Abstract:
A lock pin assembly used for clamping two plates together, that have aligning bores for receiving the lock pin assembly. The lock pin assembly includes radially extending pins that can be forced outwardly from the center of a lock pin housing forming a part of the lock pin assembly. The actuator pins are forced outwardly and cooperate with a tapered surface on a bottom plate to create a clamping force relative to an end of the lock pin housing supportable on a top plate. The lock pin housing has cam tracks on an outer side thereof, and an actuator ring surrounds and supports the pin and carries cam followers sliding in the cam tracks. The cam tracks are made such that relative rotation of the lock pin housing and the actuator ring changes the axial location of the actuator ring along the housing. The actuator ring rests on the top plate and when the actuator pins are released so they can retract and the lock pin housing and the actuator ring are relatively rotated, the lock pin housing is raised relative to the two plates to aid in removing the lock pin assembly.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application refers to and claims priority on U.S. Provisional Application Ser. No. 61/380,829, filed Sep. 8, 2010, the content of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     The present disclosure relates to a lock pin assembly that will clamp two members, such as machining tool plates, together, as is desirable in certain machining operations. The lock pin assembly not only secures the plate members, but it also can be unlocked and removed easily. 
     At the present time, there are lock pins that will lock two flat plates together with three small balls held in radial bores in a housing. The housing extends through precisely sized bores in the plates or through insert bushings on both of the plates so that a portion of the housing extends through a first plate and into the second or lower plate. The three balls in the housing then are aligned with a groove in the second plate, and upon actuation of the balls outwardly, the plates are locked together. The lock balls will provide a force that holds the plates together, but the housing or pin may be difficult to remove when a side load is placed on the plates (vertical application), or if the bores are not exactly concentric. 
     SUMMARY OF THE DISCLOSURE 
     The present disclosure provides a lock pin assembly having a lock pin housing that extends through bores in two members, typically plates, that are clamped together with the lock pin. The lock pin housing has a rotatable actuator on its exterior, at an end of the housing on the exterior of the plate members, and a cooperating cam groove and cam follower between the lock pin housing and actuator provide an axial removal force on the housing as the actuator is rotated relative to the housing. The axial removal force also backs provided lock members carried by the lock pin housing to a retracted position. As disclosed, there is at least one cam groove on the exterior of the lock pin housing, and the rotatable actuator is a ring that has a cam follower in the cam groove. With the actuator ring resting on an outer surface of one of the plate members, (the top plate as shown) when the lock pin housing is rotated while the actuator ring is held stationary (there is relative rotation between the housing and the actuator ring), the pitch of the cam groove around the exterior of the lock pin housing causes an axial force on the lock pin housing to urge it out of the bores in the two clamped plate members. The actuator rings reacts the axial force to the outer surface of the top plate member. 
     As disclosed there are two cam grooves on the lock pin housing and each has a compound pitch helical configuration that has an initial fine pitch so that very little axial movement of the housing, but high axial force, is provided as the lock pin housing and actuator ring are initially relatively rotated with the lock pin housing in a seated and locked position, and then after the lock pin housing has been loosened and moved axially a short distance, the helical cam grooves increase in pitch so that with little more relative rotation the lock pin housing is moved axially a greater distance for each degree of relative rotation of the actuator ring. 
     The lock pin housing has three radially extending lock members, in the preferred form, lock pins, extending from a center bore of the housing. The lock members are actuated outwardly by forcing an actuator ball in the center bore of the housing against inclined or cam type surfaces at inner ends of the lock members. The inner ends of the lock members extend into the center bore when they are retracted or unlocked. When the lock pin housing is inserted through a bore in a top plate member and into an aligning bore in a bottom plate member that is to be clamped to the top plate member, a force generator, as shown a set screw mounted in the housing, is used for forcing the actuator ball against the inner end inclined surfaces of the lock members to urge the lock members, pins as disclosed, outwardly from the lock pin housing. The second or lower plate member into which the housing extends has a chamfer shoulder surface around the inner or remote end of the aligning bore in the bottom plate member, and the three lock members are provided with outer end cam surfaces that will engage the chamfer surface and urge the top and bottom plate members to clamp together as the lock members are forced outwardly. 
     Removing the lock housing is accomplished by releasing the force generator or set screw from the actuator ball, which will permit the lock members to be retracted by an O-ring around the periphery of the lock pin housing that urges the lock members inwardly, and then by holding the actuator ring and rotating the lock pin housing the cam action force moves the housing axially in a direction away from the top plate member, as stated, for extracting the lock pin housing. If the lock members do not retract all the way, the chamfer in the bore in the bottom plate member will act against the outer end camming surfaces of the extended lock members to urge the lock members inwardly as the lock pin housing is moved out of the bores in the plate members. The provision of the fine pitch cam grooves as the actuator ring is initially moved provides an increased retraction force to initially axially move the lock pin housing. The cam grooves on the lock pin housing for the actuator ring can be made with a continuous pitch as well. 
     While the lock members that are carried by the lock pin housing are disclosed as pins, the lock members can be balls in radial bores of the lock pin housing, in that the spherical surfaces of balls provide camming surfaces for extending (or retracting) ball shaped lock members 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view with a pair of plates held clamped together with a lock pin assembly of the present disclosure; 
         FIG. 2  is an exploded view showing the two plates and the lock pin assembly; 
         FIG. 3  is a top plan view of the lock pin assembly in place on a pair of plates; 
         FIG. 4  is a sectional view taken as on line  4 - 4  in  FIG. 3 ; 
         FIG. 5  is a sectional view taken as on line  5 - 5  in  FIG. 3 ; 
         FIG. 6  is a fragmentary view of a cam track portion, and an actuator ring carrying cam followers with the lock pin assembly in a first fully engaged position; 
         FIG. 7  is a view taken 90° from  FIG. 6 , showing the actuator ring in a second position with a lock pin housing partially retracted from the bores in the two plates under cam action; 
         FIG. 8  is a sectional view similar to  FIG. 4  with the lock pin housing retracted the maximum amount using the cam track and actuator ring; and 
         FIG. 9  is an exploded view of the lock pin assembly of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     In  FIG. 1 , a plate assembly indicated generally at  10  is made up of a first base plate member  12  (also called a receiver plate), and a second top plate member  14  (also called a sub plate), which are locked or clamped together, using a lock pin assembly  15  made according to the present disclosure. The lock pin assembly  15 , as seen in  FIGS. 4 ,  5  and other figures includes an outer lock pin housing  16 , that has an central end bore portion  18  at an inner end, and this end bore reduces to a smaller diameter threaded bore portion  20 . The lock pin housing  16  has a hex shaped socket counter bore  22  at an outer end. An actuator set screw  24  can be threaded into the threaded bore  20 . The hex shaped socket counter bore  22  is designed to receive an Allen wrench for rotating the lock pin housing, and is of size to permit a smaller Allen wrench to be placed into the socket head of the actuator set screw  24  for tightening or loosening the set screw. The bore portion  18  is, as stated, larger than the threaded bore portion  20 , and is of size to receive an actuator ball  26  which is inserted from the remote end and that is acted on by an end portion  28  of the set screw, as will be explained. 
     The lock pin housing  16  has three radial bores, which are indicated in dotted lines in  FIG. 3  at  30 .  FIG. 4  is a sectional view taken through the centers of two of the bores  30 . Each of the bores  30  mounts a lock actuator member or pin  32 . The lock actuator members  32  are slidably mounted in the bores  30  and each has an inner end actuator surface  34  against which the actuator ball  26  will act when the set screw  24  is threaded inwardly along the bore  20 . The outer ends of the lock actuator members  32  have cam surfaces  36 , and these cam surfaces are part cylindrical so they mate with an inwardly tapered annular chamfer surface  38  that surrounds a lower end of a cylindrical lock pin housing receiving alignment bore  42  and which joins a larger cylindrical bore  40  formed in the base plate  12 . The lock actuator members  32  (called pins as shown) have grooves at their outer ends and an O-ring  35  fits in the grooves and surrounds the lock pin housing  16  and the lock actuator pins  32  to urge the pins  32  inwardly in toward the central bore  18  of the lock pin housing  16 . 
     Bore  40  in the base or bottom plate  12  thus is shouldered by the chamfer or inclined surface  38 . The smaller first alignment bore portion  42  in plate  12  adjacent to the second or upper plate  14  is bored to be exactly the same size as a second alignment bore  44  formed in the upper plate  14 . The bores  42  and  44  closely receive the outer surface of the cylindrical lock pin housing  16 , and as can be seen the remote end portion of the housing  16  extends through the alignment bore portion  42  and sufficiently far into the bore  40  so that the lock actuator pins  32  and the cam surfaces  36  of these pins or members will engage the chamfered surface  38 . 
     The upper end of the lock pin housing  16  has a shoulder flange  48 , and an actuator collar or ring  50  has a center bore through which the lock pin housing  16  extends. The actuator ring  50  is positioned around the lock pin housing  16  at the upper end of the housing and has a groove  49  that receives the flange  48 . The actuator ring  50  supports the end of lock pin housing  16  on the upper surface of plate  14 . The lock pin housing  16  also has helical cam grooves or tracks formed into the cylindrical exterior surface as shown in  FIGS. 6 and 7 . There are, as shown, a pair of the helical cam grooves or tracks  54 , each of which, as shown, extends substantially 180° around the outer surface of the lock pin housing  16 . The cam grooves  54  may extend more of less than 180°, if desired. The actuator ring  50  has a pair of radial bores 180° apart that are of size to receive cam follower balls  52 , and these cam follower balls are held in place with cap screws  56 , that extend inwardly from the outer edge of the actuator ring  50 . The cam follower balls  52  are of size to fit into the respective grooves  54 , and they form cam actuators (one in each groove) that will create, when the ring  50  is resting on the top plate  14  and held from rotation and the lock pin housing  16  is rotated using an Allen wrench in socket  22 , an axial force along the axis of the housing  16  by the cam action. The number of cam follower balls can be varied, depending on the number of cam grooves provided. 
     The helical cam grooves  54 , as shown and preferably, have compound pitches or inclines and, as shown, each has a first section  54 A that has very little pitch, or in other words, very little change in axial position relative to the axis of the lock pin housing  16  for substantially 90° around the housing. Then there is a second higher pitch section  54 B for each of the cam grooves that has a substantial change in axial position for each degree of rotation of the actuator ring  50  about the lock pin housing  16 . The incline or angle of groove section  59 B relative to the longitudinal axis of the housing  16  changes at a greater rate than the first cam groove section  54 A. 
     This means that there is a differential in the amount of force that is exerted axially on the lock pin housing  16  for each degree of rotation of the ring  50  relative to the lock pin housing  16  as the ring  50  is rotated around the housing between the movement along first cam track section  54 A and movement along second cam track section  54 B. The cam grooves may be single pitch and extend more or less than 180°, if desired. 
       FIG. 4  shows the set screw  24  threaded against the actuator ball  26  to force the lock actuator pins  32  outwardly in the bores  30  and against the chamfer surface  38  so that the lock cam surfaces  36  provide a force urging the plates  12  and  14  together due to the fact that the flange  48  bears on the collar or ring  50 , which in turn bears against the upper surface of the plate  14 . 
     The two plates  12  and  14  are clamped or locked tightly together, as shown in  FIGS. 4 and 5 . While only one lock pin assembly  15  is illustrated, typically two or more lock pin assemblies are used for securing the plates in use. When the plates are to be separated or released, the actuator set screw  24  is loosened by putting an Allen wrench through the bore  22  and into the socket head of set screw  24 , and then backing the actuator set screw away from the actuator ball  26 . In use, the plates  12  and  14  may shift slightly, or the plates may be positioned so the bores in the two plates that receive lock pin housing  16  may no longer be exactly concentric. This shifting places a side load on the lock pin housing  16  so removal is difficult, and when there are side loads the present invention aids in removal of the lock pin assembly. 
     In order to permit removal of the lock pin housing  16  under friction or side loads and/or retract the lock actuator pins  32 , and thus permit the plates  12  and  14  to be separated, a large Allen wrench is placed into the socket  22  of the lock pin housing  16  and the lock pin housing  16  is rotated, while the actuator ring  50  is held relative to the plate  14  and the lock pin housing. While the actuator ring can usually be held manually, if needed, a wrench can be used to hold the actuator ring  50  from rotating. When there is relative rotation between the lock pin housing and the actuator ring, the cam follower balls  52  follow along the cam track sections  54 A, exerting a substantial force in axial direction on the lock pin housing  16  relative to the plates  14  and  12 , because of the low pitch of the cam track section  54 A during the initial relative rotation between the lock pin housing  16  and the actuator ring  50 . This axial force will move the lock pin housing  16  axially upwardly, even under side loads, as the lock pin housing is lifted relative to the top of plate  14 . Again, the actuator ball  26  has been loosened, and the O-ring  35  will act to retract the lock pins  32 , but if the lock pins are not fully retraced, once the lock pin housing  16  starts to move axially, the pins  32  will also tend to be retracted by the chamfer surface  38  acting against the outer end camming surfaces  36 . Then, as the lock pin housing is rotated more, after it is initially loosened, the second higher pitch portion  54 B of the cam groove or track will cause a relatively rapid axial movement of the lock pin housing  16  as the lock pin housing is rotated with the cam follower balls  52  in the higher pitch cam groove section. The housing  16  lifts and it can be gripped or pried on to pull it out through the bore  42 . The plate  14  can then be separated from the plate  12 . The fine pitch of the cam grooves or tracks provides increased pull out force when it is needed most, but, again, the cam tracks can be a constant pitch or a different compound pitch. 
     The housing  16  is shown partially retracted upwardly to release the plates in  FIG. 7 , where it can be seen that the flange  48  is spaced upwardly from the bottom of the groove  49  in the ring  50  that receives the flange  48 , and that the balls  52  traveling in the cam tracks  54  have forced the lock pin housing  16  upwardly. The actuator lock members or pins  32  will be at least partially retracted into the bores  30  in this position. The lock actuator pins  32 , as shown in  FIG. 8 , will be fully retracted when the housing  16  and actuator ring  50  are rotated relative to each other so the cam follower balls  52  are moved to the ends of the cam track sections  54 B. 
     When two plates are to be locked or clamped together, such as the plates  12  and  14 , the aligning first and second bores are formed for receiving the lock pin housing  16  and one of the bores is provided with a chamfered surface surrounding the aligning bore at the remote end in one of the plates, and in this instance, the chamfered surface is at a shoulder that is formed by a larger bore  40  extending more remotely than the aligning bore  42  in plate  12 . The two plates are placed together, and the aligning bores  42  and  44  are aligned. The lock pin housing  16  is then inserted with the actuator ring  50  rotated to a position with the cam follower balls  52  at the start end of the cam track sections  54 A, so that the flange  48  is seated on recess  49  and the actuator ring  50  is resting on the upper surface of top plate  14 , The set screw  24  is backed outwardly so the actuator lock pins  32  may be retracted and the O-ring  35  has urged the pins  32  inwardly. Then, the lock pin housing  16  can be inserted into the two aligning bores in the plates  12  and  14 . The chamfered surface  38  is machined so that with the housing  16  seated in the bores, with the flange  48  seated on the groove  49  and the actuator ring  50  resting on the top surface of plate  14  to support the lock pin housing  16  on plate  14 , the pins  32  are at a level or at a plane perpendicular to the axis of the housing  16  so the surfaces  36  will engage the chamfered surface  38 . The lock pin housing  16  is seated with the actuator ring  50  resting on the top surface of plate  14 , to properly position the actuator lock pins  32 . The set screw  24  is then driven inwardly with an Allen wrench against the actuator ball  26  to force the pins  32  out of bores  30  to engage the chamfered surface  38  and tightly lock the two plates  12  and  14  together. 
     This locking arrangement or clamping arrangement using the lock pin assembly disclosed can be used for various applications in addition to use in the machine tool industry. The members that are clamped together can be any selected parts, plates or members. The removal of the lock pin housing  16  to release the two clamped members is done as previously described. 
     The drawings disclose the bores in the plates formed directly in the plate material. In practice, the plates can be bored with larger holes and inserts that have bores for receiving the lock pin housing and with one insert, for the lower plate, formed with the chamfer  38 , installed in the larger bores. The inserts can be secured in the larger bores, and also can be hardened. 
     The description and drawings show the cam groove on the lock pin housing and the cam follower carried by the actuator ring, but the cam groove or track could be formed on the inner surface of the actuator ring facing the housing, and the cam follower carried on the lock pin housing. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.