GB2126996A

GB2126996A - Bottom sheet separator-feeder

Info

Publication number: GB2126996A
Application number: GB08325189A
Authority: GB
Inventors: Kiri Banda Amarakoon; Ian Grant Brown
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1982-09-21
Filing date: 1983-09-21
Publication date: 1984-04-04
Also published as: GB2126996B; GB8325189D0

Abstract

A bottom sheet separator-feeder for separating and forwarding sheets seriatim from the bottom of a stack 7 of sheets comprises a stack tray 5 for supporting the stack, vacuum feed belts 37 extending through the front end of tray 5 for acquiring and advancing the bottom sheet in the stack, and an air knife 12 which provides a layer of air between the bottom sheet and the remainder of the stack and between the bottom sheet and the tray. Means 61 is provided for automatically varying the air pressure in the air knife 12 in dependence upon the amount of paper in the stack 7 so that the greater is the amount of paper the greater is the air pressure. In one form the weight of the stack 7 is sensed and in another embodiment the height of the stack 7 is sensed. <IMAGE>

Description

SPECIFICATION Bottom sheet separator-feeder This invention relates to bottom sheet separator feeders for separating and forwarding sheets seriatim from the bottom of a stack of the sheets. The invention is particularly concerned with such feeders comprising a stack tray for supporting a stack of sheets to be fed and feed belt means extending through at least the front of the stack tray for acquiring and advancing the bottom sheet of the stack.

In order to assist in separation of the bottom sheet from the stack, it has been proposed to provide air injection means adapted to provide a layer of air between the stack tray and the bottom sheet in the stack and between the bottom sheet and the remainder of the sheets in the stack. This air injection means suitably comprises an air knife facing the leading edge of the stack and having a plurality of spaced discharged orifices therein which provide a plurality of diverging and expanding air streams. Such air injection means are described for example in U.S. Patent Nos.

4270 746, 4 275 877, 4 284 270 and 4 305 576. In such prior art arrangements air pressure is constant and unvariable. U.S. Patent No. 4 269 406 also describes such air injection means in which the air pressure at the injection means is adjusted automatically according to the thickness of sheets in the stack. This is achieved by having vacuum feed belts arranged in a pocket in the bottom of the tray and a single blower providing negative air pressure at the vacuum feed belts and positive pressure at the air injection means. A thin sheet acquired by the feed belts will more nearly conform to the shape of the pocket than a thicker sheet thus lowering air flow to the blower compared with a thicker sheet.

The arrangement described in U.S. Patent No.

4 269 406 serves to distinguish between heavier and lighter sheets but is not sensitive to the amount of paper in the stack. It has been found that a pressure of air from the air injection means suitable for handling larger stacks of medium and heavy weight papers is not suitable for small stacks particularly small stacks of light weight papers where blow-away of the top sheets tends to occur.

The sheet separator-feeders described in the prior art documents referred to above are utilized in automatic document handlers for a photocopier in which the document set is circulated a plurality of times, the documents being delivered in turn to the platen of a photocopier and returned to the top of the stack in the tray. Sheet feeders of the type with which this invention is concerned may also be utilised for feeding copy sheets in photocopiers. In such cases not only does the stack height vary with the amount of paper that is inserted but the stack height decreases as the sheets are fed.

It has been found that improved performance is achieved in bottom sheet separator feeders of the type to which this invention is directed if the air injection pressure can be varied to compensate for stack size and the present invention is characterised in that means is provided for automatically varying the air pressure of the air injection means in dependence upon the amount of paper in the stack so that the greater is the amount of paper the greater is the air pressure.

In a bottom sheet separator feeder according to this invention the sheet acquisition and advancing means preferably comprises air previous belt means and vacuum means for applying a negative pressure at the back of the belt means to engage a sheet against the belt means. In accordance with a preferred feature of this invention the negative pressure at the back of the belt means is also automatically variable in dependence upon the amount of paper in the stack. Suitably the pressure varying means is common to the air injection means and the vacuum means.In a preferred embodiment the stack tray has a U-shaped pocket formed therein and a plurality of said vacuum feed belts are disposed in said pocket in said tray and adapted to pull the bottom sheet in the stack into the pocket and feed the sheet from beneath the sheet stack, a portion of the centre belt of said vacuum feed belt being spaced slightly above the remaining belts such that when the bottom sheet in the stack is forced into contact with the belt, a temporary corrugation is formed in the belt. Such an arrangement in combination with the air injection means has been found to provide particularly efficacious operation.

In a preferred form of the invention, the pressure either of the air injection means and the vacuum means is automatically varied in dependence upon the weight of paper in the stack. In the case of a sheet feeder the air pressure may be varied during sheet feeding proportionally to the weight of paper remaining in the stack. In one embodiment the pressure varying means includes control pressure producing means comprising a sensing aperture in the stack tray arranged to be overlaid by sheet(s) in said tray and a duct for delivering air under pressure to the aperture whereby a control pressure proportional to the stack weight is produced, and adjustment means responsive to said control pressure for varying said air pressure of said air injection means or of said air injection means and said vacuum means proportionately to said control pressure.The delivery duct is suitably a tapping off a supply duct for delivering air under pressure to the air injection means and the control pressure may be produced in the delivery duct or in a tapping off the delivery duct.

The air pressure adjustment means may comprise a valve, preferably to atmosphere, in the supply duct, or alternatively it may adjust a blower for delivering air through the supply duct, said blower suitably also serving to create negative pressure at the vacuum means.

In another form of the invention the air pressure is automatically varied in dependence of the height of the stack. Thus in one embodiment the air pressure varying means includes stack height sensing means for sensing the stack height, means for generating a control signal indicative of said stack height and adjustment means responsive to said control signal for varying said air pressure of said air injection means or of said air injection means and said vacuum means. In the case of a sheet feeder for feeding copy sheets, the stack height sensing means preferably includes means for sensing the initial height of a stack and means for sensing the consumption of a stack, for example by counting the sheets being fed. Suitably the control signal modulates the voltage or current to the motor of the blower by which the air pressure(s) is/are generated.

In order that the invention may be more readily understood, reference will now be made to the accompanying drawings in which: Figure 1 shows a document handler for a copying machine incorporating a bottom sheet separator-feeder according to the invention, Figure 2 is an enlarged, cross sectional view of the separator-feeder of the document handler shown in Figure 1 with the air injection means shown somewhat schematically, Figure 3 shows a slightly modified separator feeder with the air injection means shown in greater detail, Figure 4 is an end view, partially in section, of the vacuum feeder belts illustrated in Figure 2, Figure 5 is a top view of the document tray and feed belts of the document handler illustrated in Figure 1, Figure 6 is a perspective view of the separatorfeeder of Figures 1 to 5 showing one embodiment of pressure-varying means in accordance with this invention, Figure 7 is a scrap schematic side view of the embodiment of Figure 6, Figure 8 is a scrap schematic bottom view of the embodiment of Figure 6, Figure 9 is a schematic view of another embodiment of air pressure varying means, Figure 10 shows a mechanism for controlling the relief valve of the embodiment shown in Figure 9, Figure 11 shows a further embodiment of air pressure varying means, and Figure 12 is a schematic side view of a further embodiment of sheet feeder according to this invention, Referring to the drawings, there is illustrated an automatic document handler 1 for installation above the exposure platen 3 of a xerographic reproduction machine for repeatedly feeding documents from a stack 7 in turn to the platen 3, where they are exposed to make a copy, and back to the stack. The document handler is provided with a document tray 5 to be explained more fully hereinafter, adapted for supporting the documents 7 fece up. A vacuum belt-corrugating feeder mechanism 9 is located below the document tray for acquiring and corrugating the bottom document in the stack and forwarding the document to take-away roll pair 11 after an air injection device or air knife 12 has had time to separate sheet one from the rest of the stack.The document is then fed by take-away roll pair 11 through document guide 13 to feed-roll pair 1 5 and under platen belt 1 7 onto the platen of the copy machine for reproduction. After exposure of the document, it is fed off the platen by belt 17 into guide 19 and feed-roll pairs 21 and 23 and back to the document stack through the feed-roll 27 either directly or through an inverter mechanism 25. A diverter 29 is provided to divert the document either to the inverter or to the feed roll pair 27. The inverter 25, which is of a kind well-known in the art, serves to turn the documents over so that their opposite faces will be exposed during the next circulation.

The document handler is also provided with a sheet separator finger 35 as is well known in the art to separate the documents to be fed from those documents returned to the document handler. Upon removal of the last document from beneath sheet separator finger 35, the finger 35 drops through a slot provided in the tray, suitable sensors are provided to sense that the last document in the set has been removed from the tray and the finger is then rotated in a clockwise direction to again come to rest on the top of the documents in the stack prior to subsequent recirculation of the document set.

Referring more particularly to Figures 2, 3, 4 and 5 wherein the document separator-feeder is more clearly illustrated, there is disclosed a plurality of feed belts 37 supported for movement on feed belt rolls 38, 39 and 40. Spaced within the run of the belts 37 there is provided a vacuum plenum 41 having openings 43 (Figs. 3 and 5) therein adapted for cooperation with perforations 45 in the belts 37 to provide a vacuum for pulling the bottom document in the document stack onto the belts 37. As can be seen from Figure 3, the plenum is provided with a raised portion 48 beneath the centre belt run so that upon capture of the bottom document in the stack against belts 37, a center corrugation will be produced in the bottom sheet. Note also that the belts are below the surrounding support surfaces.Thus the document is corrugated into a double valley configuration. The flat surfaces of the vacuum belts on each side of the raised centre belt generate a region of maximum stress in the document which varies with the document beam strength. In the unlikely event that more than one document is pulled down into contact with the feed belts, the beam strength of the second document resists the corrugating action, thus gaps are opened between sheets one and two which extend to their lead edges. These gaps reduce the vacuum levels between sheets one and two due to porosity in sheet one and provide for entry of the separating air flow from the air knife 1 2. The air knife 1 2 comprised of pressurized air plenum 50 having a plurality of air jet openings 51 is provided to inject air ntc. the pocket formed between the document pulled down against the feed belt and the documents thereabove to provide an air cushion or bearing between the stack and the bottom document to minimize the force necessary for removing the bottom document from the stack.It can be understood that if two documents are pulled down toward the belts 37, since the top sheet would not be corrugated, the air knife would inject air into the space between the two documents and force the second document off from the raised belt back toward the document stack.

8y suitable valving and controls, it is desirable to provide a delay between the time the vacuum is applied to pull the document onto the belts and the start up of the feed belts to assure that the bottom document is captured on the belt before belt movement commences and to allow time for the air knife to separate sheet 1 from any sheets that were pulled down with it.

By reference to Figures 1,2 and 5 it can be seen that the document tray 5 is provided with a depressed portion or pocket 53 behind the feed belt assembly. This pocket serves a number of purposes. First, space is provided for the forward portion of the bottom document to be pulled down onto the feed belt assembly providing for formation of the two valley corrugation previously mentioned. When the bottom document is pulled onto this space and corrugated, an envelope type opening or pocket is created between the bottom sheet and the remainder of the sheets in the stack. Air injected into this space from the air knife produces an air bearing between the bottom sheet and the remainder of the stack to allow easy removal of the bottom sheet from beneath the stack.Flow of air from the pocket is restricted by the partial seal or flow restriction caused by supporting the major portion of the stack weight on the edge portions of the tray surrounding the pocket.

To further increase the efficiency of the system, the stack tray is provided with a rearward tilt as seen in Figures 1 and 2. When floatation air is provided under the stack or between the first and second sheets, gravity will allow the sheets to settle or float back against the rear tray wall.

Thus, the sheet being removed is pulled uphill while gravity helps hold the remainder of the sheets back, helping to prevent multifeeds.

By reference to Figure 1, it can be seen that a single blower unit 55 is utilized to provide subatmospheric or negative air pressure in plenum 41 and pressurized air to air knife 12.

In accordance with this invention the document separator-feeder described above is provided with means for automatically varying the air pressure of the air knife 12 in dependence upon the amount of paper in the stack in the tray 5 so that the greater is the amount of paper, the greater is the air pressure. Further as will become apparent, by virtue of the common blower for the air knife 12 and the vacuum plenum 41, the negative air pressure applied at the back of the belts 37 will also be automatically varied in dependence upon the amount of paper in the stack.

A first embodiment of air pressure varying means is illustrated in Figure 6. Variation in the air flow to the air knife 12 is provided by a valve 61 in a supply duct 62 leading from the blower 55 to the air knife 12. When the valve 61 is opened the air pressure to the air knife 12 is reduced.

Automatic adjustment of the valve 61 in accordance with the amount of paper in the tray 5 is achieved by producing a control pressure which is used to adjust the valve as will now be described.

A sensing aperture 63 in the floor of the stack tray 5 is arranged to be overlaid by sheet(s) in the tray and a delivery duct 64 which is a tapping off of the supply duct 62 delivers air under pressure to the aperture 63 whereby a control pressure proportional to the stack weight is produced in the duct 64. Thus it will be realised that the greater the weight of paper overlying the orifice 63 the greater will be the pressure build up in the duct 64. As will be seen from Figures 7 and 8 the valve 61 is so constructed that it is responsive to the control pressure. Thus, the valve 61 is a flap valve having a flap 71 which serves to obstruct an opening 72 in the wall of the duct 62. The delivery duct 64 is connected to supply duct 62 through a chamber 73 behind the flap 71.Air from the duct 62 is tapped off upstream of the flap 71 through aperture 74 and enters the duct 64 through aperture 75. It will be realised that the less the pressure in the chamber 73 the more the valve 61 will open and thus the less will be the air pressure delivered at the air injection means 12.

Since the pressure in the duct 64 will be less the lighter the stack, the valve 61 will open more for light stacks than heavier stacks so that the air pressure to the air knife 12 will be directly proportional to the weight of paper in the stack.

Thus where there are no documents in the tray the sensing aperture 63 is open to the atmosphere and therefore the pressure in the chamber 73 will drop to a minimum level and allow the flap 71 to open wide due to the differential pressure thus dropping the air knife pressure to a minimum. If a small stack of documents is placed on the tray, pressure in the chamber 73 will build up to a level proportional to the stack weight and close the flap 71 to a corresponding level due to the differential pressure and bring the air knife pressure to an intermediate level. If on the other hand a large stack is placed on the tray the aperture 63 in the tray will be sealed causing the pressure in the chamber 73 to rise to a maximum, in turn causing the flap 71 to close, bringing the air knife pressure to a maximum.

In another embodiment of air pressure varying means according to the invention, as represented schematically in Figure 9 the control pressure is developed in a tapping 65 of the duct 64, the tapping being so arranged relative to the sensing aperture 63 that the pressure developed therein is proportional to the weight of paper in stack. The control pressure P1 developed in the tapping 65 is used to operate a control device 80 which adjusts the air pressure to the air knife. As shown in Figure 9 the control device 80 may adjust the position of a flap valve 61 in the wall of the supply duct 62. The pressure P1 varies in the following manner. When the aperture 63 is open to the atmosphere, the pressure at P1 would be near atmospheric or below it due to the negative pressure created by air rushing past the tapping (pitot action).When a small stack of documents of low weight is placed on the tray the pressure P1 would build up until depending on the stack weight it will be sufficient to lift the stack off the aperture 63 causing air to leak to atmosphere and the pressure P1 will drop to a stable level. Hence the pressure P1 will be proportional to the stack weight. When a large stack of documents of high weight is placed on the tray the pressure P1 would build up to a maximum and would be equal to the supply pressure in the duct 62.

The control mechanism 80 for the adjustment means (valve 61) by which the air pressure to the air knife is varied may take various forms. For example for controlling a flap valve as shown in Figure 9 it may take the form of a simple pneumatic to mechanical transducer device as shown in Figure 10 in which the pressure P1 is used to control a piston 83 which acts on the flap valve 81. Such pneumatic to mechanical transducers may take various forms which will be apparent to those skilled in the art and may control valves of different types.

In another embodiment as shown in Figure 11 the valve 61 has a control diaphram 91 to adjust the opening of an aperture in the wall of the supply duct 62. The control device includes a control housing 92 arranged over the aperture in the duct 62 and defining a chamber 93 behind the diaphram 91. This chamber is connected to the duct 62 through an aperture 94. The pressure tapping 65 from delivery duct 64 is connected to a chamber 65 in the control housing 92 having a diaphram 96 which serves to vary a vent 97 to atmosphere on the chamber 93. Operation of the device is as follows. When the document tray is empty the aperture 63 is wide open and pressure P1 in the line 65 will be at zero or negative.

Thereforthe diaphram 96 will collapse and open vent 97 causing the pressurized air entering the chamber 93 through aperture 94 to vent to atmosphere. Therefore the pressure in the chamber 93 will be low and this will cause the diaphram 91 to collapse due to the pressure from duct 62 which will increase the gap between the diaphram and the duct causing the air knife pressure to drop. If a small stack is placed in the document tray the documents will cover up the aperture 63 causing the pressure in line 65 to build up and depending on the weight of the stack the pressure will tend to lift the stack up and the pressure P1 will stabilise at some value proportional to the stack weight. This sensed pressure will now move the diaphram 96 towards the seat of the vent 97 and partially close the vent depending on the pressure P1 and the pressure in the chamber 93.This in turn will cause the pressure in the chamber 93 to rise causing the diaphram 91 to move towards the opening in the duct 62 due to the differential pressure and reduce the opening in the duct 62 causing the air knife pressure to rise. For a large stack diaphram 96 closes vent 97 sufficiently to cause diaphram 91 to close the opening in the duct causing the air knife pressure to rise to a maximum.

While in the embodiment described above the control pressure developed is used to mechanically control a valve 61 in the supply duct 62 leading from the blower to the air knife, the control pressure may instead be used to vary the speed of the motor which drives the blower 55.

Suitable converters are a wire-wound potentiometer, an optical grey sensor and a Hall effect sensor, all of which provide for proportional variation. An opto-sensor, a magnet and reed device or a micro switch could be used to produce an on/off electrical signal.

Where the blower motor is controlled it will be realised that since the blower is also used to create a negative pressure at the vacuum feed means 9 this negative pressure is proportional to the blower speed and will be varied directly proportionately to the amount of paper in the stack. The negative pressure at the vacuum means may also be controlled in this manner in the case of valve control of the supply pressure to the air knife by providing a similar valve to the air knife adjustment valve 61 in the line between the vacuum plenum and the blower 55. By a suitable arrangement a common control means could be used for both valves or otherwise the pressure line 65 could be bifurcated and lead to two separate control devices.

Of course it may be preferred not to adjust the vacuum pressure according to stack weight. In the case of electrical control of the blower motor, the vacuum means may be supplied by a separate blower.

While an electrical signal may be used ta control the blower motor, it may instead be used to control a solenoid acting on a pressure release valve in the supply line.

In the embodiment described above the present invention has been described in relation to an automatic recircuiating document handler in which the number of sheets placed in the tray remains approximately constant during the operation of the device since sheets are being returned to the tray at the same time as they are being fed out (although an initial stack of say three or four sheets may in fact result in the tray becoming empty between each successive sheet returned to the tray during operation). The invention is however equally applicable to copy sheet feeders in which a stack of sheets placed in a supply tray is progressively consumed.

Figure 12 shows an embodiment of copy sheet separator feeder comprising a stack tray 100 in which copy sheets are placed and a vacuum separator feeder as shown in Figure 2, 4 and 5 and having an air knife 12 similar to that previously described. When a stack of sheets has been placed in the tray it is pivoted about axis 101 prior to sheet feeding buy a motor M1 which elevates the tray at a constant known speed. The motor is switched off when the top of the stack actuates a micro switch 102 and the time for the tray to elevate is determined by a timer T, this time being proportional to the height of the stack.

The timer T generates a signal indicative of time which is conveyed to a controller C which adjusts the motor M2 of the blower 55 proportionately to stack height. The greater the stack height the faster the blower will be driven and thus the greater will be the pressure of the air knife. For feeding the sheets the tray is returned to the full line position shown in Figure 12. In order to allow for diminution in the amount of paper in the stack during sheet feeding a sensor 103 senses the feeding of each sheet and signals a counter CT which is connected to the controller C. In this way the blower motor M2 can be adjusted in accordance with a number of sheets fed.

Instead of elevating the tray as shown in Figure 12 in order to sense the height of the stack the micro switch may be driven downwards against the stack. However, it will be noted that in the former case the sensor does not rest on the stack during the feeding cycle and when the tray is withdrawn for paper loading the device does not need to be deployed then replaced on the top of the stack. For detecting an empty tray condition a dimple is suitably provided in the base of the tray so that if no paper is present the micro switch arm will contact the recessed dimple and based on the timing analogue will indicate no paper present.

The device can also be programmed to detect whether the tray has been overloaded.

Although specific embodiments have been described above it will be understood that various modifications may be made to the specific details referred to herein without departing from the scope of the invention as defined in the appended

Claims

claims.

Thus, in all the embodiments described above the air pressure of the air knife is adjusted in dependence upon the amount of paper in the paper tray either by sensing the weight of the paper as in Figures 6 to 11 or by sensing the height of the stack as in Figure 12. It will be understood, however, that the height sensing technique of Figure 12 may be used in a document feeder as shown in Figures 1 to 5 and conversely the weight sensing technique shown in Figures 6 to

11 may be used in a copy sheet feeder as shown in Figure 12.

Claims 1. A bottom sheet separator-feeder for separating and forwarding sheets seriatim from the bottom of a stack of sheets, comprising a stack tray for supporting a stack of sheets to be fed, feed belt means extending through at least the front end of the stack tray for acquiring and advancing the bottom sheet of the stack and air injection means adapted to provide a layer of air between the stack tray and the bottom sheet in a said stack and between the bottom sheet and the remainder of the sheets in the stack, characterised in that means is provided for automatically varying the air pressure of said air injection means in dependence upon the amount of paper in the stack so that the greater is the amount of paper, the greater is the air pressure.
2. A bottom sheet separator-feeder according to claim 1 in which said sheet acquisition and advancing means comprises air-pervious belt means and vacuum means for applying a negative pressure at the back of the belt means to engage a sheet against the belt means, said negative pressure at the back of the belt means also being variable in dependence upon the amount of paper in the stack.
3. A bottom sheet separation-feeder according to claim 2 in which said pressure varying means is common to said air injection means and said vacuum means.
4. A bottom sheet separation-feeder according to claim 1, wherein said pressure is varied in dependence upon the weight of paper in the stack.
5. A bottom sheet separation-feeder according to claim 4 wherein said pressure is varied proportionately to the weight of paper in the stack.
6. A bottom sheet separator-feeder according to claim 5, wherein said pressure varying means includes: (a) control pressure producing means comprising a sensing aperture in said stack tray arranged to be overlaid by sheet(s) in said tray and a duct for delivering air under pressure to the aperture whereby a control pressure proportional to the stack weight is produced, and (b) adjustment means responsive to said control pressure for varying said air pressure of said air injection means or of said air injection means and said vacuum means proportionately to said control pressure.
7. A bottom sheet separator-feeder according to claim 6 in which said delivery duct is a tapping off said duct for delivering air under pressure to the air injection means.
8. A bottom sheet separator-feeder according to claim 7 in which said air pressure adjustment means comprises a valve, preferably to atmosphere, in said supply duct.
9. A bottom sheet separator-feeder according to claim 6, 7 or 8 in which said control pressure is produced in a tapping off said delivery duct.
10. A bottom sheet separator-feeder according to claim 8 in which said valve includes a control chamber connecting said supply duct and said delivery duct.
11. A bottom sheet separator-feeder according to claim 8 in which said control pressure is produced in a tapping off said delivery duct and said valve is adjusted by a transducer connected to said control pressure tapping which mechanically adjusts said valve in response to said control pressure.
12. A bottom sheet separator-feeder according to claim 8 in which said control pressure is produced in a tapping off said delivery duct and said valve is adjusted by air bled from said supply duct the pressure of such air being controlled by a valve controlled by said control pressure.
13. A bottom sheet separator-feeder according to claim 8 in which said air pressure adjustment means adjusts a blower for delivering air through said supply duct.
1 4. A bottom sheet separator-feeder according to claim 8, 9, 10, 11 or 12, wherein said blower also serves to create negative pressure at said vacuum means.
1 5. A bottom sheet separator-feeder according to claim 1,2 or 3, wherein said air pressure is automatically varied in dependence upon the height of the stack.
16. A bottom sheet separator-feeder according to claim 15, wherein said air pressure varying means includes (a) stack height sensing means for sensing the stack height, (b) means for generating a control signal indicative of said stack height, and (c) adjustment means responsive to said control signal for varying said air pressure of said air injection means or of said air injection means and said vacuum means.
1 7. A bottom sheet separator-feeder according to claim 16, wherein said stack height, sensing means includes (a) means for sensing the initial height of a stack and (b) means for sensing the consumption of the stack, for example by counting the sheets being fed.
1 8. A bottom sheet separator-feeder according to claim 1 6 or 17, wherein said control signal modulates the voltage or current to the motor of a blower by which said air pressure(s) is generated.
19. A bottom sheet separator-feeder constructed, arranged and adapted to operate substantially as hereinbefore described with reference to Figures 1 to 8 of the accompanying drawings.
20. A bottom sheet separator-feeder constructed, arranged and adapted to operate substantially as hereinbefore described with reference to Figures 1 to 5, 9 and 10 of the accompanying drawings.
21. A bottom sheet separator-feeder constructed, arranged and adapted to operate substantially as hereinbefore described with reference to Figures 1 to 5 and 11 of the accompanying drawings.
22. A bottom sheet separator-feeder constructed, arranged and adapted to operate substantially as hereinbefore described with reference to Figure 12 of the accompanying drawings.