Game with an electromagnetic ball detector

A sensor for a game having a playfield surface with a preselected point, a ferromagnetic projectile moving on said surface during play of the game, said sensor comprising:

• a magnet wrapped in a solenoidal coil for providing a continous magnetic flux during game play and positioned with respect to said preselected point to avoid contact with said projectile;
• and
• means for generating an electrical signal, proportional to projectile speed of passage and time rate of change of said magnetic flux, produced when said projectile has a trajectpory traversing the neighborhood of said preselected point, said signal being maximal for fixed values os said projectile speed when said trajectory passes diretly over said point;
• said electrical signal putputted to a circuit, wherein the projectile must be travelling at a minimum projectile speed in order to generate an electrical signal for counting.

A magnetic sensor for a pinball game having a ferromagnetic projectile moving on a gameboard during play of the game comprising:

• magnetic means having north and south poles and an axis passing through said poles, for producing a magnetic flux;
• retaining means for retaining said magnetic means below the gameboard, said axis being substantially perpendicular to the gameboard surface;
• a solenoidal coil of electrically conductive wire having terminals and a solenoidal axis retained substantially coincident with said magnetic means axis so that the rate of change of said magnetic flux is caused by passage of the projectile through said flux, and generation of an electrical signal is proportional to the projectile speed of passage thereby inducing electrical voltage differences between said terminals;
• and
• counting means having a preset threshold connected between said terminals for signalling events when said electrical voltage differences exceed said threshold to signal the passage of said projectile, wherein the projectile must be travelling at a minimum projectile speed in order to generate an electrical signal for counting.

In a game wherein at least one ferromagnetic projectile moves over the surface of a gameboard, a game projectile detector comprising:

• magnetic flux generating means disposed beneath said surface, and
• magnetic sensing means disposed beneath said surface, and out of contact with any game projectile for responding to the time rate of change of said magnetic flux within said magnetic sensing means by producing a systematically related electrical signal,
• the disposition of said magnetic flux generating means relative to a predetermined point on said surface causing said rate of change of flux to be a maximum when said game projectile traverses said point,
• wherein passage of said projectile through said flux causes generation of an electrical signal proportional to the time rate of change of said magnetic flux and to projectile speed of passage, wherein the projectile must be travelling at a minimum projectile speed in order to generate an electrical signal for counting.