Patent Application
20130059508
This application claims priority of French application no. 1157767 filed on Sep. 2, 2011, the entire contents of which is hereby incorporated herein.
This invention relates to the technical field of electric power tools used in the building and construction industries and relates more specifically to long arm sanders.
Long arm sanders are known that include, with reference to
This type of equipment is commonly referred to in the relevant professional circles by the colourful term of “giraffe sander (trademark)” due to the particular shape of the active head accommodating the hinged sanding plate. This type of sander can be used for working on ceilings and on the upper part of walls, up to a height of about 3 metres.
These long arm sanders also comprise a suction pipe (6) for the waste produced by the sanding operation, such as dust for example, said suction pipe (6) passing through the grip arm, a first end leading to the active head (3) and the opposite end being connected to a suction device (7) for collecting the waste.
In the prior art, as shown in
In order to cool the motor (11), the housing (8) comprises in the lower compartment, on either side of the longitudinal cutting plane of the housing (8), a first cooling air scoop (14a) positioned in the air inlet of the motor (11) in order to direct an air flow towards the manifold of the universal motor (11), between the rotor and the stator thereof, and a second air discharge vent (14b) positioned in the air outlet of the motor (11), in proximity to the planetary gearbox (12).
Prior art long arm sanders thus have the drawback of having a bulky motor part.
Furthermore, the motor may well overheat causing permanent damage thereto should the vents for circulating the cooling air of the motor become blocked.
Moreover, the working dust may move inside the motor and cause the rotor or stator of said universal motor to short-circuit. Indeed, the drawback of the motor part of prior art devices is that they allow the intake of air charged with abrasive dust or conductive dust which may well burn the rotor either by short-circuiting the blades of the manifold or by abrasion of the copper coil of said rotor.
Portable electric power tools are also known, such as a portable electric sander, for example, shown diagrammatically in
This type of electric power tool has the same drawbacks as prior art long arm sanders. This type of prior art tool has the drawback in particular of comprising a universal motor which has low efficiency, under 40%, is particularly noisy, the noise generated by the motor being about 90 db, gets very hot with a risk of insufficient cooling, and has a significant pressure loss, has life expectancy of about 3,000 hours, i.e. the wear time of the motor brushes.
One of the purposes of the invention is therefore to overcome these drawbacks by proposing in particular a long arm sander of straightforward and inexpensive design that has a motor part that does not take up much space and that prevents any risk of the motor being damaged by overheating.
To this end, and in accordance with the invention, a device is proposed of the type that includes at least one motor part comprising a housing in which an electric motor is positioned suitable for driving an active head part accommodating a tool such as a tool for grinding, sanding or the like, and a suction pipe intended to be connected to a suction device; said long arm sander is remarkable in that the suction pipe leads to the housing of the motor part and in that the motor comprises a so-called sealed high-frequency electric motor positioned in the central part of said housing in such a way that the sucked-in air circulates around the body of the motor.
It will be understood that, unlike prior art long arm sanders in which the motor cooling system is independent, the motor is cooled by circulation of the air of the waste suction system. Thus, the motor is cooled as soon as the sander is turned on by the air flow sucked in at the sander head, preventing any risk of overheating. The rate of airflow of the suction system cooling the motor is very much greater than the airflow needed to cool said motor.
Furthermore, the central positioning of the motor in the housing and the absence of an independent system for cooling the motor means that the space requirement of the motor part is considerably reduced.
Moreover, a high-frequency electric motor of this kind has the advantage of being particularly silent, having no pressure loss, having efficiency in excess of 70% and having long life expectancy, upwards of 12,000 operating hours, unlike the electric motors of prior art devices.
According to one particularly advantageous feature, said inventive device comprises means for guiding the sucked-in air around the body of the motor. These guide means increase the time the sucked-in air is in contact with the body of the motor in order to cool said motor sufficiently.
Preferably, said guide means comprise at least one fin whereof the longitudinal axis is merged with the longitudinal axis of the body of the motor.
In one implementation alternative, said guide means comprise a plurality of longitudinal fins extending perpendicularly to the longitudinal axis of the housing from the body of the electric motor to the inner wall of the housing.
Other advantages and characteristics will become clearer from the following description of a single implementation alternative of the inventive long arm sander, given as a non-restrictive example, with reference to the appended drawings wherein:
In the interests of clarity, in the remainder of the description, the same elements have been denoted using the same reference numbers in the various figures. Moreover, the various cross-section views are not drawn to scale.
The long arm sander according to the invention comprises in the same way as prior art sanders, as shown in
Said long arm sander also comprises a suction pipe (6) for the waste produced by the sanding operation, such as dust for example, said suction pipe (6) passing through the grip arm, a first end leading to the active head (3) and the opposite end being connected to a suction device (7) for collecting the waste.
Moreover, the motor part (2) consists of a housing (8) rigidly connected to the grip arm (1) wherein there extends the suction pipe (6) and a motor (11), commonly a so-called high-frequency electric motor. The output shaft of the motor (11) is connected to a planetary gearbox (12) whereof the output shaft is connected to a flexible drive (13) connected to the active head part (4).
According to the invention, with reference to
It will be noted that the suction device (7) comprises to advantage a known automatic start-up system so that, when the high-frequency motor (11) is turned on, the suction device (7) is automatically activated and the suction flow cools the motor (11).
The motor (11) comprises a so-called sealed high-frequency electric motor, i.e. a motor which has, in particular, an airtight body. Alternatively, the electric motor (11) and the planetary gearbox (12) may be placed in a sealed enclosure without departing from the framework of the invention.
It will be seen that said electric motor has the advantage of being particularly silent, having no pressure loss, having efficiency in excess of 70% and having long life expectancy, upwards of 12,000 operating hours.
To increase the time the sucked-in air is in contact with the body of the motor and to cool said motor sufficiently even in the event of a low suction flow rate, the inventive long arm sander comprises means for guiding the sucked-in air around and along the body of the motor (11). These guide means comprise a fin (16) whereof the longitudinal axis is merged with the longitudinal axis of the body of the motor (11).
It goes without saying that the inventive long arm sander may include one or more concentric fins (16) that may or may not have the same pitch, without departing from the framework of the invention.
In this particular embodiment example, the fin (16) is helical in shape with the pitch thereof being substantially equal to a third of the length of the housing (8).
Preferably, the fin (16) extends from the body of the motor (11) which is cylindrical in shape to the inner wall of the housing (8) which is also substantially cylindrical in shape.
It goes without saying that the housing (8) may have a transverse cross-section of any shape such as an oblong, polygonal or cylindrical shape without departing from the framework of the invention.
In this particular embodiment example, the housing (8) consists of two substantially hemi-cylindrical parts assembled by any appropriate means, such as screws for example, and the helical fin (16) is rigidly connected to the inner wall of said housing (8), the fin and the housing being obtained all in one piece by moulding for example.
With reference to
The motor (11) is positioned in the central part of said housing (8) in such a way that the sucked-in air circulates around the body of the motor (11), the space formed between the motor and the inner wall of the housing (8) forms a suction pipe (6) whereof one end leads to the active part (3) and whereof the other end is connected to the suction device (7). Thus, as previously, the motor (11) is cooled by circulation of the air of the waste suction system.
Preferably, with reference to
It goes without saying that the guide means may comprise any number of fins without departing from the framework of the invention.
Lastly, it is quite obvious that the invention may be applied to any electric power tool, whether or not it is portable, and that the examples that have just been given are only particular illustrations, and are under no circumstances restrictive in terms of the fields in which the invention may be applied.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1157767 | Sep 2011 | FR | national |
