OPW Counterbalance 788 Series User manual

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2726 Henkle Drive • Lebanon, OH 45036 • www.opw-es.com
Manual - Loading Arm
April 2011 790 Series Counterbalance
Equipment: Torsion Balance Type: 790A,B,C
Balance Unit for balancing Loading Arms
Suitable for: Loading Arm Balancing
• Easy, Precise Adjustment
• No special tools required
Specications
Type
Right-Hand: 790A-0020 (White),
790B-0030 (Yellow), 790C-0050 (Red)
Left-Hand: 790ALH-0025 (Black),
790BLH-0035 (Gray), 790CLH (Orange)
Working
Temperature Range -4°F to 176°F (-20°C to +80°C)
Installation
Spring Unit Assembly
1. Position balance unit on the bosses at back of swivel joint.
2. Fix balance unit with Bolts and Lock Washers.
3. Attach backside of Link Arm [17] to Spring Arm [15] with Pin [16] and 2 Retaining
Rings [14].
4. Remove the 4 Socket Head Screws [18] and take Snubber Block [26] off.
5. Raise loading arm to highest position (as vertical as possible).
6. Attach front side of Link Arm [17] to mounting ears on loading arm with Pin [16] and
2 Retaining Rings [14].
7. Check balancing action by pulling down the arm. If adjustment is necessary,
follow adjustment instructions below.
8. Install lock-down unit 788-L, if used, by following 788-L installation instructions.
9. Replace Cover [21] using alignment pins [1] and latches [22].
Adjustment
When to adjust torque
A. To raise loading arm higher or for more lifting action INCREASE torque.
B. To decrease loading arm vertical travel or to slow the rate at which the arm rises,
DECREASE torque.
C. Note: Prior to any disassembly, Spring balance tension should be completely relieved to allow
safe disassembly of level arm.
Torque For more lifting action increase torque. For less lifting action decrease torque.
Place ¾" socket wrench on worm gear hex drive.
To INCREASE torque rotate the worm gear hex drive
counterclockwise (to the left).
To DECREASE torque rotate the worm
gear hex drive clockwise (to the right).
Release wrench and test loading arm
lifting action.
Note: Prior to any loading arm
disassembly, spring tension should be
completely relieved.
Tip: Spring coil will be loose in housing
when completely relieved of tension.
Worm Gear Hex Drive
NEW: Easy-to-use
Spring Cover Latch

PHONE: [phone] • [phone] • Fax: [phone] • [phone]
2726 Henkle Drive • Lebanon, OH 45036 • www.opw-es.com
Manual - Loading Arm
April 2011 790 Series Counterbalance
Parts List: 790 Series Counterbalance
Index Qty Part # Description
1 4 H-31396-M Spirol Pin, 1⁄4 x 13⁄4
21 C-20185-BW Spring Regulator, R.H. Worm Gear
3 1 H-30744-M Dowel Pin .25 x 1.25
42H-01490-M Flange, Bearing, BRZ. 11⁄2" DIA x
11⁄4" LG
52H-32283-M Retaining Ring, CST ZP
6 2 H-32282-M Bearing, Cylindrical, Bronze
71 H-30743-M Washer, Thrust, ZP, 7⁄8"
8 1 C-20184-EW Drive Worm, Torsion Spring
92H-30741-M Screw, Drive #10 x 3⁄8"
10 1 H-30740-M Worm Cover Plate, Spring Balance
11 1 H-30018-M Bolt, 1⁄2"-13 x 31⁄2
12 1 H-30049-M Jam Nut, Hex, CST, ZP, 1⁄2"-13
13 1 E20074D1 790 Support Bracket, D1
14 2H-30321-M Retaining Ring, CST, 5⁄8"
15 1 D-00350-D1 Spring Arm, PTD, D1
16 1 H-30320-RE Pin, Torsion Spring, SST
Index Qty Part # Description
17 1 E-20041-D1 Link Arm, D1
18 4 H-31278-M Socket Head Screw, ZP, .31-18 X 1"
19 2H-02507-M Lockwasher, CP, 5⁄8"
20 2H-05910-M Screw, Hex Cap, CST, ZP, 5⁄8"-11
x 13⁄4"
21 1 E20116P 790 Spring Balance Cover, RH
22 2 H32321M Spring Cover Latch (SouthCo)
23 4 H32322M Screw, Thread Forming, 8-32
24 1 C-00626-M Spring, Torsion, C
25 1 H-30742-RS Bar, Safety
26 1 H-01489-D1 Snubber Block, RH, D1
27 4 H-03563-M Washer, Lock, ZP, 5⁄16"
28 1 H-01486-RB Snubber Retainer, Brass, 11⁄8-12
x 1⁄2"
29 1 H-01487-RE Snubber Plunger, SST, 15⁄16" DIA x
19⁄16" LG
30 1 H-01502-M Spring, Compression, ZP
31 1 C00635D1 Support, RH Side, D1

PHONE: [phone] • [phone] • Fax: [phone] • [phone]
2726 Henkle Drive • Lebanon, OH 45036 • www.opw-es.com
788, 789, 790 Series Counterbalance
Manual - Loading Arm
April 2011
Travel Stop 788, 789, 790 Series
Upward Downward
Remove the (4) socket head screws in snubber block, then rotate
snubber block toward pivot pin to allow for more upward travel or
away from pivot pin for less upward travel.
Replace the (4) screws and tighten.
Loosen Jam Nut (located below lever arm) and turn
stop bolt in for more downward travel or out for less
downward travel. Then hold bolt and tighten jam
nut securely.
Pivot Pin
Snubber Block
Jam Nut
Stop Bolt
Adjustment 788, 789 Series
NOTE: Left hand spring balance shown.
NOTE: The worm gear adjustment mechanism provides signicant mechanical advantage during adjustment.
Under high load conditions (790) it is recommended that the loading arm be raised to approximately 45° above horizontal.
Under low load conditions it is possible to adjust the spring torque without raising/supporting the loading arm.
For more lifting action increase torque.
For less lifting action decrease torque.
1. Raise loading arm to highest position and secure.
2. Hold Adjusting Nut of Spring Regulator [2] with
a large wrench.
3. Loosen lower Bolt of Spring Keeper and remove upper one.
Using a large screwdriver push Spring Keeper forward.
With Spring Keeper disengaged turn Spring Regulator
Adjusting Nut clockwise for more or counter clockwise
for less torque.
4. With spring tension in desired position press Spring Keeper
back into position on Spring Regulator. While holding Spring
Regulator Adjusting Nut, tighten Spring Keeper Bolts [3].
Be sure Lock Washers [4] are in place.
5. Minor adjustment can be achieved by turning the Spring
Keeper ½ position. This is done by removing the 2 Keeper
Bolts [3] and turning the Spring Keeper end for end, so that
the “teeth” of the Spring Keeper will be reversed.
Spring Keeper Bolts
788, 789 Series
Spring Keeper
788, 789 Series

PHONE: [phone] • [phone] • Fax: [phone] • [phone]
2726 Henkle Drive • Lebanon, OH 45036 • www.opw-es.com
Manual - Loading Arm
April 2011 788, 789 Series Counterbalance
No. Part
1 Torsion Spring
2Spring Regulator
3 Bolt
4 Lock Washer
5 Spring Keeper
6Spring Arm
7Lever
8 E-ring
9 Pin
10 Support Bracket
11 Bearing Flange
12 Side Support
No. Part
13 Snubber Block
14 Lock Washer
15 Bolt
16 Bolt
17 Nut
18 Screw
19 Cover (NOT SHOWN)
20 Spring Compression
21 Snubber Retainer
22 Snubber Plunger
23 E-ring
24 Pin
34 5
7
8
9
10
23
16
17
24
1231
2
6
3
11
13
14
15
18
19202122
Maintenance 788, 789, 790 Series
Lubrication The torsion balance is provided with a self-lubricating Cylindrical Bearing. Only when operating under
severe conditions, a little oil may be applied to Bearing [7]. Pins [13] on Spring Arm [23] and Link Arm [9]
should have some oil quarterly.
Safety
Danger! Before performing any maintenance, always secure the Loading Arm and remove
all tension from the counterbalance -- a torsion spring. The Loading Arm counterbalance
spring contains a substantial amount of stored energy. You must relieve this energy before
any disassembly. Failure to remove all tension from the counterbalance spring of the
Loading Arm before maintenance may cause serious personal injury or death.
WARNING! While installing and using the Loading Arm, always wear adequate personal
protection, including hard hats, gloves, and steel-toed work boots. Failure to wear
adequate personal protection may cause serious personal injury or death.
WARNING! Always follow the procedures prescribed in this Document. Failing to follow
the procedures prescribed may damage the Loading Arm and cause serious personal
injury or death. Consult Loading Arm Installation, Maintenance & Safety Manual for
more details.
Parts List: 788, 789 Series Counterbalance