Patent Application
20070238597
The present invention relates generally to machines for manipulating web material, and more particularly to the use of mass dampers in connection with interfolding apparatuses.
The use of interfolding rolls to interfold sheets of web material is known in the art. During operation of a common interfolding apparatus, grippers and tuckers on one rotating interfolding roll interact with corresponding tuckers and grippers on an adjacent rotating interfolding roll. Each time this contact occurs, each interfolding roll is subject to a force, causing the roll to deflect. When the force is released, the roll vibrates. In most cases, this vibration eventually ceases after some number of vibration cycles.
The folding frequency, or the frequency of the contact described above, depends on the number of grippers and tuckers on each interfolding roll, as well as the speed at which the rolls are rotated. When the folding frequency is equal to, or a submultiple of, the natural frequency of vibration of the interfolding roll as installed in the interfolding apparatus, the amplitude of roll vibration builds up to a higher level. For each interfolding apparatus, folding frequencies causing these higher levels of vibration occur at specific roll rotation speeds. As interfolding rolls are made longer, the stiffness and natural frequency of vibration of the rolls decreases, causing increased levels of vibration that can prevent high speed operation of the interfolding apparatus.
In one embodiment, the invention provides an interfolding apparatus including a frame, a first interfolding roll supported for rotation by the frame, a second interfolding roll, and a mass damper. The first interfolding roll is rotatable about a first axis, and the second interfolding roll is rotatable about a second axis and is disposed adjacent to the first interfolding roll to define a nip therebetween. The first and second interfolding rolls are rotatable to contact each other during rotation, and the contact between the first and second interfolding rolls creates vibration of at least the first interfolding roll. The mass damper is coupled to the frame and absorbs at least a portion of the vibration energy of the first interfolding roll to reduce vibration of the first interfolding roll.
In another embodiment, the invention provides an apparatus for manipulating web material including a frame having a support member, a roll assembly supported for rotation by the support member at a location between the ends of the roll assembly, and a mass damper. The roll assembly has a first portion between the support member and a first end of the roll assembly, and a second portion between the support member and a second end of the roll assembly. The roll assembly is operable to contact an adjacent component during rotation of the roll assembly, and the contact between the roll assembly and the adjacent component creates vibration of the roll assembly. The mass damper is coupled to the frame and absorbs at least a portion of the vibration energy of the roll assembly to reduce vibration of the roll assembly.
In another embodiment, the invention provides a method of reducing vibration of a roll assembly including providing a frame having a support member, supporting the roll assembly for rotation with the support member at a location between the ends of the roll assembly, defining a first portion of the roll assembly between the support member and a first end of the roll assembly and a second portion of the roll assembly between the support member and a second end of the roll assembly, coupling a mass damper to the frame, rotating the roll assembly, creating vibration of the roll assembly from contact between the roll assembly and an adjacent component during rotation of the roll assembly, transferring at least a portion of the vibration energy of the roll assembly through at least a portion of the frame to the mass damper, absorbing the vibration energy with the mass damper, and reducing the amplitude of the vibration of the roll assembly.
In another embodiment, the invention provides a method of operating an apparatus for manipulating web material at a desired operating speed. The method includes providing a frame, providing a roll assembly, supporting the roll assembly for rotation with the frame such that the roll assembly has a natural frequency of vibration as supported for rotation, positioning an adjacent component such that the roll assembly is operable to contact the adjacent component during rotation of the roll assembly, changing the natural frequency of vibration of the roll assembly, as supported for rotation, by coupling a spring-mounted mass structure to the frame, and rotating the roll assembly at a speed such that contact between the roll assembly and the adjacent component applies an intermittent force to the roll assembly at a frequency that is substantially the same as the natural frequency of vibration of the roll assembly as supported for rotation without the spring-mounted mass coupled to the frame.
Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. Phraseology and terminology used herein with reference to device or element orientation (such as, for example, terms like “front,” “back,” “up,” “down,” “top,” “bottom,” and the like) are only used to simplify description of the present invention, and do not alone indicate or imply that the device or element referred to must have a particular orientation. In addition, terms such as “first,” “second,” and “third” are used herein and in the appended claims for purposes of description and are not intended to indicate or imply relative importance or significance. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof, and can include additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mounting, connecting, supporting, and coupling. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.
The interfolding apparatus 2 is capable of interfolding streams of continuously flowing web material 54a, 54b. As illustrated in
As illustrated in
During operation of the interfolding apparatus 2, the interfolding roll assembly 10b rotates clockwise, and the adjacent interfolding roll assembly 10a rotates counterclockwise. Each tucker 58b of the interfolding roll assembly 10b is received in a corresponding gripper 62a of the adjacent interfolding roll assembly 10a as the tucker 58b rotates through the nip 14. Likewise, each gripper 62b of the interfolding roll assembly 10b receives a corresponding tucker 58a of the adjacent interfolding roll assembly 10a as the gripper 62b rotates through the nip 14. The succession of sheets of web material entering the nip 14 is such that a middle portion of a reference sheet from side “a” enters the nip at the same time as trailing and leading edges of downstream and upstream sheets, respectively, from side “b.” As the tucker 58b and corresponding gripper 62a rotate through the nip, the tucker 58b tucks the middle portion of the reference sheet into the gripper 62a. The gripper 62a receives the middle portion of the reference sheet and the trailing and leading edges of the downstream and upstream sheets, respectively, from the tucker 58b and folds the middle portion of the reference sheet, capturing the trailing and leading edges of the downstream and upstream sheets, respectively, within the fold.
As the interfolding roll assembly 10b continues rotation, a gripper 62b of the interfolding roll assembly 10b receives a middle portion of the upstream sheet from side “b,” the trailing edge of the reference sheet, and the leading edge of another sheet from side “a,” which is upstream from the reference sheet, from a corresponding tucker 58a of the adjacent interfolding roll assembly 10a. The folding process continues in this alternating fashion.
When the tuckers 58b and grippers 62b of the interfolding roll assembly 10b contact the corresponding tuckers 58a and grippers 62a of the adjacent interfolding roll assembly 10a during each fold, forces are applied to the interfolding roll assembly 10b. The frequency of this contact during operation of the interfolding apparatus 2 will be referred to herein as the folding frequency. As illustrated by the above discussion, the folding frequency depends on the number of tuckers and grippers that the interfolding roll assemblies 10a, 10b include, as well as the speed at which the interfolding roll assemblies 10a, 10b are rotated.
In one embodiment of the interfolding apparatus 2, the interfolding roll assembly 10b includes three tuckers and three grippers and produces an interfolded stack of web material measuring about 4.9 inches in width. The interfolding apparatus 2 is operated at about 650 feet per minute, resulting in a folding frequency of about 26.5 Hz. During operation of this embodiment of the interfolding apparatus 2, the force on the roll assembly 10b rises to about 300 pounds during each fold, and remains at about 300 pounds for about 4 degrees of rotation of the roll assembly 10b.
While the interfolding roll assembly 10b is subjected to the force from the folding contact, the roll assembly 10b deflects. When the folding contact between the roll assemblies 10a, 10b ceases, the force is removed and the roll assembly 10b rebounds and vibrates at its natural frequency as supported for rotation. In most cases, this vibration eventually ceases after some number of vibration cycles. However, with respect to the interfolding apparatus 2 without the mass dampers 6a, 6b, when the folding frequency of the interfolding apparatus 2 is about equal to, or a submultiple of, the natural frequency of vibration of the interfolding roll assembly 10b as supported for rotation by the frame 22, the amplitude of vibration of the roll assembly 10b can increase to undesirable levels. For example, referring to the embodiment described above, if the roll assembly 10b, as supported for rotation by the frame 22 and without the mass damper 6b, had a natural frequency of vibration of 26.5 Hz, operating the interfolding apparatus 2 at 650, 325, or 217 feet per minute would cause the amplitude of vibration of the roll assembly 10b to build up. In accordance with the present invention, one or more mass dampers 6b are used to control vibration of the interfolding roll assembly 10b, as will be explained in greater detail below.
As shown in
It is often preferable to use an interfolding roll assembly that includes just one continuous roll portion if the roll portion is less than about 80 inches long. If, to meet product objectives, the roll portion used is about 80 inches or longer, it is often desirable to instead use an interfolding roll assembly that includes multiple portions and is supported for rotation between the ends of the roll assembly to reduce vibration of the roll assembly. As shown in
As shown in
As also shown in the embodiment illustrated in
Similar to
As shown in
The remaining volume in the interior of the containers 138, as illustrated in
As described in detail above, in the embodiments illustrated in
As supported for rotation by the frame 22, the roll assembly 10b has a natural frequency of vibration. As supported, the roll assembly 10b can have different natural frequencies of vibration when vibrating in different spatial planes. For example, vertical vibration of the roll assembly 10b can have a different natural frequency of vibration than horizontal vibration of the roll assembly 10b. Description herein of embodiments and operation of the present invention will be confined to vibration of the roll assembly 10b in a single spatial plane, and thus, a single natural frequency of vibration for the roll assembly 10b. The natural frequency of vibration of the roll assembly 10b, as supported for rotation, can be dependent upon the characteristics of other components of the interfolding apparatus 2, as well as characteristics of the operating environment of the interfolding apparatus 2. For example, the type and structure of a floor or surface supporting the interfolding apparatus 2 can affect the natural frequency of vibration of the roll assembly 10b as supported for rotation.
When the mass damper 6b is added to the interfolding apparatus 2 by coupling the mass damper 6b to the frame 22, the combined system as shown in
The difference between Frequency A and Frequency B, and how close Frequency A and Frequency B are to the natural frequency of vibration of the roll assembly 10b as supported for rotation and without the mass damper 6b coupled to the frame 22, depends upon the ratio of the mass of the masses 154 to the mass of the roll assembly 10b. The greater the mass of the masses 154, the greater the difference is between Frequency A and Frequency B and the greater the respective differences are between Frequencies A and B and the natural frequency of vibration of the roll assembly 10b as supported for rotation and without the mass damper 6b coupled to the frame 22. In addition, the smaller the mass of the masses 154, the smaller the difference is between Frequency A and Frequency B and the smaller the respective differences are between Frequencies A and B and the natural frequency of vibration of the roll assembly 10b as supported for rotation and without the mass damper 6b coupled to the frame 22.
Thus, when tuning the mass damper 6b to a damped natural frequency of vibration between Frequency A and Frequency B, using heavier masses 154 results in a wider range of damped natural frequencies (of the mass damper 6b) that will function effectively to reduce vibration of the roll assembly 10b, and therefore the tuning does not have to be as precise. Using heavier masses 154 can therefore help to make sure the mass damper 6b will function effectively to reduce vibration of the roll assembly in multiple spatial planes, because the range of damped natural frequencies (of the mass damper 6b) that will function effectively to reduce vibration of the roll assembly 10b is wider for each orientation of vibration. In addition, because the viscosity of the damping fluid 166 can vary with temperature, the damped natural frequency of vibration of the mass damper 6b can also vary with temperature. Thus, using heavier masses 154 can potentially provide a wide enough range of damped natural frequencies that will function effectively to reduce vibration of the roll assembly 10b to accommodate variation of the damped natural frequency of vibration of the mass damper 6b due to temperature variation. As a result, when tuning the mass damper 6b, it can be advantageous to use the heaviest masses 154 that accommodate any practical constraints, such as space constraints and the like. In some embodiments, it is preferable to use mass dampers having moving mass totaling greater than 5% of the mass of the roll assembly 10b. As shown in
According to some embodiments of the invention, to tune the mass damper 6b, the interfolding apparatus 2, including the frame 22, the roll assembly 10b, the adjacent roll assembly 10a, and any other components, is first fully assembled in its intended operating environment without the mass damper 6b. The roll assembly 10b is then caused to vibrate and measurements are taken with a measurement device suitable for taking data that can be used to determine the natural frequency of vibration of the roll assembly 10b as supported for rotation. A suitable measurement device for use in this application is an accelerometer. From this data, the natural frequency of vibration of the roll assembly 10b as supported for rotation is determined. The mass damper 6b is then tuned to a damped natural frequency that is appropriate to effectively reduce vibration of the roll assembly 10b during operation of the interfolding apparatus 2. There are four variables that can be controlled in order to tune the mass damper 6b: the masses 154 used, the damping properties of the damping fluid 166 used, the spring constant of the spring elements 150 used, and the directions that the masses 154 of the mass damper 6b can vibrate in.
During testing and tuning of various mass dampers according to embodiments of the present invention, the Applicant discovered that adding the damping fluid to the mass damper 6b, in addition to adding a damping component, changes the natural frequency of the mass 154 and spring element 150 combinations. This effect is a function of the fluid specific gravity, and is caused by the kinetic energy of the damping fluid 166 flowing around the masses 154.
As described above, folding contact during operation of the interfolding apparatus 2 causes vibration of the interfolding roll assembly 10b. Vibration of the interfolding roll assembly 10b causes the masses 154 to vibrate. Through movement of the masses 154 and spring elements 150 within the containers 138, the mass damper 6b absorbs at least a portion of the vibration energy of the interfolding roll assembly 10b, as supported for rotation by the frame 22, to reduce the vibration of the interfolding roll assembly 10b. The damping component of the damping fluid 166 absorbs vibration energy from the moving masses 154 and spring elements 150, thereby reducing vibration of the masses 154, and converts the vibration energy to heat.
As stated above, adding the mass damper 6b to the interfolding apparatus 2 creates a combined system, including the roll assembly 10b and the mass damper 6b, that has two natural frequencies of vibration, one (Frequency A) higher than the natural frequency of vibration of the roll assembly 10b as supported and without the mass damper 6b coupled to the frame 22 and one (Frequency B) lower than the natural frequency of vibration of the roll assembly 10b as supported and without the mass damper 6b coupled to the frame 22. Accordingly, vibration of the roll assembly 10b can increase to undesirable levels if the folding frequency of the interfolding apparatus 2 is equal to, or a submultiple of, Frequency A or Frequency B, but the roll assembly 10b will not vibrate excessively if the folding frequency is equal to, or a submultiple of, the natural frequency of vibration of the roll assembly 10b as supported and without the mass damper 6b coupled to the frame 22. Thus, if a specific desired operating speed results in a folding frequency equal to, or a submultiple of, the natural frequency of vibration of the roll assembly 10b as supported and without any mass damper coupled to the frame, a simple spring-mounted mass (not shown) can be attached to the frame, instead of a mass damper, to operate the interfolding apparatus 2 at this desired operating speed. Attaching the spring-mounted mass will create a combined system, including the roll assembly 10b and the spring-mounted mass, that has two natural frequencies, as described above with reference to Frequency A and Frequency B. Operating the interfolding apparatus 2 at the desired operating speed is no longer a problem, therefore, because the interfolding apparatus 2 can be accelerated through any lower speeds resulting in excessive vibration and operated below any higher speeds resulting in excessive vibration.
For example, with reference to the embodiment described above (no mass damper) having three tuckers and three grippers and producing an interfolded stack of web material measuring about 4.9 inches in width, if the natural frequency of vibration of the roll assembly 10b, as supported for rotation and without the mass damper 6b, is 26.5 Hz, operating the interfolding apparatus 2 at about 650, 325, or 217 feet per minute would result in a folding frequency of about 26.5 Hz, or a submultiple thereof, and would cause the amplitude of vibration of the roll assembly 10b to build up. If a spring-mounted mass is coupled to the frame 22, the combined system, including the spring-mounted mass and the roll assembly 10b, might have natural frequencies of vibration of, for example, 24.5 Hz and 28.5 Hz (not actual measurements). As a result, operating the interfolding apparatus 2 at about 600, 300, or 200 feet per minute, as well as about 698, 349, and 233 feet per minute, would result in folding frequencies of about 24.5 Hz and 28.5 Hz or submultiples thereof, respectively, and would cause vibration of the roll assembly 10b to build up. The interfolding apparatus 2 of this embodiment could accelerate through speeds of 200, 233, 300, 349, and 600 feet per minute, and operate at 650 feet per minute.
As described in detail above with regard to
As discussed above, the roll assembly 10b has a natural frequency of vibration as supported for rotation. When the mass damper 110 is added to the interfolding apparatus 2 by coupling the mass damper 110 to the frame 22, the combined system as shown in
The difference between Frequency A and Frequency B, and how close Frequency A and Frequency B are to the natural frequency of vibration of the roll assembly 10b as supported for rotation and without the mass damper 110 coupled to the frame 22, depends upon the ratio of the mass of the masses 198 to the mass of the roll assembly 10b. The greater the mass of the masses 198, the greater the difference is between Frequency A and Frequency B and the greater the respective differences are between Frequencies A and B and the natural frequency of vibration of the roll assembly 10b as supported for rotation and without the mass damper 110 coupled to the frame 22. In addition, the smaller the mass of the masses 198, the smaller the difference is between Frequency A and Frequency B and the smaller the respective differences are between Frequencies A and B and the natural frequency of vibration of the roll assembly 10b as supported for rotation and without the mass damper 110 coupled to the frame 22.
Thus, when tuning the mass damper 110 to a damped natural frequency of vibration between Frequency A and Frequency B, using heavier masses 198 results in a wider range of damped natural frequencies (of the mass damper 110) that will function effectively to reduce vibration of the roll assembly 10b, and therefore the tuning does not have to be as precise. Using heavier masses 198 can therefore help to make sure the mass damper 110 will function effectively to reduce vibration of the roll assembly in multiple spatial planes, because the range of damped natural frequencies (of the mass damper 110) that will function effectively to reduce vibration of the roll assembly 10b is wider for each orientation of vibration. In addition, because the spring constant and damping properties of the elastomeric spring elements 194 can vary with temperature, the damped natural frequency of vibration of the mass damper 110 can also vary with temperature. Thus, using heavier masses 198 can potentially provide a wide enough range of damped natural frequencies that will function effectively to reduce vibration of the roll assembly 10b to accommodate variation of the damped natural frequency of vibration of the mass damper 110 due to temperature variation. As a result, when tuning the mass damper 110, it can be advantageous to use the heaviest masses 198 that accommodate any practical constraints, such as space constraints and the like. In some embodiments, it is preferable to use mass dampers having moving mass totaling greater than 5% of the mass of the roll assembly 10b. As shown in
According to some embodiments of the invention, to tune the mass damper 110, the interfolding apparatus 2, including the frame 22, the roll assembly 10b, the adjacent roll assembly 10a, and any other components, is first fully assembled in its intended operating environment without the mass damper 110. The roll assembly 10b is then caused to vibrate and measurements are taken with a measurement device suitable for taking data that can be used to determine the natural frequency of vibration of the roll assembly 10b as supported for rotation. A suitable measurement device for use in this application is an accelerometer. From this data, the natural frequency of vibration of the roll assembly 10b as supported for rotation is determined. The mass damper 110 is then tuned to a damped natural frequency that is appropriate to effectively reduce vibration of the roll assembly 10b during operation of the interfolding apparatus 2. There are four variables that can be controlled in order to tune the mass damper 110: the masses 198 used, the damping properties of the spring elements 194 used, the spring constant of the spring elements 194 used, and the directions that the masses 198 of the mass damper 110 can vibrate in.
As described above, folding contact during operation of the interfolding apparatus 2 causes vibration of the interfolding roll assembly 10b. Vibration of the interfolding roll assembly 10b causes the masses 198 to vibrate. Through movement of the masses 198 and spring elements 194, the mass damper 110 absorbs at least a portion of the vibration energy of the interfolding roll assembly 10b, as supported for rotation by the frame 22, to reduce the vibration of the interfolding roll assembly 10b. The damping component of the spring elements 194 takes vibration energy from the moving masses 198 and spring elements 194, thereby reducing vibration of the masses 198, and converts the vibration energy to heat.
In other embodiments of the present invention, any other type of mass damper can be used in combination with the interfolding apparatus 2 to reduce vibration of the interfolding roll assembly 10b. For example, eddy current damping, using permanent magnets and electrical conductors, can be used to damp vibration of masses.
In still other embodiments of the present invention, the mass dampers 6b, 110, as well as any other type of mass damper, can be used in combination with any other apparatus for manipulating web material. The mass dampers can be used to reduce the vibration of rolls or roll assemblies other than just interfolding rolls and interfolding roll assemblies.
The embodiments described above and illustrated in the figures are presented by way of example only and are not intended as a limitation upon the concepts and principles of the present invention. As such, it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention as set forth in the appended claims. For example, the various embodiments (and alternatives thereto) of the present invention described above and illustrated in the figures are not mutually exclusive of one another. With the exception of features, elements, and manners of operation that are mutually exclusive of or are inconsistent with one another, the features, elements and manners of operation of any of the embodiments can be employed in any of the other embodiments in any combination.
