EP0102378B1

EP0102378B1 - A method of manufacturing commutators

Info

Publication number: EP0102378B1
Application number: EP83900915A
Authority: EP
Inventors: Leif Hansen; Bjarne Ulrich Gorm Nyenstad; Torben Clausen Wrang
Original assignee: Thrige-Titan AS
Current assignee: Thrige-Titan AS
Priority date: 1982-03-12
Filing date: 1983-03-11
Publication date: 1986-07-30
Also published as: IT8320046A0; DK158803B; ZA831642B; DE3364840D1; ES8402984A1; IE830511L; IT1160802B; WO1983003324A1; EP0102378A1; DK108882A; ES520856A0; JPS59500393A; IE54519B1

Abstract

A commutator is manufactured by transversaly machining an elongate or cylindrical copper member on one side thereof for providing anchoring elements, whereafter the copper member as cylindrically rolled up is connected with a cast commutator body and is transversely cut for the mutual separation of the commutator elements. The anchoring elements are provided by subjecting the copper member to a plough up action from an undercut sticking and ploughing tool or tool set, whereby raised ribs are produced along the sides of the tool. With this production method the anchor ribs as constituted by compression displaced copper will show a high strength, whereby the method is applicable for the manufacturing of commutators even for high performance requirements.

Description

The present invention relates to a method of manufacturing commutators of the type comprising a row of mutually separated commutator elements having an exposed commutator side and an opposite side shaped with integral undercut protruding portions forming anchoring elements, which are secured to a cast commutator body, whereby the row of commutator elements is produced from an elongate unitary material member, which is machined on one side for the shaping of the said anchoring elements and is thereafter, upon being connected to or having cast therein said cast commutator body, divided into said row of separate commutator elements by way of transverse cuttings between the consecutive anchoring element carrying portion of the material member.
In traditional commutator production the commutator elements as loose members are laid into a mounting ring to form a cylindrical row of elements each of these elements having an inwardly directed side with integral protruding portions to form anchoring elements for the commutator body. The cast commutator body is placed into the cylindrical row of elements whereafter this row is cut for the mutual separation of the commutator elements. The mounting of the loose commutator elements is a time consuming work, which has proved difficult to automatize, but the achievable quality of the commutators produced in this manner is very high, primarily due to the fact that the anchoring elements may show a high degree of rigidity or stability, when they are formed - in any of several possible manners - on the single commutator elements, these elements basically being cut from a profiled rod of a suitable material, normally copper.
Many-attempts have been made to facilitate the production of the commutators, especially for avoiding the handling of the loose commutator elements. Thus, it has been a natural tendency to make use of a unitary material member shaped as a cylinder or a cylindrically rolled up material strip, which is subjected to some mechanical treatment for the formation of the anchoring elements and later on to the same kind of separation cutting as effected to the traditional row of individual commutator elements. However, the anchoring elements as produced in this manner so far have not been producible with the same high quality as those appearing on the said individual commutator elements, and a well known result is that commutators produced in the above mentioned facilitated manner have not satisfied the same high performance requirements as achievable by conventionally produced commutators. Generally the known mechanical treatments for the formation of the anchoring elements have been unapt to produce such elements with a sufficiently high rigidity or ducta- bilityto withstand high separation forces between the commutator elements and the cast body of the commutator.
A method of the above kind is disclosed in GB-A 2,049,496 wherein a flat strip of copper is machined to a row of transverse alternate grooves and ribs, whereafter the opposed ends of the ribs are subjected to the action of wedge shaped skiving knives operating to cut the end portions of the ribs free of the underlying strip material and bend the end portions outwardly therefrom, thus leaving the strip with a row of parallel anchoring elements each constituted by a rib member, a middle portion of which is integrally associated with the strip material, while both end portions thereof are diverging from the surface of the copper strip. Thereafter the strip is rolled into a cylindrical member with the said ribs located at the inner side thereof, and the cylinder is filled by a casting material, which intrudes into the wedge shaped spaces between the bent out rib end portions and their underlying (or now rather outerlying) strip surface portions. Thereafter the strip material is cut away between the neighbouring rib carrying portions leaving these portions as individual commutator segments each anchored to the casting material by the latter being present inside and outside the bent-out end portions of the ribs. However, the anchoring effect as hereby obtained is not particularly qualified, because the anchoring elements are associated with the respective commutator elements over a limited middle area only, just as the bent out rib end portions are not ideal for anchoring the commutator elements against high centrifugal forces.
It is the purpose of the invention to provide a manufacturing method of the above-mentioned kind, whereby the commutators are producible in an easy manner and yet with the anchoring elements shaped in a practically ideal way, viz. with the same preferred basic shape as normally used in the said traditional production, where the single commutator members are preshaped with a rear rib portion extending along at least a substantial length of the commutator element and provided with opposed undercut rib sides. This design has proved to provide for a high quality anchoring of the commutator elements. For the invention it is even a purpose to provide a method of producing the anchoring rib portions by a metallurgical process ensuring a high strength of these portions.
The invention provides a method of the above-mentioned kind wherein the anchoring elements are produced by subjecting the relevant side of the elongate unitary material member to a transverse plough-up action by means of undercutting ploughing tool means causing the surface material of the material member to be locally displaced generally outwardly from and upwardly along the opposite sides of the ploughing tool means, whereby the material thus displaced forms an obliquely upstanding undercut rib portion located so as to constitute, together with a corresponding oppositely oblique neighbouring rib portion, the anchoring element of a commutator element as subsequently formed by said transverse cutting.
The mechanical anchoring element forming treatment is carried out by a transverse ploughing up action on or in the relevant surface of the material member, whereby oblique anchor rib portions are formed by the displaced material, and these rib portions will be very ductile and strong, because they emanate from a compression action on the material. The preferred material is conventional commutator copper, i.e. practically pure copper, which preserves or even builds up a high strength when subjected to a cold compression deformation, which will here apply also to the root area of the rib portions.
When the anchor ribs are produced by means of an undercutting ploughing tool they will be left slanting towards each other, while in a commonly preferred shape of the anchor element two oblique ribs are arranged V-like, i.e. slanting away from each other. However, this is easily achievable by arranging for the ploughing to be carried out at the places where the material member is later on to be cut transversely for the separation of the commutator elements; hereby the anchor ribs of each element Will be constituted by the adjacent ribs of two neighboring ploughing areas, and besides the advantage will be obtained that the separation cutting is carried out in an area, from which a part of the material has been removed by the ploughing action, for the formation of the anchor ribs, i.e. the material waste as connected with the separation cutting will be reduced.
The ploughing action may be effected in a raised portion of the material member located spaced from the side edges thereof, whereby the resulting commutator elements will be provided with anchoring elements along only a partial length thereof, which is desirable for the longitudinal anchoring of the commutator elements in the cast commutator body.
The material member may be a straight profile, which is rolled up subsequent to the ploughing treatment, or it may be a cylindrical member, preferably made as a rolled up profile, which is subjected to the ploughing treatment in its cylindrical shape.
The plough up action may be effected stepwise by means of a single tool, or a multiple tool may be used. It is particularly advantageous to use two opposite multiple tools, which are mutually staggered and forced into the material member simultaneously from both edges thereof, thereby the material member will need no rigid holding means, as the forces applied from both sides will neutralize each other.
In the following the invention is described in more detail with reference to the accompanying drawing, in which:-

Fig. 1 is a perspective view of a material member from which a row of commutator elements is to be made,
Fig. 2 is a perspective sectional view of the same member and a tool for providing the anchoring elements.
Fig. 3 is a plan view illustrating the action of the tool shown in Fig. 2,
Fig. 4 is an end view of the material member as rolled into a cylindrical shape,
Fig. 5 is a perspective sectional view of a commutator unit comprising the material member of Fig. 4,
Fig. 6 is a perspective view of a finished commutator,
Fig. 7 is a perspective view of a cylindrical material member and two multiple tools for pro- . viding the anchoring elements, and
Fig. 8 is an end view of the cylindrical material member as subjected to further treatment.

The material member shown in Fig. 1 is a copper strip 2, which is profiled, by rolling or otherwise, so as to show a broad base portion 4 and a raised flat portion 6 of reduced width. This strip member, which may be supplied from a supply reel, is advanced stepwise through the working station as illustrated in Figs. 2 and 3, in which the strip 2 is supported by a carrier sole 8 and is subjected to the transverse action of a ploughing tool 10, the active part of which is an undercut plough shear 12, the front end of which is ground so as to form an undercut ploughing point or edge 14, the front point of which is located in the level of the planar underside of the plough shear 12.
The tool 10 is forced laterally against the raised material portion 6 with the surface of the plough shear 12 in level with or slightly spaced from the top side of the broad portion 4 of the strip 2. By this operation the tool will cause a furrow 16 (Fig. 3) to be ploughed in the material portion 6, because the copper will be forcibly displaced transversely by the sides of the tool front 14 to flow upwardly along the undercut opposite sides of the plough shear 12 and outwardly therefrom, to form obliquely-upstanding undercut raised anchoring ribs 18 projecting beyond the top level of the profile portion 6 on each side of the furrow 16.
When the shear 12 has thus ploughed through the entire profile portion 6 the tool 10 is retracted and the material strip 2 is advanced a step corresponding to the desired pitch between the neighbouring commutator elements of the final product, whereafter the tool is reactuated. Thus, the strip member 2 will leave the working station with a length profile as shown to the left in Fig. 3, i.e. with the profile portion 6 converted into a row of V-shaped protrusions 20 forming the anchoring elements of the later commutator elements.
Thereafter a length of the prepared strip 2 as corresponding to the circumference of the commutator to be produced is cut off, and this cut off strip is rolled up into a cylindrical member. In Fig. 4 this cylindrical member is designated 24 and its join 26. The join 26 is located midways between two anchoring protrusions 20.
Hereafter the material member may be further processed in conventional manner. At first, a rigid body 28, Fig. 5, is produced by casting into the internal space of the cylindrical member 24, and, if applicable, about a central bushing 30, whereby the casting of the body 28 will provide for a strong radial holding engagement between the undercut anchoring elements 20 and the casting material. A corresponding axial anchoring is obtained in that the body 28 is provided with a width broader than that of the raised profile portion 6, i.e. larger than the length of the anchoring elements 20.
Thereafter slots 34 (Fig. 5) are cut through the cylindrical body, whereby the commutator cylinder member 24 is divided into a row of mutually insulated commutator elements, each anchored to the body 28 by means of the associated anchoring portion 20. The end portions of these commutator elements as projecting beyond the end of the cast body 28, as shown in broken lines in Fig. 6, may be bent to form electrical connector hooks 36, if desired, the mutual distance between these hooks being increased by way of cutting a broadened notch between them; it will be understood, however, that a desired distance between these hooks may be provided initially in a simple manner by the working on the strip member 2, viz. by a stamping out of simple notches in the edge portion as shown to the left in Figs. 1 and 2.
There are rather high requirements as to the rigidity of the anchoring portions 20, but it has been found that with the use of the described simple ploughing method these portions may show. a remarkable strength, which is equal to or better than obtainable with other production methods.
As indicated by dotted lines in Fig. 3 it will be possible to use a ploughing tool having two or even more active ploughing shears 12, whereby the production speed may be increased.
By the penetration of the shearing front edge 14 of the tool into the profile portion 6 the said front end will be able, due to its inclination, to cut into the profile portion, and for this reason the plough shear 12 should be mounted on a heavily dimensioned and accurately guided tool carrier 10 (Fig. 2). The said diving effect may be reduced by subjecting the material to two or more successive operations, whereby the ploughing cuttings are effected with increasing depth and/or width.
The length profile of the anchoring portions 20 may in a simple manner be varied by a corresponding variation of the cross profile of the portion 6 at the strip member 2, e.g. for the provision of local breaks of the anchoring portions for an improved axial holding thereof in the cast body 28, just as also the cross section profile of the anchoring portions 20 may be varied widely all according to the profile of the ploughing tool or tools. The ploughed up ribs 18 may be further ploughed up, viz. by a subsequent treatment with a ploughing tool as cutting into the sides of the ribs spaced from the bottom surface between the anchoring portions 20.
In Fig. 7 is shown a profiled material strip 2 rolled up into a cylinder 40, which is placed between opposed tools 42 and 44, each of these tools comprising a circular row of ploughing tools 10, 12, 14 projecting from rear carrier members 46. In a manner not shown these carrier members are connected with means for urging them towards each other, whereby all the ploughing tools 10, 12, 14 are forced into the internally raised portion 6 of the cylinder 40 to effect the said ploughing action thereon. The ploughing tools 10, 12 of the opposed tool units 42, 44 are circumferentially staggered so as to each fit into the space between two opposed tools 10, 12 whereby all the relevant anchoring elements 20 are producible by one operation of the two multiple tools 42 and 44. Due to the equal number of separate tools 10, 12 on these multiple tools the cylindrical member 40 will be influenced by generally equal and oppositely directed sticking forces, whereby the cylindrical member 40 need not be separately supported in the direction of the movements of the multiple tools 42 and 44.
The anchor elements 20 may be shaped with any of a wide variety of possible shapes, one example being shown in Fig. 8, either by one step operation of correspondingly shaped tools or by successive operation of different tools. The shape and the size of the anchor elements may be selected according to the requirements and circumstances, e.g. the type of material used (copper, aluminium or other). The cylindrical member as provided with the anchor elements may be connected with the insulating commutator body 28 (Fig. 5) either by direct casting out thereof or by insertion into a precast body 28. The cylindrical member 40 (Fig. 7) may be a roled up strip member 2 or an entirely closed ring member produced in any suitable manner.

Claims

1. A method of manufacturing commutators of the type comprising a row of mutually separated commutator elements having an exposed commutator side and an opposite side shaped with integral undercut protruding portions forming anchoring elements (20), which are secured to a cast commutator body (28), whereby the row of commutator elements is produced from an elongate unitary material member, which is machined on one side for the shaping of the said anchoring elements (20) and is thereafter, upon being con-. nected to or having cast therein said cast commutator body, divided into said row of separate commutator elements by way of transverse cuttings (34) between the consecutive anchoring element carrying portion of the material member, characterized in that the anchoring elements (20) are produced by subjecting the relevant side of the elongate unitary material member (2, 40) to a trasverse plough-up action by means of undercutting ploughing tool means (12) causing the surface material of the material member to be locally displaced generally outwardly from and upwardly along the opposite sides of the ploughing tool means (12), whereby the material thus displaced forms an obliquely upstanding undercut rib portion (18) located so as to constitute, together with a corresponding oppositely oblique neighbouring rib portion (18), the anchoring element (20) of a commutator element as subsequently formed by said transverse cutting.

2. A method according to claim 1, whereby the transverse plough-up action is effected along axes coinciding with the axes of said subsequent transverse cuttings (34), thereby providing each commutator element with a substantially V-shaped anchor rib (20) as composed by rib portions (18) from respective neighbouring plough-up areas.

3. A method according to claim 1, whereby the material member (2, 40) is profiled with one or more raised portions (6) spaced from the side edges of the material member the plough-up action being effected substantially solely through this or these raised portions.

4. A method according to claim 1, whereby the transverse plough-up action is effected successively along the elongate material member.

5. A method according to claim 1, whereby the transverse plough up action is effected by means of two opposite sets of ploughing tools (42, 44) which are forced into the material member from opposite side edges thereof.

6. A method according to claim 1, whereby the plough up action is effected onto a material member (40) already shaped as an entirely or substantially continuous cylindrical member.

7. A method according to claims 5 and 6, whereby the interior side of a cylindrical material member (40) is subjected to said plough-up action simultaneously from both sides thereof by means of respective opposed multi-ploughing tool sets (42, 44), which are mutually staggered circumferentially of the cylinder so as to produce all the required anchoring elements in one operation.

8. A method according to claim 1, whereby the material member is subjected to two or more successive ploughing operations in each ploughing area.