DE8717755U1 - Linear drive unit - Google Patents

Description

-1-Linear drive unit

Description

The invention relates to a linear drive unit according to the preamble of claim 1.

A linear drive unit of this type is known from GB-PS 636 171.

The invention is based on the object of creating a generic air drive unit that is particularly easy to assemble.

To achieve this object, the linear drive unit is designed according to the invention as specified in the characterizing part of claim 1.

It is known from DE-GM 87 09 223 to screw end wall parts of a linear drive unit to internal components of the linear drive unit using axially running bolts. However, this does not teach the idea of holding the entire linear drive unit together using bolts that extend over the entire length of the housing and are screwed centrally to a retaining ring or motor retaining ring that is itself fixed in the housing.

\ The retaining ring is a particularly important component

the linear drive unit. On the one hand, with its internally toothed area, it is a component of the planetary gear. By means of the radial fixing bolt or bolts, it is fixed in the housing in terms of torque, but also in the axial direction, so that the reaction torque of the planetary gear is diverted into the housing via a short path. The bolts that lead from the first end wall part to the retaining ring or through it can also serve to prevent the output rod from rotating by means of the radial arms. The retaining ring also serves to support the threaded spindle radially, preferably also axially, and can therefore also absorb the axial tensile and compressive forces of the output rod. Due to the claimed construction, practically the entire "inner workings" of the linear drive unit, i.e. essentially the electric motor, if necessary the motor mounting ring, the planetary gear, the mounting ring, the nut-threaded spindle drive, the output rod, the anti-twist device of the output rod and the preferably provided limit switches together with their settings, can initially be completely pre-assembled, with all 3 components being easily accessible from the outside. This pre-assembled internal unit can then be pushed into the housing and secured in it by means of the radial fixing bolt(s) and the screw connection with the first end wall part. Finally, the second end wall part can be screwed onto the other axial end of the housing. The advantages of easy assembly have a correspondingly favorable effect when the linear drive unit has to be dismantled for any maintenance or repair work. The inventive

The advantages are particularly evident in small linear drive units with limited space.

Preferred embodiments of the invention are specified in the dependent claims. Their subject matter is made even clearer by the exemplary embodiment described below. Some aspects are then discussed in more detail.

The injection of a plastic thread into the output rod makes the manufacture of these costly components particularly efficient, since machining is not required. The measure according to claim 3 is along the same lines. If the output rod is made from a polygonal tube, the traveling nut, which is preferably injected from plastic, is anchored in the output rod in a torque-resistant manner; in addition, in this case the output rod could be secured against rotation by means of a complementary, non-circular through-opening in the end wall part and, if desired, the radial arms could be replaced by this.

Regarding claim 6, it should be noted that due to the inventive design of the linear drive unit, there is plenty of space for the limit switch(es) with their adjustment devices.

Regarding claim 8, it should be noted that the fixing bolt(s) can protrude radially beyond the housing and can be used as connection points for connecting or fastening the linear drive unit to a suitable base. This can be a pivoting fastening, which is not possible with round fixing bolts.

zen is particularly elegant. Alternatively, it is possible to attach the housing to the mounting base in some other way, for example by means of a mounting collar or by means of a connection eye on the second end wall section.

The housing is preferably at least substantially cylindrical. The end wall parts, the motor mounting ring and the retaining ring are also preferably round parts, but this is by no means mandatory.

The invention and further development of the invention are explained in more detail below using an exemplary embodiment shown in the drawing. It shows:

Fig. 1 is an axial longitudinal section of a linear drive unit, with some parts rotated about the longitudinal axis of the linear drive unit for clarity.

Fig. 2 on a larger scale, an axial longitudinal section of a retaining ring in a cutting plane perpendicular to the cutting plane of Figure 1;

Fig. 3, on a larger scale, a cross-section along HI-III in Figure 1;

Fig. 4, on a larger scale a cross-section along IV-IV in Figure 1;

Fig. 5 on a larger scale, an axial longitudinal section in the section plane of Figure 2 of a part of the linear drive unit with modified limit switch arrangement.

The linear drive unit 2 essentially consists of a cylindrical housing 4, which is closed on the right in Figure 1 by a first end wall part 6 and on the left in Figure 1 by a second end wall part 8, in which are arranged in succession in Figure 1 from left to right an electric motor 10, a motor mounting ring 12, a planetary gear 14, a mounting ring 16, a nut-threaded spindle drive 18 and two limit switches 20, 22 together with adjustment mechanism 24, as well as

an output rod 26, which is partly located inside the housing 4 and partly protrudes outwards to the right through the first end wall part 6. In addition, various bolts and arms on the nut of the nut-threaded spindle drive 18 are essential, which are described in more detail below.

A permanent magnet motor is screwed axially to the motor mounting ring 12 with its right-hand end face in Figure 1. A pinion 30 is attached to its shaft 28 in a rotationally fixed manner. The pinion 30 meshes as a sun gear with a series of circumferentially distributed planetary gears 32. These planetary gears 32 of a first planetary stage are mounted on a planetary gear carrier 3 and mesh externally with a ring gear toothing. The planetary gear carrier 34 merges on the right in Figure 1 into a pinion area as a sun gear for a second planetary stage, which is otherwise constructed like the first planetary stage. A third planetary stage follows in a similar manner, with the third planetary gear carrier 38 being designed as a flange part of the threaded spindle 40 welded to the left end in Figure 1. The parts just described together form the three-stage planetary gear 14, whereby planetary gears with fewer or more stages are also possible.

The described ring gear toothing 36 is formed on the retaining ring 16, for example on the inside of a hollow cylindrical extension of the retaining ring 16 that projects axially to the left in Figure 1.

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To the right of the flange part 38, an annular collar 42 is attached to the threaded spindle 40 by means of radial grub screws. The flange part 38 and the collar 42 abut each other radially inward in the axial direction and, further outward, take up the radially innermost area of the retaining ring 16 between them, with an axial roller bearing 44 or 46 being interposed in each case. The area between the axial bearings 44, 46 serves for the radial sliding bearing of the flange part 38 and the collar 42 and thus of the threaded spindle 40, whereby a sliding or roller bearing (not shown) can be provided there.

From the collar 42, the threaded spindle 40 in Figure 1 leads to the right into the area of the first end wall part 6, whereby the threaded spindle 40 is approximately half as long as the housing 4.

The output rod 26 is hollow, with the exception of the connection eye 48 attached to its free, outer end, and has a round, square or other polygonal cross-section. In the left end area of the output rod 26 in Figure 1, a plastic nut 50 is injected, with radial extensions 52 leading through corresponding radial holes in the output rod 26 in order to fix the part 50 more securely in the output rod 26. In Figure 1, the part 50 protrudes to the left beyond the end of the output rod 26 and there merges into three radial arms 54, which are most clearly visible in Figure 4. The output rod 26 leads through an opening 56 in the first end wall part 6, which is shaped to complement the external cross-sectional shape of the output rod 26.

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First bolts 58 lead through corresponding axial holes from the motor mounting ring 12 through the mounting ring 16 to the first end wall part 6, whereby three bolts 58 are provided distributed around the circumference. Second bolts 60 lead through corresponding axial holes from the second end wall part 8 to the motor mounting ring 12, where they are screwed in. In total, three bolts 60 are provided distributed around the circumference, which are arranged circumferentially "on a gap" relative to the first bolts 58. The first bolts 58 either have their heads to the left of the motor mounting ring 12 and are screwed into threaded parts 62 of the first end wall part 6; or they have their heads to the right in Figure 1 and are screwed into the motor mounting ring 12. It is also alternatively possible to have the first bolts 58 only run from the mounting ring to the first end wall part 6 and to have the bolts 60 run through an engine mounting ring 12 to the mounting ring 16. It is also possible to work with stud bolts without enlarged heads.

The three arms 54 each have a bore 64 in their end area, through which one of the first bolts 58 passes. The arms 54 extend radially all the way to the inner circumference of the housing 4 or to just before the inner circumference of the housing 4. The bores 64 can be provided with clearance to the first bolts 58 or without such clearance. The arms 54 of the nut 50 support the left end of the output rod 26 in Figure 1 by means of their axially displaceable contact with the inner circumference of the housing 4 and/or by means of the engagement of their bores 64 with the first bolts 58 in the radial direction. The engagement of the bores 64 of the arms 54 with the first

Bolt 58 and/or the engagement between the non-circular outer contour of the output rod 26 with the complementary opening 56 of the first end wall part 6.

Instead of holes 64 in the arms 54, radial slots open on the outside can be provided, the first bolts 58 have a smooth shaft, but could also be bolts 58 with a continuous thread or correspondingly long screws, particularly if there is play between the respective hole 64 or the respective radial slot and the bolt 58.

Furthermore, two limit switch spindles 66, 68 can be seen, which extend in the axial direction between the retaining ring 16 and the first end wall part 6. The limit switch spindles 66, 68 are accessible through axial holes in the first end wall part 6 and can be rotated, for example, with a screwdriver in order to position the limit switches 20, 22 in the axial direction and thereby adjust them. The two adjustment spindles 66, 68 are spaced apart from one another in the circumferential direction, as can be seen in Figures 3 and 4. One limit switch 20 is in threaded engagement with one adjustment spindle 66, while the other adjustment spindle 68 passes through a through hole 70 of one limit switch 20. The other limit switch 22 is in threaded engagement with the other adjustment spindle 68, while one adjustment spindle 66 passes through a through hole. In this way, the limit switches 20, 22 are secured against rotation around the respective threaded adjustment spindle and can be adjusted independently of one another. A projection 72 formed in one piece extends between two of the arms 54 and supports the two limit switches

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20, 22 are actuated, namely the limit switch 20 when the output rod 26 moves in the pulling direction and the limit switch . 22 when the output rod 26 moves in the pushing direction.

It should be noted that the arms 54 and the projection 72 do not have to be molded in one piece with the nut 50. Alternatively, it is possible, for example, to mold the arms 54 and the projection 72 onto the outside of the output rod 26 or to attach a suitably designed metal or plastic part there. The nut 50 does not have to be molded either. Alternatively, it is possible to attach a separate nut made of plastic or metal to the output rod 26.

The injection of the nut 50 into a non-circular inner cross-sectional space of the output rod 26 has the advantage that this provides a, possibly additional, anchoring of the nut 50 against twisting in the output rod 26 because the plastic extends into the corners of the inner cross-sectional shape of the output rod 26.

In Figure 2, two hollow fastening bolts 74 can be seen, which are screwed radially from the outside through corresponding radial holes 76 in the housing 4 into the retaining ring 16. The fastening bolts ensure an axial and torsion-proof fixation of the retaining ring in the housing 4 with a very high load capacity. This is an optimal place for introducing the loads from the internal unit of the linear drive unit 2 described at the beginning into its housing 4, because the retaining ring absorbs the reaction torques of the planetary gear and also supports the left end area of the threaded spindle radially and axially in Figure 1. The fastening*-

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bolts 74 can essentially be flush with the outer circumference of the housing 4. However, they can also protrude a suitable distance beyond the outer circumference of the housing 4 and thereby form connection areas for the connection or fastening of the linear drive unit 2 to a suitable base. The fastening bolts 74 can also be solid. The motor retaining ring 12 and/or the retaining ring 16 can be made of plastic or, especially for higher loads, of metal.

The extremely simple and convenient assembly of the linear drive unit 2 is carried out as follows. The retaining ring 16 is pushed onto the threaded spindle 40, to one end of which the flange part 38 has been welded, in the direction from right to left in Figure 1, with the axial bearing 44 in between. The collar 42 is then pushed onto the threaded spindle 40 in the direction from right to left in Figure 1, with the axial bearing 46 in between, and fastened. The nut 50 with the arms 54 and the output rod 26 is then screwed onto the threaded spindle 40 from the right. Now the parts of the planetary gear 14 are mounted from the left, so that the planetary gears 32 of the planetary stages are in engagement with the ring gear teeth on the retaining ring 16. Then the electric motor 10, which is screwed to the motor holder ring 12, is placed from the left so that its pinion 30 engages the planetary gears 32 of the first planetary stage. Now the first three bolts 58 are guided through the corresponding axial holes in the motor holder ring 12, in the mounting ring 16 and in the arms 54. This is followed by inserting the two adjusting spindles 66, 68 from the right through the end

switches 20 and 22 in blind holes 78 of the retaining ring 16. The first bolts 58 are then loosely screwed into the threaded parts 62 on the first end wall part 6, but without being tightened. In this state, the necessary electrical wiring to the limit switches 20, 22 and to the electric motor 10 can be easily completed because the entire internal unit described so far is still completely freely accessible from the outside. The housing 4 is then pushed over from the left. The fastening bolts 74 are now screwed into the retaining ring 16 from the outside. Only now are the first bolts 58 tightened, whereby the first end wall part 6 is pulled axially against the housing 4 and the motor retaining ring 12 is pulled axially against the retaining ring 16. The connecting cables can now be easily pulled through a cable gland 80 on the second end wall part 8. Then the second front wall part 8 is screwed to the motor retaining ring 12, thereby closing the housing 4 on the left front side.

The first end wall part 6 can be provided with a nose at a peripheral point that engages axially or radially in a corresponding recess at the end of the housing 4 in order to additionally fix the first end wall part 6 in a form-fitting manner against rotation. In the case of the second end wall part 8, such a measure is generally not necessary because the connection between the second end wall part 8 and the housing 4 is only subject to minor loads. However, the situation is different if a connection eye is attached to the housing 4 in that area.

It is understood that the retaining ring 16 and the motor retaining ring 12 have suitable openings for the passage of the cables leading to the limit switches 20, 22. Such a cable guide space is designated by 82 in the left area of the retaining ring 16 in Figure 1.

The linear drive unit 2 can easily accommodate so-called NOiTauiOtOi'en, Å&khgr;&Ggr;&igr;&agr;&udigr;&thgr;5&udigr;&eegr;&aacgr;&ogr;&idigr;&Ggr;6 GleichetXOiii—FeiTTTiänent— motors, since they can simply be flanged onto the motor support ring.

The assembly-friendly design leads to a considerable time saving when assembling the linear drive unit. 2. The assembly time is a considerable cost factor for such linear drive units.

It should be noted that the motor retaining ring 12 and the holding ring 16 do not necessarily have to abut one another directly axially. Rather, one or more intermediate parts can be present there. Such an intermediate part can serve as a ring gear for some of the stages of the planetary gear 14 with internal teeth. In particular, for the last stage of the planetary gear 14, which is subject to the highest torque, the holding ring 16 itself should serve as a ring gear.

It is also pointed out that the housing 4 can be designed to be axially divided. This makes the assembly of the linear drive unit 2 even easier. It is particularly recommended if an AC motor is used as the electric motor 10, since suitable AC motors can be fitted directly into the interior of the housing 4 or can be fitted with their motor

housing can form part of the housing 4. Designs of the linear drive unit 2 are possible in which a motor retaining ring with the specific, described function is missing and instead a different type of fixing of the electric motor 10 in the housing 4 is provided. The described advantageous effects of the invention are retained here. The first bolts 58 extend m -i r*Y\ �Lgr;λr;-&tgr;�mgr;λr;irrw&i-inaiiia -i ac \rr\n Ham HaH*önmffcrinrt &Iacgr;&Agr; ^iii rfom

first end wall part 6 and the second bolts 60 preferably from the second end wall part 8 to the retaining ring 16, whereby the two axial housing parts are held together if necessary.

Figure 5 shows a modified limit switch arrangement. Instead of the projection 72 or to this projection 72, a limit switch actuating part 84 is screwed onto the part 50, which ends in each axial direction as a plate-shaped part bevelled on both sides at a distance from the longitudinal center axis of the linear drive unit 2. The limit switches 20 and 22 are designed and arranged in this modification so that they are actuated with an actuating direction running transversely to the longitudinal axis of the linear drive unit 2, namely in each case by a bevel 86 or 88 of the limit switch actuating part 84. A safety limit switch 90 is positioned a few centimeters away in the axial direction behind the normal limit switch 20 or 22. The respective safety limit switch is combined with the associated normal limit switch 20 or 22 in such a way that it is set together with the latter by the associated setting spindle 66 or 68, whereby the axial distance between the normal limit switch and the safety limit switch remains *.-hold. The respective safety limit switch 90

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is actuated by a bevel 92 or 94 of the limit switch actuating part 84, which is opposite the bevel 86 or 88 for actuating the associated normal limit switch 20 or 22.

In Figure 5, only one pair of normal limit switch 20 and safety limit switch 90 is shown, namely the pair intended for switching off in the pulling direction of the output rod 26, while the pair intended for switching off the output rod 26 in the pushing direction is not shown for reasons of clarity.

Such provision of safety limit switches 90 is particularly preferred if an AC motor is provided as the electric motor 10. In the case of an AC motor, a contactor control is usually provided separately for both directions of rotation. If the AC motor is connected incorrectly during assembly of the linear drive unit 2 due to a cable mix-up, the limit switch 20 is actuated, for example, when the output rod 2 6 is moved in the pulling direction, but this switches the contactor responsible for the pushing direction instead of the contactor responsible for the pulling direction. The result would be considerable damage or even destruction of the linear drive unit. In the modified linear drive unit 2 according to Figure 5, however, shortly after the normal limit switch 20 is passed, the safety limit switch 90 is actuated, which completely separates the control phase of the AC motor and therefore safely stops the AC motor even if it is connected incorrectly. The same applies to the process in the pressure direction and the safety limit switch there, which is assigned to the normal limit switch 22.

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In addition, an undesirable long run-on of the AC motor is prevented by activating the safety limit switch 90.

Claims (11)

KUUNKERSCHMITT-NILSaS.MSCU. "l : !.!"I5..: u.Z.: K 33 729 S/8tö 23 Oct. 1989 Claims 1. Linear drive unit (2) with - a housing (4) ; - an electric motor (10); - a planetary gear (14) connected to the electric motor (10); - a nut/threaded spindle drive (18) connected to the planetary gear (14) with an output rod (26) secured against twisting, which converts rotational movement into linear movement; - a retaining ring (16) which has an internally toothed area serving as a hollow wheel of the planetary gear (14) and which supports the threaded spindle (40) of the nut-threaded spindle drive (18) on the gear side; - at least one radial locking pin (74) which is inserted into the retaining ring (16) from the outside through a bore (76) in the housing (4); - a removable first end wall part (6) through which the output rod (26) passes; and - a removable second front wall part (8) at the opposite housing end, characterized, that the first end wall part (6) is screwed to the retaining ring (16) or a motor retaining ring (12) by means of circumferentially distributed first bolts (58) which extend along the nut threaded spindle drive (18), t· »tr· · Ii «· ,**, 1 " lit··· e«f &igr;&igr; _·»*·· « which is arranged between the retaining ring (16) and the second end wall part (8); and that the second end wall part (8) is screwed to the retaining ring (16) or the motor retaining ring (12) by means of circumferentially distributed, axially extending second bolts (60). 2. Linear drive unit according to claim 1, characterized in that the nut (50) of the nut-threaded spindle drive (18) and/or the drive rod (26) is provided with radial arms (54) through which the first bolts (58) pass. 3. Linear drive unit according to claim 2, characterized in that that the radial arms (54) made of plastic are injection-molded onto the output rod (26). 4. Linear drive unit according to one of claims 1 to 3, characterized, that the output rod (26) is constructed with a square tube. 5. Linear drive unit according to one of claims 1 to 4, characterized in that a plastic thread is injected into the output rod (26), which is also the traveling nut of the nut-threaded spindle drive (18). 6. Linear drive unit according to one of claims 1 to 5, characterized by at least one limit switch (20; 22) which sits on an adjusting spindle (66; 68) extending between the first end wall part (6) and the retaining ring (16), and by a projection (72) on the nut (50) of the nut-threaded spindle drive (18) and/or the output rod (26) for actuating the limit switch (20, 22). 7. Linear drive unit according to one of claims 1 to 6, characterized in that the first end wall part (6) and/or the second end wall part (8) is connected to the housing (4) in a form-fitting and rotationally fixed manner. 8. Linear drive unit according to one of claims 1 to 7, characterized in that two opposing fixing bolts (74) protrude radially outward beyond the housing (4) to create a connection area with which the linear drive unit (2) is connected at the installation location for power transmission. 9. Linear drive unit according to one of claims 1 to 8, characterized in that the planetary gear (14) is multi-stage and that the internally toothed area of the retaining ring (16) forms the ring gear common to all planetary gear stages. 10. Linear drive unit according to one of claims 1 to 9, characterized in that at least one axial bearing (44, 46) for axially supporting the threaded spindle (40) of the nut-threaded spindle drive (18) is provided on the retaining ring (16). 11. Linear drive unit according to one of claims 1 to 10, characterized by at least one safety limit switch (90) which is arranged downstream of a limit switch (20).