PATENT ABSTRACT
In one embodiment, a system for providing cyclic motion includes a magnetic drive having an electrically conductive coil defining a bore and a magnetic member movable through the bore. A control provides current to the coil and selectively reverses the direction of the current to move the magnetic member through the bore. In another embodiment, the system includes a counterbalance. The counterbalance includes a biasing member for reacting against a load applied to a support, and a lever arm coupled to the biasing member for varying a preload of the biasing member. In another embodiment, the magnetic drive and the counterbalance may be incorporated into an apparatus for reciprocating a person.

PATENT DESCRIPTION
The present application claims the filing benefit of co-pending U.S. Provisional Patent Application No. 60/862,914, filed Oct. 25, 2006, which is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to machinery and mechanisms that operate in a cyclical manner, and more particularly to devices that facilitate cyclically operating such machinery and mechanisms. 
     BACKGROUND 
     Many machines and mechanisms operate in a cyclical manner. For example, rotating machinery such as turbines rotors, and reciprocating mechanisms such as paint shakers, exhibit cyclical motion. In use, these machines and mechanisms may be exposed to varying load conditions. However, many cyclically-operated machines and mechanisms are not able to accommodate varying loads while maintaining desired performance without substantial increases in power consumed. A need therefore exists for a simple, efficient system for driving cyclical machines and mechanisms, and for accommodating varying load conditions. 
     SUMMARY 
     A magnetic drive in accordance with the one aspect of the present disclosure overcomes the foregoing and other shortcomings of the prior systems for driving cyclical machines and mechanisms. In one embodiment, the magnetic drive includes an electrically conductive coil defining a bore and having first and second oppositely disposed ends. A magnetic member is movable from a first position outside the bore and adjacent the first end of the coil, through the bore to a second position outside the bore and adjacent the second end of the coil. The magnetic drive further includes a control that provides current to the coil to generate a magnetic field that interacts with the magnetic member. The control is able to reverse the direction of current through the coil and thereby act on the magnetic member as desired. 
     In another aspect of the present disclosure, a counterbalance mechanism is provided for offsetting a load applied to a supporting structure. In one embodiment, the counterbalance includes a biasing member that is adapted to be coupled to a load support for reacting against a load applied to the load support. The counterbalance further includes a lever arm coupled to the biasing member. The lever arm is selectively positionable relative to the biasing member to vary a preload of the biasing member. The counterbalance may further include a pivot that cooperates with the lever arm and which is selectively positionable relative to the lever arm to vary the preload of the biasing member. 
     In yet another aspect of the present disclosure, an apparatus for reciprocating a person includes a frame and a support platform that is constrained to move in a substantially vertical direction relative to the frame. The apparatus includes a counterbalance, as described above, with a biasing member coupled to the support platform and a lever arm coupled to the biasing member and the frame. The lever arm is selectively adjustable to vary a preload applied by the biasing member on the support platform. 
     While various embodiments are discussed in detail herein, it will be understood that the invention is not limited to these embodiments. On the contrary, the invention includes all alternatives, modifications and equivalents as may be included within the spirit and scope of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention in sufficient detail to enable one of ordinary skill in the art to which the invention pertains to make and use the invention. 
         FIG. 1  is a perspective view depicting an exemplary apparatus for reciprocating an infant support, with a cover of the housing shown in phantom. 
         FIG. 2  is perspective view of the interior components of the apparatus of  FIG. 1 . 
         FIG. 3A  is a left-side elevation view of the apparatus of  FIG. 1 , with the support platform depicted in a raised position. 
         FIG. 3B  is a left-side elevation view of the apparatus of  FIG. 1 , with the support platform depicted in a vertically centered position. 
         FIG. 3C  is a left-side elevation view of the apparatus of  FIG. 1 , with the support platform depicted in a lowered position. 
         FIGS. 4A-4F  are cross-sectional elevation views of a magnetic drive used with the apparatus of  FIG. 1 , depicting various positions of a magnetic member. 
         FIG. 5  is a cross-sectional view taken along line  5 - 5  of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  depicts an exemplary cyclically operated apparatus  10  including an exemplary magnetic drive  12  and a load off-setting, or counterbalancing, device  14  in accordance with the principles of the present disclosure. In this embodiment, the apparatus  10  is configured for reciprocating an infant so as to soothe the infant in a manner similar to that described in U.S. Pat. No. 6,966,082, assigned to the assignee of the present invention and hereby incorporated by reference in its entirety. It will be understood, however, that the drive and load off-setting devices  12 ,  14  described herein may alternatively be used in various other mechanisms, or may be used independently of one another. 
     Referring to  FIGS. 1 ,  2 , and  5 , the apparatus  10  includes a frame  16  having first and second spaced frame members  18 ,  20  interconnected by transverse beam members  22 ,  24 . In the embodiment shown, the frame members  18 ,  20  comprise substantially parallel, vertically-extending sidewalls  26 ,  28 . The frame  16  may include adjustable feet or casters  30  to support the frame  16  above a floor surface, and the frame  16 , as well as other components of the apparatus  10  may be enclosed in a housing  32 . As shown in  FIGS. 3A ,  3 B, and  3 C, housing  32  may comprise a removable upper cover  32   a  and a lower base portion  32   b.    
     The apparatus  10  further includes a pair of spaced, parallel upper control arms  34 ,  36  and a pair of spaced, parallel lower control arms  38 ,  40  (see  FIGS. 3C and 5 ) disposed between the vertically extending sidewalls  26 ,  28  of the frame  16 . Respective first ends  34   a ,  36   a  of the upper control arms  34 ,  36  and first ends  38   a ,  40   a  of the lower control arms  38 ,  40  are pivotally coupled to the frame  16  by pinned connections  42 ,  44 . The respective second ends  34   b ,  36   b  of the upper control arms  34 ,  36  (see  FIGS. 3A and 5 ) and first ends  38   b ,  40   b  of the lower control arms  38 ,  40  are pivotally coupled to a support platform  46  by pinned connections  48 ,  50 , whereby the upper control arms  34 ,  36  and lower control arms  38 ,  40  are movable with the support platform  46  to constrain movement of the support platform  46  in a substantially vertical direction. 
     A seat mount  52  may be secured to the support platform  46  to facilitate coupling an infant support  54  to the support platform  46 , whereby the infant support  54  will be constrained for movement with the support platform  46  in a substantially vertical direction. Travel limiting stops, such as a lower limit bumper  56  ( FIG. 5 ) extending downwardly from support platform  46 , and an upper limit bumper (not shown) disposed between the lower control arms  38 ,  40  and frame members  18 ,  20 , may be provided to control the limits of travel of the support platform  46 . While the travel stops are shown and described herein as bumpers, it will be recognized that various other devices and methods may be used to limit the travel of platform  46 . While this embodiment is described as being configured to accommodate an infant support  54 , it will be recognized that the apparatus may alternatively be used to reciprocate a support for a range of persons, from youths to adults, in a manner similar to that described in co-pending U.S. application Ser. No. 11/257,877, assigned to the assignee of the present invention and hereby incorporated by reference in its entirety. 
     In the embodiment shown, the frame members  18 ,  20 , the upper control arms  34 ,  36 , lower control arms  38 ,  40 , and support platform  46  are formed from sheet metal that has been stamped or otherwise worked or machined to form the respective components of the apparatus. It will be recognized, however, that various other methods for forming the frame members  18 ,  20 , upper control arms  34 ,  36 , lower control arms  38 ,  40  and support platform  46  may alternatively be used. For example, and not as limitation, the frame members  18 ,  20 , upper control arms  34 ,  36 , lower control arms  38 ,  40  and support platform  46  may be formed by molding, casting, machining, or various other methods suitable for fabricating the respective components. 
     With continued reference to  FIGS. 1 and 2 , and referring further to  FIG. 5 , the apparatus  10  may further include a tunable load-offsetting, or counterbalance, mechanism  14  for accommodating varying loads that may be applied to the support platform  46 . In the embodiment shown, the counterbalance mechanism  14  comprises a biasing member  60  disposed between the support platform  46  and the frame  16 . In this embodiment, the biasing member  60  is a spiral torsion spring having a first end  62  operatively coupled to the support platform  46 , and a second end  64  coupled to a spring lever  66  for selectively adjusting the preload, or initial deflection, of the spiral torsion spring  60  to correspond to a given load applied to the support platform  46 . The spring lever  66  comprises an elongate member having a first end  68  pivotally coupled to the support platform  46 , and a second end  70  cantilevered outwardly from the support platform  46  in a direction between the upper control arms  34 ,  36 , the lower control arms  38 ,  40 , and the vertically extending sidewalls  26 ,  28  of the frame  16 . The second end  70  of the spring lever  66  is biased in a direction toward the lower control arms  38 ,  40  by the spiral torsion spring  60 . 
     The spiral torsion spring  60  is coupled to the support platform  46  by a pair of semi-circular disks  72  that are pivotally coupled to the support platform  46  by an arbor  74  around which the spiral torsion spring  60  is wound. With the first end  62  of the spiral torsion spring  60  connected to the disks  72 , an initial, constant preload of the spiral torsion spring  60  may be selectively adjusted by rotating the disks  72  relative to the support platform  46  and then securing the disks  72  at a desired angular position relative to the support platform  46 . In the embodiment shown, a plurality of apertures  74  spaced radially from the arbor are provided around the periphery of the disks  72  and the disks are secured to the support platform  46  by inserting a pin (not shown) through at least one of the apertures  74  and through a corresponding aperture  76  formed in the support platform  46 . 
     The counterbalance mechanism  14  further includes an adjustable pivot, or fulcrum  80 , that is selectively positionable along the length of the spring lever  66  to thereby vary a preload of the platform without changing the initial deflection of the spiral torsion spring  60 . With the platform deflection substantially constant for all preloads, the system resonant frequency will also remain constant. In the embodiment shown, the fulcrum  80  comprises a roller supported on a shaft  82  extending between the vertical walls  26 ,  28  of the first and second frame members  18 ,  20 . The shaft  82  is received in corresponding slots  84 ,  86  formed in the vertical walls  26 ,  28  of the frame members  18 ,  20  whereby the roller  80  may be maneuvered to various positions along the spring lever  66  by moving the shaft  82  along the slots  84 ,  86 . To facilitate positioning the shaft  82  and roller  80  at a desired location along the slots  84 ,  86 , pinion gears  88  are provided on the shaft  82  and are rotationally fixed to the shaft  82  at respective ends  90  of the shaft  82  that extend outwardly from the vertical walls  26 ,  28 , as shown in  FIG. 2 . The pinion gears  88  intermesh with corresponding rack gears  92  provided on the vertical walls  26 ,  28  of the frame members  18 ,  20 , whereby the position of the shaft  82  and roller  80  may be selected by turning the shaft  82  to cause the pinion gears  88  to move along the rack gears  92  to a desired location. Knobs  94  may be provided on the respective ends  90  of the shaft  82  to facilitate turning the shaft  82  and pinion gears  88 . 
     With the spiral torsion spring  60  connected between the support platform  46  and the spring lever  66 , and with the spring lever  66  being pivoted about the arbor  74  of the spiral torsion spring  60 , a load applied to the support platform  46  is supported as a sprung mass by the spiral torsion spring  60 . Moreover, the static vertical position of the platform  46  and supported load relative to the frame  16  may be selectively adjusted by manipulating the shaft  82  to cause the roller  80  to move along the spring lever  66 , as described above. The support platform  46  and load, together with the spiral torsion spring  60 , therefore comprise a spring-mass system that exhibits a particular natural frequency. The support platform  46  and supported load may thus be moved upwardly and downwardly, supported on the spiral torsion spring  60 , while the upper control arms  34 ,  36  and lower control arms  38 ,  40  constrain the upward and downward movement in a substantially vertical direction. The natural frequency of the spring-mass system is related to the static deflection of the supported load upon the spiral torsion spring  60 . Accordingly, by adjusting the static vertical height of the support platform  46  relative to the frame  16 , using the roller  80  and spring lever  66 , the apparatus  10  may be adjusted or tuned to accommodate a range of loads supported on the support platform  46  while maintaining the natural frequency of the spring-mass system. Alternatively, the apparatus  10  may be adjusted with a given load to tune the spring-mass system to a desired natural frequency. 
     Referring to  FIGS. 2 ,  5 , and  4 A- 4 F, in another aspect, the apparatus  10  may include a magnetic drive  12  mounted to the frame  16  and operatively coupled to the support platform  46  to move the support platform  46  upwardly and downwardly in a cyclical fashion. In the embodiment shown, the magnetic drive  12  includes an electric coil  100  comprising conductive wire wound to define a cylindrical barrel  102  having a central bore  104  with oppositely disposed first and second ends  106 ,  108 . A magnetic member  110  is sized to be received within the bore  104  of the electric coil  100  whereby the magnetic member  110  may be moved from a first position outside the bore  104  and spaced from the first end  106  of the bore  104  (see  FIG. 4A ), through the bore  104 , to a second position outside the bore  104  and spaced from the second end  108  of the bore  104  (see  FIG. 4E ). In the embodiment shown, the magnetic member  110  comprises a stack of individual magnets  112 , however, it will be recognized that magnetic member  110  may alternatively comprise a single, unitary magnet. In another embodiment, all components of the drive  12 , except the magnetic member  110 , comprise non-ferrous materials 
     When electric current is passed through the coil  100 , a magnetic field is generated that interacts with the magnetic member  110 . Depending upon the direction of current through the coil  100 , the magnetic field generated by the coil  100  may attract the magnetic member  110 , thereby pulling the magnetic member  110  in a direction into the bore  104 , or the generated magnetic field may repel the magnetic member  110 , effectively pushing the magnetic member  110  out from the bore  104 . When the magnetic member  110  is coupled to a moveable portion of a machine or device, the electric coil  100  can be selectively operated to impart motion to the device. To this end, the drive  12  may include a control  114  (see  FIG. 1 ) operable to selectively provide current to the coil  100  and to selectively change the direction of the current, as needed, to move the magnetic member  110  through the bore  104  and thereby impart corresponding motion to the device. 
     The magnetic drive  12  is particularly useful when the motion of the device to be moved is cyclical, such as the cyclical reciprocation of the apparatus  10  shown and described herein. In the embodiment shown, the magnetic member  110  is supported on a rod  116  extending downwardly from the support platform  46  and is positioned to be received through the bore  104  of the electric coil  100  as the support platform  46  is reciprocated in a substantially vertical direction as discussed above. In one embodiment, as the magnetic member  110  moves downwardly with the support platform  46  from a raised position (see  FIG. 3A ) and approaches the first end  106  of the bore  104  (see  FIG. 4A ), no current flows through the coil  100  and no magnetic forces cooperate with the magnetic field of the magnetic member  110  to induce or hinder motion of the magnetic member  110 . As the lower edge  118  of the magnetic member  110  enters the first end  106  bore of the bore  104  ( FIG. 4B ), current is provided to the coil  100  in a manner that generates a magnetic field that attracts the magnetic member  110 , causing the magnetic member  110  to be drawn into the bore  104  through the interaction of the magnetic fields of the magnetic member  110  and the coil  100 . The coil  100  remains energized as the magnetic member  110  moves into the bore  104 . Just before the lower edge  118  of the magnetic member  110  exits the second end  108  of the bore  104  ( FIG. 4C ), the coil  100  is de-energized to allow the magnetic member  110  to continue moving in a downward direction without the influence of any magnetic field from the coil  100 . 
     Just after the lower end  118  of the magnetic member  110  exits the second end  108  of the bore  104  ( FIG. 4D ), the coil  100  is energized with current in a direction to generate a repulsing magnetic field in the coil  100  that pushes the magnetic member  110  further outside of the second end  108  of the bore  104 . Just as the upper end  120  of the magnetic member  110  exits the second end  108  of the bore  104 , the coil  100  is again de-energized and the magnetic member  110  is allowed to continue moving in a downward direction with no magnetic forces applied by the coil  100 . As the magnetic member  110  continues moving in a downward direction, the spiral torsion spring  60  is deflected by the corresponding downward movement of the support platform  46  until the spring force created by deflecting the spiral torsion spring  60  balances and gradually overcomes the downward inertial force of the loaded platform  46 , and the platform  46  begins to move in the opposite direction, upwardly away from the ground surface. Now, as the upper end  120  of the magnetic member  110  approaches the second end  108  of the bore  104  ( FIG. 4E ), no current is flowing through the coil  100  to create magnetic field lines that cooperate with the magnetic field lines of the magnetic member  110 . As the upper end  120  of the magnetic member  110  enters the second end  108  of the bore  104  ( FIG. 4F ), the coil  100  is energized to generate an attractive magnetic force that interacts with the magnetic field of the magnetic member  110  to thereby draw the magnetic member  110  into the bore  104 . The magnetic member  110  continues moving in an upward direction. Just prior to the upper end  120  of the magnetic member  110  exiting the first end  106  of the bore  104 , the coil  100  is de-energized to permit the magnetic member  110  to move upwardly, unhindered by any magnetic field generated by the coil  100 . Just after the upper end  120  of the magnetic member  110  exits the first end  106  of the bore  104 , the coil  100  is energized with current flowing in a direction that generates a repulsive force that interacts with the magnetic field of the magnetic member  110 , thereby pushing the magnetic member  110  further outside the first end  106  of the bore  104 . Just prior to the lower end  118  of the magnetic member  110  exiting the first end  106  of the bore  104 , the coil  100  is de-energized so that the magnetic field generated by the coil  100  is ceased. The magnetic member  110  continues to move in an upward direction with the support platform  46  until the forces acting on the support platform  46  due to inertia, gravity, spiral torsion spring  60 , and the load carried by the support platform  60  balance out, whereafter the support platform  46  and magnetic member  110  will begin to move downwardly toward the magnetic coil  100 . The control  114  continuously cycles current through the magnetic coil  100  in the manner described above and the motion described above is repeated so that the vertical reciprocating motion of the loaded platform  46  is maintained. 
     The magnetic drive  12  described above is particularly useful when the driven system operates at its natural frequency because a minimum amount of force is needed to be generated by the magnetic drive  12  (to overcome friction losses, for example) whereby the cyclical motion may be maintained with the minimum force applied by the drive  12 . In the embodiment shown, the natural frequency of the loaded support platform  46  may be selectively adjusted by manipulating the roller  80  along the spring lever  66 . As the support platform  46  moves upwardly and downwardly in a reciprocating fashion at the system&#39;s natural frequency the magnetic member  110  will be caused to move into and out of the coil  100  as described above, whereby the magnetic drive  12  will maintain the substantially vertical reciprocating motion. 
     Energization of the coil  100  can be automatically adjusted by the control  114  to accommodate variations in natural frequency. In the embodiment shown, the magnetic drive  12  includes a sensor  120  ( FIGS. 1 ,  2 , and  5 ) that detects the position of the magnetic member  110  relative to the electric coil  100  and provides signals to the control  114  to energize and de-energize the electric coil  100  in the manner described above. In this embodiment, the sensor  120  comprises an optical position sensor  122  operatively coupled to the frame  16 , and a position indicating member  124  coupled to the support platform  46  (see  FIG. 5 ). As the support platform  46  is reciprocated in a substantially vertical direction, the position indicating member  124  is caused to pass by the optical position sensor  122 . When the optical position sensor  122  senses the presence of the position indicating member  124 , signals are provided to the control  114  and the control  114  responds by energizing and de-energizing the electric coil  100  to operate in the manner described above. 
     The control  114  may also be configured to automatically turn the apparatus on and off, by selectively energizing and de-energizing the electric coil  100 . For example, the control  114  may be configured to discontinue energization of the electric coil  100  after a predetermined period of continuous operation, or alternatively after a continuous period of non-use. The control  114  may also be configured such that energization of the electric coil  100  is ceased if no signal is received from the sensor  120 . With such a configuration, the vertical reciprocating motion of the support platform may be stopped simply by holding the platform at a fixed position, either near the uppermost point of travel, or the lowermost point of travel, to thereby prevent the sensor  120  from sending a signal to the control  114 . In a similar fashion, the control  114  may be configured to automatically energize the electric coil  100  at the instant the control receives a signal from the sensor  120  after a period of continuous non-use. When the magnetic drive  12  is used with a system that is configured to operate at its resonance frequency, such as the apparatus  10  described above, and the system further includes a control  114  as described above, a minimum amount of power is required to maintain operation of the system. Moreover, power is conserved by the ability of the control  114  to automatically turn the drive  12  on and off as needed. In an exemplary embodiment, an apparatus  10  for reciprocating an infant support  54  may be powered by six D-cell batteries and may operate continuously for more than approximately 120 hours. 
     While the present invention has been illustrated by the description of an embodiment thereof, and while the embodiment has been described in considerable detail, it is not intended to restrict or in any way limit the scope of the appended claims to such detail. The various features discussed herein may be used alone or in any combination. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope or spirit of the general inventive concept.