GB1577407A

GB1577407A - Mechanical adjusting device

Info

Publication number: GB1577407A
Application number: GB17996/78A
Authority: GB
Original assignee: Lechler GmbH and Co KG
Current assignee: Lechler GmbH and Co KG
Priority date: 1977-05-21
Filing date: 1978-05-05
Publication date: 1980-10-22
Also published as: DE2723062B1; IT1095881B; IT7823096A0; FR2391399A1; DE2723062C2; FR2391399B3

Description

(54) MECHANICAL ADJUSTING DEVI CE (71) We, LECHLER G.m.b.H. & COM- PANY K.G., a German company, of Höhen- strasse 24, D-7012 Felibach, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to mechanical adjusting devices, particularly, although not so restricted, for adjustable slides in machine tools (special machines).

Known mechanical adjusting devices may be divided into two groups, namely: (a) non-self-locking mechanical adjusting devices, and (b) self-locking mechanical adjusting devices.

The first group includes, for example, chain and sprocket drives, rope drives, steepthread spindles, recirculating ball nuts and spindles, and also rack and pinion drives in which the teeth of the pinion are curved on their outer periphery. Although these adjusting devices work with good efficiency and usually have a relatively small specific overall volume, nevertheless they cannot be used when self-locking is required.

Among adjusting devices of the second group mention may be made, for example, of threaded spindles with nuts or highly stepped-down gearing (for example worm and wheel drives) in conjunction with adjusting devices of the first group). These adjusting devices have a different specific overall volume and, in all cases, are characterised by poor efficiency, which in many cases is due to the fact that these devices are provided with the reauired self-locking.

In addition, it is known for mechanical adjusting devices of the first group to be additionally equipped with self-locking means. Examples of such additional selflocking means include catches and pawls and a]so brake devices. The additional self-locking means must be automatically released for the forward movement of the adjusting device, but must come into action when the device is stationary. For backward movements of the adjusting device, however, there is some uncertainty except in the case of those adjusting devices which are provided for self-locking means with brake devices, which then work with reduced braking power.

Apart from the mechanical adjusting devices described above, adjusting devices of other kinds are known, for example those which work hydraulically or pneumatically.

For the sake of completeness these devices must also be mentioned. Although they often permit the best solutions from the tech- nical point of view, since they can to a very large extent be designed to comply with desired requirements, nevertheless the practical use of these per se technically optimal hydraulic or pneumatic adjusting devices is impossible in many cases because of the additional burden imposed by their construction, particularly because of high cost.

The present invention seeks to provide a mechanical adjusting device which is so constructed that ;t works with self-locking without any additional apparatus.

According to the present invention there is provided a mechanical adjusting device comprising a rack and pinion drive consisting of a pinion whose teeth are curved on their outer periphery and a rack, the number and shape of the teeth and the pitch of the pinion and rack being so arranged relative to one another that one tooth of the pinion is engaged by its flank in the rack only when the preceding tooth of the pinion is in contact with the rack by its outer periphery and the periphery of this tooth has already rolled over a determined angle on the rack.

An adjusting device according to the present invention is an intermittently operating device which is characterised in that with a uniform angular velocity of the pinion a movement phase and a rest phase of the rack driven by the pinion always alternate.

The efficiency during the movement phase of the rack corresponds approximately in order of magnitude to the comparatively good efficiency of a rack drive with involute teeth. During the rest phase of the rack, on the other hand, the mechanical efficiency of the adjusting device is zero; self-locking is thus achieved.

During the rest phase of the rack the latter may in some cases be in a completely stationary state. To this end, the teeth of the pinion may have an arcuate shape and the centre of curvature of the outer periphery of the teeth of the pinion may coincide with the axis of rotation of the pinion.

In some cases, however, it may also be expedient for the rack still to move very slowly in its rest phase. To this end, the radius of curvature of the outer periphery of the teeth of the pinion may be larger than half the diameter of the pinion. In this case the rack first performs a slight backward movement in its rest phase (that is to say a movement in the opposite direction to the actual feed movement). This slight reduction of the load (when the invention is applied to an elevating device) may result in an advantageous stabilisation of the adjusting device in the rest phase, particularly in the case of very easily running constructions.

Finally the possibility of allowing the rack to continue slightly its feed or elevating movement in the rest phase is also conceivable and in certain cases entirely expedient and advantageous. For the purposes of this in a modified embodiment of the invention each tooth of the pinion has an outer periphery which is non-arcuate in shape. Thus each tooth of the pinion may have an outer periphery which is spiral or substantially spiral. This can be achieved in a simple manner by placing the centres of curvature of the teeth in each case at the side ol the centre of the axis of rotation of the pinion.

The consequent continued movement of the rack during its rest phase can advantageously be employed for fine adjustment or as a clamping stroke or in a similar manner.

The adjusting device of the invention can be used generally in various ways; it is particularly suitable as an elevating device. The invention is intended to be applied primarily to adjusting slides in machine tools, particularly special machine tools. The invention may however in addition be immediately applied to engineering in general, for example in lifting appliances, winches, and the like.

A substantial advantage of the adjusting device of the invention consists in that the load moved can never fall automatically (for example after release of the slide clamp) by more than one tooth pitch. The rest phases in the course of the intermittently operating adjusting operations with the adjusting device provides the advantage that during movement of the slide in the upward or downward directions the operator will always have time to operate the key, crank, or handwheel. Furthermore, after an upper position which is to be adjusted has been exceeded a rest phase gives the operator an opportunity to insert gauge blocks, stops, or the like, against which the drive can then be run in order to achieve very accurate adjustment of the desired position, for example of the slide.

As an advantageous further development of the basic principle of the invention it is in addition proposed that the teeth of the pinion may have on their curved outer periphery a comparatively great length in the peripheral direction and have curved undercuts on their flanks. Because of the great width of the teeth on the outer periphery a comparatively long duration of the rest phase is achieved.

The invention is illustrated, merely by way of example, in the accompanying drawings, in which: Figure 1 is an elevation of a mechanical adjusting device according to the present invention; Figure 2 is a section on the line II--II of Figure 1; Figure 3 illustrates another embodiment of :a mechanical adjusting device according to the present invention; Figure 4 illustrates a further embodiment of a mechanical adjusting device according to the present invention Figure 5 is an elevation of a special machine tool utilising mechanical adjusting devices according to the present invention; and Figure 6 is a view in the direction of the arrow A of the machine tool shown in Figure 5.

In Figures 1 and 2, a mechanical adjusting device according to the present invention has a rack 10 and a pinion 11 forming a rack and pinion drive. The pinion 11 is mounted on a square 12 for rotation with a driven shaft 13. The direction of rotation of the pinion 11 causes the rack and the part fastened to it to perform a relative downward movement, as indicated in Figure 1 by an arrow 14.

As shown in Figure 2, the rack 10 with a plurality of teeth 15 is integrally cast in a slide-like casting 16 which is guided at 17, 18 in a machine part 19. The machine part 19 also serves to mount the drive shaft 13 of the pinion 11.

The casting 16 may, for example, be a vertically movable column of a machine tool.

The casting 16 is expediently made of nodular cast-iron; finish machining of the teeth 15 of the rack 10 is thus unnecessary.

The machine part 19, which is adapted to be moved up and down by the rack and pinion drive, carries, for example, a multispindle drilling head, a milling unit, a thread cutting unit, or the like (not shown).

In this connection reference is made to Figures 5 and 6, which are described in greater detail further on.

From Figure 1 can moreover be seen the characteristic construction of the pinion 11.

In the embodiment illustrated, the pinion 11 comprises four teeth 20 spaced uniformly apart. The teeth 20 of the pinion 11 have heads which are relatively wide in relation to their roots. On their outer periphery 21 the teeth 20 are arcuate. Flanks 22, 23 of the teeth 20 are likewise arcuate, being undercut inwardly, each two neighbouring flanks merging continuously. In addition, transitions 24 from the flanks 22, 23 to the periphery 21 are rounded.

Figure 1 also makes it clear that the teeth 15 of the rack 10 which cooperate with the teeth 20 of the pinion 11 are made relatively narrow in comparison with the distance or pitch t between neighbouring teeth 15. The teeth 15 of the rack 10 are roughly trapezoidal in shape, but at their heads are likewise rounded.

The adjusting device shown in Figures 1 and 2 works in the following manner. When the pinion 11 is turned in the direction of the arrow 14, the pinion 11 rolls with its respective flanks 23 on those flanks 25 of the teeth 15 of the rack 10 which are at the top in Figure 1. As Figure 2 shows, the teeth 20 of the pinion 11 are substantially narrower than the teeth 15 of the rack 10. The width of the rack teeth 15 is designated x in Figure 2. For reasons of stability the teeth 15 of the rack 10 are bounded on both sides by the casting 16.

If it is assumed that the rack 10 and casting 16 are the stationary parts and the machine part 19 with the pinion 11 mounted in it is the movable part, the machine part 19 will move upwards (indicated by arrow 16) when the pinion 11 turns in the direction 14. As the elevating movement of the machine part 19 together with the pinion 11 progresses, a rounding (designated by reference number 24a in Figure 1) of the flank 23 of a tooth 20a finally reaches a point 27 on the flank 25 of a tooth 15a. The point 27 represents the transition from the rectilinear portion of the flank 25 to the rounded head part of the latter. The position in which the rounding 24a and the flank 25 are in contact at the point 27, is shown in dash-dot lines in Figure 1. At this moment the elevating movement of the machine part 19 is interrupted although the pinion 11 continues to turn, because the tooth 20a of the pinion 11 now slides with its circular outer periphery 21a over the point of contact 27 slowly until a next tooth 20b of the pinion 11 reaches a next tooth 15b of the rack 10 (shown in dashed lines in Figure 1).

This moment represents the beginning of the next elevating phase.

When the pinion 11 turns in the opposite direction, the above-described operations take place in the reverse sequence, while with the pinion 11 continuing to turn uniformly the elevating phase alternates periodically with the rest phase.

The invention is in no way limited to the embodiment illustrated by way of example in Figures 1 and 2 in the drawings, in which the pinion 11 has four teeth. On the contrary, the embodiment illustrated may be modified in various ways without departing from the scope of the invention. The diameter, width, number of teeth, and the shape of the teeth of the pinion 11 and also the pitch t and the shape of the teeth of the rack 10 may be varied.

In the embodiment shown in Figure 3 teeth 28 of a rack 29 consist of round pins which are inserted into the rack 29 in the form of a carrier of light metal, a sheet metal pressing, or the like.

The rack 29 may be used as a bearer which is made of light metal, sheet metal pressings or the like in which the pins forming the teeth 28 are inserted.

In the embodiment shown in Figure 4 the teeth 30 of the rack 29 are in the form of rotatable sleeves 31 mounted on pins 32.

The sleeves 31 are preferably mounted on the pins 32 by rolling-contact bearings, preferably after the style of a needle bearing, whereby good efficiency is achieved for the adjusting device shown in Figure 4, because when the teeth 20 of the pinion 11 roll on the sleeves 31 the latter are driven and thus very low friction occurs between the teeth 20 and the sleeves 31. The pins 32 may be inserted into bearers of light metal, sheet metal pressings or the like.

Otherwise the embodiments shown in Figures 3 and 4 correspond exactly to those shown in Figures 1 and 2, so that no further explanations are required.

Figures 5 and 6 now illustrate an example of application of a mechanical adjusting device according to the present invention, for example, of a kind shown in Figures 1 to 4.

Figures 5 and 6 illustrate a machining unit in a machine tool which may comprise a number of machining units of the kind shown in Figures 5 and 6. Figures 5 and 6 are merely intended to show that the invention is applicable to the most diverse types of adjustability for machines of this kind.

The actual parts of the machining unit shown in Figures 5 and 6 which serve for machining with tools are therefore only indicated diagramatically or partly omitted.

The machining unit according to Figures 5 and 6 comprises a column 33 which for example may be in the form of a casting. A slide guide 34 having trapezoidal guide sur faces (Figure 6) is integrally cast at the bot tom of .the column 33. The column 33 is thereby mounted in a supporting device 35 so as to be adjustable in the direction of an arrow 36 (Figure 5). In the embodiment illustrated in Figures 5 and 6 there is provided on the lower face of the slide guide 34 an integrally cast rack (not shown), which may be constructed in accordance with the embodiments shown in Figures 1 to 4 or may be of a similar construction. In the supporting device 35 on the other hand there is mounted pinion 37 which may likewise be in accordance with the embodiments shown in Figures 1 to 4. If the pinion 37 is turned, for example with the aid of a crank, a handwheel, or the like, the column 33 will be adjusted in the direction of the arrow 36 in accordance with the direction of the rotation of the pinion.

Figures 5 and 6 also show that the supporting device 35 is in turin itself guided on a guide rail 38 having trapezoidal guide surfaces. The column 33 and the supporting device 35 can thus be conjointly adjusted in the direction of an arrow 39 (Figure 6). For the purpse of adjusting the device in the direction of the arrow 39, a rack (for example in accordance with the embodiments shown in Figures 1 to 4) is formed in the guide rail 38, while a pinion cooperating with the rack is mounted in the supporting device 35.

As is customary with machine tool units of this kind, the column 33 now carries the actual machining tool 41 and the drive for the latter. The machining tool may for example be a multi-spindle drilling head or a similar stock-removing machining tool.

Above the machining tool 41 is disposed a drive motor 42 (expediently an electric motor). The machining tool 41 and the drive motor 42 rest on a carrier part 43 which is adjustable in the vertical direction along the column 33. As shown in Figure 6, for this purpose there is integrally cast in the column 33 a rack which is constructed in accordance with the embodiments illustrated in Figures 1 and 2 and therefore for the sake of simplicity designated by the reference numeral 10. With this rack 10 cooperates a pinion (not shown), which is mounted at 44 in the carrier part 43 and can be operated from outside by means of a handwheel, a crank, or the like.

Figures 5 and 6 therefore show three possible applications for an adjusting device according to the invention, by means of which the machining unit can be adjusted with a self-locking action in the longitudinal direction, in the transverse direction, and in the vertical direction.

WHAT WE CLAIM IS:- 1. A mechanical adjusting device comprising a rack and pinion drive consisting of a pinion whose teeth are curved on their outer periphery and a rack, the number and shape of the teeth and the pitch of the pinion and rack being so arranged relative to one another that one tooth of the pinion is engaged by its flank in the rack only when the preceding tooth of the pinion is in contact with the rack by its outer periphery and the periphery of this tooth has already rolled over a determined angle on the rack.

2. An adjusting device as claimed in claim 1 in which each tooth of the pinion has an arcuate periphery.

3. An adjusting device as claimed in claim 2 in which the centre of curvature of the outer periphery of the teeth of the pinion coincides with the axis of rotation of the pinion.

4. An adjusting device as claimed in claim 2 in which the radius of the curvature of the outer periphery of the teeth of the pinion is larger than half the diameter of the pinion.

5. An adjusting device as claimed in claim 1 in which each tooth of the pinion has an outer periphery which is non-arcuate in shape.

6. An adjusting device as claimed in claim 1 in which each tooth of the pinion has an outer periphery which is spiral or substantially spiral.

7. An adjusting device as claimed in any preceding claim in which the teeth of the pinion have, on their outer periphery, a comparatively great length in the peripheral direction and have curved undercuts on their flanks.

8. An adjusting device as claimed in claim 7 in which adjacent said flanks of each two neighbouring teeth of the pinion merge into one another without discOn- tinuity.

9. An adjusting device as claimed in claim 7 or 8 in which a transition from the outer periphery of each tooth of the pinion to the adjoining tooth flank is rounded.

10. An adjusting device as claimed in claim 9 in which said transitions are arcuate.

11. An adjusting device as claimed in any preceding claim in which the pinion has foilr teeth spaced uniformly apart.

12. An adjusting device as claimed in any preceding claim in which the rack has teeth whose width is smaller than the pitch between adjacent teeth.

13. An adjusting device as claimed in any preceding claims in which the rack is in the form of a casting with teeth whose heads are rounded.

14. An adjusting device as claimed in claim 13 in which the rack is integrally cast in a slide guide.

15. An adjusting device as claimed in any of claims 1 to 12 in which the rack has pins to serve as teeth.

16. An adjusting device as claimed in any of claims 1 to 12 in which teeth of the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. so as to be adjustable in the direction of an arrow 36 (Figure 5). In the embodiment illustrated in Figures 5 and 6 there is provided on the lower face of the slide guide 34 an integrally cast rack (not shown), which may be constructed in accordance with the embodiments shown in Figures 1 to 4 or may be of a similar construction. In the supporting device 35 on the other hand there is mounted à pinion 37 which may likewise be in accordance with the embodiments shown in Figures 1 to 4. If the pinion 37 is turned, for example with the aid of a crank, a handwheel, or the like, the column 33 will be adjusted in the direction of the arrow 36 in accordance with the direction of the rotation of the pinion. Figures 5 and 6 also show that the supporting device 35 is in turin itself guided on a guide rail 38 having trapezoidal guide surfaces. The column 33 and the supporting device 35 can thus be conjointly adjusted in the direction of an arrow 39 (Figure 6). For the purpse of adjusting the device in the direction of the arrow 39, a rack (for example in accordance with the embodiments shown in Figures 1 to 4) is formed in the guide rail 38, while a pinion cooperating with the rack is mounted in the supporting device 35. As is customary with machine tool units of this kind, the column 33 now carries the actual machining tool 41 and the drive for the latter. The machining tool may for example be a multi-spindle drilling head or a similar stock-removing machining tool. Above the machining tool 41 is disposed a drive motor 42 (expediently an electric motor). The machining tool 41 and the drive motor 42 rest on a carrier part 43 which is adjustable in the vertical direction along the column 33. As shown in Figure 6, for this purpose there is integrally cast in the column 33 a rack which is constructed in accordance with the embodiments illustrated in Figures 1 and 2 and therefore for the sake of simplicity designated by the reference numeral 10. With this rack 10 cooperates a pinion (not shown), which is mounted at 44 in the carrier part 43 and can be operated from outside by means of a handwheel, a crank, or the like. Figures 5 and 6 therefore show three possible applications for an adjusting device according to the invention, by means of which the machining unit can be adjusted with a self-locking action in the longitudinal direction, in the transverse direction, and in the vertical direction. WHAT WE CLAIM IS:-

1. A mechanical adjusting device comprising a rack and pinion drive consisting of a pinion whose teeth are curved on their outer periphery and a rack, the number and shape of the teeth and the pitch of the pinion and rack being so arranged relative to one another that one tooth of the pinion is engaged by its flank in the rack only when the preceding tooth of the pinion is in contact with the rack by its outer periphery and the periphery of this tooth has already rolled over a determined angle on the rack.

rack are sleeves which are mounted on pins.

17. An adjusting device as claimed in claim 16 in which the teeth of the rack are sleeves mounted in rolling-contact bearings.

18. A mechanical adjusting device substantially as herein described with reference to and as shown in the accompanying drawings.