U.S. patent application number 13/595314 was filed with the patent office on 2013-08-29 for latch mechanism for manhole cover with captured operator.
The applicant listed for this patent is David M. Stadler. Invention is credited to David M. Stadler.
Application Number | 20130221688 13/595314 |
Document ID | / |
Family ID | 47756781 |
Filed Date | 2013-08-29 |
United States Patent
Application |
20130221688 |
Kind Code |
A1 |
Stadler; David M. |
August 29, 2013 |
Latch Mechanism For Manhole Cover with Captured Operator
Abstract
A latch mechanism for a manhole cover in which a rotatable
operator member has a threaded portion engaged with a threaded bore
in a cam pin which rides in a pair of cam slots in a latching
member to cause the latching member to be extended or retracted
upon rotation of the operator member in either direction. The
threads disengage when the latch member reaches a fully retracted
position so that the operating member can freely spin thereafter in
the same direction, while the threads reengage when the operator
member is rotated in the opposite direction to begin movement of
the latch member out of the housing.
Inventors: |
Stadler; David M.; (Lathrup
Village, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Stadler; David M. |
Lathrup Village |
MI |
US |
|
|
Family ID: |
47756781 |
Appl. No.: |
13/595314 |
Filed: |
August 27, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61527776 |
Aug 26, 2011 |
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Current U.S.
Class: |
292/155 |
Current CPC
Class: |
E02D 29/1427 20130101;
Y10T 292/1033 20150401 |
Class at
Publication: |
292/155 |
International
Class: |
E02D 29/14 20060101
E02D029/14 |
Claims
1. A latch mechanism including a housing with a cavity formed
therein in which a latch member is received, said latch member
movable lengthwise in said cavity to be extended or retracted to a
position a latching end portion thereof protruding from said
housing; an operator member received into an opening in said
housing and through a lengthwise extending central slot formed in
said latch member; said latch member having a pair of aligned
angled cam slots formed therein, extending in the same general
direction of said extending and retracting motion of said latch
member, each cam slot lying on either side of said central slot
receiving said operator member; a cam pin having a pair of ends
each end slidably received in a respective cam slot; said cam pin
having a threaded bore formed intermediate said pair of ends, said
operator member passing through said threaded bore and having an
external thread engageable with threads of said cam pin threaded
bore upon rotation of said operator member in either direction,
said operator member restrained against axial movement in said
housing so that as said operator member is rotated in either
direction said cam pin is moved up or down and in turn acts on the
side sides of said cam slots to move said latch member in either an
extending or retracting direction of said end portion.
2. The latch mechanism according to claim 1 wherein said lengthwise
slot limits the extent of movement of said latching member by
abutting either side of said operator member in said respective
extended and retracted position of said latching member.
3. The latch mechanism according to claim 1 wherein said threaded
portion of said operator member terminates as said latching member
reaches a fully retracted position so that the threads on said
portion and said threaded bore of said cam pin are disengaged and
no further camming action drive occurs.
4. The latch mechanism according to claim 3 wherein said operator
member is axially restrained by flanged elements fixed on either
end thereof and engaging said housing to limit axial movement in
said housing to a slight clearance.
5. The latch mechanism according to claim 4 wherein one flanged
element has a resiliently compressed element interposed between
said flange and said element to allow limited axial movement and
which also urges said threaded portion of said operator member
towards said threaded bore, causing said reengagement of said
threads of threaded portion of said operator member and said
threaded bore in said cam pin upon rotating said operator member in
a direction extending said latch member and maintaining full
retraction of said latch member with said threads disengaged.
6. The latch mechanism according to claim 3 wherein the last thread
of said threaded portion of said operator member is machined
squared to an axis of rotation of said operator member to be
tapered in width and blended into said operator member.
7. The latch mechanism according to claim 1 further combined with a
manhole cover, attached to the underside thereof at the outer
perimeter so that said latching member when extended engages a
feature on fixed structure surrounding said manhole cover when said
manhole cover is installed on a manhole vault.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. provisional
application No. 61/527,776 filed on Aug. 26, 2011.
BACKGROUND OF THE INVENTION
[0002] This invention concerns latch mechanisms and more particular
lock or latch mechanisms particularly adapted for use in securing
manhole covers in place, as described in U.S. Pat. Nos. 7,484,908
and 7,891,904 issued to the present inventor, both incorporated by
reference herein.
[0003] The mechanisms described therein use an operating member
comprised of a threaded bolt.
[0004] As described in those patents, it is advantageous that the
bolt not be allowed to be separated from the mechanism where it
could be lost or be dropped into the manhole vault. Also, removal
of the bolt by someone tampering with the cover should be
prevented.
[0005] While a mechanism for reducing the frequency of separating
the bolt is described in U.S. Pat. No. 7,891,904, that mechanism
does not positively prevent removal of the bolt from the latch
mechanism.
[0006] Accordingly, it is an object of the present invention to
provide a latching mechanism in which a threaded operator member
such as a special bolt is positively retained within the latching
mechanism so as to preclude removal of the member.
DESCRIPTION OF THE DRAWING VIEWS
[0007] FIG. 1 is a fragmentary sectional view of a manhole cover
installation having a latch mechanism according to the present
invention installed thereon.
[0008] FIG. 2 is an exploded pictorial view of the components of
the latching mechanism according to the present invention shown in
FIG. 1.
[0009] FIG. 2A is an enlarged pictorial view of the flanged nut and
spring shown in FIG. 2.
[0010] FIG. 3 is an enlarged pictorial rotated view of a cam pin
and a mating segment of a threaded operator member included in the
latching mechanism shown in FIGS. 1 and 2.
[0011] FIG. 4 is a view in partial section of the latching
mechanism shown in FIGS. 1 and 2 in the retracted unlatched
condition.
[0012] FIG. 4A is an enlarged fragmentary front view of a lower
portion of a main threaded portion of the operator member.
[0013] FIG. 5 is a view in partial section of the latching
mechanism as shown in FIG. 4 but in the latched extended
condition.
DETAILED DESCRIPTION
[0014] In the following detailed description, certain specific
terminology will be employed for the sake of clarity and a
particular embodiment described in accordance with the requirements
of 35 USC 112, but it is to be understood that the same is not
intended to be limiting and should not be so construed inasmuch as
the invention is capable of taking many forms and variations within
the scope of the appended claims.
[0015] Referring to FIG. 1, a portion of a manhole cover 10 is
shown, seated over a manhole vault 12. As described in U.S. Pat.
No. 7,891,904, the manhole cover 10 normally rests on a radially
inward extending rim 14 projecting in a liner 16 forming the vault
12.
[0016] In an explosion, the manhole cover 10 is designed to rise up
but only to a limited extent to create a space to controllably vent
gases generated by the explosion. A latch mechanism 18 is mounted
between a pair of downwardly extending, spaced apart ribs 20 fixed
to the underside of the cover 10. A latch member 22 normally
projects out radially from a latch housing 24 to engage the
underside of the rim 14 to limit upward travel of the manhole cover
10, with other fixed stop features also provided around the
perimeter of the manhole cover to keep the manhole cover 10 from
tipping as it rises to insure that the manhole cover 10 does not
fly free. As described in the above referenced patents, the
latching mechanism 18 can be allowed to pivot down when an
explosion generates a force sufficient to fracture a shear pin (not
shown) in order to allow a greater upward movement of the manhole
cover 10.
[0017] The present invention comprises an improvement of the latch
mechanism 18.
[0018] The components are shown in FIG. 2 and include the latch
housing 24 which slidably receives a cylindrical body portion 26 of
the latch member 22, with a sleeve bearing 28 sized to be slidable
fit with the cylindrical portion 26 and also itself slidable into a
bore 30 in the housing 24.
[0019] The latch member 22 has an engagement portion 32 at its
projecting end (at the left in the Drawings), formed with a flat
having a series of ribs 34 on its upper surface for engagement with
the undersurface of rim 14.
[0020] A threaded elongated operator member here comprised of a
bolt 36 has a body portion 37 slidable into a bore 38 extending
vertically into the top of the housing 24. A left hand threaded
flanged nut 40, compressed wave spring 42 received in a counter
bore 45 in the nut flange 43, and washer 44 are received on the
threaded bottom stem 46 of the operator member 36, the washer 44
engaging a flange 39 surrounding a bore 38 at the bottom thereof
formed in the housing 24 to retain the operator member 36 in the
bore 38. The spring 42 keeps the washer 44 abutting flange 39.
[0021] A slight clearance space 41 exists between the washer 44 and
the flange 43 on the flanged nut 40 which allows the member 36 to
move slightly as described below
[0022] A lengthwise extending vertical slot 48 in the center of the
latch member 22 receives the operator member 36, which passes
completely through the slot 48, with the stem portion 46 received
in a counterbore 45 extending into the bottom of housing 24, the
flanged nut 40, spring 42, and washer 44 placed on the stem 46 and
received in the counterbore 45.
[0023] A pair of aligned camming slots 50 are formed in the
cylindrical portion 26 of the member 22, each extending from one
side of the latching member 22 into the center slot 48 which each
receive a respective end of a cam pin 52 which has a central
threaded cross bore 54 through which the operator bolt 36 passes
with a threaded interengagment between a central threaded section
60 of the operator member 22.
[0024] The operator member 36 has a flanged head 56 for engagement
with a wrenching tool to be rotated, the head 54 optionally being
of a special shape for security purposes, as described in the above
referenced patents.
[0025] To extend the engagement portion of the latch member 22, the
operator member 36 is rotated in a direction so that the threaded
engagement pulls the cam pin 52 upward which thus engages the upper
wall 58 of each of the slots 50, camming the latch member 22 to the
left and causing the engagement portion 32 out of the housing 24,
as viewed in FIG. 4.
[0026] Rotation of the operator member 36 in the other direction
reverses the motion of the latch member 22, in a direction so as to
retract the engagement portion 32 of the latch member until the
catch member 22 reaches and abuts the ends of the slots 50.
[0027] The threads of threaded section 60 on the operator member 36
and the threads of the threaded bore 54 of the cam pin 52 pass out
of engagement as the operator member 36 moves down slightly allowed
by the clearance space 41 and the lowest thread in section 60 pass
out of engagement from each other.
[0028] Continued rotation of the operator member 36 in the same
direction thus has no effect on the position of the cam pin 52, and
the operator member 36 merely spins freely with the contacting
threads sliding past each other.
[0029] The section 62 of the operator member beyond the threaded
section 60 is machined to a diameter sized to be able to be
slidably received in the threaded bore 54 of the cam pin 52.
[0030] The lowest thread 64 on threads section 60 is machined to be
square to the axis of rotation, and thus abut the flat face 66
machined on the cam pin 52 (FIG. 3) flattens the uppermost thread
in the bore 54. The last thread 64 thus tapers down and its end
blends into the diameter of section 62 (FIG. 4A).
[0031] The spring 42 acting between washer 44 and flanged nut 40
urges the last thread 64 of the threaded portion 60 against the
uppermost thread in the bore 54, but rotation in the retraction
direction has no effect as the first thread in bore 54 and partial
thread 64 merely slide over and past each other. There will be a
slight clicking sound and motion as the partial thread 64 rides
past the flattened first thread in the bore 54.
[0032] The compressed wave spring 42 continues to urge these
threads together so that the latch member 32 is held fully
retracted.
[0033] When the operator member 22 is rotated in the opposite
direction, the thread 64 immediately engages the threads in
threaded bore 54 and extending motion of the latch member 22
begins. Thus, cross threading is prevented and proper reengagement
is insured.
[0034] Seals 68, 70, 72 may be provided to prevent moisture from
entering the mechanism 18.
[0035] Seal 72 is held in recess 71 to the rear of flange 43 on the
flanged nut 40.
[0036] The seal 68 normally engages the cylindrical body 26 in
service as the latch member 22 is then extended.
Operation
[0037] With the end of the latch member 22 positioned against latch
housing wall 18 of latch housing 3, clockwise rotation of operating
member 36 causes the thread 60 on operating member 36 to engage
threaded bore 54 in cam pin 52. Continued clockwise rotation of
operator member 36 advances operator member thread 60 into the
threaded bore 54 of cam pin 52 which in turn draws the cam pin 52
upward. This action develops a camming force exerted by the cam pin
52 against upper wall of each of the cam slots 50 formed in the
latch member 22. The length of central slot 48 limits the
horizontal travel of the latch member in moving from a fully
retracted to a fully extended position.
[0038] As a result, the latch member 22 is moved to extend out of
latch housing 24.
[0039] Further clockwise rotation of operating member 36 continues
until cam pin 52 reaches the end of the cam slots 50 and operating
member 22 reaches the end of slot 48. Operating member 22 is
torqued to specification, the latch member end 32 now fully
extended and locked in that position.
[0040] To retract the end 32 of latch member 22 back into the latch
housing 24, operating member 36 is rotated counterclockwise.
[0041] The upper face of the left hand threaded flanged nut 40 is
mounted to the threaded end of the operating member stem 46 and is
moved towards thrust washer 44 disposed against flange 39 at the
bottom of the latch housing 24. Counterclockwise rotation of
operating member 36 compresses wave spring 42 against flanged nut
40 and forces cam pin 52 against the lower side of each of the cam
slots 50.
[0042] As the cam pin 52 continues to be moved down against the
lower sides of slots 50, the latch member 22 is retracted by the
camming action of the cam pin 52. The latch member end 32 is fully
retracted when the threaded section 60 contacts the right hand end
of the slot 48.
[0043] When the latch member 22 is fully retracted, operator member
36 will spin freely, since the threads 60 are then totally
disengaged from the threads in the threaded bore 54 as described
above.
[0044] Compressed wave spring 42 urges the bottommost thread 64 of
threads 60 against the flattened uppermost thread in thread bore 54
of the cam pin 52. If the operator member 36 continues to be turned
counterclockwise, compressed wave spring 20 forces cam pin 52 to
the end of slot 48 and fully retracts the latch member end 32 into
latch housing 24. Continued counterclockwise rotation of operator
member 36 causes a ratcheting sound as the lowest thread rotates
past the uppermost thread in bore 54. This assures proper
reengagement of the threads 60 and the thread in threaded bore 54
when operating member 36 is again rotated clockwise.
[0045] Operator member 22 can freely rotate in the counterclockwise
direction due to the clearance 41 so that operator member head 56
will be raised up and lowered slightly with respect to the latch
housing top surface as the operator member 36 is continued to be
rotated.
[0046] Accordingly, the operator member 36 remains completely
enclosed and captured in the latch mechanism 18 at all times,
including when the latch mechanism 18 is being operated and cannot
be removed from the housing 24 without a complete removal and
disassembly of the latch mechanism 18. No torque specification is
needed when retracting the latch member 22.
* * * * *