Barrel assembly and composite stress plate

Abstract: A composite stress plate for securing insulation to a roof deck with a fastener (21) includes a metal plate (12) having a central cup (15) with a concentric aperture and a plastic insert (14) having a central throughbore for receiving the fastener (21) in a threaded manner. The plastic insert (14) may have a hub which corresponds in shape to and is adapted to snappingly engage the concentric aperture in the metal plate (12), or the insert may be received by the cup in the metal plate and retained therein. Means for preventing relative rotation between the plastic insert (14) and the metal plate (12) are provided in either case. A plurality of depressed ramps (30) are disposed within the plate having cleats for engaging the insulation. The ramps (30) enhance alignment of the composite stress plate on a barrel assembly of an installation tool and precise placement of the threaded fastener (21) into the roof deck is achieved. The barrel assembly has a plate retaining member having an engagement face with a plurality of locator projections extending downwardly therefrom. The locator projections may include three metal studs for insertion into the ramps. The locator projections engage the plate at three contact points to hold the stress plate against rotation while the fastener (21) is being threaded through the plastic insert and into the roof deck by the installation tool.

Description: The invention relates to a combination of a stress plate, a fastener and a barrel assembly according to the preamble of claim 1. Such a combination is already known from US-A-4 809 568 which will be discussed hereinafter. When roofing is installed on commercial buildings, a layer of insulation is normally secured to the roof deck. The assemblies which are used to secure the insulation generally comprise a washer-like stress plate made of either plastic or metal which receives a screw-like fastener that is threaded into the roof deck, clamping the insulation between the stress plate and the roof deck. Since insulation utilized is commonly up to six inches thick, while special applications can exceed twelve inches, it is important to keep the fastener in perpendicular alignment when installing the plate so that the stress plate properly contacts the roof deck. To facilitate this alignment, the plate and fastener are commonly installed using an installation tool, such as that described in U.S. Patent No. 4,809,568. From US-A-4 809 568 a disc-shaped plastic stress plate containing flat edge portions spaced at 90° intervals around its periphery is known. The flat portions engage flat surfaces of projections of a barrel assembly preventing rotation of the stress plate as a fastener, pre-assembled with the stress plate, is driven by a driving tool. The problem of the known combination is that the stress plate with its flat edge portions has to be aligned with the projections of the barrel assembly when being inserted into a retaining member of the assembly so that the flat edge portions engage the projections. Therefore, insert of the stress plate into the barrel assembly is time consuming. An additional problem with the known combination is vibration causing the fastener to back out of the stress plate. This will allow loss of the clamp load on the insulation which could result in destruction of the roofing system. Another problem with screw back-out is the possibility of the screw head penetrating the waterproofing membrane of the roofing system allowing water to enter the roofing system. This problem has been addressed by locking and alignment devices in plastic stress plates: see U S-A-4 361 997. Plates utilized in the past to secure insulation have generally been made solely of either metal or plastic. While plastic stress plates have the advantage of using the above-noted locking and alignment devices, they may not have the advantages of steel stress plates in several applications. In roofing membrane applications where propane fueled torches are used, there may be occasions where, if done improperly, a plastic stress plate which is commonly made of polypropylene or polyethylene could reach a temperature where the clamp load on the insulation between the stress plate and metal deck could partially release. Polymer materials are available that would prevent this; however, their cost is prohibitive to use on the total stress plate. In some applications, all-plastic plates have been found inadequate for providing peripheral support to the insulation around the point of attachment of the plate due to the fact that the outwardly extending portion of the plate is not as rigid as that of its all-metal counterpart. Thus, all-plastic plates have frequently been designed with corrugated ribs etc. to strengthen rigidity. See, for instance, US-A-4 520 606 and US-A-4 726 164. The necessity of adding sufficiently sized ribs to the plastic plate structure could increase fabrication costs and thus threaten to reduce demand in the construction industry for all-plastic plates. With a composite stress plate, an inexpensive coated metal stamping could be used for the required peripheral support while allowing a plastic insert for the advantages of alignment and head retention. As mentioned above, alignment of the fastener and the plate during installation is important as insulation thickness frequently requires use of screws up to 17,78 cm (seven inches) long, and over 304,8 cm (twelve inches) long in special applications. Thus, it is desirable to stabilize the plate on the installation tool in proper alignment with the fastener. It is also desirable to prevent relative rotation of the plate on the tool during installation as this frequently causes misalignment of the fastener. Recently, others in the art have utilized composite two-plate structure to secure insulation to roof deck. US-A-4 757 661 discloses a washer with axial ribs for attaching insulation to a roof member. The fourth embodiment of this invention is comprised of two components, a central body and a flange, and they are shown as being made of two different materials, plastic and metal. Washer and the fastener are not aligned to each other when installed on a roof deck. It is the object of the present invention to improve the known combination to secure alignment of the fastener when installing the washer-like plate and to insure that the clamp load of the fastener on the plate is maintained throughout the life of the roof structure. Furthermore, rotation of the plate on the installation tool has to be prevented when the threaded fastener is being installed. The object is achieved by a combination with the features according to claim 1. The combination comprises a composite stress plate for securing insulation with or without a membrane to a roof deck with a threaded fastener, which offers the advantages of plastic and metal in a unitary structure. The composite stress plate comprises a metal base plate having a drawn central cup with a concentric aperture, along with a plastic insert having a central throughbore for receiving the fastener in an interference-fit relationship. The plastic insert is adapted to engage the drawn cup, thus forming the stress plate. The stress plate further includes means for preventing relative rotation between the plastic insert and the metal base plate when the plastic insert is engaged in the cup. The metal base plate has an elevated portion, a bottom surface and a rim with a bearing flat located within the cup. The plate includes at least one depressed ramp for engaging a locator projection on a barrel assembly of an installation tool. Embodiments of the invention are claimed in the dependent claims. The plastic insert in a first embodiment has a head, a downwardly protruding hub, and a central throughbore for receiving the fastener in an interference-fit relationship. The hub is shaped to mate with an angular aperture in the metal base plate to prevent relative rotation between the plastic insert and the metal base plate when the fastener is threaded into the plastic insert. At least one tab depends from the hub and engages the bottom surface of the cup on the metal base plate thereby fixing the hub in engagement with the angular aperture and forming the composite stress plate. In a second embodiment, the plastic insert is completely received by the drawn central cup. The metal base plate has a crimp which extends into the cup and engages the plastic insert, thus preventing relative rotation between the plastic insert and the metal base plate. The crimp may be at the upper lip of the cup (thus comprising a "stake"), in the walls of the cup, or at the lower lip of the cup. The plastic insert and the cup may be substantially congruent in a shape which prevents relative rotation between the plastic insert and the metal base plate. The barrel assembly on the installation tool has a plate retaining member with an engagement face thereon. One or more, preferably three locator studs extend downwardly from the engagement face and are equally spaced about a central axis of the barrel assembly. After the stress plate and fastener are pre-assembled and placed on the insulation, the barrel assembly is placed over the stress plate and the installation tool begins rotating the fastener to place it into the roof deck. The engagement face engages the metal base plate and each locator stud is inserted into a corresponding depressed ramp. Each metal stud engages a contact point on the metal base plate to prevent rotation of the stress plate. A peripheral rib on the plate retaining member engages a rim on the base plate to further align the fastener and the stress plate for proper installation. Other features and advantages of the present invention will become apparent from the following detailed description in conjunction with the accompanying drawings. Fig. 1 is a plan view of a metal plate in accordance with a first embodiment of the invention; Fig. 2 is a section taken along lines II-II of Fig. 1; Fig. 3 is a plan view of a plastic insert in accordance with the first embodiment of the invention; Fig. 4 is a sectional view taken along lines IV-IV of Fig. 3; Fig. 5 is a bottom view of the plastic insert of Fig. 4; Fig. 6 is a sectional view showing the plastic insert of Fig. 3 engaged in the metal plate of Fig. 1; Fig. 7 is a bottom perspective view of the composite metal plate and plastic insert of Fig. 6, excluding the fastener; Fig. 8 is a plan view of a metal plate in accordance with a second embodiment of the invention; Fig. 9 is a sectional view taken along lines IX-IX of Fig. 8; Fig. 10 is a sectional view of a first variant of the second embodiment of the invention; Fig. 11 is a sectional view of a second variant of the second embodiment of the invention; Fig. 12 is a sectional view of a third variant of the second embodiment of the invention; Fig. 13 is a bottom perspective view of the composite metal plate and plastic insert of Fig. 11, excluding the fastener; Fig. 14 is a perspective view of an installation tool barrel assembly according to the present invention; Fig. 15 is a bottom view of the barrel assembly of Fig. 14; and Fig. 16 is a sectional view of a combined barrel assembly and composite stress plate according to the present invention. A first embodiment and a second embodiment of a composite stress plate 10 and 110, respectively, are shown in Figs. 7 and 13, respectively. Each embodiment has a metal base plate 12, 112 and a plastic insert 14, 114. Each of the metal base plates 12, 112 has a drawn cup 15, 115 in the center of the metal base plate 12, 112. The plastic insert 14, 114 has a central throughbore 20, 120 for receiving a fastener 21, 121 in an "interference-fit" or, in other words, threaded manner. The threaded engagement may be seen in Figs. 6 and 10-12. The plastic inserts 14, 114 engage the metal base plates 12, 112 and, as discussed in further detail below, means are included for preventing relative rotation between the plastic insert 14, 114 and the metal base plate 12, 112 when the two are engaged and the fastener 21, 121 is threaded into the plastic insert 14, 114. Referring generally to Figs. 1-7, details of the first embodiment of the stress plate 10 are shown. Fig. 1 shows the metal base plate 12 with the drawn cup 15 having a concentric angular aperture 22. As shown in Fig. 2, the base plate 12 includes an elevated portion 24 and a rim 26 as well as a bottom surface 28. The angular aperture 22 and the rim 26 are coplanar in a plane below and parallel to the elevated portion 24. The angular aperture 22 may be of any noncircular shape, but it is preferably an equilateral triangle. Depressed ramps 30 are stamped at three locations in the elevated portion 24. The depressed ramps 30 extend from the elevated portion 24 downward in a counterclockwise fashion, with a punched cleat 23 depending from a lower edge of each ramp 30. Each cleat 23 extends below the plane of the angular aperture 22 and the rim 26 to engage the insulation. Each depressed ramp 30 is designed to receive a projection 40 in the form of a stud on a barrel assembly 32 of an installation tool 19 as shown in Figs. 14-16. The barrel assembly 32 holds the stress plate 10, 110 in proper alignment while the threaded fastener 21, 121 is secured to the roof deck, as further discussed below. Referring now to Figs. 3-6, the plastic insert 14 is shown with a countersink 34 and a lip 36 disposed in a head 18. The head 18 may be of various shapes but is preferably cylindrical, having an outer diameter greater than the outer dimension of a downwardly protruding hub 38 which depends from the head 18. These features allow the head of the fastener 21 to become flush with the head 18 of the plastic insert 14 when the fastener 21 is inserted in the central throughbore 20, thus providing a smooth upper surface on the stress plate 10, which is desirable when subsequent layers of roofing membrane or the like are to be placed on top of the insulation after securement to the roof deck. Additionally, the hub 38 may be provided with a bevel 37 which enhances insertability of the hub 38 into the aperture 22. The hub 38 is shaped to mate with the angular aperture 22 in the metal base plate 12 in a manner which prevents relative rotation between the plastic insert 14 and the metal base plate 12. Specifically, the hub 38 is congruent with the angular aperture 22 so that when the hub 38 is inserted into the angular aperture 22, rotational movement of the hub 38 is impossible. Preferably, the hub 38 is in the shape of an equilateral triangle, corresponding to the preferred angular aperture 22 discussed above. Thus, relative rotation between the plastic insert 14 and the metal base plate 12 is prevented. The hub 38 may also include one or more tabs 41 which depend from the hub 38 and engage the bottom surface 28 of the cup 15, thereby fixing the hub 38 in engagement with the angular aperture 22. Specifically, each tab 41 depends from a face 42 on the hub 38 so that the free end of the tab 41 forms a bearing edge 44 which is radially spaced from the hub 38 and which contacts the bottom surface 28 of the cup 15. The plastic construction of the tabs 41 allows for bending of the tabs 41 when forced through the angular aperture 22, the tabs 41 snapping back into place when completely pushed through. The bearing edge 44, spaced away from the hub 38 and against the bottom surface 28 prevents back-out of the hub 38 from the angular aperture 22. The preferred embodiment has three tabs 41 depending from the hub 38, each forming an acute angle with a corresponding face 42 of the hub 38, as shown in Fig. 7. Referring to Figs. 8-13, a second embodiment of the stress plate 110 is shown. Again, the stress plate 110 has a metal base plate 112 and a plastic insert 114. The metal base plate 112 has a cup 115 with a upper concave portion 117 and a lower cylindrical portion 118. The plastic insert 114 is fully received by lower portion 118, and the plastic insert 114 has a central throughbore 120 for receiving a fastener 121 in an interference-fit relationship. As discussed above in connection with the first embodiment, the lower portion 118 may be circular or may be of any noncircular shape, such as an equilateral triangle, to prevent relative rotation between the metal base plate 112 and the plastic insert 114. The upper concave portion 117 provides a bearing flat 122 near an upper lip 128 of lower portion 118. The fastener head engages the bearing flat 122 to enhance the clamp load on stress plate 110, as long as the inner diameter of lower portion 118 is less than the outer diameter of the fastener head. In order to prevent back-out of the plastic insert 114 from lower portion 118, a crimp is formed in the cup 115 to engage the plastic insert 114. The crimp also serves to prevent relative rotation between the plastic insert 114 and metal base plate 112. Figs. 10-12 show three versions of the stress plate 110, each having a different crimp arrangement. In the first version, Fig. 10, a stake 125 is located at upper lip 128 and the stake 125 extends radially into the cup a sufficient distance to capture the plastic insert 114 and prohibit the plastic insert 114 from backing out of lower portion 118. The stake 125 is folded on top of the plastic insert 114 after its insertion into lower portion 118. The bottom of the plastic insert 114 rests on a lower lip 132 of the cup which extends radially inward from the lower portion 118. A second crimp arrangement is shown in Fig. 11. A crimp 127 is formed in the midsection of lower portion 118 and extends into the cup. The plastic insert 114 is thus constricted around its mid-section and held within the cup. Specifically, the plastic insert 114 is placed in an uncrimped lower portion 118 at rest on the lower lip 132. The crimp 127 is subsequently punched in the lower portion 118, forcing metal radially inward to the mid-section of the plastic insert 114. Finally, a third crimp arrangement is shown in Fig. 12. The plastic insert 114 is positioned so that it partially extends below the lower lip 132 of the cup. The lower lip 132 is then driven radially inward, forming a recess 136 in which the lip 132 engages the plastic insert 114. Referring to Figs. 14-16, a barrel assembly 32 used for installing the stress plate 10, 110 is shown. The barrel assembly 32 includes a plate retaining member 33 having an engagement face 35 with a peripheral rib 39. Three metal locator studs 40 extend downward from engagement face 35 and are equally spaced about a central axis of the barrel assembly 32. The studs 40 are integrally molded with the barrel assembly 32, and each stud 40 is inserted into its corresponding depressed ramp 30 when the barrel assembly 32 is placed over the stress plate 10, 110 and the fastener 21, 121 is threaded into the roof deck. Clockwise rotation of the stress plate 10, 110 caused by threading of the fastener 21, 121 through the central throughbore 20, 120 of the plastic insert 14, 114 is prevented by engagement of the projections 40 against three contact points 43, 143 on the elevated portion 24, 124 facilitated by the depressed ramps 30, 130. The projections 40 engage the ramps 30, 130 "on-the-fly" as the barrel assembly 32 are pressed downward onto the stress plate 10, 110. As the installation tool 19 rotates the fastener 21, 121, the plate retaining member 35 is pressed down onto stress plate 10, 110. At the high degrees of torque necessary to place the threaded fastener 21, 121 into the roof deck, the stress plate 10, 110 may spin clockwise, despite engagement of the cleats 23 into the insulation. The projections 40 then proceed down ramps 30, 130 until engaging contact points 43, 143 on elevated portion 24, 124 of the metal base plate 12, 112. The stress plate 10, 110 is thereby held against rotation relative to the barrel assembly 32 and the insulation and the proper clamp load of the stress plate 10, 110 on the insulation may be established. As an additional alignment feature, the peripheral rib 39 on the barrel assembly 32 engages the rim 26, 126 on the stress plate 10, 110 to insure proper horizontal placement of the metal base plate 12, 112 and rim 26, 126 on the insulation or membrane. The rib 39 also serves to "capture" the stress plate 10, 110 and further restrict its movement to insure perpendicular alignment of the fastener 21, 121 within throughbore 20. The first embodiment of the stress plate 10 has several advantages, namely: (1) the metal base plate 12 provides maximum peripheral support of the insulation; (2) the central throughbore 20 in the plastic insert 14 is not subject to rusting at this critical point of connection between the fastener 21 and the stress plate 10 as is common in prior art all-metal plates; (3) the plastic insert 14 is removable from the metal base plate 12 and thus the entire stress plate 10 need not be discarded should the central throughbore 20 become stripped during installation of the stress plate 10 with the fastener 21, rather the plastic insert 14 may be replaced; (4) the interference-fit relationship between the fastener 21 and the plastic insert 14 insures that a clamp load is maintained on the insulation throughout the useful life of the roof structure; and (5) the interference-fit prevents back-out of the fastener head from the plastic insert 14 due to various forces exerted on the roof structure. Additionally, the depressed ramps 30 enhance stability of the stress plate 10 during installation, and the projections 40 are received by the ramps 30 to engage contact points 43 and prevent relative rotation between the stress plate 10 and the installation tool. This promotes precise placement of the threaded fastener 21 into the roof deck and insures against relative rotation of the stress plate 10 and the insulation, even at high degrees of torque necessary to apply the requisite clamp load. The depending cleats 23 engage the insulation to prevent it from creeping out from under the stress plate 10 and they also prevent relative rotation between the stress plate 10 and the insulation at low degrees of torque to establish the interference-fit of the fastener 21 prior to engagement of the barrel assembly 32 on the stress plate 10. Thus, the ramps 30 have a dual function which increases overall design efficiency for the stress plate 10. A significant advantage of the second embodiment over the first embodiment is in manufacturing. Molds for the various plastic insert 14 designs discussed can be cost prohibitive, especially when they include added features such as the downwardly protruding hub 38 and the tabs 41. The plastic insert 14 of the second embodiment excludes those features and may be simply cut in successive pieces from an extruded plastic tube of appropriate cross-sectional shape. This greatly reduces manufacturing time and cost for the stress plate 10 while maintaining all the advantages of the more expensive embodiments. The plastic insert 14, 114 may be made of nylon copolymers, high density polyethylene, polypropylene or polyetherimide resins such as Ultem® made by G.E. Plastics, Inc. All embodiments of the stress plate 10, 110 may be used to secure insulation alone to roof deck, or to secure insulation in combination with an overlying membrane. In either case, the interference-fit of the fastener 21, 121 into the plastic insert 14, 114 prevents backing-out of the fastener 21, 121 from the stress plate 10, 110 in cases where the insulation is compressed, such as by walking on it, or when the stress plate 10, 110 is compressed by similar forces. When the stress plate 10, 110 together with the fastener 21, 121 are used to secure insulation alone, a larger diameter stress plate 10, 110, for example, 76,2 mm (three inches), is used. When securing both membrane and insulation, a smaller stress plate 10, 110 may be used, for example, 50,8 mm (two inches) in diameter. The various means for preventing relative rotation between the plastic insert 14, 114 and the metal base plate 12, 112 enable the interference-fit with the fastener 21, 121 to be established, and this means need not be limited to the structures disclosed herein.

Claims: In combination, a stress plate (10; 110) for securing a layer of insulation to a roof deck with a threaded fastener (21; 121) and a barrel assembly (32) for an installation tool, said barrel assembly (32) having a plate retaining member (35) at a distal end thereof, said stress plate (10; 110) having a central throughbore (20; 120) for receiving the threaded fastener (21; 121) in an interference-fit relationship, the combination comprising at least one locator projection (40) extending downwardly from said plate retaining member (35), characterized in that the stress plate is configured as a composite stress plate (10; 110) comprising a metal base plate (12; 112) having a central cup (15; 115) with a concentric aperture and a plastic insert (14; 114) with the central throughbore (20; 120), said insert (14; 114) corresponding in shape to and adapted to engage the cup (15, 115) in the base plate (12; 112), that means are provided for preventing rotation between the insert (14; 114) and the base plate (12; 112) when the insert (14; 114) is engaged in the cup (15; 115) and the fastener threads engage the central throughbore (20; 120), and that at least one depressed ramp (30; 130) in said stress plate (10; 110) is provided which extends from said stress plate (10; 110) downward in a counterclockwise fashion for receiving said locator projection (40), said locator projection (40) engaging a contact point (43; 143) on said stress plate (10; 110) adjacent said ramp (30; 130) to locate the stress plate (10; 110). The combination according to claim 1, characterized by a hub (38) on said plastic insert (14; 114) which is congruent with said concentric aperture. The combination according to claim 2, characterized in that said hub (38) enganges the concentric aperture and has at least one tab (41) depending therefrom, the free end of said tab (41) defining a bearing edge spaced away from the hub (38) and directed upward to engage a bottom surface (28) of the cup (15) in the metal base plate (12), thereby fixing the hub (38) in engagement with the concentric aperture. The combination according to any of the claims 1 to 3, characterized in that the plastic insert (14; 114) and said cup (15; 115) are substantially congruent in a shape which prevents relative rotation between the plastic insert (14; 114) and the metal base plate (12; 112). The combination according to any of the claims 1 to 4, characterized in that the means for preventing relative rotation between the plastic insert (14; 114) and the metal base plate (12; 112) includes a crimp in the metal base plate (12; 112) extending radially into said cup (15; 115) and engaging the plastic insert (14; 114). The combination according to any of the claims 1 to 5, characterized in that the ramp (30; 130) includes a cleat (23; 123) depending from a lower edge of said ramp (30; 130) for engaging the insulation. The combination according to any of the claims 1 to 6, characterized in that the locator projections (40) comprise three metal studs extending downwardly from an engagement face on the plate retaining member (35). The combination according to any of the claims 1 to 7 characterized in that the metal base plate (12; 112) includes an elevated portion (24; 124) and a rim (26; 126), said plate retaining member (35) having a peripheral rib (39), said rib (39) engaging the rim (26; 126) on said metal base plate (12; 112) to align the metal base plate (12; 112) with the fastener (21; 121) while the installation tool threads the fastener (21; 121) through the plastic insert (14; 114). The combination according to any of the claims 1 to 8, characterized in that the cup (115) has an upper concave portion (117) and a lower cylindrical portion (118) with a bearing flat located between said upper and lower portions.

Inventors: MOSSMAN JEFFREY L, MOSSMAN, JEFFREY L.
Applicants: SFS IND HOLDING AG, SFS INDUSTRIE HOLDING AG
Application year: 1992
Main classification: E04D3
IPC codes: E04D3, E04D15, F16B39, E04D5, B25B21