Abstract:
A dispenser for viscous, extrudable materials uses a sprocket-driven push chain that is drawn from a chain magazine responsive to actuation of a user trigger. The sprocket for the chain is driven by a toothed wheel, which is driven by a first, ratcheting drive pawl, which is actuated by the trigger. A second ratcheting locking pawl prevents the toothed wheel and hence the chain sprocket from rotating backward when the trigger is released. A single “button” or actuator can be actuated by one hand of a user while the user&#39;s other hand grasps a chain retractor to pull an extended chain back to a starting position whereat the dispenser can be reloaded.

Description:
RELATED APPLICATIONS 
     This application incorporates by reference the contents of co-pending patent application Ser. No. 12/684,597, filed Jan. 8, 2010, entitled “Rodless Dispenser.” This application also incorporates by reference the contents of co-pending patent application Ser. No. 12/703,613, filed Feb. 10, 2010, and which is entitled “Piston and Piston Rod for a Rodless Dispenser.” Also incorporated by reference is application Ser. No. 12/703,471 filed Feb. 10, 2010, and entitled, “Rodless Dispenser for Extrudable Materials Having a Contents Indicator.” 
     BACKGROUND 
     Mechanical dispensers for viscous or extrudable materials include common, piston-type caulking guns found in any hardware store as well as small, hand-held devices for rolling up a flexible tube, such as the tubes that dispense toothpaste. Most extrudable material dispensers employ a piston attached to one end of an elongated piston rod. The piston is advanced through a half or partial-cylinder holder, the shape of which is reminiscent of a trough, the function of which is to hold a cylindrical canister of extrudable material. 
     Extrudable material in a canister is forced from the canister through a canister tip by driving a canister-internal piston installed into the “bottom” of the canister. The piston in the bottom of the canister is hereafter referred to as a canister piston. 
     The canister piston drives extrudable material from the canister when the canister piston is driven through the canister by the piston attached to the piston rod. The piston rod is driven by a pistol grip mechanism that forms part of the dispenser. The pistol grip mechanism can be attached to either a ratcheting or ratchetless transmission device. Actuation of the pistol grip causes the piston rod to be advanced into the cylinder, which in turn drives the first piston (attached to the connecting rod) into the second piston (in the bottom of a canister of extrudable material) forcing extrudable material from the dispensing tube. As the first piston moves away from the transmission device and into the dispensing tube, extrudable material is forced from the tip of the canister. 
     A problem with prior art caulking guns or other dispensers for extrudable materials is that the push rod is relatively long and extends outwardly to make the dispenser unwieldy. The extended rod also makes the device difficult to store or set down between uses, especially when such devices are used in close quarters, as often happens when the devices are used in restaurants to dispense condiments and other extrudable food products. A dispenser for dispensing extrudable material which eliminates the push rod would be an improvement over the prior art. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a perspective view of an alternate embodiment of a rodless dispenser. 
         FIG. 2  is an exploded view of the rodless dispenser. 
         FIG. 3  is a left side view of a drive mechanism. 
         FIG. 4  is a right side view of the drive mechanism. 
         FIG. 5  is a perspective view of the right side of the drive mechanism. 
         FIG. 6  is a left side view showing the push chain, piston and drive mechanism. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , the rodless dispenser  100  is comprised of an elongated tube support  102 , a push chain drive mechanism  104  located inside a housing  106 . The housing  106  is attached to the elongated tube support  102 . A handle  108  is formed as part of or which is attached to the housing  106  and an actuating trigger  110 . The housing  106  has right and left substantially planar sides  107 ,  109 , which cover and protect components inside the housing  106 . A piston  112  is attached to and driven by a push chain, not visible in  FIG. 1 . At least part of the push chain is stored in a push chain magazine  114  attached to or formed as part of the tube support  102 . 
     When the trigger  110  is pulled toward or into the handle  108 , the piston  112  advances incrementally into the tube support  102 . When a tube of extrudable material is placed into the tube support, the piston  112  will drive the material from the tube so that the material can be dispensed. A pair of ratcheting pawls inside the housing, which comprise the drive mechanism, are configured to allow the piston to be advanced incrementally with each actuation of the trigger and held in position. The drive mechanism thus advances the piston yet prevents it from retreating in response to the opposing force that the piston “sees” when it pushes against extrudable material. 
     When the piston needs to be retracted, such as when a tube needs to be removed from the tube support, the ratcheting pawls are configured to be released together by a single actuator. The actuator that releases both pawls, and which releases the piston, is embodied as one end of a pawl that is configured to hold the piston in place. 
       FIG. 2  is an exploded view of the rodless dispenser  100 . The tube support  102  can be seen to be comprised of a roughly half cylinder or semi-cylinder  200  having first and second ends,  202 ,  204 . The push chain magazine  114  is formed from a trough  206  located at the bottom of the semi-cylinder  200 . A substantially round end panel  218  is sized, shaped and arranged to receive and be affixed to the first end  202  of the semi-cylinder  200 . The end panel  218  is considered herein to comprise a first end of the support tube  102 . A tube-retaining ring  220  having a centrally-located opening or hole  222  is attached to the second end  204  of the semi-cylinder  200  and forms a second end of the tube support  102 . 
     Several, substantially U-shaped push chain links  208  are joined to each other to form a push chain  210  having first and second opposing ends  212 ,  214 . The first end  212  of the chain  210  is attached to a bottom end of a piston rod  224 . The piston rod  224  is attached to the bottom side  226  of the piston  112 , i.e., the side of the piston  112  oriented toward the housing  106  and drive mechanism  104 . The first end  212  of the chain  208  and the piston rod  224  extend through a rectangular hole or opening  226  formed in the substantially circular-shaped end panel  218 . 
     Inside the housing  106 , the chain  210  and its links  208  wrap part way around a push chain sprocket not visible in  FIG. 2 , and extend into the magazine  114 . Inside the magazine,  114 , the second end  214  of the push chain  210  is attached to a substantially U-shaped push chain retractor  228 . 
     The U-shaped push chain retractor  228  is formed to fit over the vertical side surfaces  230  of the magazine  114 . The push chain retractor  228  is thus configured to be graspable, i.e., capable of being grasped, by a thumb and an index finger or other digit. The retractor  228  is also formed with a post or tab  232  that extends upwardly through an elongated slot  234  formed into the bottom surface  236  of the magazine  114 . Grasping the retractor  228  and sliding it or translating the retractor  228  back and forth along the length of the magazine  114  thus moves the chain  210  and its links  208  into and out of the magazine  114 , so long as the pawls described herein are disengaged to allow the chain to move freely. 
     Each of the chain links  208  is substantially U-shaped. Each link has a “first” side that opens into the U-shaped link. The first side is also sized and shaped to receive a “tooth” of a chain sprocket. A second side is substantially planar. 
     The links are sized, shaped and arranged such that the first sides of the links are able to rotate or fold toward each other, enabling the links and the chain they form to wrap around a chain sprocket. The first sides of the links are not able to rotate or fold away from each other in the opposite direction but instead lock to become rigid and substantially columnar, as long as the links are urged to rotate the open sides away from each other. 
       FIG. 3  is a side view of the drive mechanism  104 . The drive mechanism  104  is shown inside the housing  106 , but the left side  109  of the housing is shown as being removed in  FIG. 3  in order to reveal components of the drive mechanism  104 . 
     A substantially U-shaped horizontal axle support  300  is attached to and extends away from the first end  218  of the tube support  102  and part way into the housing  106 . The left and right (first and second) sides  302 ,  304  of the axle support  300  hold corresponding ends of a first axle  306 , which extends into the plane of  FIG. 3 . 
     The first end  308  of axle  306  is engaged with a hole or opening  310  formed into the first end  314  of the trigger  110 . The trigger  110  extends downwardly at an angle theta relative to the handle  108 . 
     The first end  314  of the actuating trigger  110  is formed or provided with a substantially U-shaped drive pawl support arm  318  having a slot between the opposing and substantially parallel sides  319  of the support arm  318 . The drive pawl support arm  318  and its sides  319  extend laterally away from the axle  306  and opening  310  in the first end  314  of the trigger  110  such that rotation of the trigger  110  around the axle  306  also rotates the entire drive pawl support arm  318  through the same angle of rotation. 
     The far or distal ends of the sides  319  of the drive pawl support arm  318  are provided with concentric holes  320  sized, shaped and arranged to receive a drive pawl support axle  322 . The drive pawl support axle  322  extends into both of the sides  319  of the U-shaped drive pawl support arm  318 . 
     The drive pawl  324  fits between the sides  319  of the drive pawl support arm  318 . The drive pawl  324  has a hole, not visible in the figures, through which the drive pawl axle  322  extends and by which the drive pawl  324  is rotatably supported in the drive pawl support arm  318 . Rotatably supported in the drive pawl support arm  318  means that the drive pawl  324  is able to rotate on, or rotate with, the drive pawl support axle  322  while the drive pawl  324  is inside the U-shaped drive pawl support arm  318 . 
     The drive pawl  324  has a first end  326  that is able to reach into and engage notches  328  in a fine-toothed drive wheel  330  responsive to the drive pawl rotation through the small angle. (The terms, “fine-toothed drive wheel” “drive gear” and “drive wheel” are used interchangeably hereinafter.) An opposing second end  328  of the drive pawl  322  extends downwardly from the drive pawl support arm  318 . 
     The toothed wheel  330  is circular. Its outside surface is formed or provided with equidistant, equally-spaced notches  328 . The drive pawl  322  is biased by a torsion spring  323 , best seen in  FIG. 4 , such that the first end  324  is normally engaged with a notch  328 . 
     When the second end  113  of the trigger  110 , which is attached to the first axle  306 , is pulled toward the handle  108 , the trigger  110  rotates around the geometric axis of the first axle  306 . Such actuation of the trigger  110  also rotates the drive pawl support arm  318  in the same direction. Rotation of the drive pawl support arm  318  in the direction of R will of course also rotate the drive pawl support axle  322  and the drive pawl  324  in the same direction. Since the first end  326  of the drive pawl  324  is biased to engage notches in the drive wheel  330 , rotation of the actuating trigger  110  around the first axle  306  rotates the drive wheel  330  in the same direction. The teeth in the drive wheel are cut or formed at an angle, such that the drive pawl is able to exert force on the drive wheel in one direction only. 
     As used herein, a ratchet is a mechanism comprised of a bar or pawl, which drops into successive inclined teeth of a gear so that one-way motion can be imparted to the gear by movement of the bar or pawl into the teeth of the gear. 
     The trigger  110  is biased by a spring  402  inside the handle and inside the trigger to move away from the handle  108 . The spring  402  is preferably a torsion spring, i.e., a spring that provides torque, but could also be provided by a compression spring, i.e., a spring that provides either a compressive force or a tensile force. 
     When the trigger  110  is pulled toward the handle  108 , the drive pawl engages a tooth in the drive gear and rotates the gear by the rotation of the trigger  110  around the axis of the first axle  306 . When the trigger is released, the drive pawl and the driver rotate in an opposite direction, however, because of the angle at which the teeth in the drive wheel are oriented, the first end of the drive pawl slips over the teeth in the drive gear without moving the drive gear. The drive pawl thus acts as a ratchet to the drive gear. Repeatedly squeezing the trigger  110  toward the handle  108  will thus rotate the drive wheel in one direction. 
     Still referring to  FIG. 3 , there is a second pawl  340  that is rotatably supported on a third axle. The third axle  346  is supported by the sides  107 ,  109  of the housing  106 . 
     The second pawl  340 , which is considered to be a locking/unlocking pawl, has a first end  342  that extends away from the third axle  346  and configured to extend into engagement with the notches  328  on the drive gear  330 . An opposite second end  344  of the second pawl  340  extends away from the third axle  346 . 
     The third axle  346  fits into a hole formed in the second pawl  340 . The third axle  346  rotatably supports the second pawl  340 . The third axle  346  also supports a bias spring  345 , which urges the first end  342  of the second pawl  340  into engagement with notches  328  on the drive gear  330  such that the first end  342  of the second pawl  340  provides a second ratchet for the drive wheel  330 . The second pawl  340  thus prevents the drive wheel  330  from “backing up” or reversing its rotation when the trigger  110  is released and moves away from the handle  108 . 
     The second pawl  340  is able to rotate through a small angle responsive to a compressive force applied to the second end  344  of the second pawl  342 . A compressive force, which can be provided by a user&#39;s finger or thumb, needs only be sufficient to overcome the bias applied to the second pawl  340  by the spring  345 . 
     The third axle  346 , which extends through the second pawl  340 , extends into and out of the plane of  FIG. 3 . The opposite ends of the third axle are supported in the right and left sides  107 ,  109  of the housing  106 . 
       FIG. 4  is a right-side view of the drive mechanism  104 . A bias spring  345  is wound around the third axle  346 . It provides a bias force that urges the first end  342  of the second pawl  340  into engagement with notches  328  in the drive wheel  330 . 
     As the second pawl is arranged and structured, the bias applied by the spring  345  maintains the first end  342  of the second pawl in contact with a notch  328 . The engagement of the second pawl to the toothed wheel  330  keeps the toothed wheel  330  from rotating backwardly, i.e., the second pawl limits the direction of rotation of the toothed wheel. As long as the first end  342  of the second pawl is engaged with a notch  328 , the toothed wheel  330  is unable to rotate against or counter to the direction that the toothed wheel is driven by the first pawl. In other words, the toothed wheel can only rotate in the “R” direction. 
     Both the first end  342  and the second end  344  of the second pawl  340  extend away from the third axle  346  but not necessarily in opposite directions. In a preferred embodiment as shown, the second end of the second pawl is curved such that the second end  344  of the second pawl is proximate to the second end  326  of the first pawl (not visible in  FIG. 4 ) such that depressing or forcing the second end  344  of the second pawl  340  inwardly as shown causes the second end of the second pawl into engagement with the second end  326  of the first pawl. 
     Pushing the second end of the second pawl such that the second end of the second pawl also pushes the second end of the first pawl inwardly, i.e., toward the first axle, causes the first end of both pawls to disengage from the respective notches in the drive wheel. Stated another way, the first end of the second pawl and the first end of the first pawl are both disengaged from the toothed wheel  330  when a force is applied to the second end of the second pawl sufficient to overcome the bias applied to both pawls by their respective actuating bias springs. 
     Referring now to  FIG. 5 , a toothed sprocket  360  is attached to and rotates with the toothed wheel  330  on the same first axle  306 . The second end  309  of first axle  306  is supported in the housing  106  by the second side  304  of the axle support  300 . 
     The sprocket  360  is formed to have sprocket teeth  362 , which are sized, shaped and arranged to engage or fit into the open or first side  402  of the U-shaped links  208  of the push chain  210 . The attachment of the toothed wheel  330  to the sprocket  360  means that rotation of the toothed wheel  330  will also rotate the sprocket  360 . As long as the first sides  402  of the push chain links  208  are engaged to the sprocket teeth  362 , rotation of the sprocket  360  will drive and retract the first end  214  of the push chain  210  into and out of the tube support  102 , pushing and pulling the piston  112  at the same time. 
     The links of the chain  210  are kept engaged to the sprocket and its teeth by two push chain retainers  404 ,  406 . In a preferred embodiment and as shown in  FIG. 5 , the push chain retainers  404 ,  406  are columns or pins that extend outwardly from at least one of the two sides  107 ,  109  of the housing  106 . Alternate embodiments include pads or tabs that extend over the push chain links just ahead of where the push chain links engage the sprocket teeth so that the chain links are able to travel past the retainers and engage the sprocket. 
     The push chain retainers  404 ,  406  are located relative to the sprocket and sprocket teeth in order to keep portions of the push chain  400  that wrap around the sprocket  360  in place, i.e., keep the chain links engaged to the sprocket teeth. The bottom or second push chain retainer  406  also functions to limit the rotational travel of the actuating trigger  110 . 
     As best seen in  FIG. 4 , portions of the push chain that extend outwardly or away from the sprocket, i.e., toward the first end of the tube support, are substantially straight. Those links, i.e., the ones beyond the push chain retainers, are considered herein to be “fully unfolded.” The fully unfolded links in the “top” portion of the chain, i.e., the portion of the chain that extends into the support tube  102 , are fully unfolded and able to support a compressive load, including the force applied to the first section of straight chain that extends from the top or first push chain retainer  404  forwardly to the second end of the push rod. Stated another way, the push chain retainers  404 ,  406  are located and fixed at locations along the length of the chain where the straight sections, i.e. the chain section inside the tube support and inside the chain magazine begin to bend around the sprocket. The links that engage the sprocket thus form a third intermediate or curving section of push chain links. The third or intermediate curving section is considered herein to be the number of chain links that are engaged with teeth of the sprocket. By virtue of their engagement with the circular sprocket, the links forming the intermediate section cannot be straight and are, in fact, curved. 
       FIGS. 3 ,  4  and  5  show a push chain guide  410 , best seen in  FIG. 5 . It is preferably embodied as a thin, flat curved strip of metal having a radius of curvature substantially equal to the radius of curvature described by the sprocket and push chain links engaged therewith. The opposing first and second ends  412 ,  414  of the push chain guide  410  are mounted to or attached to the two aforementioned push chain retainers  404 ,  406 . The push chain guide  410  facilitates “threading” or feeding the push chain  210  and its links  208  into engagement with the sprocket teeth during initial assembly of the drive mechanism  104 . At assembly the second end  214  of the push chain  210  can be fed or inserted into the opening in the first end  218  of the support tube  102  and then “fed” into engagement with the sprocket teeth. The push chain guide  410  thus ensures that the open sides  402  of the push chain links  208  will engage teeth  362  on the sprocket  360 . 
     Referring to  FIGS. 4 and 5 , actuating the second end  344  of the second pawl  340 , both pawls will disengage the toothed wheel, allowing the sprocket to rotate “backwardly” allowing the push chain  210  to be wrapped around the sprocket and have the second end  214  of the chain  210  pushed into the magazine  104 . When the entire length of the push chain  210  is installed, the piston rod is attached to the first end  212  of the push chain  210 . 
     For completeness,  FIG. 6  shows a side view of the rodless dispenser drive mechanism  104 , push chain  210  and piston rod  224  but with the push chain  210  removed from the magazine to show that the back or second sides of the links are able to provide a substantially straight, flat or planar surface when the first sides  402  of links  208  are rotated away from each other. The push chain  210  is shown as it would rest in the magazine  114 , with several links  208  that are adjacent to each other, “fully unfolded.” 
     When the open, first sides  402  of two more links are rotated away from each other to be fully unfolded, those chain links form a substantially straight and substantially column-like, rod-like structure. Such chain links are able to provide a compressive force along a line formed by the links that are unfolded, i.e., urged to rotate in a direction opposite the direction that the chain links are able to rotate toward each other. When the links are unfolded, the open or “first” sides  402  of each chain link  208  face upwardly. The opposing second sides  403 , which are shown as edges, are depicted by straight line segments of each link  208 . 
     The links  208  that are shown wrapped part way around the sprocket  360  are partly folded toward each other. Stated another way, the links are able to rotate toward each other as they wrap part way around the sprocket. 
     The chain links  208  that are to the left of the lower push chain retainer  406  are fully unfolded relative to each other. Since the second side  403  of each link is planar, the second sides of the fully unfolded links that are adjacent to each other and to the left of the push chain retainer  406  provide an extended flat or planar surface  600 . The planar surface  600  formed by second sides  403  of two or more fully unfolded chain links  208  is able to freely slide over the push chain retainers  404  and  406 . 
     The piston rod  224  has a geometric center line  606 . The piston  112  itself also has a center line  610 . When the piston  112  is urged against an extrudable material by force  608  applied to the piston  112  by the piston rod  224 , or when the piston  112  is urged against another, different piston inside a tube of extrudable material not shown, an opposing force  612  is distributed across the face  614  of the piston  112  driven by the piston rod  224 . The opposing force  612  on the piston  112  effectively acts through the center line  610  of the piston  112 . 
     When the T-shaped piston rod  224  is properly attached to the bottom of the piston  112 , driving force  608  from the chain  210  is effectively transmitted into the connecting rod  224  through the geometric center line  606  of the piston rod  224 . The piston rod  224  is attached to the piston such that the force  608  applied to the piston  112  from the piston rod  224  will be offset from the center  610  of the piston  112  such that the force  608  from the piston rod  224  is applied to the piston  112  below the center line  610  of the piston  112 , as described in the aforementioned patent application Ser. No. 12/703,613, filed Feb. 10, 2010, and which is entitled “Piston and Piston Rod for a Rodless Dispenser, incorporated herein by reference. Since the opposing force from extrudable material  612  acts in an opposite direction, and at a location above the point of application of the force  608  driving the piston  224  into the extrudable material, the piston  112  will tend to rotate in the tube of extrudable material. The direction of rotation R′ (read as “r” prime) will be clockwise as the piston  112  is shown in  FIG. 6 . A rotation of the piston  112  and piston rod  224  “into” the chain links will tend to urge the chain links  208  that extend forwardly from the top of the toothed drive wheel  330  to their fully unfolded position keeping them locked and able to support/provide the force  608  to the piston  112 . Stated another way, the chain links connected to the slightly rotated piston  112  and slightly rotated piston rod  224  will be locked into their fully unfolded position just by the exertion of a force  608  on the piston  112  by the chain  210 . 
     Replacing a tube of extrudable material is accomplished by the dual disengagement of the pawls, followed by or accompanied by retracting the chain  210 . The chain is retracted simply by grasping the retractor and sliding the retractor  220  outwardly toward the second end  204  of the tube support while the pawls are held disengaged from the drive wheel  330 . The dual disengagement of both pawls by the operation of a single actuator simplifies and facilitates the retraction of the piston  112  and push chain  210  into the magazine  114  and is an improvement over prior art. 
     The foregoing description is for illustration purposes only. The true scope of the invention is set forth in the claims.