This question contains details regarding how to make the edges connecting various nodes turn at right angles using draw and edge. However, I am using the petri Tikz library and thus, the edges are drawn automatically. How can I instruct Tikz to draw these edges with right angled turns?
EDIT: The code is:
\begin{tikzpicture}[node distance=1.5cm,,xscale=2,>=stealth',bend angle=45,auto]
\tikzstyle{place}=[circle,thick,draw=blue!75,fill=blue!20,minimum size=3mm]
\tikzstyle{red place}=[place,draw=red!75,fill=red!20]
\tikzstyle{transition}=[rectangle,thick,draw=brown!75,
fill=brown!20,minimum size=3mm]
\tikzstyle{every label}=[blue!75]
\begin{scope}
\path
(0, 0) node [place,tokens=1,label=above:\s{$i$}] (pi) {}
++(-1, -1) node [place] (p1) [label=above:\s{$p1$}] {}
++(1, -1) node [place] (p2) [label=left:\s{$p2$}] {}
+(-1, -1) node [place] (p3) [label=left:\s{$p3$}] {}
++(1, -1) node [place] (p4) [label=right:\s{$p4$}] {}
+(1, 0) node [place] (p6) [label=left:\s{$p6$}] {}
++(-1, -1) node [place] (p5) [label=left:\s{$p5$}] {}
++(0, -2) node [place] (po) [label=above:\s{$o$}] {}
++(0, 5) node [transition] (t1) {\s{fork}}
edge [pre] (pi)
edge [post] (p1)
edge[post,-|] [post] (p6)
edge [post] (p2)
++(-1, -1) node [transition] (t2) {\s{check\_insurance}}
edge [pre] (p1)
edge [post] (p3)
+(2, 0) node [transition] (t3){\s{contact\_garage}}
edge [pre] (p2)
edge [post] (p4)
++(1, -1) node [transition] (t4) {\s{join}}
edge [pre] (p3)
edge [pre] (p4)
edge [post] (p5)
+(3, 0) node [transition] (t5) {\s{inform\_customer}}
edge [pre and post] (p6)
++(-1, -2) node [transition] (t6) {\s{pay\_damage}}
edge [pre] (p5)
edge [pre] (p6)
edge [post] (po)
+(2, 0) node [transition] (t7) {\s{send\_letter}}
edge [pre] (p5)
edge [pre] (p6)
edge [post] (po);
\end{scope}
\end{tikzpicture}
