JPS5821501B2 - Dendoukisouchiyoukiriyuusorase Bankouzoutai - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electrically actuated devices such as portable power tools, and more particularly to an improved motor housing and fan baffle structure and method of sealing the same.

BACKGROUND OF THE INVENTION Research is continually being conducted to provide improved insulation that protects users of electrically powered equipment, such as power tools, from electrical shock.

Conventionally, a fan is mounted on the armature shaft of the electric motor, which pulls and pushes air through the holes in the tool housing.

See, for example, US Pat. No. 3,432,703.

It is customary in such devices to provide a deflection device in order to direct the air to the part to be cooled, ie through the armature and over the bearings of the armature shaft.

When molding baffles from plastic, for example, peripheral raised or feathered edges often remain after the molding process.

Normally, this edge is trimmed after molding, but this process is time consuming and labor intensive, adding to the cost of the product.

In the case of the use of these electric devices, the commutator brushes, which are generally made of graphite, wear out and their fine powder (which is a conductor of electricity)
is carried into the motor housing by cold homogenized air.

It has been observed that this graphite, if left unchecked, would form a path for electrical current, for example from the field coil to the tool front metal housing or to the air holes in the tool housing.

Furthermore, if the baffle plate periphery is not maintained at critical design dimensions, there is a possibility of air leakage between the baffle plate edge and the housing portion adjacent thereto in which a seal is to be formed.

Therefore, the cooling air is not completely circulated and is short-circuited, resulting in inefficient cooling of the motor.

The main object of the present invention is to use a fan to pass cool and equalized air and to prevent incomplete circulation of the air and to prevent the passage of current from the graphite composition to the field coil at the periphery. It is an object of the present invention to provide an electrically actuated device, such as a portable power tool, having an improved baffle plate that is certified to be sealed.

In accordance with the present invention, a sealed baffle and housing structure is achieved with cost savings and results in a reliable and efficient product.

These objects and effects will become clear from the description of the embodiments with reference to the following drawings.

In FIG. 1, a portable power tool, such as an awl 10, has a housing contained in a plastic molded field case 12, which has a rear cover, a bundle 14, and a front gear case 20, which includes bolts. It is fixed at 18.

The electric motor 17 is supported in the field case 12 and has an output armature shaft 36 which is drivingly connected to the output spindle 24 via a transmission 22 in the gear case.

The bundle 14 is operated by a trigger 31 and connected to a power source (not shown) via a cord 33 and further connected to an electric motor 1.
7 includes a trigger control switch 30 adapted to be coupled to a field coil 32 and an armature 34 forming part of the motor.

The armature 34 includes a commutator 35 with graphite brushes 37
are pressed together by a spring (only one shown).

The brush 37 wears out due to frictional engagement with the rotating commutator 35 and must be replaced from time to time.

The armature shaft 36 has a cylindrical insulator 38 that separates it from the armature windings.

The shaft 36 is journaled in a rear bearing supported in the field case 12 and a bearing 42 supported in the metal gear case 20.

The shaft 36 has a fan 44 formed with a boss 46 to draw cooling atmosphere through the inlet hole 26 and flow it over the bearing 40 via the commutator 35 and brushes 37 to the armature 34 and the field. It is made to flow between the magnetic coil 32 and the magnetic coil 32.

This cooling air is supplied to the case 12 in the radial direction by a fan 44.
It is discharged from the discharge hole 28 of.

Between the fan 44, the field coil 32, and the armature 34 there is a deflection plate 48, which according to the invention is fitted together with the field case 12; Fixed by

The baffle plate 48 fits without any gap into a part of the hole defined by the inner wall 45 of the case 12 and the web 47 integrally formed with the case 12.

The baffle plate 48 has a generally planar surface 49 with a central opening 50 surrounded around the boss 46 of the fan 44 .

The baffle plate has a pair of protruding supports 59 and 60 which engage gear case 20 to hold the baffle plate in place.

The deflector plate directs the cooling air to the electric motor 1 as shown in Figure 1.
7 from right to left and serves to direct the flow through the opening 50 toward the fan shaft.

After passing through the baffle plate 48, the cooling air is discharged radially from the discharge holes 28 by the fan 44.

If the fit between the edge of the baffle plate 48 and the inner surface of the field case is incomplete, some of the cooling air drawn by the fan 44 from the case 12 will flow between the baffle plate 48 and the case 1.
It can flow between the two.

As mentioned above, the brushes 37 wear out due to use of the electric motor 17 and emit graphite particles.

These particulates are picked up and carried by the cooling air flow through the case 12.

Since the graphite particles are heavier than the cooling air, some particles are deposited along the inner surface of the case 12.

The baffle plate acts as a barrier to these graphite particles and prevents them from entering the discharge hole 28 and/or the metal gear case 2.
This prevents the formation of a conductive path to zero.

In order to ensure a good seal between the baffle plate 48 and the surrounding field case 12, and to reduce the possibility of air leakage therebetween, the baffle plate 48 is constructed in a novel manner and integrated with the case. cooperate.

The baffle plate 48 according to the present invention is made from a plastic material, such as polypropylene, molded in the shape of a mold (not shown), generally to the internal shape of the field case 12.

Typically, this forming process results in a baffle plate 48 with a shape that is within dimensional tolerance limits.

If the molded baffle plate 48 is
It is formed with a peripheral projection indicated at 6, which occurs at the parting line of the mold.

In such cases, this protrusion 56 is typically cut away from the baffle after the baffle is molded and prior to assembly with the field case.

In the case of a pond, the baffle plate 48 may be formed with few protrusions.

However, in both cases extra costs (special steps or expensive molding operations) are required, increasing product costs.

The baffle plate 48 according to the present invention is molded with a protrusion 56 that is left in place and not cut away.

When the baffle plate 48 is then properly assembled within the field case 12, the slightly deformable projections 56 flex to bite into the inner surface of the case 12 into sealing engagement therewith.

Thus, an effective seal is provided at the junction between the peripheral edge of the baffle plate 48 and the inner surface of the field case 12 to prevent graphite particles from forming a conductive path to the device conductor portion, and furthermore, This is accomplished at a cost saving since there is no need to cut out the peripheral protrusion 56 as in the prior art.

Additionally, the effective sealing between baffle plate 48 and field case 12 increases the cooling efficiency of fan 44, which efficiency aids in the longevity of the device.

In summary, this description describes the provision of a fan baffle within the housing of an electrically actuated device, such as a moving crab, to direct cooling air into the housing, the baffle including intentional protrusions around its periphery, thereby This improves the sealing with the housing and this proves to stop the formation of conductive paths from the field coil by the graphite carried in the cooling air.

It should be understood that what has been described above is one selected embodiment of the invention and that various changes and modifications may be made without departing from the spirit of the invention.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of an electric tool to which the present invention is applied, Fig. 2 is a sectional view taken along line 2-2 in Fig. 1, and Fig. 3 is a sectional view taken along line 3-3 in Fig. 2. Figure 4 is a rear view of the deflector plate,
FIG. 5 is a side view, and FIG. 6 is an enlarged partial view of the portion indicated by arrow 6 in FIG. 12... Field case, 17... Electric motor, 32... Field coil, 34... Armature, 35... Commutator , 36... Armature shaft, 37... Brush, 44... Fan, 48... Deflector plate.

Claims (1)

[Claims] 1. A divided housing including an inlet hole and a discharge hole through which air passes, an electric motor therein, a spindle drivingly connected to the armature shaft of the electric motor, and a housing attached to and driven by the spindle. A tool, a commutator mounted on the armature shaft, a commutator brush mounted in contact with the commutator, and a motor driven by the electric motor to supply cooling air into the housing through the inlet hole and the discharge hole. In a power tool having a fan operable to move and a baffle plate between the holes extending transversely to the housing and sealed peripherally to a corresponding portion of the housing, the baffle plate typically including a thin flexible peripheral protrusion extending beyond the plate and engaging a corresponding portion of the housing, the protrusion being configured to prevent air flow around the periphery of the baffle plate and to prevent air flow at the baffle plate in the housing. A power tool characterized in that it deformably and sealingly engages a corresponding portion of the housing to prevent migration of graphite particles beyond one side of the plate.