US2274282A - Interlocking means - Google Patents

Description

' Feb. 24, 1942.

K. W. STINSON INTERLOCKING MEANS Original Filed Dec. 23, 1938 4 Sheets-Sheet 1 INVENTOR I Kari .5 7722:0/1

Feb. 24, 1942. K. w. 'SQTINSON 2,274,282

INTERLOCKING MEANS Original Filed Dec. 23, 1938 4 Sheets-Sheet 2 INVENTOR l ar/ 4157/2250/2.

ATT NEYS Feb. 24, 1942. K. w. STINSON 2,274,282

INTERLOCKING MEANS Original Filed bed. 23, 1958 4 Sheets-Sheet 5/ 1/ Y Z! Y .11..

fias'. 2/54 355592 INVENTOR l ar/ ll. 9/)250/2 BY ATTORNEYS Patented Feb. 24,1942

2.274332- INTERLOCKING MEANS Karl W. Stinson, Columbus, Ohio, assignor to Columbus McKinnon Chain Corporation, Tonawanda, N.Y.

Original application December 23, 1938, Serial No.

247,375. Divided and this application February 27, 1940, Serial No. 321,047

18 Claims. (Cl. 74-565) My invention relates in general to hoist interlocking means, and particularly to interlocking means for that type of hoist which is actuated by a reversing electric motor forming an integral part of the structure and is 'a division of application Serial No. 247,375, filed December 23, 1938. 1

It is well known to those skilled in the art that, in the manufacture of inexpensive .electric hoists, fractional horsepower motors of the single-phase, split-phase, or capacitor type induction motor are employed. The great drawback, however,

in the use of such a type of motor, is that when reversing its direction of rotation, the shaft thereof must come to a standstill before reversal can be effected. In other words,- if the reversing switch controlling the motor is quickly reversed, which is not unusual when sucha hoist is handied by the ordinary workman, the motor shaft will not have time to come to a standstill before being reversed but wil1 continue to rotate in the same direction.

One of the principal objects of my invention has been to provide a hoist having mechanical interlocking means located between the control lever of the hoist and the controller switch thereof, whereby in the event that thecontrol cords attached to the lever are too quicklyoperated in the act of reversing the rotation of the motor shaft, the control mechanism will be temporarily' locked for a period of time sufficient to permit the motor to come to a standstill.

Another object has been to provide a hoist,

having resetting means, whereby the interlocking means will be returned to the position just preceding its actuation in the event that the load carried bythe hoist is not to be reversed but is to be again moved in the same direction.

Another object has been'to providea device of such a nature that it may, if desired, be applied to existing hoists without having to redesign or alter such hoists.

Moreover, my device makes it possible to manufacture an inexpensive hoist because of the fact that an inexpensive type of electric motor can be safely employed.

Furthermore, my invention does not complicate the structure of the hoist-with WhiChllt is used nor does it add materially to the cost there- The above objects and advantages have been accomplished by the device shown in the accompanying drawings, of which: '7

Fig. l is a plan'view, partly in section, of a complete electric hoist embodying my invention, the section being taken on line I--I of Fig. 2.

Fig. 2 is a side elevation of the device, a portion thereof shown in section and taken on line 2-2 of Fig. 1. r

Fig, 3 is an end elevation of the hoist with the end cover removed, showing my invention in one ofits neutral positions.

Fig. 4 is a sectional elevation taken on lin i4 of Fig. 1, showing details of my invention. Fig. 5 is a fragmentary, sectional view taken on line 55 of Fig. 2.

Fig. 6 is a fragmentary, sectional view of the hoist taken on line 66 of Fig. 2.

Fig. '1 is a fragmentary, sectional view similar to Fig. 6 but showing the usual type of motor brake control. Figs. 8, 9 and 10 are fragmentary viewsshowing the control lever and locking mechanism of the form of my invention of Figs. 1 to 5, in? elusive, in various positions of operation.

Fig. 11 is an end, sectional elevation of a hoist equipped with a modified form of interlocking means, taken'on line H-H of Fig. 12.

Fig. 12 is a side, fragmentary, sectional elevation of the form of invention shown in Fig. 11, taken on line l2l2 of that figure.

Figs. 13 and 14 are fragmentary views showing the control and interlocking meansof the form of invention shown in Figs. 11 and 12 in variou positions of operation.

Referring now to Figs. 1' to 5, inclusive, where I show the preferred embodiment of my invention, l5 represents an electric hoist embodying my invention. The hoist is equipped with an electric motor it which is of the single-phase,

split-phase, or split-phase capacitor type which, as is well known in the art, is the most inexpensive type of electric motor. As hereinbefore pointed out, it is necessary to use this type of motor if an inexpensive electric hoist is to be manufactured. As shown in Figs. 1 and 2, the capacitor of the motor is. shown at 2B, and the controller switch is shown at 21. This controller switch, which is actuated by means to be hereinafter described, is, as is well known, for the purpose of connecting a source of electric current to the electric motor and is of such a nature that the motor can be run in either direction.

The casing parts of the hoist are represented at 23 and 33 and enclose portions of the device. The load-lift wheel 24 of my device is made an integral part of a load-life shaft 25, which is suitably mounted in bearings and concentrically arranged with respect to theaxis of the motor shaft 26. The shaft 25 is hollow and-themotor shaft 26 is preferably extended therethrough. The driving gear 30 of the hoist is mounted upon the outer end of the load-lift shaft 25. The motor shaft 26 is extendedbeyond the driving gear and has the motor pinion 3| mounted thereon. This pinion may be attached to the .motor shaft or it may form a part of an integral sleeve 32 which is carried by the motor shaft and which is suitably mounted in a bearing formed in the casing part 33. The motorshaft is extended beyond the end of this sleeve 32 and has the brake drum 34 rigidly mounted thereon, to be hereinafter more fully described.

The intermediate gear 35 of the hoist is mounted upon an intermediate shaft 36 which is journalled in suitable bearings carried by the casing parts 23 and 33. The intermediate gear, of course, is in mesh with the motor'pinion ill, and the intermediate shaft 95 has a driving pinion 49 either formed thereon or attached thereto, which pinion meshes with the driving gear 30.

The intermediate shaft 35 is tubular and pro vided with an axial bore through which the hoist control shaft 41 passes. This control shaft is mounted in suitable bearings 42 and 43 carried by the casing parts 23 and 33 and has its outer end 44 mounted in a suitable bearing-45 formed in the casing cover 49. This control shaft arrangement is the invention of Erford E. Robins, and is the subject matter of a, separate, copending application filed April 25, 1939, Serial No. 269,948. Thecover 46 is fastened by suitable means to the casing part 93 which in turn is secured to the casing part 23. Mounted upon the control shaft 4|, and preferably immediately in front of the bearing 43, is the brake cam 41. This cam acts upon spring-pressed buttons 48 which are carried at the lower ends of the brake arms 49. Each of these buttons is mounted for limited axial movement within a sleeve 59, the exterior of which is screwthreaded and carried at the end of the brake arm in a suitable threaded aperture, whereby the position of each button with respect to the arm may be accurately adjusted. A spring is carried by each of the sleeves for pressing each button inwardly. and a pin 52, moving in a slot 69, limits the extreme inward movement of the buttons. The springs 5| are so designed that when the cam, which is carried by the control shaft, is operated in the direction of lowering of the load, these springs will counteract the tension of the brake spring 53. This brake spring is mounted upon a bolt 54 which, as is customary, passes through both brake arms 49, the tension of the spring being adjusted by suitable screwthreaded means. Each of the brake arms 49 is provided with suitable brake shoes 5! which engage with the brake drum 34. Each of the brake arms 49 is pivotally attached to the casing by means of pins 68. The brake releasing means just described is the invention of Erford E. Robins and is the subject matter of a copending application. It is obvious that my brake control invention may be applied not only to a hoist having the specific type of brake releasing means just described, but also to a hoist having the usual motor brake releasing mechanism, as shown in Fig. '7. As here shown, the brake arms 49 (shown in fragmentary manner) carry screws 59 in adjustable manner, on the inner end of each of which is the usual cam-engaging disc 59. engaged by the cam B'I when rotated in either direction to cause the brake arms to be separated so as torelease the brake.

Mounted upon the extremeouter end of the control shaft M is the control lever 55 of my device. The control shaft, due to the proportions of the hoist, is out of alignment with the controller switch shaft 55, and these two shafts are connected together for rotative operation by means of a segmental gear 60 carried by the control shaft M and an intermeshing, segmental gear BI carried by the switch shaft 55. The segmental gear GI carries an arm 62 which is connected by a suitable link 63 to the usual safety trip lever 64 of the hoist. As is well known, this trip lever serves to shut off the motor when the hoist is inadvertently operated in either direction to the limit of its movements, thereby preventing the hoist from being operated beyond predetermined points.

The control lever 55 is provided with a hub III and two outwardly extending arms H and 12. Each of the arms II and I2 is provided with an aperture I3, through which the upper ends of the operating ropes I4 and 75 may be passed. A knot is preferably formed at the end of each of the ropes after its passage through the aperture for retaining the same in place. These ropes extend downwardly to within reach of the operator of the hoist, where a suitable handle 89 is provided. The control lever 55 is provided with an upwardly extending arm 8i which carries an inwardly extending pin 82. A centralizing spring 83 is mounted upon the hub E0 of the lever and has its ends 84 and 85 extended up- These discs are wardly and in engagement with the pin 82. The spring is held in position by means of the upwardly extending arm 8| and by means of a lug I6 projecting downwardly from the hub I9 of the control lever. The ends 84 and are of such length that they also engage with a stationary lock bar pin 86, which is carried by a bracket 90. The bracket 99 is preferably secured by suitable means to the casing part 33. By means of the centralizing spring 83, and the pins 82 and 86, the control lever 55 will be held normally in its neutral position, as shown in Fig. 3.

The lock bar 9| of my device is mounted above the control lever 55 and upon the lock bar pin 86 carried by the bracket 99. The lock bar is provided with a centrally arranged slot 92 which permits longitudinal sliding and oscillatory movement of the bar upon the pin 86.

The control lever arms II and 120i my device are symmetrically arranged about the axis of oscillation of the lever and each of them is provided on its upper surface with a locking abutment 93 and with a resetting abutment 94. The locking abutment 93 is provided by the stepped arrangement of the upper surfaces 95 and 96 of the arm. The resetting abutment 94 is provided on each arm by an upstanding lug I011. The locking abutments 93 and resetting abutments 94 are engageable with the lower corner edge II and the end surface I02 at either end of the lock bar during the operation of the control lever, as hereinafter described.

Referring now to the form of invention shown in Figs. 11 and 12, I05 is the control lever which is mounted upon a control shaft I06, supported at its outer end by the cover part [I0 and at its inner end by a casing I 26 in a manner described in connection with the other form of invention. This control lever has a hub I I I and two control arms H2 and .I I3. Each of these arms is provided with an aperture II 4 through which the control cords H5 and H6 are passed. The control lever in this form of invention is provided with an upwardly extending reset arm I20 which carries a reset pin I2I. Th lock bar I22 of this form of invention is provided, like in the other form of invention, with a longitudinally arranged slot I23 which is mounted for longitudinal movement and for oscillation upon a detent pin I24. This detent pin is carried by a detent bracket I25, which is suitably secured to the casing part I26 of the hoist.

' the hoist.

The lock bar in this form of invention is provided at each side of the center with a reset arm I39, which arms are interspaced in relation to each other. The reset pin I is movable within this space and between said reset arms. This bar I22 is provided at each end with an edge I3I and an end surface I32. The edge I3l and the end surface I32 at each end of the lock bar are engageable with a locking abutment I33 carried at each end of the control lever and formed by a lug I34 provided at the end'of eachof the arms. Each of the locking abutments I33 terminates at a surface I35 formed on each of the arms of the control lever.

As pointed out in the preamble, it is an'cbject of my invention to prevent the too rapid operation of the control lever when reversing the motor. In carrying out this function by the invention shown in Figs. 1 to 5, inclusive, and Figs. 8 to 10, inclusive, let it be assumed that the op- I crating cord I5 when pulled operates the con troller switch 2I to elevate the load carried by As will be clear from the structure hereinbefore described, when the cord I5 is pulled downwardly, the control lever will cause the rotation of the control shaft 4| in clockwise direction, as viewed in Fig. 3. The shaft 56 of the controller switch will be operated in counterclockwise direction through the medium of the segmental gears 60 and GI cara ried, respectively, by the control shaft and the controller switch shaft. When the controller switch shaft is thus rotated, the current from any suitable source will be allowed to flow through the, motor, causing its shaft to rotate in z.

clockwise direction. The load carried by the hook of the hoist will, therefore, be elevated. As the control lever is being rotated in clockwise direction to the position where the hoist will be operated to elevate the load, it will be moved to the position shown in Fig. 8. As shown in this View, the right-hand end of the lock bar 9I will ride along the surface 96 and drop down to the surface 95 past the locking abutment 93. It is to be assumed that the lock bar has been moved to the right to the position where the pin 86 will be at the left-hand end of the slot by gravity or by the resetting abutment 94 at the opposite end of the lever, to be hereinafter described, and as shown in Figs. 3 and 8. When the control lever is now allowed to return to neutral, by means of the centralizing spring 83,- theright-hand edge IllI will move along the surface 95until the end surface I92 at that end of the lock bar contacts the locking abutment 93. .From this point, further counterclockwise movement of the control lever will cause the lock bar to be moved up and along on the lock bar pin 86. If such movement is so timed that the motor has an opportunity to stop before reversal of its shaft is effected, the lock bar will ride on the pin until it has passed its center of gravity, whereupon it will fall in counterclockwise direction so that the left-hand edge II will contact with the surface 96 at the left-hand end of the control lever, where it will be in position to engage with the abutment 93 at the left-hand side of the control lever when the lever is returned from its reversed or counterclockwise movement when and if such lever is moved to such reversed position. Assume now that instead of a slow, measured movement of the control lever from the position shown in Fig. 8 to its neutral position (shown by full lines in .Fig. 9), or to a position of reversal (shown by dotted lines in Fig. 9), the lever is given a quick movement to and through its neutral position toward its reverse position, the abutment 93 of arm I2 will cause the lock bar 9| tobe moved upwardly upon the lock bar pin 86 to the end of the slot 92 thereof, but because of the frictional engagement of the abutment with the bar caused by the rapid movement, the bar will not be permitted to fall by gravity but will be'locked between the pin and the abutment (as shown in dotted lines in Fig. 8), whereby the control arm will be prevented from moving to its reverse position. So long as the tension is applied to the operating rope I4, the surfaces will remain in frictional engagement, but when the tension on the operating cord I4 is released and the lever is moved slightly in clockwise direction by the centralizingspring 83, as shown in the dot-anddash lines of Fig. 8, the left-hand end of the lock bar will be permitted to fall by gravity into engagement with either the surface 96 or the surface at the left-hand end of the lever, as also shown in this figure by the dot-and-dash lines. During such delayed movement of the control lever, the motor of the hoist has had opportunity to come to astandstill before the control lever can be operated to its reverse position.

In the event that the control lever has been looked, as just above described, and the motor is to be operated in the same direction without first reversing the direction thereof, the resetting abutment 94 at the left-hand end of the control lever will engage the edge IOI and surface I02 at the left-hand end of the lock bar, as shown in Fig. 10, and will serve to push the lock bar along to the right with its slot riding over the pin 86 until the lock bar has reached a point beyond the center of gravity, whereby the right-hand end of the bar will fall, its edge IIH coming in contact with the surface 95 of the arm I2 of the control lever at the right of such lever, as shown by the dotted lines of Fig. 10, where it will be ready to again engage the locking abutment 93 of the arm I2 when the or is moved on to the reversing position.

When the control lever is moved counterclockwise to effect a reversal of the motor shaft and, therefore, a lowering of the load carried by the hoist, the lever will be moved from the full line position of Fig. 9 to the dotted line position thereof, during which movement the lock bar 9| will be also moved to the dotted line position where the left-hand edge IIII and surface I92 will be engageable with the locking abutment 93 of the arm II of the lever when the lever is moved to its neutral position or to the position where the motor shaft will have its direction of rotation reversed.

It will thus be seen that each time the control lever is returned too rapidly to neutral it will be effectively locked and that, in the interim required to unlock the same, the motor will have had time to come to rest before reversal of the direction of rotation thereof can be effected.

vat the load, the control lever I95 will be rotated in clockwise direction to the full line position shown in Fig. 13. If the lock bar has not been moved to the right beyond its center of gravity in which position its lower edge I3I will be riding on the surface I35, the reset pin I 2I carried by the reset arm I29 will bear against the inner surface of the reset lug I30 at the right of the lock bar'andthus'cause the bar to be moved along on the detent pin I24 until the left-hand end of the slot of the bar is in contact with the pin, as shown in full lines in Fig. 13. When the control lever now is moved counterclockwise by the operation of the cord H5, the surface. I32 at the right-hand end of the lock bar or arm II3 will engage with the locking'abutment I33 at the right-hand end of the control lever which will serve to push the lock bar along on the detent pin I24. The end of the lock bar will remain in contact with the engaged locking abutment if the movement is too rapid and the movement of the lock bar will continue along on the pin until the right-hand end of the slot I23 is brought in engagement with the detent pin I24, as shown by dotted lines in Fig. 13, where the control lever will be locked against further movement. Such locked position will be maintained so long as the tension on the cord H5 is maintained. Upon release of such tension, in a manner similar to that described in connection with the form of invention shown in Fig. 8, the lock bar will be permitted to tip with the detent pin I24 as an axis, whereby the left-hand end of this look bar will be brought to rest upon either the top surface of the lug I34 (see Fig. 14) or the. surface I35, where it will be ready to cooperate with the control lever in looking the same, should such lever be operated in counterclockwise direction to the reverse position and then operated too quickly in clockwise direction. If the control lever is not operated to reverse the motor shaft but is again operated in the same direction, i. e., clockwise to elevate the load, the lock bar I22 will be moved to a position where it will cooperate with the control lever upon its return movement by the engagement of the reset pin I2I with the surface of the right-hand reset lug I30 thereof.

Obviously, if the control lever of either form of invention is, for instance, operated to elevate the load and then, after being in neutral position, is again operated to further lift the load without first moving the lever in reverse position, the lock bar will be returned to its righthand position where it will be in cooperative relation with the locking abutment of the control lever at the right-hand end thereof when operated the second time for further load-lifting. Likewise, when the control lever is repeatedly operated to lower the load, the movements of the lock bar will be identical with the movements above described except that the bar will be moved in the opposite direction.

While I have shown the invention of Figs. 1, 2, 3, 8, 9 and 10 as provided with the resetting abutments 94, it is obvious that these abutments may be omitted if desired since the frictional engagement of the lock bar 9i with the surfaces 96 may be, and usually is, sufficient to cause longitudinal movement of such lock bar along the pin 86. These and other modifications of the details herein shown and described may be made without departing from the spirit of my invention or the scope of the appended claims, and I do not, therefore, wish to be limited to the exact embodiments herein shown and described, the forms shown being merely preferred embodiments thereof.

Having thus described my invention, what I claim is:

1. Interlocking means for electric controller switches, comprising a pivotally mounted control lever, means connecting the lever with the switch, and a slidable lock. bar tiltably mounted above said lever and having both ends engageable with said lever for locking cooperation therewith, whereby said lever and said bar are interlocked when the speed of operation of said lever is beyond a predetermined amount.

2. Interlocking means for electric controller switches, comprising a pivotally mounted control lever, means connecting the lever with the switch, a slidable lock bar tiltably mounted for cooperation with the lever and actuated only through the movements of said lever, said bar being supported by means separate from the control lever, and abutments carried by the lever for locking engagement with the lock bar, whereby said lever and said bar are interlocked when the speed of operation of said lever is beyond a predetermined amount.

3. Interlocking means for electric controller switches, comprising a pivotally mounted control lever, means connecting the lever with the switch, a detent pin stationarily arranged above said lever and supported separately therefrom, and a slidable lock bar tiltably mounted upon said pin and having both ends engageable with said lever for locking cooperation therewith to interlock said lever and said bar when the speed of operation of saidlever is beyond a predetermined amount.

4. Interlocking means for electric controller switches, comprising a pivotally mounted control lever, locking abutments carried by said lever, means connecting said lever with said switch, a slidable lock bar tiltably mounted for cooperation with said lever, and reset means carried by said bar and said lever for resetting said lock bar, whereby said lever and said bar will be interlocked when the speed of operation of said lever is beyond a predetermined amount and said bar will be reset when the subsequent movement of the lever is in the same direction as the initial movement thereof.

5. Interlocking means for electric controller switches, comprising a pivotally mounted control lever, means connecting the lever with the switch, abutments carried by the lever, a detent pin stationarily arranged above said lever and supported separately therefrom, and a slidable lock bar tiltably mounted upon said pin and having both ends engageable with said lever for locking cooperation therewith to interlock said lever and said bar when the speed of operation of said leveris beyond a predetermined amount.

6. Interlocking means for electric controller switches, comprising a pivotally mounted control lever, means connecting the lever with the switch, abutments carried by the lever, a detent pin stationarily arranged with respect to the lever, a slidable lock bar tiltably mounted upon said pin, and reset means carried by said lever and said bar, said lock bar cooperating with said lever to interlock said lever and said bar when the speed of operation of said lever is beyond a predetermined point and to reset said bar when the subsequent movement of said lever is in the same direction as the initial movement thereof.

7. Interlocking means for electric controller switches, comprising a pivotally mounted control'lever, locking abutments carried by said lever,means connecting said lever with said switch, a detent pin stationarily arranged with respect to the lever, and a lock bar having a centrally arranged, longitudinal slot mounted upon said pin and engageable with said abutments to cause the interlocking of said bar and said lever when the speed of operation of said ments carried by said lever for engagement'with said bar for resetting said bar, whereby said lever and said bar will be interlocked when the speed of operation of said lever is beyond a predetermined amount and said bar will be reset whenthe subsequent movement of the lever is in the same direction as the initial movement thereof.

9. Interlocking means for electric controller switches, including a pivotally mounted control lever having its axis of oscillation in a substantially horizontal plane and orscillatable in both directions for actuating said switch from one extreme position to the other through neutral, means connecting the lever with the switch, and a slidable lock bar tiltably mounted for movement on each side of a vertical plane and in substantially the same planeas the plane of movement of said lever for locking cooperationtherewith, whereby said lever and said bar are interlocked when the speed of operation of said lever is beyond a predetermined amount.

10. Interlocking means for electric controller switches, comprising means for moving the switch from one position of operation to the other and including time-delay means supported independently of said first mentioned means, said time-delay means lockingly coacting with said first mentioned means in both directions of movement thereof for compelling a lapse of a predetermined time interval in the operation of the switch from one switch position to another.

11. Interlocking means for electric controller switches, comprising lever means'connected to said switch for moving the switch from one extreme operating position to another through neutral, and slidably mounted time-delay means associated with said lever means and actuated only through the movements thereof, said timedelay means being operable when said switch is in neutral position and being supported by means separate from said lever means.

12. Interlocking means for electric controller switches, including a pivotally mounted control lever movable from neutral to reverse positions of operation in uninterrupted manner when the speed of operation is within a predetermined switches, including a pivotally mounted control lock bar associated with said control lever, said lever and lock bar being provided with time-delay means compelling a lapse of a predetermined time interval in the operation of the switch from one position thereof to the reverse position thereof, and said lever and bar also being provided with reset means actuated through the movements of said lever, whereby said bar is reset when the subsequent movement of said lever is in the same direction as the initial movement thereof.

14. Interlocking means for electric controller switches, comprising a pivotally mounted control lever, means connecting the lever with the switch, and a lock bar slidably mounted above said control lever, said bar being tiltable for looking cooperation at each end with said control lever when the speed of actuation of said lever is beyond a predetermined amount and for free actuation in non-locking manner by the movements of said control lever and by gravity when the speed of actuation of said control lever is under said predetermined amount.

15. Interlocking means for electric controller switches, comprising means for moving the switch from one position of operation to the other and including time-delay means slidably and pivotally mounted for tilting movement and lockingly coacting with said first mentioned means in both directions of movement thereof for compelling a lapse of a predetermined time interval in the operation of the switch from one position to another.

16. Interlocking means for electric controller switches, comprising a pivotally mounted control lever, means connecting the lever with the switch, and a slidable lock bar tiltably mounted for locking cooperation with the lever and actuated only through the movements of said lever, and said bar and said control lever having oppositely formed substantially duplicate parts for normal alternate coaction therebetween, whereby said lever and said bar are interlocked when the speed of operation of said lever is beyond a predetermined amount.

1'7. Interlocking means for electric controller switches, comprising a control lever pivotally mounted substantially midway its length and being operable to oscillate the electric switch to its actuating positions, a slidable lock bar tiltably mounted above said lever at a point substantially midway its length and for sliding actuation by said lever, and the adjacent ends of said lever and bar being lockingly engageable when the speed of operation of said lever is beyond a predetermined amount.

18. Interlocking means for electric. controller switches comprising a pivotally mounted control lever, means connecting said lever with said switch, a slidable lock bar tiltably mounted above said lever, and means for supporting said bar independently of said lever, the supporting means permitting sliding and tilting movement of said bar when said control lever is operated at a speed below a predetermined amount, said bar coacting with said control lever and the supporting means to prevent. tilting movement of said bar when said lever is operated above such predetermined speed.

KARL W. STINSON.

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