Portable electric blower with low reaction torque

Abstract

A portable blower has an axial fan blower, a handle that has a midpoint of equilibrium, a blowing outlet that is connected downstream of the axial fan, at least one suction nozzle that is connected upstream of the axial fan and has an air intake mouth. The air intake nozzle includes a network of directional channels for homogenizing a flow of intake air, the network of directional channels being formed in the vicinity of the air intake mouth. The blower is particularly useful in the field of portable electric blowers for the maintenance of public spaces.

Claims

1. Portable leaf blower including: an axial blowing fan presenting a fan axis; a handle presenting a midpoint of equilibrium; a blowing outlet connected downstream of the axial fan; at least one intake nozzle connected upstream of the axial fan, the intake nozzle including an air intake mouth with an intake axis forming a non-zero angle with the fan axis, the intake mouth being located upstream of a first plane perpendicular to the fan axis and including the midpoint of equilibrium of the handle, and the air intake mouth being furthermore turned away from a second plane passing through the midpoint of the handle, the second plane being perpendicular to an orthogonal straight line to the fan axis and passing through the midpoint of equilibrium (E) of the handle; and a protective grid of the air intake mouth; characterized in that: the air intake nozzle includes a lattice of directional channels for homogenizing an intake air flow, the lattice of directional channels being fitted in the vicinity of the air intake mouth; the lattice of directional channels presents a lattice axis, and the lattice axis presents a point of intersection with the second plane, the point of intersection being located upstream of the first plane; and the lattice of directional channels is configured to confer to the intake air flow a directional component opposite to the fan.

2. Blower according to claim 1, in which the lattice of directional channels is formed of a single piece with the protective grid.

3. Blower according to claim 1, in which the lattice of directional channels is formed in the vicinity of the protective grid.

4. Blower according to claim 1, in which the lattice of directional channels constitutes the protective grid.

5. Blower according to claim 1, in which the channels of the lattice of directional channels are fitted in a honeycomb pattern.

6. Blower according to claim 1, in which the lattice axis is parallel to the intake axis.

7. Blower according to claim 1, in which the lattice axis forms with the intake axis an angle with a divergent component opposite to the fan.

8. Blower according to claim 1, in which the channels of the lattice of directional channels present an increasing section respectively depending on a distance separating them from the axial fan.

9. Blower according to claim 1, in which the channels of the lattice of directional channels present a decreasing length respectively depending on a distance separating them from the axial fan.

10. Blower according to claim 1, in which the intake axis forms with the fan axis an angle between 30 and 120 degrees.

11. Blower according to claim 10, in which the angle is between 45 and 90 degrees.

12. Blower according to claim 1, further including air deflectors fitted in the vicinity of the intake mouth upstream of the lattice of directional channels.

13. Blower according to claim 1, in which a distance between the intake axis and the midpoint of equilibrium of the handle is greater than a distance between the fan axis and the midpoint of equilibrium of the handle.

14. Blower according to claim 1, in which a distance between the lattice axis and the midpoint of equilibrium of the handle is greater than a distance between the fan axis and the midpoint of the handle.

15. Blower according to claim 1, in which the channels present an average length greater than or equal to twice the minimum thickness of a wall separating adjacent channels.

16. Blower according to claim 1, in which the blowing outlet presents a blowing mouth with a blowing axis forming a non-zero angle with the fan axis, the blowing mouth being turned away from the second plane.

17. Blower according to claim 16 in which the angle between the blowing axis and the fan axis is between 5 and 15 degrees.

18. Blower according to claim 1, including an electric fan drive motor, and a battery for the electric power supply to the motor, the battery being a remote battery.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows a blower of the known type carried by an operator.

(2) FIG. 2 is a section view of a part of a blower according to the invention.

(3) FIG. 3 is a section view at a larger scale of an intake nozzle of a blower according to the invention.

(4) FIG. 4 is a perspective view, seen from downstream, of a lattice of directional channels used in the intake nozzle of FIG. 3.

(5) FIG. 5 is a perspective view, seen from upstream, of a lattice of directional channels used in the intake nozzle of FIG. 3.

(6) FIG. 6 is a cross-section of the lattice of directional channels along a cross-section parallel to the axis of the lattice and the axis of the fan.

(7) FIG. 7 is a detail at a larger scale of the section shown in FIG. 6.

(8) FIG. 8 shows a blower according to the invention with an inflected blower mouth.

(9) FIG. 9 is a view of another pattern of implementation of the lattice of directional channels in which the section of the channels is increasing from the proximal end to the distal end of the lattice.

(10) The various figures are shown in free scale.

DETAILED DESCRIPTION OF IMPLEMENTATIONS OF THE INVENTION

(11) In the description below identical, equivalent or comparable parts of the various figures are identified by the same reference marks in order to facilitate referring from one figure to another.

(12) FIG. 1 shows a blower 10 of the type known, and in particular known through the document FR2964987 previously mentioned to which the invention can be advantageously applied. The blower of FIG. 1 presents a large number of characteristics in common with the blower according to the invention and described in reference to the following figures. One can thus refer to FIG. 1 for the common characteristics.

(13) FIG. 1 shows the blower as it is being carried and operated by an operator in a normal position of use for the sweeping of dry leaves. The operator holds the blower by a handle 12 fitted into the upper part of a main casing 14 of the blower.

(14) The main casing 14 essentially contains an axial blower fan 16 for the purpose of creating an air flow. The blower fan is driven by an electric motor and powered by a battery of electric accumulators 18 carried on the back of the operator. A short power cord 20 connects the battery of accumulators to a receptacle located behind the handle.

(15) In the following description, mention of a center of gravity of the blower and various planes or axes of the blower, does not take into account the battery of accumulators 18 nor the power cord 20.

(16) In front of the main casing 14, i.e. downstream of the blower fan, is mounted a blowing outlet 22 the free end of which forms a blower mouth 24, The blowing outlet is centered on a fan axis 30 of the axial blower fan. This axis forms with the ground a non-zero angle in the normal operating position. An axis of the blower mouth coincides here with the fan axis 30.

(17) In the rear of the main casing 14, i.e. upstream of the blower fan, an intake nozzle 32 is connected for sucking in air and directing it to the blower fan. The free end of the suction pipe presents an intake mouth 34 topped by a protective grid 36. The function of the protective grid 36 is to prevent debris or foreign object from being sucked in. The grid also prevents a hand from getting into the pipe so as to avoid any contact with and injury from the blower fan.

(18) One may notice that the intake nozzle 32 is bent. The intake mouth 34 is turned towards the ground when the blower is used in its normal position as shown in FIG. 1. The intake mouth 34 presents an intake axis 40 which forms a non-zero angle with the fan axis 30. On the figure this angle is close to 90. The intake axis also forms an angle with the ground in the normal operating position. The handle 14 extends in a symmetric plane of the main casing, parallel to the fan axis 30. An axis 15 of the handle 12 is essentially parallel to the ground in the normal operating position of the blower, the blowing outlet being then oriented in a preferential working direction, so as to ensure a natural position of the [operator's] hand.

(19) The handle 12 is furthermore fitted essentially perpendicular to the center of gravity of the blower so as to balance the masses in front of and behind the handle. More precisely, the handle presents a midpoint of equilibrium E, corresponding essentially to the position of the middle finger of the operator's hand as he seizes the handle.

(20) When the blower of FIG. 1 is in operation the air intake through the intake mouth 34 creates a reaction force F.sub.A1 which is applied essentially in parallel to the intake axis and which is turned towards the ground. In a similar fashion the flow of blown air exiting from the outlet 22 and the blowing mouth 24 creates a reaction force F.sub.S which is essentially applied in parallel to the fan axis and which is turned away from the ground. Thanks to the orientation of the intake mouth 34 towards the ground, the reaction forces F.sub.A1 and F.sub.S at the air intake and the air exit create at the midpoint of equilibrium E of the handle 12 torque forces which oppose each other.

(21) The intensity of the reaction force F.sub.S at the blowing end is greater than the reaction force F.sub.A1 at the intake, because of the higher air speed at the exit of the blower. Thus, and in spite of stronger leverage for the reaction force at the intake, the torque resulting from these two forces at the midpoint of equilibrium E of the handle is not zero.

(22) When the blower is not in operation, the center of gravity of the blower is essentially located below and vertical to the midpoint of equilibrium E of the handle. When the blower is in operation, the center of gravity has a tendency to swing in a rotation around the midpoint of equilibrium E towards a new position of equilibrium behind the midpoint. This new position does not necessarily correspond to a desired orientation of the air flow. It therefore requires an effort at the handle and thus at the operator's hand, in order to cancel out the rotation and maintain the blower in the desired direction of air flow.

(23) FIG. 2 shows at a larger scale and in a section view a leaf blower according to the invention. In this figure the blower fan 16 is represented in a summary and symbolic manner so as not to overburden the figure.

(24) One can observe that the intake axis 40 of the intake mouth 34 passes through the middle of the intake mouth and is perpendicular to a mid-plane of the intake mouth. The blower axis of the blowing mouth, not shown, is considered to be one with the fan axis 30.

(25) FIG. 2 also shows the midpoint of equilibrium E of the handle 12, slightly back, Le. upstream of an actuating trigger 13 of the blower.

(26) The travel of air from the intake mouth 34 to the blower fan 16 is not uniform in length. In effect, the travel varies between a minimum length for air sucked in within a proximal zone 34P of the intake mouth to and a maximum length for air sucked in within a distal zone 34D of the intake mouth. The terms proximal and distal are used to signify a distance more or less long up to the entrance of the blowing fan 16. This distance can be considered geometrically relative to the fan axis or linearly by following the curvature of the nozzle 32.

(27) In the absence of a lattice of directional channels, the intake air speed is naturally higher in the proximal zone of the intake mouth than in the distal zone, because of the shorter travel of the air. Thus the forces of reaction at the air intake, or more precisely their resultant F.sub.A1 over the entire surface of the intake mouth does not apply to the center of the intake mouth. It is offset in the direction of the proximal zone 34P of the intake mouth where the speed of the intake air is higher. This results in reduced effective leverage relative to the midpoint of equilibrium E of the handle 12, represented by the distance d.sub.A1.

(28) However, and in accordance with the invention, the air intake mouth 34 receives a lattice of directional channels 42 constituted by the juxtaposition of a large number of channels 44. The lattice is characterized by a lattice axis 50 which is determined both by the mid-plane of the lattice and by the average orientation of the channels 44 of the lattice, keeping in mind that the channels are not necessarily all parallel to each other. The lattice axis 50, considered to be at the center of the lattice, presents, relative to the intake axis 40, a divergent component opposite to the blower fan 16. On FIG. 2, the lattice axis 50 passes essentially through the center of the intake mouth, like the intake axis 40, but is tilted towards the rear above the lattice of directional channels 42.

(29) The lattice of directional channels 42 has a function of homogenizing the intake air speeds over the entire intake mouth 34. It reduces in particular the speed gradient or the disparity of the speeds between the proximal zone 34P and the distal zone 34D of the intake mouth 34. The air in each channel is in effect forced to take at the entrance of the channel a preferential direction in the channel axis. When this is not the direction the air would have taken naturally in the absence of a channel, the air meets a resistance at the channel entrance. Its entrance speed, and thus the volume of air in the channel in question are now reduced relative to those in the same section of the intake mouth in the absence of a channel. The volume of air going through the blower is thus distributed towards the channels presenting less resistance to the entrance of air. This has the effect of increasing the volume of air in the channels of the distal zone, and thus the speed of air in these channels. This results in the reaction forces in the channels of the proximal part being reduced, whereas they are increased in the channels of the distal part.

(30) The resultant of the forces of reaction at the air intake thus finds itself displaced in the direction of the center of the intake mouth. It is indicated by a vector F.sub.A2 on FIG. 2.

(31) Besides homogenizing the air speed, the lattice 42 of directional channels has the effect of orienting an air flow entering parallel to the lattice axis 50. The force of reaction to the intake of air F.sub.A2, thus also has a tendency of aligning itself along the axis 50 of the lattice.

(32) The torque exerted by the force F.sub.A2 at the point of equilibrium E of the handle 12 thus benefits from leverage d.sub.A2 that is superior to the leverage d.sub.A1 which the reaction force F.sub.A1 would have in the absence of the lattice of directional channels.

(33) One can observe on FIG. 2 that the intake mouth 34 is located behind the point of equilibrium E. More exactly, the intake mouth 34 is located upstream of a first plane P1 perpendicular to the fan axis 30 and including the point of equilibrium E of the handle. On FIG. 2 the plane P1, also perpendicular to the plane of the figure, is indicated by a broken line of dots and dashes.

(34) Incidentally, the intake mouth is oriented towards the ground. More precisely, it is turned away from a second plane P2 always passing through the midpoint of equilibrium E of the handle 12 and perpendicular to a straight line orthogonal to the fan axis 30, and passing through the midpoint of equilibrium E. On FIG. 2 this straight line coincides with the tracing indicating plane P1, The second plane P2 is also perpendicular to the plane of FIG. 2. It is indicated as a dot-and-dash-line.

(35) Finally, a point of intersection 60 between the lattice axis 50 and the second plane P2 is situated upstream of the first plane P1.

(36) All these measures make it possible to put to good use the torque created by the force of reaction to the intake F.sub.A2 at the midpoint of equilibrium E of the handle 12, to oppose it to a torque created by the force of reaction to the blowing F.sub.S. In the example of FIG. 2., the force of reaction to blowing F.sub.S is applied at the midpoint of equilibrium E of the handle with a leverage d.sub.S inferior to the leverage d.sub.A2 of the force of reaction to the intake.

(37) When the blower 10 is in operation, the force of reaction to the blowing F.sub.S generates on the handle 12, and in particular in its midpoint of equilibrium E a torque around an axis passing through the point E and constituting the intersection of the planes P1 and P2, i.e. perpendicular to the plane of the figure. The lattice of directional channels allows, in comparison to the blower known as prior art, to significantly improve the counterbalance of the blowing torque and to relieve the counterbalance needed to be exerted by the operator's hand.

(38) FIGS. 4 and 5 show a perspective view of the lattice of channels 42 formed of a single piece with the protective grid 36 of the intake mouth. FIG. 4 is a view of the lattice of channels from the downstream side of the air flow whereas FIG. 5 is a view of the lattice from the upstream side of the air flow.

(39) The protective grid 36 is formed by ribs 70 fitted concentrically to a grid center and radially by connecting to a peripheral edge 72 of the grid. The ribs 70 delimit sectors in which are located the channels 44 of the lattice 42 of directional channels. In the example of FIGS. 4 and 5 the channels are all parallel to each other and present a honeycomb section. The flange 72 of the protective grid is provided with lugs 74 and screw passages 76 for its fastening on the air intake mouth, i.e. at the end of the intake nozzle.

(40) FIGS. 4 and 5 show a general elliptical shape of the protective grid 36 and of the lattice of directional channels 42.

(41) FIG. 3 shows in a section view the fastening of the protective grid 36 and of the lattice of directional channels on the nozzle 32. The flange 72 of the grid comes to bear on a shoulder 80 of the nozzle. A comparable, more or less deep shoulder makes it possible, if necessary, to adjust the depth of the lattice of directional channels 42 in the nozzle 32 downstream of the air intake mouth 34.

(42) The end of the nozzle 32 opposite the intake mouth 34 is provided with a fastening bracket 82 by which the nozzle is attached to the main casing of the blower not shown on FIG. 3.

(43) FIG. 6 is a section view of the protective grid at the intake mouth and of the lattice of directional channels 42. It shows that the lattice of channels 42, forming here the grid of the intake mouth, is not plane. One can thus define a mid-plane M of the intake mouth with an intake axis 40 perpendicular to this plane. FIG. 6 also indicates the lattice axis 50 mentioned previously and forming an average axis relative to the axis of each of the channels. It passes through the middle of the lattice and the protective grid. In the example of FIG. 6, the channels are parallel to each other and aligned on the axis of the lattice 50.

(44) FIG. 9 shows an implementation of the lattice of directional channels integrated into the protective grid in which the section of the channels is increasing from the proximal end to the distal end.

(45) FIGS. 3 and 6 also show air deflectors 86 which extend in the vicinity of the intake mouth. The air deflectors 86 are embodied in the protective grid 36 and situated essentially upstream of the lattice of direction channels 42. The function of the air deflectors is to improve laminar air flow and to reduce the air noise.

(46) FIG. 7 shows, at a larger scale, a detail of the protective grid and the lattice of directional channels 42 at the proximal portion 34P. Small arrows indicate the strands of intake air first directed naturally toward the intake mouth 34, then channeled into the channels 44 and oriented parallel to the axis of the lattice. In the example of FIG. 7 the channels are all parallel. It is however possible to envisage producing a lattice of non-parallel channels.

(47) FIG. 8 shows a blower in accordance with the invention where the blower outlet 22 presents a blower mouth 24 slightly turned away from the second plane P2 mentioned previously. In other words, the blowing mouth 24, at the end of the outlet 22, is slightly bent downward.

(48) The force of reaction to blowing F thus has a tendency to exert itself along a blowing axis 31 which coincides no longer with the fan axis 30 but which forms with this axis a non-zero angle.

(49) This angle is chosen to be sufficiently small to limit its influence on the efficiency of the blowing action.

(50) However, the distance d.sub.S between the blowing axis 31 and the midpoint of equilibrium E is reduced comparatively to this distance taken for a blowing axis identical to the fan axis. The leverage of the force of reaction to the blowing action and the torque it exerts at the point of equilibrium is also reduced.

(51) The slight tilt of the blowing outlet, combined with the use of a lattice of channels such as described previously makes it possible to considerably reduce if not annul the torque at the handle.