Patent Application
20140154106
The present invention relates to motorized portable blowers of the type used to blow leaves, grass clippings, etc. into a heap for subsequent disposal and, in particular, to hand held blowers. Such devices are used to maintain yards and gardens in a clean and tidy state, and include back pack style blowers as well as the more numerous hand held blowers.
A typical prior art blower 101 is illustrated in
These devices are used predominantly for lawn and garden tasks and have been available in the marketplace for about 40 years following the development over the last 50 years of portable small lightweight gasoline powered engines. There are also electric powered units powered either from a mains supply or battery power.
However, gasoline blowers are now very common and consist of the gasoline engine connected to an impeller type fan that is housed in a fan housing. There is a generally central air inlet into the blower casing and a peripheral outlet of the fan housing connected to an inline rigid tube (generally formed in two parts) to direct the high speed air flow in the direction desired by the operator. This direction is changed by changing the direction or orientation of the entire hand held blower.
These devices are used, for example, to blow leaf and/or grass cuttings to a corner of a yard for easy collection for disposal (e.g. composting). Another use is to clean leaves and other debris from hard surfaces, paths, driveways and the like, quickly and efficiently without the wasteful use of water as occurs with hosing etc.
Another use is, for example, the cleaning of stadia and parks of litter left behind after a game or concert by blowing this rubbish into heaps for collection and disposal.
By far the largest use is by home owners for their own yard cleaning and maintenance jobs. Worldwide more than a million units are made every year and every manufacturer is trying to produce more powerful blowers.
The genesis of the present invention is a desire to improve the performance of existing portable hand-held blowers and, in particular, to increase the overall effectiveness of the blower.
In accordance with a first aspect of the present invention there is disclosed a portable hand-held blower comprising:
a power source having an axis of rotation,
a fan mounted on said power source to be driven thereby and located within the housing, said housing having an array of inlet apertures and a single main exit,
a handle atop said housing and mounted substantially above the centre of gravity of said blower,
said main exit having a generally S-shaped configuration to substantially align the path of air exiting said blower with said handle to prevent a torque being experienced by an operator holding said handle in use, and
said fan being moulded in a single piece from substantially rigid material;
wherein said fan comprises:
a generally flat disc each quadrant thereof having a plurality of generally radially extending blades which all extend on the same side of said disc,
which all are rearwardly swept relative to the intended direction of rotation of the disc,
which all extend to a predetermined height above a plane passing through said disc and substantially perpendicular to said axis of rotation,
said blades being tilted transversely and in the direction of rotation of said fan either as a consequence of the manufacture of said blades, or as a consequence of the forces created by the operational rotational speed of said fan, and
whereby each transversely tilted blade and its adjacent portion of said disc in front of each said blade forms an air scoop for said fan.
In accordance with a second aspect of the present invention there is disclosed a fan for a blower, said fan comprising:
a generally flat disc each quadrant thereof having a plurality of generally radially extending blades which all extend on the same side of said disc,
which all are rearwardly swept relative to the intended direction of rotation of the disc,
which all extend to a predetermined height above a plane passing through said disc and substantially perpendicular to said axis of rotation,
said blades being tilted transversely and in the direction of rotation of said fan either as a consequence of the manufacture of said blades, or as a consequence of the forces created by the operational rotational speed of said fan, and
whereby each transversely tilted blade and its adjacent portion of said disc in front of each said blade forms an air scoop for said fan.
The present invention will hereinafter be described in conjunction with the appended drawing figures wherein like numerals denote like elements.
As seen in
The housing 2 also has a main air exit 9 which is connected by means of a generally S-shaped bend 10 to an air exit tube 11 which is aligned with the longitudinal axis 4 of the handle 3. The air exit tube 11 is preferably formed from two sections 12 and 13 each of which is detachable from the other and from the remainder of the blower 1. This enables the blower to be assembled into a compact unit for transportation and/or storage.
In operation, air is sucked through the air inlet grille 6 and expelled via the main air exit 9 and air exit tube 11 whilst the entire blower is held in one hand of the operator with the arm extended downwardly so that the blower is typically about knee height. In some instances, a small amount of air, which is intended to cool the internal combustion engine, is directed from the housing 2 via various minor air exits.
As shown in
However, this desirable alignment comes with an operational penalty in that the S-shaped bend 10 constitutes a “chicane” which reduces the velocity and force of the air exiting the blower 1.
The performance of various blowers available on the market varies considerably based on subjective tests in using different commercially available types of blowers to clean leaves, etc. in the private homes of the inventors. However, in order to provide an objective assessment of blower performance, an air thrust test rig 15 as illustrated in
A sub-assembly 23 was formed from a slightly curved rectangular plate 24 which is securely connected to a force arm 25. The force arm 25 has a ball bearing 26 rotatably mounted at its free end. The entire sub-assembly 23 is pivoted on its ball bearing mounted pivot shaft 21. In order to carry out a test, the free end of an air tube 212, being 270 mm in length and 69 mm in interior diameter, is positioned at a fixed distance of 100 mm from the rest position of the rectangular plate 24, this rest position being illustrated in solid lines in
The receiving end of the rigidly mounted tube has an expanding female taper to accept the end of each single exit tube 12 of each blower being tested. The rigid tube internal diameter is slightly larger than the external diameter of each of the exit tubes of the blowers under test, thus preventing any restriction of the air thrust of the blower under test.
The thrust of the air exiting towards the rectangular plate 24 pivots the rectangular plate 24 in an anticlockwise direction as seen in
Table I tabulates the results of test conducted on prior art commercially available blowers.
In order to provide a suitable direct comparison, the inventors constructed two prototypes for each of two representative engines. Each first prototype had an air exit which was in-line with the blower fan and thus not aligned with the blower handle. Each second prototype had an S-shaped chicane twist so that the air exit was not aligned with the blower fan but was aligned with the blower handle. The first representative engine was the Toro two stroke 25.4 cc engine and the comparative results for the two stroke powered prototypes and the two stroke powered prior art blower are as set out in Table II.
The second representative engine was the Honda four stroke 25 cc engine and the comparative results for the four stroke or four cycle powered prototype are as set out in Table III.
From the three tables it can be seen that the inventors' fans have substantially fewer fan blades than the prior art fans. These fewer blades have the advantage of a lesser number of noise waveforms being generated. This is very advantageous in the reduction of noise which is generally very irritating to nearby persons. In addition, when this lower noise level is combined to a shorter overall time of use, because the inventors' fans have a more powerful thrust, the overall advantage over the prior art fans is considerable.
Turning now to
As illustrated in
As seen in the plan view in
Since the disc 30 is molded in a single piece from a substantially rigid material, such a nylon or glass filled nylon, and the thickness of the base of the blade 32 (typically 1.75-2 mm) is thinner than the thickness of the disc 30 (which is typically 2.5 mm), the net forward transverse force on the blade 32 tilts the blade 32 forwardly as indicated in
This deformation at operational speed has the consequence that the tilted blades 32 constitute an air scoop for the fan which is more effective than the blades 32 would be if the fan was not distorted in operation. Preferably the maximum extent of the blades 32 in a direction parallel to the shaft of the motor is in excess of 30 mm, and preferably in excess of 35 mm and, as indicated in the comparative Tables II and III, most preferably approximately 40 mm.
The amount of tilt, or positive distortion, of the blades 32 depends on the blade height, the thickness of the blades 32, the thickness of the disc 30, and the engine speed.
Turning now to
Each of the upright blades 132 again has a ramp portion 134 and a wing portion 135, however, the blades 132 are straight (rather than being curved as in
The nature of this distortion due to rotational forces gives rise to three possible situations, each of which is difficult to illustrate. The first situation is where the upright blades 32 are relatively less rigid than the disc 30. This has the consequence that the disc 30 does not distort and the upright blades 32 are bent or curved so as to tilt forwardly. This is the situation illustrated in
As seen
All of the above mentioned blade and fan configurations provide a more effective “scoop” and thus the above described improved fan performance.
Because these blowers have to be held by one hand, they all suffer from the conflicting requirements that they be sufficiently light in weight to be carried but must have a powerful thrust of air blast to have the ability to easily and quickly blow the intended litter/leaves etc. The blowers also suffer from vibration that is transmitted to the operator. Further, even those blowers of intermediate blowing thrust without a chicane twist are not comfortable to use because of reaction torque forces which the operator's wrist muscles must provide.
To be as light in weight as possible most gasoline engine have been in the 20 cc (“small”) to 25 cc (“midsize”) engine capacity. However, with more air thrust blowing power being required, the tendency in recent times is for manufacturers to use an increased capacity engines up to about 30 cc.
However, with the increase in engine size come inevitable drawbacks including extra weight, extra vibration, extra engine noise, and higher fuel consumption.
Most of the gasoline engines are 2 cycle engines, with 4 cycle engines being an overall smaller percentage of the market due to the 4 cycle engines of the same capacity being heavier and more expensive engines because of their extra componentry.
Because these blowers are hand held, it is important for them to be reasonably balanced with the handle situated above the unit and approximately in a centre of balance position. As a result, the blower housing is to one side of the centre of gravity and the engine is to the other side. Normally the blower air exit is substantially co-planar with the plane of the fan (as illustrated in
However, this comes at a loss of air thrust due to the two bends of “S” shaped twist, which is as a comparison, like a “chicane twist” of a car or motor cycle racing circuit where chicane twists are used to reduce the speed of, and slow down, the racing participants.
In order to overcome the loss of air blowing thrust brought about by their chicane, it appears that Husqvarna decided on a larger than usual engine capacity by using a 28 cc 2-cycle engine. As can be seen from comparison Table 1, the air thrust of this Husqvarna 125B model produced only an intermediate air thrust of 1.71 kg even with its large and powerful 28 cc engine. Since the Husqvarna engine rotates in a clockwise direction, its fan blades which are swept forwardly, appear at first glance to be similar to those of
Husqvarna have very recently also introduced a new hand blower model 425BVS without a chicane twist, and which has a 25.4 cc engine. It appears this new model was introduced to achieve a better air thrust output which was comparable with their new smaller engine, but substantially the same prior art fan design has been used.
An existing blower with a powerful air thrust and a quality brand is the Stihl BG86 which has a large 27.2 cc engine made by Stihl. This is a good example of a high output air thrust blower that has the drawback of the blower always trying to twist the operator's wrist due to the off-centre nature of the air output relative to the handle.
To overcome the problem of vibration, only two of these listed major brands have an anti-vibration handle, i.e. a handle that is more or less isolated from the engine (or provides a small reduction in the vibrations felt by the operator). However, such anti-vibration handles have the drawbacks of not only extra cost, but importantly, extra weight.
In order to ameliorate these problems, the present inventors have been able to considerably increase the air blowing thrust, even using the same engines of existing blowers. This then enables the use of the “S” bend (or chicane) to centre the air blowing outlet in line with the handle, and with the ultimate savings of weight, an efficient anti-vibration handle system can be fitted. Thus the complete blower unit of the preferred embodiments is of considerably lighter weight than its competitors but still with very high output of air thrust with no rotational torque applied to the wrist of the operator.
Thus the improved motorized hand held blower of the preferred embodiments is very comfortable to use with virtually no vibration, no twisting of the operator's wrist despite the blower's very powerful air thrust blast, and with relatively low fuel consumption due to the mid-size engine fuel usage. In addition, due to its very powerful air thrust, the blower of the preferred embodiments is used for much shorter blowing operation times. This also reduces the total volume of fuel consumed and the time during which noise is generated.
These advantages arise because of the considerably improved efficiency of air thrust volume generated by the construction of the fan which is a departure from the fans used by other brands.
With experimentation it has been found that the big improvement is the dimensional shape of the fan blade, the angle of the fan blade at the tangent point of the outside diameter of fan disc, the height and number of blades, and the general 3 dimensional operational shape of the blades caused by the distorting centrifugal force applied to the spinning disc.
Because the blower is moved from side to side (sometimes abruptly) the gyroscopic forces acting on the very high RPM fan (usually 6000 to 8000 RPM) can cause problems to the fans and/or fan housing unless the fan is made strong enough.
The fans are made of a circular molded plastics disc with blades present normally only on one side of the disc and extending substantially parallel to the axis about which the fan/disc rotates. The disc can be flat but are mostly are slightly convex with blades on the convex side of the disc.
Usually the molded plastic fan is a one piece unit (without a metal insert centre hub) but sometimes such a centre hub metal insert 133 is added.
The air inlet into the blower housing chamber, which surrounds the fan, has an inlet on the blade side of the disc fan. Generally the air inlet is substantially concentric with the blades/disc.
With fans of the prior art blowers, the radially innermost part of the blades is close to, or at, the centre of the disc. The blades extend radially outwardly towards to the outside diameter of the disc. When looking at the disc face on, i.e. in a plan view, most prior art fans have the blade end extending to the outside diameter of the disc and the radially outward portions of the blades facing in a forward direction relative to the direction of rotation of the fan or disc. That is, the blade ends are swept forwardly relative to the intended direction of rotation of the fan.
Some brands have a blade end (i.e. at the disc outer diameter) that is substantially radial, i.e. at 90° to the OD tangent portion. None of the prior art fans have rearwardly swept blades ends.
All the prior art hand blowers also have a generally low blade height (see Table 1) of less than 29 mm and with a large number of blades, from 9 to 15. This is in contrast to the preferred embodiment of the present invention which has a small number of blades (e.g. 7 to 10) but very tall blades by comparison at approximately 40 mm in height. A further substantial difference is that for the preferred embodiment the blade is rearwardly facing or rearwardly swept. The intentionally rearwardly facing blades, and these blades being fewer in number, did not require as much engine power as forwardly facing blades and therefore the blade height can be increased to maintain the engine loading and also increase the air flow and thrust. Importantly, the tall blades have the ability to change shape under the influence of centrifugal forces when rotating at high speed from being parallel to the fan axis to tilting forward or leaning from the fan axis to form a “scoop”. This scoop further increases the efficiency of the fan, and also results in a reduced vortex, or “drag”, on the trailing side of the blade. The blades can be substantially straight and rearwardly facing (as in
This forward leaning of the blade at speed is due to centrifugal forces and can only occur with rearwardly facing, or swept, blades which experience a radially directed centrifugal force component. Thus the inventors have realized such blades can be designed to have the blades (32,132) intentionally proportionally tilt forwardly.
The disc diameter and/or blade length of the preferred embodiments do not change with the centrifugal force. Also the disc, (and the blades on the one side of the disc), are strong enough to prevent any over distortion and/or destruction from inertial forces. The spinning disc of the fan has a considerable rotational angular momentum. Yet the fan housing and the blower as a whole is able to be moved quickly to and fro in an arc as the operator maneuvers to sweep up debris. So the fan disc must be strong enough to resist the inertial forces it experiences and not strike the fan housing (bearing in mind the small radial distance between the fan outside diameter and the fan housing and also the small distance between the outer edge of the fan blades and the sides of the interior of the fan housing). This disc strength and blade strength is particularly necessary due to the close tolerance required (e.g. between the spinning blades and the air chamber housing). Any touching by the components will produce significant scraping or “drag” which significantly reduces output of the blower and/or melting of the plastic components due to the high heat generated by the frictional forces.
As can be seen in Tables II and III the increase in air thrust of the preferred embodiments is very dramatic. The increase in air thrust was in the order of 60% greater for the 2 cycle Toro blower and 50% greater for 4 cycle Honda blower.
Because of the very efficient air output of the prototypes, savings in weight of the complete blower apparatus were achieved using the same Toro and Honda engines. Furthermore, an efficient 3 point anti-vibration handle system was also fitted to the respective apparatus and notwithstanding the increased weight of the anti-vibration handles, each complete blower apparatus was much lighter than the original Toro and Honda blowers (see Tables II and III).
All four prototypes, both 2 cycle and 4 cycle, and with and without with the chicane, are lighter than all major listed brands as per Tables I and II, except for one brand (Tanaka) with its measured low air thrust output of only 1.53 kg.
Except for the Stihl BG86 and Honda HHB25 blowers, none of the other listed brands have anti-vibration handle systems. If they did, this would further increase the weight of these other listed brands.
Also as a direct comparison, the Stihl BG86 blower has a large 27.2 cc 2 cycle engine which is 8.7% larger in engine capacity with higher engine power, and the Husqvarna 125B blower's 28 cc 2 cycle engine has 11.8% larger engine capacity and higher engine power, when compared, for example, to the inventors' comparative blower with the smaller 25 cc 4 stroke Honda engine that was used.
Similarly, the Stihl BG86 blower has a large 27.2 cc 2 cycle engine which is 7.1% larger in engine capacity with higher engine power, and the Husqvarna 125B blower's 28 cc 2 cycle engine has 10.2% larger engine capacity and higher engine power, when compared, for example, to the Toro engine used in the inventors' 2 cycle 25.4 cc engine.
The foregoing describes only some embodiments of the present invention and modifications, obvious to those skilled in the air blower arts, can be made thereto without departing from the scope of the present invention. For example, if desired, the underside of the disc which is illustrated as having no blades can be provided with smaller additional blades.
The term “comprising” (and its grammatical variations) as used herein is used in the inclusive sense of “including” or “having” and not in the exclusive sense of “consisting only of”.
While the principles of the invention have been described above in connection with preferred embodiments, it is to be clearly understood that this description is made only by way of example and not as a limitation of the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012905252 | Dec 2012 | AU | national |
