An injection molding apparatus comprising a clamp plate mounted to a mold in spaced relationship, a heated manifold, an actuator interconnected to and driving a valve pin, the actuator comprising a housing body, and a cooling device for cooling the actuator, wherein the manifold is disposed between the clamp plate and the mold and the housing body of the actuator is mounted in thermally conductive communication with the manifold, the cooling device comprising: a heat transmitter comprising a distal arm or member and a proximal base or member mounted in heat conductive contact to the housing body of the actuator, wherein: the distal arm or member comprises a rod or tube (507u, 507d) slidably disposed within a complementary bore (504pb, 504pba) disposed within the proximal base or member, the complementary bore and the rod or tube (507u, 507d) being configured such that an exterior surface of the rod or tube (507us, 507ds) is slidably engaged in thermally conductive contact with and against an interior surface (504pbsa, 504pbs) of the complementary bore (504pb, 504pba), the rod or tube (507u, 507d) being comprised of a thermally conductive material having a distal end surface, the rod or tube (507u, 507d) transmitting heat from the proximal arm or member to the distal end surface via engagement of the exterior surface (507us, 507ds) of the rod or tube (507u, 507d) with the interior surface (504pbsa, 504pbs) of the complementary bore (504pb, 504pba), the rod or tube (507u, 507d) being mounted within the complementary bore (504pb, 504pba) via a spring loadable interconnection to the proximal base or member, the clamp plate, the mold, the manifold, the actuator and the heat transmitter being assemblage together in an arrangement wherein the spring loadable interconnection is loaded urging the distal end surface of the rod or tube into compressed engagement with the clamp plate at least when the clamp plate, the mold, the manifold, the actuator and heat transmitter are assembled and the manifold is heated to an elevated operating temperature. a heat transmitter comprising a distal arm or member and a proximal base or member mounted in heat conductive contact to the housing body of the actuator, wherein: the distal arm or member comprises a rod or tube (507u, 507d) slidably disposed within a complementary bore (504pb, 504pba) disposed within the proximal base or member, the complementary bore and the rod or tube (507u, 507d) being configured such that an exterior surface of the rod or tube (507us, 507ds) is slidably engaged in thermally conductive contact with and against an interior surface (504pbsa, 504pbs) of the complementary bore (504pb, 504pba), the rod or tube (507u, 507d) being comprised of a thermally conductive material having a distal end surface, the rod or tube (507u, 507d) transmitting heat from the proximal arm or member to the distal end surface via engagement of the exterior surface (507us, 507ds) of the rod or tube (507u, 507d) with the interior surface (504pbsa, 504pbs) of the complementary bore (504pb, 504pba), the rod or tube (507u, 507d) being mounted within the complementary bore (504pb, 504pba) via a spring loadable interconnection to the proximal base or member, the clamp plate, the mold, the manifold, the actuator and the heat transmitter being assemblage together in an arrangement wherein the spring loadable interconnection is loaded urging the distal end surface of the rod or tube into compressed engagement with the clamp plate at least when the clamp plate, the mold, the manifold, the actuator and heat transmitter are assembled and the manifold is heated to an elevated operating temperature. the distal arm or member comprises a rod or tube (507u, 507d) slidably disposed within a complementary bore (504pb, 504pba) disposed within the proximal base or member, the complementary bore and the rod or tube (507u, 507d) being configured such that an exterior surface of the rod or tube (507us, 507ds) is slidably engaged in thermally conductive contact with and against an interior surface (504pbsa, 504pbs) of the complementary bore (504pb, 504pba), the rod or tube (507u, 507d) being comprised of a thermally conductive material having a distal end surface, the rod or tube (507u, 507d) transmitting heat from the proximal arm or member to the distal end surface via engagement of the exterior surface (507us, 507ds) of the rod or tube (507u, 507d) with the interior surface (504pbsa, 504pbs) of the complementary bore (504pb, 504pba), the rod or tube (507u, 507d) being mounted within the complementary bore (504pb, 504pba) via a spring loadable interconnection to the proximal base or member, the clamp plate, the mold, the manifold, the actuator and the heat transmitter being assemblage together in an arrangement wherein the spring loadable interconnection is loaded urging the distal end surface of the rod or tube into compressed engagement with the clamp plate at least when the clamp plate, the mold, the manifold, the actuator and heat transmitter are assembled and the manifold is heated to an elevated operating temperature.