The present invention relates generally to molded articles which may be blow molded such as a blow-molded ladder or a blow-molded staircase for a swimming pool.
Swimming pool ladders or staircases and various other articles have been made from a plastic material by a process known as “blow-molding,” as exemplified in commonly assigned U.S. Pat. No. 4,023,647 to Confer, commonly assigned U.S. Pat. No. 4,067,614 to Confer et al, and U.S. Pat. No. 4,166,833 to Schurman, all of which patents are hereby incorporated herein by reference. In the process of blow molding, a hollow thin-walled structure is formed having an exterior surface separated from an interior surface by the thin wall, and the hollow structure contains a fluid, in most cases air and/or water.
Pool Ladders with Vandal Guards
By way of background, swimming pool ladders of an A-frame type are positioned straddling a pool wall with the pool side having a ladder for entering and leaving the water (a.k.a., in-pool ladder) and an outside ladder for climbing over the outside of the pool wall (a.k.a., staircase ladder). In the past certain ladders of the foregoing type had relatively unwieldy structures for placing the outside ladder in an inaccessible position so as to prevent unauthorized entry into the pool. Also, insofar as known, ladders of the foregoing type, when disassembled, were not of a size which would fit into a box which was within the dimensions acceptable to commercial shippers. Other types of pool ladders were relatively complicated and difficult to assemble.
In U.S. Pat. No. 6,880,674; St-Hilaire wrote, “A door ladder assembly for use with the [sic] an above ground swimming pool, the assembly comprising a ladder having a plurality of steps, a door with a first side hingedly connected to one side of the ladder and arranged to hingedly move between open and closed positions, a handle being located at the top portion of the door, and a door lock to lock the door in a closed position, the door being provided with a lock operator to unlock the lock, the lock operator being located proximate the handle. The arrangement provides for easy access for an adult, while preventing a child from having access to the unlocking mechanism.” A prior version of a door gate for a pool ladder was disclosed in U.S. Pat. No. 3,225,863 to Ludlow and U.S. Pat. No. 3,968,857 to Bryan. Each of these prior pool ladder barriers are doors that swing on a hinge and are positioned over the A-frame ladder's staircase ladder. These barriers are variations of conventional vandal guards used in other industries.
An alternative vandal guard is disclosed in U.S. Pat. No. 4,579,197 to Spurling. Spurling wrote, “A ladder shield for use in preventing toddlers and the like from climbing the steps of a ladder, such as an above-ground swimming pool ladder, when the ladder or the device to which the ladder is coupled is unattended is disclosed. The ladder shield comprises a rigid yet slightly flexible shell of plastic which is sized and shaped to fit around the front and sides of the ladder so as to block access to the steps on the ladder. The ladder shield is removably secured to the ladder by a removable locking bar which when inserted extends through a pair of holes in the side walls of the shield. The locking bar is secured in place by a lock. When not being used to prevent access to the steps of the ladder, the ladder shield may be used as a mini-foot wash.”
Ladders with a Tambour
A tambour device is defined at www.dictionary.com as “a flexible shutter used . . . in place of a door, composed of a number of closely set wood strips attached to a piece of cloth, the whole sliding in grooves along the sides or at the top and bottom.” Applicant conducted a search to determine if any ladder was associated with a tambour device. The closest reference, not a relevant reference, was U.S. Pat. No. 5,046,582 to Albrecht for a foldable ladder combination with truck cargo carrier. Albrecht wrote, “Commercial truckers frequently have situations arise where they require personal access to the elevated bed of the truck's cargo carrier. The cargo carrier may be mounted on the truck frame itself as in the case of a so-called bob-tail truck; or, the cargo carrier may be a trailer pulled by a truck tractor. In either case, the conventional truck cargo carrier includes an elongated approximately horizontal cargo bed elevated about four to five feet above ground level, and an elongated structural cargo enclosure extending upwardly from, and substantially covering the cargo bed. The cargo bed has a rear end from which cargo is loaded into and unloaded from the cargo carrier, and the structural cargo enclosure has at its rear end right and left side edges in the form of vertical posts extending upward from adjacent the rear end of the cargo bed, and typically has either a single “roll-up” tambour rear door which is engaged in slots disposed at the inboard lateral faces of the posts, or has a pair of swinging doors hinged to such vertical posts, for opening and closing the rear end of the structural cargo enclosure to provide loading and unloading rear access to the structural cargo enclosure and cargo bed.”
Locking Mechanisms for Blow Molded Materials
Walter, in U.S. Pat. No. 1,911,539, Doernemann, in U.S. Pat. No. 5,536,111, Troester, in U.S. Pat. No. 5,013,508, and Tokunaga, in U.S. Pat. No. 3,759,043, all disclose a three-dimensional polymeric structure having a male and a female interlocking component. Not one of these disclosures has both interlocking components on a single side of the structure. Moreover, these references disclose both interlocking components contacting the edges of the sides, which allows easier forces to separate the components. As such, none of these references discloses an apparatus that forms at least a male and a female interlocking component on a single side, and preferably not contacting an edge of the side, of the structure.
In commonly assigned U.S. Pat. No. 7,234,780; Lipniarski wrote, “A device and method for forming an indented female connector where the dimension of the indented female connector provides for removing a male molding component without damaging a set of internal ribs formed inside the female connector. A structure comprising an indented female blow-molded connector having a first wall having a top surface and a thickness, with the first wall surrounding an opening. At least one inner wall extends substantially perpendicular to the first wall and borders the opening. At least one rib is formed in the inner wall. A bottom wall is joined to the inner wall and the distance from the rib to the top surface is greater than the thickness of the first wall. The structure further comprising a male connector having a contact edge that, when positioned inside the indented female blow-molded connector, engage the at least one rib, such that the male connector and indented female blow-molded connector are releaseably joinable with one another. Structures can be made that use the indented female blow molded connectors and male connectors including braced stools having three or four legs.” This connection system requires the male component be inserted immediately into a female locking area (a.k.a., an immediate locking system), which is difficult for easy and secure assembly.
Since most blow molded polymeric materials have an immediate locking system, most blow molded polymeric materials having an immediate locking system also require additional interconnection devices be used to secure the assembly. Those additional interconnection devices include and are not limited to rods, screws and other conventional interconnection devices. See U.S. Pat. No. 6,769,513.
The present invention is directed to a blow molded plastic object having a female interconnection system comprising a receiving area and a locking area. We are aware of one patent that discloses a similar a female interconnection system. That patent is commonly assigned U.S. Pat. No. 6,190,600; which is hereby incorporated by reference. In that patent, Lipniarski wrote, “The present invention relates to an apparatus that forms a polymeric structure. The apparatus has a mold plate, a circular trench, a male and female interconnect, a vertical gap filler, and a cylinder. The mold plate has a predetermined geometric design. The circular trench is in the mold plate and the difference between the outer diameter and the inner diameter of the circular trench is a distance D. The male interconnect and the female interconnect are interspaced between each other. Each interconnect rotates within the circular trench and has a base and an interconnection portion. Each base has a width D and slidably mates to the mold plate. Each interconnect portion has a minimum width W which is less than D. The male interconnect portion protrudes downwards relatively from its base to a distance P, likewise the female interconnect portion protrudes upwards relatively from its base to a distance P. The vertical gap filler aligns with the circular trench and has a foundation and an extension. The extension has a width greater than W, a height greater than 2P, and protrudes upwards and downwards from its foundation. The cylinder rotates each interconnect to a predetermined position and raises the vertical gap filler so the foundation connects to the mold plate before any polymeric material is applied to the apparatus to form the polymeric structure. Once the polymeric structure is formed, the cylinder lowers the vertical gap filler until the extension is below the mold plate a distance greater than P and rotates each interconnect so the polymeric structure can be removed from the apparatus.”
The claimed device in U.S. Pat. No. 6,190,600 is a mold for creating a first blow molded object that had a first male structure having a first extension and a first block and a first female structure having first receiving area and a first inhibiting area; and a second blow molded object that had a second male structure having a second extension and a second block and a second female structure having second receiving area and a second inhibiting area. Thereby the first blow molded object and the second blow molded object could have the first male structure inserted into the second receiving area and the second male structure inserted into the first receiving area. Rotating the first blow molded object in relation to the second blow molded object so the first male structure slides into the second inhibiting area and the second male structure slides into the first inhibiting area. The first and second inhibiting areas have no blow molded locking mechanism to secure the respective male structures in the inhibiting areas. Instead the inhibiting areas rely on the walls (which surround [that means a back wall] the male structure except where the male interconnect slides from the receiving area to the inhibiting area and the male extension that protrudes through an opening in the female inhibiting area) to provide a friction fit to inhibit the male structure from releasing itself from the female structure. The lack of a locking mechanism is acceptable for wave dispersion systems but not for ladders which require a more secure system. The present invention solves this problem for blow molded structures that require a secure locking mechanism.