US2236818A - Piston - Google Patents

Description

April 1, 1941.

J. FLAMMAN'G PISTON Filed Feb.

Patenvted Apr. 1, 1941 UNITED STAT-Es PATENT OFFICE PISTON tion oi' Delaware Application February 15, 1937, serial No. 125,756 1 claim. (ci. sos-11) This invention pertains to pistons and more particularly to trunk type istons constructed of thermo-expansible metall, such as aluminum, or its alloys, magnesium and the like, having a high coemciency of thermal expansion.

One of the objects of this invention'is to provide a piston of the character described which will function in a cylinder through various ranges of temperature and compensate automatically for expansion.

Further objects will appear from thefollowing description taken in connection 'with the accompanying drawing, in which:

Figure 1 is a side view illustrating one form of piston to which this invention may be applied.

Figure 2 is a longitudinal section through the wrist pin axis of the piston shown in Figure l.

Figure 3 is a sectional view of an engine cylinder illustrated with a piston therein constructed in accordance with this invention, said piston being seen in bottom view, and

Figure 4 is a fragmentary side view similar to Figure l, illustrating another form of piston to which this invention may be applied.

Referring to the drawing the piston comprises a head i and a skirtindicated generally at `2. Wrist pin bosses 3 are provided. These bosses are connected to the head I by a sti structure including one or more longitudinal ribs il extending from the upper portion of each wrist pin boss to the inner side of the head. Similarly, one or more reinforcing ribs may be arranged to extend across the head on the interior thereof. The structure thus described including the head, the ribs d andl the wrist pin bosses Tis made stiff and rigid so as to provide a. strong frame structure adapted to deliver the thrust of the gas explosion to the connecting rod.

'I'he skirt 2 is separated from the head l adjacent the two thrust faces. The thrust face which takes the thrust of the power stroke, shown in interior view in Figure r2, may or may not be separated from the heady by a horizontal slot or gap 6. This face is solid or uncut longitudinally, while the opposite face, shown in Figure 1, is separated from the head l by a slotA or gap 1, and

in addition is cut by a longitudinal slot l. extend-V ing up" into and communicatingwith the gap 1. In some cases it may be desirable to extend the the regions of the thrust faces and the -skirt is webs i4 connecting the skirt with the bosses. In

orderto `provide still more ample relief at the top, the relieved portions may be extended from the yregions opposite the bosses-around toward one or both thrust faces so 'as to approach, to a greater or less extent, the bearing axis of the bearing or thrust face. In the form of piston illustrated in the drawing this relieved portion is formed to approach more closely, to the bearing axis at the head end of the skirt than therebelow, thereby providing the so-called Keystone relief.

A bridge il spans the slot preferably just below the circumferential slot l. The middle portion ofthis bridge is relatively thin so as to be comparatively flexible, while each end of the bridge has an anchorage i2 having an extended connection with the skirt on the inside and, therefore, relatively rigid. A gap I3 may be provided in the bridge, and this gap as well as the bridge 3o itself, is formed in the casting when made in the 35 skirt at the top. In the complete piston, therefore, the corners I0 will be supported.

The piston is made in theusual manner .with the head-provided with the usual ring grooves il of smaller diameter than the'skirt. This skirt 40 may alsobe given the usual taper so as to be slightly smaller at the top than at the bottom.`

When such a piston is placed in the cylinder and subjected to the heat of the gases, the head will, of course, expand radially in all directions.

This radial expansion of the head is transmitted to the skirt only in the regions of the wrist pin bosses where, however. the skirt isrelieved to permit such expansion. Such radial expansion of the head is not transmitted to the region of slot 8 clear to the open end of the piston skirt 50 the thrust face between the bosses, because of as shown in Figure l. In other cases this slot ,f may beterminated at a point l as shown in Figure 4, short of the open end of the skirt. l

This cutting of the circumferential slot or slots the isolation brought about by the circumferential slot.l vAs a result. therefore, the isolated thrust tace ls drawn in so as to compensate for expension on that diameter, while expansion along in the piston isolates the skirt from the head in the line oi' the wrist pin bosses has been compensated for by the relief. Such drawing in of the thrust face is permitted because of the bridge which, however, prevents undue ilexure of the skirt at the top, particularly at the corner and, therefore, insures quiet operation. It will be understood that where the head is also isolated from the skirt at the unslotted face, there will be a drawing in on that face also as expension takes place along the line of the bosses.

It will be obvious that various changes may be made in the details of construction, within the scope of the appended claim, without departing from the spirit of this invention. It is understood, therefore, that the invention is not limited to the specific details shown or described.

Having thus described the invention, what is claimed is:

A trunk piston of thermo-expansible material having a head, a skirt, and wrist pin bosses connected to the head, said skirt having cylinderbearing thrust faces and having relieved areas adjacent said wrist pin bosses and between said thrust faces to permit thermal expansion in the direction of the wrist pin axis, one of said thrust faces being separated from the head by a slot extending horizontally between said relieved areas adjacent the top of the skirt, said thrust face having another slot extending vertically and y medially thereof downwardly from said horizontal slot defining separate bearing corners adjacent the junction of said horizontal and vertical slots, and a bridge member anchored interiorly to the respective bearing corners and bridging the vertical slot adjacent the horizontal slot, and interior anchorage between said bridge and the respective bearing corners being circumferentially extended substantially across the thrust face. said bridge member being constructed and arranged4 to prevent undue fiexure of the separate bearing corners.

JOHN FLALMANG.

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