Scotch yoke arrangement

A scotch yoke arrangement (31) having an outer yoke member (29) mounted for reciprocal movement along a first, fixed axis (25) and a slide mechanism mounted within said yoke member (29) on a substantially cylindrical crank pin (38), said crank pin (38) extending substantially symmetrically along and about a second axis (42), said second axis (42) being spaced from and substantially parallel to a third axis (24), said third axis (24) being fixed relative to and substantially perpendicular to said first, fixed axis (25), said crank pin (38) including the second axis (42) thereof being rotatably driven about said third axis (24) wherein said scotch yoke arrangement translates the rotational motion of the crank pin (38) about said third, fixed axis (24) to reciprocally move said yoke member (29) along said first, fixed axis (25),

• said slide mechanism having first and second portions (44,44′) and being mounted for sliding movement along a fourth axis relative to said yoke member (29) with said first and second portions (44,44′) moving along said fourth axis substantially perpendicular to said first, fixed axis (25) as said yoke member (29) reciprocally moves along said first, fixed axis (25), said slide mechanism rotatably receiving said crank pin (38) between said first and second portions (44,44′) and being moved substantially perpendicular to said first, fixed axis (25) thereby wherein said yoke member (29) has at least two inwardly facing surfaces (64) and each of said first and second portions (44,44′) of said slide mechanism has an outwardly facing surface (64′)
• respectively positioned adjacent to one of said inwardly facing surfaces (64) of said yoke member (29), said scotch yoke arrangement further including first bearing members between the respective outwardly facing surfaces (64′) of said first and second portions (44,44′) and the inwardly facing surfaces (64) of said yoke member wherein adjacent pairs of said inwardly and outwardly facing surfaces (64,64′) respectively have at least one groove (66′) in the outwardly facing surface (64′) extending along said fourth axis and substantially perpendicular to said first, fixed axis (25) with a plurality of said bearing members being positioned between said inwardly and outwardly facing surfaces (64,64′) in said respective one groove (66′) and wherein the respective one grooves (66′) in the outwardly facing surfaces (64′) respectively extend a first distance along said fourth axis and perpendicular to said first, fixed axis (25) and the inwardly facing surfaces (64) respectively extend a second distance along said fourth axis and perpendicular to said first, fixed axis (25) wherein the respective first distance is substantially less than the respective second distance and wherein the bearing members between each of said adjacent pairs of inwardly and outwardly facing surfaces (64,64′) are always contained within the respective first distance of the outwardly facing surface (64′) in each of said adjacent pairs of inwardly and outwardly facing surfaces (64,64′) and do not extend beyond the respective first distances of the outwardly facing surfaces (64′) as the first and second portions (44,44′) slidingly move relative to the yoke member (29), each respective one groove (66′) in the respective outwardly facing surface (64′) having a substantially continuous rim portion extending about a fifth axis substantially perpendicular to the fourth axis and a depressed portion extending substantially along said fourth axis away from the rim portion and away from the inwardly facing surface (64) adjacent said respective outwardly facing surface (64′).