Patent Application
20110247472
The present invention relates to a belt brake for a band saw such as a band saw on a sawmill utilized for sawing lumber.
A conventional band saw is often used in sawmills. Such a band saw typically has a relatively large, circular, endless band saw blade, mounted along the path of travel of wood placed on a suitable moving bed with a drive mechanism for advancing the wood against the blade. Alternatively, the wood remains stationary and the band saw is mounted on a carriage which is capable of transverse displacement along the wood.
The blade moves in a generally circular path, typically around two rotating coplanar band wheels, one of which is powered by a motor, either via direct drive or a belt drive. The second band wheel rotates under the force transmitted through the movement of the blade. In the case of a belt drive, a tensioning pulley may provide variable tension to the belt so that an operator can activate or deactivate the rotation of the blade by adjusting tension on the tensioning pulley, rather than starting or stopping the motor. This method creates much less wear on the motor and belt. Often the tensioning pulley is adjusted by means of a clutch.
One problem with such a method, however, is that when the tension on the belt is decreased, though the blade eventually comes to a stop, entropy from the large and heavy band wheels results in continued rotation for a fairly long time before the blade stops completely. This creates a safety issue for the user, since the user may deactivate the band saw and forget that it is still in motion. This safety issue is exacerbated by the fact that the sound from the motor may change when the clutch is activated.
There are several prior inventions for band saws.
U.S. Pat. No. 4,275,632 describes a portable sawmill comprising a U-shaped support or carriage, holding a band saw. Canadian Patent No. 1,200,180 describes a portable sawmill having a band saw on a carriage. The LumberMate™ band sawmill (Canadian Patent No 2,488,216 and Canadian Industrial Design Application no. 132823) is a portable sawmill having a band saw with a circular band saw blade which rotates around two band saw wheels.
There is a need for an improved band saw having a brake assembly for stopping the blade of the band saw when it is deactivated by a user.
According to one aspect of the invention is provided a band saw having1. A band saw having: an endless saw blade driven around a first band wheel and a coplanar second band wheel configured to provide a cutting area between the first band wheel and the second band wheel; a motor for driving the saw blade; the motor providing rotational force to drive a band wheel; further characterized such that: the band saw comprises a brake belt, the brake belt having a first end, a second end, and a belt surface between the first end and the second end, the brake belt being configured such that a portion of the belt surface travels along a brake wheel connected to the first band wheel or the second band wheel; at least one of the first end and second end being displaceable such that the brake belt has a first, tense position which provides frictional force to the brake wheel, and a second, loose position which provides significantly less or no frictional force to the brake wheel.
In certain embodiments, the brake belt is biased towards the first, tense position.
In certain embodiments, the brake belt can be displaced from the first, tense position to the second, loose position by a user.
In yet further embodiments, the displacing of the first and/or second end of the brake belt and the moving of the tensioning pulley is synchronized.
In yet further embodiments, when the tensioning pulley is in the first, disengaged position, the brake belt is in the first, tense position, and when the tensioning pulley is in the second, engaged position the brake belt is in the second, loose position.
In yet further embodiments, wherein the tensioning pulley is connected to a clutch handle by means of a Bowden cable, which is capable of displacing a pivoting clutch assembly on which the tensioning pulley is mounted.
In yet further embodiments, the first end and/or the second end of the brake belt is connected to the pivoting clutch assembly.
The present invention provides a simple and effective adjustable band brake for a band saw. As shown (but optionally), the band brake is integrated into a clutch mechanism of a band-driven band saw.
The band brake provides braking action on the band saw blade. Without such a brake, the bandwheels and blade would continue rotating for a prolonged period of time, notwithstanding that the operator has released the engine throttle to idle. The band brake provides an effective, reliable and low cost solution in a manner that can fit within the very narrow confines of the bandwheel guard housing.
The brake provides substantial safety over a non-braking band saw. As set out below, the brake can be configured such that it is automatically engaged upon release of the engine throttle.
An embodiment of the present invention will now be described as shown in
As seen in
Tensioning pulley 44 can also be used as a clutch for the saw blade 28; instead of continuously shutting off and turning on the motor 38 to activate the cutting action of saw blade 28, tension can be released from drive belt 40 by adjusting tensioning pulley 44. Releasing tension in drive belt 40 results in the free spinning of drive pulley 42 and a decrease of rotatory force on saw blade 38, resulting in the stopping of the saw blade 38. Starting and stopping saw blade 38 in this manner decreases wear on motor 38 and drive belt 40, improving the longevity of these parts. However, starting and stopping saw blade 38 in this manner, without a brake, would result in the free spinning of saw blade 38 before it eventually comes to a stop once the entropy of the saw blade 38 and the band wheels 24, 26 is dispersed.
As seen in
The brake assembly is shown in
Thus, in this manner, presently provided is a simple and efficient braking mechanism for a band saw, whereby the clutch mechanism is combined with the braking mechanism. The braking mechanism allows reliable and cost effective braking in a manner that can fit within the very narrow confines of the bandwheel guard housing.
As would be understood by a person of skill in the art, the provided embodiment can be modified for specific needs. For example, in some applications, both of the ends of the brake belt can be attached to the pivoting assembly, to provide additional frictional force on the brake wheel 62, or where it is desired to provide more uniform braking force. In other applications, the brake belt can be attached to a second, separate pivoting assembly, operated for example by a second Bowden cable. This can be useful where a different amount of displacement is required for the brake belt as compared to the tensioning pulley, or, for example, where a different biasing strength is needed. The second Bowden cable can be attached to the clutch handle, or, alternatively, may be attached to a separate brake handle, for operation of the brake separately from the clutch. In certain other embodiments, depending on the desired configuration and the design limitations of the specific band saw, the brake belt can travel along a brake wheel on the free band wheel instead of on the drive band wheel.
It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2,696,974 | Apr 2010 | CA | national |
