US2471477A - Piston packing - Google Patents

Description

H. BONNAUD PISTON PACKING May 31, 1949.

Filed Nov. 26, 1946 4 I W- I k I Fig. 1

fi zwww M m% #5 M Patented May 31, 1949 UNITED STATES PATENT OFFICE PISTON PACKING Paris, France Application November 26, 1946, Serial No. 712,320 In France March 8, 1946 8 Claims.

My invention relates to improvements in the arrangement of flexible cup packings which are mounted on the pistons of reciprocating machines in order to make them fluid-tight in the cylinders. It is known that these piston packings, which are generally made of leather, are used in preference to metal piston rings in some machines for reasons of operational necessity or of lack of lubrication, as is the case in particular in low temperature gas expending machines with external production of energy.

I-Ieretofore, such packings were generally made in the shape of circular angle section, the inner flange of which is pressed between a plate of the same diameter as the piston and crowns, or the body of the piston itself, whereas the outer flange is bent down on to the cylindrical periphery of the piston and is directed towards the pressure with respect to which it is required to obtain fluid-tightness. Consequently, in single-acting machines, all the packings have their outer flange turned towards the bottom of the cylinder, whereas in doubleacting machines a number of packings have their outer flange turned in one direction, and an equal number of packings have their outer flange turned in the opposite direction. Figure l of the accompanying drawing shows. by way of example, an axial section of a double-acting piston provided with four flexible packings arranged in the usual known manner. In this figure, a is the rod of the piston locked by the nut c, d is an upper crown, e an upper intermediate crown, a lower intermediate crown and g a medial crown. The packings 7', k, l, m, are

pressed between the various crowns by means of L;

the nuts n sunk in the upper crown d and screwed on the studs which are arranged in a circle and are themselves screwed in the body 19 of the piston. But the clampin of all these packings, whether it be efiected as in the drawing by means of nuts and studs, or whether it be efiected by means of screws, or any other similar device, can never be considered to be a locking which is comparable to that obtained in the assembling of metal parts to one another, this being due to the plasticity, which becomes almost indefinite in the course of time, of the packings thus clamped. During operation, the clamping devices for the packings are in fact subjected to alternating stresses which produce a flattening effect on said packings and finish by permanently squeezing them, so that play is set up between them and the assembling crowns. This play, although small for each packing, is multiplied for the clampin device by the number of packings clamped by same, i. e. by the total number of packings with which the piston is provided, and it tends to be increased by the action of the impacts on the piston which are produced by the reversal of the motion at the dead centres; in double-acting machines, this action is further aggravated by the reversal of the pressure at said dead centres.

The studs or clamping devices are thus subjected to alternate impacts which it is difiicult for them to withstand, whatever be the safety coeiiizcient adopted for their operation. Consequently these parts may easily break before the periodic inspection required by the normal wear of the flexible packings, and in that case, their remains fall inside the cylinder and are liable to cause serious damage. Actually, there exist braking and safety devices for preventing the nuts or the broken ends of the studs from falling into the cylinder, but these known devices, which in any case complicate the construction of the pistons, may themselves have been disturbed by the repeated impacts hereinbefore mentioned and be incapable of fulfilling their function at the required time.

One object of the invention is to delay sufficiently the effects of the flattening so that the failures can normally only occur after a much longer time than the maximum life of the packings.

Another object is to provide, as a complementary safeguard, such an arrangement of the clamping members that their remains, in the exceptional case of their breaking, cannot fall into the cylinder, this latter result being obtained by the particular arrangement of the usual parts, without the addition of any special part.

According to the invention there is provided for each packing a clamping device which is independent of the device for clamping the other packings; it is also possible to clamp by means of the same clamping device, several packings forming a packing group, instead of one packing, said device being likewise independent of the device 01' devices for clamping the other packings or groups of packings. In this manner, the

play due to the compression of the packings and which produces at the dead centres impacts on the clamping members, is no longer multiplied by the total number of the packings of the piston, but only by the number of packings clamped together by the same clamping device. In prac tice, it is generally sufiicient, for safety, to divide the packings into two or three groups, each of these being clamped in an assembling crown of the piston, independently of the assembly crown of the othergroups.

Furthermore, the invention provides for the parts of the clamping device for a group of packings, for example the nuts of the clamping studs; to be enclosed inside the piston after same has been mounted, and to be arranged preferably in the opposite direction to the" clamping parts," for example the nuts of the studs, of the adjacent group. In this manner, in the eventof a breaking of clamping members, the remains of the studs and their nuts stay imprisoned inside the piston; the absolute safety which this. provides is not to an additional device whichit may not be possible to rely on, but simply to the special arrangement of the studs and of their nuts. The

Referring to the drawing; Figure 1 shows an axial section of a piston with flexible cup packings arranged according to the present practice, and Figure 2, given merely by way of example, shows an axial section of a piston with flexible cup paclcings arranged according to the invention.

Figure 1 has been hereinbefore described.

Referring to Figure 2, B is a double-acting piston, A is the piston rod and C is the nut locking the piston on the rod. J, K, L, M are four cup packings, which are distributed here in two clamping groups; D is an upper crown screwed on the body of the piston, E an upper intermediate crown, F a lower intermediate crown, G an upper medial. crown-andI-I a lower medial crown. The packings J, K, which are separated by the medial crown G, are clamped by means of the nuts N sunk in the upper intermediate crown E and screwed on the studs 0 which are them selves screwed in the upper crown D, whereas the packings L, M which are separated by the medial crown H, are clamped by means of the nuts P sunk in the lower intermediate crown F and screwed on the studs Q which are themselves screwed in the body of the piston B. The packings J and K belonging to the upper clamping group have their flanges turned in opposite directions in order to produce fluid-tightness upwards and downwards, and the packings L and MI belonging to the lower clamping group are arranged similarly, but it would also be possible to turn the flanges of the two upper packings upwards and the flanges of the two lower packings downwards, this arrangement being however 'more bulky. It can be seen that in the case in which the studs 0 or Q break, their remains and also their nuts cannot come out of the piston within which they are imprisoned bythe sole fact of the arrangement adopted according to the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A device for clamping flexible packings on a piston, in which the whole of the packings is divided in groups, clamping means for each group of packings independent of the ones for the other group of packings, said clamping means including studs and nuts enclosed inside the piston.

2. A device for clamping a plurality of flexible packings on a piston, comprising clamping means for each packing, studs" and nuts forafastening the clamping means to-the piston, theclamping means for one packing being independent of those for the other packings, said studs and nuts being enclosed inside the piston and said clamping means.

3. A device for clamping a plurality of flexible packings on a piston, comprising clamping means for each packing, studs and nuts for fastening the clamping means to the piston, the clamping means for one packing being independent of those for the other packings, said studs and nuts being enclosed inside the piston and said clamping means, the studs for any one clamping means all extending in the same direction and having the nuts on the corresponding ends thereof and the studs for the clamping means of an adjacent packing extending in the opposite direction and having the nuts on the opposite ends thereof.

4. A device for clamping flexible packings on a piston in which the whole of the packings is divided in groups, clamping means for each group.

of packings independent of those for an adjacent group of packings, said clamping means including studs and nuts, the studs and nuts of one clamping means being enclosed inside the piston after same has been assembled, and the direction of each stud, originating in the end of this stud bearing the corresponding nut and running towards the other end of the same stud, being the same as the direction of the other studs of the same clamping means, and-this direction being opposite to the corresponding direction of the studs of the clamping means for the adjacent packing.

5. A piston of the'character described commie-- ing means interposed between the ring and its associated clamping means, and fastening means carried by the enlarged portion of the piston within the external diameter thereof, fastening means carried by the ring within the external diameter thereof, the fastening means of the enlarged portion and of the ring extending axially toward each other and through the associated clamping means.

6. A piston of the character described comprising a body having an enlarged portion of relatively large diameter at one end thereof, a

ring having an external diameter equal to that:

of said enlarged portion of the piston detachably mounted on the other end of the piston, packing clamping means associated with the en-- larged portion of the piston, packing clampingmeans associated with said ring, both said.

clamping means lying between said enlarged portion and said ring, packing means interposed between the enlarged portion and its associated clamping means, packing means interposed between the ring and its associated clamping means, fastening means carried by the enlarged portion of the piston within the external diameter thereof, fastening means carried by the ring within the external diameter thereof, the fastening means of the enlarged portion and of the ring extending axially toward each other and through the associated clamping means, and enlarged bodies on the inner ends of the fastening means, said clampin means having recesses in their adjacent surfaces for receiving the enlarged bodies on the inner ends of the fastening means.

7. A piston of the character described comprising a body having an enlarged portion of relatively large diameter at one end thereof, a ring having an external diameter equal to that of said enlarged portion of the piston detachably mounted on the other end of the piston, packing clamping means associated with the enlarged portion of the piston, packing clamping means associated with said ring, both said clamping means lying between said enlarged portion and said ring, packing means interposed between the enlarged portion and its associated clamping means, packing means interposed between the ring and its associated clamping means, studs carried by the enlarged portion of the piston within the external diameter thereof, studs carried by the ring within the external diameter thereof, the studs of the enlarged portion and of the ring extending axially toward each other and through the associated clamping means, and nuts on the inner ends of the studs for securing the clamping means in clamping position.

8. A piston of the character described comprising a body having an enlarged portion of relatively large diameter at one end thereof, a ring having an external diameter equal to that of said enlarged portion of the piston detachably mounted on the other end of the piston, packing clamping means associated with the enlarged portion of the piston, packin clamping means associated with said ring, both said clamping means lying between said enlarged portion and said ring, packing means interposed between the enlarged portion and its associated clamping means, packing means interposed between the ring and its associated clamping means, studs carried by the enlarged portion of the piston within the external diameter thereof, studs carried by the ring within the external diameter thereof, the studs of the enlarged portion and of the ring extending axially toward each other and through the associated clamping means, and nuts on the inner ends of the studs for securing the clamping means in clamping position, said clamping means having recesses in their adjacent surfaces for receiving the nuts.

HENRI BONNAUD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,602,536 McElroy Oct. 12, 1926 2,306,838 Volpin Dec. 29, 1942 FOREIGN PATENTS Number Country Date 7,903 England Apr. 4, 1913

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