Improvements in Spirit-levels.
Year: 1887

page_text: Date of Application, 20th Dec., 1887
Specification Accepted, 3rd Feb., 1888
Improvements in Spirit-levels.
1, GUSTAVUS COOK, of 50 State Street, in the City of Watertown, in the County of
Jefferson, in the State of New York, one of the United States of America, Millwright,
do hereby declare 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 —
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My invention relates more especially to the class of levels commonly known as
"spirit-levels" or carpenters' levels," wherein the bubble-tube is mounted in a
wooden or metallic bar or holder with true parallel fiducial faces.
The object of my invention is to provide such level with a spindle-shaped bubble-
tube extending transversely across a frame let into an aperture in the bar, whereby the
middle of the tube is left uncovered and visible, and the bubble may be observed from
both sides by transmitted light, and whereby the level may be turned with either edge
up, as desired, the spindle-shape of the tube and the absence of an opaque covering
rendering this practicable. The bubble-tube is protected by glass or other transparent
plates at the sides, and the frame carrying the tube is made adjustable, so as to bring
the bubble to the center when the level-bar is resting on a standard level surface.
I also mark the center of the tube with a line or band, which bisects the bubble when
the latter is in the center of the tube; or two bands to embrace the bubble may
be employed.
In the drawings which serve to illustrate my invention, Figure 1 is a side view of
a spirit-level provided with my improvements, parts of the bar being broken away to
show the arrangement of the adjusting mechanism. Figure 2 is a transverse section of
the level on a scale double that of Figure 1. The plane of the section is indicated by
line 22 in Figure 1. Figure 3 is a view of the level-mountings detached from the bar
and drawn to the same scale as Figure 2. Figure 4 illustrates a slightly modified
arrangement of the adjusting screw.

page_text: In an
Let A represent an ordinary rectangular level-bar with parallel faces a a.
aperture formed in this bar is fitted loosely a ring B, provided with a lug b, by which the
ring is pivoted at one side in the bar on a pin c. In this ring B is mounted the bubble-
tube C, which extends diametrically across the ring B. This tube is of a spindle
shape, having that degree of swelling or enlargement at the middle that is desirable
to impart steadiness to the bubble. In the margins of the ring B are formed rabbets
to receive plates DD of glass or other suitable transparent material. These inclose the
space in the ring B occupied by the bubble-tube, and protect the latter from injury.
EE are flanged retaining rings, secured to the bar A by screws or other suitable
means. These rings closely embrace the ring B and plates D; tightly enough to
keep the same in place, but not so tightly as to prevent the movement of the ring in
adjusting.
On the opposite side of the ring B from the lug b is a lug d, with a screw-threaded
eye in its extremity, into which screws an adjusting-screw e, having a bearing in a
plate g, let into the wood of the bar A. When the bar is of metal, this plate will
not be required. In a recess in the bar and embracing the body of the screw e is a
spring h, one end of which rests on the lug d, and the other against a shoulder formed
above in the bar. I usually form the spring-recess by boring in from the face a of
the bar, and then fitting a plug in the hole above the spring, as indicated in Figure 3,
where this plug and the adjacent part of the bar are shown in section.
It will readily be understood by inspection of Figure 3 that the screw e and
spring will enable the ring B to be adjusted up or down at one side enough to
bring the axis of the bubble-tube into a position parallel with the faces a of the bar.
In Figure 4 I have shown the adjusting screw e so arranged that the spring / is not
needed. In this construction the head of the screw has a bearing in a sunken plate g¹,
a flush plate g extending over the screw-head and having an aperture somewhat
smaller than the screw-head, but of sufficient size to admit a screw-driver for adjusting
the screw: Or the plate o may be without an aperture, in which case the screw can
be reached by removing the plate. This will prevent the screw from being tampered
with by unauthorized persons.
It will be seen that my construction makes it a matter of indifference which face a
of the bar is applied to the work or surface to be levelled. In either case the
bubble-tube will be convex on the upper side, owing to its form. The bubble-tube is
also exposed to view from both sides, and is at the same time fully protected against
injury by the plates D. The mark i across the middle of the bubble-tube enables the
workman to bring the bubble exactly to the center without difficulty.
In order to insert the bubble-tube in its sockets or bearings in the ring, the ring
may be cut in a plane coinciding with the axis of the tube, the tube placed, and the halves
of the ring secured together by soldering or by means of screws; or the bearings in the
ring may be made large enough to allow the larger portion of the tube to pass through,
the tube being then inserted and secured by cement or otherwise. This method of
inserting the tube forms no part of my invention, and any mode may be employed.
In order that the level may be used to ascertain whether a wall or other structure is
plumb, it is furnished with another bubble-tube C', mounted in precisely the same
manner as the tube C, except that its axis is at right angles to the axis of the latter.
This tube C and its mountings are so clearly shown as to require no further
description.
To prevent dust from entering the space occupied by the bubble-tube, the trans-
parent plates D D may be cemented in the ring B. This ring or frame B need not
be of the circular form shown. It may be square or polygonal.
Having now particularly described and ascertained the nature of my invention and
in what manner the same is to be performed, I declare that what I claim is :-
:-
Firstly A level having a transparent bubble-tube supported at its ends and left
visible at its middle part, so that the level may be inverted or employed with either
face uppermost.
Secondly-A level having an aperture in its bar inclosed at the sides with plates

page_text: of transparent material and a bubble-tube extending across the said aperture within
the space inclosed by the said transparent plates.
Thirdly The combination, with the apertured bar, of the ring mounted adjustably
therein, the plates of transparent material mounted in the said ring, the bubble-tube
of spindle-shape, mounted in and extending across the said ring, and mechanism for
adjusting the ring in the bar.
:
Fourthly A level having a spindle-shaped bubble-tube provided with a mark
across its middle to serve as a bubble-index when the level is used, the said tube being
mounted in and extending across an aperture in the bar, whereby it is rendered
visible from both sides.
Fifthly The combination, with the bar A, of the ring B, pivoted in the bar on
the pin c and provided with a lug d, the bubble-tube mounted in the said ring, the
screw e, screwed into the lug d on the ring, and the spring h, embracing the screw e,
and arranged between the lug d and a shoulder on the bar A, substantially as
set forth.
Dated this 19th day of December A.D. 1887.
G. G. M. HARDINGHAM,
191, Fleet Street, London, E.C.,
Agent for the Applicant.