US1699819A - Piston for use in fluid-pressure engines - Google Patents

Description

Jan. 22, 1929- C 1,699,819

E. TALBOT PISTQN FOR USE'IN FLUID PRESSURE ENGINES Filed Jan. 1927 2 Sheet s-Sheet 1 Jan. 22, 1929. 1,699,819

E. TALBOT PISTON FOR USE IN FLUID PRESSURE ENGINES Filed Jan. 5, 1927 2 sham-sheet 2 Patented Jan. 22, 1929.

UNITED STATES ERNEST TALBOT, OF LOWESTOIET, ENGLAND.

PISTON FOR USE IN FL'UID-PR ESSURE ENGINES.

Application filed January 3, 1927, Seriai No. 158,768, and in Great Britain January 131926.

This invention relates to pistons for use in fluid pressure engines, of the kind in whlch the skirt and the head or ring-carrying portion are formed separately from one another.

The principal object of the invention 1s to provide a simpler and less costly method of forming the skirt and of attaching it to the head. of the piston, whereby, not only can the piston be made considerably lighter and more efiicient than usual, but also accurate weight and fitting of each piston is ensured without diflicnlty when large quantities of a standard size are being manufactured. A further obj set is to insure a resilient contact of the skirt with the cylinder walls to adapt itself tochanges of temperature under working conditions, and to minimize the heat transfer between the head and the skirt of the piston.

In the accompanying drawings, which show various methods of carrying out the invention,

Figure 1 is anelevation of a complete p1ston in part-section on the axial plane of the piston and piston pin,

Figure 2 is an end view as seen from below Figure 1, i j i Figure 3 is asectional elevation of the head part only of the piston, the plane of the sec tion beingtransverse to the plston pln axis,

Figure 4 is a view similar to Figure 3 showing a modified form ofhead, whilst Figure 5 is a view similar to Figure 2 showing alternative attachment means for the skirt to a head as shown in Figure 4.

Figure 5 is a similar view to Figure 5 showing a modified attachment means, i

Figure 6 is a plan of a strip of metal from which the skirt shown in section in Figure 7 is produced by rolling the strip,

Figure 8 is a fragmentary view of a strip alternative to that shown in Figure 6,

Like numerals indicate like parts throughout the drawings. v

In one method of carrying out the invention, the skirt 2 initially is constituted by a flat disc of metal, which is pressed into the form of a cup having a flat bottom, its sides constituting the actual skirtof the piston. A cruciform hole bounded by the edges 3, 4: is pierced in the bottom of the cup, leaving four spaced inward projections or tongues adapted, by their edges 4:, to engage the sides of the gudgeon pin bosses 5 provided in the separately formed head and giving clearance for the small end of the connecting rod by the gaps formed between the edges 3, 3 of the stitute a split skirt having the splitinclined projections. Two such pressings located with their projections in contact may be secured by the same fasteners 6 to flanges or ledges 7 (Figure 3) formed on the gudgeon pin bosses, and in this example adjacent their central plane. Thus the inward projections or tongues serve both for the attachment of the skirt and to the head also as an accurate register in their mutual attachment. Preferably in each construction the head is reduced in diameter below the ring-carrying portion, and the wall of the reduced portion between the bosses 5 maybe cut away as shown.

If preferred, instead of piercing a cruciformaperture in the disc, a plain slot 9 (Fig ure 5) adapted to provide for the angular movement of the connecting rod would suffice, and the flat parts .at the sides of the slot would then constitute the projecions for attachment to the underside of the bosses 5, as shown in Figure 4, and upon the latter would be arranged registerslO or dowels 11 adapted toengage corresponding cut away parts 12 or perforations 13 in the projections. The flanges 7 are also employed to increase the area of support fort-he projections and to providesufficient room for holes 14 for the fasteners, which may be of any preferred kind. Figure 5 shows alternative kinds of registers, that at 10, Figure 5, having a curvature about the cylinderaxis on its engagement side, whilst that at 11, Figure 5 is of plain circular form. i

In the construction shown in Figure 2 and to provide for the transmission of the side thrust from the gudgeon pin bosses to the skirt, the inner edges 4 of the projections which abut the bosses may be flanged as at 40 to provide a greater contact surface (see also Figure 7). Also, the edges of the skirt, either in .the foregoing or following constructions, may be rounded at each end 24 so as to avoid a scraping action on the cylinder walls.

Asan alternative, (Figures 6 and 7) the skirts may be formed of strips 15 of metal, the ends 16 of which are parallel to one another .butnot at right angles to the sides. These are bent into cylindrical form and con to the piston travel. The top and bottom edges of the skirt as thus formed are spun, pressed or otherwise bent inward to stiifen the skirt as at 24 (Figure 1), and by the formation of V or U shaped slits 17 around the wall of the skirt, tongu 3s 18 are formed which are bent inwards preferably at right angles to the side of the skirt, and thus form the attachment means for connecting it with the head. If the skirt were to be formed in two parts as in Figure 1, the tongues 18 would be formed at the ends of each, that is, at the edge of each strip 15, (Figure 8), so thatthey might abut one another and be secured together to the head.

In either of thelatter arrangements, certain of the tongues may be rigidly secured to the heads, whilst others engage it resiliently so that a better working engagement of the skirt in the cylinder is ensured throughout all changes of temperature under working conditions.

Where the projections or tongues are four in number in a single or two-part skirt, it will be necessary to provide apertures19 in the skirt to enable the gudgeon pin to be inserted. Alternatively, the pin may be put in place before the skirt is attached, the skirt then serving to retain the pin.

On the other hand, if the plane of the projections or tongues is below the axial plane of the gudgeon pin as in Figure 4, then the apertures formed in producing the tongues, as by the slits 17 in Figure 6, may be so situated as to serve for the insertion or removal of the pin.

Obviously, if preferred, when formin the skirt by bending a strip 15 into circular orm, the strip could be in two or more parts so that thereby theskirt would be longitudinally divided at a corresponding number of places, the object of suchan arrangement being to obtain the resilient expanding type of skirt. In either arrangement the grain (if any) in the skirt would be so arranged as to give maximum strength to the tongues.

Where a large number of the same type of piston is required, the skirt might be formed of seamless drawn tube having a finished size and polished, and having the projections or tongues inits sides or on its edge, but the invention is not limited to Wrought metal, as a hardcast iron skirt could be provided with the projections ready formed in the finrangement would be that by the use ofa metal or alloy for the head having a greater c0- eificient of expansion than that of the skirt, the lattercould expand under the effect of the ,heat atthe points forming the tongues owing to the grip ofthe alloy on the tongues lessening slightly as the temperature rises.

The object of this is to ensure that the skirt will have the spring imparted to it during the process of manufacture so that when assembled by fasteners to the head or placed in the casting die, the tendency would be to spring outward against the cylinder wall. If, therefore, the head is cast on to the inward projections or tongues, there will be sufficient expansion of the alloy at points adjacent the projections to allow the latter to slip or slide outwards as the cylinder expands. It is not intended to allow or cause the skirt to be expanded by the radial expansion of the head.

Alternatively the converse efieet upon the skirt could be obtained if the material of which the head is formed has a lower coefiicient of expansion than the skirt, and in all the previously described constructions the piston headmay or may not make contact with the cylinder walls.

The skirt, whether it is made of drawn tube having a olished and finished exterior surface or is ormed by bending a strip to circular form, may be slightly distorted, for instance, by maklng it slightly oval so as to ensure a resilient pressure on the cylinder walls in the direction which will prevent sla of the piston. hen the skirt is formed of drawn tube, 1t may comprise two parts as are shown in Figure 1, and the tongues may be formed at the meeting edges ofthe two tubes in the manner shown at 1.8, Figure 8, for the fiat strip, As before the tongues on one part of theskirt can register with those upon the other, so that the same fastenerswillserve for both. Such a construction is one which is peculiar- 1y suited for the economical production of a number of similar pistons, particularly where uniformity of weight is essential.

The method herein describedfor the fory mation of. the skirt may be appliedto such pistons as are formed with a waist. Thus each portion of the skirt may be made from a flat disc, and the bottom edge may be bottled or spun-in so that clearance is provided and there is little or no interference with the oilfilm on the cylinder wall.

In any of the constructions shown, the junction between the ring-carryin portion of the head and the adjacent end of the skirt may be utilized to provide a groove for a piston ring, as is shown at 20 in Figure 1.

The principal advantages derived from the foregoing constructions are (13 The skirt may be formed from polished material so that grinding or other machining of the outersurfaces is avoided.

(2) The attachment of the skirt and head may be such that a resilient pressure exists between the skirt and the cylinder walls, thus preventing slap and taking up wear, although I am aware that a like resulthas been obtained by making the skirt of any ordinary piston slightly larger and thereafter splitting it to enable it to enter the cylinder bore.

(3) The skirt can be assembled and attached to the head in a jig or fixture correspending to a cylinder, so that subsequent I finishing or fitting is avoided.

From the foregoing it will be seen that it is possible to manufacture rapidly and economically pistons which will require no subsequent fitting in the cylinders and will have substantially the same Weight as one another when manufactured What I claim as my invention and desire to secure by Letters Patent of the United States is 1. In a piston for a fluid pressure engine, the combination of a head, a skirt formed separately from the head and spaced projections around the skirt adapted to form the connecting means with the head, said projections being formed in the Walls of the skirt and thereafter bending the tongues inwardly to form the projections substantially as set forth.

2. A piston as claimed in claim 1, in which the skirt is formed from a strip of metal bent into circular form, the meeting edges constituting a split in the skirt which is inclined to the axis of the piston, substantially as set forth.

3. A piston as claimed in claim 1, in which the edges of the projections are formed with flanges, substantially as set forth.

In testimony whereof I have signed my name to this specification.

ERNEST TALBOT.

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