Patent Publication Number: US-6708734-B2

Title: Vibrational removal of excess particulate matter

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to loading particulate matter into a plurality of moving cavities. In many industrial applications, it is desirable to load relatively fine particulate matter into a series of moving cavities at relatively high speeds. This loading is accomplished by dropping a precisely metered cascade of particulate matter into a preform holding the cavities. The cavities typically are formed between spaced-apart, solid components. While this approach is generally effective, it does suffer from some disadvantages. First, even with a large amount of material in the particulate matter cascade, it is not always possible to fill each cavity completely because the particulate matter does not always settle or compact completely into each cavity. Second, the particulate matter can settle on the solid components rather than fall into a cavity. This spilled material can interfere with the later sealing of the cavity. 
     The problem described above is particularly applicable to cigarette filter plug manufacture where it is well known to fill the cavities of a continuous filter preform with particulate matter such as carbon granules or some other smoke altering material prior to ultimate use in cigarette filters. These cavities are created between solid cellulose acetate plugs and are wrapped with a porous plug wrap paper. In the prior art, carbon granules deposited in the filter plug preform fill the majority of each cavity. However, it is desirable to maximize this filling as any empty space in a cavity adversely effects air flow in a finished cigarette. Air jets are used to clean the cellulose acetate material by removing any excess carbon granules therefrom. However, this procedure is somewhat unreliable to the extent of missing some of the granules on the cellulose acetate material and also unnecessarily removing some of the granules from the plug cavities. 
     SUMMARY OF THE INVENTION 
     Accordingly, one of the objects of the present invention is an assembly that enhances particulate matter retention during filling of a moving cavity of a filter plug preform. 
     Another object of the present invention is a method for enhancing retention of particulate matter in the cavities of a filter plug preform and for removing excess matter from the surface of the preform that includes the step of applying vibration to the preform in the vicinity where the particulate matter is deposited. 
     In accordance with the present invention, an assembly comprises a transport for continuously moving a filter plug preform in a downstream direction. A particulate matter supply is located in proximity to the transport, and a feed functions to deposit particulate matter from the supply into spaced apart cavities in the moving filter plug preform. A vibrator engages the filter plug preform on the transport to vibrate the preform and thereby enhance particulate matter retention in the cavities. 
     Preferable the vibrator is an ultrasonic vibrator such as an ultrasonic welder horn. Ultrasonic welder horns vibrate in excess of 20,000 cycles per second. Fundamentally, the vibration is subtle in nature and similar to that of a tuning fork. The present invention utilizes such intense controlled vibration as a cleaning tool, and the vibration is transferred to a filter plug preform as the preform moves along its path of travel during filter plug manufacture. 
     Particulate matter introduced to the vibrating filter plug preform bounce away from the preform and settle in designated surface cavities in the preform. The vibration functions to enhance particulate matter retention and also to remove a significant amount of any excess particulate matter from the preform. 
     Preferably, the assembly includes a vacuum source near the transport for removing any particulate matter and recycling that matter to the supply. Moreover, the ultrasonic welder horn may include a horn tip, and the horn tip may have a concave preform engaging surface. Such surface may extend less then 180° around the circumference of the perform cavity or more than 180°, as desired. Alternatively, the horn tip may have a convex preform engaging surface or a flat surface. 
     The particulate matter may comprise carbon granules loaded into the spaced apart cavities in a filter plug preform. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Novel features and advantages of the present invention in addition to those mentioned above will become apparent to persons of ordinary skill in the art from a reading of the following detailed description in conjunction with the accompanying drawings wherein similar reference characters refer to similar parts and in which: 
     FIG. 1 is a side elevational view of an assembly for enhancing carbon granule retention and for removing excess granules from a filter plug preform using an ultrasonic welder horn, according to the present invention; 
     FIG. 2 is a partial top plan view of the assembly of FIG. 1 showing the roller conveyor for the filter plug preform; 
     FIG. 2A is a sectional view taken along line  2 A— 2 A of FIG. 2; 
     FIG. 3 is a fragmental side elevational view of the ultrasonic welder horn and filter plug preform of FIG. 1, according to the present invention; 
     FIG. 4 is a fragmental side elevational view of a modified ultrasonic welder horn, according to the present invention; 
     FIG. 5 is a fragmental side elevational view of another modified ultrasonic welder horn, according to the present invention; and 
     FIG. 6 is a fragmental side elevational view of still another ultrasonic welder horn, according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring in more particularity to the drawings, FIGS. 1,  2  and  2 A illustrate an assembly  10  for enhancing the retention of particulate matter in the cavities  11  of a filter plug preform  12  and for removing any excess particulate matter therefrom. The term “preform” as used herein refers to a continuous rod of spaced apart wrapped solid segments  13  that form a plurality of open-topped cavities  11  there between. See FIGS. 2 and 2A. The term “particulate matter” refers to any granular material that one of ordinary skill in the art would recognize as suitable for use. Such materials include, but are not limited to, various forms of carbon and APS silica gel. Any reference herein to carbon should be broadly construed to include the term particulate matter. 
     Generally the filter plug preform includes cellulose acetate material segments  13  between the cavities  11 , and the objective is to fill the cavities with particulate matter such as carbon while ultimately keeping the cellulose acetate material free of carbon. Assembly  10  includes a particulate matter hopper  14  with a motor driven metering device  16  connected at the lower end of the hopper. Carbon granules  18  or a similar smoke altering material are metered and delivered to a feed tube  20 . Because the delivery is not stopped between cavities  11 , some excess granules  18   a  will be deposited on the cellulose acetate segments  11 . This excess material interferes with glue application at a later manufacturing step. 
     Filter plug preform  12  is continuously moved in a downstream direction by a transport  22  in the form of a conveyor belting  24 . The filter plug preform is conveyed by the transport below the feed tube  20 , and carbon granules  18  from the hopper  14  flowing through the feed tube are deposited in the cavities  11  of the preform. As the granules are deposited they rest within the cavities of the preform. Ultimately, the carbon laden preform cavities and adjacent cellulose acetate are fashioned into individual pieces for use in cigarette filters. 
     A vibrator  30  such as an ultrasonic vibrator, preferably the vibrational horn of an ultrasonic welder is positioned for engaging the preform  12  on the transport  22  and vibrating the preform to enhance carbon retention in the cavities  11 . The vibration further serves to remove a significant amount of any excess carbon granules  18   a  from the cellulose acetate  13 . It will be readily appreciated by one of ordinary skill in the art that a standard ultrasonic welder is not useful in the practice of the present invention as there is no need to join two components. Moreover, an ultrasonic welder includes an anvil as described in U.S. Pat. No. 5,772,814 against which the components to be joined are held together during a welding operation. As shown in FIG. 1, the ultrasonic horn  30  is secured to a mounting surface  32  by a motor driven lead screw  34 . The screw is journaled to support bearings  36  and is received within a carriage  38  of the welder. As a drive motor  40  is activated the lead screw turns in one direction or the other thereby moving the ultrasonic horn toward and away from the transport  22  and filter plug preform  12 . 
     Ultrasonic welders are old in the art and primarily used in welding operations to join multiple pieces of metal or plastic. Normally these welders vibrate in excess of 20,000 cycles per second. In the present invention the ultrasonic horn  30  is used as a tool to enhance retention of carbon granules in the cavities of filter plug preform  12  and also to remove excess carbon granules from the adjacent cellulose acetate material. U.S. Pat. Nos. 5,651,494, 5,772,814 and 6,089,438 describe ultrasonic welders and welding techniques in the traditional sense of welding several work pieces together. The content of each of these patents is fully incorporated herein by reference. 
     Assembly  10  may also include a vacuum  50  below transport  22  for receiving any excess carbon granules and recycling the granules back to hopper  14 . Alternatively, any excess particulate matter may be disposed of if recycling is not desirable. 
     Horn  30  includes a horn tip  60 , and the horn tip may have a concave preform engaging surface  62 ,  64  as shown in FIGS. 3 and 4. Concave surface  62  may extend less than 180° around the circumference of the preform, as shown in FIG. 3, and concave surface  64  may extend more than 180°, as shown in FIG.  4 . Alternatively, the horn tip may have a convex preform engaging surface  66 , as shown in FIG. 5, or a flat filter plug engaging surface  68 , as shown in FIG.  6 . 
     In operation, the horn  30  operates to settle the carbon granules in the cavities  11 . Also, the horn causes the cellulose acetate to vibrate whereby any carbon on this material simply bounces away from the filter plug. It should be noted that the practice of the present invention does not require the complete removal of all excess material  18   a  from each segment. The purpose of the present invention is met if a significant portion of such material is removed. After the cavities are filled with carbon and excess material is addressed as just described, cover flaps  70  on the sides of preform are folded over the cavities and the cellulose acetate and secured in place. 
     Although the present invention has been described in connection with exemplary embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without departing from the spirit and scope of the invention as defined in the appended claims.