US3851502A

US3851502A - Yarn detector switch-upper

Info

Publication number: US3851502A
Application number: US00337924A
Authority: US
Inventors: A Hopkins
Original assignee: CONTROL SWITCH Inc
Current assignee: CONTROL SWITCH Inc
Priority date: 1973-03-05
Filing date: 1973-03-05
Publication date: 1974-12-03
Anticipated expiration: 1991-12-03

Abstract

An upper switch for monitoring the year as it is being drawn from a supply spool to stop the knitting machine and light an indicator lamp under abnormal conditions that it detects such as an undue increase in yarn tension above a predetermined adjustable value, break in the yarn, absence or end of yarn, or a decrease in yarn tension or a large amount of slack in the yarn. In this upper yarn detector switch, parts that wear have been made readily replaceable, the switch lever counterweight has been made adjustable and arranged to decrease the applied weight as the switch lever falls, the switch has been provided with a contact making cam that won''t hang up, and improved tripping tension adjusting and indicating means and other improvements have been provided.

Description

Unite States Patent [19] Hopkins Dec. 3, 1974 1 YARN DETECTOR SWITCH-UPPER [75] Inventor: Alton W. Hopkins, Newtown [21] Appl. No.: 337,924

[52] US. Cl 66/163, ZOO/61.13, ZOO/61.18 [51] Int. Cl D04b 35/14 [58] Field of Search 66/163, 157, 161; 57/81;

FOREIGN PATENTS OR APPLICATIONS U.S.S.R 66/163 1,028,522 2/1953 France 66/163 Primary ExaminerJames Kee Chi Attorney, Agent, or Firm H. R. Rather; Wm. A. Autio 5 7 ABSTRACT An upper switch for monitoring the year as it is being drawn from a supply spool to stop the knitting machine and light an indicator lamp under abnormal conditions that it detects such as an undue increase in yarn tension above a predetermined adjustable value, break in the yarn, absence or end of yarn, or a decrease in yarn tension or a large amount of slack in the yarn. In this upper yarn detector switch, parts that wear have been made readily replaceable, the switch lever counterweight has been made adjustable and arranged to decrease the applied weight as the switch lever falls, the switch has been provided with a contact making cam that wont hang up, and improved tripping tension adjusting and indicating means and other improvements have been provided.

12 Claims, 8 Drawing Figures YARN DETECTOR SWITCH-UPPER BACKGROUND OF THE INVENTION Yarn detector switches have been known heretofore such as those shown in E. Vossen U.S. Pat. Nos. 2,290,303; 2,515,479 and 3,257,518 and C. S. Martin et al. U.S. Pat. No. 2,744,174.

While these yarn detector switches have been useful for their intended purposes, this invention relates to improvements thereover.

SUMMARY OF THE INVENTION This invention relates to upper yarn detector switches for use where the yarn leaves the supply spool for the knitting machine for sensing the yarn and stopping'the knitting machine when undue tension, slack, absence of yarn or the like is detected.

An object of the invention is to provide an improved upper yarn detector switch.

A more specific object of the invention is to provide a yarn detector switch with improved, readily replaceable wear parts. 7

Another specific object of the invention is to provide a yarn detector switch affording replacement of electrical contact members and components (bulb and resistor) without special tools or soldering.

Another specific object of the invention is to provide a yarn detector switch with an improved yarn feeler counterweight structure that is adjustable and operable to decrease the applied counterweight as such feeler actuates toward switch closure.

Another specific object of the invention is to provide a yarn detector switch with an improved movable contact that won't hang up under yarn feeler operation.

Another specific object of the invention is to provide 7 a yarn detector switch with improved tripping tension adjusting and indicating means. Another specific object of the invention is to provide yarn re-positioning means requiring minimum operator technique and skill.

Another specific object of the invention is to provide grounding of all surfaces that come into contact with the yarn during normal operation of the knitting machine.

Other objects and advantages of the invention will hereinafter appear.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged isometrid view of an upper yarn detector switch constructed in accordance with the invention;

FIG. 2 is a front elevational view thereof with the front cover removed to show the internal parts;

FIG. 3 is a right side elevational view thereof;

FIG. 4 is a vertical cross-sectional view taken along line 44 of FIG. 2;

FIG. 5 is a horizontal cross-sectional view taken along line 5-5 of FIG. 2;

FIG. 6 is an isometric view of the stationary contact member shown in FIG. 2;

FIG. 7 is an isometric view of the electrical connector member shown in FIG. 2; and

FIG. 8 is a circuit diagram thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1-3, there is shown an upper yarn detector switch according to the invention. This switch has an insulating housing 2 including a removable front cover 4 secured to the housing by three screws 6. A mounting bracket 8 is secured to the housing for snapin mounting of the switch to a horizontally-running strip or bar, this mounting bracket or clip also serving as one terminal for the electrical circuit therein. The yarn runs below guide bracket 10, above the yarn tension trip lever or snag arm 12, and below the yarn feeler lever or switch arm 14 as shown in FIGS. 2 and 3.

The housing is provided with a mechanism enclosing portion 2a and a yarn supporting portion 2b. The mechanism enclosing portion is generally square-shaped in front view with rounded corners as shown in FIG. 2 providing a compartment of sufficient depth as shown in FIGS. 4 and 5 for housing the operating mechanism, This compartment is closed by front cover 4 as shown in FIGS. 1, 4 and 5. The housing is preferably molded of plastic material so that yarn supporting portion 2b is integral with mechanism enclosing portion 2a thereof. Yarn supporting portion 2b tapers generally toward the right from the right wall of the compartment of portion 2a and is provided with a front-to-back groove 20 on its underside near its tip to provide a passageway for the yarn as shown in FIG. 2. j

The compartment in the housing is provided with a number of molded wals and projections hereinafter described for positioning and retaining the elements of the operating mechanism.

The operating mechanism comprises generally the following parts: I

l. A toggle (overcenter) spring mechanism for trip lever 12.

2 Adjusting means affording external manual adjustment of the tension of the toggle spring mechanism thereby to select the magnitude of yarn tension at which the switch will trip.

- 3. A switch operated by the feeler lever. 4. A yarn detector electrical circuit including the switch and a resistor in series.

5. An indicator lamp connected in the yarn detector circuit in series with the switch and in parallel with the resistor.

The toggle spring mechanism is mounted on a bracket plate 16 that lies against the rear wall of the compartment primarily, and has two forwardly bent portions 16a and 16b that lie against the upper wall of the compartment as shown in FIG. 5, and has a downwardly bent portion that lies against the front cover as shown in FIG. 4, this portion 16c being bent down from forward portion 16b to form a pivot for the toggle spring mechanism. This bracket plate is secured to the housing by a pair of rivets including a pivot 18 that is inserted through a hole in the rear wall of the housing and a hole in the bracket plate and is staked within the compartment as shown in FIG. 4 to secure it in place. The other rivet 20 shown in FIGS. 2 and 5 goes through portion 16a of the bracket plate and the upper wall of the housing and serves also to secure combined mounting clip and terminal 8 to the housing as well as securing the bracket plate within the housing compartment.

The bracket plate is provided with a pair of aligned notches for pivoting crank shaft 22. For this purpose, a front notch 16d is provided in portion 166 as shown in FIG. 2 and a like rear notch is provided directly behind it in the main body of the bracket plate that lies against the rear wall of the compartment. These two notches are spaced from one another by the depth of the compartment as shown in FIG. 5 and afford space therebetween for the central swinging portion of crank shaft 22. The opposite ends of the crank shaft extend through holes in the rear wall and front cover and through

respective bushings

2d and 4a thereon as shown in FIG. 5. The extreme ends of this crank shaft are flattened to fit into slits in the ends of trip lever 12 to afford turning of the crank shaft by the trip lever in response to undue yarn tension.

A tension spring-24 of the helical type provides the toggle action. The center' of the swinging part of crank shaft 22 is provided with a re-entrant bend to form a notch for retaining one end book of spring 24 as shown in FIG. 5. A fixed but adjustable slide member 26 is provided with a hole as shown in FIG. 4 for retaining the other hook of this spring so that the spring is stressed in tension therebetween.

The aforementioned tension adjusting means comprises slide member 26 and a worm 28 that meshes with a rack 26a on the lower surface of slide member 26. As

shown in FIG. 2, the left end portion of slide member 26 is slidably held in a groove between an upper wall 2e and a lower wall 2f integrally molded in the housing. Wall 2e has a forwardlyprojecting' portion 2g at its right end as shown in FIGS. 2 and 5 to form a rest for portion 160 of the bracket plate to retain the latter securely. in its place, the remainder of this wall being slightly narrower to provide clearance for the upper endof pointer 30. Worm 28 is tapered to remain in mesh with the slightly angularly-disposed rack 26a. This worm is integral with a horizontal shaft 280 that terminates in an externalknob 28b having a hexagonal shapefor manual turning. This'worm is held in place by a pair of walls 211 and 2j forming a groove therebetween molded in the housing through which groove the worm shaft passes, these walls bearing against the worm and the left wall ofthecompartment bearing against 'the knob to hold the worm fixed within the housing. In addition, bracket plate 16 is provided with a forwardlyprojecting finger l6e having a tab 16f bent over the tip of the shaft beyond the worm to keep the worm from rising out of its slot in the housing as shown in FIGS. 2 and 4. Another projection 2k integrally molded in the housingis located below this tip of the worm shaft to hold the worm up against and in mesh with the rack.

The part of the shaft 28a immediately adjacent the knob also passes through a groove in the left wall of the compartment tohold it fixed but rotatable. I

Slide member 26 is provided with a notch in its front edge for retaining the circular upper end of pointer 30 and for'rotating this pointer as the slide member is moved by turning the knob. This pointer is pivoted at its intermediate portion on a short round projection 2m integrally molded on wall 212. A curved wall 2n is.

molded in the housing directly below the tip of the pointer to make this pointer visible through the transparent cover by providing a light colored background for the black pointer.

' The aforementioned yarn detector circuit extends as shown in FIGS. 2 and 8 from mounting clip 8 through its rivet 20, bracket plate 16 and pivot 18 to movable cam contact 32. This circuit then continues from stationary spring contact 34 (shown also in FIG. 6), resistor 36 and connector 38 (also shown in FIG. 7) and the rivet through the rear wall to external connector 40. Lamp bulb 42 is connected between stationary contact 34 and connector 38 in parallel with resistor 36.

As shown in FIG. 4, pivot 18 serves a number of purposes. As hereinbefore described, it serves as a rivet to secure bracket plate 16 to the housing. It also serves as a pivot for the rear arm of feeler lever 14. For this purpose, it is provided with a round bore shown in FIG. 4 extending partway in from its outer end in which the forwardly-bent end of the rear arm of the feeler lever is pivoted and in which the feeler lever is held by its own spring bias. Pivot 18 also serves to pivotally support movable cam contact 32. For this purpose, pivot 18 is provided with a reduced diameter forward end ,portion that extends into the centerhole of the movable contact to freely support the latter for rotation thereon. v

Movable contact 32 is thus freely pivoted for engaging stationary spring contact 34. As shown in FIG. 2, movable contact 32 is bowknot shaped having cam segments on opposite sides 180 apart so that either cam can be positioned in assembly for engagement with the stationary contact. The center hole therein is provided.

45 snapped into a groove in the shaft at the inner end of bushing 4b. The inner end of this drivershaft has a driver finger 44a, eccentrically offset from its center, and a leveling surface at its other side with a recess therebetween for accommodating the reduced end of pivot 18. This driver finger enters one of the slots'in movable contact 32 and the levelingsurface holds the movable contact concentrically on pivot 18 so that when feeler lever 14 pivots counterclockwise, the movable contact will freely rotate to be camrned into sliding engagement with contact spring 34 to close the switch.

The slot 44b in the external head of driver shaft 44 is shaped to retain the front arm of the feeler lever. As shown in FIG. 1, this slot is provided with a central constriction and the end portion of the front arm of feel er lever 14 is provided with a pair of spaced flattened, wider sections entering on opposite sides of this-constriction whereby the feeler lever is snapped in and held in place by its own spring bias.

The external head of driver shaft 44 is provided with means for mounting an adjustable counterweight 46.

- This means comprises a tapped eccentric projection 44c extending from one .edge of the head at substantially a angle counterclockwise from and relative to driver finger 440 so that when the driver finger is at the top, the counterweight will extend substantially horizontally to the left. This counterweight is a metal stud treaded at one end to a substantial length for adjustment into or out of eccentric projection 44c of the driver, this adjustment being made by turning the counterweight at screwdriver slot 46a at its other end.

Following along the yarn detector circuit in the direction it was traced above, the next element is stationary contact 34. As shown in FIGS. 1 and 4, the narrow upstanding portion thereof extends down alongside the movable contact where it can be engaged and then takes a 90 turn left where it enlarges to a wider lefthand section as shown in FIG. 6. This wider section has a notch 34a at its rear edge fitting over a complementary lug in the housing below wall 2n to securely retain it in place. Additionally, this left-hand section of contact 34 is held slightly bowed between the lower surface of wall 2n and spaced wall and stud 2p and 2q molded within the base as shown in FIG. 2. Stud 2g has a hole for receiving one rearwardly-bent wire of resistor 36 for mechanically mounting the latter, and contact 34 has a downwardly-angled connector spring finger 34b shown in FIG. 6 pressing on this resistor wire to make an electrical connection to the resistor as shown in FIG. 2. To provide clearance for connection finger 34b, stud 2q is slightly shorter than wall 2p.

The other wire of resistor 36 is connected by connector 38 to external terminal 40. For this purpose, connector 38 has the configuration shown in FIG. 7. It is riveted at its upper end through the rear wall to terminal 40 as hereinbefore described. It extends down along wall 2p as shown in FIG. 2. A notch 38a is provided in the rear edge of this connectoi as shown in FIG. 7 to fit over a complementary lug at the root of stud 2: to retain the connector in secure position in the housing.

' The part of this connector strip directly above corner stud 2r is provided with a clamp for clamping the other wire of resistor 36. For this purpose, the connector strip is provided with a leftward re-entrant bend 38b and a spring finger 380 is sheared from the forward edge and bent at an angle past this bend. This spring finger is then pressed clear of the bend and the resistor wire inserted within the bend and the finger allowed to spring back against the wire to bias it within the bend to make a pressure electrical connection.

The left end of connector 38 is provided with a lamp socket 38d. For this purpose, the connector strip is provided with a round hole having a short slot at its edge as shown in FIG. 7. The edge of this hole is then formed with a gradual angle with one side of this slot formed up and the other side formed down to fit the threads of the lamp bulb. When the lamp bulb is screwed in this socket, the center terminal thereof is pressed against downwardly angled tongue 340 of contact 34 as shown in FIGS. 2 and 6 to connect the trip indicator lamp across resistor 36.

Cover 4 is provided with a pair of lugs 4b and 4c fitting into corresponding notches above lamp 42 and shaft 28a, respectively. Cover 4 is also provided with an integrally molded forwardly extending stud 4d to hold driver shaft 44 from rotating to facilitate assembly of the cover and insertion of driver finger 44a into the slot lever 14. This stop allows movable contact 32 to engage stationary spring contact 34 and to deflect the latter a limited amount for good contact.

As will be apparent from FIGS. I and 2, yarn tension trip lever 12 may be moved down or clockwise a small amount whereupon crank shaft 22 passes the line of action of spring 24 to snap lever 12 all the way. Lever 12 stops when crank shaft 22 abuts the upper wall of the housing. The yarn may then be placed across the bend of lever 12 and this lever moved up or counterclockwise until it snaps over-center into the position shown in FIG. 2. In thus moving up, the yarn carries feeler lever 14 along with it so that the feeler lever rests on the yarn. Thus, the yarn will pass between the upward re-entrant bend in bracket 10 and the downward reentrant bend in trip lever 12 and below feeler lever 14.

In the case of a snag in the yarn or undue tension or the like, the yarn will pulltrip arm 12 down until it will snap over-center. This allows feeler arm 14 to fall clockwise to close the switch to stop the knitting machine and light the indicator lamp.

In case of undue slack in the yarn, or breakage, or end of yarn, feeler arm 14 falls and closes the switch with the same result as above.

As will be apparent, the parts that wear are readily replaceable. Bracket 10 is inserted at its left end in a notch 2t in the bottom of the housing adjacent the indicator lamp and its right ends are bent toward one another and snap into holes 2a in the right end yarn supporting portion 2b of the housing. When this bracket wears by rubbing of the yarn thereon, its ends can be spread apart clear of holes 214 and the bracket removed and readily replaced with a new one.

Feeler arm 14 is also readily replaceable should it wear by rubbing of the yarn. Its rear arms can be spread apart so that the forwardly-bent end on its rear arm clears the hole in pivot 18 (FIG. 4) and its front arm clears the slot in the head of driver shaft 44 (FIG. 1). A new feeler lever can readily be assembled in its place.

Similarly, trip lever 12 is readily replaceable should it wear by the yarn running thereover. Its two arms can be spread apart clear of the ends of crank shaft 22 and the lever removed and replaced with a new one.

As will be apparent from FIG. I, counterweight 46 is readily adjustable by inserting a screwdriver into slot 460 and turning the counterweight in or out. Its effective weight varies with the length of its horizontal lever arm from the axis of the driver shaft. Its applied counterweight decreases as the feeler lever falls to enhance closing of the switch. As this feeler lever falls, its counterweight is carried clockwise above the axis of the driver shaft so that the horizontal projection of its lever arm decreases in length thereby to decrease the counterweight.

While the apparatus hereinbefore described is effectively adapted to fulfill the objects stated, it is to be understood that the invention is not intended to be confined to the particular preferred embodiment of upper yarn detector switch disclosed, inasmuch as it is susceptible of various modifications without departing from the scope of the appended claims.

I claim:

I. A yarn detector device comprising:

an insulating housing;

a pair of electrical terminals on said housing;

a toggle spring mechanism comprising an overcenter spring biased crank shaft in said housing with the opposite ends of said crank shaft extending out through opposite walls of said housing;

means providing an eye for passage of yarn comprising:

an external guide member supported on said housing and providing one side of said eye;

and an external trip member supported on said crank shaft and biased toward said guide member by said toggle spring mechanism to provide the other side of said eye through which the yarn passes, and being responsive to undue tension in the yarn or a snag to trip across the line of action of said toggle spring mechanism thereby to open said eye and release the yarn therefrom;

a switch within said housing;

switch operating means accessible externally of said housing;

an external feeler member supported on said switch operating means and normally engaging the yarn adjacent said eye and being movable upon release of the yarn or in case of undue slack, break or end of yarn to operate said switch to close an electrical circuit between said terminals for stop motion purposes;

and quick disconnect joints between said external guide member and said housing and between the aforementioned external trip and feeler members and their respective supporting crank shaft and switch operating means enabling ready replacement of the wear parts.

2. The invention defined in claim 1, wherein:

said external trip member comprises a generally U- shaped lever having a pair of spaced substantially parallel arms connected by a yoke that abuts said housing when said trip member is biased to close said eye;

and said quick disconnect joints comprise slits on the ends of said arms and flat portions on the ends of said crank shaft received into said slits by spreading said-arms apart and allowing them to spring onto said crank shaft.

3. The invention defined in claim 1, wherein:

said external guide member comprises a generallyU- shaped bracket having a pair of spaced substantially parallel arms'connected by a yoke;

and said quick disconnect joints comprise a notch on said housing for retaining said yoke, a pairof aligned holes on opposite sides of said housing, and the ends of said arms being bent toward one another for receipt in said holes when said arms are spread apart and allowed to spring tllereinto,

4. The invention defined in claim 1, wherein:

said external feeler member comprises a generally U-shaped feeler lever having a pair of spaced substantially parallel arms connected by a yoke, the 'parts of the arms near the yoke resting on the yarn and positioned in close proximity to said trip member which provides support to said feeler member through the'yarn, and positioned with only a slight gap between said feeler member at its yoke end and the housing which prevents undesirable bounce during uneven yarn demand by the knitting machine;

and said quick disconnect joints comprise a pivot in said housing including a hole therein and a bent end on one of said arms received in said hole, a recess in said switch operating means and the end of the other arm being formed for rigid retention in said recess when said arms are spread apart and allowed to spring into said hole and said recess.

5. The invention in claim 1, wherein:

said external guide member comprises a generally U- shaped guide bracket having a pair of spaced substantially parallel arms connected by a yoke;

like re-entrant bends in said arms providing a downwardly-open yarn guide forming a two-part upper side for said eye;

said external trip member comprises a generally U- shaped trip lever having a pair of substantially parallel arms connected by yoke and spaced a shorter vdistance apart to pass freely between the arms of said external U-shaped guide bracket;

like re-entrant bends in the arms of said trip member providing an upwardly-open yarn guide forming a two part lower side for said eye;

and said external feeler member comprises a generally U-shaped feeler lever having a pair of substantially parallel arms connected by a yoke and spaced a still shorter distance apart to pass freely between the arms of said external U-shaped trip lever.

6. The invention defined in claim 1, wherein:

said switch operating means comprises:

a rotary shaft journaled in a wall of said housing having means on its external end for securely supporting said feeler member for rotation by the latter and having driver means on its internal end for operating said switch within said housing;

an elongated threaded counterweight;

and means integral with said external end of said rotary shaft providing a threaded hole for adjustably supporting said counterweight at a predetermined angle relative to said feeler member providing an adjustable counterweight for the latter.

7. The invention defined in claim 6 wherein:

said counterweight extends substantially horizontally in one direction and said feeler member extends substantially horizontally in the opposite direction when-said feeler member is engaging the yarn;

and said counterweight is rotated in an angular direction above said shaft to reduce its effective weight when the yarn allows said feeler member to rotate in an angular direction below said shaft.

8. The invention defined in claim 1, wherein switch comprises:

a resilient stationary contact within said housing;

a freely rotatable mo /able contact having a cam for sliding engagement with said resilient stationary contact;

and a pivot in said housing supporting said movable contact for freerotary motion;

and said switch operating means comprises a rotary shaft journaled in said housing and having an eccentric driver finger for actuating said movable contact.

9. The invention defined in claim 1, wherein said toggle spring mechanism also comprises:

means for adjusting the tension of said overcenter spring thereby to adjust the yarn tension at which the device will trip comprising:

a slide plate connected to the other end of said overcenter spring while the first end thereof biases said crank shaft and having a rack therealong';

a pair of walls in said housing betwen which said slide plate slides;

and a worm mounted in said housing meshing with said rack and having a shaft terminating in an external knob affording manual adjustment of said spring tension.

10. The invention defined in claim 9, wherein said toggle spring mechanism also comprises:

a pointer for indicating the adjusted tension of said overcenter spring;

a pivot in said housing pivotally supporting one portion of said pointer;

means on said slide plate coupled to another portion of said pointer for varying the indication when said knob is turned;

and a transparent window in a wall of saidhousing over said pointer and a tension scale alongside said window.

11. The invention defined in claim 1, wherein said circuit comprises:

a resistor in circuit with said switch;

and an indicator lamp extending through a wall of said housing and connected across said resistor for indicating a tripped condition.

12. The invention defined in claim 1, wherein said external guide member, trip member and feeler member are provided with configurations which afford ease in replacing the yarn back into operative position following tripping.

Claims

1. A yarn detector device comprising: an insulating housing; a pair of electrical terminals on said housing; a toggle spring mechanism comprising an overcenter spring biased crank shaft in said housing with the opposite ends of said crank shaft extending out through opposite walls of said housing; means providing an eye for passage of yarn comprising: an external guide member supported on said housing and providing one side of said eye; and an external trip member supported on said crank shaft and biased toward said guide member by said toggle spring mechanism to provide the other side of said eye through which the yarn passes, and being responsive to undue tension in the yarn or a snag to trip across the line of action of said toggle spring mechanism thereby to open said eye and release the yarn therefrom; a switch within said housing; switch operating means accessible externally of said housing; an external feeler member supported on said switch operating means and normally engaging the yarn adjacent said eye and being movable upon release of the yarn or in case of undue slack, break or end of yarn to operate said switch to close an electrical circuit between said terminals for stop motion purposes; and quick disconnect joints between said external guide member and said housing and between the aforementioned external trip and feeler members and their respective supporting crank shaft and switch operating means enabling ready replacement of the wear parts.

2. The invention defined in claim 1, wherein: said external trip member comprises a generally U-shaped lever having a pair of spaced substantially parallel arms connected by a yoke that abuts said housing when said trip member is biased to close said eye; and said quick disconnect joints comprise slits on the ends of said arms and flat portions on the ends of said crank shaft received into said slits by spreading said arms apart and allowing them to spring onto said crank shaft.

3. The invention defined in claim 1, wherein: said external guide member comprises a generally U-shaped bracket having a pair of spaced substantially parallel arms connected by a yoke; and said quick disconnect joints comprise a notch on said housing for retaining said yoke, a pair of aligned holes on opposite sides of said housing, and the ends of said arms being bent toward one another for receipt in said holes when said arms are spread apart and allowed to spring thereinto.

4. The invention defined in claim 1, wherein: said external feeler member comprises a generally U-shaped feeler lever having a pair of spaced substantially parallel arms connected by a yoke, the parts of the arms near the yoke resting on the yarn and positioned in close proximity to said trip member which provides support to said feeler member through the yarn, and positioned with only a slight gap between said feeler member at its yoke end and the housing which prevents undesirable bounce during uneven yarn demand by the knitting machine; and said quick disconnect joints comprise a pivot in said housing including a hole therein and a bent end on one of said arms received in said hole, a recess in said switch operating means and the end of the other arm being formed for rigid retention in said recess when said arms are spread apart and allowed to spring into said hole and said recess.

5. The invention in claim 1, wherein: said external guide member comprises a generally U-shaped guide bracket having a pair of spaced substantially parallel arms connected by a yoke; like re-entrant bends in said arms providing a downwardly-open yarn guide forming a two-part upper side for said eye; said external trip member comprises a generally U-shaped trip lever having a pair of substantially parallel arms connected by yoke and spaced a shorter distance apart to pass freely between the arms of said external U-shaped guide bracket; like re-entrant bends in the arms of said trip member providing an upwardly-open yarn guide forming a two part lower side for said eye; and said external feeler member comprises a generally U-shaped feeler lever having a pair of substantially parallel arms connected by a yoke and spaced a still shorter distance apart to pass freely between the arms of said external U-shaped trip lever.

6. The invention defined in claim 1, wherein: said switch operating means comprises: a rotary shaft journaled in a wall of said housing having means on its external end for securely supporting said feeler member for rotation by the latter and having driver means on its internal end for operating said switch within said housing; an elongated threaded counterweight; and means integral with said external end of said rotary shaft providing a threaded hole for adjustably supporting said counterweight at a predetermined angle relative to said feeler member providing an adjustable counterweight for the latter.

7. The invention defined in claim 6, wherein: said counterweight extends substantially horizontally in one direction and said feeler member extends substantially horizontally in the opposite direction when said feeler member is engaging the yarn; and said counterweight is rotated in an angular direction above said shaft to reduce its effective weight when the yarn allows said feeler member to rotate in an angular direction below said shaft.

8. The invention defined in claim 1, wherein switch comprises: a resilient stationary contact within said housing; a freely rotatable movable contact having a cam for sliding engagement with said resilient stationary contact; and a pivot in said housing supporting said movable contact for free rotary motion; and said switch operating means comprises a rotary shaft journaled in said housing and having an eccentric driver finger for actuating said movable contact.

9. The invention defined in claim 1, wherein said toggle spring mechanism also comprises: means for adjusting the tension of said overcenter spring thereby to adjust the yarn tension at which the device will trip comprising: a slide plate connected to the other End of said overcenter spring while the first end thereof biases said crank shaft and having a rack therealong; a pair of walls in said housing betwen which said slide plate slides; and a worm mounted in said housing meshing with said rack and having a shaft terminating in an external knob affording manual adjustment of said spring tension.

10. The invention defined in claim 9, wherein said toggle spring mechanism also comprises: a pointer for indicating the adjusted tension of said overcenter spring; a pivot in said housing pivotally supporting one portion of said pointer; means on said slide plate coupled to another portion of said pointer for varying the indication when said knob is turned; and a transparent window in a wall of said housing over said pointer and a tension scale alongside said window.

11. The invention defined in claim 1, wherein said circuit comprises: a resistor in circuit with said switch; and an indicator lamp extending through a wall of said housing and connected across said resistor for indicating a tripped condition.