Positioning device for the work-piece backing plate of a table sawing machine

A positioning device for the work-piece backing plate of a table sawing machine includes a machine seat, a work-piece backing plate and a position-limiting device. The work-piece backing plate has its opposite sides respectively fixed with a rack engaged with a gear set installed in the interior of the machine seat. The work-piece backing plate can be controlled by the gear set to move forward and backward on the machine seat. The position-limiting device is assembled in the interior of the machine seat for restricting and fixing the work-piece backing plate in position to prevent the work-piece backing plate from shifting bias in the course of processing, able to elevate processing precision.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a positioning device for the work-piece backing plate of a table sawing machine, particularly to one able to prevent the work-piece backing plate from shifting bias to elevate precision in processing.

2. Description of the Prior Art

The work-piece backing plate of a conventional table sawing machine, as disclosed in a U.S. Pat. No. 6,736,042 B2, is provided at one side with an eccentric handle to be turned for actuating the opposite ends of a connecting rod to tightly clamp the side edges of a work table and firmly position the work-piece backing plate.

However, the handle of the work-piece backing plate of the conventional table sawing machine is exposed out of the outer edge of the table sawing machine for the sake of being operated conveniently. Therefore, in case of carelessness, an operator is likely to bump against the handle and get injured or cause damage to the handle.

SUMMARY OF THE INVENTION

The objective of this invention is to offer a positioning device for the work piece backing plate of a table sawing machine, composed of a position-limiting device that is pivotally assembled at a preset location between two racks of a work-piece backing plate. A rotary arm assembled inside the table sawing machine can be turned to control the position-limiting device to press tight the two racks of the work-piece backing plate and firmly fix the work-piece backing plate in position to prevent the work-piece backing plate from shifting bias, able to elevate processing precision. In addition, the rotary arm is positioned inside the table sawing machine, able to protect a user from bumping against the rotary arm and getting injured.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of a positioning device for the work-piece backing plate of a table sawing machine in the present invention, as shown inFIGS. 1,2and3, includes a machine seat10, a work-piece backing plate20and a position-limiting device30.

The machine seat10has its topside provided with a work table11having a saw base12assembled thereon.

The work-piece backing plate20positioned at a preset location on the topside of the work table11has its opposite sides respectively fixed with a rack21sliding in a slide groove13respectively provided at the opposite sides of the work-piece backing plate20. The work table11is further fixed at a preset location with a gear set111engaged with the two racks21to be turned for controlling the two racks21to move forward or backward.

The position-limiting device30is pivotally assembled at a preset location between the two racks21, composed of two end shafts31,32, a threaded shaft33, an elastic block34, a driven shaft35, a combining plate36and a rotary arm37.

The two end shafts31,32respectively have the outer end positioned at a preset location in the interior of the worktable11and the inner end bored with a pivotal hole311,321.

The threaded shaft33has one end bored with a pivotal hole331to be pivotally riveted with the pivotal hole311of the end shaft31and the other end formed with male threads332screwed thereon with a nut333.

The elastic block34is a hollow tubular body341having an elastic member342fitted therein. The hollow tubular body341has one end threadably connected with the threaded shaft33whose length positioned in the elastic block34can be controlled by the nut333. The hollow tubular body341has the other end connected with the driven shaft35.

The driven shaft35has one end connected with the elastic block34and the other end bored with a pivotal hole351.

The combining plate36has its opposite ends respectively bored with a pivotal hole361,362to be respectively and pivotally riveted with the driven shaft35and the end shaft32. The combining plate36is further bored with a slide slot363in the center.

The rotary arm37is pivotally connected with a turning handle371at a preset portion projecting out of the machine seat10and has its inner end secured with a long fixing plate372bored with a threaded hole373in the other end distant from the rotary arm37. A bolt374with a circular shank375is inserted through the slide slot363of the combining plate36and firmly screwed with the threaded hole373of the fixing plate372, able to slide horizontally in the slide slot363.

In using, referring toFIGS. 1,4and5, before the position-limiting device30is actuated to be tightened, the two end shafts31,32are respectively and pivotally positioned at a preset location between the two racks21, and the gear set111can be freely turned to adjust the position of the work-piece backing plate20. After the work-piece backing plate20is adjusted to a proper position, the turning handle371of the rotary arm37is swung to drive the fixing plate372to swing eccentrically and actuate the bolt374thereon to turn the combining plate36and the position-limiting device30, letting the shafts of the position-limiting device30pushed and kept in a tightened condition. At this time, the two end shafts31,32are respectively extended outward to push against the two racks21to force the two racks21to tightly press the two slide grooves13and become impossible to slide in the slide grooves13. In addition, the nut333screwed on the threaded shaft33of the position-limiting device30can be turned to control the length of the threaded shaft33positioned in the interior of the ho low tubular body341of the elastic block34so as to enable the threaded shaft33to control the compressed extent of the elastic member342in the elastic block34. Therefore, when the position-limiting device30is not actuated to be tightened, it still can be kept in a firmly tightened condition.

To sum up, this invention has the following advantages.

1. The rotary arm of the position-limiting device is pivotally positioned under the worktable of the table sawing machine, able to prevent a user from bumping against the rotary arm due to carelessness.

2. The position-limiting device can be actuated to firmly fix the work-piece backing plate in position for preventing the work-piece backing plate from shifting bias in the course of processing, able to elevate processing quality.

3. The elastic member fitted in the elastic block enables the position-limiting device to be kept in a firmly tightened condition when the position-limiting device is not yet actuated to be tightened, able to prevent the components of the position-limiting device from turning freely and losing efficacy.