Abstract:
A joint for an articulated mechanism includes a housing and a rotatable member within the housing. There is a friction member mounted on the housing between the housing and the rotatable member. There is a spring normally biasing the friction member against the rotatable member to inhibit the rotation of the rotatable member. There is an actuator within the housing operatively coupled to the housing. The actuator member moves the friction member away from the rotatable member when actuated to facilitate rotation of the rotatable member. A plurality of joints are used to connect together a series of shafts, some of which may be equipped with clamps or other tools for securing workpieces.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to articulated mechanisms and, in particular, to articulated mechanisms employing joints which can be locked or unlocked to move to a selected position.  
           [0002]    Various mechanisms have been devised to hold tools or workpieces in a desired position. For example, gooseneck mechanisms have been used for lamps as well as articulated arms. However such devices are not always suitable for tasks where it is desired to hold an object selectively in a fixed position without movement or alternatively to easily allow movement of the object when desired.  
           [0003]    Earlier patents show lockable ball joints used on articulating apparatuses of various types. For example U.S. Pat. No. 4,616,632 to Wigoda discloses surgical retractors which include ball joints. Foot controllers allow locking of the joints. One version of the invention employs solenoids.  
           [0004]    U.S. Pat. No. 5,857,492 to Salamun discloses an electromagnetic friction lock between a spherical joint and its seat.  
           [0005]    U.S. Pat. No. 4,527,925 to Bauer et al. discloses a ball joint having a locking element including a spring.  
           [0006]    U.S. Pat. No. 4,606,522 to Heifetz shows a jointed holder for holding articles. It includes ball joints which may be tightened.  
           [0007]    U.S. Pat. No. 3,638,973 to Poletti discloses a ball joint where pressurized fluid is utilized to make the joint rigid. One application is a surgical retractor.  
           [0008]    U.S. Pat. No. 4,767,231 to Wallis discloses an adjustable arm having ball joints. The joints can be locked by applying a compressive force to a push rod.  
           [0009]    Russian Patent SU 611039 describes a lockable ball and socket joint using an electromagnet and a spring-like device.  
           [0010]    Despite these prior art devices, however, there is a need for a simple, effective, but easy to use articulated mechanism which employs lockable joints.  
         SUMMARY OF THE INVENTION  
         [0011]    There is provided, according to one embodiment of the invention, a joint for an articulated mechanism. The joint includes a housing and a rotatable member adjacent to the housing. A friction member is mounted on the housing between the housing and the rotatable member. There is a biasing member normally biasing the friction member against the rotatable member to inhibit rotation of the rotatable member. There is an actuator within the housing operatively coupled to the housing which moves the friction member away from the rotatable member when actuated to facilitate rotation of the rotatable member.  
           [0012]    There is provided, according to another embodiment of the invention, an articulated apparatus which includes a plurality of shafts and articulated joints between the shafts. Each joint includes a housing, a rotatable member adjacent to the housing and a friction member mounted on the housing between the housing and the rotatable member. A biasing member normally biases the friction member against the rotatable member to inhibit rotation of the rotatable member. There is an actuator within the housing operatively coupled to the housing which moves the friction member away from the rotatable member when actuated to facilitate rotation of the rotatable member.  
           [0013]    For example, at least one articulated joint includes a spherical member connected to the shaft. The housing preferably has a first end, a second end and a hollow interior with a semi-spherical recess at the first end. The spherical member is within the housing member adjacent to the semi-spherical recess. The friction member is between the spherical member and the semi-spherical recess. A ferromagnetic member is within the housing on a side of the spherical member opposite the semi-spherical recess and adjacent to the spherical member. The biasing member is a spring biased between the second end of the housing and the ferromagnetic member to bias the ferromagnetic member against the spherical member and thereby bias the spherical member against the semi-spherical recess to resist movement of the spherical member and the shaft. The actuator is preferably a solenoid mounted on the housing within the hollow interior between the second end of the housing and the ferromagnetic member to attract the ferromagnetic member when actuated to free the spherical member and the shaft for movement. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 is an isometric view of a pair of articulated mechanisms, according to an embodiment of the invention, holding a workpiece mounted on a vise;  
         [0015]    [0015]FIG. 1 a  is an isometric view of one of the mechanisms of FIG. 1;  
         [0016]    [0016]FIG. 2 is a sectional view of one of the joints thereof, shown in the locked position;  
         [0017]    [0017]FIG. 3 is a fragmentary sectional view similar to FIG. 2, showing the joint unlocked and with the shaft in a different position;  
         [0018]    [0018]FIG. 4 is a sectional view of a second joint of the mechanism of FIG. 1 in the locked position;  
         [0019]    [0019]FIG. 5 is a sectional view similar to FIG. 4, showing the joint in the unlocked position and the shaft in a different position;  
         [0020]    [0020]FIG. 6 is sectional view of a third joint of the mechanism of FIG. 1, showing the joint in the locked position;  
         [0021]    [0021]FIG. 7 is a sectional view similar to FIG. 6, showing the joint in the unlocked position; and  
         [0022]    [0022]FIG. 8 is an isometric view, partly broken away, of the joint of FIG. 6 and  7  and fragments of the arms connected thereto. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]    Referring to the drawings and first to FIG. 1, this shows a pair of articulated mechanisms  10  and  10   a  holding a workpiece  12  held in a vise  14 . In this example, the workpiece is a disk of sheet metal shown in the process of having a series of teardrop shaped apertures  16  sawn therethrough with a saw  18 . However the shape of the workpiece and the tool being employed are merely examples of myriads of other uses for these mechanisms. The mechanism  10   a  is the same as the mechanism  10  although it is shown in a different position. Thus only mechanism  10  is described in detail below. Both mechanisms are shown mounted on a base  20 .  
         [0024]    Referring to FIG. 1 a,  the mechanism includes three joints  24 ,  26  and  28  and three shafts  30 ,  32  and  33 . Shaft  30  extends between joints  24  and  26  and is straight in this embodiment. Shaft  32  extends between joints  26  and  28  and has a 90° bend  36 . Shaft  33  is straight and extends between joint  28  and a clamp  40  which includes a pair of jaws  42  and  44  and an adjustment knob  46  for moving the jaws. It should be understood that the invention is applicable to many other configurations of articulated mechanisms using more or fewer shafts, shafts of different lengths, appearances and shapes and may be used for other tools and objects besides the vise  40 . Also the shaft may be straight or bent as illustrated or angled in varying amounts. Also more or fewer joints me be employed.  
         [0025]    Joint  24  is shown in better detail in FIG. 2 and  3 . The joint includes a hollow housing  50  which is somewhat capsule-shaped in this example, having a semi-spherical first end  52 , a flat end  56  and a hollow interior  58 . There is a semi-spherical recess  60  within the housing adjacent the first end  52 . This is covered with a high-friction material  62 . This is vulcanized rubber in this example but other high-friction materials can be substituted.  
         [0026]    A rotatable member, in this example, a spherical member  64 , is located within the housing such that the friction member  62  is between the housing and the rotatable member. Shaft  30  fits tightly in a socket  66  in the spherical member and is thus connected thereto. It can be connected in alternative ways such as by threads, adhesive or soldering, depending upon the materials.  
         [0027]    There is also a biasing member, in this case a coil spring  68 , within the housing and which normally biases the friction member  62  against the rotatable member  64  as seen in the position of FIG. 2. This inhibits movement of the rotatable member and thereby shaft  30 . The spring is operatively biased against a ferromagnetic member, in this example plunger  70 , which is located within the housing on a side of the spherical member  64  opposite the semi-spherical recess  60 . The plunger includes a piston-like portion  72  which slidably engages inside walls  74  of the housing. There is a projection  76  extending towards the spherical member which has a partially spherical surface  78  pressing against the rotatable member  64 .  
         [0028]    There is a shaft  80 , of a non-ferromagnetic material in this example, extending rotatably through circular aperture  82  at end  56  of the housing. The shaft is rigidly connected to shaft-like projection  84  of plunger  70  by means of narrower projection  86  of the shaft fitting within cylindrical recess  88  of the extension. A series of pins  90  secure the two members together. Other means could be used for connecting them together such a adhesives, screws or other known types of connectors.  
         [0029]    A series of screws  92  extend threadedly through corresponding threaded apertures  94  in end  56  of the housing. A ring  96  is positioned between the screws and the coil spring  68 . Thus the screws can be used to adjust the position of the ring  96  further from or closer to end  56  of the housing and thus increase or decrease the force exerted by the spring  68  on the spherical member  64 .  
         [0030]    There is a rotary bearing, in this example, a roller bearing race  100  positioned between the coil spring  68  and plunger  70 . This allows for rotation of the housing  50  and shaft  30  about rod  80  when the spherical member  64  is locked as shown in FIG. 2.  
         [0031]    A solenoid  110  is positioned within the housing between the plunger  70  and end  56 . The solenoid in this example is fitted within the interior of coil spring  68  and extends about rod  80 . There is a ferrous alloy ring  112  in this example at the end of the solenoid adjacent to the plunger  70 .  
         [0032]    [0032]FIG. 2 shows the joint  24  in the position where the solenoid is not energized. In this case the coil spring  68  bears against the bearing  100  and plunger  70  to press the rotatable member  64  between plunger  70 , the housing and friction member  62 . This in turn pushes the plunger against the friction member  62  to lock the joint. Alternatively, looking at the joint from another point of view, it may be also said that the spring pushes against the ring  96  and consequently the housing and thereby pushes the friction member against the rotatable member to lock the joint.  
         [0033]    [0033]FIG. 3 shows the joint in the position when solenoid  110  is energized. This draws the plunger  70 , which is of a ferromagnetic material, away from the rotatable member  64 , thereby creating a gap  130  between the rotatable member and the friction member  62 . This permits the shafts  30  to be moved to a different position as shown in FIG. 3.  
         [0034]    As seen in FIG. 1 a,  the shaft  30  is rotatable in a arc about slot  122  in the housing. The rod  80  is not shown in FIG. 1, but can be used to mount the joint on base  20 . This allows rotation of the joint about the base. Alternatively, the rod  80  could comprise an additional arm connecting the joint to a tool, another object, or a further joint.  
         [0035]    Referring to FIGS. 4 and 5, these show joint  26  in more detail. Many of the internal components of the joint are generally similar to those of the previous joint and therefore are given the same number with the additional designation “0.1”. In this example housing  26  is in three parts  131 ,  132  and  133 . In this example, the friction member  62 . 1  is mounted on partially spherical surface  78 . 1  of ferromagnetic member  70 . 1  instead of on semi-spherical surface  60 . 1  of the housing. Coil spring  68 . 1  is compressed between shoulder  134  near end  56 . 1  of the housing and shoulder  136  of the ferromagnetic member. End  56 . 1  of the housing is covered by a plate  140 . The spring normally biases the ferromagnetic member  70 . 1  towards the rotatable member  64 . 1  such that the friction member  62 . 1  engages the rotatable member to inhibit rotation thereof. This effectively locks shafts  30  and  32  in the positions shown. There is an adjustment screw  144 , plastic in this example, extending threadedly through end  52 . 1  of the housing and contacting rotatable member  64 . 1 . This allows adjustment of the resistance to movement of the rotatable member  64 . 1  inside the housing so that, when solenoid  110 . 1  is actuated, its looseness can be set or adjusted to the user&#39;s preference.  
         [0036]    When the solenoid  110 . 1  is actuated, as shown in FIG. 5, it draws ferromagnetic member  70 . 1  away from rotatable member  64 . 1  against the force of the spring  68 . 1  and thereby creates a gap  130 . 1  between the rotatable member and the friction member  62 . 1 . This allows rotation of arm  32  about gap  150  in the housing between its two portions  131  and  132  of the housing.  
         [0037]    Brackets  160  and  162  connect shaft  30  to portions  131 ,  132  and  133  of the housing respectively and thereby interconnect the portions of the housing.  
         [0038]    The type of articulation permitted by joint  26  is different from that of joint  24 . It may be seen that joint  24  allows for axial pivoting of the housing about rod  80  and yaw-like pivoting of shaft  30  relative to the housing. Joint  26  on the other hand permits rotation of member  64 . 1  axially with respect to the housing and yaw-like pivoting of arm  32  in the gap or plane between the housing components  131 ,  132  and  133 .  
         [0039]    [0039]FIG. 6, 7 and  8  shows the third joint  28  which permits hinge-like movement of the shafts  32  and  34  about the axis of the housing. In this embodiment like parts have like numbers as in the previous joints with the additional designation of “0.2”. In this example the housing  28  is in two portions  131 . 2  and  132 . 2  similar to the embodiment of FIGS. 4 and 5. End  52 . 1  of the housing is formed by a disk-like member  170  on the end of arm  32 . The rotatable member is not spherical in this embodiment as in the previous embodiments but rather is a disk-like member  172  formed on the end of arm  33 . Friction member  62 . 2  is positioned between ferromagnetic member  70 . 2  and rotatable member  172 .  
         [0040]    Disk-like member  170  has a hollow rod  178  which extends towards hollow ferromagnetic core  180  inside solenoid  110 . 2 . A locking tab  182  locks the core  180  and the rod  178  together to prevent relative rotation. The two portions of the housing are held together by a screw  190  extending through the hollow core and the hollow rod  178 . The screw is fitted with a nut  192  and washer  194 .  
         [0041]    There is a C-clip  196  extending about the hollow rod  178  which keeps member  172  and arm  33  in place when the member  172  is released by the solenoid  110 . 2 .  
         [0042]    In this embodiment, the spring  68 . 2  normally biases the ferromagnetic member  70 . 2  and the friction member  62 . 2  against the member  172  and thereby inhibits rotation of the member and arm  33  relative to the housing and shaft  32 . When the solenoid  110 . 2  is energized, it draws ferromagnetic member  70 . 2  together with friction member  62 . 2  away from member  172 , thereby releasing the shaft and forming a gap  130 . 2  as shown in FIG. 7. This permits relative rotation of the shafts.  
         [0043]    [0043]FIG. 1 shows a series of switches  200 ,  202  and  204  which are used to energize the solenoids in joints  24 ,  26  and  28  respectively.  
         [0044]    It will be understood by someone skilled in the art that many of the details provided above are by way of example only and are not intended to limit the scope of the invention which is to be interpreted with reference to the following claims.