction and method of operation-of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read inconnection with the accompanying drawings, in which:

FIG. 1 is a partial elevational view of a suction head disposed above a stack of sheets which are to be fed by the suction head.

FIG. 2 is a partial plan view of the suction head shown in FIG. 1.

FIG. 3 is a plan view, partially in section, showing the various operating. elements of the suction head according to one embodiment of the invention.

FIG. 4 is an elevation view of the various operating elements shown in FIG. 3.

Referring to the drawings, there is shown a suction head 2 arranged above a stack of sheets 1 of a printing machine (not shown). The suction head 2 is disposed centrally, considered in a lateral direction, and in the region of the rear edge of the stack of sheets 1. The height of the stack of sheets 1 can be adjusted by various means (not shown) for example by pneumatically or electrically operated devices. The suction head 2 always feeds the top sheet of the stack of sheets 1 to further transport means which consists of a tape roller 8 and timing rolls 9. The aforementioned feeding is effected with the cooperation of a sensing foot 3, separator suction grippers 4 and

conveyer suction grippers

5,6,7.

The conveyer suction grippers 5 to 7 are attached to a carrier bar 10 which is divided into three sections,

namely, a central rigid part 11 and the two

outer carrier tubes

12 and 13 which are rotatably mounted on the outer longitudinal ends of the central rigid part 11.

The conveyer suction gripper 6 is designed as a drop or gravity gripper and is mounted on the central bar section 11. The suction gripper 6 situated exactly along the center line of the suction head 2 as shown in FIG. 2. The conveyer suction gripper 5 is attached to the carrier tube 13, and the conveyer suction gripper 7 to the carrier tube 12. Both conveyer suction grippers 5 and -7 are also designed as dropor gravity grippers. The central bar section 11 is operatively connected by means of two

brackets

14 and 15 to a shaft 16 which is mounted in sleeve, bearings 18 and which are pivoted at the free end of a conventional oscillating crank 17 of an eccentric drive (not shown). A support arm 19 is fixed to the bracket 15 at about halfway along the length of bracket 15. The support arm 19 projects vertically and rotatably carries a roller 20 which travels in a guide rail 21. The guide rail .21 is secured to a housing 22 of the suction head 2. As can be seen in FIG. 4, the guide rail 21 is curved in arc fashion in such a manner to compensate the swinging motion of the conveyer suction gripper 6 which would otherwise be caused by the oscilatory motion of the crank 17.

A guide lever 23 is secured to the carrier tube 12 and the free end of the guide lever carriers a guide roller 24 which travels in a U-shaped guide rail 25. The guide rail 25 is pivoted at its rear end about a fixed horizontal axis 30, the angular position of the guide rail 25 relative to the horizontal can be changed by a setting device 26.

'of the suction head housing 22 and is pivoted at 52, 53

respectively to the two

guide rails

25 and 29. The arrangement is such that any pivotal movement of the U- shaped guide rail 25 about axis 31 is transmitted to the other U-shaped guide rail 29. For example, when the U-shaped guide rail 25 swings upwardly, the opposite U-shaped guide rail 29 swings downward by the same angle. The setting device 26 is provided with a hand wheel 33 above the suction head housing 22 and is operable to pivot the guide rail 25 upwardly or downwardly about fixed pivot axis 30.

The two.

U-shaped.guide rails

25 and 29 are also curved in the form ofan arc like the guide rail 21 in such a manner that the

conveyer suction grippers

7 and 5 secured to the

outer carrier tubes

12 and 13 are maintained in a vertical disposition during the oscillating movement of the crank 17.

The separator suction gripper 4 and the conveyer suction grippers 5 to 7 are operatively connected to and in communication with a rotary valve 34 mounted on the suction head 2 by means of hose lines 35. Two other hoses 36 connect the rotary valve 34 with a blower or other pressure or vacuum generator. A further hose 50 leads from the rotary valve 34 to a blower rod 38 at which loosening blowers 39 as well as a stripper brush 40 are mounted. Another hose 37 leads to the sensing foot 3.

The operation of the apparatus hereinabove described is as follows. If a sheet transported by the conveyer suction grippers 5 to 7 isfed askew to the transport means 8, 9 for example, because the pile is not cut square or the surface of the pile is different or out of alignment as indicated by the sheet 41 in FIG. 2 for example, the guide rail 25 is pivoted about the horizontal axis 30 by means-ofthe hand wheel 33 via the setting device '26. When this occurs the opposite guide rail 29 is pivoted by the same angle in the opposite direction as previously explained. The adjustment takes place to such an extent that the two outer conveyer suction grippers 5 and '7 execute during the transport of the sheet, on the basis of the adjustment of their

guide rails

25 and 29, oscillating movements in opposite directions of such magnitude that the tilt of the sheet is cancelled by rotation of

suction grippers

5 and 7 each the same amount about the-middle conveyer suction gripper 6. As a result the sheet 41 is passed on to the roller 8 and the timing rolls 9 in proper alignment. The aforementioned oscilating movement of the outer

conveyer suction grippers

5 and 7 about the suction gripper 6 starts when the

conveyer suction grippers

5 and 7 are in their rear position indicated at 42 in FIG. 2 and has its maximum extent in the front position of the conveyer suction grippers as indicated at 43 in FIG. 2. Accordingly the suction cups of the

conveyer suction gripper

5 and 7 always occupy the same position in their rear position 42 as is the case of the suction cup of the not-rotatable central conveyer suction gripper 6. It will be seen that the aforementioned oscillating movement is achieved because the guide rails 25 and 29 are pivotally moved about axis 30 in opposite pivotal directions. Due to the fact that the two outer

conveyer suction grippers

5 and 7 execute opposite oscillating motions, the oscillation movement of each

conveyer suction gripper

5 or 7 needs to be only half as large as if the oscillating motion was carried out with only one conveyer suction gripper as in known devices. Because all the conveyer suction grippers are designed as-gravity suction grippers, the suction cup of the central conveyer suction gripper 6 can rotate about its vertical axis, so that the sheet to be aligned can be swung around such vertical axis without the formation of creases. The use of three conveyer suction grippers has another advantage in that the support air discharging from the sensing foot 3 can lift the front edge of the sheet 41 reliably onto the belt roller 8.

The invention is not limited to the illustrated embodiment. For example, the invention may be modified in such a manner to provide a lever linkage instead of the

guide arms

23 and 27, such that the

conveyer suction grippers

5 and 7 can be advanced still further in the direction toward the belt roller 8 and timing rolls 9.

I claim:

1. Sheet feeding apparatus for printing presses and the like in which sheets are lifted from a stack and transported towards a sheet feed device, comprising carrier means, operable means for moving said carrier means between apick-up position and a feed position, said carrier means comprising a carrier bar having a central section and two outer sections rotatably mounted on either side of said central section, two outer suction grippers, one carried on each of said outer sections, first slide bar means carried by each of said outer sections, and positional means comprising a rocker arm operable to adjust each of said slide bar means to the same angular extent but in opposite directions so that said slide bar'means cause rotation of the outer sections through equal but oppositely directed angles relative to the central section during forward movement of the carrier bar, and adjustment means for said rocker arm, said outer suction grippers being operable thereby to align a sheet as the latter is transported from said stack towards said sheet feed device.

2. Sheetfeeding apparatus according to claim 1 a central suction gripper carried on said central section of said carrier bar, said central suction gripper and said outer suction grippers being generally aligned along a straight line extending perpendicular to said path of movement of said carrier means when the latter is in said pick-up position, said positional means being operable to vary the path of said slide bar means so that said outer suction grippers and said central suction gripper are aligned along a straight line which extends at an acute angle relative to said path of movement of said carrier means when the latter is in said feed position.

3. Sheet feeding apparatus according to claim 2 wherein said means operable to vary the paths of said slide bar means comprise a pivotal drive member pivotal back and forth about a pivot axis to impart a back and forth oscillating motion to said first slide bar means, said carrier means comprising second slide bar means maintaining said central suction gripper in a vertical plane disposition during said oscillating motion of said first slide bar means.

4. Sheet feeding apparatus according to claim 3 wherein said drive member is a crank, having a free end oscillating along an arcuate path, drive holder means pivotally mounted on said free end of said crank and extending in the direction of sheet feed, second slide bar means operatively associated with said drive holder means to provide rectiliniearly movement of the free ends of said drive holder means, said carrier bar being disposed at said free end of said drive holder means whereby said carrier bar is subjected to a rectiliniear movement.

5. Sheet feeding apparatus according to claim 4 wherein said second slide bar means comprises U- shaped guide rails extending generally in the direction of sheet feed in an arcuate configuration.

6. Sheet feeding apparatus according to claim 5 wherein rollers are mounted on said drive holder means, said rollers being movably carried in said U- shaped guide rails, 7. Sheet feeding apparatus according to claim 1 wherein said first mentioned slide bar means comprises U-shaped guide rails extending generally'in the direction of sheet feed in an arcuate configuration. I

8. Sheet feeding apparatus according to claim 7 wherein said first mentioned slide bar means comprises levers attached to said outer sections of said carrier bar, said levers having mounted thereon rollers which are movably carried in said U-shaped guide rails.

Claims

1. Sheet feeding apparatus for printing presses and the like in which sheets are lifted from a stack and transported towards a sheet feed device, comprising carrier means, operable means for moving said carrier means between a pick-up position and a feed position, said carrier means comprising a carrier bar having a central section and two outer sections rotatably mounted on either side of said central section, two outer suction grippers, one carried on each of said outer sections, first slide bar means carried by each of said outer sections, and positional means comprising a rocker arm operable to adjust each of said slide bar means to the same angular extent but in opposite directions so that said slide bar means cause rotation of the outer sections through equal but oppositely directed angles relative to the central section during forward movement of the carrier bar, and adjustment means for said rocker arm, said outer suction grippers being operable thereby to align a sheet as the latter is transported from said stack towards said sheet feed device.

2. Sheet feeding apparatus according to claim 1 a central suction gripper carried on said central section of said carrier bar, said central suction gripper and said outer suction grippers being generally aligned along a straight line extending perpendicular to said path of movement of said carrier means when the latter is in said pick-up position, said positional means being operable to vary the path of said slide bar means so that said outer suction grippers and said central suction gripper are aligned along a straight line which extends at an acute angle relative to said path of movement of said carrier means when the latter is in said feed position.

5. Sheet feeding apparatus according to claim 4 wherein said second slide bar means comprises U-shaped guide rails extending generally in the direction of sheet feed in an arcuate configuration.

6. Sheet feeding apparatus according to claim 5 wherein rollers are mounted on said drive holder means, said rollers being movably carried in said U-shaped guide rails.

7. Sheet feeding apparatus according to claim 1 wherein said first mentioned slide bar means comprises U-shaped guide rails extending generally in the direction of sheet feed in an arcuate configuration.