Ratchet and release mechanism for swing arm of table saw

Patent metadata

Field	Value
Publication number	US-9962778-B2
Application number	US-201514968984-A
Country	US
Kind code	B2
Filing date	Dec 15, 2015
Priority date	Dec 15, 2014
Publication date	May 8, 2018
Grant date	May 8, 2018

Abstract

A table saw includes a safety system to protect a user from injury. The safety system detects a sensed condition and rapidly moves a saw blade away from the user. The safety system includes a dual ratchet mechanism to prevent the blade from rebounding back above a work surface after an initial rapid retraction of the blade. The table saw has a swing arm that rotates to move the blade below the work surface. A first ratchet engages a first contact surface of the swing arm after rotation of the swing arm over a first range of angular displacements to prevent counter rotation of the swing arm. A second ratchet engages a second contact surface of the swing arm after rotation of the swing arm over a second range of angular displacements to prevent counter rotation of the swing arm.

First claim

What is claimed is:

1. A table saw, comprising:
a frame that supports a work surface;
a swing arm that cooperates with the frame via a pivot, the swing arm defining first and second contact surfaces disposed concentrically about and proximate to the pivot;
a blade rotatably attached to the swing arm at a position spaced from the pivot, the blade having an operating position in which the blade extends above the work surface and a retracted position in which an uppermost extent of the blade is positioned below the work surface, the swing arm rotatable about the pivot to move the blade from the operating position to the retracted position in response to a sensed condition;
a first ratchet configured to cooperate with the first contact surface so as to maintain the blade in the retracted position after the swing arm rotates over any one of a first range of angular displacements from the operating position; and
a second ratchet configured to cooperate with the second contact surface so as to maintain the blade in the retracted position after the swing arm rotates over any one of a second range of angular displacements from the operating position, the second range of angular displacements including angular displacements that are greater than angular displacements of the first range of angular displacements;
wherein the first and second ratchets are independently pivotable about a common axis, the common axis spaced from the pivot through which the swing arm cooperates with the frame.

2. The table saw of claim 1 , further comprising a carriage supported by the frame and configured to move relative to the frame, wherein:
the swing arm cooperates with the carriage via the pivot,
the operating position of the blade is adjustable via a linear displacement of the swing arm relative to the frame, and
the angular displacement of the of swing arm to move the blade from the operating position to the retracted position varies depending on the linear position of the swing arm relative to the frame.

3. The table saw of claim 2 , wherein:
the first range of angular displacements of the swing arm corresponds to a respective first range of operating positions of the blade, and
the second range of angular displacements of the swing arm corresponds to a respective second range of operating positions of the blade.

4. The table saw of claim 2 , wherein:
the first contact surface defines a first stop face that cooperates with the first ratchet to maintain the blade in the retracted position,
the second contact surface defines a second stop face that cooperates with the second ratchet to maintain the blade in the retracted position, and
a position of the second stop face about the pivot is staggered relative to a position of the first stop face about the pivot to account for the varying angular displacements of the swing arm.

5. The table saw of claim 4 , wherein:
the first contact surface includes (i) a first ready surface disposed at a first radial distance from the pivot and (ii) a first active surface disposed at a second radial distance from the pivot, the first radial distance being greater than the first active surface, the first stop face formed at an intersection of the first ready surface and the first active surface
the second contact surface includes a second ready surface disposed at a third radial distance from the pivot and a second active surface disposed at a fourth radial distance from the pivot, the third radial distance being greater than the fourth radial distance, the second stop face formed at an intersection of the second ready surface and the second active surface.

6. The table saw of claim 4 , wherein:
the first ratchet has a first tip portion with a first angled face, the first stop face is angled, and cooperation between the first angled face and the first stop face causes the first ratchet to ramp towards the first active surface and fully engage the first stop face, and
the second ratchet has a second tip portion with a second angled face, the second stop face is angled, and cooperation between the second angled face and the second stop face causes the second ratchet to ramp towards the second active surface and fully engage the second stop face.

7. The table saw of claim 4 , wherein:
the first ratchet and the first stop face are configured to one or more of absorb and transfer forces resulting from an impact between the first ratchet and the first stop face during a counter rotation of the swing arm after the swing arm rotates over any one of the first range of angular displacements, and
the second ratchet and the second stop face are configured to one or more of absorb and transfer forces resulting from an impact between the second ratchet and the second stop face during the counter rotation of the swing arm after the swing arm rotates over any one of the second range of angular displacements.

8. The table saw of claim 7 , further comprising a wear plate positioned over at least a portion of the second stop face, the wear plate protecting the second ratchet and the second stop face from damage resulting from repeated impacts therebetween.

9. The table saw of claim 5 , wherein:
the first and second ratchets contact the first and second ready surfaces, respectively, when the blade is in the operating position,
after rotation of the swing arm over any one of the first range of angular displacements, the first ratchet contacts one or more of the first active surface and the first stop face, and
after rotation of the swing arm over any one of the second range of angular displacements, the first ratchet contacts one or more of the first active surface and the first stop face and the second ratchet contacts one or more of the second active surface and the second stop face.

10. The table saw of claim 5 , wherein:
the first and second ratchets contact the first and second ready surfaces of the swing arm, respectively, when the blade is in the operating position,
after rotation of the swing arm over any one of the first range of angular displacements, the first active surface is rotated under a first tip portion of the first ratchet and the first tip portion is biased into contact with the first active surface via a first biasing member, and
after rotation of the swing arm over any one of the second range of angular displacements, (i) the first active surface is rotated under the first tip portion of the first ratchet and the first tip portion is biased into contact with the first active surface via the first biasing member and (ii) the second active surface is rotated under a second tip portion of the second ratchet and the second tip portion is biased into contact with the second active surface via the second biasing member.

11. The table saw of claim 1 , wherein the first and second ratchets are biased against the first and second contact surfaces, respectively, via respective first and second biasing members.

12. The table saw of claim 4 , further comprising a stop attached to the frame and configured to arrest the rotation of the swing arm from the operating position,
wherein the cooperation of one or more of the first and second ratchets with the first and second stop faces, respectively, ensures that the blade is maintained in the retracted position after a counter rotation of the swing arm from the stop.

13. The table saw of claim 1 , wherein a portion of the second range of angular displacements of the swing arm is equal to a portion of the first range of angular displacements of the swing arm.

14. The table saw of claim 1 , wherein the first ratchet has (i) a main body portion that extends along a pl

Assignees

• Bosch Tool Corp
• Bosch Gmbh Robert

Inventors

• Talesky Mark S
• Koegel Jan
• Taylor Brian
• Szweda Timothy
• Chaganos Gregory

Classifications

• B23D45/06

  with a circular saw blade arranged underneath a stationary work-table · CPC title

• 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

• B27B5/16

  Saw benches (B27B15/06 takes precedence) · CPC title

• B23D45/068

  the saw blade being adjustable according to depth or angle of cut (B23D45/061, B23D45/065 take precedence) · CPC title