GB2167992A

GB2167992A - Producing profiles of non-circular cross-section

Info

Publication number: GB2167992A
Application number: GB08507777A
Authority: GB
Inventors: Josef Pomikacsek
Original assignee: Linsinger Ernst & Co GmbH
Current assignee: Linsinger Ernst & Co GmbH
Priority date: 1984-12-10
Filing date: 1985-03-26
Publication date: 1986-06-11
Also published as: GB8507777D0; DE3444945A1

Abstract

Apparatus for producing a non-circular profile or cross-section on an elongate workpiece, preferably of metallic material, in a plane transverse to the longitudinal axis, includes at least one tool 5, e.g. a cutting element, which circulates around the workpiece for example in progressive cutting, and is controlled in the radial direction by a copying track 1 which is arranged concentrically with the profile 2 to be produced and which can consist of a specific geometric curve, the cutting parameters of the tool remaining approximately constant throughout engagement with the workpiece. The apparatus is particularly suitable for producing helical rotors for pumps. <IMAGE>

Description

SPECIFICATION Apparatus for producing profiles of non-circular cross-section, e.g. Mohno pump rotors The invention relates to apparatus for producing non-circular profiles on elongate workpieces, preferably of metallic material, in a plane transverse to the longitudinal axis, with the aid of a cutting tool, e.g. cutting elements or the like which are mounted on a cutter head and which move relative to the workpiece, in particular (but not solely) for machining Mohno pump rotors.

It is known to machine spindles of spindle pumps of non-circular cross-section on copying lathes. In this type of machining only low productivity and accuracy are possible, on account of the single cutter and on account of the cutter delivery angle - relative to the cutting point tangents which is not constant. Where the profile of, for example, non-circular cross-section extends over a substantial length, observation of optimum cutting parameters can no longer be ensured and after the profile has exceeded a certain length the copying method can no longer employed. In addition, machining by means of copying lathes requires relatively prolonged machining times.

A further process is known from the German Offenlegungsschrift (Laid-Open Specification) 33 17 178, in which non-circular cross-sections are machined with circulating cutters. In this solution the radial movement of the cutting point is achieved by kinematic displacements, and the setting of this movement still requires an awkward and precise adjustment for respective cross-sections. In addition, this process is only suitable for specific geometrical shapes.

It would be desirable to be able to produce noncircular profiles on elongate workpieces, preferably of metallic material, with a high degree of precision, i.e. while observing minimum tolerances, under optimum cutting conditions, with a high degree of productivity and short machining times, even for workpieces of extreme length.

The invention provides apparatus in which one or more tools or cutting elements, circulating in progressive cutting, are controlled in the radial direction by a copying track arranged concentrically with the profile to be produced. The cutting elements can consist for example of cutting plates, milling cutters, paring knives, or the like.

It is particularly advantageous if the inside and outside of the copying track (in the radial direction) are exactly concentric with one another.

Preferably, one or more copying rollers are provided which engage without play on the inside or outside of the copying track and which effect the radial copying movement of the tool.

In one embodiment an inner copying roller(s) and an outer copying roller(s) are rigidly connected to one another by a connexion member and the tool or tools is or are mounted on the said connexion member so that during the radial movement and the circulating movement about the workpiece as determined by the profile the cutting tool or tools has or have an approximately constant geometrical relationship, e.g. cutting angle, relative to the workpiece surface to be machined.

In a further advantageous embodiment the connexion member, which supports the tool, is mounted in a guide element in such a way that the bearing axes are parallel to the workpiece axis.

A particularly advantageous embodiment consists in that the guide element, to which the connexion member together with the tool is secured, is connected in a sliding manner, to a driving part, on or in a radially disposed, linear guide track and absorbs the reaction forces occurring in the working direction during engagement. This embodiment is particularly suitable for producing triplescrew Mohno pump stator cores.

In a further advantageous embodiment the connexion member is connected to the driving part by connexion elements. These connexion elements can be joints or linear guide elements.

It is particularly advantageous that, in use of the apparatus, the geometrical relationship (in particular the cutting angle viewed towards the cutting point tangents in the case of cutting tools) are constant by virtue of the positioning of the inner and outer copying rollers arranged radially on the copying track. This permits an optimum geometrical arrangement of the tools, e.g. cutting elements.

A further advantage is that a plurality of different profiles can be produced without complicated resetting procedures, by interchanging the copying tracks.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an end view of apparatus for producing a cross-section of a double-screw rotor for Mohno pumps with an articulated guide member; Figure 2 is an axial sectional view of the apparatus shown in Figure 1; Figure 3 is an end view of apparatus for producing a cross-section of triple-screw rotors with a linear guide member and three cutters operating in progressive cutting; and Figure 4 is an axial sectional view of the apparatus shown in Figure 3.

Figures 1 and 2 illustrates apparatus in which a copying track 1 is arranged concentrically with the workpiece profile 2 to be produced or the longitudinal axis of the workpiece. Copying rollers 3 and 4 rolling on the copying track 2 are connected to each other by a connexion member 6 including a securely connected tool holder for a cutting element 5. Figures 1 and 2 show an embodiment with a guide element 7 which is connected by way of a connexion element or joint 8 to the connexion member 6 and to a connexion element or joint 9 with a driving part 10. When the driving part 10 is rotated, the connexion members 6 together with the cutting elements 5 are drawn by the guide elements 7 along the copying track 1, which, on account of its shape or geometrical curvature, produces the required movement of the cutting elements 5, which can be arranged offset in a stepped manner.With suitably large radii of the copying track 1 an embodiment for example with copying rollers 3 and 4 arranged in pairs or as a plurality adjacent to one another is possible so as to ensure much more precise guidance of the connexion member 6 with the tool or cutting element 5.

Figures 3 and 4 illustrate a modified embodiment in which the tools or cutting elements 5 are secured to connexion members 6 which are connected to guide members 12 by way of joints 13.

These guide members 12 are precisely guided by guide elements 11 on the driving part 10 and are movable in the radial direction, so as to make possible the profile-dependent radial movements of the cutting elements 5. The guide members 12 absorb in the axial direction the reaction forces which act upon the cutting elements 5. This embodiment according to Figures 3 and 4 is particularly suitable for machining workpieces 2 such as tool cross-sections for triple-screw Mohno pump rotors. The cutting elements 5 are offset in a stepped manner relative to one another, so that progressive cutting is attained and in this way a considerable removal of material is made possible.

The invention is not restricted to the embodiments illustrated and described. It also embraces all those modifications and further developments as well as partial and subsidiary combinations of the features and steps described andlor illustrated which would occur to the person skilled in the art.

Claims

1. Apparatus for producing a non-circular profile on an elongate workpiece, in a plane transverse to the longitudinal axis, comprising at least one material removing tool arranged to circulate around the workpiece and being movable relative to the workpiece, the circulating tool being controlled in the radial direction by a copying track arranged concentrically with the profile to be produced.

2. Apparatus as claimed in claim 1, in which radially inner and outer sides of the copying track are concentric with each other.

3. Apparatus as claimed in claim 1 or 2, in which the radial copying movement of the tool is transmitted to it by one or more copying rollers engaging without play on the radially inner andlor outer side of the copying track.

4. Apparatus as claimed in claim 3, in which the inner and outer copying rollers are rigidly connected to one another by a connexion member.

5. Apparatus as claimed in claim 4, in which the connexion member is mounted on a guide element so that the bearing axes are parallel to the workpiece axis.

6. Apparatus as claimed in claim 5, in which the guide element is connected in a sliding manner on or in a radially disposed, linear guide track on a driving part.

7. Apparatus as claimed in claim 5, in which the connexion member is connected to a driving part by connexion elements and the guide element.

8. Apparatus as claimed in any of claims 4 to 7, in which the tool is firmly secured to the connexion member.

9. Apparatus for producing a non-circular profile on an elongate workpiece, substantially as described with reference to, and as shown in, Figures 1 and 2 or Figures 3 and 4 of the accompanying drawings.