Patent Publication Number: US-7900978-B2

Title: Return spring assembly for a lock mechanism

Description:
BACKGROUND OF THE INVNETION 
     1. Field of the Invention 
     The present invention relates to spring mechanisms used with lock mechanisms to return a handle to an original position after the handle has been rotated to open a door. The invention is particularly directed to spring mechanisms to be used with lever handles and lock mechanisms having lock function controls extending outward from a latchbolt mechanism to return the lever handle to a horizontal position. 
     2. Description of Related Art 
     Lock mechanisms are driven by inner and outer handles mounted on corresponding spindles that extend from the handles on opposite sides of the door to a lock mechanism located within a bored opening in the door. A latchbolt portion of the lock mechanism is located within a smaller bored opening that extends inward from the edge of the door and perpendicularly intersects the larger bored opening, which extends between the opposite faces of the door. 
     After one of the handles is turned to open the door, it must be returned to its initial position and this return function is typically accomplished with one or more springs. The return springs may be integrated into the lock or they may be located in a separate housing mounted inside the bored opening and/or on the surface of the door at the base of the handle. 
     When round doorknobs are installed, relatively little force is required to return the doorknob to its initial position, however, it has become more common to install lever handles. Although lever handles are easier to operate, they require the return spring assembly to produce significantly more torque to lift the offset portion of the lever handle against the force of gravity and return it to the initial horizontal orientation. As a consequence, it has become necessary to use larger and more powerful return springs than were previously necessary for round doorknobs. 
     Larger springs generally require more space than can easily be found inside the lock mechanism, so separate return spring mechanisms are widely used—one located on each side of the door. When the return spring mechanism is mounted on the outer surface of the door, however, it produces a relatively thick and bulky appearance, which is unsightly. A thinner appearance is preferred, and this requires that the springs be located at least partially inside the bored opening of the door. However, positioning the return spring assembly inside the bored opening in the door limits the space available for the lock mechanism, which must also be located within the bored opening. 
     Conventional designs that position the return spring assembly inside the bored opening use one or more springs that extend around substantially the entire inner perimeter of the bored opening on each side of the door. This provides the maximum space for the spring and allows it to maximize the torque produced. The spring force on each side of the door may come from one large compression spring, or from a pair of compression springs arranged end to end, or from a coiled torsion spring. In each case, however, the spring extends around a substantial portion of the inside perimeter of the bored opening. 
     This use of the inner perimeter of the bored opening is acceptable for many door lock mechanisms where the locking mechanism is in a central lock core. In these designs the interaction between the user and the locking mechanism comes from a button or key on the handle that connects to the locking mechanism through linkages or mechanisms that are located close to or directly on the axis of the bored opening in the door. By placing the lock control linkages close to this axis, the linkages are positioned well inside the perimeter space required for the locking springs and there is no interference between the springs and the lock mechanism linkages. 
     However, in other lock mechanism designs, of the type for which this invention is particularly suitable, the locking mechanism is more closely integrated with the latchbolt portion. In these designs, the lock control linkages extend directly outward from the latchbolt mechanism at the front of the lock mechanism bored opening and the lock linkages are far from the axis of rotation of the handles. As a result, the lock control linkages in such designs will interfere with the springs in a conventional spring return mechanism where the springs occupy the entire inner circumference of the bored opening. 
     Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a return spring assembly that is compatible with lock mechanisms having a control linkage extending outward from the latchbolt mechanism. 
     It is another object of the present invention to provide a return spring assembly that does not extend into the space at the front of a bored opening in a door and has the spring mechanism located at least partially inside the bored opening to provide a reduced visual thickness as compared to return spring assemblies that are mounted outside the bored opening on the surface of the door. 
     It is another object of the present invention to provide a return spring assembly that provides additional support to the latchbolt mechanism of a lock mechanism. 
     Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification. 
     SUMMARY OF THE INVENTION 
     The above and other objects, which will be apparent to those skilled in this art, are achieved in the present invention which is directed to a return spring assembly for a lock mechanism adapted for installation in a bored opening in a door. The return spring assembly includes a spring housing having an outer flange and an inner portion having a curved section. The outer flange has a diameter greater than the bored opening and makes supporting contact with an outer surface of the door when the return spring assembly is inserted into the bored opening. 
     The inner portion extends at least partially into the bored opening in the door when the outer flange is in contact with the face of the door to provide a thinner appearance. The curved section extends less than one hundred eighty degrees around the perimeter of the inner portion and more deeply into the bored opening than the remainder of the inner portion, preferably at least half the thickness of the door. 
     An annular spring channel is formed in the spring housing and holds a compression spring that acts to return the handle to the horizontal orientation. Two spring drivers, preferably identical, compress the spring from opposite directions. The first spring driver has a first arm engaging a first end of the spring and the second spring driver has a second arm engaging a second end of the spring. Each spring driver includes a center opening shaped to engage a spindle driven by a handle. 
     The first spring driver moves as the handle is rotated in a first direction to compress the spring from the first end of the spring and the second spring driver moves as the handle is rotated in an opposite direction to compress the spring from the second end of the spring. The spring drivers are driven with lost motion, the first spring driver remaining stationary as the second spring driver moves to compress the spring from the second end and the second spring driver remaining stationary as the first spring driver moves to compress the spring from the first end. 
     In one aspect of the invention, the center of each spring driver includes an opening defined by a partial rotation of the cross-sectional shape of the spindle, which is typically square. This produces a cross-shaped opening and the opening provides a lost motion engagement between the spring driver and the spindle. 
     In another aspect of the invention, the curved section of the spring housing extends into the bored opening in the door into supporting contact with the lock mechanism. This provides a rugged connection between the lock and the door and the return spring assembly. Preferably, the curved section of the spring housing extends into the bored opening in the door into supporting contact with an upper side of the lock mechanism. A second return spring assembly having a second spring housing and a second curved section is typically inserted from the opposite side of the door and the two curved sections contact opposite, upper and lower, surfaces of the lock mechanism to trap it and secure it therebetween. 
     In still another aspect of the invention, the spring housing includes four bosses that act as stops for the spring driver arms at opposite ends of their travel. The arm of the first spring driver contacts a first one of the bosses when the first spring driver is not being driven; the arm of the second spring driver contacts a second one of the bosses when the second spring driver is not being driven; the arm of the first spring driver contacts a third one of the bosses when the first spring driver is driven to maximally compress the spring; and the arm of the second spring driver contacts a fourth one of the bosses when the second spring driver is driven to maximally compress the spring in the opposite direction from the first spring driver. 
     In the most highly preferred embodiment of the invention, the arm of the first spring driver contacts the first one of the bosses when the second spring driver is driven to maximally compress the spring and the arm of the second spring driver contacts the second one of the bosses when the first spring driver is driven to maximally compress the spring from the opposite direction. This design shares the loads between the two arms at the limits of travel and strengthens the design significantly. 
     In still another aspect of the invention, the spring housing includes an opening for receiving a lock linkage extending outward from the lock mechanism. The opening for the lock linkage is located opposite the spring and spring channel, and the spring and spring channel extend only partly around the inner perimeter so that the spring does not interfere with the lock linkage extending through the opening as would occur with a prior art design using springs around the entire inner perimeter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features of the invention believed to be novel and the elements characteristic of the invention are set forth with particularity in the appended claims. The figures are for illustration purposes only and are not drawn to scale. The invention itself, however, both as to organization and method of operation, may best be understood by reference to the detailed description which follows taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is an exploded perspective view of a return spring assembly for a lock mechanism according to the present invention. 
         FIG. 2  is also an exploded perspective view of the return spring assembly in  FIG. 1  taken from an opposite direction. 
         FIG. 3  is a front elevational view of a return spring assembly according to the present invention. The cover plate has been removed to show the relationship of the internal components and the return spring assembly is shown as it would appear with the handle in the non-rotated position. 
         FIG. 4  is a front elevational view of a return spring assembly corresponding to the view in  FIG. 3  except that the return spring assembly is shown as it would appear with the handle rotated counterclockwise. 
         FIG. 5  is a front elevational view of a return spring assembly corresponding to the view in  FIG. 3  except that the return spring assembly is shown as it would appear with the handle rotated clockwise. 
         FIG. 6  is a perspective view showing two return spring assemblies according to the present invention, one for each side of the door, installed with a lock mechanism. The lock mechanism is shown generically and is not intended to indicate any particular lock design. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS(S) 
     In describing the preferred embodiment of the present invention, reference will be made herein to  FIGS. 1-6  of the drawings in which like numerals refer to like features of the invention. 
     Referring to  FIG. 1 , the return spring assembly  10  of the present invention includes a spring housing  12  having an outer flange  14  and an inner portion  16 . The outer flange  14  has a diameter greater than the diameter of the bored opening in the door into which the spring assembly will be inserted. As can be seen in  FIG. 6 , the inner portion  16  of the spring housing  12  is inserted into the bored opening of the door  18  until the outer flange  14  makes contact with the face of the door. 
     The inner portion has a diameter less than the diameter of the bored opening in the door and extends at least partially into the bored opening in the door when the outer flange is in contact with the face of the door. This allows the return spring assembly to provide a thin and attractive appearance when a scalp, rose or escutcheon plate covers it. 
     Referring again to  FIG. 1 , the inner portion  16  has a curved section  20  extending less than one hundred eighty degrees around the perimeter of the inner portion. When installed, the curved section  20  extends more deeply into the bored opening in the door  16  than the remainder of the inner portion  16 . 
     As can be seen in  FIG. 6 , the return spring assembly  10  of  FIG. 1  is designed to cooperate with a second identical return spring assembly  22 . The first assembly is located on one side of the door  18  with its curved section  20  extending above the latchbolt lock mechanism  24 . The second return spring assembly  22  is inserted from the opposite side of the door with its corresponding curved section  26  extending below the latchbolt lock mechanism  24 . The two return spring assemblies  10  and  22  are rotated relative to each other so that they trap the latchbolt lock mechanism  24  between their corresponding curved sections  20  and  26 . 
     As can be seen in  FIG. 1 , the inner portion  16  of the spring housing  12  has an annular spring channel  28  formed in it that receives a compression spring  30 . The compression spring  30  is held between a first spring driver  32  and a second spring driver  34 . Spring driver  32  includes a first arm  36  having a projection  38  that engages a first end  40  of the spring  30 . The second spring driver  34  has a second arm  42  with a second projection  44  that engages the second end  46  of the spring  30 . 
     Hub  48  rotates in the spring housing  12  and has an opening  50  that receives and engages a conventional spindle from a handle. The opening  50  has a shape that matches the square cross section of a conventional spindle, however other shapes may also be used. 
     The center of the first spring driver  32  includes an opening  52  defined by the partial rotation of the cross-sectional shape of the spindle. The center of the second spring driver  34  also includes an opening  54  defined by the partial rotation of the cross-sectional shape of the spindle. The shape of the openings  52 ,  54  in the centers of the spring drivers is such that they provide lost motion engagement between the spring driver and the spindle. 
     The return spring assembly  10  also includes a scalp lock  56  for attaching a scalp, rose or escutcheon, a cover plate  58  and a pair of cover screws  60 ,  62  that attach the cover plate to the spring housing  12 . The cover plate  58  holds the spring  30 , the spring drivers  32 ,  34  and the hub  48  in the housing  12 . As can be seen in  FIG. 2 , the scalp lock  56  attaches to a cylindrical lip  63  on the spring housing  12 . 
     In the preferred design, the scalp lock  56  is made of plastic and radial grooves allow the ring to flex sufficiently to engage the cylindrical lip  63  and/or a scalp, rose or escutcheon attached to the outer surface of the return spring assembly. 
       FIG. 3  shows the assembled return spring assembly  10  with the cover plate  58  removed. The spring  30  is shown uncompressed, in the position it is in when the corresponding handle is horizontal (not rotated). As can be seen here, the spring  30  extends only partially around the inner perimeter of the return spring assembly  10 . This arrangement provides clearance at the right side of  FIG. 3  for opening  64  and for any desired lock control linkage or button to extend outward from the latchbolt lock mechanism  24  through opening  64  to the surface of the door. 
     In conventional return spring assembly designs, one or more return springs are located around substantially the entire perimeter of the spring assembly. The design of the present invention, as illustrated in  FIG. 3 , with a single spring around only part of the perimeter, allows the latchbolt lock mechanism  24  to be controlled through linkages extending through opening  64  located in the space on one side of the spindle that would otherwise be occupied by a return spring in a conventional design. 
     The operation of the spring drivers and the lost motion interaction between the spindle and the spring drivers  32 ,  34  can be understood by a comparison of  FIGS. 3-5 . The lost motion operation of the spring drivers derives from the shape of the central openings  52 ,  54  in the spring drivers. 
     The shape of the central openings is defined by a partial rotation of the cross sectional shape of the spindle. In the preferred design, the spindle  66  is conventional and its cross-sectional shape is a square. The square cross-sectional shape is partially rotated by approximately the angle that the handle is to be allowed to rotate relative to the horizontal to define the shape of the central openings  52 ,  54 . This produces the approximately cross-shaped central opening seen in the drawings. 
     As a result of this shape, a square shaft spindle  66  can turn inside the spring driver openings  52 ,  54  over a limited range without turning the spring driver. At the limits of rotation, however, the spindle engages the opening and begins to turn the spring driver. As can be seen in  FIG. 3 , the two spring drivers  32 ,  34  are identical, but they have been flipped so that the projections  38  and  44  face each other. The central openings  52 ,  54 , despite being in the identical position on identical spring drivers, end up rotated relative to each other due to the relative rotated position of the spring drivers. 
     Accordingly, if spindle  66  begins to rotate clockwise from the rest position, it turns only the second spring driver  34  and compresses spring  30  from only the second end  46  without turning the first spring driver. The spring is compressed until the position seen in  FIG. 4  is reached. However, if the spindle  66  rotates counterclockwise, it turns only the first spring driver  32  and compresses spring  30  from the first end  40  without turning the second spring driver  34  until the position seen in  FIG. 5  is reached. When no force is applied to the handle, the compression spring  30  expands and drives both spring driver arms  36 ,  42  away from each other to the position seen in  FIG. 3 , which returns the handle to the horizontal position. 
     The spring housing  12  is also provided with a pair of openings  68 ,  70  that receive corresponding screws and studs to attach the first return spring assembly  10  to a second spring assembly  22  as seen in  FIG. 6 . This clamps the first and second spring assemblies together and grips the door  18  between the respective outer flanges and holds the latchbolt lock mechanism  24  securely between the respective curved sections  20 ,  26 . 
     This design integrates the latchbolt lock mechanism  24 , the return spring assemblies  10 ,  22  and the door  18  into a cohesive unit that is highly resistant to a brute force attack. It is particularly designed to resist the excess force that can be applied through lever handles. In furtherance of this design goal, the spring driver arms  36 ,  42  contact bosses  72 ,  74 ,  76  and  78  at the base of the arms  36  and  42  when the spindle reaches the limits of rotation. 
     As can be seen in  FIG. 4 , when the handle and spindle are turned clockwise, the second spring driver can turn until its arm  42  contacts boss  78 . As the second spring driver reaches the limit of rotation, the first spring driver  32  is engaged due to the shapes of the openings in the center of the spring drivers. Any attempt to continue the clockwise rotation of the spindle is resisted by the contact between the second arm  42  and the boss  78  and by the contact between the first arm  36  and the boss  74 . 
     In a similar manner, any attempt to excessively rotate the handle and spindle in the counterclockwise direction is resisted by the combined contact between the first arm  36  and boss  76  and the second arm  42  and boss  72 . It will also be seen that each spring driver arm has a rounded or filleted connection to the spring driver at the base of the arm to reduce stress at this point and prevent the arm from breaking or cracking under high loads. Each boss is provided with a corresponding rounded shape to match the filleted base of the spring driver arms. This design effectively transfers any excess force applied to the handle through the return spring assembly to the door. 
     In the preferred designs, the spring drivers  32 ,  34  are formed from a flat sheet of material and are in face to face contact, except that they are reversed so that the projections  38 ,  44  face each other to engage the ends of the spring  30 . Identical pieces reduces the parts count and decreases manufacturing cost, as well as reducing errors in assembly. 
     In the preferred design, the curved section on the housing extends around the perimeter of the return spring assembly less than one hundred eighty degrees, and extends into the door more than half the thickness of the door. This ensures that the curved sections from return spring assemblies on opposite sides of the door do not interfere with each other, but extend sufficiently to engage the top and bottom of the latchbolt lock mechanism  24 . 
     While the present invention has been particularly described, in conjunction with a specific preferred embodiment, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. It is therefore contemplated that the appended claims will embrace any such alternatives, modifications and variations as falling within the true scope and spirit of the present invention.