The documents WO 97/01734 and EP 0 829 686 A1 have safety mechanisms whose functioning is based on specifications of the actuator's surface geometry in its contact area with the finger on performing the lighting manoeuvre. The different solutions claimed in these documents have the objective of reducing the friction coefficient between finger and actuator. In this manner, to achieve the actuator's rotation, it is necessary to increase the force applied with the finger in a radial direction in the lighting manoeuvre.
Even though the embodiments mentioned present simple, economic execution solutions, they base the safety in the increase in the operation force, fundamentally in radial direction, with the object of managing to increase the tangential pull force component of the finger that causes the actuator's rotation. Logically, the minimum operating force necessary to cause the actuator to rotate will only depend on the spark wheel's reaction force on the stone, with this being limited by the spring's compression force. The value of the force is further limited, both by the space restrictions of the spring's chamber in the lighter and by the stone's life. In this situation, said minimum reaction force of the pull train on the stone will depend on its wear, given that the spring's compression stroke is limited by the stone; thus, this minimum force will be reduced with the lighter's use, for which reason, the reliability of the safety mechanism will not be guaranteed.
The document U.S. Pat. No. 5,520,197 discloses a lighter with several safety mechanisms, fundamentally based on having an element that forms part of the trim, and which obstructs contact between finger and actuator. They base the safety on the minimum effort necessary to deform this structural element with the finger and accede therewith to the actuator, furthermore, combining spark wheel blocking systems with operating levers.
The document U.S. Pat. No. 5,096,414 discloses a lighter with a safety system wherein the actuators rotate freely on an axis coaxial with the spark wheel. They base the safety in the accessibility of the finger to the spark wheel due to the finger's deformation on increasing the operating force in a radial direction on the actuators.
The document U.S. Pat. No. 4,717,335 discloses a lighter wherein the safety is based on the spark wheel's limited path due to a mechanical stop placed thereon. This solution, in addition to the ergonomic problems it provides, does not make it too difficult for children to obtain a flame, taking into account that they may have a lot of time available, that tests are especially attractive for them, and that the lighting manoeuvre being visually noticeable, will be rapidly assimilated from learning by imitation.