US118118A - Improvement in caissons for sinking piers - Google Patents

Description

.JAMES B. EADS, OF ST. LOUIS, MISSOURI.

IMPROVEMENT IN CAISSONS FOR SINKING PlERS.

Specification forming part of Letters Patent No. 118,118, dated August l5, 1871.

To all whom it may concern:

Be it known. that I, JAMES B. EADS, of St. Louis, in the county et St. Louis and State of Missouri, have invented certa-in new and useful Improvements in Caissons for Sinking' Piers, of which the following is a specication:

My invention consists, first, in placing the airlocl: either partialiy or wholly within the main air-chamber of the caisson; and secondly, in the use ofa water-tight air-sh aft to communicate with the air-chamber, whereby the outer skin or caisson inclosing the masonry may be dispensed with.

Figure l shows, partly in elevation and partly in longitudinal section, the caisson and lower portion of the pier, the section being taken on the line Y Y, Fie. 2. Fig. 2 is a horizontal section .at the line X X, Fig. l. Fig. 3 shows, half in elevation and half in section, at the line Zl Z, Fig. et, the caisson and lower portion of the pier, the shafts communicating with the air-lock being placed outside the masonry andthe caisson extended ateach end beneath the shaft. Fig. 4 is a horizontal section at the line Z Z, Fig. 3.

A is the `shell of the caisson, which extends both upward and downward from the horizontal top B ofthe air-chamber. O are girders ruiming from end of the caisson and attached to the top B and the sides. D are brackets also attached to both top and sides of the air-chamber, imparting rigidity to the structure. The caisson, besides its partial support by the pressure of air beneath it, rests upon the broad bases of the girders C and upon a course of timber, E, which is extended around the inner side of the shell. c are apertures in the girder C to allow the passage of the workmen from one compartment of the airehamber to another. =,Ffis'tlle""I''iisomy of the pier. Gare-watertight shafts whose upper ends are open to the air, and which may be made of metal, wood, or other suitable substance. These shafts extend vertically through or beside the masonry, and their lower ends communicate, by

A a manhole, J, with an air-loch, K. The air-lock communicates, by a man-hole, L, with the interior of the main air-chamben rI he man-holes J andL have doors J and L whose edges are made closed. The air-locks are generally about ve feet in diameter and from seven to twelve feet high. Both doors J and L are made to open toward the main air-ch amber, so that the extra or plenal pressure of air will always keep one or both of the doors closed.

Previous to the introduction of my improvement the air-lock was placed at the upper end of Y a vertical shaft which was in direct communication with the air-chamber of the caisson, and, as the caisson descended and the masonry was built up, the shaft was increased in height by the addition of sections thereto; for this purpose the air-lock had to be removed from the shaft and the compressed air permitted to escape from the main air-chamber and shaft, the water and mud entering to take the place of the air and rendering the whole interior wet and dirty, the workmen remaining idle while the sectional addition was made to the shaft and the water again forced from the air-chamber. Thus the air-chamber an d shaft were continually kept in an unhealthy condition, calculated to injuriously aifect the operatives. This shaft constituted an element of danger, as it furnished a chamber for the reception of the whole amount of air contained in the caisson, in case ofthe latter subsidin g rapidly from any cause, such as entering a quicksand; in this case the workmen might not have sufficient warning to enable them to reach the shaft, and their lives would be sacriticed.

My lock, bein g placed in the air-ch amber, leaves no space (as the shaft before mentioned) for the escape of air .under extraordinary pressure, and on any rapid subsidence of the caisson the men could not be deprived of air, the air being limited to half the space, exertin g double the raising power upon the caisson, and so checking its descent. The position I give to the air-locks ena-- bles the connnunication between the pier-top and the air-chamber to be made by means of shafts whose tops are open to the outer air. The shaft-s may be built even with the top ofthe pier during construction, or be kept somewhat in advance thereof, and may be made of wood, metal, or any materia-l found suitable, either wood or metal answering the purpose satisfactorily.' By making the shafts water-tight l am enabled to dispense with the outer skin of the caisson inclosing the masonry, the said skin being built only of suicient height to form a coder-dani, if any is needed, at the first setting of the caisson in position. When the water-tight skin of the caisson inolosin g the masonry is built up, as the pier de scends so as to keep the skin above the waterlevel, the shafts communicating with the air-locks need not be water-tight; but the construction of this skin involves great expense, and the difiiculty is so great of rendering it water-tight against the extreme pressure of the water that any means enabling this skin to be dispensed with is valuable. This end is accomplished by making my shafts water-tight to exclude the water which percolates through the joints of the masonry.

In some cases the piers have insuflicient area to admit of shafts being made in the body of the masonry without seriously weakening the structure. In such cases I locate the water-tight airshafts outside the masonry, as shown in Figs. 3 and 4, the caisson having extensions Al beneath the shafts so as to clear a way for the descent of the said shafts, the said extensions being of any y suitable form.

Where the excavation is made in sand or fine gravel (even if some larger stones are found) the made through coarse' gravel, clay, and larger stones these matters are removed by a dredge which operates in a shaft open at top and bottom and extending from above the water-level to a point below the caisson.

Neither the means for removal of the excavated material nor the pumps for forcing air into the air-chamber are shown, as these provisions are well understood and constitute no part of my present improvement.

I do not claim an air-lock applied at the lower end of a pneumatic pile, as described in a patent granted to F. E. Sickles on the 1st of February, 1870, independently of a caisson for con strncting piers.

The following is what I claim as new: y

l. In connection or combination with a caisson for sinking piers of masonry or other material,

the airlock K placed at or near the bottom. of the air-shaft'Gr and partially or wholly within the air-chamber of said caisson, substantially as herein set forth.

2. The extensions A of the caissons, substantially as and for the purpose set forth.

In testimony of which invention I hereunto set my hand.

Witnesses:

SAML. KNIGHT, Gno. C. FABIAN.

JAS. B. EADS.

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