US2077688A

US2077688A - Piston

Info

Publication number: US2077688A
Application number: US32533A
Authority: US
Inventors: Oscar F Gottlieb
Original assignee: Oakes Products Corp
Current assignee: Oakes Products Corp
Priority date: 1935-07-22
Filing date: 1935-07-22
Publication date: 1937-04-20
Anticipated expiration: 1954-04-20

Description

April 20, 1937 o. F. GOTTLIEB 2,077,588

PISTON Filed July. 22, 19:55 3 SheetS Shet 2 Qatar 3 65:! (1'96.

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April 1937 I o. F. GOTTLIEB 2,077,688

PISTON Filed July 22, 1935 s Sheets-Sheet 3 Patented Apr. )0, 1937 UNITED STATES PISTON Oscar F. Gottlieb,

Oakes Products Corporation,

Lake Blufi, 111., assignor to North Chicago,

111., a corporation of Michigan Application July 22,

2 Claims.

This invention relates to brazed pistons. I More particularly the invention relates to pistons having a cast iron head brazed to a steel skirt to form a strong and rigid light weight piston.

It is an important object of this invention to provide pistons having a cast or forged head portion integrally united to a steel skirt.

Another important object of this invention is to provide pistons having a forged or cast-head portion integrally brazed to a skirt portion formed from sheet metal.

A still further object of this invention is to provide a piston having a cast iron head portion with dependent ears formed thereon and brazed to a skirt formed from sheet steel.

Another important object of this invention is to provide brazed pistons from two different types of metal having similar coeflicients of expansion.

A still further object of this invention is to provide a process of making pistons that includes the brazing of a skirt portion onto a head portion preferably in a reducing or hydrogen atmosphere.

Another object of this invention is to provide a method for manufacturing pistons that includes the steps of assembling a piston head portion and a piston skirt, placing a brazing wire at the junction between the piston and skirt and heating the assembly in a reducing atmosphere for melting the wire to integrally unite the head portion with the skirt fportion.

Other and further objects of this invention will be apparent from the disclosures in the specifi cation and the accompanying sheets of drawings which disclose preferred embodiments of this invention.

.On the drawings:

Figure 1 is a vertical cross sectional view of a piston according to this invention.

Flgure'2 is a plan view of a sheet metal disc from which the piston skirt of this invention may be made.

Figure 3 is a cross sectional view of the disc shown in Figure 2 and indicating the manner in which the disc is stamped or drawn into, a cup shaped member.

Figure 4 is a vertical cross sectional view of a cup shaped member formed from the disc shown in Figure 2 and illustrating the bottom of the cup shaped member that is cut away to form the piston skirt from the cup member.

Figure 5 is a plan view of a strip of sheet metal for forming a piston skirt according to an alternative method.

Figure 6 is an assembled view of the strip shown in Figure 5.

1935, Serial No. 32,533

(or. sna -14) Figure '7 is a vertical cross sectional view, with parts in elevation, showing the head portion of I a piston according to this invention. Figure 8 is a vertical cross sectional view, with parts in elevation; showing the manner in which the skirt portion and the head portion are assembled, and also showing the manner in which the brazing wire is positioned for the brazing operation.

Figure 9 is cross sectional view taken substantially along the line IX-IX of Figure 8.

Figure 10 is a fragmentary vertical cross sectional view of a brazed piston according to this invention, showing the braze between the head portion and the skirt portion. 4

Figurell is a side elevational view ofa modifled form of brazed piston according to this invention.

Figure 12 is a cross sectional view taken substantially along the line XII-XII of Figure 11.

Figure 13 is a cross sectional view taken substantially along the line XIII-XIII of Figure 12.

As shown on the drawings:

In Figures 1 and '7 to 10 inclusive, the reference numeral 10 indicates a forged or cast iron piston head having two oppositely disposed lugs or ears H and 12 extending therefrom. Each ear II and I2 is provided with a horizontally disposed cylindrical boss portion 13 which may be drilled out to form openings 14 for receiving a Wrist pin therethrough. The boss portions 13 are reinforced by webs such as 15 and 16 formed integrally on the inside of the lugs or ears II and I2 and extending from the boss portion 13 to the head 10.

As best shown in Figure 7, the head l0 has an annular flange 11 extending therefrom to define an annular shoulder 18 around the head 10.

As shown in Figure 1, a plurality of grooves l9 are formed in the periphery of the head Ill for receiving piston rings.

A steel skirt 20 is slipped over the ears H and 12 of the head 10 and around the flange 11 until it abuts the shoulder 18 of the head. The skirt 20 is formed according to the methods shown in Figures 2 to 6.

In Figure 2 the reference numeral 21 indicates a circular metal disc of sheet steel. As indicated in Figure 3, the metal disc 21 is spun or drawn into a cylindrical cup member 22. Any simple sheet metal stamping operation or spinning operation can be used to form a cylindrical cup from the disc 2 I.

As shown in Figure 4, the cup 22 is next formed into the piston skirt 20 by punching out a circular cutting operation, while the other end of the strip metal disc 23 from the base of the cup to provide a circular opening 24. It is preferred to out the metal disc 23 of smaller diameter than they diameter of the cup 22 so as to form an inturned flange 25 around the base of the piston skirt 20. The flange 25 adds rigidity to the piston skirt.

If desired, the piston skirt 20 may be formed according to the method illustrated in Figures 5 and 6. In Figure 5 the reference numeral 26 indicates a strip of sheet metal such as steel having a width of the desired height for the piston skirt ,20 and a length sufficient to form the circumference of a piston skirt of the desired diameter. One end of the strip 26 has a dovetailed groove 21 cut therein by any suitable stamping or 26 has a dovetailed tab 28 formed thereon for fit- .ting into the groove 21.

The so-formed strip 26 is then bent around a mandrel to form a cylinder 29 shown in Figure 6 with the dovetailed end 28 seated into the dovetailed groove 21 formed in the other end and with the edges of the strip in abutting relation. A brazing-wire 38 is laid. over the seam formed between the interlocking ends of the cylinder 29 and the ends of the cylinder are then brazed together in the same operation involving the brazing of the head ID to the piston skirt 20 as will be hereinafter described. While the wire 30 has been shown to be placed on the outside of the cylinder 29, it should'be understood that it can also be placed on the inside of the cylinder. It should also be understood that other forms of interlocking tabs and grooves may be used in place of the tab 28 and the groove 21.

When the piston skirt 20 is slipped onto the head In, the piston is then inverted as shown in Figure 8 and brazing wires3| and 32, as shown in Figures 8 and 9, are placed over the flange 11 of the head ID. The wires 3| and 32 are composed of copper, brass or bronze and are bent arcuately as shown in Figure 9, to fit around the flange |'I in abutting relation to the inside of the skirt 20.

As shown in Figures 8 and 9, the wires 3| and 32 do not extend over the ears II and 2, but if desired the wires may be looped over these ears.

The piston is then inserted in the inverted position shown in Figure 8 in a brazing furnace where it is heated to a temperature above the melting point of the wires 3| and 32. The copper or bronze forming the wires 3| and 32 is melted and flows by capillarity between the closely abutting surfaces ofthepiston skirt 20 and head Ill. The

molten metal even flows up aroun'dthe ears H and I2 to form a braze between the ears and the side of .the piston skirt.

The brazing is preferably carried out in a reducing atmosphere which may suitably be hydrogen or a mixture of gases relatively richin hydrogen, carbon monoxide and nitrogen. Comparatively little oxygen should be present in the at mosphere of the brazing furnace if a satisfactory braze is to be obtained and the formation of scale prevented.

If desired, the assembled parts of the piston may be placed on a traveling conveyor with the piston head l0 contacting the conveyor. The assembled units are then, run into a. furnace having a reducing or hydrogen atmosphere and heated to a temperature sufficiently high to effect the brazing operation. Where copper brazing wires are used, the temperature should be about 2040 F. Where bronze wires are used, the

temperature can be slightly lower, namely in the the piston skirt 20 and the head III to form a braze 33 (Figure 10) which extends around the entire periphery of the flange l1 and even up around the ears H and I2.

When the brazing operation is'complete, the piston can be removed from the furnace through a cooling chamber that is also supplied with a. reducing or non-oxidizing atmosphere so that the metals of the piston may reach a sufliciently low temperature to prevent oxidation during the cooling down period.

When the piston skirt 20 is formed according to the method disclosed in Figures 5 and 6, the brazing wire 30 of copper or bronze is disposed over the abutting edges of the strip-26 forming the cylinder '29 and melts'down together with the wires 3| and 32 to form an integrally united piston skirt during the same operation in which the piston skirt is united to the head.

When the brazed piston has cooled down, the boss portions l3 of the ears II and |2rmay be drilled as shown in Figure 1 to form openings l4,

. modified form of a piston according to this invention in which the reference numeral 40 indicates a forged or cast iron piston head having a pair of dependent ears 4| and 42 extending on opposite sides thereof. The ears 4| and '42 are 1 provided with cylindrical boss portions 43 which may be drilled to provide openings as shown in Figure 12 for receiving a wrist pin.

Grooves 45 are formed around the periphery of the head 40 for receiving piston rings (not shown). i

As shown in Figure 12, a web 46 is formed across the insideof the head 40 and extends downwardly at both ends 4611 thereof to reinforce the ears 4| and .42.

A depending flange 41 extends around the periphery of the head 40 at the lower end thereof and has a somewhat smaller diameter than the diameter of the head 40 to form a shoulder 41a between the flange 46 and the head 40.

, A piston skirt 48 is first formed according to either of the methods disclosed in Figures 2 to 6 and is then provided with a pair of

spacedslots

49 and 50 on each side thereof to define two oppositely disposed strips 5| and 52 which are bent inwardly'as best shown in Figure 1,3'to form' reinforcing portions across the central portion of the skirt 48. The excess metal is crimped to tion. Since the ears 4| and 42 extend through openings 54 formed in the strips 5| and 52 of the piston skirt, these ears are not united to the skirt and only one brazing 'wire need belooped aovzcafs around the inside periphery of the flange 48 instead of using two individual wires as shown in Figures 8 and 9.

The piston with the brazing wire therein is then brazed in a furnace in the same manner described in connection with Figures 1 and 8 to 10 to form a braze 55 around the periphery of the flange 41, therebyintegrally uniting the piston skirt l8 with the head 40.

It should be understood that according to this invention pistons may be made from two different metals. I prefer however to use a cast head portion of grey iron anda skirt portion of mild steel.

The brazing wires of copper, brass or bronze have great amnity for the cast iron head and, when placed in the piston as described above, readily flow by capillary action between all contacting portions of the iron head and the steel skirt to integrally unite the skirt to the head. The resulting piston is much stronger than a cast iron piston and can be made of light gauge metal thereby producing aproduct of about'the same weight as aluminum pistons. At the same time, however, the pistons of this invention have a coeflicient of expansion about the same as the coemcientof expansion of the engine block and thus need not be loosely fitted into the block as is the case when aluminum pistons are used.

It has been found by tests that the steel skirts cannot be torn away from the head portion without heating the piston aboveth melting point 1 of the brazing material. Since the temperatures of an internal combustion engine never reach temperatures at which the brazing material becomes molten, there is no danger of the brazed pistons of this invention ever separating during use I am aware that many changes may be made a d numerous details of construction may be v ried through a wide range without departing it re, do not purpose limiting the patent granted hereon otherwise than necessitated by the prior art.

I claim as follows: d a I 1. A composite piston comprising a cast iron liead portion having depending ears extending therefrom on opposite sides thereof, said ears carrying apertured bosses on-the ends thereof-for receiving the ends of a wrist pin, a cylindrical steel skirt portion telescoped on part of the head portion and having a pair of spaced cuts therein on each side thereof defining web portions therebetween, said web portions being indented to reinforce the skirt and having parts thereof cut away to receive the depending ears of the head and a thin film of a' copper containing brazing material between and alloyed with the telescoped portions of the head and skirt tointegrally unite said portions.

2.; A composite internal combustion engine a piston comprising a cast 'iron head portion including a reduced section, a steel skirt titted about and telescoped by said reduced section and having its outer surface flush with that of. the head portion, a thin film of a brazing material between and alloyed with the telescoped portions of the head; and skirt to integrally unite said portions, said head portion havingv depending ears extendfrom the principles of this invention, and I, thereing therefrom onopposite sides thereof formin wrist pin bosses, said skirt portion having a pair of spaced cuts therein on each side thereof de fining web portions. therebetween and said web portions being'indented to reinforce the skirt.

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