Patent Publication Number: US-2022227171-A1

Title: Caster swivel restriction structure

Description:
TECHNICAL FIELD 
     The present invention relates to an improvement in a structure which restricts swiveling of caster wheels. 
     BACKGROUND ART 
     In a swiveling type caster having a wheel swiveling around a main shaft, as disclosed in, e.g., WO2015/118672, a structure in which an anti-swivel plate portion fixed to a lower end of an operation shaft which abuts against a cam surface of a cam rotatably incorporated in an upper portion of a stem and moves up and down is combined with an engagement member which is fixed to a support yoke pivotally supporting the wheel and engages with the anti-swivel plate portion to restrict swiveling has been known as a structure which restricts the swiveling. 
     Here, the anti-swivel plate portion has many identically shaped convex portions annularly arranged on a lower surface of a discoid base at equal intervals along an outer periphery, and the engagement member is formed of a concave receiving portion which constrains the support yoke so that it does not move in a circumferential direction around the operation shaft when the convex portions are fitted therein. 
     Here, the receiving portion of the engagement member is integrally provided with the support yoke of the caster and swivels together with the support yoke, and hence its position is not fixed. 
     On the other hand, the anti-swivel plate portion is fixed to the operation shaft, the operation shaft moves up and down but does not swivel, and hence the convex portions formed on the anti-swivel plate portion are just displaced up and down at fixed positions. 
     Thus, many convex portions are arranged on the lower surface of the anti-swivel plate portion at equal intervals along an outer peripheral edge. 
     On the other hand, when left and right (a swiveling direction) sidewalls of the concave portion of the receiving portion are formed into tapered surfaces, applying a load from above enables slightly swiveling the support yoke side and fitting the convex portions in the receiving portion only if the convex portions of the anti-swivel plate portion can abut against the tapered surfaces even though they are not matched with the receiving portion at the time of braking. 
     However, in case of the above-described structure, there is a problem that the tapered sidewalls must be formed to the receiving portion, machining takes time, a thick metal must be used, and a cost of the material increases. 
     In recent years, the support yoke side of the caster is made of a synthetic resin, and a structure in which a plurality of concave portions are aligned on a metal plate to configure the engagement receiving portion and the engagement receiving portion is held on a support base made of the synthetic resin has been adopted. 
     In this case, to strengthen concavo-concave fitting, the concave receiving portion is a through hole formed in a metal plate, and a tip of the convex portion protrudes downward beyond the receiving portion. 
     Thus, a hollow must be held between the metal plate having the receiving portion provided thereon and the resin support base which supports the metal plate so that a gap portion is formed below the receiving portion. 
     Further, since fitting each convex portion on the anti-swivel plate portion in any receiving portion of the metal plate can suffice, providing the plurality of receiving portions arranged on the metal plate is effective but, when positions of the convex portion and the receiving portion deviate from each other at the time of swivel braking, a downward load applied due to downward movement of the convex portion of the anti-swivel plate portion is applied to a position between the respective receiving portions, and hence there is a risk that the metal plate downwardly deforms. 
     CITATION LIST 
     Patent Literature 
     Patent Document 1: WO2015/118672 
     SUMMARY OF INVENTION 
     Technical Problem 
     A problem to be solved by the present invention is to provide a caster swivel restriction structure with enhanced durability which cushions a downward load applied due to a downward movement of convex portions on an anti-swivel plate portion and avoids deformation of a metal plate having a receiving portion formed thereon when positions of the convex portions of the anti-swivel plate portion and the receiving portions of the engagement member deviate from each other at the time of swivel braking. 
     Solution to Problem 
     According to the present invention, to solve the problem, the present invention is characterized by providing a caster swivel restriction structure including: an operation shaft which moves down at the time of braking a swiveling caster and moves up at the time of releasing the braking; an anti-swivel plate portion which is fixed to the operation shaft and has many convex portions annularly arranged on a lower surface thereof; a swivel brake plate including a plurality of through holes arranged to enable fitting of some of the convex portions; and a support base portion which supports the swivel brake plate and is fixed to a support yoke of the swiveling caster, 
     wherein the swivel brake plate includes a body piece having the plurality of through holes arranged therein and latch pieces which downwardly bend from the body piece, 
     the support base includes latch hole portions into which the latch pieces are vertically slidably fitted and inserted and an upper surface fitting portion provided to face the body piece of the swivel brake plate, and 
     biasing members which support the body piece aloft and are downwardly compressible are interposed between the body piece and the upper surface fitting portion, and a gap portion is provided. 
     Advantageous Effect of the Present Invention 
     In the swivel brake plate having the through holes engaging with the convex portions of the anti-swivel plate portion, at the time of disposing the swivel brake plate to the support base configured for attachment to the support yoke, the gap portion is formed between the upper surface fitting portion of the support base and the body piece of the swivel brake plate so that the convex portion tips protrude from the through holes when the convex portions are fitted in the through holes. 
     Since the biasing members are interposed in this gap portion, cushioning is effected even if the anti-swivel plate portion moves down and downwardly presses the body piece, and the body piece can be prevented from being bent by the gap portion even if the convex portions are not matched with the through holes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view showing a mounting state of a support base and a swivel brake plate according to Example 1; 
         FIG. 2  is a perspective view showing the swivel brake plate from a lower front side; 
         FIG. 3  is a plan view of the support base; 
         FIG. 4  is a perspective view of a state where the swivel brake plate has been attached to the support base; 
         FIG. 5  is a front view of the same; 
         FIG. 6  is a perspective view of an anti-swivel plate portion fixed to an operation shaft; 
         FIG. 7  is an enlarged view of a primary part of a support yoke to which the support base having the swivel brake plate mounted thereto has been attached; 
         FIG. 8  are explanatory parts showing swivel brake states, where (a) shows a standby state, (b) shows a fitted state, and (c) shows a contact state; 
         FIG. 9  are explanatory drawings for comparing a state where no coil spring is provided, where (a) shows a standby state, (b) shows a fitted state, and (c) shows a contact state; and 
         FIG. 10  show an example of a caster having a swivel restriction structure, where (a) is a side elevation and (b) is a longitudinal section view. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     According to the present invention, a load applied to a swivel brake plate is cushioned by repulsive biasing members when convex portions are not matched with a receiving portions between the swivel brake plate and a support base at the time of swivel braking, and deformation or damage to the swivel brake plate is avoided to realize durability. 
     A preferred embodiment of the present invention will now be described hereinafter with reference to the drawings. 
     Example 1 
     a swivel restriction structure according to this example is a swivel restriction structure incorporated in a swiveling type caster  1 , a caster structure has an operation shaft  8  which moves down at the time of swivel braking of the swiveling caster and moves up at the time of releasing the braking, an anti-swivel plate portion  9  which is fixed to the operation shaft  8  and has many convex portions  10  annularly arranged on a lower surface thereof, and a metal swivel brake plate  12  having through holes  11  arranged so that some of the convex portions  10  can be fitted therein, and a hard synthetic resin support base portion  16  which supports the swivel brake plate  12  and is fixed to a support yoke  3  of the swiveling caster  1 , and any other structures can be applied to a well-known caster (see  FIG. 10 ). 
     That is, the caster shown in  FIG. 10  as an example includes a stem  4  erected on the support yoke  3  pivotally supporting a wheel  2 , a cam  6  which is incorporated above the stem  4  and rotated by a rotary shaft  5 , a plurality of cam surfaces for braking or braking-canceling formed at predetermined positions on an outer peripheral surface of the cam  6 , the operation shaft  8  which abuts against the cam surfaces and slides up and down, the anti-swivel plate portion  9  fixed to a lower end of the operation shaft  8 , the swivel brake plate  20  mounted to the support base  16  which is fixed to the support yoke  3  and engages with the anti-swivel plate portion  9  to restrict swiveling of the support yoke  3 , and a brake shoe portion  7  which is provided below the anti-swivel plate portion  9  and abuts against a tread surface of the wheel  2  by downward movement of the operation shaft  8  to carry out braking. 
     In the present invention, the caster structure is not restricted to the above-described structure, and any structure which is disclosed in Japanese Patent No. 5604022 (WO2015/11867) and others and restricts swiveling by the upward or downward movement of the operation shaft  8  can suffice. 
     The anti-swivel plate portion  9  is horizontally fixed to a lower part of the operation shaft  8  which moves down at the time of restricting swiveling (braking may be performed simultaneously with the swiveling restriction) and moves up at the time of releasing the braking (see  FIG. 6 ). 
     The anti-swivel plate portion  9  has a well-known structure including many convex portions  10  which radially extend and are annularly arranged at equal intervals on a lower surface of a discoid base. 
     In the illustrated example, each convex portion  10  is formed into an illustrated shape provided by cutting off a tip of a cuboid to form a gradually thinned shape, but a downwardly protruding convex shape can suffice. 
     The support base  16  which supports the swivel brake plate  20  is fixed to the support yoke  3  which is disposed to the operation shaft  8  through a swivel bearing portion B to enable swiveling and pivotally supports the wheel  2 . 
     As clearly shown in  FIG. 2 , the swivel brake plate  20  has a body piece  21  having a plurality of (five in the illustrated example) through holes arranged therein and latch pieces which bend downward from the body piece  21 . 
     The latch pieces include a pair of left and right first latch pieces  22  and  23  which bend at both ends of the body piece  21  in an extending direction and a pair of second latch pieces  24  and  25  which bend on the right and left of a rear side of the body piece  21  which is a side away from the anti-swivel plate portion  9 . 
     The latch pieces which support the body piece  21  to move up and down in a parallel fashion can suffice, either the first latch pieces  22  and  23  or the second latch pieces  24  and  25  can suffice, or a structure having a latch piece added at an intermediate position can be adopted. 
     The plurality of through holes  11  formed in the body piece  21  are holes into which the convex portions  10  are fitted, and they are arranged at equal intervals in an arc shape with the same curvature as the array of the convex portions  10 . 
     Thus, at the time of restricting swiveling, five convex portions  10  of the anti-swivel plate portion  9  are matched and fitted in five through holes  11  of the swivel brake plate  20 . 
     In the drawings, reference signs  26  and  27  denote slots formed in the first latch pieces  22  and  23 , and a length of the up-and-down movement of the swivel brake plate  20  is restricted in a range of a length of each slot with the use of screws fixed to a later-described sidewall of the support base  16 . 
     Further, as shown in  FIG. 1  and  FIG. 3 , in the support base  16 , an upper surface fitting portion  12  which is surrounded by three walls which are left and right wall portions  17  and  18  on which the swivel brake plate  20  is mounted and a rear wall portion  19  connecting the wall portions  17  and  18  and whose anti-swivel plate portion  9  side is opened is formed. 
     The upper surface fitting portion  12  is set to a size which enables mounting the body piece  21  of the swivel brake plate  20  thereon. 
     Furthermore, in the support base  16 , first hole portions  13  and  14  having a rectangular cross section into which the first latch pieces  22  and  23  of the swivel brake plate  20  are slidably fitted are formed at positions on the left and right sides of the upper surface fitting portion  12  which are in contact with the left and right wall portions  17  and  18 . 
     In the present invention, the holes having a depth which allows the first latch pieces  22  and  23  to freely vertically slide can suffice, and the holes do not have to be pierced. 
     Moreover, at intermediate positions on the left and right wall portions  17  and  18 , bolt or pin fixing screw holes  17   a  and  18   a  which are fixed crossing the first hole portions  13  and  14  and also fixed through the slots  26  and  27  of the first latch pieces  22  and  23  to retain the swivel brake plate  20  are formed. 
     Likewise, in the support base  16 , rectangular second hole portions  15   a  and  16   b  into which the second latch pieces  24  and  25  of the swivel brake plate  20  are slidably fitted are formed on left and right sides of a position which is in contact with the rear wall portion  19  at the rear of the upper surface fitting portion  12 . 
     In this example, the second hole portions  15   a  and  15   b  are set as holes which are longer than lengths of the second latch pieces  24  and  25  and have a depth which is equal to or larger than a depth which realizes the contact with hole bottom portions when at least the swivel brake plate  20  moves down at the maximum. 
     It is to be noted that reference signs  31  and  32  denote mounting pieces configured to fix the support base  16  to the support yoke  3 . 
     The upper surface fitting portion  12  of the support base  16  is recessed with a depth which is not smaller than a thickness of the swivel brake plate  20 . 
     In the upper surface fitting portion  12 , a pair of left and right receiving holes  12   a  and  12   b  configured to support lower ends of coil springs S as an example of the biasing members are formed. 
     The receiving holes  12   a  and  12   b  are preferably set to a depth which enables complete sinking of the compressed coil springs S. 
     Thus, the first latch pieces  22  and  23  of the swivel brake plate  20  are inserted into the first hole portions  13  and  14  of the support base  16 , the second latch pieces  24  and  25  are inserted into the second hold portions  15   a  and  15   b  of the support base  16  at the same time, and the body piece  21  is mounted on the upper surface fitting portion  12 . 
     In the upper surface fitting piece  12 , lower ends of the pair of left and right coil springs S and S are erected with lower ends thereof fitted in the receiving holes  12   a  and  12   b.    
     Thus, upper ends of the coil springs S and S abut against a bottom surface of the swivel brake plate  20  so that the swivel brake plate  20  is held at a hollow position (see  FIG. 4 ,  FIG. 5 , and  FIG. 7 ). 
     In this example, since the coil springs are used as the biasing members, flat abutting surface portions  21   a  and  21   b  against which the upper ends of the coils springs S abut are formed on the bottom surface of the body piece  21  of the swivel brake plate  20  at positions where these portions do not overlap the through holes  11  on the left and right outer sides of a group of the through holes. 
     The biasing members are not restricted to compression springs, and torsion springs, leaf springs, formed wires, and the like may be used. 
     Additionally, as the biasing members, block-shaped rubber or the like may be used. 
     Since the above-described structure is adopted, as shown in  FIG. 8( a ) , at the time of swivel braking, the operation shaft  8  moves down, the anti-swivel plate portion  9  gets closer to the swivel brake plate  20 . At this time, the swivel brake plate  20  is still held in a hollow posture by the coil springs S. 
     Then, when the anti-swivel plate portion  9  moves down, the swivel brake plate  20  is pressed down against the biasing force, the swivel brake plate  20  and the anti-swivel plate portion  9  are integrally constrained upon the fitting of the convex portions  10  into the through holes  11  of the swivel brake plate  20 , thereby restricting the caster  1  from swiveling (see  FIG. 8( b ) ). 
     At this moment, even if the considerable downward force is applied to the swivel brake plate  20 , this force is buffered by the coil springs S, and hence a superfluous load is not applied to the body piece  21 . 
     On the other hand, when the convex portions  10  are not matched with the through holes  11  even though the anti-swivel plate portion  9  moves down, the body piece  21  of the swivel brake plate  20  further compresses the coil springs S with the use of the convex portions  10 , and the compression continues until the compressed coil springs S completely sink in the receiving holes  12   a  and  12   b.    
     In this state, since the body piece  21  of the swivel brake plate  20  comes into contact with the flat surface of the upper surface fitting portion  12 , the downward force of the anti-swivel plate portion  9  is dispersed to the support base  16  through the body piece  21  and the upper surface fitting portion  12 , thereby preventing the body piece  21  from being deformed or damaged (see  FIG. 8( c ) ). 
     In this state, when the anti-swivel plate portion  9  or the support yoke  3  slightly swivels and the convex portions  10  are matched with and fitted in the through holes  11 , a swivel restricting posture shown in  FIG. 8( b )  is realized. 
     On the other hand, when the biasing members, e.g., the coil springs are not provided, the state of  FIG. 9( a )  is likewise achieved but, at the time of swiveling restriction show in  FIG. 9( b ) , the downward force of the anti-swivel plate portion  9  directly acts on the swivel brake plate  20  without being buffered, and a downward load is applied to the body piece  21 . 
     Further, as shown in  FIG. 9( c ) , when the convex portions  10  are not matched with the through holes  11 , the considerable downward force is directly applied to the body piece  21 , and the body piece  21  is apt to be deformed toward the gap portion  30  formed between itself and the upper surface fitting portion  12 . 
     As described above, the effects obtained by providing the coil spring are obvious. 
     The present invention is not restricted to the structure of the foregoing example and, as a matter of course, the design of the present invention can be variously modified without changing a gist of the present invention. 
     REFERENCE SIGNS LIST 
     
         
           1  swiveling caster 
           2  wheel 
           3  support yoke 
           4  stem 
           5  rotary shaft 
           6  cam 
           7  brake shoe portion 
           8  operation shaft 
           9  anti-swivel plate portion 
           9   a  upper surface receiving portion 
           9   b  lower surface receiving portion 
           10  convex portion 
           11  through hole 
           12  upper surface fitting portion 
           12   a ,  12   b  receiving hole 
           13 ,  14  first hole portion 
           15   a ,  15   b  second hole portion 
           16  support member 
           17 ,  18  left or right wall portion 
           17   a ,  18   a  screw hole 
           19  rear wall portion 
           20  swivel brake plate 
           21  body piece 
           21   a ,  21   b  abutting surface portion 
           22 ,  23  first latch piece 
           24 ,  25  second latch piece 
           26 ,  27  slot 
           30  gap portion 
         B swivel bearing portion 
         S coil spring