Patent Application
20100229679
1. Field of the Invention
The present invention relates to a positioning structure for telescopic inner and outer tubes.
2. Description of the Prior Art
There are many telescopic tube structures existing on the market, such as an umbrella rod, a tent rod, a fordable chair rod and the like. This telescopic tube structure is composed of an inner tube and an outer tube connected to each other. When in use, the inner tube is pulled out from the outer tube to lengthen the tube. When not in use, the inner tube is retracted into the outer tube to shorten the tube for storage and carriage. This telescopic tube structure is often used on a rod member for adjusting its length, such as a tent rod. With the telescopic tube structure, a tent is able to adjust its height and a mop handle may be adjusted for a different user.
The aforesaid telescopic tube structure needs to secure the inner and outer tubes for maintaining the pulled length. A conventional positioning structure comprises fixing holes and fixing protuberances to engage with each other. This positioning structure has the following shortcomings:
Thus it can be seen, the conventional positioning structure for a telescopic tube is not convenient in use and doesn't provide a stepless adjustment. Accordingly, the inventor of the present invention has devoted himself based on his many years of practical experiences to the development of a positioning structure for a telescopic tube.
The objective of the present invention is to provide a stepless positioning structure for a telescopic tube, which is convenient to position the telescopic tube and provides a stepless adjustment.
According to the present invention, there is provided a stepless positioning structure for a telescopic tube, comprising a spindle, a spring, an elastic sleeve, a ball socket, and a plurality of balls; the elastic sleeve having a first central through hole, an inner end fixed to an inner end of an inner tube, and an outer end provided with an engaging section, the engaging section having a reduced portion at an outer end thereof; the ball socket being disposed in an outer tube, the ball socket having a second central through hole and a plurality of chambers formed on a side wall thereof, the chambers interconnecting with the second central through hole of the ball socket, either of upper and lower ends of each chamber being formed with a curve surface; the balls being accommodated in the chambers of the ball socket; the spindle being inserted through the spring, the first central through hole of the elastic sleeve, and the second central through hole of the ball socket, the spring holding against an inner end of the spindle and the elastic sleeve respectively, an outer end of the spindle being secured to an outer end of the ball socket.
Preferably, the balls are in a drum shape.
Preferably, the ball socket is composed of an upper cover and a lower cover, the upper cover being provided with a number of engaging hooks and the lower cover being formed with a number of engaging notches to engage with the engaging hooks.
Preferably, the upper cover and the lower cover are formed with recesses facing each other to form the chambers, at least one of the recesses having a bottom formed with the curve surface.
Preferably, either of the upper cover and the lower cover is formed with recesses to form the chambers, the recesses each having a bottom formed with the curve surface.
Preferably, the outer end of the spindle is formed with an engaging groove, the spindle being inserted through the upper cover of the ball socket, an engaging ring being provided to engage with the engaging groove.
Preferably, the engaging section has a straight portion at an inner end thereof.
The balls of the present invention are driven by the engaging section of the elastic sleeve to extend out the chambers or retract into the chambers. When the balls extend out the chambers to hold against the inner wall of the outer tube, the inner and outer tubes will be positioned by the balls. This provides a confinement function. When the balls retract into the chambers, the inner and outer tubes will be adjustable as desired. This structure provides a stable engagement, achieves a stepless adjustment, and is convenient for operation.
In addition, one end of each chamber is formed with the curve surface corresponding in shape to the balls. When the balls are not held by the engaging section of the elastic sleeve, the balls are in a free status. The curve surface makes the balls retract into the chamber so the friction between the balls and the inner wall of the outer tube is obviated, preventing the balls from being jammed.
Furthermore, the balls are shaped like a drum, increasing contact area between the balls and the outer sleeve so as to increase friction and enhance locking force.
Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings.
As shown in
The elastic sleeve 3 has a first central through hole 31, an inner end fixed to an inner end of an inner tube 8 (referring to
The ball socket 4 is disposed in an outer tube 9, referring to
The balls 5 are accommodated in the chambers 42 of the ball socket 4 for increasing contact area and friction to enhance locking force. The balls 5 may be in a drum shape.
The spindle 1 is inserted through the spring 2, the first central through hole 31 of the elastic sleeve 3, and the second central through hole 41 of the ball socket 4. The spring 2 holds against the inner end of the spindle 1 and the elastic sleeve 3, respectively. The outer end of the spindle 1 is secured to the outer end of the ball socket 4. In this embodiment, the outer end of the spindle 1 is formed with an engaging groove 11. When the spindle 1 is inserted through the upper cover 43 of the ball socket 4, an engaging ring 7 is provided to engage with the engaging groove 11 so as to secure the spindle 1 at the outer end of the upper cover 43 of the ball socket 4.
When the present invention is in use, the inner end of the elastic sleeve 3 is secured to the end of the inner tube 8, and then the inner tube 8 and the positioning structure are inserted into the outer tube 9, as shown in
As shown in
When the inner and outer tubes 8 and 9 are expanded or retracted to a desired position, the push rod 7 is loosened to release the spindle 1, the balls 5 hold against the inner wall of the outer tube 9 to position the inner and outer tubes in place.
Except the push rod 7, the inner and outer tubes may be provided with a wire rope or a pull rope to control the movement of the spindle 1, providing a far end control positioning function.
Although particular embodiments of the present invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the present invention. Accordingly, the present invention is not to be limited except as by the appended claims.
