Drive unit for a strapping device

Abstract

A drive unit for a strapping device strapping an item to be packed with a plastic tape which is laid around it includes a motorized tensioning device and a motorized welding device for the plastic tape. The tensioning and welding device can be driven by the same electric motor which can be brought alternatively into an operative connection with the devices with freewheels connected therebetween. A problem has occurred in drive units of this type that they are relatively complicated to assembly and have problematic operational reliability under certain boundary conditions. To bypass these problems, the electric motor includes at least one shell extension which protrudes beyond it at one axial end with the result that the drive elements which have up to now been mounted separately in the housing of a strapping device can be supported directly on the electric motor which then acts as a drive unit.

Claims

1. A drive unit for a strapping device for strapping a package with a plastic tape positioned around the same, comprising a motor-driven tensioning device and a motor-driven welding device for the plastic tape, wherein the tensioning and welding devices can each be driven by a single electric motor having a first end portion and a second, opposite end portion, which, with interposition of freewheels, can alternately be brought into operative connection with the tensioning and welding devices, wherein the electric motor includes: a casing extending from the first end portion; a cover covering a front end of the casing; a shaft end extending through the cover and forwardly from the cover; and a casing extension extending beyond the second end portion of the electric motor at an axial end thereof, wherein the casing extension is fittable in a form of a separate component on the casing of the electric motor such that the casing extension is formed in one piece with the cover of the electric motor, and wherein one of the freewheels, at least one rolling-contact bearing, and at least one O ring are disposed within the casing extension and about the shaft end, the O ring being disposed radially between the rolling-contact bearing and the casing extension.

2. The drive unit as claimed in claim 1, wherein the casing extension has at least one axial fixing component.

3. The drive unit as claimed in claim 2, wherein the axial fixing component is an outer groove.

4. The drive unit as claimed in claim 2, wherein the axial fixing component is at the second end portion of the electric motor which is provided with a bevel gear.

5. The drive unit as claimed in claim 1, wherein the casing extension is provided with at least one rotation-prevention means.

6. The drive unit as claimed in claim 1, wherein an inner surface of the casing extension forms a cavity therein adjacent the second end portion of the electric motor.

7. The drive unit as claimed in claim 1, wherein the casing extension extends contiguously with the front end of the casing.

8. The drive unit as claim in claim 7, wherein the casing extension has a rear end received within the front end of the casing and directly attached to the cover.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages and features of the present disclosure can be gathered from the following description of an exemplary embodiment and with reference to the drawings, wherein:

(2) FIG. 1 shows an exploded illustration of a drive unit with a casing extension projecting beyond the electric motor at the axial ends of the latter;

(3) FIG. 2 shows an exploded illustration of the housing part of a strapping device with a drive unit according to FIG. 1;

(4) FIG. 3 shows the sectional view through a strapping device with drive unit installed; and

(5) FIG. 4 shows an exploded illustration of a prior-art drive unit for a strapping device together with parts of the housing for such a strapping device.

DETAILED DESCRIPTION

(6) The figure shows an electric motor 1, which is driven electrically via a (storage) battery (not illustrated), wherein the motor shaft, which is connected to the rotor of the electric motor, has its two ends 2, 3 projecting out at opposite ends of the electric motor 1. Seated at said shaft ends are freewheels 4, 5, which transmit a rotary movement of the shaft ends in opposite directions.

(7) These freewheels have, on the one hand, a bevel gear 6 and, on the other hand, a spur gear 7 positioned on them.

(8) The bevel gear 6 has a shank 8, on which two rolling-contact bearings 9 are seated. In the same way, the spur gear 7 has a collar 10, on which a rolling-contact bearing 11 is seated.

(9) Rubber buffers in the form of O rings 12 and 13 are pushed onto the aforementioned rolling-contact bearings 9 and 11, respectively.

(10) Also evident in FIG. 4 is a torque support 14, which is screwed firmly on the electric motor 1, via screws 15, by means of a flange disk 16.

(11) The assembled drive unit is inserted into matching holders on housing parts 17, 18, wherein the bevel gear 6 then meshes with a mating gear 19, which is seated on a shaft 20, which is accommodated in the housing part 18 by rolling-contact bearings 21.

(12) To give a better overview, with the exception of an actuating lever 28, the rest of the add-on parts have not been illustrated.

(13) In the case of the strapping device, once assembled, the tensioning device (not illustrated specifically here) is opened, by actuation of the lever 28, in order for the tape to be placed in position and, once the tape has been placed appropriately in position, a pushbutton (not illustrated) is used to drive the electric motor 1 in a first direction of rotation, wherein the electric motor drives the bevel gear 6 via the freewheel 4 and therefore tensions the plastic tape which is to be welded.

(14) When the tape is tensioned, the electric motor 1 is reversed and rotates in the opposite direction, wherein the freewheel 4 causes the gear 6 to remain in position and the freewheel 5 then drives the spur gear 7, by means of which a welding device, as described above, is driven to oscillate or vibrate.

(15) During rotating operation of the electric motor 1, the torque of the latter is supported in relation to the housing part 18 via the torque support 14.

(16) The above described reversal of the electric motor 1 gives rise to tilting moments which, on account of the elasticity with which the rolling-contact bearings 9 and 11 are supported in relation to the housing parts 17 and 18 via the rubber buffers or O rings 12 and 13, respectively, result in relative movements which can then ultimately lead to the shaft ends 2 or 3 being damaged.

(17) In order to overcome this problem, a drive unit is developed as illustrated in FIG. 1. In this figure, like parts are provided with like reference signs.

(18) It is also the case with the electric motor 1 illustrated in FIG. 1 that the shaft ends 2, 3 of the electric motor have seated on them a respective freewheel 4, 5, on which are respectively seated a bevel gear 6 and a spur gear 7. These, as described above, are provided in the same way with a shank 8 or a collar 10, on which rolling-contact bearings 9, 11 are seated.

(19) Once again, rubber buffers in the form of O rings 12, 13 are seated on the rolling-contact bearings. In the example illustrated here, these O rings, however, are inserted into the interior of casing extensions 22, by way of which the electric motor 1 has its casing extended at its axial ends.

(20) Therefore, vibrations transmitted for example by the bevel gear 6 are supported in relation to the electric motor or the casing extension 22 thereof, which projects beyond the electric motor at its one axial end, via the ball bearings 9 and the O rings, and therefore the relative movement between the electric motor 1 and the support is minimized and thus cannot result in the shaft end 2 being subjected to loading. The drive unit illustrated in FIG. 1 is then inserted in the assembled state, as can be seen in FIG. 2, into appropriate housing parts 17, 18, wherein the electric motor is activated in the same way as already described above for the assembled strapping device.

(21) FIG. 3 illustrates a corresponding drive unit in the installed state. It is possible to see the electric motor 1 with its shaft ends 2, 3, on which are seated the freewheels 4, 5, which then bear the bevel gear 6 and the spur gear 7, respectively. The shank 8 of the bevel gear 6 then has the rolling-contact bearing 9 seated on it, said bearing being supported in relation to the casing extension 22 via the O rings, wherein just one rolling-contact bearing 9 is provided in the example illustrated here, rather than two, as is the case in FIGS. 1 and 2. Two O rings 12 are then positioned on said rolling-contact bearing, it being possible to compensate for a double fit via said O rings 12.

(22) In the example illustrated here, an encircling groove 23 can be seen on the casing extension 22, said groove functioning as an axial fixing means and, for this purpose, corresponding with an annular holder 24 provided on the housing part 18. The annular holder 24, as seen in the axial direction of the electric motor 1, is relatively tight up against the mating gear 19, with which the bevel gear 6 meshes, and therefore a spacing can be maintained relatively precisely here.

(23) In order for this spacing to be established to good effect in production terms, the casing extension 22 is designed, as can be seen, in the form of a separate part and is fitted onto the casing 1a of the electric motor 1 having a cover 22a. All that is required here is for the casing extension 22 to be produced with a high level of precision, in order for it to be possible for the predetermined dimensions to be maintained precisely. The casing extension illustrated here serves, at the same time, as a cover for the electric motor, in which, in the case of the embodiment illustrated here, in particular the motor controller and a bearing for the motor shaft are also accommodated.

(24) It should also be mentioned that it is also possible for the groove 23 to be arranged in a non-central position, as seen in relation to the casing extension, or for a flange, protrusion or the like to be provided instead.

(25) At the opposite end, the electric motor 1 also has two pins 25 provided over its casing 1a. These pins engage in corresponding recesses 26, 27 on the electric motor 1 and/or on the housing 18 and therefore establish an integrated rotation-prevention means and thus a moment support for the electric motor 1. As an alternative, it is also possible for the pins 25 to be configured in the form of threaded pins and to be screwed into corresponding threaded bushings.

(26) On account of the design explained here, the above-described drive unit according to the present disclosure can be deemed to be capable of quick and straightforward assembly and to operate very reliably during subsequent operation.

LIST OF REFERENCE SIGNS

(27) 1 Electric motor 2 Shaft end 3 Shaft end 4 Freewheel 5 Freewheel 6 Bevel gear 7 Spur gear 8 Shank 9 Rolling-contact bearing 10 Collar 11 Rolling-contact bearing 12 O ring 13 O ring 14 Torque support 15 Screws 16 Flange disk 17 Housing part 18 Housing part 19 Mating gear 20 Shaft 21 Rolling-contact bearing 22 Casing extension 23 Groove 24 Annular holder 25 Pins 26 Recess 27 Recess 28 Actuating lever