wrote:

On Sunday, 8 March 2020 13:32:25 UTC, Clive Arthur wrote:
On 08/03/2020 11:00, tabbypurr wrote:
On Saturday, 7 March 2020 19:51:11 UTC, Clive Arthur wrote:
On 07/03/2020 12:14, Roger Hayter wrote:

snip

I suspect the pedal design is at least twice that age, probably
somewhere between 1910 and 1930. Quick googling doesn't really give an
answer, but electric Singer machines were first made in 1910 and must
have had some sort of speed control.


The rheostat design was patented by Singer in 1949.

it was in widespread use before then

Yes, the patent was granted in 1945, not 1949 as I wrote, it's
specifically for controlling sewing machines. One of the claims
mentions an 'improved controller of the carbon disk compression type'
which means that the rheostat was already around.

It's a US patent US2371772A - the USPTO isn't very rigorous today, maybe
they were better then.

It's just the 'improvement' that was patented then. Resistive piles were
in use in the 1800s, and wirewound blocks with a wiper arm were a more
common sewing machine foot control option.

I'd expect far better performance from the wiper type than a carbon pile.


NT
I'd expect less durability and reliability.

--

Roger Hayter