IMPROVEMENTS IN SCREW CLAMPS
Year: 1880

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PROVISIONAL SPECIFICATION left by the said Henry Metham at the
Office of the Commissioners of Patents on the 11th December 1880.
HENRY METHAM, of Church Street, Deptford, in the County of Kent.
IMPROVEMENTS IN SCREW CLAMPS."
The Invention has for its object improvements in screw clamps, and relates to
means whereby a readily portable clamp is constructed, which is lighter, cheaper,
and more convenient in use than screw clamps constructed in the manner heretofore
adopted.
For this purpose I employ two arms hinged together, preferably by means of a
rule joint, and I operate such arms by a right and left handed screw working in a
nut pivotted in a recess in each arm.
The swivel jaws are each formed with a curved face, leaving a rise or projection
at each corner.
Instead of hinging the two arms directly to each other a link or bar may be
interposed between them to lengthen the clamp.
Each nut and the two pivots or trunnions thereof are preferably formed in one
piece, and the two recesses in the arms are formed with open sides, which, after the
insertion of the pivotted nuts, are closed by side plates fixed thereto.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Henry Metham in the Great Seal Patent Office on the 11th June
1881.
HENRY METHAM, of Church Street, Deptford, in the County of Kent.
"IMPROVEMENTS IN SCREW CLAMPS."
This Invention relates to an improved construction of screw clamp capable of
being applied to exert either a compressing or expanding action, as may be
required, and which is more portable and more convenient to use than screw
clamps of the ordinary construction. It is moreover capable of use in situations
where, and of application to purposes for which, an ordinary screw clamp would
not be available.
The screw clamp of this Invention consists of a pair of arms hinged at one end
together, or to a link, bar, or chain (according to the dimensions of the work), and
provided at the other or free ends with jaws jointed to the arms so as to preserve
the parallelism of their faces in tightening up the clamp, and enable the jaws to be
adjusted either for a compressing or an expanding action of the clamp. The arms
of the clamp are drawn together or forced apart as required by a right and left
handed screw working through swivelling nuts pivoted in apertures in the arms.
In order to adapt the Invention for flooring and other purposes, one of the
jaws of the clamp may itself be a screw clamp adapted to grip a joist or other
timber, whilst the other jaw is applied against the plank to be secured.
DESCRIPTION OF DRAWINGS.
Figure 1 is an elevation of this improved clamp, part of one of the arms being
broken away to represent the nut; Figure 2 is a section of the arm taken through
the line 1-1, Figure 1; Figure 3 represents a modification; Figures 4 and 5 show
part of the arms of the same clamp when extended by means of a link and bar
respectively to embrace work of larger dimensions; Figure 6 shows a face and
edge view of a jaw, having a stud or projection at each corner; Figure 7 shows an
edge, and Figure 8 a side view of a clamping jaw, which might be substituted for
one of the jaws shown in Figure 1 to adapt the clamp for flooring and planking
purposes.
The same letters of reference indicate the same parts in all the Figures.
A, A, are the two arms of the clamp hinged together at B, preferably by a rule
joint, or to a link, bar, or chain, as hereafter described; C, C, are the jaws of the
clamp respectively hinged to the other ends of the arms A, preferably by rule
joints at D, so as to compensate for the varying angle of the arms and maintain the
parallelism of the jaws, and so as to admit of the jaws being thrown over from the
position in which they are represented in full lines to the position represented in
dotted lines in Figure 1, when the pressure is to be applied by the forcing apart
instead of the drawing together of the arms. The jaws C may be of round, square,
or other form, and their faces may be flat, concave, or convex, and may be smooth
or roughened (diamond pointed or otherwise), or they may have studs or pro-
jections c, Figure 6, at the corners according to requirements. Each jaw has a
tenon or lug at the centre at back, which is received between the forked end of the
arm (or vice versa), and the joint pin may be rivetted, but is preferably a screw
bolt secured by a nut, as shown, to admit of the substitution for the jaw C of the
clamping jaw hereafter described; E is the right and left handed screw by which
the arms are operated in either direction, and F, F, are the nuts through which it
works. Each arm A is preferably curved and formed at about the middle of its
length with an aperture or eye A¹ to receive its nut F, which is pivoted upon side

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pivots G, G, so as to swivel and allow of the varying angle of the arms.
pivots G pass through holes in the sides of the eye A¹, and are threaded and
Screwed into tapped holes in the sides of the nuts. Or the pivots may be turned
on the nuts, and one side of the eye A¹ may be made separate and rivetted, or
otherwise united to the arm after the nut has been inserted, as shown in Figure 3,
but by thus dividing the eye the arm is weakened. The right and left handed
screw E is of a suitable length, and may be replaced by a longer one when the
clamp is extended by the link, bar, or chain hereafter referred to, the knob or
head e of the screw being removable to permit the insertion and removal of the
screw E. For this purpose the knobe is fitted on the squared end of the screw E,
as shown in Figure 1, and the knob e' at one end of the sliding cross handle E' is
similarly removable to enable the cross handle to be withdrawn, and knob e to be
unscrewed; or the knob e may be provided with a rigid handle and form a key or
spanner in lieu of the sliding cross handle. The joint at B is a screw bolt secured
by a nut to admit of the arms being readily detached and hinged to the ends of a
link G¹, as in Figure 4, the one end of this link being forked, and the other tenoned
for connection respectively with the tenon and forked ends of the arms A. Instead
of a single rigid link a chain of jointed links may be used when great length is
required, and the clamp is to be used for compression only, or a flat or Ţ iron bar H
may be used, as in Figure 5, forked at one end to receive the tenoned end of the
one arm A which is jointed thereto, the forked end of the other arm A embracing
the bar, and being jointed thereto at any one of a row of holes in the bar.
In Figures 7 and 8 A is part of one of the arms of the clamp, to whose end is
jointed in place of the jaw C, before described, a small clamp formed of two
jaws I, I, of which one is fixed to a base I2 having a central lug at back for
connection with the arm A, and the other I is movable and is closed up towards
the first by a screw K working through the part 12, the jaw I¹ being guided by
rods L sliding through lugs on the back of the clamp. The faces of I, I', and I³,
may be serrated or spiked to ensure a firm hold of the joist or timber to which it
may be applied.
The several parts of this clamp may be made of malleable iron, malleable cast
iron, or other metal, but I prefer to make the arms and jaws of malleable cast iron,
the screw and the bar, link, or chain of wrought iron, and the nuts of gun metal.
Having described the nature of my said Invention, and the manner of performing
the same, I declare that what I claim as my Invention to be protected by the
herein before in part recited Letters Patent is,-
1st. A screw clamp constructed to operate either by compression or expansion,
substantially as shown and described.
2nd. The combination with the arms of a screw clamp, of jaws hinged to the
ends thereof so that the parallelism of the jaws is maintained, and they are capable
of being adjusted for a compressing or expanding action of the clamp, substantially
as shown and described.
3rd. A pair of arms hinged together at one end, or to a link, bar, or chain, a
right and left handed screw and swivelling nuts mounted in the arms, all combined
to operate substantially as shown and described for the purpose specified.
In witness whereof, I, the said Henry Metham, have hereunto set my hand
and seal, this Eighth day of June, in the year of our Lord One thousand
eight hundred and eighty one.
HENRY METHAM. (L.S.)