BATTERY-POWERED, LOW-NOISE BACKPACK BLOWER

[0001] This application is based on and claims priority from U.S. Provisional Patent Application No. 62/065,079 filed on Oct. 17, 2014, which is incorporated herein by reference in its entirety for all purposes.

[0002] The present invention relates generally to the field of lawn, leaf and turf blowers, and specifically to battery powered backpack blowers.

[0003] In general, backpack leaf blowers are well known, especially in the commercial turf care industry. Most such backpack blowers are gas powered, that is, they have a gasoline engine that powers the blower. In such gas powered blowers, the gasoline engine needs to be very small and light, in order to fit into the backpack form factor. Accordingly, most such backpack blowers have air-cooled 2-cycle engines. Such blowers are often very noisy. A typical gas backpack blower will spin a small fan at about 9,000-10,000 rpm. Such a blower will generally deliver about 500 cfm at 150 mph out of the tube, and will cause about a 75-84 db noise level at 50 feet of distance. Further, 2-cycle engines run hot and emit a large amount of air pollution, have high operating costs because of the gasoline/oil mixture, and can be difficult to start with a pull string and manual choke lever. Particularly in a commercial setting, where use of such blowers can be all day long, operators can feel sick from the odors and fumes of gas engines, and feel fatigue from the work of starting and carrying the noisy gas-powered blowers. Most operators will do anything they can to avoid using the backpack blowers, in large part because the heat from the user builds up between the user's back and the blower, which leads to substantial discomfort.

[0004] One attempt at a solution to the heat and noise, air pollution, hard starting, and high operating cost problems associated with 2-cycle gas engine powered blowers, has been to try electric powered blowers. Some weight can be eliminated if a corded version is used, but the fact that the blower is corded so severely limits the physical range of use that it is impractical for commercial applications. And conventional handheld cordless versions are much smaller, and generally have a small battery that will only run 9-12 minutes at top speed, requiring constant recharging with the delays and inefficiencies associated with the charging. At the same time, even electric powered blowers have not solved the problem of noise, as the fans they have used to move the air have been at least as much a source of the noise as has been the gas powered engines. Most hand-held battery-operated cordless blowers spin a very small ducted fan at about 18,000-22,000 rpm. Most hand-held battery-operated cordless blowers move air at about 400 cfm at a maximum speed of about 130 mph, and most such cordless blowers cause about 65-70 db of noise at 50 feet of distance.

[0005] The present invention relates to improvements over the apparatus described above and to solutions to some of the problems raised or not solved thereby.

[0006] The invention provides a backpack blower, having a fan frame, with a bottom plate and a motor plate. The motor plate has an opening of a certain area which functions as an air inlet. The bottom plate and motor plate are connected to and separated by a side wall, and both are generally ring shaped, except having an air outlet area. A fan assembly, positioned within the fan frame, has a bottom ring and a top ring, which are spaced apart from each other by a plurality of vanes. Each vane is angled and curved substantially the same as all the other vanes with respect to the center of the bottom ring. A motor is provided to rotate the fan assembly within the fan frame, and thus move air from the air inlet to the air outlet. A removable battery pack has electrical connectors for mating with electrical connectors mounted to the fan frame. A controller is electrically connected to the motor and to the battery pack, for using power from the battery pack to energize the motor and thus rotate the fan to move air from the air inlet to the air outlet. A harness frame is connected to the fan frame and has an opening in air flow communication with the air inlet, so that, when the motor is rotating the fan assembly, air is drawn in through the harness frame opening. With the harness frame positioned adjacent to the operator's back, the air flow through the harness frame opening has the effect of cooling the operator. A main cover with air intake openings is connected to the motor plate and to the harness frame and positioned over the motor plate opening.

[0007] Other objects and advantages of the invention will become apparent hereinafter.

[0018] Referring now to the drawing figures, the invention provides a backpack style leaf and lawn blower 10. In the embodiment shown, the blower 10 includes a fan frame 12. Fan frame 12 includes a substantially flat bottom plate 14, which is generally circular except for an outlet area 14a which will be explained below. Fan frame 12 also includes a substantially flat motor plate 16 which is also generally circular except for its matching outlet area 16a. Motor plate 16 is positioned above and substantially parallel to bottom plate 14, with the outlet areas 14a and 16a aligned over each other. The bottom plate 14 and the motor plate 16 are maintained at a predetermined separation from each other by a side wall 18 mounted substantially perpendicular to, and at the periphery of, the bottom plate and motor plate. The centers of the bottom plate 14 and motor plate 16 form a line substantially parallel to the side wall 18.

[0019] The motor plate 16 has an opening 20 at its center which is generally round, the diameter of which about half of the diameter of the motor plate itself, except that there are motor mounting arms 21 extending generally radially inward from the inner edges of the opening.

[0020] The embodiment shown includes a centrifugal fan assembly 22 with forward curved vanes 32. The fan assembly 22 is positioned within the fan frame 12, that is, between the bottom plate 14 and the motor plate 16, and within the side wall 18. The fan assembly 22 includes a bottom ring 24, and a top ring 26. The rings 24, 26 have similar diameters. Top ring 26 has a top ring opening 30 at its center, the diameter of which opening is about 70% of the outside diameter of the top ring. The plane of the top ring 26 is spaced apart from and parallel to the plane of the bottom ring 24, held at a predetermined spacing by a number of the vanes 32, spaced generally equally about the circumference of the rings. The embodiment shown in FIGS. 2 and 5 has 11 vanes, but other numbers of vanes could also work well. In the embodiment shown in isometric isolation in FIG. 5, each of the vanes 32 is connected to both rings 24, 26. From the inner edge of top ring 26, each vane 32 tapers down to a point of connection to the bottom ring 24 at a point about 75% of the distance from the outer circumference to the center. The outer 30% of each vane 32 is curved or angled in the direction of the rotation of the fan assembly, that is, forward, at an angle of about 35 degrees.

[0021] As shown in FIG. 2, the invention provides a motor 34 to rotate the fan assembly 22. In the embodiment there shown, the motor 34 is an outrunner-type motor, which is advantageous because such a motor runs at a lower speed, eliminating the weight and complexity of a gearbox or reducer, while at the same time producing more torque than an inrunner-style motor. As shown in more detail in FIG. 7 but also in some of the other drawing figures, motor 34 has a motor body 36 that is connected to and rotates with a motor shaft 38, and a motor stator 39 mostly inside the motor body. Motor stator 39 is rigidly affixed to a motor mounting bracket 40 which, as shown best in FIG. 2, has motor bracket arms 41 extending generally radially outward, the ends of which are bolted or otherwise removably attached to the motor mounting arms 21. Since motor mounting arms 21 are part of the motor plate 16, the stator 39 of motor 34 is thus non-rotatably connected to the motor plate 16. The motor shaft 38 is rigidly connected to the bottom ring 24 of the fan assembly 22 by means of a fan hub 42. Bottom ring 24 may have a one or more bottom ring openings 28, to accommodate attachment of the fan hub 42. Thus when the motor shaft 38 is rotated with respect to the motor mounting bracket 40, the fan assembly 22 is rotated with respect to the motor plate 16 and the fan frame 12 in general.

[0022] The side wall 18 does not entirely enclose the fan assembly 22, instead having an outlet 44 which allows escape of the air being moved by the fan assembly, and in fact, use of the blower 10 as a blower. The area of the outlet opening is about 25% of the area of the motor plate opening 20, so as to provide proper air flow and pressure. As shown in FIG. 1, to the outlet 44 is removably attached one end of a hose or flexible tube 46. The other end of the flexible tube 46 has a blower tube 48 attached to it. Any suitable flexible or non-flexible tubes or nozzles may be used to accomplish the various operations for which the blower 10 will be used. To the blower tube 48, or the end of the flexible tube 46 nearest the blower tube, is attached a control handle 50, which can be used to direct the flow of air out of the nozzle as desired when the blower 10 is in use. The control handle 50 may also be provided with a power switch 50a to turn the power ON and a lever 50b to adjust the airflow from “low” to “high.” There may also be a momentary trigger switch 50c for “boost” or maximum speed. Such controls would make the blower 10 very easy to start and stop compared to taking the blower off the user's back and pulling a rope to start a gas blower.

[0023] Mounted to the outer surface of the motor plate 16 is a main cover 52. Considering as the front of the blower 10 the outlet 44, and that the direction of air flow from the outlet is out the front of the blower, the bottom end of the main cover 52 is connected to the motor plate 16 at the back of the blower. The main cover 52 acts as a guard, rising at a forward angle and thereby covering the motor 34 and the larger motor plate opening 20, and being perforated with small openings 52b so as to still permit entry of air into the motor plate opening, as shown by arrows 53 (FIGS. 9 and 10). The sides of the main cover 52 are connected to the motor plate 16 by side plates 54 and 56 and are generally closed. Side plate 54 (FIG. 3) is on the left, is generally triangular in shape, and is connected along a bottom edge to the motor plate 16, and along one side edge to the main cover 52. Side plate 56 (FIG. 4) is on the right, is also generally triangular in shape, and is connected along a bottom edge to the motor plate 16, and along one side edge to the main cover 52.

[0024] A harness frame 58 (shown in isometric isolation in FIG. 6) is connected to the opposite side edge of each of the side plates 54, 56, and to the motor plate 16, as well as, at the top thereof, to the main cover 52. Thus the entire motor plate opening 20 is covered by the assembly of the main cover 52, the side plates 54 and 56, and the harness frame 58. When the blower 10 is in use, harness frame 58 fits in the area of the back of the user or operator 59. Harness frame 58 also has openings 60, so as to allow air to be drawn in around the user when the blower 10 is in use and the fan assembly 22 rotating. A handle opening 61 near the top of the harness frame 58 permits the harness frame to be used as a handle, by which to carry the blower 10. Shoulder straps 62 are provided, connected to the harness frame 58, to permit the user to carry the blower 10 on the user's back. The air flow resulting from the openings 60 in the harness frame 58, as shown by arrows 63, has a beneficial cooling effect, relieving some of the heat build-up that results for a user of conventional backpack blowers, making the blower 10 much more pleasant to use.

[0025] The power source for the blower 10 is a battery pack 64 which is easily removable and replaceable, in an opening 52a provided for that purpose in main cover 52. Some of the drawing figures show the opening 52a with the battery pack 64 having been removed, so as to show the battery pack support plates 66, 68 under the main cover 52. As shown in FIG. 8, a battery connector 70 is provided near the bottom of the battery pack 64 goes, such as on the battery pack support plate 86, so as to connect with the battery pack when inserted in the opening 52a. The battery connector 70 is electrically connected and provides power to a controller 74, which is in turn connected to the motor 34 to provide power. The control handle 50 may also be connected to the controller 74, to enable the operator to control the blower 10, such as by varying the speed of the blower in ways known to persons of skill in the art.

[0026] Given the generally horizontal orientation of the fan assembly 22 and the straight-line orientation between the outlet 44 and the hose 46, the invention provides a blower 10 that produces higher static pressure and has much quieter operation than prior backpack leaf blowers, but still has very good air flow. Blower 10 generally has a top speed of about 4700 rpm, compared to, as described above, 9,000-10,000 rpm for commercial gas backpack blowers and about 18,000-22,000 rpm for most hand held cordless blowers. Fan assembly 22 will deliver 504 CFM at 150 mph out of the tube with 58 db noise level at 50′ distance. As stated above, a typical gas backpack blower that delivers 500 cfm at 150 mph out of the tube causes about a 75-84 db noise level at 50′ distance. Since noise doubles for every 6 db change, blower 10 is about 3-4 times quieter than a conventional gas blower. Most handheld battery-powered cordless blowers move about 400 cfm of air at a maximum of about 130 mph, and cause about 65-70 db of noise—still 2-3 times louder than blower 10, with much less air movement performance. As described above, these hand held blowers also have a disadvantage in that their small battery will only run 9-12 minutes at top speed. With its large battery pack 64, blower 10 will run over 60 minutes at the best speed of the handheld blowers, or about 45 minutes at its top speed of 150 mph. Run time such as that is about the same as in a commercial gas backpack blower using a full tank of gasoline. Further, as shown in FIG. 10, based upon the orientation of the outlet 44, operation of the blower will cause a reaction where the blower is lifted slightly in the direction of arrow 76, making it feel lighter on the user's shoulders.

[0027] While the apparatus hereinbefore described is effectively adapted to fulfill its intended objects, it is to be understood that the invention is not intended to be limited to the specific preferred embodiments set forth above. Rather, it is to be taken as including all reasonable equivalents to the subject matter described.