US1983673A - Method of expanding pistons - Google Patents

Description

Dec. 11, 1934. R MUNDT METHOD OF EXPANDING PISTONS Original Filed May 9, 1932 Patented Dec. 11, 1934 UNITED STATES METHOD OF EXPANDING PISTONS Robert Mundt, Cedar Rapids, Iowa Original application May 9, 1932, Serial No.

610,198. Divided and this application February 25, 1933, Serial No. 658,555

3 Claims.

This invention relates to methods of forming pistons and has particular relation to a method of expanding pistons so that they will be a close running fit in the cylinders with which they are to be used.

The present application is a division of my 00- pending application Serial Number 610,198 filed May 9th, 1932, and covering an invention in devices for expanding pistons.

I have observed, and it is well known in the art, that pistons of internal combustion engines, compressors and the like become loose and worn in service so that loss of compression results and piston slap develops. Even in new engines the pistons are sometimes poorly fitted, and by the methods known to the prior art would, of necessity, have to be replaced in order to secure a properly functioning motor.

I have observed that most pistons are constructed with oppositely disposed openings in the side walls thereof below the piston rings and that in most cases the skirt of the piston is provided with one or more slots to take care of differential expansion of the cylinder and piston. The side walls of the piston are held or reinforced by means of struts which extend across the openings before mentioned and the bosses in which the piston pins are located constitute parts of these struts. The struts are usually provided with one or more openings on each side of the piston pin boss, presumably in order to lighten the weight of the piston.

I have devised a means for and a method of expanding the struts and the skirt of the piston so that the diameter of the piston may be increased sufiiciently that it may be made a close running fit in the cylinder with which it is to be used. :The circumference of the piston is likewise increased and the expansion throughout may be controlled in minute, sharply-defined, increments so that accurate fitting of the piston may be secured.

An object of my invention'is to provide means of, and a method for, expanding a piston to any desired diameter and circumference.

Another object of, my invention is to provide a means for closely controlling the process of expanding a piston.

Another object of my v invention is to: provide 'a relatively simple, eiiicient, and inexpensive device for expanding pistons.

Other and further features and objects of my invention will be more apparent to those skilled in the art upon a consideration of the accompanying drawing and following specification, wherein is disclosed several exemplary embodiments of the invention, with the understanding,

however, that such changes may be made therein as fall within the scope of the appended claims without departing from the spirit of the invention.

In the drawing and in the following specification there will be described several devices embodying means for practicing my improved method of expanding pistons.

Figure 1 is a side elevational view of the piston expanding device. The piston has been shown in dotted lines to illustrate theposition it occupies while it is being expanded.

Figure 2 is a view in front elevation of'a device which may be located in the vertically-extending, slideably-engaged plunger which is utilized for applying'pressure to expand the piston.

Figure 3 is a View in side elevation of the piston,

the mandrels, and a portion of the plunger, and shows the piston in the position it occupies while the device is being used to expand the skirt of the piston.

' Figure 4 is a View in side elevation of a portion of the standard, of the piston, shown in dotted lines, and of the mandrels used in expanding the struts of the piston.

Figure 5is a View in perspective of a mandrel constructed according to an embodiment of my invention, and

Figure 6 is a view in elevation of a pair of mandrels constructed according to an embodiment of my invention.

Referring now to the drawing and particularly 'to' Figure 1 thereof, there is shown at 10 a base,

substantially rectangular in shape, and having an upthrust central portion 11 provided with a suitably-shaped, rectangular opening 12 in which astandard 13 may be located. The base 10 may be secured to a suitable support 14 such as a table or the like by means of bolts 16. Of course,

] the base may be held in a vise or similar clamp if desired.

The cross-sectional shape of the standard 13 is immaterial but the opening 12 in the base must correspond to the shape of the lower end of the standard in order that the standard will be a tight'fit in the base. In the present instance, however, I prefer to utilize a standard which is substantially rectangular in cross-section so that it may be fastened in a vise or the like without the necessity of using a base. The object of this construction, of course, is to permit the standard to be used as desired either in connection with a base which is permanently located on a work bench, or as a toolwhich may be used in connection with Vises or other clamping devices which are available in a shop.

The standard 13 includes an upright portion 15 and a horizontally-extending jaw portion 17. A horizontally-extending guide 18 is a part of the standard 13 or is secured to it in a suitable manner as by means of bolts or the like. A lower jaw 33, hereinafter more particularly described, is also a part of the standard13 or is secured to it in any suitable manner.

The upper jaw 17 has a vertically extending slot 19, preferably rectangular in shape, near its outer end, and the jaw is provided with a'pair of depending guides 21 and 22 whichare malignment with the slot 19. A pair of links 24 are pivotally engaged to the upper jaw 17 by means of a bolt or pivot-pin 25 and the link '24 is free1to move through a limited are for a purpose hereinafter explained. A plunger 26 is disposed Within the slot 19 at the end of the jaw 17 and extends downwardlythrougha corresponding open- .ing "2.7 in the 1 lower .guide :18.

A lever 28 is pivotally attached $170 :the link :24 as by means of a bolt or pivot-pin 29, and'to the plunger 26 as by meansof a bolt or pivotpin 31.

In a preferred embodimentof the invention-the outer end of the .lever .28 is formed in circular cross-section and apipe extension handle :32 :may be slippedon over thexend of therleverzto permit a long :lever arm to be used. It may readily be understood that the length of the lever arm .28 may be sufiicientlygreat thatyby reason of the short distance between the pivots :29 and 31,. a very appreciable pressure may be brought to bear upon the .plunger 26. Since :the plunger .26 :cannot move sidewise because it .is confined by-the slots 19 and 27, the rlinks-24pivot about on :pivot pin .to ,accommodatethe changing horizontal component of the lever arm between .pivots .29

and 31.

The horizontally-extending jaw 33 .is secured to, or is -,a part of, the standard l'3aandaffords a rest or anvil on which the piston :34 may be placed. The outer end of the jaw .33 is drilled with-a downwardly extending opening .36 inorder that :a cone-shaped mandrel :37 :having .131 cylindrical stem portion, may be inserted in the opening.

The mandrel 37 maybe in the shape of a truncated cone as shown in Figural or maybe a full cone as shown at 37a in Fig-ure according to whether the strut or the skirt .is to .be expanded. A recess .38 ispr-ovided in-the .lowerendof the plunger 26 in order to accommodate .thehead .or tip of the mandrel 3'] when theplunger is pressed down on the piston strut. An adapter 39, shown in Figure 3, may be inserted in recess 38 in the end of the plunger when desired.

Most of the pistons of-the present-day art are comprised of a light head 41, shown best in Figure 3, and a barrel portion 42 having a thin skirt portion 43 at the lower end thereof. A pair of oppositely-disposed, substantially-rectangular openings .44 are provided in the barrel portion. of the piston and. depressed tongues 46 extend from the head to the skirt of the-piston. This .portion of the piston does not ordinarily make contact with the cylinder walls. A pair of struts 47 extend across the openings 4.4 at right angles to the tongues 46 and the struts are rigidly attached to or are a part of the opposite parts. of the barrel-42.

A boss 48 in each of the tongues 46 affords means for pivotally securing a piston pin 49 to the piston, anda connecting rod 51 is attached to the pin 49 at its mid-portion, between the tongues 46. The strut 47 is provided with one or more openings 52 on each side of the tongue 46, presumably for lightening the piston. The struts 47 determine the spacing apart of the walls of the barrel 42 as lengthening or shortening of the struts 47 changes the diameter of the barrel portion of the piston.

My inventionmakes use ofthe described piston construction and particularly the strut structure for increasing the diameter and hence the circumference of the barrel portion of the piston. It maybereadily understood that by inserting the cone-shaped-mandrel 37 in the openings 52 and applying pressure on the strut by means of the plunger -26'the=openings 52 may be expanded and thegportionsof the struts adjacent to the openings stretched to increase the efiective length of the :struts.

If the diameter of the cylinder to which the piston belongs is accurately determined the various open'ings '52 may be each expanded slightly and in -successionto expand the piston. If micrometer measurements of the piston are made during this expanding process the piston maybe expanded to any desired dimension, within reasonable limits'and the expanding process closely controlled so that it will be a close running fit Within the cylinder in which it isto be used. The jaw 33 is sufliciently narrow that the connecting rod .5'l may be :left in the'piston during the expanding process-and the connecting rod placed firston one side of .the jaw and then on theother to permit :the struts to be expanded.

It is sometimes quite desirable to expand the skirt 43 of the piston as well and this is acconn -plished by removing the truncated-cone mandrel 3'7 and replacing it with the coneeshaped mandrel 37a, which-may be either :a relatively sharp point or may be slightlye'long-ated like a small chisel such :as the mandrel 37b shown in'Figure '5. An adapter 39, which is provided with a flat lower face, and astem portion adapted to 'be'inserte'd in the recess 39 of the plunger 26, is located in the plunger. The piston may then be placedbver the "end 'of'the {Ia-W33 'to a depth determined by a U-shaped stop 53 which is clamped to the jaw 33 as by means of a 'thumb screw be. The stop accurately determines the position of the edge of the skirt of the piston with reference 'to the mandrel 37a and when the plunger 26 is brought down against thef-aoe of the piston "the'point of .the-cone shaped mandrel 37a is driveninto the inner wall of the skirt '43 to dent it andslightly expand the skirt at the point where the pressure is applied. I

By'slowly rotating the piston and drivingthe mandrel-37a into the inner wall thereof at successive points a series of open'ings or dents are made in the-inner wall. The effect of this op- 'eration is to stretch'the materialof the skirt of the piston at the-points where pressure is applied so that when the series of dents have been made entirely around the skirt of the piston it will be found that its diameter and circumference have been increased. The operation may be repeated until the skirt-is of the required size. This same operation maybe applied to other parts of the piston such as the struts and fins in order to stretch them also.

Ihave found that it is possible to increase'the diameter of both the barrel and the skirt of a piston as much as 20/1000 of an inch, which is amply sufiicient'in the great majority of cases to take care of almost any degree of wear in a piston. Although the piston may be expanded to even a greater extent than 20/1000 of an inch, as a matter of practice if the piston needs to be expanded to a greater extent than this I have found it desirable to substitute a new piston for the worn one.

While the diameter of the piston may be readily increased, I have found it desirable that each strut opening or each part of the skirt of the piston should be expanded to substantially the same degree and therefore, in another embodiment of my invention, shown in Figure 2, I have utilized a pressure-indicating device 56 in the plunger 26. The plunger is of course of two parts 26a and 26b, with the part 26a slidably engaged in the part 26b so that it may move in and out with reference thereto. A spring (not shown) is interposed between parts 26a and 26b in accordance with well-known practice. The pressure-indicating device 56 may be any of the types well known in the art and one part of the device engages the portion 26a and another part of the device engages the portion 261) so that when pressure is applied on the plunger 26 by means of the lever arm 28 the needle 57 is moved over the scale 58 of the indicator 56 to indicate the degree of pressure applied. If pressure is applied to the lever 28 until the needle reaches the same position on the dial 58 at each successive application of pressure to the piston, then the parts of the piston, Whether they are the struts or the skirt, will be uniformly stretched or expanded.

My method of expanding may be applied to all parts of the piston. The pointed mandrels 37a and 371) may be applied by pressure to the skirt, the barrel, and the struts to expand any part of the piston as desired by denting the parts and thus stretching the metal about the dent. The tip 37b has a chisel-like point but the stretching and expanding action is substantially the same as that secured by the pointed mandrel 37a, that is, the metal about the point of application of the mandrel is slightly displaced and stretched. When the mandrel 37b is employed the stretching action is extended along a line instead of occurring about a point and thus a given area of metal may be stretched more in one direction than in another.

I sometimes prefer to utilize the blunt type of mandrels shown in Figure 6. The upper mandrel 390 is substantially the same as the mandrel 39 but is preferably slightly concaved at its lower face. The mandrel 37c employs the same stem as the mandrels 37a and. 37b but the upper part of the mandrel is substantially the same as the lower part of the mandrel 390 except that its upper surface is preferably convex. In using the blunt mandrels the mandrels 39c and 3'70 are placed in the plunger 26 and the lower jaw 33, and the skirt 43 or other part to be stretched is placed between the mandrels and pressure applied. When pressure is applied the skirt tends to move to the position shown by the dotted lines thus stretching the metal on the inner part of the skirt and thus expanding the piston.

It may readily be understood that I have provided a means for uniformly and accurately expanding the barrel, struts, and skirt of the piston and that the degree of expansion may be quite accurately controlled. The device is quite simple in construction and is reliable and eflicient in operation.

Although I have described several preferred embodiments of my invention it is apparent that modifications may be made by those skilled in the art. For instance the location of the mandrel may be changed as desired and it may be located in the end of the plunger. The mandrels may be quite dull at their ends or may be formed in a dull chisel-like tip, but the method of enlarging the piston is substantially the same, that is, the piston is enlarged by stretching the skirt, struts, fins, barrel and other parts thereof. The location of the lever arm may or in fact any suitable reversal of parts from that described may be used. These and such other modifications as may occur to those skilled in the art may be made without departing from the spirit and scope of the invention as set forth in the appended claims.

Having thus described my invention, what I desire to secure by Letters Patent is:

1. The method of expanding a piston comprising stretching the struts thereof by making openings in the struts thereof and driving the openings in the struts onto a mandrel.

2. The method of expanding a piston having struts therein for connecting the sides thereof comprising providing openings through the struts and expanding the struts as desired by driving a pointed mandrel into the openings and against the walls thereof.

3. A method of expanding a piston comprising providing openings and driving a mandrel into the openings to expand the metal about the openings.

ROBERT MUNDT.

also be changed in the part to be expanded

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