Damper pulley assembly having a safety device
A damper pulley assembly has a hub; a seismic mass connected to the hub to define a dynamic torsional vibration damper; a pulley connected to the hub; elastic means for connecting the pulley in torque-transmitting mode to the hub; and one-way stop means for arresting the pulley in a first stop position with respect to the hub or the seismic mass in a first direction, when the elastic means reach a predetermined torsional load.
1. A damper pulley assembly comprising a hub; a seismic mass connected to said hub to define a dynamic torsional vibration damper; a pulley connected to said hub; and elastic means for connecting said pulley in torque-transmitting mode to said hub; wherein by comprising a first one-way stop means for arresting said pulley in a first stop position with respect to said hub or said seismic mass in a first direction, when said elastic means reach a predetermined torsional load;
a second one-way stop means for arresting said pulley in a second stop position with respect to said hub or said seismic mass in a second direction opposite said first direction;
wherein said first one-way stop means comprise a projection carried by one of said pulley and said hub or by said seismic mass; and a first stop carried by the other of said pulley and said hub, or by said seismic mass,
wherein said second one-way means comprise a second stop which cooperates selectively with said projection, and
wherein said elastic means comprise a spiral member made of a material at least predominantly stressed by the torque transmitted between said hub and said pulley when said pulley is in said first stop position; adjacent turns of said spiral member being radially detached when said pulley is in said first stop position; and
further comprising a first and a second shoe carried by said spiral member; and
in that said second stop has a fixed angular position, so that the torque between said hub and said pulley is transmitted predominantly by said second stop when said pulley is in said second stop position such that the second stop position corresponds to a substantially unloaded condition of the spiral spring.
2. A damper pulley assembly as claimed in claim 1 ,wherein adjacent turns are detached when said pulley is in said first stop position.
3. A damper pulley assembly as claimed in claim 1 , wherein said pulley comprises a stop member; and in that said spiral member comprises a free end portion cooperating with said stop member.
4. A damper pulley assembly as claimed in claim 1 , wherein said stop member is spaced angularly apart from said first and said second shoe when said pulley is in said second stop position.
5. A damper pulley assembly as claimed in claim 1 , wherein said pulley is supported radially by said seismic mass; and in that said first one-way stop means are interposed between said hub and said pulley.
6. A damper pulley assembly as claimed in claim 1 , wherein said first one way stop means are interposed between said hub and said seismic mass.
7. A damper pulley assembly as claimed in 1 , wherein said elastic means are side by side with said seismic mass.
8. A damper pulley assembly as claimed in claim 1 , wherein said seismic mass surrounds said elastic means.
9. A damper pulley assembly as claimed in claim 1 , wherein said pulley comprises a multiple-groove wall; and by comprising a stop member fitted inside said multiple-groove wall and cooperating with said hub or said seismic mass to define the axial position of said pulley.
10. A damper pulley assembly as claimed in claim 1 , wherein said free end portion slides on said first and second shoes with respect to said pulley before reaching said first or said second stop position.