GB2092997A - Sheet feeding apparatus - Google Patents

Abstract

For feeding sheets to, and removing them from, a cutting machine of the kind having an angularly movable jaw which closes against a fixed jaw to cut sheets, apparatus comprising arms 7 for handling the sheets which are rotated about a common axis between work stations. At a first station holders on the arms 7 pick up sheets and then carry them to a second station where they are loaded on to the movable jaw and subsequently removed from that jaw by the holders after cutting. The arms deposit the cut sheets at a third station. Sheets are held by suction at the holders. The arms 7 extend radially of a vertical rotational axis. They are supported on a hub 31 on which is a co-axial annular gear 38 rotated by a pneumatically reciprocated rack 43, the gear being drivingly connected by a ratchet wheel 42 and pawl to the hub to rotate the hub in one direction only. The arms are urged to pivot downwards by pneumatic dampers 65 but by engagement with a sloping guide rail 70 are swung upwards as they approach the second station. A lift cylinder 18 supports the arms horizontally at the second station and a further guide rail maintains them horizontal as they travel to the third station. <IMAGE>

Description

SPECIFICATION Sheet feeding apparatus This invention relates to sheet feeding apparatus for supplying sheets of paper, card, board or like material to a cutting machine.

One known kind of cutting machine used extensively in the printing and packaging industries comprises a pair of jaws one of which is fixed and substantially upright and carries a cutting blade or blades, and the other jaw is angularly movable towards and away from the fixed jaw about a pivotal axis adjacent the bottom end of the fixed jaw and provides a platen on which the sheet material to be cut is placed, the sheet material being cut when the movable jaw is closed against the fixed jaw. Hitherto it has been usual for the sheet material to be fed on to the movable jaw by hand which can be laborious, requires care in positioning the sheet material and puts the person feeding the cutting machine at some possible risk of injury from the jaws and cutting blade or blades.

The present invention enables sheet material to be fed automatically to such a cutting machine.

According to the present invention a sheet feeding apparatus is provided suitable for use with a cutting machine of the kind set forth, comprising a plurality of arms having holders and angularly movable by power driven means about a common axis between a plurality of work stations to which each arm in turn is indexed, the work stations comprising a first one at which each arm in turn picks up sheet material by its holder from a store, a second one at which the sheet material picked up by an arm is loaded on to the movable jaw of the cutting machine to be cut and that sheet material after having been cut is removed by the same arm from the cutting machine, and a third one at which cut sheet material is deposited for collection, and means controlling operation ofthe holders and power driven means whereby operation of the arms at the first and third stations is linked with operation of the arm at the second station.

The sheet feeding apparatus may be adapted so that its operation is controlled by the cutting machine with which it is to be associated in use. For example the means controlling operation of the holders and power driven means may be coupled to the system controlling operation of the cutting machine so that operation and angular movement of the arms are directly related to the closing and opening movements of the movable jaw of the cutting machine. In a simpler arrangement, which is included in a preferred embodiment of the invention, each arm of the apparatus, or a member carried by the arm, is adapted to co-operate at the second station with the movable jaw of the cutting machine, or part movable therewith, and in so doing to.

operate the means controlling operation of the holders and power-driven means.

By arranging for operation of the holders and power driven means to be controlled by the cutting machine the feeding of sheet material to, and its removal from, the cutting machine by the apparatus can be closely controlled. Moreover it will be understood that with the arrangement described above in which the arms co-operate at the second station with the movable jaw, the control is achieved in a manner which requires very little or no modification of the cutting machine. If any modification at all is required it will normally be confined to the provision of a part with which the arms can cooperate at the second station. However, the known cutting machines often have a bar across the free end of the movable jaw which will suffice for the arms to co-operate with so that modification is unnecessary.Accordingly the sheet feeding apparatus may be readily applicable to existing cutting machines to convert them from manual to automatic feed of sheet material.

There may be four arms although only three of the arms will be at the stations at any one time, the fourth one occupying an idle position intermediate the third and first stations.

Preferably the holders pick up the sheet material by suction and it is convenient in such an arrange mentforthe apparatus to be powered entirely pneumatically. The holder at each arm may comprise a plurality of suction pads or heads which act together to hold the sheet material. Their relative positions may be variable to suit the size of sheet material to be handled by the apparatus. In the preferred embodiment, each arm when at the second station is arranged to be lifted by the moving jaw of the cutting machine as that jaw closes and falls with the jaw as it opens.During the lifting and falling movement the arm operates a pneumatic control which causes suction to be stopped at the holder of that arm as the arm rises, thereby to allow the sheet material to drop from the holder on to the movable jaw, and causes suction to be re-applied to the holder as the arm falls so that the holder then picks up the cut sheet material as the movable jaw opens. Suction may be cut off and applied at the holders of the other arms at the same time, and is applied to the holders as the arms move from one station to another.

The angular movement of the arms between the stations may be effected by means of a pneumatically operated piston which operates reciprocally a rack in mesh with a gear associated with a support on which the arms are carried. A pawl and ratchet may be provided in association with the gear to limit the rotation of the arms to one direction only.

Whilst it is convenient for the apparatus to be powered entirely pneumatically, the arms may be moved angularly by other powered means if desired.

The apparatus may include a stand or other suitable support which enables the apparatus to be positioned adjacent the cutting machine with which it is to be used and be self supporting. It may be arranged to be fixed to the floor, for example by means of bolts, to prevent any possibility of its being moved unintentionally from the required position for use, or moving during use in consequence of movement of the arms.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which, Figure 1 is diagrammatic plan view of a sheet feeding apparatus in accordance with the present invention and a cutting machine, Figure 2 is vertical axial section through the upper part of the apparatus, and Figure 3 is an enlarged fragmentary plan view of an outer end part of an arm and holder of the apparatus.

The cutting machine, indicated generally at 1 in Figure 1, is of the kind previously described having an upright, fixed jaw 2 having one or more cutting blades, not shown, and a movable jaw 3 hinged about a pivotal axis 4 adjacent the bottom end of the fixed jaw for angular movement towards and away from the fixed jaw. In its fully open position the movable jaw is normally inclined upwardly at about 30 to the horizontal. There is a bar 5 at the free end of the movable jaw extending parallel to the pivotal axis 4 and projecting from the free end.

The sheet feeding apparatus comprises, as shown in detail in Figure 2, a stand 6 and four arms 7 supported on the stand which extend radially to, and are rotatable by a pneumatically powered drive about, a vertical axis.

The stand 6 has splayed legs 8 which are fitted with lockable castors, not shown, and which suport a flat, circular metal bed plate 9. Co-axially on top of the bed plate 9 is fixed a tubular pillar 10 on which is mounted externally at an intermediate part of its height an annular metal flange 11. At one side of the pillar 10, on a support plate 12 fixed on edge to the top of the bed plate 9 radially of the pillar, there is a generally L-shaped bracket 13 a horizontal limb 14 of which extends towards and is at the level of the flange 11. A reinforcing web 15 is secured in the angle of the bracket 13. An upright limb 16 of the bracket has a downwardly projecting portion 17 extending below the level of the horizontal limb 14 and secured against an edge of the support plate 12 to ensure stability of the bracket.A pneumatic lift cylinder 18 is mounted vertically on the back ofthe upright limb 16 by angle brackets 19 fixed to that limb, the piston 20 of the cylinder extending up wards. Also at the level of and joined to the annular flange 11 an elongated carrier plate 21 is mounted , substantially tangentially above the bed plate 9 by support plates 22,23. The carrier plate extends at right angles to the direction of the horizontal limb 14 of the bracket 13 at the opposite side of the rotational axis of the arms 7 to the bracket. A double-acting, pneumatic drive cylinder 24 is mounted horizontally along part of the carrier plate 21 projecting from the bed plate, its piston 25 extending towards the bed plate.

Mounted on an externally reduced diameter upper end portion 26 of the pillar 10 are two ball bearings 27 separated axially by a spacer 28 and located axially on the end portion by a shoulder 29, defined where the diameter of the pillar is reduced, and a circlip 30 sprung into a groove in the upper end portion. Outer races of the ball bearings 27 support a hub 31 having a skirt portion 32 surrounding the ball bearings and a crown portion 33 which extends over the upper ball bearing and has a central aperture of larger diameter than the pillar 10 which projects partially into the aperture. Secured to the bottom of the hub skirt portion 32, below the lower ball bearing, is a retainer ring 34 which is freely rotatable with the hub about the pillar 10.The retainer ring 34 has four equally spaced crown ratchet teeth, not shown, on its underside with which four upwardly spring-loaded detent pins 35 co-operate. The detent pins 35 are vertically slidable in holders 36 adjustably secured by nuts 37 to the annularflange 11 on the pillar, the adjustment enabling the spring loading on the detent pins to be varied. Freely rotatable about the retainer ring 34 and encompassing the lower half of, and partially extending under, the hub skirt portion 32, about which it is also freely rotatable, is an annular drive gear 38, of nylon or like self-lubricating material, which is fixed to the bottom of a co-axial annular gear bearing 39 of similar material.The latter encompasses the upper half of the hub skirt portion 32, about which it also is freely rotatable, and has an internal lip 40 which seats on an annular shoulder 41 of the hub defined between the skirt and crown portions. An internally toothed ratchet wheel 42 is secured co-axially on top of the gear bearing and is engaged by a pawl, not shown, pivoted on the crown portion 33 of the hub 31. Thus the drive gear 38 can rotate the hub 31 in one direction about the pillar but moves relative to the hub when rotated in the opposite direction. Engagement of the detent pins 35 with the ratchet teeth of the retainer ring 34 holds the hub positively in positions to which it has been rotated by the drive gear.

The drive gear 38 is in mesh with a rack 43 carried by the piston 25 of the drive cylinder 24. Movement of the piston to its fully extended position moves the rack sufficiently to rotate the drive gear through 90".

The hub 31 rotates with the drive gear as the rack is moved on the outward stroke of the piston.

Fixed by studs 44 to, and supported by tubular spacers 44' (through which the studs extend) above, the hub 31 is an annular arm support 45 having four evenly spaced pairs of bearing lugs 46 projecting laterally from its circumference. The four arms 7 of the sheet feeding apparatus are pivoted at their inner ends about horizontal axes to the bearing lugs 46 by hinge pins 47, one arm to each pair of bearing lugs, the arms thus being at 900 intervals around the arm support 45. At its centre the arm support is bolted to an external annularflange 48 atthe upper end of a co-axial, tubular centre boss 49 which extends through and depends below the arm support and is mounted on a rotary union 50 mounted in turn on an end plate 51 fixed in the upper end of the pillar 10.

Externally screw-threaded spigots 52,53 of the union 50 engage respectively in an internal screw thread in the bore of the centre boss 49 and screw threaded hole in the end plate 51 to secure the union to the centre boss and end plate. A gasket 54 is fitted on the spigot 52 between the union and centre boss.

The union permits rotation of the centre boss, and hence the arm support, relative to the pillar with the hub 31, and has an axial through-passage.

Co-axial with the centre boss 49, and thus co-axial with the arm support 45, is a vertically extending tubular spindle 55 which has an externally screwthreaded bottom end portion 56 screwed into the upper end of the internally screw-threaded bore of the centre boss and retained by a locking nut 57. At its upper end the spindle 55 has a locking external screw thread 58 by means of which an internally screw-threaded air manifold 59 is secured on top of the spindle. A support boss 60 fits on and is welded to the manifold 59. The support boss 60 has four pairs of lugs 61 evenly spaced around and projecting laterally from its circumference, and the boss is fixed such that the pairs of lugs are at corresponding angular positions about the axis of the spindle to the bearing lugs 46 of the arm support 45.

Each of the arms 7 is of inverted T-section tapering towards the outer end of the arm. At its inner end each arm has an upstanding member 62 to the back of which is fixed an eye projection 62' which fits between one of the pairs of bearing lugs 46 of the arm support 45 and is hingedly retained thereto by the respective hinge pin 47. The upper end of the upstanding member 62 is formed with two spaced, co-axial hinge eyes between which is pivotally connected by a pivot pin 63 the outer end of the piston 64 of a pneumatic damper 65. The damper 65 has its cylinder 66 pivoted between a pair of the lugs 61 of the support boss 60. The piston 64 is normally urged towards an extended position in which it urges the associated arm 7 downwards about its pivoted connection to the arm support 45.A stop 67 projecting rearwardly from the bottom of the upstanding member 62 of each arm abuts against the end of a bolt 68 projecting from the underside of the arm support and limits, adjustably, the extent of the downward movement of the arm underthe loading of the damper.

A roller 69 is mounted on the underside of each arm 7 with its rotational axis extending lengthwise of the arm. The roller 69 is positioned to engage with a sloping guide rail 70 which extends arcuately (through approximately 1300) and concentrically about the rotational axis of the arms. The guide rail 70 has legs, not shown, at opposite ends by which it is mounted on the bed plate 9 of the stand 6. It is mounted with its highest end nearest to the Lshaped bracket 13 and its ends being equally spaced respectively from that bracket and a point on the bed plate 9 diametrically opposite the bracket. An arm 7 when engaged with the highest end of the guide rail 70 is inclined upwardly away from its pivotal axis at the arm support 45, and when engaged with the lowest end of the guide rail is inclined downwardly.

At the opposite side of the bracket 13 to the highest end of the inclined guide rail 70 is a horizontal, concentrically arcuate, guide rail, not shown, on legs secured on the bed plate, which is supported at a slightly lower level than the highest end of the inclined guide rail corresponding substantially to the level to which the end of the piston 20 of the lift cylinder 18 is lowered in its retracted position.

At the outer end of each arm two bars 71 are carried on the underside of the arm in a substantially symmetrical cross-shaped configuration, as shown in Figure 3. Some adjustment of the bars 71 along the arm and relative to one another is possible through bolt and slot connections between the bars and arm. The bars 71 are made from lengths of rigid metal strip having their end portions 72 twisted through 90" from their main body portions. The bars are attached to the arm with the opposite side faces of the main body portions in planes parallel to the undersurface of the arm. Vacuum pad units 73 are attached to the end portions 72 of the bars, their suction pads 74 being directed downwards away from the arm. The units are adjustable on the bars upwardly and downwardly.

Air pipes, not shown, connect the vacuum pad units 73 of all the arms to the air manifold 59, the pipes being fastened along the arms 7. Air is exhausted from the manifold for operation of the pad units by means of an electrically operated air pump, not shown, which is connected to the manifold by a pipe, not shown, having a connector which screws into an axial threaded hole 75 in the bed plate 9 to connect the pipe with the interior of the pillar 10, and thence from the interior of the pillar by way of the through-passage in the rotary union 50 to the bore of the centre boss and the bore of the spindle 55 to the manifold. The air pump also operates the lift cylinder 18.

Attached to the bed plate 9 diametrically opposite to the L-shaped bracket 13 is an angled support 76 which projects upwardly and outwardly away from the rotational axis of the arms. The support 76 carries a microswitch 77 with which the arms engage when they are in their lowermost positions diametrically opposite the L-shaped bracket.

For use the sheet feeding apparatus is positioned adjacent to the cutting machine so that the L-shaped bracket 13 is nearest to the cutting machine and an arm 7, when in the position in which it engages the piston 20 of the lift cylinder 18 carried by the bracket, extends substantially horizontally over, centrally of, the movable jaw 3, when that jaw is open, in a direction normal to the fixed jaw 2, the arm engaging with the bar 5 on the jaw. The lockable castors allow the apparatus to be manoeuvred around readily by hand. When the apparatus is in the required position the castors are locked, and preferably the legs are bolted to the floor to retain the apparatus in the set position.At a station A at 90 to the bracket 13 (indicated as station B in Figure 1), in the clockwise direction as viewed in Figure 1, a store of paper or board sheets to be fed to the cutting machine is provided adjacent to the apparatus. At a station C 180from station A a collecting tray or other suitable receptabie is positioned adjacent to the apparatus to receive the paper or board sheets after they have been cut by the cutting machine.

Operation of the sheet feeding apparatus with the cutting machine will now be described. The air pump simultaneously exhausts air from the vacuum pad units 73 of all four arms and a cycle of operations of the apparatus is initiated by movement with the movable jaw of the cutting machine of whichever one of the arms is at station B. Assume that an arm has moved to station B from station A where it has picked up a paper or board sheet from the store by suction applied through the vacuum pad units. The arm arrives at station Bwhilstthe movable jaw of the cutting machine is in its fully open position; the sheet held by the arm is directly over that jaw. As the movable jaw closes it lifts the arm.When the arm reaches a pre-determined angular raised position (preferably approximately 45" to the horizontal) a micro-switch, not shown, is operated which opens an electric circuit to the air pump and exhaustion of air from the vacuum pad units ceases. The sheet is thereby released from the arm and falls on to the movable jaw. The arm remains in contact with the movable jaw as the latter completes its closing movement to cause the sheet to be cut. As the movable jaw opens subsequently the arm lowers with it inoperatively until it reaches the predetermined angular position again, when the microswitch is operated to close the electric circuit to the air pump so that air is once more exhausted from the vacuum pad units. The latter consequently pick up the cut sheet from the movable jaw.

As the air pump is operated the drive cylinder 24 is also operated to project its piston and so move the rack 43 forwards. The rack rotates the drive gear 38 through 90 , and, since the hub 31, arm support 45 and spindle 55 turn with the drive gear, the arms are turned through the same angle. Thus the arm which has just picked up a cut sheet from the cutting machine moves round to station C along the horizontal guide rail. The arm immediately behind that arm moves in turn into station B, having picked up a sheet from the store at station A when the suction was applied to the vacuum pad units of all the arms when the arm previously at station B operated the micro-switch as the movable jaw of the cutting machine opened.The arm which had previously been at station C moves on to a fourth station D, which is a rest or idle position, and as it reaches that station it operates the micro-switch 77 on the support 76 which causes the air supply to the drive cylinder 24 to be altered to retract the piston and the rack. The pawl prevents the drive gear 38 from turning with the rack as it retracts and the detent pins 35 locate the arms positively in the stations to which they have been turned.

When next the suction at the vacuum pad units is cut off, that is when the moving jaw of the cutting machine is moving towards the closed position, the arm at station C drops the cut sheet it has removed from the cutting machine on to the collecting tray or other receptacle.

As arms rotate from station D to station A and station B their rollers 69 engage with the sloping guide rail 70 and so are gradually lifted. At station B they engage with the piston 20 of the lift cylinder 18 which is raised to the level of the highest end of the sloping guide rail as the arms are turning to receive the arm moving to station B, and which as soon as it is engaged bythe arm returns to its retracted position to lower the arm to a substantially horizontal position for co-operation with the moving jaw of the cutting machine. Operation of the lift cylinder 18 is linked with the operation of the drive cylinder 24.

A tray or other suitable support means may be mounted on the stand 6 for the storing of sheets at station A, and likewise the collecting tray or other receptacle at station C may be mounted on the stand.

Claims (28)

1. A sheet feeding apparatus suitable for use with a cutting machine of the kind set forth, comprising a plurality of arms having holders and angularly movable by power driven means about a common axis between a plurality of work stations to which each arm in turn is indexed, the work stations comprising a first one at which each arm in turn picks up sheet material by its holder from a store, a second one at which the sheet material picked up by an arm is loaded on to the movable jaw of the cutting machine to be cut and that sheet material after having been cut is removed by the same arm from the cutting machine, and a third one at which the cut sheet material is deposited for collection, and means controlling operation of the holders and power driven means whereby operation of the arms at the first and third stations is linked with operation of the arm at the second station.

2. A sheet feeding apparatus according to Claim 1 in which there are four of the jaws, three of which are respectively positioned at the first, second and third stations during a sheet feeding operation, and the fourth one occupies an idle position intermediate the third and first stations.

3. A sheet feeding apparatus according to Claim 1 or Claim 2 in which each arm is movable up and down and is arranged such that when it is at the second station it operates by said up and down movement the means controlling operation of the holders and power driven means.

4. A sheet feeding apparatus according to Claim 3 in which the holders are adapted to pick up the sheet material by suction, and each arm when it is at the second station is adapted to operate a pneumatic control which as the arm moves upwards causes suction to be stopped at the holder of the arm, and which as the arm moves downwards causes suction to be applied to said holder.

5. A sheet feeding apparatus according to Claim 4 in which suction is arranged to be stopped and to be applied to the holders of all of the other arms simultaneously with the suction at the holder of the arm at the second station, and suction is applied to the holders of all the arms as the arms move from one station to another.

6. A sheet feeding apparatus according to Claim 4 or Claim 5 in which the holder at each arm comprises a plurality of suction pads or heads which act together to hold the sheet material.

7. A sheet feeding apparatus according to Claim 6 in which the relative positions of the suction pads or heads of each holder are variable to suit the size of sheet material to be held.

8. A sheet feeding apparatus according to any preceding claim in which the means controlling operation of the holders and the power driven means is adapted to be controlled by the cutting machine with which it is to be associated in use.

9. A sheet feeding apparatus according to Claim 8 in which said means is adapted to be coupied to the system controlling operation of the cutting machine such that operation and angular movement of the arms are related to the closing and opening movements of the movable jaw of the cutting machine.

10. A sheet feeding apparatus according to Claim 8 in which each arm, or a member carried by the arm, is adapted to co-operate at the second station with the movable jaw of the cutting machine, or part movable therewith, and in so doing to operate the means controlling operation of the holders and power driven means.

11. A sheet feeding apparatus according to Claim 10 as dependent from Claim 3, or as dependent from any of Claims 4 to 7, in which each arm is arranged such that when it is at the second station it can be lifted by the moving jaw of the cutting machine with which the apparatus is associated in use as the jaw closes, and falls with the moving jaw as it opens, said movement of the arm with the moving jaw operating the means controlling operation of the holders and power driven means.

12. A sheet feeding apparatus according to Claim 11 as dependent from any of Claims 4 to 7 in which each arm when lifted by the moving jaw of the cutting machine at the second station is arranged to operate a pneumatic control to cause suction to be applied to the holder.

13. A sheet feeding apparatus according to any preceding claim in which the arms are carried by a common support which is rotatable about the common axis by means of a power driven reciprocally movable rack co-operating with a drive gear rotatable with the support, means being provided in association with the gear to limit rotation of the support, and thereby of the arms, to one direction only.

14. A sheet feeding apparatus according to Claim 13 in which the means provided in association with the gear to limit rotation of the support to the one direction comprises a ratchet wheel rotatable with the support and a pawl which is restrained from rotation with the support.

15. A sheet feeding apparatus according to Claim 13 or Claim 14 in which ratchet teeth rotatable with the support co-operate with spring-loaded detent elements which are restrained from rotation with the support and by their engagement with the ratchet teeth retain the support positively in positions to which it has been rotated by means of the rack.

16. A sheet feeding apparatus according to any of Claims 13 to 15 in which the rack is driven by a pneumatically operated piston.

17. A sheet feeding apparatus according to Claim 13 in which the support is rotatable with a hub which is supported by a bearing on a pillar which is fixed against rotation and about the axis of which the hub and support rotate, the hub carrying a co-axial ring on which are crown ratchet teeth with which springloaded detent elements co-operate which are fixed against rotation with the hub and which by their co-operation with the crown ratchet teeth are adapted to retain the hub positively in angular positions to which the hub is rotated, the hub also carrying the drive gear which is annular and co-axial with the hub and is rotatable relative to the hub, and a co-axial ratchet wheel which is rotatable with the drive gear relative to the hub and is engaged by a pawl pivoted on the hub which drivingly connects the ratchet wheel with the hub when the ratchet wheel is rotated in one direction only by the drive gear, thereby to rotate the hub and the arms.

18. A sheet feeding apparatus according to any of Claims 3 to 7, or any of Claims 8 to 17 as dependent from Claim 3, in which the common axis of rotation of the arms is vertical, and the arms are pivoted about horizontal axes and are normally urged to pivot downwardly about the horizontal axes.

19. A sheet feeding apparatus according to Claim 18 in which the arms are urged to pivot downwardly about the horizontal axes by pneumatic dampers supported on a carrier rotatable with the arms, which dampers extend radially of the common axis of rotation of the arms and are attached to the arms.

20. A sheet feeding apparatus according to Claim 18 or Claim 19 in which a guide extends concentrically about the common rotational axis of the arms along part of the rotational path of travel of the arms extending through the first work station and towards the second work station, the guide sloping upwardly towards the second work station and the arms co-operating with the guide as they travel along that part of the rotational path of their travel such that they are caused to be swung upwardly about their horizontal axes towards an upwardly inclined position as they approach the second work station.

21. A sheet feeding apparatus according to any one of Claims 18 to 20 in which a guide extends horizontally concentrically about the common rotational axis of the arms along part of the rotational path of travel of the arms extending from the second work station to the third work station, the arms co-operating with the guide as they travel between the second and third work stations such that they are maintained at a constant level between those two stations.

22. A sheet feeding apparatus according to Claims 20 and 21 in which the horizontally extending guide is at a lower level than the upper end of the sloping guide such that the arms are maintained substantially horizontal as they travel between the second and third work stations.

23. A sheet feeding apparatus according to Claim 22 in which a lift cylinder is provided at the second work station having a vertically movable piston with which the arms engage when they reach the second work station and which operates to lower the arms from the level of the upper end of the sloping guide to the level of the horizontal guide.

24. A sheet feeding apparatus according to any preceding claim in which the arms, means controlling operation of the holders and power driven means are mounted on a stand which has support means mounted thereon for the storing at the first work station of sheets to be picked up by the arms, and a receptacle at the third work station to receive cut sheets deposited by the arms for collection.

25. A sheet feeding apparatus according to Claim 24 in which the stand is mounted on lockable castors.

26. In combination a cutting machine of the kind set forth and a sheet feeding apparatus as claimed in any preceding claim which loads sheets to be cut into the cutting machine and removes them from the cutting machine after they have been cut.

27. Asheetfeeding apparatus substantially as described herein with reference to and as illustrated by the accompanying drawings.

28. The combination according to Claim 26 substantially as described herein with reference to and as illustrated by the accompanying drawings.