Binocular telescope

A binocular telescope has a pair of eye-pieces set in threaded mounts and includes a mutual drive for the simultaneous focusing of both eye-pieces, whereby both eye-pieces are connected non-positively with each other via a frictional clutch which slides through when a predetermined limiting torsional movement is exceeded. The binocular telescope combines such advantages of a central drive as, for instance, convenient and accurate setting, along with the advantages of diopter setting, namely accuracy and easy readability.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention is concerned with a binocular telescope with eye-pieces set 
in threaded mounts and having a mutual drive for the simultaneous focusing 
of both eye-pieces. 
2. Prior Art and Technical Considerations 
In the case of binocular telescopes which are intended to be waterproof and 
resistant to tropical conditions the setting of the focal length of the 
eye-pieces cannot be carried out by means of the eye-piece bridge normally 
used since, in the case of this design, it is impossible to obtain 
sufficient sealing between the eye-piece, or eye-piece tube, and the 
telescope housing. Consequently, in existing binocular telescopes mutual 
adjustment of both eye-pieces is carried out by means of a so-called 
central drive. Normally, in the case of this design a driving or focusing 
gear is arranged on the common or joint axis of the two halves of the 
telescope and the rotation of this gear is transfered on to focusing rings 
of the two telescope halves via a gear transmission, thereby producing 
synchronous focal length adjustment. 
In order to carry out diopter adjustment of eye-pieces which are rigidly 
connected with each other via the gear transmission, an intermediate gear 
of the gear unit can be shifted axially thereby disengaging it from the 
gear unit so that the eye-pieces can be adjusted relative to one another. 
After this adjustment the intermediate gear must be shifted axially again 
and thus meshed with the rest of the gear-wheels. The individual 
adjustment of the eye-pieces carried out in such a manner is most 
troublesome, and it is not suitable for example for telescopes intended 
for military use. 
A binocular telescope already exists having two separate focusing wheels 
arranged on the joint axis whereby each focusing wheel is connected to a 
focusing ring of an eye-piece via a corresponding toothed gear. The two 
focusing wheels are arranged so closely to one another that they can be 
mutually manipulated and resulting in synchronous focal length adjustment 
of the eye-pieces. If, in order to adjust the diopters, only one eye-piece 
has to be adjusted, it is only necessary to turn one focusing wheel. This 
arrangement is disadvantageous, however, in that, on the one hand, an 
accidental shift of the diopters can easily take place and, on the other 
hand, it cannot be guaranteed that both focusing gears are really turned 
through exactly the same angle when there is corresponding manipulation. 
It is also known that a belt drive can be employed instead of the gear 
transmission for the purpose of transmitting rotary action of a focusing 
wheel to the focusing rings of the eye-pieces. It has already been 
suggested that one of the focusing rings be arranged on the eye-piece tube 
in such a manner that it is clamped on the latter by means of a screw-type 
cap in order to make adjustment of the eye-pieces relative to one another 
feasible. After loosening the screw cap, the belt drive can be 
manipulated, i.e., an eye-piece can be adjusted without the other 
eye-piece being driven along with it. The screw cap must be tightened 
after this adjustment. Also, in the case of this design, it is considered 
a disadvantage that comparatively troublesome manipulation is necessary 
for a diopter adjustment. 
OBJECT OF THE INVENTION 
The object of invention is to provide a binocular telescope of the 
afore-described type wherein the adjustment of the diopters can be carried 
out quickly and simply, in other words if possible, with a single 
manipulation. 
In accordance with the invention, this afore-described object is 
accomplished in such a manner that both eye-pieces are connected 
non-positively with one another via a friction clutch which slides through 
when a certain limiting torsional moment is exceeded. 
According to the instant invention, under normal conditions, both 
eye-pieces are frictionally connected to one another, i.e., the adjustment 
of one eye-piece, or of one focusing wheel, results inevitably in the 
synchronous focal length adjustment of the other eye-piece. However, 
should the adjustment of the eye-pieces relative to one another be 
necessary--for example in order to adjust the diopters--it is sufficient 
to hold one eye-piece or focusing wheel and then turn the other one in 
relation to it. In the case of this adjustment a certain limiting 
torsional force has to be overcome. Additional manipulation as for 
instance the disengagement of one part or the re-engagement of another is 
not therefore necessary. 
In a further embodiment of the invention both eye-pieces can be adjusted 
via a central drive in a manner known per se, whereby the clutch is 
arranged between the gear chains which connect the eye-pieces to one 
another. Preferably, the central drive should be mounted a shaft upon 
which a focusing wheel is mounted so as to be torsionally rigid. Since, in 
normal situations, both gear chains are coupled by the clutch, the 
focusing of the eye-pieces can be carried out in such a manner that the 
focusing wheel on the shaft of the central drive is adjusted accordingly. 
In order to adjust the diopters, it is only necessary to hold one 
eye-piece and to turn the other as far as is necessary to overcome the 
retaining force of the clutch. 
In a further embodiment of the invention two focusing wheels, which are 
rigidly connected to the eye-pieces, are arranged beside each other on the 
axis of rotation of the central drive, so that the clutch is situated 
between the focusing wheels. This approach has the advantage that scales 
can be affixed to the focusing wheels off of which the diopter setting in 
question can be read. Preferably, the clutch should be a plate spring 
which is secured in place between the focusing wheels. In this case, the 
tension of the plate spring is selected in such a manner that its biasing 
force is sufficient to transmit the adjusting forces, which normally 
occur, from one focusing wheel to the other. 
According to a further embodiment of the invention the clutch consists of a 
spring, in particular a plate spring, which presses a loose driving wheel 
of a gear chain against a driving wheel which is connected rigidly to the 
shaft of the other gear chain. The loose driving wheel is arranged on the 
shaft of the central drive. This approach is advantageous in that the 
plate spring need only have small dimensions since it only has to supply a 
pressing force which, dependent on the coefficient of friction for the 
transmission of the adjustment torsial moment, must be present between two 
driving wheels. Consequently, the clutch can be constructed even more 
compactly. 
According to a further embodiment of the invention both eye-pieces can be 
adjusted in a manner known per se via a central drive. The clutch is 
arranged between a lens tube, which is axially adjustable only, and an 
adjusting tube of an eye-piece, whereby the adjusting tube is on the one 
hand, axially adjustable by the central drive and, on the other hand, 
rotatable relative to the central drive when the retaining force of the 
clutch has been overcome. Accordingly the lens tube and the adjusting tube 
of the other eye-piece are rigidly connected to one another and are only 
axially movable. Consequently, the diopter scale can be affixed as in the 
case of ordinary telescopes so that the set difference can be clearly read 
off. 
With this approach the central drive should preferably be a gear-wheel 
drive with intermediate gears which, on the one hand, are rigidly 
connected to a shaft with an adjusting wheel and which, on the other hand, 
are rigidly connected to the focusing rings surrounding the eye-pieces. 
The focusing rings should preferably have an internal thread which is in 
engagement with an external thread on the adjusting tubes. 
The axially movable and rotating lens should preferably have an external 
flange which is pressed against a counter flange on the adjusting tube by 
a plate spring propped against the eye-piece adaptor. A clutch 
construction of this nature is especially space-saving and can be produced 
at low cost. 
A main advantage of the binocular telescope according to this invention 
lies in the fact that the diopter adjustment can be carried out extremely 
simply and quickly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Joint frames 2 and 4 are swivel-mounted for both telescopes on the rigid 
joint axis 1. The joint frame 2 is not fully illustrated in FIG. 1 since 
its construction is a mirror image of joint frame 4. In the following 
description, only one telescope is described, however it is to be 
understood that the construction of the other telescope is an identical 
mirror or reflected image of the first. 
The eye-piece 6 is mounted in a bore-hole of the joint frame 4. The 
eye-piece 6 consists of several tubes which fit into one another and whose 
particular construction is of no importance with respect to the present 
invention. It is only important to realize that the adjustment of one 
focusing ring 8, which surrounds the eye-piece, results in an axial 
adjustment of the latter in one or other direction, the focal length being 
adjusted accordingly. The focusing ring 8 is connected with a drive belt 
10. This drive belt 10 is connected to a driving gear 12 arranged on the 
joint axis 1 so that it can be rotated. The driving gear 12 is connected 
rigidly to a focusing wheel 14. 
A further focusing wheel 16 is positioned adjacent to the focusing wheel 
14. The former (focusing wheel 16) is connected to the joint axis 1 in 
such a manner that it is torsionally rigid. On the upper end of the joint 
axis 1, a further driving gear 18 is key mounted the latter being also 
connected to the joint axis 1 in such a manner that it is torsionally 
rigid. Upon turning the joint axis 1 by focusing wheel 16, driving gear 18 
is rotated and consequently the belt 10 is rotated. The belt 10 is trained 
around the focusing ring of the eye-piece which is not illustrated but 
which is constructed identically to the illustrated eye piece. 
A plate spring 20 is secured in place between the focusing wheels 14 and 
16. The bias of this plate spring is great enough that so that the 
adjustment of either focusing wheel, 14 or 16, results in the other 
focusing wheel being driven by friction. The illustrated eye-piece 6 is 
therefore manipulated by focusing wheel 14, driving gear 12, drive belt 10 
and focusing ring 8. The second eye-piece, which is not illustrated, is 
manipulated by focusing wheel 16, joint axis 1, driving gear 18 and drive 
belt 10' which leads to the focusing ring of the second eye-piece. 
Since the two focusing wheels 14, 16 are frictionally connected to one 
another any adjustment of one wheel leads to the synchronous focal length 
adjustment of both eye-pieces. This adjustment is independent of which one 
of the two focusing gears is adjusted and is dependent on whether the two 
focusing gears are adjusted simultaneously. 
If only one eye-piece is to be turned, one of the focusing gears is held 
and the other one is turned, whereby the force of friction due to the 
plate spring 20 is overcome. The bias of the spring 20 is selected 
preferably in such a manner that, on the one hand, when one gear is turned 
the other focusing gear will definitely be driven along but that, on the 
other hand, the adjusting force is not immoderately high when one gear is 
held so that one eye piece can be adjusted without the other eye piece 
moving. 
Since it is extremely simple to carry out the adjustment of the diopters in 
this manner, no measures need be provided to compensate the diopter 
adjustment when the joint frame is being moved. 
It is a known fact that the eye-pieces are mutually maladjusted when the 
two joint frames 2 and 4 are folded around the joint axis 1, or when the 
angle enclosed by both joint frames 2, 4 is enlarged or reduced. In the 
case of binocular telescopes with belt drive already known, complicated 
designs are intended solely to avoid such diopter maladjustment. In the 
present case, however, the adjustment of the diopters can be carried out 
so simply and easily that these complicated designs can be done without. 
FIG. 2 shows a second embodiment of the binocular telescope wherein the 
belt drive is replaced by first and second gear trains wherein the first 
gear train is positively connected to one eye piece and the second gear 
train is connected to the other eye piece via a clutch. In the joint axis, 
a shaft 1 is mounted which carries a driving gear 22 with outer gearing 
connected to the upper part of the upper end of the shaft. A focusing gear 
26 is secured on the other end of the shaft 1 in such a manner that it is 
torsionally rigid. A further driving gear 24 is positioned on the shaft 
above the driving gear 22 so as to be freely rotatable on the shaft 1. The 
joint frames are designed as a gear housing 56 in which intermediate gears 
27, 28 are disposed, whereby driving gear 22 is in mesh with the 
intermediate gear 27 and driving gear 24 is in mesh with the intermediate 
gear 28. 
The intermediate gear 27 is in mesh with the outer gearing of a focusing 
ring 30, which has the same function and design as the focusing ring 8 in 
the embodiment illustrated in FIG. 1. The intermediate gear 28 is 
correspondingly in mesh with the outer gearing of the focusing ring for 
the second eye-piece which is not illustrated. The adjustment of the 
focusing rings again results in the axial adjustment of the eye-pieces and 
consequently in a change of the focal length. 
A plate spring 32, which is secured between a lock washer 34 and driving 
gear 24, is arranged on the end of the shaft 1 situated in the joint 
frame. Driving gear 24 is pressed against driving gear 22 by the force of 
the spring 32. In this case the initial force is so large that the 
frictional force between both driving gears is sufficient to adjust or 
drive along the driving gear 24 when the driving gear 22 is adjusted via 
shaft 1 and focusing gear 26. The plate spring only has to supply the 
bias. Its effective diameter for the transmission of the torsional moment 
depends on the size of the driving gears. 
Adjustments of the diopters is carried out by holding the eye-piece, not 
illustrated and by simultaneously adjusting the focusing gear 26. In so 
doing, the retaining force of the "frictional clutch" is overcome, i.e., 
the eye-piece 6 is adjusted via driving gear 22, intermediate gear 27 and 
focusing ring 30, while the eye-piece, not illustrated, remains 
motionless. It goes without saying that the adjustment can also be carried 
out by holding the second eye-piece and turning eye-piece 6. 
FIG. 3 schematically illustrates a third embodiment of the binocular 
telescope. This embodiment offers the additional advantage that the 
diopter adjustment can be clearly and reproducibly set and read off. 
As in the case of the embodiment according to FIG. 2, which has been 
previously described, a shaft 1 with an adjusting wheel 26 thereon is 
provided, whereby a driving gear 36, used as an intermediate gear, is 
secured on the upper end of the shaft 1, within the housing 56. The 
driving gear 36 is in mesh with the intermediate gears 27, 28, which are 
positioned in the joint frame and which are in mesh with the focusing 
rings 30, and 30' respectively. The focusing rings 30, 30' have internal 
threads, preferably helical acme threads which run in contact with the 
helical external thread of an adjusting tube 38. The upper end of the 
adjusting tube 38 is so constructed that the eye-piece adaptor 40 can be 
affixed to it. 
A counter flange or inwardly projecting shelf 422 is constructed in the 
upper part of the adjusting tube 38. This counter flange is turned 
radially towards the inside and an inwardly projecting shelf 44a of the 
lens tube 44 rests on it. The lens tube 44 is designed in such a manner 
that it can only undergo axial adjustments. Furthermore, it cannot be 
rotated. 
The lens tube 44 is pressed against the counter flange 42 of the adjusting 
tube 38 by means of a plate spring 46 having one surface thereof against a 
second inwardly projecting shelf 42b in such a manner that both parts are 
frictionally connected or coupled to each other for axial motion. The 
shelves 42a and 44a form overlapping surfaces which are engaged by the 
spring 46 to form a friction clutch. For its part, the plate spring 46 is 
propped against a projection on the adjusting tube 38, the projection 
being correspondingly designed. Referring to the other eye-piece, the lens 
tube and the adjusting tube form an integrated or rigid structure 48 which 
can be moved axially in a guide tube 50 which is provided with a slot for 
this purpose. Unlike the previously described eye-piece, the adjusting 
tube cannot be turned. 
A sealing bellows 54, which should preferably be pasted or adhered into 
position, and which seals the lens tube against moisture, is arranged 
between the lens tubes 44 and 48 and an eye-piece fitting 52 which is 
screwed into the housing of the telescope. The bellows permits axial 
motion, within the limits necessary for an adjustment of the focal length. 
The focusing of the eye-pieces is carried out in the usual fashion by 
adjustment of the adjusting gear 26. An adjustment of the adjusting gear 
26 causes a corresponding adjustment of the shaft 1, of the central gear 
36, of the intermediate gears 27, 28 and consequently an adjustment of the 
focusing rings 30 and 30' as well. These focusing rings run in contact 
with the adjusting tubes 38, 48, by means of a helical acme thread, in 
such a manner that a corresponding axial adjustment of the adjusting 
tubes, and thus an adjustment of the lens tubes, results when the focusing 
rings are rotated. 
The adjustment of the diopters is carried out by turning the eye-piece 
adaptor 40, and consequently the adjusting tube 38, relative to the 
housing 56 of the telescope. The desired diopter adjustment can be clearly 
determined by means of a diopter scale affixed to the eye-piece adaptor 
40. The bias of the plate spring 46 is such that the eye-piece adaptor 40 
can be turned using a reasonable amount of force. 
The adjustment of the lens tubes of both eye-pieces relative to one another 
may be carried out in various ways. In situations where the acme thread 
between the focusing ring 30 and the adjusting tube 38 provides little 
resistance so that practically no force is transmitted to the focusing 
ring 30 when the eye-piece adaptor 40 is rotated, the adjusting tube 38 in 
the focusing ring will be screwed up or down and the lens tube 44 will be 
moved accordingly along with it. As already explained in the case of the 
other eye-piece, the lens tube 44 runs in a guide tube with a slot in such 
a manner that it can only be moved axially. 
However, in the case of the acme thread providing high resistance, so that 
when the eye-piece adaptor 40 is turned, the focusing ring 30 is driven 
through the saame angular distance, the focusing ring 30' is also adjusted 
by the same amount via the gear train 27, 36, 28. The rotation of the 
focusing ring 30' results, however, in a corresponding adjustment of the 
lens tube 48. If the friction of the acme thread between the focusing ring 
30 and the adjusting tube 38 has a medium value, so that the focusing ring 
30 is driven with corresponding backlash by the eye-piece adaptor 40, both 
lens tube 44 and lens tube 48 will be adjusted. However, the sum of both 
adjustments corresponds exactly to the desired diopter adjustment. 
Hence, the special advantage of this embodiment lies in the fact that for 
adjusting the diopters no other part, as for example, the focusing wheel 
26 has to be held. It is sufficient to rotate only the eye-piece adaptor 
40 as required. The setting can be carried out in a reproducible manner 
and exactly by means of a diopter scale affixed to the eye-piece adaptor 
40. Thus the diopters are set in precisely the same way as the common, 
widespread telescopes with an eye-piece bridge. It is therefore not 
necessary to adapt oneself to a different way of doing things when using 
the telescope according to this invention. The embodiment of the binocular 
telescope as described combines the advantages of a central drive, such as 
for instance convenient and accurate setting, along with the advantages of 
diopter setting similar to traditional telescopes with an eye-piece 
bridge, namely accuracy and easy readability.