CA2504221A1

CA2504221A1 - Electrical press device

Info

Publication number: CA2504221A1
Application number: CA 2504221
Authority: CA
Inventors: Ralf Kosan; Kai Seelig
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-11-01
Filing date: 2003-10-09
Publication date: 2004-05-13
Also published as: EP1601522A1; BR0315838A; AU2003277819A1; DE20218396U1; KR20050074510A; DE10251387A1; WO2004039569A1; JP2006504533A; DE10251387B4

Abstract

The invention relates to an electrical pressing device comprising an electri c motor (2); a step-up gear (8); a spindle drive (66) embodied as a threaded roller screw drive, the threaded spindle (14) thereof being connected to the step-up gear (8), and the threaded nut (16) thereof being guided in a cylindrical housing (22) in a rotationally fixed and axially displaceable manner and being connected to a pressing tool, for converting a rotational movement of the electric motor (2) into a linear movement of the pressing tool; a displacement sensor (30) for determining the distance covered by the pressing tool; and a sensor (10) for determining the compressive force of th e pressing tool. The threaded spindle (14) is mounted in the housing by means of a pre-stressed set of angular ball bearings (12), the first angular ball bearing (46) being used to absorb tractive forces and the second angular bal l bearing (48) being used to absorb compressive forces. The internal rings of the angular ball bearings (46, 48) are clamped next to each other, against a shaft shoulder (54) of the threaded spindle (14), by means of a shaft nut (52), and the outer rings of the angular ball bearings (46, 48) are clamped next to each other, against a projection (58) of the housing, by means of a housing nut (56), suchthat the inventive device can absorb essentially identical tractive or pressure forces, without axial play.

Description

Electrical press deVlce The invention relates to an electrical press device with an electric motor, a step-up gear, a spindle drive in the form of a satellite roller screw, the thread spindle of which is connected to the step-up gear and the threaded nut of which is guided in a cylindrical housing in a non-cotatable meaner, and such that it can be axially displaced, and is connected to a pressing tool, for converting a rotary motion of the electric motor into a linear motion of the pressing tool, a travel sensor for determining the distance travelled by the pressing tool, and a sensor for de-termining the pressing force of the pressing tool.
A press device of this kind is known from DE 100 11 859 C2, in which the thread spindle is supported against the housing in the axial direction by a flange shoulder sad a tapered roller bearing. The tapered roller bearing is only secured against axial displacement on the thread spindle by means of a retaining ring and can in effect not tranafa any axial forces in the direction of traction. Nor is this necessary in the known pressing-in device, since pressing fords merely have to be generated in one direction (the diration of pressing).
The invrntion sets out to achieve the object of developing as electrical press device of the kind desedbod at the begirming such that pressing forces (traction and pressing forces) can be generated, the aim being to keep the diameter of the cylindrical housing as small as possible.
A further object of the invention consists in providing an electrical press device that can be firmly attached to a machine frame or the h'ke in a freely selectable manner with regard to its axial position. This is not possible in the known press device, since the housing there is equipped with a mounting flange, so that the press device can only be attached in a pre-determined position.

A further objat the invention consists in providing a simpler structural design for the guide for the threaded nut of the spindle dnvc, which is non-rotatable and can be axially displaced relative to the housing.
The first-mentionod object of the invention is achieved by an electrical press device with as eloctric motor, a step-up gear, a spindle drive in the form of a satellite roller xrew, the thread spindle of which is connected to the step-up goat and the threaded nut of which is ,guided in a cylindrical housing in a uon-rotatable manner, and such that it can be axially displaced, and is connected to a pressing tool, for converting a rotary motion of the electric motor into a linear motion of the pressing tool, a travel sensor for determining the distance travelled by the press-ing tool, and a sensor for determining the pressing force of the pressing tool, the press device being charactcrisai by the fact that the thread spindle is mountod in the housing by means of a pre-loaded set of angular contact ball bearings, the first angular contact ball bearings) of which is (ate) suitable for supporting traction forces and the second angular contact ball bear-ings) of which is (are) suitable fvr supporting pressing forces, the inner rings of the angular contact ball bearings being contiguously clamped by a lock nut against a shaft shoulder of the thread spindle, and the outer rings of the angular contact ball bearing being contiguously clamped by a housing nut against a housing shoulder, so that substantially equally great trac-tion or pressing forces can be supported without any axial play.
it can be provided for the set of angular contact ball bearings to have two first and two second angular contact ball bearings.
It is advantageously provided for the step-up gear to be designed as a mufti-stage transmis-sion, where the step-up gear may have a rtan~nission ratio o f for example, i=S .
It is conveniently provided for the electric motor to be controlled electrically and to have an angle encoder on the motor shaft, a means being present to determine the path travelled by the pressing tool by reference to the angle signals of the angle encoder, the transmission ratio of the step-up gear and the thread pitch of the spindle drive.

It is advantageously provided for a torque sensor to be disposed betweai an output shaft of the step-up gear and the thread spindle. The torque sensor may have a transmitter for trans-miffing measurod data contact-&ec. The torque sensor is preferably easily accessible and exchangeable in order for it to be adapted to different pressing forces. In this way, it is pos-sible to make as full a use as possible of different measuring ranges of torque sensors, even with difTerent pressing forces, so that the accuracy of measurement increases.
It is advantageously provided for there to be a closable opening in the housing, offering access to the torque sensor.
The invention further provides that thtre is a motor brake disposed on the motor shaft, which is applied in the absence of current and is released when current is carried.
This ensures that, even if a transmission does not stop automatically, any motion of the press device is prevent-ed in the event of a power failure.
It is advantageously provided for there to be a sprung stop between the threaded nut and the housing for determining the zero position of the travel measuring device.
The stop can be designed as a sprung ring on the threaded nut.
The thread spindle preferably has a multiple-start, especially five-start, thread.
The threaded nut can be retained in an axially stepped support sleeve, which is guided in the housing in a non-rotatable manner, and such that it can be axially displaced.
In a preferred embodiment, it is provided that the support sleeve is connected to, or forms, an inner sleeve of an axial guidance system with rccirculating ball bearings, the outer sleeve of which is connected to the housing in a non-rotatable manna.

The support sleeve can have a cylindrical supporting part with a relatively large diameter and a smaller-diameter sleeve bolted to it, forming the pressing ram.
The housing preferably has an outer cylindrical clamping surface for fixing the press device in a freely selectable axial clamping position.
For this purpose, a double-cone set of clamps can be disposed on the clamping surface.
Further advantages and features of the invention will become apparent from the following description of a preferred embodiment, reference being made to a draw ng in which Fig. 1 shows a partially cut side elevation of a press device in accordance with the invention;
Fig. 2 shows an enlarged detail from Fig. 1 in the region of the set of angular contact ball beatings;
Fig. 3 shows au enlarged detail fmm Fig. 1 in the region of the axial guidance system with recirculating ball bearings;
Fig. 4 shows a cross-sectional elevation along line N -1'V in Figs. 1 or 2;
and Fig. 5 shows a cross-sectional elevation along line V - V in Figs. 1 or 3.
Referring first to Fig. 1, which shows an electrical press device according to the present invention in a partially cut-out side elevation: major components of the press device ate an electric motor 2 with a motor brake 6 acting on its motor shaft 4, a sttp-up gear 8, a torque sensor 10, a set of angular contact ball bearings 12, in which is carriod a thread spindle 14 which, together with a threaded nut 16, forms a spindle drive 66, and a support sleeve 18 retaining the threaded nut 16, said support sleeve for its part being carried in an axial guid-ance system with roeirculating ball bearings Z0, which in turn is supported in a cylindrical _5-housing 22 which has a eylindnieal outer clamping surface Z4 for fixing it in a freely select.
able position on a machine part 26 or the like by means of a set of clamps 28.
Disposed on the motor shaft 4 is arr angle encoder 30 as a zero-based measuz~ement sensor, and there is a resolver 32 present to evaluate the signals of the angle encoder in order to obtain a distance signal. This is done by refemttg, in a known manner, to the transmission ratio of the step-up gear 8 and the thread pitch of the spindle drive b6 (thread spindle 14, threaded nut 16).
The motor brake 6 is designed such that it is applied by means of springs in the absence of current and prevents the motor shag from rotating, but is released when the power supply is present.
The step-up gear 8 could be designed as a planetary gear, though in the preferred embodiment it is designed as a mufti-stage transmission with a transmission ratio of e.g.
i=5. An input shaft 34 of the step-up gear 8 is connected to the motor shaft 4, while an output shaft 36 of the step-up gear is connected to the thread spindle 14 and carries the torque sensor 10. The torque sensor 10 is equipped with a transmitter, so that wireless or sliding-contact-free transmission of the measured values is possible. The torque sensor 10 is relatively easily accessible via a closable opening in the housing 38 and is therefore easy to exchange, so that a torque sensor can be used which is adapted in each case to a pressing force to be achieved in that particular case. This offers the advantage that, with a torque sensor that is adapted to a particulax maxi-mum torquelpressing force, as full a use as possible can be made of the measuring range of the torque sensor, so that the measuring accuracy is maximised. In this way, an accuracy of less than 1 % of the maximum or ultimate value can be achieved, and thus also a correspond-ing accuracy in setting a desired pressing force, which is determined by the torque.
The thread spindle 14, now referring also to Figs. 2 and 4, is carried in the housing 22 by means of a set of angular contact ball bearings designated as a whole by 12, which in the present case has a bearing sleeve 40 and an outer guide 42 belted to it.

In the embodiment described here, the set of angular contact ball bearings 12 consists of a total of four angular contact ball bearings, each of which can support the same axial and radial forces, which is indicated by resultant load vxtors 44 running at 45°
to the longitudinal axis 50, Two first angular contact ball bearings 46 arc disposed in each case to support traction forces (acting towards the left in Figs. 1, 2), and two second angular contact ball bearings 48 are disposed in each case to support pressing forces (acting towards the right in Figs. 1, 2). The inner rings of the angular contact ball bearings are directly contiguously clamped by a lock nut 52 against a shaft shoulder 54 of the thread spindle, while the outer rings of the angular contact ball bearings arc correspondingly contiguously clamped by a housing nut 56 against a housing shoulder 58. The angular contact ball bearings are manufactured in such a way that, when the lock and housing nuts arc tightened, no play reanains, but, on the contrary, the two pairs of bearings 46 and 48 aligned in opposite directions are pre-loaded, so that substantially the same traction or pressing forces can be supported without any axial play occurring. A
further advantage of this construction is that no particular dimensional tolerances need to be observed in the region of the bearing sleeve or the thread spindle, as far as the axial dimen-sions arc concerned, since tightening the inner and outer rings with the lock or housing nuts is sufftcient for faultless functioning without any play, Adjoining the shaft shoulder 54 is the thread spindle 14 with, in this case, a five-start thread portion 60, the length of which is dimensioned such that the desired pressing tasks can be performed.
With its thread portion 60 and the threaded nut 16 and rollers, the thread spindle 14 forms the spindle drive 66, which takes the form of a satellite roller screw (also referred to as a plane-tary roller ihrcad spindle drive). The threaded nut 16 is connected to the support sleeve 18 in a non-rotatable manner by means of a feather key 68, which can be moved in the axial direction inside the outer guide 42. Fastening bolts 70 fix the threaded nut 16 within the support sleeve 18 via a fastening ring 72, with a ring 76 sprung by means of pressure springs 74 forming a sprung stop on the fastening ring 72 or the support sleeve 18. When the spindle drive moves backwards (towards the right) the threaded nut with the ring 76 runs up against the housing _7_ shoulder 58 of the bearing sleeve 40, as a result of which the torque sensor 10 detects an increase in torque, so that it is possible in this way to determine the zero position.
The support sleeve 18 is formed from a supporting part 18a with a relatively large diameter retaining the threaded nut 16, and a sleeve 1 Sb with a smaller diameter bolted to it and form-ing the pressing ram. The sleeve 18b is carried in, or forms, an inner sleeve of the axial guid-ance system with recirculating ball bearings 20 (Figs. 3 and 5), the outer sleeve 21 of which is secured in the housing or the outer guide 42 by retaining rings 77 such that it cannot be axial-ly displaced and is connxtcd to it in a non-rotatablc manner by means of a feather key 78. A
pressing tool (not shown) is mounted on the end of the sleeve 18b.
The set of clamps 28 has conical clamping members, with which the press device can be fixed to the machine part 26 in a freely selectable axial clamping position on its outer guide 42.

-$-List of reference numerals 2 Elxtric motor 52 Lock nut 4 Motor shaft 54 Shaft shoulder 6 Motor brake 56 Housing nut 8 Step-up gear 58 Housing shoulder Torque savor 60 Thread portion 12 Set of angular contact ball bearings 66 Spindle drive 14 Thread spindle 68 Feather key 16 Threaded nut 70 Fastening bolt 18 Support sleeve 72 Fastening ring 18a Supporting Part 74 Pressure spring 18b Sleeve 76 Ring Axi2~1 guidance system with recirculating77 Retaining ball bearings ring 21 Outer sleeve 78 Feather key 22 housing 24 Clamping surface 26 Machine part 28 Set of clamps Angle encoder 32 Resolver 34 Input shaft 36 Output shaft 38 Opening in the housing Bearing sleeve 42 Outer guide 44 Resultant load vector 46 First angular contact ball bearing 48 Second angular contact ball bearing Longitudinal axis

Claims

1. An electrical press device with an electric motor (2), a step-up gear (8), a spindle drive (66) in the form of a satellite roller screw, the thread spindle (14) of which is connected to the step-up gear (8) and the threaded nut (16) of which is guided in a cylindrical housing (22) in a non-rotatable manner, and such that it can be axially displaced, and is connected to a pressing tool, for converting a rotary motion of the electric motor (2) into a linear motion of the press-ing tool, a travel sensor (30) for determining the distance travelled by the pressing tool, and a sensor (10) for determining the pressing force of the pressing tool, characterised in that the thread spindle (14) is mounted in the housing (22) by means of a pre-loaded set of angular contact ball bearings (12), the first angular contact ball bearing(s) (46) of which is (are) suitable for supporting traction forces and the second angular contact ball bearing(s) (48) of which is (are) suitable for supporting pressing forces, the inner rings of the angular contact ball bearings being contiguously clamped by a lock nut (52) against a shaft shoulder (54) of the thread spindle (14), and the outer rings of the angular contact ball bearing (46, 48) being contiguously clamped against a housing shoulder (58) by a housing nut (56), so that substan-tially equally great traction or pressing forces can be supported without any axial play.

2. The press device as claimed in claim 1, characterised in that the set of angular contact ball bearings (12) has two first (46) and two second angular contact ball bearing (48).

3. The press device as claimed in either of claims 1 or 2, characterised in that the step-up gear (8) is designed as a multi-stage transmission.

4. The press device as claimed in any of the preceding claims, characterised in that the step-up gear (8) has a transmission ratio of, for example, i=5.

5. The press device as claimed in any of the preceding claims, characterised in that the electric motor (2) is controlled electrically and has an angle encoder (30) on the motor shaft (4), a means (32) being present to determine the path travelled by the pressing tool by refer-ence to the angle signals of the angle encoder (30), the transmission ratio of the step-up gear (8) and the thread pitch of the spindle drive (66).

6. The press device as claimed in any of the preceding claims, characterised in that a torque sensor (10) is disposed between an output shaft (36) of the step-up gear (8) and the thread spindle (14).

7. The press device as claimed in claim 6, characterised in that the torque sensor (10) has a transmitter for transmitting measured values contact-free.

8. The press device as claimed in either of claims 6 or 7, characterised is that the torque sensor (10) is easily accessible and exchangeable in order for it to be adapted to different pressing forces.

9. The press device as claimed in any of claims 6 to 8, characterised in that a closable opening is provided in the housing (38), offering access to the torque sensor (10).

10. The press device as claimed in any of the preceding claims, characterised in that there is a motor brake (6) disposed on the motor shaft (4), which is applied in the absence of current and is released when current is carried.

11. The press device as claimed in any of the preceding claims, characterised in that a sprung stop (76) is provided between the threaded nut (16) and the housing (22) for determin-ing the zero position of the travel measuring device.

12. The press device as claimed in claim 11, characterised in that the stop is designed as a sprung ring (76) on the threaded nut (16).

13. The press device as claimed in any of the preceding claims, characterised in that the thread spindle (14) has a multiple-start, e.g. five-start, thread.