Patent Publication Number: US-7900319-B2

Title: Hinge structure for self-closing doors

Description:
FIELD OF THE INVENTION 
     The present invention finds application in the field of hinges and suspension hardware for doors or the like, and particularly relates to hinge structure for self-closing doors. 
     The hinge structure of the invention can assure self-closing of any kind of door, window or shutter, whether horizontally or vertically oriented, particularly of glass doors. 
     The invention further relates to an assembly incorporating such hinge structure. 
     BACKGROUND OF THE INVENTION 
     Hinge structure for self-closing doors or the like, particularly glass doors or the like are known in the art. 
     These prior art hinge structures comprise, as is known, a stationary element to be fixed to the frame of a door, a first movable element to be attached to the door and pivotally mounted to the stationary element for rotating about a longitudinal axis between an open door position and a closed door position. 
     These prior art hinge structures further comprise means for automatically returning the door to said closed position during opening thereof. 
     These prior art hinge structures suffer from certain well-recognized drawbacks. 
     A first drawback is their bulky size, heavy weight and high cost, caused by their being formed of many different parts, which further complicate their assembly and maintenance. 
     Furthermore, they exhibit poor versatility and have to be replaced or anyway adjusted as the door or frame on which they are mounted changes. 
     Also, these prior art hinge structures do not assure controlled motion of the door during opening and closing thereof. This problem is particularly felt with glass doors, whose closing and opening movements must be smooth, to avoid irreversible damages to the door itself. 
     However, the behavior of these prior art structures is highly affected by the mass of the door on which they are mounted. 
     Furthermore, in operation, these prior art hinge structures are subjected to variations in their closing position, which leads to inconveniences and higher maintenance costs. 
     Moreover, the known structures do not allow the automatic closing movement of the door upon the opening. 
     SUMMARY OF THE INVENTION 
     The main object of this invention is to obviate the above drawbacks, by providing an hinge structure allowing for easy and convenient maintenance, that has high performance, simple construction and low cost properties. 
     One object of the invention is to provide a hinge structure that allows the automatic closing of the door from the open position. 
     A particular object is to provide a hinge structure that allows the controlled motion of the door with which it is connected. 
     A further object is to provide a hinge structure that can support doors and windows of heavy weight without changing their behavior and without requiring any adjustment. 
     A further object of the invention is to provide a hinge structure that has a minimized number of parts and can be adapted to multiple shells of different shapes and sizes. 
     Yet another object of the invention is to provide a hinge structure that can keep its closing position unaltered with time. 
     Another object of the invention is to provide a highly safe hinge structure that offers no resistance to the closing motion even when pulled abruptly. 
     These and other objects, as better explained hereafter, are fulfilled by a hinge structure as defined in claim  1 . 
     Advantageously, the closing means may be held in the first operating chamber, and the hydraulic damping means may be held either in the first operating chamber or in a second operating chamber, other than the first chamber. 
     In another aspect, the invention relates to a hinge assembly for self-closing doors or the like as defined in claim  20 . 
     Advantageous embodiments of the invention are defined in accordance with the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the invention will be more apparent upon reading the detailed description of a few preferred, non-exclusive embodiments of the hinge structure and assembly of the invention, which are described as non-limiting examples with the help of the annexed drawings, in which: 
         FIG. 1  is a plan view of a door with the hinge structure of the invention mounted thereto; 
         FIG. 2  is an axonometric view of a first embodiment of the hinge structure of the invention, in the closed door position; 
         FIG. 3  is a sectional side view of the hinge structure of  FIG. 2 , as taken along a plane A-A; 
         FIG. 4   a  is an exploded view of the hinge structure of  FIG. 2 , in a first preferred, non exclusive configuration; 
         FIG. 4   b  is an exploded view of the hinge structure of  FIG. 2 , in a second preferred, non exclusive configuration; 
         FIGS. 5   a  and  5   c  are axonometric views of the closing means  4  of the hinge structure of the invention; 
         FIG. 5   b  is a sectional view of a few details of  FIG. 5   a , as taken along a plane M-M; 
         FIG. 6  is an enlarged view of certain details of the hinge structure of  FIG. 5 ; 
         FIGS. 7   a  and  8   a  are sectional views of the hinge structure of  FIG. 2 , as taken along a plane B-B in the closed door and open door positions respectively; 
         FIGS. 7   b  and  8   b  are sectional views of the hinge structure of  FIG. 2  as taken along a plane B-B in partly open door conditions, during door opening and door closing respectively; 
         FIGS. 9 and 10  are sectional views of alternative embodiments of the hinge structure of  FIG. 2  as taken along a plane A-A; 
         FIG. 11  is an axonometric view of a second embodiment of the hinge structure of the invention; 
         FIG. 12  is a sectional view of the structure of  FIG. 11 , as taken along a plane C-C; 
         FIG. 13  is a sectional view of the structure of  FIG. 11 , as taken along a plane D-D; 
         FIG. 14  is an exploded view of the structure of  FIG. 11 ; 
         FIG. 15  is an exploded view of the first and second plunger elements of the structure of  FIG. 11 ; 
         FIG. 16  is an exploded view of certain details of  FIG. 11 , in which the stationary element is indicated by dashed lines; 
         FIG. 17  is a sectional view of a first preferred non exclusive embodiment of the pin of the structure of  FIG. 11 ; 
         FIG. 18  is a sectional view of the pin of  FIG. 17 , as taken along a plane E-E; 
         FIG. 19  is a sectional view of a second preferred non exclusive embodiment of the pin of the structure of  FIG. 11 ; 
         FIGS. 20 to 23  are sectional views of the device of  FIG. 11 , as taken along planes F-F and G-G, in the closed door position, in a partly open position during door opening, in the open door position and in a partly open position during door closing respectively. 
         FIG. 24  is a view of a door with the second embodiment of the hinge structure of the invention mounted thereon; 
         FIG. 25  is an axonometric view of the assembly of the invention; 
         FIG. 26  is an axonometric view of the assembly of the invention in which the first and second hinge structures are shown in exploded configuration; 
         FIG. 27  is an axonometric view of the assembly of the invention in which the first and second stationary elements are shown by dashed lines; 
         FIG. 28  is a view of the assembly of the invention in which the first and second hinge structures are cut away along respective planes H-H, H′-H′; 
         FIG. 29  is a view of the assembly of the invention in which the first and second hinge structures are cut away along respective planes L-L, L′-L′, and in which they are in the closed door position; 
         FIG. 30  is a view of the assembly of the invention in which the first and second hinge structures are cut away along respective planes L-L, L′-L′, and in which they are in an intermediate opening position; 
         FIG. 31  is a view of the assembly of the invention in which the first and second hinge structures are cut away along respective planes L-L, L′-L′, and in which they are in the open door position; 
         FIG. 32  is a view of the assembly of the invention in which the first and second hinge structures are cut away along respective planes L-L, L′-L′, and in which they are in an intermediate closing position. 
     
    
    
     DETAILED DESCRIPTION OF A FEW PREFERRED EMBODIMENTS 
     Referring to the above figures, there are shown embodiments of a hinge structure for self-closing doors or the like, generally designated by numeral  1 , which may be mounted, preferably but without limitation, on glass doors. 
     In all its embodiments, the hinge structure  1  essentially comprises a stationary element  2  to be fixed to a frame T of a door P and a movable element  3  to be fixed to the door P. The movable element  3  is pivotally mounted to the stationary element  2  for rotating about a first longitudinal axis X between an open door position and a closed door position. 
     The hinge structure  1  further comprises closing means, generally designated by numeral  4  and hydraulic damping means, generally designated by numeral  5 , which may consist in the embodiments described herein without limitation, of a predetermined amount of oil. 
     The closing means  4  operate on the first movable element  3  for automatically returning the door to the closed position during opening, and the hydraulic damping means  5  operate on such element  3  to oppose and damp the movement produced by the closing means  4 . 
     A peculiar feature of the invention, common to all the embodiments described herein, is that the closing means  4  and the hydraulic damping means  5  are held in at least one first operating chamber  6  within the stationary element  2 . 
     By this arrangement, a hinge structure can be obtained that allows controlled pivotal motion of the door. This means that, when the door is in an open door position, the closing means  4  will operate on the movable element  3  and generate a torque to cause the door P to rotate to its closed position about the axis X. On the other hand, at each time, the hydraulic damping means  5  will operate on such movable element  3  to generate a resistant torque opposite to the torque generated by the closing means  4 . 
     The hinge structure of the invention also provides high safety, as it offers no resistance to the closing motion even when pulled abruptly. This will prevent any injury to careless users, particularly children. Regardless of the force exerted on the door, the latter will always return smoothly to the closed door position, thereby providing a childproof safety. 
     The hinge structure of the invention is also particularly efficient and cost effective, as it can keep its initial characteristics unaltered with time even when used in severe conditions with high moisture content and passage of moisture. 
     Furthermore, thanks to the provision that the closing means  4  and the hydraulic damping means  5  are wholly contained in at least one first operating chamber  6  within the stationary element  2 , the hinge structure  1  is particularly convenient to handle, and has a small size, and minimized space requirements. Therefore, its installation requires no particular masonry or excavation works. As shown in the annexed figures, the structure  1  is fixed to the frame of a door (or to a wall) along the vertical extension of the door, above the level of the floor or the wail to which the stationary element is fixed. 
     The closing means  4  include a first cam element  11  unitary with the first movable element  3  and having a first substantially flat contact surface  16 , and a first plunger element  12  movable within said first operating chamber  6  along a transversal axis Y between a compressed end stroke position, corresponding to the open door position, and an extended end stroke position, corresponding to the closed door position. The plunger element  12  has a front face  17  which is susceptible to contact engage the surface  16  of the cam element  11 . 
     According to the invention, the first contact surface  16  of the first cam element  11  is offset with respect to the longitudinal axis X by a predetermined distance g such as the front face  17  of the plunger element  12  in its extended end position is positioned beyond said longitudinal axis X. 
     By this arrangement, an excellent control on the closing movement of the door is allowed. In fact, the offset of the contact surface  16  with respect to the longitudinal axis X allows the automatic closing of the door. This means that, when the door P is closed, starting from the fully open position, as shown in  FIGS. 8   b ,  22  and  31 , thanks to the distance g between the axis X and the surface  16 , the front face  17  of the piston element  12  will promptly (after a few degrees of rotation) start to interact with the surface  16 , thereby rotating the door P to the closed door position, as shown in  FIGS. 7   a ,  20  and  29 . 
     A first preferred, non exclusive embodiment of the invention is shown in  FIGS. 2 to 8 , in which there is only one operating chambers  6  containing the closing means  4  and the hydraulic damping means  5 . 
     In this embodiment, as shown in  FIGS. 4   a  and  4   b , the stationary element  2  may be defined by a base  7  to be fixed to the frame T by means of screws to be inserted in the holes  8 ,  8 ′,  8 ″,  8 ′″, whereas the movable element  3  may in turn comprise two half shells  9 ,  9 ′ to be clamped together by screws  10 ,  10 ′. 
     Advantageously, the closing means  4  may include a cam element  11 , better shown in  FIG. 5   a , which is able to pivot about the axis X integrally with the movable element  3  and is susceptible of cooperating with a plunger element  12 , better shown in  FIG. 5   c , which is longitudinally movable within the operating chamber  6 . 
     The term “cam” as used herein is meant to indicate a mechanical member of any shape, which is adapted to turn a circular motion into a straight-line motion. 
     Conveniently, in this embodiment, the plunger element  12  operates along a line Y substantially orthogonal to the one defined by the longitudinal axis X, for minimized space requirement. As particularly shown in  FIGS. 7 and 8 , the line Y is defined by the axis of the cylindrical operating chamber  6 . 
     A pin  13 , particularly shown in  FIG. 5   a , which defines the axis X, is provided in the stationary element  2 . The pin  13 , which has to be mounted in a cylindrical receptacle  24  of the stationary element  2 , has a suitably shaped central portion  14  which defines the cam element  11  and side portions  15 ,  15 ′ to be connected to the movable element  3 . By this arrangement, the cam  11  rotates integrally with the movable element  3 . 
     The cam element  11 , which is defined by the central portion  14  of the pin  13  comprises a substantially fiat surface  16 , parallel to the axis X and abutting against the front face  17  of the plunger element  12 . By rotating about the axis X, the surface  16  interacts with the front face  17  of the plunger element  12  to cause its straight-line motion along the line d. For this purpose, the operating chamber  6  and the cylindrical receptacle  24  are in mutual communication at the contact area between the surface  16  of the pin  13  and the front face  17  of the plunger element  12 . 
     Advantageously, as particularly shown in  FIG. 5   b , the surface  16  has a distance g from the axis X of 1 to 6 mm, preferably of 1 mm to 3 mm and more preferably of about 2 mm. Thanks to such distance, the closing movement of the door will be completely automatic. 
     As shown in  FIG. 5   c , the plunger element  12  is composed a counter spring  18 , a locking cap  19 , a cover cylinder  20  and a check valve  21 , which defines means for controlling the flow of oil  5  in the chamber  6 , as better explained hereinbelow. The whole is “packed” and introduced, with the help of a gasket  22 , in the operating chamber  6 , with the locking cap  19  defining the bottom wall thereof. 
     It will be understood that the check valve  21  may be also mounted within the cover cylinder  20 , as shown, for example in  FIG. 4   b . In this case, the front face  17  of the plunger element  12  is defined by the front face  23  of the cover cylinder  20 . 
     As particularly shown in  FIGS. 7   a ,  7   b ,  8   a  and  8   b , the end wall  32  of the plunger element  12 , which defines the front face  17  thereof, is susceptible of dividing the operating chamber  6  into a first and second variable volume compartments  33 ,  34 , which are adjacent and in fluid communication with each other. The counter spring  18  is placed in the first compartment  33 . 
     This embodiment of the hinge structure of the invention allows for very simple installation. The installation procedure is simply carried out by fitting the pin  13  in the cylindrical receptacle  24  of the stationary element  2 , connecting the side portions  15 ,  15 ′ thereof to the movable element  3  by introducing the surfaces  25 ,  25 ′ of the pin  13  in the receptacles  26 ,  26 ′ of the half shell  9 ′, inserting the oil seals  27 ,  27 ′, if any, thrust bearings  28 ,  28 ′ and thrust bearing supports  29 ,  29 ′ in the receptacle  24 , securing the pin  23  to the shell  9 ′ using the screws  30 ,  30 ′ and clamping together the half shell  9  and the half shell  9 ′ so installed by the screws  10 ,  10 ′. The plunger element  12 , packed as described above, is introduced in its operating chamber  6 , and the locking cap  19  is tightened. 
     Such assembly procedure is completed by introducing oil  5  in the operating chamber  6 , for hydraulic damping of the closing movement produced by the closing means  4 . For this purpose, a through hole  31  may be formed in the stationary element  2  to define an oil loading channel allowing communication between the operating chamber  6  and the external environment, as shown in  FIG. 4   a . It will be understood that the amount of oil to be loaded in the chamber  6 , as well as the volume of the latter, is variable depending on the mass of the door P to be moved. 
     The operation of the hinge structure  1  is shown in  FIGS. 7   a ,  7   b ,  8   a  and  8   b.    
     In the closed door position, as shown in  FIG. 7   a , the flat surface  16  of the pin  13  and the front face  17  of the plunger element  12  are in contact with, substantially parallel to and abutting against each other. The counter spring  18  is precompressed between the cylinder  20  and the cap  19 . In this position, substantially the whole amount of oil  5  is in the first variable volume compartment  33 , which has the maximum volume. Also, the counter spring  18  is at its maximum elongation. 
     When a user opens the door P by applying an external load E L  thereto, the door P moves in the direction of arrow F 1  from the closed door position to an open door position, as shown in  FIG. 7   b . This movement causes the flat surface  16  of the pin  13  to rotate about the axis X, and thence interact with the front face  17  of the plunger element  12  to compress the counter spring  18 . The flat surface  16  of the pin  13  and the front face  17  of the plunger element  12  are angularly spaced apart by an angle α which increases as the door is being opened. The end wall  32  of the plunger element  12  is thus displaced along the line Y in the direction V. At the same time, due to the motion of the partition wall  32 , the oil  5  is transferred from the first compartment  33 , whose volume decreases, to the second compartment  34 , whose volume accordingly increases, through the orifice  35  of the check valve  21 . 
     In the embodiments illustrated herein, the check valve  21  is defined by an elongate extension  36  of the end wall  32  coaxial to the cylindrical operating chamber  6  and is of the normally open type, i.e. allowing the passage of oil  5  from the first compartment  33  to the second compartment  34  while the door is being opened and preventing it from flowing back as the door is being closed. 
       FIG. 8   a  shows the fully open door position. In this position, the flat surface  16  of the pin  13  and the front face  17  of the plunger element  12  are perpendicular to each other. As shown in this figure, substantially the whole amount of oil  5  is in the second variable volume compartment  34 , which has the maximum volume, while the first compartment  33  has the minimum volume. Also, the counter spring  18  is in its maximum compression position, which corresponds to its minimum elongation. 
     When a user rotates the door P from the fully open door position or, equivalently, when a user releases the door from a partly open door position (i.e. when the external load E L  no longer acts thereon), the closing means  4  will start to operate on the movable element  3  to automatically return the door P to the closed position. At the same time, the hydraulic damping means  5  will start to operate on the movable element  3  to oppose and damp the closing movement produced by the closing means  4 . 
       FIG. 8   b  shows the above condition, with the door P in a partly open door position during door closing, in the direction of arrow F 2 . In this position, the flat surface  16  of the pin  13  and the front face  17  of the plunger element  12  are angularly spaced apart by an angle α which decreases as the door is being closed. The previously compressed spring  18  performs its opposing action by pushing the front face  17  of the plunger element  12  against the surface  16  of the pin  13 , thereby causing the surfaces  16  and  17  to slide one against the other and the end wall  32  to move along the line Y in the direction V′. At the same time, due to the motion of the partition wall  32 , the oil  5  is transferred from the second compartment  34 , whose volume starts to decrease, to the first compartment  33 , whose volume accordingly increases. However, the oil  5  will no longer flow through the orifice  35  of the check valve  21 , which is closed, but will flow back into the first compartment  33  through a tubular space  37  between the side wall  38  of the operating chamber  6  and the side wall  39  of the cover cylinder  22  of the plunger element  12 . Convenient adjustment of the size of the air space  37  may increase or decrease the damping effect provided by the oil  5 , which makes the hinge structure of the invention exceptionally safe. 
     In an alternative configuration of the invention, as shown in  FIG. 10 , at least one hole  40  may be formed on the side wall  39  of the cover cylinder  20  of the plunger element  12 , to facilitate and/or control the backflow of oil  5  into the first compartment  33 . Suitable configuration of the sizes and/or number of holes  40 , allows to control the return movement of the door P to the closed door position. 
     In a further alternative embodiment of the invention, as shown in  FIG. 9 , the structure  1  may comprise a screw  41  for throttling the air gap  37  and thereby adjusting its size as desired, to change the backflow velocity of the oil  5 , and thus adjust the damping effect. 
       FIGS. 11 to 24  show without limitation a second embodiment of the hinge structure of the invention, generally designated by numeral  1 ′. The latter essentially comprises a stationary element  2  and a movable element  3  to be fixed to a door P by the two half shells  42 ,  42 ′. The stationary element  2  is designed to be fixed to a stationary support S, such as a wall or a floor, through the skirting  43 , as shown in  FIG. 24 . 
     This second embodiment differs from the first embodiment in that, while the closing means  4  are held in a single first operating chamber  6 , the hydraulic damping means  5  are held both in this first operating chamber  6  and in a second operating chamber  44 , which is in fluid connection therewith. As shown in  FIG. 14 , both the first operating chamber  6  and the second operating chamber  44  are wholly contained in the box-like housing defined by the stationary element  2 . 
     This configuration allows controlled movement of very heavy doors P and/or gates. This result is achieved thanks to the second operating chamber  44 , which provides additional volume for the hydraulic damping means  5 , whereby motion of objects of very large mass may be effectively controlled. 
     In this second embodiment, the closing means comprise, in addition to the first cam element  11 , a second cam element  45 , which is able to pivot about the axis X integrally with the first cam element  11 , as particularly shown in  FIG. 17 , Furthermore, the second cam element  45  cooperates with a second plunger element  46 , which is longitudinally movable along the line Y″ within the second operating chamber  44 . 
     Advantageously, the line Y′, which is defined by the axis of the second cylindrical operating chamber  44 , is parallel to the line Y of motion of the first cam element  11 , thereby minimizing space requirements. 
     In the second embodiment, the central portion  14  of the pin  13 , which is always held within the stationary element  2  in a cylindrical receptacle  24 , defines both the first cam element  11  and the second cam element  45 . 
     The pin  13  is then designed to be fixed to the movable element  3  by means of the attachment surfaces  25 ,  25 ′ of the end portions  15 ,  15 ′. Particularly, the top surface  25  is designed to be introduced in a groove  47  of the half shell  42  of the movable element  3 , and the bottom surface  25 ′ is introduced in the skirting  43  to be fixed to the floor S. 
     In this embodiment, both the first cam element  11  and the second cam element  45  are formed by specially shaping the central portion  14  of the pin  13 . The first cam element  11 , like in the first embodiment, comprises a first substantially flat surface  16 , parallel to the axis X and abutting against the front face  17  of the first plunger element  12 . The second cam element  45 , placed above the first, is substantially defined by a wall  48  having a pair of second substantially flat surfaces  49 ,  49 ′, parallel to the axis X and substantially perpendicular to the first surface  16 . 
     The wall  48 , with its surfaces  49 ,  49 ′ abuts against the front face  50  of the second plunger element  46 . For this purpose, as better shown in  FIG. 16 , the cylindrical receptacle  24  is designed to communicate both with the first operating chamber  6  and with the second  44 , at the area of contact between the first cam element  11  and the first plunger element  12  and at the area of contact between the second cam element  45  and the second plunger element respectively. 
     The latter, like the first plunger element, is substantially composed of a second counter spring  51 , a second locking cap  52 , a second cover cylinder  53  and a second check valve  54 , which defines means for controlling the flow of oil  5  in the second operating chamber  44 , as explained above. The whole is “packed” and introduced, with the help of a second gasket  55 , in the second operating chamber  44 , with the locking cap  52  defining the bottom wall thereof. 
     As particularly shown in  FIGS. 20 to 23 , the end wall  50  of the second plunger element  46  is defined by a wall  56  which is susceptible of dividing the second operating chamber  44  into a third and fourth variable volume compartments  57 ,  58 , which are adjacent and in fluid communication with each other. The counter spring  51  is placed in the fourth compartment  58 . 
     The stationary element  2  has a channel  60 , clearly shown in  FIG. 13 , for putting the first and second operating chambers  6 ,  44  in fluid communication with each other. Furthermore, the channel  60  comprises a throttling screw  61 , for adjusting the damping effect of the hydraulic means  5 . 
     In the second embodiment described herein, the check valve  21  is of the normally open type, i.e. allowing the passage of oil  5  from the first compartment  33  to the second compartment  34  while the door is being opened and preventing it from flowing back as the door is being closed, whereas the check valve  54  is of the normally closed type, i.e. allowing the passage of oil  5  from the third compartment  57  to the fourth compartment  58  while the door is being opened and preventing it from flowing back as the door is being closed. 
     This embodiment of the hinge structure of the invention allows for very simple installation, like the first embodiment. The installation procedure is simply carried out by fitting the pin  13  in the cylindrical receptacle  24  of the stationary element  2 , connecting the side portions  15 ,  15 ′ thereof to the movable element  3 , as described above, inserting the oil seals  27 ,  27 ′, if any, thrust bearings  28 ,  28 ′ and thrust bearing supports  29 ,  29 ′ in the receptacle  24 , and clamping together the half shell  42  and the half shell  42 ′ so installed by the screws  10 ,  10 ′,  10 ″. The first plunger element  12 , packed as described above, is introduced in its operating chamber  6 , and the locking cap  19  is tightened, whereas the second plunger element is designed to be packed and introduced in the second operating chamber  44 . 
     Such assembly procedure is completed by introducing oil  5  in the operating chambers  6  and  44 , for hydraulic damping of the closing movement produced by the closing means  4 . This may be accomplished using the loading channel  31  in the stationary element  2 , which puts the external environment in communication with the second operating chamber  44 , the latter being in turn in fluid communication with the first operating chamber  6 . It will be understood that the predetermined amount of oil loaded through the channel  31  will be distributed among the first  33 , the second  34 , the third  57  and the fourth  58  variable volume compartments. The channel  31 , which is particularly useful for adding oil  5  when needed, is closed by the cap  59 . 
     The operation of the hinge structure  1  is better shown in  FIGS. 20 to 23 . 
       FIG. 20  shows the relative position of the closing means  4  and the hydraulic damping means  5  in the closed door position. In this position, the front face  17  of the first plunger element  12  abuts against and is parallel to the flat surface  16  of the first cam element  11  to keep the door closed, like in the first embodiment. The front face  50  of the second plunger element  46  abuts in turn against and is perpendicular to the wall  48  with its surfaces  49 ,  49 ′. 
     The first counter spring  18  is precompressed between the cylinder  20  and the cap  19 , and the second counter spring  51  is compressed between the cap  52  and the cylinder  53 . In this position, the first  33  and third  57  variable volume compartments have the maximum volume, and the second  34  and fourth  58  have the minimum volume. Also, the counter spring  18  is at its maximum elongation, and the second counter spring  51  has its minimum elongation (maximum compression position). 
     As the door P is opened, i.e. as an external load E L  is applied thereon, the movable element  3  will start to pivot about the axis X relative to the stationary element  2 , the pin  13  will move in the direction of arrow F 1 , and the first surface  26  of the first cam element  11  and the second surfaces  49 ,  49 ′ of the second cam element  45  will start to pivot integrally therewith. This partly open door position during door opening is shown in  FIG. 21 . 
     Due to the rotation of the pin  13 , and the resulting thrust exerted by the surface  16  on the front face  17  of the first plunger element  12 , the latter starts to move along the line Y in the direction V. At the same time, the second plunger element  48  starts to move along the line Y′ in the direction V′ opposite to the direction V. As the door is being opened, the angle α between the first flat surface  16  of the pin  13  and the front face  17  of the first plunger element  12  starts to increase, whereas the angle β between the flat surfaces  49 ,  49 ′ of the second plunger element  46  starts to decrease. 
     Thus, the volume of the first compartment  33  starts to decrease, as loading of the first spring  18  occurs. Furthermore, as the volume of the first compartment  33  decreases, the oil  5  therein starts to flow out through the orifice  35  of the valve  21  into the second variable volume compartment  34 , which starts to receive oil  5  and increases its volume. 
     At the same time, due to the rotation of the surfaces  49 ′,  49  and the resulting thrust exerted by the front face  50  of the second plunger element  46  thereon, the volume of the fourth compartment  55  starts to increase, as release of the second spring  51  occurs. Also, the volume of the third compartment  57  starts to decrease, therefore the oil  5  therein starts to flow into the fourth compartment  58 , whose volume accordingly increases. 
       FIG. 22  shows the fully open door position. It will be appreciated that the device of the invention allows 90° opening of the door also in the other direction. In this position, the fourth compartment  58  will have the maximum volume, whereas the second compartment  34  will have the minimum volume. The first spring  18  is in its maximum load condition (minimum elongation), and the second spring  51  is in its minimum load condition (maximum elongation). 
     As a user releases the door or moves it from the position of  FIG. 22  to the closed position, the first spring  18  starts to be released, and the first plunger element  12  starts to push on the surface  16  of the pin  13  thereby rotating it in the direction of arrow F 2  back to the closed door position. At the same time, the surfaces  49 ,  49 ′ compress the second spring  51 , so that the volume of the fourth compartment  58  starts to decrease and oil flows out of it. 
       FIG. 23  shows the above condition, with the door P in a partly open door position during door closing, in the direction of arrow F 2 . In this position, the first flat surface  16  of the pin  13  and the front face  17  of the first plunger element  12  are angularly spaced apart by an angle α which decreases as the door is being closed, whereas the second flat surfaces  49 ,  49 ′ of the pin  13  and the front face  50  of the second plunger element  46  are angularly spaced apart by an increasing angle β. 
     The previously compressed first spring  18  performs its opposing action by pushing the front face  17  of the first plunger element  12  against the first surface  16  of the pin  13 , thereby causing the surfaces  16  and  17  to slide one against the other and the first end wall  32  to move along the line Y in the direction V. Now, the second spring  51  is also compressed due to the pressure of the second wall  48  of the second cam element  45  against the second plunger element  46 , which moves along the line Y′ in the direction V′, opposite to the direction V. 
     The second valve  54  is of the normally closed type and does not allow the passage of the working fluid through its orifice  62 , whereby oil  5  is forced to flow out at the hole  63  into the air gap  63  defined by the side walls  65 ,  66  of the second operating chamber  44  and the second cover cylinder  53  respectively. The outflowing oil  5  flows through the channel  60  into the first compartment  33  whose volume progressively increases. 
     The first valve  21 , which is of the normally open type, does not allow the passage of oil  5  through its orifice  35 , wherefore oil will flow from the second compartment  34  to the third compartment  57 , which are in fluid communication with each other. 
     In fact, in the second embodiment as shown in the figures, the working fluid follows a counter-clockwise path within the box-like housing defined by the stationary element  2 , to hydraulically delay the rotary motion of the movable element  3  with respect to the return movement thereof to the closed door position. Likewise, the working fluid is also delayed during door opening, so that the hinge structure of the invention is highly safe even for outdoor installations, In which wind or a careless user might exert an excessive load on the door. 
     In an alternative embodiment of the invention, as shown in  FIG. 19 , the first cam element  11  of the pin  13  may have a rounded peripheral surface, e.g. formed by turning, to allow the door P to be moved back to the closed door position from any open door position. This embodiment is particularly advantageous for fire doors. 
       FIGS. 25 to 32  show a preferred, non exclusive embodiment of a hinge assembly, generally designated by numeral  70 , to be mounted on self-closing doors P or the like. The assembly  70  comprises a first and a second hinge structures  71  and  72 , each comprising a stationary element  2 ,  2 ′ to be fixed to the frame T of the door P and a movable element  3 ,  3 ′ to be fixed to the door P. The movable elements  3 ,  3 ′ are pivotally mounted to their respective stationary elements  2 ,  2 ′ for rotating about the axis X. In this embodiment, the door P acts as a “drive shaft” between the two hinge structures  71 ,  72 . 
     As particularly shown in  FIG. 28 , the closing means  4  and the hydraulic damping means  5  are held in two operating chambers  6 ,  44  within the box-like housing defined by the first stationary element  2  of the first hinge structure  71 , whereas the second hinge structure  72  comprises second damping means  80 , which may also consist of a predetermined amount of the same oil as used in the first hinge structure  71 , contained in another operating chamber  81  within the box-like housing defined by the second stationary element  2 ′. 
     In other words, the first hinge structure  71  operates on the movable element  3  (and thence on the movable element  3 ′) to generate the torque C required to cause the door P to pivot to its closed position about the axis X, whereas the second hinge structure  72  operates on its movable element  3 ′ (and thence on the movable element  3 ) to hydraulically damp the movement produced by the hinge structure  71 , thereby generating a resistant torque C′ opposite the torque C. 
     This configuration allows for optimized motion control of very heavy doors and gates, during both the opening and closing movements. 
     Concerning both construction and operation, the first hinge structure  71  is very similar to the first embodiment as shown herein in  FIGS. 1 to 10 , or to the lower half of the second embodiment as shown herein in  FIGS. 11 to 24 . However, the second hinge structure  72  is very similar, still in terms of construction and operation, to the upper half of the second embodiment as shown herein in  FIGS. 11 to 24 . The only functional and structural difference between the latter and the hinge assembly  70  is that the operating chambers  6 ,  44  and the operating chamber  81  are not in fluid communication with each other, although their operation is identical. In an alternative embodiment, the assembly  70  of the invention may be formed of the first embodiment of the hinge structure, as shown in  FIGS. 1 to 10  (with the closing means held in a single operating chamber  6 ) and the hinge structure  72 . 
     The second hinge structure  72  comprises a second pin  13 ′ having a corresponding contact surface  82  which is designed to interact with another plunger element  83  associated to the second damping means  80 . 
     The contact surface  82  of the second pin  13 ′ is substantially perpendicular to the surfaces  16  and  49  of the first pin  13  of the first hinge structure  71 . 
     Furthermore, the second pin  13 ′ has a central portion  14 ′ that defines a corresponding cam element  86 , as well as side portions  87 ,  87 ′ that are appropriately shaped for connection with the second movable element  3 ′. 
     The cam element  86  interacts with the corresponding plunger element  83  as described above. 
     The second hinge structure  72  further comprises a corresponding check valve  84  located at an end wall  85  of the plunger element  83  to allow the passage of oil  80  during door closing and prevent backflow thereof during door opening. The wall  85  divides the operating chamber  81  into respective variable volume compartments  88  and  89 , a counter spring  90  being located in the compartment designated by numeral  88 . 
     As particularly shown in  FIGS. 29 to 32 , the check valves  21 ,  54  and  84  associated to their respective plunger elements  12 ,  46  and  83  are of the normally open type. 
     A further difference between the second hinge structure  72  and the upper half of the second embodiment as shown in  FIGS. 11 to 24  is that the second check valve  84  is of the normally open type (like the first valves  21 ,  54 ), i.e. allows the passage of oil  5  from the fourth compartment  58  to the third compartment  57  during door opening and prevents backflow thereof during door closing. 
     Thus, unlike the second embodiment as shown in  FIGS. 11 to 24 , the first valves  21 ,  54  and the second check valve  84  operate in the same directions, i.e. open during door opening and close during door closing. 
     The first and second hinge structures  71  and  72  are assembled in the same manner as those described above. Two channels  78 ,  79  are provided for filling oil  5  once the assembly has been completed. 
     In operation, the first and second hinge structures  71 ,  72  are mounted to the door P and cooperate to control its pivotal movement about the axis X. As shown in  FIG. 26 , their pins  13  and  13 ′ are configured in such a manner that the overlapping flat surfaces of the former and the opposite flat surfaces  82 ,  82 ′ of the latter are perpendicular to each other. 
     To adjust the alignment of the door P, the first hinge structure  71  may have suitable adjustment dowels  75 ,  76 . 
     The operation of the assembly  70  is identical to that of the second embodiment of the hinge structure as shown in  FIGS. 11 to 24 , except that the flow of oil  5  is controlled by normally open check valves  21 ,  54 , whereas the oil  80  is controlled by the valve  84 , which is of the same type. 
       FIG. 29  shows the first and second hinge structures  71 ,  72  in the closed door P position, and  FIG. 31  shows the first and second hinge structures  71 ,  72  in the fully open door P position. It will be understood that, while  FIGS. 29 to 32  only show the upper portion of the hinge structure  71 , the parts of the lower portion, not shown, operate exactly like those of the upper portion. 
     As the door P is opened by a user, i.e. as an external load E L , is applied thereon, e.g. in the direction of arrow F 1  as shown in  FIG. 30 , the first pin  12  and the second pin  13 ′ pivot about the axis X and cause the overlying surface  16  and the opposite flat surfaces  82 ,  82 ′ respectively to rotate about the same axis X. The spring  18  of the first plunger element  12  starts to be compressed, whereas the spring  90  starts to be released. 
     Thus, the volume of the first compartment  33  starts to decrease, as loading of the first spring  18  occurs. Furthermore, as the volume of the first compartment  33  decreases, the oil  5  therein starts to flow out through the orifice  35  of the valve  21  into the second variable volume compartment  34 , which starts to receive oil  5  and increases its volume. 
     At the same time, due to the rotation of the surfaces  82 ′,  82 , the volume of the compartment  89  starts to increase, as the spring  90  starts to be released. Also, the volume of the compartment  88  starts to decrease, therefore the oil  80  therein starts to flow into the adjacent compartment  89 , whose volume accordingly increases. However, since the valve  84  is of the normally open type, the oil  80  cannot pass through the orifice of the valve, and will flow into the compartment  89  through an air gap  91  between the side wall  92  of the operating chamber  81  and the side wall  93  of the plunger element  83 . 
     As a user releases the door or moves it from the position of  FIG. 31  to the closed position, the first spring  18  starts to be released, and the first plunger element  12  starts to push on the surface  16  of the pin  13  thereby rotating it in the direction of arrow F 2  back to the closed door position. At the same time, the surface  82  (or  82 ′, depending on the door opening direction) compresses the spring  90 , so that the volume of the compartment  89  starts to decrease and oil  80  flows out of it. 
       FIG. 32  shows the above condition, with the door P in a partly open door position during door closing, in the direction of arrow F 2 . The previously compressed first spring  18  performs its opposing action by pushing the front face  17  of the first plunger element  12  against the first surface  16  of the pin  13 , thereby causing the surfaces  16  and  17  to slide one against the other and the first end wall  32  to move along the line Y in the direction V. Now, the second spring  90  is also compressed due to the pressure of the cam element  86  against the plunger element  83 , which moves along the line Y′ in the direction V′, opposite to the direction V. 
     The first valve  21 , which is of the normally open type, does not allow the passage of oil  5  through its orifice  35 , wherefore oil will flow from the second compartment  34  to the first compartment  33  through the air gap  37  between the side wall  38  of the operating chamber  6  and the side wall  39  of the cylinder  20 . The valve  84 , whish is also of the normally open type, allows the passage of oil  80  through its orifice, to cause it to flow from the variable volume compartment  89  to the compartment  88 . 
     It will be understood that both the first  71  and the second  72  hinge structures may include fluid flow control means, like in the first and second embodiments described hereinbefore. This will afford control during both opening and closing of the door P. Thus, the door may be designed to oppose no (or very low) resistance at low closing speeds, and to increase its resistance as the door P closing speed increases. 
     Thanks to this arrangement, if the door is mounted outdoors, it can be designed to be easily opened by users, while not being slammed because of external agents, such as wind or the like. 
     The above disclosure clearly shows that the hinge structure and assembly of the invention fulfill the intended objects and particularly meet the requirement of assuring controlled movement of the door both during opening and closing thereof. 
     During door closing, such controlled movement prevents the door from banging against its frame, thereby ensuring integrity and long life thereof. 
     On the other hand, during opening, such controlled movement will prevent any abrupt opening of the door P due to gusts of wind, to protect both the door and any user within its operating range. 
     The hinge structure and assembly of the invention are susceptible of a number of changes and variants, within the inventive concept disclosed in the appended claims, All the details thereof may be replaced by other technically equivalent parts, and the materials may vary depending on different needs, without departure from the scope of the invention. 
     While the hinge structure and assembly have been described with particular reference to the accompanying figures, the numerals referred to in the disclosure and claims are only used for the sake of a better intelligibility of the invention and shall not be intended to limit the claimed scope in any manner.