Caster locking mechanism and carriage

Abstract

A wheeled carriage has a chassis with a plurality of swivel casters, and a locking assembly actuated by a foot pedal located along the front of the carriage. Pushing down on the foot pedal rotates a cam that engages a cam follower on a "T" bar frame supporting two locking rings which respectively overlie two of the caster wheels to move the rings into a locking position in engagement with the wheels to lock the wheels and the casters in any position. The cam follower surface includes a ramp portion engageable by the cam for driving the rings to their locking position and a horizontal latch portion engageable by the cam in its "overcenter" position for holding the rings in their locking position. A lifter bar is engageable by the user's foot to rotate the cam back off the follower and permit the rings to resiliently return to their release position. The cam and follower surfaces are so arranged that a limited rotation of the cam through less than about 25 degrees is sufficient to move the assembly between its release and locking configurations so that the locking assembly can be used where only a few inches of clearance beneath the chassis is available.

.[.We claim.].   .Iadd.What is claimed is.Iaddend. : 
     
       1. In a caster locking assembly including mounting means adapted to be coupled to an associated load, a caster wheel rotatably carried by the mounting means for rolling engagement with an underlying support surface, .Iadd.the caster having a swivel yoke supporting the caster wheel and carried by the mounting means for rotation about a swivel axis, .Iaddend.and a locking ring resiliently carried by the mounting means .Iadd.substantially coaxially with the swivel axis .Iaddend.and overlying the wheel, the locking ring lying in a plane and .Iadd.having a central axis substantially perpendicular to said plane and .Iaddend.being movable between a release position out of engagement with the wheel and a locking position firmly frictionally engaging the wheel for locking thereof, the locking ring being resiliently biased toward its release position, the improvement comprising: a cam follower coupled to the locking ring and having a follower surface including .[.an inclined.]. .Iadd.a planar .Iaddend.ramp portion .Iadd.inclined with respect to said plane,.Iaddend.a locking cam carried by the mounting means for rotation about a pivot axis inclined with respect to the direction of movement of the locking ring and having a cam surface disposed for camming engagement with said follower surface, and actuator means coupled to said cam for effecting rotation thereof between release and locking conditions, .[.said cam surface being out of engagement with said follower surface when said cam is disposed in its release condition for permitting the locking ring to move to its release position,.]. movement of said cam from its release condition to its locking condition moving said cam surface .[.into.]. .Iadd.in .Iaddend.camming engagement with said ramp portion of said follower surface for driving the locking ring to its locking positioni , whereby the locking ring in its locking position effectively prevents swiveling of the caster. .[. 
     
     
       2.  The caster locking assembly of claim 1, wherein the caster includes a swivel yoke supporting the caster wheel and carried by the mounting means for rotation about a swivel axis, the locking ring being disposed substantially coaxially with the swivel axis and, in its locking position, effectively preventing swiveling of the caster..]. 
     
     
       3. The caster locking assembly of claim 1, wherein said cam follower includes a latch portion intersecting said ramp portion at the upper end thereof and engageable by said cam surface for holding the locking ring in its locking position. 
     
     
       4. The caster locking assembly of claim 3, wherein said follower surface further includes a stop portion intersecting said latch portion and engageable with said cam surface for limiting the rotational movement of said cam. 
     
     
       5. The caster locking assembly of claim 1, wherein said cam has a part-circularly cylindrical portion coaxial with said pivot axis and a generally triangular prismatic tip portion projecting from said body portion for engagement with said cam follower. 
     
     
       6. The caster locking assembly of claim 3, wherein said actuator means includes a locking shaft carried by the mounting means for rotation about the pivot axis, said cam being carried by said shaft for rotation therewith. 
     
     
       7. The caster locking assembly of claim 6, wherein said actuator means further includes foot pedal means projecting from said locking shaft substantially normal to the pivot axis for access by the foot of a user, said foot pedal means being depressible by the user's foot to rotate said locking cam from its release condition to its locking condition. 
     
     
       8. The caster locking assembly of claim 7, wherein said actuator means further includes a lifter bar projecting laterally from said foot pedal means and elevated a predetermined distance thereabove sufficient so that when said locking cam is disposed in its locking condition there is sufficient clearance beneath said lifter bar for insertion of a user's foot for lifting of said actuator means to rotate said locking cam from its locking condition back to its release condition. 
     
     
       9. In a caster locking assembly including mounting means adapted to be coupled to an associated load, a pair of caster wheels respectively rotatably carried by the mounting means for rolling engagement with an underlying support surface, a locking frame resiliently supported by the mounting means, and a pair of locking rings carried by the locking frame .Iadd.and lying in a plane .Iaddend.and respectively overlying the wheels .Iadd.and having substantially parallel central axes substantially perpendicular to said plane.Iaddend., the locking frame being movable between a release position wherein the locking rings are out of engagement with the wheels and a locking position wherein the locking rings respectively firmly frictionally engage the wheels for locking thereof, the locking frame being resiliently biased toward its release position, the improvement comprising: a cam follower carried by the locking frame and having a follower surface including .[.an inclined.]. .Iadd.a planar .Iaddend.ramp portion .Iadd.inclined with respect to said plane.Iaddend., a locking cam carried by the mounting means for rotation about a pivot axis inclined with respect to the direction of movement of the locking rings and having a cam surface disposed for camming engagement with said follower surface, and actuator means coupled to said cam for effecting rotation thereof between release and locking conditions, .[.said cam surface being out of engagement with said follower surface when said cam is disposed in its release condition for permitting the locking frame to move to its release position,.]. movement of said cam from its release condition to its locking condition moving said cam surface .[.into.]. .Iadd.in .Iaddend.camming engagement with said ramp portion of said follower surface for driving the locking frame to its locking position. 
     
     
       10. The caster locking assembly of claim 9, wherein the caster includes a swivel yoke supporting the caster wheel and carried by the mounting means for rotation about a swivel axis, the locking ring being disposed substantially coaxially with the swivel axis and, in its locking position, effectively preventing swiveling of the caster. 
     
     
       11. The caster locking assembly of claim 9, wherein said pivot axis substantially bisects a line which interconnects the swivel axes and is substantially perpendicular thereto. 
     
     
       12. The caster locking assembly of claim 9, wherein said follower surface includes a latch portion intersecting said ramp portion at the upper end thereof and engageable by said cam surface for holding the locking frame in its locking position. 
     
     
       13. The caster locking assembly of claim 9, wherein the locking frame is in the form of an elongated resilient metal bar .[.couple.]. .Iadd.coupled .Iaddend.at one end thereof to the mounting means in cantilever fashion and carrying the locking rings and said cam follower adjacent to the other end thereof, said bar being normally disposed in the release position of the locking frame and being resiliently deflectable from that position. 
     
     
       14. In a wheeled carriage including a chassis, a plurality of swivel yokes carried by the chassis for rotation respectively about substantially parallel swivel axes, a plurality of wheels respectively carried by the yokes for rotation about axes disposed substantially perpendicular respectively to the swivel axes, a locking frame resiliently supported by the chassis, and at least two locking rings carried by the locking frame and respectively overlying at least two of the wheels substantially coaxially with the corresponding swivel axes, the locking frame being movable between a release position wherein the locking rings are out of engagement with the associated wheels and a locking position wherein the locking rings firmly frictionally engage the associated wheels for locking thereof, the locking frame being resiliently biased toward its release position, the improvement comprising: a cam follower carried by the locking frame and having a follower surface including .[.an inclined.]. .Iadd.a planar .Iaddend.ramp portion .Iadd.inclined with respect to a plane which is substantially perpendicular to the swivel axes.Iaddend., a locking cam carried by the chassis for rotation about a pivot axis inclined with respect to the direction of movement of the locking rings and having a cam surface disposed for camming engagement with said follower surface, and actuator means coupled to said cam for effecting rotation thereof between release and locking conditions, .[.said cam surface being out of engagement with said follower surface when said cam is disposed in its release condition for permitting the locking frame to move to its release position,.]. movement of said cam from its release condition to its locking condition moving said cam surface .[.into.]. .Iadd.in .Iaddend.camming engagement with said ramp portion of said follower surface for driving the locking frame to its locking position. 
     
     
       15. The carriage of claim 14, wherein the chassis .[.i.]. .Iadd.is .Iaddend.generally rectangular in shape, the at least two wheels being disposed at one end of the chassis. 
     
     
       16. The carriage of claim 14, wherein said actuator means includes a locking shaft carried by the chassis for rotation about said pivot axis, said cam being carried by said shaft for rotation therewith, foot pedal means projecting from said locking shaft substantially perpendicular to said pivot axis toward the front of the chassis for engagement and depression by the foot of a user to rotate said cam from its release condition to its locking condition. 
     
     
       17. The carriage of claim 16, wherein said actuator means further includes a lifter bar projecting laterally from said foot pedal means and elevated a predetermined distance thereabove sufficient to permit insertion of a user's foot beneath said lifter bar when said cam is disposed in its locking condition for lifting of said actuator means to rotate said cam from its locking condition to its release condition. 
     
     
       18. The carriage of claim 16, wherein the locking frame includes means rotatably supporting said shaft adjacent to one end thereof, and further comprising auxiliary support means carried by the chassis for rotatably supporting said shaft adjacent to the other end thereof. 
     
     
       19. The carriage of claim 18, and further comprising guide means carried by the locking frame and cooperating with said shaft to inhibit lateral movement of the locking frame during operation of said actuator means. 
     
     
       20. The carriage of claim 14, wherein the locking frame is in the form of an elongated resilient metal bar coupled at one end thereof to the chassis in cantilever fashion and carrying the locking rings and said cam follower adjacent to the other end thereof, said bar being normally disposed in the release position of the locking frame and being resiliently deflectable from that position. 
     
     
       21. The carriage of claim 14, wherein said cam rotates through an angle of less than 25 degrees between the release and locking conditions thereof.