US3042977A - System for making pads from bark fibers - Google Patents

Description

July 10, 1962 N. v. POLETIKA ETAL 3,042,977

SYSTEM FOR MAKING PADS FROM BARK FIBERS 2 Sheets-Sheet 1 Filed March 19, 1959 INVENTORS Nicholas VPoIefika Rodri k E. Black 07 @453 KOKV N BY Attorneys WW /M N L NN July 10, 1962 N. v. POLETIKA ETAL 3,042,977

SYSTEM FOR MAKING PADS FROM BARK FIBERS 2 Sheets-Sheet 2 Filed March 19, 1959 JNVENTORS Nicholas Polefika Rodrick E. Black Attorneys Y B J 85 v9). l fv 1/ mm us me TMMVWH luli. I IA; mm MN n N9 mm RN" 1 U. o o k N on ited States Patent 3,842,977 STSTEM 50R MAKENG FAQS FROM BARK FIBERS Nrcho ias V. Poletiira and Rodrick E. Biack, Fort Bragg,

alrf., assigners to Union Lumber Company, San Francrsco, Caiifi, a corporation of Caiifornia Filed Mar. 1?, 1959, Ser. No. 800,551 15 Ciaims. (Si. 19-1445) This invention relates to the production of pads or mats or" fibrous material, and more particularly to a process and apparatus for such purpose involving the air felting of redwood bark fibers.

Pads consisting of a filler of yieldable fibrous material such as excelsior or straw, enclosed in a wrapping such as paper or similar material, are widely used in industry as a means to protect articles being shipped or stored, as insulation, etc. In the forming of such pads, it is generally believed that the thickness of the pad is a critical factor, and that a thick, loosely packed filler will provide more desirable characteristics than a thin or densely packed filler. Prior procedures and apparatus have consequently been primarily concerned with ways of providing thick layers of padding with which to surround the material to be protected or insulated. On the other hand, thin dense pads providing the same or improved characteristics would oifer many obvious advantages: they would require less of the fibrous filler, be less expensive to manufacture, and occupy less space. The provision of tmn dense pads having improved characteristics is therefore highly to be desired.

In general, an object of the present invention is to provide an improved method and apparatus for the felting of bark fibers whereby relatively thin felted pads of enhanced uniformity of thickness and fiber distribution and improved characteristics are produced.

Another object of the invention is to fabricate felted pads from redwood bark fibers that are highly resilient and which possess enhanced resistance to compression, making them suitable for cushioning, padding, insulation and the like.

A further object of the invention is to provide an improved method and apparatus for the forming of felts or pads of this character, involving the deposition of redwood bark fibers on a movable membrane or other similar conveyor.

Another object of the invention is to provide means for control of such method and apparatus whereby pads of highly uniform, improved characteristics can be continuously formed.

Other objects and advantages of the invention will be apparent from the following detailed description of an exemplary embodiment of the invention, and from the drawings in which:

FIGURE 1 is a view in side elevation of apparatus capable of carrying out the method of the invention;

FIGURE 2 is a view in top plan thereof; and

FIGURE 3 is a detail view in section and in elevation of portions of the apparatus employed in the shredding and felting of the bark fibers. V

In general, the method and apparatus of the present invention makes possible an improved felting of bark fibers, specifically in the production of felted pads of enhanced uniformity of thickness, density and fiber distribution. The procedures of the invention can be carried out in conjunction with customary lumber mill operations in which a supply of bark fibers, particularly redwood bark fibers, is continuously produced. The disclosed apparatus performs the functions of compressing a loose feed of bark fibers and of supplying the compressed fibers at a predetermined, substantially constant rate to a shredder.

The shredder subjects the compressed fibers to a very rapid tearing and separating action and expels shredded,

3,42,977 Patented July 10, 1962 individualized fibers at a uniform rate into a moving stream of air. The airborne fibers are then carried to a settling chamber, with the cross section of the air stream being gradually increased to reduce the velocity of the fibers so that they are uniformly distributed in free flight within the chamber. The falling fibers collect as a loosely felted fibrous mass on a moving membrane which forms alower wall of the chamber. As this fibrous mass is removed from the chamber, the fibers are gradually compressed and set into a continuous shape-retaining felted pad. The pad which is now of desired thickness and density, may be covered with paper or other suitable protective wrapping, or coated with a suitable binding agent, andcut into individual pads of a desired size.

The preferred embodiment of the apparatus illustrated in the drawings comprises a number of separate operating stations including a fiber depositing station 16, a feed conveying station 12, a shredding station at 14 including a feed compression zone at '16, a fiber distributing station at 18, an air felting station at 20, a discharge compression zone at 22, and pad wrapping and cutting stations at 24 and 26. As will be apparent from the following description, the operations of these various stations tend to supplement one another and to cooperate in providing the desired characteristics to the final pad product.

' The Fiber Depositing Station drawn through the outlet 32 and the heavier bark fibers discharged through the outlet 34 to the feed conveyor. Apparatus for this purpose may be of well known design and need not be further described.

Feed Conveyor Station The feed conveyor station functions as a constant feeding mechanism adapted to supply bark fibers at a constant rate per unit of time to the shredder. The mechanism includes a continuous belt conveyor 36 which is associated along its upper reach with a platform 38 of a scale 49. The conveyor is driven by meansof a variable speed motor 42 through a suitable speed control 44- responsive to the instantaneous weight of the feed deposited on the belt and passing over the scale platform 38. Any suitable control mechanism, of known design, can be employed for this purpose such as the potentiometer control 46 responsive to movement of the indicator 48 of the scale. It will be understood that the speed of the conveyor 36 is controlled by the instantaneous weight of material passing over the scale platform as registered by the indicator 48.

At the discharge end of the feed conveyor, the fibers are fed at a substantially constant rate into the shredder feed chute 50. This chute delivers the fibers at constant rate to the shredder feed conveyor 52 which is independently driven by the variable speed motor 54. As will later appear, the speed of this conveyor functions to control the density of the final pads being produced by the apparatus.

Shredding Station At the shredding station the fibers are first matted and then subjected to a very rapid tearing and separating j FIGURE 3).

Referring particularly to FIGURE 3, the shredder includes an initial compression zone 16 created by shredder feed rolls 69, 62 and 64. These rolls are preferably powered by a suitable gear train (not shown), adapted to rotate the periphery of the rolls ata gradually increasing rate above the shredder conveyor belt 52., Preferably, these rolls should rotate to provide a peripheral speed of from 4 to 8 times that of the belt 52, with the roll 62 rotating at a rate intermediate that of the rolls 6% and 64.

-As illustrated, the feed rolls are spaced at decreasing distances above the belt 52 in the directionof conveyance and each is provided with a plurality of rows of teeth 66. The rolls 6th and 62 are provided with rows of relatively long teeth arrangedin parallel fashion across the roll and function to initially mat down the loose fibers on the shredder feed belt to insure their delivery to the shredder feed rolled. The feed roll 64 is positioned adjacent the dischargeend of the conveyor 52 and is spaced closely adjacent the belt, the body of the roll being preferably about /2 inch above the belt. The feed roll 64 is provided with" several rows of short needle-like teeth adapted to grasp the fibers and to force or sweep them into the shredder roll.

The shredder roll 68 is of substantial diameter and is provided with a plurality of closely spaced, relatively short needle-like teeth '79 (not proportionately shown in This roll is rotated at very high speed relative to the feed rolls, and functions to pull the fibers from the belt 52 and to expel them outwardly into an air stream createdin the inlet duct 72 of the fiberdistribution system 13. For best results, it has been found that the shredding roll 68 should rotate to provide :a peripheral speed of the order 'of about 8000 feet per minute.

Fiber Distributing Station The. fiber distributing system serves to assist in the removal of individualized barlc fibers from the shredder and to positively distribute the fibers evenly across a fiber.

settling zone at the air felting station. 7

The illustrated apparatus comprises an air induction system. including the blower 74, air inlet passage '76, and thexfiberiinlet duct 72. The blower should be capable of developing anair stream in the passage 76 of the order of from 4000 to 6000' feet per'minute. The

I stream of air moving through the passage 76 creates substantial induction forces which assist in the movement of fibers upwardly through the inlet duct 72. The passage 76 is constructed to provide a gradually increasing cross section so that the'speed of the fibers being sucked into the'air stream is' gradually reduced as the fibers are discharged into thefelting chamber. A pl-u-" rality of adjustable vanes 78 are positioned in the inlet passage, preferably just ahead of the point of fiber discharge into the moving air stream. The vanes 78 can be used to control the velocity of the entering air, and

consequently the velocity at which the' individualized fibers are delivered into the settling chamber of the felting station. 1

4 the air stream being discharged into the felter settling chamber. For best results, the average velocity of all air entering the chamber should be within the range from about 900 to about 1269 feet per minute, and the velocity of air leaving the chambershould be of the order of 200 to 300 feet per minute.

Air F lting Station v The air felting station 26 comprises essentially an expansion chamber 82in which a movable membrane is positioned to receive the individual fiber falling in free flight from the discharge outlet 77 of the air induction system. The membrane 82 functions as a discharge conveyor and preferably is of such construction that the fibers can collect on its surface without restricting free passage of exhaust air through the membrane. By way of illustration, the membrane can be an endless flexible screen or wire cloth. The membrane functions to collect the freely'falling fibers as a loosely felted mass of substantially uniform density and fiber distribution, and to convey the same through the discharge compression zone 22- to the further processing stations of the apparatus. The speed of the membrane can be independently controlled by the variable speed motor 99 which, as described later, can be used in conjunction with the motor 54 to control the final density of the fibers.

' Felting in the chamber 8d may be assisted by the provision of suction means below the movable membrane, for example as at fitl'in FIGURE 3. The suction means serves to accelerate the settling of the fibers onto the conveyor and to provide an initial interfelting of the fibers prior to compression in the zone 22,

In the compression zone, the loosely felted fibers are gradually compressed to set the fibers in the form of a continuous shape-retaining pad or felt of desired thickness and of uniform density. In the illustrated apparatus, initial compression is achieved by an overhead conveyor belt 86 .soarranged that its lower reach 88 acts to gradually compress the felted fibers against the discharge conveyor. Final compression is achieved by means of the rolls 102 'as the felted pad is discharged from the station.

Essentially, the felting station functions to provide an expansion zone 80 of reduced pressure, in relation to the pressure in the air inlet passage 76 wherein the individualized' bark fibers are allowed to gradually settle onto the moving membrane or conveyor 82. It also provides a zone wherein the individual fibers are evenly distributed across the conveyor, continuously, to provide a felted mass of remarkable uniformity of fiber distribution and thickness. Finally, the. felting station provides means for compressing the uniformly distributed fibers to set As suggested in FIGURE 2, the vanes 78 can be The variables of air and fiber supply are in turn controlled to insure an even distribution of the fibers in the same to a continuous felted pad whichwill retain the desired uniform fiber distribution and density, whereby these characteristics can be carried into the finished product.

The Wrapping and Cutting Stations In the illustrated apparatus, kraft paper or other material suitable as an exterior wrapping is fed into position between the final conveyor 96 and the felted pad and is subsequently folded as at 98 to provide a protective wrapping completely surrounding the pad. The pad is next cut into desired lengths byconventional apparatus at the station 26 to produce a completed product. Additionalprocessing can be carried out as desired, for example, the pads can be provided with end wrappings,

V be treated with. water repellents, 'etc.

Product 7 Control by the process. Thus, the feed conveyor 36 can be regulated to insure a constant input of fibers in pounds per minute from the sawmill operations by means of aproper setting or" the scale 40 and motor feed control 44, 4 6. For example, in a typical operation, control might be established to deposit fibers on the conveyor 52 at a rate between about 0.5 to 0.75 pound per minute per square foot of belt area. The variable speed motor 54, which controls the rate at which fibers are fed to the shredder, can similarly be employed to control the quantity of fibers being fed to the fiber distributing station 18. In general, it is desirable that the conveyor 52 be operated at a speed consistent with the final desired density of the pad, also the initial rate of feed determined by the feed conveyor 36 and scale controller 4%, 44, 46. Accordingly, in some instances, it may be desirable to regulate the speed of the shredder feed belt 52 in direct response to the weight control provided by the conveyor 36, as suggested by the dotted line 1% in FIGURE 1.

The final thickness and density of the pads is determined by the variable speed motor 99, which regulates the speed of the discharge conveyor 82. As will be etadent from FIGURE 3, a faster speed of this conveyor will produce a pad which is somewhat less dense whereas a slower speed will produce a pad of greater density. Again it may sometimes be desirable to control movement of the discharge conveyor in response to variations in the rate of feed, as suggested by the dotted line 104.

Operation Reviewing briefly the operation of the system, clean, dry bark fibers are fed through the inlet 30 to the cyclone 28 and discharged through the outlet 34 onto the feed conveyor 36. As the conveyor 36 moves over the platform 38 of the scale at the speed control unit 44, 46 regulates the speed of the conveyor to insure a constant rate of feed of bark fibers to the shredder feed conveyor 52. As the fibers are conveyed into the shredder by the conveyor 52, they are progressively matted down and forced ahead at an increasing rate by the feed rolls 60, 62 and 64. The latter roll is spaced closely adjacent the conveyor and insures a positive forced feed of the matted fibers against the rapidly rotating shredder roll 68. The short needle-like teeth of this roll separate the individual fibers from the matted feed and hurl them into the air induction inlet 72 of the fiber distributing station 18. The latter distributes the substantially individualized fibers into a moving air stream of gradually increasing cross section leading into the air felting zone. The velocity of the air stream is controlled by the adjustable vanes 78 in the passage 76 so that as the fibers are discharged into the expansion chamber 89 of the air felting station, they rapidly lose speed to fall in free flight onto the discharge conveyor 32. The essential function of the fiber distributing system is to insure that the fibers are very evenly distributed across the felting chamber so that they form a loosely felted mass of substantially uniform density and thickness on the conveyor 82. Uniformity of felting is also insured by the construction of the felting chamber and by the downward inclination of the overhead conveyor 88. As the loosely felted mass is conveyed out of the felter station, the fibers are gradually compressed by the conveyor 88 and by the rolls 162 to provide a final shape-retaining pad of desired uniform density and predetermined thickness. The pad is subsequently overwrapped with paper or treated with a binder and cut to desired lengths at stations 24-. 26.

The uniform fiber distribution of the pads of the invention renders them highly efiective for a Wide variety of purposes but particularly in the packaging of foods subject to bruising during normal handling or transit. An example of the latter is the so-called tight fill packing of fruit, wherein a pad is held tightly in compression between the lid and theunwrapped contents of a box. The pads of the invention, containing redwood bark fibers,

have proved unusually successful in preventing bruising or other damage to the fruits, and seem to provide these results over a wide range of pad thicknesses and weights. Byway of illustration, pads containing redwood fibers on the order of 0.06 pound per square foot, wrapped in the kraft paper envelope, have proved .to be at least as effective in repeated drop and vibration tests as similar pads containing excelsior in much greater amounts (0.225 pound per square foot). This is true despite a substantial reduction in thickness of the pads to about 0.15 to 0.40 inch (as compared to about 0.6 5 inch for the excelsior). The redwood pads also demonstrated considerably greater strength and durability during testing than did the excelsior pads. These results (which indicate a substantial improvement in shock absorbing characteristics) are believed attributable almost entirely to the improved distribution of the fibers in the pads during the felting. 0n the other hand, the reduced thickness of the pads permits the packing of as much as 5 to 10% additional fruit in. each packing box without any loss in protection to the fruit.

The following table is illustrative of the results obtainable with the pads of the invention, and particularly the uniform characteristics of the pads over a wide range of Weights or thicknesses. Pads of the weight indicated in the table were each used in a group of 4 to 6 boxes, and the vanious groups employed in a series of comparative tests. One group of boxes packed with common excelsior.

pads was also included as a reference. At the end of the tests, each group or type of pad was scored on an arbitrary scale ranging from 1 for the best to 5 for the Worst.

boxes were filled with randomly arranged, naked Bartlett pears. Pads as described in the table, wrapped in kraft paper, were placed on top of the fruit, and covers seated on top of the pads with a force of 1 to 3 pounds per square inch. Each box was filled with from 36 to 38 pounds of the pears, depending on the pad thickness. Each box was then dropped from a height of 12 inches on one top corner and on the six faces and then vibrated for 1% hours at 500 cycles per minute, with a stroke of inch. This treatment was chosen from experience as one that would produce sufiicient looseness and surface injury in the fruit to give a measure of the relative effectiveness of the different pads. The boxes were stored for a week at 31 F. to develop maximum appearance of fruit injury and then opened and scored by each of five observers.

Flavor tests using pears, plums and peaches have also indicated that the redwood bark pads will not stain fruit or impart flavors or odors to the packed fruit.

These and other characteristics of the pads produced by the procedures and apparatus of the invention have been established in a series of tests conducted as a service project by the University of California Forest Products Laboratory, at Davis, California (Report entitled Evaluation of Redwood Bark Fruit Pads, dated October 29, 1958), aswell as in other tests and reports.

While the invention has been particularly illustrated and described in connection with a preferred embodiment thereof, it is capable of other variations and modifications within the scope of the claims appended hereto. For example, the system has been particularly described in con nection with the production of relatively thin" dense pads Specifically, pads ranging up to 2.0 inches in thickness and containing up to 0.25 pound of fibers per'square foot can be produced. Accordingly, it should be understood that the disclosures herein are intended primarily to be illustrative and not in any sense limiting.

We claim:

1. In apparatus for the felting of bark fibers in the continuous formation of felted pads: feed conveyor means including a depositing region for fibers being fed into the apparatus, a device responsive to the weight of the fibers being fed and adapted'to maintain a relatively constant rate of feed of fibers by said conveyor means, feed compression means comprising a plurality of rolls spaced at decreasing distances above said conveyor means in the direction of conveyance, shredding'means adjacent said feed'compression means and adapted to rapidly separate individual fibers from said compressed feed,said shredding means including a roll having projecting portions and adapted to rotate at a peripheral speed substantially in excess of the speed of said conveyor means, duct means leading from said shredding means to an expansion chamber, said duct means including an inlet air passage of gradually increasing cross section whereby individual fibers are conveyed to fall in free flight in said expansion chamber, discharge conveyor means in said expansion chamber and in the path of said freely falling fibers, and compression means positioned within said expansion chmber and adapted to compress the loosely felted mass of fibers collecting on said discharge conveyor into a continuous felted pad.

2. Apparatus as in claim 1 wherein said rolls comprising the feed compression means are mounted for rotation to provide gradually increasing peripheral speeds in the direction ofconveyance. r

3. Apparatus as in claim 1 wherein said duct means is provided with a plurality of adjustable vanes providing rate to' a compression zone, progressively compressing and accelerating the feed in such zone to achieve a matting of the fibers, positively feeding the compressed matted fibers into a shredding zone, subjecting the copressed matted fibers in said shredding zone'to a very rapid tearing action to separate and expel individual fiers from the zone, applying fluid pressure to individualized fibers at a point remote from said shredding zone .to thereby induce an air current to convey the fibers away from the shredding zone, uniformly distributing the fibers into an air stream expanding into a settling zone of reduced pressure, permitting said shredded fibers to fall in free flight .in said settling zone onto a moving membrane, whereby said shredded fibers are evenly distributed on said membrane, and conveying the fibers at a predetermined rate away from said settling zone while simultaneously compressing the same to form a felted pad of predetermined uniform density and thickness.

direction of conveyance*ofthefibers through the process.

7. A method as in claim 4- including the step of applying suction in said settling zone to the under side of said moving membrane, to assist in producing said fiuid pressure.

8. In a continuous method of felting redwood bark fibers to produce relatively thin dense felted pads characterized by enhanced shock absorbing properties, resiliency and resistance to compression, the steps of feeding a substantially constant Weight of loose fibers per unit of time into a compression zone, progressively compressing and accelerating'the fibers in said compression zone to achieve a predetermined desired thickness, positively feeding the compressed fibers endwise into a shredding zone, subjecting said compressed fibers to a very rapid tearing and separating action in said shredding zone whereby shredded individualized fibers are expelled from said zone, inducing conveyance of said shredded individualized fibers away from said shredding zone by means of positive uni-directional fiuid pressure coupled with forces in suction, said induced conveyance resulting in uniform distribution of said fibers in free flight in a settling zone of reduced pressure, collecting said uniformly distributed fibers on a moving gas permeable membrane, conveying the resulting uniformly felted fibers away from saidsettling zone while simultaneously compressing the same to form a continuous pad of predetermined uniform density, and wrapping said continuous pad with a layer of fibrous protective material and cutting the same into shorter segnents to successively form a plurality of wrapped pads.

9. In apparatus for the felting of bark fibers in the continuous formation of felted pads; feed conveyor means comprising a depositing region for bark fibers,

means regulating the speed of said conveyor means where by a relatively constant density of fibers being fed is maintained, feed compression means including a plurality of rolls spaced at decreasing distances above said conveyor means adapted to compact said fibers on said conveyor means, shredding means adjacent said feed compression means and adapted to rapidly separate individual fibers from said compacted feed, said shredding means including a roll having projecting portions and adapted to rotate at a peripheral speed in excess of the speed of said conveyor means, duct means leading said separated individual fibers to an expansion chamber, said duct means including an air inlet passage of gradually increasing cross section, blower meansassociated with said inlet passage wherebyfibers can be conveyed into said expansion chamber to fall in free flight within said'chamber, and discharge conveyor means within said expansion chamber adapted to collect the freely falling fibers as a loosely felted mass of substantially uniform density and fiber distribution.

j 10. Apparatus as in claim 9 wherein suction means are provided within the expansion chamber and beneath said discharge conveyor means.

11. Apparatus as in claim 10 wherein discharge com pression means are positioned within said expansion chamber, said compression means cooperating with the discharge conveyor means to set the loosely felted fibers into a continuous pad prior to their discharge from the expansion chamber. V v j 12. Apparatus as in claim 11 wherein said discharge compression means includes an overhead conveyor converging against said discharge conveyor, in the direction of conveyance.

13. In apparatus for the felting of redwood bark fibers in the continuous formation of felted pads: feed conveyor means comprising a deposi ing means for fibers being fed intothe apparatus, feed compression means overlying a discharge end of said conveyor means and adapted to progressively compress andxaccelerate said fibers in. the direction of movement of said conveyor means, shredding means immediately adjacent and above said feed compression means and the discharge end of said conveyor means, said shredding means being adapted to rapidly separate individual fibers from the compressed feed being fed endwise against the same, such shredding means including roll means having an irregular surface and adapted to rotate at a peripheral speed substantially in excess of the speed of said conveyor means, duct means leading from said shredding means to an expansion chamber including an inlet passage for air whereby individual fibers are conveyed to fall in free flight in said chamber, discharge conveyor means adapted to collect said freely falling fibers as a loosely felted mass of substantial uniform density and fiber distribution, and compression means associated with said discharge conveyor means to uniformly compress said loosely felted fibers.

14. Apparatus as in claim 13 wherein said feed conveyor means includes a first conveyor associated with a control device adapted to maintain a relatively constant rate of feed per unit of conveyor area, and a second conveyor associated with said feed compression means adapted to discharge compressed feed to said shredding means.

15. A device as in claim 14 wherein said control device includes a scale associated with said first conveyor, and variable speed drive means for the conveyor responsive to the scale.

References Cited in the file of this patent UNITED STATES PATENTS Miller Dec. 18, 1883 Warren et al. Jan. 21, 1906 Maussner et a1 Sept. 18, 1923 Whitaker Feb. 4, 1930 Hausrnan Oct. 7, 1930 Brown et a1 Oct. 24, 1933 Watts Mar. 26, 1940 Drill Apr. 27, 1943 Rainford et al Dec. 28, 1943 Harris et a1 Dec'. 23, 1952 Schubert et al Apr. 21, 1953 Duvall July 21, 1953 Lannan Feb. 15, 1955 Downey Ian. 10, 1956 Mottet June 2, 1959 FOREIGN PATENTS Great Britain Ian. 8, 1935 Great Britain Dec. 15, 1947 Germany May 2, 1941

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