US3643193A

US3643193A - Time-delay solenoid

Info

Publication number: US3643193A
Application number: US81751A
Authority: US
Inventors: Robert E Prouty
Original assignee: Essex International Inc
Current assignee: Raytheon Technologies Corp
Priority date: 1970-10-19
Filing date: 1970-10-19
Publication date: 1972-02-15
Anticipated expiration: 1989-02-15
Also published as: CA939719A

Abstract

A time-delay solenoid includes a cylindrical permanent magnet and a coil wound cylindrical bobbin mounted within a single housing and adapted to exert opposite forces on a plunger. The plunger having a ball check valve connected to one end thereof is slidably secured for movement inside a tube within the solenoid. The valve acts to impede movement of the plunger in one direction through a viscous fluid in the tube.

Description

United States Patent 1151 3,643,193 Prouty 1 Feb. 15, 1972 [54] TIME-DELAY SOLENOID 1,868,256 7/1932 Rippl ..335/62 2,519,055 8/1950 Kyle et a1. 335/62 X [72] 2,561,355 7/1951 Fish ..335/230 x [73] Assignee: Essex International, Inc., Fort Wayne, Ind. 2,915,681 1959 T y 35/229 X [22] Filed: 1970 Primary Examiner-G. Harris [21] APPLNOJ 81,751 AnorneyMolinare,Allegretti,Newitt&Witcoff [57] ABSTRACT [52] US. Cl ..335/240, 335/62, 335/241 [51] A time-delay soleno1d 1nc1udes a cylmdncal permanent mag- [58] Field of Search "335/59 61 62 63 net and a coil wound cylindrical bobbin mounted within a sin- 240 4 f 6 i gle housing and adapted to exert opposite forces on a plunger. The plunger having a ball check valve connected to one end thereof is slidably secured for movement inside a tube within [56] References Cited the solenoid. The valve acts to impede movement of the UNITED STATES PATENTS plunger in one direction through a viscous fluid in the tube.

1,730,688 10/1929 Rippl ..335/62 8 Claims, 3 Drawing Figures 22 i 20 24 /2 I A 2/ 1 2 O/ E 5 6 74 g 72 72246 4 5 3 52 7a Q 70 343632 58 Ell ll/ 3 PAIENTEDFEB 15 I972 3. 643. 1 93 SHEET 2 OF 2 INVENTOR. ROBE/Q7 P190077 AT TORNEKS' 1 TIME-DELAY SOLENOID BACKGROUND OF'THE INVENTION This invention relates generally to a time-delay solenoid. A solenoid is a device which produces mechanical movement of a ferrous article in response to a magnetic field generated from a coil by an electrical current. A time-delay solenoid is one in which the mechanical movement is delayed a certain time after energizing and/or deenergizing a solenoid coil.

The uses for a time-delay solenoid are many'and varied. One example is in connection with a conventional washing machine. In such a device, a latch for the washing machine door should lock quickly at the initiation of the washer spin cycle so that'the machine cannot accidentally be opened during this time. Also, the door latch should unlock, but not until the rotatable tank in the washing machine has been brought to a co'mplete'stop, which is sometime after the termination of power for spinning the tub. Such a time-delay solenoid has many other applications, including for example, a use in connection with a self-cleaning oven which must be locked until cooled.

Some time-delay solenoids in the prior art have employed ballcheck valves in conjunction with a ferrous article to be moved. These valves have operated to obstruct movement of the ferrous article in one direction through a fluid. In such devices, the gravitational field of the earth is employed to return the ferrous article to its normal position within the solenoid. When the force of gravity is relied upon, the solenoid must be placed for operation in the upright position thus limitingthe location of the device. In another device, a pennanent magnet was employed in conjunction with a solenoid coil to return a ferrous member to its normal position within a solenoid. However, this device was not adapted as a time-delay solenoid.

Accordingly, it is desirable to produce a time-delay solenoid which, when energized, will act quickly and which when deenergized,'will delay for a given predetermined time interval. It is further desirable to provide a device which is simple and economic to construct which will operate efficiently, and which may be mounted for operation at any desired position. It is also desirable to produce such a device having components which may be mounted in a single compact casing and which may be easily replaced upon failure thereof.

SUMMARY OF THE INVENTION In a principal aspect, the present invention is related to a time-delay solenoid which includes a hollow outer casing, a hollow bobbin secured within the outer casing at one end of the casing and adapted to receive a solenoid coil and a substantially cylindrical hollow permanent magnet secured within the other end of the outer casing adjacent to and coaxial with the bobbin, the bobbin and permanent magnet forming a channel therewithin. The solenoid also includes a nonmagnet tube slidably mounted within the channel for movement therealong.

The tube is sealed at one end by a magnetic plug and at the other by a metallic sleeve and is adapted to contain a viscous liquid. A ferrous plunger is slidably mounted within the tube to move the tube'within the channel having a ball check valve at one end of the plunger. The ball check valve provides an obstruction to movement of the plunger in one direction in response to force from the permanent magnet and provides a passageway for fluid allowing unobstructed movement of the plunger in theother direction in response to force from the coil whenthe coil is energized.

BRIEF DESCRIPTIONOF THE DRAWINGS There follows a brief description of the drawings which show a presently preferred embodiment of the present invention wherein like numerals refer to like elements and wherein:

FIG. I is a perspective of the time-delay solenoid of this invention;

FIG. 2 is a cross section of the time-delay solenoid of FIG. 1 taken along the line 2-2; and

As may be seen in FlG. l, a time-delay solenoid I0 is enclosed in an outer casing 12 which may be formed of brass tubing or other suitable material. A steel bracket 14 is connected to one end of the solenoid 10 for mounting the solenoid 10 for use.

As may be seen more clearly in FIGS.'2 and 3, the outer casing 12 is of substantially cylindrical'shape. Within the outer casing I2 at the left end thereof is an inner casing I6 which may be formed of steel tubing or other suitable material. The inner steel casing 16 secures a hollow bobbin 18 therein which is mounted at one'end of the outer casing 12 coaxial with both the inner casing 16 and the outer casing 12. The bobbin is adapted to receive-a wound coil 20 of the solenoid 10.

A hollow permanent magnet 22 of substantially cylindrical shape is mounted within the outer casing 12 at the other end thereof adjacent the bobbin I8. A washer 24 is secured on flange members 26 projecting from the bobbin 18 between the bobbin l8 and the permanent magnet 22. The permanent magnet 22 abuts the washer 24 and a portion of the flange members 26. The permanent magnet 22 and bobbin 18 are longitudinally related along the axis of the outer casing 12 and form a channel 28 therein, along the axial length of the outer casing 12.

Secured within the channel 28 is a tube 30 which may be formed of stainless steel or other nonmagnetic material. The tube 30 is slidably mounted within the channel 28. The tube is sealed at one end 32 by a plug 34 which is formed of magnetizable material such as steel rod or the like. The plug may be secured to the slidable tube by silver soldered joints 36.

The tube 30 is sealed at the opposite end 37 by a sleeve 38 which may be formed of stainless steel or other nonmagnetic material. The sleeve 38 is connected to the slidable tube 30 by means of weldedjoints 40.

As can be seen, the tube 30 is hollow and forms an inner passage 42. Slidably secured within the passage 42 is a magnetic plunger 44 of substantially cylindrical shape. A first flange 46 projects from one end 48 of the plunger 44 and a second flange 50 projects from the other end 52 of the plunger 44.

A ball check valve 54 is secured at the end 48 of the plunger 44. The valve 54 includes a movable ball 56 entrapped within a chamber 58 between an orifice 60 and a pin 62 secured to the plunger 44. An end washer 63 is connected to the outer casing 12 and functions to retain the components of the solenoid within the casing 12.

A spring 64 is-mounted along the outer surface of the sleeve 38. The spring 64 serves to bias the sleeve 38 and its associated tube 30 and plug 34 towardthe left as seen in FIG. 1. A spring 68 is mounted between the base 70 of the sleeve 38 and the pin 62. This spring 68 serves to bias the plunger 44 towards the leftin respect to'the sleeve 38 and tube 30.

Connected to the plug 34 are shading rings 72 at either side thereof. Theseshading rings 72 serve to prevent a magnetic lock between the plug 34 and the plunger 44 when the plunger 44 makes contact with the plug 34, and to dampen noise when the plug 34 contacts the bracket 14. An actuator rod 74 is threadably secured to the center section 76 of the plug 34. When the plug 34 is moved towards the left as shown in FIG. I, the actuator rod is moved through a slot 78 defined in the bracket 14 and itperforms the desired function of the solenoid.

The component parts of this solenoid 10 are relatively simple in structure and designed to fit entirely within the outer casing 12. The assembly of the solenoid I0 is facilitated since the components may be easily fitted within the casing 12 in succession. The'fluid within the tube 30 is sealed by plug 34 and sleeve 38 and may be put into the tube 30 before the tube 30 is installedwithin the channel 28 of the solenoid l0.

While in the foregoing, a complete embodiment of the present invention has been described, a description of the steps involved in the operation of this device is added for greater understanding.

The permanent magnet 22 produces a magnet field oriented to exert a force tending to move the plunger 44 towards the right as seen in FIG; 2. Accordingly, when no current is supplied to the coils 20 of the solenoid 10, the magnetic field from the permanent magnet 22 is sufficient to produce a force on the plunger 44 causing it to compress the spring 68. This force also causes the plunger 44 to act on the base 70 of the sleeve 38 which in turn compresses the spring 64. Thus, the coil 20 of the solenoid 10 shown in FIG. 2 is deenergized.

When the coil 20 is energized, a second magnetic field is generated creating a force opposing that produced by the magnet 22. The external circuit (not shown) for supplying current to the coil 20 is designed to produce a force on the plunger 44 greater than that produced by the magnet 22. Thus, when the coil 20 is energized, a net force is exerted on the plunger 44 causing it to move towards the left as seen in FIG. 2. Since the passage 42 is filled with viscous fluid, for example, oil, the fluid flows toward the right into the ball check valve 54 through the orifice 60, past pin 62 and towards the spring 68. Since the ball 54 is biased towards the right in the chamber 58, it produces little obstruction to the flow of fluid toward the spring 68.

The plunger 44 continues to move towards the left contacting the plug 34. This movement then continues with the plunger 44 pushing the plug 34 and connected tube 30 and sleeve 38 towards the left until the plug 34 abuts the bracket 14. In this position, the actuator rod 74 projects to its full extent beyond the bracket 14.

In one application, the brass actuator rod 74 is employed for locking the door on an automatic washing machine (not shown). In this application, it is desirable to have the actuator rod or latch 74, lock swiftly with the commencement of the spin cycle of a washing machine (not shown). The coil 20 may be connected to be energized by the current used to drive the washer (not shown) in the spin cycle so that the solenoid I operates automatically without the need of an additional source of power.

This function is, of course, accomplished by the solenoid of this invention since the plunger 44 moves toward the left without obstruction by the ball check valve 54 as has been described. When the spin cycle of the washing machine (not shown) is completed, and no current is delivered to the solenoid coils 20, it is desirable to have the actuator rod or latch 74 remain locked until rotation of the washing machine tub (not shown) is entirely completed.

When the current to the coils is'terminated, no field is produced by the coils 20 and the force from the magnet 22 produces a movement of the plunger 44 from left to right. This movement is resisted by the obstruction of fluid movement at the ball check valve 54 by the ball 56 which is seated against the orifice 60. In this position, the fluid must flow between the

flanges

46 and 50 of the plunger 44 and the tube 30. This restricted flow prevents swift movement of the plunger 44 towards the right and thus prevents movement of the actuator rod 74 towards the right.

Because the solenoid 10 of this invention is designed with a permanent magnet for moving the plunger 44 to its normal position against the end washer 62, the solenoid 10 may be mounted without regard to whether or not the solenoid 10 is in the vertical position. The spring 64 which biases the sleeve 38 towards the left insures that the delay interval of the time delay solenoid 10 will be sufficient even with the solenoid in the upright position.

Because the fluid is contained entirely within the passage 42, the parts of the solenoid which require repair or adjustment (such as a short-circuited solenoid coil) may easily be replaced without draining the fluid.

While in the foregoing there has been described a preferred embodiment of the present invention, it is to be understood that other embodiments of this invention may be made by those skilled in the art without departing from the true spirit and scope of this invention.

What is claimed is:

l. A time delay solenoid comprising, in combination:

a substantially cylindrical hollow outer casing;

a hollow bobbin secured within said outer casing at one end thereof and adapted to receive a solenoid coil;

a substantially cylindrical hollow permanent magnet secured within said outer casing at the other end thereof adjacent to one end of said bobbin, said hollow bobbin and said hollow magnet forming a channel therealong;

a tube slidably mounted within said channel for movement therealong and adapted to contain a viscous liquid; and

an inner-ferrous plunger slidably mounted within said tube to move said tube within said channel having a ball check valve at one end thereof, said valve adapted to obstruct movement of said plunger in one direction in response to force from said permanent magnet when said coil is deenergized and to allow free movement of said plunger in another direction within said tube in response to force from said coil when said coil is energized.

2. The apparatus as set forth in claim 1 including a means for continuously biasing said tube in said other direction in relation to said casing.

3. The apparatus as set forth in claim 1 including a means for biasing said plunger in said other direction in relation to said tube.

4. The apparatus as set forth in claim 1 including a hollow inner casing adapted to encase said bobbin.

5. The apparatus as set forth in claim 1 including an actuator rod connected to one end of said tube and adapted to move in and out of said outer casing in response to movement of said plunger.

6. The apparatus as set forth in claim I wherein said tube is sealed at one end thereof by a metallic plug.

7. The apparatus as set forth in claim 6 wherein said tube is sealed at the other end thereof by a nonmagnetic sleeve.

8. The apparatus as set forth in claim 1 wherein said plunger is substantially cylindrical and includes a flange projecting from one end thereof and adapted to provide a narrow passage for said fluid between said plunger and said tube when said plunger moves in relation to said tube.

Claims

1. A time delay solenoid comprising, in combination: a substantially cylindrical hollow outer casing; a hollow bobbin secured within said outer casing at one end thereof and adapted to receive a solenoid coil; a substantially cylindrical hollow permanent magnet secured within said outer casing at the other end thereof adjacent to one end of said bobbin, said hollow bobbin and said hollow magnet forming a channel therealong; a tube slidably mounted within said channel for movement therealong and adapted to contain a viscous liquid; and an inner ferrous plunger slidably mounted within said tube to move said tube within said channel having a ball check valve at one end thereof, said valve adapted to obstruct movement of said plunger in one direction in response to force from said permanent magnet when said coil is deenergized and to allow free movement of said plunger in another direction within said tube in response to force from said coil when said coil is energized.

6. The apparatus as set forth in claim 1 wherein said tube is sealed at one end thereof by a metallic plug.