Device for describing an ellipse

A device for describing an ellipse on a surface, including in combination:

• a stationary portion having positioning means for locating and retaining a fixed position on said surface and a path-generating portion having two mutually perpendicular guides,
• a housing rotatably attached to said stationary portion and having a sidewall with an enclosed slot,
• a rotatable follower assembly in said housing having first and second followers, one engaging each said guide, and adjusting means for determining the position of the second follower relative to said first follower, and
• a radius rod having one end secured near the outer edge of said follower assembly and extending out through said slot to a distal end having scribing means.

A device for describing an ellipse on a surface, including in combination:

• a stationary portion having positioning means for locating and retaining a fixed position on said surface and a path-generating portion with an upper surface having first and second mutually perpendicular recesses,
• a housing rotatably attached to said stationary portion and having a cylindrical wall with an enclosed slot and an upper end wall,
• a rotatable cylindrical cam with a path-defining circular projection that rotates in and rides snugly back and forth in said first recess, guide means for engaging in said second recess, and adjusting means for determining the position of said guide means relative to the center of said circular projection, and
• a radius rod having one end secured near the outer periphery of said cam and extending out through said slot to a distal end having scribing means.

A device for describing an ellipse, including in combination:

• a stationary portion having a square bottom portion with corners and a plurality of sharp points projecting downwardly for determining the center of an ellipse and a path-generating portion with an upper surface having a diametrically-extending recess and, perpendicular to said recess, a diametrically-extending first slot,
• a rotatable housing rotatably attached to said stationary portion and having a cylindrical wall with an enclosed second slot and an upper end wall,
• a rotatable cylindrical cam with an upper face, a lower face having a path-defining circular projection that rotates in and rides snugly back and forth in said recess, an enclosed third slot extending diametrically across the lower face of said cam and half of said projection, a cylindrical wall having a radial opening therethrough aligned with and leading into said third slot, and a tangential opening parallel to said third slot,
• an eccentricity-determining rod fitting slidably in said third slot and having an inner end extending vertically out from said third slot into said first slot, for movement back and forth therein,
• securing means for securing said eccentricity-determining rod in any desired position relative to said third slot, thereby determining the eccentricity of the ellipse to be described, and
• a radius rod having one end secured in said tangential opening of said cam and extending out through said second slot to a distal end having scribing means.

A device for describing an ellipse, including in combination:

• a cylindrical shell having an enclosed first arcuate slot and an inwardly-extending bottom flange,
• stationary device-locating and path-generating means having a cylindrical disc fitting in said shell and bearing against said flange, for rotation of said shell relative to said disc, and having a bottom surface at the bottom of the shell and an upper surface having a diametrically-extending enclosed second slot and, perpendicular to said second slot, a diametrically-extending recess, said stationary means also having a square bottom plate outside said shell, secured rigidly to the bottom of said cylindrical portion and having a lower face, a plurality of sharp pointed members extending down from said lower face for determining the position of said device-locating and path-generating means relative to a base surface on which the ellipse is to be described,
• a rotatable cylindrical cam with an upper face, a lower face having a path-defining circular projection that rotates and rides back and forth in said recess, an enclosed third slot extending diametrically across said cam and to the center of said projection, and a cylindrical face having a radial opening therethrough aligned with and leading into said third slot and a tangential opening parallel to said third slot,
• an eccentricity-determining rod fitting slidable in said third slot and having an inner end extending vertically out from said third slot into said second slot, for movement back and forth therein,
• securing means for securing said eccentricity-determining rod in any desired position relative to said third slot and thereby determining the eccentricity of the ellipse to be described, and
• a radius rod having one end secured in said tangential opening of said cam and extending out through said first slot to a distal end having scribing means.

A device for describing an ellipse, including in combination:

• a cylindrical shell having an enclosed first slot extending through about 90.degree. thereof,
• a path-generating disc fitting snugly but rotatably inside said shell having a bottom surface at the bottom of the shell and an upper surface, a diametrically-extending enclosed second slot therethrough, and, perpendicular to said second slot, a diametrically-extending recess in said upper surface,
• a square bottom plate secured to the bottom surface of said disc and having a lower face from which project a plurality of sharp points for determining the position of said disc relative to a base surface on which the ellipse quadrant is to be described,
• a cylindrical cam with an upper face, a lower face having a path-defining circular projection that rotates in and rides snugly back and forth in said disc's recess, an enclosed third slot extending diametrically across said cam and across half of said projection, and a cylindrical face having a radial opening therethrough aligned with and leading into said third slot and a tangential opening parallel to said third slot,
• an eccentricity-determining rod fitting slidably in said third slot and having an inner end extending vertically out from said third slot into said second slot, for movement back and forth therein,
• a radius rod having one end secured in said tangential opening of said cam and extending out through said first slot to a distal end,
• securing means for adjustably securing said eccentricity-determining rod in a desired position relative to said third slot and thereby determining the eccentricity of the ellipse to be described, said securing means having a control portion on the upper face of said cam,
• a circular top closure member having an annular shelf making a snug closure against the top rim of said shell and an opening affording access to said control portion, and
• scribing means for cutting or marking said base surface, adjustably secured to the distal portion of said radius rod,
• the radius rod being moved from a first end of said first slot to the other to describe a quadrant of an ellipse, the shell then being rotated while the bottom plate and radius rod remain stationary until the first end of the first slot again engages the radius rod, describing another quadrant of the ellipse, and so on until the complete ellipse is described.