Abstract:
An apparatus for securing a caster to an object having a hole with interior walls has a tubular body with upper and lower ends, the lower end being adapted to connect to a caster and the upper end being split and defining at least two upwardly extending friction grip arms, the upper end of each arm defining an outwardly extending friction grip portion and the outer dimension defined by all of the friction grip portions being slightly larger than the minimum corresponding dimension of the hole.

Description:
FIELD OF THE INVENTION 
     The present relates to the field of caster hardware and in particular to friction grip caster sockets for securing casters to furniture legs and the like. 
     BACKGROUND OF THE INVENTION 
     Caster devices are generally secured to the bottom of tubular legs either by one-piece or multiple-piece caster sockets or by multiple-piece expansion devices. For example, in U.S. Pat. No. 4,805,260, a slotted sleeve is disposed within the bottom of a tubular leg. A caster-stem or bolt, extending upwardly from a caster, extends through the sleeve and is threaded into a conical expander, the expander extending down through a central passage in the sleeve. As the bolt is rotated, the conical expander is drawn toward the caster, thereby expanding the sleeve against the interior walls of the leg and tightly securing the caster and expander device to the leg. A similar device is shown in U.S. Pat. No. 2,173,950. 
     Typical of the one-piece caster sockets are the devices shown in U.S. Pats. Nos. 2,294,807, 2,169,882, and 1,649,526. In these patents, the caster socket is generally tubular with an outwardly extended flange at its base and is split upwardly from its bottom to a point relatively close to a domed upper end, thereby forming two, somewhat resilient and inwardly deformable sections. The socket may then be inserted into a hole defined in the furniture, the lower sections of the socket deforming slightly inwardly, thereby providing a friction fit to hold the socket in place within the hole. In U.S. Pat. No. 3,128,495, a caster socket has a body having no slits and having, at its top and bottom, a series of incompressible, radially outwardly extending splines. The upper and lower portions of the socket are thin walled, allowing them to deform slightly inwardly upon insertion into a tubular member to provide an internal friction grip. 
     While the multiple piece expansion devices provide a means for securing a caster to a tubular member, they can be expensive and somewhat time consuming to assemble and install. The one-piece caster sockets, on the other hand, may be less expensive and easier to install, but they may not be as reliable or long lasting. 
     What is needed is an inexpensive, easy to use and long-lasting device for securing casters to furniture and the like. 
     SUMMARY OF THE INVENTION 
     Generally speaking, a caster socket is provided for securing a caster to an article of furniture or the like. 
     A caster socket has a tubular body with upper and lower ends, the lower end being adapted for securement to the upstanding stem of a caster and the upper end being split and defining at least two upwardly extending friction grip arms, each arm defining an outwardly extending friction grip portion. The outer dimension defined by the combined friction grip portions is slightly larger than the corresponding inner dimension of the hole or recess in the particular object to which the caster will be attached. The socket may be inserted into the hole or recess, upper end first, causing the grip arms to deform inwardly and allowing the socket to be completely inserted into the hole or recess. In one embodiment, a caster may then be attached to the socket by screwing the threaded, upstanding stem into a threaded passageway in the bottom of the socket. 
     It is an object of the present invention to provide an improved device for securing casters to articles of furniture and the like. 
     It is another object of the present invention to provide an inexpensive and easy to use device for securing casters to articles of furniture and the like. 
     Further objects and advantages of the present invention will become apparent from the following description of the preferred embodiment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a caster socket in accordance with the preferred embodiment of the present invention. 
     FIG. 2 is an elevational view of the caster socket of FIG. 1, rotated 45 degrees therefrom. 
     FIG. 3 is a top view of the caster socket of FIG. 2. 
     FIG. 4 is a top view of the caster socket of FIG. 2 and shown connected to a caster assembly and installed within a tubular furniture leg. 
     FIG. 5 is a side, cross-sectional view of the caster socket of FIG. 4, cross-section being taken along the lines 5--5 and viewed in the direction of the arrows. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. 
     Referring now to FIGS. 1 through 5, there is shown a friction grip caster socket 10 in accordance with the preferred embodiment of the present invention. Socket 10 is a one-piece device which is adapted for insertion into a square cross-sectioned, tubular member such as the bottom end of a table leg, and is adapted for receiving and holding the pintle or stem of a caster. Socket 10 generally includes a tubular body 11, the upper portion of which is split to form four, spaced apart, upwardly extending friction grip arms 13. At the top of each arm 13 is an outwardly extending friction grip portion 15. Each grip portion 15 defines an outwardly facing, flat friction grip surface 17. Each grip surface 17 is oriented 90 degrees with respect to the grip surface 17 of an adjacent arm 13 and is adapted to correspond with one corresponding interior wall of the mating, square cross-sectioned tubular leg 20 (FIG. 3). Above grip surface 17, each grip portion 15 defines an arcuate and beveled guide surface 19. In combination, the four guide surfaces 19 of grip arms 13 form a frustoconical leading end 22 for facilitating entry of socket 10 into a tubular member such as table leg 20 or into any desired object having an appropriately shaped hole. 
     In the present embodiment, socket 10 is designed to be installed into a tubular leg 20 which has interior walls 21 and a square cross-section. In its uninstalled condition (FIGS. 1 and 2), the outer diameter of cylindrical body 11 below grip portions 15 is substantially constant and is substantially equal to the width defined between opposing interior walls 21 of leg 20. The width W of socket 10 measured between opposing friction grip surfaces 17 (FIG. 2) is approximately between 1/16 and 1/8 greater than the diameter of tubular body 11, and therefore approximately between 1/16 and 1/8 greater than the distance between opposing interior walls 21 of tubular leg 20. 
     Caster socket 10 is molded from an appropriate engineering resin. The composition of socket 10, the wall thickness of arms 13, and the vertical distance between the bases 23 of slots 24 and the bottom edges 25 of grip surfaces 17 are designed to permit a stiffly resilient, inward deformation of arms 13 and a fairly substantial spring force in resistance thereto. 
     Below bases 23 of slots 24, body 11 defines a threaded bore 27 which is adapted to receive the threaded stem of a conventional caster assembly 29. The interior diameter 30 of the passageway defined by grip arms 13 is greater than the outer diameter of threaded stem 28. Stem 28 is thus allowed to extend upwardly somewhat, into the passageway amid arms 13, without interfering with the inward deformation of arms 13. 
     In operation, threaded stem 28 of caster assembly 29 may be screwed up into caster socket 10 until assembly 29 is firmly secured to socket 10. Socket 10, with assembly 29 attached, is then inserted into tubular leg 20, with guide surfaces 19 facilitating entry of the leading end 22. (Socket 10 may, of course, be inserted before the caster assembly is attached). As the greater dimensioned grip portions 15 contact the lower end 32 of tubular leg 20, beveled surfaces 19 cam arms 13 inwardly, allowing socket 10 to be forcibly inserted up into tubular leg 20. The stiffly resilient nature of inwardly deformed arms 13 creates concentrated frictional forces between grip surfaces 17 and inner walls 21. Since the frictional forces are exerted at the upper end of socket 10, even if caster assembly 29 and socket 10 were partially dislodged from tubular leg 20, the frictional forces would continue to be exerted between surfaces 17 and walls 21 until socket 10 was substantially completely removed from tubular leg 20. Because the outer diameter of tubular body 11 is substantially equal to the distance between the opposing walls 21 of leg 20, caster socket 10 is laterally stable within leg 20. 
     While the present embodiment is described and shown having caster stem 28 threadedly secured to caster socket 10, alternative embodiments are contemplated wherein caster assembly 29 may be secured to socket 10 in other appropriate and conventional manners. 
     Alternative embodiments are also contemplated wherein the shape of body 11, the number of arms 13, and the angular relationship among friction grip surfaces 17 are adapted for installation within a tubular member having other than square cross section. For example, a socket 10 may have a round tubular body, two or more arms 13, and friction surfaces 17 which are arcuate, all for frictional engagement within a round cross-sectioned tubular member. 
     While socket 10 has been described herein as being designed for insertion into a tubular member such as leg 20, it is also contemplated that socket 10 may be installed within an appropriately sized hole in any object to which it is desired that a caster be attached. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all change and modifications that come within the spirit of the invention are desired to be protected.