MXPA01009156A - Method and apparatus for forming an apertured pad - Google Patents

Abstract

An apparatus and method for manufacturing a pad (24) wherein a rotatable forming screen (22) which has a generally cylindrical surface and at least one outwardly projecting nob (50) is employed. The nob (50) is positioned on the forming screen (22) whereby the nob (50) is circumscribed by the material, e.g., cellulosic fluff, deposited on the forming screen to form the pad (24). The pad (24) is transferred from the forming screen (22) to a moveable transfer surface (34). The transfer surface (34) may be either flat or round and moves at a velocity which is at least as great as the velocity of the forming screen. The nob (50) located on the forming screen includes a thrust surface disposed on a trailing edge (66) of the nob (50). The thrust surface imparts a compressive force on the pad during the release of the pad (24) from the forming screen (22). The compressive force is at least partially directed towards the transfer surface (34) and thereby assists in the release and transfer of the pad (24).

Description

METHOD AND APPARATUS FOR FORMING A PAD WITH OPENINGS Background of the Invention The present invention relates to the apparatus and methods used to form pads with openings. More specifically, the present invention relates to the apparatuses and methods used to form the absorbent pads with openings which can be used in such products as disposable diapers, training pants, incontinence garments, catamenial products and others. absorbent articles.

Conventional absorbent pads often consist primarily of a cellulose fluff or other fibrous material. Such absorbent pads can be used in the manufacture of products subject to emergence loads. The expected emergence charges may exceed the rapid absorption capacity of conventional absorbent pads. The openings placed in the pads, however, can increase the fast absorption capacity of the pad. Such openings may consist of voids that are empty or that are to be filled with a material having different properties than the rest of the pad. Such openings can be used for purposes other than the increase i of the rapid absorption capacity of the pad. For example, when the pad with openings is used in a disposable diaper, the openings can provide an additional hollow space for storing and receiving solid waste or to provide a space for expansion of the superabsorbent materials.

Conventional manufacture of the apertured pads involves air placement of a wipe pad on a forming drum. The pad is subsequently provided with openings in a separate cutting, calendering or the like process. U.S. Patent No. 5,242,435 describes, among others, the calendering and pergraving of a cellulose pulp fluff sheet. U.S. Patent No. 5,785.97 discloses a different method for forming a pad with openings which involves, among others, the use of raised portions on a forming surface used to form an absorbent composite fabric.

Synthesis of the Invention The present inventors have recognized the difficulties and problems inherent in the prior art and in response to this have developed an improved apparatus and method for forming a pad with openings.

In one aspect, the present invention provides an apparatus for manufacturing a pad wherein the apparatus comprises, for example, includes but is not limited to a rotating forming grid which has a generally cylindrical surface and at least one head projecting toward outside. The head is located on the grid in a position where the head is circumscribed by the forming grid. The forming grid can rotate at a rate which defines a first tangential speed of the grid. A source of material is placed on one side of the forming grid so that a layer of material can be placed by air on the forming grid and the head can be circumscribed by the layer of material. The layer of deposited material has a first surface in contact with the forming grid and a second opposing surface. A movable transfer surface is engageable with the second surface of the material layer. The transfer surface can move in a direction which essentially corresponds to the movement of the layer of material and to a second velocity which is at least as great as the first tangential velocity of the forming grid. The apparatus also includes means for attracting the layer of material to the transfer surface which may, in some embodiments, be a source of vacuum placed in a communication operative with the transfer surface. The head located on the forming grid includes a pushing surface positioned on a tail edge of the head. The pushing surface imparts a compressive force on the material layer at the point where the material layer is engageable with the transfer surface and as the forming grid and the transfer surface move at their respective first and second speeds. The compressive force exerted by the thrust surface of the head includes a component vector which is directed towards the transfer surface.

In some embodiments of the apparatus, the speed of the transfer surface may be 101, 102, 103 or a greater percentage of the tangential speed of the forming grid in the. place of transfer.

In other embodiments of the apparatus, the transfer surface may be either a flat surface or an essentially cylindrical surface. In those embodiments where the transfer surface is an essentially cylindrical surface, the forming grid may have a radius which is smaller, approximately equivalent or greater than the radius which defines the transfer surface. When the forming grid has a larger radius, the radius of the forming grid may be more than twice or three times the magnitude of the radius of the transfer surface.

The head placed on the forming grid can have many different shapes. The head may have side walls which are tilted inwardly by about 5o to form an angle of approximately 85 ° with the forming grid. Such heads may have a shape which defines a trunk. The apparatus may also include a plurality of heads located on the forming grid. The heads may also be resusable to the grid such as, for example, by the use of threaded fasteners to secure the heads to the forming grid. The use of resalable heads allows the heads on the forming grid to be interchanged in a relatively convenient manner.

The present invention also provides a method for forming a pad with openings. One such method includes providing a forming grid with at least one head projecting outward and rotating the forming grid so that the grid has a first tangential velocity. A pad is formed on the forming grid so the pad completely surrounds the head. The pad has a first surface in contact with the forming grid and a second opposing surface. A movable transfer surface is provided on one side of the second surface of the pad and moves in a direction which essentially corresponds to the movement of the pad and at a speed which is at least as great as the tangential speed of the pad. forming grid. The transfer surface is brought into contact with the second surface of the pad and the pad is transferred to the transfer surface. During the transfer of the pad, a tail edge of the head exerts a compressive force on the pad where the compressive force includes a component vector which is directed towards the transfer surface.

In some embodiments of the method, the speed of the transfer surface may be 101, 102, 103 or a greater percentage of the tangential velocity of the forming grid at the transfer location.

In other embodiments of the method, the transfer surface can be either a flat surface or an essentially cylindrical surface. In those embodiments where the transfer surface is an essentially cylindrical surface, the forming grid may have a radius which is smaller, essentially equivalent to or greater than the radius of the transfer surface. When the forming grid has a larger radius, the radius of the forming grid may be greater than 2 or 3 times the magnitude of the transfer surface radius.

A variety of heads shaped differently can be used with the methods of the present invention. The heads may have side walls which are tilted inwardly by about 5o to form an angle of approximately 85 ° with the forming grid. Such heads can also have a shape which defines a trunk.

A plurality of heads can be used on the forming grid. The heads may also be resuable to the grid such as, for example, by the use of threaded fasteners to secure the heads to the forming grid. The use of the resalable heads allows one or more of the heads present on the forming grid to be exchanged by a different head in a relatively convenient manner.

The apparatus and method of the present invention provides numerous advantages. The configuration and relative movement of the forming grid and the transfer surface of the apparatus and the method allow the tail edge of the head to exert a compressive force on the fluff pad which includes a component vector directed towards the head. transfer surface. That part of the compressive force which is directed towards the transfer surface aids in the transfer of the pad to the transfer surface.

In addition, by having the tail edge of the head exerting a compressive force on the pad, the tail edge of the head will not exert a compressive force on the pad. If the leading edge of the head were to exert a compressive force on the pad, there would be a significant possibility that the head would damage or remove the pad material adjacent to the leading edge of the head. In contrast, the apparatus and methods of the present invention create an opening with a relatively clean defined perimeter.

The apparatus and methods of the present invention also provide an efficient manufacture of pads with openings. A calendering or cutting operation after forming is not required to form the openings in the pads of the present invention. In addition, the elimination of the calendering or cutting operation after the formation also eliminates the fragment and the additional handling associated with such a process of creation of openings after formation.

Another advantage of the present invention is that it can be implemented using resonable heads. When the resusable heads are used, they can be easily exchanged for heads configured differently. This ability allows the size of the opening and the geometry of the same to be easily adjusted to optimize the operation of the pad.

Brief Description of the Drawings The invention will be more fully understood and the additional advantages will be apparent when reference is made to the following detailed description of the invention and the accompanying drawings, in which: Figure 1 is a partial side view of an apparatus according to the present invention; Figure 2 is a partial side view of the apparatus of Figure 1 with the side wall of the operator removed from the transfer roller; Figure 3 is a top view of a pad with openings, - ' Figure 4 is a side view of a forming drum and a transfer roller where a head on the transfer roller is located on the normal line which intersects the centers of both the forming drum and the transfer roller; Figure 5 is a side view of the apparatus of Figure 4 where the forming drum has rotated 0.75 °; The figure is a side view of the apparatus of figure 4 wherein the forming drum has rotated 1.50 °; Figure 7 is a side view of the apparatus of Figure 4 where the forming drum has rotated 2.25 °; Figure 8 is a side view of the apparatus of Figure 4 where the forming drum has rotated 3.00 °; Figure 9 is a side view of the apparatus of Figure 4 where the forming drum has rotated 4.50 ° i Figure 10 is a side view of the apparatus of Figure 4 where the forming drum has rotated 5.25 °; Figure 11 is a side view of the apparatus of Figure 4 where the forming drum has rotated 6.00 °; Figure 12 is a side view of the apparatus of Figure 4 where the forming drum has rotated 1.5 ° and which illustrates the compressive forces exerted by the head; Figure 13 is a side view of the apparatus of Figure 4 where the forming drum has rotated 3.0 ° and which illustrates the compressive forces exerted by the head; Figure 14 is a side view of the apparatus of Figure 4 where the forming drum has rotated 4.5 ° and which illustrates the compressive forces exerted by the head; Fig. 15 is a side view of a forming drum and a flat conveyor in which a head on the forming drum has rotated 4 ° beyond a normal line located at the point where the forming drum is closest to the conveyor; Figure 1 is a side view of the apparatus of Figure 15 wherein the forming head has rotated to a point ° beyond the normal line; Figure 17 is a side view of the apparatus of Figure 15 wherein the forming head has rotated to a point 8 ° beyond the normal line; Figure 18 is a side view of a head; Figure 19 is a top view of a forming grid and a plurality of heads.

The corresponding reference characters indicate corresponding parts through the various views. The embodiments described are set forth to illustrate and exemplify the invention. The embodiments described are not intended to be an exhaustive illustration of the invention or to be considered as limiting the scope of the invention to the precise forms described.

Detailed description of the invention An apparatus for forming a pad with openings is illustrated in Fig. 1. A part of the cylindrical forming drum 20 is shown in Fig. 1. A forming grid 22 defines the cylindrical surface of the forming drum.

. The forming grid 22 has openings there which allow passage of the process air but which are small enough to prevent passage of the material used to form the pad 24. The forming grid 22 also includes the heads 50 which form both the openings 52 inside the pad 24 as helping to release the pad 24 from the forming drum 20. The heads will be discussed in more detail below.

The pad 24 is formed by depositing the material on the forming grid within the forming chamber 2 in an air laying process. A variety of forming chambers are known in the art and provide a source of material adjacent the forming grid 22. A vacuum source operatively associated with the forming drum 20 removes air from the forming chamber 2 through the forming grid 22 and therefore deposit the material on the forming grid 22.

A wide variety of materials can be used with the present invention to form the pad with openings 24. Sometimes, pads 24 are used in consumer products that are intended to absorb liquids or secretions from the body and the materials used to form such pads. They will generally include at least some absorbent materials. Such pads are frequently formed by a mixture of hydrophilic fibers and superabsorbent materials. The materials which can be used to form pad 24 include cellulose pulp, cotton, rayon and other natural and synthetic fibers. The superabsorbent materials can be mixed with these materials to increase the absorbency of the pad. A lint material derived from the wood pulp is commonly used to form the absorbent pads, and such lint material can be employed with the apparatus illustrated in FIGS. 1 and 2. The detailed description which is presented herein discusses the present invention. in terms of a pad 24 formed with such a waste material but the alternate materials can also be employed with the present invention.

Before entering the forming chamber 2, the compressed wood pulp can be pulverized in a hammer mill or other fibrillating equipment to produce the fluff material. The use of hammer mills and similar fibrillator equipment is well known in the art. The fluff material is then carried from the hammer mill to the forming chamber 2. The fluff can also have additional materials added thereto, such as the superabsorbent materials, either before or after depositing the fluff material on the forming grid 22. ' A junction unit 28 is not required, but it may advantageously be positioned after the forming chamber 2 to remove the excess fluff from the pad 24. The assembling unit 28 includes a bolt assembly roller 30 and a removal air duct 32. The removal air duct 32 can be advantageously used to recycle the removed material. For example, the duct 32 can transport the removed material to the hammer mill or to the forming chamber 2 where the removed material can be reintroduced into the manufacturing process. Alternatively, the duct 32 can transport the material to a temporary storage chamber before reintroducing the material into the manufacturing process or using it as a component in an alternate waste or recycling method.

After removal of the excess fluff material, the pad 24 is carried from the forming drum 20 to a transfer surface 34. The transfer surface 34 can be formed by means of a cylindrical transfer roller 3 as shown in FIG. Figures 1 and 2.

As shown in Figures 15-17 and discussed below, the transfer surface 34 can also be formed by means of a flat conveyor 38.

The forming drum 20 uses a vacuum source to deposit the fluff material on the forming grid 22 in the area of the forming chamber 2. In the transfer area 40 where the pad 24 is transferred from the forming drum 20 to the surface of transfer 34, the forming drum 20 does not exert a vacuum. A blown pad air blade 42 is located near the transfer area 40. Both the lack of a forming drum vacuum and the air knife 42 assist in the transfer of the pad 24 to the transfer surface 34 in the transfer area 40.

In the illustrated apparatus, the cylindrical transfer roller 3 is a vacuum tumbling roller. The transfer surface 34 of the transfer roller 3 is a perforated surface and a vacuum source 43 is operatively associated with the transfer roller 3 whereby the transfer surface 34 pulls a vacuum in the transfer area 40. The use ' of a vacuum within the transfer roller 3 attracts the pad 24 to the transfer surface 34 and thus aids the transfer of the pad 24 to the transfer surface 34. A second air knife 44 is located inside the transfer roller 3 for disengaging the transfer roller pad 3. The transfer surface 34 does not exert a vacuum on the pad 24 in the area of the air knife 44.

In the apparatus illustrated in Figures 1 and 2, the pad 24 is deposited on a first tissue 4 by leaving the vacuum area of the transfer roller 3 and is disengaged from the transfer roller 3. A second tissue 48 is subsequently deposited on the opposite surface of the pad 24. The tissues 4 and 48 help to maintain the integrity of the pad 24 as it is subsequently assembled into a product and placed in use. The use of such tissue layers with an absorbent pad is well known in the art. The use of such tissues 4 and 48, however, is not required and pad 24 can be assembled into a product without the use of such tissue layers. Alternate layers, such as a layer of a polymer meltblown material can also be used to increase the integrity or cohesion of the pad 24.

It is also known to place a layer of tissue on a forming roller and form a lint pad directly on the tissue layer. When the heads 50 are employed on a forming grid 22 according to the present invention, however, a tissue layer is preferably not used on the forming grid. Such a tissue layer would be difficult to conform to the surface of both the forming grid 22 and the heads 50 and the openings 52 formed by the heads 50 would be more feasibly deformed by the presence of such a tissue layer.

After the positioning of the tissues 4 and 48 on the opposite sides of the pad 24, the pad 24 is disengaged. The pad 24 is compressed between two pressure point rollers to discourage the pad 24.

The disengagement of the pad 24 reduces the thickness of the pad 24 and this may also slightly elongate the openings 52 formed in the pad 24. The illustrated apparatus forms a continuous pad which must be cut into individual pads in the manufacture of the pad. the absorbent products. The outer side perimeter of the pad 24 illustrated in FIG. 3 can be defined by the outer side perimeter of the forming grid or by subsequently cutting the pad 24. A jet of water expelled at a high pressure and speed or a cutting operation with matrix can be used to efficiently cut the pad 24 to define its outer perimeter. It is also possible to deposit individual discrete pads on the forming grid 22 by segregating different parts of the forming grid 22 in a manner which is known in the art.

The openings 52 are best seen in Figure 3. In the illustrated embodiment, the openings 52 extend through the full thickness of the pad 24. It is also possible for the openings 52 to extend only partially through the thickness of the pad 24. .

The openings 52 are formed by the heads 50 located on the forming grid 22. Although not seen in Figures 1 and 2, the heads 50 are illustrated in Figures 4-19. The heads 50 form an appendix or protuberance on the forming grid 22. When the pad 24 is removed from the forming grid 22, the pad has an opening 52 or a hollow space at the location where the pad 24 was circumscribed to the head 50. By forming the openings 52 in this manner, a subsequent cutting or calendering process is not required to form the openings 52.

In the apparatus and in the method illustrated in FIGS. 1 and 2, the assembling unit 28 is positioned to remove all the fluff material which is disposed outwardly from the distal end 0 of the head 50. The assembling unit 28 thus makes that the knobs 50 intersect the pad surface 25 positioned opposite the forming grid 22. The openings 52 formed by the apparatus and the method illustrated in FIGS. 1 and 2 therefore extend through the entire thickness! of the pad 24.

In the alternate embodiments of the present invention the openings 52 formed in the source 23 of the pad in contact with the forming grid 22 may not extend through the full thickness of the pad 24.

For example, if the configuration of the heads 50 and the assembly unit 28 allows the fluff material to not only circumscribe but also cover the distal end 0 of the heads 50 when the fluff material was deposited on the forming grid, the openings 52 they will extend only partially through the thickness of the pad 24 and thus take the form of a recess with a perforation, eg, an opening 5__, in only one surface of the pad 24.

The heads 50 can be formed from a wide variety of different materials. For example, heads 50 can be formed of plastic or metal materials. The metallic heads are advantageous because they are durable and have a relatively low coefficient of friction. An aluminum head provided with a Teflon release coating (eg, polytetrafluoroethylene) can be used to provide a low friction and durable head. For example, a release coating found suitable for use with aluminum heads was obtained under the Hard Coating Coating of Pioneer Coating having offices in Green Bay, Wisconsin. A knob 50 that has such durability and a low coefficient of friction can also be obtained by placing a Teflon coating on a steel body. Teflon coatings obtained under the brand name of either Norcoat-2 or Norcoat-3 from Pioneer Coating that has offices in Green Bay, Wisconsin, can be used to coat the steel heads.

The heads 50 can advantageously be attached to the forming grid 22 by using the threaded fasteners 54 inserted through the forming grid 22 and engaging a threaded hole 5 in the head 50 as shown schematically in Figure 18. The heads can also be formed by including a projecting threaded shaft on the head so that the shaft can be threaded into an opening in the forming grid 22 or _ hooked by a nut on the opposite side of the forming grid 22.

The use of the threaded fasteners 54 allows the heads 50 to be conveniently fastened, released and resumed to the forming grid 22. When such heads are used, a first set of heads can be relatively and conveniently exchanged for a second set of heads that have a different size or geometric shape to alter the size and shape of the openings in the resulting pad. The use of threaded fasteners also allows the individual heads to be interchanged. i It is envisioned that the use of the resilient heads on the forming grid 22 may also allow the head positions to be reconfigured to alter the pattern of the openings 52 formed in the pad 24. Insertion of a threaded fastener through the grid Forming 22, however, can damage the grid.

The heads 50 can also be welded or otherwise permanently fixed to the forming grid 22. Less substantial materials and fastening methods can also be used to form and hold the heads 50. For example, the foam rubber heads 50 Adhered to a forming grid 22 with a double-sided tape have been successfully used for limited production runs and these can be removed or reconfigured without damaging the forming grid 22.

Figure 19 illustrates a forming grid 22 with a plurality of heads 50 joined thereto in a first pattern. Also shown in FIG. 19 are dotted lines 21 which designate the position where the outer side edges of the lint pad 24 will be located after the lint material has been deposited on the forming grid 22. As can be seen of Figure 19, the knobs 50 lie within the interior region of the forming grid so that the heads 50 will be completely circumscribed by the fluff material deposited on the forming grid 22. In other words, if a projection similar to a head 50 was placed along the side edge of the forming grid 22 so that it would define a part of the lateral perimeter of the lint pad 24 (and corresponded to the dotted line 21) this would not be completely circumscribed or surrounded by the lint material deposited and would not define an opening inside the pad.

The illustrated heads 50 do not include the perforations or openings on either the side walls or the distal end of the head 50 and, therefore, the process air is not pulled directly through the illustrated heads 50.

It would be possible, however, for the heads to include such openings on the side wall surface 58 to allow the process air to be moved through them in addition to the remainder of the forming grid 22. If the openings 52 did not extend completely through the thickness of the pad 24, it would be desirable for the distal end 0 of the heads to include openings or both the side wall surface 58 and the distal end 0 to include openings.

When the heads 50 without openings are employed on a forming grid 22, the total area of the forming surface which includes the openings is reduced. For the pad 24 illustrated in FIG. 3 which is intended for use in a diaper, there are 32 openings and the surface area of the openings / knobs is approximately 15% of the total surface area of the pad / surface. . An alternate configuration of the pads 50 which results in a pad similar to that shown in Figure 3 but with only 1 openings can also be used to produce an absorbent pad very suitable for use in a diaper.

Advantageously, the surface area of the head can also be between about 7 to about 15%, about 5 to about 25%, or less than about 50% of the total forming surface area. As used herein, the surface area of the head is the cross-sectional area of the head at the base of the head where the head is attached to the forming grid and the total forming surface area includes the area of the head. forming grid on which the fluff material is deposited plus the head surface area.

The heads 50 can have a variety of different configurations. For example, the cross section of the heads 50 can define a circle, an oval, a star, a diamond, a rectangle or any other geometric figure. In addition, the cross-sectional shape of the heads 50 can vary over the height of the heads 50. For example, the heads 50 can be provided with a light taper so that the distal end 0 of the head 50 has an area which is smaller than the cross-sectional area of the base of the head at the point where the head is attached to the forming grid 22. The taper inward of the side wall 58 may advantageously be in the range of from 0 ° to about of 15 °. For example, the side walls may advantageously have a taper i inwardly of approximately 5 ° or 7 °.

Alternatively, the surfaces of the side wall 58 of the head 50 may be perpendicular to the forming grid 22, lean slightly outward, or vary over the perimeter or height of the head 50. For example, a head 50 may have an edge front 8 which is perpendicular to the forming grid and a tail edge which is slightly inwardly inclined and thus has an inclination which varies on the perimeter of the head 50. A head 50 which is perpendicular near of its base (for example it has a 0 ° taper) but tapering inward near its far end will have an inclination which varies over the height of the head 50. Thus, the heads 50 can take a variety of different shapes. The configuration of the heads 50, however, must account for the interaction of the head 50 and the pad 24 during the release of the pad 24 from the forming grid 22 which is described in more detail below.

The heads illustrated in Figures 4-18 have circular cross sections that have a diameter of 1.91 centimeters (0.75 inches) at the base of the head, a height of either 1.27 centimeters, or 1.59 centimeters (0.5 or 0.25 inches). ) and a slight taper inwards. As best seen in Figure 18, the side wall 58 has an inward tilt, illustrated by an angle 2, of about 5 ° whereby the angle formed between the side wall sloping inward 58 and the forming grid 22 is around 85 °. Therefore, the head illustrated in Figure 18 is a trunk (for example this defines a truncated cone).

For pads 24 intended for use with conventional absorbent products, the diameter or the longest side dimension of the heads 50 may be advantageously varied from between about 0.95 centimeters (0.375 inches) to about 5.08 centimeters (2 inches). The pattern formed by the heads 50 on the forming grid 22 can be varied significantly. However, it is generally advantageous to maintain a distance between each head 50 which is at least as large as the diameter of the head (or the longest lateral dimension of the head 50) or the height of the head 50.

An advantageous feature of the heads 50 of the present invention is its ability to assist in the transfer of the pad 24 from the forming grid 22 to the transfer surface 34. This appearance of the heads 50 is illustrated schematically in Figures 4-17.

Figures 4 to 11 and 12 to 14 illustrate the transfer of a pad with openings 24 from a cylindrical forming drum 20 to a cylindrical transfer roll 3. For purposes of clarity, a single head 50 is illustrated in Figures 4 to 11 by rotating it and progressively releasing the pad with openings 24. A normal line 4 which connects the centers of both the forming drum 20 and the transfer roller 3 is illustrated in Figures 4 to 11 and provides a common reference point in each one of these figures. The forming grid 22 and the transfer surface 34 are rotated respectively around the i centers of the forming drum 20 and transfer the roller 3 in opposite directions of rotation so that the forming grid 22 and the transfer surface 34 have a common direction of linear or tangential movement where they intersect the normal line 4. Thus, the transfer surface 34 moves in a direction which essentially corresponds to the movement of the pad 24 in the area closer to the normal line 4.

The point at which the forming grid 22 and the transfer roller 3 are closer to each other lies along the normal line 4. ' In the transfer area near the line 4, the lint pad 24 has a first surface 23 in contact with the forming grid 22 and the movable transfer surface 34 is placed on one side of the second opposing surface 25 of the pad 24 At the point where the forming grid 22 and the transfer surface 34 are closer, for example, at their intersection with the normal line 4, the forming grid 22 has a first tangential velocity (oriented perpendicular to the normal line 4) and the transfer surface has a second tangential velocity (oriented perpendicular to the normal line 4). The transfer surface 34 is engaged with the second surface 25 of the pad 24 at or near the normal line 4 in the transfer area 40.

A vacuum source 43 operatively associated with the transfer roller 3 attracts the pad 24 to the transfer surface 34. As the pad 24 moves with the transfer surface 34 it is released from contact with both the forming grid 22 and the head 50. Figures 4 to 11 progressively illustrate the release of the pad 24 at i where the forming grid 22 is generally cylindrical and has a diameter which is more than 3 times the magnitude of the diameter of the transfer surface 34 which is also generally cylindrical The forming grids having a diameter of approximately 154.4 centimeters (0.8 inches) can be advantageously used with the transfer surface 34 that have a diameter of approximately 42.4 centimeters (1.7 inches) to provide a ratio of drum diameter forming / transfer surface diameter of 3,.

Advantageous configurations can also be obtained by using a forming grid 22 having a radius which is twice or three times as large as the radius of the transfer surface 34. The alternate modes can also be employed by forming the grids 22 which have a radius which is approximately equivalent to or smaller than the radius of the transfer surface 34.

For example, the use of a flat transfer surface 34 can be considered the use of a transfer surface 34 having an infinite radius.

Figures 4-14 illustrate a forming drum 20 having a diameter of 154.4 centimeters and a transfer surface with a diameter of 42.4 centimeters; wherein the tangential velocity of the transfer surface 34 is equivalent to the tangential velocity of the forming grid 22; and knob 50 has a height of approximately 1.27 centimeters (0.5 inches).

Figure 4 illustrates a representative head 50 when centered on the normal line 4. Figure 5 illustrates the point at which the head 50 has rotated 0.75 ° (or 0.013 radians) around the center of the forming drum 20 beyond the normal line 4. Figures 11 illustrate the head 50 after it has been rotated respectively 1.5 °; 2.25 °; 3rd; 4.5 °; 5.25 ° and ° beyond the normal line 4.

As can be seen in figures 4 to 11, the tail edge of the head 50 sticks on the fluff pad 24 during the release of the pad 24 from the head 50 and the forming grid 22. That part of the tail edge of the head 50 which sticks on the pad 24 exerts a compressive force on the pad 24 and forms a push surface 5. The push surface 5 is located on the tail edge instead of the leading edge 8 of the head 50 due to the relative tangential speeds of the forming grid 22 and of the transfer surface 34 in the transfer area 40 and the spatial configuration of the forming grid 22, of the head 50 and of the transfer surface 34 in the transfer area 40.

The leading edge 8 of the head 50 will stick to the pad 25 and exert compressive forces thereon if the transfer surface 34 has a relatively low speed compared to the speed of the forming grid 22. The spatial configuration of the forming grid 22, of the head 50 and of the transfer surface 34 in the transfer area 40 will determine the precise point at which a relative increase in the speed of the transfer surface 34 causes the tail edge of the head 50 to exercise a compressive force on the pad 24 instead of the leading edge 8 of the head 50.

When a forming grid 22 and a transfer surface 34 are used both of which are generally cylindrical and 'where the radius of the transfer surface 34 is smaller than the radius of the forming grid 22, the tail edge of the head 50 will generally stick on the fluff pad 24 when the transfer surface 34 has a tangential velocity which is at least as great as the tangential velocity of the forming grid in the transfer area. Additional relative increases in the speed of the transfer surface 34 to 101, 102 or 103% of the speed of the forming plate 22 in the transfer area 40 can also be advantageous. An excessive difference in the relative speeds of the transfer surface 34 and the forming grid 22, however, can cause damage to the pad such as stretching and cracking of the pad 24 during the release and transfer process.

In the embodiment illustrated in Fig. 1, the apparatus can be advantageously operated so that the forming grid 22 has a tangential velocity of about 304.8 meters / minute (1000000 feet / minute) and the transfer surface 34 has an approximately equivalent tangential speed. Conventional forming grids are frequently operated at rates which produce tangential speeds within the range of approximately 91.4 meters / minute (300 feet / minute) to 304.8 meters / minute (1,000 feet / minute). The present invention can advantageously use a forming grid 22 that operates within this speed range but is not limited to this range of speeds.

Figures 12-14 are amplifications of the head 50 in the same rotational positions shown respectively in figures 8 and 9. The compressive pressure exerted by the pushing surface 5 on the pad 24 can be denoted by a force vector 70. which represents the division and the magnitude of the total compressive pressure exerted by the thrust surface 5 located on the tail edge of the head 50 against the pad 24. The actual compressive force 70 exerted by the thrust surface 5 will vary in magnitude when the head 50 is removed from the pad 24. That part of the tail edge of the head 50 which forms the thrust surface of 5 will also change upon removal of the head 50 from the pad 24.

The current magnitude of the compressive force 70 will depend on the number of variables, including not only the spatial configuration of the forming grid 22, of the head 50 and of the transfer surface 34, but also of the materials used to form the head 50 and the pad 24. For example, the modulus of elasticity and the Poisson's ratio of both the head 50 and the pad 24 will affect the magnitude of the compressive force 70j '. As a general rule, denser pads will result in the head exerting greater compressive forces. There will also be frictional forces existing between the head 50 and the pad 24 which, when added to the compressive force 70, will result in a net force having a magnitude and operation slightly different from that of the compressive force 70.

In relation to the spatial configuration of the apparatus, a higher head will generally produce larger compressive forces than a shorter head and a smaller diameter forming grid will generally produce compressive forces larger than a larger diameter forming grid. The determination of an exact magnitude of the compressive force 70 can be very complex. For the purposes of Figures 12-14, however, the magnitude of the compressive force 70 has been simplified and is represented at a constant value of 2.00 units of force.

The orientation of the compressive force 70 is easier determined than the magnitude of the force 70. The direction of the compressive force 70 * is determined primarily by the spatial configuration of the forming grid 22, of the head 50 and of the transfer surface 34 and the relative movement of these apparatus components determines the area and depth to which the head 50 sticks on the pad 24.

A variable which can affect the net force exerted by the head 50 on the pad 24 is the frictional resistance between the pad 24 and the head 50.

The compressive force vectors 70 are illustrated in the figures of the present application rather than the net force vectors. The orientation of the illustrated vectors 70 will essentially correspond to the orientation of the net force exerted by the head 50 on the pad 24 if the interconnection between the head 50 and the pad 24 is presumed to be frictionless. Such a presumption is reasonable for heads 50 such as those illustrated in the figures which have a friction reducing coating and a slightly inward taper.

The compressive force 70 can be defined by two component vectors which are illustrated in the figures 12 to 14. One of the component vectors 72 is directed towards the transfer surface 34 and is normal to the transfer surface 34 at the location closest to the point on the thrust surface 5 corresponding to the origin of the compressive force 70. The second component vector 74 is at a right angle to the first component vector 72 and is oriented opposite the direction of travel of the pad 24. When added together, the vectors 72 and 74 are equivalent to the compressive force vector 70. Because the first component vector 72 has an orientation which is normal to the transfer surface 34, it aids in the transfer of the pad 24 to the transfer surface 34.

The orientation of the compressive force 70 is determined in part by the shape and configuration of the head 50. When it is placed by air, it clears it on the forming grid 22, this is subjected to a vacuum and is therefore strongly attracted towards the grid. Forming 22. By rotating the forming grid 22 towards the transfer side 40, the blank forming pad 24 is no longer subjected to a vacuum and expands slightly outwardly from the forming grid 22. During this expansion of the clearing material, the pad 24 also expands laterally to engage the side walls 58 of the heads 50, if the waste material no longer engages the side walls 58 of the heads 50. (The front part of the side wall 58 forms the front edge 8 of the head 50 while the rear part of the side wall 58 forms the tail edge of the head 50).

Due to this expansion of the fluff material, the biasing or recessing of the head 50 will result in the fluff material expanding into the recessed space between the forming grid 22 and the head 50 when the vacuum is no longer attracting the erase against the forming grid 22.

Depending on the angle of such a chamfer or outer taper, some of the fluff material may be trapped between the head 50 and the forming grid 22 during the release of the pad 24 and causing damage to the pad 24.

For these reasons, the release of the pad 24 can be improved by providing a light inward taper for the head 50 whereby the head 50 has a smaller cross-sectional area at the distal end than at its base. The heads 50 may advantageously have side walls 58 which have an inward tilt of about 5 degrees or greater to aid in the release of the pad. By using the side walls 58 having an inclination which is about 5 degrees, the openings 52 formed by the head 50 will have interior surfaces which do not diverge significantly from an orientation perpendicular to the outer surfaces of the pad 24 and yet they will facilitate the release of the pad 24 as demonstrated in figures 12 to 14.

As shown in figure 12 when the knob 50 has rotated 1.5 degrees beyond the normal line 4, the first component vector 72 of the compressive force 70 comprises a relatively small part of the total compressive force 70. In the illustrated configuration, and examining only the compressive force and not any frictional forces, the first component vector 72 has a magnitude of 0.33 units of force i for each 2.0 units of total compressive force 70. Figure 3 illustrates the point at which the head 50 has rotated 3 degrees beyond the normal line 4. At this point, the first component vector 72 has a magnitude of 0.57 units per 2.0 units of total compressive force 70. Figure 14 illustrates the point at which the head 50 has rotated 4.5 degrees beyond the normal line 4. At this point, the first component vector 72 has a magnitude of 0.79 units per 2.0 units of total compressive force 70.

Therefore, in the configuration illustrated in Figs. 12 to 14, the percentage of the total compressive force 70 which is normally directed to the transfer surface 34 increases upon release of the head 50 from the pad 24. It can also be seen from Figs. to 14 that the total area of the pushing surface 5 progressively decreases upon release of the head 50 from the pad 24 and that the extension of the strike of the pushing surface 5 on the pad 24 progressively increases upon release of the pad 24.

Figures 15-17 illustrate the transfer of a perforated pad from a cylindrical forming grid 22 to a flat conveyor 38. The transfer surface 34 of the flat conveyor 38 can be operatively associated with a vacuum source whereby a vacuum to bring the pad 24 to the flat conveyor 38 and assist the transfer.

The transfer of the pad 24 to the flat transfer surface 34 can be aided by the glue edge 8 of the knobs 50 imparting a compressive force on the pad 34 in the same manner as described above for the transfer of a pad 24 to the cylindrical transfer surface 34. When the transfer is to a flat transfer source 34, however, the relative speed of the transfer surface 34 will have to be increased in relation to the speed of the forming grid to ensure that this is the tail, rather than the leading edge 8 of the head 50 which strikes the pad 24. i The forming grid 22 and the head 50 illustrated in Figures 15 a are similar to those illustrated in Figures 12 to 14. Figures 15 to 17 however, show a flat transfer surface 34 where the transfer surface 34 of the flat conveyor 38 has a speed which is 103 percent of the forming grid 22. The arrow 39 indicates the direction of travel of the flat conveyor 38.

For the apparatus illustrated in Figures 15 to 17, when the speed of the flat transfer surface 34 is equivalent to the speed of the forming grid 22, the leading edge 8 of the knob 50 will strike on the pad 34.

When the flat transfer surface 34 has a speed which is 101 percent of the speed of the forming grid 22, the head 50 will strike the pad 34 with both the leading edge 8 and the tail edge and at approximately equal magnitudes in points different during the release process. When the speed of the flat transfer surface 34 has been increased relatively to 102 per cent of the speed of the forming grid 22, however, it will be the tail edge; of the head 50 which will strike primarily on the pad 34 and the head 50 will therefore assist in the transfer of the pad 24 to the flat transfer surface 34. If the speed of the flat transfer surface 34 exceeds 103 percent of the speed of the forming grid surface, for example, this has a pulling of more than 103 percent, a pad 24 formed primarily of the cellulosic fluff material can be damaged by cracking or stretching.

For the embodiment illustrated in Figures 15 to 17, when the forming grid 22 has a speed of approximately 304.8 meters / minute (1,000 feet / minute) and the flat transfer surface 34 has a speed of approximately 102 to 103 percent of the forming grid speed, the leading edge of the head 50 will stick on the head 24 and a pad 24 formed of the cellulosic fluff material will hardly experience stretching or cracking due to the difference in velocities. « It is noted that a particular relative difference in the tangential velocity of the forming grid 22 and the transfer surface 34 corresponds to a particular relative difference in the tangential linear advance of the forming grid 22 and the transfer surface 34 regardless of the speed absolute of the forming grid 22 and of the transfer surface 34. For example, if the transfer surface 34 has a speed of 101 percent of the forming grid 22, the transfer surface 34 will advance 101 centimeters for every 100 centimeters that the grid and formator 22 advances, regardless of their absolute speeds.

Although this invention has been described in detail, it will be readily apparent to a person of ordinary skill in the art that various changes and modifications may be made without departing from the spirit and general principles of the invention. All such changes and modifications are contemplated as being within the scope of the present invention as defined by the appended claims. Furthermore, this application is intended to cover such deviations from the present disclosure as fall within the known or customary practice in the art.

Claims (53)

R E I V I N D I C A C I O N S

1. A method for making a pad, said method includes: providing a forming grid with at least one head projecting outwards; i rotating said forming grid so that the forming grid has a first tangential velocity; forming the pad on said forming grid wherein the pad completely surrounds said at least one head, the pad has a first surface placed in contact with said forming grid and a second surface positioned opposite the first surface; providing a mobile transfer surface adjacent to the second pad surface, said transfer surface t moves in a direction essentially corresponding to the movement of the second adjacent surface, said transfer surface moving at a second speed which is therefore less as big as said first speed; engaging said transfer surface with the second adjacent surface; and i transferring the pad to said transfer surface wherein a tail edge of said head exerts a compressive force on the pad, said compressive force includes a component vector directed toward said transfer surface.

2. The method as claimed in clause 1 characterized in that the second surface of the pad is intersected by said head.

3. The method as claimed in clause 1 characterized in that the transfer surface is a flat surface.

4. The method as claimed in clause 3 characterized in that said second speed is greater than said first speed.

5. The method as claimed in clause 3 characterized in that said second speed is at least about 102 percent of said first speed.

The method as claimed in clause 3 characterized in that said second speed is at least about 103 percent of said first speed.

7. The method as claimed in clause 1 characterized in that said transfer surface is a cylindrical surface.

8. The method as claimed in clause 1 characterized in that said forming grid includes a plurality of heads projecting outwards.

9. The method as claimed in clause 1 characterized in that said at least one head is resubrurably secured to said forming grid.

10. The method as claimed in clause 9 characterized in that said at least one head is threadably clamped. t

11. The method as claimed in clause 1 characterized in that said at least one head has a distal end and said side walls extend from said forming grid to said distal end, said head has a first cross-sectional area in said forming grid and a second cross-sectional area in said distal end, at least a part of said side walls has an inward inclination of at least about 5 degrees.

12. The method as claimed in clause 11 characterized in that said at least one head is a trunk.

13. The method as claimed in clause 1 characterized in that said transfer step further includes using a vacuum to attract the pad to the transfer surface.

14. A method for manufacturing a pad, said method includes: i providing a forming grid, said forming grid defining a first cylindrical surface with a first radius and having at least one head projecting outwardly; rotating said forming grid so that said forming grid has a first tangential velocity; forming the pad on said forming grid whereby the pad completely surrounds said at least one head, the pad has a first surface placed in contact with said forming grid and a second surface positioned opposite the first surface; providing a rotating transfer surface adjacent to the second surface of the pad, said transfer surface defining a second cylindrical surface with a second radius; engaging said transfer surface with the second surface of the pad at a second tangential speed which is at least as large as said first speed, said forming grid and said transfer surface having opposite rotational directions; Y transferring the pad to said transfer surface whereby a trailing edge of said head exerts a compressive force on the pad, said compressive force includes a component vector directed toward said transfer surface.

15. The method as claimed in clause 14, characterized in that the second surface of the pad is intersected by said head.

1. The method as claimed in clause 14 characterized in that said second speed is greater than said first speed.

17. The method as claimed in clause 14, characterized in that said second speed is at least about 101 percent of said first speed.

18. The method as claimed in clause 14 characterized in that said second speed is at least about 102 percent of said first speed.

19. The method as claimed in clause 14 characterized in that said second velocity is at least about 103% of said first velocity.

20. The method as claimed in clause 14 characterized in that said at least one head has a distal end and side walls extending from said forming grid to said distal end, said head has a first cross-sectional area in said grid former and a second cross-sectional area at said distal end, said first cross-sectional area i is greater than said second cross-sectional area, at least a portion of said side walls has an inward slant of at least about of 5 degrees.

21. The method as claimed in clause 20 characterized in that said at least one head is a trunk.

22. The method as claimed in clause 14 characterized in that said forming grid has i a plurality of heads projecting outwards.

23. The method as claimed in clause 14 characterized in that said at least one head is resubstantially secured to said forming grid.

24. The method as claimed in clause 23 characterized in that said at least one head is threadably clamped.

25. The method as claimed in clause 14 characterized in that said first radius is essentially equivalent to said second radius.

2. The method as claimed in clause 14 characterized in that said first radius is larger than said second radius.

27. The method as claimed in clause 14 characterized in that said transfer step further includes using a vacuum to attract the pad to the transfer surface.

28. An apparatus for manufacturing a pad, said apparatus comprises: a rotary forming grid, said forming grid having a generally cylindrical surface and at least one outward projecting head, said at least one outwardly projecting head being internally positioned on said forming grid so that said forming grid circumscribes said head, said forming grid being able to rotate at a rate that defines a first tangential velocity; a source of material placed on one side of the forming grid so that a layer of material can be deposited on said forming grid and said at least one head can be circumscribed by the layer of material which thus forms the pad and has a first surface arranged in contact with said forming grid and a second surface positioned opposite said first layer; a mobile transfer surface, said transfer surface is engageable with the second surface of the layer of material, said transfer surface can move in a direction that corresponds essentially to the movement of the layer of material engageable and at a second speed, said second speed being at least as large as said first speed; i means for attracting the layer of material to said transfer surface; Y a pushing surface positioned on a tail edge of said at least one head, said head surface imparts a compressive force on the layer of engagable material upon moving said forming grid and said transfer surface respectively at said first and second speeds, said compressive force includes a component vector directed towards said transfer surface.

29. The apparatus as claimed in clause 28, characterized in that said transfer surface is an essentially planar surface.

30. The apparatus as claimed in clause 29 characterized in that said second speed is greater than said first speed.

31. The apparatus as claimed in clause 29 characterized in that said second speed is at least about 102 percent of said first speed.

32. The apparatus as claimed in clause 29 characterized in that said second speed is at least about 103 percent of said first speed.

33. The apparatus as claimed in clause 28 characterized in that said transfer surface is an essentially cylindrical surface.

34. The apparatus as claimed in clause 28 characterized in that said forming grid includes a plurality of outwardly projecting heads placed internally on said forming grid so that the forming grid circumscribes each of said plurality of heads.

35. The apparatus as claimed in clause 28 characterized in that said at least one head is resusable on said forming grid.

3. The apparatus as claimed in clause 35 characterized in that said threaded fastener ensures said at least one head.

37. The apparatus as claimed in clause 28 characterized in that said at least one head has a distal end and said side walls extend from said forming grid to said distal end, said head having a first cross-sectional area in said grid forming and a second cross-sectional area at said distal end, in a portion of said side walls having an inward inclination of at least about 5 degrees.

38. The apparatus as claimed in clause 37 characterized in that said at least one head is a trunk.

39. The apiathe as claimed in clause 28 characterized in that it further comprises an assembly device, said assembling device is positioned to remove excess material placed outwardly from a distal end of said at least one head.

40. The apparatus as claimed in clause 28 characterized in that said means for attracting the layer of material comprises a vacuum source placed in operative communication with said transfer surface.

41. An apparatus for manufacturing a pad, said apparatus comprises: a rotary forming grid, said forming grid defining a first generally cylindrical surface with a first radius and having at least one head projecting outwards, said at least one head projecting outwardly is placed internally on said forming head by what said forming grid circumscribes said head, said forming grid can rotate at a rate that defines a first tangential velocity; a source of material placed on one side of the forming grid so that the layer of material can be placed by air on said forming grid and said at least one head can be circumscribed by the layer of material, the layer of material therefore forms a pad and has a first surface placed in contact with said forming grid and a second surface positioned opposite said first layer; a rotating transfer surface, said transfer surface defining a second generally cylindrical surface with a second radius, said transfer surface being engageable with the second surface of the material layer, said transfer surface and said forming grid having the opposite rotating directions , said transfer surface can move at a second tangential speed, said second speed being greater than said first speed; i a vacuum source placed in an operational communication with said transfer surface whereby said layer of material is attractable to said transfer surface; Y a pushing surface positioned on a tail edge of said at least one head, said pushing surface imparts a compressive force on the layer of engagable material as said forming grid and said transfer surface respectively move at the first and second speeds, said compressive force includes a component vector directed towards said transfer surface.

42. The apparatus as claimed in clause 41 characterized in that said first radius is essentially equivalent to said second radius.

43. The apparatus as claimed in clause 41 characterized in that said first radius is larger than said second radius.

44. The apparatus as claimed in clause 41 characterized in that said second speed is greater than said first speed.

45. The apparatus as claimed in clause 41 characterized in that said second speed is at least about 101 percent of said first speed.

46. The apparatus as claimed in clause 41 characterized in that said second speed is at least about 102 percent of said first speed.

47. The apparatus as claimed in clause 41 characterized in that said second speed is at least about 103 percent of said first speed.

48. The apparatus as claimed in clause 41 characterized in that said forming grid includes a plurality of outwardly projecting heads placed internally on said forming grid so that said forming grid circumscribes each of said plurality of heads.

49. The apparatus as claimed in clause 41 characterized in that said at least one head is resusable on said forming grid.

50. The apparatus as claimed in clause 49 characterized in that it also comprises a threaded fastener that ensures said at least one head.

51. The apparatus as claimed in clause 41 characterized in that said at least one head has a distal end and said side walls extend from said forming grid to said distal end, said head has a first cross-sectional area in said grid Forming and said second cross-sectional area at said distal end, a portion of said side walls has an inward inclination of at least about 5 degrees. i

52. The apparatus as claimed in clause 51 characterized in that said at least one head is a trunk.

53. The apparatus as claimed in clause 41 characterized in that it further comprises an assembling device, said assembling device is positioned to re excess material placed outwardly from a distal end of said at least one head. SUMMARY An apparatus and method for manufacturing a pad wherein a rotating forming grid is used which has a generally cylindrical surface and at least one head projecting outwardly. The head is placed on the forming grid so that the head is circumscribed by the material, for example, the cellulose fluff, deposited on the forming grid to form the pad. The pad is transferred from the forming grid to a mobile transfer surface. The transfer surface can be either flat or round and can move at a speed which is at least as large as the speed of the grating for worship. The head located on the forming grid includes a pushing surface positioned on a tail edge of the head. The pushing surface imparts a compressive force on the pad during release of the pad from the forming grid. The compressive force is at least partially directed towards the transfer surface and therefore aids in the release and transfer of the pad.