Document Handling Device Provided With A Number Of Rotatable Hollow Drums With Suction Openings

Abstract

Suction openings in a rotating drum are alternately connected to or disconnected from the vacuum maintained inside the drum, when this is necessary to grip and transport a document, and to release it, respectively. Activation of a group of suction openings is effected by a diaphragm valve, supported by the drum in the interior thereof, with associated pneumatic logical switching means to operate the valve. The switching means have ports, connected to the high and low pneumatic feed levels, existing outside and inside the drum, respectively, and to a pneumatic signal line, providing a connection, insensitive to the drum rotation, with an external, fixed source of control signals for document transport. Other control signals may be generated by the presence or absence of a document on the drum. Various drums of this kind, rotating in opposite directions, are disposed closely together to form a high speed selective document transport system.

Description

BACKGROUND OF THE INVENTION

In general the invention relates to high speed document handling devices and more specifically to selective transport devices provided with a number of rotatable hollow drums with suction openings in their cylinder walls.

For a number of years already systems for the selective transport of single documents, such as cards or slack forms, have been known, which are built up from a number of elementary transport units. Each elementary transport unit comprises a driven rotatable drum, the internal cavity of which is connected to a vacuum pump via a hollow shaft. Suction openings in the cylinder wall communicate with the vacuum, maintained inside the drum. A document presented to the drum is gripped and transported until it is released.

Two methods to control gripping and releasing have been used up till now. A first method comprised the use of external mechanical or pneumatic means, permitting the document to approach the drum closely, so that it is gripped; other similar means are used in another place to separate the leading edge of the document from the drum, so that the document is peeled off and entirely released. The second method comprised switching the vacuum in the drum.

Both known methods for the selective control of the document transport unit with rotating drum are attended by difficulties and drawbacks. A difficulty with external mechanical and pneumatical means is that they require separate actuation, accurate adjustment and frequent maintenance, which renders the device cumbersome and expensive. A further drawback is that the uninterrupted energization of the suction openings is indeed convenient, but relatively costly because the exertion of suction in the absence of a document resulting in a heavy load for the vacuum pump without any useful result.

On the other hand vacuum switching is indeed suitable for reducing the greatest losses, but it has the drawback of operating comparatively slowly, because of the relatively large volume to be evacuated again each time, which also causes unreliable operation and still considerable losses. If it is attempted to improve the pneumatic slowness by decreasing the volume of the vacuum space, this causes the disadvantage that the buffer effect of a locally large volume of vacuum close to the suction openings is lost, with the adverse effect that a perforation or tear in the document will strongly affect the suction force and consequently render proper operation uncertain. Furthermore, a thick-walled drum enclosing a small vacuum space will have the disadvantage of a much higher mechanical moment of inertia as compared with thin-walled drums.

SUMMARY OF THE INVENTION

The object of the invention is to remove the above-mentioned difficulties and drawbacks by providing an improved device for the selective transport of documents, with a number of rotating drums provided with suction openings.

More specifically, the object of the invention is to provide a rotating drum with suction openings, combining a low mechanical moment of inertia with low pneumatic losses, while gripping and releasing of documents can be controlled easily, surely and quickly by low power pneumatic signals.

According to the invention these objects are achieved by providing a pneumatically actuated diaphragm valve, supported by the drum inside the internal vacuum chamber, opposite a suction opening or group of suction openings, and adapted either to close these openings to the vacuum or to place them in free communication therewith, and pneumatic logical switching means, likewise supported by the drum inside the vacuum chamber and connected to the diaphragm valve for selective actuation thereof, in order to render the suction openings operative any time a document is to be gripped, or to close the openings when no document is to be gripped or a document previously gripped is to be released. This offers the advantages that during operation the vacuum inside the large vacuum chamber need never be switched off and subsequently established again, but can be maintained permanently, while all the suction openings can be very quickly switched between the unactuated and the fully actuated states. The diaphragm valve combines very rapid operation with extremely long life, simple and inexpensive construction and low weight, which properties are all favorable for the present application.

Pneumatic logical switching means have been known for some years in various embodiments, which likewise combine light weight and simple construction with rapid operation and long life.

According to the invention these switching means preferably comprise a pneumatic power switch, connected, by way of a channel opening into the drum wall, to the surrounding atmosphere, which is the required high pneumatic level, whereas the other side of the switch is connected, by way of an orifice, to the vacuum in the vacuum chamber, which serves as the required low pneumatic level, the switch selectively connecting the diaphragm valve to either the high or the low level, in response to pneumatic switch control signals. This power switch may advantageously be a fluid amplifier, preferably a bistable jet amplifier with at least one control input, connected to a source of pneumatic control signals.

In a first embodiment the pneumatic logical switching means are connected to an external, fixed source of pneumatic control signals for document transport by way of at least one signal line, which is insensitive to rotation of the drum. A signal line insensitive to rotation is preferably provided with a pnuematic slip ring, as will be described in further detail hereinafter.

In a second embodiment a pneumatic signal line is connected to an observation orifice in the cylindrical drum wall, appropriately disposed, so that signals are generated by the presence or absence of a gripped document on the drum.

According to the invention there are preferably two suction openings or groups of suction openings in a drum, each energized by a separate diaphragm valve with associated separate pneumatic logical switching means, the first group of which is controlled in accordance with the above-mentioned first embodiment for gripping the leading edge of a document, the second group being controlled in accordance with the above-mentioned second embodiment, for automatically gripping or releasing the trailing edge of said document.

Further characteristics and advantages of the invention will be evident from the following detailed description of a preferred embodiment with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view, partly cut away and partly sectioned, of a simple preferred embodiment of the invention, comprising two rotating drums.

FIGS. 2a and 2b show two different operational states of a first group of suction openings in the drum wall, with an associated first diaphragm valve and first pneumatic logical switching means, as a detail of the device of FIG. 1.

FIGS. 3a and 3b show two different operational states of a second group of suction openings in the drum wall, with an associated second diaphragm valve and second pneumatic logical switching means, as another detail of the device of FIG. 1.

FIG. 4 shows a section of the hollow drum shaft, detail of the device of FIG. 1, here shown to a larger scale.

DETAILED DESCRIPTION OF THE INVENTION

The simple embodiment of the invention shown in FIG. 1 comprises two rotatable hollow drums 11 and 12 with suction openings. The drums are disposed with a small space between and will be driven in opposite directions. A document taken along on one of the drums passes the other drum very closely, so that it is presented to the other drum to grip it. The document can thus be transferred from one drum to the other, if this is so determined by externally generated control signals. It is also possible for the document to remain on one drum or the other for a longer time and to be carried round repeatedly until the moment it is transferred to the other drum. In FIG. 1 a document 10 is shown which is being transferred from drum 11 to drum 12. The peripheral velocities of the two drums are equal. Also, in this example, equal dimensions have been selected for the two drums. Therefore, only drum 12 will be described in detail. Drum 12 has a flat bottom integral with the cylindrical wall. The open top can be hermetically sealed by means of a lid, provided with a packing ring (as drawn partially at 13 for drum 11). The cylindrical wall is provided with two groups of suction openings 14 and 15. Inside drum 12, opposite openings 14, is valve housing 16, which has a wedge-shaped recess 17 (FIG. 2a), the wide end of which rests against wall 12, around the group of openings 14, the narrow end converging into throat 18.

As shown in FIG. 2a, throat 18 can be closed by means of a diaphragm 19, in which case the suction openings 14 are not energized. However, if diaphragm 19 is retracted from throat 18, as shown in FIG. 2b, recess 17 will communicate, by way of throat 18, disk-shaped cavity 20 and channel 21, with the internal space of drum 12, containing air of subatmospheric pressure, hereinafter to be called "vacuum," during operation of the device. How the vacuum inside drum 12 is effected, will be described later.

It will be evident that the retracted position of diaphragm 19 in FIG. 2b causes suction through the openings 14, air being sucked in from the outside atmosphere and drawn to the vacuum through throat 18 and channel 21. The suction can grip a document 10, if this is already in the vicinity, so that the openings 14 are closed by the document and in the aggregate only little air is drawn in to enable gripping of the document. Thus it will be evident that switching the suction openings by means of a diaphragm valve makes low losses possible, in that only the pressure in the comparatively small volume of recess 17 is switched and the vacuum inside the comparatively large internal space of drum 12 can be kept constant.

Diaphragm 19 is switched at high speed on account of its very small mass and it has long life. A suitable material is, for example, a polyurethane film of 0.1 to 0.3 mm thick. The diaphragm rests against a perforated supporting disk 24 when it has not been made operative (FIG. 2b). Pressure developed behind disk 24 will make diaphragm 19 operative and lift it (FIG. 2a), to close throat 18, the quickly restored vacuum in disk shaped cavity 20 outside diaphragm 19 aiding in pressing the diaphragm tightly against throat 18.

Cavity 25 in valve housing 16 behind disk 24 and diaphragm 19 form part of pneumatic logical control means, generally indicated with 30. As can be seen in FIG. 1, these comprise a channel 31, communicating with the outside atmosphere through an orifice 32 in the lid (not shown) of drum 12 (or in the bottom of 12, if so desired). The other end of channel 31 is connected to a cavity 33, serving as a local source of high pneumatic pressure to feed a jet amplifier of known design. The latter furthermore comprises the following channels: a throat 34, two legs 35 and 36 at an acute angle and two control orifices 37 and 38. One leg 35 opens into cavity 25 and is furthermore connected to the internal space of drum 12 via exhaust port 39, the other leg 36 directly opening into this vacuum space. The vacuum inside drum 12 serves as the low feed level for the pneumatic logical control means 30. Channel 31 may be provided with a dust filter. It is well known that as regards the position of the legs 35, 36 in respect of throat 34, a jet amplifier of symmetrical construction may assume an arbitrary one of two stable operational states, dependent on the most recent control signal received in either of the two control orifices 37 and 38. As can be seen in FIG. 1, the latter are connected by means of tubes 141, 142, respectively, coupled, along channels to be described later, to an external fixed source (not shown) of pneumatic control signals. Thus, if lastly a pressure signal was received by way of tube 141 and control orifice 37, the jet streaming from throat 34 will be directed into leg 35, building up a pressure in cavity 25 behind diaphragm 19, to close throat 18 and make suction openings 14 in drum 12 inoperative (FIG. 2a). However, as soon as a pressure signal is supplied by way of tube 142 and control orifice 38, the jet from throat 34 is deflected to leg 36, the pressure built up in cavity 25 disappearing immediately by way of exhaust port 39 to the surrounding vacuum. Consequently, diaphragm 19 is retracted against disk 24, to make throat 18 free. The openings 14 are made operative to suck and to grip document 10 (FIG. 2b).

Upon initiating operation of the document handling device, vacuum is applied to the interior of drum 12 and a pressure control signal is applied by way of duct 37 (FIG. 2a). The resulting pressure build-up in cavity 25, due to the jet from throat 34, causes diaphragm 19 to move from the relaxed straight position of FIG. 2b and assume the bowed position shown in FIG. 2a. Although ambient pressure is present at both cavity 33 and exteriorly of openings 14, the diaphragm will move to close off throat 18. The precise reasons for this behavior are not understood but the pressure differentials are sufficient to produce the described reaction.

Switching between inoperative and operative states of the suction openings 14 is effected very quickly and at a time that can be determined accurately, i.e., in a position of drum 12 that can be determined accurately. At a rotation rate of, e.g., 2,000 rpm an angle of rotation of 1.degree. corresponds to a time of 0.08 msec. The delay in consequence of the operation of jet amplifier 30 and diaphragm valve 19 together is very small and well reproducible. The presence of a large local buffer space for the vacuum, namely the whole interior of drum 12, guarantees a quick start of the suction, with a likewise reproducible, small delay. The delay of the low-power control-pressure signal between the external signal source and control orifice 37 is constant and can be measured. The local availability of high and low pneumatic feed levels makes it possible to apply local signal processing and signal amplification, which ensures reliable operation.

FIGS. 3a and 3b show that the second group of suction openings 15 in drum 12 is controlled by a second diaphragm valve 19, in a manner identical to that described for the openings 14 in FIGS. 2a and 2b. The operative state of suction openings 15 is shown in FIG. 3b. The only difference has relation to the pneumatic logical control means 30' for controlling the pressure in cavity 25 behind diaphragm 19 in FIGS. 3aand 3b. In this example these comprise a channel 41, connecting cavity 25 to an observation opening 42 in the cylindrical drum wall 12. A narrow bleeder 43 connects channel 41 to the vacuum space surrounding valve housing 26. Observation opening 42 is located in cylinder wall 12, between the groups of openings 14 and 15, as represented in FIG. 1.

When the leading part of document 10 is gripped by the first group of suction openings 14, as illustrated in FIG. 1, observation opening 42 will be covered by the document as soon as drum 12 has rotated sufficiently. Consequently space 25 behind diaphragm 19 in valve housing 26 is shut off from the outside atmosphere, the air present being drawn away to the surrounding vacuum through bleeder 43. After a constant delay a sufficient vacuum has been obtained in cavity 25, diaphragm 19 being retracted from throat 18, so that openings 15 communicate with the vacuum via channel 21 and are made operative to grip document 10. Bleeder 43 is so narrow that said delay corresponds to the time for rotating the drum through the angle between observation opening 42 and the group of suction openings 15. Thus also the trailing part of document 10 is tightly gripped by drum 12 in consequence of the energization of the second group of suction openings 15, which is effected automatically at the proper time.

If, conversely, document 10 is to be transferred from drum 12 to drum 11 (or other means, not shown, such as a third drum), this is effected by applying, at the appropriate time, shortly before the transfer begins, a pneumatic signal to control orifice 37 of the pneumatic switching means 30 by way of tube 141. As described with reference to FIG. 2a, the suction openings 14 become inoperative, consequently. The leading part of document 10 is no longer gripped by drum 12 and is transferred to drum 11, which is possible in consequence of its having a similar first group of suction openings, which are opposite the first suction openings 14 in drum 12 at this moment and are energized by similar control means. Upon further rotation of drum 12 further portions of document 10 are transferred, to release observation opening 42, the document being drawn loose therefrom with little force. This also ends the energization of the second group of suction openings 15, as shown in FIG. 3a, whereupon the trailing portion of document 10 is transferred without difficulty. From this it will be evident that during transfer the document is never entirely loose from the two synchronized drums. Consequently the correct time position of a document on one of the synchronized drums will not be lost, even after many hundreds of transfers of this document between the drums, as verified experimentally. In the device according to the invention the risk of paper jamming has therefore been virtually eliminated.

As with the diaphragm controlling vacuum in openings 14, diaphragm 19 for also controlling the vacuum applied to openings 15 will move from the relaxed, straight position of FIG. 3b to the bowed position shown in FIG. 3a when the drum interior is initially evacuated. This change will block the application of vacuum to openings 15. Again the precise reasons for this reaction are not fully understood since the affected volumes have not been fully investigated as to comparative pressures. However, the pressure differentials are adequate to produce the diaphragm movement.

The manner in which vacuum is effected inside drum 12 and the path along which pneumatic signals are applied to control logic 30 will now be described with reference to FIGS. 4 and 1.

The bottom of drum 12 is secured, by means of screws 50, to flange 51 of a hollow shaft 52 and also to flange 53 of a gear 54, adapted to be driven by a toothed belt, not shown. Hollow shaft 52 is open at the top and communicates with the inside space of drum 12 by way of an opening in the bottom of the drum. The lower end of shaft 52 is solid and comprises two channels, as shown in FIG. 4. At half its height shaft 52 has a number of circular openings. Shaft 52 is rotatably supported in a fixed bushing 55 by means of a needle roller bearing 56 and a ball bearing 57. Bushing 55 will be secured to a supporting frame. The lower end of bushing 55 is closed with a screwed cap 58.

The vacuum inside drum 12 is effected by a connection with a vacuum pump, not shown, along the following path: the hollow space inside shaft 52, an annular recess 60 in bushing 55 opposite said circular openings in shaft 52, nipple 61, tube 62, and T-piece 63, branch 64 of which is connected to the pump. This connection is independent of the rotation of shaft 52 on account of the annular recess 60, with which a channel in the rotatable part 52 and a channel in the fixed part 55 communicate. Such a connection will be called a "pneumatic slip ring." Leakage is prevented by two O-rings 65 and 66, disposed for sealing purposes in recesses in bushing 55 on either side of pneumatic slip ring 60.

Pneumatic control signals from an external control unit are applied along either of two parallel paths: tubes 70 and 71, pneumatic slip rings 72, 73, respectively, connected to tubes 74, 75, respectively, by way of channels in the solid lower part of shaft 52. These tubes run through the cavity in shaft 52; their upper ends are held by a strip 76 and are connected to the tubes 141, 142, respectively, which, as described, are connected to the pneumatic logical control means 30.

It will be evident that the simple embodiment of a selective high-speed document transport device according to the invention, described in the foregoing, may be altered and extended in many ways without departing from the essence and scope of the invention. Whereas the simplest embodiment would comprise a single drum, the number of drums may be three or any larger number, dependent on the function contemplated, such as reading, endorsing, classifying, sorting or any other document processing. Two drums are already sufficient to successively expose both surfaces of a document without any restriction, as would be imposed by pressure or guide means, which are superfluous here. The total absence of such external rolls, belts, nozzles, etc. makes it easy to arrange several drums in any desired configuration. The dimensions of the drums need not necessarily be equal; their diameters may be in a proportion of 1:2 or another simple proportion. It is only necessary for the peripheral velocities of the drums to be equal and that the suction openings 14 for the leading document edge in one drum will be opposite similar openings in the adjacent drum.

Furthermore, it is possible to vary the pneumatic logical switching means 30 and 30', which are carried along in the drum for operation of the valve diaphragms 19. Signal amplification may be applied for example in several stages. If a monostable signal amplifier is used instead of a bistable one, a single external signal line will be sufficient, but this requires a more intricate switching logic. For example, an external signal, received with no document on the drum, would mean that a document is to be gripped. Observation of the document gripped, by means of an observation opening such as 42, would result in an indefinite extension of the gripping instruction. Another external signal, received with a document on the drum, would mean releasing the document. Such variations will now be evident for an expert in the field of pneumatic switching logic.

Claims

What is claimed is:

1. Apparatus for transporting documents comprising:

a rotatably supported drum having at least one first opening and one second opening in the surface thereof communicating with the interior of said drum, said openings being spaced on said surface to be covered by the leading and trailing portions respectively, of a document carried on said drum surface;

means providing a vacuum within said drum interior;

first and second valve means, each actuatable to selectively connect their respective first and second openings with said vacuum to attract a said document to said surface;

first switching means in said drum for actuating said first valve means in response to a fluid pressure signal; and

second switching means in said drum including an observation port on said surface for actuating said second valve means in response to the presence of a said document being carried on said surface.

2. Apparatus as described in claim 1 wherein

said observation port is located on said surface between said first and second openings to be covered by a document when carried by said drum.

3. Apparatus as described in claim 7 wherein said second switching means includes a duct connected to said observation port and said duct includes a bleeder orifice connected with said drum vacuum, said bleeder orifice being of a size to establish a fluid pressure in said duct less than ambient pressure when said observation port is covered by said document.

4. Apparatus as described in claim 1 wherein

said first valve means is actuatable between a first position to connect its said openings to said vacuum and a second position to connect said openings with fluid at the ambient pressure, and

said first switching means is operable in response to first fluid pressure signals to actuate said first valve means to said first position and to second fluid pressure signals to actuate said valve means to said second position.

5. Apparatus as described in claim 1, wherein

said first valve means includes a flexible diaphragm and said first switching means includes a fluid pressure amplifier responsive to said fluid pressure signals for actuating said diaphragm.

6. Apparatus as described in claim 5 further including wall means enclosing said first openings, and converging to a valve port facing said flexible diaphragm therefor that is narrower than the portion of drum surface having said openings therein.

7. Apparatus as described in claim 6 wherein

said flexible diaphragm is adapted to block said converging valve port from said vacuum and has an area greater than said valve port exposed to the output pressure of said amplifier which contributes a force to keeping said valve port closed.