Patent Publication Number: US-2010123276-A1

Title: Force control strut

Description:
The present invention is a divisional of U.S. application Ser. No. 11,361,659 filed Feb. 23, 2006. 
    
    
     The present invention relates to a strut for controlling movement of a movable member such as a hood, top, door, hinged cover or other devices, which strut changes the force encountered by the movable element at various positions to thereby control motion. 
     INCORPORATION BY REFERENCE 
     The invention involves an elongated strut incorporating a compression spring or springs to control the force exerted on a movable element by either retracting or extending the strut. The movable element controls a structure such as a pivoted door or hood so the strut controls motion by controlling force. It is known to use an elongated strut having a cylindrical tube with a reciprocating element biased by one or more coil springs so the force of movement changes at different linear positions. A representative strut is shown in U.S. Pat. No. 6,773,002, which patent is incorporated by reference herein as background technology. Such elongated strut with coil springs controlling the linear force and, thus, movement has been modified to provide a damper mechanism carried by the extendable and retractable rod movable with respect to the tubular housing constituting the supporting structure of the strut. A dampened strut is described in United States Patent Publication No. US 2004/0222579, which publication is also incorporated by reference as background technology. Utilizing these two patented items, the purpose and operation of a motion controlled strut is known technology and need not be repeated. 
     BACKGROUND OF INVENTION 
     Coil spring elongated struts incorporated by reference herein utilize compression springs; however, these struts are not effective in controlling and selectively dampening the motion of the member to which they are attached. The prior art method for controlling the motion of an extendable strut is to match the compression spring rod loads to the application load, such as the weight of an automobile hood or trunk. Due to design limitation it is not always practical to exactly match or offset the load of the movable strut as it swings through its arc of movement. Consequently, closing speed of the hood or trunk lid varies throughout the movement stroke of these devices. There is a need to control motion of movement at a desired rate in various positions of the total travel. 
     SUMMARY OF THE INVENTION 
     The design of the present invention encompasses the concept of using a well known compression spring rod, such as shown in U.S. Pat. No. 6,773,002 wherein the compression spring strut replaces the solid movable rod with a rod having an internal damper mechanism. The invention utilizes a damper in combination with the rod of the prior art compression spring rod type strut. The damper used in the present invention is designed for low force, motion control applications. The damper can be used to allow the compression spring rod to compress at a controlled rate while extending without any dampening action. To control the force by using a dampening action during extension, the damper plunger is connected to the bottom plug. In this concept, there is a dampening action in the extension direction as well as in the compression or retraction directions. The invention involves combining a damper mechanism with a standard compression spring type of strut to provide force control during movement of a rod member in the compression direction. 
     In accordance with the invention, there is provided a force control strut which causes a controlled force during at least part of the stroke of a compression spring strut. The force or motion control strut comprises an elongated housing having a straight guide tube with inner cylindrical surface and axially opposite first and second ends. A rod member has an inner end reciprocally movable inside the housing and along the guide tube and an outer end extending outwardly from the first end of the housing. A guide member is secured to the first end of the housing to form a bushing allowing reciprocation of the rod member axially in the housing between a retracted position with the rod collapsed in the housing and an extended position with the rod protruding from the housing. At the bottom of the guide tube there is a fixed plug that closes the end of the housing. A cylindrical guide piston is fixed to the inner end of the movable rod and is slidable along the inner cylindrical surface of the tube. Between the piston and one end of the housing is a coil spring that biases the rod in a given direction in the housing. As so far described, the strut is like the compression spring rod shown in U.S. Pat. No. 6,773,002. The coil spring forces the rod member outwardly so that closing a member using the strut is balanced by the reactive force of the coil spring. In this manner, the strut exerts a force on the movable element controlled by the strut either in the retracted closing position or the extending opening position. To add a further control force during movement of the rod, a damper mechanism is combined with the movable rod. The damper mechanism includes a plunger reciprocally mounted in an elongated force controlled passageway inside the movable rod. The plunger of the damper mechanism is movable outwardly from an end of the rod facing inside the elongated housing. The distal end of the plunger is engageable with the bottom plug closing the housing. In this manner, the plunger is forced into the passageway to create a controlled force dampening movement of the operating rod in the housing. 
     In one embodiment, the main coil spring is located between the bottom plug and the guide piston of the rod. In another embodiment of the invention, the main coil spring is between the guide member and the guide piston. Consequently, the rod of the strut is either biased in the extended position or the retracted position according to the location of the main coil spring. To add the force controlling action of the damper mechanism, the distal end of the plunger merely abuts against the bottom plug as the rod member is retracted. Consequently, the damper force occurs only after the retraction or compression motion of the rod has caused the plunger of the damper mechanism to engage the bottom plug. In another embodiment, damping control is introduced in both the retraction and the extension direction. In this embodiment, the plunger is attached to the bottom plug. Thus, the plunger adds a damping force on a retraction and extension of the rod member. To change the controlled damping force created during the two opposite movements of the rod, the internal damper piston has at least one check valve. Thus, movement in one direction is dampened to a lesser amount than movement in the other direction. The disclosure reveals there are several embodiments and implementations of the invention. Essentially, a damper mechanism is added to a compression spring rod shown in U.S. Pat. No. 6,773,022. This concept allows several versions of a combined reciprocating rod with a damper plunger in a coil spring strut. The configuration of the damper mechanism and its connection with respect to the housing structure allows these several versions of the basic inventive concept. 
     The primary object of the present invention is the provision of an elongated strut having a coil spring biasing a rod member in either the retracted or extended position with a damper mechanism forming a part of the movable rod to add a controlled force during at least a portion of the travel of the rod. 
     Another object of the present invention is the provision of a strut, as defined above, which strut adds a dampening force during a certain portion of movement of the rod into and out of an elongated compression spring housing. The strut is capable of adding a controlled dampening force to different selected portions of the movement of the main rod of the strut. 
     Yet another object of the present invention is the provision of a strut, as defined above, which strut is easily manufactured, more economical and provides more force and motion versatility than existing struts. 
     Yet a further object of the present invention is the provision of a strut, as defined above, which strut controls the movement of a hood, door, cover, lid or other pivotal structures so that the movement of the structure has increased force control over a portion of the rod movement in a common coil spring strut. 
     These and other objects and advantages will become apparent from the following description, taken together with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a pictorial view representing the primary use of the present invention wherein a door, hood, cover or lid is movable from an open position to a closed position against the force generated by the preferred embodiment of the present invention; 
         FIG. 2  is an exploded view of the first embodiment of the present invention wherein the strut is primarily a compression strut; 
         FIG. 3A  is a side elevational view of the strut shown in  FIG. 2  assembled with the strut in the extended rest position; 
         FIG. 3B  is a cross-sectional view, as shown in  FIG. 3A , with the rod partially compressed; 
         FIG. 3C  is a cross-sectional view of the strut, as shown in  FIGS. 3A and 3B , with the rod fully compressed into the housing; 
         FIG. 3D  is a cross-sectional view of the strut, as shown in  FIGS. 3A ,  3 B and  3 C, as the rod is being extended or returned by assistance of the coil spring; 
         FIG. 4  is a pictorial view of a shelf movable in a vertical direction under the control of a strut constructed in accordance with a second embodiment of the present invention; 
         FIG. 5  is an exploded view of the second embodiment of the present invention wherein the strut has a damping action in both the extension and the compression directions; 
         FIG. 6A  is a cross-sectional view of the strut shown in  FIG. 5  with the rod in the fully extended position and the coil spring at rest; 
         FIG. 6B  is a cross-sectional view of the strut, as shown in  FIG. 6A , with the rod of the strut partially compressed against the damping action of the damper mechanism; 
         FIG. 6C  is a cross-sectional view of the strut, as shown in  FIGS. 6A and 6B , with the rod fully compressed; 
         FIG. 6D  is a cross-sectional view of the strut, as shown in  FIGS. 6A ,  6 B and  6 C, with the rod moving in the extension direction against a controlled higher damper force; 
         FIGS. 7A ,  7 B,  7 C and  7 D are cross-sectional views of a strut similar to the strut shown in  FIGS. 6A ,  6 B,  6 C and  6 D with the main coil spring moving the rod toward the retracted position; and, 
         FIGS. 8A and 8B  are a strut similar to the strut as shown in  FIGS. 7A-7D , with the plunger attached to the bottom plug, as shown in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The compression spring rod shown in U.S. Pat. No. 6,773,002 (Adoline patent) utilizes an elongated housing with a reciprocal rod movable within the housing. One or more coil springs control the force profile in the compression or retracted direction, in the extended or retraction direction or in both directions. Operation of the coil spring structure in the Adoline patent is determined by the orientation of the control spring or springs. To adjust the spring force profile, two springs are often used and are wrapped in opposite directions, the springs having different modulus of expansion, different lengths or different combinations of such spring parameters. This type of coil spring is employed in an elongated strut to control the force necessary to open or close a pivoted member, such as a door, lid or cover. The present invention is an improvement over this prior coil spring device by adding further force controlling characteristics, for use in either the retracted or compression direction or in the extended, retracted direction. The preferred embodiment of the invention relates to an improved motion control strut operated in the compression orientation for controlling the force profile used while closing a lid. Application of such embodiment is schematically shown in  FIG. 1  wherein two spaced struts A are mounted on box B for controlling the closing action of lid, door or cover C. This first preferred embodiment of the invention is shown in  FIGS. 1 ,  3 A,  3 B,  3 C and  3 D. Strut A has an elongated housing  10  with the length necessary to determine the stroke of the strut. The housing has a first end  12  and a second end  14  defined by the ends of guide tube  20  closed at the first end by guide member  30  in the form of a bushing. This bushing has internal journal passage  32  and is held on the end of housing  10  by the combination of groove  34  in member  30  and crimped rim  36  on the first end of tube  20 . To close the opposite end of the tube, bottom plug  40  is fixed by the interaction of groove  42  in the plug and crimped rim  44  on the second end of the tube. In this manner, member  30  and plug  40  close the opposite ends of tube  20  defining elongated housing  10  and having inner surface  22  for guiding reciprocal movement of rod member  50  extending through journal passage  32 . In accordance with the prior Adoline patent, rod member  50  has an outer end  52  with first external connector  54  connected by threaded bore  54   a  and stud  54   b.  Inner end  56  of reciprocal rod member  50  carries guide piston  60  slidable along surface  22  of tube  20  and connected to the end of rod member  50  by the interaction of groove  64  and crimped rim  66 . To mount strut A onto the structure as shown in  FIG. 1 , there is a second external connector  70  attached to fixed bottom plug  40  by stud  70   b  threaded into bore  70   a.  Since the first embodiment of the invention is a compression controlled strut A the coacting coil spring  80  is positioned between piston  60  and fixed bottom plug  40 . In accordance with known technology, coil spring  80  which controls the compression force profile of rod member  50  often includes two concentric coil springs wrapped in opposite directions and having different lengths, different spring coefficients modulus or combination of these spring parameters to determine and force profile required to close lid C of box B. In operation, connector  54  of rod member  50  is moved to the right as shown in  FIG. 3B  when cover C is closed. This collapses coil spring  80 , or combines springs as previously discussed, to control the force profile of the closing action for cover C. The present invention relates to an improvement in this type of elongated strut. 
     Compression strut A is modified so rod member  50  is combined with a damper mechanism  100  comprising a force controlling passageway  102  filled with an appropriate liquid. Plunger  104  with a piston  110  on the inner end of the plunger is reciprocated in passageway  102 . Controlled force is determined by a calibrated bleed orifice  112  in piston  110 . Movement of plunger  104  in either direction is dampened by the calibrated bleed orifice  112  so that distal end  114 , having tip flange  116  secured to the plunger by stud  116   a  threaded into bore  116   b,  exerts a force based upon the interaction of piston  110  in passageway  102 . The first embodiment of the invention shown in  FIG. 2  is operated in accordance with the progressive positions of rod member  50  as illustrated in  FIGS. 3A ,  3 B,  3 C and  3 D. Extension coil spring  120  surrounds plunger  104  and exerts an outer directed force between tip flange  116  and terminal portion  122  of rod member  50 . In this first embodiment of the invention, plunger  104  is not connected or fixed to plug  40  but periodically abuts against or engages bottom plug  40  for adding the dampening force of mechanism  100  to the coil spring controlled force of strut A. As shown in  FIG. 3A , strut A is in its extended rest position with tip flange  116  extended outwardly from rod  50  but spaced a distance a from fixed bottom plug  40 . As lid or cover C is closed against the force exerted by strut A, initial movement of rod member  50  is against the force of coil spring  80  until rod member  50  moves the distance a. At that time, tip flange  160  engages bottom plug  40  to add the damping effect of piston  110  to the force profile experienced by downwardly moving cover C. This addition or combination of the coil spring force and the added damper force is continued until rod member  50  is fully compressed, as shown in  FIGS. 3B and 3C . Consequently, the force of the coil spring or springs in tube  20  is added to the damping of mechanism  100 . To extend rod member  50 , tip flange  116  is immediately withdrawn from plug  40  so damper mechanism  100  has no effect in the retraction direction. During the retraction action as shown in  FIG. 3D , extension coil spring  120  acting against end  122  of rod member  50  shifts plunger  104  to the fully retracted position by moving piston  110  in passageway  102 . This action has no effect upon the extension movement of rod member  50 , but merely prepares the damper mechanism by shifting the plunger to the position shown in  FIG. 3A . Thereafter, strut A is conditioned for movement again between the positions shown in  FIGS. 3A ,  3 B and  3 C. In this manner, the compression of strut A is controlled first by the coil spring and then by a combination of the coil spring and novel damping mechanism  100 , with the damping effect controlled by calibrated bleed orifice  112 . 
     As shown in  FIGS. 4 and 5  a second embodiment of the invention operated in accordance with the positional views shown in  FIGS. 3A ,  3 B,  3 C and  3 D. Struts A′ are mounted between the top of legs L and movable shelf S to control the movement of shelf S as illustrated in   FIG. 4 . Strut A′ is constructed to exert a damping control force in both movement directions of rod member  50 . Many components used in first embodiment strut A are the same as components illustrated for use in the second embodiment strut A′. This particular strut is modified by attaching distal end  114  of plunger  104  onto bottom plug  40  by an attachment  200  in the form of stud  200   a  threaded into bore  200   b.  By using this second embodiment, damper mechanism  100  operates in both the extended direction of rod member  50  and the retracted direction of rod member  50 . As shown in  FIG. 6A , coil spring  80  is expanded to its rest position in housing  10 , which extended position involves a small space between piston  60  and guide member or bushing  30 . In the position shown in  FIG. 6A , shelf S has been lowered and the movement has been controlled by the force of coil spring  80  as restricted by the damping force of damper mechanism  100 . To retract the shelf, rod member  50  is moved to the right as shown in  FIG. 6B  to compress coil spring  80  against the resistance of force caused by the spring. At the same time, damper mechanism  100  controls the spring compression direction of rod member  50 . Piston  110  moves in passageway  102  to add controlled force. In one implementation of this embodiment, calibrated orifice  122  controls movement of piston  110  in both directions. However, in the illustrated embodiment, one way valve  210  allows easier movement of the rod member as it is retracted. Retraction against coil spring  180  continues as shown in  FIG. 6C  where spring  80  is fully compressed and plunger  104  is moved into passageway  102  in a controlled damping action. Since one way valve  210  is opened in this direction, the damping force applied in compression is less than the damping force added to the spring force in extension as illustrated in  FIG. 6D . During such extension, valve  210  is closed and the movement of piston  110  in force controlling passageway  102  is determined by the action of calibrated orifice  122 . By attaching distal end  114  of plunger  104  onto bottom plug  40 , the damper mechanism operates in both directions. 
     As illustrated in  FIGS. 6A-6D , strut A′ adds a controlling damper force during movement of rod member  50  in both directions. The amount of damping force changes with velocity and can be varied in the opposite directions, if desired. This action is different from strut A shown in  FIG. 2  where the added damping force occurs only during compression of the strut. Strut A is modified to produce a retraction controlled strut  250  as shown in  FIGS. 7A-7D . In this embodiment of the invention, compression spring  80  is replaced by compression spring  260  located between guide member or bushing  30  and piston  60  riding along surface  22  of tube  20 . End flange  116  periodically abuts against bottom plug  40 , as in strut A. This causes controlled retraction, as illustrated. In  FIG. 7A , strut  250  is at rest with rod member  50  retracted into housing  10  and plunger  104  collapsed into passageway  102 . During extension, as illustrated in  FIG. 7B , rod member  50  is moved outwardly against compression spring  260 . Damper mechanism  110  has no effect and spring  120  merely moves plunger  104  to the right cocking it for the next retraction of strut  250 . The fully extended position of rod member  50  is illustrated in  FIG. 7C . This position has been reached by movement against the compressive force of coil spring  260  which, as in other embodiments, may be two oppositely wound coil springs with different lengths, different spring modulus or a combination of these parameters. After strut  250  is fully extended as shown in  FIG. 7C , it is retracted as shown in  FIG. 7D  until it reaches the position shown in  FIG. 7A . This retraction is controlled by the relaxation of coil spring  260  at a controlled rate together with a controlled movement of plunger  104  into passageway  102 . A single calibrated orifice  122  controls the movement of piston  110  in both directions. This damper force acts against the spring expansion force of coil  260 , only when the coil is being retracted as shown in  FIG. 7D . 
     The damping force and spring force are combined during movement of rod member in both directions when coil spring  250  is between guide journal  30  and piston  60 . When the rod member is moved in the retracted direction and, distal end  114  is connected to bottom plug  40  by attachment arrangement  200 . The spring acts against the damper force when rod member  50  is retracted or extended. This modification of strut A′ of  FIG. 7  is schematically illustrated in  FIGS. 8A-8D . In this embodiment, piston  110  includes a one way valve  210  so that there is a substantial damping force exerted during the retraction of rod member  50  as shown in  FIG. 8D . Movement of the rod in the opposite direction as shown in  FIG. 8B  has a lesser amount of damping force applied against movement of spring  260 . 
     All embodiments of the invention combines a damper force to a coil spring operated strut so that a damping force is applied to movement of the strut in one or more directions. Several embodiments and implementations of this invention are illustrated; however, a person skilled in the art could devise other uses of a center damper mechanism to add a damping force in one or both directions of a coil spring controlled strut.