US2317715A - Spirit level - Google Patents

Description

April 27, 1943. E. D. BALL SPIRIT LEVEL Filed June 5, 1942 1g 1 SEEEEEEEQEEE I Patented Apr. 27, 1943 srnnr LEVEL Edgarv Dale Ball, Derby, England, assignor of onehalf to George H. Alexander Machinery'Limited, Birmingham, England ApplicationiJnne-S, 1942*, Serial No. 445,935 In Great Britain June .18, 1941 4 Claims.

' The object of this invention is to facilitate the construction of high-class spirit levels, and also to enable the sensitivity of such levels to be readily adjusted.

The invention comprises the combination of a hollow body part, a substantially straight glass or other suitable tube containing the liquid and bubble, and'means within the body part for flexing the tube.

The invention also comprises the combination with a spirit level as specified in the preceding paragraph, of externally operable means for adjusting the fiexure of the tube.

In the accompanying sheet of explanatory drawings:

Figures 1, 2 and 3 are respectively a sectional side elevation, an end elevation, and a plan of a spirit level constructed in accordance with the invention.

Figure 4 is a section on the line 4 i of Figure 1.

In carrying the invention into effect as shown, I employ a hollow rectangular metal or other rigid body part 0. having its upper portion made to an open channel-like form. Arranged longitudinally within the channel-like upper portion of the body part a is a substantially straight glass or other transparent tube b' containing the usual liquid and bubble, the latter being indicated by c, and being visible through the open upper side of the body part. The tube b is supported by a pressure bar at which is also arranged longitudinally within the channel-like upper portion of the body part a, and which is grooved to accommodate the adjacent portion of the tube, the latter being arranged to project beyond both ends of the pressure bar. Any convenient means are employed for preventing endwise movement of the pressure bar d within the body part a. Thus, the pressure bar at may be provided as shown with a laterally projecting pin e which engages a vertical groove in the adjacent portion of the body part. The tube b is retained within the body part a by a pair of abutment pieces g which embrace and support the upper sides of the end portions of the tube, and the pressure bar (1 bears at its ends (either directly or through the agency of pads h) on the underside of the tube at positions spaced from the ends of the tube the arrangement being such that the tube can be flexed slightly by the pressure exerted on it by the pressure bar. For enabling this pressure to be varied the pressure bar it rests on a longitudinally adjustable wedge piece 2' in the form of a slightly tapered bar, this wedge piece being slidably fitted in the bottom of the chainnel-like upper portion of the body part a. The taper of the wedge piece 2' is so slight that it cannot easily be illustrated, but it is suiiicient to enable the required flexing of the tube b to be effected by the pressure bar d upon the wedge piece being moved to an appropriate extent relatively to the pressure bar, the distance between the positions at which the pressure bar acts onthe tube being such that the intervening portion of the tube when flexed has a true arcuate form.

When, as in the example shown, it is desired that the user of the spirit level above described shall be able to adjust the flexure of the tube b and consequently the sensitivity of the level, I mount in one end of the body part a and in alignment with the wedge piece i, a, rotatable but axially immovable screw 7 which at its inner end engages'a screw threaded hole k in the adjacent end of the wedge piece, the outer end of the screw being provided with a head m whereby it can be rotated. Axial movement of the screw 7' is prevented by the engagement of a spring-loaded ball or other detent n in the body part a with a circumferential groove 0 in the screw. The effect of rotating the screw :i is to move the wedge piece 2' relatively to the pressure bar d and so alter the amount of fiexure of the tube b. For indicating the amount of movement imparted to the wedge piece 1', the latter may be provided at one side with a scale 17 which can be seen through an opening q in the body part a, and which is movable with the wedge piece relatively to an index mark on the body part. A stop 1* in the body part a at the end of the wedge piece 2' remote from the adjusting screw 7 serves by contact with this end of the wedge piece to determine one limit position of the wedge piece.

To enable fine adjustment in the initial setting of the tube 11 to be obtained, the abutment pieces 9 are slidably adjustable in inclined guides s formed on or secured to the ends of the body part a. These guides s are of dove-tail form and are slit longitudinally where indicated by t to provide parts between which the corresponding abutment pieces can be secured under the action of screws u passing transversely through the said parts. For enabling the abutment pieces 9 to be individually adjusted, screws 11 engaging screw threaded holes w in the guides s are provided with collars a: which engage recesses 11 in the abutment pieces, so that axial movement of either of these screws is accompanied by adjusting movement of the corresponding abutment piece. The adjusting screws and holes w are situated between the split parts of the corresponding guides s, so that when these parts are caused by the securing screws u to grip the abutment pieces 9 they also serve to grip and secure the adjusting screws 12.

In the example shown the body part a is formed beneath its upper channel-like portion,

with a longitudinal opening 2 which serves to reduce the weight of the level, the under surface 7 of the body part being formed with intersecting grooves if desired.

By this invention I am able greatly to facilitate the construction of spirit levels required for use in accurate measurements, and to impart conveniently to the level any desired degree, of

sensitivity. Moreover I am able to make the sensitivity variable by the user so that the one level can be readily adapted to different requirements.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. A spirit level comprising the combination of a hollow body part, a substantially straight tube containing liquid and a visible bubble, and means within the body part for flexing the tube.

2. A spirit level as claimed in claim 1 and having externally operable means for adjusting the flexure of the tube.

3. A spirit level having in combination a hollow body part, a substantially straight tube containing liquid and a visible bubble, a pair of abutment pieces by which the end portions of the tube are supported at one side of the tube, and means within the body part for flexing the tube, the said means comprising a pressure bar 10 by which the opposite side of the tube is supported at positions spaced from the ends of the tube, and a wedge piece supported by the body part, the pressure bar being arranged between the tube and the wedge piece.

4; A spirit level having in combination a hollow body part, a substantially straight tube containing liquid and a visible bubble, a pair of abutment pieces by which the end portions of the tube are supported at one side of the tube,

means within the body part for flexing the tube, the said means comprising a pressure bar by which the opposite side of the tube is supported at positions spaced from the ends of the tube, and a wedge piece supported by the body part,

the pressure bar being arranged between the tube and wedge piece, and screw means whereby the wedge piece can be moved relatively to the pressure bar for varying the pressure exerted by the bar on the tube.

EDGAR DALE BALL.

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