Improvements in Lifting Jacks.
Year: 1888

page_text: Improvements in Lifting Jacks.
A communication from abroad by ANDREW WARREN, of St. Louis, in the City of
St. Louis, State of Missouri, United States of America, Manufacturer and
Merchant.
I, CHARLES AUBREY DAY, Fellow of the Institute of Patent Agents, of 321, High
Holborn, in the County of Middlesex, do hereby declare the nature of the said
Invention, 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 improvements in jacks. One feature of the invention is
a tapering lifting bar whereby a very effective grip is obtained in connection with a
simple form of gripping mechanism bearing upon a plain surface of the bar.
The invention also includes mechanism for lowering the bar with a load
thereon; and further it includes details of construction relating to the lever for
operating the head and in other particulars hereinafter set forth.
The invention is illustrated in the accompanying drawings in which :-
Figure 1 represents a side elevation of my lifting jack.
Figure 2 a central vertical section from front to rear.
Figure 3 is a horizontal section through the standard.
Figure 4 shows a side elevation of the jack with modified form of lifting lever
and head.
Figure 5 is a central vertical section through the lifting head and grinding

page_text: The standard A of the jack is of ordinary exterior dimensions and shape and the
base is shaped to suit the work intended. It is channelled to receive a lifting bar B.
The upper part of the channel, which is about the gripping chamber, is fitted closely
to the lifting bar, but below the chamber is cast with a larger channel so that it may
not require fitting. The bar B is a plain smooth bar tapering from the upper end
downward, the lower end having the ordinary lifting foot. The grip upon the bar
both in the lifting head and in the standard is caused by a wedging action against the
plain surface of the bar both for lifting and holding, and the taper upon the bar is for
the purpose of increasing the effectiveness of this grip, and to render it secure under
all circumstances, as for example when the bar becomes smeared with any greasy
substance. On the upper end of the standard is pivoted at m, a lifting handle E. It
is preferably made forked and thus has two bearings, one on each side, so that it may
lift squarely upon the head and avoid binding. The end of the lever as shown in
figure 1 is formed with a curved or cam face upon which rests a projection provided
with friction rollers p, on the lifting head D. The face o, of the cam bears such
relation to the pivot m, that when the pivot is down, the rollers of the projection on
the head rests on the low part of the cam, but as the handle is raised the higher parts
are brought beneath the rollers and thus the lever is caused to act with a wedging
action upon the head.
Over each cam surface o, is a loop 9, which forms with said can surface a curved
slot fitted to receive the projection or stud with its roller and to allow it to travel
throughout the whole movement of the lever, the loop serving to bring down the head
by a positive movement when the lever is depressed. Within the head D any suitable
gripping mechanism may be provided. One of the convenient forms is shown in
figure 2. Its main feature that of the roller g, working in a chamber having an
inclined wall is a well known mechanical device for gripping. The recess in the
chamber in which this roller works opens into the lifting bar channel throughout its
whole vertical extent. It is narrow at the bottom and the rear wall is inclined so
that the roller by its own gravity tends to wedge against the face of the lifting bar,
which wedging tendency is increased as the lifting bar is drawn downward by its load.
The wedging action is twofold, being caused by the inclination of the rear wall and
also by the inclination of the face of the tapering bar.
This wedging action is brought into effect whenever the head is lifted by the lover,
and the bar being gripped in the head is raised therewith. When the head is lowered
the bar being held by a grip in the standard as hereinafter described, the roller is
released by the reverse movement of the incline of the wall of the gripping chamber
which is then away from the roller.
To insure the release of the roller from its grip between the wall and the face of
its lifting bar, when the head is lowered, a pin K is fixed in the upper part of the
standard in line with a hole in the lower part of the head and with the roller, so that
it may enter the chamber as the head is lowered and lift the roller out of gripping
contact. In order to cause the roller to act promptly and prevent any lost motion
provide a pin on the upper part of the head arranged to press against the roller by a
spring interposed between the upper end of the pin, and a block H; the spring
permits the roller to rise sufficiently for its work, but causes it to return promptly to
nip between the bar and the rear wall.
Manifestly the weight of the roller would cause it when in vertical position to
operate without springs. The rear wall of the gripping chamber is made removable,
and it consists of a plate which may be of hardened steel, marked e. The lower end
rests in a groove and the upper end is held by a set screw so that the plate may be
removed when worn. The chamber in the standard is substantially the same as the
chamber in the head. In order to release the roller in the chamber of the standard
for the purpose of letting the bar down I have provided a releasing bar 2 which works
vertically in a slot in the standard, and at its upper end projects into the lower part
of the chamber of the standard as shown in figure 2, and the lower end projects
outwardly so that it may be reached by the hand or foot of the operator, and by it
the roller may be lifted out of the nip.

page_text: When the weight is applied to the lifting bar the gripping device in the chamber
are under great strain, and when plain bars are used the roller bears always upon the
same point, on the rear inclined plate, which soon wears. But with the tapering bar
the position of the roller constantly shifts as the bar rises so that the wear is distributed
over the surface of the plate, thereby greatly increasing the durability of the plate.
The different positions are shown in full and dotted lines in the standard chamber in
figure 2.
To make the implement capable of being put in compact form the handle is made
extensible by means of a solid portion G¹ which slides into tubular portions G, though
it may be made in one piece as shown in figure 4 at G2.
The taper may be formed in the bar by means of a groove or channel increasing in
depth towards the lower end, the channel being shown in cross section in figure 3. In
this case the side walls of the channel act as guides for the ends of the rollers.
Instead of the fixed rear wall heretofore described I have shown in figure 5 a
movable rear wall with a holding device behind it so that the wall may be allowed to
retreat slightly while the bar is held by the gripping device with its load, and thus
the load is lowered gradually, or it may be held at any point. As shown at d, the
wall is pivoted in the chamber at the upper edge and is preferably made of hardened
steel plate. The pivoted pin has its bearings in the side wall of the chamber and
some strong holding device is required to prevent the wall from being pushed back
by the great strain put upon the gripping roller. For this purpose I have provided
a cam lever F pivoted in ears in the standard behind the rear wall. The cam face
of the holding device is the periphery of the pivoted end of the lever and when the
lever is drawn down as shown in figure 5 the high part of the cam bears upon the rear
face of the movable wall. As the free end of the lever is raised the lower face of
the cam rides on the bearing point of the plate, and when the lover is up in the
position shown in dotted lines in figure 5 the low face of the cam is against the plate
and the lower edge of the plate back to its rear limit.
In order that the cam lever may hold in whatever position it happens to be left, and
at the same time may be readily moved I arrange the bearing face of the movable
plate in its relation to the cam face so that the point of contact of the cam face with
the wall shall be in line with the center of the gripping roller and the center of the
pivot of the cam lever. For this purpose the cam lever is pivoted low, and the face
of the cam is formed to correspond with the shape and position of the pivoted plate.
Preferably the cam lever is weighted.
Instead of the cam lever other devices may be used to hold the movable plate such
as a wedge as in figure 6. Obviously by working the lever gradually up, the rear
wall is allowed to retreat and the weight is thus lowered, but may be arrested at any
point.
While I have shown the inclined rear wall and roller as the gripping device in
connection with the tapering bar, it will be understood that other gripping devices
such as eccentrics or wedges may be used in the place of a roller and inclined wall.
The movable rear wall and its holding device is useful also in connection with a plain
bar, and its use is not limited to the combination shown.
I do not limit myself to any particular form of lifting lever as a lever may be
provided as shown in figure 7 to lift by depresssion instead of elevation as in the other
figures.
A removable wearing plate may be provided for the face of the tapered lifting bar
as shown in figure 6.
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. In combination in a lifting jack, a grip and a lifting bar having a taper from
upper to lower part substantially as described.
2. In combination with a lifting bar of a jack a grip and an adjustable holding

page_text: device therefor whereby the grip may be gradually released and the weight lowered
substantially as described.
3. In combination with the standard and head of a jack and with gripping devices
in said standard and head, a lifting bar and a lever pivoted on the standard having
cam faces bearing up projections on the head substantially as described.
4. In a lifting jack having a standard provided with a holding grip and a head
provided with a grip, a grooved tapered lifting bar and suitable operating means for
lifting said bar substantially as described.
T.: no
100
DAY, DAVIES & HUNT,
321, High Holborn, London, W.,
Agents for the Applicant.