Lightweight sprocket
The present invention relates to lightweight sprocket, consisting of a central portion ( 1 ) made from light metal alloy, to which a peripheral toothed portion ( 2 ) made from ferrous alloy is joined, using rivets ( 3 ) for joining said portions ( 1,2 ), where said joining is created between radial beams ( 21 ) of the peripheral toothed portion ( 2 ) and pocket-like recess ( 13 ) in the central portion ( 1 ), radial beams ( 21 ) being overlapped across bottoms of pocket-like recesses ( 13 ), and where a thickness of radial beams( 21 ), at least over the joining area, is decreased by 10 to 60%, in relation to full thickness of said toothed peripheral portion ( 2 ), and a thickness of a bottom of the pocket-like recess ( 13 ) in the central portion ( 1 ) is decreased by 20 to 70%, in relation to full thickness of the central portion ( 1 ) of the sprocket.
1. A motorcycle sprocket, consisting of a central portion ( 1 ) made from a metal alloy and having pocket recesses ( 13 ), to which a peripheral toothed portion ( 2 ) made from ferrous alloy and having radial beams ( 21 ), is joined, using rivets ( 3 ) for joining said portions ( 1 , 2 ), which rivets are made of titanium alloy or stainless steel alloy and where said joining is created between said radial beams ( 21 ) of the peripheral toothed portion ( 2 ) and said pocket recesses ( 13 ) in the central portion ( 1 ), said radial beams ( 21 ) being overlapped across bottoms of pocket recesses ( 13 ), and where a thickness of said radial beams ( 21 ), at least over the joining area, is decreased by 10 to 60%, in relation to the full thickness of said toothed peripheral portion ( 2 ), and a thickness of a bottom of said pocket recesses ( 13 ) in the central portion ( 1 ) is decreased by 20 to 70%, in relation to full thickness of the central portion ( 1 ) of the sprocket, characterized in, that a centering of the peripheral toothed portion ( 2 ) in relation to the central portion ( 1 ) acts over an outer circumference of the central portion ( 1 ) of said sprocket and that a side clearance between the radial beams ( 21 ) of the peripheral toothed portion ( 2 ) and side walls of the pocket recesses ( 13 ) of the central portion ( 1 ) is created, said clearance being 0.5 to 10% of the rivet ( 3 ) shank diameter.
2. A sprocket, according to claim 1 , characterized in, that a centering of the peripheral toothed portion ( 2 ) in relation to the central portion ( 1 ) acts over an outer circumference of the central portion ( 1 ) of said sprocket.
3. A sprocket, according to claim 1 , characterized in, that lightening openings ( 14 ) are created in the central portion ( 1 ) of the sprocket.
4. A sprocket, according to claim 3 , characterized in, that at least a circumferential strip is created between said lightening openings ( 14 ) and the outer circumference of the central portion ( 1 ), where the thickness of said strip, in radial direction, is at least 50% of the full thickness of said central portion ( 1 ).
5. A sprocket, according to claim 4 , characterized in, that a wall is created between the lightening openings ( 14 ) and the pocket recesses ( 13 ) of the central portion ( 1 ), where a height of said wall is the same as the full thickness of said central portion ( 1 ) and a width of said wall is at least 50% of the full thickness of said central portion ( 1 ) of the sprocket.
6. A sprocket, according to claim 1 , characterized in that the radial beams ( 21 ) include side walls ( 17 ).
7. A sprocket, according to claim 1 , characterized in that the pocket recesses ( 13 ) include circumferential walls ( 15 ).
8. A sprocket, according to claim 1 , characterized in that the radial beams ( 21 ) include side walls ( 17 ) and the pocket recesses ( 13 ) include circumferential walls ( 15 ).