Improvements in Clamps for Bicycle Seat-posts.
Year: 1899

page_text: Date of Application, 10th Jan., 1899-Accepted, 11th Feb., 1899.
COMPLETE SPECIFICATION.
Improvements in Clamps for Bicycle Seat-posts.
I, LEONARD BUDD GAYLOR, Manufacturer, of 120, West 5th Street, Erie, County
of Erie and State of Pennsylvania, United States of America, do hereby declure
the nature of this invention and in what manner the same is to be performed, to
be particularly described and ascertained in and by the following statement;-
My invention relates to improvements in bicycles and has special relation to
so-called internal clamping devices for the seat-post. By that I mean devices
located within the tubular parts of the structure, whereby they will be hidden
from view, the appearance of the bicycle improved, its cost greatly reduced, and
the ease with which the seat may be adjusted and its rigidity when in position
increased. Prior to my invention a large number of devices for the purposes
stated have been employed, but all of them, so far as I am aware, are more or
less unsatisfactory, because, in some instances of disfiguring the machine, in others
imperfect gripping or holding action, in others lack of durability, and for various
other reasons.
By my invention the desired object is attained in a completely satisfactory
manner, as I have demonstrated after exhaustive tests, by the employment of
but two exceedingly simple and inexpensive parts in addition to those necessarily
present as parts of the frame; and by their use the seat-post may be quickly and
easily clamped in any desired position, and released for adjustment at will.
The drawing hereof illustrates a view, partly in elevation and partly in vertical
section, showing my preferred method of embodying the invention in or with the
frame of the bicycle. I show so much only of the several parts of the frame and
of the seat-post as are necessary to a proper understanding of the invention.
A represents parts of the frame upon which the usual frame connection or forg-
ing B is mounted or attached. The forging is bored out about three-sixteenths of
an inch, more or less, larger in diameter than the usual hole in which the seat-
post is inserted, thus producing the shoulder C. Into this opening is inserted a
short tube, D, which has an internal diameter quite closely fitting the external
diameter of the seat-post, E, and the height or length of the tube is at least
one-half its interior diameter-preferably nearly equal to the total diameter and
it is made of relatively thin metal, so that when subjected to the pressure of the
clamping nut it will assume an ovoid form (in cross section) and its sides will be
flattened down against the seat-post, thus greatly increasing the area of frictional
contact, and yet upon releasing the pressure of the nut, the tube will spring back
into its normal form, thus automatically releasing all grip upon the seat-post.
This short tube must fit loosely in the hole in the forging, so as to have free
lateral movement to the desired extent, and its ends are formed on a slight bevel,
for reasons hereinafter explained.
The upper end of the forging Bis screw-threaded, preferably but not necessarily
on its inner surface, as seen at F, and a correspondingly threaded clamping
nut, G, provided with a wrench-hole, H, or its equivalent, whereby it may be
turned, is adapted to be screwed into the end of the forging. The relative size

page_text: and arrangement of the parts is such that when they are assembled and the nut
partly screwed in it will bear upon the upper arc or part of the tube D, which is
supported at its diagonally opposite are or part by the shoulder C.
The operation of the invention is this: The seat-post is passed through the
hollow nut, G, and through the tubo 1), which, as stated, it fits somewhat snugly,
and is moved up or down until the desired adjustment is attained. Then the nut
is screwed down until it impinges upon the upper edge of the tube D, and as soon
as this occurs, inasmuch as the tube D is rigidly supported by the shoulder C on
the forging, any further screwing down of the nut causes the tube D to exert a
most powerful gripping action on the seat-post, by reason of the fact that, since
the tube fits the post with considerable snugness prior to the pressure of the
nut, as soon as it is applied to the tube the surfaces of the two parts are brought
into very great frictional contact, and the area of such contact is very extensive,
for two reasons: first, the tubular clamp is of such length that it has a large area
of contact with the post; second, the pressure of the nut upon the edge of the
tube tends to force it downwardly and outwardly, and this pressure being resisted
by the shoulder Con the opposite side, the downward movement
prevented, and, 2.8 a result, the upper portions of the tube on one
side, and its lower portions on the other side, come into contact with the seat-
post, and the resistance of these points of contact to the further movement of the
clamping tube causes it to assumie an ovoid form, whereby its lateral sides also are
brought forcibly into contact with the sides of the post at right angles to those
upon which the tube first makes contact.
19
It will be seen from the foregoing that when the clamping nut is screwed
down to the desired position the clamping tube is in close frictional contact with
the seat-post, and that the area of such contact must necessarily be great, because
this contact is not only at the sides where the nut and the shoulder Care, but
also throughout nearly the entire circumference of the clamping tube, by reason
of its assuming the ovoid form referred to. In this manner great friction is
engendered between the clamping tube and the post, whereby the latter is held
with remarkable rigidity and without disfigurement or crushing or distorting
action upon either of the parts. This feature is of great consequence in con-
sideration of the fact that the seat-post must be hollow and made of relatively
thin metal.
A peculiar feature of my invention is the ease and effectiveness of its operation.
By the exercise of an astonishingly small amount of power upon the clamping
nut, a seat-post may be clamped so as to hold a very heavy rider; and also the
device operates with such effectiveness that a one-third revolution of the clamp-
ing nut will effect the most rigid clamping action and positive release. It will
be understood that the action of the release is just the reverse of the clamping
action; that is to say, the moment the nut begins to ascend, the clamping tube
automatically assumes its normal form, whereby the right and left strains, so
to speak, are first relaxed, and immediately thereafter, as the nut further ascends,
the direct strains at the point of its contact with the clamping tube and at the
point of its support are relaxed. When this takes place the tube merely encircles
the seat-post, free to move slightly in all directions, and through it the seat-
post will slide freely.
A highly polished surface, both on the interior of the tube and the exterior of
the post, will not prevent the rigidity of the holding action, which is purely that
of the pressure or frictional contact of the surfaces against each other throughout
a considerable area, in contradistinction to any indentation or cutting action by
the clamp upon the post; indeed, prefer to round off the upper and lower edges
of my tubular clamp so as to avoid any possibility of such indenting, tooth-like
or cutting action. Owing to the peculiar form of my clamp and its operation,
the parts are practically indestructible, and the seat-post permanently maintains
its original condition, without indentations or distortion.

page_text: In order to prevent the tubular clamp from turning, as upon a vertical axis, in
case it should have any tendency so to do, I provide certain interlocking surfaces
between it and some suitable part of the forging as, for instance, a notch
formed in the tubular clamp, and a pin J, or equivalent tooth-like part on the
forging. This form I have found a desirable one because it embodies certain
mechanical features conducing to its permanence and effectiveness.
It will be obvious to those who are skilled in this art, that modifications may
be made in the construction and arrangement of the parts without departing
from the essentials of the invention, and I therefore do not limit myself to the
special construction shown. Among such possible changes is the following:
instead of the ends of the tubular clamp D being formed on an incline, any other
construction which will cause it to be supported eccentrically at one part and
the pressure of the nut or equivalent device upon it applied eccentrically at another
and preferably opposite part, will fulfil the object sought.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:-
1. A frictional holding device for a bicycle seat-post, comprising a frame con-
nection or forging provided with external projections to receive the frame tubes,
a short tube made of relatively thin, elastic metal adapted to spring as described
under the pressure of the clamping nut, having an interior diameter slightly
greater than the exterior diameter of the seat-post, and a height or length equal
to at least half the diameter of the seat-post, enclosed within a recess in said
frame connection and hidden by it, and which embraces the tubular seat-post,
said short tube being eccentrically supported at one point, and a threaded nut to
apply pressure upon it at another point, for the purposes set forth.
2. In a bicycle, the combination of a frame connection or forging provided with
external projections to receive the frame tubes, a shoulder or recess within the
forging, a fixed pin or projection, a hollow tubular seat-post, a short tube, as
shown, made of relatively thin, elastic metal adapted to spring under the action
of the clamping nut, embracing the seat-post and having a notch at its lower
edge to engage with said pin or projection, and said clamping nut arranged to
apply pressure upon the short tube, for the purposes set forth
4444
Dated 18 10th day of January lov
REGINALD W. BARKER,
Applicant's Agent, 56, Ludgate Hill, London, E.C.