Arrangement for rotatable adjustment of a cap on an eyepiece housing

The present application is a divisional of U.S. application Ser. No. 10/217,462, filed Aug. 14, 2002, now U.S. Pat. No. 6,779,899, the entire contents of which are incorporated herein by reference.

This application claims benefit of and priority to Federal Republic of Germany Priority Application 101 39 173.0, filed Aug. 16, 2001 including the specification, drawings, claims and abstract, which is incorporated herein by reference in its entirety.

The invention relates to an arrangement for rotatable adjustment of a cap on an eyepiece housing with a stationary pin pointing radially outward from the eyepiece housing and a groove which is assigned to the pin, arranged on the inner side of the cap and rises in the axial direction.

An arrangement of this type is known from U.S. Pat. No. 5,784,207 What is known as an eyepiece cup is arranged longitudinally displaceably on an eyepiece housing, in order for it to be possible for glasses-wearers and normal-sighted observers to set an optimum position of the eye in relation to the exit pupil of the eyepiece. A screw is attached to the eyepiece housing, the head of which is guided in a groove which is in the inner wall of the eyepiece cup. By rotating the eyepiece cup, the height of the eyepiece cup is adjusted relative to the eyepiece housing. Provided opposite the groove-guide in the cross section of the arrangement, between the eyepiece cup and the eyepiece housing, is a catch arrangement for different extension positions of the eyepiece cup. The catch arrangement consists of a plate spring element which is provided with a nose and is arranged on the eyepiece housing, the nose engaging in appropriately shaped notches in the inner wall of the eyepiece cup.

The large number of parts makes assembly more difficult and is expensive. The resilience of the catching element wears out as a result of material fatigue. Demounting of the eyepiece cup for cleaning purposes is not envisaged.

An eyepiece housing with an adjustable, in particular asymmetrically shaped eyepiece cup is known from DE 299 04 366 U1. A guide, which likewise consists of a groove and a pin, is intended to ensure that the eyepiece cup is stopped in the displacement end positions concerned and always has the same orientation in the circumferential direction. To this end, catching positions are provided, which are arranged on a line parallel to the longitudinal axis of the eyepiece housing. As the guide groove is inclined in relation to the longitudinal axis, its direction always has to be diverted, in relation to the designated line parallel to the longitudinal axis, for passage into the catching position. The catching is brought about by an angular change in direction of the guide groove.

While it is true that this guide manages without additional moving parts, it nevertheless requires a relatively complex shape of the guide tracks, which can wear at the angular diversions to the catch position when used for a relatively long time. Demounting of the eyepiece cup is not envisaged in this case either.

It is therefore an object of the invention to provide a simple and cost-effective fastening, guidance and catching arrangement for an eyepiece cup to be adjusted rotatably on an eyepiece housing, which manages with only one moving mechanical component which is non-sensitive to environmental influences and, for cleaning, can be removed from the eyepiece housing, cleaned and replaced rapidly and without additional tools.

According to the invention, this object is achieved in an arrangement of the type referred to in the introduction by virtue of the characterizing features of the invention.

In one embodiment of the invention, there is an arrangement for rotatable adjustment of a cap on an eyepiece housing with a stationary pin pointing radially outward from the eyepiece housing and a groove which is assigned to the pin, arranged on the inner side of the cap and rises in the axial direction, wherein, in a plane at right angles to the longitudinal axis ( 4 ) of the eyepiece housing ( 10 ), three pins ( 11 ) are arranged on the latter, the heads of which pins have at least approximately the same spacing from the longitudinal axis ( 4 ), and wherein the sliding bottom ( 7 ) of the groove ( 3 ) assigned to each pin ( 11 ) has a smaller spacing in relation thereto, so that the cap ( 1 ) bears against the pins ( 11 ) under prestress.

In another embodiment of the invention, there is an arrangement for rotatable adjustment of a cap on an eyepiece housing wherein the grooves ( 3 ) have catching recesses ( 8 , 8 ′, 8 ″) in their sliding bottom ( 7 ), the shape of which recesses is adapted to the heads of the pins ( 11 ) and the depth of which recesses is selected in such a way that, in the catching positions, the cap ( 1 ) bears against the pins ( 11 ) under a prestress which is reduced in relation to the position on the sliding bottom ( 7 ).

In another embodiment of the invention, there is an arrangement for rotatable adjustment of a cap on an eyepiece housing wherein the undersize of the sliding bottom ( 7 ) in relation to the head of the pin ( 11 ) is 1.0% to 2.0%, and the corresponding undersize of the catching recesses ( 8 , 8 ′, 8 ″) is 0.01% to 0.9% of the spacing of the head from the longitudinal axis ( 4 ).

In another embodiment of the invention, there is an arrangement for rotatable adjustment of a cap on an eyepiece housing wherein the grooves ( 3 ) are, in their part ( 6 ) located next to the lower edge ( 5 ) of the cap ( 1 ), angled in the opposite direction to the axial incline, and are open at the lower edge ( 5 ) of the cap ( 1 ).

In another embodiment of the invention, there is an arrangement for rotatable adjustment of a cap on an eyepiece housing wherein the delimitation ( 9 ) of the grooves ( 3 ) running out at an acute angle in relation to the lower edge ( 5 ) of the cap ( 1 ) is milled off parallel to the longitudinal axis ( 4 ).

In another embodiment of the invention, there is an arrangement for rotatable adjustment of a cap on an eyepiece housing wherein the grooves ( 3 ) have a catching recess ( 8 ) in the corner of the angle.

In another embodiment of the invention, there is an arrangement for rotatable adjustment of a cap on an eyepiece housing wherein the heads of the pins ( 11 ) are spherically shaped.

In another embodiment of the invention, there is an arrangement for rotatable adjustment of a cap on an eyepiece housing wherein the heads of the pins ( 11 ) are spherically polished.

In another embodiment of the invention, there is an arrangement for rotatable adjustment of a cap on an eyepiece housing wherein the cap ( 1 ) comprises an abrasion-resistant, elastically deformable plastic with a low coefficient of thermal expansion.

In another embodiment of the invention, there is an arrangement for rotatable adjustment of a cap on an eyepiece housing wherein the cap ( 1 ) comprises a glass-fiber-reinforced polycarbonate.

In another embodiment of the invention, there is an arrangement for rotatable adjustment of a cap on an eyepiece housing wherein the cap ( 1 ) is provided with a removable cover ( 2 ) made of an elastomeric material.

Illustrative embodiments are shown diagrammatically in the drawings and are described in greater detail below with reference to the figures, in which, in detail:

FIG. 1 shows a longitudinal section through the cap,

FIG. 2 shows a longitudinal section through the eyepiece housing, and

FIG. 3 shows a cross section of the arrangement in the assembled state.

FIG. 1 shows a cap 1 , onto which an elastomeric cover 2 , for example, is pulled. For cleaning, the cover 2 can, by virtue of its elasticity, be easily removed from the cap 1 and pulled back on again. It serves in particular for soft contact against a glasses lens or against the eye socket of the observer.

The cap 1 comprises three grooves 3 which are offset symmetrically in its cylindrical inner wall and are inclined in relation to the longitudinal axis 4 of the arrangement. That end 6 of the groove 3 located next to the lower edge 5 of the cap 1 is angled in the opposite direction to the inclination of the groove 3 and is open toward the edge 5 . Let into the sliding bottom 7 of the groove 3 are local recesses 8 , 8 ′, 8 ″ which serve for catching. The catching recess 8 is located in the corner of the angle of the groove 3 . This catching position corresponds to the most raised cap position.

By milling off the delimitation 9 of the groove 3 , which runs out at an acute angle in relation to the lower edge 5 of the cap 1 , parallel to the longitudinal axis 4 , an enlarged opening of the groove 3 at the lower edge 5 of the cap 1 is produced.

FIG. 2 illustrates an eyepiece housing 10 to which radially outwardly pointing pins 11 are attached. For assembly, the cap 1 is put onto the eyepiece housing 10 and perhaps rotated slightly, the pins 11 sliding into the enlarged openings of the grooves 3 . As the diameter of the cap 1 in the region of the sliding bottom 7 of the grooves 3 is smaller than the corresponding diameter of the circumscribed circle containing the heads of the pins 11 , the cap 1 has to be pushed onto the pins 11 under slight pressure. The undersize of the sliding bottom 7 in relation to the respective pin 11 is preferably 1.0% to 2.0% of the spacing of the head from the longitudinal axis 4 , and the corresponding undersize of the catching recesses 8 , 8 ′, 8 ″ is preferably 0.01% to 0.9% of the spacing of the head from the longitudinal axis 4 .

As can be seen from FIG. 3 , the cap 1 is deformed in cross section to form a circular triangle when pushed onto the sliding tracks 7 of the grooves 3 . In this connection, the illustration in FIG. 3 is exaggerated to provide a better view. The heads of the pins 11 therefore slide on the sliding bottom 7 of the grooves 3 under prestress generated by the cap 1 by deformation.

Further rotation counterclockwise brings the cap 1 into the first catching position 8 . While it is true in this connection that the prestress is relieved slightly, it nevertheless continues to ensure play-free catching of the cap 1 owing to the undersize which exists. In the first catching position 8 , further rotation counterclockwise is not possible. Of course, the grooves 3 can be configured so that the cap is moved into the first catching position by clockwise rotation.

On clockwise rotation, the cap 1 is first brought out of the catching recess 8 counter to the catching resistance and it then screws itself further and further onto the eyepiece housing 10 until the next catching recess 8 ′ and then the final catching recess 8 ″ is reached.

To release the cap 1 from the eyepiece housing 10 , the cap 1 merely has to be brought into the catching recess 8 . Then, a pull on the cap 1 with subsequent rotation clockwise is sufficient for it to be possible to remove the cap 1 . The change in the direction of rotation therefore constitutes a safeguard against unintentional removal of the cap 1 . Of course, the grooves 3 can be configured so that the cap is removed with a subsequent rotation counter-clockwise.

The cap 1 is preferably made from an abrasion-resistant, elastically deformable plastic with a low coefficient of thermal expansion. Since the heads of the pins 11 slide in the grooves 3 under prestress and also have to be pressed out of the catching recesses 8 , 8 ′, 8 ″ counter to the prestress, an abrasion-resistant material lengthens the lifetime of the arrangement. A spherical, in particular spherically polished surface of the heads of the pins 11 is advantageous in terms of lifetime and sliding comfort on adjustment of the cap 1 . As the eyepiece cups, in particular on telescopes, are frequently exposed to extreme temperature variations, it is important, for maintaining the prestress generated by deformation, that this prestress is not reduced appreciably by thermal expansion. A glass-fiber-reinforced polycarbonate has been found to be especially suitable with regard to the two desired characteristics.