You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a Continuation application under 35 U.S.C. §120 based upon co-pending U.S. patent application Ser. No. 14/750,055 filed on Jun. 25, 2015, which claims priority to U.S. patent application Ser. No. 14/330,070 filed on Jul. 16, 2014, which claims priority to U.S. provisional application 61/847,653 filed on Jul. 18, 2013. Additionally, this present application claims the benefit of priority of co-pending U.S. patent application Ser. No. 14/750,055 filed on Jun. 25, 2015. The entire disclosure of the prior application is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to an overhead door backup spring system for use in connection with providing an emergency spring counterweight for overhead doors upon failure of a main spring counterweight. 
         [0004]    2. Description of the Prior Art 
         [0005]    Overhead door backup spring systems are desirable for allowing a user to still operate an overhead door, such as a garage door, even when the main spring counterweight has failed. The majority of overhead doors include multiple door panel sections that are hinged together and which travel along parallel side tracks or rails from a closed vertical position to an open horizontal position. These overhead doors normal utilize a torsion spring connected to a shaft which supplies the force to counter balance the door during the opening operation. The spring has a life cycle and will break or fail when reached. 
         [0006]    When the spring fails, the user will call a garage door technician to make a house-call to replace the broken spring. Many users are not able to manually lift the full weight of the garage door because the spring is not providing the counter lifting force. In some cases, the user&#39;s vehicle is in the garage, which is now trapped and thus the technician would be required to make an emergency house-call. The emergency house-call can cost the user an increased rate over planned service calls. 
         [0007]    Known garage door auxiliary spring systems specifically use a second spring that is connected to the shaft and which provides a lifting force for the door during only a portion of the travel path. 
         [0008]    While the above-described devices fulfill their respective, particular objectives and requirements, the aforementioned patents do not describe an overhead door backup spring system that allows providing an emergency spring counterweight for overhead doors upon failure of a main spring counterweight 
         [0009]    Therefore, a need exists for a new and improved overhead door spring system that uses an extra spring providing an emergency spring counterweight for overhead doors upon failure of a main spring counterweight. In this regard, the present invention substantially fulfills this need. In this respect, the overhead door backup spring system according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides an apparatus primarily developed for the purpose of providing an emergency spring counterweight for overhead doors upon failure of a main spring counterweight. 
       SUMMARY OF THE INVENTION 
       [0010]    In view of the foregoing disadvantages inherent in the known types of garage door auxiliary spring systems now present in the prior art, the present invention provides an improved overhead door backup spring system, and overcomes the above-mentioned disadvantages and drawbacks of the prior art. As such, the general purpose of the present invention, which will be described subsequently in greater detail, is to provide a new and improved overhead door backup spring system and method which has all the advantages of the prior art mentioned heretofore and many novel features that result in an overhead door backup spring system which is not anticipated, rendered obvious, suggested, or even implied by the prior art, either alone or in any combination thereof. 
         [0011]    To attain this, the present invention essentially comprises an activation unit for operating upon failure of a spring. The activation unit has a plunger including an extension. The extension is operably associated with a portion of the spring. The plunger is configured to be operable upon failure of the spring 
         [0012]    The plunger can be rotatably and slidably received in a plunger sleeve which surrounds the plunger. The extension can be a plunger pin extending out from the plunger, with the plunger pin slidably received in a sleeve slot defined in the plunger sleeve. The activation unit can further include a plunger spring that biases the plunger away from the spring. 
         [0013]    The plunger of the activation unit can further being engageable with an engagement unit of an overhead door backup spring system upon failure of the spring. The engagement unit can be engageable with an auxiliary spring engagement unit in an engaged position upon operation of the activation unit upon failure of the spring. The engagement unit can be operably associated with an auxiliary spring, with the engagement unit being configured to transfer torque from the auxiliary spring to a shaft of an overhead door in the engaged position. 
         [0014]    There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood and in order that the present contribution to the art may be better appreciated. 
         [0015]    The activation unit may also include an activation spring attached to an activation bar extending from the spring. The activation spring has a spring force less than a torque of the spring to move the activation bar upon failure of the spring. 
         [0016]    There are, of course, additional features of the invention that will be described hereinafter and which will form the subject matter of the claims attached. 
         [0017]    Numerous objects, features and advantages of the present invention will be readily apparent to those of ordinary skill in the art upon a reading of the following detailed description of presently preferred, but nonetheless illustrative, embodiments of the present invention when taken in conjunction with the accompanying drawings. In this respect, before explaining the current embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of descriptions and should not be regarded as limiting. 
         [0018]    As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
         [0019]    It is therefore an object of the present invention to provide a new and improved activation unit that has all of the advantages of the prior art garage door auxiliary spring systems and none of the disadvantages. 
         [0020]    It is another object of the present invention to provide a new and improved activation unit that may be easily and efficiently manufactured and marketed. 
         [0021]    An even further object of the present invention is to provide a new and improved activation unit that has a low cost of manufacture with regard to both materials and labor, and which accordingly is then susceptible of low prices of sale to the consuming public, thereby making such activation unit economically available to the buying public. 
         [0022]    Still another object of the present invention is to provide a new activation unit that provides in the apparatuses and methods of the prior art some of the advantages thereof, while simultaneously overcoming some of the disadvantages normally associated therewith. 
         [0023]    Lastly, it is an object of the present invention to provide a new and improved method of using an activation unit. The method can include the steps of moving a portion of a spring upon failure of the spring. Then engaging the portion of the spring with an extension of a plunger. Then moving the plunger upon engagement with the portion of the spring. 
         [0024]    These together with other objects of the invention, along with the various features of novelty that characterize the invention, are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be made to the accompanying drawings and descriptive matter in which there are illustrated embodiments of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein: 
           [0026]      FIG. 1  is a top elevational view of an embodiment of the overhead door backup spring system constructed in accordance with the principles of the present invention and fitting to an existing overhead door spring and shaft assembly, with the phantom lines depicting environmental structure and forming no part of the claimed invention. 
           [0027]      FIG. 2  is a top perspective view of the overhead door backup spring system of the present invention. 
           [0028]      FIG. 3  is a cross-section view of the activation linkage and the backup spring engaging assembly of the overhead door backup spring system in the non-engaged position taken along line  3 - 3  of  FIG. 1 . 
           [0029]      FIG. 4  is a cross-section view of the activation linkage and the backup spring engaging assembly of the overhead door backup spring system in the engaged position. 
           [0030]      FIG. 5  is a cross-section view of the activation linkage and the backup spring engaging assembly of the overhead door backup spring system in the non-engaged position taken along line  5 - 5  of  FIG. 3 . 
           [0031]      FIG. 6  is a cross-section view of the activation linkage and the backup spring engaging assembly of the overhead door backup spring system in the engaged position. 
           [0032]      FIG. 7  is a side perspective view of the safety spring assembly of the overhead door backup spring system in the non-engaged position. 
           [0033]      FIG. 8  is a side perspective view of the safety spring assembly of the overhead door backup spring system in the engaged position. 
           [0034]      FIG. 9  is a top perspective view of an alternate embodiment of the overhead door backup spring system of the present invention. 
           [0035]      FIG. 10  is a side perspective view of the activation linkage and the backup spring engaging assembly of the alternate embodiment overhead door backup spring system of  FIG. 9 . 
           [0036]      FIG. 11  is a side perspective view of an alternate embodiment of the overhead door backup spring system of the present invention. 
           [0037]      FIG. 12  is a cross-sectional view of the activation linkage of the alternate embodiment overhead door backup spring system in the non-engaged position taken along line  12 - 12  of  FIG. 11 . 
           [0038]      FIG. 13  is a cross-sectional view of the activation linkage of the alternate embodiment overhead door backup spring system of  FIG. 11  in the engaged position. 
           [0039]      FIG. 14  is a top perspective view of an alternate embodiment overhead door backup spring system of the present invention. 
           [0040]      FIG. 15  is a front perspective view of the alternate embodiment overhead door backup spring system with the control assembly removed for clarity and the plunger sleeve being transparent so as to view the interior of the activation unit. 
           [0041]      FIG. 16  is a perspective view of the activation unit of the alternate embodiment overhead door backup spring system of the present invention. 
           [0042]      FIG. 17  is a cut-away perspective view of the activation unit of the alternate embodiment overhead door backup spring system of the present invention. 
           [0043]      FIG. 18  is a front perspective view of the control assembly of the alternate embodiment overhead door backup spring system of the present invention. 
           [0044]      FIG. 19  is a front perspective view of the control assembly of the alternate embodiment overhead door backup spring system of the present invention. 
           [0045]      FIG. 20  is a rear perspective view of the control assembly of the alternate embodiment overhead door backup spring system of the present invention. 
           [0046]      FIG. 21  is a top perspective view of the engagement assembly of the alternate embodiment overhead door backup spring system of the present invention with a transparent plunger sleeve and a transparent pillow block. 
           [0047]      FIG. 22  is a cross-sectional view of the activation unit and engagement assembly in the non-engaged position. 
           [0048]      FIG. 23  is a cross-sectional view of the activation unit and engagement assembly in the engaged position 
           [0049]      FIG. 24  is a front perspective view of the alternate embodiment overhead door backup spring system of the present invention. 
           [0050]      FIG. 25  is a front side view of the alternate embodiment overhead door backup spring system of the present invention. 
           [0051]      FIG. 26  is a top elevational view of the alternate embodiment overhead door backup spring system of the present invention. 
       
    
    
       [0052]    The same reference numerals refer to the same parts throughout the various figures. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0053]    Referring now to the drawings, and particularly to  FIGS. 1-26 , an embodiment of the overhead door backup spring system of the present invention is shown and generally designated by the reference numeral  10 . 
         [0054]    In  FIGS. 1 and 2 , a new and improved overhead door backup spring system  10  of the present invention for providing an emergency spring counterweight for overhead doors upon failure of a main spring counterweight is illustrated and will be described. More particularly, the backup spring system  10  can be retrofitted to an existing overhead door spring and shaft assembly  2 . It can be appreciated that the present invention can be integrated in new overhead door spring and shaft assemblies. Standard overhead door spring and shaft assemblies  2  are secured to a wall or beam  3 , and include a shaft  5  connected to bearings  4  at its ends, and a main spring  6  connected to the shaft  5  and a main spring bracket  7 . The main spring  6  provides torque to the shaft  5  which provides a lifting force to an overhead door (not shown). 
         [0055]    When the main spring  6  fails, the door is always in the closed position and/or will remain in the closed position. The user would be required to manually lift the entire weight of the door, and in cases where the user is not able to lift the door and the user&#39;s vehicle in the garage, then the user would require an emergency service call from a technician. The emergency service call can be very expensive, even double a standard service call rate. 
         [0056]    The backup spring system  10  includes an auxiliary spring  12 , a control assembly  22  and an engagement assembly  50 . The auxiliary spring  12  is held in a coiled state by the control assembly  22 , thereby storing potential energy or torque and releasing such upon activation of a line  24  by the user. The control assembly  22  simultaneously releases the torque energy of the auxiliary spring  12  and transfers it to the engagement assembly  50 , which then transfer it to the shaft  5 . 
         [0057]    The auxiliary spring  12 , can be but not limited to, a coil spring fitted over the shaft  5  so that the shaft is received in the auxiliary spring  12 . The auxiliary spring  12  is attached to a mounting bracket  16  via a coupler  14  at a first end, which secures the first end of the auxiliary spring  12  to the mounting bracket  16  and prevents the auxiliary spring  12  from rotating. A second end of the auxiliary spring  12  includes a fitting  18  having a plurality of extensions or spring posts  20  extending radially outwardly therefrom. The second end of the auxiliary spring  12  and fitting  18  are configured to be rotatable about the shaft  5 . 
         [0058]    Regarding  FIGS. 2-6  the control assembly  22  can be fitted to a mount  28  which is attached to the beam  3  or can be attached directly to the beam  3 . The line  24  activates the control assembly  22  and can run over a pulley  26 , thereby allowing the line  24  to be positioned remote from the control assembly  22 . The control assembly  22  includes a lever  30  pivotably mounted to the mount  28  via a pivot pin or hinge  32 . 
         [0059]    The hinge  32  is located between free ends of the lever  30 , with the line  24  coupled at one end and an engagement rod  40  coupled to an opposite end, as best illustrated in  FIGS. 3 and 4 . A retaining rod  34  is coupled to the lever  30  between the hinge  32  and the engagement rod  40 . The retaining rod  34  passes through at least two linear bearings  36  fitted to the mount  28 . The linear bearings  36  hold the torque of the auxiliary spring  12  in a pre-wound state, thus creating the potential energy or torque required to rotate the shaft  5  upon activation. The retaining rod  34  extends out past the linear bearings  36  so as to protrude between the spring posts  20  and thus engage with one of the spring posts  20  to hold the auxiliary spring  12  in the pre-wound state. 
         [0060]    The control assembly  22  additionally includes a fork  42  that is pivotably coupled to the mount  28  via a fork hinge  44 , and is configured so that the shaft  5  passes between forks thereof. A fork stop  46  extends away from the mount  28  adjacent the fork  42  so as to limit the travel of the fork  42  away from the engagement assembly  50 . The engagement rod  40  is additionally coupled to a fork extension  43  spaced away from and connected to the fork  42 . The engagement rod  40  transfers rotational movement of the lever  30  to pivotal movement of the fork  42 . 
         [0061]    The engagement assembly  50  features a central bore configured to receive the shaft  5  therethrough, and includes a disk  52 , a pillow block  56  and an engagement disk  64 . The disk  52  and engagement disk  64  are slidable on the shaft  5 , and at least two sliding rods  54 . The disk  52  includes a surface configured to contact the fork  42 . The sliding rods  54  extend away from the disk  52 , through the pillow block  56  by traveling on a bearing race, and are coupled to the engagement disk  64 . 
         [0062]    The pillow block  56  features a cutout  58  that has a threaded bore therethrough for receiving a set screw  60 . The set screw  60  is configured to engage with the shaft  5  and retain the pillow block  56  to the shaft  5  while preventing the pillow block  56  to rotate about the shaft  5 . The pillow block  56  additionally includes a linear bearing  62  fitted to a recess in the pillow block  56  and to the engagement disk  64 , and is configured to slide on the shaft  5 . 
         [0063]    The engagement disk  64  includes a plurality of engagement posts  66  extending away from the engagement disk  64  toward the fitting  18 , wherein the engagement posts  66  are parallel with the shaft  5 . The engagement posts  66  are configured to engage with the spring posts  20 , upon movement of the disk  52  produced by the fork  42 . 
         [0064]    Regarding  FIGS. 3 and 5 , the lever  30 , fork  42 , disk  52  and engagement disk  64  are in a non-engaged position. In the non-engaged position, the retaining rod  34  is between the spring posts  20  and in contact with at least one of the spring posts  20 . The fork  42  is not engaged with the disk  52 , so the disk  52  and the engagement disk  64  are positioned away from the auxiliary spring  12 , thus the engagement posts  66  are not located between the spring posts  20 . The linear bearings  36  hold the retaining rod  34  in place, preventing the retaining rod  34  from moving upward or downward by the resulting torque from the pre-wound auxiliary spring  12 . 
         [0065]    Regarding  FIGS. 4 and 6 , the user would pull on the line  24 , thereby pivoting the lever  30  about the hinge  32  and thus pulling the retaining rod  34  and the engagement rod  40  in a direction opposite that of the line  24 . The lever  30  pulls the retaining rod  34  out of engagement with the spring posts  20 . Simultaneously, the engagement rod  40  pulls the fork  42  toward the disk  52  and pushes the disk  52  towards the fitting  18 . The sliding movement of the disk  52  slides the sliding rods  54  through the pillow block  56  and pushes the engagement disk  64  towards the fitting  18 . The sliding movement of the engagement disk  64  pushes the engagement posts  66  between the spring posts  20 . This simultaneous disengagement of the retaining rod  34  and engagement of the engagement posts  66  allows the auxiliary spring  12  to freely rotate, and thus transfers the torque of the auxiliary spring  12  to the pillow block  56  via the sliding rods  54  received therethrough, and then to the shaft  5  so as to assist in lifting the door coupled to the shaft  5 . 
         [0066]    Regarding  FIGS. 7 and 8 , the backup spring system  10  can also include a safety assembly for the line  24 , so as to prevent the line  24  from being activated when the main spring  6  is not broken. The safety assembly can be associated with the main spring bracket  7  or an additional main spring bracket  70 . The bracket  70  features a first bore  72 , and a second bore  74  in communication with the first bore  72 . The line  24  passes through the first and second bores  72 ,  74  and includes a washer  25 . The washer  25  is sized larger than the second bore  74  so as to prevent the washer  25  from passing therethrough when the user pulls on the line  24 , as best illustrated in  FIG. 7 . The first bore  72  is configured to allow the washer  25  to pass therethrough. 
         [0067]    A shoulder bolt  76  is connected to the main spring  6 , and passes through the second bore  74 . A safety spring  78  is connected to and pulls on the shoulder bolt  76 ; however the torque of a non-broken main spring  6  overcomes the pull of the safety spring  78 . 
         [0068]    In operation, when the main spring  6  fails, the safety spring  78  pulls the shoulder bolt  76  from one end of the second bore  74  toward the other end. The shoulder bolt  76  contacts the washer  25  and pushes it away from the second bore  74  and toward the first bore  72 , as best illustrated in  FIG. 8 . Once the washer  25  is adjacent the first bore  72 , then the user can pull the line  24  and the washer  25  will then pass freely through the first bore  72 . 
         [0069]    Regarding  FIGS. 9 and 10 , an alternate embodiment backup spring system  80  is described. The backup spring system  80  includes the auxiliary spring  12 , a fork  42 ′ activated by the line  24 , and an engagement assembly. The main spring  6  is connected to the shaft  5  and a mounting bracket  82 . A first engagement fitting  84  is rigidly connected to the shaft  5 , and it includes a plurality of extensions  86  extending toward the auxiliary spring  12  parallel with the shaft  5 . 
         [0070]    The auxiliary spring  12  is secured at one end so as not to rotate, and includes a pillow block  96  at an opposite end adjacent the first engagement fitting  84 . The fork  42 ′ is pivotably connected to the wall or mount  28  via a hinge  44 ′, and is activated by the line  24  via a fork extension  43 ′. The fork  42 ′ is configured so that the auxiliary spring  12  passes through the forks, so as to make contact with the pillow block  96 . 
         [0071]    The engagement assembly includes a pillow block  96  which slides along the shaft  5  passing therethrough and is coupled to a disk  98 . A bore  100  is defined through the center of the disk  98  and features multiple notches  102 . A geometric stop block  104  is rigidly fitted to the shaft  5 , and positioned so that its corners are received in the notches  102 . The stop block  104  retains the auxiliary spring  12  in a pre-wound state. 
         [0072]    A plurality of bearings or rollers  106  connected to the disk  98  contact the stop block  104  and allows the pillow block  96  and disk  98  to slide freely over the stop block  104  when acted upon by the fork  42 ′. 
         [0073]    Multiple sliding posts  108  connect the disk  98  to a second engagement fitting  110  which includes a plurality of extensions  112  extending toward the first engagement fitting  84  parallel with the shaft  5 . The extensions  112  of the second engagement fitting  110  are configured to mesh with the extensions  86  of the first engagement fitting  84  when moved into an engagement position by the fork  42 ′. 
         [0074]    When the fork  42 ′ is pivoted by the line  24 , it pushes the pillow block  96 , the disk  98  and the second engagement fitting  110  toward the first engagement fitting  84 . The disk  98  travels over and past the stop block  104  so that the stop block  104  is received in a hollow interior of the pillow block  96 , thereby allow the pillow block  96  to freely rotate around stop block  104 . The extensions  112  of the second engagement fitting  110  engage with the extensions  86  of the first engagement fitting  84 , thereby transferring the torque of the pre-wound auxiliary spring  12  to the shaft  5 . 
         [0075]    Regarding  FIG. 11 , an alternate embodiment backup spring system  120  is described. The backup spring system  120  includes the auxiliary spring  12 , a control lever  130 , a fork  42 ″ and an engagement assembly. The auxiliary spring  12  is held in a coiled state by the control lever  130 , thereby storing potential energy or torque and releasing such upon activation of the line  24  by the user. The control lever  130  and the fork  42 ″ simultaneously release the torque energy of the auxiliary spring  12  and transfer it to the engagement assembly, which then transfer it to the shaft  5 . 
         [0076]    The auxiliary spring  12  is attached to a mounting bracket via a coupler at a first end, which secures the first end of the auxiliary spring  12  to the mounting bracket and prevents the auxiliary spring  12  from rotating. A second end of the auxiliary spring  12  includes the fitting  18  featuring the spring posts  20  extending radially outwardly therefrom. The second end of the auxiliary spring  12  and fitting  18  are configured to be rotatable about the shaft  5 . 
         [0077]    The control lever  130  and a control bracket  122  can be fitted to the mount  28  which is attached to the beam  3  or directly to the beam  3 . The line  24  passes through a first bore  124  defined through the control bracket  122  and is coupled to the control lever  130  and the fork  42 ″. The fork is pivotably connected to the mount  28  via a hinge  44 ″, and the control lever  130  is pivotably mounted to the mount  28  via a pivot pin or hinge  132 , as best illustrated in  FIGS. 12 and 13 . The fork  42 ″ is moved upon activation of the line  24  and is configured so that the shaft  5  passes between forks. 
         [0078]    The hinge  132  is located between free ends of the control lever  130 , with the line  24  coupled at one end and a retaining rod  34 ′ coupled to an opposite end. The retaining rod  34 ′ passes through a second bore  126  defined through the control bracket  122 . The second bore  126  hold the torque of the auxiliary spring  12  in a pre-wound state, thus creating the potential energy or torque required to rotate the shaft  5  upon activation. The retaining rod  34 ′ extends out past the control bracket  122  so as to protrude between the spring posts  20  and thus engage with one of the spring posts  20  to hold the auxiliary spring  12  in the pre-wound state. 
         [0079]    The engagement assembly includes a pillow block  96 ′ which slides along a stop block  104 ′ that is rigidly attached to the shaft  5 . An engagement disk  64 ′ is fitted to the pillow block. A bore  100 ′ is defined through the center of the engagement disk  64 ′ and is configured to receive the shaft  5  therethrough. The stop block  104 ′ is rigidly fitted to the shaft  5 , and is configured to retain the pillow block  96 ′ and transfer any rotational movement to the shaft  5 . The pillow block  56 ′ is slidable on the stop block  104 ′, and has a surface configured to contact the fork  42 ″. 
         [0080]    The engagement disk  64 ′ includes a plurality of engagement posts  66 ′ extending away from the engagement disk  64 ′ toward the fitting  18 , wherein the engagement posts  66 ′ are parallel with the shaft  5 . The engagement posts  66 ′ are configured to engage with the spring posts  20 , upon movement of the engagement disk  64 ′ produced by the fork  42 ″. 
         [0081]    Regarding  FIG. 12 , the control lever  130 , the fork  42 ″, and engagement disk  64 ′ are in a non-engaged position. In the non-engaged position, the retaining rod  34 ′ is between the spring posts  20  and in contact with at least one of the spring posts  20 . The fork  42 ″ is not engaged with the disk  52 , so the disk  52  and the engagement disk  64  are positioned away from the auxiliary spring  12 , thus the engagement posts  66 ′ are not located between the spring posts  20 . The second bore  126  holds the retaining rod  34 ′ in place, preventing the retaining rod  34 ′ from moving upward or downward by the resulting torque from the pre-wound auxiliary spring  12 . 
         [0082]    The control lever  130  may include a line slot  136  and a rod slot  134  which allow for rotational movement of the control lever  130  with lateral movement of the line  24  and retaining rod  34 ′. 
         [0083]    Regarding  FIG. 13 , the user would pull on the line  24 , thereby pivoting the control lever  130  about the hinge  132  and thus pulling the retaining rod  34 ′ in a direction opposite that of the line  24 . The control lever  130  pulls the retaining rod  34 ′ out of engagement with the spring posts  20 . Simultaneously, the line  24  pulls the fork  42 ″ toward the pillow block  96 ′, which pushes the pillow block  96 ′ and engagement disk  64 ′ towards the fitting  18 . This simultaneous disengagement of the retaining rod  34 ′ and engagement of the engagement posts  66 ′ allows the auxiliary spring  12  to freely rotate, and thus transfers the torque of the auxiliary spring  12  to the pillow block  96 ′ via the stop block  104 ′, and then to the shaft  5  so as to assist in lifting the door coupled to the shaft  5 . 
         [0084]    In  FIGS. 14-26 , an alternate embodiment of the overhead door backup spring system of the present invention is shown and generally designated by the reference numeral  200 . 
         [0085]    The alternate overhead door backup spring system  200  of the present invention for providing an emergency spring counterweight for overhead doors upon failure of a main spring counterweight is illustrated and will be described. More particularly, the backup spring system  200  can be retrofitted to an existing overhead door spring and shaft assembly. It can be appreciated that the backup spring system  200  can be integrated in new overhead door spring and shaft assemblies. 
         [0086]    Regarding  FIG. 14 , the backup spring system  200  includes an auxiliary spring  12 , an activation unit  220 , a control assembly  240 , an engagement assembly  280 , and an auxiliary spring engagement assembly  300 . The auxiliary spring  12  is held in a coiled state by the control assembly  240 , thereby storing potential energy or torque and releasing such upon activation of by the backup spring system  200  automatically upon failure of the main spring  6 . The activation unit  220  automatically activates the control assembly  240  which simultaneously releases the torque energy of the auxiliary spring  12  and transfers it to the engagement assembly  280 , which then transfer it to the shaft  5 . 
         [0087]    The auxiliary spring  12 , can be but not limited to, a coil spring fitted over the shaft  5  so that the shaft is received in the auxiliary spring  12 . The auxiliary spring  12  is attached to a mounting bracket  208 , and a spring pin  204  and bracket slot  205  arrangements which prevents the main spring  6  from rotating until failure. While the auxiliary spring  12  is retained in a torqued or tensioned position by the control assembly  240  and engagement assembly  280 . 
         [0088]    Referencing  FIGS. 14-17 , the activation unit  220  includes an activation bar  210  coupled to the main spring  6 , so as to rotate about the shaft  5  upon failure of the main spring  6 . The torque of the main spring  6  keeps the activation bar  210  in the non-engagement position and is retained by a side edge of a slot defined in the bracket  208 . An activation spring  211  is attached to the bracket  208  and to the activation bar  210  to provide a pulling force that counteracts the torque of the main spring  6 , as best illustrated in  FIG. 16 . The pulling force of the activation spring  211  is less than the torque of the main spring  6 . Upon failure of the main spring  6  its torque is reduced below the pulling force of the activation spring  211 . The activation spring  211  is now able to pull the activation bar  210  into the engaged position. 
         [0089]    A release member or bar  212  is attached to and able to move with the activation bar  212  upon failure of the main spring  6 . The release member  212  can include a bore configured to receive the activation bar  212  therethrough, or a bracket attachable to the activation bar  212 . The release member  212  is operated by the activation bar  210  so as to rotate or move along a pin  214  by way of a slot  213  defined through the release member  212 . 
         [0090]    A linkage can be used to operate the control assembly  240 . The linkage can include a stop  216  is fitted to a control shaft or line  218 , and is biased by a stop spring  217  located to produce a force on the control shaft  218 . In the non-engagement position, the release member  212  prevents the stop  216  from moving, thus retaining the control shaft  218  in position. When the release member  212  is operated by the activation bar  210 , the slot  213  is aligned with the stop  216  thereby allowed the spring  217  to move the control shaft  218 . 
         [0091]    A plunger sleeve  222  extends from the bracket  208 , opposite the main spring  6 , and is secured to the bracket  208  or to the shaft  5  by a bearing  206 . The plunger sleeve  222  includes a J-shaped or L-shaped slot  224 , as best illustrated in  FIG. 17 . 
         [0092]    A plunger  226  is slidably received in the plunger sleeve  222 , and is biased away from the bracket  208  by a plunger spring  230 . The plunger  226  includes a plunger pin  228  extending through the slot  224  and which is in operable location with the activation bar  210 . The plunger  226  can also include a recess configured to receive a first end of the plunger spring  230 , while a second of the plunger spring  230  abuts the bearing  206  or bracket  208 . The activation bar  210  can have a forked end so as to receive a section or the plunger pin  228 . 
         [0093]    The shape of the slot  224  prevents the plunger  226  from moving away from the bracket  208  in a non-engaged position because a wall or edge of the slot  224  contacts the plunger pin  228  in a direction substantially perpendicular to the sliding movement of the plunger  226  produced by the plunger spring  230 . Once the plunger pin  228  is rotated by the activation bar  210  upon failure of the main spring  6  to an engaged position where the plunger pin  228  is free to travel down the slot  224  thereby allowing the plunger  226  to move away from the bracket  208 . 
         [0094]    Referencing  FIGS. 18-20 , the control assembly  240  includes first and second plate assemblies in a spaced relationship with each other. The first plate assembly includes a pair of first plates  244  mounted to a wall or mount  242  via a plurality of fasteners  248 . The first plates  244  are spaced apart from each other via spacers  249  located about the fasteners  248 , thus created a gap between the first plates  244 . The first plates  244  define corresponding J-shaped or L-shaped plate slots  246  that are aligned with each other. The plate slots  246  include a first section parallel with a longitudinal axis of the control shaft  218 , and a second section that is perpendicular to the longitudinal axis of the control shaft  218 . 
         [0095]    A control shaft block  250  is fitted to an end of the control shaft  218 , and is slidably or moveably received in the gap between the first plates  244 . The control shaft black  250  can be located so as to slidably rest upon at least one of the spacers  249 , thereby providing support for the control shaft block  250 . 
         [0096]    The second plate assembly includes a pair of second plates  262  mounted to the wall or mount  242  via a plurality of fasteners  263 . The second plates  262  are spaced apart from each other via spacers  249  located about the fasteners  263 , thus created a gap between the second plates  262 . The second plates  262  can also define corresponding J-shaped or L-shaped plate slots so that first plates can be used to produce the second plates  262 . Each of the second plates  262  includes facing detents or bumps  264 . 
         [0097]    A control bar  252  is slidably received in the gaps of the first and second plates  244 ,  262 . The control bar  252  includes a post  254  that is received in the plate slots  246 , and an engagement block  256  located between the first and second plate assemblies. The engagement block  256  defines a bore  258  configured to receive the control bar  252 , and a set screw configured to secure the engagement block  256  to the control bar  252  in an adjustable position. 
         [0098]    The section of the control bar  252  located between the second plates  262  is positioned so as to be adjacent with and below the detents  264 , thereby creating a pivot point while allowing the control bar  252  to slide there along. 
         [0099]    A control bar spring  260  is connected to a spacer or pin  265  located near a top of the second plates  262 , and to the control bar  252  at a location between adjacent or near the first plates  244  or the engagement block  256 , as best illustrated in  FIGS. 18 and 19 . The control bar spring  260  produces an upward force on the control bar  252 . 
         [0100]    The control shaft block  250  is operable coupled to an end section of the control bar  252  so as to slide or move the control bar  252  upon movement of the control shaft  218 . When the control bar  252  moves, the post  254  slides along the first section of the plate slots  246  prevents the control bar  252  from moving upward until it is aligned with the second section of the plate slots  246 . At this position, the control bar spring  260  pulls on the control bar  252  thereby pivoting it against the detents  264  and lifting the post  254  up the second section of the plate slots  246 . 
         [0101]    An engagement lever assembly is pivotably connected to the second plates  262  via a pair of lever members  266  which are spaced apart from each other so as to receive the second plates  262  therebetween. A first end of the lever members  266  are pivotably fitted to at least one of the second plate fasteners  268  located near a lower corner of the second plates  262 . A second end of the lever members  266  extend past the second plates  262 . A first lever bar  270  extends from the second end of the lever members  266  and includes a linkage end. 
         [0102]    A second lever bar  272  includes a linkage end connected to the linkage end of the first lever bar  270  so as to extend the second lever bar  272  away from the first lever bar  270  at an angle different from the first lever bar  270 . The first lever bar  270  can be rotatably connected to the lever members  266 , and/or the second lever bar  272  can be pivotably connected to the first lever bar  270 . The first lever bar  270  can be biased by a spring so as to rotate the second lever bar  272  in a predetermined direction. 
         [0103]    Referencing  FIGS. 21-23 , the engagement assembly  280  features a central bore configured to receive the shaft  5  therethrough, and includes an engagement disk  282 , a pillow block  290  and the auxiliary spring engagement assembly  300 . 
         [0104]    The engagement disk  282  includes a plurality of engagement posts  284  extending away from the engagement disk  282  toward the pillow block  290 , wherein the engagement posts  284  are parallel with the shaft  5 . Each of the engagement posts  284  includes an annular recess  288  located at predetermined distance on the posts  284 , and a tapered free end  286 . The free end  286  features a base having a diameter larger than a diameter of it respective post  284  to create a ledge, and a tapering tip. 
         [0105]    The engagement disk  282  also includes a surface configured to rotatably contact the plunger  226 , and is configured to slide along the shaft  5  when operated by movement of the plunger  226 . The engagement disk  282  can slide along the shaft  5  by way of a linear or thrust bearing. It can be appreciated that the engagement disk  282  and/or the plunger  226  and/or the plunger sleeve  222  can include a magnet (not shown) to assist retaining the engagement disk  282  in the non-engaged position. 
         [0106]    The pillow block  290  is located between the engagement disk  282  and the free end  286  of the engagement posts  284 , and is retained therebetween by the ledge of the free end  286 . The pillow block  290  features a cutout or keyway  298  that has a threaded bore therethrough for receiving a set screw  299 . The set screw  299  is configured to engage with the shaft  5  and retain the pillow block  290  to the shaft  5  while preventing the pillow block  290  from rotating about the shaft  5 . The keyway  298  allows the position of the pillow block  290  on the shaft  5  to be adjusted. 
         [0107]    The pillow block  290  includes a plurality of longitudinal bores  292 , and a plurality of retention balls  294  each being moveably located in bores defined in the pillow block  290 . The bores associated the retention balls  294  are in communication with one of the longitudinal bores  292 , and it can be appreciated that these bores are defined from the interior or exterior of the pillow block  290 . The longitudinal bores  292  are each configured to slidably receive at least one of the engagement posts  284  therethrough from the non-engaged position to the engaged position. Each of the retention balls  294  includes a spring for biasing the ball  294  toward the engagement post  284 . When the annular recess  288  of the engagement post  284  is aligned with a corresponding ball  294 , the ball is received in the recess  288  to retain the engagement post  284  in a predetermined position. 
         [0108]    The auxiliary spring engagement assembly  300  is located at an end of the auxiliary spring  12 , and includes a cylindrical extension  302 , a plurality of spring posts  304  extending radially outward from the cylindrical extension  302 , and a spring post disk  308  located between the spring posts  304  and an end of the backup spring  12 . The auxiliary spring engagement assembly  300  is rotatably supported about the shaft  5  by a bearing. The cylindrical extension  302  has a diameter that allows it to be received between the free ends  286  of the engagement posts  284 . 
         [0109]    Each of the spring posts  304  include a notch  306  configured to receive at least one of the ledges created by the free end  286  of the engagement post  284 , when the engagement posts  284  are in the engaged position. The notches  306  retain engagement between the engagement posts  284  and the spring posts  304  while preventing the engagement posts  284  from retracting back to the non-engaged position until desired by the user. The spring posts  304  have a length allowing at least one of them to contact and abut against the engagement block  256 , thereby retaining the auxiliary spring  12  in a pre-wound stated. The auxiliary spring  12  is allowed to transfer its torque to the engagement posts  284  when in the engaged position because the engagement block  256  is moved out of contact with the spring post  304 . 
         [0110]    The spring post disk  308  is slidable along the cylindrical extension  30 , and has a diameter allowing contact with free end of the second lever bar  272 . The spring post disk  308  is pushed toward the spring posts  304  by the biased force of the second lever bar  272 . The spring post disk  308  has a surface configured to be contacted by the tip of the free end  286  of the engagement posts  284  in the engaged position. The biasing force of the second lever bar  272  against the spring post disk  308  keeps the free ends  286  of the engagement posts  284  from advancing into the engaged position until desired. 
         [0111]    In operation, as best illustrated in  FIGS. 24-26 , the alternate embodiment backup spring system  200  is initially in the non-engaged position where the activation unit  220  is not activated and the plunger  226  is retracted, the control bar  252  is not pivoted and the post  254  is in the first section of the plate slots  246 , the engagement block  256  is in contact with at least one of the spring posts  304 , and the engagement posts  284  are not engaged with the spring posts  304 . 
         [0112]    In this non-engaged position, the torque of the pre-wound auxiliary spring  12  is retained as potential energy by the engagement block  256  in contact with at least one of the spring posts  304 . The main spring  6  and shaft  5  are allowed to rotated and operate normally because the activation bar  210  abuts the edge of the slot in the bracket  208  by the torque of the main spring  6 . The spring post disk  308  is urged toward the spring posts  304  by the second lever bar  272  to prevent accidental engagement of the engagement posts  284  with the spring posts  304 . 
         [0113]    Upon failure of the main spring  6 , the main spring torque is reduced below the pulling force of the activation spring  211 , which automatically pulls or rotates the activation bar  210 . The activation bar  212  consequently pushes the plunger pin  228  into the plunger sleeve slot  224  allowing the plunger spring  230  to push the plunger  226  against the engagement disk  282 . Simultaneously, the activation bar  212  moves the release member  212  that releases the stop  216  and allows the stop spring  217  to move the control shaft  218 . 
         [0114]    The force of the plunger  226  pushes the engagement disk  282  and thus pushes the engagement posts  284  toward an opened space between the spring posts  304 . The free ends  286  of the engagement posts  284  will contact the spring post disk  308  and push it away, thus allowing the free ends  286  to engage with the notches  306  of the spring posts  304 . 
         [0115]    Movement of the control shaft  218  moves the control shaft block  250  which moves the control bar  252 . The movement of the control bar  252  simultaneously moves the post  254  into the second section of the plate slots  246  allowing the control bar spring  260  to pivot the control bar  252  against the detents  264 , and move the engagement block  256  out of engagement with the spring post  304 . 
         [0116]    With the engagement block  256  out of engagement with the spring post  304 , and the engagement posts  284  engaged with the spring posts  304 , the alternate embodiment backup spring system  200  is now in the engaged position. In the engaged position, the potential energy of the pre-wound auxiliary spring  12  is now transferred to the engagement posts  284  and thus to the pillow block  290 , which transfers it to the shaft  5 , thereby allowing the overhead door to operate until the main spring  6  is repaired or replaced. 
         [0117]    While embodiments of the overhead door backup spring system have been described in detail, it should be apparent that modifications and variations thereto are possible, all of which fall within the true spirit and scope of the invention. With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention. And although providing an emergency spring counterweight for overhead doors upon failure of a main spring counterweight have been described, it should be appreciated that the overhead door backup spring system herein described is also suitable for any sliding element or closure which uses a spring for counter force or assisting force. 
         [0118]    Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

Summary:
The present invention essentially comprises an activation unit of an overhead door backup spring system operable upon failure of a spring, and method of using an activation unit. The activation unit has a rotating and sliding plunger that is operated upon failure of a spring. The activation unit can be used with an engagement unit that is engageable with an auxiliary spring to transfer torque from the auxiliary spring to an overhead door shaft. A plunger sleeve supports and guides the plunger by way of a sleeve slot that receives a plunger pin extending from the plunger. A plunger spring biases the plunger, while the sleeve slot retains the plunger in a biased state until activation by a portion of the spring upon failure of the spring.