US2215129A

US2215129A - Manhole step

Info

Publication number: US2215129A
Application number: US305084A
Authority: US
Inventors: Herbert N Morris
Original assignee: Individual
Current assignee: Individual
Priority date: 1939-11-18
Filing date: 1939-11-18
Publication date: 1940-09-17
Anticipated expiration: 1957-09-17

Description

Sept. 17, 1940. H. N. MORRIS MANHOLE STEP Filed Nov. 18, 1939 INVENTOR 6 5. as? 7' /V. Mame/s ATTORNEYS Patented Sept. 17, 1940 UNITED STATES ATENT 6 Claims.

This invention relates to an improvement in members adapted to be set in cast concrete structures, and, more particularly, to cast iron steps for cast concrete manholes or similar structures of cast concrete.

As is well-known, it is necessary to provide manholes or similar structures with steps set in the structure. Such steps are usually U-shaped memberscomp-rising a tread portion supported 10 by arms which are set in the structure. Such steps may be steel, but are preferably cast iron, due to the tendency of steel to corrode. Heretofore, the cross-sections of the step arms have been either rectangular or circular. The rectangular cross-sections were preferable to the circular cross-sections since they were stronger and could be secured more firmly in the concrete or mortar. Round cross-sections present a minimum surface to the mortar or concrete in which they are secured and are prevented from loosening only by the adhesion of the mortar or concrete to the surface of the arm.

No particular problem of installation arises when steps having arms rectangular in crosssection are supported in brickwork, since the steps may be placed in position as the bricks are laid. When the steps having arms rectangular in cross-section are supported in cast concrete structures, however, installation problems arise.

The concrete must be cast around the arms of the steps which are inserted through the wooden or metal forms into which the concrete is poured. To insert the rectangular cross-sectioned step arms through the wooden form, a carpenter must cut a rectangular opening in the form for each step arm with a keyhole saw or broach the hole with a chisel. This operation is time-consuming and expensive.

It is an object of this invention to provide a step for concrete structures with arms having cross-sections which will permit the step to be set quickly and inexpensively into a wooden or metal concrete form and which will eliminate the necessity of keyholing or broaching step openings through the form. It is another object of this invention to provide a cast iron manhole step arm which will have a cross-section of substantially maximum strength.

It is a still further object of this invention to provide a manhole step which may be securely held in cast concrete by both adhesion and me chanical engagement between the step arm and the concrete which is cast about it.

further objects and advantages will be apparent Other and from the following specification, claims, and drawing in which: 1

Fig. l is a perspective View illustrating a manhole step made according to this invention;

Fig. 2 is a cross-section taken along the line 5 22 of Fig. 1;

Fig. 3 is a cross-section taken along the line I 33 of Fig. 1;

Fig. 4 is a view similar to Fig. 2 but illustrating a modification of this invention; and 10 Fig. 5 is an elevation of a portion of a form drilled to receive a manhole step as illustrated in Fig. 1.

In the drawing, in which like reference characters refer to like parts, it is a manhole step 15 made according to this invention. Preferably the manhole step is of cast iron, though any other suitable material may be used, and is comprised of a tread I I supported by a pair of parallel arms I 2 and 13 disposed at. right angles to the tread 20 H. As shown in Figs. 1 and 3, the tread ll may be rectangular in cross-section and is preferably provided with a flat upper surface suitably knurled to prevent slipping and to afford an adequate foothold.

The arms l2 and it are of a suitable length to allow the step to be anchored in the cast concrete and to support the tread ll away from the wall of the manhole or similar structure, so that the step afiords an adequate depth of tread. As

shown in Figs. 1, 2, and i, the cross-section of the arms l2 and i3 is comprised of a plurality of substantially tangent circular areas. The circular areas making up the cross-section of the arms may be of equal size, but are preferably of different size, the larger circular area or areas being located in the upper portion of the crosssection in order to obtain the maximum strength for the amount of cast iron in the arm. In the preferred form of the invention, as shown in Figs.

1 and 2, the cross-section of the arm is substan- 40 tially in the form of an inverted figure 8, being comprised of a larger upper circular area I5 and a smaller tangent lower circular area I6, the circular portions being joined by the fillets I1 and I8. In the preferred cross-section, the tension load on the arms is carried by the larger circular portion l5 and the compression load is carried by the lower circular portion I6.

It is obvious that the circular areas making 50 up the cross-section of the arm need not be precisely tangent, but may be spaced apart or may intersect. Furthermore, the circular areas may be of any convenient number and may be arranged in any suitable manner. For 55 example, in the modified cross-section shown in Fig. 4, the cross-section is made up of three circular areas in a substantially clover leaf arrangement in which the larger upper circular portions l9 and 26 carry the tension load and the smaller lower circular portion 2| carries the compression load. Also, in order to provide mechanical engagement by the arms of the step against longitudinal movement in the concrete in which the arms are anchored, the ends of the arms may be curved in substantially parallel planes, as at 22 and 23 of the arms I2 and I3, respectively.

To insert the step it! into a form prior to pouring the concrete of the structure, a suitable opening 24, as shown in Fig. 5, is provided in the form for each arm of the step by locating

centers

25 and 26 spaced a vertical distance from each other equal to the vertical distance a between the centers of the circular areas l5 and 16 of arms l2 and 53.

Holes

35 and 36 which are equal in diameter to the circles l5 and [6, respectively, are then bored with ordinary augurs. The nibs Zl and 28 protruding between the

tangent holes

35 and 35 may be removed with a chisel, or, because the nibs ex tend across the grain, by simply driving the end of an arm of the step through the

holes

35 and 36.

After the steps are inserted in the form in the simple manner described and properly braced, the concrete is then poured into the form. The configuration of each arm not only provides ample surface for adhesion of the concrete to the arm, but, because of the cusps of concrete which form between the tangent circular portions of the cross-section, the arm is mechanically engaged in the concrete. Additional mechanical engagement between the arm and the concrete is also provided by the curved ends of the arm. I

From the foregoing it is apparent that a step made according to this invention may be quickly and readily inserted into a form by simply boring into the form two holes for each arm of the step, thus eliminating the keyholing or broaching operations necessary heretofore. Furthermore, step arms having a cross-section according to this invention are stronger than step arms having the rectangular or round cross-sections employed heretofore.

Since the preferred embodiment of this invention may be modified by those skilled in the art, without departing from the essence of it,

;this invention is not limited to the preferred embodiment disclosed, either in whole or in part, but is limited only by the following claims.

What is claimed is:

1. As an article of manufacture, a step adapted to be supported in a cast concretestructure comprising a tread and an arm supporting said tread, said arm being adapted to be inserted through a form for concrete and to protrude from a concrete structure and having a cross-section, the contour of which comprises connected arcs of a plurality of circles.

2. As an article of manufacture, a step adapted to be supported in a cast concrete structure comprising a tread portion and an arm supporting said tread portion, said arm being adapted to be inserted through a form for concrete and to protrude from a concrete structure and having a cross-section comprised of a plurality of substantially tangent circular portions and fillets included between said circular portions.

3. In an article of manufacture of v the class described, an arm adapted to be inserted through a form for concrete and to be anchored in a concrete structure, said arm having a cross-section, the contour of which comprises connected arcs of a plurality of circles, whereby cusps of concrete will be mechanically engaged between the arcuate portions of said arm.

4. In an article of manufacture of the class described, a substantially U-shaped step adapted to be supported in masonry, said step comprising a tread and a parallel pair of arms supporting said tread, each of said arms having a cross-section, the contour of which comprises a plurality of connected arcs of a circle.

5. In an article of manufacture of the class described, a substantially U-shaped step adapted tobe supported in masonry, said step comprising a tread and a parallel pair of arms supporting said tread, each of said arms having a section consisting of two substantially tangent circular portions and fillets included between said circular portion, the ends of the arms being similarly curved in substantially parallel planes.

6. In an article a of manufacture of the class described, a substantially U-shaped step adapted to be supported in masonry, said step comprising a tread and a parallel pair of arms supporting said tread, each of said arms having a cross-section, the contour of which comprises connected arcs of a plurality of adjacentcircles.

HERBERT N. MORRIS.