EP2969390A1

EP2969390A1 - Guard lock release mechanism for power saw

Info

Publication number: EP2969390A1
Application number: EP14769351.9A
Authority: EP
Inventors: Daniel WINTERNITZ; Jan Koegel; Ji YAO
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2013-03-15
Filing date: 2014-03-11
Publication date: 2016-01-20
Also published as: WO2014150549A1; EP2969390A4

Abstract

A power saw includes a cutting arm, a blade guard pivotably supported by the cutting arm and movable to a closed position and an open position, a guard lock lever pivotably supported by the cutting arm and movable to a locked position and an unlocked position, and a guard lock release mechanism. The guard lock release mechanism includes a first release lever extending from the guard lock lever and a second release lever extending from the first release lever. The first release lever includes a first contact end configured to be manually pressed to move the guard lock lever from the locked position to the unlocked position, and the second release lever includes a second contact end configured to be manually pressed to move the guard lock lever from the locked position to the unlocked position.

Description

GUARD LOCK RELEASE MECHANISM FOR POWER SAW

[0001] This application claims the benefit of priority of U.S. provisional application serial no. 61/792,602, filed March 15, 2013, and U.S. provisional application serial no. 61/792,776 filed March 15, 2013. The disclosures of the above-identified patent applications are both incorporated herein by reference in their entirety.

Field

[0002] This disclosure relates generally to power saws and particularly to a mechanism for locking and releasing a lower blade guard of a power saw.

Background

[0003] Power saws are used for cutting and shaping workpieces, such as, hardwood, manufactured wood products, construction lumber, metal construction materials, and the like. One type of power saw, commonly referred to as a chop saw, typically includes a base configured for placement on a stand, a table, or on the ground. The base defines a workpiece support surface, which is used to support a workpiece to be cut by the chop saw. A support assembly of the chop saw extends from the base, and a cutting arm assembly is movably connected to the support assembly. The cutting arm assembly includes an electric motor configured to rotate a circular saw blade.

[0004] A workpiece is cut with the chop saw by moving the cutting arm assembly downward relative to the base, such that the rotating saw blade is moved through the workpiece. After completing the cut, the cutting arm assembly is moved upwards to extract the saw blade from the kerf formed in the workpiece. [0005] On at least some chop saws, the cutting arm assembly includes an upper blade guard that defines a blade guard space. An upper portion of the saw blade is positioned in the blade guard space, such that the upper blade guard covers approximately an upper half of the saw blade. Additionally, the cutting arm assembly includes a movable blade guard, sometimes referred to as a lower blade guard, which is configured to rotate about a hub relative to the upper blade guard. A biasing member biases the lower blade guard toward a closed position in which the lower blade guard covers most of a lower portion of the saw blade. When cutting a workpiece, the lower blade guard moves relative to the upper blade guard toward an open position, against the force of the biasing member, to expose a portion of the saw blade thereby enabling the saw blade to extend into the workpiece.

[0006] Some chop saws include a guard lock and a guard lock release mechanism

("GLRM") associated with the lower blade guard. The guard lock is movable between an engaged position and a disengaged position. In the engaged position, the guard lock prevents the lower blade guard from rotating/moving to expose the saw blade. In the disengaged position the guard lock enables rotation/movement of the lower blade guard.

[0007] The GLRM, of known power saws, is coupled to the guard lock. The GLRM is configured to move the guard lock between the engaged position and the disengaged position in response to being contacted by the user. Typically, the GLRM is moved in a first direction to release the guard lock and then is moved in a second direction to engage the guard lock. The GLRM typically includes a biasing member configured to normally bias the guard lock toward the engaged position.

[0008] The GLRMs of known power tools are typically inconvenient to operate. In particular, it is typically unclear with which hand a user should operate the GLRM. In particular, upon viewing most known GLRMs, the typical user is unsure if his/her left or right hand should be used to operate the GLRM. Additionally, most known GLRMs are suitable for operation with a particular hand; that is, the GLRM is not intended for ambidextrous use.

[0009] Therefore, it is desirable for a power saw to include a GLRM that effectively controls the guard lock associated with the lower blade guard and that is also intuitive and comfortable to operate.

Summary

[0010] According to an exemplary embodiment of the disclosure, a power saw includes a cutting arm, a blade guard pivotably supported by the cutting arm and movable to a closed position and an open position, a guard lock lever pivotably supported by the cutting arm and movable to (i) a locked position in which the guard lock lever prevents movement of the blade guard to the open position, and (ii) an unlocked position in which the guard lock lever permits movement of the blade guard to the open position, and a guard lock release mechanism. The guard lock release mechanism includes a first release lever extending from the guard lock lever and a second release lever extending from the first release lever. The first release lever includes a first contact end configured to be manually pressed to move the guard lock lever from the locked position to the unlocked position, and the second release lever includes a second contact end configured to be manually pressed to move the guard lock lever from the locked position to the unlocked position.

[0011] According to another exemplary embodiment of the disclosure, a guard lock release mechanism for a power saw having a guard lock lever supported by a cutting arm, includes a first release lever and a second release lever. The first release lever extends from the guard lock lever and includes a first contact end configured to be manually pressed to move the guard lock lever from a locked position to an unlocked position. The second release lever extends from the first release lever and includes a second contact end configured to be manually pressed to move the guard lock lever from the locked position to the unlocked position.

Brief Description of the Figures

[0012] The above-described features and advantages, as well as others, should become more readily apparent to those of ordinary skill in the art by reference to the following detailed description and the accompanying figures in which:

[0013] FIG. 1 is a perspective view of a power saw including a guard lock and a guard lock release mechanism, as described herein;

[0014] FIG. 2 is a perspective view of a portion of the power saw of FIG. 1, showing the guard lock and the guard lock release mechanism in an engaged configuration that prevents movement of a lower blade guard of the power saw;

[0015] FIG. 3 is another perspective view of a portion of the power saw of FIG. 1, showing the guard lock and the guard lock release mechanism in the engaged configuration;

[0016] FIG. 4 is a perspective view of a portion of the power saw of FIG. 1, showing the guard lock and the guard lock release mechanism in a disengaged configuration that enables movement of the lower blade guard, the guard lock release mechanism has been moved to the disengaged position with the thumb of a user's left hand;

[0017] FIG. 5 is a perspective view of a portion of the power saw of FIG. 1, showing the guard lock and the guard lock release mechanism in the disengaged configuration, the guard lock release mechanism has been moved to the disengaged position with the thumb of a user's right hand;

[0018] FIG. 6 is a perspective view of a portion of the power saw of FIG. 1, including another embodiment of the guard lock and the guard lock release mechanism;

[0019] FIG. 7 is a perspective view of a portion of the power saw of FIG. 1 , including yet another embodiment of the guard lock and the guard lock release mechanism;

[0020] FIG. 8 is a perspective view of another power saw including a blade guard linkage, as described herein;

[0021] FIG. 9 is a perspective view of the blade guard linkage of FIG. 8 shown in isolation;

[0022] FIG. 10 is a perspective view of the power saw of FIG. 8, with the lower blade guard in a closed position;

[0023] FIG. 11 is a perspective view of the power saw of FIG. 8, with the lower blade rotated toward an open position; and

[0024] FIG. 12 is a perspective view of the power saw of FIG. 8, showing the lower blade guard held in an open position by the blade guard linkage of FIG. 8.

Detailed Description

[0025] For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiments illustrated in the drawings and described in the following written specification. It is understood that no limitation to the scope of the disclosure is thereby intended. It is further understood that the present disclosure includes any alterations and modifications to the illustrated embodiments and includes further applications of the principles of the disclosure as would normally occur to one skilled in the art to which this disclosure pertains.

[0026] As shown in FIG. 1, a power saw, shown as a metal dry cutter / chop saw 100, includes a base 104, a support arm 108 extending from a rear side of the base, and a cutting arm assembly 112. The base 104 is configured for placement on a work surface (not shown), such as a workbench, a power saw stand, or simply a ground surface. The base 104 is at least partially formed from a rigid material such as aluminum, steel, high strength plastic, or the like. An upper surface of the base 104 is configured to define a workpiece support surface 116. The workpiece support surface 116 is a substantially flat surface on which a user may position a workpiece (not shown) to be cut by the chop saw.

[0027] The cutting arm assembly 112 is configured for pivotal connection to the support arm 108 by a pivot shaft 120. In particular, the cutting arm assembly 112 is configured to pivot about the pivot shaft 120 to and between a raised position (shown in FIG. 1) and a lowered position (not shown). A biasing member 124 biases the cutting arm assembly 112 toward the raised position.

[0028] The cutting arm assembly 112 includes a cutting arm 126, an electric motor 128, a saw blade 132 (shown in phantom), a handle portion 136, an upper blade guard 140, a lower blade guard 144, a guard lock lever 148, and a guard lock release mechanism ("GLRM") 152. The cutting arm 126 is formed from metal or any other sufficiently rigid material such as composite materials or any other material as desired by those of ordinary skill in the art.

[0029] The electric motor 128 is supported by the cutting arm 126 and includes a motor shaft (not shown). The motor shaft is configured to rotate in response to the electric motor 128 being coupled to a source of electrical energy. Rotation of the motor shaft is coupled to an arbor assembly (not shown), which supports the saw blade 132. In one embodiment, the electric motor 128 is a brushless DC motor; however, the electric motor may be any type of universal AC motor or electric motor, as desired by those of ordinary skill in the art.

[0030] The saw blade 132 is a circular saw blade configured to be mounted on the arbor assembly of the cutting arm assembly 112. The saw blade 132 includes a highly abrasive perimeter, as commonly provided on carbide tipped cutting blades for cutting metal. Alternatively, the perimeter of the saw blade 132 includes a plurality of cutting teeth for cutting wood, for example; or the saw blade is a diamond cutting blade for cutting tiles, for example.

[0031] The handle portion 136 is an approximately "D" shaped handle that fixedly extends from the cutting arm 126. The handle portion 136 defines a grip portion 138 configured to be manually grasped by a left or a right hand of a user as the user pivots the cutting arm assembly 112 between the raised position and the lowered position. The handle portion 136 includes a power switch 156, which is movable to connect and to disconnect the electric motor 128 from the source of electrical power.

[0032] The upper blade guard 140 fixedly extends from the cutting arm 126. The upper blade guard 140 is configured to cover approximately the upper half of the saw blade 132. To this end the upper blade guard 140 defines a cavity (not shown) in which the upper half of the saw blade 132 is positioned.

[0033] The lower blade guard 144 is pivotably supported by the cutting arm 126. The lower blade guard 144 is configured for rotational movement between a closed position (FIG. 1) and an open position (not shown). In the closed position a cavity (not shown) defined by the lower blade guard 144 covers approximately the lower half of the saw blade 132 (i.e. any portion of the saw blade not covered by the upper blade guard). In the open position the lower half of the saw blade 132 is exposed to enable the saw blade to contact the workpiece.

[0034] With reference still to FIG. 1, the chop saw 100 further includes a fence 160 and a clamp assembly 164. The fence 160 defines a surface 168 against which a workpiece to be cut is positioned. The fence 160 is pivotable relative to the base 104 to enable the user make angled cuts with the chop saw 100. The clamp assembly 164 is connected to the base 104 and is configured to secure a workpiece against the fence 160 so that the workpiece remains stationary during the cutting operation.

[0035] As shown in FIG. 2, the guard lock lever 148 includes a pivot arm 172, a biasing member 176 (FIG. 3), and a contact bumper 180. The pivot arm 172 is pivotably supported by the upper blade guard 140 of the cutting arm 126 by a pivot shaft 184. Specifically, the pivot arm 172 is configured to be pivoted between an engaged / locked position (FIGs. 1-3) and a disengaged / unlocked position (FIGs. 4 and 5). The pivot arm 172 is formed from metal that, in one embodiment, is stamped and bent into shape. Alternatively, the pivot arm 172 is formed from any rigid material, as desired by those of ordinary skill in the art.

[0036] The contact bumper 180 is fixedly connected to the pivot arm 172. The contact bumper 180 is formed from a resilient material, such as plastic, rubber, or any other rubber-like elastomeric material. When the pivot arm 172 is in the engaged position the contact bumper 180 is configured to prevent rotation of the lower blade guard 144 to the open position by obstructing movement of the lower blade guard. When the pivot arm 172 is in the disengaged position, the pivot arm moves the contact bumper 180 to a position that enables the lower blade guard 144 to rotate to the open position. Positioning the pivot arm 172 in the disengaged position is also referred to as "releasing" the guard lock lever 148. [0037] As shown in FIG. 3, the GLRM 152 includes a first release / linked lever 188 and a second release / linked lever 192 that extending from the first linked lever 188. The linked levers 188, 192 are formed from metal or any other rigid material as desired by those of ordinary skill in the art. In one particular embodiment, the linked levers 188, 192 are formed from plastic.

[0038] The first linked lever 188 is configured as an approximately "L" shaped lever (see

FIG. 3). The first linked lever 188 extends from and is fixedly connected to the pivot arm 172 of the guard lock lever 148. A stop tab 198 extends from the first linked lever 188.

[0039] The first linked lever 188 includes a contact end 200, which is angled with respect to the rest of the first linked lever 188, such that the contact end is positioned in an ergonomically appropriate location. In one embodiment, the contact end 200 is angled approximately 30 degrees with respect to the rest of the first linked lever 188; however, other angles are equally sufficient. The contact end 200 is configured to be located in a position that is convenient for a user to touch with his/her left hand thumb when grasping the handle portion 136. In particular, the content end 200 is configured to be manually pressed to move the guard lock lever 148 from the locked position to the unlocked position.

[0040] The contact end 200 includes a plastic cap or an elastomeric cap structure 204 that is positioned over at least a portion of the contact end. The elastomeric cap 204 is formed from a brightly-colored and/or contrastingly-colored material, such as plastic for example, in order to be easily seen by the user. The elastomeric cap 204, in one embodiment, is the same color as the power switch 156. In another embodiment, the elastomeric cap 204 is not included on the contact end 200 and the user contacts the bare contact end 200.

[0041] The second linked lever 192 is configured as an approximately "C" shaped lever and is pivotably supported / connected by a pivot shaft 196 to the first linked lever 188. A contact end 208 of the second linked lever 192 is angled with respect to the rest of the second linked lever, such that the contact end is positioned in an ergonomically appropriate location. In one embodiment, the contact end 208 is angled approximately 80 degrees with respect to the rest of the second linked lever 192. The contact end 208 is configured to be located in a position that is convenient for a user to touch with his/her right hand thumb when grasping the handle portion 136. In particular, the content end 208 is configured to be manually pressed to move the guard lock lever 148 from the locked position to the unlocked position.

[0042] The contact end 208 includes a plastic cap or an elastomeric cap structure 212 that is positioned over at least a portion of the contact end. The elastomeric cap 212 is formed from a brightly-colored and or contrastingly-colored material, such as plastic for example, in order to be easily seen by the user. In another embodiment, the elastomeric cap 212 is not included on the contact end 208 and the user contacts the bare contact 200.

[0043] The pivot shaft 196 extends through the first linked lever 188 and the second linked lever 192 to pivotably connect the linked levers 188, 192. A fastener, such as a hex nut, is threadingly engaged with the pivot shaft 196 to secure the pivot shaft to the linked levers 188, 192 and to prevent separation of the linked levers 188, 192. The pivot shaft 196 is spaced apart from the handle 136 of the cutting arm assembly 112. The pivot shaft 196 defines a pivot point of the linked levers 188, 192 that is movable with respect to the cutting arm 126 depending at least on the position of the pivot arm 172 (first position in FIG. 3, second position in FIGs. 4 and 5). Accordingly, the pivot point (as identified by pivot shaft 196) of linked levers 188, 192 is a free floating pivot point.

[0044] The second linked lever 192 is configured to be pivoted about the pivot shaft 196 between an engaged position (FIGs. 1-3) and a disengaged position (FIG. 5) relative to the first linked lever 188. A biasing member 216 associated with the pivot shaft 196 is configured to bias the second linked lever 192 toward the engaged position in a counterclockwise direction (as shown in FIG. 3) until a stop end 220 of the second linked lever 192 contacts the stop tab 198, which prevents further movement of the second linked lever 192 about the pivot shaft 196 in the counterclockwise direction.

[0045] In operation, the GLRM 152 enables a user to release the guard lock lever 148 using either the user's left hand thumb or the user's right hand thumb. With reference to FIG. 4, left hand operation the GLRM 152 is described. A left hand cutting operation begins with the user wrapping his/her left hand fingers around the grip portion 138 of the handle portion 136 and positioning his/her fingertips against the power switch 156. Next the user positions his/her left thumb against the elastomeric cap 204 positioned over the contact end 200 of the first linked lever 188. The ergonomic position of the contact end 200 makes it convenient for the user to contact the elastomeric cap 204 even without looking at the GLRM 152. The contact end 200 is right where a user would expect it to be located.

[0046] To release the guard lock lever 148 the user manually presses the elastomeric cap

204 in the release direction 224 and pivots the first linked lever 188, the pivot arm 172, and the second linked lever 192 about the pivot shaft 184 until the pivot arm 172 and the contact bumper 180 are in the disengaged position. The pivot point defined by the pivot shaft 196 moves with respect to the handle portion 136 and the cutting arm 126 in response to the movement of the pivot arm 172. The force against the elastomer cap 204 does not result in movement of the second linked lever 192 relative to the first linked lever 188 (i.e. the second linked lever remains in the engaged position). [0047] With the guard lock lever 148 in the disengaged position the user squeezes the power switch 156 to activate the electric motor 128 and then moves the cutting arm assembly 112 toward the workpiece support surface 116 to cut a workpiece. After the workpiece is cut the user returns the cutting arm assembly 112 to the raised position, releases pressure on the power switch 156, and releases pressure on the cap 204. When pressure on the cap 204 is released the biasing member 176 returns the pivot arm 172 to the engaged position. Therefore, the guard lock lever 148 returns to the engaged position when the user release the handle portion 136.

[0048] With reference to FIG. 5, a right hand cutting operation begins with the user wrapping his/her right hand fingers around the grip portion 138 of the handle portion 136 and positioning his/her fingertips against the power switch 156. Next the user positions his/her right thumb against the elastomeric cap 212 positioned over the contact end 208 of the second linked lever 192. The ergonomic position of the contact end 208 makes it convenient for the user to contact the elastomeric cap 212 even without looking at the GLRM 152. The contact end 208 is right where a user would expect it to be located.

[0049] To release the guard lock lever 148 the user manually presses the elastomeric cap

212 in the release direction 228 to move the second linked lever 192 toward the disengaged position. The release direction 228 is different from the release direction 224. The force in the direction 228 causes (i) the second linked lever 192 to pivot relative to the first linked lever 188 about the pivot shaft 196, and (ii) the pivot arm 172 (with the contact bumper 180) to pivot about the pivot shaft 184. As the second linked lever 192 pivots about the pivot shaft 196, the stop end 220 is moved away from the stop tab 198, such that the stop end is spaced apart from the stop tab. [0050] With the guard lock lever 148 in the disengaged position the user completes the cutting operation as described above. Specifically, after the cut has been completed and the electric motor 128 has been deenergized the pressure on the cap 212 is released. The release in pressure enables (i) the biasing member 176 to bias the pivot arm 172 toward the engaged position, and (ii) the biasing member 216 to bias the second linked lever 192 toward the engaged position until the stop end 220 contacts the stop tab 198.

[0051] Accordingly, in operation the GLRM 152 enables convenient, intuitive, and ambidextrous release of the guard lock lever 148. Additionally, the GLRM 152 offers visual clarity for how the GLRM functions. The GLRM 152 enables control of the guard lock lever 148 before and during the cutting operation. The GLRM 152 is robust, simple, and more reliable than other systems. The GLRM 152 relieves the user of the confusion and discomfort of other GLRM systems.

[0052] In another embodiment, the first linked lever 188 is slidably connected to the second linked lever 192 and is configured for sliding movement between the engaged position and the disengaged position. Also, in another embodiment, the GLRM 152 includes a single lever that performs the functions of both the first linked lever 188 and the second linked lever 192. In a further embodiment, the linked levers 188, 192 pivot about a pivot axis that is parallel to the arbor shaft, rather than perpendicular to the arbor (as described above).

[0053] As shown in FIG. 6, in another embodiment a combined guard lock and GLRM

300 includes a guard lock 304 and a GLRM 308. The combined unit 300 is formed from a single piece of stamped and bent material, typically sheet metal. The GLRM 308 includes a contact pad 312 that is configured for ambidextrous operation. The GLRM 308 is operable with the "heel" or the wrist of the user's hand. [0054] As shown in FIG. 7, in another embodiment a combined guard lock and GLRM

400 includes a guard lock 404 and a GLRM 408. The combined unit 400 is formed from a single piece of stamped and bent material, typically sheet metal. The GLRM 408 includes a contact pad 412 that is configured for ambidextrous operation. Additionally, the GLRM 408 is operable with the "heel" or the wrist of the user's hand.

[0055] In the exemplary embodiments described above, the power saw is shown and described as a chop saw 100. In another embodiment the GLRM 152, 308, 408 is usable with any other power saw that includes a rotatable lower blade guard including miter saws and the like.

[0056] Guard Linkage Embodiment

[0057] As shown in FIG. 8, a power saw, shown as a metal dry cutter / chop saw 500, includes a base 504, a support arm 508 extending from a rear side of the base, and a cutting arm assembly 512. The base 504 is configured for placement on a work surface (not shown), such as a workbench, a power saw stand, or simply a ground surface. The base 504 is at least partially formed from a rigid material such as aluminum, steel, high strength plastic, composite materials or the like. An upper surface of the base 504 is configured to define a workpiece support surface 516. The workpiece support surface 516 is a substantially flat surface on which a user positions a workpiece (not shown) to be cut by the chop saw.

[0058] The cutting arm assembly 512 is configured for pivotal connection to the support arm 508 by a pivot shaft 520. In particular, the cutting arm assembly 512 is configured to pivot about the pivot shaft 520 to and between a raised position and a lowered position (not shown). A biasing member 524 biases the cutting arm assembly 512 toward the raised position. [0059] The cutting arm assembly 512 includes a cutting arm 526, an electric motor (not shown), a saw blade 532 (FIGs. 11 and 12), a handle portion 536, an upper blade guard 540, and a lower blade guard 544. The cutting arm 526 is formed from metal such as aluminum or steel. Alternatively the cutting arm 526 is formed from any high strength material as desired by those of ordinary skill in the art, such as high strength plastic, composite materials and the like.

[0060] The saw blade 532 is a circular saw blade configured to be mounted on the arbor assembly 550 of the cutting arm assembly 512. The saw blade 532 includes a highly abrasive perimeter, as typically provided on carbide tipped cutting blades for cutting metal. Alternatively, the perimeter of the saw blade 532 includes a plurality of cutting teeth for cutting wood, for example; or the saw blade is a diamond cutting blade for cutting tiles, for example.

[0061] The handle portion 536 is an approximately "D" shaped handle that fixedly extends from the cutting arm 526. The handle portion 536 is configured to be grasped by a user as the user pivots the cutting arm assembly 512 between the raised position and the lowered position.

[0062] The upper blade guard 540 fixedly extends from the cutting arm 526. The upper blade guard 540 is configured to receive approximately the upper half of the saw blade 532. To this end, the upper blade guard 540 defines a cavity (not shown) in which the upper half of the saw blade 532 is positioned.

[0063] The lower blade guard 544 is pivotally connected to the cutting arm 526 via a mounting plate 556. The lower blade guard 544 is configured for pivotal movement between a closed position (FIG. 8) and an open position (FIGs. 11 and 12) about a pivot shaft 546. In the closed position a cavity (not shown) defined by the lower blade guard 544 receives approximately the lower half of the saw blade 532 (i.e. any portion of the saw blade not covered by the upper blade guard). In the open position the lower half of the saw blade 532 is exposed to enable the saw blade to contact the workpiece. A biasing member 558 (shown in phantom) biases the lower blade guard 544 toward the closed position.

[0064] The mounting plate 556 is connected to the cutting arm 526 with a fastener 562 and a fastener 566. The fastener 562 is removable from the cutting arm 526 to enable the mounting plate 556 to pivot about the fastener 566 between a first position shown in FIG. 8 and a second position shown in FIG. 12. In another embodiment, the fastener 566 is removable from the cutting arm 526 to enable the mounting plate 556 to pivot about the fastener 562 between a third position and a fourth position.

[0065] The chop saw 500 further includes a fence 560 and a clamp assembly 564. The fence 560 defines a surface 568 against which a workpiece to be cut is positioned. The fence 560 is pivotable relative to the base 504 to enable the user make angled cuts with the chop saw 500. The clamp assembly 564 is connected to the base 504 and is configured to secure a workpiece against the fence 560 so that the workpiece remains stationary during the cutting operation.

[0066] With continued reference to FIG. 8, a linkage arm 572 is connected to the lower blade guard 544 and the support arm 508. The linkage arm 572 is formed from metal. In another embodiment, the linkage arm 572 is formed from any rigid material as desired by those of ordinary skill in the art.

[0067] As shown in FIG. 9, the linkage arm 572 includes an opening structure 576 defining an opening 580 and a slot structure 584 defining a slot 588. The opening 580 extends through the linkage arm 572 and receives a fastener 592 (FIG. 8). The fastener 592 is configured to pivotally connect the linkage arm 572 to the support arm 508. The slot 588 receives a pin 596 (FIG. 1) which slidably and pivotally connects the linkage arm 572 to the lower blade guard 544.

[0068] The slot 588 is configured as a compound slot that includes a slide region 600 which opens to a blade change region 604. The slide region 600 is defined by an approximately semi-circular end wall 608, an opposite end wall 612, and two substantially parallel sidewalls 616. The distance from the end wall 608 to the end wall 612 is approximately 6 cm in one embodiment, and the distance between the sidewalls 616 is approximately 1cm in one embodiment. In other embodiments, the distances are different than the exemplary distances previously described.

[0069] The blade change region 604 is defined by an approximately semi-circular end wall 620, a shoulder 624 opposite to the end wall 620, and a sidewall 628. The distance from the end wall 620 to the shoulder 624 is approximately 2 cm.

[0070] In operation, the linkage arm 572 is configurable in two states including a cutting operation state and a blade change state. In the cutting operation state, the pin 596 is slidably positioned in the slide region 600. In this state when the cutting arm assembly 512 is moved between the raised and lowered positions, the linkage arm 572 operates to smoothly open and close the lower blade guard according to the typical four bar linkage design. In particular, movement of the cutting arm assembly 512 from the raised position to the lowered position causes the pin 596 to abut the end wall 608, which results in rotation of the lower blade guard 544 toward the open position. The linkage arm 572 also guides the lower blade guard 544 toward the closed position about the pivot shaft 546, as the cutting arm assembly 512 is moved from the lowered position to the raised position. [0071] In the blade change state the linkage arm 572 positions the lower blade guard 544 in the open position and prevents the cutting arm assembly 512 from being moved to the lowered position.

[0072] With reference to FIG. 10, to use the linkage arm 572 in the blade change state, first the cutting arm assembly 512 is moved to the raised position and the lower blade guard 514 is moved to the closed position. Next, the fastener 562 is removed from the cutting arm 526 to enable pivotal movement of the mounting plate 556 relative to the cutting arm 526.

[0073] As shown in FIG. 11, next the user rotates the lower blade guard 544 in a clockwise direction toward the open position against the biasing force of the biasing member 558. The rotation of the lower blade guard 544 causes the pin 596 to slide in the slide region 600 of the slot 588 toward the end wall 612 and also causes the mounting plate 556 to move toward the second position (FIG. 12). The user continues to rotate the lower blade guard 544 until the pin 596 is positioned against the end wall 612 and mounting plate 556 is in the second position. Then the user holds the lower blade guard 544 in the above-described position.

[0074] Next, with reference to FIG. 12, the user rotates the linkage arm 572 in the clockwise direction to cause the pin 596 to exit the slide region 600 and to enter the blade change region 604. The user rotates the linkage arm 572 until the pin 596 is positioned against the shoulder 624 and/or the sidewall 628.

[0075] Thereafter, the user releases the lower blade guard 544, which causes the biasing member 558 to bias the lower blade guard toward the closed position. This biasing force biases the pin 596 against the shoulder 624, and due to the rigidity of the linkage arm 572, the lower blade guard 544 is prevented from rotating to the closed position. When the linkage arm 572 is in the blade change state, the lower blade guard 544 is maintained in the open position, as shown in FIG. 12.

[0076] The linkage arm 572, the lower blade guard 544, the cutting arm 526, and the support arm 508 form a four bar linkage system. When the linkage arm 572 is in the blade change state, the four bar linkage system is positioned in an over-center configuration, which prevents rotation of the lower blade guard 544. The linkage arm 572 is in the over-center configuration when the linkage arm 572 overlaps or is moved to the right of (with reference to FIG. 12) the pivot shaft 546. The four bar linkage system is prevented from entering the over- center configuration when the pin 596 is positioned in the slide region 600.

[0077] With the lower blade guard 544 being held in the open position by the linkage arm 572, the arbor assembly 550 is exposed and the user is able to change the saw blade 532 without having to hold the lower blade guard in the open position. Accordingly, the user is able to manipulate the arbor assembly 550 of the cutting arm assembly 512 with one hand and to support the saw blade 532 with the other hand.

[0078] Also, when the linkage arm 572 is in the blade change state, the cutting arm assembly 512 is prevented from being rotated toward the lowered position. Again, this is due to the rigidity of the linkage arm 572 and the over-center orientation of the linkage arm (as described above). Accordingly, the linkage arm 572, when configured in the blade change state, prevents a user from performing cutting operations.

[0079] In another embodiment, the linkage arm 572 is connected to the support arm and the lower blade guard of a miter saw or any other power saw that includes a pivotable/rotatable blade guard. [0080] While the disclosure has been illustrated and described in detail in the drawings and foregoing description, the same should be considered as illustrative and not restrictive in character. It is understood that only the preferred embodiments have been presented and that all changes, modifications and further applications that come within the spirit of the disclosure are desired to be protected.

Claims

Claims What is claimed is:

1. A power saw comprising:

a cutting arm;

a blade guard pivotably supported by the cutting arm and movable to a closed position and an open position;

a guard lock lever pivotably supported by the cutting arm and movable to (i) a locked position in which the guard lock lever prevents movement of the blade guard to the open position, and (ii) an unlocked position in which the guard lock lever permits movement of the blade guard to the open position; and

a guard lock release mechanism including a first release lever extending from the guard lock lever and a second release lever extending from the first release lever, the first release lever including a first contact end configured to be manually pressed to move the guard lock lever from the locked position to the unlocked position, and the second release lever including a second contact end configured to be manually pressed to move the guard lock lever from the locked position to the unlocked position.

2. The power saw of claim 1, wherein:

the second release lever is pivotably supported by the first release lever; and

the second release lever is configured to pivot relative to the first release lever in response to the second contact end being manually pressed.

3. The power saw of claim 2, wherein:

the second release lever is movable to an engaged position and a disengaged position relative to the first release lever,

the guard lock release mechanism further includes a biasing member configured to bias the second release lever toward the engaged position, and

the second release lever is moved toward the disengaged position in response to the second contact end being manually pressed.

4. The power saw of claim 3, wherein:

the biasing member is configured to bias a stop end of the second release lever toward a stop tab of the first release lever, and

the stop end is opposite from the second contact end.

5. The power saw of claim 2, wherein the second release lever is pivotably supported by the first release lever at a free floating pivot point.

6. The power saw of claim 5, wherein:

the guard lock lever is configured to move to the unlocked position in response to (i) the first contact end being manually pressed in a first release direction, and (ii) the second contact end being manually pressed in a second release direction different from the first release direction; and the free floating pivot point is configured to move relative to a handle of the power saw in response to (i) the first contact end being manually pressed in the first release direction, and (ii) the second contact end being manually pressed in the second release direction.

7. The power saw of claim 1, wherein the guard lock lever is configured to move to the unlocked position in response to (i) the first contact end being manually pressed in a first release direction, and (ii) the second contact end being manually pressed in a second release direction different from the first release direction.

8. The power saw of claim 1, wherein the guard lock release mechanism further includes:

a first cap structure positioned over the first contact end; and

a second cap structure positioned over the second contact end,

wherein the power saw further includes a power switch of a color and the first cap structure and the second cap structure are the same color.

9. The power saw of claim 1, further comprising:

a handle supported by the cutting arm and defining a grip portion configured to be manually grasped by a left hand or a right hand of a user to move the cutting arm to a raised position and a lowered position,

wherein the first contact end is positioned to be manually pressed by a left thumb of the user when the user manually grasps the grip portion with the left hand, and

wherein the second contact end is positioned to be manually pressed by a right thumb of the user when the user manually grasps the grip portion with the right hand.

10. A guard lock release mechanism for a power saw having a guard lock lever supported by a cutting arm, the guard lock release mechanism comprising:

a first release lever extending from a guard lock lever and including a first contact end configured to be manually pressed to move the guard lock lever from a locked position to an unlocked position; and

a second release lever extending from the first release lever and including a second contact end configured to be manually pressed to move the guard lock lever from the locked position to the unlocked position.

11. The guard lock release mechanism of claim 10, wherein:

the second release lever is pivotably supported by the first release lever; and the second release lever is configured to pivot relative to the first release lever in response to the second contact end being manually pressed.

12. The guard lock release mechanism of claim 11, wherein:

13. The guard lock release mechanism of claim 12, wherein:

the stop end is opposite from the second contact end.

14. The guard lock release mechanism of claim 13, wherein the second release lever is pivotably supported by the first release lever at a free floating pivot point.

15. The guard lock release mechanism of claim 14, wherein:

the guard lock lever is configured to move to the unlocked position in response to (i) the first contact end being manually pressed in a first release direction, and (ii) the second contact end being manually pressed in a second release direction different from the first release direction; and

the free floating pivot point is configured to move relative to a handle of a power saw in response to (i) the first contact end being manually pressed in the first release direction, and (ii) the second contact end being manually pressed in the second release direction.

16. The guard lock release mechanism of claim 10, wherein the guard lock lever is configured to move to the unlocked position in response to (i) the first contact end being manually pressed in a first release direction, and (ii) the second contact end being manually pressed in a second release direction different from the first release direction.

17. The guard lock release mechanism of claim 10, further comprising:

a first cap structure positioned over the first contact end; and

a second cap structure positioned over the second contact end,

wherein a power saw further includes a power switch of a color and the first cap structure and the second cap structure are the same color.