Abstract:
A controllable device for applying a flowable material such as anti-seize composition to a workpiece utilizes a plurality of elongated nozzles insertably accommodated through a fixture plate to deposit such material onto the workpiece in a predetermined pattern. The fixture plate is provided with a corresponding number of apertures which accommodate different sizes and numbers of nozzles so that material may be applied to a large variety of workpieces without significant maintenance and modification to the device. The fixture plate is essential to define a predetermined clearance between an outlet through which the flowable material escapes from a nozzle and a surface onto which such material is applied and further cleans the nozzles in between application cycles to prevent overrun on to a workpiece surface. A corresponding method is provided which transfers flowable material from a storage reservoir to a plenum in flowable communication therewith which temporarily retains the material until an application cycle begins.

Description:
This patent claims priority to U.S. Provisional Application No. 60/101,491, filed on Sep. 23, 1998, entitled “Apparatus and Method for Controllable Application of a Flowable Material to a Workpiece”. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to an apparatus and method for even and controllable application of a flowable material to workpieces on assembly lines, such as automotive wheel hubs. More particularly, the present invention relates to a dispenser head assembly which employs a fixture plate for accurate and even application of a flowable material to a workpiece adjacent thereto. 
     BACKGROUND OF THE INVENTION 
     It is known in several industries, such as the automotive industry, to use sealants, adhesives, corrosion resistors and other flowable materials to accomplish various mechanical functions. Adhesives, for example, are often used on threads to prevent uncoupling between adjacent threaded components such as wheel studs and lug nuts. Corrosion resistant materials are likewise applied between wheel hubs and disc rotors to prevent hub/rotor misalignment and subsequent braking degradation. Use of such materials is desirable due to the low cost of the material in relation to the high cost of damage to vehicle components in the form of repair costs and legal liability. 
     As these industries demand and use more flowable materials during manufacture and assembly of parts, various methods have been developed to include application of the desired material to the object part as part of the assembly process, yet simultaneously retain the speed of production of the final product and minimize the cost thereof. Accordingly, equipment is constantly custom designed to not only address the general problem of how to consistently apply the flowable material, but also the specific problem of how to adapt the application method to a particular manufacturer&#39;s specifications. 
     In the past, such equipment has been designed to apply flowable products in an independent process rather than in an assembly-line type function. Heretofore, such application processes required modification in accordance with product specifications, which can vary from manufacturer to manufacturer and even within a manufacturer&#39;s own inventory. In order to change the process, the corresponding machinery which executed the process would likewise be modified from application cycle to application cycle. Subsequently, “down time” due to maintenance and modification of such machinery is prevalent, resulting in minimal production efficiency and maximum manufacturing costs. 
     Since the assembly line is pervasive in a multitude of industries and accordingly inherent to the proper and efficient production of a final product, it is desirable to provide a system which integrates the application method into an already existing manufacturing infrastructure. It is further desirable to design and construct appropriate corresponding equipment for accomplishing this task, wherein the machinery is easily customized to meet particular product specifications with minimal associated costs and complications. 
     The present invention provides an apparatus and method of applying a flowable material to a workpiece which can be integrated into an assembly line superstructure and which requires minimum maintenance and modification between application cycles. The apparatus is provided with easily machineable, replaceable and interchangeable parts which provide application capability to a multitude of workpieces without requiring modification of the parts from workpiece to workpiece, such that most workpieces can be processed using this technology. 
     SUMMARY OF THE INVENTION 
     One advantage of the present invention is the provision of a device which can be controlled to apply flowable material to a workpiece in a desired pattern. Such a device is desirable because it enables application to a variety of products in a precise, well-defined and repeatable manner. 
     Another advantage of the present invention is the use of a plurality of removably attached machined tubes or nozzles which deliver flowable material to a workpiece. Such tubes are desirable so that they may be easily replaced by tubes or nozzles of similar or different parameters or easily interchanged with one another so as to reduce maintenance time between application cycles. 
     It is yet another advantage of the present invention to provide a fixture means, such as a plate, which incorporates a plurality of holes which telescopically intercept the tubes or nozzles therethrough. Such fixture means is essential to define a predetermined clearance between an outlet through which flowable material escapes a tube or nozzle and a surface onto which such material is to be applied. Failure to define this clearance will result in uneven application of the material and subsequent mechanical malfunction. Such fixture means is further desirable to clean such tubes or nozzles between each application cycle to prevent overrun onto a workpiece surface. Removal of excess material is effected with each linear actuation of the tubes through the apertures, providing a clean tube outlet prior to each material dispensation. 
     It is still another advantage of the present invention to provide an associated method of controllably applying flowable material using the disclosed apparatus. During such a method, flowable material which is stored in a storage reservoir is pumped by a first pump to a second pump in fluid communication therewith. The second pump pressurizes and transfers the material to a plenum where the material is temporarily retained. The plenum is linearly moved toward a surface of the fixture means so that the tubes or nozzles affixed thereon are telescopically intercepted by corresponding apertures in the fixture means to a height where a predetermined clearance between the tube outlets and the surface of the workpiece is defined. During the linear actuation, material which has overrun from the tubes is wiped away due to the close spacing of the apertures, permitting run-off of the excess material into a separate container. Material flows from the tubes and is applied to the workpiece in a predetermined pattern which corresponds to the arrangement of the tubes. The workpiece is removed for assembly further down the assembly line, and the plenum is linearly actuated away from the fixture means to complete the application cycle. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a schematic representation of a dispensing system utilizing the application apparatus of the present invention. 
     FIG. 2 shows a side view of a support structure supporting an application apparatus of the present invention. 
     FIGS. 3A and 3B show a top view and a cross-section, respectively, of a dispersion plate of a plenum used in an application apparatus of the present invention. 
     FIGS. 4A and 4B show a top view and a cross section, respectively, of a manifold plate of a plenum used in an application apparatus of the present invention. 
     FIGS. 5A and 5B show a top view and a cross section, respectively, of a fixture plate used in an application apparatus of the present invention. 
     FIG. 5C shows a schematic of a top view of a fixture plate used in the present invention. 
     FIG. 6 shows a schematic view of a fixture plate and wheel hub assembly subject to an application process using the application apparatus of the present invention. 
     FIG. 7 shows the fixture plate and wheel hub of FIG. 6 in combination with a plenum having a plurality of flowable material conduits passing through said fixture plate. 
     FIG. 8 shows the fixture plate of FIGS. 6 and 7 removed from said plenum wherein flowable material which overflows from said plenum is caught in an adjacent catch basin. 
     FIG. 9 shows a wheel hub having a plurality of bores with a plurality of beads of flowable material applied on a face thereof. 
     FIG. 9A shows the wheel hub of FIG. 9 wherein said beads of material become a thin fluid film after torquing. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the present invention, a dispense head assembly dispenses a controlled plurality of “dots” or “beads” of flowable material, such as anti-seize material, onto a workpiece, such as a hub face. Within this assembly, a positive displacement pump injects a controlled and repeatable amount of the material into a series of precision located and machined tubes, nozzles or the like (collectively referred to as “tubes”) that vary in flow area. The tubes are fed flowable material from a common plenum for distribution of “dots” of material, the position and location of which are controlled by the tubes. A linear motion moves the tubes through a fixture plate which is adjacent the plenum during the dispense process. The tubes project up through the fixture plate to accurately locate the tubes in relation to the hub face, ensuring a predetermined, repeatable gap between the tubes and the hub. By creating sufficient flow resistance and fluid back pressure, this gap establishes a uniform plenum pressure to ensure accurate and controllable dispensation of fluid to all tubes. The fixture also acts as a containment barrier to keep the work area clean of material which overflows from the tubes into a catch basin positioned near the dispense head assembly. 
     Now referring to the drawings, in which like elements are identically numbered, and particularly referring to FIG. 1, a dispensing system  1  for applying a flowable material to a workpiece is shown having a pail pump assembly  2  and a dispense head assembly  10 . Pail pump assembly  2  includes a pail pump  3  which is a conventional pump known and used in the art. Pump  3  pressurizes and transfers flowable material  4  from a pail  5  containing flowable material  4  therein to line  7  which interconnects pail pump assembly  2  and dispense head assembly  10 . Such flowable material may be any material applied to a workpiece to perform its inherent purpose including anti-corrosion agents, lubricating agents and the like. Other flowable materials having other purposes and consistent with the operation of the present invention may also be utilized. 
     Material  4  is conveyed under pressure through route  7 , shown here as a fluid line, to dispense head assembly  10  from which it is subsequently applied to a work piece, shown herein as a wheel hub. Although a wheel hub is shown herein, it is understood that any workpiece conducive to the operation of the present invention may be used. Dispense head assembly  10  includes a positive displacement pump  11 , a plenum  13  for storing flowable material prior to its application to a wheel hub and a fixture plate  15  which facilitates delivery of material  4  to an adjacent wheel hub. Plenum  13  is provided with an array of custom-sized elongate flowable material conduits  17  assembled thereon. Conduits  17  convey flowable material in a predefined manner from the common plenum to a hub placed adjacent fixture plate  15 . 
     Each conduit  17 , which may be a tube, nozzle or the like, is configured and machined to correspond to the parameters of a workpiece which will receive the flowable material thereon. The conduits are given a predetermined arrangement which is sought to be applied to a workpiece. Conduits  17  are removably attached to an upper surface of common plenum  13  so as to facilitate easy modification of the dispenser head assembly. The conduits can be interchangeable with one another or replaceable by conduits of equal dimension or conduits of varying dimensions, depending on the size of the dot to be applied and the pattern needed to achieve adequate coverage over an area of a workpiece to be processed. In this manner, the number of conduits  17  and the dimensions thereof may be easily altered to conform to the specifications of a particular hub, for example, thereby enabling use of the application apparatus with most wheel hub types, regardless of source. 
     Plenum  13  and fixture plate  15  of dispenser head assembly  10  may be configured to support a hub  19  as shown in FIG.  2 . Plenum  13  is assembled upon a support structure  21  which includes a frame  23  and a slide  25  which permits linear motion of the plenum in relation to fixture plate  15 . Frame  23  can be mounted to a fixed foundation such as a table or floor plate to minimize the vibrations experienced in a frame attached thereto. Although support structure  21  is shown as a generally conventional structural assembly, it is understood that other support configurations conducive to proper operation of the present invention may be implemented. 
     Now referring to FIGS. 3A,  3 B,  4 A and  4 B, plenum  13  can be seen to include a dispersion plate  13   a  which serves as a top surface of plenum  13  and a manifold plate  13   b  which serves as a bottom surface of plenum  13 . Referring particularly to FIG. 3A, dispersion plate  13   a  is a substantially circular plate having a plurality of bores  14  which can accept a corresponding number of wheel studs  30  (shown in FIGS. 6 and 7) from a hub  19  therethrough. Dispersion plate  13   a  is additionally provided with a plurality of closely spaced orifices  18  through which a plurality of conduits  17  may be supported so as to draw a flowable material from within the plenum through the conduits for application to a hub face  19   a.    
     Further referring to FIG. 3B, a cross section of dispersion plate  13   a  is shown. Dispersion plate  13   a  is provided with a circumferential protrusion  20  having a sloped surface  22  defined thereon and through which a narrow passageway  24  is formed. Passageway  24  is sized and shaped so as to insertably accommodate a conduit  17  therethrough. Sloped surface  22  allows any flowable material which a escapes from an outlet of conduit  17  to run off dispersion plate  13   a  due to gravity. The inclusion of a sloped surface eliminates the probability that overflowing material will be applied to a work piece during a dispense cycle, thereby reducing the likelihood of misapplication and subsequent mechanical malfunctions. 
     In dispersion plate  13   a , orifices  18  are sized, spaced and numbered to permit alteration of the number and arrangement of conduits  17  as they correspond to the specifications of the particular workpiece being worked upon. It is desirable to provide such orifices in a manner which will allow conduits  17  to be configured and subsequently modified so as to accommodating any changes in workpiece specifications which may occur between application cycles. In this manner, it is not necessary to disassemble the application apparatus every time a new type of wheel hub is selected to receive application of a flowable material. It is only necessary to change the location, size and or number of the conduits to correspond to the proper application pattern. 
     Referring particularly to FIGS. 4A and 4B, manifold plate  13   b  is a similarly substantially circular plate having a plurality of through bores. Through bores  12  provide adequate spacing and accommodation for affixing plenum  13  to a support structure  21 , such as is done by a threaded fastening element, rivet or the like (not shown). However, fastening of plenum  13  to an accompanying support structure can be effected by any means conducive to the operation of the present invention. 
     Manifold plate  13   b  is also provided with at least one inlet port  26  through which flowable material  4  enters prior to application to a wheel hub. Port  26  is sized and configured to accommodate pressurized fluid material  4  as it is pumped from pump  11  into plenum  13 . Plenum  13  acts as a temporary reservoir just between dispense cycles wherein flowable material enters, is stored for a short duration and is almost immediately dispensed through conduits  17  to a wheel hub. Thus, inlet port  26  must allow conduits  17  to draw material  4  from plenum  13  under a pressure suitable for a predefined application pattern to be duplicated from workpiece to workpiece. 
     Dispense head assembly  10  further includes a fixture plate  15 , shown in FIGS. 5A,  5 B and  5 C. Fixture plate  15  is a substantially circular plate which generally conforms to the geometry of a hub  19  placed adjacent thereto. Fixture plate  15  includes a top surface  32 , a bottom surface  34  and a circumferential wall  36  extending therebetween. A recessed portion  38  is offset from a plane in which top surface  32  is defined by a distance which accommodates placement of similarly shaped wheel hub  19  therein. 
     Referring particularly to FIGS. 5C and 6, a plurality of through bores  40  are defined through fixture plate  15  which accommodate wheel studs  30  of hub  19  during a dispense cycle. The fixture plate fixes the dispersion plate  13   a  of the plenum accurately in relation to the hub so as to provide acceptance for lug nuts. Fixture plate  15  is further defined as having a plurality of closely spaced apertures  42  which corresponds to an array of material conduits  17  having common plenum  13 . As the number of conduits  17  may be altered to correspond to the geometry and specifications of a particular wheel hub, so can the number and size of apertures  42  be altered accordingly. It is desirable to permit such changes in the fixture plate so that only the fixture plate  15  needs to be changed in accordance with a change in wheel hub geometry. The entire apparatus does not need to be disassembled or maintained separately, thereby accommodating most of the wheel hub types used in the industry and simultaneously reducing the time and cost associated with an application procedure. It is understood that apertures  42  are registrable with conduits  17  to ensure proper alignment thereof. 
     Having described the components of the dispense head assembly  10  of the present invention, the details of the preferred embodiment of the invention as well as its operation, may be described with respect to FIGS. 6-8. 
     To begin a dispense cycle, a pail pump  3  (shown in FIG. 1) pumps a flowable material  4  stored in a pail  5  through line  7  to positive displacement pump  11  of dispense head assembly  10 . Positive displacement pump  11  pumps material  4  into plenum  13 , connected thereto. Material  4  enters plenum  13  through an inlet port  26  defined in manifold plate  13   b . Material  4  enters conduits  17 , which act as needles that apply the material to an adjacent wheel hub in dots or beads according to the application pattern defined by a predetermined conduit array determined by the specification of the workpiece being processed. 
     Now referring to FIG. 6, a wheel hub  19  having studs  30  is located adjacent a fixture plate  15  such that hub face  19   a  is adjacent top surface  32 . Hub  19  is positioned accurately above fixture plate so as to define a predetermined clearance c. Predetermined clearance c is distance between a bottom surface of a workpiece (i.e. hub face  19   a ) and top surface  32  of fixture plate  15 . Proper definition of this clearance distance is essential to even and predictable application of the flowable material to hub face  19   a  in the desired application pattern. Without this clearance, the material will be improperly applied to the hub, resulting in an imbalance of the hub with respect to the fixture plate, improper location of flowable material thereon and subsequent functional flaws in the wheel hub assembly. After positioning is complete, wheel hub  19  is affixed to fixture plate  15  so as to maintain such predetermined clearance and prevent dislocation of wheel hub  19  in relation to fixture plate  15 . 
     After wheel hub  19  has been properly positioned, plenum  13  is linearly moved so that conduits  17  are inserted through and retained in apertures  42  (See FIG. 5A) in fixture plate  15 , as shown in FIG.  7 . Conduits  17  enter through bottom surface  34  and extend through top surface  32  of fixture plate  15 . Conduits  17  are fabricated and arranged so as to correspond to the configuration of the hub  19  and controllably apply flowable material  4  to hub face  19   a . The conduits  17  are provided with an outlet  17   a  from which flowable material is dispensed. Outlet  17   a  is located a predetermined distance from hub face  19   a  which is less than the predetermined clearance c, so that material flowing therefrom is accurately dispensed thereon. This predetermined distance is defined as the distance between hub face  19   a  and outlet  17   a  which results in dispersion of flowable material in a bead like formation in a pattern corresponding to the conduit array. Linear movement of the conduits in relation to the fixture plate can be effected manually or automatically by any suitable means, such as a machine-operated slide. 
     Conduits  17  inject material  4  from plenum  13  onto hub face  19   a . By setting the conduits at the precise height to get a predetermined clearance distance, even application of the material onto the hub face is achieved in the desired pattern. The material is pumped and placed on the hub face in beads or dots  50 , as shown in FIG.  9 . After application of the dots, a disc brake rotor and a wheel may be assembled with the wheel hub. Lug nuts are coupled with the wheel studs  30  of hub  19  and accordingly torqued. Due to the torquing, the dots  50  of material  4  are “compressed” into a thin fluid film  52  which covers the surface area of hub face  19   a . Spacing of the dots  50  is precisely determined prior to application so that this “spreading out” of the dots will create film  52  without overrun. 
     After a dispense cycle is completed and the application apparatus is in an “off dispense” mode, flowable material  4  remains under pressure in the plenum and contains air therein. Therefore, the material tends to “drool” out of conduits  17 , as shown in FIG.  8 . The close spacing of apertures  42  in fixture plate  15  enable the fixture plate to clean the material conduits between dispense cycles to prevent overrun of material onto a hub face  19   a . As plenum  13  is raised toward fixture plate  15  during a dispense cycle, fixture plate  15  cleans the outlet  17   a  of each conduit  17  so that there is no overrun of material. The conduits, then, are cleaned during each dispense cycle. Overflowing material which escapes from plenum  13  runs off sloped surface  22  and is retrieved in a catch basin  60  adjacent thereto. 
     Thus, the disclosed application apparatus and associated technique allows for a precise, repeatable and controlled method of placing metered material onto the hub at discrete locations. Application machines can be custom designed to meet the requirements of each hub configuration so that most hubs can be processed using this technology. Thus, it would only be necessary to change the set-up of the detachable components such as the fixture plate and the material conduits without effecting a major reconfiguration of the system as a whole, thereby lowering assembly and maintenance costs and reducing lag time between dispense cycles. 
     Various changes to the foregoing described and shown structures would now be evident to those skilled in the art. Accordingly, the particularly disclosed scope of the invention is set forth in the following claims.