A device for selectively masking portions of transparent visual material to be projected by an overhead projector onto a screen including an opaque flexible sheet attached at one side to the overhead projector and at the other to a rod portion of a spool. When not in use the opaque flexible sheet is wound onto the spool. A portion, or all, of the transparent material may be blocked from projection by rolling the spool over the transparent material so that the opaque flexible sheet covers the undesired material.
申请公布号
US5112123(A)
申请公布日期
1992.05.12
申请号
US19910705357
申请日期
1991.05.24
申请人
FAGAN, DECEASED, ROBERT;FAGAN, PERSONAL ADMINISTRATOR, BY ELLEN
发明人
FAGAN, DECEASED, ROBERT;FAGAN, PERSONAL ADMINISTRATOR, BY ELLEN