Overrunning drum having an amplifying device

A wheel brake, particularly an overrunning wheel brake, comprising a brake drum having an axis;

• a first brake shoe displaceable in forward and rearward directions and arranged to move toward said brake drum in a radial direction to be pressed against said brake drum with a pressure force;
• a support member which supports said first brake shoe;
• a second brake shoe connected with and together with said support member and displaceable in said forward and rearward directions and also arranged to be pressed against said brake drum with a pressure force;
• amplifying means arranged to cooperate with only said first brake shoe and to amplify the pressure force with which said first brake shoe is pressed against said brake drum, said amplifying means including a first formation provided on said support member and a second formation provided on said first brake shoe and cooperating with said first formation so as to amplify the pressure force during movement of said first brake shoe in said forward direction, said second formation on said first brake shoe being formed by a curved outer surface portion adjacent said drum and a lifting track portion adjacent said support member, said curved outer portion and said lifting track portion forming a wedge-shaped portion on said first brake shoe converging in said forward direction, said first formation including a guiding member on said support member cooperating with said wedge-shaped portion;
• means for displacing said first brake shoe in said forward direction so that, upon the displacement in said forward direction, said first brake shoe cooperates with said amplifying means and is pressed against said brake drum with the amplified pressure force, said displacing means including a tightening member arranged to act on said support member so as to displace said support member together with said first brake shoe in said radial direction;
• and urging means provided on said first brake shoe and normally spaced from said second brake shoe, said urging means arranged so that, when said first brake shoe is displaced in said rearward direction, said urging means abuts an end portion of said second brake shoe and urges and displaces said second brake shoe in said rearward direction, said second brake shoe acts upon said support member and thereby on said amplifying means which, in turn, cooperates with said first brake shoe, thereby said first brake shoe is also pressed against said brake drum with the amplified pressure force, so that said first brake shoe is pressed against said brake drum with the amplified pressure force not only during the displacement in said forward direction but also during the displacement in said rearward direction, said first brake shoe having an open end portion facing toward said tightening member, and said urging means being provided on said end portion of said first brake shoe, and arranged to displace said second brake shoe in a circumferential direction.