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RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. Section 119 to U.S. Provisional Application No. 62/369,737, filed Aug. 1, 2016, entitled “DOOR CLOSER”, the contents of which are incorporated herein by reference in their entirety. 
     
    
     BACKGROUND 
     Technical Field 
       [0002]    The present invention relates to door closers, more particularly, to hydraulic door closers whose opening cycle and closing cycle is controlled by the movement of hydraulic fluid within the door closer. 
       Background of the Invention 
       [0003]    Hydraulic overhead concealed door closers typically include a spindle that extends below the closer housing to connect to the door as well as a cap on the bottom of the closer housing that faces the door. In such prior designs, the spindle extends through the cap. Unfortunately, such caps are often not effective in preventing hydraulic fluid within the door closer from leaking, which is aided by gravity. 
         [0004]    Fluid may also leak around the exterior of the spindle due to the fact that spindles may not have an entirely smooth exterior surface. 
         [0005]    In prior designs, one or more adjustment valves are usually present. The adjustment valves control the flow of hydraulic fluid through the door closer. Without sealing around the valves, the valves are prone to leakage of hydraulic fluid. 
         [0006]    Moreover, in prior designs, the end caps are typically comprised of aluminum whereas the closer housing is typically comprised of a different material (namely, steel) and the use of different materials can lead to leakage. 
         [0007]    Finally, backcheck is feature on some door closers that prevents the door from crashing into the wall when it is opened suddenly. However, existing backcheck designs on the market use a fixed spring instead of an adjustable spring so that the strength of the spring force in the existing designs cannot be adjusted by the user. 
         [0008]    Therefore, there is a need for new door closers that are less prone to leakage. There is also a need for new door closers with backcheck that also include an adjustable spring. 
       BRIEF SUMMARY 
       [0009]    The present disclosure provides a door closer that is less prone to leaking and/or includes backcheck with an adjustable spring as described herein. 
         [0010]    In some embodiments, the door closer includes one or more features that may resist leakage of hydraulic fluid: 1) the top cap is opposite the spindle and is on top of the housing so that gravity does not cause fluid to leak through the cap; 2) epoxy and an O-ring at the interface between the top cap and the housing of the door closer; 3) use of a rubber seal around the spindle, which may be in the form of a circular piece of rubbex with an inner wall and outer wall and the rubber seal may compress the inner wall against the spindle to create a seal, and the seal may be comprised of metallocene butadiene rubber; 4) use of dual O-rings on each valve stems, namely, adjustment valves that include—three ridges/lip, a bottom ridge, a middle ridge, and a top ridge and an O-ring is between the bottom ridge and the middle ridge and a different O-ring is between the middle and between the top ridge; and/or 5) use of caps that are made of steel (the same material as the housing) instead of aluminum and use of epoxy on the end caps. The present disclosure also provides use of backcheck with an adjustable spring. The aforementioned is intended to provide a brief summary of some of the features of the present disclosure and is not intended to limit the present disclosure. 
         [0011]    In some embodiments, the present overhead concealed door closer system comprising: a) a door frame defining a door opening, the door frame comprising a door frame width and a door frame top located above the door opening; b) a door comprising a door top and a door width, the door configured to pivot from a closed position in which the door covers the door opening, the door width is substantially parallel to the door frame width and the door top faces the door frame top, to an open position in which the door does not cover the door opening and in which the door width is not substantially parallel to the door frame width; c) a hydraulic overhead concealed door closer located in the door frame top and comprising: i) a housing comprising an interior, a top side, a bottom side opposite the top side and facing the door top when the door is in the closed position, a housing height extending from the housing top side to the housing bottom side and generally perpendicular to the door frame width and the door width, a front side, a rear side, a housing thickness extending from the housing front side to the housing rear side and generally perpendicular to the housing height and generally perpendicular to the door width when the door is in the closed position, a proximal end, a distal end, a housing width extending from the housing proximal end to the housing distal end and generally perpendicular to the housing height and the housing thickness and generally parallel to the door width when the door is in the closed position; a cylinder located in the housing interior, the cylinder having a cylinder length generally parallel to the housing width; a moveable piston located in the cylinder and configured to move at least partially along the cylinder length, the moveable piston dividing the housing interior into a proximal chamber and a distal chamber; iv) hydraulic fluid located in the proximal chamber and the distal chamber; v) at least one channel located in the housing interior and configured to transport hydraulic fluid between the proximal and distal chambers, the at least one channel having a channel length generally parallel to the housing width and the cylinder length; vi) a cam assembly comprising a spindle, the spindle having a spindle height generally parallel to the housing height and a spindle perimeter generally perpendicular to the spindle height, the spindle extending below the housing bottom side, the spindle configured to rotate about a spindle rotational axis generally parallel to the spindle height (rotate means at least partially rotate); vii) an arm attached to the spindle and to the door top; and viii) a top cap having a top cap diameter generally perpendicular to the housing height and sealing the distal chamber from the door frame, the top cap located at the top side of the housing and opposite to the spindle (more particularly opposite the tip of the spindle that extends below the bottom side of the housing). Optionally, pivoting the door from the closed position to the open position is configured to cause the spindle to rotate (i.e., partially rotate) about the spindle rotational axis and cause the piston to move within the cylinder at least partially along the cylinder length. Optionally, the spindle does not extend through the top cap. Optionally, the system further comprises a spindle seal, the spindle seal surrounding and compressing against the perimeter of the spindle and located below the top cap. Optionally, the spindle seal comprises a diameter generally perpendicular to the housing height. Optionally, the system further comprises a bottom bearing located between the spindle seal and the cam assembly, the bottom bearing comprising a diameter generally perpendicular to the housing height. Optionally, the top cap further comprises a top cap circumference and further wherein the system further comprises an O-ring surrounding the top cap circumference. Optionally, the top cap is attached to the housing via epoxy and threading. Optionally, the top cap and the housing are comprised of the same material. Optionally, the system further comprises at least one valve controlling the flow of the hydraulic fluid within the at least one channel, the at least one valve comprising a valve stem having a valve stem height generally parallel to the housing height and further wherein the valve stem comprises a top ridge (comprising a top ridge diameter perpendicular to the housing height), a middle ridge located below the top ridge (and comprising a middle diameter generally perpendicular to the housing height), and a lower ridge located below the top ridge and the middle ridge (and comprising a lower ridge diameter generally perpendicular to the housing height), a top O-ring located between the top ridge (and comprising a top O-ring diameter generally perpendicular to the housing height) and the middle ridge and compressing against the valve stem and a lower O-ring located between the middle ridge and the lower ridge and compressing against the valve stem (and comprising a lower O-ring diameter generally perpendicular to the housing height). Optionally, the system further comprises at least one end cap located on the proximal end of the housing, the end cap comprising an end cap diameter generally perpendicular to the housing width, at least one spring located distally relative to the end cap and the piston, the spring comprising a proximal end attached to the piston and a distal end, the spring having a relaxed position and a compressed position, and further wherein moving the door from the closed position to the open position is configured to cause the door arm to cause the spindle to rotate about the spindle rotation axis and cause the spring to move from the relaxed position to the compressed position and the piston to move distally (and the in the general direction of toward the spindle) within the cylinder. Optionally, the end cap is configured to seal the hydraulic fluid within the proximal chamber and the housing and the end cap are comprised of the same material. Optionally, the end cap further comprises a circumference and further wherein the system further comprises an O-ring, the O-ring surrounding and compressing against the end cap circumference. Optionally, pivoting the door from the closed position to the open position is configured to cause the piston to move distally (and generally towards the spindle) and move hydraulic fluid located distal to the piston distally within the cylinder. Optionally, moving the piston distally within the cylinder is configured to cause hydraulic fluid to move from the distal chamber through the at least one channel and into the proximal chamber. Optionally, pivoting the door from the open position to the closed position is configured to cause the piston to move proximally (and generally away from the spindle) and move hydraulic fluid located proximal to the piston proximally within the cylinder. Optionally, moving the piston proximally within the cylinder is configured to cause hydraulic fluid to move from the proximal chamber through the at least one channel and into the distal chamber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  illustrates a front perspective view of a hydraulic door closer of one embodiment of the present invention. 
           [0013]      FIG. 2  illustrates a front exploded perspective view of the hydraulic door closer of  FIG. 1 . 
           [0014]      FIG. 3  illustrates a bottom perspective view of the hydraulic door closer of  FIG. 1 . 
           [0015]      FIG. 4  illustrates a bottom exploded perspective view of the hydraulic door closer of  FIG. 1 . 
           [0016]      FIG. 5  illustrates a top plan view of the hydraulic door closer of  FIG. 1 . 
           [0017]      FIG. 6  illustrates a cross-sectional view of the hydraulic door closer of  FIG. 5 , taken along line  6 - 6  of  FIG. 5 . 
           [0018]      FIG. 7  illustrates a close-up cross-sectional view of the area of the hydraulic door closer denoted by the circled region labelled  7  in  FIG. 6 . 
           [0019]      FIG. 8  illustrates a close-up cross-sectional view of the hydraulic door closer denoted by the circled region labelled  8  in  FIG. 6 . 
           [0020]      FIG. 9  illustrates a front, exploded view of the hydraulic door closer of  FIG. 1 . 
           [0021]      FIG. 10  illustrates a proximal, exploded perspective view of a portion of the hydraulic door closer of  FIG. 1 ; in  FIG. 10 , the housing is transparent to better show the channels. 
           [0022]      FIG. 11  illustrates a cross-sectional view of the hydraulic door closer of  FIG. 1 ;  FIG. 11  shows the location of the piston during the process of moving the door from the closed position to the open position. 
           [0023]      FIG. 12  illustrates a cross-sectional view of the hydraulic door closer of  FIG. 1 ;  FIG. 12  shows the location of the piston when the door is in the open position. 
           [0024]      FIG. 13  illustrates a cross-sectional view of the hydraulic door closer of  FIG. 1 ;  FIG. 13  shows the location of the piston during the process of moving the door between the opened and closed positions. 
           [0025]      FIG. 14  illustrates a cross-sectional view of the hydraulic door closer of  FIG. 1 ;  FIG. 14  shows the location of the piston when the door is in the closed position. 
           [0026]      FIG. 15  illustrates a side elevation view of the hydraulic door closer of  FIG. 1  in use in a door. 
           [0027]      FIG. 16  illustrates a bottom perspective view of the hydraulic door closer of  FIG. 1 ; the spindle is not shown for ease of viewing. 
           [0028]      FIG. 17  illustrates a sectional view of the hydraulic door closer of  FIG. 16 , taken along line  17 - 17  of  FIG. 16 . 
           [0029]      FIG. 18  illustrates a sectional view of the hydraulic door closer of  FIG. 16 , taken along line  18 - 18  of  FIG. 16 . 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    With reference to  FIGS. 1-18 , the present invention provides a hydraulic door closer system  10 . In the drawings, not all reference numbers are included in each drawing for the sake of clarity. Preferably, the hydraulic door closer is an overhead concealed door closer.  FIGS. 1-18  are engineering drawings, drawn to scale. However, it will be appreciated that other dimensional proportions between the components are possible. 
         [0031]    Referring further to  FIGS. 1-18 , in some embodiments, the system is a hydraulic overhead concealed door closer system  10  comprising: a) a door frame  12  defining a door opening  14 , the door frame  12  comprising a door frame width  16 , a door frame height  18  generally perpendicular to the door frame width  16 , and a door frame top  17  located above the door opening  14 ; b) a door comprising a door top  20  and a door width  22 , the door configured to pivot from a closed position in which the door covers the door opening  14 , the door width  22  is substantially parallel to the door frame width  16  and the door top  20  faces the door frame top  17 , to an open position in which the door does not cover the door opening  14  and in which the door width  22  is not substantially parallel to the door frame width  16 ; and c) a hydraulic overhead concealed door closer  24  that may be located in the door frame top  17 . The hydraulic overhead concealed door closer  24  may include i) a housing  26  comprising an interior  28 , a top side  30 , a bottom side  32  opposite the top side  30  and facing the door top  20  when the door is in the closed position, a housing height  34  extending from the housing top side  30  to the housing bottom side  32  and generally perpendicular to the door frame width  16  and the door width  22 , a front side  36 , a rear side  38 , a housing thickness  40  extending from the housing front side  36  to the housing rear side  38  and generally perpendicular to the housing height  34  and generally perpendicular to the door width  22  when the door is in the closed position, a proximal end  44 , a distal end  42 , a housing width  46  extending from the housing proximal end  44  to the housing distal end  42  and generally perpendicular to the housing height  34  and the housing thickness  40  and generally parallel to the door width  22  when the door is in the closed position. The hydraulic overhead concealed door closer  10  may also include a cylinder  48  located in the housing interior  28 , the cylinder  48  having a cylinder length  50  generally parallel to the housing width  46  as well as a moveable piston  52  located in the cylinder  48  and configured to move at least partially along the cylinder length  50 , the moveable piston  52  dividing the housing interior  28  into a proximal chamber  56  and a distal chamber  54 . The door closer may include multiple cylinders  48 , each of which may have a piston  52 . The door closer interior also includes fluid, e.g., hydraulic fluid, located in the proximal chamber  56  and the distal chamber  54 . The door closer  10  may also include at least one channel  58 A and  58 B located in the housing interior  28  and configured to transport hydraulic fluid between the proximal and distal chambers  56  and  54 , the at least one channel  58 A and  58 B having a channel length  60  generally parallel to the housing width  46  and the cylinder length  50 . Multiple channels  58 A and  58 B and drains  119 ,  120 ,  121  and  122  such as those shown in the drawings are possible. The door closer  10  may also include a cam assembly  62  comprising a spindle  64 , the spindle  64  having a spindle height  66  generally parallel to the housing height  34  and a spindle perimeter  68  generally perpendicular to the spindle height  66 , the spindle  64  extending below the housing bottom side  32 , the spindle  64  configured to rotate about a spindle rotational axis  70  generally parallel to the spindle height  66  (rotate means at least partially rotate). The system may also include an arm  72  attached to the spindle  64  and to the door top  20 . The arm  72  may close around the spindle  64  and be adjustable using for example an Allen wrench. The door closer  10  may also include a top cap  78  having a top cap diameter  80  generally perpendicular to the housing height  34  and sealing the distal chamber  54  from the door frame  12 , the top cap  78  located at the top side  30  of the housing  26  and opposite to the spindle  64 . The top cap  78  may be located directly above the spindle  64 . As shown in the drawings, the spindle  64  generally does not protrude through the top cap  78 . Optionally, pivoting the door from the closed position to the open position is configured to cause the spindle  64  to rotate (i.e., partially rotate) about the spindle rotational axis  70  and cause the piston  52  to move within the cylinder  48  at least partially along the cylinder length  50 . Optionally, the system further comprises a spindle seal  82 , the spindle seal  82  surrounding and compressing against the perimeter  68  of the spindle  64  and located below the top cap  78 . Optionally, the spindle seal  82  comprises a diameter  84  generally perpendicular to the housing height  34 . Optionally, as best seen in  FIG. 7 , the spindle seal  82  has an inner wall  83 , an outer wall  85 , a v-shaped channel  87  between the inner wall  83  and outer wall  85 , an open top end  89  (as best seen in  FIGS. 2 and 7 ) and a closed bottom end  91  (as best seen in  FIGS. 3 and 7 ). Prior to assembly into the housing  26 , the inner wall  83  is angled (e.g., at approximately an angle of between about 10 to about 30 degrees relative to the outer wall  85 ). Once the spindle seal  82  is placed in the housing  26 , it pushes against the spindle  64  for better sealing. The spindle seal  82  may be comprised of rubber, for example. 
         [0032]    Optionally, the system further comprises a bottom bearing  86  located between the spindle seal  82  and the cam assembly  62 , the bottom bearing  86  comprising a diameter  88  generally perpendicular to the housing height  34 . The system may also include a top bearing  128  located above the spindle seal  82 . Optionally, the top cap  78  further comprises a top cap circumference  90  and further wherein the system further comprises an O-ring  92  surrounding the top cap circumference  90 . Optionally, the top cap  78  is attached to the housing  26  via epoxy and threading. Optionally, the top cap  78  and the housing  26  are comprised of the same material. Optionally, the system further comprises at least one valve  94 A,  94 B, and  94 C controlling the flow of the hydraulic fluid within the at least one channel  58 A and  58 B, the at least one valve  94 A,  94 B, and  94 C comprising a valve stem  96  having a valve stem height generally parallel to the housing height  34  and further wherein the valve stem  96  comprises a top ridge  98  (comprising a top ridge diameter perpendicular to the housing height  34 ), a middle ridge  100  located below the top ridge  98  (and comprising a middle diameter generally perpendicular to the housing height  34 ), and a lower ridge  102  located below the top ridge  98  and the middle ridge  100  (and comprising a lower ridge diameter generally perpendicular to the housing height  34 ), a top O-ring  104  located between the top ridge  98  (and comprising a top O-ring diameter generally perpendicular to the housing height  34 ) and the middle ridge  100  and compressing against the valve stem  96  and a lower O-ring  106  located between the middle ridge  100  and the lower ridge  102  and compressing against the valve stem  96  (and comprising a lower O-ring diameter generally perpendicular to the housing height  34 ). The valves  94 A-C, which may be adjustable via a screw driver, may also be secured into housing  26  through the use of locking rings/washers  131  that are stamped into the housing  26  above the valves  94 A-C, and prevent the valves  94 A-C from screwing out of the housing  26 . More particularly, the locking rings  131  may have a diameter that is slightly larger than the diameters of each of the housing ports leading to the valves  94 A-C, and the locking rings  131  are press fit/stamped to force the locking rings  131  through the smaller ports. 
         [0033]    Optionally, the system further comprises at least one end cap  108  located on the distal end  42  of the housing  26 , the end cap  108  comprising an end cap diameter  110  generally perpendicular to the housing width  46 , at least one spring  112  located proximally relative to the end cap  108  and the piston  52 , the spring  112  comprising a distal end  116  attached to the piston  52  and a proximal end  114 , the spring  112  having a relaxed position and a compressed position, and further wherein moving the door from the closed position to the open position is configured to cause the door arm  72  to cause the spindle  64  to rotate about the spindle rotation axis  70  and cause the spring  112  to move from the relaxed position to the compressed position and the piston  52  to move distally (and in the general direction of toward the spindle  64 ) within the cylinder  48 . Optionally, the spring  112  is adjustable by a user, e.g., by turning a component on the end cap  108 . Optionally, the end cap  108  is configured to seal the hydraulic fluid within the proximal chamber  56  and further wherein the housing  26  and the end cap  108  are comprised of the same material. Optionally, the end cap  108  further comprises a circumference and further wherein the system further comprises an end cap O-ring  118 , the end cap O-ring  118  surrounding and compressing against the end cap circumference. Optionally, pivoting the door from the closed position to the open position is configured to cause the piston  52  to move distally (and generally towards the spindle  64 ) and move hydraulic fluid located distal to the piston  52  distally within the cylinder  48 . Optionally, moving the piston  52  distally within the cylinder  48  is configured to cause hydraulic fluid to move from the distal chamber  54  through the at least one channel  58 A and  58 B and into the proximal chamber  56 . Optionally, pivoting the door from the open position to the closed position is configured to cause the piston  52  to move proximally (and generally away from the spindle  64 ) and move hydraulic fluid located proximal to the piston  52  proximally within the cylinder  48 . Optionally, moving the piston  52  proximally within the cylinder  48  is configured to cause hydraulic fluid to move from the proximal chamber  56  through the at least one channel  58 A and  58 B and into the distal chamber  54 . 
         [0034]    Optionally, the system is assembled as shown in  FIG. 2 , with the bottom bearing  86  placed in the port/opening  126  in the housing  26  that the top cap  78  closes, followed by the cam assembly  62 , followed by the top cap  78 . The top cap  78  is positioned by moving the top cap  78  toward the port/opening  126  in the housing  26 . As shown, the spindle  64  does not protrude through the top cap  78 . 
         [0035]    The system may be sold without the door, door frame  12 , and arm  72 . The present disclosure may also be used in a method that includes providing the door closer  10  and installing the door closer  10  in a door frame  12  and attaching the door closer  10  to a door. 
         [0036]    The spring  112  may be bolted to the cam assembly  62  using the bolts  130  shown in  FIG. 9 . 
         [0037]    The at least one channel may include several channels  58 A and  58 B that are regulated by several valves (e.g., a backcheck valve  94 C which is nearest to the spindle  64 , a sweep valve  94 B, and a latch valve  94 A that is furthest from the spindle  64 ), as well as drains  119 ,  120 ,  121 , and  122  and balls  123 . 
         [0038]    Operation of the Door Closer 
         [0039]    One example of operation of the door closer  10  will now be described. It will be understood that the operation provided is exemplary. 
         [0040]    The Operation of the Sweep and Latch Valve 
         [0041]    Opening the backcheck valve  94 C reduces backcheck and makes the door easier to open. Closing the sweep valve  94 B and latch valve  94 A makes the sweep and latch closing of the door slower. 
         [0042]    While opening backcheck valve  94 C, close sweep valve  94 B and latch valve  94 A 
         [0043]    The door is moved from the closed position to the open position. 
         [0044]    The spindle  64  rotates, moving the piston  52  distally towards the spindle  64  and the housing distal end  42 , compressing the spring  112 . The piston  52  moves through the backcheck drain hole  119 . Fluid in the distal chamber  54  moves to the proximal chamber  56  by moving through the main hole  132 , upwardly through the backcheck drain hole  119  where the fluid is blocked by steel ball  123 , and then travels through the drain hole  122 . 
         [0045]    The spring  112  relaxes, and the piston  52  moves proximally towards the end cap  108 , causing the spindle  64  to return to the start position. 
         [0046]    With the movement above, opening the sweep valve  94 B makes the fluid in the proximal chamber  56  move to the distal chamber  54  using sweep drain hole  121 , sweep valve  94 B, drain hole  122  and piston  52 . 
         [0047]    When fluid in the distal chamber  54  is moving, if the piston  52  is blocking sweep drain hole  121 , sweeping is done. See  FIG. 11 . 
         [0048]    When sweeping is done, opening the latch valve  94 A will allow leftover fluid in the proximal chamber  56  to move back to the distal chamber  54  using latch drain hole  120 , upwardly through latch valve  94 A, downwardly through sweep valve  94 B, out drain hole  122  and piston  52 , as a result the door is fully closed. See  FIG. 12 . 
         [0049]    The Operation of the Backcheck Valve 
         [0050]    Fully close backcheck valve  94 C, the door is opened, rotating the spindle  64  and moving the piston  52  distally (toward the spindle  64 ), as fluid moves from the distal chamber  54  to the proximal chamber  56  via the backcheck drain hole  119 . While the piston  52  is blocking the backcheck drain hole  119 , the piston  52  cannot move since fluid is controlled by backcheck drain hole  119  only. See  FIG. 12 . 
         [0051]    When the piston  52  is not moving, the spindle  64  cannot rotate further due to the intense pressure in the housing interior  28 . This is what is referred to as backcheck. 
         [0052]    (When the backcheck valve  94 C is fully closed, a very small amount of oil flows in the gap between the cylinder  48  and piston  52 , allowing the door to open slowly further). 
         [0053]    The items referred to above are labelled in the drawings per the below legend. 
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 system 
                 10 
               
               
                   
                 door frame 
                 12 
               
               
                   
                 door opening 
                 14 
               
               
                   
                 door frame width 
                 16 
               
               
                   
                 door frame height 
                 18 
               
               
                   
                 door top 
                 20 
               
               
                   
                 door width 
                 22 
               
               
                   
                 closer 
                 24 
               
               
                   
                 housing 
                 26 
               
               
                   
                 interior 
                 28 
               
               
                   
                 housing top 
                 30 
               
               
                   
                 housing bottom 
                 32 
               
               
                   
                 housing height 
                 34 
               
               
                   
                 front side 
                 36 
               
               
                   
                 rear side 
                 38 
               
               
                   
                 housing thickness 
                 40 
               
               
                   
                 distal end 
                 42 
               
               
                   
                 proximal end 
                 44 
               
               
                   
                 housing width 
                 46 
               
               
                   
                 cylinder 
                 48 
               
               
                   
                 cylinder length 
                 50 
               
               
                   
                 piston 
                 52 
               
               
                   
                 distal chamber 
                 54 
               
               
                   
                 proximal chamber 
                 56 
               
               
                   
                 channel 
                 58A &amp; B 
               
               
                   
                 channel length 
                 60 
               
               
                   
                 cam assembly 
                 62 
               
               
                   
                 spindle 
                 64 
               
               
                   
                 spindle height 
                 66 
               
               
                   
                 spindle perimeter 
                 68 
               
               
                   
                 spindle rotational axis 
                 70 
               
               
                   
                 arm 
                 72 
               
               
                   
                 top cap 
                 78 
               
               
                   
                 top cap diameter 
                 80 
               
               
                   
                 spindle seal 
                 82 
               
               
                   
                 Spindle seal inner wall 
                 83 
               
               
                   
                 spindle seal diameter 
                 84 
               
               
                   
                 Spindle seal outer wall 
                 85 
               
               
                   
                 bottom bearing 
                 86 
               
               
                   
                 Spindle seal groove 
                 87 
               
               
                   
                 bottom bearing diameter 
                 88 
               
               
                   
                 Spindle seal top 
                 89 
               
               
                   
                 top cap circumference 
                 90 
               
               
                   
                 Spindle seal bottom 
                 91 
               
               
                   
                 top cap o-ring 
                 92 
               
               
                   
                 at least one valve 
                 94A, B, C 
               
               
                   
                 valve stem 
                 96 
               
               
                   
                 top ridge 
                 98 
               
               
                   
                 middle ridge 
                 100 
               
               
                   
                 lower ridge 
                 102 
               
               
                   
                 top o-ring 
                 104 
               
               
                   
                 lower o-ring 
                 106 
               
               
                   
                 end cap 
                 108 
               
               
                   
                 end cap diameter 
                 110 
               
               
                   
                 spring 
                 112 
               
               
                   
                 spring distal end 
                 114 
               
               
                   
                 spring proximal end 
                 116 
               
               
                   
                 end cap o-ring 
                 118 
               
               
                   
                 back check drain hole 
                 119 
               
               
                   
                 latch drain hole 
                 120 
               
               
                   
                 sweep drain hole 
                 121 
               
               
                   
                 drain hole 
                 122 
               
               
                   
                 steel ball 
                 123 
               
               
                   
                 Port of housing 
                 126 
               
               
                   
                 Top Bearing 
                 128 
               
               
                   
                 Bolts 
                 130 
               
               
                   
                 Locking ring 
                 131 
               
               
                   
                 Main drain hole 
                 132 
               
               
                   
                   
               
             
          
         
       
     
         [0054]    Having now described the invention in accordance with the requirements of the patent statutes, those skilled in the art will understand how to make changes and modifications to the disclosed embodiments to meet their specific requirements or conditions. Changes and modifications may be made without departing from the scope and spirit of the invention. In addition, the steps of any method described herein may be performed in any suitable order and steps may be performed simultaneously if needed. 
         [0055]    Terms of degree such as “generally”, “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. For example, these terms can be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies. In addition, the steps of the methods described herein can be performed in any suitable order, including simultaneously.

Summary:
A hydraulic door closer is disclosed. The hydraulic door closer may include a top cap surrounded by an O-ring that is located at the top of the hydraulic door closer housing opposite a spindle to seal the hydraulic fluid within the housing. In addition to or in lieu of the top cap design, the door closer may include a locking washer to secure the valves to the housing; epoxy and an O-ring at the interface between the top cap and the housing of the door closer; use of a dual-walled rubber seal around the spindle; use of dual O-rings on each valve stems; use of caps that are made of the same material as the housing instead of aluminum and use of epoxy on the end caps; and/or use of backcheck with an adjustable spring.