Sheet product dispenser with spring assembly

Abstract

A dispenser for dispensing sheet product is provided. The dispenser includes a housing with an outlet through which sheet product is dispensed. A knife drum is rotatable with respect to the housing. A knife is movable between a retracted position within the knife drum and an extended position where the knife protrudes outside of the knife drum to cut the sheet product. A cam follower surface is fixed with respect to the housing. A cam follower is attached to the knife and operable to engage the cam follower surface and travel therealong to transition the knife between the retracted position and the extended position. A spring assembly biases the knife drum during rotation toward a predetermined position. The spring assembly comprises a first spring and a second spring. The spring assembly is attached at a single mount position that is fixed with respect to the housing.

What is claimed: 
     
         1 . A dispenser for dispensing sheet product, the dispenser comprising:
 a housing configured to accommodate at least one source of sheet product, wherein the housing defines an outlet through which a leading end of the sheet product is dispensed;   a knife drum that is rotatable with respect to the housing;   a knife that is movable between a retracted position within the knife drum and an extended position with at least a portion of the knife protruding outside of the knife drum, wherein the knife is operable to cut the sheet product;   a cam track;   a cam follower operable to travel along the cam track to transition the knife between the retracted position and the extended position during a rotation cycle of the knife drum; and   a spring assembly attached to the knife and comprising one or more springs, wherein the one or more springs are configured to charge and discharge during the rotation cycle of the knife drum as the cam follower travels along the cam track,   wherein the spring assembly and the cam track are designed such that a maximum pull force required by the user during the rotation cycle of the knife drum is less than or equal to approximately 1.0 lbf.   
     
     
         2 . The dispenser of  claim 1 , wherein the spring assembly and the cam track are designed such that any pull force from the user is only required for approximately 200 degrees or less of the rotation cycle of the knife drum. 
     
     
         3 . The dispenser of  claim 1 , wherein the spring assembly and the cam track are designed such that pull force required during charging of the one or more springs is stable. 
     
     
         4 . The dispenser of  claim 3 , wherein the spring assembly and the cam track are designed such that the pull force required during charging of the one or more springs varies less than or equal to approximately 0.2 lbf over a range of approximately 30 degrees to 50 degrees of the rotation cycle of the knife drum, wherein the rotation cycle of the knife drum is 360 degrees. 
     
     
         5 . The dispenser of  claim 1 , wherein the spring assembly and the cam track are designed such that, during the rotation cycle of the knife drum, the one or more springs charge and discharge non-sinusoidally to modulate pull force required by a user to complete a dispense. 
     
     
         6 . The dispenser of  claim 1 , wherein the one or more springs comprises at least a first spring and a second spring, wherein the first spring is independently chargeable and dischargeable from the second spring. 
     
     
         7 . The dispenser of  claim 6 , wherein a first change in energy for the first spring is different over the rotation cycle of the knife drum than a second change in energy for the second spring. 
     
     
         8 . The dispenser of  claim 1 , wherein the spring assembly comprises a 4-bar linkage. 
     
     
         9 . The dispenser of  claim 8 , wherein the spring assembly comprises a first movable pivot point and a second movable pivot point, wherein both the first movable pivot point and the second movable pivot point are movable with respect to the cam track as the knife drum rotates. 
     
     
         10 . A dispenser for dispensing sheet product, the dispenser comprising:
 a housing configured to accommodate at least one source of sheet product, wherein the housing defines an outlet through which a leading end of the sheet product is dispensed;   a knife drum that is rotatable with respect to the housing;   a knife that is movable between a retracted position within the knife drum and an extended position with at least a portion of the knife protruding outside of the knife drum, wherein the knife is operable to cut the sheet product;   a cam track;   a cam follower operable to travel along the cam track to transition the knife between the retracted position and the extended position during a rotation cycle of the knife drum; and   a spring assembly attached to the knife and comprising one or more springs, wherein the one or more springs are configured to charge and discharge during the rotation cycle of the knife drum as the cam follower travels along the cam track,   wherein the spring assembly and the cam track are designed such that, during the rotation cycle of the knife drum, the one or more springs charge and discharge non-sinusoidally to modulate pull force required by a user to complete a dispense.   
     
     
         11 . The dispenser of  claim 10 , wherein the spring assembly and the cam track are designed such that the pull force from the user is only required for approximately 200 degrees or less of the rotation cycle of the knife drum. 
     
     
         12 . The dispenser of  claim 10 , wherein the spring assembly and the cam track are designed such that the pull force required during charging of the one or more springs is stable. 
     
     
         13 . The dispenser of  claim 10 , wherein the spring assembly and the cam track are designed such that the pull force required during charging of the one or more springs varies less than or equal to approximately 0.2 lbf over a range of approximately 30 degrees to 50 degrees of the rotation cycle of the knife drum, wherein the rotation cycle of the knife drum is 360 degrees. 
     
     
         14 . The dispenser of  claim 10 , wherein the one or more springs comprises at least a first spring and a second spring, wherein the first spring is independently chargeable and dischargeable from the second spring. 
     
     
         15 . The dispenser of  claim 14 , wherein a first change in energy for the first spring is different over the rotation cycle of the knife drum than a second change in energy for the second spring. 
     
     
         16 . The dispenser of  claim 10 , wherein the spring assembly comprises a 4-bar linkage. 
     
     
         17 . The dispenser of  claim 16 , wherein the spring assembly comprises a first movable pivot point and a second movable pivot point, wherein both the first movable pivot point and the second movable pivot point are movable with respect to the cam track as the knife drum rotates. 
     
     
         18 . A dispenser for dispensing sheet product, the dispenser comprising:
 a housing configured to accommodate at least one source of sheet product, wherein the housing defines an outlet through which a leading end of the sheet product is dispensed;   a knife drum that is rotatable with respect to the housing;   a knife that is movable between a retracted position within the knife drum and an extended position with at least a portion of the knife protruding outside of the knife drum, wherein the knife is operable to cut the sheet product;   a cam track;   a cam follower operable to travel along the cam track to transition the knife between the retracted position and the extended position during a rotation cycle of the knife drum; and   a spring assembly attached to the knife and comprising one or more springs, wherein the one or more springs are configured to charge and discharge during the rotation cycle of the knife drum as the cam follower travels along the cam track,   wherein the spring assembly and the cam track are designed such that pull force required during charging of the one or more springs varies less than or equal to approximately 0.2 lbf over a range of approximately 30 degrees to 50 degrees of the rotation cycle of the knife drum, wherein the rotation cycle of the knife drum is 360 degrees.   
     
     
         19 . The dispenser of  claim 18 , wherein the spring assembly and the cam track are designed such that any pull force from the user is only required for approximately 200 degrees or less of the rotation cycle of the knife drum. 
     
     
         20 . The dispenser of  claim 18 , wherein the one or more springs comprises at least a first spring and a second spring, wherein the first spring is independently chargeable and dischargeable from the second spring, wherein a first change in energy for the first spring is different over the rotation cycle of the knife drum than a second change in energy for the second spring.