Dover OPW 788 Series User manual

Worm Gear Hex Drive
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790 Series Counterbalance
PART #H30790PA
790-SERIES-IOM-EN-01/2021
NOTE: Prior to any loading arm disassembly, spring tension should be
completely relieved. Tip: To relieve tension, arm should be pushed up as
much as possible and supported while spring tension is relieved. Spring
coil will be loose in housing when completely relieved of tension.
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
Specifications
Type: Right-Hand: 790A-0020 (White),
790B-0030 (Yellow), 790C-0050 (Red)
Left-Hand: 790ALH-0025 (Black),
790BLH-0035 (Gray), 790CLH-0045 (Orange)
Working Temperature Range:
-40°F to 176°F (-40°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).
Easy-To-Use
Spring Cover Latch

Index Qty Part # Description
1 4 H-31396-M Spirol Pin, 1⁄4x 13⁄4
2 1 C-20185-BW Spring Regulator, R.H. Worm Gear
3 1 H-30744-M Dowel Pin .25 x 1.25
4 2 H-01490-M Flange, Bearing, BRZ. 11⁄2" DIA x 11⁄4" LG
5 2 H-32283-M Retaining Ring, CST ZP
6 2 H-32282-M Bearing, Cylindrical, Bronze
7 1 H-30743-M Washer, Thrust, ZP, 7⁄8"
8 1 C-20184-EW Drive Worm, Torsion Spring
9 2 H-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 2 H-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 2 H-02507-M Lockwasher, CP, 5⁄8"
20 2 H-05910-M Screw, Hex Cap, CST, ZP, 5⁄8"-11 x 13⁄4"
21 1 E20181 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
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Parts List: 790 Series Counterbalance*
*790C (Right-Hand) shown in image. Spring Coil (24) would change depending on model.
** For 790A Units, Link Arm (17) would be C00636DI.

Jam Nut
Stop Bolt
Pivot Pin
Snubber Block
788, 789 Series
Spring Keeper Bolts
Adjusting Nut
Spring Keeper
Spring Regulator
790 Series Counterbalance
Travel Stop 788, 789, 790 Series
Upward
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.
Adjustment 788, 789 Series
When to adjust torque
NOTE: Left hand spring balance shown.
NOTE: The worm gear adjustment mechanism provides significant 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.
Torque
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.
Downward
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.

34 5
7
8
9
10
23
16
17
24
1231
2
6
3
11
13
14
15
18
19202122
NOTE: All information subject to engineering and/or other changes. All trade names are copyrighted. Patents Pending. ©2021 OPW Engineered Systems
©2021 Delaware Capital Formation, Inc. All Rights Reserved. DOVER and the DOVER logo are registered trademarks of Delaware Capital Formation, Inc.,
a wholly-owned subsidiary of Dover Corporation.
www.opw-es.com
|
2726 Henkle Drive
|
Lebanon, Ohio 45036, USA
|Phone: [phone]
790 Series Counterbalance
Parts List: 788, 789 Series Counterbalance
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.
No. Part No. Part
1Torsion Spring 13 Snubber Block
2Spring Regulator 14 Lock Washer
3 Bolt 15 Bolt
4Lock Washer 16 Bolt
5Spring Keeper 17 Nut
6Spring Arm 18 Screw
7 Lever 19 Cover (NOT SHOWN)
8 E-ring 20 Spring Compression
8 Pin 21 Snubber Retainer
10 Support Bracket 22 Snubber Plunger
11 Bearing Flange 23 E-ring
12 Side Support 24 Pin
DANGER 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 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 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.