Abstract:
A pulley tensioner for applying torque or tension to a pulley includes a spring system configured to encircle the periphery of the pulley. The spring system is anchored to the pulley housing or some other fixed location. The spring system is made up of one or more coil springs which are wrapped around the periphery of the pulley. Where multiple springs are used, preferably each spring has a different spring constant and length. This allows the operator to select the desired tension depending upon the operating parameters of the printer. The applied tension may be further modified/tuned by using an additional spring member to anchor the spring system to the pulley housing or some other fixed location.

Description:
This is a continuation of copending application Ser. No. PCT/US98/09644 filed May 11, 1998. 
     CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Patent Application claims the benefit of U.S. Provisional Application No. 60/046,538 filed May 15, 1997. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to tensioner apparatus. In particular, the disclosure relates to ribbon supply tensioners for use in printing apparatus. 
     2. Description of the Related Art 
     In modern printers, a variety of feed and take-up mechanisms are required to be driven and/or wound in order to transport printing media, ribbon, backings, etc. In most applications, these feed and take-up mechanisms require tensioning structure to maintain a desired amount of tension on the transport system and to minimize or eliminate roll out. One structure used in the art to provide tension is a clutch mechanism. Such a mechanism typically includes a friction plate intended to impart a predetermined torque to the feed and/or take-up mechanisms during operation. See, for example, U.S. Pat. No. 4,797,690. Although adequate for their intended function, these clutch mechanisms are typically expensive and require several assembly/adjustment steps to insure proper operation. 
     One simple and inexpensive tensioning mechanism is the wrapped coil spring developed by Fargo Electronics Inc. for a ribbon supply system in the Prodigy Plus™ thermal transfer printers. In that system, a single coil spring was wrapped around a pulley connected to the ribbon supply system. Each end of the spring was anchored to the housing such that about 180° of the periphery of the pulley was continually engaged by the spring. In this manner, a continuous tensioning was applied and was directly proportional to the spring constant K of the coil spring and the length of extension. While this system was adequate and inexpensive, it did not allow for adjustments for different media and gave little or no recoil when the pulley direction was reversed. Thus, wrinkling and/or tearing or the ribbon supply could result. 
     Accordingly, a need exists in the art for a simple, versatile, adjustable tensioning system which is configurable for different media and can impart a useful degree of recoil regardless of rotational direction. 
     SUMMARY 
     A pulley tensioner for applying torque or tension to a pulley is disclosed which includes a spring system configured to at least partially encircle the periphery of the pulley. The spring system is anchored to the pulley housing or some other fixed location by either an elastic or inelastic member. The spring system is made up of one or more coil springs which springs are wrapped at least partially around the periphery of the pulley. In one embodiment it is contemplated that each spring has a different spring constant and length. This allows the operator to select the desired tension depending on the operating parameters of the printer. The applied tension may be further modified or tuned by using one or more springs to anchor the spring system to the pulley housing or some other fixed location. 
     This novel system provides a versatile torque adjustment capability while increasing desirable recoil in either forward or reverse rotational directions. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The objects and features of the present disclosure, which are believed to be novel, are set forth with particularity in the appended claims. The present disclosure, both as to its organization and manner of operation, together with further objectives and advantages may best be understood by reference to the following description, taken in connection with the accompanying drawings, in which: 
     FIG. 1 is a perspective view illustrating the pulley member incorporating the novel torque adjustment structure according to the present disclosure; 
     FIG. 2A is a plan view of color coded springs incorporating the spring system according to the present disclosure; 
     FIG. 2B is a plan view of the spring system according to the present disclosure configured to increase torque upon the pulley member; 
     FIG. 2C is a plan view of the spring system according to the present disclosure configured to decrease torque upon the pulley member; 
     FIG. 3A is a perspective view illustrating the pulley tensioner according to the present disclosure being utilized in the printing apparatus; 
     FIG. 3B is a perspective side view of FIG. 3A illustrating the pulley tensioner of the present disclosure being utilized in the printing apparatus; 
     FIG. 4 is an exploded perspective view of a printing apparatus illustrating the pulley tensioner mounted to a pulley housing according to the present disclosure; and 
     FIG. 5 is a perspective view of the pulley member of FIG. 1 with the novel torque adjustment structure including an alternate embodiment utilizing an attachment member. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiments of the disclosure, which are illustrated in the accompanying figures. Turning now to the figures, wherein like components are designated by like reference numerals throughout the various figures, attention is first directed to FIGS. 1-3. 
     A pulley tensioner  10  in conjunction with a pulley housing  12  is shown having an annular pulley member  14  in a rotational relationship with spring system  16 . Pulley member  14  includes an outer periphery  18  containing annularly spaced walls  20  for retaining spring system  16  therein. Pulley member  14  is rotationally coupled to pulley housing  12  through center hub portion  22  which rotates with pulley member  14  and is fixedly attached through a center of pulley member  14  by annular collar  24  and set screw  26 . Pulley housing  12  includes a spring system attachment hook  34  for fixedly attaching spring system  16  to pulley housing  12 . 
     Spring system  16  is in a rotational relationship with pulley member  14 , center hub  22  and ribbon supply hub  44 . Spring system  16  preferably includes a configuration set of three separate helically wound spring members  28 ,  30  and  32 , each having looped ends  36  for engaging other spring ends or for attachment to pulley housing  12 , as will be discussed in detail below. Spring members  28 ,  30  and  32  are sized to fit within outer periphery  18  and between annularly spaced walls  20  of pulley member  14 . As shown in FIG. 1, a looped end  36  of spring member  32  is fixedly attached to pulley housing  12  through attachment hook  34 . Spring system  16  may be coupled to pulley housing  12  by a variety of apparatus including but not limited to attachment hooks, detents, notches or clips. In the present embodiment, spring system  16  utilizes a configuration set having three separate spring members  28 ,  30  and  32 ; however, the present disclosure is also applicable to spring systems including one or more separate springs or elastic members fashioned in the same or similar manner described herein. 
     With particular reference to the spring system  16  as represented in FIGS. 1,  2 B and  2 C, three separate helically wound spring members  28 ,  30  and  32  are being utilized in a fashion which provides rotational force, i.e. torque, to pulley member  14  during rotation thereof. The use of three or more springs as part of the spring system  16  greatly increases the torque or degree of recoil imparted on pulley member  14  in both forward and reverse rotational directions. Each of spring members  28 ,  30  and  32  include looped ends  36  which include a loop of wire in an overlapping configuration which allows each loop end  36  to be joined to another looped end  36 . In the present embodiment shown in FIGS. 1 and 2B, looped ends  36  of spring member  28  are attached to the looped ends  36  of spring member  30  along the outer periphery  18  of pulley member  14 . In addition, corresponding looped ends  36  of spring members  28  and  30  are each coupled to a looped end  36  of spring member  32  while opposite looped end  36  of spring member  32  is anchored to attachment hook  34  of pulley housing  12 . In this arrangement, the torque imparted onto pulley member  14  can be altered dependent upon the configuration of spring members  28 ,  30  and  32  and corresponding spring dimensions and spring constants K associated with any of spring members  28 ,  30  or  32 . 
     With particular reference to FIGS. 1,  2 B and  2 C, the spring members  28 ,  30  and  32  of pulley tensioner  10  are arranged into two alternate configuration sets  56  and  58 , although any number of sets may be configured since spring members  28 ,  30  and  32  can all be interchangeably coupled together. The springs or elastic members disclosed throughout the present disclosure vary according to various spring dimensions such as spring length, wire gauge, number of coils and spring constants K. As such, the present embodiments through configuration sets  56  and  58  include spring members  28 ,  30  and  32 ; each having different spring attributes including different spring lengths and different spring constants K 1 -K 3 , although spring or elastic members of equal attributes is also contemplated. Each configuration set  56  and  58  imparts a different torque force upon pulley member  14 . The pulley tensioner  10 , as shown in FIGS. 1 and 2B, imparts upon pulley member  14  an increase in torque or recoil when spring members  28  and  30  are attached in an end loop  36 -to-end loop  36  fashion along outer periphery  18  of pulley member  14  with spring member  32  as an attachment spring member used to secure spring members  28  and  30  to attachment hook  34  of pulley housing  12 . Similarly, but with a resulting decrease in torque or recoil to pulley member  14 , FIG. 2C shows spring members  28  and  32  in an end loop  36 -to-end loop  36  attachment along outer periphery  18  with spring member  30  as the attachment spring member. Dependent upon the configuration of spring members  28 ,  30  and  32 , pulley member  14  experiences either an increase or decrease in rotational torque. The amount of torque or recoil imparted upon pulley member  14  is dependent on the particular spring dimensions including corresponding spring constants K attributable to the type of springs making up spring system  16 . While any number of springs may be used to make up a configuration set of spring system  16  of the present disclosure, the above mentioned preferred embodiments utilize spring members  28 ,  30  and  32  coupled to one another in interchangeable fashion as is shown in FIGS. 1,  2 B and  2 C. 
     In another preferred embodiment, the individual spring members  28 ,  30  and  32  of spring system  16  are color coded or contain other indicia pertaining to respective length, dimension, force, spring constant K or other measurable attributes. In this manner, choice as to relevant configuration sets of spring members  28 ,  30  and  32  is made readily apparent. For instance, as is shown in FIG. 2A, spring members  28 ,  30  and  32  are color coded where S represents silver and Y represents yellow, although any color combination is contemplated. A color code, such as depicted in FIG. 2A, allows a user to readily recognize and configure respective configurations of the spring system  16  to achieve the desired increase or decrease in torque imparted upon pulley member  14 . 
     In alternate embodiments, the spring system  16  of the present disclosure can include varying elastic, as well as, non elastic members. For instance, as shown in FIG. 5, spring system  16  may be fixedly attached to attachment hook  34  of pulley housing  12  with attachment member  33 . Attachment member  33  may be constructed of elastic materials such as rubber products or spring-type metals. Attachment member  33  may also be constructed of inelastic materials such as cable, wire, rope and the like. Similarly, the entire spring system  16  may include individual spring members constructed of elastic materials other than helically wound spring members such as leaf springs, rubber members, spring-type metals and the like. It is also contemplated that attachment member  33  may include multiple spring, elastic or inelastic members. 
     With reference to FIGS. 3A and 3B, a preferred embodiment of pulley tensioner  10  according to the present disclosure is shown in conjunction with a printing apparatus  40 . As is shown in phantom in FIGS. 3A and 3B, pulley tensioner  10  operates opposite ribbon supply hub  44 . The pulley tensioner  10  of the present disclosure is specifically designed to provide rotational torque to ribbon supply hub  44 . Printing apparatus  40  includes both ribbon supply hub  44  and media supply hub  46 , as well as, ribbon rewind hub  42  and media rewind hub  48 . In operation, printing apparatus  40  utilizes both media  47  and ribbon  45  supply to create a printed image or label. In that regard, both the media  47  and ribbon  45  must be drawn from their respective hubs  44 ,  46  through the printing head  50  and back into the take-up or rewind hubs  42 ,  48 . In printing apparatus  40 , the tension or rotational torque associated with ribbon supply hub  44  is an important feature of the printing process, in that, proper torque and tension results in less jamming or wrinkling of printing ribbon  45  when being wound or unwound from ribbon supply hub  44 . Pulley tensioner  10  provides torque to ribbon supply hub  44  during both supplying (forward rotation) and rewinding (reverse rotation) of printing ribbon  45  through printing head  50 . Specifically, the present embodiment is directed to providing rotational torque or recoil to ribbon supply hub  44 , although it is contemplated that the present disclosure could also be applicable to media  47  and media supply hub  46  or any other similar hub or pulley arrangement. 
     With reference to FIGS. 2B,  2 C and  4 , a perspective view of printing apparatus  40  and pulley tensioner  10  according to the present disclosure is shown. Pulley housing  12 , as well as, attachment hook  34  are fixedly attached to printer housing  41  and include through holes for the passage of ribbon supply hub  44  and ribbon rewind hub  42 . Bracket  55  is used to space pulley housing  12  outwardly from printer housing  41  along ribbon supply hub  44  and ribbon rewind hub  42 . Pulley  14  is attached to center hub portion  22  of ribbon supply hub  44  through a connecting assembly  52  including a series of bearings, washers and spacers, as is known in the art. Pulley tensioner  10  also includes sensor  53  for sensing the amount of ribbon being displaced by printing apparatus  40 . Center hub portion  22  includes a tapered end portion having a flat surface for acceptance of annular collar  24  and set screw  26  for fixedly coupling pulley member  14  to center hub portion  22 . As was previously described, pulley member  14  includes spring system  16  and a configuration set of spring members  28 ,  30  and  32  each having different spring dimensions and spring constants K 1 -K 3 . This set of spring members  28 ,  30  and  32  can alternatively be configured for either increasing (configuration set  56 ) or decreasing (configuration set  58 ) the amount of torque transferred from spring system  16  to pulley member  14 . 
     In operation, the pulley tensioner  10  of the present disclosure can be specifically adjusted dependent on the degree of torque or recoil required with the particular ribbon  45  or media  47  being utilized within printing apparatus  40 . Dependent upon the requirements of the particular printing process of printing apparatus  40 , the torque imparted upon pulley member  14  can be easily adjusted by simple rearranging or replacing of a configuration set of springs making up spring system  16 . Adjusting or fine tuning the amount of torque or recoil imparted upon pulley member  14  and consequently upon ribbon  45  is accomplished by several simple steps. First, the printer cover (not shown) is removed from printing apparatus  40  to thereby gain access to pulley tensioner  10 . Second, the existing spring or elastic system is removed from pulley member  14  and pulley housing  12 . Third, an alternate configuration set of springs or elastics having the desired torque effect is installed onto pulley member  14  and pulley housing  12 . Examples of configurations sets are shown in FIGS. 1,  2 B and  2 C, although any other configuration set of springs or elastic materials is also contemplated. Lastly, the printer cover is replaced to complete the process. 
     As best seen in FIGS. 1,  2 B- 2 C, and  5 , the simple rearrangement of spring members  28 ,  30  and  32  can increase or decrease the torque imparted upon pulley member  14 . Similarly, a substitution with attachment member  33  which can be constructed from a variety of materials, as described earlier, will also impart specific forces upon pulley member  14 . As can be said with all configuration sets making up the spring systems associated with pulley tensioner  10 , the actual torque forces imparted from the spring systems to pulley member  14  can be pre-calculated and known prior to installation of the particular spring system. This would give a user of pulley tensioner  10  the ability to choose the specific amount of torque or recoil needed for a particular printing process. 
     The aforementioned embodiments describe pulley tensioner  10  in use with printing apparatus  40 ; however, the present disclosure is also applicable with other systems or apparatus requiring the use of a pulley tensioner system requiring adjustable torque or recoil response. 
     It will be understood that various modifications may be made to the embodiments disclosed herein. For example, the pulley tensioner of the present disclosure may also be used with multiple pulley configurations and multiple spring systems. Therefore, the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.