How to draw pneumatic symbols?

Question

I want to create this symbol:

I tried it with circuitikz, but didn't really get it. I read some tutorials about creating own components (CircuiTikZ — create new component) but that didn't help me.

Has anybody an idea how to solve this? May it doesn't work with circuitikz, but with something else. I just want to create a circuit plan for pneumatics/hydraulics the same way circuitikz does.

Thank you very much for helping.

For german speaking people: http://golatex.de/viewtopic,p,93369.html

Answer 1

The following code produces a symbol similar to the one you want, so you might apply some fine tuning and work with it.

\documentclass{memoir}
\usepackage{amsmath,tikz,circuitikz}

% first optional argument: scale factor
% second argument: coordinate of centre
\newcommand{\drawtennisball}[2][1]{
    \draw[shift={#2},scale=#1]
        (0,0) circle [radius=1]
        (-0.707106781186548,-0.707106781186548)
             .. controls (-0.35,-0.35) and (0.35,-0.35) .. 
        (+0.707106781186548,-0.707106781186548)
        [yscale=-1]
        (-0.707106781186548,-0.707106781186548)
             .. controls (-0.35,-0.35) and (0.35,-0.35) .. 
        (+0.707106781186548,-0.707106781186548)
    ;
}

\begin{document}
Note $\frac {\sqrt2}2=\frac 1{\sqrt2}\approx0.707106781186548.$

\begin{circuitikz}
    \drawtennisball{(2,0)}
    \draw (2,-1) -- (2,-3);

    \drawtennisball[2]{(-1,1)}
    \draw (-1,-1) -- (-1,-4);
\end{circuitikz}

\end{document}