A MANDREL WITH CONCENTRICAL CLAMPS
Year: 1881

page_text: LETTERS PATENT to Charles Croissant, Mechanical Engineer, and Pierre
Philippe Huré, Ironmonger, both from Paris, in the Republic of France, for
PROVISIONAL SPECIFICATION left by the said Charles Croissant and Pierro
Philippe Huré at the Office of the Commissioners of Patents on the 14th May
1881.
CHARLES CROISSANT, Mechanical Engineer, and PIERRE PHILIPPE HURE, Iron-
monger, both from Paris, in the Republic of France. "A MANDREL WITH
CONCENTRICAL CLAMPS."
The mandrel or chuck forming the subject of the present Invention is applicable
to lathes, boring and shaping machines, and other machine tools, and is constructed
in the following manner :-
The body or case of the mandrel or chuck is externally of a truncated conical
shape, with a milled part for more secure holding by the hand or otherwise. In
the interior of the body or case is a socket, the back end of which is adapted to
screw on to the mandril of the lathe, or to fit or screw into the tool box of the
machine in which it is to be used; over the said socket and between it and the
internal surface of the body or case is fitted a conical screw adapted to turn easily
on the said socket. This conical screw is retained on the said socket by means of
a nut screwed on to the back thereof. On the interior of the truncated conical
body or case are formed three or more grooves, which converge towards the virtual
apex of the said truncated conical body or case. In these grooves are fitted and
adapted to slide therein corresponding clamps or gripping pieces, the front ends of
which are adapted to grip and hold any article placed between them, the size of
which does not exceed the maximum diameter for which the mandrel or chuck has
been designed. The inside edges of the hinder ends of these clamps or gripping
pieces are cut with screw threads, which correspond to and take into the screw
threads formed on the conical screw which turns on the aforesaid socket. The
aforesaid conical screw is extended so as to cover the base of the mandrel or chuck

page_text: and is either milled at its edge to facilitate its rotation by hand or is otherwise
formed or adapted to be turned round by a key or other instrument.
If preferred the clamps or gripping pieces may have the screw threads formed on
the outsides of their hinder ends instead of inside thereof, and in that case instead
of being actuated by a conical male screw they would be moved by a conical
screwed nut or female screw.
It will now be understood that when the body or case of the mandrel or chuck
is held fast, and the aforesaid conical screw or nut is. turned on the socket, the
screw thread on such conical screw or nut operates the clamps or gripping pieces,
causing them to slide inwards or outwards in the grooves of the body or case; and
as these grooves converge towards the apex of the conical body or case the outer
or gripping ends of these clamps or gripping pieces approach towards or recede
from each other radially, according to the direction in which the said conical screw
is turned on the socket. The outer or gripping ends are shaped according to the
shape of the article they are intended to hold.
According to these arrangements none of the working parts of the mandrel or
chuck are visible externally, and they are all secured against dust, dirt, or blows.
The clamps each made of a single piece are very rigid, and are guided their whole
length; the tightening screw or nut acts directly upon them, and they move
uniformly, and in parallel lines towards the piece which they are intended
to hold.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Charles Croissant and Pierre Philippe Huré in the Great Seal Patent
Office on the 12th November 1881.
CHARLES CROISSANT, Mechanical Engineer, and PIERRE PHILIPPE HURÉ, Iron-
monger, both from Paris, in the Republic of France. "A MANDREL WITH
CONCENTRICAL CLAMPS."
The mandrel or chuck forming the subject of the present Invention is applicable
to lathes, boring and shaping machines, and other machine tools, and is constructed
with concentric clamps, fitted into converging grooves in the body of the mandrel
or chuck, and adapted with screw threads behind, which take into corresponding
screw threads formed on a conical screw or nut fitted and held in the said body of
the mandrel. On turning the said conical screw or nut in one direction by taking
hold of it with the hand, or by a key upon a part thereof which covers the base of
the mandrel, the clamps are pushed out so as to approach each other, and thus to
grip or clamp between them the object to be held. On turning the screw or nut in
the opposite direction the clamps or gripping pieces are drawn apart, and the object
released. The mandrel is pierced through its centre with a hole equal to the
largest diameter it is desired to grip.
In the Drawings hereto annexed, Figure 1 represents an elevation of the new

page_text: mandrel with the clamps drawn back; Figure 2, a longitudinal section; Figure 3,
a corresponding front view, and Figure 4, a back view with the clamping screw
removed.
Figures 2 and 6 show in section and end view respectively the mandrel with the
clamps pushed out and clamped quite close together.
Figures 7 and 8 show two views of one of the clamps.
Figure 5 shows another example adapted to be screwed on to the lathe or other
machine tool for which it is intended.
Similar letters of reference indicate like parts in all the Figures.
The body or case a of the mandrel or chuck is externally of a truncated conical
shape with a milled part a' for more secure holding by the hand or otherwise. In
the interior of the body or case «, and attached thereto by the partition c, is a
socket b, the back end of which is adapted to fit or screw on to the mandrel of the
lathe or other machine in which it is to be used. Between the said socket b and
the internal conical surface of the body or case a is fitted a conical nut or screw d
adapted to turn easily on the said socket b, and freely in the body or case a.
This conical screw d having to turn on the socket b only is retained in place thercon
by means of a washer nut a screwed on to the back thereof.
The conical body or case has formed in it three mortices f. f, f, which converge
towards the same point in the virtual axis of the truncated cone, and in which are
fitted the three clamps m, m, m.
Beyond the partition c the mandrel is solid, except as regards a central hole c,
which is enlarged at e¹, and goes through the body or case. In this front portion
the mortices of circular section similar to the bodies of the clamps are continued
into the hole e by mortices with parallel sides, between which slide the flat
gripping parts of the said clamps, which hold any article placed between them
which does not exceed in diameter the size of the hole c. The inside edges of the
hinder ends of these clamps or gripping pieces m, m, m, are cut with screw threads
which correspond to and take into the screw threads formed on the conical screw d,
which turns on the aforesaid socket b, whereby all three clamps may be moved
inwards or outwards at pleasure. The aforesaid conical screw d is extended so as
to cover the base of the mandrel or chuck a, and is either milled at its edge d¹ to
facilitate its rotation by hand, or is otherwise formed or adapted to be turned
round by a key or other instrument. In the example shown in the Drawing the
milled part a' is obtained by counter-sinking.
If preferred the clamps or gripping pieces may have the screw threads formed on
the outsides of their hinder ends instead of inside thereof, and in that case instead
of being actuated by a conical male screw they would be moved by a conical
screwed nut or female screw.
It will now be understood that when the body or case a of the mandrel or chuck
is held fast, and the aforesaid conical screw d, d', or nut is turned on the socket b
the screw thread on such conical screw or nut operates the clamps m, m, m, causing
them to slide inwards or outwards in the grooves of the body or case, and as these
grooves converge towards the apex of the conical body or case the outer or gripping
ends of these clamps approach towards or recede from each other radially, according
to the direction in which the said conical screw is turned on the socket. The outer
or gripping ends are shaped according to the shape of the article they are intended
to hold.
According to these arrangements none of the working parts of the mandrel or
chuck are visible externally, and they are all secured against dust, dirt, chips, or
blows, and derangements of all kinds. The clamps, each made of a single piece, are
very rigid, and are guided their whole length; the tightening screw or nut acts
directly upon them, and they move uniformly and in parallel lines towards the
piece which they are intended to hold. Their great strength allows of their
exerting a gripping effect at least one third more powerful than that obtained with
the tools of this kind heretofore known. The construction is economical, strong in
all its parts, and in no way weakened by the converging grooves of the clumps.

page_text: The example shown in the Drawing allows of holding from zero to 12 millemetres
with very great force without fear of breaking any of the parts.
The body a of the mandrel is not completely cut through on any radius,
consequently it can resist very considerable strains.
The example shown in Figure 5 only differs from the other in having the hole e¹
of the socket furnished with a screw thread b₁ for screwing the mandrel on to the
lathe or other machine tool.
When it is necessary to take precautions against damaging the piece to be
operated upon by the screwing up of the clamps, these latter may be covered with
copper or other soft metal.
Having now described the nature of the said Invention, and the manner in
which the same is to or may be carried into effect, we would have it understood
that we do not confine ourselves to the particular forms of the various component
parts, the number of clamps, the dimensions, or the materials employed, as the same
may be varied according to circumstances without departing from the nature of the
said Invention, but what we do claim is,-
The new or improved mandrel or chuck herein before described and illustrated in
the Drawings hereto annexed, consisting essentially,―
First. Of a truncated conical part a with central socket b, such part a being
bored out at the front end to the maximum diameter of the piece the mandrel is
intended to hold, and at the hinder end to an enlarged diameter, and in the solid
part of which are formed three or other suitable number of converging mortices f.
Second. Of three or other suitable number of clamps m of the same section as
and fitting into the mortices f in the above mentioned truncated conical body, such
clamps being formed solid with guide stems, which are screw threaded at their
hinder ends.
Third. Of a truncated conical screw or nut d, d¹, fitted easily on to and held on
the socket b of the mandrel, the screw threads of such screw or nut taking into the
screw threads of the clamps for the purpose of forcing the latter outwards or
inwards, the said screw or nut d, d, being also furnished with countersunk or
other milling d¹.
Fourth. Of a nut g screwed on to the socket 6 of the mandrel, and holding in
place the gripping screw or nut d of the gripping clamps m.
In witness whereof, we, the said Charles Croissant and Pierre Philippe Huré,
have hereunto set our hands and seals, this Eleventh day of November, in
the year of our Lord One thousand eight hundred and eighty one.