FR2721768A1 - Electric hand tool whose protection and safety insulation is made by a plastic material. - Google Patents

Abstract

To manufacture economically and with high quality, a hand-held electric tool equipped with a collector motor supplied with alternating current in particular by the network and which comprises a rotor (10) made of a stack of sheets (12), in particular sheet metal strips carrying notches (13) for housing a coil winding (17), a rotor shaft (11) provided with longitudinal and transverse protection insulation (14) interposed between the shaft (11) and the stack of sheets (12), as well as a service insulation (15) enveloping in particular the coil winding (17) at least in part, in particular in the notches (13), a common insulation of protection and service constituted by a coating of the rotor (10), in particular of the stack of sheets (12) and of the rotor shaft (11), made of a single material, in particular injectable.

Description

"Electric hand tool with protective insulation and

  safety is carried out by a plastic material ".

State of the art.

  The subject of the invention is a hand-held electric tool equipped with a collector motor supplied with alternating current, in particular by the network, and which comprises a rotor made of a stack of sheets, in particular of sheet metal lamellae carrying housing slots. '' a coil winding a rotor shaft provided with longitudinal and transverse protection insulation inserted between the shaft and

  sheet stacking as well as service insulation

  in particular at least partially winding the coil winding of the rotor, in particular in the notches

  Electric tools have been known for a long time.

  hand operated by a collector motor supplied by the network at a voltage of 110 to 230 volts. The motor comprises a rotor in which, between the stack of sheet metal lamellae and the rotor shaft, is mounted an insulation of

  plastic protection. This provides security

  protect the user from dangerous electrocution. The protective insulation is, in Germany,

  defined by standard SEV 1059/1981 which provides resistance

  disruptive breakdown voltage of 5000 volts, for 3 seconds

des, with an intensity of 200 mA.

  Regarding protective insulation

  of hand tools, the requirements for resistance

  are particularly high due to the powerful

  these important to transmit, between 200 and 2000 watts, for speeds reaching 30,000 rpm. In addition, it is necessary to take into account strong vibrations, for example in strikers, and the stress of back and forth in hard material. The resistance to disruptive breakdown must be

  insured during the maximum period of use of the ma-

  China. There should be no cracks or breaks in the insulation. In addition, variations in the surface finish,

  promoting leakage currents are also excluded.

  The rotor of the known hand tool contains a

  service insulation in the stacking notches of the

  sheet metal plates used to receive the winding of the bo-

  bine ,. This service insulation is composed of either

  insulation paper previously folded and deposited around the roll

  tor, or a thin-walled plastic pipe,

  elastic, deposited around the rotor. The insulation must prevent

  expensive between the turns of the coil a short circuit which

  could cause machine failure. The collection

  engine known in hand tools is like

  stacking of sheets, isolated from the rotor shaft by a pro-

  length of the plastic insulating jacket.

  On each of the front faces of the sheet pack is installed a strip of insulating cardboard with a thickness of about 3 mm, serving as protective insulation

and service.

  Furthermore, patent DE-OS 32 43 213 describes a small electric motor as used in motor vehicles. The rotor of this motor, driven by

  a battery, is fitted with plastic insulation

  than arranged between the stack of sheets and the rotor shaft

  as well as in the notches of the sheet metal package.

  A small engine of this kind does not require protective insulation because the voltage of a motor vehicle battery, unlike that of the network,

9/19/1995

  is relatively harmless to humans. In addition, these pe-

  breast motors are smaller and lighter than those

  mented by the network. The mechanical stresses in these

  small motors are generally weak, so the iso-

  lation itself is only subject to low mechanical stresses. Any cracks in the insulation can actually reduce engine power, but they

  pose no danger to the user.

Advantages of the invention.

  The invention relates to a hand-held power tool characterized in that a coating of the rotor in particular of the stack of sheets and of the shaft consists of a single plastic material, in particular injectable and is used for the

  both protective insulation and safety insulation.

  According to other characteristics of the invention

tion:

  - the material is a thermoplastic, in particular a polyoxy-

  methylene reinforced with glass fiber or a polyacetal, - the material is a thermosetting, - the thickness of the plastic layer along the rotor is between 0.1 and 3 mm and the thick layers are continuous and in particular progressive, - the service insulation inside the notches has a thickness of at least 0.1 mm, and the protective insulation has a thickness of at least 1.5 mm, - the rotor weighs at least 300 g , has a diameter of at least

  mm and is intended to rotate at least 10,000 rpm.

  The invention also relates to an engine and a

  rotor characterized in that a coating of the rotor

  killed with a single injectable material, serves both

  protective insulation and service insulation, including

  between the stack of sheets and the rotor shaft.

  The hand tool, as well as the motor and the rotor according to the invention have the advantage that the service insulation and

  protective insulation, made of the same material, can

  wind can be performed in a single operation, so that the stack of sheets is secured to the rotor shaft, securely and with mechanical rigidity. In addition, since the notches in the stacking of sheets do not have their dimensions modified by the thin-walled plastic insulation, their capacity for receiving the windings of the box

  bine is increased. The rotor can therefore be made more com-

  pact. The better filling rate of the notches reinforces the heat transmission between the stacking of sheets and

  winding, which allows better cooling

  smoothing of the engine and therefore better efficiency

  energy with this new engine.

  The monobloc nature of protective insulation

  tion and service, made in particular of polyoxymethylene or polyacetal, (abbreviated as POM), leads to significant

  savings compared to engines used so far.

  This was a surprise mainly because of the differences

  problematic and important references in the thicknesses of

  wall of service insulation and pro-

  tection, in particular in the transition zones, these difficulties entailing, to be reduced during manufacture, high development costs. Until then, it appeared to those skilled in the art too complex and too costly to create protective and service insulation in one piece

of the same material.

  The cost in time, transport and energy

  to manufacture the motors according to the invention is weaker

  ble only according to the process used until then.

  The realization of the protective insulation, by injection around the engine, eliminates the cost of the assembly of cardboard front strips as well as the

  corresponding maintenance and other consequences.

Drawing.

  The accompanying drawing shows an example of a

  Lization of the invention described in more detail below.

  - Figure 1 is a perspective view, par-

  partially in section, of a rotor according to the invention; - Figure 2 is a cross-sectional view of the rotor of Figure 1; - Figure 3 shows, enlarged, a detail of Figure 2; - Figure 4 shows a complete rotor with its winding and the closure of its notches; - Figure 5 is a sectional view of the rotor of

Figure 4.

  Description of the exemplary embodiment.

  The rotor 10 shown in Figure 1 comprises a shaft 11 carrying substantially in its middle a stack of

  sheets 12 consisting of individual lamellae not shown

  tees, having notches 13 serving as housing for a

  coil winding not shown.

  Between the stack of sheets 12 and the shaft of the ro-

  tor 11 is a protective insulation 14 which covers

  vre the front faces of the stack of sheets 12 to descend to the shaft 11 and cover it in the manner of a tube. In addition, this insulation 14, on the two front faces of the stack of sheets 12 rises radially outward to the periphery of this stack, thereby forming a plastic cover 15 with a thickness of 2.5 at 3 mm. The protective insulation 14 between the stack 12 and the shaft 11 has a thickness of approximately 1.5 mm and extends along the front faces of the stack

  up to the inside of the cover 15. From the covers

  keys 15 the insulation extends along the walls of the notches 13 passing generally abruptly in the form of a 0.2 mm thick film constituting the service insulation. Service insulation 16 and protective insulation 14 constitute guarantees against training

  cracks and detachment at the usual speeds of the mo-

  universal speed, 30,000 rpm, as well as

  usual high overheating conditions for universal motors

salts in hand tools.

  On the left side of the protective insulation

  tion with respect to the direction of observation, is fitted, by pressure, a manifold not shown here, but indicated on the

  figure 4. The protective insulation 14 located on the opposite side

  the collector and overflowing on the end faces of the stack of sheets, is designed to receive a wheel

breakdown not shown.

  The section, represented in FIG. 2, of the rotor without winding (as in FIG. 1) shows the shaft 11 of the rotor carrying the protective insulation 14,

  concentric and annular in shape, itself enclosed

  centrally by stacking of sheets 12. The profile of the notch 13 serving as a housing for the coil winding

  not shown, as well as the service insulation 16 covered

  vrant the internal walls of the notches 13, appear clearly. A zone of the stack 12, bearing the reference

  18, is shown individually, enlarged, by the fi-

gure 3.

  In this zone 18 of FIG. 2, enlarged in FIG. 3, the edge of the stack of sheets 12 appears. We clearly see the thin layer of the service insulation 16 ending in a slope along the upper edge of the wall

of the notch 13 of the stack 12.

  Figure 4 is a side view, partly in section, of the rotor 10 comprising a coil winding 17, a collector 19 and a ball bearing 22. We also see the shaft 11, the stack of sheets 12, the notches

  13 receiving the coil winding 17, the pro-

  cover 14 and the plastic cover 15.

  FIG. 5 shows a notch 13 of the rotor 10 of FIG. 4, with the coil winding 17 and

  the shutter 20 in insulating cardboard opposing a displacement

  winding 17 in the notches 13 as well as the penetration of dust, dirt and moisture in the

  notches 13, between the layers of the winding 17.

Claims (8)

R E V E N D I C A T IONS   1) Hand-held electric tool equipped with a collector motor supplied with alternating current, in particular by the network, and which comprises a rotor (10) made of a stack of sheets (12), in particular of sheet metal lamellae carrying enco- ches (13) for housing a coil winding (17), a rotor shaft (11) provided with longitudinal and transverse protective insulation (14) interposed between the shaft (11) and the stack of sheets (12), as well as a service insulation (15) enveloping in particular the coil winding (17) of the rotor (10) at least in part, in particular in the notches (13), characterized in that a coating the rotor (10), in particular the stacking of sheets (12)   and the shaft (11), is made of a single plas-   tick, especially injectable and serves both as insulation   protection and safety insulation.   2) hand tool according to claim 1,   characterized in that the material is a thermoplastic, no-   particularly a glass fiber reinforced polyoxymethylene or a polyacetal.   3) Hand tool according to claim 1, ca-   characterized in that the material is a thermosetting.   4) Hand tool according to claim 1, 2 or 3, characterized in that the thickness of the plastic layer along the rotor (10) is between 0.1 and 3 mm and the   thick layers are without discontinuity and in particular pro- aggressive.   ) Hand tool according to one of claims   1 to 4, characterized in that the service insulation (15) inside the notches (13) has a thickness of at least 0.1 mm, and the protective insulation has a thickness of at least minus 1.5 mm.   6) Hand tool according to one of claims   above, characterized in that the rotor weighs at least 300 g, has a diameter of at least 20 mm and is designed to rotate at least 10,000 rpm.   7) Motor for hand tool according to the preamble of claim 1, characterized in that a coating of the rotor (10) made of a single injectable material, serves as both protective insulation and service insulation , in particular between the stacking of sheets (12) and the shaft (11) of the rotor.   8) Rotor for the hand tool motor according to the preamble of claim 1, characterized in that   coating of the rotor (10) made of a single material   disposable, serves as both protective insulation and service insulation, especially between stacking of sheets (12) and the shaft (11) of the rotor.   9) Rotor according to claim 8, characterized   in that the stack of sheets (12) has its periphery devoid of   view of insulating material, and in particular made of bare metal.