Abstract:
A strip of drywall tape is simultaneously coated on its opposite front and rear surfaces as the tape is applied to a corner joint formed between a pair of abutting wall boards such as drywall panels. A tape guide provided on a drywall taping head guides a folded strip of drywall tape over a first reservoir of flowing drywall compound. The compound flows through the first reservoir and against the V-shaped front surface of the tape. The compound continues to flow over and around the front surface and over the rear surface of the tape and laterally into a pair of secondary reservoirs.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to a tool for coating both sides of a strip of drywall tape with drywall joint compound, and relates in particular to an applicator head which simultaneously distributes pressurized joint compound directly to an exposed or outer surface of a drywall tape and to an underside or inner surface of a drywall tape as the applicator head is moved over a corner joint. 
     2. Description of Prior Developments 
     The joints formed between adjoining drywall or wallboard panels are generally covered with a lamination of joint compound and fibrous drywall tape to hide the cracks defined by and between the abutting panels. Joint compound and tape are typically applied manually by trowel or by a pressurized hand-operated tape and compound applicator to lay down a thin layer of compound and tape over each joint. The compound is typically applied only to that side of the tape which faces the wallboard panel. 
     Once the initial layer or coat of joint compound and tape is applied, it is smoothed over with a tool, such as a roller, and allowed to dry overnight. A relatively narrow and thin coating of joint compound is subsequently applied over the initial lamination of joint compound and tape using a trowel or a pressurized joint compound applicator. This second operation covers the exposed or outer side of the drywall tape and sandwiches the tape between the first layer of joint compound and the newly applied layer. 
     This second layer of joint compound is then allowed to dry. After it dries, a third wider layer of joint compound is then applied over the second layer. Sanding is then required to smooth over the joint. 
     Such prior methods are not only time consuming, but are also labor intensive and require considerable skill to achieve a smooth taped joint. Particular skill is needed to apply tape and compound over a corner joint. Accordingly, a need exists for a method and apparatus which reduces the time and effort required to form a finished wallboard joint having a wallboard tape sandwiched between two layers of wallboard compound during a single stroke of an applicator. 
     A further need exists for a method and apparatus for simultaneously applying wallboard compound to both sides of a wallboard tape as the wallboard tape is pressed against a joint between abutted wallboard panels. 
     A further need exists for such a method and apparatus which applies tape and compound to corner joints in a single application requiring no further application of compound to complete the taped joint. 
     The aforementioned objects, features and advantages of the invention will, in part, be pointed out with particularity, and will, in part, become obvious from the following more detailed description of the invention, taken in conjunction with the accompanying drawings, which form an integral part thereof. 
     SUMMARY OF THE INVENTION 
     The present invention has been developed to fulfill the needs noted above and therefore has as an object the provision of a method and apparatus for applying drywall compound to both sides of a wallboard tape as the tape is applied to a wallboard joint. 
     Another object of the invention is the provision of a method and apparatus for forming finished wallboard joints in a single step wherein wallboard compound is simultaneously applied to both sides of a wallboard tape as the tape is dispensed through an applicator and over a wallboard joint. 
     Yet another object of the invention is to provide such a method and apparatus for applying wallboard tape and compound to a corner joint where wallboard panels meet at substantially right angles. 
     These and other objects are achieved with the present invention which is directed to a method and apparatus for applying wallboard compound to front and rear sides of a wallboard tape as the tape is pulled through a taping applicator. Pressurized wallboard compound is fed to an applicator head through which a length of longitudinally-folded wallboard tape is guided. As the tape passes through the applicator head, wallboard compound is directed against the outer surface of the wallboard tape as well as around the outer surface of the tape and onto the rear or inner surface of the tape. 
     A pair of reservoirs or recesses is formed in the applicator head on both sides of the folded tape to apply a thin layer of joint compound over the tape and beyond the lateral edges of the tape. In this manner, a layer of joint compound is applied to the joint and laterally beyond the side edges of the tape so as to provide sufficient compound for a seamless laterally-tapered layer of joint compound. 
     The aforementioned objects, features and advantages of the invention will, in part, be pointed out with particularity, and will, in part, become obvious from the following more detailed description of the invention, taken in conjunction with the accompanying drawings, which form an integral part thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a schematic perspective view of a drywall tape and compound applicator constructed in accordance with the invention; 
     FIG. 2 is a partial perspective view of the applicator head of FIG. 1; 
     FIG. 3 is a view in section taken through section line  3 — 3  of FIG. 2; 
     FIG. 4 is a view similar to FIG. 3, showing a section of drywall tape as it passes through the applicator head in a folded V-shaped form; 
     FIG. 5 is a view similar to FIG. 4, showing the flow paths of joint compound over both sides of the drywall tape; and 
     FIG. 6 is a view in section through the joint of FIG. 5 after the application of drywall tape and compound. 
    
    
     In the various views of the drawings, like reference characters designate like or similar parts. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will now be described in conjunction with the drawings, beginning with FIG. 1 which shows a system  10  for applying drywall compound  12  to both sides of a drywall tape  14  as the tape is being applied to a joint  16  defined between a pair of abutting drywall or wallboard panels  18 . System  10  includes a pressurized source of drywall compound or “mud”  12  which may be mixed in a bucket  20  and pumped through a hose  22  in a known fashion. For example, motor  24  drives a pump  26  which receives compound  12  from a port formed in the bottom of bucket  20  in a manner such as that disclosed in U.S. Pat. No. 5,230,608 which is incorporated herein by reference. 
     The pressurized compound, which typically has a consistency similar to soft flowable putty, is driven through hose  22  into a hand-held nozzle  28  of the type used on garden hoses. Nozzle  28  is screwed into an applicator head  30  which will be described in more detail further below. A roll  32  of wallboard tape  14  is mounted to a pair of matched brackets  34  which are rigidly affixed to a mounting plate  36  mounted to the applicator head  30 . 
     A yoke  38  is attached to each bracket  34  for receiving an axle or shaft  40  which rotates along with the tape roll  32  in each yoke  38 . A roller  42  is also mounted between the brackets  34  on a fixed shaft  44 . The tape is dispensed from roll  32  over roller  42  and into an elongated guide slot  46  formed in a tape guide  100  provided on the applicator head  30 . As the tape  14  enters the guide slot  46 , it is longitudinally folded in half in a manner similar to that shown in U.S. Pat. Nos. 4,689,107 and 4,775,442 which are incorporated herein by reference. The tape  14  is guided through the guide slot  46  by a pair of guide surfaces which define a narrow elongated passage through applicator head  30 . This passage or slot is located along adjacent and parallel to the vertex of the V-shaped applicator head  30 . 
     As the tape  14  passes through the applicator head  30 , wallboard compound  12  is applied to virtually the entire surfaces of both sides of the tape. Wallboard compound  12  is also applied to both wallboard panels  18 ,  18  beyond the lateral edges  48 ,  48  of the tape  14 . In this manner, as the applicator head  10  is moved upwardly along joint  16  in FIG. 1, the wallboard tape  14  is laminated between thin layers of wallboard compound  12 . 
     If necessary, the laminated or layered tape and compound can be flattened against each wallboard panel  18 , 18  with a putty knife or trowel after the tape is severed or cut from the applicator head  30 . 
     As seen in FIG. 2, the applicator head  30  includes a generally V-shaped applicator body  50  which may be cast and/or machined from a metal such as aluminum or formed from a wear-resistant plastic material such as nylon or polycarbonate. Body  50  includes a pair of side walls  52 ,  54  which are disposed at a substantially right angle with one another so as to match the contour of a corner joint such as corner joint  16  formed between panels  18 ,  18  in FIG.  1 . 
     An inlet port  56  is formed through a central connector  58  mounted to the rear surface of body  50 . Port  56 , as seen in FIG. 3, communicates with a flow channel  60  which extends through connector  58 . The free end  62  of nozzle  28  may be threaded into grooves tapped into a bore  64  formed through mounting plate  36 . Bore  64  is aligned with an inlet  65  in channel  60  to allow compound  12  to pass through the nozzle  28 , mounting plate  36  and connector  58  and exit from port  56 . 
     A pair of guide walls  66 ,  68  formed in applicator body  50  extends along opposite sides of connector  58  and port  56  between a floor  70  and roof  72  which are also formed in the applicator body  50 . The walls  66 ,  68 , floor  70  and roof  72  define a first dispensing trough or reservoir  74  which first receives the compound  12  flowing through port  56 . 
     Second and third dispensing troughs or reservoirs  76 ,  78  respectively extending from guide walls  66 ,  68  communicate with the first dispensing trough  74 . The second and third troughs  76 ,  78  are respectively formed as recesses in side walls  52 ,  54  on opposite sides of the first trough  74 . 
     A pivoting frame  80  is mounted around body  50  in the same manner as that disclosed in aforementioned U.S. Pat. No. 4,767,297. Frame  80  includes a pair of upper frame members  82 ,  84 , a pair of side frame members  86 ,  88  and a pair of bottom frame members  90 ,  92 . The upper and lower frame members are rigidly interconnected to the bottom or lower frame members  90 ,  92  by the side frame members  86 ,  88 . 
     The bottom frame members  90 ,  92  are pivotally connected at their abutting inner ends on body  50  and biased outwardly by an internal spring as disclosed in U.S. Pat. No. 4,767,297, incorporated herein by reference. As the applicator head  30  is pressed against the wallboard panels  18 ,  18 , the frame  80  maintains biased contact against the panels with bottom frame members  90 ,  92  and side frame members  86 ,  88 . A pair of rollers  94 ,  96  is mounted to sidewalls  52 ,  54  to reduce friction as the applicator head rolls and slides over the panels  18 ,  18 . 
     An important feature of the invention is the provision of a tape guide  100  provided on the applicator head  30 . Tape guide  100  is formed as a thin slot having parallel side walls aligned in applicator body  50  at the juncture or vertex between side walls  52 ,  54 , and located above the first reservoir  74 . The tape guide  100  includes the guide slot  46  noted above. Guide slot  46  has an elongated narrow inlet and an elongated narrow outlet and a channel that extends completely through the tape guide  100  and communicates with the first reservoir  74 . 
     The tape guide  100  has a length and width sufficient to closely hold and guide a longitudinally doubled over or folded over length of tape  14  as shown in dashed lines in FIG.  2 . The tape guide  100  is located between the second and third reservoirs which are located laterally of the tape guide. 
     As the tape enters and leaves the tape guide  100 , it forms a bow tie shaped profile. As the applicator head  30  is manually pushed or pulled over joint  16 , the tape is pulled into slot  46  and is pinched longitudinally together as it enters slot  46  and converges and tapers into a flat doubled over folded shape. As the tape exits slot  46 , it diverges into a V-shaped profile as it is pulled over the V-shaped junction between the bottom frame members  90 ,  92 . Excess compound is scraped from the outer side of the tape as it slides over the frame members  90 ,  92  and excess compound is squeezed and scraped from the inner side of the tape as the inner side of the tape is pressed against panels  18 ,  18  by the frame members  90 ,  92 . 
     As seen in FIGS. 2 and 4, the tape  14  is folded and held in position by the tape guide  100  in a generally V-shaped profile as the tape is pulled over and in front of port  56  and the first reservoir  74 . As seen in FIG. 5, the compound  12  flows through nozzle  28 , mounting plate  36 , connector  58  via channel  60 , exits from port  56  and enters the first reservoir  74 . Some of the compound initially flows directly against the outer or upper surface  102  of the tape  12  and some compound flows over the inner or under surface  104  of the tape  12 . The compound then flows laterally past the edges of the tape via reservoirs or troughs  76 ,  78  to cover the wallboard panels  18 ,  18  as required to produce a smooth finished joint. 
     The folded V-shaped profile of the tape  12  passing in front of the first reservoir  74  is narrower than the width of the first reservoir  74 , i.e. narrower than the interior spacing between guide walls  66 ,  68 , so that the compound  12  which fills the first reservoir  74  flows both into the V-shaped pocket formed by the outer surface of the tape and also over and around to the inner side of the tape to cover the rear or inner side of the tape. The compound then flows laterally under pressure into the second and third reservoirs  76 ,  78 . In this manner, both sides of the tape are covered with compound. 
     The compound  12  which flows into the second and third reservoirs forms thin tapered layers of compound over the tape and panels. These compound layers extend laterally beyond the lateral edges  48 ,  48  of the tape, as shown in FIG.  6 . The laminated joint produced by tape  14  and compound  12  is somewhat thicker over the center folded portion of the tape and tapers laterally into a thinner layer of compound as the compound flows laterally outwardly of the central fold and beyond the side edges of the tape. These tapered layers of compound are formed naturally by the scraping and spreading action of the spring biased bottom frame members  90 ,  92  and are desirable for producing a seamless joint both over and beyond the edges of the compound-covered tape. As further seen in FIG. 6, the tape  12  is sandwiched or layered between two layers of compound  12  with a single stroke of applicator head  30 . A putty knife or trowel may be used to smooth out the tape and compound in a known fashion after it has been applied by applicator head  30 , but no additional application of compound is required. This results in a significant savings in time and labor. 
     There has been disclosed heretofore the best embodiment of the invention presently contemplated. However, it is to be understood that the various changes and modifications may be made thereto without departing from the spirit of the invention.