Information
-
Patent Grant
-
6645096
-
Patent Number
6,645,096
-
Date Filed
Thursday, October 24, 200222 years ago
-
Date Issued
Tuesday, November 11, 200321 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Taylor; Jay G.
- Prescott; John F.
- Miller; Ice
-
CPC
-
US Classifications
Field of Search
US
- 108 115
- 108 119
- 108 120
- 108 127
- 108 129
- 473 496
-
International Classifications
-
Abstract
A collapsible table tennis table in accordance with the present invention includes a first and second table portions pivotably attached to a rigid central support unit. The central support unit comprises two unitary curvilinear members each formed of a single piece of appropriate material such as steel tubing. The central support unit is easily assembleable using appropriately formed connecting members which are attached using wing bolts so that tools are not required for assembly. Exterior legs are pivotably attached adjacent to the exterior edges of the table members. The table portions are also pivotably attached to the respective curvilinear members so that the table portions can be pivoted from an essentially horizontal position to an essentially vertical position for storage and movement. The central support unit typically has wheels to facilitate the movement of the assembled table. The foldable table tennis table in accordance with the present invention has the advantage of being able to be packaged in a minimal profile package for shipment to the customer, and can be easily assembled by the customer by hand without the need of any tools.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a foldable table tennis table which can be folded into a compact unit for easy movement and storage and which can be shipped from the factory in a compact form in packaging with a minimum profile. The present invention can also be easily assembled by the customer by hand without the need for any tools.
2. Description of the Prior Art
Foldable table tennis tables are well known in the art. It has long been recognized that it is desirable to have a table tennis table which is foldable into a more compact, easily moved and easily stored configuration. However, prior art foldable table tennis tables have a number of deficiencies which have detracted from their desirability. Many of the prior art foldable table tennis tables have complex structure which is expensive to fabricate and difficult to assemble, particularly by a retail customer who may not have the necessary tools for proper assembly. Such prior art tables typically must be shipped in large, bulky containers which take up substantial space in storage and in transit thereby increasing the shipping costs. For example, some of the prior art foldable table tennis tables such as those disclosed in U.S. Pat. No. 3,342,149-Kruissink, U.S. Pat. No. 3,318,269-Kinn and U.S. Pat. No. 2,901,304-Fihe disclose foldable table tennis tables having a relatively complex welded wheel support unit which is both expensive to fabricate and difficult to package and ship to a customer. Additionally, prior art foldable table tennis tables of the type disclosed in U.S. Pat. No. 5,816,957-Dadbeh have a relatively complex structure with a wide wheel base which makes it more expensive to manufacture and more difficult to store in confined spaces.
Accordingly, it would be desirable to provide a collapsible table tennis table which is relatively inexpensive to fabricate, easily packaged and shipped in a compact, minimally sized package, easily assembled by the customer by hand without the need of any tools and is foldable into a relatively compact arrangement which is easily stored in a minimal amount of space.
SUMMARY OF THE PRESENT INVENTION
The present invention provides a foldable table tennis table which is capable of being fabricated without the necessity for welding or other expensive labor intensive operations, which can be boxed and shipped to the customer in a compact, minimal profile package and which can be assembled easily and quickly by the customer by hand without the need for tools. Such a table in accordance with the present invention is typically partially assembled at the factory so that the various members requiring tools for assembly are attached at the factory leaving only minimal assembly without tools by the customer. Due to the unique design, the preassembled parts are folded into a relatively flat configuration and the remaining parts are capable of being shipped in a similar flat configuration so that very compact, minimal profile packaging is required for shipment.
A foldable table tennis table in accordance with the present invention comprises first and second unitary curvilinear member formed of a single piece of material such that each has a first lower portion and a first and second upwardly extending supporting portions. The supporting portions have first and second ends with the first ends being integrally joined to the lower portion. The first and second curvilinear members are joined together by first and second connecting members connected between the first and second curvilinear members to form a rigid central support unit. An additional connecting member may be connected between the respective lower portions of the first and second curvilinear members. First and second table portions each having an upper and lower surface, a center edge and an outer edge and two opposing side edges are respectively pivotably connected to the central support unit at the second ends of the supporting portions of the first and second curvilinear members adjacent the center edge of the first and second table portions.
Thus, the first and second table portions can be pivoted from an essentially horizontal playing position where the center edges of the table portions are in close proximity to one another to an essentially vertical position for movement and storage. The present invention is designed so that the outer edges of the first and second table portions are essentially parallel and slightly closer together than the inner edges of the first and second table portions when the table portions are pivoted to their essentially vertical position so that it is less likely that the table portions will accidentally pivot back to a horizontal position during movement and storage.
The foldable table tennis table in accordance with the present invention also has at least one first and at least one second exterior leg member attached to the lower surface of the first and second table portions respectively adjacent the outer edge of the first and second table portions. The first and second exterior leg members are typically pivotably attached to the respective first and second table portions so that the exterior leg members can be folded against the lower surface of the first and second table portions respectively or pivoted until they are essentially perpendicular to the table portion. The first and second exterior leg members, when pivoted perpendicular to the table portions, contact the floor to support the first and second table portions in an essentially horizontal position. A connecting member may be pivotably connected between the first curvilinear member and the first exterior leg member, and another connection member pivotably connected between the second curvilinear member and the second exterior leg member in such a manner such as to cause the first and second leg members to be automatically pivoted against the lower surface of the respective table portions as the table portions are pivoted from the essentially horizontal position to the essentially vertical position.
The first exterior leg member may comprise first and second extensions each pivotably attached at one end to the first table portion. A detachable unitary curvilinear support member can be detachably connected to the other ends of the first and second extensions to provide a leg member that will extend and contact the floor and support the table portions in an essentially horizontal position. The unitary curvilinear support member may be detached to facilitate shipping of the table in a compact package with a minimal profile. Similarly, the second exterior leg member may also comprise third and fourth extensions pivotably attached to the second table portion and a comparable detachable second unitary curvilinear support member.
Typically, wheels are attached to the first and second lower portions of the first and second unitary curvilinear members to allow the rigid central support unit and attached first and second table portions to be easily rolled from place to place when the table portions are in the essentially vertical storage position. To facilitate assembly, the first and second curvilinear members have apertures formed there through that align with apertures in the first and second connecting members. During assembly, the apertures are aligned and removable fasteners that are capable of being tightened and loosened by hand without the necessity for tools are inserted through the apertures and tightened by hand to assemble the rigid support unit.
These and other objects, advantages and features shall hereafter appear in the following detailed description of the preferred embodiment which are provided for the purposes of illustration, but not, for limitations of the scope of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a side view of a foldable table of the present invention oriented in the essentially horizontal playing position with dotted lines showing one half of the table being pivoted toward the essentially vertical position.
FIG. 2
is a side view of a first embodiment the present invention showing the respective table portions being pivoted to their essentially vertical position.
FIG. 3
is an end view of a first embodiment of the present invention showing the table portion in an essentially vertical position.
FIG. 4
is a side view of an alternative embodiment of the present invention.
FIG. 5
is a end view of the embodiment illustrated in FIG.
4
.
FIG. 6
is a side, partially fragmented view of the end of a side connecting member of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to
FIGS. 1
,
2
and
3
, a foldable table
10
constructed in accordance with the teachings of the present invention is illustrated. Table
10
comprises a first table portion
12
and a second table portion
14
which are essentially rectangular in shape. First and second table portions
12
and
14
each have a center edge
16
and an outer edge
18
and side edges
20
and
22
. First and second table portions also each have an essentially flat upper playing surface
24
and an essentially flat lower surface
26
.
An essentially rigid central support unit
28
is provided comprising first curvilinear member
30
and second curvilinear member
32
joined together by connecting members
34
and
35
to form an essentially rigid central support unit
28
.
First and second unitary curvilinear members
30
and
32
are formed from a singular unitary piece of material and typically of tubular steel or other metals. First and second curvilinear members
30
and
32
are both formed to have a lower portion
36
which is essentially straight and normally parallel to the floor when assembled. Upwardly extending first and second supporting portions
38
and
40
are integrally formed at the ends of lower portion
36
by bending the tubular member so that supporting portions
38
and
40
are essentially perpendicular to the lower portion
36
.
The first and second curvilinear members
30
and
32
also comprise upper extension
42
and
44
which are similarly formed by bending the upper ends of the curvilinear members until they are essentially parallel with lower portions
36
. Thus, each of the first and second curvilinear members
30
and
32
comprise a single unbroken piece of material which is formed into an essentially U-shaped structure. This structure provides advantages over the prior art as it is easily and inexpensively fabricated and is very strong.
Upper extensions
42
and
44
are each attached to the lower surface
26
of first and second table portions
12
and
14
by bracket members
46
which allow first and second table portions
12
and
14
to be easily pivoted around the upper extensions of the first and second curvilinear members from the essentially horizontal position shown in
FIG. 1
to the essentially vertical position shown in
FIGS. 2 and 3
and back again.
Wheels
47
may be appropriately affixed to the lower portions
36
of first and second curvilinear members
30
and
32
to facilitate movement of the table when the table portions are in their essentially vertical position. Wheels
47
may typically comprise pivotably mounted wheel units which will allow the wheel to rotate about a vertical axis to allow movement in any direction.
Also attached to the lower surface of first and second table portions respectively are first exterior leg member
48
and second exterior leg member
50
. First and second exterior leg members
48
and
50
are pivotably connected by bracket members
52
and
54
so that the exterior leg members can be pivoted from a position essentially perpendicular to the table portions
12
and
14
illustrated in
FIG. 1
to the position illustrated in
FIGS. 2 and 3
wherein the exterior leg members are folded against the lower surface of the respective table portions
12
and
14
.
To facilitate shipping and storage, first and second exterior leg members
48
and
50
may be formed in multiple pieces. As illustrated in
FIGS. 2 and 3
, exterior leg member
48
comprises a first and second leg extension
56
and
58
each pivotably connected to the table portion by bracket member
52
. The first exterior leg member also comprises a unitary curvilinear support member
60
which is formed of a single unitary piece of material such as tubular metal material into an essentially U-shaped structure. The ends
62
of curvilinear support member
60
are formed to mate with the free ends
57
and
59
of extensions
56
and
58
in a detachable manner so that curvilinear support member
60
can be disengaged from extensions
56
and
58
. For example, ends
62
can be formed with a taper so that they can be inserted into hollow ends of extensions
56
and
58
and a suitable retaining mechanism, such as a detent, may be used to hold the support member
60
onto the extensions
56
and
58
. Second exterior leg member
50
may be formed in the same manner with comparable extensions and support member.
With reference to
FIG. 6
, side connecting members
34
may be formed with apertures
64
formed there through dimensioned to align with comparable apertures (not shown) in supporting portions
38
and
40
of first and second curvilinear members
30
and
32
. Similarly bottom connecting member
35
has apertures formed there through (not shown) which are dimensioned to align with comparable apertures (not shown) in lower portions
36
of the first and second curvilinear members. Hand operable fasteners (not shown), typically bolts (with hand operable wing nuts), are seated through the apertures and tightened by hand to attach the connecting members
34
and
35
to the curvilinear members
30
and
32
to form the rigid central support unit
28
.
Also, the ends of connecting members
34
are tapered slightly so that the outer surface
66
is angled slightly as indicated by the angle “a” as indicated in
FIG. 6
so that when the first and second curvilinear members are joined together by the side connecting members
34
the curvilinear members are angled toward one another slightly as illustrated in
FIGS. 1 and 2
so that when the first and second table portions
12
and
14
are pivoted to their essentially vertical position shown in
FIG. 2
, the outer edges
18
of the table portions are essentially parallel and slightly closer together than the center edges
16
of the respective table portions. Because of that slight angular tilt, the table portions
12
and
14
will remain in an essentially upright position with the lower edges
16
pressed against the supporting portions
38
and
40
of the respective first and second curvilinear members. This arrangement aids in preventing the table portions from accidentally pivoting and falling back to a horizontal position during movement and storage.
With reference to
FIG. 1
, an alternative configuration is shown in dotted lines. A connecting member
70
is pivotably connected between first curvilinear member
30
and first exterior leg member
48
and another connecting member
71
is pivotably connected between second curvilinear member
32
and second exterior leg member
50
. As illustrated by the dotted lines in
FIG. 1
, as the table portion
14
is pivoted upwardly to the position identified by
14
′ (as shown in dotted lines), connecting member
71
causes exterior leg member
50
to pivot towards table member
14
′ (as shown in dotted lines) and when the table portions are as shown in
FIG. 2
, the connecting members
70
will cause the exterior legs to fold until they are flat against the lower surface of the respective table portions
12
and
14
. Thus, the connecting members
70
and
71
may optionally be added to facilitate folding of table
10
.
With reference to
FIGS. 4 and 5
, an alternative embodiment of the exterior leg members is illustrated. In
FIGS. 4 and 5
, all of the various common elements are numbered the same as
FIGS. 1
,
2
and
3
. The exception is the exterior legs
74
, each of which comprise a single elongated member pivoted at one end by bracket
76
and capable of being pivoted to a position essentially 90 degrees to the bottom surface of table portions
12
and
14
respectively to support the table portions
12
and
14
in an essentially horizontal position. Additionally, connecting members of the type illustrated in FIG.
1
and identified by the numerals
70
and
71
may be connected between the respective leg members
74
and the respective curvilinear members
38
and
40
to allow the leg members
74
to be automatically pivoted when the table portions are elevated to their essentially vertical position.
The design of the present invention is both economical to fabricate, shippable in a very confined, minimal profile package and easy to assemble. With reference to
FIGS. 1
,
2
and
3
, curvilinear members
30
and
32
are easily and inexpensively formed by a bending operation using steel tubing material. Similarly, exterior leg member
48
and
50
can be easily formed by cutting first and second extensions
56
and
58
at the appropriate length from tubing material and forming the curvilinear support member
60
by bending tubular material into the U-shaped form shown in FIG.
3
. An appropriate taper can be added to ends
62
by a rolling operation. Factory assembly and packaging of the foldable table tennis table in accordance with the present invention is relatively simple due to the simplicity of construction and minimal number of parts. The first and second curvilinear members
30
and
32
are respectively attached to the first and second table portions
12
and
14
using bracket members
46
which are appropriately attached at the factory screws or other fasteners to the lower surface of the respective table portions adjacent the center edge as illustrated in
FIGS. 1
,
2
,
3
,
4
and
5
. In the
FIGS. 1
,
2
and
3
embodiment, first and second extensions
56
and
58
are attached by screwing pivotably attached bracket members
52
and
54
to the lower surface of the respective table portions using screws or other appropriate fasteners at the factory. In the
FIGS. 4 and 5
embodiment, leg members
74
are similarly attached by screwing pivotably attached bracket members
76
to the lower surface of the table portions at the factory.
For packaging purposes, the curvilinear members
30
and
32
are respectively pivoted until they are against the lower surface of the respective table portions
12
and
14
and totally within the parameters of the edges of table portions
12
and
14
. In the
FIGS. 1-3
embodiment, extensions
56
and
58
are pivoted until they contact the lower surface of the respective table portions and the curvilinear support member
60
is detached and placed against the lower surface of the table portion between the center edge and bracket members
46
so that the curvilinear support members are totally within the perimeter of the edges of the respective table portions. The connecting members
34
and
35
are placed flat against the lower surface of the table portion within the perimeter of the curvilinear member and the upper playing surfaces of the two table portions
12
and
14
are placed flat against one another. In this manner, the packaging for the entire table need only to be big enough to encompass the perimeter of the two table portions
12
and
14
placed one on top of the other and wide enough to encompass the two table portions and the attached curvilinear members and extensions when in a flat folded position.
Similarly, with the
FIGS. 4 and 5
embodiment, leg members
74
need only be pivoted flat against the surface of the respective table portion and the curvilinear members pivoted upwardly flat against the lower surface
26
of the table portion and the respective connecting members
34
and
35
placed flat against the lower surface
26
within the perimeter of one of the curvilinear members along with the fasteners necessary to attach the connecting members. Thus, either embodiment of the table
10
can be packaged in a very compact shipping container.
Assembly of the foldable table tennis table in accordance with the present invention upon delivery to a customer is extremely easy. The two table portions are removed from the box and placed on their sides parallel to one another. The curvilinear members
30
and
32
are pivoted until the apertures in the connecting members
34
and
35
can be aligned with the corresponding apertures drilled in the curvilinear members
30
and
32
. The fasteners are inserted through the apertures. The fasteners (not shown) typically comprise bolts with wing nuts which can be tightened by hand without the need of tools to assemble the central support unit
28
. However, any type of hand operable fastener will suffice. Wheels
47
, are typically of the pivot type that have a stem that can be inserted into pre-drilled apertures in the lower portions
36
. In the
FIGS. 1-3
embodiment, the curvilinear support member
60
is attached to the free ends of extensions
56
and
58
using a detent or other suitable locking mechanism. The table is then ready to be pivoted to a playing position as illustrated in
FIG. 1
with the two table portions
12
and
14
in an essentially horizontal position.
For the
FIGS. 4 and 5
embodiment, the central support unit
28
is assembled in the same manner as the
FIGS. 1-3
embodiment and no further assembly is required for leg members
74
other than to pivot them to a position perpendicular to the lower surface so that they will support the table in an essentially horizontal position.
If the table includes the automatic leg folding arrangement illustrated by the dotted lines
70
and
71
in
FIG. 1
, additional assembly will be required to connect the connecting members
70
and
71
between the curvilinear members and the exterior legs. This assembly can also be accomplished by pre-formed appropriate apertures in the respective members and using wing nuts for the attachment of members
70
and
71
so that no tools are required.
It should also be recognized that while the embodiment illustrated in
FIGS. 1-6
show a central support unit with lower portions
36
of the curvilinear members
30
and
32
being essentially parallel to the inner edges
16
of the table portions
12
and
14
, and the connecting members
34
and
35
, perpendicular to the inner edges
16
of the table portions
12
and
14
, the central support unit could alternatively easily be fabricated so that could be rotated 90 degrees, and still achieve all of the advantages and features of the present invention. For example, upper extensions
42
and
44
could be formed to be essentially perpendicular to both the lower portion
36
and the supporting portions
38
and
40
. Also the length of the connecting members
34
and
35
and the length of the lower portions
36
could be adjusted appropriately. The supporting unit could then be rotated 90 degrees and the table portions attached so that one table portion
12
is pivotably attached on one end of the curvilinear members and the other table
14
is attached to the other end of the curvilinear members. To facilitate safety, in this alternative construction, the upper ends of supporting portions
38
and
40
could be tilted slightly toward one another during the bending operation so that the table portions tilt toward one another slightly when raised to the essentially vertical position.
While the present invention has been described in conjunction with the above-described embodiments hereof, it should be recognized that various modifications, variations, and changes may be made as will be readily apparent to those of ordinary skill in the art and those modifications, variations and changes are intended to be within the scope of the present invention as defined by the following claims.
Claims
- 1. A foldable table tennis table comprising:first singular continuous curvilinear member comprising a first horizontally disposed lower portion, said first lower portion having first and second ends, said first singular continuous curvilinear member also comprising upwardly extending first and second supporting portions, said upwardly extending first and second supporting portions each having first and second ends, said first supporting portion being formed at its first end to the first end of said lower portions, and the second supporting portion being formed at its first end to the second end of said first lower portion; second singular continuous curvilinear member comprising a second horizontally disposed lower portion, said second lower portion having first and second ends, said second singular continuous curvilinear member also comprising upwardly extending first and second supporting portions, said upwardly extending first and second supporting portions each having first and second ends, said first supporting portion integrally joined being formed at its first end to the first end of said second lower portions, and the second supporting portion being formed at its first end to the second end of said second lower portion; at least two connecting members, said connecting members connected between said first and second curvilinear members thereby forming said first and second curvilinear members and said connecting members into a rigid central support unit; a first table portion and a second table portion each having an upper playing surface and a lower surface, a center edge, an outer edge and two opposing side edges, said lower surface of said first and second table portions being pivotally connected to the central support unit adjacent said center edges of said first and second table portions, so that said first and second table portions can be pivoted from an essentially horizontal playing position where the center edges are in close proximity to one another to an essentially vertical storage position with the outer edges of said first and second table portions are essentially parallel and slightly closer together than the inner edges of said first and second table portions.
- 2. A foldable table tennis table as claimed in claim 1, further comprising at least one first exterior leg member attached to the lower surface of the first table portion adjacent to the outer edge of the first table portion, and at least one second exterior leg member attached to the lower surface of the second table portion adjacent the outer edge of the second table portion, said first and second exterior leg members being extendable to contact a floor to support the first and second table portions in an essentially horizontal position.
- 3. A foldable table tennis table as claimed in claim 2, wherein said first exterior leg member and second exterior leg member are pivotally attached to the respective first and second table portions so that said exterior leg members can be folded against the lower surface or said first and second table portions respectively.
- 4. A foldable table tennis table as claimed in claim 2 or 3, wherein said first exterior leg member and second exterior leg member are respectively connected to said central support unit in a manner so that said first and second exterior legs automatically fold against said lower surface of said table portions as said table portions are raised from the essentially horizontal position to the essentially vertical position.
- 5. A foldable table tennis table as claimed in claim 2, wherein:said first exterior leg member comprises a first and a second extension pivotally attached at a first end to the first table portion and a first curvilinear support member having first and second ends, said first and second ends being detachably connectable to a second end of said first and second extensions respectively; said second exterior leg member comprises a third and a fourth extension pivotally attached at a first end to the second table portion and a second curvilinear support member having first and second ends, said first and second ends being detachably connectable to a second end of said third and fourth extensions respectively.
- 6. A foldable table tennis table as claimed in claim 1, wherein wheels are attached to said first and second lower portions of said first and second singular continuous curvilinear members to allow said rigid central support unit and attached first and second table portions to be easily rolled from place to place when said table portions are in the essentially vertical storage position.
- 7. A foldable table tennis table as claimed in claim 1, wherein said connecting members have apertures formed there through at each end thereof, and said first and second singular continuous curvilinear members have apertures formed there through that align with the apertures in said connecting members, and removable fasteners are inserted through said apertures to attached said connecting members to said curvilinear members.
- 8. A foldable table tennis table comprising:first singular continuous curvilinear member comprising a first horizontally disposed lower portion, said first lower portion having first and second ends, said first singular continuous curvilinear member also comprising upwardly extending first and second supporting portions, said upwardly extending first and second supporting portions each having first and second ends, said first supporting portion being formed at its first end to the first end of said lower portions, and the second supporting portion being formed at its first end to the second end of said first lower portion; second unitary curvilinear member formed to have a second lower portion, said second lower portion having first and second ends, said second curvilinear member also comprising upwardly extending first and second supporting portions, said upwardly extending first and second supporting portions each having first and second ends, said first supporting portion being formed at its first end to the first end of said second lower portions, and the second supporting portion being formed at its first end to the second end of said second lower portion; first and second connecting members, said first connecting member connected between said first supporting portions of said first and second singular continuous curvilinear members and said second connecting member connected between said second supporting portions of said first and second singular continuous curvilinear members thereby forming said first and second singular continuous curvilinear members and said first and second connecting members into a rigid central support unit; a first table portion having an upper playing surface and a lower surface, a center edge, an outer edge and two opposing side edges, said lower surface being pivotably connected to the second ends of said first supporting portions of said first curvilinear member adjacent said center edge of said first table portion; a second table portion having an upper playing surface and a lower surface, a center edge, an outer edge and two side edges, said lower surface being pivotably connected to the second ends of said second supporting portions or said second curvilinear member adjacent said center edge of said second table portion; whereby said first and second table portions can be pivoted from an essentially horizontal playing position where the center edges are in close proximity to one another to an essentially vertical storage position with the outer edges of said first and second table portions being essentially parallel and slightly closer together than the inner edges of said first and second table portions.
- 9. A foldable table tennis table as claimed in claim 8, where in said first and second connecting members are connected between said first and second supporting portions of said first and second singular continuous curvilinear members so that said first supporting portions of said first and second curvilinear members, and the second supporting portions of said first and second curvilinear members are tilted toward one another so that the second ends of said first supporting members are closer together than the first ends of said first supporting members and the second ends of said second supporting members are closer together than the first ends of said second supporting members.
- 10. A foldable table tennis table as claimed in claim 8, wherein said first and second connecting members have apertures formed there through at each end thereof, and said first and second supporting portions of said first and second singular continuous curvilinear members have apertures formed there through that align with the apertures in said first and second connecting members, and removable fasteners are inserted through said apertures to attached said connecting members to said supporting portions.
- 11. A foldable table tennis table as claimed in claim 7 or 10, wherein said fasteners are capable of being tightened and loosened by hand.
US Referenced Citations (33)
Foreign Referenced Citations (1)
Number |
Date |
Country |
2048660 |
Dec 1980 |
GB |