Patent Application
20190344397
The invention relates to belt sanders and more particularly to an up-and-down motion mechanism for a belt sander, the up-and-down motion mechanism including an electric motor, two cams and a worm drive, so that a belt sander disposed above the motor may repetitively move up or down as the motor activates.
A conventional motion mechanism for a belt sander including a continuous loop of sandpaper mounted on two end drums and comprises an electric motor, a pivotal member, a link, and a reduction gear assembly. After activating the electric motor, the drums may move laterally due to operative cooperation of the motor shaft, the pivotal member, the link and the reduction gear assembly. As a result, the continuous loop of sandpaper may move laterally.
However, the conventional motion mechanism for a belt sander is disadvantageous because the movement of the belt sander is not smooth, its operation is not reliable, and the mechanism is complicated.
Thus, the need for improvement still exists.
It is therefore one object of the invention to provide an up-and-down motion mechanism for a belt sander including a continuous loop of sandpaper mounted on two end drums, comprising a detachable worktable including an opening with the belt sander up-and-down moveably disposed therethrough, two bifurcations on an underside, a housing mounted to the underside, a chute disposed under both one drum and the opening, and two cylindrical columns extending downward from the underside of the worktable;a base including a plurality of posts releasably secured to the underside of the worktable; a control device mounted to the base; an electric motor disposed in the housing and including an upper motor shaft rotatably connected to one drum, a lower worm screw, two legs, at least one first hollow cylindrical member slidably put on one cylindrical column, and at least one second hollow cylindrical member slidably put on the other cylindrical column; and a transmitting assembly disposed in the housing and including a rotational shaft rotatably disposed through the legs, a worm wheel with the rotational shaft disposed through and meshing with the worm screw, two cams secured to two ends of the rotational shaft respectively, two links with the electric motor disposed therebetween, each link having one end connected to one arm and the other end connected to one bifurcation, and a biasing member having one end anchored at a bottom of the electric motor and the other anchored at the underside of the worktable.
The above and other objects, features and advantages of the invention will become apparent from the following detailed description taken with the accompanying drawings.
Referring to
A detachable worktable 2 includes an opening 21 with the belt sander 1 up-and-down moveably disposed therethrough, two bifurcations 22 on the underside, a housing 23 mounted to the underside with a portion of the opening 21 disposed thereabove, a chute 24 disposed under both one drum 12 and the opening 21, and two cylindrical columns 25 extending downward from the underside of the worktable 2.
A base 3 includes four posts 31 releasably secured to the underside of the worktable 2. A control device 4 mounted to the base 3.
An electric motor 5 is disposed in the housing 23 and includes an upper motor shaft 51 rotatably connected to one drum 12 via an adapter 54, a lower worm screw 52, two legs 53, and three hollow cylindrical members 55 in which one hollow cylindrical member 55 is slidably put on one column 25 and the other two hollow cylindrical members 55, aligned vertically, are slidably put on the other column 25. Both the motor shaft 51 and the worm screw 52 rotate at the speed as the motor 5 activates.
A transmitting assembly 6 is disposed in the housing 23 and includes a rotational shaft 61 rotatably disposed through the legs 53, a worm wheel 62 with the rotational shaft 61 disposed through and meshing with the worm screw 52 to transfer motion in 90-degree, two cams 63 secured to two ends of the rotational shaft 61 respectively, two links 64 with the motor 5 disposed therebetween, each link 64 having one end connected to one arm 63 and the other end connected to one bifurcation 22, and a torsion spring 65 having one end anchored at a bottom of the motor 5 and the other anchored at the underside of the worktable 2.
In response to activating the motor 5, the motor shaft 51 rotates and in turn, one drum 12 rotates. Thus, the continuous loop of sandpaper 11 shapes and finishes, for example wood. Generated sawdust is discharged to a collector (not shown) through the chute 24. The subject of the invention is discussed below.
The worm screw 52 rotates to rotate the worm wheel 62 which in turn rotates the cams 63. Further, the rotary motion of the worm wheel 62 is transformed into linear motion (i.e., repetitive up-and-down motion) of the links 64 due to the provision of the cams 63. Furthermore, the motor 5 is capable of repetitively moving up-and-down because the cylindrical members 55 are slidably put on the columns 25. As a result, the belt sander 1 repetitively moves up-and-down. This has the advantages of balancing the load of the continuous loop of sandpaper 11 and prolonging the useful life of the continuous loop of sandpaper 11. It is noted that the provision of the torsion spring 65 can assist in the returning of the motor 5 to its original position after being lowered or lifted.
While the invention has been described in terms of preferred embodiments, those skilled in the art will recognize that the invention can be practiced with modifications within the spirit and scope of the appended claims.
