Improvements in Tractors for Obstetric Forceps.
Year: 1890

page_text: Date of Application, 25th Nov., 1890-Accepted, 17th Jan., 1891
COMPLETE SPECIFICATION.
Improvements in Tractors for Obstetric Forceps.
I, ALBERT BENEDICT LYMAN, of 2100 St. Paul Street, in the City of Baltimore and
State of Maryland, United States of America, Doctor of Medicine, do hereby declare
the nature of my invention for "IMPROVEMENTS IN TRACTORS FOR OBSTETRIC
FORCEPS and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
This invention relates to an improved tractor adapted for application to a pair of
obstetric forceps after the same are in position whereby the blades of the forceps may
be made to accurately follow the pelvic curve.
The said invention consists, first, in a tractor adapted to enter the space between
the shanks of the forcops and bear directly on the lock thereof, and form a rigid
continuation of the shanks in order that a certain curved movement is commu-
niented thereto, independently of that imparted to them by the secondary curve of
the blades.
The said invention consists, secondly, in a peculiar construction of the tractor
whereby the curved path of the same may be changed at pleasure to conform to
structural peculiarites in the patient, independently of the curvature of the blades.
In other words, the secondary curvature of the blades of standard forceps is made
to conform to the general natural curvature of the pelvis, but in view of the norinal
deviation of the curve of the pelvis from the are of a circle, and individual structural
peculiarities, it is evident that it is practically impossible for the blades of the
instrument to be constructed so as to suit all cases.
The second part of the invention has, therefore for its object, the construction of a
removable tractor which may be made to change the natural path of the forceps as
effected by the secondary curvature of the blades.
In the further description of the said invention which follows, reference is made to
the accompanying drawings forming a part hereof and in which,
Figure 1 is an exterior side view of a pair of locked forceps to which the improved
tractor is applied.
Fig. 2 is an edge view of Fig. 1 as seen from the concave portion of the blades.
Fig. 3, is a view, the reverso of Fig. 2, or one looking from the convex portion of
the blades.
Fig. 4, is an enlarged view of the tractor extended, and Fig. 5 a similar view of the
same closed.
Fig. 6 illustrates a modification in the construction of the tractor handle.
Figs. 7 and 8 illustrate a further modification in the construction of the tractor.
Referring to Figs. 1 to 5, inclusive, A, represents the blades, B, the shanks and
the handles of the forceps. The fenestrum of the blados is denoted by a, and the
lock by b.
D is the tractor, consisting of the shank, c, hook, d, stem e, and handle. The stem
is jointed to the shank in such manner that the two parts may be closed for con-
venience in transportation, and opened so that they may be brought to a practically
right angle with each other.
The stem, e, is provided with a double or triple thread of course pitch, and on it is
placed a spherical nut, g, having a pin, h, which passes loosely through the handle f,
to admit of the latter being turned thereon.
The adjustability of the handle, on the stem e, admits of a change in the curved
ath of the forcep blades effected by the use of the tractor as described for the reason
that the further the handle is moved out, the shorter will be the radius of the curve
described by the instrument in oneration, and vice versa.

page_text: A cap, on the end of the stem prevents accidental removal of the nut, and the
shank, c, has two lugs, j, which bear against the handles on the forceps as power is
applied to the tractor.
The width of the opening in the hook, d, is such as to prevent any unnecessary
loose motion between the tractor and the forceps when force is applied to the handle
of the tractor in the operation of the instrument.
It will be observed that power applied to the handle, of the tractor in the direction
of the arrow in Fig. 1, tends to move the lower end of the handles of the forceps
inward as well as downward; or in other words, to move the blades B of the forceps
in a curve approximating that of the polvis, and this curvature may be varied by the
adjustment of the nut, g, longitudinally of the stem a, so as to correct any departure
in the secondary curvature of the blades of the forceps from the pelvic curve of the
patient, and also to adapt the instrument to the anatomically normal, or to any
accidental irregularity in the curve of the pelvis.
It will be seen that the tractor described can be instantly applied to any of the
commonly used forceps, as it does not depend for its connection thereto on studs,
pins or any other projections which in different instruments would, or wight differ in
size, character or position; and further that power applied to the tractor has no
tendency to alter the relative positions of the two members of the forceps, and therefore
cannot spread or close their blades.
From the foregoing description of the invention it will be understood that by its
use in connection with forceps having a secondary curve, direct axial traction may be
effected in obstetric operations, whore abnormal structure in the patient would prevent
a satisfactory result with forceps which depend on the secondary curvature alone for
the preservation of the axial position of the blades.
In Fig. 6, a spade-handle is shown attached to the spherical nut g, instead of the
cross handle illustrated in the other figures.
In Figs. 7 and 8, the lugs j, are formed by a cross bar adapted to slide on the
shank c, which has beveled or chamfered edges to form a dovetailed connection-
Fig. 8 is a cross section of Fig. 7, taken on the dotted line a-z. By having lugs j,
adjustable in position on the shank, they may be set to suit forceps of any length
of handle, and to bear on any part of the handles within the range of their
movement.
The beveled edges of the shank are cut away at m, so as to make a space to
admit of the attachment and detachment of the bar.
One end of the bar is perforated, and through the hole a cord may be passed for
binding the shank and the handles together.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what 1
claim is :-
1 In combination with a pair of obstetric forceps, a tractor which consists of a
hooked shank adapted for connection with the lock of the forceps, having a threaded
stem which is at practically a right angle with the shank, a nut on the threaded stem,
and a bandle attached to the said stem, substantially as, and for the purpose
specified.
2-A tractor for a pair of obstetric forceps which consists of a booked shank with
a stem projecting from it at practically a right angle, and a handle on the said stem,
substantially as, and for the purpose specified.
3-A tractor for a pair of obstetric forceps which consists of a hooked shank
having a jointed stem extending therefrom with a handle dependent from the said
stem, substantially as, and for the purpose specified.
4-A tractor for a pair of obstetric forceps, which consists of a hooked shank having
a jointed threaded stem projecting therefrom with a nut thereon, and an adjustable
handle dependent from the said nut, substantially as, and for the purpose specified.
5-A tractor for a pair of obstetric forceps which consists of a hooked shank with

page_text: a stem projecting at practically a right angle therefrom, and a handle connected to
the said stem, and lugs on the said shank which as the tractor is drawn down, bear
against the handles of the forcops and communicate the inward movement of the
tractor to the handles of the forceps, substantially as, and for the purpose specified.
Dated this 21st day of October 1890.
ALBERT BENEDICT LYMAN, M.D.
Haseltine, Lake & Co.,
45, Southampton Buildings, London, Agents for the Applicant.