  The measurements of the statistical properties of the Cosmic Microwave
Background (CMB) fluctuations enable us to probe the physics of the very early
Universe especially at the epoch of inflation. A particular interest lays on
the detection of the non-Gaussianity of the CMB as it can constrain the current
proposed models of inflation and structure formation, or possibly point out new
models. The current approach to measure the degree of non-Gaussianity of the
CMB is to estimate a single parameter which is highly model-dependent. The
bispectrum is a natural and widely studied tool for measuring the
non-Gaussianity in a model-independent way. This paper sets the grounds for a
full CMB bispectrum estimator based on the decomposition of the sphere onto
projected patches. The mean bispectrum estimated this way can be calculated
quickly and is model-independent. This approach is very flexible, allowing
exclusion of some patches in the processing or consideration of just a specific
region of the sphere.
