Safety device for a workpiece holder

In a workpiece holder (10) for supporting the inner surface of a workpiece (74) including:

• a support structure (12) having a central bore (28);
• spokes (30) carried by said support structure (12);
• means (38) for engaging said workpiece and for projecting into said bore, said means being slidably attached to said spokes (30) and extending perpendicular to the longitudinal axis (23) of said bore (28), said means (38) having distal ends (40) engaging said workpiece and proximal ends (44) projectable into said bore (28);
• a cam (48) located within said bore (28) having a sloped cam surface (50) engaging said proximal ends (44) and movable between a first position at which said proximal ends project into said bore (28) thereby retracting said means (38) on said spokes (30) and a second position wherein said cam surface (50) moves said proximal ends (44) outwardly thereby extending said means (38) on said spokes (30) into engagement with said workpiece (10), the improvement comprising:
• latch means (56) for preventing said cam (48) from moving from said second position toward said first position, said latch means (56) includes a projection (58) carried by said support structure (12) which is selectively extendible into engagement with said cam (48).

In a workpiece holder (10) for supporting the inner surface of a workpiece (74) including:

• a support structure (12) having a central bore (28);
• spokes (30) carried by said support structure (12);
• means (38) for engaging said workpiece and for projecting into said bore, said means being slidably attached to said spokes (30) and extending perpendicular to the longitudinal axis (23) of said bore (28), said means (38) having distal ends (40) engaging said workpiece and proximal ends (44) projectable into said bore (28);
• a cam (48) located within said bore (28) having a sloped cam surface (50) engaging said proximal ends (44) and movable between a first position at which said proximal ends project into said bore (28) thereby retracting said means (38) on said spokes (30) and a second position wherein said cam surface (50) moves said proximal ends (44) outwardly thereby extending said means (38) on said spokes (30) into engagement with said workpiece (10), the improvement comprising:
• latch means (56) for preventing said cam (48) from moving from said second position toward said first position;
• said cam (48) includes a substantially flat surface (76) opposite said cam surface (50) and said latch means may be extended into said bore (28) from said support structure (12) adjacent said flat surface (76).

In a workpiece holder (10) for supporting the inner surface of a workpiece (74) including:

• a support structure (12) having a central bore (28);
• spokes (30) carried by said support structure (12);
• means (38) for engaging said workpiece and for projecting into said bore, said means being slidably attached to said spokes (30) and extending perpendicular to the longitudinal axis (23) of said bore (28), said means (38) having distal ends (40) engaging said workpiece and proximal ends (44) projectable into said bore (28);
• a cam (48) located within said bore (28) having a sloped cam surface (50) engaging said proximal ends (44) and movable between a first position at which said proximal ends project into said bore (28) thereby retracting said means (38) on said spokes (30) and a second position wherein said cam surface (50) moves said proximal ends (44) outwardly thereby extending said means (38) on said spokes (30) into engagement with said workpiece (10), the improvement comprising:
• latch means (56) for preventing said cam (48) from moving from said second position toward said first position, said latch means (56) includes a rod (58) extending from said support structure (12) and means (64) for biasing said rod into engagement with said cam (48).

A workpiece holder (10) for supporting the inner surface of a workpiece (74) including:

• a hollow cylindrical hub (16) having a cylindrical wall (29) and a longitudinal central bore (28);
• spokes (30) carried by said hub (16) and having a first means (38) slidably attached to said spokes (30) and extending radially through said wall (29);
• a cam (48) having a cam surface (50) and a flat rear surface (76) and being movable between a first position at which said first means (38) project into said bore and a second position at which said sloping face (50) moves said first means (38) radially outwardly, the improvement comprising:
• a latch means (56) for releasably locking said cam (48) in said second position including a rod (58) extending through said wall (29) into said bore (28) and into intimate contact with said rear surface (76).