US2341959A

US2341959A - Piston expander

Info

Publication number: US2341959A
Application number: US350426A
Authority: US
Inventors: Harold K Switzer
Original assignee: Individual
Current assignee: Individual
Priority date: 1940-08-03
Filing date: 1940-08-03
Publication date: 1944-02-15
Anticipated expiration: 1961-02-15

Description

Patented Feb. 15, 1944 UNITED STATES PATENT OFFICE PISTON EXPANDER Harold K. Switzer, Newport, Ky. Application August 3, 1940, Serial No. 350,426

(Cl. Sil-) 4 Claims.

This invention relates to the art of expanding or reshaping pistons which are of improper size. In the operation of internal combustion engines the pistons may become collapsed or misshapen due to the repeated expansion and contraction to which they have been subjected over a period of time under varying temperature conditions.

The looseness which results from the collapse and distortion of the piston is objectionable for several reasons. The efficiency of the engine is substantially decreased by pistons of improper size or shape and the objectionable piston slap commonly heard in older engines, is a characteristic symptom of the defect.

'I'his invention is particularly directed to a simple, inexpensive hand tool for expanding pistons by rapid and easy manipulation of the tool relative to the piston. pistons in which this tool may be utilized is fully described and claimed in my United States Patent No. 2,289,941 of July 14, 1942. Heretofore, complex peening machines have been utilized for the reshaping operation. It has been necessary to dismantle the engine and remove the pistons from it before they could be operated upon in the peening machine, and the entire job is both expensive and tedious.

In contrast, the principal object of the present invention has been to provide a Very simple tool with which the pistons can be operated upon, reshaped and expanded while they are in the engine or after they have been removed from it.

Briefly, the present invention contemplates a tool by means of which the material of the piston series` of lines extending longitudinally of the piston skirt. The metal of the skirt along these lines of pressure contact is swaged, and peculiarly the piston is thereby expanded. In a typical expanding operation, the portion of the skirt opposite the thrust side of the piston is worked upon to accomplish the reshaping of it; however other parts of the piston also may be treated forother reshaping or expanding purposes.

For use in the practice of the method described and claimed in my aforesaid patent, this invention contemplates a simple and inexpensive tool which may be employed satisfactorily by an ordinary automobile mechanic. This tool includes a pair of hardened metal wheels. One of the wheels is flat peripherally and is of substantial width. The other may be relatively thin and the periphery may be rounded. The two wheels are arranged to cooperate with one another to exert a skirt is contacted under pressure along a` 'taken on a line through the piston skirt at the swaglng action'upon the metal of a piston skirt placed therebetween.

The tool normally is used so that the thin wheel rests on the interior surface of the piston skirt, and a handle is provided for the tool so that the wheels 'may be moved along lines 1ongi` tudinally of the skirt to compress the metal; it isy thiscperation which expands the skirt circumferentially. v Y v Except in extraordinaryinstances the toolis used to operate upon the pistons without dismantling them from the engine block, for instance with the oil pan and the connecting rod bearings removed the piston whichis to be operated upon is drawn downwardly to a polntlat which the skirt of it is disposed beneath the block; the skirt is now accessible and readily may be reshaped and expanded. f

The tool may be used with substantially all types of pistons, for instance those made of cast iron and semi-steel as Well as those made from aluminum alloys. The operation of expanding or reshaping a piston requires but a fraction of the time required by past methods.

For use in conjunction with the tool, an object of the present invention also has been to provide a shieldadapted to be fitted around the piston skirt so as to keep the outer roller of the tool from marring the metal surface as the reshaping operation is performed-l In the use of such a protector the major swaging action is accomplished by the thin wheel at the interior of the piston. In other instances it is also practiced, by means of the present improvement,to expand the piston to an oversize dimension and then machine it back to size as in a lathe.

In the drawings:

Figure 1 is a perspective View showing a piston in the process of being expanded by a hand tool made according to the present invention;

Figure 2 isa fragmentary cross sectional view point where the tool isacting;

Figure 3 is a side View of the hand tool shown inFigure 1 wherein the details of construction are shown in cross section;

Figure 4 is a perspective View of a guard `which may be utilized to protect the piston against marring by the tool;

Figure 5 is a fragmentary cross sectional view taken longitudinally through the piston;

Figure 6 is a View similar to Figure 5 in which the tool has been modified slightly to accommodate a piston having a strengthening ridge running around the inside of the piston near the lower edge of the skirt;

Figure 'l illustrates a modified form of the tool in which a stationary swage block is utilized in place of the thinner roller;

Figure 8 is a cross sectional view taken on line 8-8 Figure '7, further illustrating the modification.

Figure 9 is a diagrammatic cross sectional View taken laterally through one of the cylinders of an internal combustion engine illustrating the manner in which a piston may be expanded without removing it from the cylinder.

Figure l0 is a cross sectional View taken on line Ill-I0 of Figure 9.

In the drawings the piston shown is a relatively typical aluminum alloy piston having a` The use ofthe tool with other T slot in its skirt. types of pistons will be discussed at a later point in the description. The thin-walled portion of the piston, termed the skirt, is indicated at l5.

The tool illustrated in the drawings, comprises twoarms I6 and I1. Thearms aresecured to a bracket I8- by nutswhich engage threaded portions I9 extending through holes in the bracket from the ends ot the The arms extend substantially parallel bracket.v The bracketis bent downwardly at an angle to the arms, as at 20, and is secured to a handle- 2| by a screw or other means.

Apair of `wheels 22 and 23 is mounted in slots inthe ends of the arms respectively. The wheels arefjournalled Aonpins 24'press fitted in appropriate holes inthe respectiveends ofthe brackets. One of rowi and .rounded peripherally while the other, indicated iat 23, is wide and flat peripherally.

Medially ofthe length of the arms means is provided for adjustingthe arms` toward and from one another. The adjustment means comprises a screw `25'which is threaded intoone of the arms andv-locked therein by a threaded collar 26. The screwH extends at right angles to the arm and passes througha'hole in the other arm. Beyond the second arm nut 21. Thus, by tightening the thumb nut the two arms are drawn together. A slight exing or springiness inthe arms I6 and I1 aids materially in producing a vsmooth operation of the tool.

A shield'28, shown in Figure 4, comprising a thin sheet of'spring steel m-ay be utilized to keep the outerwheel from marring the outer surface of the piston. The shield is placed around the skirt ofthe piston and is retained in placev by its own spring action. In most instances, the shield is' not necesssarythough it maybe used as a special precaution against marring the surfaceof the piston.

Operation The expansion operation may be performed, as has been the practice heretofore, byremoving the piston from the. cylinder. In this instance, the piston is clamped orheld headdown on the work bench. When used on aluminum alloy types of piston, the wheelsA are first rolled up and down the skirt on both sides ofthe slot as near the pin bosses as is practical. The wheels should be rolled longitudinally of the pistonsv in straight lines, with the thinner wheel on the inside of the piston. After each stroke, the tool is moved nearer the slot. It is only necessary to swage van areafof approximately 3A; of an inch from each pin b`oss. Five or six strokes of the tool are thus sufficient to expand the piston about four to six toone another from the thewheels, indicated at 22, isnarthe screw is engaged by a thumb `the wheels; bowing out one-thousandths of an inch. The tool should be adjusted so that the wheels exert only a light squeezing pressure on the metal of the piston skirt since it is not necessary or desirable to gouge the metal to expand pistons by this method.

This same procedure may be used on semisteel pistons as well as other aluminum pistons, that is, swaging the skirt of the piston near the pin bosses on the side oppositethe one subjected to thrust.

Cast iron pistons react somewhat differently to the swaging action of the method than do aluminum alloy pistons. Cast iron expands beneath where the wheels are rolled. Cast aluminum pistons expand at the slot, that is, the collapsed section of the skirt near the slot is reshaped by swaging the areas on both sides of the slot adjacent the pin bosses. Cam ground pistons which have become rounded through use may be reshaped by swaging the metal of theskirt in these same areas, that is, near the pin bosses. This causes the cam.4 groundpiston to reassume its slightly oval shape. To reshape a cast iron piston,y the wheels are.rol1ed over the skirt in the area directly opposite the center of thrust. Cut-away skirt pistons or slipper pistons made of cast iron. are also reshaped bythis latter method of employing the tool.

Certain pistons having a rib around the inside of. the piston below the pin bosses require .a slightly modified tool, (Figure-6). In this instance the thinner wheel is journalled off-center of the arm so that thearm clears the rib. Referring to Figures 7 and 8, a modified form of the thin swaging wheel isshown.. Herea swage block 29 is substituted. The block is secured inv a slot in the. end of one of the arms, by a pin 3D; The operating surfaceoi the block comprises a rounded ridge 3l similar to the rounded peripheral ridge of the thin swaging'wheel.y

A practical advantage of .considerable importance provided' by the present invention is that pistons mayin many instances be expanded 4without removing them completely from the cylinders. The manner in which this is accomplished. is disclosed in Figures 9 and 10. This practice is not applicable in the cases of V-type or radial engines. To prepare the piston, the oil pan and the connecting rod bearings are removed. The piston to be treated is then pulled down to expose the skirt and the connectingrod and crankshaft are moved to one side as shown in Figure Y 9. In most engines, the piston can be brought down tov reston the throws of the crankshaft as shown. They expanding operation can then be carried out asv described above.' The piston may be slipped back up into place to check the fit as the expanding operation proceeds.

In some cases, the handleof the tool interferes with the operation of thetool because of' obstructions. In these instances, the handle. can be reversed by changing the position of the arms I6 and I1.

skillful and judicious use of it, the piston skirtY may be squeezed or thinned to the desired degree, thus creating compensatory expansion of the piston skirt so that it better ts the cylinder.

The tool is susceptible toy 2,341,959 3 Having described my invention, I desire to be said rollers being adapted to exert a squeezing limited only by the following claims: action on the piston skirt, one of said rollers 1. In a piston expanding tool having a handle having an outwardly tapered tread for the dismetal swaging elements carried one by each of tread for supporting the portion of the skirt opsaid arms; one of said metal swaging elements posite to that with which the rst named roller a narrow rounded tread for engaging the piston 10 4. In a tool for expanding a piston by swaging surface. the skirt of the piston along lines extending 1on- 2. In a piston expanding tool, a pair of arms gitudinally of said skirt a pair of spaced arms spaced apart and connected adjacent one of their adapted to straddle a piston skirt, a swaging elerespective ends, a metal displacing element cai'- ment carried by each of said arms, one of said ried by each of said arms, sala elements being 15 swaging elements presenting a narrow tread suradapted to engage the skirt of a piston on opface for displacement of the metal in the piston each of said arms with its axis transverse thereto, HAROLD K. SWITZER.