Abstract: This assembly comprises a cup containing a thermally-expandable material, a piston designed to move in translation along an axis (X-X) under the action of the thermally-expandable material, a guide (40) for guiding the piston and intended to be fixed to the cup, and a buffer (60) made of an elastomer material and designed to be interposed between the thermally-expandable material and the piston. The guide is provided with a bore (41) that is intended to be centered on the axis and comprises a first bore portion (41.2) having a constant cross-section, a second bore portion (41.1) provided to receive the piston and having a cross-section that is both constant and smaller than that of the first bore portion, and a third bore portion (41.3) that continuously connects the first and second bore portions.

Abstract: This assembly comprises a cup containing a thermally-expandable material, a piston designed to move in translation along an axis (X-X) under the action of the thermally-expandable material, a guide (40) for guiding the piston and intended to be fixed to the cup, and a buffer (60) made of an elastomer material and designed to be interposed between the thermally-expandable material and the piston. The guide is provided with a bore (41) that is intended to be centered on the axis and comprises a first bore portion (41.2) having a constant cross-section, a second bore portion (41.1) provided to receive the piston and having a cross-section that is both constant and smaller than that of the first bore portion, and a third bore portion (41.3) that continuously connects the first and second bore portions.