US2304360A - Electric lifting device - Google Patents

Description

D 8, 1 42- F. w. HORSTKOTTE 2,304,360

ELECTRIC LIFTING DEVICE I Filed Dec. 24, 1940 2 Sheets-Sheet 1- Z3 /2 [we 3790752 INVENTOR FknER/ak WHo RSTKO 77's Dmyafl ATTORNEY Dec. 8, 1942. F. w. HORSTKOTTE ELECTRIC LIFTING DEVICE Filed Dec. 24, 1940 2 Sheets-Sheet 2 LINEETARTEE INVENTOR Fkg'DE/P/cyq W Ho/vs r/ro F'TE ATTORNEY Patented Dec. 8, 1942 the art is referred this specification. I v .v

, 'Ifqilltistrate mechanism adapted to"apply the" of great intensity, as for." enampl It 15am bi ct t'tntr sntim i steam cylinder fare many cited, but they have been] concomitants of .apparatu ing therequired function, a I) Such apparatus is ordinarily :u'sed nterinittently and for only a, verysnialldrahtion of total working time, hence it is an object to as- "sociate a suitable electric motor with suitable" ,other elements in such a comhinationthat wheri""-- a starting impulse is manually'-given, 'the motor has initial room in its operating cyn attain speed and power without having tofac'cfept substantial loaduntil itfhas done this; yet it must and does enter the work part'of the cycle without shock uch as "may be expected with employment ,of aclutchg'jwhich in this'finvention is not used.

" It istherefore another obiectiof the present in-*" v vention to provide electrically operated apparatus" ,having operating chamacigeristics as indicated,

, but omittinga clutch heretofore always deemed necessary.

' j succinctly; t is anfobject of thisinventionto' arrange an electrical substitute for the steam cylinder and piston device, that fulfills all 0: 3

' shaft and 3 is a shunt brake, see Fig. VIII, and

the functio'ns of the-latter atits 'best anddoes not have its inherent --infirmities, such as a tendency toovershootdue to resilient steam when To-comply with Sec. 4888 mg arm forthrowing a log onto asaw carriage.

- This -however, is only one of;;the very numerous 1 applications .wherein it :is an advance-over the 3 reciprocating steam '2 cylinder and; piston;'henceathe'drawings will not' -be regarded asilimiting but illustrative only. For the scope of the invention,-,v;; 2-

to-the claimsat the closer'of' me(:l'ianical principles of this invention; drawings a. s.';' i have sh 'y 7 my new invention operatiyely connected to a load-' electric' power as instantly availablelas' steam cylinder, withjpiston hereto for, such. requirements.

accompany and area-made 1'0WS v a 'Fig; I is a side elevation oft-an operative log lifting device forthrowing a logonto a saw-car- 1 riage that embodies the principlenfthe present invention andthis flgure alsoincludes a diagram- -='matic layout :of the electricalconnections more -c'ompletelyi shown in detailv in Fig .}VI II;

Fig. II is a- -left hand end" view of the structure sh'own'in Fig-'VI Q- 1 Figrnr is a anaemia Fig. I; IV-is a. section taken at=IV-IV,,Fig. I,

- thelast two figureswbeing especially useful to show Fig.. V';.,'1' Fig. VII is a, "useful in cases-,whereavery long stroke is re- 1 the positioneof limit switches and their employ- 'ment i-as hereinafter; described};

Fig-V is a-diagram showing ho wa pair of limit switches vmay be usedwith a single operative cam,

f' the structure being otherwise thesamein princit pleas that shown in Fig. I; I e

'Fig.- VI isa view in orthograp pro)ection of view of'an alternate construction,

-quired' or "where more than two or three limit switchesare desirable in- 1eac h cycleof operation;

FigavIlI-isawiringdiagram for the structure shown in Fig. I, from which'any skilled electrician the-load changes, or reversely to drop a' load due to steam conde'nsation, .often .occurring with ex-" 1 tremerapidity.. The very substantial waste of v "power"; of a steam lifter using. steam non-ex pansively is also avoided.

may make up a wire diagram for any-variation thereof employing the same principle.

In the drawings, flrst-,consideri ng Fig. I:. l is an electric motor: of the 3 phase squirrel cage 1 type with an 'exceedinglyhigh' starting torque, "8,150 capable of carrying a momentary overload of several hundred percent, 2 is the motor drive is the single phase circuit-for the brake. This type of brake is set;by a spring and opened by gears-run in oil, delivering the motor power to an output shaft 6; at relatively slow speedand correspondingly increased torque. This motorgear will have to be strong enough tooperate satisfactorily when the motor is delivering its maximum overload capacity..

A crank-'I-is-mount d on the shaft 5. It has a crankpin. Bto- .wh-ich .oneend of. theconnecting rod 9 is journalledn The --;other ,end'of the connecting rod! is journalled between theforks ID of the rockerv arm ll, which is made rigid with the rockshaftll. A wrist pin ll-' holds theconnecting rod 9-operatively between the forks.

The rock shaft 12 is adapted to oscillate under influence of the motor I by means of the transmissions heretofcre described and, when so oscillated, will apply great power to the lifter arm I3, a well known device for throwing a log from a log-deck to a saw carriage, as indicated in Fig. -11, though always heretofore such a lifter has been operated by a double acting steam cylinder of considerable size. In practice there will be at least two of these lifter arms.

It will be at once apparent that any other severe but short time lift, other than the one shown, may be accomplished by appropriate driven electrically operated devices according to this invention. Note here that a crank or similar transmission has a neutral zone of operation while it is going over its bottom center. Being halted at the bottom center of its stroke or just before it reaches the bottom, and assuming that the reduction in the motorgear is considerable, a motor with a high pullout torque will attain a high speed and consequent pulling power before it must accept any substantial part of the load, represented here by a log L, in dotted outline, then the great momentary overload capacity of the motor will be put to good use, be-

cause the lift will be completed well short of the time when the copper windings of the motor can overheat due to abnormal current flow.

It is believed that this marks the first time this inherent motor characteristic has been put to beneficial use, save to occasionally prevent damage when some operated part is stuck.

That this structure may be operated with a facility superior to the steam cylinder lifter which it replaces, may now be examined into.

We will assume that the electric lifter is at rest, as shown at Fig. I, with the crank-pin 8 somewhere within the neutral zone of its revolution, as shown. The limit switch has been opened by the cam 2| on the hub of the crank 1; hence the primary line 22 of the electric motor circuit is dead. The head-sawyer will step on the manually operable, normally open switch 23, thus closing the secondary electric line 24 and 25, whereupon the limit switch 20 is by-passed, the manual switch 23 takes over control, the shunt brake 3 instantly releases and the motor operates the electric lift after the manner described.

If actuation of the manual switch is momentary only, being released as soon as the lift starts, then the limit switch 20 takes over the control, until the cam 2| lifts the arm 30, of the limit switch 3|, whereupon the secondary line is again opened with the lifting arm II on top in the position shown in Fig. II and the motor stops abruptly.

The brake will stop the motor i without overrun suiiicient to interfere with successful operation, when a log turner or a device for shoving the log further onto the carriage may be worked,

the lifter l3 meanwhile holding the log L exactly where it was placed for any desired length of time, something for whichthe steam cylinder is not well suited.

If, on the other hand, -mere throwing of the log onto the carriage is sumcient', then the operator will keep the manual switch closed until the arm l3 begins the downward part of its cyclic operation, when he releases it and the limit switch 20 assumes control automatically. This cycle of operations is more certain than that of a steam cylinder and does not involve the very large waste of power occasioned by a direct steam pressure in a cylinder.

In Figs, V and VI. there is shown a disc ll, upon which is mounted a single cam ll, cooperative with limit switches .42 and 43. The mode of operation of this form is identicalwith that shown in Fig. I, but by placement of the limit switches differently, a single cam serves just as well as two cams in the other structure. It will be apparent that cam operated limit switches can be placed adjacent any part having a cyclic path of operation.

Fig. VII illustrates a chain 50 mounted on a driving sprocket 5| and a driven sprocket 52, to which is pinned a connecting rod 53. A single limit switch 54 will be opened by a cam 55, shown as an attachment link of the chain 60. Obviously this structure lends itself well to carrying several more cams than are conveniently disposable within the working cycle of the transmissions of Fig. I- The purpose of this figure is to show that by proper modification of the structure shown in Fig. I an operating cycle of a lifter can be varied even more widely than with the well known steam cylinder lift and with the added advantage that wherever it is stopped, ii will stay, indefinitely until it is purposely moved forward. In practice, there are at least two and generally three positions on the lifting side of the operating cycle, with nothing on the return side save a limit switch positioned to stop the crank-pin or equivalent structure within the neutral zone and preferably Just at its beginning, lucidly expressed by using a marksmans simile, at five-o-clock."

Having disclosed my invention and explained its principle so that it can take its proper place in the art, what I claim as new and desire to secure by Letters Patent is:

1. Anflelectric log lifting and moving device comprising a lifter arm, a crank connected to said arm, an electric motor operatively connected to said crank, control means for said motor comprising a power circuit, two automatic limit switches in said circuit, means for operating said limit switches seriatim to stop the motor with the crank in its next succeeding neutral zone, and a normally open manual switch effective to bypass both automatic limit switches for continuous operation of the motor when it is forcibly held in closed Position.

2. An electrically operated lifter device comprising a reciprocating lifter crank, means for reciprocating the lifter comprising an electric motor, speed reducing transmission means connected intermediate the motor and the crank, a pair of cams revoluble at crank speed and synchronized therewith, anelectric. circuit for said motor, a pair of automatic limit switches in said circuit, an operating cam for each switch. a bypass circuit, and a normally open manual switch in said circuit effective upon operation to take over control from both of the automatic limit switches, each limit switch and cam for operating the same being timed to stop the crank in its next succeeding neutral zone.

3. An electric lift comprising an electric motor. a power circuit for said motorycontrol means comprising a normally open manual switch and two automatic limit switches, a reciprocable lifter, transmissions between the lifter and the motor, a crank forming part of said transmissions, and limit switch operating means synchronous with the crank and timed to operate one of the limit switches and stop the motor with the crank in its nearest neutral zone, the said manual switch effective to assume and hold control of the motor when manually closed.

4. In an electric lifter, an electric motor therefor, transmissions for said motor effective to change rotary to reciprocating motion at reduced speed, crank and connecting rod means in series with other parts in said transmissions, a pair of revoluble cams synchronized with the crank, a pair of, normally closed limit switches arranged to be opened seriatim by the cams to stop the motor and leave the crank in a neutral zone, and a normally open manually operable switch arranged to supersede the control of any given limit switch that may have stopped the motor, to

restart the same, each limit switch being eflective, seriatim, to stop the crank as it enters its next neutral zone.

5. An electric lilting device comprising an electric motor, a crank driven thereby, speed reducing transmissions therebetween, a litter operable by the crank, said trons comprising one part having a cyclic path of movement. cams made rigid with said last named part, a pair of normally closed'limit switches arranged to be opened seriatim by said cams, each of said limit switches eilective to stop the motor leaving the crank in its nearest neutral zone when contacted by a cam, and a normally open manual switch effective to by-pass both limit switches when closed.

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