Until the 1980s computer printers normally used continual stationery, paper with sprocket holes, made into a fanfold stack with slits cut to give tear-off lines. Cut sheet paper handling appeared around 1980s with feeders made by Rutishauser for the Diablo 1630 / 1640 and another for the Apple Imagewriter. Neither was noted for reliability; they ran unattended in the sense that they would sometimes run for an hour without missing the top or bottom of the page or jamming.

Today's laser and inkjet printer trays are a huge improvement on these predecessors. Paper jams are quite rare and when they happen the problem can usually be traced to damp paper, or cured by changing one or two rollers and a separation pad.

Typewriters did not normally need much by way of a paper feed mechanism because the typist would pick up and position the paper. The platen roller was normally made of rubber and a couple of rows of idle-roller underneath maintained a firm grip on the paper so that it moved in time with the carriage-return line-feed action.

US Patent 1,104,504 by Ivar G Holiday (1914) provides a way to feed cards into a typewriter rapidly. The problem with record cards is that they don't contain all that much, so the typist would spend more time feeding cards than typing. Having a magazine full of cards ready to use removes part of the problem.

Patent 1203657 by JH Sheckler for Underwood Typewriter (1916) develops a magazine for loose sheets, envelopes, telegraphs and suchlike.

Patent 2,227,643 (1941) gives a sheet feeder and positioner for typewriters which positions paper on a humped ramp and pushes it into the printer using a rubber wheel driven from the platen.

Despite a series of inventions over a century cut-sheet handling remained rather unreliable. IBM and others developed the ability to feed cards automatically, but ordinary paper has rather different properties. Paper bends and creases to easily.

Cut sheets can be picked off a stack and fed reliably using a vacuum pickup mechanism. Vacuum cups grip the top surface of the sheet and lift it, the pickup assembly moves forward and throws the sheet into the feed path. This kind of mechanism is almost infallible, but expensive; there is a huge difference between what can be afforded on a million dollars worth of printing press and a thousand dollars worth of laser printer.

Laser printers are based on the general idea of a copier. Photocopiers have generally used cut sheets and the methods used mainly originated there. Basically the machine needs a tray for every common document size it might be presented with.

Computer printers began to to use cut-sheet as a matter of course when the idea of a laser printer took off in the mid 1980s.

Laser printers needed to handle cut sheets because their purpose was to impress with the quality of output, and part of the image presented by a document would be paper quality. A laser-printed

Trays hold paper and have the pickup and perhaps feed rollers at the front. Most printers have two trays:

- a main tray that is built in under the printer and holds somewhere between 150 and 500 sheets of A4. This might ideally be called a cassette.

- a multi-purpose tray that folds down at the front of the printer and takes a few envelopes or several sheets of paper such as letterhead, photo sizes or oversized papers like banners.

Cheap printers often have a multipurpose tray or cassette, one or the other, not both. A common arrangement is to have a 150 sheet tray and a priority slot instead of a multi-purpose tray. The priority tray just inserts one sheet of paper (a letterhead for instance) onto the top of the ordinary paper stack.

Any printer can be shared on a network, but a printer with a 150 sheet tray and a priority slot will prove a nuisance because the tray is likely to need frequent refilling and use of the priority slot will mean crossing the room.

Most recent printers feed their output to the top. That means an S shaped paper feed path. Ordinary office paper flows round the bends; heavy materials like cards can't bend so easily. To handle this a lot of printers will feed heavy media from the multi-purpose or priority slot to a fold down straight-through output tray on the rear.

Trays do get broken. Fold down input and output trays stick out where people walk, or drop ledger files. A ream of paper is heavy so paper guides and stops sometimes snap when the tray is being refilled. Individual plastic guides are sometimes but a complete cassette assembly is a frequently needed spare so it often is available.

Trays can usually be added to the more capable printers, typically feeding paper into it from underneath. An extra tray is desirable if people regularly use letterhead paper because it will hold more sheets than the multi-purpose tray, look neater and be less vulnerable to damage. Extra trays are a common accessory but printer makers commonly charge quite a lot for them particularly if they are bought as "aftermarket" items.

Tray Names

Tray terminology can be confusing.

The actual tray that the paper sits in is often called a cassette. Tray could mean the same thing but might also mean an entire assembly with a housing for the printer to sit on when you add an extra accessory tray. HP describe this housing for an extra tray the sheet-feeder. Lexmark call the housing the drawer which is confusing because the word drawer would normally mean the thing that slides in and out.

If that wan't enough some manufacturers count the multi-purpose tray as tray 1 (HP do this) whilst others call it MP and the first cassette is tray-1.

So taking one printer as an example; if you ask for:

Tray 2 for a Laserjet 5100 ... tray 2 is built into the machine, therefore what you asked for is likely to be interpreted as the cassette for tray 2 - RG5-7188.

If all you have done is break the endstop (RB2-2023 commonly breaks) then just ask for the part - in this case it should be available as a separate item.

If you ask for tray 3 there is a choice. It could mean the 250 sheet paper feeder and cassette Q1865A or the 500 sheet feeder and cassette Q1866A. It isn't very likely to mean those things as new items because HP long ago stopped selling them, but it might mean refurbished units. HP describe the housing that the printer sits on as the sheet feeder. If what you want is the cassette that inserts into it those parts are RG5-7188 (250 sheet) and RG5-7164 (500 sheet).

Printers haven't been around for all that long and the English language hasn't yet adapted to have a familiar word that means precisely the right thing. We try to use part numbers and diagrams where possible.

Complexity of cassettes vary. Little inkjet trays holding 100 pages or so are commonly just a plastic assembly with paper guides and stops. There is often a spring-loaded metal base to hold paper up against the feed rollers.

If the paper capacity is 250 sheets or more then the force exerted by a spring is not sufficient and the printer will often have a motorised tray lift.

Where paper is commonly handled in different sizes it can make sense to have two or three different sized cassettes ready to swap into place. This seems to be fairly common in the US but unusual in the UK, perhaps because of our standardisation on A4.

Big, fast printers typically have at least one 2,000 sheet feeder either built into their base or in a cabinet that parks alongside. These units do tend to be quite complex and expensive with belt or chain lift motors to handle the weight of paper.

Cassettes can cause misfeed problems. The paper guides should surround the paper and ensure it is in a neat stack and feeds straight into the paper path. The guides should not actually grip the paper. Adjust the guides so that they touch the paper then back off a millimetre or so. Cassettes designed for faster printers have prefixed guide positions.