US2151213A - Solenoid - Google Patents

Description

W. F. KELLEY SOLENOID March 21, 1939.

Filed Dec. 3, 1937 FIG .3

FIGA

FIG.5

FIGJ

II Il INVENTOR WALTER F. KELLEY ATTORNEY Patented Mar. 2l, 1939 unirse STATES SOLENOID Walter F. Kelley, Whitestone, N. Y., assignor lto Remington Rand Inc., Buialo, N. Y., a corporation of Delaware Application December 3, 1937, Serial No. 177,924

3 Claims.

This invention relates to solenoids and more particularly to improvements in solenoids which include `a movable core or plunger as'part of their mechanism.

Solenoids with movable cores designed to actuate other mechanisms by a change ofcurrent in their windings, possess many advantageous characteristics, such as high operating eiiciency, small space required, and quick action. Consequently, they have been employed inl many 'maf chines in a variety of designs,

The solenoid described hereinafter includes a casing which encloses all the moving parts, a fully protected winding. and a plunger which has many unique features.

The principal object of this invention is to provide a solenoid with a plunger which will not Other objects and structural details of the inl vention will be apparent from the following description when read in connection with the accompanying drawing, wherein:

Fig.` 1 is a central section view of the entire assembly;

Fig. 2 is a section taken along line 2-2 of Fig. 1;

Fig.3 is a plan view of the insulating end disc which holds the electrical wiring in place;

Fig. 4 is a plan view of the slotted washer of insulating material which holds tls terminal Wires;

Fig. 5 is a plan view of a slotted phosphor bronze washer for supporting the winding;

Fig. 6 is a bottom view of the plunger showing the eddy current slots.

Although the solenoid is not necessarily in a vertical position when in use, it is always inclined enough to allow the plunger to be drawn back to its normal position by gravity. In this description the solenoid will be considered as standing in. a vertical position (Fig. l) and the upper portion will be called the top, while the lower portion will be called the bottom.

The fundamental principle underlying the op-l eration of power solenoids is, that the production of motion is accomplished when and only when such motion reduces the reluctance of the entire magnetic circuit. The total reluctance of any magnetic ciruit is equal to the combined reluctances of the separate parts, and if these parts are connected in series, then the total reluctance is equivalent to the algebraic sum of the parts. Since the magnetic ilux must enter a free plunger or armature at one point and leave it at another, there are always two air gaps in the magnetic circuit when the plunger is inv its position corresponding to a value of current equal to zero. When the solenoid current is caused to flow, the plunger or armature moves in a direction tending to shorten one or both air gaps and hence reduce the reluctance in the magnetic circuit. The presend invention employs a design in which only one air gap is reduced, the other remaining constant. Hereinafter, the two air gaps will be designated as variable and constant, it being understood that the variable air gap produces the power necessary for motion and the constant air gap produces no power at all.

The outside casing of the solenoid consists of a soft iron tube I0, which isturned in at the bottom to form an annular shoulder II thereby forming a hole I2 in the bottom of the casing, large enough for the passage of an iron plunger 5) and an insulating disc I6 which forms part of A the coil assembly. r

Inside the metal tube I5 is placed another tube I8 of phenol resin as shown (Fig. 1). This tube provides a low friction surface for the bottcm shoulder of the plunger to slide on and furl ther helps to denitely determine the equivalent airv gap in this portion of the magnetic circuit.

The solenoid winding Il is wound upon a tube 20 made of phenol resin and is supported at ITI SEI)

. I3 together-with its bottom flange member I4, as

each end by insulator discs I6 and 2|. The winfiing is protected on the outside by the iron cas- Aing I0. The upper insulator disc 2l contains two' notches 22 and 23 (Fig, 3), said notches being provided to permit the passage of the two ends of the solenoid winding, 24 and 25 (Fig. 2)

through the disc 2| to their respective connections. A guide ring 26. composed of insulation material (Fig. 4) containing a slot 21 is placed on the disc 2I so that the notch 23 of disc 2I is in line with the slot 2l. This arrangement permits a wire to pass through the notch and slot as shown in Fig. 2.

The ends 24 and 25 (Fig. 2) of the solenoid winding Il are soldered to Wires 30 and 3l, which wires in turn are Wound around the ring 2B one-half of a turn and then passed through holes in a cap member 34. The insulation of the wires is slightly thicker than the ring 23 so that when the wires are placed in position, they protrude over the top of the ring. A shoulder 35 is formed in the top of casing lll on which shoulder, cap 34 is positioned. The upper edge of cap 34 is chamfered to permit the edge of casing Ill to be turned over the ehamfer and thereby permanently fasten the cap together with the sole noid winding Il, in place. When the easing I0 is crimped over the edge of the cap 34, said cap will be forced down until it engages shoulder 35. Since the insulation of the wires 30 and 3l is slightly thicker than the ring 26, the Wires are consequently compressed by the cap 34 and tightly held in place. This prevents any movement of the wires at their soldered joints, thereby protecting them from breaking.

Secured to the cap 34 is a nipple 36 which is provided with a concentric hole 31, used as a guide for a. non-magnetic rod 38 that may be fastened to the plunger of the solenoid or engaged by it. The nipple 36 is further provided with a bottom extension piece 40 which fits lnside the insulator tube .20 and is partly supported therein. The nipple 36 is secured to the cap 34 by bolts or rivets or the two may be integrally cut from the same piece. A thread 4I is cut on the nipple 36 as indicated to aid in securing any mechanism which may be used to transmit the actuated plunger impulse. i

The plunger I3 oi' the solenoid rides inside of the tube 2U, said tube acting as a bearing for the plunger. In order to eliminate any binding action which might occur due to misalignment, a shoulder 42 is provided at the upper end of the plunger I3, the diameter of said shoulder being slightly smaller than the diameter of the insu lator tube 20. The diameter of the remaining cylindrical portion is slightly less than the diameter of the shoulder so that the only point of contact between lthe cylinder 20 and plunger I3 is the shoulder 42.

At the bottom of the plunger I3, the flange member I4 is attached by any of the well known methods or the entire plunger and bottom flange may be turned from a solid piece of metal. The diameter of the ange is slightly less than the inside diameter of the phenol resin tube I8 in order to provide freedom of motion throughout the length of said tube without permitting any serious change in air gap length.

The space between the flange I4 and the inside iron tube I5 is termed air gap even though the space is filled almost entirely with phenol resin. Such parlance is common among those skilled in the art and is justified because the magnetic permeability of the phenol resin is the same as that of air. The air-gap in this face may vary depending upon other design factors and magnetic characteristics of the iron used. In any event the reluctance of this constant air gap may be made quite small in comparison to the variable air gap, because the area is so large.

Winding I1.

'I'he area extends around the periphery of the flange and is further enlarged by adding an extension 43 to the upper edge of the flange as shown.

A soft rubber washer 44 is placed on the cylindrlcal portion oi' the plunger I3, next to the flange I4 to act as a resilient shock absorber at the end of theplunger stroke. Another soft rubber washer 45 is placed inside the casing next to the shoulder Il and forms a cushion for the plunger to fall upon when it returns under the force of gravity, after the magnet has been deenergized. This rubber washer 45 also forms a convenient means for holding the plunger within the casing when in use or for removing it for inspection. Removal is accomplished by distorting the washer so that it may be taken out through the hole I2 after which the plunger slides out Without further obstruction.

When the coil is energized, a strong magnetic ileld is set up in the soft iron components and in the two air gaps. The path of these magnetic lines is as follows: From the plunger I3 where the greatest field strength is maintained, through the variable air gap 46, to the nipple extension 40, spreading out through the cap 34, down through the easing Il), into the tubing I5, across the constant air gap to the flange I4 and back to the plunger I3. Since a movement of the plunger I3 upward will shorten the variable air gap 46 and not change the constant air gap, the plunger will move up unless restrained by a force greater than that set up by the magnetic iield. Assuming that the plunger is not so restrained, it moves swiftly upward gaining in tractive force as the variable air gap is shortened until the rubber washer 44 strikes the phosphor bronze ring I9 and stops the plunger motion. The top surface of the plunger never reaches the bottom surface of nipple extension 40 because the parts are so proportioned that the washer 44 stops the upward movement just short of contact.

Because freedom for motion must be provided between the flange and the tubular phenol guide, it follows that these parts may be eccentric by the necessary clearance and that the air gap at opposite ends of a diameter may vary by double the normal clearance distance. This tends to unbalanee the magnetic eld and the consequent radial or side-acting forces on the fiange. The construction is also vfor the purpose of keeping the clearance at a minimum in order to maintain a minimum unbalance of the radial forces and friction.

The fact that the phenol tubing I8 constrains the flange I4 to a small lateral motion also keeps the main plunger I3 in line with the phenol tubing 20 which forms the inside of the electrical The dimensions are such that the only contact the plunger I3 can make with the phenol tubing 2 0, is at the topmost portion 42, which by reason of its larger diameter, holds the remaining portion of the plunger clear.

The net result of this form of structure is a continuously aligned plunger with a constant low reluctance air gap at the flanged portion, and negligible friction due to lateral attraction.

While I have described what I consider to be a highly desirable embodiment of my invention, it is obvious that many changes in form could be made without departing from the spirit of my invention, and I, therefore, do not limit myself to the exact form herein shown and described, nor to anything less than the whole of 75 my inventionv as hereinbefore set forth, and as hereinafter claimed.

What I claim as new, and desire to secure by Letters Patent, is:

1. In a solenoid having a tubular iron casing, a coil within said casing, an iron plunger axially movable partly within said coil and partly within said casing, iron flanges at each end of said plunger, the iiange within said coil being only slightly larger than the plunger, the iiange within said casing being at least twice as large as the plunger, the periphery of each ange formed with a cylindrical surface concentric with the plunger, tubes of non-magnetic material mounted Within the said coil and within the said iron casing, whereby the periphery of the larger flange is movable within said tubing along the axis thereof but is laterally constrained to less than ten per cent of the distance between said ange and said tubular iron casing.

2. In a solenoid having a tubular iron casing, a coil within said casing, a movable iron plunger within said coil of cylindrical form having anged end portions, each having a diameter larger than the diameter of the middle portion thereof, two phenol resin tubular members, one positioned inside of said coil to slidably engage the smaller of said plunger flanges, the other positioned outside of said coil but inside of said casing to slidably engage the larger of said plunger anges, the larger ange being at least twice the diam eter of the smaller ilange.

3. In a solenoid having an iron casing, a coil and a movable iron cylindrical plunger, an iron ilange formed on each end of said plunger, said flanges provided with coaxial cylindrical peripheries each having a diameter larger than the diameter of the middle portion of said plunger, one of said flanges being slidably mounted within said coil, the second iiange being slidably mounted within a non-magnetic tube adjoining the said casing, the second of said flanges being at least twice the diameter of the smaller iiange and both flange portions forming series elements in the magnetic circuit of said solenoid.

WALTER. F. KELLEY.

Images