US1742452A - Piston - Google Patents

Description

Jan. 7, 1930. M, TIBBET S 1,742,452

PISTON Filed June 12, 1926 Brae ATTOENEK Patented Jan. 7, 1930 HILTON TIIBBETTS, OF DETROIT,

MICHIGAN, ASSIGNOR T0 PACKARD MOTOR CAR COM- PM, 01 DETROIT, MICHIGAfi, A. CORPORATION 01 MICHIGAN PISTON Application filed June 12, 1926; Seriallio. 115,427.

My invention relates to devices for compensating for dimensional changes 1n mechanical elements and due to expansion or contraction resulting from temperature variation, to which such an element jected.

The general object of the invention is to 7 control or modifysuch changes soas to maintain certain of the dimensions of the element substantially in a state of constancy or mainm tain a predetermined relationship between I the degree of frictional resistance between the such an element and a cooperating element.

A particular object is to provide a piston for an internal combustion engine whose diameter will remain substantially constant One method, heretofore, of attempting to overcome this'piston difliculty has been by providing a split skirt for the pistonso that it would automatically spring inwardly when subjected to increased temperature, and when pressed by the cylinder walls, and automatically spring outwardly when subjected to decreased temperature and released by said cylinder wall, under the theory that a substan.

tially constant diameter of the piston would thus be maintained and a proper fit secured under all variations of temperature to which the piston would be .subjected.

However, in some cases it has been found that pistons constructed as just described, and partlcularly-when made of aluminum, contract and change their diameter to such an extent as to become, when cold, loose and hence noisy. It will-be apparent; also, that piston and cylinder will vary materially by changes in the temperature, and especially in the case of an aluminum piston and iron cylinder, even though it might not be noisily loose when-cold.

In carrying out the principles of my inven-' tion, I provide the mechanical element with athermally operated device which when subjected to variations of temperature produces a force resulting in motion which is trans-' mitted to the element and caused to oppose the force which would produce movement in may be sub-- under the conditions of varying temperature provide the skirt of the latterwith a longitudinal slot so that such skirt .is normally capable of circumferential dimensional ex-- pansion or contraction independently of tem- In applying such principle to a piston, I

perature variation. To the skirt I connect a thermally actuated d vice and in such a manner that a variation f temperature will effect. a movement in the device, which is transmitted to the skirt wall'and in a direction such as will decrease the diameter of the skirt in case it expands or maintain the diameter in case it tends to expand and increase the diameter in case it contracts or maintain its diameter in case it tends to contract.

The said invention therefore consists of means hereinafter fully described and particularly pointed out in the claims.

The annexed drawing and the following description set forth in ple of my invention may be employed.

. In said annexed drawing:

Figure 1 represents an axial section of apiston embodying my invention.

Fig. 2 represents a transverse section taken indicated by line vII----II In the illustrated embodimentof my invention, the piston l is,p,rovided with a head 2 and a; skirt 3 integral with or joined to the head, the skirt and head being separated at the wall portions thereof by a circumferential slot 4 extending completelyaround the periphery of the piston 1, as'shown in Figure detail certain means for carrying out my invention, the disclosed means, however, constituting but two of the a various mechanical forms in which the princi- 1. 'The skirt wall is intersected by a slot 5 extending longitudinally from top to-bottom of same, and is shown in the drawing to be in clined with reference to the pistons axis.

As thus far described, the piston is of a construction heretofore known and does not constitute any part of my invention;

- duce its It will be observed, however, that'the piston so constructed permits the skirt normally to be subjected to a dimensional change independently of temperature variation and also is sub ect to such change as a result of such variation. By this I mean, that an exterior mechanical compressive force may be applied to the dismounted skirt torediameter and thereby contract the slot 5, or an expansive force applied to increase such diameter and enlarge the slot. Also that when subjected to increased temperature its diameterwill be increased and the circumferential extent of the metal also increased, while the slot is also somewhat enlarged.

The above-construction is, however, in the form of my invention shown in Figs. 1 and 2, modified by providing additional metal upon the interior of the wall of the skirt in the form of bead-like additions 6-6, respectively immediately adjacent the slot 5, and in these beads are respectively embedded and fixedly secured, as forexample by casting, the ends of a thermally-actuated loop-formed device 7 consisting of two flat superposed pieces of metal having ,diiferent co-eflicients of expansion asfor example steel and brass, that plate having the greater coefiicientof expansion being located upon the outside of the loop. As is well known, such a combination of metals when subjected to varying tempera-- ture warps and produces or tends to produce motion in the device. In this case an increase of temperature will cause the ends of the approach or tend to approach and a loop to decrease would cause same to recede or tendto recede from eachother, and in either case may be used to transmit force to the wall of the skirt adjacent to theslot. The force thus applied by the loop device 7 acts circumferentially of the skirt 3 andprovides a circumferential dimensional change therein which is uniformly distributed about the circumference of the skirt. 1.

Such proportions and dimensions of the loop and its constituent parts and character of the metals are selected as will be necessary to produce a movement of the loop ends, sufficient in its transmission to the s irt wall to counteract and equalize any expansive or contractive force developed interiorly of "the skirt metal and due to the variation of temperature to which the piston is subjected in the operation of the engine, and the external diameter of the skirt will hence remain substantially constant for all temperatures, as

it will be understood that the amount of a movement produced by the loop will vary substantially directly as the temperature.

Should it be found that it is also desirable to allow for theex ansion of the cylinder wall, the loop 'may force exerted upon the skirt would be sufliciently less than an absolutely equalizing for example,

e designed so that the rather than completely equalized. In this way allowance may be made for cylinder expansion and a constant relationship secured etween the friction surfaces of the piston and cylinder so as to effect a constant frictional relation thereof for all the temperatures.

The proper design of the loop and proportioning of its parts may be determined empirically for any. given engine, set of operating conditions, or character of piston, as will be apparentto those skilled in the art.

It will also be apparent to those skilled in the art that various forms of thermally operated devices may be used to accomplish the. above-described object, and I have illustrated. one such modification in Fig. 3.

. In this latter instance, the device is generally flat with a centrally located bow 8, its

ends being fixedly secured in ribs 99 respectively and preferably near the skirt wall as shown,,so as totake advantage of; all the leverage ossible. In this latter form the metal havmg the greater coefficient of expansion would be located inwardly, that is on the side of thedevice adjacent the piston wall.

What I claim is:

1. The combination with a mechanical element normally,capable of circumferentially uniform dimensional changes independently of temperature variation; of a thermally actuated device connected with said element and adapted to apply force thereto circumferentially opposed to that force tending to effect circumferential dimensional change in said element and due to temperature variation; whereby such last-mentioned change may be controlled.

2. The combination with a hollow cylindrical mechanical element normally capable of circumferentially uniform dimensional changesindependently of temperature variation; of a thermally actuated device cbnnected with said element and adapted to apply force thereto circumferentially opposed '7 to that force tending to effect circumferential dimensional change in said element and due to temperature variation; said device being arranged so as to maintain a substantially constantcircumferential dimension on the longitudinally extending slot and provided with a thermally actuated device connected with the piston wall on 0 posite sides of said slot, said device adapte to apply force to said opposite sides varying as its temperature. I

5. A hollow piston having a head, and a skirt formed with a longitudinal slot, the wall of said skirt being se arated from said head throughout the perip ery of the piston, said skirt being provided with a thermally actuated device connected with the wall tion adjacent said slot and adapted under the influence of an increased temperature to apply a :torce to said wall portion tending to contract said slot.

6. A piston having a head, and a skirt formed with a longitudinal slot, thewall of said skirt being separated from said head; and a thermally actuated device connected with said skirt and adapted, when subjected Y to an increased temperature, toexert on said sk1rt a force acting uniformly circumferentially and opposed to that force set up therein. by such increased temperature.

7. A piston having ahead, and a skirt formed with .a longitudinal slot, the wall of said skirt being separated from said head; and a thermally actuated device connected with said skirt upon opposite sides of said slot and adapted, when subjected to an increased temperature, to exert on said skirt aforce opposed to that force set up therein by such increased temperature.

8. A hollow piston having its wall formed with a slot and provided with a device comprised of two metals of difierent coeflicients of expansion and connected with said wall upon opposite sides of said slot and adapted upon thermal expansion to contract said slot.

9. A hollow piston having its wall formed with aslot and provided w1th a device comprised of two super os'ed metal plates of dif-' ferent coefiicients 0 expansion and connected with said wall upon opposite sides of said slot and adapted upon thermal expansion to contract said slot. 7

10. A hollow piston having its wall formed with op osed beads and a slot therebetween, and a evi'ce comprised of two' superposed metal plates of difierent coeflicients of expansion and connected at its ends respectively to the outer walls of said beads, the outer metal plate'having the greater coeflicient of expansion.

11. A piston having a head, and a skirt formed with a lon 'tudinal slot extending from its top to its ottom, thewall of said skirt being separated from said head; and a thermally actuated device connected with said skirt and. adapted, when subjected to an increased temperature, to exert on said skirt a force entirely opposed to-that force set up therein by suc increased tem eratura 12. A piston having a hea and a I por- MILTON TIBBETTS. 7

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