US2460129A - Apparatus for manufacture of fibrous articles - Google Patents

Description

Jan. 25, 1949. P. E. ls TA APPARATUS FOR MANUFACTURE OF FIBROUS ARTICLES 2 She'ets-Sheet 1 Filed Aug. 10, 1946 His Attorney} Jam.25,1949. P. E. ISTA APPARATUS FOR MANUFACTURE OF FIBROUS ARTICLES 2 Sheets-Sheet 2 Filed Aug. 10; 1946 tion or edge of the cone Patented Jan; 25, 1949 APPARATUS FOR MANUFACTURE OF FIBROUS' ARTICLES Paul E. Ista, Paris,

Electric Company,

France, assignor .to General a corporation of New York Application August 10, 1946, Serial No. 689,803 In France April 10, 1945 Section 1,

Public Law 690, August s, 1946 Patcnt'expires May 28, 1965 2 Claims.

' This invention relates to a method of making fibrous articles and means for carrying out such method. More particularly,the invention relates to the forming of unitary and integral fibrous articles, different portions of which have different physical characteristics, the variation in properties from one portion to another being sharp and distinct.

ity is, of course, well known to make fibrous articles by depositing fibers from a fibrous susform by maintaining the fibrous suspension. Furthermore, fibrous articles having various physical properties in different portions of the article have been manufactured by supplying fibers from fibrous suspensions contained in a chamber supplying different properties in the different portions of the ultimate fibrous article. According to this latter method the chambers have been separated by walls, the bottom edges of which are permanently spaced 2. short distance above the surface of the form in order to permit formation of a complete fibrous article as the fibers are de.-

posited.v As a result. appreciable mixing of thesuspensions. in the space between the bottom edges of the takes place throughout the forming operation. This procedure causes areas of appreciable width in the article in which the various types of fibers have been deposited from a mixture of the suspensions and, as a result, the delineation of properties from the one portion of the article: to an-- other tendszto begradual, lacking, the sharpness:

desirable for many-applications;

In certain applications,

producing articles it: is desirable to have certain portions: of. the, article. of. a dense and relatively rigid nature andiotherportions of a more flexible nature. For example,

especially in the manufacture of those types of; sound-producing articles which operate as microphones as: well: as loud speakers, it has been found that the fidelity of sound transmission is better when the cone is relatively rigid and the rim porfrom which the cone is suspended, is of maximum flexibility or suppleness. In order to obtain a fiber structure which will possess the above properties, it is essential that the gradation of" properties from those inherent in the material of the cone portion to those of the rim portion be as sharply defined as possible. It is thus necessary to reduce to a minimum the amount of; mixing of fibers permittedv between. the suspensions supplying the cone portion and rim portion of the form.

fibers capable of affordingwalls and the surface of the form for: example, in the: manufacture of" fibrous; diaphragmatic soundin the forming of the diaphragmatic sound-producing articles, and

It is, therefore, an object of this invention to provide a process for producing fibrous articles having different portions of difierent physical characteristics in which the gradation of properties from one portion of the article to another is sharp and distinct. This objective is acface of the form so as to limit mixing of the various fibrous suspensions. A zone of reduced pressure is maintained on the opposite side of the form from the fibrous suspensions causing the suspending liquid to be pulled through the form, leaving the fibers deposited and integrated on the form. In this manner, integration of the various portions of the fibrous articles may be obtained without the extensive mixing of the fibrous suspensions prior to the deposition of the fibers, which mixing has been characteristic of processes heretofore employed. The nature of the deposition of fibers at the boundaries of the various portions will hereinafter be described in detail.

A further object of the invention is a forming means by which the above method may be expeditiously carried out on aconmiercial basis. One device which'I have found to be efiective comprises a foraminous form, chambers associated with. different; portions, of the form which contain the fibrous suspensions supplied to the diif'erent portions of the mold, and a means ior separating the: edges of the walls of these chambers' from. the surface of the form to. the degree and at the times desired in carrying out the forming operation. This separation of the edges of the walls of the chambers can be accomplished by various means. For example, the chamber walls may be raised or lowered by mechanical or other means, maintaining the form in a fixed position in the meanwhile. 1

Another modification includes chambers which remain stationary during the forming process and a form which is resiliently mounted and which is moved away from the lower edges of the chambers as the forming operation proceeds. In this latter device various meansof moving the form away from the edges of the chamber walls may be employed. For example, the variations m form may be used advantageously to move the form as the fibers are deposited and integrated thereon.

The features ofthe nvention desired to be protected herein are pointed out in the appended the pressure differential over the foraminous 3 claims; The invention itself, together with its furtherl'obiects and advantages, may best be understood by reference to the following de-' scription taken in conjunction with the accompanying drawings, in which Fig. 1 is a view in partial section of one modification of m device for forming a fibrous article; Fig. 2 is an enlarged sectional view of the portion of a foraminous form at one of the points at which a wall separating two columns of fibrous suspensions is against the form; Fig. 3 shows the same portion of the form with the wall spaced from the form; Figs. 4 and 5 illustrate sectional views of the same portion of the form as the process proceeds; Figs. 6, 7 and 8 are sectional views of the lower portion of devices which are further modifications of the device shown in Fig. 1 in which means are provided for separately controlling the degree of reduced pressure in various portions of the zone under the foraminous form; Fig. 9 is a sectional view of the lower portion of a device which is still another modification of the invention; Fig. 10 is a further illustration of the device shown in Fig. 9 with the form in a difi'erent position.

Referring more in detail to the drawings, the device illustrated by Fig. 1 is of the type in which the foraminous form, here shown as a form for a diaphragmatic sound-producing device, is maintained in a stationary position during the operation of the device and the inner chamber wall is movable. In the figure the outer cylindrical wall or tank I is removably secured by means of a hinge 2 and latch mechanism 2 to the vacuum or reduced pressure tank or chamber 4. The foraminous form 5 covered by a perforated sheet of metal or screen 24 is held between the lower edge of the outer cylindrical wall and the upper edge of the vacuum tank and is gasketed by means of gasket rings 6 and l to prevent passage of liquid from the tank above the form to the vacuum tank below the form around the circumference of the form. A movable inner cylindrical wall 8 is located inside of and in concentric relationship with the outer cylindrical wall. This movable wall is maintained in position with respect to the outer wall by means of spacing elements 9. Thus the inner and outer cylindrical walls form a central cylindrical chamber and an annular chamber for holding and supplying dissimilar fibrous suspensions 2| and the outer annular chamber and the fibrous suspensions are admitted to the respective chambers through pipes l9 and 20. The columns of fibrous suspensions are supported on the surface of the water 22 which has previously been admitted to the chambers, as shown in Fig. 1. The suction valve I1 is opened while the lower edge of wall I is in contact with the form and water is drawn from the suction chamber and the chambers above the form until the lower level ofthe fibrous suspensions reach the surface of the form. As liquid continuesto be withdrawn from 22 to the form. Wall 8 may be moved in a vertical direction by various means. However, for purposes of illustration, ,a crank I0 operating cams H through shaft I2 is shown as the operating means. The shaft l2 rotates in bearings 13 slidably secured to the outer tank I and bearings H in inner tank walls 8. The cams H ride on the edges of outer tank I. Suction line i5 and water inlet line i6 controlled by valves l1 and I8, respectively, are connected to the vacuum tank 4. Fibrous suspension is admitted to inner tank 8 by means of pipe i9 and to the annular space between the inner and outer tanks by means of pipe 20;

Employing the above described device, the forming process is carried out in the following manner: The suction valve i1 is closed and the water inlet valve I8 is opened for a sufiicient time to admit water to the vacuum tank and the chambers or tanks above the form 5 to a level slightly above the form. The lower edge of the internal cylinder is then placed against the form by means of the crank and cam mechanism so as to isolate the inner chamber from the system the fibers suspended in the baths 2| and 22 are deposited and integrated on the surface of the form, the suspending medium passing on through the form and out through the suction outlet.

The effectiveness of the method of this invention as carried out by the device described in the foregoing will be more clearly understood by reference to Figs. 2, 3, 4 and 5 which show an enlarged sectional view of a portion of the form at a point where the movable cylinder wall separates the fibrous suspensions.

At the beginning of the forming operation a very thin layer of fibers 25 and 26 settles on both the central conical section of the form and on the rim portion. After a predetermined time the cylinder wall 8 is raised slightly and a small amount of the fibrous suspension from bath 2! moves under the edge of the wall toward the rim portion, as shown at 21 in Fig. 3, because of the fact that the fibers deposited from bath 2! are finer and tend more rapidly to build up resistance to flow of liquid than do the coarser fibers deposited from bath 22 on the rim portion. As soon as the rates of fiow through the two portions of the cone equalize, the fibers of bath 22 are again deposited on the entire width ofthe rim portion and the fibers of bath 2| are deposited on the cone portion as shown in Fig. 4. This process of alternate deposition of fibers from the two baths continues as the wall 8 is raised, with the result illustrated in section in Fig. 5, until the operation is complete.

When the fibrous article has been built up to the desired thickness, the upper portion of the device, including both of the cylinder walls and the lifting mechanism for the inner cylinder are removed from their position on the form and the vacuum tank by loosening the latch mechanism 3 and swinging the upper portion away from the form by means of hinge 2.

The devices illustrated in Figs. 6, 7 and 8 operate in a manner similar to that just described for Fig. 1 except that more accurate control of the vacuum produced in the zone of reduced pressure under various portions of the form may be obtained by means of valves 25, 28, 21 and 28. This is accomplished in the device shown in Fig. 6 by means of the valve 25 controlling the rate of flow of water from the reduced pressure zone under the conical section of the form, and in the device shown in Fig. 7 by means of the valves 28 controlling the rate of flow from the zone under the rim portion of the form. Fig. 8 illustrates a still further modification in which the suction on both portions of the form can be separately controlled by means of the-valve 21 controlling the flow from the central portion and the valves 28 controlling the flow from the rim portion.

Figures 9 and 10 illustrate a sectional view of a still further modification of the device of the invention. This device includes a foraminous form 29 covered by a perforated sheet of metal or screen 30 which is arranged to move vertically in the upper or cylindrical portion of the vacuum chamber or tank 3| and an outer cylindrical tank 32 which is situated above the form and removably secured by means of flange 33 at the bottom of the tank to the vacuum tank below the form. An inner cylinder 34 in fixed relationship to the outer cylinder 32 and spaced therefrom by spacer members 35 is also located above the form in concentric relationship to the cylinder 32. A suction line 36 and a water inlet line 3'! controlled, respectively, by valves 36 and 39 are con nected to the vacuum chamber 3 I. A gasket ring 40 situated in a recess around the circumference of the form abuts against the inner wall of the cylindrical portion of the vacuum tank in such a manner as to prevent the fibrous suspensions from escaping around the edges of the form during the operation'of the device.

Various means may the form in the vacuum chamber during operation. One means which has been found to work successfully utilizes the variation in pressure differentials between the fiber suspension chambers over the form and the vacuum tank to produce movement of the form. "A resilient mounting means is provided around the circumference of the vacuum tank which normally biases the form against the lower edges of the cylinders 32 and 34. A number of springs 4 I the tension of which may be varied by means of adjusting screws 42, are illustrated as the resilient mounting means in Figs. 9 and 0. However, instead of springs, other flexible devices such as rubber wedges, hydraulic cylinders, or flexible pneumatic-devices might also be employed. The force required to move the form against the resilient means may be determined from the operating characteristics desired.

The initial steps in the operation of the device shown in Figs. 9 and 10 including the charging of the fibrous suspensions into the cylinders above the form are identical to those set forth in connection with the device illustrated in Fig. 1. At the beginning of the operation the metal screen supported by the form is in contact with the lower edgesof cylinders 32 and 36 so that the fibrous suspensions in the two chambers are isolated from each other. As the vacuum is brought to bear on the fibrous suspensions and fibers are deposited on the form, the form is drawn downward and gradually moves away from the edges of the cylinder walls until the form attains its final position as shown in Fig. 10.

The movement of the mold, which is slow at be employed for moving prising a foraminous form,

constituent portions can ture of diaphragmatic sound-producing devices. However, it is to be understood that numerous other applications of the process and device are within the scope of this invention. For example, in the field of heat insulation, fibrous molded elements having different heat insulation characteristics depending upon the properties of their be realized. As a further example of the possibilities of this invention molded packing elements having different physical characteristics in difierentportions of the elements may be manufactured. Thus, it is possible to produce unitary elements, portions of which are soft and flexible for containing the items to be packaged or packed and other portions which are relatively strong and rigid to serve as a protective framework. Furthermore, it is possible to produce sheaths or envelopes having a portion easy to remove by tearing and another portion of relatively high strength and resistance to tearing. A still further application of this invention is in the manufacture of tropical helmets in which the crown portion of the helmet must be light and permeable and the rim portion'rigid and strong. I

What I claim as new and desire to secure by Letters Patent of the United States is? h 1. A device for making a fibrous article comchambers situated holding and supplying fibers of said form, said portions above said form for to different portions being defined by the lower edges of the walls of said chamber, means situated below said form for maintaining'a zone of reduced pressure at the lower side thereof and pressure sensitive means for separating said form and said edges,

, more fibers are deposited on the form, because of the increasing resistance which the fibers offer to the passage of the liquid through the form and the resulting increased pressure differential over the form. It may easily be seen that a suitable adjustment of the elasticity of the springs 4| makes it possible to control the velocity and the elongation of the displacement which is imparted to the mold.- The deposition and integration of the fibers and the periodic extension of fiber depositions from one chamber, under the edge of the wall of the inner cylinder, onto the portion of the form under the other chamber takes place in the same manner as that described in connection with the operation of the device illustrated in Fig. 1.=

The ,foregoing description of the method and device of this invention relates to the manufacsaid separating means comprising a pressureresponsive resilient spring mount for said form which is reactive to changes in pressure below said form.

2. In a device for making a fibrous soundproducing article, a foraminous form, chambers situated above said form for holding and supplying fibers to difierent portions of said form, said chambers being defined by the lower edges of cylindrical walls concentrically arranged, means situated below said form for maintaining a zone of reduced pressure at the lower side thereof, whereby fibers are attracted to and integrated on the upper surface of the form, said form being normally biased against the lower edges of said cylindrical walls by means of a resilient pressure-sensitive spring mounting for said form which is movable downward when said pressure is reduced.

PAUL E. ISTA.

REFERENCES CITED The following-references are of record in the

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