The different ways in which window sashes may be arranged are as follows.
Methods of Arranging Sashes.
(a) Fixed, so that they cannot be opened, see Figs. 541 to 543.
(b) Hinged on either side, so as to open like a door in one leaf or two, see Figs. 550 to 552.
(c) Hinged on either the top or bottom rail.
(d) Suspended by lines over pulleys with counterweights, so that they slide up and down, see Figs. 545 to 549.
(J) Hung on pivots near their centres, see Fig. 540.
The construction of sashes will first be explained, then that of the frames in which they are hung, and then the method of hanging.
The sash itself is of nearly the same construction in all these cases.
Fixed Sashes and Hinged Sashes (see Figs. 541 and 551) consist simply of rails (r) and styles (s) framed together, and sash bars (sb), the spaces thus formed being intended to be fitted in with glass.
Fig. 535 shows the construction of an ordinary pair of sashes which are to be hung so as to slide past each other up and down, as described at p. 271, and illustrated in Figs. 545 to 549.
It will be seen that the rails (r) and sash bars (sb) are tenoned into the styles (s) and wedged. In consequence of the narrowness of the meeting rails (mr), their tenons have to be the full width of the rails, and therefore the mortise has to be cut through to the end of the style, leaving no wood1 on its outer side, see Fig. 535. The joints between the sash bars are explained at p. 267.
In some cases the lower ends of the styles of the upper sash are continued beyond the meeting rail (mr), and furnished with a moulded horn (h, Fig. 5 3 6). This strengthens the joint by providing an outer side to the mortise and prevents the meeting rail from striking the sill when the sash is lowered.
1 A temporary horn is left on which the sash is wedged up, one wedge being used as at M, Fig. 535.
In a fixed sash the vertical sash bars are tenoned into the top and bottom rails, and run continuously between them, being mortised to receive the horizontal bars, which are cut into lengths and tenoned in between them.
Fig. 535. Sashes to be double hung.
When a sash is to be hung, those bars that are in the direction of the blows or jars it will receive when it is opened or closed, should be made continuous, and the other bars cut and tenoned. Thus, in a sash to slide up and down, the vertical bars, and in a casement the horizontal bars, are continuous.
Fig. 537 is a Plan of the junction of a vertical and a horizontal sash bar for a sliding sash known as franking. The vertical bar, (V V) is not severed, but merely mortised to receive the tenons (t t) formed on the ends of the portions of the horizontal bars (H H). These latter are scribed, as shown from a to b, to fit the moulding (c d) of the vertical bar. The tenons are sometimes made the full width of the square (x y) of the sash bar, as shown in Fig. 538. When the mouldings of the sash bar form an angular edge as in the lamb's tongue moulds, or frequently in superior work, the joint is mitred instead of being scribed - that is, an angular notch is cut upon the vertical bar, and a corresponding angle formed upon the end of the horizontal bar to fit it, as shown in Fig. 5 3 8.1
In very good work the joint is further secured by a dowel inserted between the horizontal bars to assist the tenons.
The sash bars have a double rebate (r r), Fig. 537 a, on the outside to receive the glass, and a similar rebate is formed all round the outside of those edges of the styles and rails which are next to the glass. In Fig. 537, the glass, together with the putty which secures it, is shown on the right side of the sash bar.
Fig. 538. Scantlings of Sashes.
Sashes are generally from 1 1/2 to 2 inches thick. The rebates have a depth from the face equal to about 1/3 the thickness of the sash for ordinary glass, but greater when plate glass and fillets are used (Fig. 528). The width of the rebates is about 1/4 inch.
The lower rail of the upper sash and the upper rail of the lower sash (mr mr) are called the "meeting rails." They are made wider than the others (each by the thickness of the parting bead), and are bevelled off, as shown in Fig. 545 (or, in some cases, rebated), so as to fit closely where they meet.
The styles and top rails are generally about 2 inches wide, and the meeting rails (in order to obstruct the light as little as possible) about 1 1/4 inch. The bottom rail for extra strength is made deeper, generally 3 to 4 inches, and has its under side bevelled (Fig. 545), and sometimes also throated or checked (Fig. 539), to fit the oak sill.
1 From S.M.E. Course.
The lower surface of the bottom rail should in the best work be checked out to fit the oak sill (see Fig. 539), and its back edge slightly splayed, so as not to strike the inside bead as the sash is lowered. The outer side of the inside bead may also be splayed to fit the lower side, so that the joint between them is tightened as the sash descends.
Occasionally the throat is formed nearly on the extreme front edge of the bottom rail, as shown in Fig. 540, so that when closed it is immediately in front of the throat upon the oak sill described at page 270. When there are two sashes, as in Fig. 545, the under edge of the top or meeting rail of the lower sash is grooved instead of being rebated. A reference to Fig. 545 will show that this is necessary, in order that the meeting rails may be of the same thickness where they come in contact.
The inside of the sash bars, styles, and rails may be left square, moulded, bevelled, or chamfered, according to taste.
An example of a bevelled or chamfered bar is given in Fig. 541, and a moulded bar is shown in Figs. 537 and 544. A square bar is rectangular in section, not ornamented in any way.
Fixed Sashes are put into solid frames, close up against the rebate, and screwed there. A bead stop is sometimes fixed on the outside to keep the joint between frame and sash more secure. Fanlights are sashes, generally fixed over a door, as shown in Figs. 524, 525. The sash is necessarily on the same side of the frame as the door, in order to be in the same plane with the latter.
These are hung "single"' in solid frames (see Fig. 540).
The sash has pivots fixed on the styles in prolongation of its horizontal axis. These pivots fall into slots in small iron sockets fixed in the frame to receive them.
If it is required that the window should fall to and close itself, the pivots are placed slightly above the centre line.
Fig. 539. Checked Bottom Hail.
When the window is opened the lower part should move outwards, as shown in Fig. 540.
Fig. 540. Sash hung on Centres.
In this sash the horizontal bars (if any) extend continuously across, being mortised to receive the vertical bars. In large sashes a centre rail may be introduced.
A bead is fixed on the upper half of the outside, and on the lower half of the inside of the frame against which the sash abuts; the remaining portion of the bead is fixed upon the sash itself, so as to show a continuous bead when the window is shut.
Instead of fixing separate beads upon the frame, it is sometimes rebated to answer the same purpose.
Sashes hung in this manner are well adapted for windows out of reach, as they can be opened and shut from below by cords.
Sashes sliding laterally are seldom required. Those which move in a vertical plane may be arranged to move on rollers between beads on a solid frame, or the under side of the sash may be deeply grooved so as to fit over a water bar fixed in the sill.