High speed rotary-blade hedge trimmer

An electric hedge trimmer is provided, comprising: an elongated frame, comprising: an elongated support bar having first and second ends; first and second brackets extending perpendicularly in a first direction from the first and second ends, respectively; and a top handle extending perpendicularly from the support bar in a second direction. The electric trimmer further comprises: an electric motor secured to the first bracket; a cutting bar having a first end coupled to the electric motor and having a second end coupled to the second bracket; a plurality of cutting blades spaced around to the cutting bar; and a main handle secured to the electric motor.

RELATED APPLICATION DATA

The present application is related to commonly-owned U.S. Provisional Application Ser. No. 62/195,631, entitled HIGH SPEED ROTARY BLADE HEDGE TRIMMER, filed on Jul. 22, 2015, which application is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to reciprocating blade hedge trimmers.

BACKGROUND ART

One problem with conventional reciprocating-blade hedge trimmers is that it they are limited in their ability to cut thick branches due to the size of the gap between the teeth of the blades.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide an electric hedge trimmer, comprising: an elongated frame, comprising: an elongated support bar having first and second ends; first and second brackets extending perpendicularly in a first direction from the first and second ends, respectively; and a top handle extending perpendicularly from the support bar in a second direction. The electric trimmer further comprises: an electric motor secured to the first bracket; a cutting bar having a first end coupled to the electric motor and having a second end coupled to the second bracket; a plurality of cutting blades spaced around to the cutting bar; and a main handle secured to the electric motor.

Embodiments of the present invention further provide an electric hedge trimmer, comprising: an elongated frame, comprising: an elongated support bar having first and second ends; first and second brackets extending perpendicularly in a first direction from the first and second ends, respectively; a top handle extending perpendicularly from the support bar in a second direction. The electric trimmer further comprises; an electric motor secured to the first bracket; a cutting bar having a first end coupled to the electric motor and having a second end coupled to the second bracket; a plurality of cutting blades spaced around to the cutting bar; and a main handle secured to the electric motor. The electric trimmer has: a first configuration comprising a vortex chamber having an arcuate surface removably secured between the first and second brackets, the vortex chamber including a baffle extending from the arcuate surface towards a center of radius of the vortex chamber, the vortex chamber and baffle configured to partially shield the blades; or a second configuration comprising a safety arm guard removably secured to the frame and configured to shield an operator from the cutting blades.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1-4illustrate perspective views of an embodiment of a high speed electric hedge trimmer100of the present invention.FIG. 5is an exploded view of the trimmer100. In contrast to conventional, reciprocating-blade hedge trimmers, the trimmer100employs elongated rotary cutting blades102. More specifically, the trimmer100includes an elongated frame110with a top handle112secured perpendicularly to the frame110. The trimmer100also includes a removable vortex chamber120having a shape that, when in place, provides a hood covering the cutting blade102. The vortex chamber120has an arcuate top surface122of approximately 90° relative to a center of radius and a baffle124extending perpendicularly towards the center of radius from a top edge of the top surface122. Preferably, a plurality of strengthening ribs line the inner surface of the vortex chamber120. A plurality of safety blades130may be secured to the vortex chamber120at the junction of the arcuate surface122with the baffle124. The safety blades130comprise an elongated bar132to which a plurality of tines134are secured (or molded). The tines134extend away from the vortex chamber120and curve approximately 90° relative to the center of radius. A “former”126is secured to each end of the vortex chamber120to help provide additional rigidity to the vortex chamber120. Each former126comprises an arcuate frame of approximately 180° and an elongated base between the ends of the arcuate frame126A. When installed, each former126covers the edge of the vortex chamber120and safety blades130as seen in, for example,FIG. 5. An end cap128is secured to each former126to cover the open ends of the vortex chamber120.

The cutting blades102are secured to a cutting bar104. The blades102are preferably helical, each extending both around the cutting bar104and over the length of the cutting bar104, to provide some vortex force towards the mulching module160. Alternatively, the blades102may be linear, each extending linearly along the cutting bar104. While any number of cutting blades102may be secured to the cutting bar104, the number of blades102is preferably three or four. As will be described, the cutting bar104is driven by an electric motor140. In the embodiment illustrated in the Figures, the rotating cutting blades102have a diameter of approximately ¾ inch and can cut branches up to approximately 1½ inches in diameter. Longer blades will allow the operator to cut larger branches, though practical limitations may be imposed by the size of the motor140.

In addition to the top handle112, the frame110comprises an elongated support bar114with a bracket116A,1166(collectively116) on each end. As illustrated in the exploded view ofFIG. 5and in the close-up view of one end of the frame110, the brackets116A,116B extend perpendicularly downward (towards the center of radius of the vortex chamber120, and also to the center of radius of the cutting bar104and beyond) and have several openings formed therethrough. The vortex chamber120, formers126, and end caps128are secured to the frame brackets116A,116B with screws through the three A openings. The housing of the motor140is secured to a first frame bracket116A through the three B openings. The C opening of the first bracket116A provides an opening for a Delrin®-lined sleeve bushing142through which the drive shaft156of the motor140extends to couple with one end of the cutting bar104(see alsoFIG. 14). The C opening in the second bracket116B is configured to receive a mechanism150(seeFIGS. 8, 9) to tighten and loosen the cutting bar104for removal, replacement, and reversal. Spacers may be used between the frame brackets116A,116B and the vortex chamber120and between the frame brackets116A,116B and the motor140.

It will be appreciated that there are various ways in which to secure the cutting bar104to the motor140and frame brackets116A,116B. In the embodiment illustrated (see, for example,FIGS. 14, 15), the motor shaft and shank156may be coupled through the frame bracket116A to the cutting bar104with a pin/hole joint152secured with a locking sleeve159. A similar mechanism150may be used to couple the cutting bar104to the frame bracket116B. As noted immediately above, the mechanism150also permits the user to tighten and loosen the cutting bar104for removal, replacement, and reversal. In addition to the pin/hole joint152, the tensioning mechanism150may include a knob154secured to one end of a shaft and shank156that extends through the opening C in the frame bracket116B. The shank156is secured to the inside ring of a roller bearing158. The outer ring of the roller bearing158is secured to the cutting bar104via the pin/hole joint152.

To secure the cutting bar104to the motor140and frame bracket116B, the tensioning mechanism150is loosened by unscrewing the tensioning knob154, thereby moving the roller bearing158outward from the opening C in the frame bracket116B. The ends of the cutting bar104are inserted into the pin/hole joints152and the locking sleeves159, covering the ends of the cutting bar104and the respective shanks156, are securely tightened (FIG. 8). The tensioning knob154may then be rotated to pull the roller bearing158into the opening C in the frame bracket116B (FIG. 9), thereby securing the cutting bar104to the motor140and frame bracket1166. To remove the cutting bar104, the process is reversed. The bearing includes ears connected to the inner race of the ball bearing (not shown), which ears be snug fit to and straddle the bracket116B to prevent the ball bearing from free spinning. A pin/hole joint and safety sleeve in the other frame bracket116A may be used to removably couple the other end of the cutting bar104to the motor shaft156.

A main handle146may be secured to the top of the motor140and an electrical switch148secured to the main handle and wired between the motor140and a DC power source (not shown). In the embodiment illustrated, the switch148is a three-position slide switch. In a first position, current flows to the motor140in one direction; in a second position, current is reversed and flows to the motor140in the opposite direction; and, in a third position, the motor is off and no current flows. It will be appreciated that other types of mechanical and electronic switches may be used and that a means to vary the speed of the motor may be used as well, either integrated with the switch148or as a separate controller. Preferably, too, the top handle112includes a deadman safety switch149wired in series with the main switch148. Consequently, the motor140will only operate if the operator holds deadman switch149is held closed, and power to the motor140will be cut off immediately if the operator releases the deadman switch149.

The embodiment illustrated in the Figures also includes a motorized mulching module160having an intake secured to an opening120A in the top of the vortex chamber120. An impeller162draws the clippings from the vortex chamber120into a volute chamber164(FIG. 10) and expels them through a chute166into a collection bag (not shown). It will be appreciated that the dimensions shown inFIG. 10are merely representative and not limiting.

The trimmer100is preferably powered by a rechargeable battery pack (not shown) that may be secured to the trimmer100or, to reduce the weight the operator has to hold, be worn in a belt pack. For example, a 56 volt, 4.0 mah rechargeable battery pack may be used to power the two motors. The main motor140may be a 1,750 watt DC motor capable of approximately 20,000 revolutions per minute. The motor in the mulching module160may be a 400 watt DC pancake motor. The cutting bar104may be a Dyneema bar with stainless steel blades102, such as three. The handles146, and the vortex chamber120may be formed from any appropriate material, including being double-walled with an outer skin of, for example, Fiberglas reinforced polymer (GFPR) and an inner skin of, for example, a ballistics grade polymer or Dyneema®. The volute chamber164may also be formed from any appropriate material, including Dyneema and GFPR, which provides weight and cost savings. The frame110and other components may be also formed from any appropriate material, such as carbon reinforced polymer with cyanate ester resin (CFPR) and Dyneema.

FIG. 11illustrates a cross-sectional view of the hedge trimmer100in use. The operator holds the trimmer100with a hand on each handle112,146and turns the switches148,149on. With the cutting bar104and blades106turning, the operator may move the trimmer100along the top of the hedge being trimmed (left to right inFIG. 11). The main switch148is set to have the blades102turning in a direction such that their cutting edge faces the direction of travel when they are at the bottom of their rotation (counter-clockwise inFIGS. 11 and 12). The baffle124and safety blades130of the vortex chamber120prevent clippings from being thrown out of the vortex chamber120. Instead, they are drawn into the mulching module160for collection. In the configuration illustrated, the trimmer100is able to remove approximately 1¾ inch of hedge in one pass, which is the approximate distance between the bottom of the vortex chamber120and the bottom of the cutting circle of the blades102.

For a greater depth of cut, the trimmer100may be reconfigured by removing the vortex chamber120and safety blades130and reversing the cutting bar104and blades102. A safety arm guard170may be secured to the frame110(FIG. 7). The operator reverses the direction of the cutting blades102(FIG. 13) and is able to remove approximately 3½ inches of hedge in one pass, which is the approximate distance between the bottom of the arm guard170and the bottom of the cutting circle of the blades102. In contrast with the previously described first configuration, clippings are not collected through the mulcher module160but must be cleaned later from where they fall on the hedge or the ground. Additionally, while the arm guard170provides some protection for the operator, the blades102are not covered by the vortex chamber120, which also serves as a safety shield.

The trimmer100may be manufactured in any practical cutting width. However, widths of 14 inches, 17 inches, and 20 inches are convenient widths for both commercial and residential operators. It will also be appreciated that any dimensions indicated in the Figures are merely representative of an embodiment of the trimmer of the present invention and are not intended to be limiting.