IMPROVEMENTS IN APPARATUS FOR DETERMINING RECIPROCATING. MOTION IN A STRAIGHT LINE
Year: 1880

page_text: PROVISIONAL SPECIFICATION left by Henry Marc Brunel at the Office
of the Commissioners of Patents on the 30th December 1880.
"
HENRY MARC BRUNEL, of Delahay Street, Westminster, in the County of
Middlesex. IMPROVEMENTS IN APPARATUS FOR DETERMINING RECIPROCATING.
MOTION IN A STRAIGHT LINE."
Reciprocating motion is usually determined to take place in a line straight or
approximately straight by arranging the moving part to slide in straight guides or
to be guided by apparatus of the nature of a parallel motion in which radial arms
rocking on centres act in combination to produce motion in a straight or nearly
straight path. Combinations of the latter kind have usually been so arranged
that the parts move in one plane or in parallel planes, the motions of some of the
parts in their curved paths correcting as it were the curvatures resulting from the
motions of others of the parts also in curved paths. My Invention relates to
apparatus for determining motion in a straight line by a combination of radial
arins rocking on centres or axes but in different planes, as I will explain with
reference to the accompanying diagrammatic Drawings and to the Figures and
letters marked thereon. Referring to Fig. 1, if a radial arm A B pivotted at one
of its ends A have jointed to it at its other end B another radial arm B C, it is
obvious that the arm A B being free to rock on A the point C may be guided to
reciprocate in a straight line, the arms taking the positions indicated by the dotted
lines in the Figure. By employing broad arms rigid in their plane and in every
direction, and mounting them on lengthened axes, so as to give them wide spread
bearings at their working joints, these bearings being made to fit the axes without
permitting end play, as indicated in perspective in Fig. 2. The motion of C must
necessarily take place in the plane to which the lines of the two parallel axes are
perpendicular. If C besides being connected to one pair of arms A B, BC, be also
connected to another similar pair a b, b C, as shewn in perspective at Fig. 3, the
motion of C must also take place in the plane perpendicular to the axes a and b.
Now if the plane a b, C, make any angle other than 180° with the plane A, B, C,
the two planes will intersect each other, and as the intersection of two planes is a
straight line, the point C being compelled to move in both planes must move in

page_text: their intersecting line, that is to say, in a rectilineal path. Obviously there might
be a number of sets of arms such as AB, BC, or a b, b C, arranged around the path
of C, all the planes of motion determined by them intersecting in one and the same
straight line, but two sets, as indicated at Fig. 3, are sufficient to determine the
rectilineal path of C, their operation being most effective when the plane of motion
determined by the one is at right angles to the plane of motion determined by the
other. From the above illustrations it will be understood that apparatus according
to my Invention consists of two or more sets of rocking frames jointed to the
reciprocating part that is to be rectilineally guided, each rocking frame consisting
of two members, of which the first A B or ab is pivotted on an axis at its base, and
has the second BC or bC jointed on a parallel axis to its upper edge, these
frames being arranged so that the planes perpendicular to the axes of their
respective joints intersect each other in the desired line of motion.
In what precedes I have supposed that only one point C has to be guided in a
rectilineal path, and I have therefore treated the upper frames as being of triangular
form. They might however be rectangular and jointed to a solid body as indicated
in Fig. 4, the axes of their jointings to the body being parallel respectively to the
axes of their other joints. Such a body will thus be guided to move rectilineally
parallel to itself, every point in it having its motion determined along the inter-
section of two planes which are perpendicular respectively to the axes of the joints
of the two sets of rocking frames.