Caster

Abstract

A conventional endless belt is made of a comparatively flexible member such as rubber. When the endless belt comes in contact with a gap, part of the belt is pushed inward against the gap to be depressed and as a result, a greater power is needed for the endless belt to climb over the gap and it becomes easily jamed. According to the present invention, a caster of an endless structure is provided which is almost jam-proof even in the case of a bigger gap. The caster comprises a first wheel 3 supported on a mounting leg 2 , a second wheel 4 supported by an axle 8 on one end of a suspension arm 7 of which the other end is supported by an axle 6 which also supports the first wheel 3 , and a wrap-around member 5 which is wrapped around the first and second wheels 3 and 4 . The wraparound member 5 is formed an endless belt form by connecting independent pieces 25 to each other. The outer peripheral section of each piece 25 is provided with a wider section and when the wraparound member is depressed and warps, the wider section is adapted to touch a wider section of the adjacent piece 25 , thereby preventing further depression.

1 . A caster having first and second wheels disposed forward and back and an endless wrap-around member wrapped around the first and second wheels, characterized in that the wraparound member consists of a plurality of pieces continuous in the circumferential direction, each piece being provided with an outer peripheral section and an inner peripheral section which are moveable independent of the adjacent pieces and permit the wraparound member to bend along the first and second wheels, and the outer peripheral section is adapted to contact the outer peripheral sections of the adjacent pieces when the wrap-around member is pushed inside the surface of rotation by an external force, thereby preventing the wrap-around member from being depressed inside the surface of rotation in excess of a predetermined amount.  
     
     
         2 . The caster according to  claim 1 , wherein when the outer peripheral section is provided in such a manner that the outer peripheral sections of the adjacent pieces contact each other, when they are close on a common tangent of the first and second wheels.  
     
     
         3 . The caster according to  claim 1 , wherein each piece is independently formed and connected to the others by a connecting member in a circular shape.  
     
     
         4 . The caster according to  claim 1 , wherein the piece is provided with a tire section on the outer peripheral side and a wheel guide section into which the outer peripheral sections of the first and second wheels are fitted.  
     
     
         5 . The caster according to  claim 4 , wherein the tire section and the wheel guide section are respectively formed as separate bodies.  
     
     
         6 . The caster according to  claim 1 , wherein the first and second wheels overlap each other when viewed from the direction perpendicular to the surface of rotation.  
     
     
         7 . The caster according to  claim 1 , wherein the first and second wheels have different diameters and a plurality of wheels with a smaller diameter is provided in the direction of the axis of rotation.  
     
     
         8 . The caster according to  claim 1 , wherein the wrap-around member is provided with a tire section on the outer peripheral side and a wheel guide section on the inner peripheral side, the tire section is formed of a continuous endless belt, and the wheel guide section is provided to engage each outer peripheral section of the first and second wheels and is combined with the tire section to form the piece.  
     
     
         9 . The caster according to  claim 1 , wherein the wrap-around member is provided with a tire section on the outer peripheral side and a wheel guide section on the inner peripheral side, the wheel guide section being provided to engage each outer peripheral section of the first and second wheels and formed of a continuous endless belt, and the piece is formed by the tire section and the wheel guide section.  
     
     
         10 . The caster according to  claim 1 , wherein the wraparound member is formed of a single endless belt in its entirety and slits cut in from the outer peripheral side at the same intervals in the longitudinal direction and grooves, wider than each slit, formed from the inner peripheral side at the same intervals in the longitudinal direction form the piece.  
     
     
         11 . The caster according to  claim 1 , wherein the first wheel is provided in such a manner that the diameter is ⅕ or less of that of the second wheel and its thickness is substantially the same as that of the second wheel, wherein the first wheel is disposed close to the outer periphery of the second wheel so that the first and second wheels are disposed on the same straight line when viewed from the direction of each thickness.  
     
     
         12 . The caster according to  claim 11 , wherein a plurality of first wheels is provided along the outer periphery of the second wheel.  
     
     
         13 . The caster according to  claim 1 , wherein each piece is provided with a protrusion on one side of the piece in the front and rear direction and a depression on the other side thereof, wherein the protrusion of one piece is inserted into a depression of the other piece which is adjacent forward and back, thereby connecting a wall section surrounding the depression to the protrusion by a single shaft.  
     
     
         14 . The caster according to  claim 1 , wherein a joint piece provided with pipe sections on either end of the piece in the front and rear direction is provided and each pipe section is fitted into each depression formed on the pieces which are adjacent forward and back, thereby connecting each piece to the pipe sections by a single connecting shaft.  
     
     
         15 . The caster according to  claim 1 , wherein a connecting plate having a pair of connecting holes is provided, each connecting hole being caused to correspond to a through-hole formed on the central section of the adjacent piece in the front and rear direction, and a connecting shaft is inserted into these connecting holes and through-hole, whereby each piece is connected by such a single connecting shaft.