Machine element or mechanism – Elements – Cams
Patent
1992-10-01
1994-05-10
Herrmann, Allan D.
Machine element or mechanism
Elements
Cams
108 7, 248371, 411537, F16H 5300
Patent
active
053097882
DESCRIPTION:
BRIEF SUMMARY
This invention relates to drawing apparatus which includes a drawing board or easel for use by artists, draughtsmen and architects for example. Such boards or easels may be used to support a sheet of canvas, card or paper whilst the user makes a sketch or drawing or does a painting or plan or writes upon it. This invention also relates to a tilt coupling device for use in the drawing apparatus, but having other uses also.
Existing drawing boards are often provided with some form of stand, enabling the board to be placed on a table or stood on the floor or ground for use. The latter form of support is often used by artists for sketching or painting outdoor scenes. However, some artists find the. conspicuousness of using such a drawing board unacceptable, particularly if they are novices in the field. In addition, existing supports are not ideal for use at night or in inclement weather.
U.S. Pat. No. 3,739,478 discloses a clipboard for attachment to the steering wheel of a motor vehicle. A circular baseplate has adjustable spring clips for snapping over a steering wheel, and a circular board is rotatably mounted on the baseplate. U.S. Pat. No. 4,139,217 discloses a desk which is provided with spring clips to mount on a steering wheel. In both of these earlier proposals the board is inclined at the same angle as the steering wheel so that with most if not all motor vehicles the board may be in the wrong position for many uses.
In accordance with this invention there is provided a drawing apparatus comprising a drawing board having mounting means for mounting the drawing board on the steering wheel of a motor vehicle, the mounting means being arranged so that the drawing board can be mounted in a plurality of different inclinations relative to the wheel.
The mounting means may comprise a pair of limbs which project from the rear of the drawing board and which can be folded to a stowed position against the rear of the drawing board. The mounting means may further comprise a support plate which projects from the rear of the drawing board and which can be folded to a stowed position generally parallel with the rear of the board or easel. The support plate is preferably coupled to a swivel plate which is coupled to the rear of the drawing board for rotation about an axis which is substantially normal to the plane of the drawing board.
The drawing apparatus preferably includes a viewfinder comprising a viewing member provided with a grid or index marks, the viewing member being mounted on an arm arrangement which is in turn secured to a device e.g. a clamp for attaching to the drawing board.
It is known in some precision optical instruments to vary the inclination of a main part of the instrument relative to a base by relative rotation of a pair of superimposed wedge-shaped cam members. Rotation is achieved simply by a pair of handles each secured to a respective cam member. Moreover, the instrument is held to the base by a spring metal joint located internally of the cam members, with the result that the instrument is only poorly fixed relative to the base.
In accordance with this invention there is provided a tilt coupling device comprising first and second mounting members having two wedge-shaped cam members, at least one of the cam members being rotatable relative to the other cam member and to the adjacent mounting member in order to change the inclination of one mounting member relative to the other, the device further comprising a series of teeth formed on one of the cam members, and a pinion meshed with said series of teeth and carried on an operating shaft, such that rotation of the operating shaft causes rotation of said one cam member relative to the other.
Preferably a slip ring is disposed between the opposed cam surfaces of the two cam members, the operating shaft being mounted to the slip ring and the pinion being mounted both with said series of teeth formed on said one cam member and with a series of teeth formed on the other cam member.
The tilt coupling device maybe used in the drawing apparatus,
REFERENCES:
patent: 683405 (1901-09-01), Jaeger
patent: 960899 (1910-06-01), Guyer
patent: 3010339 (1961-11-01), Brock
patent: 3018992 (1962-01-01), Lore
patent: 3364810 (1968-01-01), Hickerson
patent: 3739478 (1973-06-01), Elenberger
patent: 4533103 (1985-08-01), Ina
Herrmann Allan D.
Laub David W.
Schindler Edwin D.
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