Bow string peep sight

A bow string peep sight comprises a disk having a string hole for receiving a bow string to be kept in a position perpendicular to the disk. Outside the string hole the disk is provided with a transparent sighting area having the shape of a sector of a circle ring concentric to the string hole and extending over an angle of between 120.degree. and 270.degree.. When the bow is drawn the disk is tilted, thereby revealing to the archer a single sighting opening outwardly appearing to be limited by two elliptic arcs. The sighting hole is made sufficiently small to ensure an exact aiming. Owing to the great angular distance between the ends of the sighting area, the single sighting opening is formed independent of the twist of the bow string.

TECHNICAL FIELD 
This invention relates to a peep sight for mounting on the bow string of an 
archery bow and of the type comprising a body adapted to be fastened on a 
bow string in a position perpendicular thereto and provided with a 
transparent area inwardly as well as outwardly limited by circular arcs 
concentric to said box spring. 
BACKGROUND ART 
A bow string peep sight of this type is described in U.S. Pat. No. 
4,454,857, said peep sight comprising a wheel having a central elongated, 
hollow hub portion extending perpendicular to the plane of the wheel for 
receiving the bow string. The wheel is provided with a continuous rim 
portion connected to the hub by spokes and leaving a transparent sighting 
area between the rim portion and the hub. The wheel of the known peep 
sight is plane at one side but is provided on the opposite side with a 
conical recess ensuring said sighting area to be sharp-edged at its outer 
limitation. When such a peep sight is tilted owing to the drawing of the 
string a sighting aperture is revealed--provided the eye is close to the 
sight--between the hub and rim, said aperture being limited inwards by a 
straight line defined by the outer face of the hub and outwards by a 
relatively long elliptic arc defined by the inner edge of the rim portion. 
In far the most cases, a spoke is positioned in the visual fields of the 
sighting apertures. However, the presence of a spoke within the used 
sighting aperture blurs the view through said aperture to a certain 
degree. Furthermore, the elliptic arc limiting each sighting aperture 
outwards has a close resemblance to a semi-circle and, therefor in most 
cases the sighting aperture is too large for ensuring a correct aiming. In 
most cases, it is inconvenient that two sighting apertures are formed--one 
on each side of the string--since the wrong aperture may be chosen 
especially when the aiming period is very short. 
OBJECT OF THE INVENTION 
An object of this invention is to provide a bow string peep sight of the 
type concerned which ensures a sight being as distinctive as possible, and 
which in use allows only a single sighting aperture to be visible at a 
time, where the sighting aperture has limited dimensions and is approx. 
quadrangularly limited by four elliptic arcs ensuring an exact sighting. A 
further object of this invention is to ensure that the sighting aperture 
is always free of disturbing elements. 
DISCLOSURE OF THE INVENTION 
According to the present invention the body constituting the peep sight is 
provided with a transparent sighting area shaped as a sector of a circle 
ring extending over an angle of between 120.degree. and 270.degree., 
whereby at the front side as well as at the rear side of the body said 
sighting area is outwardly limited by a front outer circular arc and a 
rear outer circular arc, respectively, where said two arcs are positioned 
in two spaced planes perpendicular to the hub axis. The sighting area is 
furthermore inwardly limited by two edges of axially spaced portions of 
the body leaving between them a recess occupied by a transparent 
medium--normally air. 
As a result the outer limitation of the sighting aperture appears to be 
composed of a first outer elliptic arc corresponding to a portion of the 
outer front circular arc and of a second outer elliptic arc corresponding 
to a portion of the outer rear circular arc and forming an angle with said 
first outer elliptic arc. In addition, the inner limitation of the 
sighting aperture appears as two elliptic arcs also defined by said edges 
and forming an angle with each other and with the outer elliptic arc. Thus 
the sighting aperture appearing when the peep sight is tilted owing to a 
drawing of the string comprises a relatively small area. Furthermore it is 
easy for the eye to imagine cross hairs interconnecting the corners of the 
quadrangle and thereto to define the center of the sighting aperture. As a 
result, a possibility of a very exact aiming exists. Suitably the body of 
the peep sight is composed at two round bowlshaped plates interconnected 
at their outer edges and provided with alike sighting areas, said sighting 
areas being defined by a transparent portion, for example an opening, 
shaped as a section of a circle ring covering an angle of between 
120.degree. and 270.degree.. Such a body can be given a larger thickness 
and thereby a more distinct area than an ordinary more disk-like body, and 
nevertheless it can be of a lower weight than such a body.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The peep sight of FIGS. 1 to 3 comprises a cylindrical body 10 having a 
plane front side face 12 and spaced therefrom a plane rear side face 14. 
At its central portion, the body 10 is on both sides provided with a hub 
16 extending outwards from the corresponding body side face 12 and 14, 
respectively, and having a hub bore 18 adapted to receive a bow string 20 
shown in FIGS. 2 and 3 only. 
The body 10 is provided with a transverse hollow area 22 at each side of 
the body 10 outwardly limited by a half-circle 24 and 26, respectively, 
and at the ends thereof by lines 28 tangential thereto. The hollow area 22 
has a bottom 29 tangential to the outside of the hubs 16. 
Opposite to the half-circles 24 and 26 each hub 14 is provided with a 
thickening 30 formed integral with the body 10 and provided with an 
axially extending slit 32 also extending through the portions of the hubs 
16 outside the thickening 30. On the same plane as the slit 32, a 
corresponding slit 34 extends through the outer part of the body 10, which 
is thereby divided into two halves interconnected by a hinge member 36 
bridging the slit 34. Consequently, it is possible to open the peep sight 
when it is to be arranged on the bow string whereupon the slit 32 can be 
squeezed together by means of a screw 37 axially interconnecting the two 
halves in which the slit 32 divides the thickening 30, and the peep sight 
can be fastened to the bow string. Furthermore, the screw 37 allows a 
simple adjustment of the position, i.e. also the angular position, of the 
peep sight on the bow string. 
The semi-circles 24 and 26 define together with inner edges 38 and 40 of 
the hubs 16 a transparent sighting opening 41 of the peep sight. 
When the bow string is drawn into shooting position and therefore takes up 
a slanted position, the peep sight is correspondingly tilted whereby only 
a portion of the sighting opening 41 forms a visual sighting aperture 41, 
cf. FIG. 3. This sighting area is limited by two outer elliptic arcs 44 
and 46 corresponding to a portion of the rear semi-circle 24 and of the 
front semi-circle 26, respectively, and by opposite elliptic arcs 48 and 
50 corresponding to a portion of the rear inner edge 38 and the front 
inner edge 40, respectively, of the hubs 14. It is obvious that the size 
and the position of the virtual sighting aperture 42 relative to the bow 
string are the same within a certain twisting angle of the bow string of 
up to 180.degree.. 
The quadrangular shape of the sighting aperture 42 ensures a much more 
accurate aiming than the half-moon shaped sighting apertures obtained by 
the hitherto known peep sights of the type in question. Unlike the 
previously obtained half-moon shaped apertures the quadrangular shape 
implies that it is easy to imagine cross hairs interconnecting the corners 
of the quadrangle and thus to find the exact center thereof even when a 
fast aiming is necessary. 
The shape and dimensions of the peep sight of the present invention depend 
inter alia on the individual archer and the bow used. Bow strings are 
standardized as to thickness depending on the strength of the bow. 
Therefore the diameter of the hub bore 18 should fit the actual bow 
string. Furthermore the size of the virtual sighting aperture depends to a 
certain degree on the applications. In target shooting, a sighting 
aperture is for instance attempted to be as small as possible, whereas the 
bow hunter might prefer a slightly larger hole for a better survey. As to 
the outer dimensions of the peep sight, it is appropriate to chose such 
sights preventing the archer from simultaneously seeing both the target 
through the sighting aperture 42 and outside the body 10 with his shooting 
eye. In practice the max. diameter of the body is from 10 to 15 mm. 
Although not strictly necessary it turned out to be appropriate that the 
body 10 is provided with an inner recess 52 at the outer periphery of the 
transparent sighting area 41, wherby the semicircles 24 and 26 define 
relatively sharp edges of the transparent area 41. As a result the 
elliptic arcs 44 and 46 limiting the sighting aperture 42 outwardly appear 
very sharp and in no way blurred as may be the case when the said two 
semi-circles are interconnected by a cylindrical fase, possibly owing to 
reflex. 
Another embodiment of a peep sight of the present invention is shown in 
FIGS. 4 and 5. The body 10 of this peep sight comprises in principle two 
thin round bowl-shaped plates 70 and 72, each plate being provided with an 
opening 82 shaped as a sector of a circular ring. The plates 70 and 72 are 
conveniently made from aluminium or a similar light material and are at 
their center interspaced by a hub 74 having a hub bore 76 adapted to 
receive the bow string 20. For fixing the peep sight on the bow string 20 
a slit tube piece 78 of al elastic material is used. The inner diameter of 
the tube corresponds to the thickness of the bow string, whereas the outer 
diameter of the tube corresponds to the hub bore 76 of the hub 74. The 
tube 78 is opened and the bow string is inserted, whereafter the tube 78 
is put into the hole 76 in the hub 74 to wedge the peep sight on the bow 
string 14. The edges of the plates 70 and 72 may be joined together with 
glue or in any other convenient manner whereby an aerodynamic shape is 
achieved. With an appropriate distance between the plates 70 and 72, and 
the disk in the slanted shooting position as appears from FIG. 5 the 
openings 72 reveal a virtual sighting aperture 80 of a 
quadrangular-looking shape actually consisting of four small elliptical 
areas. 
Besides the described embodiments the peep sight of the present invention 
may be given many other exterior shapes depending on the choice of 
material and the appearance preferred. It is essential that the sighting 
area through which the archer peeps and aligns the peep sight and target 
is shaped as a sector of a circular ring concentric to the bow string and 
in a plane perpendicular to the longitudinal axis of the bow string. 
Further, the dimension of the sighting area in the longitudinal direction 
of the bow string must be adjusted so that when the bow is drawn, there 
will appear a virtual sighting aperture which will be constant with 
respect to size, shape, and position in relation to the bow string even if 
the string sight is rotated a certain angle around the longitudinal axis 
of the bow string. 
Above, the sighting area is described as an aperture shaped as a sector of 
a circular ring in one or two disks. It is possible, however, to 
accomplish this sighting area by making the disk or plate from a 
transparent material and mask the disc or plates os that a transparent 
area shaped as a sector of a circular ring is left.