U.S. patent number 3,843,855 [Application Number 05/361,881] was granted by the patent office on 1974-10-22 for anti-holddown device with diaphragm actuating switch and piston.
Invention is credited to John H. Danielson.
United States Patent |
3,843,855 |
Danielson |
October 22, 1974 |
ANTI-HOLDDOWN DEVICE WITH DIAPHRAGM ACTUATING SWITCH AND PISTON
Abstract
This specification discloses an anti-holddown switch actuating
mechanism in which a switch is operated by an increase in air
pressure upon actuation of a piston-like plunger in a closed
chamber, and means are provided to bleed off the increase in air
pressure at a predetermined rate to insure opening of the switch a
predetermined time after actuation thereof.
Inventors: |
Danielson; John H. (East Haven,
CT) |
Family
ID: |
26958190 |
Appl.
No.: |
05/361,881 |
Filed: |
May 21, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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276886 |
Jul 31, 1972 |
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Current U.S.
Class: |
200/83J; 200/83T;
200/520; 200/34; 200/345 |
Current CPC
Class: |
H01H
13/54 (20130101) |
Current International
Class: |
H01H
13/54 (20060101); H01H 13/50 (20060101); H01h
035/34 (); H01h 035/38 () |
Field of
Search: |
;200/33R,34,83T,160,159R,82R,83R,83S,83J |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Schaefer; Robert K.
Assistant Examiner: Tolin; Gerald P.
Attorney, Agent or Firm: DeLio and Montgomery
Parent Case Text
This application is a continuation-in-part of my co-pending
application, Ser. No. 276,886, filed July 31, 1972, and now
abandoned.
Claims
What is claimed is:
1. An anti-holddown switching device comprising a housing member
defining a pressure chamber having opposite ends, a flexible
diaphragm closing said chamber at one end thereof, a switch
disposed adjacent said diaphragm at said one end of said chamber
and operable by said diaphragm when the pressure on said diaphragm
reaches a predetermined value, a piston in said chamber adjacent
the other end thereof and movable in a direction to decrease the
volume of said chamber between said piston and said diaphragm and
increase the pressure therein, a passage defined in said housing
member by which pressure in said chamber between said piston and
said diaphragm is bled therefrom, whereby pressure created in said
chamber by said piston is reduced and said diaphragm releases said
switch after a predetermined time independent of the position of
said piston in said chamber.
2. The device of claim 1 further including a second passage in said
housing member providing one way communication of air into said
chamber between said piston and said diaphragm.
3. The device of claim 2 further including an opening in said
housing member providing communication to said second passage from
a point on the other side of the piston from said diaphragm.
4. The device of claim 2 further including a filter in said second
passage.
5. The device of claim 1 wherein said passage provides
communication to the ambient atmosphere.
6. The device of claim 1 wherein said passage provides
communication to the chamber on the other side of the piston from
said diaphragm.
7. An anti-holddown switching device comprising a housing member
defining a pressure chamber having opposite ends, a flexible
diaphragm closing said chamber at one end thereof, a switch
disposed adjacent said diaphragm at said one end of said chamber
and operable by said diaphragm when the pressure on said diaphragm
reaches a predetermined value, a piston in said chamber adjacent
the other end thereof and movable in a direction to decrease the
volume of said chamber between said piston and said diaphragm and
increase the pressure therein, a first passage defined in said
housing member by which pressure in said chamber between said
piston and said diaphragm is bled therefrom whereby, pressure
created in said chamber by said piston is reduced and said
diaphragm releases said switch after a predetermined time
independent of the position of said piston in said chamber, means
defining a second passage providing one-way communication of air
into said chamber between said piston and said diaphragm, and an
opening in said housing member providing communication to said
second passage from said chamber.
8. The device of claim 7 wherein said first passage provides
communication to the ambient atmosphere.
9. The device of claim 7 wherein said first passage provides
communication to the chamber on the other side of the piston from
said diaphragm.
Description
This invention relates to switches, and more particularly relates
to switch actuating mechanisms which are termed anti-holddown
devices in that the switch will open after a predetermined time
after actuation thereof regardless of whether the operator
maintains pressure on an operating knob or plunger.
Switches are often used in industry to operate forming tools and so
arranged that the operator is required to depress two switch
handles or levers simultaneously in order to operate the device.
The general reason for this is to insure that the operator's hands
are removed through a forming operation of the machine and thus
minimize the possibility of injurious accident.
However, in many cases, the machine operators have attempted to
disable the safety feature by laying a heavy object on or tying
down one of the switches so that the switch would be permanently
closed. This has led to the development of switches or
switch-operating mechanisms which have a time-delay built in so
that the switch will open a predetermined time after the closing
thereof; hence, the name of anti-holddown switch.
The present invention relates to switches of this type and operates
through the creation of an increased air pressure due to depression
of a plunger. This build-up in pressure is bled off and the switch
will then open a predetermined time later determined by the bleed
rate. Such switches are generally known. However, those which are
known are rather complicated in construction and expensive.
Accordingly, the present invention provides a switch actuating
mechanism for an anti-holddown device which is simplified in
construction, positive in operation in both the closing and opening
modes and may be utilized with virtually any type of switch
mechanism.
Briefly stated, the invention in one form thereof comprises wall
means defining a cylindrical bore which is closed at one end
thereof by a flexible diaphragm. A return biased piston or plunger
is received within the bore and upon depression thereof increases
the pressure in the chamber to a magnitude sufficient to flex the
diaphragm and operate a switch. A passage is defined in the wall
means communicating with the ambient atmosphere and the area of
said passage may be controlled to predetermine the rate at which
pressure is bled off and therefore the opening of the switch. A
further passage may be defined in the walls communicating, in one
direction, with the ambient atmosphere to aid in resetting of the
piston.
An object of this invention is to provide a new and improved switch
actuating and release mechanism of the type described.
Another object of this invention is to provide a switch actuating
mechanism of the type described having new and improved means for
regulating the time of resetting of a switch operated thereby.
A further object of this invention is to provide a switch actuating
mechanism of the type described having new and improved means for
decreasing the time of resetting of the switch operating
piston.
The features of the invention which are believed to be novel are
particularly pointed out and distinctly claimed in the concluding
portion of this specification. The invention, however, both as to
its operation and organization, together with further objects and
advantages thereof, may best be appreciated by reference to the
following detailed description taken in conjunction with the
drawings, wherein:
FIG. 1 is a top plan view of a device embodying the invention;
FIG. 2 is a view seen in the plane of lines 2--2 of FIG. 1;
FIG. 3 is a view seen in the plane of lines 3--3 of FIG. 2;
FIG. 4 is a view seen in the plane of lines 4--4 of FIG. 2;
FIG. 5 is a view similar to a portion of FIG. 2, showing another
embodiment of the invention;
FIG. 6 is a view seen in the plane of lines 6--6 of FIG. 5; and
FIG. 7 is a view seen in the plane of lines 7--7 of FIG. 5.
A device 10 embodying the invention comprises an operating knob 11
threadably attached to a plunger 12 at one end of the plunger. The
other end of the plunger carries a resilient piston member 13
disposed within a cylindrical bore 14 defined by a housing means
15. The device, as shown, is attached to a mounting panel or other
support 16.
Plunger 12 extends through a top wall member 17 which is secured to
a support member 18 threaded along its upper portion 19 to receive
a matingly threaded clamping collar 20. One or more resilient
spacing members 21 may be disposed between member 18 and panel 16
to insure tight fastening of the apparatus to the panel member. A
return spring 22 acts between the upper surface of wall member 17
and a spring seat 23 carried on plunger 12. A flexible diaphragm
and cover 24 may enclose the spring return mechanism as
illustrated.
As thus far described, the mechanism from wall 17 up including the
plunger 12 (without piston 13) is a fairly common, manually
operated, spring return actuating device.
A mounting member 26 is secured to housing 15 as by means of bolts
26a. A standard switching mechanism 27 is carried by member 26. The
switch within housing member 27 has an operating plunger 28 which
is spring returned. Plunger 28 is engaged by a contact button 29
carried by a flexible diaphragm 30 of rubber, nylon, or similar
material disposed between the bottom of housing 15 and member 26
and sealing the lower end of cylindrical bore 14.
When operating knob 11 is depressed to move plunger 12 and piston
member 13 downwardly, the air pressure in cylindrical bore 14
increases which distends diaphragm 30 downwardly carrying contact
button 29 therewith. The plunger 12 is of insufficient length to
directly actuate the switch. Button 29 depresses plunger 28 to
close the switch. The increase in air pressure in cylindrical bore
14 may bleed off through a small orifice 31, a passage 32 defined
in wall member 15 and, hence, through passages 33 and 34 to the
ambient atmosphere. The effective area of passage 33 is controlled
by a tapered portion 35 on an adjustment screw 36 where the tapered
portion 35 extends into passage 33 and regulates the area thereof.
By varying the position of adjustment screw 36 the effective area
of passage 33 for bleeding of pressure from cylindrical bore 14 may
be regulated.
Thus, as the air pressure in cylindrical bore 14 is increased to
cause contact button 29 to depress switch plunger 28, the air
pressure in cylindrical bore 14 will be greater than atmospheric
and will begin to bleed off through orifice 31, passage 32 and
passages 33 and 34.
After a predetermined time, dependent upon the setting of screw 36,
the pressure in cylindrical bore 14 will have decreased to a point
where it is insufficient to distend diaphragm 30 and hold plunger
28 down. The bias on switch plunger 28 will release the switch
regardless of whether the operator maintains knob 11 in a depressed
condition. Assume that the operator has released knob 11 after
actuation of the switch, and plunger 12 starts to move upwardly
under the influence of energy previously stored in spring 22. Due
partially to the sealing engagement of piston 13 against the wall
of bore 14 and the resulting friction thereof, there will be a
delay in complete resetting of knob 11. Also, as the spring 22
moves the piston upwardly the pressure in cylindrical bore 14 will
decrease as the volume increases. This acts as a resistance against
spring 22. To overcome this and provide a more positive return, a
one-way fluid diode 38 is provided, carried in a recess 39 provided
therefor in housing 15. Diode 38 provides communication through
openings 40 and 41 to bore 14.
The fluidic diode 38 has a filter 42 provided at the opening
thereof in communication with passage 40. Fluidic diode 38 acts as
a check valve. When piston 13 is moved to compress the air in bore
14, the diode 38 remains closed. However, as the piston 13 moves
upwardly as viewed in FIG. 2 and the pressure in bore 14 decreases,
ambient air may flow through orifice 40, filter 42, diode 38,
passage 41 and into bore 14 to increase the recovery rate of the
actuating mechanism. Additionally, an opening 40a is provided in
bore 14 leading to passage 39 so that as piston 13 rises, the air
therein is provided with an escape. Filter 38 guards against any
possibility of a build-up of dust or other solids in bore 14.
A device embodying the invention is relatively economical to
manufacture and produce inasmuch as it utilizes a readily available
standard actuating mechanism as previously described, and a common
switch. These elements may be readily attached to the pressure
section as by means of bolts 44 which attaches housing member 15 to
member 17 and bolts 45 which attaches switch 27 to member 26.
It will be understood that when the switch is normally used, i.e.,
depression and release of knob 11, switch plunger 28 is released
after actuation thereof. Piston 13 then quickly recovers aided by
the air admitted through diode 38.
A further embodiment of the invention is shown in FIGS. 5 - 7
wherein like parts to the structure of FIGS. 1 - 4 bear like
reference numerals.
In the second embodiment, the increased pressure in bore 14 due to
depressing piston 13 is bled off to the upper portion of bore 14
through passage 34a defined in the upper surface of housing 15. A
passage 33a provides communication between passages 33 and 34a.
There is no direct communication to the outside of housing 15. The
rate of bleed is determined by the setting of valve screw 36 and
tapered portion 35 thereof in passage 33, as heretofore
explained.
This arrangement recirculates the air within housing 15, and
minimizes the amount of fresh air brought into the housing, thereby
minimizing the possibility of dirt and dust entering the chamber
defined by housing 15 or from clogging passage 34 from the
outside.
In operation, as plunger 12 is depressed, piston 13 moves down,
increasing the pressure therebelow and forcing diaphragm 30
downwardly to actuate switch 27. The pressure commences to bleed
off through orifice 31, passage 32, 33 and 34a to the portion of
bore 14 above piston 13. This relieves the pressure below piston 13
and times release of the switch as heretofore explained. At the
same time, the amount of air otherwise entering bore 14 above
piston 13 is minimized. As piston 13 rises under the bias of spring
22, the air above piston 13 is expelled through passage 40a and
will be drawn through filter 42 and fluid diode 38 to the lower
portion of bore 14 through passage 41.
While the foregoing description describes an embodiment of the
invention in closing a normally open switch, it will be apparent
that the actuator may be utilized to open a normally closed
switch.
It may thus be seen that the objects of the invention set forth as
well as those made apparent from the foregoing disclosure are
efficiently attained. Modifications to the disclosed embodiments of
the invention as well as other embodiments thereof may occur to
others skilled in the art. Accordingly, the appended claims are
intended to cover all modifications to the disclosed embodiments as
well as other embodiments thereof which do not depart from the
spirit and scope of the invention.
* * * * *