Seems slightly curious.... do you not have the illustrations that go with this patent?

--------------------------------------------------
Note added at 13 heures (2017-01-17 08:50:28 GMT)
--------------------------------------------------

Yes, but normally a broom-handle fits into some kind of socket, where it is retained in place e.g. by a thread or a pin; it is not at all obvious how a broom-handle can be held in any kind of channel, nor what sort of purpose this might serve. Your explanation below hardly makes it any clearer, since I think you must have got a little muddled up: « un manche à balai doté d'un capuchon dans sa partie supérieure et à l'intérieur de ce capuchon vient s'insérer le manche du balai » ???

I have given you one possible translation of 'channel', with the proviso that the context is very far from clear!
Normally with patents, you do have the figures that probably explain everything and will give a much clearer idea of exactly what form this channel takes?

--------------------------------------------------
Note added at 13 heures (2017-01-17 08:53:29 GMT)
--------------------------------------------------

There is something else odd about your context, which may possibly explain the confusion; the use of the quaint word 'broomstick' instead of the more usual 'broom-handle' rather tends to suggest a non-ntaive speaker of EN — which may thus cast some doubt on the accuracy of other terms being used, including possibly this 'channel'.