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Table Tennis Balls: Celluloid Halves Blown in an Out-of-Round Mould (Jaques 1935)
J. M. Jaques · Public domain (US patent)
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Table Tennis Balls: Celluloid Halves Blown in an Out-of-Round Mould (Jaques 1935)

A celluloid table tennis ball is two stamped halves sealed with acetone, then blown out round by its own air in a hot mould. The overlapped seam shrinks a little as it cools, so the ball ends slightly narrower across the seam. John Jaques made the mould wider across the seam by just that amount, so the ball cools truly round. Source: J. M. Jaques, US 2,025,455 (1935). The patent gives no sheet thickness, ball size or temperatures. The press, pot and micrometer are ours. Picture: the patent drawing.
Kati
1 day

Maagizo

1

Stamp two halves from hot sheet

Stamp two half-balls out of celluloid sheet while it is hot. The patent gives no temperature.

Vifaa kwa hatua hii:

SeluloidiSeluloidi1 karatasi

Zana zinazohitajika:

Kalibu ya kubana nusu tufeKalibu ya kubana nusu tufe
Mkandamizo wa kugonga batiMkandamizo wa kugonga bati
2

Seal the halves with acetone

Wet the edges of both halves with acetone, fit them together with the edges overlapping and let them seal. You now have a closed rough ball with a seam round its middle.

Zana zinazohitajika:

AsetoniAsetoni
3

Measure the seam shrinkage

Blown balls come out narrower across the seam than across the poles: about one to two ten-thousandths of an inch on the celluloid balls Jaques measured. For your own celluloid, measure it on a test ball.

Zana zinazohitajika:

MaikromitaMaikromita
4

Use a mould wider at the seam

The split mould is not a true sphere. Measured in the plane where its two halves meet (diameter A), it is wider than at right angles to that plane (diameter B) by the amount the seam shrinks, and it has small vents to let air out.

Zana zinazohitajika:

Kalibu ya mpira ya vipande viwiliKalibu ya mpira ya vipande viwili
MaikromitaMaikromita
5

Set the ball seam to joint

Lay the rough ball in the mould with its seam exactly on the mould joint, and hold it there with a little petroleum jelly so it cannot move.

Zana zinazohitajika:

Kalibu ya mpira ya vipande viwiliKalibu ya mpira ya vipande viwili
VaseliniVaselini
6

Blow it out in hot water

Close the mould and put it in hot water. The air inside the ball expands and blows the ball out to fill the mould.

Zana zinazohitajika:

Kalibu ya mpira ya vipande viwiliKalibu ya mpira ya vipande viwili
Sufuria KubwaSufuria Kubwa
MajiMaji
7

Cool and take out

Let the mould cool, then open it and take the ball out. As the seam shrinks it comes back to the same diameter as the rest, so the ball is as near round as it can be.

Zana zinazohitajika:

Kalibu ya mpira ya vipande viwiliKalibu ya mpira ya vipande viwili

Vifaa

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    1 karatasi
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