US3390255A

US3390255A - Stepping mechanism for use in a pinball machine or the like

Info

Publication number: US3390255A
Application number: US478256A
Authority: US
Inventors: Roman F Garbark
Original assignee: GOTTLIEB AND CO D
Current assignee: MYLSTAR ELECTRONICS Inc; GOTTLIEB AND CO D
Priority date: 1965-08-09
Filing date: 1965-08-09
Publication date: 1968-06-25
Anticipated expiration: 1985-06-25

Description

June 25, 1968 R. F. GARBARK 3,390,255

STEPPING MECHANISM FOR USE IN A PINBALL MACHINE OR THE LIKE I5 Sheets-Sheet 1 Filed Aug. 9, 1965 EMVEMTOR) ROMAN F. GARBARK 4? CATTor-zmsy/ Jun 25, 1968 R- F. GARBARK STEPPING MECHANISM FOR USE IN A PINBALL MACHINE OR THE LIKE 3 Sheets-Sheet 2 Filed Aug. 9, 19 5 VEMTQ ROMAN F, GARB 3 6:1:W6%7W, GM

(:flfl'cmsyw June 25, 1968 GARBARK 3,390,255

STEPPING MECHANISM FOR USE IN A PINBALL MACHINE OR THE LIKE 3 Sheets-Sheet 5 Filed Aug. 9, 1965 ROMAN F. GARBARK United States Patent 3,390,255 STEPPING MECHANISM FOR USE IN A PINBALL MACHINE OR THE LIKE Roman F. Gal-bark, Westchester, Ill., assignor to D.

Gottlieb & Co., Chicago, Ill., a corporation of Illinois Filed Aug. 9, 1965, Ser. No. 478,256 14 Claims. (Cl. 235-92) The present invention relates to stepping mechanisms and more particularly to an improved counter mechanism of the drum type suitable for tallying the score in a coinoperated amusement device.

It is an object of the present invention to provide a stepping mechanism which is faster and more reliable and efficient than prior devices used for this purpose. More specifically it is an object to provide a stepping mechanism which is capable of accurate stepping with only small amounts of input power, which has low inherent friction and in which inertial forces are reduced to a minimum. It is a related object to provide a stepping mechanism which is durable and capable of consistent operation over many thousands of counting cycles.

It is another object of the present invention to provide a stepping mechanism which consists of a minimum of simply formed parts and which has a high degree of compactness enabling similar units to be assembled side by side in compact relation, one unit for each decimal order desired.

It is a further object of the invention to provide a stepping mechanism which is inherently inexpensive making use of low cost parts which serve multiple purposes, which is easily assembled and easily serviced.

It is still another object of the invention to provide a novel stepping mechanism which includes a printed circuit switch board as an integral part of the construction producing a high degree of reliability of contact with a minimum of loading upon the drive mechanism. In short it is an object of the present invention to provide a stepping mechanism which is reliable and which is capable of operating for long periods without special lubrication, cleaning or other maintenance.

Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reference to the drawings in which:

FIGURE 1 is a diagrammatic perspective showing a pinball machine of the type employing the present invention.

FIG. 2 is a perspective view of a counting assembly employing several of the stepping mechanisms.

FIG. 3 is a vertical section taken along the line 33 through one of the stepping mechanisms of FIG. 2 in the deenergized condition.

FIG. 4 is a horizontal section taken along the line 4-4 in FIG. 3.

FIG. 5 is an exploded perspective illustrating the ratchet driving elements. Y

FIG. 6 is a fragmentary section taken through the ratchet driving elements along the line 66 in FIG. 3.

FIG. 7 is a perspective showing the inside surface of the printed circuit assembly.

FIG. 8 is a fragmentary exploded perspective showing the contacts on the circuit board.

FIG. 9 is a fragmentary perspective showing the wiper assembly.

FIG. 10 is a vertical section similar to FIG. 3 but with certain parts omitted and showing the device in its energized condition.

FIG. 11 is a fragmentary elevation of the switch contact assembly.

FIG. 12 is a fragmentary section taken along the line 3,390,255 Patented June 25, 1968 "ice 12-12 in FIG. 3 showing the mode of securing individual stepping mechanisms in the supporting channels.

While the invention has been described in connection with the preferred embodiment, it will be understood that it is not intended to be limited to the particular embodimen shown but it is intended to cover the various alternative and equivalent constructions included within the spirit and scope of the appended claims.

Turning now to FIGURES 1 and 2 there is shown an amusement device in the form of a pinball machine 20 having a play field 21, a plunger 22, a coin receiver 23, and a console 24 which may have one or more counting assemblies 25 for the purpose of tallying the score.

A typical counting unit 25 has three stepping mechanisms which are identical to one another, and in the discussion which follows emphasis will be placed upon the distinguishing features and advantages of the improved mechanism. As is conventional in counter practice, an electrical impulse fed to the unit in the lowest decimal order causes that unit to index forwardly one step, and upon completion of a revolution a carry impulse is transmitted from the unit of lowest order to the unit in the next higher order. Such unit, in turn, produces a carry impulse which is transmitted to the unit of still higher order, so that the size of the number which can be totaled and displayed is limited only by the number of stepping units used. Switching means is normally provider for restoring the counter to zero count at the end of play. Since the electrical wiring for the counting and restoring functions is conventional, it need not be described.

The stepping mechanism, or stepping unit, shown in FIG. 3 and in the succeeding figures includes a frame plate 31, which may be of steel and which forms one of the side walls of the unit. The plate is preferably bent at 32 to form an end wall 33 and bent again to form a mounting flange 34 (see especially FIG. 4). Projecting at right angles from the center of the plate 31 is a stub shaft 35 having its base spun or riveted in place as shown at 36 and having a groove 37 formed on its tip for receiving a snap washer as will be described.

Telescoped over the shaft 35 is a rotatable indicator drum 40 having a central hub 41 and web 42 including a set of spokes 43 terminating in an outer shell 44. As shown, the shell is preferably formed of ten fiatted areas carrying the numerals 1-9 and 0. The web 42 is recessed to define, with the shell, what may be termed a drum hollow 45.

Turning next to the driving means for the drum, a rack plunger is provided of generally flat configuration inter posed between the frame plate 31 and the drum hollow 45. The plunger has lateral edges 51, 52 which are parallel to one another and which are received for reciprocating movement in

guide members

53, 54, the latter being integral with the frame plate and arranged generally opposite one another, adjacent the outer end 55 of the plunger. At its inner or driven end 56 the plunger is transversely bent to form a yoke having a U-shaped notch 57. Buttons 58 reduce friction.

To drive the plunger a solenoid 60 is provided having a coil 61 and a central core or armature 62, the outer end of which is formed with a head 63 which is captively received in the slot 57. It is one of the features of the solenoid 60, as brought out in FIGS. 4 and 5, that the frame plate 31, and the end portion 33 which is integral with it, forms a portion of the external magnetic circuit of the solenoid. The circuit is efficiently completed by a generally L-shaped pole piece 65, made of steel stock, consisting of a first portion 66 which extends along one side to the coil and a second portion 67 which is bent around the face of the coil carrying mounting pads 68 which are secured, by suitable machine screws, to the inside surface of the frame plate. It is one of the features of the design that the mounting pads 68 are spaced from one another so as to guidingly embrace the inner end of the rack plunger 50. The guidance provided by the

guides

53, 54 plus that provided by the pads 68 insures that the plunger undergoes pure reciprocation.

For the purpose of restoring the rack plunger 50 to an initial position when the solenoid is deenergized, and thereby providing the driving force for the drum, a rack drive spring 70 is arranged parallel to the rack plunger, with one end secured to an integral ear or hook 71 on the plunger and the other end anchored to the frame plate via the guide member 53.

In carrying out the present invention the reciprocating movement of the plunger is converted to rotary step-bystep movement by means of a rotary drive pawl, or drive spool, 80 of cylindrical shape having axially facing pawl teeth at its inner end. The drive pawl i arranged coaxially in the drum and extends sideways from the rack member into the drum hollow for engagement with cooperating surfaces formed on the web 42 of the drum. The rotary pawl member 80 is caused to oscillate by a rack-andpinion connection with the plunger. A rack, indicated at 81, is formed along one side of a central window opening 82 in the plunger. The cooperating pinion, or gear, 83 is formed integrally at the outer end of the pawl member and, since a relatively short pawl stroke suflices, the toothed segment is partial rather than being complete. The pawl member is preferably made of nylon or equivalent, the plunger of stainless steel.

For advancing the drum 40 incident to oscillation of the pawl member, a set of ratchet teeth 85 are provided on the web 42 of the drum facing axially and spaced closely adjacent the drum hub 41 to cooperate with the set of pawl teeth, indicated at 86, formed on the inner end of the pawl member. For the purpose of biasing the pawl member relative to the drum, the pawl member has a cylindrical hollow 87 (see FIG. 6) defining an internal annular seat or shoulder 88 for seating a coil spring 89. The base of the spring is supported on an annular embossment 90 which serves as a guide, or hearing, for the outer end of the pawl member. In order to prevent retrograde movement of the drum, a set of index teeth 92 are provided on the drum web 42 but at a greater radius than the ratchet teeth 85. An index pawl, or keeper pawl, 93 is provided in the form of a thin cantilever spring having a tip 94 and a base which is adjustably anchored to the frame by a pair of machine screws 95. A slot 96 formed in the base permits endwise adjustment for accurate positioning with respect to the index teeth.

In accordance with one of the more detailed features of the construction, the rack drive spring 70, and its attaching hook 71 on the plunger are located off of the center line of the plunger in such a position as to produce, in addition to the driving force, a small amount-of rotational torque in the plane of the plunger in such a direction as to urge the rack 81 resiliently into engagement with the teeth of the pinion 83, thus taking up any lost motion at the region of engagement and compensating for any wear which may occur at the teeth. In analyzing this effect, the stationary guide 53 at the outer end of the plunger may be considered as the fulcrum. Suflicient play is provided between the pads 68 and the inner end of the plunger to insure that take-up movement will occur at the rack teeth.

In a typical operating sequence, the solenoid 60 is energized, sucking in the solenoid core 62 and causing movement of the plunger to the right as viewed in FIGS. 3, 4 and 5. The stationary index pawl 93, engaging one of the index teeth 92, holds the drum in position so that one step of idle clicking takes place between the ratchet teeth 85 and the pawl teeth 86 on the rotary pawl member. Elongation of the rack drive spring 70 serves to store the energy used for driving purposes. At the termination of the solenoid input pulse, the plunger is released by the solenoid for leftward movement under the urging of the rack drive spring, accompanied by rotation of the rotary pawl member which is translated, via the ratchet and pawl teeth, 85, 86, into a step of forward movement, or indexing, of the drum. During such forward movement an idle click occurs at the index pawl 93.

For the purpose of blocking the drum in a precisely indexed position, a dog is provided on the rack plunger which cooperates with a series of reinforcing ribs formed on the inside of the drum. Thus there is provided on the outer end of the plunger a dog 100 in the form of an integral, bentover tab, which is in the normal path of movement of a series of reinforcing ribs 101. As will be apparent from FIG. 5, the reinforcing ribs are of triangular shape, anchored along one edge to the respective spokes '43 in the drum and, along an adjacent edge, to the. drum shell 43. When the'solenoid is energized, the dog 100 is, of course, retracted. Thus when the solenoid is subsequently released the drum is free to begin a step of rotation under the urging of the drive spring 70. However, as the plunger approaches its normal, outwardly extended limit position, the dog 100 is interposed in the path of movement of the approaching one of the reinforcing ribs 101, thereby stopping the drum in a precise, registered position. In this connection it may be noted that no special stop need be provided for limiting the outward movement of the plunger. The stop function is performed by engagement between the edge 82a of the window 82 in the plunger with the smooth surface 83a adjacent the toothed segment 83 on the rotary pawl member.

It is one of the features of the present construction that the drum 40 may be formed of a single molded piece of plastic in extremely light cross section resulting in a minimum of inertia so that extremely rapid indexing may occur with only a small amount of energy from the rack drive spring 70. In order to further reduce the energy requirement, the ratchet teeth 85, pawl teeth 86, and index teeth 92 are made extremely shallow so that only small amounts of energy need be expended in flexing the pawl biasing spring 89 and the leaf spring which forms the index pawl 93. In order to maintain a high degree of reliability with a shallow tooth height, and to preclude any possibility that deformation might take place in the web portion 42 of the drum due to its thin section combined with the dimensional changes which may occur in plastic materials, for example as a result of age, a camming ridge reinforcement is provided between the ratchet teeth 85 and index teeth 92. The ridge not only insures against web deformation but serves as a cam surface to operate a cam follower coupled to a switch operating member for switching purposes. Thus, referring to FIGS. 5 and 6, a thin, cylindrical camming ridge is provided on the drum. Such ridge, in spite of its narrow radial dimension, has a substantial web-stiffening effect.

Cooperating with the cam is a switch operator 111 (see FIGS. 10 and 11) in the form of a bent piece of wire having a cranked cam follower 112 and a switch arm 113. The latter controls a switch 115 formed of a series of stacked switch blades. For seating the switch operator 111 and for establishing a normal position for the operator, a switch lever spring 116 is provided. The latter is hooked ontoa cranked offset 117 of small radius in a direction to keep the operator seated in notches formed in a pair of

supports

118, 119 integral with the frame plates. It will be apparent that the spring serves to fcenter the switch operator in a precise position without reliance upon any stops whatsoever. Moreover it may be also noted that a relatively stiff spring 116 may be used, thereby keeping the switch operator seated in spite of shock and vibration, without, however, imposing any great amount of torque loading. Indeed, the amount of loading, or restoring effect, may be tailored to any desired amount simply by changing the radius of the offset 117. The net result is that positive actuation of the switch 115 may be achieved with only limited torque requirements at the cam 110 and consequently with only negligible loading of the rack drive spring 70.

In accordance with one of the aspects of the present invention, a circuit board is utilized as the opposite side wall of the stepping mechanism arranged parallel to the frame plate 31. Thus referring to FIGS. 7 and 8, a printed circuit board 130 is used having mounting

legs

131, 132 which are secured to the flange 34 of the frame plate and which define a central clearance space 133 which clears the solenoid pole piece 66. The opening .135 in the board receives the tip of the stub shaft 35. For commutation as the drum is indexed from one position to the next, segmented contacts, ten in number, are provided equally spaced about the shaft and connected to respective terminals 136 conveniently provided at the edge of the circuit board. In order to avoid necessity for using a pigtail, a concentric ground plate 137, isolated by an accompanying insulator 138, is riveted to the board. The ground terminal is brought out to terminals 139 at the respective edges of the circuit board.

For contacting the contact segments and ground plate, a resilient wiper assembly 140 is provided in the form of a thin sheet of Phosphor Bronze having a first wiper arm 141 and second wiper arm 142. The wiper assembly, in the present instance, is rigidly coupled to the hub of the drum by making the end of the hub of castellated shape as shown at 145 fitted into a correspondingly shaped opening 146 in the body portion of the wiper. The end 145 of the hub is received in a thrust bearing 147 formed of plastic or the like. Such thrust bearing, pressing against the land surrounding the opening .135 in the circuit board, serves to maintain the drum in a fixed axial position, notwithstanding the thrust of the pawl biasing spring 89. A spring retaining clip 148, fitted into the groove 37 at the end of the shaft, together with an accompanying spring washer 149 serve to complete the assembly. Since the spacing between the wiper assembly and the circuit board is maintained constant depending upon the thickness of the thrust bear-ing 147, the wiper arms 141, 142 may be precisely adjusted to provide adequate contact with the contact sectors and ground plate but with a minimum loading upon the drive spring 70.

The net result of the above construction is to produce a stepping mechanism which fulfills all of the objects originally set forth. Only a small amount of energy is required to produce rapid, positive action. Lubrication and other operating parameters are noncritical; thus maintenance is reduced to a minimum. When maintenance of the contacts is required, it is a simple matter, involving the removal of only two screws and a spring clip to expose the contacts on the circuit board for inspection or cleaning.

While the present invention has to do primarily with the construction of the individual stepping mechanisms, mention may also be made of the manner in which such stepping mechanisms are integrated in a typical counting unit. Thus, referring again to FIG. 2, the counting unit 25 has a top plate 151 and bottom plate 152 which are equipped, at their ends, with mounting brackets 153. The top and bottom plates, which may be constructed either identically or as mirror images of one another, carry aligned channels 155, formed of soft slippery plastic, for example, polyethylene, which may be riveted or otherwise secured in place for cushioned channeling the presented upper and lower edges of the respective stepping units, free of any supporting contact with the circuit boards. Each unit may be locked in position by providing registering holes in the frame plates and channel members respectively engaged by a suitable spring clip, for example, a clip. having the shape indicated at 160 in FIG. 12. Illumination is provided by lamps 165 mounted in suitable sockets provided in a lamp strip member 166, secured to the respective top and bottom plates by soft rubber grommets 167 engaging registering openings. The

plastic channels serve to mufile the vibration which is incident to normal operation, and the grommet mounting provides further protection, against vibration, for the lamps 165.

I claim as my invention:

1. In a stepping mechanism for use in a pinball machine or the like, the combination comprising a frame plate mounting a shaft, an indicator drum having a hub journaled on the shaft and having a central web recessed to define a drum hollow, a flat rack member arranged adjacent the drum hollow, means including a solenoid and return spring for reciprocating the rack member, a rotary pawl member extending axially into the drum hollow, a first set of axially facing ratchet teeth on the web adjacent the hub, a set of pawl teeth on the pawl member for cooperating with the first set of ratchet teeth, means for biasing the pawl member endwise, a second set of axially facing ratchet teeth surrounding said first set, a keeper pawl secured with respect to the frame plate for cooperating with the teeth of the second set, and a rack and pinion connection between the rack member and the pawl member so that when the rack member is reciprocated by the solenoid the rotary pawl member oscillates for indexing of the drum through one step of movement.

2. In a stepping mechanism for use in a pinball machine or the like, the combination comprising a frame plate having a stub shaft, an indicator drum arranged parallel to the frame plate having a hub journaled on the shaft and a central web recessed to define a drum hollow, a flat rack member interposed between the frame plate and the drum hollow, means including a solenoid and return spring for reciprocating the rack member, a set of axially facing ratchet teeth on the web surrounding the hub, a rotary pawl member of hollow cylindrical construction journaled on the hub and extending from the rack memher into the drum hollow, said pawl member having a set of pawl teeth on the inner end thereof for cooperating with the set of ratchet teeth and having an internal annular shoulder, a coil spring in the pawl member seated on the shoulder for pressing the pawl member toward the ratchet teeth, a rack on the rack member, gear teeth on the outer end of the pawl member so that upon successive actuations of the solenoid the drum is indexed forwardly step by step.

3. In a stepping mechanism for use in a pinball machine or the like, the combination comprising a frame plate mounting a shaft, an indicator drum having a hub ournaled on the shaft and having a central web defining a drum hollow, a flat rack member arranged adjacent the drum hollow, means including a solenoid and return spring on the frame plate for reciprocating'the rack member, a rotary pawl member extending axially from the rack member into the drum hollow, a set of axially facing ratchet teeth on the web, a set of cooperating pawl teeth on the pawl member, means for biasing the pawl member toward the web, and a rack and pinion connection between the rack member and the 'pawl memher for oscillating the pawl member.

4. In a stepping mechanism for use in a pinball machine or the like, the combination comprising a frame plate mounting a shaft, an indicator drum having a hub ournaled on the shaft and having a central web which is recessed in the drum to define a drum hollow, a rack member arranged flatly adjacent the drum hollow, means including a solenoid and return spring for reciprocating the rack member, a rotary pawl member extending axially from the rack member into the drum hollow, first and second sets of axially facing ratchet teeth on the web, a set of pawl teeth on the inner end of the pawl'member for cooperating with the first set of ratchet teeth, a keeper pawl on the frame plate for cooperating with the second set of ratchet teeth to prevent retrograde movement of the drum, a rack and pinion connection between the rack member and the rotary pawl for extending the drum forwardly upon successive energizations of the solenoid, a switch mechanism having an operator, the drum including the web portion thereof being formed of plastic in thin light cross section, and a cylindrical camming ridge integral with the web between the first and second sets of ratchet teeth for cammingly engaging the switch operator and for providing reinforcement of the web so that the ratchet teeth are maintained accurately in position notwithstanding dimensional changes in the plastic.

5. In a stepping mechanism for use in pinball machine or the like, the combination comprising a frame plate mounting a shaft, an indicator drum having an outer cylindrical shell and a hub journaled on the shaft as well as a central web recessed to define a drum hollow, a rack member arranged flatly adjacent the drum hollow, means including a solenoid and return spring for reciprocating the rack member, a rotary pawl member extending axially from the rack member into the drum hollow, a set of axially facing ratchet teeth on the web adjacent the hub, a set of cooperating pawl teeth at the inner end of the pawl member, means for biasing the pawl member endwise for engagement of the teeth, a rack and pinion connection between the rack member and the pawl member so that successive actuations of the solenoid cause the drum to be indexingly advanced, said drum having reinforcing ribs extending radially inward from the shell into the drum hollow, and a dog on the rack member so positioned as to be interposed in the path of movement of the ribs when the solenoid is deenergized for positively blocking the drum and for holding the same in indexed position.

6. In a stepping mechanism for use in pinball machine or the like, the combination comprising a frame plate mounting a shaft, an indicator drum having an outer cylindrical shell and a central web recessed to define a drum hollow, a rack member in the form of a generally flat strip interposed between the frame plate and the drum hollow, a rotary pawl member of generally cylindrical shape extending from the rack member into the drum hollow, said web having a set of axially facing ratchet teeth and said pawl member having a cooperating set of axially facing pawl teeth, means for biasing the pawl member with respect to the drum to maintain the teeth in engagement, rack teeth formed on the rack member, gear teeth formed on at least a segment of the pawl member for meshing therewith, a solenoid coupled to one end of the rack member, guiding means at the other end of the rack member so that the rack member moves in a straight line when the solenoid is energized, a rack drive spring interconnected between the frame and the rack member for producing return movement of the rack memher when the solenoid is deenergized, the rack drive spring being connected to the rack so as to provide a component of force in a direction to maintain engagement free of play between the rack teeth and the gear teeth.

7. In a stepping mechanism for use in a pinball machine or the like, the combination comprising a frame plate mounting a shaft, an indicator drum on the shaft having an outer cylindrical shell and a central web which is recessed therein to define a drum hollow, a rack member arranged flatly adjacent the drum hollow, a rotary pawl member of generally cylindrical shape extending axially from the rack member into the drum hollow, a set of axially facing ratchet teeth on the web and a set of cooperating pawl teeth on the inner end of the pawl member, means for biasing the pawl member with respect to the drum to maintain the teeth in contact, a central opening in the rack member for accommodating the outer end of the pawl member, the rack member having a rack on one side of the opening and the pawl member having teeth for meshing therewith, a solenoid coupled to one end of the rack member, guiding means for engaging the other end of the rack member for guiding the same for reciprocating movement, a rack drive spring arranged along the edge of the rack member which is opposite the rack and connected to the rack member at a point intermediate the solenoid and guiding means so that the spring serves not only to return the rack member when the solenoid is deenergized but to apply a component of force to the rack member to maintain the rack member mesh with the teeth on the pawl member.

8. In a stepping mechanism for use with a pinball machine or the like, the combination comprising a frame plate mounting a shaft, an indicator drum journaled on the shaft and having an outer cylindrical shell and central web defining a drum hollow, a rack member arranged flatly adjacent the drum hollow, means including a solenoid connected to one end of the rack member together with a return spring for reciprocating the same, a rotary pawl member of generally cylindrical shape extending axially into the drum hollow, a set of ratchet teeth on the web and a set of cooperating pawl teeth on the inner end of the pawl member, a rack and pinion connection between the rack member and the pawl member, a switch mechanism, a switch operator for the switch mechanism, a cylindrical camming ridge on the web surrounding the ratchet teeth, said switch operator being in the form of a length of wire rockably supported on the frame plate and having one end bent to form a cam follower crank for riding on the camming ridge so that the switch is actuated at a predetermined phase position of the drum.

9. In a stepping mechanism for use with a pinball machine or the like, the combination comprising a frame plate mounting a shaft, an indicator drum journaled on the shaft and having an outer cylindrical shell and central web defining a drum hollow, a rack member arranged flatly adjacent the drum hollow, means including a solenoid connected to one end of the rack member together with a return spring for reciprocating the same, a rotary pawl member of generally cylindrical shape extending axially into the drum hollow, a set of ratchet teeth on the web and a set of cooperating pawl teeth on the inner end of the pawl member, a rack and pinion connection between the rack member and the pawl member, a switch mechanism, a switch operator for the switch mechanism, .a cylindrical camming ridge on the web surrounding the ratchet teeth, said switch operator being in the form of a length of wire rockably supported on the frame plate and having one end bent to form a cam follower crank for riding on the camming ridge so that the switch is actuated at a predetermined phase position of the drum, the switch operator having a cranked offset of short radius at the central portion thereof and having a tension spring connected thereto tending to resiliently center the spring operator for maintaining the cam follower crank in engagement with the camming ridge.

10. In a stepping mechanism for use in .a pinball machine or the like, the combination comprising a frame plate mounting a stub shaft at right angles thereto and forming the side wall of an enclosure, said plate having a laterally bent portion forming the end Wall of the enclosure and defining a mounting flange, an indicator drum journaled on the shaft and having an outer cylindrical shell as well as a central web recessed to define a drum hollow, a flat rack member arranged adjacent the drum hollow, a solenoid at said end wall coupled to one end of the rack member, a return spring connected to the rack member, a rotary pawl member extending axially from the rack member into the drum hollow, a set of axially facing ratchet teeth on the web and a set of cooperating pawl teeth on the inner end of the pawl members, means for biasing the pawl member endwise for maintaining the teeth in axial engagement, a rack and pinion connection between the rack member and the pawl member, a printed circuit board arranged parallel to the frame plate to define an opposite side wall and secured to said mounting flange, contact sectors on said printed board, and a resilient wiper arm secured to the drum for contacting the sectors in succession as the drum is indexed by the solenoid.

11. In a stepping mechanism for use in a pinball machine or the like, the combination comprising a frame plate of magnetic material defining a side wall and having a bent over portion defining an end wall, an indicator drum having a hub journaled on the shaft and having a central web defining a drum hollow, a rack member arranged flatly along the frame plate adjacent the drum hollow, a solenoid having a coil and plunger, said plunger being coupled to the rack member, a return spring connected to the rack member, a rotary pawl member extending axially from the rack member into the drum hollow, a set of axially facing ratchet teeth on the web, a set of cooperating pawl teeth on the pawl member, and a rack and pinion connection between the rack member and the pawl member for oscillating the pawl member, said solenoid coil being mounted closely adjacent the end wall and side wall so that the frame plate forms a magnetic circuit for the solenoid.

12. In a stepping mechanism for use with a pinball machine or the like, the combination comprising a plurality of vertical frame plates spaced side by side and having aligned stub shafts thereon, indicator drums on the stub shafts, each of said indicator drums having an outer cylindrical shell carrying indicia and a central web recessed to define a drum hollow, each of said drums having a rack member arranged flatly adjacent the drum hollow, reciprocating means including solenoids and associated return springs for reciprocating the rack members, each of said drums having a rotary pawl member located in the drum hollow having a ratchet connection at one end with the respective drum and having rack and pinion connection at the other end with the adjacent rack member, upper and lower horizontal mounting plates arranged parallel to one another, said mounting plates having channel members mounted thereon in respective vertical alignment, the frame plates being dimensioned for sliding reception into aligned ones of said channel members for display of indicia on the drums.

13. In a stepping mechanism for use with a pinball machine or the like the combination comprising a plurality of stepping mechanisms each having a rectangular frame plate and a circuit board in spaced parallel relation, said frame plates having aligned stub shafts thereon, indicator drums on the stub shafts, each of said indicator drums having an outer cylindrical shell carrying indicia and a central web recessed to define a drum hollow, each of said drums having a rack member arranged flatly adjacent the drum hollow, reciprocating means including solenoids and associated return springs for reciprocating the rack members, each of said drums having a rotary pawl member located in the drum hollow having a ratchet connection at one end with the respective drum and having rack and pinion connection at the other end with the adjacent rack member, upper and lower horizontal mounting plates arranged parallel to one another, said mounting plates having channel members of soft plastic material mounted thereon in respective vertical alignment, the frame plates being dimensioned for sliding reception between aligned ones of said channel members with the circuit boards free of any supporting contact with the mounting plates.

14. In a stepping mechanism for use in a pinball machine or the like the combination comprising a frame plate mounting a shaft at right angles thereto, an indicator drum journaled on the shaft having an outer cylindrical shell and a central web recessed to define a drum hollow, a rack member arranged flatly adjacent the drum hollow, means including a solenoid and return spring for reciprocating the rack member, a rotary pawl member extending axially from the rack member into the drum hollow, a set of axially facing ratchet teeth on the web and a set of cooperating pawl teeth on the pawl member, a rack and pinion connection between the rack member and the pawl member, a circuit board on the opposite side of the drum from the frame plate and secured to the latter in parallel relation, contacts in a circular locus on the circuit board, a resilient wiper arm secured to the drum for wiping the contacts, a thrust bearing interposed between the wiper arm and the circuit board, and a biasing spring in the rotary pawl member for urging the pawl member into axial engagement with the drum and for urging the drum into bottoming engagement with respect to the circuit board thereby to maintain an accurate spacial relationship between the wiper arm and the contacts on the circuit board.

References Cited UNITED STATES PATENTS 2,193,629 3/1940 Hopping 235-92 2,883,194 4/1959 Bogner 235-92 3,341,694 9/1967 Heimberger 235-92 MAYNARD R. WILBUR, Primary Examiner.

G. J. MAIER, Assistant Examiner.