Table saw

Elevation and blade tilt mechanisms for table saws are disclosed. The elevation and tilt mechanisms may include an indexable position adjustment system configured to adjust the position of the blade relative to the table in discrete increments. Such table saws may also include a trunnion assembly with an elevation carriage slideably mounted to front and rear brackets, the brackets being tiltable with the elevation carriage relative to the table, and the elevation carriage being adapted to maintain the tilt of each bracket relative to the other bracket in a fixed orientation.

FIELD

The present disclosure relates to power tools and particularly to power tools with tool positioning mechanisms.

BACKGROUND

Power tools often include some type of elevation mechanism to adjust the height or position of a cutter. In a table saw, for example, an elevation mechanism allows the height of the blade to be adjusted and a tilt mechanism allows the angle/tilt of the blade to be adjusted. These mechanisms should be easy to use and economical. Prior systems suffer from being difficult to adjust or unnecessarily complex.

DETAILED DESCRIPTION

FIG. 1shows a table saw10having a table12with an opening14and a blade16projecting through opening14. Blade16is supported on an arbor18mounted in an elevation carriage20. A riving knife22is also mounted to elevation carriage20. Elevation carriage20has front and rear support arms24,26that threadedly engage on front and rear threaded shafts28,30. Rotation of shafts28,30by elevation control shaft32via miter gears34causes elevation carriage20to move up and down shafts28,30. Shafts28,30are supported by front and rear brackets36,38respectively. Brackets36,38are pivotally connected to table12via tilt plates40,42, respectively, which allow elevation carriage20(and thereby blade16) to tilt relative to table12. Representative tilt plate40is shown in more detail inFIG. 7. Tilt plates40and42, elevation carriage20, support arms24,26, shafts28,30, elevation control shaft32, miter gears34, and brackets36,38comprise an example of a trunnion assembly, shown generally at43inFIG. 1.

It should be noted that in saw10tilting torque is transferred directly through elevation carriage20rather than though a separate trunnion link as is found in prior art saws. This provides a simpler structure by avoiding the need for a rigid trunnion link assembly or member.

FIGS. 2-4shows a saw110having a table112with an opening114and a blade116projecting through opening114. Blade116is supported on an arbor118mounted in an elevation carriage120. Elevation carriage120has front and rear support arms124,126that slideably engage front and rear brackets136,138, respectively. Brackets136,138are pivotally connected to table112via tilt plates like tilt plates40and42, which allow elevation carriage120(and thereby blade16) to tilt relative to table112.

Elevation carriage120is driven up and down on brackets136,138by the interaction of front and rear elevation pinions144,146with front and rear racks168,170secured to elevation carriage120. Elevation pinions144,146are mounted to elevation control shaft132. Rotating elevation control shaft132with elevation handle152drives elevation carriage120up and down brackets, such as bracket148, to control the elevation of blade116through opening114. A strap, chain or other similar member wrapped around elevation shaft132or crank arm attached thereto, could likewise be used to convert rotational movement of elevation shaft to vertical displacement of elevation carriage120. Although elevation carriage120is shown with the direct torque transfer configuration illustrated inFIG. 1, the elevation mechanism is equally applicable to more traditionally constructed trunnion or elevation assemblies.

FIG. 5illustrates bracket148in more detail with the addition of an indexable control154for elevation control shaft132. Bracket148includes guide two slots156(the lower one being obscured by the indexable control). A guide assembly158is secured to elevation carriage120and rides in each slot156. As shown inFIG. 6, each guide assembly includes a screw160, a bushing162and washers164to provide structure to slideably retain elevation carriage120to bracket148. Guide assemblies158are preferably a relatively close fit in slots156to provide accurate and slop free linear motion of elevation carriage120on brackets148,150. The two point connection between elevation carriage120and brackets148,150insures that both brackets and the carriage are maintained in alignment as the carriage tilts or the blade is raised and lowered. Notably, this alignment between the front and rear brackets is maintained without the need for a trunnion link separate from the elevation carriage. Elevation carriage120may also be thought of as a unified trunnion/elevation carriage since it serves the purpose of the trunnion link as well as the elevation carriage.

Indexable control154shown inFIG. 5includes an indexing gear180connected to handle152and adapted to rotate with shaft132. Indexing gear180includes teeth182disposed around the perimeter adapted to selectively mesh with teeth184formed on indexing rack186. Handle152and gear180are secured together and slideably mounted on shaft132as shown inFIGS. 8 and 9. More particularly, handle152has a central bore188that fits slideably over shaft132and is held in place by a screw190, washer192and spring194at one end and a cross pin198fixed through shaft132ridding in a slot-like pocket196.

When handle152is pulled to the left (out from the front of the saw), spring194is compressed as pin198slides in slot196. The limited compression of spring194prevents pin198from coming out of slot196. As a result, the handle remains rotatably coupled to shaft132to rotate pinions144,146and selectively raise and lower the blade. When the handle is pulled to the left, it disengages the teeth of gear180and rack186, allowing the handle to be rotated. When the handle is released, spring194pushes gear180back into engagement with rack186. This prevents the elevation carriage from falling under its own weight and backdriving pinions144,146. In addition, in the pictured embodiment, the finite pitch of teeth184,182only allows the elevation shaft to lock at indexed locations. The pitch of the teeth in conjunction with the diameter of the pinions will result in a specific blade elevation change per tooth. Typical dimensions are chosen to generate an incremental elevation change of approximately 1/32ndof an inch and full up to full down elevation change with a single revolution. Other values are equally within the scope of the invention and the specifics are chosen based on the desired operating characteristics of the saw. For instance, it may be desirable in some applications to have finer elevation adjustments and or more or less handle turns to raise or lower the blade. Alternatively, gear and rack could be replaced with corresponding untoothed components that locked by frictional engagement, such as a taper lock, to eliminate the indexing feature while still allowing fast and simple elevation adjustment. It should also be understood that gear180could be replaced with a single pointer that engaged teeth on rack186—although this might require rack186to be extended to allow a greater range of elevation adjustment. Similarly, rack186could be replaced with a single point that could selectively engage gear180.

A similar indexing control200is shown inFIGS. 10-13and adapted to selectively set the tilt of the blade relative to the table at discrete locations. In particular, indexing control200includes a tilt indexing gear202with teeth204distributed around the perimeter. A central bore206fits over the elevation shaft (not shown) so that gear202can rotate independently of the elevation shaft. Gear202fits into an arcuate slot208between an upper rack210and a lower rack212. Slot208and racks210,212are preferably molded in a plastic housing214forming part of the enclosure of the saw. One of racks210,212is displaced forward or rearward relative to the other so that gear202can be shifted forward or back to selectively engage one or both racks.

It can be seen that with gear202engaged in both racks, it is not possible to tilt the blade due to the engagement of teeth204with racks210,212preventing the gear from either rotating in or translating along the slot. However, by shifting gear202forward or back to disengage one of the racks, such as by pushing or pulling on a handle connected to the gear, it is then possible to tilt the blade since gear202would be free to rotate and move in slot208. By correct choice of arc radii, tooth pitch and gear diameter it is possible to have engagement of gear202in the racks only occur at predetermined angular intervals. In the illustrated embodiment, displacement of the teeth of gear202by one tooth in lower rack212will cause a ½ degree tilt of blade. This incremental transition is shown sequentially for 0 to 1.5 degrees of tilt inFIGS. 10-13.

An alternate embodiment of an indexing control system is shown at300inFIGS. 14-16. Control300includes a stepped tilt indexing gear302. Gear302includes a small gear304and a large gear306secured to rotate together. Small gear304is positioned to interact with upper arc308while large gear306selectively meshes with lower arc310. The offset of the upper and lower arcs described above can be readily seen. Control300also includes an elevation positioning gear312and a corresponding rack314. Elevation positioning gear312includes a hub316. Stepped gear302fits over hub316, and is thereby supported by the hub while gear302remains free to rotate around the hub.

Hub316is slideably mounted to an elevation shaft318and positioned by two pins320press fit into holes322formed in shaft318. A spring324is captured between the pins and fits in cavity326. The ends of cavity326are sized to allow shaft318to slide but catch spring324. As a result, if a handle328which is secured to the hub is pulled or pushed, spring324is compressed, but allows the assembly to slide back and forth by a small amount. The spring also restores the assembly to a neutral position (shown inFIG. 14) when the handle is released.

When the indexing control is positioned as shown inFIG. 14, both the tilt and elevation are locked because small gear304meshes with upper arc308, large gear306meshes with lower arc310and gear312meshes with rack314. When handle328is pushed in (to the left as shown inFIG. 15) elevation positioning gear312is disengaged from rack314allowing handle328to be rotated to raise and lower the blade, while gears304,306still mesh with arcs308,310locking the tilt of the blade in place. If, on the other hand, handle328is pulled out, as depicted inFIG. 16, elevation positioning gear312remains engaged with rack314, but large gear306comes disengaged from rack310, which allows the blade to tilt by rolling of small gear304on rack308. The blade can be tilted by simply moving the handle to one side or the other without rotating the handle. On first inspection, this is very similar to the system ofFIGS. 10-13, however, the use of a step gear causes the indexing to occur at smaller intervals for a given tooth size and arc radius. This is advantageous to provide the ability to set the tilt in finer increments and/or to allow for the use of larger teeth which may reengage more easily or be more robust.

It can be seen that the indexing control system ofFIG. 14-16provides the advantage of a single handle and one handed control of both tilt and elevation in a table saw. There is no need to release a clamp or other mechanism to release the system to tilt or elevate the blade. The system is nonetheless robustly held in place when the handle is not pushed or pulled. The system is also very mechanically simple and economical to construct.

It is believed that the disclosure set forth above encompasses multiple distinct inventions with independent utility. While each of these inventions has been disclosed in its preferred form, the specific embodiments thereof as disclosed and illustrated herein are not to be considered in a limiting sense as numerous variations are possible. The subject matter of the inventions includes all novel and non-obvious combinations and subcombinations of the various elements, features, functions and/or properties disclosed herein. No single feature, function, element or property of the disclosed embodiments is essential to all of the disclosed inventions. Similarly, where the claims recite “a” or “a first” element or the equivalent thereof, such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements.