Operating device for electric hoist

An operating device for an electric hoist having a DC motor for raising and lowering an object, comprises a low speed adjusting setting unit (VR1) and a high speed adjusting setting unit (VR2) provided in a control box of the hoist. The operating device further comprises in the control box a two-step push-button switch (PB-U) for the raising operation for switching over the low speed adjusting setting unit and the high speed adjusting setting unit to connect either of the units (VR1 and VR.sub.2) to a speed-change control circuit by pushing the two-step push-button switch (PB-U) to either of first and second step positions, and a two-step push-button switch (PB-D) for the lowering operation for switching over the low speed adjusting setting unit (VR1) and the high speed adjusting setting unit (VR2) to connect either of the units to the speed-change control circuit by pushing the two-step push-button switch (PB-D) for the lowering operation to either of first and second step positions.

BACKGROUND OF THE INVENTION 
This invention relates to an operating device for an electric hoist whose 
raising or lowering speed is easily changed from low to high speed and 
vice versa by two-step push-buttons and the low and high speeds are simply 
controlled in low and high speed ranges. 
The term "hoist" as used herein is intended to designate means having a DC 
motor for lifting an object, inclusive a chain block. 
An operating device for an electric hoist such as an electric chain block 
has been widely used. With such a hitherto used operating device, a 
control box is connected to a cable depending from a main body of the 
electric hoist and is provided with push-button switches for raising and 
lowering operations and a variable resistor for adjusting raising and 
lowering speeds. 
In raising or lowering an object at an appropriate speed by a hoist having 
such an operating device, an operator is pressing either of the 
push-button switches by a finger of his one hand which grips the control 
box and at the same time he operates the variable resistor by his other 
hand for adjusting the hoisting speed. Therefore, the operation of the 
device is very troublesome. 
SUMMARY OF THE INVENTION 
It is a primary object of the invention to provide an operating device for 
an electric hoist, which eliminates the above described disadvantage of 
the prior art and capable of switching over low and high operating speeds 
and controlling the speeds for raising and lowering operations. 
In order to accomplish this object, an operating device for an electric 
hoist having a DC motor for raising and lowering an object according to 
the invention comprises a low speed adjusting setting unit and a high 
speed adjusting setting unit provided in a control box of the hoist, and 
further comprises in the control box a two-step push-button switch for a 
raising operation for switching over said low speed adjusting setting unit 
and said high speed adjusting setting unit to connect either of said units 
to a speed-change control circuit by pushing said two-step push-button 
switch to either of first and second step positions, and a two-step 
push-button switch for a lowering operation for switching over said low 
speed adjusting setting unit and said high speed adjusting setting unit to 
connect either of said units to said speed-change control circuit by 
pushing said two-step push-button switch for a lowering operation to 
either of first and second step positions. 
In order that the invention may be more clearly understood, preferred 
embodiments will be described, by way of example, with reference to the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1-5 illustrate a first embodiment of the invention. An electric hoist 
comprises a main body 1 and a control box 3 connected to a cable 2 
depending form the main body 1. In the control box 3, there are provided a 
low speed adjusting setting unit VR1 including a variable resistor adapted 
to be connected to a speed-change control circuit 4, and a high speed 
adjusting setting unit VR2 including a variable resistor. The control box 
3 is provided with a two-step push-button switch PB-U for winding-up 
operation and a two-step push-button switch PB-D for winding-off 
operation. When the switch PBU or PBD is actuated by pushing a push-button 
(later explained) to first step position, the low speed adjusting setting 
unit VR1 is connected to the speed-change control circuit 4. When the 
switch PBU or PBD is actuated by pushing the pushing-button to second step 
position, the high speed adjusting setting unit VR2 is connected to the 
speed-change control circuit 4. Adjusting knobs 5 and 6 for the low and 
high speed adjusting setting units VR1 and VR2 are provided on a front 
surface of the control box 3 for adjusting the raising and lowering speed 
within low and high speed ranges, respectively. The front surface of the 
control box 3 is provided at an upper portion with a cover 7 pivotally 
connected thereat for covering the knobs 5 and 6. The cover 7 is 
maintained in its closed position covering the knobs 5 and 6 by a spring 
action of a spring 8 to prevent operation of the knobs 5 and 6 of the 
units VR1 and VR2 during the operation of the electric hoist. 
The front surface of the control box 3 is fixed with indication plates 
having low and high speed graduations 9 and 10 corresponding to the units 
VR1 and VR2. On the front surface of the control box 3 are provided 
push-buttons 12 and 13 for the two-step push-button switches PB-U and 
PB-D. 
FIG. 5 is an operation control circuit for the electric hoist according to 
the invention. When the push button 12 is pushed to the first step 
position, a raising contact pair A of the two-step push-button switch PB-U 
is turned on to start the raising operation of the hoist. Under this 
condition, as the low speed adjusting setting device VR1 is previously 
connected to the speed control circuit 4, the raising operation is 
effected at a predetermined low speed set by the low speed adjusting 
setting unit VR1. 
When the push-button 12 is further pushed to the second step, a high speed 
contact pair B of the push-button switch PB-U is turned on to excite a 
relay R so that a switch 14 of the relay R is switched over to connect the 
high speed adjusting setting unit VR2 to the speed control circuit 4. 
Therefore, the raising operation is effected at a predetermined high speed 
set by the high speed adjusting setting unit VR2. 
When the push-button switch PB-U is returned to the first step, the raising 
operation is again effected at the low speed. Upon releasing the pushing 
force from the switch PB-U, the raising operation is stopped. 
When the push-button 13 is pushed to the first step position, a lowering 
contact pair C of the two-step push-button switch PB-D for lowering 
operation is turned on to start the lowering operation of the hoist. Under 
this condition, as the low speed adjusting setting unit VR1 is previously 
connected to the speed control circuit 4, the lowering operation is 
effected at the predetermined low speed set by the low speed adjusting 
setting unit VR1. 
When the push-button 13 is further pushed to the second step position, a 
high speed contact pair D of the push-button switch PB-D is turned on to 
excite the relay R so that the switch 14 is switched over to connect the 
high speed adjusting setting unit VR2 to the speed control circuit 4. 
Accordingly, the lowering operation is effected at a predetermined high 
speed set by the high speed adjusting setting unit VR2. 
When the push-button switch PB-D is returned to the first step position, 
the lowering operation is again effected at the low speed. Upon releasing 
the pushing force from the switch PB-D, the lowering operation is stopped. 
When the two-step push-button switch PB-U for a raising operation is pushed 
by the push-button 12, an interlocking contact pair E is turned off. Under 
this condition, even if the two-step push-button switch PB-D for a 
lowering operation is pushed by the push-button 13, the a lowering circuit 
remains inoperative. On the other hand, the two-step push-button switch 
PB-D for lowering operation is pushed by the push-button 13, an 
interlocking contact pair F is turned off. Under this condition, even if 
the two-step push-button switch PB-U is pushed by the push-button 12, the 
raising circuit remains inoperative. 
FIGS. 6 and 7 illustrate another embodiment of the control device according 
to the invention. As shown in FIGS. 6 and 7, adjusting shafts 15 and 16 of 
the low and high speed adjusting setting units VR1 and VR2 may be formed 
in their extending ends with grooves 17 for engaging a tool such as a 
screw driver, thereby preventing the adjusting shafts 15 and 16 from being 
rotated by a hand of an operator. Moreover, the low and high speed 
adjusting setting units VR1 and VR2 may be enclosed as a whole in the 
control box 3 so that these units are not adjusted or manipulated by the 
operator at will. 
For constituting the low and high speed adjusting setting units VR1 and 
VR2, means capable of changing electric signals by mechanically operating 
means, for example, potentiometer may be used instead of the variable 
resistor. Moreover, the speed control circuit 4 may be provided in the 
control box 3. 
A preferable control circuit for the operating device according to the 
invention will be explained in more detail. 
FIG. 8 illustrates a control circuit for use in the operating device 
according to the invention, which comprises an operating circuit 61, a 
phase control circuit 62, a full-wave rectifying circuit 63, a normal and 
reverse rotating circuit 64, a dynamic brake resistor DBR and a DC motor 
65. The operating circuit 61 consists of a raising circuit 61a, a lowering 
circuit 11b, high and low speed change circuit 61c, and variable resistors 
VRL and VRH. The raising circuit 61a is a series circuit of a low speed 
contact pair L of a push-button switch PB-U for the raising operation, a 
normally closed contact pair MD-1 of a relay MD for the lowering 
operation, and a relay MU for the raising operation. The lowering circuit 
61b is a series circuit of a low speed contact pair L of a push-button 
switch PB-D for the lowering operation, a normally closed contact pair 
MU-1 of a relay MU for the raising operation and a relay MD for the 
lowering operation. The high and low speed change circuit 61C is a circuit 
of a high and low speed change relay MH connected in series to a parallel 
circuit of high speed contract pairs H of push-button switches PB-U and 
PB-D for raising and lowering operations. 
The push-button switches PB-U and PB-D are two-step operable switches. The 
low speed contact pairs L are closed by pushing the switches to first step 
positions, while both the low speed contact pairs L and the high speed 
contact pairs H are closed by pushing the switches to the second step 
positions. Upon releasing the switches, both the contact pairs L and H are 
opened. 
The variable resistors VRL and VRH are connected in parallel and are 
switched over by switch-over contacts MH-1 of the high and low speed 
change relay MH. The variable resistors VRL and VRH serve to control the 
speeds within low and high speed ranges in a stepless manner, 
respectively. 
The phase control circuit 62 comprises a capacitor C, a two-way trigger 
diode SBS (trigger element D such as silicon bilateral switch or the like) 
and a triode AC switch T. 
The normal and reverse rotating circuit 14 comprises normally opened 
contact pairs MU-2 and MU-3 of a relay MU for the raising operation, and 
normally opened contact pairs MD-2 and MD-3 of a relay MD for the lowering 
operation. To a dynamic brake resistor DBR are connected in series a 
normally closed contact pair MU-4 of a relay MU for the raising operation 
and a normally closed contact pair MD-4 of a relay MD for the lowering 
operation. 
With the control circuit constructed as above described, when the 
push-button switch PB-U for the raising operation is pushed to the first 
step position, the lower speed contact L of the switch PB-U is closed to 
permit alternate current from an alternate current power source AC through 
the contact L and normally closed contact pair MD-1 to the relay MU for 
the raising operation. Therefore, the relay MU for the raising operation 
is actuated to close the normally opened contact pairs MU-2 and MU-3 of 
the relay MU and to open the normally closed contact pairs MU-1 and MU-4 
of the relay MU. As a result, the alternate current from the power source 
AC is controlled in phase in the phase control circuit 62 and then 
full-wave rectified in the full-wave rectifying circuit 63. The rectified 
current is supplied into the DC motor 65 so as to energize it in a normal 
rotating direction to rotate the load sheave (later described) in a normal 
rotating direction. At this time, as the high and low speed change relay 
MH is inoperative and its low speed contact L is closed, the rotating 
speed of the direct current motor 65 is controlled in stepless manner by 
adjusting the variable resistor VRL. At this moment, however, as the 
normally closed contact pair MU-4 of the relay MU for the raising 
operation is kept opened, any direct current does not flow through the 
dynamic brake resistor DBR, so that dynamic braking is not effected. 
When the push-button switch PB-U for the winding-up operation is pushed to 
the second step position, both the low and high speed contacts L and H are 
closed to keep operative the relay MU for the raising operation and the 
high and low speed change relay MH is actuated to switch over its 
switch-over contacts MH-1 to the high speed contact H. Under this 
condition, the rotating speed of the DC motor 65 can be controlled within 
a high speed range in a stepless manner by adjusting the variable resistor 
VRH. 
When the push-button switch PB-U for the winding-up operation is released, 
the relay MU for the winding-up operation becomes inoperative to open the 
normally opened contact pairs MU-2 and MU-3 and close the normally closed 
contact pairs MU-1 and MU-4 of the relay Mu. As a result, the direct 
current to the DC motor 65 is interrupted, and the power generated in the 
DC motor during the rotation of its rotor due to inertia is consumed in 
the dynamic brake resistor DBR so that the rotation of the rotor is 
decelerated at a moderate deceleration. 
Moreover, if the push-button switch PB-D for the lowering operation is 
pushed to the first step position, the lower speed contact L of the switch 
PB-D is closed to permit alternate current from the alternate current 
power source AC through the contact L and the normally closed contact pair 
MU-1 to the relay MD for the lowering operation. Therefore, the relay MD 
for the lowering operation is actuated to close the normally opened 
contact pairs MD-2 and MD-3 and to open the normally closed contact pairs 
MD-1 and MD-4. As a result, the alternate current from the power source AC 
is controlled in phase in the phase control circuit 62 and then 
full-wave-rectified in the full-wave rectifying circuit 63. The rectified 
current having a polarity opposite to that in the normal rotation of the 
DC motor is supplied to the DC motor so as to energize the DC motor in a 
reverse direction to rotate the load sheave in a reverse rotating 
direction. At this time, as the high and low speed change relay MH is 
inoperative and the low speed contact L of the switch-over contacts MH-1 
is closed, the rotating speed of the DC motor 65 can be controlled within 
a low speed range in a stepless manner by adjusting the variable resistor 
VRL. 
At this time, moreover, as the normally closed contact pair MD-4 of the 
relay MD for the lowering operation is maintained opened, any direct 
current does not flow through the dynamic brake resistor DBR, so that the 
dynamic braking is not effected. 
When the push-button switch PB-D for the lowering operation is released, 
the relay DM for the lowering operation becomes inoperative to open the 
normally opened contact pairs MD-2 and MD-3 and close the normally closed 
contact pairs MD-1 and MD-4. As a result, the power generated in the DC 
motor during the rotation of its rotor due to inertia is consumed in the 
dynamic brake resistor DBR so that the rotation of the rotor is 
decelerated at a moderate deceleration. 
Moreover, when the push-button switch PB-D for the lowering operation is 
pushed to the second step position, both the low and high speed contacts L 
and H of the switch PB-D are closed to keep operative the relay MD for the 
lowering operation and the high and low speed change relay MH is actuated 
to switch over its switch-over contacts MH-1 to the high speed contact H. 
Under this condition, the rotating speed of the DC motor 65 can be 
controlled within a high speed range in a stepless manner by adjusting the 
variable resistor VRH. 
FIGS. 9a and 9b illustrate input and output waveforms at the phase control 
circuit 62. The input alternate current IN sinusoidal wave as shown in 
FIG. 9a is controlled in phase in the phase control circuit 62 into the 
alternate current of the waveform as shown in FIG. 9b. The alternate 
current shown in FIG. 9b is full-wave-rectified in the full-wave 
rectifying circuit 63 into direct current of a waveform shown in FIG. 10a 
or FIG. 10b, either of which is supplied to the DC motor 65 according to 
the raising or lowering operation, that is, the normal or reverse rotation 
of the DC motor 65. 
The power to be supplied to the DC motor 65 is adjusted by adjusting the 
variable resistors VRH and VRL for setting speeds in the phase control 
circuit 62. In this case, by suitably selecting ranges of resistance 
values adjustable by the variable resistors VRH and VRL, the following 
controlling is possible. For example, when the raising or lowering 
operation is effected at the high speed range, the variable resistor VRH 
is operated to control one fourth period T.sub.1 which is a first half of 
a half wave. When the operation is effected at the low speed range, the 
variable resistor VRL is operated to control one fourth period T.sub.2 
which is a latter half of the half wave. 
A construction of a chain block as one example of an electric hoist 
controlled by the circuit above described will be explained hereinafter. 
FIG. 12 is partial sectional view illustrating the mechanical portion of 
the stepless variable speed change electric chain block. The mechanical 
portion of this chain block is substantially similar in construction of 
that of the Japanese patent application No. 36,500/85 filed by the 
assignee of this case corresponding to U.S. patent application Ser. No. 
832,788. 
As shown in FIG. 12, a load sheave shaft 33 integral with a load sheave 35 
is journaled by bearing 38 and 39 in the gear box 40 in parallel with a 
driving shaft 21 formed at one end with a driving gear 22. A support ring 
41 is fitted on the load sheave shaft 33 so as to engage one end of the 
load sheave 35 and is further fitted on a center hole of a support member 
42 in the form of a dish-shaped spring made of a spring steel. Moreover, 
an urging ring 43 made of a steel is fitted on the other end of the load 
sheave shaft 33 so as to engage the bearing 38 and further fitted in a 
center hole of an urging member 44 in the form of a dish-shaped spring 
made of a spring steel. 
A cam support 24 made of a steel is rotatably and axially slidably fitted 
on a mid-portion of the load sheave shaft 33 between the support member 42 
and the urging member 44. A retainer disc 27 made of a steel between the 
cam support 24 and the urging member 44 is fitted on the load sheave shaft 
33 axially slidably but nonrotatably relative thereto. A brake receiving 
disc 29 between the cam support 24 and the support member 42 is also 
fitted on the load sheave shaft 33 axially slidably but nonrotatably 
relative thereto. A ratchet wheel 28 for braking is rotatably fitted on a 
boss of the brake receiving disc 29 through a sleeve bearing 45. A pawl 51 
for braking (FIG. 13) is pivotally mounted on the gear box and is urged 
into engagement with the ratchet wheel 28 by means of a spring (not 
shown). 
An intermediate driven gear 23 is fitted on an outer circumference of the 
cam support 24 axially slidably but against rotation relative thereto. 
Friction plates 30 and 31 are fixed to side surfaces of the driven gear 
23, respectively, by means of welding, adhesive or the like. A friction 
plate 32 between the ratchet wheel 28 and a flange of the brake receiving 
disc 29 is fixed to a side surface of the ratchet wheel 28 by means of 
adhesive. The cam support 24 is formed on a side of the brake receiving 
disc 29 with a plurality of cam grooves 26 in the form of arcs 
circumferentially spaced apart from each other and concentric to the load 
sheave shaft 33. Each cam groove 26 has a sloped bottom to change the 
depth of the groove and receives a brake releasing cam member 25 in the 
form of a steel ball in this embodiment. Moreover, the cam support 24 is 
formed on a side of the retainer disc 27 with a plurality of recesses 46 
circumferentially spaced apart from each other in a circle concentric to 
the load sheave shaft 33 for receiving steel balls 47. 
An external screw-thread portion 48 provided on the other end of the load 
sheave shaft 33 extends outwardly from the gear box 40. An adjusting nut 
49 is threadedly engaged with the external screw-thread portion 48 of the 
load sheave shaft 33 out of the gear-box 40 and at the same time engages 
one end of the collar 50. A tightening force of the adjusting nut 49 urges 
the central portion of the urging member 44 through the collar 50, the 
bearing 38 and the urging ring 43 to clamp the retainer disc 27, the 
intermediate driven gear 23, the ratchet wheel 28, the flange of the brake 
receiving disc 29 and the friction plates 30, 31 and 32 interposed 
therebetween with the aid of the support member 42 and the urging member 
44. 
In this embodiment, a torque limiter is constructed by the urging member 44 
and the support member 42 and the intermediate driven gear 23, the 
retainer disc 27, the brake receiving disc 29, the ratchet wheel 28, and 
the friction plates 30, 31 and 32 between the members 44 and 42. Moreover, 
a mechanical brake assembly for preventing load from dropping is formed by 
the pawl 51 adapted to engage the ratchet wheel 28; the cam support 24 
having cam grooves 26; the brake releasing cam members 25; and the ratchet 
wheel 28 held through the retainer disc 27, the brake receiving disc 29, 
the intermediate driven gear 23 and the friction plates by the spring 
forces of the support member 42 and the urging member 44. 
In order to adjust the transmission torque of the torque limiter after the 
electric chain block has been assembled, such an adjustment is performed 
by simply rotating the adjusting nut 49 out of the gear-box after an 
electric equipment receiving cover 51 has been removed without requiring 
disassembling of the electric chain block. 
With the above arrangement, when the push-button switch PB-U for the 
winding-up operation in the operating circuit is pushed to a first or 
second step portion to energize the DC motor 65 in the normal direction to 
rotate a driving shaft 21 in a winding-up direction, a driving gear 22 of 
the driving shaft 21 is driven to cause a cam support 24 to rotate through 
a driven gear 23. The brake releasing cam member 25 are therefore located 
at deeper positions in the cam grooves 26, so that the intermediate driven 
gear 23, the retainer disc 27, the ratchet wheel 28, the brake receiving 
disc 29 and the friction plates 30, 31 and 32 are clamped by the preset 
clamping force. Accordingly, the rotation of the intermediate driven gear 
23 is transmitted through the retainer disc 27 and the brake receiving 
disc 29 to the load sheave shaft 33 and the load sheave 35, thereby 
effecting the raising operation within the torque set by the torque 
limiter. 
When the push-button switch PB-D for the raising operation in the operating 
circuit is pushed to a first or second step position, the DC motor 65 is 
energized in the reverse direction to cause the driving shaft 21 to rotate 
in the lowering direction, so that the cam support 24 is rotated in a 
reverse direction by the driving gear 22 through the intermediate driven 
gear 23. Accordingly the brake releasing cam members 25 are moved into 
shallower positions in the cam grooves 26 to extend higher from the side 
surface of the cam support 24, so that the cam support 24 and the brake 
receiving disc 29 move away from each other by the extending action of the 
brake releasing cam members 25. As a result, the mechanical brake assembly 
is released so that the load sheave 35 is rotated by a weight of the load 
faster than the rotating speed driven by the DC motor 65. However, such a 
rotation of the load sheave 35 results in clamping of the mechanical brake 
assembly, so that the lowering operation is performed at a speed 
substantially equal or near to the speed driven by the DC motor 65 by the 
repetition of the releasing and clamping of the brake assembly. 
When the DC motor 65 is deenergized after the load is raised or lowered to 
a desired height, the transmission mechanism of the block tends to rotate 
in a reverse direction by the weight of the load. However, such a rotation 
will clamp the mechanical brake assembly into a unitary body, and after 
the brake assembly has been clamped, the further rotation will be 
prevented by the pawl 28 and the ratchet wheel 51. 
Although the chain block has been shown, this is only by way of example, 
and the hoist according to the invention is not limited to this example. 
In short, the invention is applicable to a hoist inclusive a chain block 
having a DC motor for driving a shaft for lifting a load. 
Moreover, the variable resistors VRH and VRL for controlling speeds within 
high and low speed ranges may be rotary switch type variable resistors as 
shown in FIG. 14. The speeds are stepwise controlled by the use of taps 
R.sub.1 -R.sub.6. 
Furthermore, instead of the variable resistor VRH and VRL, a plurality of 
fixed resistors R.sub.1 -R.sub.3 are connected in parallel, and speed 
control within the high and low speed ranges is effected in plural steps 
with the aid of rotary switches LS.sub.1 and LS.sub.2. 
According to the invention, the low and high speed adjusting setting units 
VR1 and VR2 adapted to be connected to the speed-change control circuit 4 
are provided in the control box 3 connected to the cable 2 depending from 
the main body 1 of the electric hoist. In the control box 3, moreover, 
there are provided the two-step push-button switches PBU and PBD for 
raising and lowering operations so that the units VR1 and VR2 are switched 
to be connected to the speed-change control circuit 4 by pushing the 
push-button switches PBU and PBD to the first and second step positions. 
Therefore, the electric hoist can be operated for raising operation at 
predetermined low speeds only by pushing the two-step push-button switch 
PB-U or PB-D to the first step position for raising or lowering operation. 
Moreover, the electric hoist can be operated for raising or lowering 
operation at a predetermined high speed only by pushing the two-step 
push-button switch PB-U or PB-D to the second step position for winding-up 
or -off operation. Therefore, raising or lowering operation of the 
electric hoist can be easily effected at a low or high speed most suitable 
for the location where the electric hoist is used, by single-handed 
operation by an operator. Moreover, as the low and high speed adjusting 
and setting units VR1 and VR2 are arranged in the control box 3 at a low 
level within operator's reach, the electric hoist can be easily adjusted 
to be set at low and high speeds optimum for a nature and a configuration 
of an object to be lifted after the electric hoist in once settled. 
Furthermore, according to the invention, the switching over from the high 
speed operation to the low speed operation and vice versa is effected and 
the speed control within high and low speed ranges is effected in a 
stepless manner with the aid of the control circuit. Therefore, the hoist 
according to the invention is high in responsibility to switching over the 
operating speeds and has a superior performance in stepless speed control 
has various advantages as above described. 
It is further understood by those skilled in the art that the foregoing 
description is that of preferred embodiments of the disclosed devices and 
that various changes and modifications may be made in the invention 
without departing from the spirit and scope thereof.