US3422691A

US3422691A - Overtravel control mechanism for stepping switches

Info

Publication number: US3422691A
Application number: US584550A
Authority: US
Inventors: William Warren Wright
Original assignee: Guardian Electric Manufacturing Co
Current assignee: Guardian Electric Manufacturing Co; Case LLC
Priority date: 1966-10-05
Filing date: 1966-10-05
Publication date: 1969-01-21
Anticipated expiration: 1986-01-21
Also published as: GB1182503A; FR1514671A; DE1613105A1; DE1613105B2

Description

Jan. 21, 1969 w. w. WRIGHT 3,422,691

OVERTRAVEL CONTROL MECHANISM FOR STEPPING SWITCHES Filed Oct. 5. 1966 I N VEN TOR W/LL/AM W IVR/GHT 3 3 2 I l 0 3 3 H O 3 C 2 A TTORNE Y5 United. States Patent 8 Claims This invention relates generally to electromagnetically operated switches or relays and, more particularly, to incremental motion, multi-position switches known as stepping switches.

In the conventional stepping relay, an electromagnet is employed to drive a pawl which engages with a toothed ratchet wheel, the ratchet being advanced by a single increment each time the electromagnet is energized. It is often desirable that the stepping switch be capable of very rapid operation, particularly in those applications where the switch must have the ability to be advanced by several increments in a very short period of time. The moving parts of such a switching mechanism must accordingly be subjected to rapid acceleration. In consequence, at the instant the necessary motion is completed, these parts are moving at a relatively high velocity. It is then necessary to stop further rotation of the ratchet wheel in order to maintain the new position and to return the remaining moving parts to their initial position in preparation for the next operation.

It is a general object of the present invention to absorb the kinetic energy of the moving parts in a stepping switch and to prevent inertial overtravel of the moving ratchet wheel.

Overtravel control devices employed in prior stepping switches have normally taken the form of rigid stops positioned in the path of one or more moving parts for blocking forward motion beyond a predetermined point. In these arrangements, a high pressure impact takes place at the end of each stroke since the moving parts which must be stopped are moving at maximum velocity. As the switch is operated, these repeated impacts cause premature wear which greatly reduces the life of the mechanism. Hard, durable metal parts are therefore normally required to retard wear at the point of impact. Moreover, precautions must be taken to protect the remainder of the switch from the effects of the shock created by the impact. In addition, the vibration and noise produced is highly objectionable in many applications.

It is accordingly a further object of the present invention to absorb the kinetic energy of the moving parts of a stepping switch without the usual, undesirable impact effects.

It -is a related object of the present invention to increase the operating life of an electromagnetically operated stepping switch.

The stop member employed in prior overtravel control schemes must be accurately positioned, often within a few thousandths of an inch, to stop forward motion at precisely the proper point, neither too soon nor too late in the stroke, and at a time when the velocity of the moving parts is at its maximum value. This critical adjustment must be made by skilled manufacturing personnel, greatly increasing the cost of the switch assembly operation, and consequently tending to limit production.

It is accordingly a further object of the present invention to reduce the cost of manufacturing quality stepping 3,422,691 Patented Jan. 21, 1969 switches by eliminating the necessity for critical adjustments in the overtravel control mechanism for such a switch.

When conventional overtravel control schemes are employed, the switch becomes locked in position whenever the driving magnet is continuously energized. The pawl becomes locked against the overtravel stop and, being in engagement with the ratchet wheel, in turn locks this wheel in position. It is often desirable, however, to manually (or otherwise) operate the switch by turning the ratchet wheel in the forward direction even though the driving magnet is energized.

It is accordingly a further object of the present invention to permit the switch to be advanced while the driving pawl is in its operated position.

In a principal aspect, the present invention takes the form of an improved overtravel control mechanism for an electromagnetic stepping switch. According to a principal feature of the invention, a spring loaded catching member is employed to intercept the pawl as it is carried in an arcuate path by the racthet wheel. After engagement, the spring load catching member operates to retard further motion of both the pawl and the ratchet. By eliminating the usual high pressure impact at the end of the stroke, wearing is reduced, thus permitting the use of an impact absorbing material for the catching member which thus provides still softer operation.

These and other objects, features and advantages of the present invention will become more apparent through a consideration of the following detailed description. Dur ing the course of this description, reference will frequently be made to the attached drawing in which:

FIGURE 1 is a perspective view of an electromagnetic stepping switch embodying the principles of the invention;

FIGURE 2 is an end view of the switch shown in FIG- URE 1;

FIGURES 2A-2D are enlarged end views of the ratchet wheel, pawl and catching member shown in a sequence of positions during the course of the operation of the switch;

FIGURE 2E is a partial end view of the stepping switch as shown in FIGURE 2 illustrating the manner in which the catching member may be fully deflected to provide manual override capability;

FIGURE 3 is a side view of the stepping switch shown in FIGURES l and 2; and

FIGURE 4 is a top view of the stepping switch shown in FIGURES l, 2 and 3.

The electromagnetically operated stepping switch shown in perspective in FIGURE 1 includes an electromagnet indicated generally at 11 mounted on a frame indicated generally at 14. The frame 14 is shaped to provide a pair of upwardly extending flanges at 16 and 17 as well as three downwardly and outwardly extending mounting lugs, two of which are seen at 18 and 19 in FIGURE 1. The third mounting lug 20 is shown in the top view of FIGURE 4.

The magnet 11, when energized, pulls against an armature indicated generally at 22. The armature 22 is mounted for pivotal movement about the upper edge of flange 16 and is held in place by a projection 23 which extends upwardly from the top of the flange 16 through a slot in armature 22. When the magnet 11 is de-energized, a spring 25 holds the armature 22 in spaced relation from the magnet 11. Spring 25 is connected between a rearwardly projecting lug 27 bent outwardly from the mount- 3 ing frame 14and rearwardly projecting lug 29 on the armature 22. A pawl 30 is pivotally mounted on the armature 22 by means of a fastening pin 32. A bridge member 33 affixed to the forward end of armature 22 surrounds the pawl 30 yet permits the pawl 30 to pivot laterally about pin 32.

When the electromagnet 11 is energized, the armature 22 is pulled in to force pawl 30 downward to a position of first engagement with a ratchet wheel indicated generally at 35. A spring 37 coupled between the end of pawl 30 and a lug 38 on the upwardly extending flange 17 biases pawl 30 laterally toward the ratchet wheel 35. The forward end of pawl 30 is inserted through an opening 34 in flange 17 and into a rectangular window 39 defined by a catching member 40. The catching member 40 is pivot-ally mounted about a pin 41 through the flange 17. In FIGURE 1, a portion of the flange 17 is cut away to better illustrate the position and shape of the catching member 40.

As clearly seen in FIGURE 2 of the drawings, a coil spring connected between an upwardly projecting lug 42 on the catching member 40 and a lug 43 on flange 17 normally holds catching member 40 against an eccentric stop member 44 which is held flush against the flange 17 by means of a screw 46. By loosening screw 46 and rotating the eccentric stop member 44, the rest position of the catching member 40 may be quickly and accurately adjusted.

As illustrated by FIGURES 2A-2D, the rectangular window 39 in catching member 40 serves to guide the pawl 30 into engagement with the appropriate tooth in ratchet wheel 35 and, near the end of the stroke, intercepts the pawl 30 to retard further motion of both the pawl 30 and the ratchet wheel 35. As seen in FIGURE 2A, the forward end of the pawl 30 is precisely located in its rest position at the upper inside corner of the window 39, the pawl 30 being held against inside wall 47 of window 39 by spring 37. As the magnet 11 is energized, the pawl 30 is forced downward and is guided by the inside wall 47 to a position of first engagement with the ratchet wheel 35. Further downward motion of the pawl 30 causes the ratchet wheel 35 to rotate and imparts lateral motion to the pawl 30 (from right to left in FIGURE 2). At the position shown in FIGURE 20, the pawl 30 is wedged between the outer wall 48 of window 39 and the shoulder surface 50 defined by one tooth of the ratchet wheel 35. The catching member 40 thus serves to intercept the pawl 30 and acts through the pawl 30 to retard further motion of the ratchet wheel 35. Since the catching member 40 is pivotally mounted and spring loaded by spring 41, the window 39 in catching member 40 is permitted to move (to the left as seen in FIGURE 2) to some extent to allow the kinetic energy of the pawl and ratchet wheel to be gradually absorbed without pronounced impact. FIG- URE 2D of the drawings shows the catching member 40 at the point of greatest deflection. Thereafter, the spring 41 tends to return the catching member 40 to its original position, also forcing the ratchet wheel 45 to return to its desired location from the overthrown position shown in FIGURE 2D.

The ratchet wheel 35 is further located by means of a conventional spring loaded ball detent arrangement comprising a leaf spring 51 and a metal ball 53 which is held within a collar 54. The leaf spring 51 is fixedly mounted to the frame 14 by means of a screw 56 (which also mounts the magnet 11 to the frame 14). Leaf spring 51 forces the ball 53 upward into the notch separating adjacent teeth on the underside of the ratchet wheel 35 as shown in FIGURE 2.

The ratchet wheel 35, which is preferably constructed of a low friction plastic, such as Delron (acetol resin) or Lexan (polycarbonate resin), rotates a shaft 60 journaled to the flange 17 by means of a mounting barrel indicated at 63. The armature 60 is held in place by means of a spring clip 65 which engages with a peripheral groove in 4 the shaft 60 and which is separated from the barrel 63 by means of a low friction washer of Delron or Lexan.

As will be readily appreciated by those skilled in the art, a second pawl or dog may be employed in conjunction With the ratchet wheel 35 to prevent the rotation of the ratchet 35 and shaft 60 in the reverse direction. In addition, electrical contact blades associated with armature 22 or ratchet 35 may be positioned to open at a precise point in the stroke.

As clearly seen from FIGURE 2C of the drawings, when the electromagnet 11 is continually energized, the pawl 30 is held in a locked relationship between the catching member 40 and the ratchet wheel 35, preventing rotation of the ratchet wheel 35 in either direction. In order to permit the ratchet wheel 35 to the manually advanced by forced rotation of the shaft 60, the catching member 40 contemplated by the invention deflects to an extreme position as shown in FIGURE 2E of the drawings allowing the teeth on ratchet wheel 35 to bypass the pawl 30.

The novel overtravel control mechanism contemplated by the present invention may also be used in conjunction with known indirect acting stepping switches; that is, switches in which the ratchet is advanced when the magnet is de-energized.

It is to be understood that the embodiment of the invention which has been described is merely illustrative of one application of the principles of the invention. Numerous modifications may be made by those skilled in the art without departing from the true spirit and scope of the invention.

What is claimed is:

1. In a stepping relay having a ratchet wheel and an electromagnetically driven pawl which engages with and advances said wheel, said pawl being carried in an arcuate path as said wheel is advanced, improved overtravel control mechanism which comprises a spring loaded catching member positioned to intercept said pawl at a predetermined point and to thereafter retard further motion of said pawl along said arcuate path.

2. An improved overtravel control mechanism as set forth in claim 1 including means for adjusting the position of said predetermined point of interception.

3. An improved overtravel control mechanism as set forth in claim 1 wherein said catching member acting through said pawl retards the further motion of said ratchet wheel after said pawl passes said predetermined point of interception.

4. An improved overtravel control mechanism as set forth in claim 1 wherein said catching member is mounted on said relay for pivotal motion in a plane substantially perpendicular to the axis of rotation of said ratchet wheel.

5. An improved overtravel control mechanism as set forth in claim 4 wherein said catching member is normally spring loaded against a stop member adjustably mounted on said relay.

6. In a stepping relay having a ratchet wheel, a pawl, and an electromagnet for driving said pawl in a first direction to engage with notches in said wheel and to advance said wheel by an incremental amount, said pawl being carried in an arcuate path by said wheel after engagement thereby imparting motion to said pawl in a second direction perpendicular to said first direction,

an improved overtravel control mechanism which comprises a spring-loaded catching member positioned to intercept said pawl at a predetermined point along said arcuate path and to thereafter retard further motion of said pawl in said second direction.

7. An improved overtravel control mechanism as set forth in claim 6 wherein said spring loaded member acts against said wheel through said pawl to retard further motion of said wheel after said pawl has passed said predetermined point of interception.

3. An improved overtravel control mechanism as set forth in claim 7 wherein said spring loaded member com- 5 6 prises an elongated member mounted on said relay for References Cited pivotal motion in a plane substantially perpendicular to UNITED STATES PATENTS the axis of rotation of said wheel, said member having an aperture therein for receiving said pawl, said aperture be- 2,150,680 3/1939 Fuller 74 142 ing defined by a first and second opposing and substan- 2,990,723 7/1961 Holpuch 74 142 5 3,106,849 10/1963 Valleau 74142 tially parallel side walls, said pawl being normally spring loaded against said first side wall such that said first side wall serves to guide said pawl from its rest position to a FRED MATTERN lma'y Exammer' position of engagement with said ratchet wheel. WESLEY S. RATTIFF, Assistant Examiner.

Claims

1. IN A STEPPING RELAY HAVING A RATCHET WHEEL AND AN ELECTROMAGNETICALLY DRIVEN WHICH ENGAGES WITH AND ADVANCES SAID WHEEL, SAID PAWL BEING CARRIED IN AN ARCUATE PATH AS SAID WHEEL IS ADVANCED, IMPROVED OVERTRAVEL CONTROL MECHANISM WHICH COMPRISES A SPRING LOADED CATCHING