Closure fasteners – Bolts – Swinging
Reexamination Certificate
2000-01-21
2004-02-24
Estremsky, Gary (Department: 3677)
Closure fasteners
Bolts
Swinging
C292S127000
Reexamination Certificate
active
06695363
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to latching mechanisms, and more particularly to latching mechanisms for securing accessories in a radiation therapy system.
BACKGROUND OF THE INVENTION
Radiation therapy systems for the treatment of cancer are well known in the art.
FIG. 1
illustrates one such system manufactured by Siemens Medical Systems, Inc.™. The system
10
includes a platform
20
onto which a cancer patient lies. The rotating gantry
30
administers the radiation to the patient. The rotating gantry
30
includes an accessory holder
100
onto which accessory trays (not shown) may be inserted. The trays help an operator aim the radiation beam onto the patient. For example, a tray may contain a block or a filter to vary the concentration of the radiation beam. The tray may also have a hole patterned to match the shape of a patient's tumor to help focus the radiation beam. The trays are made of metal, typically one to two inches thick.
FIGS. 2A and 2B
illustrate a top view and a cross-sectional view, respectively, of an accessory holder for a conventional radiation therapy system. The accessory holder
100
is herein described with simultaneous reference to
FIGS. 2A and 2B
. The accessory holder
100
comprises a frame
102
which contains three slots
104
,
106
,
108
into which accessory trays, such as tray
110
, may be inserted. The trays are latched to the frame
102
by latching mechanisms
112
,
114
,
116
. Each of the latching mechanisms
112
and
114
comprises a lock
118
. The lock
118
has a head
120
at one end and a protrusion
122
at the side of the lock
118
nearer the tray
110
. A roll pin
124
couples the lock
118
to a release assembly
126
. Coupled at the opposite end of the release assembly
126
is a release button
128
which when pressed, compresses a button spring
130
.
The latching mechanisms
112
and
114
are coupled to the frame
102
by a retainer assembly
132
which includes a retainer shaft
134
. When the tray
110
is inserted into the slot
104
, the protrusion
122
of the lock
118
engages a notch
136
on the tray
110
, preventing the tray
110
from sliding out of the slot
104
. An opening
154
in the frame
102
allows the lock
118
to freely engage the notch
136
. When the release button
128
is pressed, the release assembly
126
pivots the lock
118
counterclockwise about the retainer shaft
134
, releasing the tray
110
. This is facilitated by the wedging action between an elongated hole
152
of the release assembly
126
and the roll pin
124
. The release button
128
is spring loaded. This button spring
130
keeps the lock
118
engaged when a tray is inserted. A crescent washer
138
is used to constrain the latching mechanisms
112
and
114
in the direction of the retainer shaft
134
axis. The compliance of the crescent washer
138
limits the friction in the latching mechanisms
112
,
114
while maintaining precision. The spacer
140
maintains the proper height alignment between the latching mechanisms
112
and
114
and their respective slots
104
and
106
. The latching mechanism
116
for slot
108
uses a retainer ring
142
to loosely constrain the parts. The release assembly
144
, the roll pin
146
, the lock
148
, and the spacer
150
for latching mechanism
116
perform the same functions as those for latching mechanisms
112
and
114
.
However, the dislodgment of the roll pin
124
and/or the loss of release button spring
130
force due to breakage of the spring
130
or loosening of the release button
128
have been known to occur. If one of these failures occur, then the tray
110
is in danger of sliding out of the accessory holder
100
and falling onto a patient on the platform
20
, possibly causing serious injuries.
Accordingly, what is needed is a system and method for a secondary lock for securing accessories in a radiation therapy system. The secondary lock should decrease the possibility of a failure of the accessory holder's latching mechanism. The present invention addresses such a need.
SUMMARY OF THE INVENTION
The present invention provides a method and system for a secondary lock for securing accessories in a radiation therapy system. The latching mechanism provided in accordance with the present invention includes a primary lock, a secondary lock, and a retainer shaft. The primary lock includes a head at a first end of the primary lock, and a protrusion at a first side of the primary lock. The secondary lock includes a main body, an engagement tang at a first end and a first side of the main body, and a locking tang at the first end and a second side of the main body. The retainer shaft is coupled to the primary lock and the main body of the secondary lock, where the secondary lock is fixedly positioned when the protrusion engages the accessory and the head resides between the engagement tang and the locking tang. The secondary lock creates a fail-safe locking system, such that the secondary lock causes the primary lock to continue to engage an accessory tray even if failure occurs elsewhere in the latching mechanism. This lowers the probability of failure of the latching mechanism significantly, resulting in a safer radiation therapy system. The secondary lock of the latching mechanism also remains in a disengaged position when no tray in inserted, allowing trays to be inserted without the need to press the release button first to set the secondary lock into the disengaged position.
REFERENCES:
patent: 362936 (1887-05-01), Chantrell
patent: 983647 (1911-02-01), Romines
patent: 2955859 (1960-10-01), Krause
patent: 3194595 (1965-07-01), Wheeler
patent: 3841693 (1974-10-01), Reynolds
patent: 3891254 (1975-06-01), Lile
patent: 3918750 (1975-11-01), Okamoto
patent: 4053177 (1977-10-01), Stammereich
patent: 4159153 (1979-06-01), Yoshikawa
patent: 4720611 (1988-01-01), Ishii
patent: 4759574 (1988-07-01), James
patent: 4875724 (1989-10-01), Gruber
patent: 5785362 (1998-07-01), Nadherny
patent: 6523867 (2003-02-01), Yeh
Estremsky Gary
Siemens Medical Solutions USA , Inc.
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