I try to remember to include a warning as to the size of each photo which you may download, so you may judge whether you wish to wait that long for it.
Note that there are many details left out of these drawings - in particular the fretwork to allow the air to flow, and the sound to escape. I will leave it to the photos to provide the details which might clutter the drawings too much, and detract from what they are attempting to explain. The colors here are used to keep the left and right hand ends distinct in the mind. I have never seen one so colored.
In this section, we'll follow the train of actions through the button box, starting at
the part with which you normally interface, and continuing through to the
valve, which allows airflow through to the reeds (which will be covered in
the next section.)
Action Box (buttons, levers, valves)
In this section, we'll follow the train of actions through the button box, starting at the part with which you normally interface, and continuing through to the valve, which allows airflow through to the reeds (which will be covered in the next section.)
in front of the bellows with the reedpan installed as usual. The fingerboard is leaning against the bellows, and seen from the inside. Note the detailed fretwork made visible by the backlighting. (Except where it is shadowed by the corner of the bellows and reedpan.)
Here is an overall drawing of the linkage. From here, we'll go on to details of each portion.
The drawing here is intended to show the basic linkages of the concertina's valve assembly. The style depicted here is one of the oldest that I have seen in use. I will later draw in some of the other styles (or show them in photos), but the basic principles remain the same. Note that the top view of the lever (not shown in the DRAWINGS), is frequently not straight, especially for the inner two rows of buttons, but rather is bent as necessary to reach the proper button by passing around one or more other buttons. As should be obvious, depressing the button lifts the valve pad assembly from the hole in the valve board. This allows air to flow into the chamber in the reed pan below, and through whichever reed is appropriate for the direction of bellows travel. What perhaps is not obvious from the drawing is that each valve pad and valve hole are round. Accordions commonly have rectangular valve plate assemblies. Some particularly large concertina reeds may have a pair of overlapping valve holes, and a valve pad which was oversized, but has had two sides cut off to fit. Occasional other valve pads will have a side cut off to allow it to clear the adjacent pads.
There are detail differences between the Wheatstone and the lachenal metal buttons. In particular, the Wheatstone is fabricated by pressing a deep-drawn metal cap over a body of wood in the older ones, or plastic in the later ones.
In contrast, the Lachenal buttons are all metal. They are fully-machined on the exterior surface, and the body is hollowed, either by casting or drilling. There is also a small vent hole drilled at an angle to connect a part of the button on the interior of the concertina to the cavity. The hole in the button is covered with a silver-soldered cap. On some really heavily used Lachenals, you may find a button or two sufficiently heavily worn so there is a crescent opening into the body.
The older concertinas have buttons of bone, frequently with the note names engraved on the ends for the "white keys", the "C" dyed red, and the accidentals dyed black.
A very few instruments may be found with glass buttons. Needless to say, there is a very good chance of one or more of these being replacements.
This photo shows just how busy the area of the buttons is in the English concertina. To get a proper feel, reduce the size of the image till it is the size of the image in a 35mm slide. (24mm x 36mm, or about 1" x 1.5"). (This is about the size of the "thumbnail" photo which advertises this photo. At that size, the image will be close to life size. It is provided significantly enlarged to make the details a bit easier to see. In this particular instrument, the felt pieces are black, making some details harder to see.
The buttons in this particular instrument are examples of the mid period of Wheatstone buttons. The early ones were turned of bone, and were commonly engraved on the ends with the note names. The accidentals were black, and the Cs were red. In the period represented here, the buttons consisted of a light hardwood body, with a deep-drawn cup of nickel silver (I believe) pressed onto the body. In the Boosey & Hawkes period, (most easily identified by the fact that the word "Wheatstone" on the manufacturer's label is in quotes), the body of the button is manufactured of a white semi-soft plastic, which, over the years, has become somewhat brittle, so a bump against the side of a button snaps it off at the weakest point, where the lever passes through the body. (I have seen such breaks in the wood-bodied buttons as well, but never (yet) in the bone buttons.)
While the early Lachenals had the same bone buttons as the Wheatstones of that period, when Wheatstone moved to metal-capped buttons, Lachenal went to buttons fabricated entirely of metal. The button seems to be a casting, machined on the outside, while rough on the inside. The metal is solid down where the lever passes through, but the main length is hollow. There is a flat metal cap silver-soldered onto the end. These buttons are far more flat-topped than the drawn button caps of the Wheatstones. (The bone button period had entirely flat-topped buttons.)
There have been more exotic buttons. There were Lachenals (at least) made with glass buttons. These, of course, are the most fragile of all, and the hardest to find (or make) replacements for. If I had such an instrument, I would be strongly tempted to mount some grain-of-wheat light bulbs inside the cluster, and power them from an external source while playing in a dimly-lit room. (However, if you do this, please try to avoid drilling any holes in the wood of the instrument. Make sure that anything you do can be undone, since the instrument is an antique, and deserves respect on that basis, as well as its being a musical instrument.
The lever design is that of the later Wheatstones, too. You should be able to tell that the central lever has a rivet securing it to its pivot mount. These levers are stamped from sheet brass, rather than formed by flattening round brass wire, as are the ones in the drawing above.
This view gives a better image of the spring, whose function (in this design) is to hold the valve closed, and to hold the button extended to where it can be pressed.
On the older design of lever, as shown in the drawing above, the spring serves the additional function of holding the 'U' of the lever firmly into the 'U' of the pivot base, which is staked into the action plate.
Now, we'll finish up the action box part with an image of the valve pads, themselves.
Each valve pad, when lifted by the lever, as a result of pushing the button, uncovers a hole, which allows air from or to the bellows (depending on direction of pressure), which flows through the reeds (covered in the next section) to produce the note(s).