Abstract:
The present invention provides a tab-lock fastener for connecting first and second vent pipes typically used to exhaust products of combustion of natural gas appliances. The tab-lock fastener includes a guide and a tab-lock receptacle formed on a male end of the first vent pipe, an engaging tab formed on a female end of the second vent pipe, and a locking tab formed on the female end of the second vent pipe. The first and second vent pipes are assembled by inserting the male end of the first vent pipe into the female end of the second vent pipe so that the engaging tab is received in the guide and twisting one of the vent pipes with respect to the other vent pipe. The locking tab engages a wall of the tab-lock receptacle to prevent untwisting and unwanted disconnection of the vent pipes.

Description:
This application claims the benefit of Provisional application No. 60/311,147, filed on Aug. 9, 2001. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to vent pipe and more specifically, but not by way of limitation, to a tab-lock fastener for interlocking vent pipe sections. 
     BACKGROUND 
     Vent pipes and chimneys are commonly found in homes to vent the products of combustion to the atmosphere. Home appliances such as space heaters, decorative fireplaces, hot water heaters, and wood-burning stoves typically include vent pipes. The vent pipes are usually made from a ductile material, such as sheet metal, and are assembled in place and installed to custom fit the vent pipe to a given space. Vent pipes are usually located between walls, in attics and in crawl spaces where there is little room to work. As a result, the manipulation of the vent pipes is difficult, particularly with regard to connecting vent pipe sections. 
     Over the years, local regulatory codes have also become more stringent regarding the sealing of the vent pipes to prevent leaking of the gaseous combustion products into a living space and to generally improve energy efficiency. Accordingly, the connection between adjoining sections of vent pipe must be secure to avoid venting combustion products to the living space. 
     There have been devices for connecting adjoining sections of vent pipe. For example, U.S. Pat. No. 4,874,191 issued to Green teaches a flue gas conduit connector for joining together ends of lengths of flue gas conduit. The lengths are locked by means of locking tabs on the outer surface of one of the flue gas conduits. The tab is bent over a locking ring on the other flue gas conduit. The two ends are provided with complementary taper joints and a sealing gasket to provide a leak-proof flue passage. 
     While functional, the vent pipe connectors taught by Green U.S. Pat. No. 4,874,191, and by others, can be time-consuming and cumbersome to install. In the past, some vent pipe installers have used sheet metal screws to secure vent pipe joints. Although this practice is not widely accepted, some installers have adopted it as a necessary measure to ensure that vent pipe joints will not part accidentally during other stages of construction. For example, a vent pipe can be subjected to accidental disassembly when a termination cap located at the top of a gas vent pipe assembly is removed to allow installation of roofing materials, such as shingles and flashings. 
     When inserting sheet metal screws into vent pipe joints, an installer must use tools and sheet metal screws that are not supplied with the vent pipe. Another drawback occurs when using sheet metal screws with a double-wall vent pipe, such as a B-vent. A B-vent is a double-wall vent pipe that typically has a sheet metal outer wall and an aluminum inner wall, and an installer can accidentally drive a sheet metal screw through both the outer and inner walls of the assembly. Penetration of the inner wall is usually unacceptable and requires the installer to remove and reinstall the B-vent. Additionally, the use of sheet metal screws can result in an undesirable, audible ticking noise during the heating and cooling cycles of the gas vent under normal use. This ticking noise is caused by the sheet metal screw being positioned next to, and contacting, the aluminum inner wall of the gas vent pipe. 
     There exists a need for a connector to join vent pipe sections that is easy to work with, that can be quickly installed, and that maintains the structural integrity of the vent pipe sections. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a tab-lock fastener for vent pipe for connecting vent pipe sections such as is typically used to exhaust combustion products of natural gas appliances. The tab-lock fastener includes an locking tab formed on female end of a first vent pipe section and a guide groove formed on a male end of a second vent pipe section; also, a locking tab is provided on the female end of the first vent pipe section. The first and second vent pipe sections are assembled by inserting the male end of the first vent pipe section into the female end of the second vent pipe section, the vent pipe sections aligned so that the locking tab of the first vent pipe section is disposed to be in the guide groove of the second vent pipe section. The vent pipe sections are then rotated relative one to the other so that the locking tab is aligned over a tab-lock receptacle formed in the male end of the second vent pipe section. The vent pipe sections are interlocked by bending the locking tab to engage a wall of the tab-lock receptacle to prevent unwanted disconnection of the first vent pipe section from the second vent pipe section. 
     The features and advantages of the present invention will become apparent upon reading the following detailed description along with the associated drawings and the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation view of two spaced apart, axially aligned sections of gas vent pipe constructed in accordance with the present invention. 
     FIG. 2 is a side elevation view of the two sections of gas vent pipe of FIG. 1 joined together. 
     FIG. 3 is an enlarged, detailed view of the gas vent pipes of FIG. 2 with the tab-lock engaged. 
     FIG. 4 is a side elevation view of two spaced apart, axially aligned sections of gas vent pipe constructed in accordance with another embodiment of the invention. 
     FIG. 5 is a side elevation view of two spaced apart, axially aligned sections of gas vent pipe constructed in accordance with yet one other embodiment of the invention. 
     FIG. 6 is a side elevation view of two spaced apart, axially aligned sections of gas vent pipe constructed in accordance with one further embodiment of the invention. 
     FIG. 7 is an enlarged, detailed view of the gas vent pipe of FIG. 6 with the tab-lock engaged. 
     FIG. 8 is a cross-sectional view of a double-wall vent pipe section. 
     FIG. 9 is a schematic view of a typical installation of a fireplace using a double-wall vent pipe. 
    
    
     DESCRIPTION 
     Referring to the drawings in general, and particularly to FIG. 1, shown therein is a tab-lock fastener  100  for a vent pipe, or other ductile pipe, constructed in accordance with the present invention. A first vent pipe section  102 A has a formed male end  104 A and a formed female end  106 A. The male end  104 A has four circumferentially spaced about guides or channels  107 A, each of which has an entry area  108 A, a slot  110 A and a tab-lock receptacle  112 A. The female end  106 A of the first vent pipe section  102 A has four circumferentially spaced about, inwardly embossed engaging tabs  114 A (only one of which is completely shown in FIG.  1 ), and a minimum of one locking tab  116 A that is preferably formed as an integral part of the first vent pipe section  102 A. It will be understood that, while only one locking tab  116 A is shown, the first vent pipe section  102 A can be constructed with a plurality of such locking tabs. 
     A second vent pipe section  102 B of the vent pipe has a formed male end  104 B and a formed female end  106 B. The male end  104 B has four circumferentially spaced about guides or channels  107 B, each having an entry area  108 B, a slot  110 B and a tab-lock receptacle  112 B. The female end  106 B has four circumferentially spaced about, inwardly embossed engaging tabs  114 B and at least one locking tab  116 B preferably formed as an integral part of the first vent pipe section  102 B. The term “tab-lock fastener” as used herein includes the locking tab  116 A and either the tab-lock receptacle  112 B or any other structure which prevents the rotation of the first vent pipe section  102 A with respect to the second vent pipe section  102 B. 
     To assemble the first vent pipe section  102 A onto the second vent pipe section  102 B, an installer axially positions and aligns the engaging tab  114 A of the female end  106 A of the first vent pipe section  102 A directly over the guide channel  107 B of the male end  104 B of the second vent pipe section  102 B. It will be noted that the vent pipe section  102 A will need to be slightly rotated from the position shown in FIG. 1 in order to engage the second vent pipe section  102 B. After the sections  102 A and  102 B are aligned for engagement, the vent pipe sections  102 A and  102 B are pushed towards each other, causing the engaging tabs  114 A to slide into the entry areas  108 B until the female end  106 A overlaps the male end  104 B. Next, the first vent pipe section  102 A is rotated in a clockwise manner from a top down perspective of the vent pipe, causing the engaging tabs  114 A to slide into the slots  110 B of the male end  104 B. The slots  110 B allow the engaging tabs  114 A to travel through a limited angular rotation, at which point the engaging tabs  114 A will be fully engaged in the male slots  110 B. Preferably, the guides  107 A and  107 B, as well as the engaging tabs  114 A and  114 B are inwardly embossed. 
     In FIG. 2, the two vent pipe sections  102 A,  102 B are joined as the engaging tab  114 A is fully engaged into the slot  110 B (not visible in FIG.  2 ). The locking tab  116 A on the first vent pipe section  102 A is positioned directly over the tab-lock receptacle  112 B (not visible in FIG. 2) so that, when the locking tab  116 A is pressed inwardly by the installer, the first vent pipe section  102 A is locked or secured to the second vent pipe section  102 B. The installer can easily deform, or bend, the locking tab  116 A to extend inwardly because the vent pipe is made preferably made of a ductile material, such as sheet metal. The locking tab  116 A is configured so that the locking tab  116 A inelastically deforms when the locking tab  116 A is pressed with sufficient force. 
     FIG. 3 is an enlarged, detailed view of interlocked portions of the vent pipe sections  102 A,  102 B, shown in FIGS. 1 and 2. The locking tab  116 A has been bent inwardly into the tab-lock receptacle  112 B. Should an untwisting force be exerted on the gas vent pipe sections  102 A,  102 B, an edge of the locking tab  116 A will move into contact with the wall surface of the rectangularly formed tab-lock receptacle  112 B, resulting in an interference that prevents further untwisting of the pipe joint assembly until the locking tab  116 A is bent away from interfering engagement with the tab-lock receptacle  112 B. 
     FIG. 4 shows a pair of vent pipe sections  202 A,  202 B having a tab-lock fastener  200  also constructed in accordance with the present invention. A locking tab  216 A is located on female end  206 A of the first vent pipe section  202 A. A rectangular inward embossment forming a tab-lock receptacle  212 B is located on male end  206 B of the second vent pipe section  202 B. Upon assembly of the vent pipe sections  202 A and  202 B, the locking tab  216 A is bent inwardly to engage the tab-lock receptacle  212 B to secure the pipe joint sections  202 A,  202 B in the manner described above for FIG.  3 . For the embodiment of FIG. 4, the tab-lock receptacle  212 B is located away from entry area  208 B and slot  210 B. The tab-lock receptacle  212 B, the entry area  208 B and the slot  210 B form guide channel  207 B. The locking tabs  216 A,  216 B are oriented circumferentially to be positioned over corresponding tab-lock receptacles  2123 A,  212 B, and lockingly engaged therewith when the tab-lock fastener  200  is interlocked. 
     Shown in FIG. 5 is another embodiment of the present invention, a tab-lock fastener  300  formed on first and second vent pipe sections  302 A,  302 B. The design of the tab-lock fastener  300  allows an installer to pre-set a locking tab  316 A prior to assembling the joint section. Prior to assembly, the locking tab  316 A is pressed inwardly (typically about ¼ inch) and then female end  306 A of the first vent pipe section  302 A is slipped onto male end  304 B of the adjoining second vent pipe section  302 B as previously described for other embodiments described hereinabove and shown in FIGS. 1-4. The locking tab  316 A pressingly engages the male end  304 B of the second vent pipe section  302 B twisting the first vent pipe section  302 A relative to the second vent pipe section  302 B. The locking tabs  316 A,  316 B are oriented to extend in a longitudinal direction. 
     Upon fully twisting the first vent pipe section  302 A into a fully locked position, an edge  320 A of the locking tab  316 A travels past edge  309 B of the entry area  308 B, at which time the elastic memory of the locking tab  316 A causes it to extend into the entry area  308 B to lock the tab  316 A. Thereupon, any accidental disassembly of the first vent pipe section  302 A from the second vent pipe section  302 B is prevented by the interference of the locking tab edge  320 A encountering the wall edge  309 B of the entry area  308 B. As for the afore described other embodiments, one may disassemble the first vent pipe section  302 A from the second pipe section  302 B by lifting the locking tab  316 A out of the entry area  308 B using a prying tool such as a flat blade screwdriver or a small knife blade. For the embodiment of FIG. 5, a portion of the entry area  308 B acts as a tab-lock receptacle. Another way of stating this is that the tab-lock receptacle of the tab-lock fastener  300  is located on, or coincident with, the entry area  308 B. 
     In FIG. 6, another embodiment of the present invention, a tab-lock fastener  400  is shown formed on vent pipe sections  402 A,  402 B. A slotted hole  420 B is used in lieu of the inwardly embossed impression used for other embodiments on the male end of the vent pipe sections. Prior to assembly, a locking tab  416  is pressed inwardly (typically about ¼ inch) and female end  406 A of the vent pipe is then slipped onto male end  404 B of the adjoining vent pipe section. In slipping the female end  406 A onto the male end  404 B, engaging tabs  414 A slide into entry areas  408 B and the female end  406 A is rotated clockwise (from a top down perspective in FIG. 6) with respect to the male end  404 B. In twisting the first vent pipe section  402 A with respect to the second vent pipe section  402 B until the tab-lock fastener  400  is fully engaged, the locking tab  416 A travels over a ridge of receptacle  412 B. The receptacle  412 B contains a slot  420 B sized to permit entry engagement by the locking tab  416 A. After the female end  406 A is twisted over the ridge of the receptacle  412 B past the slot  420 B, the female end  406 A is then reverse rotated so that the locking tab  416 A slips into the slot  420 B. The full engagement of the locking tab  416 A in the slotted hole  420 B prevents inadvertent disjoinder of the tab-lock fastener  400 , while providing for disassembly of the vent pipe sections  402 A,  402 B as may be desired. 
     To disassemble the vent pipe sections  402 A,  402 B, the female end  406 A is rotated clockwise slightly to disengage the locking tab  416 A from the slot  420 B; the locking tab  416 A is pried outward; the outwardly embossed receptacle  412 B is depressed with a prying tool such as a screwdriver; the female end  406 A is rotated until the engaging tabs  414 A align with the entry areas  408 B; and the female end  406 A is removed from the male end  404 B. 
     FIG. 7 is an enlarged, detailed view showing the engaged locking tab  416 A of the tab-lock fastener  400 . An edge  422 A of the locking tab  416 A is shown engaged in the slot  420 B. The locking tab  416 A is shown in a dashed line because the locking tab is not itself visible when the locking tab  416 A is engaged in the inwardly-embossed receptacle  412 B. 
     Each of the embodiments shown in FIGS. 1-7 represent a ductile pipe that is single-wall and, as well, double-wall ductile pipe, such as B-vent, Direct-Vent, or factory built chimney pipe. For the double-wall embodiments, only an outer wall is visible in FIGS. 1-7. 
     The present invention is not limited by the kind of pipe on which the tab-lock fastener is used. For illustration purposes only, one typical vent pipe is shown in cross-section in FIG.  8 . Shown therein is a cross-section of a double-wall vent pipe  500  having an inner wall  502  and an outer wall  504 , there being an annular space  506  formed between the inner and outer walls  502 ,  504 . The inner wall  502  of the vent pipe  500  is supported concentrically by a spacer (not shown) inside the outer wall  504 . For some applications, such as in the instance of chimney pipe, the annular space  506  contains an insulation material  508 ; in some other cases, the annular space may be air. Typically both the inner and outer walls are made of a ductile material; sometimes, the inner and outer walls will be made of the same material, while in other cases, the inner wall may be made of different materials, for example, the inner wall may be made of aluminum while the outer wall is made of steel. 
     Shown in FIG. 9 is a typical installation incorporating the present invention. Shown therein is a sealed combustion appliance, such as a decorative fireplace  600 , having a double wall vent pipe  602  that has been made up of vent pipe sections of the type described hereinabove. The vent pipe  602  is connected to the fireplace  600  and extends to an exterior wall  604  (or to a ceiling or roof) to vent combustion gases and to entrain air to support combustion. The fireplace  600  typically contains a fire chamber in which a gas flame is supported on ceramic logs to generate heat for a living space. In the installation illustrated in FIG. 9, the double wall vent pipe  602  penetrates the exterior wall  604  of the living space. The combustion gases from the fireplace  600  are vented through a tubular space defined by an inner wall  606  of the vent pipe  602 . Air needed to sustain combustion is supplied to the fireplace  600  through an annular region defined between the inner wall  606  and an outer wall  608  of the vent pipe  602 . A vent cap  610  on the distil end of the double wall vent pipe  602  prevents birds, debris and other contaminants from entering the vent pipe  602 . 
     It is to be understood that, even though numerous characteristics and advantages of various embodiments of the present invention have been set forth in the foregoing description, together with details of the structure and function of various embodiments of the invention, this detailed description is illustrative only. Changes may be made in detail, especially in matters of structure and arrangements of parts within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed without departing from the spirit and scope of the present invention. 
     In addition, although the embodiments described herein are directed to a tab-lock fastener for vent pipe, it will be appreciated by those skilled in the art that the tab-lock fastener can be used for other devices without departing from the spirit and scope of the claimed invention.