Method and apparatus for lining manholes

A method and apparatus for providing a liner for manholes, drainage systems, sewer system and the like, wherein multiple layers of liner material are sprayed onto the mandrel and outer shell engaging particles are embedded in and partially covered with the liner material. The liner is then placed into a mold and concrete or other suitable material is poured around the liner. The outer shell engaging particles form a mechanical bond between the liner and the concrete, thereby preventing future separation and failure of the liner.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates generally to an apparatus for producing
 liners for manholes, drainage pipes, sewer pipes and the like.
 2. Description of the Prior Art
 Liners for manholes and other drainage or sewer system are known in the
 art. Typically, a liner is applied to a deteriorating manhole in order to
 rehabilitate the manhole and return it to a safe and working condition.
 Application of such liner systems requires that the surfaces of the
 existing structure be thoroughly cleaned prior to application of the liner
 material to insure a strong bond between the material and the underlying
 structure. It is also common to seal the surface of the existing structure
 with a watertight sealant prior to application of the liner material to
 prevent water and other foreign substances from leaking between the liner
 and the structure, thereby causing the liner to disbond and fail.
 One such liner system is described in U.S. Pat. No. 5,618,616 (Hume). There
 a multilayered liner system is provided for rehabilitating waste water
 system components. The existing, deteriorated structure is thoroughly
 cleaned to allow proper bonding of the liner material. A first primer
 layer is applied to seal the surface and then a plurality of additional
 foam and barrier layers are applied, as required. Each layer is sprayed
 applied. This method is time consuming, expensive and can be dangerous, as
 the personnel applying the liner may be exposed to harmful chemicals in a
 closed space with little or no air flow.
 Systems have been developed whereby an entire manhole assembly may be
 constructed prior to installation. Such systems are useful for replacing
 deteriorated or non-functional manholes in existing waste water system or
 for providing a chemical and corrosion resistant manhole for use in new
 waste water system construction. Such a system is described in U.S. Pat.
 No. 5,303,518 (Strickland). A plastic liner having a provisions for
 creating mechanical lock with an outer shell of concrete is provided
 wherein the a plurality of projections extend outwardly from the liner
 into the concrete outer shell. The concrete flows around and between the
 projections thereby mechanically locking the liner to the concrete. The
 projections are integral to the liner and therefore, the liner material
 must be a material capable of being molded or shaped to form such
 projections, for instance, polyethylene or polyvinylchloride (PVC). In
 certain cases, additional processing may be required to provide a
 completed liner. Such processing may include cutting or milling the
 exterior surface of the liner to provide sufficient gaps or spaces for
 concrete to bond to the liner.
 SUMMARY OF THE INVENTION
 The present invention provides a method and apparatus for producing a liner
 system around which a manhole, drainage system, sewer system or the like
 can be installed to create a lined, interior surface having a concrete
 outer shell. In this way, the outer shell of the manhole is protected from
 the harsh internal environment encountered in most sewer and drainage
 systems, yet the manhole does not require retrofitting to provide a liner.
 In addition, the liner will mechanically bond to the outer shell of the
 manhole to prevent separation and subsequent failure of the liner and
 manhole.
 The apparatus of the present invention produces a liner for use in
 constructing manholes, drainage systems, sewer systems and the like. The
 apparatus typically includes a rotatable mandrel having a moving slide
 collar, at least one sprayer for applying liner material to the mandrel
 and a rock dropper capable of covering the entire length of the mandrel.
 The mandrel should be constructed such that the completed liner can be
 easily removed therefrom without breaking, cutting or otherwise damaging
 the integrity of the liner. For instance, the mandrel may be provided with
 a non-stick or reduced friction surface allowing a completed liner to
 simply slide off the mandrel when complete. The mandrel may be pre-sized
 in order to provide an adequate liner diameter. Therefore, depending on
 the specific application the mandrel will have varying diameter. For
 manhole liners, a mandrel with a 4' diameter is common. The mandrel will
 be rotatable such that an even coating of liner materials may be disposed
 on the surface thereof. Any suitable apparatus for rotating the mandrel
 may be used. In order to supply varying lengths of liner, the mandrel may
 be provided with a moveable slide collar which can be adjusted to produce
 a liner of a specified length.
 The liner producing apparatus of the present invention also includes at
 least one sprayer capable of applying an even coating of liner material
 along the length of the mandrel. Depending on the specific application,
 multiple liner materials may be sprayed onto the mandrel, a plurality of
 sprayers may be used to avoid problems which may be caused by mixing
 materials in the sprayer or delays required to clean the sprayer after
 each material is applied. Multiple sprayers may also be used where the
 desired length of the liner is such that a single sprayer cannot
 adequately cover the entire mandrel. The sprayers may be automated. The
 liner material may also be applied to the mandrel manually, using
 hand-held, compressed air driven sprayers.
 The rock dropper of the present invention is used to apply a uniform layer
 of rocks or other suitable particles to the mandrel after at least one
 coat of liner material has been applied. The rocks, once deposited on the
 mandrel, will be bound in place in the liner material. An additional layer
 of liner material may be applied to at least partially cover the rocks and
 form bonding loops, protrusions or bonding particles thereon. The loops
 being capable of forming a mechanical bond with the outer shell.
 Although a liner may be produced as a single extended tube, typically, the
 liner is typically composed of a plurality of shorter tubes or sections
 which are joined to form the complete liner. The individual sections may
 have a flange at one or both ends capable of engaging adjacent sections
 such that the adjoined sections for a sufficiently tight seal to prevent
 leakage through the joint. A gasket may be included between each section
 to further aid in creating an adequate seal.
 Once a liner is produced and properly sized, the liner is inserted into a
 larger mold. The liner is appropriately positioned within the mold and the
 outer shell material is then poured or injected into the mold to form the
 outer shell around the pre-formed liner. The loops on the liner surface
 extend into the outer shell material, forming a mechanical bond therewith.
 In another embodiment, the liner may be used to repair existing waste water
 or sewage structures by providing a liner which may be inserted into the
 existing structure. Concrete may then be poured between the liner and the
 existing structure for secure the liner in place. This both strengthens
 the structure and provides protection against future exposure to harsh
 chemicals or other deteriorating or corrosive substances.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 As shown in FIG. 1, the liner system L provides an internal liner structure
 10 mechanically bonded to a concrete outer shell S to form a manhole M.
 The liner structure 10 may be a single, elongated tube or shaft, or may be
 a series of smaller tubes joined to form a single unit which extends from
 the upper or roof portion of the manhole 12 to the floor of the manhole
 14. To allow ingress and egress of water and other fluids and gases
 through the manhole, a pipe or other conduit 16 may be passed through a
 hole or opening 18 in the lower portion of the manhole. Preferably, the
 hole is bored through the concrete shell and liner after the manhole has
 been constructed. A molded hat section may be used to mount the pipe 16 in
 the bored hole 18 and to provide a suitable seal 20 between the hole 18
 and the pipe. Benches and inverts may be added after the manhole has been
 installed, as required by the specific application for which the manhole
 is used.
 FIG. 2 shows the liner forming apparatus A of the present invention. A
 mandrel 100 having a predetermined diameter is provided upon which the
 various liner materials may be applied. The mandrel 100 may be formed from
 any suitable material that will allow the liner 10 to slide from the
 mandrel once the liner is completely formed and dried. Preferably, the
 mandrel is formed primarily from polyurea. The mandrel 100 may be mounted
 on a hub 102 positioned at one end of the mandrel. The hub 102 may have a
 larger diameter than the mandrel 100, thereby forming an end plate at the
 point of attachment between the hub and the mandrel and may be formed of
 any suitable material, such as stainless steel. The hub further provides a
 surface perpendicular to that of the mandrel, thereby providing a surface
 on which a flange may be formed at a first end of the liner. A shaft 104
 is attached to the hub, away from the mandrel, such that the shaft is
 positioned along the central axis of the mandrel. The shaft 104 is
 attached, directly or indirectly, to a motor 106 or other apparatus
 capable of producing rotational motion capable of turning the entire
 rotating assembly, which includes the shaft 104, hub 102 and mandrel 100.
 The motor may be any commonly used in the industry. A slidable ring or
 collar 100 may be mounted along any point of the mandrel 100, said collar
 108 having a surface 110 which is perpendicular to the mandrel surface for
 forming a flange at an end of the liner opposite that of the hub 100. The
 slidable collar 108 may be removed from the mandrel at an end opposite the
 hub to allow removal of the liner from the mandrel once the liner is
 completed.
 The rotating assembly is rotated by the motor at a constant, predetermined
 speed, preferably 2-6 rpm. A spray nozzle or nozzles 112 are positioned
 above and at one end of the mandrel and are preferably designed to operate
 using compressed air. The nozzles 112 are mounted on a track to allow
 lateral movement of the nozzles during the application of the liner
 material. The nozzles are set to move a predetermined rate from one end of
 the mandrel to the other. The nozzles will further have a spray pattern
 114 such that they are capable of completely covering a predetermined area
 of the mandrel on each rotation. The predetermined area is typically
 determined by the desired thickness of the liner material (i.e., a
 narrower coverage area will typically produce a thicker layer of liner
 material) and the speed the nozzles will move along the mandrel. The
 thickness of the coating material applied by the nozzles may, in part, be
 determined by the physical configuration of the nozzle, for instance,
 nozzle orifice size or diameter, and the pressure with which the liner
 material is supplied to the nozzle. For instance, a nozzle having a larger
 orifice will apply a thicker coating; likewise, providing the liner
 material at a higher pressure will also result in the thicker coating. The
 rate of movement of the nozzles along the track will depend primarily on
 the size and speed of rotation of the mandrel. As the mandrel 100 rotates
 under the nozzle 112, a coating or liner material 116 is sprayed from the
 nozzles onto the mandrel creating an even and uniform cylinder of liner
 material. At each end, a collar or flange 118 will be formed where the
 liner material is sprayed onto the hub or the slidable collar.
 In an alternative embodiment, the nozzles may be fixed and the rotating
 assembly may be configured to provide for lateral movement of mandrel such
 that the mandrel may move laterally below the nozzles.
 In yet another embodiment, the spray nozzles may be hand held and an
 operator may apply the liner material manually by moving the nozzle along
 the mandrel as it rotates and ensuring that an even and uniform coating of
 liner material is applied.
 A rock dispensing apparatus or rock dropper 120 is positioned above the
 mandrel. Preferably, the rock dropper is positioned directly above the
 mandre. As the nozzles 112 move along the length of the mandrel, the rock
 dropper 120 follows along a substantially parallel, lateral path
 dispensing a plurality of rocks 122 or other suitable material onto the
 wet surface of the liner material 116. As the liner material dries, the
 rocks are bound or fixed in place and prevented from falling from the
 liner material as the mandrel rotates. The rocks create a plurality bumps
 or raised areas on the outer surface of the liner. The rocks may be of any
 suitable size, but preferably range in size from 0.5" to 0.75". In
 addition to rocks, any suitable material which will bond to the liner
 material create bumps or raised areas on the outer surface of the liner
 may be used.
 After the rocks are dispensed and bound to the surface of the liner, a
 second nozzle or set of nozzles, travels from a first end of the mandrel,
 laterally to the second end of the mandrel, in similar fashion to the
 first nozzles. The second set of nozzles apply a second coat of liner
 material, covering the first layer of liner material and the rocks
 embedded therein. The thickness of the second coating layer may be changed
 or adjusted in the same manner as the first coating layer, i.e., by
 altering the size of the orifice in the injector or by providing the
 coating material to the nozzle at a higher pressure. As shown in FIG. 3,
 as the second coat of liner material is applied, loops, voids or tunnels
 150 form in the second coating layer between adjacent rocks 122. These
 loops, voids and tunnels 150 provide space wherein the concrete of the
 outer shell may flow, thereby creating a secure mechanical bond between
 the liner and the outer shell. It should be understood that the second
 coating layer may be applied using any of the methods of application of
 the first.
 The liner material of the present invention is preferably a relatively
 quick drying polyurea. It should be understood, however, that any suitable
 material may be used as a liner material. The polyurea should be capable
 of setting before the mandrel has completed one revolution, but not before
 the rocks are applied. At the point in the revolution where the rocks are
 applied, the liner material should be tacky or sticky enough to hold the
 rocks in place.
 The liner material may be formed as a single piece or may be formed in
 relatively shorter sections, depending on the specific application. Where
 multiple sections are used, each section may be joined mechanically, for
 instance, using screws, pins or the like and a gasket may be disposed
 between the flanges of the adjacent sections prior to joining. The
 sections may also be joined chemically, such as with a suitable adhesive.
 To form a completed, preassembled manhole, the liner 10 is placed into the
 center of a mold. Preferably, an expandable support column is disposed in
 the center of the mold, around which the liner may be fitted. The column
 provides support for the liner while the concrete is poured into the mold
 around the liner. The area between the outer surface of the liner and the
 inner surface of the mold is then filled with concrete. The concrete flows
 completely around the liner and into the spaces formed thereon, creating a
 mechanical bond when the concrete is allowed to dry. Once dry, the support
 column may be collapsed and the entire manhole assembly may be transported
 to a required location. Where shorter liner segments are used, a specific
 application may require the stacking of more than one manhole segment. As
 shown in FIG. 4, a gasket material 184 may be disposed between the manhole
 segments 180, 182 to prevent subsequent leakage when the manhole M is
 placed into service. Preferably, the gasket is a Ramnek gasket. A sealant
 layer or tape 186 may be placed over the joint 188 where two manhole
 segments meet to further prevent leakage of gas or liquid into or out of
 the manhole. Where necessary, a hole may be cut into the manhole, such as
 near the bottom for drainage, sewer or other lines to attach to the
 manhole.
 The bottom or floor of the manhole 14 may be precast simultaneously and
 integrally with a lower section of lined manhole, or the floor may be
 formed in the field at the time of installation of the manhole. The floor
 may be lined or unlined and is preferably formed from concrete. Similarly,
 the top or roof of the manhole 12 may be cast simultaneously and
 integrally with a upper section of lined manhole or may be formed in the
 field at the time of installation. The roof 12 of the manhole M is
 typically formed from concrete and lined with a material of the same or
 similar composition as that used for the manhole walls. However, it should
 be understood that the roof may remain unlined as well. Any ring and cover
 assembly 22 maybe used on top of the manhole, as is common in the
 industry.
 The foregoing disclosure and description of the invention are illustrative
 and explanatory thereof, and various changes in the size, shape and
 materials, and components, as well as in the details of the illustrated
 construction may be made without departing from the spirit of the
 invention.