Table saw with cutting blade safety feature

Patent metadata

Field	Value
Publication number	US-10413979-B2
Application number	US-201615230035-A
Country	US
Kind code	B2
Filing date	Aug 5, 2016
Priority date	Aug 5, 2016
Publication date	Sep 17, 2019
Grant date	Sep 17, 2019

Abstract

A power tool has a base defining a work surface, a rotary cutting blade extending through an opening in the work surface, a drive motor for imparting rotational movement to the cutting blade and a power train coupled between the drive motor and the cutting blade to transmit rotation movement from the drive motor to the cutting blade. A swing arm assembly carries the cutting blade and is pivotably supported on the base at a pivot axis.
In one aspect of the present disclosure, the power tool includes a safety system operable in response to an emergency signal that includes a mechanism for stopping the rotation of the cutting blade, whereby the rotational inertia of the cutting blade is converted after the rotation is stopped to pivoting of the swing arm assembly carrying the blade when the rotation of the blade is stopped.

First claim

What is claimed is:

1. A power tool comprising:
a base defining a work surface;
a rotary cutting blade extending through an opening in the work surface, said cutting blade including a drive axle;
a drive motor for imparting rotational movement to the cutting blade;
a power train coupled between the drive motor and the drive axle of the cutting blade to transmit rotational movement from the drive motor to the cutting blade;
a swing arm assembly pivotably supported on the base at a pivot axis, the swing arm assembly carrying the cutting blade and including a latch configured to support the swing arm assembly in an operating condition in which the cutting blade extends through the opening in the work surface and configured to be released to permit the swing arm assembly to pivot about the pivot axis to a safety position in which the cutting blade is beneath the work surface; and
a safety system operable in response to an emergency signal and including a mechanism for stopping the rotation of the cutting blade, whereby the rotational inertia of the cutting blade is converted after the rotation is stopped to pivoting of the swing arm assembly carrying the blade when the rotation of the blade is stopped, wherein the mechanism for stopping rotation of the blade includes;
an auto-locking hub mounted on said drive axle and rotationally coupled to the power train;
a jam ring surrounding said auto-locking hub and rotationally fixed in relation to said drive axle and said auto-locking hub; and
a plurality of rollers disposed between said auto-locking hub, said drive axle and said jam ring,
wherein said auto-locking hub, jam ring and rollers are configured to transmit rotation between said auto-locking hub and said drive axle in a first operating position and to lock the drive axle to the jam ring in a locking position upon a change in relative rotational speed between the auto-locking hub and said drive axle, whereby the rotation of said cutting blade is stopped in said locking position.

2. The power tool of claim 1 , further comprising at least one sensor operable to sense an emergency condition associated with the cutting blade and to generate an emergency signal in response thereto.

3. The power tool of claim 1 , wherein the latch is configured to be released by the rotational inertia of the cutting blade.

4. The power tool of claim 1 , wherein:
the power train includes;
a pulley assembly between the drive motor and a drive axle supporting the rotary cutting blade, the pulley assembly including a drive pulley rotationally coupled to the drive motor and a driven pulley rotationally coupled to the drive axle; and
a first stage between the drive motor and the drive pulley, the first stage including;
a first gear rotationally coupled to the drive motor;
a first stage shaft rotationally coupled to the drive pulley; and
a second gear in slidable splined engagement with the first stage shaft for transmission of rotation therebetween, and a disengageable engagement with the first gear for selective transmission of rotation therebetween; and
the safety system includes a clutch arrangement for moving said second gear out of engagement with said first gear.

5. The power tool of claim 4 , wherein the safety system further includes a friction pad and the clutch arrangement is configured to move said second gear into friction engagement with said friction pad as or after the second gear has disengaged with said first gear.

6. The power tool of claim 4 , wherein the auto-locking hub is rotationally coupled to said driven pulley of said pulley apparatus.

7. The power tool of claim 1 , wherein said mechanism includes a friction pad fixed to said swing arm assembly and frictionally engaged to said jam ring.

8. The power tool of claim 7 , wherein the frictional engagement between said friction pad and said jam ring is adjustable to adjust the deceleration of the cutting blade.

9. The power tool of claim 1 , wherein the safety mechanism further includes:
a rear hub slidably mounted on said drive axle adjacent an axial end face of said auto-lock hub;
a sliding rotational engagement between said rear hub and said drive axle; and
a plurality of pins projecting from said rear hub toward said auto-lock hub for selective engagement within corresponding cavities defined in said axial end face of said auto-lock hub.

10. The power tool of claim 9 , wherein the safety mechanism further includes a hub actuator operable in response to said emergency signal to move said rear hub away from said auto-lock hub to disengage said plurality of pins from said corresponding cavities to permit angular movement of said auto-lock hub relative to said drive axle of said cutting blade.

11. The power tool of claim 10 , wherein said hub actuator includes an electromagnet.

12. The power tool of claim 1 , wherein said clutch arrangement includes a clutch actuator operable in response to said emergency signal to actuate a clutch plate arranged to move said second gear out of engagement with said first gear.

13. The power tool of claim 12 , wherein said clutch actuator includes an electromagnet.

14. A cutting blade assembly for a power tool having a base defining a work surface, a drive motor supported by the base and operable to impart rotational motion and a power train coupled to the drive motor to transmit rotation movement from the drive motor, the cutting blade assembly comprising:
a rotary cutting blade including a drive axle couplable to the power train for rotation;
a swing arm assembly carrying the cutting blade having a pivot yoke for pivotably mounting to the base at a pivot axis and including a latch configured to support the swing arm assembly in an operating condition in which the cutting blade extends through an opening in the work surface, the latch further configured to be released to permit the swing arm assembly to pivot about the pivot axis to a safety position in which the cutting blade is beneath the work surface; and
a safety system operable in response to an emergency signal and including a mechanism for stopping the rotation of the cutting blade, whereby the rotational inertia of the cutting blade is converted after the rotation is stopped to pivoting of the swing arm assembly carrying the blade when the rotation of the blade is stopped, wherein the mechanism for stopping rotation of the blade includes;
an auto-locking hub mounted on said drive axle and rotationally couplable to the power train;
a jam ring surrounding said auto-locking hub and rotationally fixed in relation to said drive axle and said auto-locking hub; and
a plurality of rollers disposed between said auto-locking hub, said drive axle and said jam ring,
wherein said auto-locking hub, jam ring and rollers are configured to transmit rotation between said auto-locking hub and said drive axle in a first operating position and to lock the drive axle to the jam ring in a locking position upon a change in relative rotational speed between the auto-locking hub and said drive axle, whereby the rotation of said cutting blade is stopped in said locking position.

15. The cutting blade assembly of claim 14 , wherein said mechanism includes a friction pad fixed to said swing arm assembly and frictionally engaged to said jam ring.

16. The cutting blade assembly of claim 15 , wherein the frictional engagement between said friction pad and said jam ring is adjustable to adjust the deceleration of the cutting blade.

17. The cutting blade assembly of claim 14 , wherein the safety mechanism further includes:
a rear hub slidably mounte

Assignees

• Bosch Tool Corp
• Bosch Gmbh Robert

Inventors

• Frolov Andrew
• Voong Gary L

Classifications

• B23D45/067

  the saw blade being adjustable according to depth or angle of cut · CPC title

• B23D47/08 Primary

  of devices for bringing the circular saw blade to the workpiece or removing same therefrom · CPC title

• B27G19/02

  for circular saws · CPC title

• B27B5/38

  Devices for braking the circular saw blade or the saw spindle; Devices for damping vibrations of the circular saw blade, e.g. silencing {(vibration-damping of sawing machines or devices working with circular saw blades B23D47/005)} · CPC title

• B27B5/381

  with at least one brake member contacting saw blade portions · CPC title