US3188411A - Run button with safety lockout for a press control circuit - Google Patents

Description

June 8, 1965 K. K. LUENSER 3,188,411

RUN BUTTON wxm SAFETY LOCKOUT F011 A PRESS CONTROL CIRCUIT Original Filed Jan. 29, 1959 I s Sheets-Sheet 1 uvvmrom June a, 1965 K. K. LUENSER 3,188,411

RUN BUTTON WITH SAFETY LOCKOUT FOR A PRESS CONTROL CIRCUIT Original Filed Jan. 29, 1959 3 Sheets-Sheet 2 1w g r 80 /7? INVEN TOR.

United States Patent 3,188,411 RUN BUTTON WITH SAFETY LOCKOUT FQR A PRESS CONTROL CIRCUHT Kurt K. Luenser, Monee, Ill., assignor to Verson Allsteel Press Company, Chicago, Ill., a corporation of Delaware Original application Jan. 29, 1959, Ser. No. 789,932, new Patent No. 3,056,431, dated Get. 2, 1962. Divided and this application Aug. 21, 1961, Ser. No. 132,775

1 Claim. (Cl. 200-56) This application is a division of copending United States patent application, Serial No. 789,932, filed January 29, 1959, now Patent No. 3,056,481, dated October 2, 1962.

The present invention relates to machine controls, and more particularly to a new and improved run button switch assembly for use in a control system for metal working presses of the mechanical type having a clutch interposed between the flywheel and the eccentric drive for the press slide.

It is customary in presses of this type to construct them so that they may have a continuous operation of repeated cycles, a single cycle or run, and an inch cycle where the movement of the slide is constantly under the control of the press operator.

In presses of great tonnage capacity, more than one operator may be in attendance, and it is frequently desirable for the press to be operable for many of a number of different positions around the machine, or from a station somewhat removed from the press. Safety controls have been devised which incorporate a pair of switch closing buttons to be operated simultaneously by every operator at his station when a press cycle or run is to be initiated. This system requires an operator at each station, and if the press be provided with five or six stations, the number of operators needed would be excessive. Consequently, manufacturers using such presses require that the control buttons be equipped with lockouts or bypasses to provide for flexibility in operating the press from any one or combination of the various stations. Unfortunately, with large presses not all of the stations are within sight of each other, and consequently some means must be provided for protecting the press operators during the operation of locking out the control buttons which are not to be used.

A system has been devised, and is in use, incorporating an antilock circuit which theoretically prevents the press from operating if all of the run or control buttons are inadvertently locked out. This circuit requires the use of extra relays and switches, and thus increases its cost over systems not so equipped. Unfortunately, this system does not always function as it is intended. If all the run buttons are locked out when the power is on and the press selector switch is in the run position, as distinguished from continuous operation or inching positions, the clutch might be energized momentarily during the locking out operation of the run button. Energization of the clutch might also occur if all the control buttons are locked out, the selector switch is in either of the run or the continuous operation positions, and the relay fails with the power on. Energization of the clutch would, of course, startle the operator and not necessarily injure him, but under some circumstances it could cause a complete press stroke, with the possible personal injury to an operator who was not visible to the person locking out the run buttons. On the other hand, if the clutch selector switch were set in the continuous operation position, the clutch would remain energized until a stop button was pressed. It is'obvious, under these circumstances, that a very serious accident could occur. Thus the system which is currently in use has an inherent danger in it which should be avoided if at all possible.

The abovesaid copending application describes and claims a novel press control system wherein it is possible to incorporate lockouts on each of the run buttons so that they may be moved from the use position to the bypass or lockout position at any time without any danger of the press being operated inadvertently, even though the selector switch be in the run or continuous position and the power be on.

It is a principal object of the present invention to provide a new and improved switch structure for use in control circuits wherein the switch closing contact members are manually movable, and certain circuits are broken, and other circuits are closed sequentially and not simultaneously upon the manual movement of said members.

Another object is to provide in a press control system incorporating inching control circuits whereby the press may be operated on the inching cycle from different positions or stations, with safety to the operator, a new and improved inching button which may be placed in the use or lockout position without danger to the operator.

Other objects and advantages will become apparent from the following description, taken in conjunction with the accompanying drawings, wherein FIG. 1 is an enlarged elevational view of the run button panel, with the control button and key control mounted thereon;

FIG. 2 is a rear view of the run button and control assembly of FIG. 1;

FIG. 3 is a vertical cross sectional view, taken along the line 33 of FIG. 1, looking in the direction of the arrows, and showing the switch structure in the use position;

FIG. 4 is a vertical cross sectional view similar to FIG. 3, showing the switch structure in the lockout or bypass position;

FIG. 5 is a vertical sectional view taken substantially along the line 5-5 of FIG. 3, looking in the direction of the arrows;

PEG. 6 is an enlarged fragmentary detail sectional view, taken along the line 66 of FIG. 5, looking in the direction of the arrows; and

FIG. 7 is a diagram of a typical electrical operating circuit incorporating the safety features of the present invention.

A typical press, with which the improved switch of the present invention may be advantageously used, may be of the type disclosed in the David C. Verson and Albert Clements Patent No. 2,286,943, suitably controlled for example by the circuit of FIG. 7 herein.

Briefly, the press includes a frame having a crown, a bed, and a reciprocable slide movable in vertical gibs. In the press crown are mounted a motor, a flywheel driven by the motor and which is connected through a clutch, a clutch and brake assembly, and suitable gearing, to a pair of large gears which drive an eccentric for pitman connected to the slide to reciprocate the latter.

The clutch and clutch brake assembly are of the pressure fluid operated type (either hydraulic or pneumatic), and the supply of fluid thereto is under the control of a solenoid operated valve 46 (FIG. 7), the solenoid 48 of which is incorporated in control circuit 50 of FIG. 7, within which the improved switch of the present invention may be utilized.

Power for the control system (FIG. 7) is obtained from the lines L1 and L2 which are connected to a first section 52 of the circuit controlling the single or run cycle and the continuous operation cycle, and a second section 54 controlling the inching cycle. These circuits, in turn, are connected to the clutch solenoid 48, the

clutch relay CR, and the anti-repeat relay AR. The

solenoid 48 and the two relays CR and AR are arranged in parallel. The circuit 50 incorporates a pair of manually operated emergency stop switches 56 which are in series with the line L1 and the two circuit sections 52 and 54. These switches are normally closed, but may be opened in an emergency to stop the press operation at any instant and for any reason.

The press control includes a selector switch which has four positions, namely, ofi, continuous cycling, run or single cycle operation, and inching operation. Thi selector switch is conventional and it is not shown in physical detail in the drawings, but certain contacts from it are shown and indicated as follows: SS1 is a switch in series with the stop switches 56 and controls the energization and use of the circuit section 52; SS2 is in parallel with SS1 and in series with the stop switches 56 and the inch- 4 7d are connected in series with each other and the conductors 58 and the switch AR1.

The control system with the switch assemblies R in the positions shown in FIG. 7 contemplates operation of the press from a single station, it being observed that three of the four switches R4 are in the bypass position, that is, closed, with the corresponding switches R1 open;

the fourth switch is in the use position, or open, and the corresponding switch R1 is closed. With the selector switch in the run position, the switch SS1 is closed and a circuit'is established through the switch SS1, the closed switch R1, through the series of normallyclosed switches ing circuit section 54, and controls the operation of the latter; SS3 is in a holding circuit 5'7 and is closed when itis desired to operate the press on continuous or repeated cycles. 7

The clutch relay CR is in series with a normally open switch AR1 which is closed upon energization of the antirepeat relay AR. The relay AR is energized immediately upon closing of the selector switch SS1 through a circuit which includes any one of parallel connected switches R1 which are connected to a conductor 58, and a series of normally closed switches R2, and a normally closed switch CR1 which is opened upon energization of the clutch relay CR. In the specific example shown, there .are four switches R1 arranged in parallel between the selector switch SS1 and the conductor 58, and there are four switches R2 which are connected in series between the conductor 58 and tie normally closed switch CR1.

In order that the operation of the press continue after being initiated with the relay AR remaining energized after opening a switch R2 and the switch CR1, a holding circuit as is provided and includes a normally open switch ARZ and a position limit switch LS1; The holding circuit 6i) is in parallel with the switches R2 and CR1 so that when the clutch is energized and the switch CR1 opens, the holding circuit will remain closed and there- "fore the anti-repeat relay AR will remain energized until the position limit switch LS1 is opened. The opening of w the limit switch LS1 to deenergize the anti-repeat relay 'AR is a function of the control system on run cycles to prevent another cycle without-pressing the appropriate control button. The timing of the switch LS1 may vary, butit is usually set to open at approximately 270 operation of the eccentric, at which time the press slide will "have been returned about'half way toward its top or normal stop position in the press stroke.

The improved run button switch assembly of the present invention, indicated in general by the reference character R, and showninstructural form in FIGS. 1 to 6, indudes, in addition to the switches R1 and R2, switches R3'and R4. As seen in FIG. 7, the switches R3 and Rd are arranged in parallel sets, with all the parallel sets 'being connected in series between the conductor 58 and -'the switch AR1. The switches R2 and R3 are mechanically interconnected and are manually operated by a push button "62 in such fashion that when the button 62 is depressed the switch R2 opens before the switch R3 closes. The switches R1 and R4- are interconnected and are operated by a key 64 through a conventional tumbler 66 and are so arranged that when the key is turned from the/use to the bypass position (FIG. 1), the switch R1 opens before the switch R4 closes, and when the key 64is turned from the bypass to the use position the switch R4 opens before the switch R1 closes. How this is accomplished will be apparent from the description of switch structure illustrated in FIGS. 1 through 6. It will be noted that one terminal of each of switches R3 and R4 is connected to a binding post 68, while the other terminal of each of the switches R3 and R4 is connected to a binding post 76, and that the binding posts 68 and R2 and the normally closed switch CR1, and the antienergizing the holding circuit 60 for the anti-repeat relay AR, andthe former conditioning the circuit to the clutch relay CR for energization of the latter.

The press cycle is initiated by closing the switch R3 which is associated with the open switch R4, and an instant before this is done the switch R2, corresponding thereto, is opened (the switches R2 and R3 being mechanically interconnected) and a circuit is established from the switch SS1 through the closed switch R1, the conductor 58, the three closed switches R4, the single closed switch R3, theclosed switch ARI, and the clutch relay CR. Energization of the relay CR opens the switch CR1 in series with the anti-repeat relay AR, but that relay will not be .deenergized'since the holding circuit switch ARZ will have previously been closed. Energization of the clutch relayCR closes the three clutch relay switches CR2, CR3, and CR4. These switches are in series with each other and with theclutch solenoid 42 the conductor 58, the switch S53, and a camoperated switch LS2. The cam switch LS2 and the selector switch SSS are connected in parallel. The cam switch LS2 closes upon movement of the slide in the downward direction, and remains closed until the slide is restored to its uppermost position. The selector switch SS3 is closed only when the press is set to run on continuous or repeated cycles, and consequently it is open when the master selector switch is set in the run position and has no with full safety, a conductor 72 interconnects the circuit between the clutch relay CR and the switch AR1, with the circuit connection between the switches CR2 and CR3. Thus, when the clutch relay is energized, the

switches CR2, CR3, and CR4 will close, and will remain closed until the cam switch LS2 is opened, the circuit energizing the clutch relay, during this time, being the line L1, stop switches 55, switch SS1, closed switch R1, conductor 5%, limit switch LS2, switch CR2, conductor 72, and clutch relay CR to the line L2. The clutch sole noid is energized by the same circuit, except that it includes the switches CR3 and CR4 and the solenoid 48, the latter all being in parallel with the clutch relay CR. As the slide returns to its top position, the switch LS2 opens, and the'circuit to the switches CR2, CR3, and CR4- is opened. Since the switch R3 was closed only momentarily in order to start the press cycle and should not be held closed manually by the operator, the circuit to the anti-repeatrelay AR will open when the slide is half way restored to its top position upon opening of the position limit switch LS1.- However, the limit switch LS1 recloses shortly before the slide reaches its top position.

if the operable run buttons 62 were released the relay AR will be energized, as previously described. Should 'the run buttons 62 remaindepressed, the switches R2 be conditioned for another cycle which can be started by depressing momentarily the appropriate button 62.

In view of the fact that when the switch assembly R is moved from the use to the bypass or lockout position, the switch R1 opens before the switch R4 closes, there can be no possibility that all four switches R4 will be closed at a time when any one of the switches R1 is also closed. Thus, it will be impossible for the press to be inadvertently operated during a change of the run button controls R from use to bypass condition, and vice versa. Furthermore, it will be noted that it is impossible to operate the press at any time when all four of the controls R are in bypass position, because all of the switches R1 will be open and the circuit section 52 connected to the conductor 58 through the selector switch SS1 cannot be energized. This circuit, utilizing the improved run button switch mechanism of FIGS. 1 to 6, therefore, provides a safety system which is as foolproof as can be devised, and yet permits extreme flexibility in operating the press solely from any one or combination of the control assemblies R.

The inching control circuit section 54, which is arranged in parallel with the run and continuous operation circuit section 52, includes the selector switch SS2 which is connected in series with a plurality of parallel switches I1 and a conductor 74, the conductor 74 being comparable to the conductor 58. The inching buttons and switch assemblies I each have three sets of switches. In addition to the switch I1, each is provided with a switch I4 which is similar to the switch R4 and has a similar function, and a switch I3 which is similar to switch R3 of the assembly R.

In FIG. 7 all of the inching switch assemblies I are shown in the bypass position, which is the position they may occupy when the press is being operated for continuous or run cycling, although this is not essential with the switch SS2 open during such operations. If it is desired that the inching operation be carried out, the selector control is moved to the inch position to close switch SS2 and open switches SS1 and SS3. One of the switch assemblies I will be moved from the bypass to the use position, in which case the switch 14 will open before the corresponding switch 11 closes. Then the press may be inched by depressing the button 76 for the switch assembly I which is in the use position. This closes the switch I3 in parallel with open switch I4 and which remains closed only as long as the button 76 is held depressed. A circuit is established from the line L1 and stop switches 56 through the selector switch SS2, a closed switch I1, conductor 74, a pair of witches I4, a manually closed switch I3, conductors 78 and 72, and clutch relay CR to the line L2. Energization of the clutch re lay CR closes switches CR3 and CR4 to energize the solenoid 48. It will also close the switch CR2, but this is incidental, since the remainder of the circuit 57 is open (switch SS1 being open). The switches CR3 and CR4 will remain closed only a long as the switch I3, which corresponds to the open switch I4, is manually held closed by depressing the button 76. The movement of the slide is thus under full and sole control of the operator.

It will be observed that it is impossible that the inching circuit 54 be inadvertently energized even if all the switches I4 are closed and the selector switch SS2 is closed with the power on since all of the switches 11 will be open. Closing one of the switches I1 will, immediately prior thereto, open the corresponding switch 14, and consequently it will be necessary manually to close the corresponding switch I3 before the clutch relay CR .and the clutch solenoid 48 can be energized to operate the press. It will be appreciated, therefore, that the safety features of this circuit are complete.

Should it be desired to operate the press on continuous or repeated cycling, the master selector switch is moved to the continuous operation position in which the selector switches SS1 and SS3 are closed and the selector switch SS2 is open. At least one switch assembly R is set in the use position and those not set in the run position will be locked out or bypassed. The anti-repeat relay AR is energized as previously described to condition the circuit to the clutch relay CR for energization. The run buttons 62 set in use position are depressed to energize the circuit to the clutch relay CR which then closes the switches CR1, CR2, and CR3. The press will operate on repeated cycles since the relay CR will remain energized (even though the anti-repeat relay and its holding circuit will be deenergized) through the following circuit: line L1, stop switches 56, selector switch SS1, closed switch R1, conductor 58, selector switch SS3, switch CR2, conductor 72, and relay CR to the line L2. The clutch solenoid 48 will also remain energized since the energized clutch relay CR holds the switches CR2 and CR3 cloesd. This operation may be terminated by opening one of the switches 56 or by moving the master selector control to the off position.

The switch assembly R is shown in physical detail in FIGS. 1 through 6. The assembly is mounted on a base or frame 89 which may be made of any suitable material, particularly one that can withstand machine shop usage. In the frame are mounted the push button 62 which is slidably positioned in a bore 82, and the lock tumbler 66 which is rotatably mounted in a bore 84. Adjacent the lock and on a beveled surface 86 are indicated the two positions of the tumbler 66, as for example, the use and the bypass positions. Consequently, the press operator, by looking at the run button assembly R, can tell whether any particular button is that which may be used for operating the press, or if it is locked out or bypassed. If it is in the use position shown in FIG. 1, then depressing the button 62 will energize the press, provided all of the remaining switch assemblies R are in the bypass position or are similarly manually actuated. If, however, the switch tumbler 66 indicates that this switch is in bypass position, then it cannot be used for operation of the press. From a safety standpoint it is advisable that the key 64 be completely removable from the tumbler 66 and entrusted to a supervisory employee so that it is his decision and judgment for the switch assembly R to be put into the use condition or into the bypass condition, respectively.

The switch R2 includes a pair of contact blades 88 and 90 connected respectively to binding posts or terminals 92 and 94. The switch R2 is normally closed by a movable circular contact member 96 which has a central opening and is slidably carried upon the reduced outer end 98 of a switch operator member 100. The operator member 100 is fixed in the push button 62 and is movable thereby. The contact blades 88 and 90 are mounted in a recess 102 in an insulating mounting block 104 which is fixed to the base or frame 80 in a rectangular recess 166 formed therein. The actuator member 100 projects through an opening 108 in the mounting block 104 from the recess 196 and into the recess 102.

The push button 62 is urged in the outward direction by a spring 110 surrounding the member 10%) and which acts between an inner face 112 of the mounting block 104 and a shoulder 114 on the push button 62.

The reduced extension 98 of the operator 100 carries a second movable circular contacting member 116 which is adapted to bridge between a pair of contact blades 118 and 120 which are connected respectively to the terminals 68 and 70 and constitute the run but-ton switch R3. In the normal position of the run button 62 the contacting or bridging member 116 is separated and spaced from the contacts 118 and 120, and thus the circuit in which these contacts are connected is normally open. A spring 122 is carried by the extension 98 between the contacting members 6 and 116 and urges them apart, being retained on the extension 98 by a washer 124 and a cotter pin 126.

It will be noted that the maximum distance that the contacting members 96 and 116 may be spaced apart on I in the use position.

the operator extension 98 is less than the distance between thepair of contacts 88 and'fitiand the pair of contacts 118 and 120. Thus, whenthe push button 62 is depressed, a

shoulder 127 on the operator 1% moves the switch member 96 away from the contact blades 88 and 99 to open the switch R2. This occurs before the switch member 116 comes against and bridges across the contacts 118 and 124 to close the switch R3. Thus, the circuit containing the switch R2 is broken before the circuit containing the switch R3 is completed.

The switch R1 includes a pair of contacts 128 and 13% connected, respectively, to binding posts 132 and 134 which are'carried in the mounting block 1%. A circuit between the contacts 128 and 13% is closed when the switch structure R is in the use position, by a circular bridging orcontacting member 136 carried on the extension '38 of an operator 140. It will be noted that the operator 1dtiis larger than the extension 1% to form a shoulder '141'therebetween which contacts the bridging-switch memjmember 146 of circular shape carried adjacent the outer end of the operator extension 138 and is prevented from sliding thereoil? by a washer 148 and a cotter pin 15%.

The switch contactors 13s and 146 are urged apart by a spring 152 encircling the extension 138, and the maximum distance the contactors may be separated is less than the spacing distance between the pair of contact blades 12% and 13d and the pair of contact blades 142; and 144. Consequently, it is impossible for theswitch Rd to be closed before the switch R1 has been opened, and vice versa.

At its inner end the operator 140 is integral with a slide block 156 (FIGS. and 6) which is enclosed within a sleeve158. The inner end of the sleeve 158 has a boss 16% thereon which is press fitted into a cylindrical recesslldZ in the base St).

The slide block 156 is guided for reciprocation axially of the sleeve by a group of cage forming fingers 164, 166, 168, and 174 which are fixed to or are integral with a hub or base member 172 which is rotatably mounted in the base of the sleeve 158. The inner faces of the four guide fingers form a relatively wide slideway or guideway 174 for the slide block 156 and a second and narrower guideway 176 for a locking pin 178. The hub 17?. has an extension lfilwhich projects into the opening 84 in the base sa. The extension 132 has a tongue and groove driving connection 186 with the tumbler 66 used for'locking out the switch assembly R.

The tongue and groove drive between the lock tumbler 66 and the hub 172 provides a rotational drive for the cage fingers 16 i, 166, 168, 170, to rotate thernand through them the slide block 156. As the slide block is rotated, it is moved inwardly and outwardly of the sleeve 158 by a pair of pins 183 which have their inner ends fitted into holes 1% in the opposite ends of the slide block, and their outer ends projecting into cam slots 192 1 formed in the cylindrical wall of the sleeve 15%. When the pins are at the end of the cam slot closest to the sleeve boss 164), the slide block 156 and the switch operator 140 are retracted, and the switch assembly R is When the pins 1% are at the opposite'and outer ends of the slots 192 then the slide block 156 is advanced and the switch operator 1% is projected to close the switch R4 and to open the switch R1, and

" the switch structure R is in the lockout or bypass position. It will be noted that at their opposite ends the cam slots 192 are formed with short flat or straight sections vided to prevent such operation.

194 which permit a slight lost motion before the pins 188 move the slide block 156 either inwardly or outwardly of the sleeve.

The slide block 156 is locked ineither its retracted or projected position by the pin 17% which extends across the sleeve and has its opposite ends projecting into V- shaped locking slots 1%, and the apices of the VS form the over dead center position. The pin 1'78 is urged outwardly of the sleeve 156 by a spring 198 confined between the pin 178 and a recess 2% formed in the'cage hub 172. When the key is turned to operate the slide block and move it outwardly, the slight straight or circumferential sections 194 of the'slot 192 give the assembly a chance to pull the locking pin 1'78 leftwardly as seen in FIG. 6, and therefore out of a slot 292 formed in the base of the slide block and into which it fits when the slide block is completely retracted (FIG. "6). The locking pin 178 prevents the assembly controlling the position of the contacting members 136 and 146 'for the switches R1 and R4 to be inadvertently moved from either the use or the bypass" positions. This provides an additional safety'feature for the switch'structure R to insure the proper operation of thecontrol system. I

The assemblyfor the switch operator 1% as it extends through the base 84) is insulated therefrom by a sleeve of insulating material 204 which is also press fitted into the bore 162 in the base 89. Furthermore, the mounting block 1th.?- is likewise insulated from the base '84? even though the former is made of an insulating material, by

a sheet of insulating material 206, whichis provided with suitable apertures for the sleeves 158 and N4, the operator 1%, the spring 11 and theinner endof the push button 62.

it is desirable, when the key operatedmechanism controlling the position of the switches R1 and R4 is in the bypass position as shown in FIG. 4, that it be impossible for the push button 62 to be depressed to open the switch R2 and close the switch R3, and an interlock 2% is pro- This interlock comprises a lever or bar 210 pivotally mounted .at 212 on the outer end of apost 214, which is carried by the insulating block 164 between the switch assemblies R1, R4, and R2, R3. At its upper end, as viewed'in FIGS. 2, 3, and 4, the lever or bar 216 carries a roller 216 which is adapted tobe contacted by the outer end of the operator extension lFati. At its opposite end the lever or arm 210 carries an'engaging shoe 218 which has a fiat surface which is adapted to be contacted by the outer end of the operator extension'98. In its extreme positions the lever 21d is shown in its neutral or use position, wherein it is possible for the run button 62 to be depressed (FIG. 3 In this position, when the run button 62 is depressed, the switch R2 opens and switch R3 closes, and the outer 1 end of the operator extension 98 may come into contact moved to their outer positions, thelever 210 is rocked about the pivot as far as it will go, contacting and holding the switch operator 1% and its extension 93, and thereby preventing operation of the run button "62. This will prevent opening of the switch R2 and closing of the switch 'RS, which would be undesirable when the switch mechanism R is in the bypass position. The lever 210 is provided so that should an operator not notice that the switch unit R is in th bypass position, the lever will prevent, him from depressing the button 62 and this will call his attention to the fact that the unit is bypassed. If the interlock lever 21d were not provided, an operator might not realize that the particularunit or assembly R was not required to stroke or runthe press, thus giving the operator a false sense of security. This feature is very important Where there is more than one operator attending the press and provides another safeguard for the operators.

From the foregoing description of the construction and operation of the control circuit and system, and the safety run button switch R, as particularly illustrated in FIGS. 1 to 6, it is deemed that the operation of the system is clear and that it is unnecessary that it be repeated in detail.

It is obvious that the safety features which are incorporated in the press and system are suflicient to prevent any operator from becoming injured as a result of carelessness in changing the press circuitry from run operation to bypass operation, even though all of the stations having run buttons be moved to the lookout or'bypass conditions at one time.

From the foregoing description, it will be apparent that the circuits and mechanism therein provided accord the operator maximum safety. It is manifestly impossible for the press to be inadvertently operated even during such times as the run or inching switch assemblies R and I are being changed from their use positions totheir bypass positions, and vice versa. It is submitted, therefore, that the objectives which were claimed for this invention at the outset of this specification have been fully attained by the run button switch mechanism herein illustrated and described.

While there has been shown and described a preferred embodiment of the present invention, it will be apparent that further numerous variations and modifications thereof may be made without departing from the underlying principles of the invention. Therefore it is desired, by the following claim, to include within the scope of the invention all such variations and modifications by which substantially the results of this invention may be obtained from the use of substantially the same or equivalent means.

What is claimed as new and useful, and desired to be secured by United States Letters Patent, is:

A switch construction comprising a first operator axially movable between first and second positions for controlling a set of contacts, a second axially movable operator for controlling another set of contacts, a manual push button connected to said second operator, interlock means engageable by said both operators for preventing the movement of said second operator when said first operator is in its first position, said first operator having a plurality of lugs projecting therefrom transverse to its longitudinal axis, a stationary sleeve encircling said first operator and having peripheral angularly disposed camming slots therein in which said lugs are slidably engaged, said first operator having an elongated base, a drive cage having a plurality of fingers embracing said elongated base and rotatably mounted within said sleeve, a key operated tumbler connected to said drive cage for rotating said cage and said first operator whereby said lugs slide in said camming slots to move said first operator between said first and second positions, said elongated base having a slot in its bottom, a pin movably mounted in said slot in a position transverse to said first operator and extending therebeyond, a pair of V-shaped slots in said sleeve into which the ends of said pin project to lock first operator in its first and second positions, and a spring extending between said cage and said pin to hold said pin in said slot.

References Cited by the Examiner UNITED STATES PATENTS 957,262 5/10 Savage 200-5O 2,440,690 5/48 Jacobi 200-153 2,680,368 6/54 McKitrick 200-44 FOREIGN PATENTS 748,354 5/56 Great Britain.

BERNARD A. GILHEANY, Primary Examiner.

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