Electrical terminal blocks

A terminal block is secured in position in an opening in a sheet-metal panel, with terminal screws extending at a small angle to the panel. Screw-driver thrust against the screws is resisted by engagement of the body of the terminal block against an edge of the opening. Resilient detents for holding the terminal block assembled to the panel are at the sides of the terminal block and are not affected by screw-driver thrust. The terminal block is locked to the panel along one edge of the opening by hooks extending from barriers between the circuit connectors. A circuit coding strip is carried by these hooks, useful in preliminary wiring and after the block is mounted on the panel. One illustrative terminal block has plug-in contacts that are engaged by companion plug-in contacts of a plug-in unit. The body of the plug-in unit cooperates with detent-bearing portions of the stationary terminal block so as to block releasing deflection of the detents preliminary to engagement of the plug-in contacts and during the forcible completion of the plug-in operation. The plug-in unit has a shouldered projection that is received between parts of the stationary terminal block to establish preliminary alignment between both sets of plug-in contacts. The projection and its shoulder are separable from and cooperate as a fulcrum with mating stationary structure in a pivotal plug-in motion of the plug-in unit. One or more tapered cavities in the plug-in unit receive a screw driver which thereafter serves as a lever extension for forcibly pivoting the plug-in unit into or out of its plugged-in condition.

FIELD OF THE INVENTION 
This invention relates to electrical terminal blocks and to companion 
plug-in units. 
BACKGROUND OF THE INVENTION 
Terminal blocks commonly have one or more circuit connectors. In case of a 
terminal block serving as a plug-in receptacle, the connector includes an 
electrical conductor having a wire-fastening terminal at one end and its 
opposite end is formed to act as a plug-in contact. Other terminal blocks 
include wire-fastening terminals at the opposite ends of a conductor. 
Commonly screws or screw-operated clamps are used as the wire fasteners. 
The present invention has various novel aspects that apply to terminal 
blocks having circuit connectors bearing two wire fasteners and to plug-in 
terminal blocks and plug-in units. This invention also has features 
applicable to plug-in connectors in particular, comprising a plug-in 
terminal block and a companion plug-in unit. 
It has been proposed that terminal blocks having terminal screws (including 
binding-head screws, clamp-actuating screws and others) should be disposed 
for easy access where a first panel supports a terminal block and another 
panel is placed opposite the first so close to allow only a small space 
between the panels. As one step in meeting this requirement of limited 
access, it has been proposed that the terminal screws should be directed 
parallel to or at a small angle to the panel that supports a terminal 
block. It has also been proposed that the terminal block should be mounted 
in an opening in the panel, arranged to make circuit connections extending 
through the panel opening. In that case, the terminal block is to have a 
shoulder engaging an edge of the panel opening, and the terminal screw (or 
a row or rows of screws) advantageously is to be arranged on an insulating 
body so that screw-driver thrust against the screw(s) is directed at least 
approximately at the shoulder that bears against the panel opening. This 
arrangement avoids imposing screw-driver thrust against the terminal block 
in a way that would stress whatever means is provided for holding the 
terminal block assembled to the panel. 
SUMMARY OF THE INVENTION 
In the novel terminal blocks described below, an insulating body is 
provided with hook means for retentive engagement with an edge of an 
opening in a panel, and the insulating body can be swung about the edge 
and against the panel. Detent means retains the body in assembly to the 
panel, especially a pair of oppositely directed resilient detents 
cooperable with the margins along side edges of the panel opening. To 
special advantage, the resilient detents extend through the panel opening, 
and are integral portions of the insulating body of the terminal block. 
The insulating body has a shoulder close to an edge of the panel opening 
opposite the edge engaged by the hook means. Terminal screws of the 
circuit connectors extend at least approximately toward one of those edges 
to provide reaction to operating thrust of a screw driver without imposing 
stress of the screw driver against the detent means. 
The hook means in the illustrative terminal block is provided by a row of 
hooks extending from barriers projecting between the circuit connectors, 
where the terminal block has a row of circuit connectors. A circuit coding 
strip has apertures receiving the hooks. The coding strip is useful to 
guide an electrician in wiring a terminal block before the block is 
mounted on a panel. The circuit coding strip is confined between the hooks 
and the panel edge when the terminal block is received in the panel 
opening and the same strip then serves as a permanent code marker for the 
circuits. 
The detents are shaped to provide locking faces to engage the panel 
surface, but the outward exposed faces of the detents slope so as to be 
cammed in the release direction when they are pressed against the edges of 
a panel opening when the terminal block is being assembled to the panel. 
At times it is important to remove the terminal block from the panel. For 
facilitating this operation, the panel in the illustrative embodiment has 
a struck-up abutment near but spaced from each detent. A screw driver can 
be pressed against the panel between such struck-up abutment and the 
nearby detent and then a twist of the screw driver will enforce releasing 
deflection of the detent so that the terminal block is freed and can be 
pushed out of the panel opening. 
In the case of plug-in connectors, there is a plug-in unit that is to 
establish firm contact with plug-in contacts of the terminal block. The 
plug-in contacts move into mutual engagement along a line or lines 
extending through the panel opening. Where firm contact pressure is 
involved there may well be substantial stress tending to dislodge the 
detent means during the plugging-in operation. The novel plug-in unit has 
a blocking portion that is disposed closely adjacent to the detent means 
before and during mutual engagement of the plug-in contacts, preventing 
release of the detent means despite potentially large forces applied to 
the plug-in contact and transmitted against the terminal block in the 
direction that would drive the terminal block out of the panel opening if 
the detent means were overpowered and released. The detent blocking means 
of the plug-in unit prevents such release of the detents. 
At one side of the insulating body of the plug-in unit in the illustrative 
embodiment of the invention described below there are two tapered cavities 
complementary to the blade of a screw driver. These cavities are formed in 
the side of the plug-in unit remote from a side where the plug-in unit has 
a separable pivot. When a screw driver is inserted into such a cavity, it 
acts as a lever extension of the plug-in unit to aid in driving the 
plug-in unit into or out of its plugged-in position. This is of special 
advantage where the enclosure in which the plug-in terminal block is 
mounted affords only limited access for applying pressure to the plug-in 
unit. The provision of plural arcuately separated cavities for a screw 
driver allows such cavities to be used successively for short operating 
strokes where the access space for the screw driver is severely 
restricted. 
As already indicated, the illustrative embodiment of the plug-in unit has 
means providing a fulcrum, and the contacts of the plug-in unit move in an 
arc in the plug-in operation. A projection on the plug-in unit, and an 
adjoining shoulder, provide a guide establishing radial alignment of the 
moving plug-in contacts with the plug-in contacts of the stationary 
terminal block. The edge of the panel opening provides a pivotal axis 
although (at the expense of complicating the connector) the pivotal axis 
could be formed as part of the terminal block. Cooperating parts of the 
plug-in unit and the terminal block provide for preliminary lateral 
alignment of the plug-in contacts. In the illustrative embodiment, the 
same structure that arrests the detents of the stationary terminal block 
against release is utilized as this lateral alignment means. Moreover, 
there are insulating barriers on the plug-in terminal block and on the 
plug-in unit that separate the plug-in contacts of each circuit connector 
from its neighbors, and the lateral alignment means facilitates meshed 
assembly of those insulating barriers. 
A further novel feature of the illustrative plug-in unit promotes easy 
wiring. The circuit wires extend from an enclosure in which the plug-in 
terminal block is mounted. Taking advantage of the ready availability of a 
sheet-metal edge on or near such enclosure, the plug-in unit has a 
relatively narrow and deep groove extending into the insulating body at 
the side thereof remote from the terminal screws and parallel to the row 
of screws. The terminal block then can be supported on the edge of an 
available sheet-metal part during wiring of the plug-in unit. 
The various novel features of the invention outlined above are embodied in 
the illustrative plug-in connector shown in the accompanying drawings and 
described in detail below. Certain of the novel features may well be used 
without others, and they may be adapted to other forms of wiring devices 
without departing from the spirit of the invention. The nature of the 
invention including its various novel features and their advantages will 
be better understood from the following detailed description of the 
illustrative embodiment.

Referring now to the drawings, the illustrative plug-in terminal block 20 
appears separately in FIGS. 1, 3 and 12, and this plug-in terminal block 
is shown assembled to a sheet-metal panel 22 in FIGS. 2, 4, 5, 11, 13 and 
14. The companion illustrative plug-in unit 24 appears separately in FIGS. 
6, 7, 8 and 9, and it appears in phantom lines in FIG. 11. Both the 
terminal block 20 and the plug-in unit 24 appear in plugged-in assembly in 
FIGS. 10 and 14 as a connector, together with sheet-metal panel 22. In 
FIG. 10, sheet-metal panels 24 and 25 form part of a sheet-metal enclosure 
containing electrical apparatus (not shown) that is to be wired. The 
connector provides a means for making readily separable connections for 
multiple wires, either between different parts of the contained electrical 
apparatus or between the contained electrical apparatus and external 
circuits. 
As seen in FIG. 10, the parts 20 and 24 of the connector have wire 
fasteners that include screws 26 and 28, respectively. Each of the axes of 
the screws 26 of terminal block 20 extends at a small angle to panel 22, 
and therefore these screws are accessible for operation by a screw driver 
if it should become necessary to tighten or release an inserted wire, 
where the screw driver is directed downward in FIG. 10 at a small angle to 
panel 22. Panel 22 and other parts of the enclosure inhibit convenient 
access to wire-securing screws from other angles. Thus, the enclosure 
would prevent easy access to the wire-securing screws of a more 
conventional terminal block having wire-securing screws extending 
perpendicular to panel 22. No broad novelty is claimed for terminal blocks 
having such angled wire-securing screws for promoting easy operating 
access. 
As seen in FIGS. 1, 3 and 10, plug-in terminal block 20 includes a body 30 
of molded insulation such as nylon, supporting and containing conductors 
32 each shaped at one end to provide a female plug-in contact 32b. Screw 
26 is threaded into the top wall of a rectangular clamp 34 for each 
conductor 32. A wire, or occasionally plural wires, can be inserted 
between terminal portion 32a of conductor 32 and wall 34a of the clamp, to 
be gripped securely upon tightening of screw 26. Screw fastener 26, 34 and 
contact 32a for making one circuit connection and conductor 32 b for 
making another circuit connection and conductor 32 are here collectively 
called "a circuit connector", being all the parts for making one circuit 
connection. Thus, in FIG. 1 terminal block 20 has seven "circuit 
connectors". 
The clamp form of fastener for a wire is illustrative. As one other 
alternative, a simple wire-binding screw may be used, where the screw-head 
tightens to wire against the conductor (32). Moreover, in practice the 
terminal block itself takes the form of a complete connector in another 
application of certain aspects of the invention, omitting plug-in unit 24. 
For example (FIG. 16), two clamps 34' and clamp operating screws 26' or 
other wire fasteners may be provided at the ends of a conductor 32' 
(retaining parts 42, 46, etc.) as a circuit connector for joining two 
wires. 
Plug-in terminal block 20 is formed to include surfaces 36 and shoulders 
38, for engaging the face and the edge, respectively, of panel 22, at an 
opening proportioned to admit the terminal block. As seen in FIG. 2, 
shoulders 38 rest against one edge 22a of a rectangular opening in panel 
22. 
Conductors 32 are suitably supported in respective cavities in body 30, 
formed in part by barriers 40. These barriers have projecting hooks 42. 
Each end wall 44 of body 30 together with the adjacent barrier 40 are 
unified at their upper edges where there is a wider hook 42a. Each wall 44 
and the adjacent barrier are also unified at their rear edges as parts of 
body 30. End walls 44 are resilient and bear respective ribs 46. Each rib 
has a shoulder 46a (FIG. 12) that is to bear against a sheet-metal panel. 
The opposite or outer surfaces of ribs 46 slope in relation to the plane 
defined by abutment surfaces 36 and abutment portions 52 of body 30 (FIG. 
4) behind hooks 42. The angle of the sloping surfaces, about 45.degree. in 
an example, is made suitable for the sloping surface to act as a cam in 
cooperating with the lateral edge of a panel opening, to flex end walls 44 
inward when body 30 is being forced into full assembly with a panel 
opening. End wall and rib 46 form a resilient detent for holding block 30 
in the panel opening, so that block 30 has a pair of oppositely directed 
detents. These detents extend along sides of block 30 and are essentially 
unaffected by thrust applied to screws 26. 
Body 30 of terminal block 20 is mounted on a panel 22 in the following 
manner. Hooks 42 are inserted in the panel opening and engaged over edge 
22b of the panel, and then body 30 is swung about edge 22b until the outer 
cam surfaces of ribs 46 bear against edges of the panel. Applying firm 
force against body 30 forces end walls 44 to flex inward, so that ribs 46 
snap over the lateral edges of the panel opening. At this point, shoulders 
38 are closely adjacent the bottom edge 22a of the panel opening so as to 
restrain body 30 against shifting downward, and surfaces 36 confront the 
rear of the panel. Portion 52 of body 30 (FIG. 12) opposite hooks 42 
limits forward shift of body 30 into the panel opening. 
Hooks 42 and ribs 46 retain body 30 in assembly to panel 22. Shoulders 38 
are well suited to resist or provide reaction to thrust applied to screws 
26 when tightening or loosening those screws. Little if any of this thrust 
is imposed against hooks 42 and detents 44, 46. 
Panel 22 has lanced-out abutments 22c adjacent ribs 46, for facilitating 
removal of terminal block 20 from panel 22. A screw driver can be applied 
to the face of panel 22 between rib 46 and abutment 22c (FIG. 13); and 
when the screw driver is twisted, rib 46 on flexible wall 44 is forced to 
clear the lateral edge 22d of the panel opening. Slight rearward pressure 
swings body 30 about hooks 42 and frees the body for removal from the 
panel. 
As shown in FIG. 1, a circuit coding strip 48 as of flexible plastic has a 
series of openings that receive hooks 42 and tightly admit the necks 50 
under the hooks 42. Coding strip 48 has a series of circuit labels "P-1", 
"P-2", etc. aligned with the respective circuit connectors, each 
comprising a conductor 32, its plug-in contact 32b, and its wire fastener 
consisting of wire-securing screw 26 and clamp 34. Before terminal block 
20 is mounted on panel 22, it is advantageous to apply strip 48 to the 
terminal block, and to wire the terminal block. Then strip 48 may be 
removed, using some force where the fit is tight. Terminal block 20 is 
forcibly inserted into the panel opening and locked in place by ribs 46 
snapping over lateral edges 22d of the panel opening. There is clearance 
between hooks 42 and the opposed abutment portion 52 of body 30, enough 
clearance to enable strip 48 to be slipped forcibly over hooks 42 and onto 
necks 50, as shown in FIG. 4. In that condition the label strip is flexed 
by enforced positioning of its upper half between panel 22 and hooks 42 
while its lower half is forced outward by engaging a sloping portion 54 of 
each barrier 40 below each hook 42. The enforced flexed condition of strip 
48 supplements the action of hooks 42 in securely retaining label strips 
48 in position. Label strips 48 can thus serve for circuit identification 
both before and after the terminal block has been mounted on a panel. 
As an alternative to the label mounting configuration of FIG. 4, it is seen 
in FIG. 5 that label strip 48 need not be removed from the terminal block 
after being used in wiring the terminal block. With the circuit coding 
strip 48 on body 30 as shown in FIG. 1, the upper half of strip 48 can be 
tucked behind panel 22 as hooks 42 are engaged in front of the panel. 
While part of the coding strip is concealed in this arrangement, that 
would be of no consequence where the strip has sufficient area exposed 
through the panel opening for the required circuit designations. 
As noted above, terminal block 20 may be modified by adding a second 
wire-securing device such as a screw and clamp to each wire securing 
device 26, 34 shown, correspondingly, omitting plug-in contact 32b. Such 
added screw and clamp are shown in FIG. 16, where screws 26' and clamps 
34' cooperate with conductor 32'. Screws 26' are all exposed for operation 
from above. The stress developed against body 30 when any of the screws is 
operated (both as to the plug-in terminal block and the modification) is 
directed toward the lower edge 22a of the panel opening; and in that case, 
locking ribs 46 are largely or wholly immune to such stresses, and remain 
fully effective to hold body 30 in its installed position in the panel 
opening. Should it become necessary to remove terminal block 20 (or the 
modification of FIG. 16) a screw driver is applied to panel 22 between rib 
46 and the adjacent abutment 22c (FIG. 13) and the screw driver is 
twisted, thereby flexing the wall 44 that supports rib 46, enabling each 
end of body 30 to be pushed out of the panel opening. 
FIGS. 6-9 show an illustrative plug-in unit 24 that mates with plug-in 
terminal block 20. Each male plug-in contact 54a is disposed between a 
pair of barriers or insulating walls 56 (see especially FIG. 6) projecting 
integrally from body 58 of insulation such as nylon. Spaces 60 are 
provided between successive pairs of barriers 56. Contacts 54a are 
distributed at positions to be aligned with contacts 32 of the terminal 
block 20, and spaces 60 are distributed at positions to receive barriers 
40 of terminal block 20. Wire-securing screws 62 may be threaded into 
conductors 54, or wire-securing clamps 64 may be operated by screws 28 to 
tighten an inserted wire against respective conductors 54. Each wire 
fastener and the conductor that provides plug-in contact 54 form a circuit 
connector of the plug-in unit. 
Block or body 58 has a series of projections 66 and an adjoining shoulder 
68. The lateral extent of projections 66 (collectively) is such as to fit 
the space 70 (FIGS. 1 and 2) between portions of body 30 which bear 
surfaces 36 and 38. When projections 66 are inserted into space 70 of a 
terminal block 20 on a panel 22, shoulder 68 rests on the same lower edge 
22a of the panel opening that abuts terminal block shoulders 38. In this 
condition, barriers 40 of the terminal block are aligned with spaces 60 
between pairs of barriers of the plug-in unit, each male contact 54a is 
aligned laterally and arcuately with a respective female contact 32, and 
ribs 71 at the ends of body 58 are disposed closely adjacent the inside 
surfaces of end walls 44 of the terminal block. At this point, and before 
any arcuate plugging-in motion (see FIGS. 11 and 14), end walls 44 are 
blocked against any such inward flexing movement as might release ribs 46 
from their locking contact with panel 22. Consequently, when the male 
plug-in contacts 54a subsequently are driven forcibly into tightly 
gripping female contacts 32b, that force cannot dislodge the terminal 
block from the panel. 
Counterclockwise pivoting of unit 24 is complete when the parts are related 
as shown in FIG. 10. A substantial effort may be needed to enforce this 
operation, particularly when there is firm contact pressure between the 
plug-in contacts, where the contacts are large, and where there are many 
pairs of plug-in contacts. The space or access for a person's hands to 
apply plugging-in pressure may be restricted, as by a frame F and by a 
panel 26 close to panel 22. Body 58 is here formed with a pair of sockets 
72 at different arcuate locations in relation to the arcuate fulcrum 
defined at the junction of projections 66 and shoulder 68. One of these 
sockets can be engaged by a screw driver and operated through an angle in 
the direction of the broken-line arrow in FIG. 10, for easily achieving 
the plug-in operation. Both sockets may be used in succession where the 
operating angle of the screw driver is small, as limited by close spacing 
of panels 22 and 26. The same sockets and screw driver are effective in 
easily extracting the plug-in unit from its plugged-in condition shown in 
FIG. 10, by operating screw driver S in the direction represented by the 
solid line arrow. 
Individual screws may be forcibly turned for tightening or releasing a wire 
of plug-in unit 24 in its plugged-in condition. However, it is more 
practical to wire the whole unit before it is plugged in. A slot 74 (FIG. 
8) is formed in body 58, parallel to the row of screws and opening in the 
direction opposite to the exposure of the screw heads so that an 
electrician who is to wire the unit can support unit 24 on an edge of any 
available panel P, which enters slot 74. Such a panel is commonly at hand 
in situations where such connectors are to be installed. Panel P in slot 
74 resists tilting of unit 24, and since the plane of panel P includes a 
line perpendicular to (if off-set from) the screw axes, it resists the 
tendency of the plug-in unit to turn when screws 28 and 62 are tightened. 
Slot 74 thus provides an important adjunct of the plug-in unit, greatly 
facilitating the wiring operation. 
The plug-in terminal block and plug-in unit of FIGS. 1-14 incorporate 
various distinctive features, some of which may be used without others and 
some of which may be modified. For example, what may be called a 
"fixed-circuit" terminal block (for want of a better term) as shown in 
FIG. 16 and described above retains some of the novel features found in 
the plug-in terminal block 22. Further, while certain advantages of the 
terminal block and plug-in unit relate to screw-type wire fasteners, 
screw-less fasteners for bare wires or for wires with fittings such as 
spring clips have their usefulness with many of the disclosed novel 
features not related to the use of screws. In addition, while it has been 
indicated that the plug-in unit cooperates with an edge 22a of the panel 
opening as a fulcrum, that fulcrum could be incorporated in the terminal 
block as shown in FIG. 15. In the form shown there, insulating body 30' 
includes a transverse bar 30a carried at its end by transverse walls and 
separated by a slot from wall 30b. Projections 66 of the plug-in unit and 
the adjoining shoulder 68 cooperate pivotally with bar 30a during a 
plug-in operation. Bar 30a forming part of a modified terminal block 20' 
thus replaces edge 22a of the panel opening as the pivotal fulcrum. 
The dimension of plug-in unit 24 between shoulder 68 and the uppermost end 
of insulating block 58 may be made small, as shown, and yet a large amount 
of leverage is developed by screw driver S (FIG. 10) when plug-in and 
removal effort is to be applied to unit 24. If only a few contacts 54a 
were involved, or if the contacts were small so as to offer little 
mechanical resistance to applied plug-in effort, it would not be important 
to use screw-driver S (FIG. 10) for added leverage. If only a modest 
amount of added leverage were desired (additional to that developed by 
pushing directly against block 58) then block 58 could be formed with a 
short integral lever extension replacing the separable lever extension 
represented by screw-driver S. 
The foregoing and other variations in the plug-in connectors described in 
detail above are contemplated modifications. Still others will be obvious 
to those skilled in the art. Consequently, the invention should be given 
broad construction, in accordance with its full spirit and scope.