Machine element or mechanism – Gearing – Rotary bodies
Reexamination Certificate
1999-06-02
2001-03-27
Lorence, Richard M. (Department: 3682)
Machine element or mechanism
Gearing
Rotary bodies
C074S424830, C074S459500
Reexamination Certificate
active
06205878
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an apparatus, which converts a rotational movement into a back and forth movement and is also referred to as a ball roller spindle.
In German Patent Application No. G 94 00 721.7, an apparatus is described for converting a rotational movement into a back and forth lifting motion or the reverse. The known apparatus has a spindle with at least one guiding groove in an outer surface, a bearing body and a force transfer device with a ball mechanism. The spindle and the bearing body are disposed so that they can be shifted rotationally as well as axially relative to one another. The ball mechanism is mounted in a continuous borehole in the bearing body in such a manner that it protrudes into the guiding groove on one side and, on an opposite side, protrudes towards the outside over the wall section of the bearing body. A ball race is fitted onto the bearing body and supported at the ball mechanism, placing the latter under tension in the direction of the guiding groove. In order to prevent the ball race from being pushed in an axial direction out of a region of the ball mechanism with a result of releasing driving balls of the ball mechanism, either a groove, V-shaped in cross section, is provided in an inner surface of the ball race or the apparatus is only intended for smaller lifts for the known mechanisms for each ball mechanism of the majority of ball mechanisms.
Moreover, an apparatus for controlling valves, robots or tool machines is described in European Patent Application No. EP 0 337 418 A1. For this known apparatus, a ball mechanism is supported in a guiding groove of a spindle and in an axial groove of a housing enclosing the spindle and bearing body. At the same time, the spindle is mounted rotatably in a housing. The known apparatus can be used in a variety of ways to effect relative motions between the spindle, the bearing body and the housing or for equipment produced from these structural elements, such as metering pumps. However, these devices have a comparatively complicated construction and therefore are relatively expensive to manufacture.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an apparatus which converts a rotational movement into a back and forth movement, reliably prevents an axial shift of a ball race relative to a ball mechanism, and has a simple structure with a cost of manufacturing less than that of manufacturing known systems.
This objective is accomplished with an apparatus in which the ball race has at least one driving ball bearing surface which is disposed essentially concentrically to the wall section and an arresting mechanism for fixing the ball race in position with respect to an axial movement relative to the ball mechanism.
The apparatus for converting a rotational movement into a back and forth movement has a spindle with an outer surface having at least one guiding groove, a bearing body with a wall section surrounding the outer surface of the spindle concentrically, and a force transfer device with at least one ball mechanism, comprising at least one driving ball.
The spindle and bearing body are disposed, so that they can be rotated and shifted axially relative to one another. The ball mechanism is mounted in a bearing bore in the wall section and protrudes into the guiding groove as well as through the wall section. A ball race, which biases at least one ball mechanism toward the guiding groove, is fitted onto the bearing body.
Pursuant to the invention, the ball race has at least one driving ball bearing surface, disposed essentially concentrically with respect to the wall section, and one arresting mechanism.
With respect to axial movement of the ball race relative to the ball mechanism, the position of the ball race is fixed by means of the arresting mechanism.
The driving ball bearing surface, disposed concentrically to the wall section of the bearing body, can be produced with little technological effort and therefore relatively inexpensively. In order to prevent axial shifting of such a ball race having a cylindrical inner surface, which can be easily manufactured, from a rolling region of the ball mechanism, the ball race has an arresting mechanism, which prevents relative axial motion between the ball race and the bearing body. By these means, it is ensured that the driving balls of the ball mechanism are not released under any circumstances by the cylindrical inner surface supporting the ball mechanism, so that they cannot fall or cannot be driven out of the bearing bore of the bearing body.
Moreover, the driving balls, guided or taken up in the bearing bore, are disposed so that a driving ball is guided in a guiding groove of the spindle and in the bearing bore and the driving ball above is guided at the inner cylindrical surface and in the bearing bore. Instead of a double ball arrangement, a single driving ball which is guided supported in the guiding groove of the spindle, the bearing bore of the bearing body, and the cylindrical inner surface of the ball race is optionally provided. The bearing bore in the bearing body for use with the single ball is to be constructed with a correspondingly larger diameter. However, an advantage is that only a single driving ball is sufficient for the ball mechanism.
Preferably, the arresting mechanism of the ball race has at least one ring shoulder in a region of end faces of the ball race. The ring shoulder has a diameter, which is smaller than a diameter of the driving ball bearing surface, so that an inner shoulder is formed at the ring shoulder in a front end region of the latter, with which the driving ball, facing the respective shoulder, is in contact. By these means, an axial shifting of the ball race relative to the ball mechanism is prevented. Since preferably several ball mechanisms are to be provided, especially in the case of ball races with a relatively large axial length, and the bearing body has several bearing bores for accommodating such ball mechanisms, it is not necessary, when the respective shoulders are present in the end face regions of the arresting mechanism, that the driving balls of the ball mechanism, guided between the outer shoulders at the inner shoulders, have an additional lateral guide. Rather, it is sufficient that the ball mechanisms, lying between the ball mechanisms, which are the outer ball mechanisms in the longitudinal direction, are supported only at the inner cylindrical surface of the ball race. It is, however, also possible that the driving ball bearing surface, disposed concentrically to the wall section of the bearing body, has small, flat groove-like ball bearing surfaces, so that, preferably for each ball mechanism which lies between the ball bearing surfaces in contact with the inner shoulders, there is at least a slight guidance to prevent axial movement of the ball race relative to the ball mechanism.
In accordance with a further preferred example, the arresting mechanism of the ball race is constructed as an inclined surface, a direction of which is inclined with respect to the longitudinal axis of the spindle. The inclined surface, forming the actual inner shoulder, represents a conical section surface, so that the driving balls of the ball mechanism, lying furthest towards the outside and contacting this inner shoulder, have at least a theoretically pointwise contact, which is particularly advantageous from the point of view of friction.
In accordance with a further development, however, it is also possible that a shape of the inner shoulder is essentially congruent with a surface of the driving ball. This means that the surface of the inner shoulder is constructed so that it is in contact with the surface of the driving ball of the respective ball mechanism, as a result of which the guidance for the driving balls is particularly good.
Preferably, at least one of the two ring shoulders is connected integrally with the ball race. It is, however, also possible that both ring shoulders are connected integrally with the ball race. In the latter case,
Jordan and Hamburg LLP
Lorence Richard M.
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