Cushion dome

Oct. 1, 1957

W. F. MALSBARY

CUSHION DOME

2,808,070

Filed April 29, 1955

<img file="US2808070A_D0001.tif" />

<img file="US2808070A_D0002.tif" />

United States Patent Office

2,308,070

Patented Oct. 1, 1957

2,808,070 CUSHION DOME

Walter F. Malsbary, Oakland, Calif., assignor to Malsbary Manufacturing Company, Oakland, Calif., a corporation of California

Application April 29,1955, Serial No. 504,819

Claims. (Cl. 138—26)

The present invention relates to improvements in a cushion dome for a conduit, adapted for cushioning or damping pulsations in the conduit due to the starting and stopping of a flow of liquid through the conduit.

My invention was developed for use particularly in connection with the Malsbary cleaning machine as illustrated, for instance in Patent No. 2,295,228, in which a liquid is pumped through a pipe line by means of a reciprocating pump against a head, but it may be used to advantage in any installation in which it becomes necessary to provide cushioning means for absorbing or damping shocks due to the starting and stopping of a flow of liquid through a pipe line or due to pump pulsations.

Heretofore, the common expedient for cushioning the shocks has been the well-known air dome in which a body of compressed air is confined with respect to the water passing through the line, so as to be subject to the pressure thereof. But these air domes usually have to be of considerable size as compared with the remainder of the installation, and are subject to the further handicap that the passing water or other liquid tends to entrain the air, so that, as a rule, specific means have to be provided for continuously re-supplying the air to the dome to compensate for the continuous loss of air.

In the present invention it is proposed to provide a simple cushioning means which does not depend upon the presence of a compressed body of air, and which can be built into a compact structure of relatively small proportions.

More particularly, it is proposed to provide a relatively small housing forming a chamber communicating with the liquid conduit, the housing having an opening to the atmosphere, and to use a heavy rubber cushion covering the opening and cooperating therewith in allowing the cushion to play or vibrate with respect to the opening in response to the pulsations in the conduit.

While the general idea of providing a heavy rubber cushion playing against an opening is not new, it is proposed in the present invention to provide certain improvements in the cushion, which tend to utilize a larger proportion of the cushion in absorbing pulsations, to render the cushion more effective, to extend the life of the cushion and to overcome certain defects apt to develop in the cushion during extended use.

Further objects and advantages of my invention will be disclosed as this specification proceeds, and the new and useful features of my invention will be fully defined in the claims attached hereto.

The preferred form of my invention is illustrated in the accompanying drawing, forming part of this application, in which:

Figure 1 shows an axial section through my cushion dome; and

Figure 2, an end view of the same.

While I have shown only the preferred form of my invention, it should be understood that various changes or modifications may be made within the scope of the claims attached hereto, without departing from the spirit of the invention.

Referring to the drawing in detail, my cushion dome comprises in its principal parts, a cylindrical housing 1 closed at both ends by means of plates 2, which in. turn are provided with central openings 3, and two heavy bodies 5 4 of rubber disposed in opposite ends of the housing to serve as sealing elements for the openings.

The two heavy bodies leave a central space clear, as at 5, and this central space is connected to a conduit 6 by means of a short pipe 7.

The housing in its preferred form, is about five inches long, and has a diameter of approximately four inches. The openings in the opposite ends of the housing are approximately two inches in diameter, so as to leave rim sections 8 about one inch in width.

While these dimensions may be changed, of course, to suit various conditions, the proportions should be approximately maintained for best results.

In the drawing the cushion dome has been shown in duplex form, with two openings and two rubber bodies or sealing elements, but it would be feasible also to close one end of the housing completely, and to omit the corresponding sealing element, in which case the closed end could be moved much closer to the opposite sealing element.

It has been previously suggested to use a sealing element made in the form of a heavy flat disc lying against the end of the housing, the general idea being that the pump pressure would force a limited portion of the disc to bulge into and beyond the opening under pressure of the liquid, and would play in said opening in response to pump pulsations.

While this arrangement was generally satisfactory and performed the desired function, it was found, under actual working conditions, that certain difficulties developed. This was due to the fact that only a limited portion of the rubber partook of the vibratory movement, while the remainder was relatively inert, with the result that a certain fatigue developed in the material between the vibratory section and the inert material.

This again caused the vibrating section to gradually separate and tear loose from the inert material and to be blown through the opening by the pump pressure. There was also a certain tendency for the rim of the plain disc to separate from the wall of the housing and to break the 45 seal.

In the present invention it is proposed to provide a rubber body of such a shape that the vibratory movement due to pump pulsations extends substantially through the entire body to avoid the fatigue element while at the 50 same time the pump pressure tends to crowd the rim of the rubber body against the wall of the cylinder perfecting the seal.

It was also found, in actual practice, that the rubber flowing into and vibrating in the opening, had a tendency 55 to weaken along the rim of the opening, in spite of the fact that the edge of the rim was rounded, and in the present invention it is proposed to shape the body of rubber in such a manner that no portion thereof flows into the opening and the entire vibratory movement is 60 confined to a space within the housing opposite the opening.

In accordance with these observations, the rubber body 4 is made substantially concavo-convex in form, presenting a convex inner face 10 to the liquid and a concave 65 outer face 11 opposite the opening 3.

The body is cylindrical in form to fit against the inner face of the cylinder. The inner face 10 is made convex⁷throughout the entire area, while the. concave section 11 is substantially co-extensive with the size of the opening, 70 leaving a flat rim section 12 bearing on the inside face of the rim 8 of the housing.

The curves of the surfaces 10 and 11 may be approxi40

3,808,070 . .· 3' mately concentric, although the curve 10 is preferably drawn to a slightly larger radius, as shown.

The rubber body is made of substantial thickness, sufficient to prevent the same, .from being crowded .through the opening by pump pressure. In the form shown, it is . approximately one and one-quarter inches thick along the center line.

The body is composed of soft, yielding, rubber, so as to deform and vibrate in response to .pump pressure and pump vibrations. For pressures from 30-150 pounds, it may.have a durometer reading of approximately 45, and for pressures from 150-250 pounds, a durometer reading of 50.

In operation, the housing ! is secured upon the pressure: conduit 6 in the usual manner, by means of the pipe 7, so as to allow the liquid from the-conduit to enter the space 5 between the two rubber bodies.

. As the space or chamber 5 is filled with liquid under pump pressure, the pressure bears uniformly on each convex face 10 and converges, through practically the entire body of the rubber, upon the concave section, tending to straighten out the latter and to force the rubber material into the cavity.

As a result, the cavity will substantially disappear, and the rubber material will be crowded into an approximately straight:plane against the opening 3.

As the pump is made to operate, the pump pulsations will act on .the faces 10 of the rubber bodies,: producing similar pulsations throughout the bodies, and causing the faces .11 to vibrate toward and away from the openings for absorbing or damping the pump pulsations.

It will be noted that in the shock-absorbing action practically- all the rubber material takes part in the vibratory movement and that there is little material remaining inert. Since thus the stresses are distributed over a wider area, there will be less fatigue, and a better absorption of pulsations.

The pressure of the liquid tends to straighten out the curvature of the inner face 10 of each rubber body, and there is a definite tendency for the rubber to expand toward the side wall of the cylinder for improving the sealing action.

Since the rubber material at the concave section does not actually enter the opening 3, but merely flattens toward the opening, there is little danger of the rubber cutting against the rim of the opening, although it is advisable, of course, to round out the near edge, as shown at 12.