Detachable insulating cover assembly for greenhouses and the like

A detachable insulating cover assembly for greenhouses and similar structures using plastic cover sheets for the creation of a stationary air layer, the sheets being held in place by manually clampable and releasable fastener assemblies, each consisting of a fastener base with a stem and a fastener cap, the fastener bases being detachably clampable to the base flange of T-bars which form the skeleton of the greenhouse, using transversely movable attachment members with retaining noses that reach behind the edges of the T-bar base flange in the clamped position. Several variants of attachment members are disclosed.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to flexible insulating cover structures, and, 
more particularly, to a detachable insulating cover assembly which is 
adapted for use in connection with greenhouses and similar structures, 
having large surfaces which are to be covered with removable low cost 
insulating sheets, in order to reduce convective heat loss to the outside 
of the structure. 
2. Description of the Prior Art 
It is known that convective heat loss through the walls of a structure, 
especially a light structure such as a greenhouse, can be greatly reduced 
through the attachment of inexpensive insulating cover sheets of 
transparent plastic material to the inside of the walls. Comparative 
measurements have revealed energy savings of up to 40 percent. 
Particularly advantageous for this purpose are so-called bubble sheets 
which consist of two layers of thin plastic film which enclose between 
them rows of small air cushions. 
In one known application, large surfaces of bubble sheet are simply being 
bolted to the structural members of a greenhouse, using screws and 
hold-down washers (as described in the periodical "Zierpflanzenbau", Issue 
No. 9, Apr. 28, 1976, pp. 315-318). 
In my copending U.S. patent application, Ser. No. 835,540, of Sept. 22, 
1977, now U.S. Pat. No. 4,174,596 I have disclosed a detachable insulating 
cover assembly for greenhouses and the like which features a cover sheet 
of flexible air-impermeable plastic material which is attached to a wall 
element of the greenhouse by means of a plurality of spaced fastener 
assemblies which are arranged along a clamping line near the edge of the 
sheet, a typical fastener assembly consisting of a fastener base which is 
permanently attached to the wall element, which is a structural member or 
a glass panel, for example, and a fastener cap which, when attached to the 
fastener base, clamps the cover sheet to the latter. For this purpose, 
each fastener base has a pointed stem over which the cover sheet is 
impaled, prior to attachment of the fastener cap. The edges of each cover 
sheet are sealed against the greenhouse structure, so that a closed air 
space is obtained which contains stationary air which serve as an 
effective barrier to convective heat transfer. 
The cover sheets are removable from the greenhouse structure by releasing 
the fastener caps and by pulling the cover sheet from the stems of the 
fastener assemblies. However, the fastener bases remain in place, glued to 
the inside of the window panels. 
It has now been found that there are situations, where it is desirable to 
attach the fastener assemblies to the structural skeleton of the 
greenhouse in such a way that the fastener bases are likewise removable 
from the structure. Such an arrangement has to take into consideration the 
fact that greenhouses of different age, with different structural 
components, have to be so equipped. For example, in older greenhouses, the 
glass panels are in most cases held in place by means of sealing putty, 
their back side being located very closely to the supporting faces of the 
skeleton members. The latter are in most cases T-bars, the upstanding 
central web of the T-bar being located between the edges of two adjacent 
glass panels. Adding to the problem of limited space between the flange 
portions of the T-bar and the back sides of the glass panels is the 
problem of the presence of hardened putty in that space, so that, in the 
past, there existed a general reluctance towards attempts to find a 
solution to this problem, especially in view of the fact that the 
temporary attachment of fastener assemblies to a structural member had to 
be accomplished without drilling holes into the structural member. 
One prior art attempt at attaching insulating cover sheets to structural 
members of a greenhouse involves the use of U-shaped leaf-spring clamps 
which open to the width of the structural member, and then clamp the 
lateral side faces of the latter, when released. This type of clamp is 
basically identical with the binder clip, an item of office hardward which 
is primarily used as a temporary clamp for a stack of loose-leaves, or the 
like. One disadvantage of this type of clamp is that it is generally not 
suitable for regular T-bars, but that it requires special structural 
profiles with much larger lateral surfaces, in order to provide a reliable 
sheet clamping action against these surfaces. (The use of such spring 
clamps has been suggested by Sibco Universal S.A., 92081 Paris, La 
Defense.) 
Another attempt at a solution to this problem is disclosed in German 
Gebrauchsmuster (Utility Model) No. 78 02 785, which suggests a fastener 
base in the form of a one-piece, twice refolded leaf spring with claw-like 
extremities which reach around the longitudinal edges of the T-bar, 
thereby attaching the clamp to the structural member. To the top portion 
of the leaf spring is attached a stem for the attachment of a fastener 
cap. This proposed clamp has the disadvantage of requiring a special tool 
for its installation and removal. It also presents a problem with respect 
to the stability of attachment. 
SUMMARY OF THE INVENTION 
Underlying the present invention is the primary objective of providing an 
improved solution to the earlier-mentioned problem of attaching fastener 
assemblies to the back side of a T-bar of a greenhouse structure, with the 
requirement that the fastener assembly be easy to attach and remove and 
mass-produceable at low cost. 
The present invention proposes to attain this objective by suggesting an 
insulating cover assembly which is similar to that which is disclosed in 
my above-mentioned earlier patent, but which has fastener assemblies whose 
fastener bases are removably clampable to the T-bar and fastener caps 
which are insertable over the stems of the fastener bases, in order to 
clamp the cover sheet between them. 
In a preferred embodiment of the invention, the fastener base is attached 
to the T-bar of the greenhouse skeleton by means of two attachment members 
which are movable relative to one another, so as to place bent-over 
retaining noses on the outer edge of each attachment member behind the 
longitudinal edges of the flange portions of the T-bar. In this engaged 
position, the two attachment members are locked against each other by the 
frictional action of a wedge-type interaction and/or by the clamping 
action of the fastener base, when the latter is screwed onto an upstanding 
stem stud which is carried by one of the attachment members. 
Several modifications of this preferred embodiment are proposed, using 
either symmetrically arranged, substantially identical attachment members 
which place the fastener assembly in the middle of the T-bar profile, or 
unequal laterally offset attachment members which place the fastener 
assembly above or near a longitudinal edge of the T-bar. The two 
attachment members may be sheet metal stampings, overlapping each other, 
or they may be injection-molded plastic parts which cooperate in the 
clamped position with a snap-type elastic engagement. It is further 
possible to arrange the two attachment members so that they produce a 
wedging action against each other in the clamped position, or that they 
maintain their clamped position by means of barbs. 
Still another embodiment of the invention suggests a toggle-action lock 
between the two attachment members, for greater ease in manual placement 
and removal of the fastener assembly. Furthermore, it is also possible to 
arrange the attachment members in such a way that one of the two members 
is a leaf spring which bridges the back of the T-bar from side to side, 
carrying attachment noses on both ends which, in the flat condition of the 
leaf spring, are spread apart and, in a convexly curved condition produced 
by the second attachment member, exert a clamping action against the edges 
of the T-bar. 
Lastly, it is also possible to provide the attachment of the fastener base 
by means of a single attachment member which can be clamped against the 
edges of the T-bar with an angular motion which brings two diametrically 
opposed retaining noses of the member into clamping engagement behind the 
edges of the T-bar, a pair of flexible positioning fingers retaining the 
attachment member in its clamped position. For removal, the positioning 
fingers are lifted, so that the attachment member can be rotated out of 
its clamping position. 
In a majority of the aforementioned embodiments of the invention, the 
fastener base is connected to the attachment members, after the latter are 
clamped in place, whereby the fastener base also serves to secure the 
attachment members in their clamped position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
For a complete description of the present invention, to the extent that it 
is not given hereinbelow, reference is made to my copending U.S. patent 
application Ser. No. 835,540 of Sept. 22, 1977, which is now U.S. Pat. No. 
4,174,596. The descriptive portion of this patent should be considered 
incorporated herein by reference. 
The various clamping devices which are illustrated in FIGS. 1 through 29 
concern themselves with the removable attachment of a fastener assembly to 
a structural member of a building, more particularly of a greenhouse. 
Commonly, the skeleton members of such a greenhouse are T-bars, as shown 
in FIG. 1, which hold the edges of adjoining glass panels by means of 
putty or special rubber profiles and retaining clips riding on the web 
portion of the T-bars. 
For each fastener assembly, i.e. at each point where the cover sheet is 
attached to the T-bar 16, there is provided a set of attachment members, 
in most cases two members which cooperate to create a clamping engagement 
with the flat base flange to the T-bar 16. The various figures of the 
drawings show different versions of attachment members, all having the 
same purpose. 
Similar or analogous parts in the various embodiments are therefore 
designated with the same reference numerals, each embodiment having a 
different letter suffix. Accordingly, the embodiment of FIGS. 1 and 2 uses 
the letter a, the embodiment of FIGS. 1a through 1d uses the letter b, and 
the embodiment of FIGS. 2 and 3 uses the letter c, etc. 
A typical set of attachment members consists of a base carrying member 10 
to which the fastener base 18 is attached, or attachable, and a clamping 
member 13 which cooperates with the base carrying member 10. The two 
attachment members 10 and 13 have retaining noses 12 and 14 at their 
extremities. The retaining noses 12 and 14 extend rearwardly and inwardly, 
so as to grip the edge portions of the base flange of the T-bar 16 from 
behind in a releasable clamping action. The noses 12 and 14 are pointed, 
so that they can penetrate any putty or other sealant that may be in the 
gap between the base flange of the T-bar 16 and the glass panel 17. In 
each case, the attachment members are moved relative to each other in a 
direction which is substantially parallel to the forwardly facing mounting 
surface 45 of the T-bar 16. 
In FIG. 1 of the drawing, the attachment members consist of two stampings 
which are similar in shape, each having a rectangular outline with a 
bent-over edge portion carrying two retaining noses 12a and 14a, 
respectively. While the clamping member 13a has a central slot 15a, the 
base carrying member 10a has attached to it a stem stud 11a which engages 
the slot 15a, when the two attachment members 10a and 13a are mounted on 
the T-bar 16. The mounting of the attachment members involves placement of 
the members in an overlapping relationship against the mounting surface 45 
of the T-bar, followed by a lateral closing movement in the direction of 
arrow A, until both members abut against the lateral edges of the T-bar 
base flange. In this position, a fastener base 18a is screwed onto the 
stem stud 11a, with the result that the base flange 30 of the fastener 
base exerts a clamping action against the clamping member 13a, thereby 
holding the attachment members in their clamped position. The stem 111a of 
the fastener assembly may be of the elevated type, having a separated 
clamping flange 28 which is spaced from the base flange 30 by means of 
longitudinal connecting ribs 29, or the clamping flange 28 may also serve 
as the base flange, in which case the stem 111a itself is the part which 
carries the thread engaging the stem stud 11a. 
In the embodiment of FIGS. 1a through 1d, the two attachment members are 
likewise stampings, made from flat stock, as shown in FIG. 1a. In this 
case, however, the two members are functionally identical, in terms of 
serving as base carrying member 10b or clamping members 13b. The two 
members have matching upstanding tongue portions which, when joined 
together in the clamped position of the device, form a central stem stud 
11b over which the fastener base 18b can be forcibly inserted. Once 
inserted over the stem stud 11b, the fastener base 18b is held in place, 
thanks to an outwardly kinked outline of the tongue portions which 
constitute the stem stud 11b. The bore in the fastener base 18b may be 
cylindrical or tapered. 
The embodiment which is shown in FIGS. 2 and 3 is very similar to that of 
FIG. 1, except for the fact that the stem stud 11c is located laterally 
outside the area of the base flange of the T-bar 16. For this purpose, the 
clamping member 13c is elongated to reach a distance beyond the width of 
the mounting surface 45 of the T-bar, and the cooperating base carrying 
member 10c is located in its entirety on one side of the T-bar 16. Its 
stem stud 11c reaches through an open slot 15c of the clamping member 13c. 
This configuration also allows for a modified version in which the stem 
stud is replaced by a regular screw which may or may not be rotationally 
attached to the base carrying member 10c. 
In the embodiment of FIGS. 4 and 5, the two attachment members are 
injection-molded parts, the stem 111d being an integral part of the base 
carrying member 10d and serving at the same time as a clamping and 
retaining element in cooperation with the clamping member 13d. For this 
purpose, the latter reaches again sideways beyond the width of the 
mounting surface 45 of the T-bar 16, having in its protruding extremity an 
open slot 15d which cooperates with the diameter of the stem 111d in such 
a way that an interference-type clamping fit is obtained. A retaining lip 
14d of the clamping member 13d and a similar retaining lip 12d of the base 
carrying member 10d reach behind the lateral edges of the T-bar 16, into 
the gap 50 which is formed by the sealing element 27 taking the place of 
the putty. The base carrying member 10d, instead of carrying the stem 
111d, may also carry a stem stud 11d over which a hollow fastener base 
with a separate stem is then inserted. The clamping engagement between the 
slot 15d of the clamping member 13d and the stem 111d can be further 
improved by providing a slightly tapered bottom portion of the stem 111d 
which, when the clamping member 13d is lifted, is disengaged from its slot 
15d, thereby facilitating the transverse approaching movement of the 
attachment members. 
The embodiment of FIGS. 6 and 7 resembles that of FIGS. 4 and 5, inasmuch 
as injection-molded parts are used, but it differs therefrom by suggesting 
an engagement between the base carrying member 10e and the clamping member 
13e which is provided outside the stem 111e. This clamping engagement is 
in the form of a transverse slot 15e in the clamping member 13e and a 
matching extension on the stem carrying member 10e. Serrated surfaces on 
the slot and extension provide a frictional engagement between the 
attachment members. 
In FIGS. 8 and 9, the clamping member 13f is provided with a tapered slot 
15f which is open in the longitudinal direction of the T-bar 16, 
cooperating with the stem 111f of the base carrying member 10f in such a 
way that a longitudinal displacement of the latter produces a transverse 
approaching movement between the attachment members, as the stem 111f 
slides along the cam surface 21 of the slot 15f. The inclination of the 
cam surface 21 with respect to the longitudinal axis a--a of the T-bar is 
such that a self-locking wedging action is obtained between the attachment 
members 10f and 13f. A washer 33 placed over the stem 111f serves as a 
support for the cover sheet (not shown). Again, the stem 111f may also be 
a stem stud 11f to which a separate fastener base with a hollow stem is 
attached. 
The embodiment of FIGS. 10 through 14 shows attachment members which are in 
the form of metal stampings. However, unlike the previously described 
stamped attachment members which overlap each other, the base carrying 
member 10g and the clamping member 13g of this embodiment are arranged to 
be mounted on edge, so as to form a frame-like assembly in the clamped 
position. FIG. 14 shows the base carrying member 10g in a developed 
outline which illustrates how the retaining nose 12g and a stud-carrying 
lug are produced as integral portions of the stamping. Rows of openings 54 
in the leg portions of the clamping member 13g and cooperating barb-like 
tongues 53 on the insides of the base carrying member 10g provide a secure 
engagement between the attachment members in the clamped position. 
The embodiments of FIGS. 15 and 16 resembles that of FIGS. 8 and 9, 
inasmuch as the clamping approach between the base carrying member 10h and 
the clamping member 13h is in the longitudinal sense of the T-bar 16, 
whereby cooperating inclined cam surfaces 19 and 20 of the two attachment 
members produce a transverse approaching motion of the retaining noses 12h 
and 14h of the members behind the T-bar edges. The stem 111h is an 
integral part of the base carrying member 10h, a fastener cap being shown 
attached thereto and clamping the cover sheet 25 between it and the base 
carrying member 10h (FIG. 16). 
FIG. 17 shows a modification of the embodiment of FIGS. 15 and 16, the two 
attachment members 10i and 13i being in the form of sheet metal stampings, 
rather than injection-molded plastic parts. The cam surfaces 19i and 20i 
are formed by upended edge portions of the two attachment members 10i and 
13i. 
In the embodiment of FIGS. 18 and 19, a central base carrying member 10k 
cooperates with two clamping members 13k, serving as a cam lock between 
the latter. For this purpose, the two clamping members 13k have oppositely 
inclined slots 15k which present cam surfaces to the stem stud 11k of the 
base carrying member 10k. The latter, when advanced in the longitudinal 
sense of the T-bar 16, thus pulls the two clamping members 13k 
transversely against each other, so that their retaining noses 14k move 
behind the edges of the T-bar 16. In the clamped position, a fastener base 
18k with a stem 111k is attached to the stem stud 11k, thereby securing 
the attachment members in their clamped position. 
In FIGS. 20 and 21 is shown an embodiment of the invention which features 
two attachment members which are interconnected by means of a toggle 
linkage. The latter consists of a toggle arm 35 which engages a pivot loop 
23 on the extremity of the base carrying member 10m and two pivot loops 
123 of the base clamping member 13m. A pivoting motion of the toggle arm 
35 about its pivot center at 23 creates a lateral movement of the clamping 
member 13m relative to the base carrying member 10m and the T-bar 16, so 
that, in the open position of the lock, the retaining noses 14m and 12m of 
the attachment members are freely engageable over the edges of the T-bar 
16. By then lowering the toggle arm 35 against the base carrying member 
10m, a lateral clamping action between the attachment members is achieved. 
In this position, the toggle linkage is self-locking. This clamped 
position is further secured by the fastener base which is inserted over 
the stem stud 11m, following flattening of the toggle linkage. 
FIGS. 22 through 24 show an embodiment in which the clamping member 13n 
reaches over the entire width of the T-bar 16, carrying retaining noses 
14n on both extremities. In its free state, the clamping member 13n is 
long enough to permit engagement of its retaining noses 14n over the edges 
of the T-bar 16. Clamping engagement with the latter is achieved by 
bending the clamping member 13n away from the mounting surface 45 of the 
T-bar, using for this purpose the base carrying member 10n. The latter, in 
addition to having the appropriate curvature to fit under the raised 
clamping member 13n, has a wedge-shaped entry portion with which it lifts 
the clamping member 13n, when it is advanced in the direction of the axis 
a--a of the T-bar. To the extent that the stem 111n of the base carrying 
member 10n would interfere with the advancement of the latter into the 
clamping position, the clamping member 13n has a slot 15n. The clamping 
member 13n may be made of spring steel. 
In the embodiment of FIGS. 25 and 26, the clamping member 13q resembles the 
clamping member of FIG. 22, except that its slot 15q is not an open slot 
and that the clamping movement of the base carrying member 10q is 
rotational instead of linear. For this purpose, the base carrying member 
10q has provided in its body two grooves 100 which, when placed in 
alignment with the clamping member 13q, allow the latter to assume a 
near-flat condition in which its retaining noses 14q are freely engageable 
over the edges of the T-bar 16. By rotating the base carrying member 10q 
approximately 90 degrees, the clamping member 13q is raised and bent into 
a convexly curved shape, while its retaining noses 14q engage the edges of 
the T-bar 16. The base carrying member 10q carries a stem 111q, or a stem 
stud, if a separate fastener base is provided. 
In FIGS. 27 through 29 is illustrated an embodiment of the invention in 
which a rotatable base carrying member 10p carries the retaining noses 12p 
for both sides of the T-bar 16 and in which the separate clamping member 
has been omitted, its place being taken by two positioning fingers 13p 
which lock the attachment member in its clamping position, against an 
accidental release from the T-bar 16. Two transverse slots 44p give the 
positioning fingers 13p the necessary flexibility, so that they can be 
lifted, in order to disengage their locking noses 43p from the edges of 
the T-bar 16. The attachment member 10p may be a sheet metal stamping or 
an injection-molded part. As a sheet metal stamping, it offers higher 
rigidity and a superior locking action of the positioning fingers 13p. The 
two retaining noses 12p of the member 10p are in the form of bent-over 
extremities of two diametrically opposite triangular extensions of the 
stamping. In order to attach the member 10p to the T-bar 16, the member is 
simply placed against the mounting wall 45 in an orientation in which the 
retaining noses 12p barely clear the lateral edges of the T-bar 16. 
Because the locking noses 43p tend to lift the member 10p from the 
mounting surface 45, it is necessary to apply a slight pressure against 
the member 10p, while manually rotating it in a clockwise direction, until 
the retaining noses 12p are engaged behind the T-bar edges and the locking 
noses 43p of the positioning fingers snap over the T-bar edges. 
It should be understood, of course, that the foregoing disclosure describes 
only preferred embodiments of the invention and that it is intended to 
cover all changes and modifications of these examples of the invention 
which fall within the scope of the appended claims.