US3586314A

US3586314A - Sheet feeding device

Info

Publication number: US3586314A
Application number: US779752A
Authority: US
Inventors: Luigi Samoggia
Original assignee: Individual
Current assignee: Cefin SpA
Priority date: 1968-01-18
Filing date: 1968-11-29
Publication date: 1971-06-22
Anticipated expiration: 1988-06-22
Also published as: ES357054A1; GB1242423A; DE1804969A1; FR1581974A

Abstract

An automatic sheet feeding device, particularly for feeding machines for processing thin metal plates, wherein the sheet feeder is formed by two columns supported by feet displaceable on longitudinal guides fixed to the machine base in which the two columns are connected together by means of cross pieces along which a horizontal beam is displaced whilst guided by sleeves connected to the beam itself comprising a pair of shafts, a reducing gear, two side members being connected to the beam, the first side member fixed and the second side member variable according to the width of the sheets to be fed, and located at the ends of said shafts, said shafts being located in an axial direction relative to the side members but free to rotate about their own axes, two pulleys are adjustably secured on said shafts, a keyed chain pinion for transmitting drive from the reduction gear to one of said shafts, a driving chain for effecting such transmission and an idler pulley for tensioning said chain.

Description

United States Patent [72] Inventor LuigiSamoggia 32 Via Gandino, Bologna, Italy 21 Appl No 779,752 [22] Filed Nov. 29, 1968 [45] Patented June 22, 1971 [32] Priority Jan. 18.1968 331 Italy [31 1 1507mm;

[54] SHEET FEEDING DEVICE 19 Claims, 7 Drawing Figs.

52 [1.5.01 .J 271/12, 271/26, 271/45, 271/62 {51] lnt.Cl B65h 5/02, B6511 1/18 [50] Field ofSearch 281/45,26; 62, 58, 57, 12

[56] References Cited UNITED STATES PATENTS 990 311 4/1911 Stratton 271/58 2989307 6/1961 Weidenhammer 271/62 3.199363 8/1965 Muller 271/26 3,249354 5/1966 Egnaczaketal l. 3.341.194 9/1967 Bentzman ABSTRACT: An automatic sheet feeding device, particularly for feeding machines for processing thin metal plates, wherein the sheet feeder is formed by two columns supported by feet displaceable on longitudinal guides fixed to the machine base in which the two columns are connected together by means of cross pieces along which a horizontal beam is displaced whilst guided by sleeves connected to the beam itself comprising a pair of shafts, a reducing gear, two side members being connected to the beam, the first side member fixed and the second side member variable according to the width of the sheets to be fed, and located at the ends of said shafts, said shafts being located in an axial direction relative to the side members but free to rotate about their own axes, two pulleys are adjustably secured on said shafts, a keyed chain pinion for transmitting drive from the reduction gear to one of said shafts, a driving chain for effecting such transmission and an idler pulley for tensioning said chain.

PATENTED M22197: 3586314 INVENTOR: LUIGI SAMOGGIA Attorney FIG.

' PATENTED JUN22|97| INVENTORQ LUIGI SAMOGG-IA By Wmfw Attorney PATENTED JUNZ 21971 SHEET t 0F 6 INVENTOR: LUIGI SAMOGGIA Attorney PATENHEU M22 ism sum 5 0r 6 v QNN INVENTOR: LUIGI SAMOGGIA .8 SN a 5 2- .-& (1.3

v mum wNN Attorney @Jzaw PATENTEDJUNZZIBH 1 3586.314

- SHEU 6 [1F 6 FIG.

INVENTOR: LUIGI SAMOGGIA QMCOM Attorney SHEET FEEDING DEVllCE The present invention concerns an improved sheet feeding device suitable for application to a wide range of machines and in particular for feeding automatic complete sheet" presses.

A machine which performs operations of various kinds on sheet materials requires the sheets themselves to be fed to the machine in a clearly defined position and at definite times, associated with the method of operation of the machine.

Whilst it is generally possible for this feeding operation to be performed by hand, the progressive automation of machinery and the increasing speed of such machinery has led to the design and use of suitable machines or auxiliary devices, the so called automatic sheet feeders," which have the task of raising the sheets one after the other from a pile and feeding them to the machine for which they are intended, in the desired position and at the desired times, the timing being normally obtained by means of suitable members interconnecting the basic driving mechanism of the working machine and the sheet feeder so as to compel them to operate synchronously.

The advantages in the use of sheet feeders may be summarized as:

The possibility of completely utilizing the increased productive capacity of modern machinery, which is not possible as a rule with manual feeding:

Elimination of the disadvantages due to handling the sheets, among which there may be mentioned damage of the surfaces and distortion of the corners:

Reduction of the work of the operator to loading the piles of sheets at long intervals and consequent possibility of feeding several machines by only one operator.

In the case of machines operating on thin metal plates (black tin-plated steel strip, aluminum sheeting and the like) automatic sheet feeders were formerly applied to machines effecting the varnishing and lithographic printing of the sheets themselves, such machines having first reached a speed of production and degree of automation which rendered the adoption of a system of automatic feeding if not indispensable, at least highly advisable. The sheet feeders which had been designed and used for these machines were of a very complex and expensive construction since the sheets were relatively heavy compared with sheets of paper, and since the operational speed had been appreciably increased.

When, subsequently, other machines operating on thin plates, such as cutters having circular blades, and guillotines, reached a speed of production which, whilst being below that of varnishing and printing presses, made the use of suitable automatic sheet feeders, it was usual to adapt sheet feeders which were identical, or almost identical, with those already in use for varnishing and printing presses, despite the fact that the services rendered by such sheet feeders, particularly with regard to speed, could only be partially exploited, and despite the fact that there were definitely parts of the sheet feeders which, in this particular application, could have been simplified or completely eliminated without disadvantage.

in order to avoid these difficulties, which for economic reasons limited the spread of sheet feeders in the field of the processing of thin plates, sheet feeding devices of simplified type were subsequently designed. These generally included permanent magnets as indispensable parts of their operation, and therefore they were suitable only for feeding sheets of steel plate and were not applicable to aluminum sheets or sheets of other nonmagnetic materials, through conventional sheet feeders, with suitable adaptations, operate on these latter materials also.

Apart from some sheet feeders of conventional type, most known feeders are not suitable for feeding another important class of machinery for processing the sheeting, i.e. presses for the entire sheet which, having been made recently completely automatic, are capable of an increased output with an eventual reduction in the amount of labor required for their operation, and the elimination of the disadvantages due to the handling of the sheets whenever an automatic sheet feeder can be used. Hence the purposes for which the present invention has been designed are:

Simplification of construction as compared with conventional sheet feeders, and consequent reduction in cost, without in any way diminishing their uses, the first of which is their ready adaptability to the various sizes of sheets which may be processed on machines to which it is connected.

The possibility of feeding, with only slight modification, either magnetic metal sheets, nonmagnetic sheets, or sheets other than metal.

The possibility of connecting the sheet feeder, in its more developed version, to presses for the entire sheet, and in simplified versions to circular cutters, guillotines and similar machinery for processing sheeting, low speed lithographic machinery, and the like.

Since the invention uses some known mechanisms it is considered suitable to refer only briefly to them and then to pass to the description of the invention, with reference to the accompanying drawings in which:

FIG. 1 is a side view ofa known sheet feeder,

FIG. 2 is a side view of a known sheet feeder of simplified W FlG. 3 is a side view of a sheet feeder of the present invention, applied to a press for the entire sheet,

FIG. 4 is a plan view of the sheet feeder of FlG. 3,

FIG. 5 is a view of the driving mechanism of the sheet feeder shown in FIGS. 3 and 4,

FlG. 6 is a side view of a simplified sheet feeder of the present invention, for application to cutters and like machinery,

FIG. 7 is a view of the driving mechanism of the sheet feeder shown in FIG. 6.

As shown in FlG. l, a conventional sheet feeder comprises a strong base, in the front part of which is located a base surface 1 for supporting a pile 2 of sheets, usually disposed on a pallet 3 which makes it possible to raise the pile from a store by means of a fork truck and to transfer it by way of the truck itself or a roller path to the base surface 1. The latter is supported by chains 4 meshing with chain pinions 5 actuated through suitable gears by an electric motor 6, to raise and lower the platform itself according to the requirements of the work; the raising and lowering of the platform may also be obtained in any other manner, for example by means of a hydraulic cylinder. Once the pile is loaded on the base surface 1 in the desired position, the base surface itself is raised until the upper sheet of the pile reaches a height predetermined by a suitable control device.

To detach the top sheet from the pile, raise it and start the advance movement thereof towards the operating machine 7, rear suction members 8 and front suction members 9 are provided.

Each suction member is connected to the end of a piston displaceable within a cylinder connected to a flexible tube to a center distributor 10, which is actuated synchronously with the operating machine 7, being connected thereto by a chain 11.

The distributor 10 is connected by a tube to the vacuum pump 12, actuated by an electric motor.

When a cylinder is put in communication with the vacuum pump, it first causes the descent of the associated piston until the suction member comes into contact with the sheet, then the piston rises carrying the sheet until, when the piston reaches the upper end of its movement, the distributor l0 puts the cylinder in communication with the atmosphere and the sheet is released by the sucker.

The cylinders 13 of the rear suckers 8 are fixed, whilst those 14 of the front suckers 9 are connected to rocker arms 15 actuated by a gear mechanism which receives its drive from the chain H and is therefore synchronized with the main machine. The object of the rear suckers is partly to raise the sheet to separate it from the rest of the pile, whilst those at the front, which then come into action, complete the lifting of the sheet and insert it between the driving rollers 16, which are also rotated by a mechanism driven by the chain 11 which actuates the belt conveyors 17 to advance the sheet until it drops onto the table of the operating machine 7 (this position of the sheet is shown in broken lines in FIG. 1).

On the table are chain conveyors or slides having a reciprocating motion, and provided with teeth, which raise the sheet and move it on.

The frame 18 supporting the belt conveyors 17 is provided with displaceable lateral abutments 19 receiving their synchronized motion from the chain 11, to center the sheet to facilitate its movement into the correct position on the table of the machine 7.

To facilitate detachment of the sheets from the pile, since they tend to remain in contact with each other either under the effect of the adhesiveness of their surfaces or, especially at high speeds of the sheet feeder, due to air pressure, magnetic separators 20 are provided which produce a repelling effect between one sheet and the other.

When the sheets are of nonmagnetic magnetic material, such as aluminum, and when the separators 20 would not be effective, blowers 21 are used connected by way of the center distributor 10 to the feed of the pump I2 which, in such a case, also acts as compressor.

Despite the above-mentioned arrangement, it may however happen that two or more sheets are raised and remain clinging together and are inserted together between the rollers 16; to avoid any consequent damage in such a case, a scanner or feeler roller 22 is provided which, by rising to an unusual extent when two or more sheets pass through together, actuates a microswitch 23 and an electromagnet 24 which acts on a deflector 25, which guides the double sheet between the driv ing rollers 26.

These rollers finally convey it into the associated grid 27 where the double sheet remains without disturbing the operation of the unit. Gradually as the sheets are fed to the machine 7, the upper level of the pile 2 lowers and it is necessary to return it periodically to the original point to allow the suckers to work. For this purpose a scanner 28 is provided which starts up the motor 6, or brings into action a mechanism connected at one end to the chain ll and at the other end to the shafts carrying the pinions 5.

Various types of simplified sheet feeders are known which are adapted to feeding circular blade and guillotine cutters, although there are considerable differences between them.

The basic principles thereof may be understood by reference to FIG. 2.

In view of the fact that a fork truck 29 is generally necessary to lift the piles from the store, the same truck is used to feed the machine 30, cutting out the base support I of FIGv I and all the members for operating the base support itself. The truck 20 is provided with means for displacement by hand and a lifting device formed of a hydraulic cylinder connected to a pump actuated by an electric motor, and is also provided with a cable and plug 31 which enables it to be connected to a current source to supply it with power. A scanner 32 is provided to stop the lifting movement of the fork 33 when the upper level of the pile is at the height necessary for feeding the sheets; it also returns the top of the pile to such a level when, after a certain number of sheets have been fed, the height of the pile has diminished beyond a certain limit.

The base of the sheet feeder, considerably simplified and light in weight due to the aforementioned elimination of the base support, is also provided with a scanner 32, and two suckers 34, each connected to the end of a piston displaceable within a cylinder 35 fixed to the base and connected by tubing to a combined vacuum pump-compressor 36 actuated by a motor.

Under the action of the vacuum, the pistons of the cylinders 35 descend, the suckers engage the front edge of the sheet and raise it, separating it from the rest of the pile by means of the magnetic separators 37 and the blowers 38, connected to the pump-compressor 36.

The suckers raise the sheet until it is brought into contact with the rollers 39, which, being magnetized hold the sheet (which must be of magnetic material), whilst the suckers relinquish it and remain in the raised position.

The magnetic rollers 39 and the drive rollers 40 are connected together and actuable by means of an electric motor 41. An electric pulse from the machine 30 starts the motor 41 at the required moment and the sheet is introduced by the rollers 39 between the rollers 40 which carry it forward, making it drop on the table of the machine 30. A scanning system (not shown in FIG. 2) causes the suckers to drop when the sheet is no longer below them; immediately afterwards the motor 41 stops and the cycle begins again.

The belt conveyor 17 and the displaceable abutments 19 of the conventional sheet feeder shown in FIG. 1 are not included in the simplified sheet feeders since the cutter is provided with its own abutment system. They may however carry a device detecting a double sheet, but the deflector 25, the rollers 26 and the grid 27 shown in FIG. I are not usually provided, and the double sheet detector stops the cutter and sheet feeder unit.

Even more simplified types of sheet feeders are known which do not use the suckers 34, but are merely based on the use of permanent magnets to separate the sheets and raise them, whilst the movement of the machine is effected by means of belts; the said sheet feeders do not usually comprise members for synchronizing with the operating machine and are therefore only suitable for the simpler types of cutters; they cannot be connected to machines provided with abutments or other reciprocating motion members.

The sheet feeder according to the present invention, whilst utilizing parts of known techniques and members present in conventional sheet feeders as shown in FIGS. l and 2, also makes use of other components, the combination of which, with the first mentioned members, results in improvements such as enable the feeder to be used with automatic presses acting on whole sheets.

The table of a press for the complete sheet does not comprise members for bringing the sheet into contact with the abutment positioning said sheet at the beginning of the working cycle, nor could such members be included without incurring very considerable complications in construction, in view of the requirement that the table should remain completely bare so as to permit the displacements of the longitudinal truck and of the transverse truck, to the latter of which the sheet remains secured for the complete duration of processing.

Therefore, whenever the travel of the sheet to the table of the press is automatically effected, neither the sheet feeder of FIG. 1, nor that of FIG. 2 nor other types which are even more simplified, to which reference has been made, are suitable, since they do not have a device capable of bringing the sheet into contact with the abutments without blocking the movement of the press carriages.

FIGS. 3, 4 and 5 clearly show the members used in the sheet feeder of the present invention, in its application to a complete sheet press.

The table of the press has tapped holes 53 for the cutting tool and 154 for other tools acting on the already cut sheet. Above the table a longitudinal carriage slides, formed by two

side pieces

101 and 102 and rods 103 on which a transverse carriage 104 is displaced, carrying a crosspiece 105 to which two pincers 106 and 1107 are secured in a suitable position for locking the sheet and the two

front abutments

108 and 109.

It is not necessary to make extensive modifications to the press for the application of the sheet feeder, except with regard to the lateral abutment which, instead of being formed by a pneumatically controlled retractable abutment, disposed above the table 100, is now formed as a simple tooth 110 pivotably connected to the structure of the sheet feeder in the desired position required from time to time by the reference points of lithographed sheets; it is necessary to locate a lateral push member 1111, below the table 100 retractable in a manner which will be described hereinafter and projecting at the desired moment through a slot formed in a suitable position in the table 100 itself, together with a rear push member 112, also retractable in a manner which will be described hereinafter and projecting through a suitable slot at the appropriate moment. Interconnections between the pneumatic and electric circuits of the press and the corresponding circuit of the sheet feeder are also necessary.

The structure of the sheet feeder and the movements which are capable of being made by the displaceable parts thereof will first be described with reference to FIGS. 3, 4 and 5.

These figures show the sheet feeder applied to the righthand side of the press; this arrangement is suitable only for sheets having lithographic reference points as shown in FIG. 4 by black triangles and in which the reference indicated by 168 is on the right-hand side of the sheet.

In cases where this reference 168 is on the left-hand side, it is necessary to apply the sheet feeder to the left-hand side of the press with any necessary variations of the arrangement shown in the Figures; this does not represent a limitation of the invention, since the lithographic reference position in use is determined once and for all for the sheets to be processed on a particular press.

It should be remembered that the side view shown in FIG. 3 is partly in section on the line A-A of FIG. 4; hereinafter it is assumed that the dimensions of the sheets are those to which the machine has been set up to operate.

The sheet feeder comprises two

columns

113 and 114, each supported by a base 115 displaceable on a guide 116 and securable thereto in any position within the limits of the said guide, for the purpose of permitting the exact positioning of the sheet feeder relative to each particular length of sheet to be processed. The two guides 116 are fixed to the base 117 of the press by means of a connecting plate 118 and associated screws. The

columns

113 and 114 are connected together by means of crosspieces having a

circular section

119, 120, 121 which simultaneously reinforce the unit and support some members which will be referred to hereinafter. Displaceable on the

columns

113 and 114 is a horizontal crosspiece 122 guided by means of

sleeve

123 and 124 connected to the crosspiece itself.

Connected to the crosspiece 122 are two

edge members

125 and 126, the first in a fixed position and the second in a position variable according to the width of the sheets to be fed, the distance between the said members being made slightly greater than the said width in order to permit the sheets to slide easily whilst remaining guided.

Two

shafts

127 and 128, connected in an axial direction relative to the edge member 126, but free to rotate about their axes, are disposed at the ends of the

edge members

125 and 126. Two

pulleys

129 and 130 are fixed on the

shafts

127 and 128 in positions variable according to the width of the sheet, since they have to be disposed approximately in the center of the

edge members

125 and 126; a chain pinion 131 axially connected to the edge member 125 rotates the shaft 127 which is grooved, whilst the pinion 131 is provided with a key, the drive from the reduction gear 132 fixed to the plate 133 being connected in turn to the base 115. It will be clearly seen from the drawing that the drive is transmitted regularly, whatever the position of the crosspiece 122 along the column, due to the arrangement of the chain 134 which is tensioned between the driven pinion 131 and the driving pinion 135 by way of the pinions 136 loose on the crosspiece 120 and the

loose pinions

137 and 138 axially connected to the fixed edge 125.

A belt 139 of material having a high coefficient of friction is tensioned between the

pulleys

129 and 130 by means of a tension pulley 140, carried by an arm pivotably connected to the crosspiece 141, the forked ends of which straddle the

pulleys

129 and 130 and are supported by the

shafts

127 and 128. The crosspiece 141 carries small spring loaded arms 142 at its lower end, each of which carries a small roller 143, and presses it against the belt 139, compelling it to remain in con tact with the plate 144, below it, which has a very highly polished or smooth surface with a low coefficient of friction and is fixed to the crosspiece 122 by means of screws, in order to allow for variation in the width of the sheets.

It will be understood that, whenever a sheet to be fed is interposed between the belt 139 and the plate 144, and the gear 132 is in operation, the sheet, by virtue of the different friction coefficients of the belt and the plate, is carried along by the belt, in a direction which extends from the intake to the outlet of the sheet feeder.

A loose roller 152 below the pulley is pressed against the pulley by a spring (not shown), to effect the intake of the sheets into the space between the belt 139 and the plate 144.

A pneumatic cylinder 145 is pivoted at its lower end on the crosspiece 121 and the rod 146 of its piston is pivoted on the cross bar 122 so that when the cylinder is energized by compressed air, the crosspiece 122 with all this connected to it, is in the raised position shown in full lines in FIG. 3, whilst, when the cylinder is connected to atmosphere, the crosspiece 122 with everything connected to it is in the position shown in chain dotted lines in FIG. 3, with the plate 144 resting on the table 100 of the press. It is obvious that the movement of the piston of the cylinder 145 must be such that, in the raised position, the trucks of the press not shown can rapidly pass below the plate 144 so as to avoid any interference.

Means is provided for delivering metal sheets one by one from a pile of sheets to the sheet feeder. An arm 147 is mounted on the crosspiece 120 in such a manner that it can swing and be laterally secured in a position where it is above the belt 139.

Towards the right-hand end (with reference to FIGS. 3, 4, 5) of said arm there is pivoted, in an adjustable position along the arm itself, a horizontal shaft 148 to which two

arms

149 and 150 provided at their lower end with connected by tubes to a vacuum pump 151 are adjustably connected.

For very wide sheets, one or two extra arms may be provided, having suckers identical with 149 and 150 and cooperating therewith to permit of improved engagement and insertion of the sheets.

On the right end of the arm 147 there is a rod 155 in an accurately adjusted position for the purpose (since the suckers are formed of elastically deformable material) of permitting exact sensing of the level of the pile and therefore acting as a scanner.

Connected to the shaft 148 is an arm to which is pivotally 157 connected one end of a draw bar 158 of adjustable length comprising two rods the ends of which are provided with threads respectively right and left and are connected together by a sleeve 159.

The other end of the drawbar 158 has a pivot receiving a loose roller 160 and connected to one end of a bell crank lever 161. The fulcrum of the crank lever 161 is formed by a pivot connected to the left end of the arm 147, so that the four

members

147, 157, 158 and an arm of the crank lever 161 produce an articulated quadrilateral structure capable of assuming any required conformation, once the length of its arms is determined, depending on the angle between two of the arms. In order clearly to determine the succession of these conformations, a plate 162 is provided which is secured to the crosspiece 119 in such a position that the roller 160 engages a suitably shaped edge of the plate.

A pneumatic cylinder 163 is secured to the front of the plate 162 so that the piston rod of this cylinder is disposed above the other arm of the crank lever 161 which engages with it in view of the weights of the various parts.

When the piston descends under the influence of compressed air in the cylinder 163, the piston rod presses downwardly against the end of the lever 161 and since this lever cannot rotate freely on account of the roller 160 which rests against the plate 162; the left end of the arm 147 descends and the right end rises, raising the sucker-carrying

arms

149 and 150 which move to the position 164, shown in chain dotted lines in FIG. 3 at which point the roller 160 reaches the lower end of the path defined by the approximately vertical edge of the plate 162.

At this point, since the support provided by the vertical edge of the plate 162 is missing, the lever 161 rotates in a clockwise direction for all the remaining movement of the piston in the cylinder 163, the roller 160 remaining in contact with the path defined by the approximately horizontally extending lower edge of the plate on account of the distribution of the weight of the various parts; consequently, the suckercarrying

arms

149 and 150 rotate, moving to the position 165 shown in chain dotted lines in FIG. 3. The position 165 is such that a sheet clinging to the suckers is receiving in this position between a pulley 130 and the roller 152, as shown in chain dotted lines in FIG. 3 at 166. Once the sheet is inserted, the piston in the cylinder 163 rises and it is necessary to obtain the return of the articulated quadrilateral to the starting position and of the sucker-carrying

arms

149 and 150. For this purpose, a spring 170 is provided which cooperates with the various parts to effect said return.

In order to arrange the pile of sheets to be fed in a suitable position, the sheet feeder of the present invention preferably uses a specially adapted fork lift truck. Alternatively the sheet feeder of the present invention can make use, instead of this truck, of a normal fork lift truck, similar to that mentioned above in connection with the simplified sheet feeder shown in FIG. 2. Alternatively use may be made ofa load platform, the height of which varies both under the control of an operator or consequent upon an electric signal from the device checking the level of the stack.

Having described above the structure of the essential parts of the sheet feeder applied to the press, and the movements of which are subjected to the displaceable members thereof, its cycle of operation will now be described with particular reference to the driving mechanism shown in FIG. 5, which also shows the principal components of the electric circuit and the pneumatic devices for the actuation of the sheet feeder. To commence the working cycle of the sheet feeder, the press must be placed at the beginning of a work cycle, with the motor running, friction gear disengaged,

pincers

106 and 107 open, longitudinal and transverse trucks in starting position, (or in the position indicated in FIG. 4). As to the sheet feeder itself, it must be connected both electrically and pneumatically to the press, so that compressed air is admitted to the cylinder 145 and the crosspiece 122 to which it is connected is in the raised position shown in full lines in FIG. 3. On the assumption that he wishes to make use of a fork lift truck 167 for supporting the sheets, the operator brings the truck carrying the stack of sheets to the sheet feeder by hand and positions it between the two vertical edge members 169 which are secured in a suitable position on the base of the sheet feeder, so that the stack comes into contact with the plane defined by the said edge members. He then connects the electric circuit and the pneumatic devices of the truck to the corresponding circuits of the sheet feeder and starts the vacuum pump 151 with which the starting of the pump motor is effected, sending oil into the cylinder of the elevator truck and thus raising the stack. When the stack comes into contact with the scanner 155, a small rotation in a counterclockwise direction of the arm 147 is effected and the actuator of the microswitch 171, which had been urged into a rest position by the arm itself, is released, thereby stopping the pump motor of the truck. At the same time the suckers fixed to the

arms

149 and 150, which are connected to the vacuum pump 151 stick to the upper sheet ofthe stack. At this moment the operator pushes a button, (not shown in the FIGS.) which starts the reduction gear 132 and the admission of compressed air to the cylinder 163, through an electrically operated valve, (not shown). Due to the above-described mechanism, the insertion movement of the sheet between the belt 139 and the roller 152 takes place; at this moment, the arm 157 triggers the actuator of the microswitch 172, the connection between the suckers and pump 151 is interrupted by means of a three way electrically operated valve (not shown), and the suckers are connected with the atmosphere. The sheet becomes detached from the suckers and the belt 139 carries it forward towards the table 1110.

In its travel, the sheet strikes against the actuator of the microswitch 173, which stops the reduction gear 132, admits air to the cylinder 163, discharges the cylinder itself, returns the sucker-carrying

arms

149 and 150 to the starting position (shown in full lines in FIG. 3) and actuates a three way electric valve (not shown) which shuts off the air from the cylinder 145 and opens it to atmosphere. At the same time the electromagnet 174 is excited which retracts a tooth 175 against the spring 177, thus releasing the projection 176 connected to the stem 146. The unit comprising tooth 175 and projection 176 forms a locking device for safety purposes, preventing the crosspiece 122 and its attachments from interfering, in the absence of compressed air or electric power, with the trucks of the press during the processing ofa sheet.

When the rod 146 is free to descend, the conveyor unit descends and the plate is brought into contact with the table 100, whilst at the same time the actuator of the microswitch 178 is pressed by a projection connected to the rod 146, said actuator restarting the drive of the reduction gear 132. Consequently, the sheet, rising on the movement of the tooth 110 forming the side abutment, moves onto the table and slides over it, having first been advanced by the belt 139 and then continuing by inertia, until the front edge of the sheet comes into contact with the push member 111 which projects relative to the table 100 under the action of a pneumatic cylinder 179 to the piston of which the push member itself is connected, whilst being able to move parallel to the length of the sheets. The sheet, advancing, loads the spring 1811 and the push member 111 moves back until it engages with the actuator of the microswitch 181 which causes the admission of compressed air to the pneumatic cylinder 1&2 by means of an electrically operated valve. As soon as the microswitch 181 is actuated, the tooth 111, under the action of the spring 180, advances, bringing the sheet into engagement with the abutment and positions it therefore longitudinally, so that it becomes located in the position shown in full lines in PK]. 4 and indicated by 184. immediately afterwards, admission of air into the cylinder 182 advances the sheet towards the

abutments

108 and 109 by means of the tooth 112 connected to the resilient arm 183 which in turn is connected to the piston rod in the cylinder 182. When the sheet has come into contact with the abutments, in the position shown in chain dotted lines in FIG. 41 and indicated by 185, the microswitch 186 connected to the edge member 126 is pressed by the sheet itself. Since the sheet is positioned between the pincers 1116 and 107, the microswitch 186 operates the electromagnet which controls the closing of the pincers, the engagement of the friction gear of the press, the operation of the already mentioned electric valve connected to the cylinder 145 and of a three-way electrically operated valve (not shown) connected to the cylinder 179, which relieves the cylinder itself. Thus, the starting of the press and the processing of the sheet, the withdrawal of the push member 111 below the level of the table and the raising of the conveyor connected to the crosspiece 122 are effected simultaneously. Whilst the press carries out the processing of a sheet, with the conveyor in a raised position, a projection connected to the rod 146 operates the microswitch 187 which effects, by way of the above-mentioned electrically operated valve, the admission of air to the cylinder 163. In this manner another sheet is raised from the stack and is inserted between the belt 139 and the pulley and is moved forward until it comes into contact with the actuator of the microswitch 173 which stops the reduction gear 132 and the discharge of air from the cylinder 163, with consequent return of the arms carrying the suckers to the starting position. The sheet remains on the plate 144 until the press has completed the working cycle on the first sheet, which cycle concludes with the repositioning of the longitudinal and transverse trucks in the starting position (indicated in Fit]. 4). This repositioning operates the electrically operated valve connected to the cylinder 145 and discharges it. From this moment the feeding cycle relative to the second sheet proceeds identically with that described above in connection with the first sheet. The cycle is repeated until the stack is exhausted. As the sheets are gradually removed from the pile, the upper level thereof drops until the rotation in a clockwise direction of the arm 147 which follows it, operates the microswitch 171 which starts the pump motor of the elevator truck to readjust the upper level of the pile. This happens until the pile itself is exhausted, without interfering in any way with the feeding of the sheets to the press. Once a pile is exhausted, the adjacent switch 189, fixed at the side of the pile itself on a level with the scanner 155 and therefore with the upper sheet is operated, since it is sensitive to the presence ofa conductive metal sheet or foil and insensitive to nonmetal materials, such as the wood of which the pallet 190 is formed and on which the pile rests. This indicates the exhaustion of the pile and acts so that the electrically operated valve between the suckers and the pump 151 remains closed in order to prevent damage and at the same time calls the attention of the operator by means of an acoustic and/or visual signalling system. The operator, attracted by the signals, disconnects the electric and/or pneumatic connections between the sheet feeder and elevator truck by which the pump 151 and the working cycle of the sheet feeder are stopped. The operator then attends to the loading of a new pile of sheets and repeats the operations already mentioned above to begin the operation of the trucksheet feederpress assembly again.

In the sheet feeder of the present invention magnetic separators 188 are provided when the sheets are of magnetic material, and these are replaced for nonmagnetic sheets by blower nozzles which may be connected to the feed of the pump 151 or to the compressed air supply.

If, however, despite these devices, two or more sheets are raised together and inserted together between the belt 139 and the roller 152, the microswitch 191 is actuated, this switch being provided with a roller actuator. This causes excitation of the electromagnet 192 which actuates the deflector 193 which moves the position shown in chain dotted lines in FIG. 3 deflecting the sheets into the slide 194. After the expulsion of the double sheet the resumption of the normal feeding cycle of the sheets recommences; the microswitch 191, no longer pressed by the sheets, controls the discharge of the cylinder 163 and operates a timing device whereby the aforementioned electrically operated valve causes readmission of air to the cylinder 163 after a period sufficient to ensure that contact of the suckers with the upper sheet of the pile has already taken place. The removal of some of the suckers from a single sheet and the insertion of the sheet between the belt 139 and the plate 144 until it actuates the microswitch 173, restarts the normal operating cycle of the sheet feeder as described above.

A description will now be given ofa simplified version of the sheet feeder suitable for application to cutters and other machines. Reference is made to FIGS. 6 and 7 showing the application to a cutter (or other machine) provided with a chain conveyor, though the invention may be applied to machines provided with other feeding systems. It should be remembered that FIG. 6 is partly in section near the center portion of the cutter.

The base of the sheet feeder in the simplified version shown in FIGS. 6 and 7 comprises two sides 200 secured to the side of the table 201 of the cutter which is provided with a center chain conveyor 202 carrying feeding teeth 203 spaced equally apart along the chain itself. The chain 202 is operated by a wheel 204 which causes it to advance with every turn by an amount exactly corresponding to the space between two consecutive teeth 203. At the inlet of the table 201, the chain 202 is tensioned by a pinion 205 connected to a shaft 206 supported by the table 201.

The shaft 206 drives two or more conveyor rollers 207. Above the rollers 207 the same number of rollers 208 are located, keyed on a shaft 209, which is supported by the two sides 200 in such manner that, apart from being loosely rotatable about its own axis, the shaft is capable of displacement in a vertical direction, so that the rollers 208 bear by their own weight on a sheet 210 which is introduced between them and the rollers 207 below. If the chain 202 is set in motion and a sheet 210 is introduced between the

rollers

207 and 208, it is carried along by friction until it drops onto the table of the cutter where it is engaged by one of the teeth 203 and moved forward, sliding between two side parts (not shown). If, instead of having one central chain 202, the machine to which the sheet feeder is applied, is provided with another feeding system in which it is not possible or practical to incorporate the conveyor rollers 207, the rollers themselves may be carried on a shaft supported by the sides 200 and the drive of the rollers 207 may be obtained by way of a motor or reduction gear 211 as shown in chain dotted lines in FIG. 6.

The insertion of the sheets between the

rollers

207 and 208 is effected by a device identical to that already described with reference to its application to a press for the entire sheet. A rocker arm 213 is keyed on a shaft 212, supported by the side plates 200 and displaceable relative to its axis, near the righthand end of which a horizontal shaft 214 is pivoted on which two arms 215 and 216 are mounted, being provided at the bottom with suckers connected by tubes to a vacuum pump 217. At the right-hand end of the arm 213 a scanner rod 218 is positioned for checking the level of the pile. The arm 213, the disc 219, the draw bar 220 and the bell crank lever 221 constitute an articulated system which, due to the plate 222 of the pneumatic cylinder 224 and the spring 225, effects the movement of the sucker-carrying arms in a manner identical to that already described with reference to the application to a press for the complete sheet. The pneumatic cylinder 224 can, in cases where the cutter does not require a fresh supply of compressed air for operation, be connected for convenience to the vacuum pump 217 through the pipe 233 shown in chain dotted lines in FIG. 7. Similarly, for the simplified version, a sheet feeder of the present invention may preferably be provided with an adapted fork truck 226 or may with an ordinary fork truck or a pile-carrying table.

The cycle of operation of the simplified sheet feeder will now be described with particular reference to FIG. 7. To commence this cycle, the electric circuit of the sheet feeder, the principal components of which will'be referred to hereinafter, must be connected to the electricity supply system. If a specially adapted fork truck 222 is used, the operator brings the truck carrying the pile of sheets by hand to the sheet feeder and positions it between the two vertical sides 227, which are fixed on a base supported by two columns 228 connected to the table 201. The pile must come into contact with the plane defined by the sides 227. The operator then connects the electric circuit of the truck to the corresponding circuit of the sheet feeder and the pneumatic system of the truck to the compressed air system of the sheet feeder, if the latter is provided with one. He then operates the vacuum pump 217 which starts the pump motor to fed oil to the cylinder of the elevator truck; consequently, the pile rises. When the pile has come into contact with the scanner 218, a short counterclockwise rotation of the arm 213 is produced, the actuator of the microswitch 229, which is urged into the position of rest of the arm itself, is released, thereby stopping the pump motor of the truck. At the same time the suckers fixed to the arms 215 and 216, being connected to the pump 217, stick to the top sheet of the pile. The cutters are now brought into action and the chain 202 carrying the teeth 203 is driven by the wheel 204. If the rollers 207 are driven by the chain 202 they will also be in motion, otherwise a motor or reduction gear 211, adapted to the control of the rollers themselves, must be used. A cam 230, keyed on the shaft carrying the wheel 204 actuates the three-way pneumatic valve 231 in synchronism with the movement of the teeth 203, which connects the cylinder 224 either with the compressed air source or with the vacuum pump 217.

In each case, the movement of the piston in the cylinder 224 is effected and, by means of the above described link system, the movement of the sucker-carrying arms insert the sheet between the

rollers

207 and 208 which drive it forward; meanwhile, as soon as the disc 219 triggers the actuator of the microswitch 234, the interruption of communication between the suckers and pump 217 and the simultaneous communication of the suckers with the atmosphere are effected by means of a three-way electrically operated valve (not shown). The sheet is detached from the suckers and continues, driven by the

rollers

207 and 208, until it drops onto the table of the cutters a moment before one of the teeth 203 comes into contact with the rear edge of the sheet. The cam 230 is shaped in such manner that, as soon as the rear edge of the sheet has left the

rollers

207 and 208, the pneumatic valve 231 puts the cylinder 24 communication with the atmosphere whereby the link system actuating the arms 215 and 216 returns them to the starting position and the microswitch 234, through the abovementioned three-way electric valve, brings the suckers into communication with the pump 217 again. As soon as the cam 230 comes again into contact with the actuator of the pneumatic valve 231, the sheet feeding cycle is repeated; this continues until the pile is exhausted. As the sheets are removed from the pile, the upper level thereof drops until a short clockwise rotation of the arm 213 which follows the level causes the actuation of the microswitch 229 which starts the motor pump of the elevator truck to reestablished the upper level of the pile. This happens until the pile itself is exhausted without in any way interfering with the feeding of the sheets to the cutters.

Once a pile is exhausted, the adjacent switch 235 fixed to the side of the pile itselflevel with the scanner 218, signals the exhaustion of the pile, holds the electric valve interposed between the suckers and the pump 217 in a closed position.

The operator, whose attention is attracted by the signals, stops the cutter, the motor or reduction gear 211 and the vacuum pump 217, then disconnects the electric connections and any pneumatic connections between the sheet feeder and the truck lift. The operator then loads on a new pile of sheets and repeats the start procedure.

In the simplified sheet feeder described, magnetic separators 236 or blower nozzles are provided, which may be connected to the feed of the pump 217 or the compressed air supply. If, however, despite these devices, two or more sheets are raised together and inserted together between the

rollers

207 and 208, the microswitch 237 is actuated; this excites the electromagnet 238, actuating the deflector 239 which, moving to the position shown in chain-dotted lines in FIG. 6, brings the sheets to the pair of rollers 2410 and 241. Since the lower rollers of these pairs of rollers are driven, whilst the upper rollers of the pairs of

rollers

240 and 241 are displaceable in a direction normal to their axis, the double sheet is carried forward and dropped on the appropriate grid 2415 held by supports 246 fixed to the side of the table 201. As soon as the double sheet has left the actuator the microswitch 237 dcenergizes the electromagnet 238 and the deflector 239 returns to the normal position under the action ofa spring (not shown).

It is obvious that in all the above, either in the description of the sheet feeder applied to a press for the entire sheet, or in the description of the simplified version applied to a cutter or other machinery, it is possible, instead of or in replacement of the electric circuits comprising microswitches, relays, electric valves and electromagnets, to use corresponding fluid members, for example pneumatic switches, or detector, pneumatic amplifiers, pneumatic valves and cylinders, without departing from the scope of the claims of the present invention.

Whatl claim is:

1. An automatic sheet feeding device, particularly for feeding thin metal sheets to a machine having a table, comprising two vertical columns spaced from one another on a line extending transversely of said table, a sleeve vertically slidable on each of said columns, a crosspiece extending between and connecting said sleeves, a sheet feeding unit carried by said unit comprising a horizontal plate having a smooth upper surface, spaced parallel shafts above said plate, pulleys on said shafts and a belt running on said pulleys and having a lower run extending along said upper surface of said plate, said belt having a higher coefficient of friction than said plate, means for driving one of said pulleys, means for delivering a single sheet between said plate and said belt to be transported across said plate by said belt and means for moving said sleeves, crosspiece and feeding unit vertically on said columns to bring said plate to a level to feed said sheet from between said plate and belt onto said table.

2. A sheet feeding device according to claim 1, in which said means for driving one of said pulleys comprises a power driven drive sprocket, disposed below said sheet feeding unit, an idler sprocket disposed above said unit, a driven sprocket on the shaft of said pulley, a chain running on said drive sprocket, idler sprocket and driven sprocket and guide rollers carried by said unit and guiding said chain to said driven sprocket in all positions of said unit.

3. A sheet feeding device according to claim 1, in which said unit comprises a horizontal beam carried by said crosspiece and having forked ends supported by said shafts.

4. A sheet feeding device according to claim 3, in which spring pressed rollers carried by said beam engage the lower run of said belt to press it toward said plate and a spring biased idler roller carried by said beam engages the upper rum of said belt to tension said belt.

5. A sheet feeding device according to claim 1, in which said means for moving said feed unit vertically comprises a pneumatic cylinder and piston acting between said cross bar and a stationary support, and means for supplying fluid under pressure to said cylinder.

6. A sheet feeding device according to claim 5, comprising an electromagnetically releasable safety catch for preventing downward movement of said unit if power is off.

7. A sheet feeding device according to claim 1, comprising control means actuated by movement of said sheet by said belt for stopping said belt and initiating downward movement of said unit when said sheet has moved to a selected position.

8. A sheet feeding device according to claim 7, comprising control means actuated by movement of said unit to restart said belt when said unit has moved down to a selected position.

9. A sheet feeding device according to claim 1, in which said sheet delivering means comprises an articulated quadrilateral mechanism, depending sucker arms carried by said mechanism, suckers on said arms and means for actuating said mechanism to move said arms vertically and angularly to pick up a sheet from a pile of sheets and deliver it to said feeding unit.

10. A sheet feeding device according to claim 9, in which said actuating means comprises a bell crank lever one arm of which is a member of said quadrilateral mechanism, a roller carried by said one arm, a guide plate engaged by said roller and a cylinder having a piston rod engaging the other arm of said bell crank lever.

11. A sheet feeding device according to claim 10, in which said quadrilateral mechanism comprises a first arm pivotally mounted intermediate its ends, a transverse shaft at one end of said first arm, said shaft carrying said sucker arms, a second arm fixed to said shaft, said one arm of said bell crank lever and a draw bar of variable length connecting said second arm with said one bellcrank lever arm.

12. A sheet feeding device according to claim 9, comprising means for sensing the level of the top of said pile of sheets comprising a feeler carried by said quadrilateral mechanism and engageable with the top of said pile and a microswitch actuatable by said quadrilateral mechanism.

13. A sheet feeding device according to claim 12, comprising means for sensing the exhaustion of the sheets of said pile, said pile being supported on a nonconductive conductive support, said sensing means comprising means engaging the top sheet of said pile and responsive to the conduction of said metal sheets.

14. A sheet feeding device according to claim 1, comprising means for positioning a sheet on said table, said positioning means comprising abutments for two edges of said sheet, pressure fluid operable means for moving said sheet into engagement with said abutments and microswitches for controlling said pressure fluid operable means.

15. A sheet feeding device according to claim 1, comprising means for sensing a double sheet delivered by said delivery means and means controlled by said sensing means for deflecting said double sheet away from said feeding unit.

16. A sheet feeding device according to claim 1, in which said belt has a forward end portion supported by one said pulley ahead of said plate, and in which a guide roller is positioned under said one pulley, said sheet delivered by said sheet delivering means passing between said guide roller and said pulley.

17. A sheet feeding device according to claim 16, comprising means for sensing a double sheet delivered by said sheet delivering means and means controlled by said sensing means for deflecting said double sheet, said deflecting means being between said guide roller and said plate.

18. A sheet feeding device according to claim I, in which said sheet feeding unit comprises two side members one of which is fixed to said crosspiece and the other of which is movable along said crosspiece to vary the distance between said side members, said shafts extending between said side members.

19. An automatic sheet feeding device, comprising a conveyor arrangement and means for feeding a sheet to the conveyor arrangement, the feeding means including an arm, at

least one suckermounted on the arm for engaging a surface of a sheet to be fed, and a linkage including four articulated members arranged in the form of a quadrilateral, the linkage including a first member pivotally mounted between its ends, a second member pivotally connected adjacent one end of the first member, the second member forming part of a lever, a roller pivotally connected at one end of the second member, a third member pivotally connected by one end to the opposite end of the roller, and a fourth member pivotally connected to the opposite end of the third member and pivotally connected to the opposite end of the first member, said arm being connected to the fourth member for movement therewith, a stop positioned to engage the roller when the linkage occupies a first inoperative position, resilient means for biasing the linkage towards said first inoperative position, and means for exerting a force on the linkage to move the linkage between the first inoperative position and a second delivery position, said force exerting means being arranged to engage a surface of the lever whereby the first member is caused initially to pivot, so that the arm is lifted, subsequent pivotal movement of the first member causing the roller to clear the stop and permit pivotal movement of the second member and consequently the relative pivotal movement of the linkage to cause the linkage to move to the second delivery position at which position the sucker is adjacent an entrance zone of the conveyor arrangement.

Claims

18. A sheet feeding device according to claim 1, in which said sheet feeding unit comprises two side members one of which is fixed to said crosspiece and the other of which is movable along said crosspiece to vary the distance between said side members, said shafts extending between said side members.

19. An automatic sheet feeding device, comprising a conveyor arrangement and means for feeding a sheet to the conveyor arrangement, the feeding means including an arm, at least one sucker mounted on the arm for engaging a surface of a sheet to be fed, and a linkage including four articulated members arranged in the form of a quadrilateral, the linkage including a first member pivotally mounted between its ends, a second member pivotally connected adjacent one end of the first member, the second member forming part of a lever, a roller pivotally connected at one end of the second member, a third member pivotally connected by one end to the opposite end of the roller, and a fourth member pivotally connected to the opposite end of the third member and pivotally connected to the opposite end of the first member, said arm being connected to the fourth member for movement therewith, a stop positioned to engage the roller when the linkage occupies a first inoperative position, resilient means for biasing the linkage towards said first inoperative position, and means for exerting a force on the linkage to move the linkage between the first inoperative position and a second delivery position, said force exerting means being arranged to engage a surface of the lever whereby the first member is caused initially to pivot, so that the arm is lifted, subsequent pivotal movement of the first member causing the roller to clear the stop and permit pivotal movement of the second member and consequently the relative pivotal movement of the linkage to cause the linkage to move to the second delivery position at which position the sucker is adjacent an entrance zone of the conveyor arrangement.