US2707230A - Railroad switch operator - Google Patents

Description

April 1955 e. c. BELTMANY ET AL 2,707,230

RAILROAD SWITCH OPERATOR Filed Jan 29, 1948 4 Sheets-Sheet 1 a (ze ogye ajeli/zzaze .April 26, 1955 cs. (2. BELTMAN ETAL 2,707,230 RAILROAD SWITCH OPERATOR Filed Jan. 29, 1948 4 Sheets-Sheet 2 INVENTORLS' Sazzzzze CZJVeredzzV},

6207 42 Cjelimzz BY 1 1 V p R April 1955 G. c. BELTMAN ETAL RAILROAD SWITCH OPERATOR 4 Sheets-Sheefc 3 Filed Jan. 29, 1948 MMN April 1955 G. c. BELTMAN ETAL 2,707,230

RAILROAD SWITCH OPERATOR Fil ed Jan. 29, 1948 4 Sheets-Sheet 4 INVENTORS. Jam! Q. @QCZZZ United States Patent RAILROAD SWITCH OPERATOR George C. Beltman, Chicago, and Samuel A. Meredith, Elmhurst, 1]].

Application January 29, 1948, Serial No. 5,074

14 Claims. (Cl. 246-240) Our invention relates to railroad equipment and includes among its objects and advantages switch operating means of maximum durability and convenience in operation, and a system for controlling and operating a plurality of such means.

In the accompanying drawings:

Figure l is a plan view of a section of track, including a pair of switch points and indicating the positioning of an operator according to the invention;

Figure 2 is an enlarged plan view of the operator of Figure l with the cover removed;

Figure 3 is a side view of the master cam plate, as in section on line 3-3 of Figure 2;

Figure 4 is a detail section on line 4-4 of Figure 3;

Figure 5 is a view of the sequence switch and its cam, as in section on line 5-5 of Figure 2;

Figure 6 is a detail of the drive connection, as in section on line 6-6 of Figure 2;

Figure 7 is a detail section of the lost-motion connection on line 7--7 of Figure l; and

Figure 8 is a wiring diagram of a complete switch and operator with associated signals and remote tower controls.

In the embodiment of the invention selected for illustration the conventional rails 10 and 12 are supported on ties 14. The switch points 16 are interconnected by the transverse drag link 18, and actuated by the push rod 20. The push rod 20 is connected to the actuating mechanism in the housing 22 by means of the rod 24 and a resilient lost-motion connection in the housing 26, illustrated in detail in Figure 7.

The remote end of the rod 24 is pivotally connected at to the end of a short crank 32 at the bottom of a vertical shaft 34, which carries an upwardly facing bevel gear 36. A horizontal actuating shaft 38 is connected to a bevel gear 40 having the same number of teeth as the gear 36. It will be apparent that with the parts in the position of Figure 2 the switch points will be in the opposite position from that of Figure l but that rotation of the shaft 34 through 180 will move the switch points to the position of Figure 1.

We provide automatic means for rotating the shaft 38 through successive 180 increments, always in the same direction, and for stopping it accurately in predetermined position at the end of each increment. The three-phase squirrel cage motor 42 is connected through the speed reducer 44 to a countershaft 46 equipped with a modified Bendix drive transmission including the spring 48 and the steep pitch thread 50, on which the drive pinion 52 is mounted.

A master plate 54 carries peripheral teeth 56 positioned to be engaged by the pinion 52 and rotated thereby in clockwise direction. Instead of the customary biasing weight, the pinion 52 has a sleeve 58 on which is fitted a light friction retarding means for holding the pinion 52 in mesh as long as the driven member is pushing back to receive power from the pinion. The brake illustrated is an arm 60 passing through a fixed guide eye 61. The other end of the arm half encircles the bendix shaft and a complementary member 62 pivoted to the arm at 64 lies over the sleeve 58 and is resiliently held in the position of Figure 6 as by the tension bolt 64 adjusted by the takeup wing nut 66 against the tension of a compression spring 68. The arm 60 and cap 62 carry shoes 70 of friction material for exerting a light biasing friction on the sleeve 58 at all times.

The starting and stopping of the master plate 54 is accurately determined by the control pin 72 slidable in the housing 74 and resiliently pressed toward the master plate. The master plate has duplicate cam portions spaced 180 apart for arresting the motion of the plate. Each such cam portion includes a coasting groove 74 of such a depth that letting the end of the pin drop into the groove will open an electric circuit and of such length that the moving parts can coast approximately to rest before the end of the pin drops into the holding hole 76.

The electrical means illustrated for lifting the pin 72 include the solenoid 78 connected to turn the rock shaft 80, which rock shaft carries an arm and a connecting link 82 for pulling the pin away from the plate and for simul taneously closing an electric switch 84.

Referring now more particularly to Figures 2, 5 and 8, the 220-volt power lines L-1, L-2, and lL-3 may be connected to the squirrel-cage motor 42 by the conventional main control switch 86, actuated by the solenoid 88. Two manually-operated push buttons and 92 are indicated as mounted on the end of the housing 22. It will be obvious that these parts can be duplicated in a control tower by the conventional expedient of running a cable to the tower 89 with a pair of buttons 91 and 93 in parallel with the buttons 90 and 92. With the parts in the condition indicated in Figure 8, if the operator completes a contact through the button 90, action will result as follows: the 1l0-volt power line 94 has a circuit through a normally closed track safety switch 95, a solenoid 96, a sequence switch 98 and push button 90 to the return line 100. This actuates the primary control switch 102 and completes a circuit from line L-1 through the closed hand safety switch 104, switch 102 and pin solenoid 78, to line L4. The pin solenoid lifts the pin and closes the switch 84 which completes a circuit as follows: from line L-l through hand safety switch 104, solenoid 88 and switch 84 back to L-2. The energizing of solenoid 88 closes the main motor switch 86 and the motor starts.

The sequence switch 98, as best illustrated in Figure 5, is moved from the full line position of Figure 8 to the dotted line position of Figure 8 and back again by suitable mechanical means. We have illustrated a sequence cam 106 and a switch-operating arm 112 carrying the contact roller 114 for the mechanical shifting of the switch 98. The displacement of the cam 106 will move switch 98 over to the dotted line position and this will deprive solenoid 96 of energy and let switch 102 fall open again. However, by the time this happens, switch 84 is being held shut mechanically because the point of the pin 72 is riding up on the surface of the master plate 54. Therefore, the motor will continue to function. until the coasting groove 74 comes under the end of the pin. This will open switch 84 and the motor is immediately deprived of energy and will begin to coast or slow down. We have indicated three condensers 116 connected into all three legs of the wiring for the motor 42, between the motor and the switch 86. When the switch is thrown open these condensers function as an electrical load sufficient to damp the movement of the motor and reduce the coasting time. And when the motor is operating under load, they merely function to improve the power factor. Accordingly, at a time when the motor has almost, but not quite, stopped, the end of the pin drops into the stop hole 76 and the cycle of operations is at an end. The master plate and its shaft 38 has turned through exactly and the same is true of the vertical shaft 34, and the switch is now open if it was previously closed, or vice versa.

It will be noted that if an ignorant or careless worker closes the push button 90 and stands there holding it closed, nothing will happen except the desired operation of changing the condition of the switch. it will be necessary for him to transfer his attention from switch 90 to switch 92 to achieve the next operation of returning the switch to its original condition if and when that is desired.

In most installations it is desired to take precautions to prevent changing the condition of the switch after one truck of a car has passed through the switch and before the other truck of the same car has also passed through.

Referring to Figure 8, the rail sections and 12 adjacent the switch may be insulated so that the wheels and axles of a passing car establish a circuit. The transformer 97 maintains voltage of six volts on the solenoid 99 and thus holds the track safety switch 95 closed. When the axles of a passing car connect the sections 10 and 12, the conductors 101 and 103 establish a short circuit across the solenoid 99 so that the switch will fall open, and as long as it remains open it is impossible for anyone manipulating the switches or 92 or the switches 91 or 93 to change the condition of the switch. In any installation where this additional safety factor is not needed the contacts of the switch 95 may be connected by a bridge 105, in which case the transformer 97 has no function and may be left out if desired.

Conventional means may be employed for indicating, either at the switch or at any remote place, the exact condition of the switch itself. We have diagrammatically indicated switch and signal boxes 118 and 120 shown in Figures 1 and 8. The boxes may receive power from power line 94 through a connector 122 with a return circuit through conductor 124. Each signal has an interior switch and a light bulls-eye 126 and 128, respectively. In the position of Figures 1 and 8 the switch 118 is open and the bulls-eye 126 is lit. We have also indicated remote duplicate bulls-eyes 126B and 128B which may be located in the control tower 89 or any convenient and conspicuous place, in addition to the bulls-eyes at the side of the switch.

Referring now to Figure 7, the sleeve generally indicated by the reference character 26 in Figure 1 comprises a long sleeve portion 130 and a short sleeve portion 132, threaded on one end of the portion 130. Inside the sleeve 130 is the compression spring 134 which lies between two washers 136 and 138 and is under substantial initial compression load. The washer 138 is prevented from moving to the left by abutment with the adjacent shoulder 140 of the central rod 142, and the washer 136 has similar abutment with the adjustable nut 144. The end of the short portion 132 adjacent the washer 136 is of small enough diameter to abut and push against the washer 136. The opposite end of the sleeve 130 carries the interior ring 146, which has similar abutment with the washer 138. The rod 142 is continued beyond the end of the sleeve 130 to include a guide section 148 shaped for guiding engagement with the ring 146. The outer end of the guide portion 148 is a connecting eye 150 for connection to the next element in the chain. During contraction the nut 144 is guided in the extension 132.

It will also be apparent that tension may elongate the connection to the same extent. In case of tension the rod 142 slides out of the sleeve 130 and washer 136 moves toward the opposite end of the sleeve 130 and compresses the spring.

The extreme end of the extension 132 is provided with conventional connecting means illustrated as a bifurcated terminal having a transverse bore 152.

Manual operation It is essential in most situations on railroads that personnel be able to operate the switches even if the power should fail. We have indicated manual operating means so associated with the automatic operating means that the two systems of operation cannot interfere with each other. The hand lever 154 is pivoted in the first instance at 156 in the horn of the yoke 158 and, in the position illustrated in Figure 2, is restrained against counterclockwise movement by being hooked into a notch in the plate 160. The shaft 38 is hollow and houses a plunger 162 which tends to hold the rod 154 in the position of Figure 2. The opposite end of the plunger 162 is positioned to abut the throw-out lever 164 pivoted at 166 and held in the position illustrated by the spring 168. Movement of the lever 164 a few degrees in a clockwise direction mechanically engages the link 82 and pulls the pin 72 out of the master plate. It simultaneously opens the normally closed hand safety switch 104, and upon reference to Figure 8 it will be apparent that as long as this hand safety switch remains open, no portion of the automatic control system can possibly function to cause the motor to do anything. Thus the operator grasping the lever 154 and pulling it out of the hook disconnects the switch 104 and almost instantaneously thereafter lifts the pin 72. A slight further increment of movement about the pivot 156 will bring the projecting flange 170 at the inner end of the lever 154 into a slot 172 in the end of shaft 38. The operator can now rotate the lever 154 and yoke 158 together around the axis of shaft 38, and shaft 38 and the master plate 54 are constrained to rotate also. Thus the operator can rotate the lever in a counterclockwise direction and, having brought it down on the other side, hook it into place in the guide and retaining plate 174 on the other side. Movement of the lever into position where the plate 174 will retain it will move the heel 170 back to the axial position of Figure 2 so the lever 164 closes the switch 104 and replaces the pin 72, and the assembly is ready for the next operation, either manual or electric. To prevent the lever 154 from letting the shaft 162 move out and connect the electrical drive, during manual movement of the switch, we provide a cross-piece 176 to engage the lever throughout its movement so that it cannot pivot in around the pivot 156 until the shifting of the switch is completed. It will also be noted that, in manual operation, the master plate does not always travel in the same direction but may be and, in fact, must be turned in clockwise and counterclockwise direction.

Without further elaboration others may readily adapt the invention for use under various conditions of service by employing one or more of the novel features involved, or equivalents thereof. As at present advised with respect to the apparent scope of the inventon we desire to claim the following subject matter.

We claim:

1. In an operator for opening and closing railroad track switches and the like, in combination: a master cam plate; mechanical connections, including an actuating crank connected for synchronized rotation through the same angle as said master plate at all times, between said plate and switch for moving said switch from open to closed position and back to open position during successive increments of motion of said master plate; and means for actuating said master plate, comprising, in combination: a motor; a power drive from said motor to said plate; electric control means for operating said motor; and manual means for mechanically moving said master plate through the same increments; said manual means including, in combination: an operating lever: means actuated by an initial movement of said lever for rendering the entire electric control inoperative; and means rendered operative only by full manual completion of a manually initiated increment, for disconnecting said lever and restoring said electric control to operative condition.

2. In an operator for opening and closing railroad track switches and the like, in combination: a master cam; means guiding said cam in a predetermined closed path; means for moving said cam in said path through successive equal increments of motion in the same sense; completion of said path involving a first predetermined amount of travel; each of said increments involving a second predetermined amount of travel; one of said travel amounts being an aliquot portion of the other; a first manually operated electrical control means for initiating an increment; automatic means not subject to operator control for completing an initiated increment; said automatic means rendering said first manually operated means inoperative; a second manually operated electric control means automatically rendered operative by said automatic means; manually actuated means for initiating and completing an increment; said manually operated means including a control element normally inoperative to move said master cam; guide means compelling said manual operating element to move in a predetermined path; means actuated by the initial movement of said operating element for rendering said electrical means inoperative; and means rendered operative by completion of a manually actuated increment for disconnecting said manual element at the completion of an increment and subsequently rendering said electric means again operative.

3. In an operator for opening and closing railroad track switches and the like, in combination: a master cam; means guiding said cam in a predetermined closed path; means for moving said cam in said path through successive increments of motion; completion of said path involving a first predetermined amount of travel; each of said increments involving a second predetermined amount of travel; one of said travel amounts being an aliquot portion of the other; a first manually operated electrical control means for initiating an increment; automatic means not subject to operator control for completing an initiated increment; said automatic means rendering said first manually operated means inoperative; a second manually operated electric control means automatically rendered operative by said automatic means; manually actuated means for initiating and completing an increment; said manually operated means including a control element normally inoperative to move said master cam; guide means compelling said manual operating element to move in a predetermined path; means actuaated by the initial movement of said operating element for rendering said electrical means inoperative; and means rendered operative by completion of a manually actuated increment for disconnecting said manual element at the completion of an increment and subsequently rendering said electric means again operative.

4. In an operator for opening and closing railroad track switches and the like, in combination: a master cam; means guiding said cam in a predetermined closed path; means for moving said cam in said path through successive increments of motion, all in the same direction; completion of said path involving a first predetermined amount of travel; each of said increments involv ing a second predetermined amount of travel; one of said travel amounts being an aliquot portion of the other; a first manually operated electrical control means for initiating an increment; automatic means not subject to operator control for completing an initiated increment; said automatic means rendering said first manually operated means inoperative; and a second manually operated electric control means automatically rendered onerative by said automatic means.

5. An operator according to claim 4 in which said cam is the periphery of a rotary plate.

6. In. an operator for opening and closing railroad track switches and the like, in combination: a master cam; means guiding said cam in a predetermined closed path; means for moving said cam in said path through successive increments of motion, all in the same direction; a first manually operated electrical control means for initiating an increment; automatic means not subject to operator control for completing an initiated increment; said automatic means rendering said first manually operated means inoperative; and a second independent manually operated electric control means automatically rendered operative by said automatic means, for initiat' ing a subsequent increment.

7. In an operator for opening and closing railroad track switches and the like, in combination with a conventional pair of switch points and a conventional push rod for pushing them back and forth; a crank for actuating said push rod; a fixed vertical axle carrying said crank; said crank having its free end connected to said push rod and being of such length that in one dead center position it pushes said switch points to one extreme position and in the other dead center position diametrically opposite said first dead center position it pulls said switch points to the opposite extreme position; poweroperated means including an electric motor and a transmission from said motor to said axle for rotating said axle through successive increments always in the same direction; automatic stop means operatively associated with said transmission for arresting the movement of said axle each time said crank comes to dead center position, and concomitantly interrupting the power supply to said motor, and disconnecting said transmission from said motor; a hand control lever mounted on a fixed axis and rotatable around said axis to and fro between predetermined extreme positions; said hand control lever including a portion mounted for displacement by axial movement substantially parallel to said fixed axis with respect to the remainder of said lever; holding means engaging said axially movable hand lever portion when said lever is in either extreme position to prevent .ro tation of said lever about said fixed axis; said holding means being shaped to clear said hand lever when said axially movable hand lever portion is axially displaced; means actuated by the axial displacement of said axially movable lever portion for first disconnecting said motor from its power source, second, mechanically releasing said vertical axle to permit movement thereof, and third, mechanically connecting said hand lever to said fixed axle; said holding means restraining said hand lever from rotation until after all three axial increments of movement are completed, whereby said hand lever becomes operative, independent of and Without interference by said motor, to throw said switch from either open or closed position to the other position, starting with said hand lever in either extreme position.

8. In an operator for opening and closing railroad track switches and the like, in combination with a conventional pair of switch points and a conventional push rod for pushing them back and forth; a crank for actuating said push rod; a fixed vertical axle carrying said crank; said crank having its free end connected to said push rod and being of such length that in one dead center position it pushes said switch points to one extreme position and in the other dead center position diametrically opposite said first dead center position it pulls said switch points to the opposite extreme position; power-operated means including an electric motor and a transmission from said motor to said axle for rotating said axle through successive increments always in the same direction; automatic stop means operatively associated with said transmission for arresting the movement of said axle each time said crank comes to dead center position, and concomitantly interrupting the power supply to said motor, and disconnecting said transmission from said motor; a hand control lever mounted on a fixed axis and rotatable around said axis to and fro between predetermined extreme positions; said hand con trol lever including a relatively rigid portion movable about said fixed axis only, and a relatively movable portion mounted for a different displacement other than by rotation about said fixed axis; holding means engaging said relatively movable hand lever portion when said lever is in either extreme position to prevent rotation of said entire lever about said fixed axis; said holding means being shaped to clear said relatively movable portion when displaced; means actuated by said displacement of said relatively movable lever portion for first disconnecting said motor from its power source; second, mechanically releasing said vertical axle to permit movement thereof, and third, mechanically connecting said hand lever to said fixed axle; said holding means restraining said entire hand lever from rotation until after all three increments of separate movement of said relatively movable portion are completed, whereby said hand lever becomes operative, independent of and without interference by said motor, to throw said switch from either open or closed position to the other position, starting with said hand lever in either extreme position.

9. In an operator for opening and closing railroad track switches and the like, in combination with a conventional pair of switch points and a conventional push rod for pushing them back and forth; a crank for actuating said push rod; a fixed vertical axle carrying said crank; said crank having its free end connected to said push rod and being of such length that in one dead center position it pushes said switch points to one extreme position and in the other dead center position diametrically opposite said first dead center position it pulls said switch points to the opposite extreme position; power-operated means including an electric motor and a transmission from said motor to said axle for rotating said axle through successive increments always in the same direction; automatic stop means operatively associated with said transmission for arresting the movement of said axle each time said crank comes to dead center position, and con comitantly interrupting the power supply to said motor, and disconnecting said transmission from said motor to said axle; a hand control lever mounted on a fixed axis and rotatable around said axis to and fro between predetermined extreme positions; said hand control lever belng normally disconnected from said transmission and inoperative; and movable means actuated by a preliminary displacement of said hand control lever for first, renderng said motor inoperative, second, subsequently connecting said hand control lever to said axle for manual actuation of said switch; and third, keeping said hand lever connected and said motor inoperative so long as said switch and lever occupy any intermediate position between the fully open and the fully closed positions.

10. In an operator for opening and closing railroad track switches and the like, in combination with a conventional pair of switch points and a conventional push rod for pushing them back and forth; a crank for actuating said push rod; a fixed vertical axle carrying said crank; said crank having its free end connected to said push rod and being of such length that in one dead center position it pushes said switch points to one extreme position and in the other dead center position diametrically opposite said first dead center position it pulls said switch points to the opposite extreme position, power-operated means including an electric motor and a transmission from said motor to said axle for rotating said axle through successive'increments always in the same direction; automatic stop means operatively associated with said transmission for arresting the movement of said axle each time said crank comes to dead center position, and concomitantly interrupting the power supply to said motor, and disconnecting said transmission from said motor to said axle; a hand control lever mounted on a fixed axis and rotatable around said axis to and fro between predetermined extreme positions; said hand control lever being normally disconnected from said transmission and inoperative; and movable means operatively connected to said motor and said hand control lever for first rendering said motor inoperative, second, subsequently connecting said hand control lever to said axle for manual actuation of said switch; and third, keeping said hand lever connected and said motor inoperative so long as said switch and lever occupy any intermediate position between the fully open and the fully closed positions.

11. In an operator for opening and closing railroad track switches and the like, in combination with conventional switch points movable between closed and open positions; a rotary member; a linkage connecting said member to said switch points; said linkage including an element pivoted to said rotary member to be moved by continuous rotation of said rotary member to a first sub stantially dead center position where said switch is open and a second substantially dead center position where said switch is closed; motor-driven means including a motor and a transmission from said motor to said rotary member for turning said rotary member from said first dead center position to said second dead center position and vice versa by successive rotary movements all in the same direction; a hand-operating member; and changeover means operative only whenever said rotary member is in either dead center position, for keeping said motor disconnected from said rotary member, and connecting said rotary member to said hand-operating member; said hand-operating member being mounted for to and fro movement between predetermined extreme positions; said hand-operating member actuating said rotary member in to and fro movement; the connection between said handoperating member and said rotary member including a portion of said transmission from said motor.

12. In an operator for opening and closing railroad track switches and the like, in combination with conventional switch points movable between closed and open positions; a rotary member; a linkage connecting said member to said switch points; said linkage including an element pivoted to said rotary member to be moved by continuous rotation of said rotary member to a first substantially dead center position where said switch is open and a second substantially dead center position where said switch is closed; motor-driven means including a motor and a transmission from said motor to said rotary member for turning said rotary member from said first dead center position to said second dead center position and vice versa; a hand-operating member; and changeover means operative only whenever said rotary member is in either dead center position, for keepingsaid motor disconnected from said rotary member, and connecting it to said hand operating member; said hand-operating member being mounted for to and fro movement between predetermined extreme positions; the connection between said hand-operating member and said rotary member including a portion of said transmission from said motor.

13. In an operator for opening and closing railroad track switches and the like, in combination with a'conventional pair of switch points and a conventional push rod for pushing them back and forth; a crank for actuating said push rod; a fixed axle carrying said crank; said crank having its free end connected to said push rod and being of such length that in one dead-center position it pushes said switch points to one extreme position and in the other deadcenter position diametrically opposite said first dead-center position it pulls said switch points to the opposite extreme position; power-operated means including an electric motor and a transmission from said motor to said axle for rotating said axle through successive increments always in the same direction; said transmission including a horizontal intermediate shaft; automatic stop means operatively associated with said transmission for arresting the movement of said axle each time said crank comes to dead-center position, and concomitantly interrupting the power supply to said motor, and disconnecting said transmission from said motor; a hand-control lever including a portion mounted for displacement by axial movement substantially along the axis of said intermediate shaft; holding means engaging said axially movable hand-lever portion when said lever is in either extreme position to prevent rotation of said lever about said fixed axis; said holding means being shaped to clear said hand-lever when said axially movable hand-lever portion is axially displaced; means actuated by the axial displacement of said axially movable lever portion for first disconnecting said motor from its power source; second, mechanically releasing said axle to permit movement thereof, and third, mechanically connecting said hand-lever to said axle; said holding means restraining said hand-lever from rotation until after all three axial increments of movement are completed, whereby said hand-lever becomes operative, independent of and without interference by said motor, to throw said switch from either open or closed position to the other position, starting with said hand-lever in either extreme position.

14. In an operator for opening and closing railroad track switches and the like, in combination with conventional switch points movable between closed and open positions; a rotary member; a linkage connecting said member to said switch points; said linkage including an element pivoted to said rotary member to be moved by continuous rotation of said rotary member to a first substantially dead-center position where said switch is open and a second substantially deadcenter position where said switch is closed; motor-driven means including a motor and a transmission from said motor to said rotary member for turning said rotary member from said first dead-center position to said second deed-center position and vice versa by successive rotary movements all in the same direction; said transmission including an intermediate shaft and bevel gears connecting said intermediate shaft to said crank shaft; a handoperating member; and changeover means operative only whenever said rotary member is in either dead-center position, for keeping said motor disconnected from said rotary member, and connecting said rotary member to said hand-operating member; said hand-operating member being mounted for to and fro movement between predetermined extreme positions; said hand-operating member actuating said rotary member in to and fro movement; the connection between said hand-operating member and said rotary member being at said intermediate shaft,

References Cited in the file of this patent UNITED, STATES PATENTS 458,489 Ramsay et al Aug. 25, 1891 902,035 Wightman Oct. 27, 1908 1,139,964 Goldsmith May 18, 1915 1,209,146 Gray Dec. 19,1916 1,493,495 McCoy May 13, 1924 1,667,473 Howe Apr. 24, 1928 1,711,060 OMeara Apr. 30, 1929 1,820,756 McWhirter Aug. 25, 1931 1,889,022 Little Nov. 29, 1932 2,100,296 Wight Nov. 23, 1937 2,320,171 Bone May 25, 1943 2,372,214 Leopsinger Mar. 27, 1945 2,402,400 Hewitt et a1. June 18, 1946 Laze Sept54, 1951

Images