US2128662A - Piston - Google Patents

Description

,1938. A. 1.. NELSON 2,128,662

PISTON Original Filed June 8, 1925 2 Sheets-Sheet 1 A. NELSON Aug. 30, 1938.

PISTON 5 2 Sheets-Sheet 2 Original Filed June 8, 192

Shun-1 ml, Ado/phLNelson Patented Aug. 30, 1938 UNITED STATES PATENT OFFICE PISTON Mich.

Application June 8, 1925, Serial No. 35,703 Renewed May 6, 1938 2 Claims.

My invention relates to a piston and it is an object of the same to make a piston of metal with suitable thermal qualities as, for instance, aluminum alloy and at the same time to control or decrease the expansion of the skirt to practically that of the.well-known cast-iron pistons. While I propose to decrease or control the expansion of the entire skirt, it is particularly important to decrease the expansion in a positive way at the upper portion of the skirt, which portion must be of sufliciently rigid construction to sustain the thrust load of the connecting rod. Experience in the use of the ordinary aluminum pistons shows that if aluminum forms the material of the webs which join the skirt to the bosses, particularly the portions nearest the head, the expansion of this metal will cause unduly high pressure between the cylinder and that part of the piston which may be designated as the shoulders i, e., the parts between the piston pin bosses and the head opposite thewebs,whichparts are directly subjected to the thrust of the expansion of the webs and of the connecting rod.

According to my construction these webs are 25 omitted and are replaced with struts of suitably rigid relatively inexpansible metal cast in place above the pin bosses, the ends of the struts being embedded in the upper part of the skirt and the middle part of each strut being embedded in a pin boss.

The lower part of the skirt, not being subject to as high temperatures as the upper part of the piston, I propose to support same directly from the lower part of the piston pin bosses by means of webs or flanges as may be conveniently cast integrally with the skirt and bosses.

Referring to the accompanying drawings, which are made a part hereof and on which similar reference characters indicate similar parts,

Figure 1 is an elevation 01' my device, Figure 2, an elevation partly in section at right angles to Fig. .1, Figure 3, a central section at right angles to Fig. 2,

Figure 4, a horizontal section of the piston.

Figure 5, a horizontal section of a modifiedform, f Figure 6, a horizontal section of still another orm,

Figure 7, a vertical section of a piston of modified form, Figure 8, an elevation of the same partly broken away on a plane at right angles to that of Fig. 7, and

Figure 9, a detail of the strut used in said modified form.

In the drawings reference character in indicates a piston head of any desirable or conventional form this piston head having depending 6 therefrom integral bosses ii providing bearings for receiving a piston pin. These bosses are cast in one piece with the head and with the skirt 1! which is separate from the bosses and from the head except at the lower end of each boss where the skirt and bosses are cast in one piece or otherwise rigidly secured to each other as by a web indicated at l3. The connection between the head and the boss is strengthened by a radial outer flange l4 and a radial inner flange l5 which flanges in efiect form a post extending length:- wlse of the bearing in the boss directly above the axis of the bearing such post providing a strong support extending from the upper end of the head to the boss. A similar flange l6 extends from the lower side of the boss to the lower part of the skirt and coacts with a rib I1 (Fig. 3)

c to strengthen the connection between the piston boss and the skirt.

To further strengthen the upper end of the skirt I provide a pair of struts l8 of material such as steel which is relatively inexpansible as A compared with the material of the remainder of the piston. The struts, as will be seen in Figure 4, may be curved at the ends to provide holding portions embedded in the edges of the upward projections of the skirt and each strut may also have a transverse ridge or other inequality at H! in -its intermediate partwhich is buried in the piston pin boss or a part rigid therewith to help in holding the bosses and their skirt sections in correct relative position.

It is of .less importance to positively control the expansion in the lower part of the skirt and I do not propose to do this by means of struts as this would complicate the construction unduly. This part of the skirt may be ground to an oval form to permit expansion of the metal below the pin bosses or other suitable methods may be used to provide for expansion as by means of slots l9 extending up from the lower end of the skirt. The temperature of the lower part of the skirt is low compared with other parts of the piston and therefore the pressure at the bottom of the skirt is also relatively low. Where the slots are used they should extend about half-way up the skirt. In some instances no slots or reliefs at the bottom of the skirt are necessary as only a small portion of the heat in the piston head can get to the skirt and the clearance at the upper 5 end of the skirt can be made so close with my construction that a more liberal clearance can be allowed at the lower end of the skirt in which case the skirt is machined to a tapered form without slots or reliefs. Whether the bottom of the skirt forms a complete annulus or is interrupted by slots I9 the general form will be that of an annulus with upward extensions separated by recesses which as here shown are wider than the bosses and extend below the bosses though these proportions are not essential.

In the construction shown in Figure the struts 20 are curved. With this construction the struts will be flexed as the head expands carrying the bosses l l outward and will so be made to resist outward movement of the extensions 2| of the skirt thus rendering the expansion of the skirt very small.

The construction shown in Figure 6" is similar to that in Figure 5 except that the struts 22 are of angular form with a straight portion embedded in the pin bosses, and straight portions at an angle to that first-named reaching from the pin bosses to the skirt sections 23. The operation is similar to that in Figure 5. p

The construction shown in Figures 7, 8,'and 9 illustrates a modified way of attaching the lower part of the skirt to the lower part of the piston pin bosses. Flange I3 is extended sidewise doing away with flange I1 and rib "5 of Figure '1. The construction also shows a modified strut l8 partly enveloping the bosses. The strut form is easily modified to suit pistons of various proportions. To weaken the lower part of the skirt slot I9" is shown on one side of the skirt only, and extends almost to the top edge of the skirt.

It will be obvious to those skilled in the art that various changes may be made in my device without vdeparting from the spirit of the invention and therefore I do not limit myself to what is shown in the drawings and described in the specification but only as indicated in the appended claims.

Having thus fully described my said invention, what I claim as new and desire to secureby Letters Patent, is:

1. A piston comprising a head, piers depending from the head and carrying piston pin bosses, a skirt of light-weight material having a relatively high rate of thermal expansion comprising a lower ring-like part and thrust faces extending upwardly from the ring-like part at opposite sides of the skirt, the upper ends of the thrust facesbeing separated from the head by slots, the ring-like part extending without interruption from one thrust face to the other below each pin boss, a tie extending downwardly and radially from each pin boss to the ring-like part, said ties being homogeneous with the pin bosses and with the ring-like part, and struts of material having a lower rate of thermal expansion than the skirt material, the struts extending approximately at right angles to the axis of the piston pin bosses and having their opposite ends buried in the thrust faces and their middle parts engaged by the material of the piers.

2. A piston comprising a head, piers depending from the head and carrying piston pin bosses, a skirt of light-weight material having a relatively high rate of thermal expansion comprising a lower ring-like part and thrust faces extending upwardly from the ring-like part at opposite sides of the skirt, the upper ends of the thrust faces being separated from the head by slots, the ring-like part extending without interruption from one thrust face to the other below each pin boss, a tie extending downwardly and radially from each pin boss to the ringlike part, said ties being homogeneous with the pin bosses and with the ring-like part, the, outer surface of the lower end of the skirt having an oval shape with the minor axis of the oval parallel to the axis of the pin bosses, and struts of material having a lower rate of thermal expan-- sion than the skirt material, the struts extending approximately at right angles to the axis of the piston pin bosses and having their opposite ends buried in the thrust faces and their middle parts engaged by the material of the piers.

ADOLPH L. NELSON.

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