Metal working – Method of mechanical manufacture – Obtaining plural product pieces from unitary workpiece
Reexamination Certificate
2002-05-10
2004-06-01
Bryant, David P. (Department: 3726)
Metal working
Method of mechanical manufacture
Obtaining plural product pieces from unitary workpiece
C029S416000, C029S525010, C029S557000, C083S053000, C188S2180XL
Reexamination Certificate
active
06742233
ABSTRACT:
The invention relates to a brake disk and method for producing a friction ring, particularly for brake disks having friction rings constructed of more than one ring part, particularly axle brake disks for rail vehicles having two axially offset ring bodies divided corresponding to the friction ring and a method for their manufacturing are known in a plurality of constructions.
Patent Document DE 43 08 910 C2 discloses a brake disk for disk brakes with a friction ring which can be acted upon on one side by at least one brake shoe and has at least two friction ring segments. Each ring segment is held on a carrier body by connection elements which prevent radial relative displacements of the ring segments. The friction ring also has recesses on at least one side which are open toward the carrier body and are symmetrically arranged with respect to the junction points of the ring segments. The recesses are shallower than the width of the ring segments.
Furthermore, the friction ring has ring grooves as recesses which are arranged bridging the junction points and whose axes extend parallel to the axis of the friction ring, in which case a ring body can be inserted in each ring groove and fills the ring groove at least approximately completely and bridges the junction point. This arrangement prevents the junction point between the two ring segments from growing wider in the event of an occurrence of high centrifugal or other forces. Relative radial displacements also avoided. The connection elements as constructed require virtually no additional installation space.
However, this solution is very costly to make because the recesses and ring bodies must be precisely cut. Furthermore, in addition to the division, an additional high-expenditure machining of the ring segments is required. A casting is also conceivable, but requires a special casting mold.
European Patent Document EP 0 166 879 B1 shows a brake disk with a divided friction ring, particularly an axle brake disk for rail vehicles having two axially offset ring bodies divided corresponding to the friction ring. Two mutually axially opposite ring bodies are connected with one another by radially extending ribs. A screwed connection bridges the mold seam between the friction ring parts with prestress, the mutually opposite faces of the friction ring parts in the areas of the screwed connection and their lateral boundary resting against one another but have a distance from one another in the remaining areas. The screwed connection enables the ring bodies to experience a secure connection with no gaps in the friction surfaces of the brake disk. In addition, unintentional deformations of the ring bodies and the buildup of excess tensions is avoided. This solution is also costly to make.
European Patent Document EP 0 636 217 B1 shows a one-piece brake disk with two separation zones dividing it into two parts. Subsequently, a fastening device is positioned on each separating zone and extends over this separating zone. Finally the brake disk is broken at the separating zones into two semicircular parts. This method is relatively inexpensive because the brake disk itself can be manufactured at low cost, and the replacement of a worn-out brake disk with a new brake disk is quite simple. However, corresponding connection elements must be provided to prevent relative displacement of the ring segments. Another significant disadvantage is that this method can only be used for brake disks made from brittle materials, such as gray cast iron. Furthermore, these brittle friction rings must be thick and heavy in order to avoid fracture. As a result, such friction rings are not suitable for a use in rail vehicles because, as a rule, only wide friction rings are used there. However, these cannot be broken but at most can be destroyed. Another disadvantage is the resulting further development of the profile surface. However, the breakage zone does not prevent unevennesses in the surface of the friction ring. Therefore, deeper zones of wear may occur, which may result in an uneven wearing of the brake linings.
Furthermore, the solutions described in the indicated patent documents are not cost-effective for the manufacturing of brake disks of a small width and their design for higher speeds.
The present invention further develops a brake disk having a divided friction ring such that the disadvantages indicated in the prior art are avoided. Simple devices are used such that the junction point between two ring segments cannot widen even when high centrifugal forces or other forces occur, and simultaneously an axial and radial displacement relative to one another is avoided. The connection elements require virtually no additional installation space, so that the brake disk can also be constructed to be unventilated or with only short cooling ribs. Furthermore, this brake disk is inexpensive to make.
The brake disk comprises a friction ring having at least two ring segments—a first ring segment and a second ring segment. The ring segments are produced by a mechanical separation process from a one-piece or one-part ring-shaped basic body. According to the invention, the separation of the ring segments from the basic body is done by a hydrocutting method, particularly a water torch cutting method. The separating line is constructed such that the end areas engage in one another while forming a separation gap therebetween.
The area of contact between the segments is called a junction area or separation area. In this case, the term “junction area” relates to the meeting of the mutually opposite surfaces of the two mutually adjacent ring segments under stress, while these surfaces are to be assigned to the “separation area” under the aspect of the course of the separating line of the ring-shaped basic element in the circumferential direction. The adjacent ring segments are coupled with one another in the separation or junction area by means of at least one connection element. The at least one connection element extends along and passes through at least a partial area of the end areas of the ring segments. This reduces the space requirement for the installation of the connection elements. When the brake lining is in contact with the friction ring, the connection elements do not project beyond the latter and cannot damage the brake lining.
The meshing of the individual ring segments in the junction or separation area is accomplished by protrusions and recesses are formed on the respective mutually opposite separation surfaces of the individual friction ring segments. These protrusions and recesses are complementarily formed so that the protrusions of one segment engage in recesses on the other ring segment.
The method according to the invention has a minimal number of required process steps and a low requirement of installation space and at low cost. The basic element may already be finished with respect to its surface treatment because, after the cutting operation, no additional surface-processing steps are required for the surface machining. For this reason, conventional one-piece friction rings can also be used as the one-piece basic element.
The very fine hydrojet or water torch generates only a minimal cutting gap, resulting in a low loss of material, and the individual ring segments can therefore be fitted into one another with a very accurate fit. This separation gap caused by the cutting, is in the one millimeter range, which virtually ensures a contact of the end areas of the individual ring segments. When the ring segments are connected, no additional measures are generally required to fix the position of the individual elements with respect to one another. When the individual ring segments are mounted, the connection is capable of absorbing all circumferential tensions on the friction ring.
The technique of hydrocutting, particularly water torch cutting, is a type of mechanical separation which, in addition to its suitability for very complex shapes and undercuts, permits a machining with very little deformation in the area of the cut. As a result, no
Barnes & Thornburg LLP
Bryant David P.
Cozart Jermie E.
Knorr-Bremse Systeme Für Schienenfahrzeuge GmbH
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