Power transmission device easy to mount on a driver

A power transmission device for installation between a driver including an output rotary shaft and a mounting portion, and a driven machine, comprising:

• a hollow tubular shaft adapted to be fitted on said output rotary shaft of said driver for rotation therewith;
• an annular output element mounted concentrically on one end of said tubular shaft for rotation relative thereto;
• an annular input element rigidly fitted concentrically on an intermediate portion of said tubular shaft for rotational movement together with said tubular shaft;
• an annular operating element mounted concentrically on another end of said tubular shaft for rotational movement relative to said tubular shaft through a predetermined circumferential angle;
• an annular friction plate interposed between said output element and said input element and mounted on said output element for rotational movement therewith and for displacement axially of said tubular shaft for frictional engagement with said input element;
• a first spring for urging said friction plate toward said input element;
• an annular brake element arranged concentrically of said tubular shaft and interposed between said operating element and friction plate for displacement axially of said tubular shaft for frictional engagement with said friction plate, said brake element having a plurality of through holes formed therein along a given circumference at circumferentially spaced locations;
• means responsive to rotation of said operating element for causing displacement of said brake element axially of said tubular shaft and relative to said operating element;
• a plurality of guide elements adapted to be secured to said mounting portion of said driver and axially fitted through respective ones of said through holes of said brake element for permitting axial displacement of said brake element along said guide elements and prohibiting circumferential displacement of said brake elements;
• and
• a plurality of second springs engaging respective ones of said guide elements and urging said brake element toward said operating element,
• said input element having at least one first opening formed at a location axially alignable with each of said guide elements, said friction plate having at least one second opening at a location axially alignable with said first opening of said input element so that said guide elements and said second springs can be mounted into and removed from said power transmission device through said first and said second openings when aligned with each other;
• and
• wherein said friction plate comprises a radially extending inner peripheral portion which is urged by said first spring, a first tapered portion obliquely and radially outwardly extending from said inner peripheral portion toward said output element, a second tapered portion located radially outwardly of said first tapered portion and obliquely and radially outwardly extending toward said input element, and an annular peripheral portion radially outwardly extending from said second tapered portion, so that said friction plate covers said input element and said output element.