US1805957A - Automotive piston - Google Patents

Description

y 1931- A. A. STEPHENS 1,805,957

AUTOMOTIVE PI S TON Original Filed Dec. 30, 1926 Patented May 19', 1931 PATENT OFFICE 'aimonn A. swarms, or nav'mrron'r, Iowa AUTOMOTIVE PISTON Application filed Decembei 80, 1926, Serial No. 158,110. Renewed September 27, 1980.

This invention relates to pistons for internal combustion en 'nes particularly of the automotive type, an more especially to that "gyple of piston composed of a non-ferruginous It has been-suggested heretofore to lessen iston friction in internal combustion motors .y substituting for a cast iron piston one composed of a lighter material, such as an alumilo nous alloy. Such attempts have notbeen entirely successful. The substituted pistons have proved generally inefiicient in operation. This has been due primarily to clearance problems. The aluminous material used while of less specific gravity than iron has greater thermal expansion and hence in orderto prevent scoring of the'cylinder walls, when the piston was operating at normal running temperatures, a relatively large initial clearance had to .be allowed.

" Attempts havebeen made to eliminate these disadvantages-inhering in aluminum pistons. The proposedv constructions comprehended two general types. The first type comprised a piston body of aluminum, the s 'rt of which was split at one or more places. The other type included pistons having aluminum .bodies whichwere provided with some means to prevent the expansion of the skirt. These pistons while presenting some advantages were not entirely satisfactory. The split skirt type did not insure the requisite strength. The reinforced skirt type was subjecte to great strains due to the restraining of the normal expansion.

It is'anobject of .this'invention to rovide a piston of a material having a speci cgrave it dgr with a minimum of clearance.

Another object is to provide a composite piston comprising aluminous and fer'ruginous portions. I

A further object is to provide a piston having an aluminous body and easily replaceable sections of a material of less thermal expansion than aluminum.

With these and other equally important objects which will appear more fully from the following description, my invention comprehends a piston having an aluminum body.

less thaniron which operates in a cylinportion which is provided with exterior expansible circumferential sections of amaterial having a coeificient'of thermal expansion closely approximating that of the cylinder bore, and the provision of meanscooperating with the sections and body to determine the expansibility of the sections.

To facilitate an understanding of the invention there is shown in the accompanying drawings a device which mechanically embodies the principles of my invention. In these drawings the identifying numerals refer to similar parts throughout the several views, of which Figure l is an elevation of a piston;

Fig. 2 is a section on the line 2-2 of Fig. 1;

Fig. 3 is a sectional view similar ,to Fig. 2 showing a modification of the device;

Fig. 4 is an enlarged detail view of the restraining member mounted in position;

Fig. 5 is a view similar to Fig. 2 showing a further modification;

Fig. 6 is a perspective view of the restraining. member.

In the drawings is shown a full-skirted piston of an aluminous alloy having a head portion. 1 and an integral continuous skirt portion 2. The skirt portion is formed with integral wrist pin bosses 3. It will'be understood that these bosses are provided with bushings which support the journals of a wrist pin in the conventional manner. The bosses maybe, and preferably are, formed with a plurality of-reinforcing flanges. It is also desirable to tap the bosses to rovide a passage for lubricating hydrocar ons to the wrist pi-n bearings.

The head portion of the piston is cast with grooves to receive the compression rings 4 and 5 and an oil ring 6. The head rtion is also formed with a relatively wide and deep groove to receive a separate annular bearing section 7. This section is composed of a metal having a coeflicient of thermal expansion very nearly equal to that of the material of the cylinder bore. This may be of a ferru 'nous material, such as cast iron. It is to understood that the term ferruginous is used in the specification to desi nate materialwhich has the thermal properties of iron, while by the term aluminous is comprehended the various alloys of a specific gravity which is relatively small as compared with iron.

The piston skirt at a point below the wrist pin bosses is provided with a second annular section 7. These sections are of the same structure so that a description of but one will be 'ven, it being understood that what is s'ai of the one applies equally to the other.

The piston skirt may be provided with an integral quadrantal extending portion on its I thrust side. This protruding segment extends the full length of the piston skirt and serves as 'a bearing surface as described in my pending application Serial N 0. 101,940. As is shown in Fig. 2 the annular section 7 is nested within the condnes of groove 8, which, as has been'inti-mated, is relatively wide and deep as compared to the compression ring grooves. Thegroove 8, as shown, extends completely around the exterior surface of the piston body "and is of the same width and depth throughthrust segment hereinbefore described.

As shown particularly in Fig. 4, the backing member 10 is bored to present a round aperture 11. The backing member is adapted to receive the restraining member 12. This comprises a round base plate 13 having integral parallel projections 14. The top faces 15 of the pro ections are angularly dlsposed with respect to the horizontal plane of the base plate 13 and the side faces 16 converge towards each other, .for a urpose to appear more fully hereinafter. T e ends of the projections 14 extend beyond the circumference of the base plate. It will be appreciated that the backing member 10 can be prepared for the reception of the restraining means by boring a hole therethroughof the same diameter as that of the base plate 13.

The annular section 7 is channeled at 17 to receive the extensions 14. .As will be observed from an inspection of Fig. 3, the channels 17 are considerably wider than the members 14 so that the annular sections may move cirgumferentially with respect to' the piston od I The assemblage and operation of the device will be apparent from the foregoing description. When the piston is to be assembled the resilient members 9 are placed in the two grooves 8 so that the gap between their ends coincides with the extended thrust segment. The filler block, which has been previously bored and fitted with the restraining member is then placed in the groove. As was alluded to hereinbefore, the extensions 14 project beyond the circumference of the base plate 13. When the assembled backing plate and restrainin means are positioned in the groove the en s of the extensions lie closely adjacent the groove lands and thus prevent.

any twisting movement of the restraining member in the socket of the filler block. The annular split sections 7 are-then forced over the sides of the piston until they register with the grooves, the projections 14 taking into the channels 17.

Under the action of the resilient memb r 9' the section 7 will expand. The bottom of the channel 17 will ride upon the inclined faces 15 and provide a snug engagement therebetween. The inclination of the faces 15 in conjunction with the angularity of the side faces provide, in effect, an undercut which insures a more positive engagement of the restraining means with the ring section. It

will be seen that the ring will be expanded,

under the action of the. spring 9, to the limit allowed by the restraining means. The described arrangement of elements allows-free contraction but only a determinative expansion of the ring.

When the piston is installed the sections 7 fit flush with the cylinder bore.- After the preliminary running .in, the rings will be worn down to a glazed surface and a desirable small clearance between the bearing sections and cylinder bore will obtain. By preventing undue expansion of the ring, seizing or scoring is precluded. The interposition of the resilient medium between the ring and piston body allows the latter to freely expand or contract under varying cylindertemperatures without affecting the circumference of the ring sections,'and thus provide a piston which combines the advantages attending the use of a piston of a light weight and one of small clearance.

In Fi 3 is shown a modification-of the piston depicted in Fig. 1. In this device the backing late is eliminated. The roove 8 is cast sot at it presents varying epths, the

portion 8' being of'less depth than the remainderof the groove so that the rings=7 rest flatly against this portion. This provides-a simpler structure susceptible of easy assemblage. In this case the piston body, in the center of the shallow part of the groove, is

spot bored. The restraining member 12 is then inserted directly in the iston body.

A further modification oi the device is shown in Fig. 5. By proper choice of materials the extending member 12 ma serve not only to limit the expansion of the nu section, but it may also directly take the t rust of the ring. As shown, in this figure, the resilient member 9 is extended around nearly the entire circumference of the piston, the free ends being positioned adjacent the restraining means 12. By providing a wide base plate for the ring engaging extensions 14, a structure rugged enough to take the piston thrust is insured. The relatively large piston contacting area presented by the base plate allows a greater distribution of this thrust. The inclination of the ring engaging faces 15 insures a fiat engagement with the interior of the ring and thus minimizes the danger of breakage.

It will now be seen that I have provided a piston construction which is very light and of great strength, operable in a cylinder bore with a small clearance. The advantageous results of the device are accomplished by the use of relatively few, simple parts which are inexpensive to manufacture and easy to install and replace.

I claim:

1. A restraining means for a bearing ring of the character described comprising a sub stantially circular base plate and chord extensions formed integral with the plate to slidably engage the internal face of the bearing ring and thereby limit its circumferential expansion.

2. A piston comprisin a head and skirt formed with wrist pin earings, compression rings carried in grooves in the piston head, a plurality of annular expansible sections of a greater width than the compression rings mounted above and below the wrist pin bosses, means to restrain the expansion of the sections and transmit the thrust of the piston directly to the section comprising a circular plate seated in the piston body and integral extending parallel chord like portions adapted for sliding engagement with the sections.

3. A piston comprising a body portion including a head and skirt, the body portion being bored at one side, a separate expansible section carried by the piston, a restraining means including a portion seated in the bored portion of the piston and a plurality of extensions for engaging the internal face of the sections to restrain their expansion.

4. A piston having a head and skirt, a plurality of annular expansible sections mounted in grooves above and below the wrist pin bosses, a filler member interposed between the ring and grooves, means to restrain the expansion of the sections comprising a circular plate fitting in the filler member and having integral projecting portions adapted to engage the sections.

5. A piston comprising. a head and continuous skirt of an aluminous material, separate annular expansible extensions of a material of different thermal expansion than aluminium, and means detachably engaging the piston body and sections comprising a

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