U.S. patent number 3,649,060 [Application Number 04/886,479] was granted by the patent office on 1972-03-14 for combined astragal and flush bolt structure.
This patent grant is currently assigned to The Steelcraft Manufacturing Company. Invention is credited to Robert O. Ruff.
United States Patent |
3,649,060 |
Ruff |
March 14, 1972 |
COMBINED ASTRAGAL AND FLUSH BOLT STRUCTURE
Abstract
A combined astragal and flush bolt arrangement for a pair of
doors in which upper and lower flush bolts are arranged to lock the
inactive door in a closed position within its door frame, the
active door being latched by a conventional lock to the inactive
door for normal service. The astragal is generally T-shaped in
cross section, comprising a longitudinal mounting rail secured to
the free edge of the inactive door and having a right angular head
rail which provides a stop against which the active door seats in
its closed position. The longitudinal mounting rail includes an
internal slideway, the flush bolts being slidably confined within
upper and lower portions of the slideway and having outer end
portions arranged to project outwardly beyond the rail into the
keepers of the header and sill of the door frame.
Inventors: |
Ruff; Robert O. (Cincinnati,
OH) |
Assignee: |
The Steelcraft Manufacturing
Company (Cincinnati, OH)
|
Family
ID: |
25389102 |
Appl.
No.: |
04/886,479 |
Filed: |
December 19, 1969 |
Current U.S.
Class: |
292/42; 49/368;
292/DIG.21; 292/147 |
Current CPC
Class: |
E06B
3/365 (20130101); E05C 1/04 (20130101); E05B
17/007 (20130101); Y10S 292/21 (20130101); Y10T
292/1024 (20150401); Y10T 292/0846 (20150401); E05C
7/045 (20130101) |
Current International
Class: |
E06B
3/36 (20060101); E06B 3/32 (20060101); E05C
1/04 (20060101); E05C 1/00 (20060101); E05C
7/00 (20060101); E05C 7/04 (20060101); E05B
17/00 (20060101); E05c 001/16 (); E05c 007/04 ();
E05c 009/04 () |
Field of
Search: |
;292/42,145,147,32-43,DIG.21 ;49/366,367,368,DIG.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
967,947 |
|
Aug 1964 |
|
GB |
|
1,040,221 |
|
Oct 1958 |
|
DT |
|
Primary Examiner: Wolfe; Robert L.
Claims
Having described my invention, I claim:
1. A combined flush bolt and astragal device for attachment to the
swinging edge portion of a door, said flush bolt being adapted to
cooperate with a keeper mounted in a door frame for latching and
unlatching the door to the door frame as desired, comprising,
an astragal having a head rail and a mounting rail, said astragal
being structured to allow attachment to the swinging edge of a door
by fasteners without deforming that swinging edge except as may be
required for said fasteners, and said mounting rail having
structure that defines a slideway extending longitudinally thereof
which is positioned between the non-deformed swinging edge of the
door and the interior face of said mounting rail so as to enclose
said slideway after said astragal has been attached to the swinging
edge of the door,
a flush bolt slidably confined within an end portion of said
slideway and having an end portion arranged to protrude beyond the
end of the mounting rail, said flush bolt likewise being enclosed
between the swinging edge of the door and the interior face of said
mounting rail after said astragal has been attached to the swinging
edge of the door,
manual means for shifting said flush bolt, when the astragal is
attached to the door, between a lock position for latching the door
to a door frame in a closed position and an unlock position for
allowing the door to be swung to an open position, and
structure defining an elongated slot in said mounting rail, said
manual means being accessible through said elongated slot, and said
elongated slot only being of sufficient length to allow
longitudinal movement of said flush bolt between the lock and
unlock positions.
2. A combined astragal and flush bolt device as set forth in claim
1 in which said mounting rail includes
a pair of spaced parallel limbs projecting generally at right
angles from the interior face of said mounting rail, the inner ends
of said limbs being seated against the swinging edge of the door
when said astragal is attached to the door, and the interior face
of said mounting rail and the opposed surfaces of said limbs which
face one another delineating said slideway.
3. A combined astragal and flush bolt device as set forth in claim
2 in which the ends of said limbs each include an inturned lip with
said lips projecting toward one another, the interior face of said
mountings rail, the opposes surfaces of said limbs and the internal
surfaces of said inturned lips providing a self-contained slideway
between said mounting rail and the swinging edge of the door in
which said flush bolt is confined.
4. A combined astragal and flush bolt device as set forth in claim
1 in which said manual means includes a purchase opening formed in
said flush bolt in registry with said elongated slot, said purchase
opening being accessible for finger engagement through said
elongated slot to allow longitudinal movement of said flush
bolt.
5. A combined astragal and flush bolt device as set forth in claim
1 in which said fasteners for attaching said astragal to the
swinging edge of the door comprise screws passing through said
mounting rail and into the swinging edge, and including
means for limiting the longitudinal motion of said flush bolt
comprising an elongated slot formed in said flush bolt, one of said
screws passing through said elongated slot and cooperating with the
ends of said slot to limit the extent of longitudinal motion of
said flush bolt.
6. A combined astragal and flush bolt device as set forth in claim
1 including
friction means associated with said flush bolt to pivotally hold
said flush bolt in its retracted or extended position with respect
to said slideway.
7. A combined astragal and flush bolt device as set forth in claim
6 in which said friction means includes
a pair of opposed tines fixed to said flush bolt which are
sufficiently thin to provide a spring action, said flush bolt being
installed within said slideway with said tines sprung inwardly
toward one another against the opposed surfaces of said
slideway.
8. A combined astragal and flush bolt device as set forth in claim
1 which is particularly adapted for use with an active door and an
inactive door where both are hingedly mounted in a door frame, said
astragal and flush bolt device being attachable to the inactive
door, wherein said head rail and mounting rail are of T-shaped
configuration so that a part of said head rail serves as a stop for
the active door, and wherein at least said astragal is fabricated
of metal, and including
a thermal barrier strip fixed to that edge of said mounting rail
opposite said head rail, said thermal barrier strip serving to
interrupt heat transfer through said astragal from that environment
in which said thermal barrier strip is located to that environment
in which said head rail is located.
9. A combined astragal and flush bolt device as set forth in claim
8 in which said mounting rail includes a compound flange projecting
from the interior face of said mounting rail, said compound flange
being located at the edge of said mounting rail opposite said head
rail, said compound flange having a flange which projects toward
the swinging edge of the inactive door when said astragal is
attached to the inactive door, and said thermal barrier strip being
clamped between said flange and the swinging edge when said
astragal is attached to the inactive door.
10. A combined astragal and flush bolt device as set forth in claim
8 including a weather strip mounted to said astragal, said weather
strip having a flexible limb adapted to seat between the
overhanging portion of said head rail and the active door when the
active door is in a closed position so as to provide a weather seal
between said astragal and the active door.
Description
BACKGROUND OF THE INVENTION
Sliding bolts of the type contemplated by the invention have been
in use for many years in door installations which involve a double
door frame having two doors hinged along the opposite sides of the
frame. They are used extensively in offices, industrial or
commercial buildings and also for residential use. In each case,
one of the doors, which may be called the "inactive door" is
ordinarily kept latched in its closed position by sliding bolts
engaging the header and sill or threshold of the frame, while the
active door swings with reference to the inactive door and includes
a standard latch having a latch bolt engaged in the edge of the
inactive door. The inactive door may be unlatched and swung to its
open position, along with the active door, to provide a full width
door opening when it is necessary to move large pieces of furniture
or equipment through the doorway or for other reasons which require
a wide door opening.
The conventional sliding bolts for the inactive door may be
installed either in the free edge of a wood door or a door formed
of sheet metal. The sliding bolts for a wood door may require the
upper and lower edge portions of the inactive door to be milled out
to receive a fixed mounting element of some type in which the
sliding bolt is confined for shifting motion from its latching to
its unlatching position. In a door formed of sheet metal, it may
also be necessary to indent or recess the upper and lower end
portions at its free or swinging edge to accommodate the mounting
elements for the sliding bolts.
One of the primary objectives of the invention has been to provide
a generally hollow astragal strip (particularly for sheet metal
doors) including an internal slideway for shiftably confining
respective flush bolts in the upper and lower end portion of the
astragal, the combined astragal and flush bolts providing a neat
and trim appearance and eliminating the need for fitting and for
conventional mounting elements and other components as are
ordinarily required.
According to this concept, the astragal is in the form of a strip
which is generally T-shaped in cross section, comprising a
longitudinal mounting rail for attachment to the free edge of the
inactive door, with a right angular head rail formed along one edge
of the mounting rail. The mounting rail is secured by screws to the
free swinging edge of the door and includes the internal slideway
for the flush bolts, while the right angular head rail provides an
overhanging stop engageable with the free marginal portion of the
active door when in its closed and latched position.
Another objective has been to provide an astragal of one-piece,
self-contained design which permits the use of simplified flush
bolts which are concealed and slidably confined within the
astragal, thereby to simplify the construction of the flush bolts
and astragal.
According to this aspect of the invention, the T-shaped astragal is
in the form of an extrusion, preferably of aluminum, the mounting
rail (which is secured to the edge portion of the inactive door)
having a pair of spaced, parallel limbs formed on its internal
surface. The inner ends of the internal limbs are seated against
the edge of the inactive door and delineate a slideway for the
flush bolts which are spaced from the surface of the door.
Each flush bolt is in the form of a flat bar formed preferably of a
hard plastic material such as nylon to reduce friction, the width
dimension of the strip being disposed in the plane of the edge of
the door, that is, in the direction of its swinging motion, with
the outer ends of the flush bolts protruding into engagement with
the keepers. By virtue of this arrangement, the flat bars, which
constitute the flush bolts, have sufficient strength and rigidity
to resist forces tending to open the inactive door.
In order to hold the flush bolt in its adjusted position, the inner
end of each bolt includes a forked portion providing spaced spring
tangs engaging the sides of the slideway for frictional engagement
with the slideway. Each bolt further includes a circular hole for
finger engagement, while the mounting rail is slotted in this area
for clearance in shifting the flush bolt to its latched or
unlatched position.
A further objective has been to provide an astragal particularly
for doors formed of sheet metal, in which the metallic astragal
includes a thermal barrier strip for preventing the passage of heat
by conduction due to metal-to-metal contact between the astragal
and metal doors.
For this purpose, the edge portion of the longitudinal mounting
rail, opposite the head rail, includes a thermal barrier strip
formed of a plastic material interposed between the door surface
and edge portion of the astragal. In addition, there is provided a
plastic weather strip arranged to seat between the surface of the
overhanging flange of the head rail and the marginal edge portion
of the active door to provide a weather seal. By virtue of the
thermal barrier strip at one edge, and the weather seal at its
opposite edge, the astragal is thermally insulated from both sheet
metal doors to prevent conduction of heat from the doors across the
astragal.
The various features and advantages of the invention will be more
fully apparent to those skilled in the art from the following
detailed description in conjunction with the drawings.
In the drawings:
FIG. 1 is an elevation showing a pair of double doors installed in
a double door frame and incorporating the astragal and flush bolts
of the invention with the bolts in their latching position.
FIG. 2 is an enlarged fragmentary sectional view, taken along the
line 2--2 of FIG. 1, further detailing the construction of the
doors and showing the astragal and flush bolt, with the doors in
closed position corresponding to FIG. 1.
FIG. 3 is an enlarged fragmentary sectional view taken from FIG. 2,
detailing the astragal, its thermal barrier strip, weather strip,
and the flush bolt within the slideway formed in the astragal.
FIG. 4 is a fragmentary prospective view, illustrating the upper
portion of the door and the header of the door frame with the upper
flush bolt engaged within the header and locking the inactive door
in its closed position.
FIG. 5 is a view taken along the line 5--5 of FIG. 1, showing the
edge portion of the inactive door with its upper and lower portions
broken away to further illustrate the engagement of the upper and
lower flush bolts with respect to the header and sill or
threshold.
FIG. 6 is a fragmentary view similar to FIG. 5, showing the flush
bolts shifted to their disengaged position for opening the normally
inactive door.
DOOR FRAME AND DOORS
In the structure selected to illustrate the principles of the
present invention (FIG. 1) the double doors, indicated at 1 and 2
are of sheet metal construction, while the door frame 3 is milled
from or made of wood. It will be understood that the door frame 2
may also be sheet metal construction if desired. The door frame
comprises the vertical jambs 4 and 5, a horizontal header 6 and a
threshold or sill 7 secured to the floor 8. The doors 1 and 2 are
hinged as at 10 to the opposite jambs 4 and 5 of the double door
frame in the usual way.
Generally speaking, the door 1 is inactive, that is, it normally
remains in its closed position, being secured to the header 6 and
threshold 7 by upper and lower flush bolts of the invention, which
are indicated generally at 11 in FIG. 1. The active door 2 includes
the usual latch mechanism (not shown) which is operated by the knob
12 for opening and closing door 2 with respect to the inactive door
1. The latch mechanism includes a latch bolt indicated at 13 which
engages a keeper 14 secured to the edge of the inactive door 1
(FIG. 5). The latch mechanism also includes a lock (not shown)
operated by a key in the usual way such that, with the latch bolts
11--11 engaged, the active door 2 can be locked with respect to the
inactive door, which normally is locked by the bolts 11--11.
As best shown in FIG. 2, the jambs 4 and 5 and header 6 are of
composite construction, each comprising a casing 15 secured within
the framing members (not shown) of the door opening which is formed
in the wall 16. The casings 15 for the jambs and header are
identical, each section being milled to provide an inset or rabbet
17 (FIGS. 2 and 4) which forms the opening for the doors and
delineating a stop rail 18 against which the doors seat when in
their closed position. The casing sections 15 preferably have a
width equal to the wall thickness, with their opposite edges flush
with the wall surface on opposite sides. The casing sections
further include fascia or trim strips 19 for the jambs and header
(FIGS. 1 and 2) which overlie the marginal portion of the casing to
provide a finished appearance.
Both doors 1 and 2 may be sealed with respect to the casing members
by weather stripping which engages the marginal portion of the
doors, the weather stripping being mounted in the jambs and header.
For this purpose (FIGS. 2 and 4) each stop rail 18 (jambs and
header) includes a groove or slot 20 located at the base of the
stop rail 18. Each weather strip, indicated generally at 21, is on
one-piece construction formed of a plastic material having
rubberlike characteristics to provide a sealing action.
Each weather strip 21 (FIG. 4) comprises a pair of limbs 22 and 23
angularly related to one another to form a V-shaped cross section.
The limb 22 forms the base and seats against the stop rail 18. Limb
22 includes a tailpiece 24 having barbs anchored within the groove
20 of stop rail 18, while the limb 23 normally (with the doors
open) projects outwardly in angular relation to the base limb 22.
When the doors are closed (FIGS. 2 and 5) the limb 23 is compressed
against the limb 22 to provide the weather sealing effect.
A similar weather strip, indicated generally at 21 is mounted upon
the astragal 25 for providing a weather seal between the swinging
edges of the doors 1 and 2 in their closed position as explained
later.
The seal strips 21 are not disclosed in detail and have been
selected as a preferred example of a structure for weather sealing
the doors. Sealing strips of this type are disclosed and claimed in
detail in the copending application of Claud Frederick, Jr. Ser.
No. 878,441, filed Nov. 20, 1969.
The astragal strip 25 and the flush bolts 11--11 may be installed
in a door formed of wood if desired. However, in the example
disclosed herein, the structure is embodied in a door formed of
sheet metal, as noted above. Described with particular reference to
FIGS. 2 and 3, the sheet metal doors 1 and 2 are of similar
construction and are of composite design. Each door comprises the
opposed sheet metal face panels 26 and 27 which are spaced apart
from one another and form the opposite sides of the door.
In the present structure, the panel 27 includes edge flanges 28--28
along the opposite vertical sides of the door. The free edge
portion of each flange 28 is bent inwardly to a generally U-shaped
formation, indicated at 30, which forms a groove adapted to receive
a lip 31 from projecting inwardly from a flange 32 formed along the
edge of the opposed panel 26. The door includes a filler or core 33
formed of relatively thin fibrous sheets which extend transversely
between the spaced panels 26 and 27. The filler reinforces the
composite door and provides a sound-deadening effect.
Both vertical edges of the door are of similar construction;
however, the edge portion of the panel 27 along the hinged side of
the door is slotted to receive one leaf 34 of the hinge 10 (FIG.
2). The leaf 34 is secured in place by screws (not shown) passing
through holes formed in the flange 28, through the hinge leaf 34
and into a reinforcing plate 35 located internally of the flange
28. The mating leaf 34 of the hinge is secured by similar screws
(not shown) passing into casing 15 of the jamb 4 or 5. The hinged
connection is in duplicate with respect to the jambs 4 and 5 for
the doors 1 and 2.
The upper and lower edges of each door include closure strips
36--36 (FIG. 1) having opposed flanges engaging the internal
surfaces of the panels 26 and 27. If closure strips 36 are of
laminated construction they may be secured with an adhesive, or if
formed of sheet metal, they may be spot welded to the door panels
to complete the assembly of the composite door.
ASTRAGAL CONSTRUCTION
The astragal, previously indicated at 25, comprises a strip,
generally T-shaped in cross section (FIGS. 3-6), which extends
along the edge of the inactive door 1 for its full length from top
to bottom. In the present example, the strip is formed of aluminum,
preferably by the extrusion process. The T-shaped astragal includes
the longitudinal mounting rail 38 (FIGS. 3 and 4) which overlies
the edge flange 28, to which it is secured by the series of screws
37. The openings for the screws are countersunk in the usual way so
that the screw heads lie flush with the exposed surface of rail 38.
The mounting rail 38 includes a head rail 40 disposed at right
angles to the rail 38 and providing a seat or stop for the active
door 2.
In a residential installation, or one which is not extensively used
by the public, the doors usually are arranged to swing inwardly,
and in this event the head rail 40 is located to the outside of the
building. However, when the doors are installed in a public
building such as a business or industrial establishment, then the
doors are arranged to swing outwardly as a safety measure in the
event of a fire or the like. In this case, the head rail 40 is
disposed to the inside of the building permitting the doors to
swing outwardly, the structure and installation being identical in
both instances except that the location of the doors and astragal
relative to the opening is reversed.
It will be noted in FIG. 3, that the edge flange 28 at the swinging
edges of the doors slope inwardly from the door panel 27 to the
door panel 26 in the direction of door swing, whereas the mounting
rail 38 of the astragal is disposed at right angles to the panels
26 and 27. In order to establish this right angular relationship,
the compound flange indicated generally at 41 (FIG. 3) at the
juncture of the mounting rail 38 and head rail 40, is made longer
than the compound flange, indicated generally at 42 at the opposite
end portion of the mounting rail 38, thereby to compensate for the
slope of the flange 28. It will be understood at this point, that
the flanges 41 and 42 seat against the sloping edge flange 28, the
astragal being clamped in position by the screws 37, previously
noted. The astragal is located with reference to the edge flange 28
by the portion 43 of head rail 40 which includes a lip 44 engaging
panel 26. The opposite portion 45 of head rail 40 projects
outwardly beyond mounting rail 38 in a position to provide a stop
which engages the marginal edge portion of the panel 26 of active
door 2.
It will be noted in FIG. 3 that the compound flange 41, which is
coextensive with the astragal, is generally hollow, comprising a
longitudinal slot 46 formed in rail 38 and opening into one side of
a generally square groove 47 which also extends longitudinally of
the astragal. The tailpiece 24 of the astragal weather strip 21
includes longitudinal barbs, as noted earlier. The barb on one side
of the tailpiece is engaged against one side of slot 46 and the
opposed barb is engaged against a ledge 48 formed at the juncture
of slot 46 and the square groove 47, thus anchoring the astragal
weather strip 21 in position with its base limb 22 seated against
mounting rail 38.
The free limb 23 of the weather strip normally projects at an acute
angle to the base strip 22 when the active door is open, as shown
in full lines in FIGS. 3 and 4. When the active door 2 is closed,
the marginal edge portion of its panel 26 engages the free limb 23
and forces it in pressure engagement against the overhanging
portion 45 of head rail 40, as indicated in broken lines in FIG. 3,
thus establishing a weather seal between the astragal and active
door 2.
The compound flange 42 at the end portion of rail 38 opposite head
rail 40 includes a groove 50 which is delineated by a flange 51
spaced outwardly from flange 42 (FIG. 3). A thermal barrier 52
(FIG. 3) is interposed between the end portion of mounting rail 38
and the corner portion of the door 1 (panel 27 and flange 28) to
prevent the flow of heat from the sheet metal door section to the
metallic astragal 25. Strip 52 is generally S-shaped in cross
section and is formed of a heat insulating plastic material such as
extruded vinyl.
One end portion 53 of barrier 52 interfits the groove 50, which
forms a keyway, and the intervening section 54 of the strip is
clamped against door flange 28 by the lip or flange 51 of mounting
rail 38. The remaining portion of the barrier strip 52 has its
outer surface flush with the surface of mounting rail 38 and
includes a curved portion 55 which joins a right angular section
56, the end portion of which overlies the marginal edge of the door
panel 27. The barrier strip 52 is thus clamped in place by the
astragal 25 and provides a nonmetallic spacer between the surface
of the mounting rail 38 and the metal shell of the inactive door 1.
The limb 23 of the astragal weather strip 21, in a similar manner,
provides a thermal barrier between the metallic astragal 25 and the
metallic shell of the active door 2.
FLUSH BOLTS
As noted earlier, the flush bolts 11 for the upper and lower
portions of door 1 are both slidably confined in the astragal 25,
the cross sectional configuration of the astragal mounting rail 38
being coextensive for its full length for this purpose. Described
particularly with reference to FIG. 3, the interior portion of the
mounting rail 38 is configurated to provide a slideway 57 for the
flush bolts 11--11. The slideway 57 is delineated by the spaced
limbs 58 and 60 which project at right angles from the longitudinal
rail 38 and form a part of the compound flanges 41 and 42. The
limbs 58 and 60 each include an inturned lip 61 which is spaced
inwardly from the longitudinal rail 38, the lips being seated
against the edge flange 28 of the inactive door 1. The internal
surfaces of the inturned lips 61--61 engage the marginal portions
of the flush bolts 11 and thus complete the self-contained slideway
57 in which the flush bolts are confined.
The flush bolts 11 for the upper and lower portions of the inactive
door 1 are of duplicate configuration except that their positions
are reversed (FIG. 5). Described in detail (FIGS. 4--6) each flush
bolt 11 is generally in the form of a flat bar formed of a plastic
material such as molded nylon to reduce friction and its main body
portion 62 (FIG. 3) has a thickness and width which interfits the
slideway 57 with a slight amount of clearance, as indicated at
63.
The outer end of each body section 62 includes a latching tongue 64
having a width less than the body section 62 and joined to the body
section by the curved shoulder 65. In the extended latching
position of the bolts, (FIGS. 4 and 5) the latching tongues project
outwardly beyond the upper and lower edges of the astragal and door
and through keeper plates 66--66 which are secured by screws 67 to
the header and to the threshold. Each keeper plate 66 is provided
with a rectangular opening 68 dimensioned to receive the protruding
tongue 64. The header and threshold each include a clearance
aperture formed behind the keeper plate 66 in the usual way to
receive the tongue.
It will be noted, at this point, that the tongue 64 extends
widthwise in the door opening direction so that its greatest
sectional dimension is disposed in the direction of thrust. This
enables the tongue to resist without danger of breakage forces
tending to swing the door towards its open position. The body
section 62 of the bolt, being confined in the slideway 57
counteracts such thrust forces without undue stress being imposed
upon the parts.
In order to confine each flush bolt 11 within its slideway for
shifting motion to its engaged or disengaged position, the upper
portion of each body section 62, inwardly from tongue 64, includes
an elongated clearance slot 70 (FIGS. 4-6). The shanks of the
screws 37, near the opposite ends of the astragal pass through the
slots 70, thus limiting the sliding motion of the flush bolt to an
extent approximately equal to the length of the tongue 64.
The inner end portion of the body section 62 of each bolt is forked
as at 71 (FIGS. 4-6) to delineate the prongs or tines 72--72 which
are sprung outwardly into frictional engagement with the internal
surfaces of the limbs 58 and 60 (FIG. 3) which delineate slideway
57. For this purpose, the tines 72 are relatively thin in cross
section to provide a spring action and they are slightly curved
outwardly as at 73--73 beyond the side edges of the body section
62. Upon installation of the flush bolt 11 the curved surfaces
73--73 are sprung inwardly toward one another, therefore they are
spring urged against the opposed surfaces of the slideway. The
spring action holds the flush bolts 11--11 in position, whether in
extended latching position, or in the retracted release
position.
The body section 62 of each latch bolt further includes a circular
purchase opening 74, the diameter of which is sufficient to provide
a finger hold for shifting the bolt. The mounting rail 38 is
provided with respective longitudinal slots 75 in alignment with
each opening 74 and having a length sufficient to permit the flush
bolt to be shifted to its extended or retracted position (FIGS. 5
and 6). The throw or extent of motion of each flush bolt is
determined by the engagement of screw 37 with the opposite ends of
clearance slot 70. This corresponds with the extent of bolt motion
provided by the purchase opening 74 and slot 75.
* * * * *